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Factors Affecting the Fracture Resistance of Post-Core Reconstructed Teeth: A Review
Abstract
This article presents a review of the literature on factors that affect the resistance to fracture of post-core reconstructed teeth.
Articles cited in a MEDLINE search were obtained from the journals and reviewed with respect to factors affecting fracture resistance of post-core reconstructed teeth.
A large part of the literature reviewed emphasizes the stress distribution during insertion of posts and during function. Other factors, like post length, post diameter, amount of remaining dentin, post material, post adaptability, post design, cement, core material, core and crown design, biocompatibility of post material, use of treated tooth, and load experienced by restored tooth, are also found to influence the fracture resistance of a reconstructed tooth. Of all the factors enumerated, crown design, occlusal forces, and use of the treated tooth are found to have direct impact on the longevity of the restored tooth.
Literature indicates that (1) preservation of tooth structure is a must; (2) posts should not be used with the intention of reinforcing the tooth; (3) review of functional and parafunctional forces must be undertaken before restoring the tooth, as these will influence the prognosis; and (4) controlled prospective clinical studies evaluating each factor should be undertaken.
... The revolutionary concept is based on a specific preparation that can be used in order to adapt the restoration to the remaining tissue, not the opposite. 6 The purpose of this article is to illustrate a clinical case of a maxillary molar treated with a ceramic endocrown, emphasizing the details of its preparation and principles of tissue preservation. ...
... 5 In 2008, Magne and Knezevic developed the correct choice of restorative materials considering ceramics and composites in intracoronal molar restorations. 6,7 Using this concept for maxillary premolars and maxillary incisors was an idea given by many authors throughout their studies, but they require more evidence to support it. ...
... SCL is the removal of hard and soft tissue supporting teeth surgically in order to avoid a violation of the biological width in case of a short clinical crown, traumatic injury, and deep caries. 5,6 However, the survival rate of adjacent teeth may be influenced by this surgery. 7 Orthodontic extrusion may be a clever solution in cases of fractured external roots. ...
... 14 However, more recent research suggests that a post-and-core should be used for retentive purposes only. 15,16 Post and core should be avoided if sufficient retention can be achieved from existing tooth substance, as its presence has been associated with an increased risk of root fracture due to increased stress in the root surface. 15,17 The type of prosthetic restoration could also affect the prognosis of endodontically treated teeth. ...
... 15,16 Post and core should be avoided if sufficient retention can be achieved from existing tooth substance, as its presence has been associated with an increased risk of root fracture due to increased stress in the root surface. 15,17 The type of prosthetic restoration could also affect the prognosis of endodontically treated teeth. 18 Extraction of endodontically treated teeth has been suggested to occur more often in FDP abutments than in SC abutments. ...
... The presence of a post could increase the stress on the root surface and subsequently increase the susceptibility to fracture. 15,17,65 In an in vitro study, fractography analysis of fractured non-vital teeth was performed to evaluate the fracture pattern of the dentin. 65 High tensile unfavorable stress distribution was observed on the root surface of non-vital tooth with parallel smooth sided stainless steel post, as a result of high stiffness of the metallic post which lead to root fracture. ...
Purpose:
To evaluate the survival rate of full coverage fixed prosthetic restorations, single crowns (SCs), and fixed dental prostheses (FDPs), taking into consideration the potential influence of tooth-vitality, presence and type of post, and type of prosthetic restoration material.
Materials and methods:
Two authors independently conducted the search in PubMed, Web of Science, and Scopus electronic databases search as well as hand searches were conducted in October 2022 to identify clinical human studies on full coverage single crowns and fixed dental prostheses supported by vital and/or non-vital abutments and/or a combination of both, with a minimum observation period of 24 months.
Results:
Out of 4198 and 22 studies identified through database and hand searching respectively, 26 studies fulfilled the inclusion criteria and were included in the analysis of the present systematic review. Included studies scored six points and more according to Newcastle-Ottawa Scale (NOS). The highest estimated 5-year survival rate was observed for (metal-ceramic and all-ceramic) SCs on vital teeth (98.3 %; 95% CI [98.1, 98.6]) and all ceramic SCs on non-vital teeth with fiber post (95.0%; 95% CI [94.5- 95.4]). Metal-ceramic SCs on vital teeth (97.1 %; 95% CI [95.6- 98.7] showed a statistically significant higher estimated 5-year survival rate compared to metal-ceramic SCs with cast metal post (90.7%; 95% CI [87.4- 94.0%], P < 0.001), fiber post (91.3%; 95% CI [90.9- 91.6%], P < 0.001) and without post (85.7%; 95% CI [80.7, 90.6%], P < 0.032). All-ceramic SCs with fiber post had a statistically significant higher estimated 5-year survival rate (95.0%; 95% CI [94.5- 95.4]) compared to metal-ceramic SCs on non-vital teeth with fiber post (91.3%; 95% CI [90.9- 91.6%], P < 0.001). Single crowns (All-ceramic and metal-ceramic) with fiber post had a statistically significantly higher estimated 5-year survival rate of (92.7%; 95% CI [92.4- 92.9%]) than SCs made of metal-ceramic and retained by cast metal post (90.7%; 95% CI [87.4- 94.0%], P < 0.001). For FDPs, the 5-year survival rate was significantly higher for FDPs on vital abutments (84.9%; 95% CI [75.9, 93.9]) compared to FDPs retained by non-vital abutment/s (81.3%; 95% CI [80.3, 82.2], P = 0.049) irrespective to presence, type of post, and FDPs material. The results are limited by the limited number of studies and the presence of uncontrolled cofounding clinical variables.
Conclusions:
Within the limitations of the study, tooth vitality is suggested to contribute positively to the survival of single crowns and fixed dental prostheses. This article is protected by copyright. All rights reserved.
... Endodontically treated teeth (ETT) present a greater risk of biomechanical failure than vital teeth, [1][2][3] and the longevity of a restored tooth thus depends on the amount of tooth structure remaining and on the efficiency of the restorative procedure used to replace lost structural integrity. 3,4 Posts should only be placed to retain a core within the remaining tooth structure and do not strengthen the tooth. ...
... 16 Although the impact of a low modulus of elasticity is controversial, some have argued that stiff posts are necessary, 4,8,9 while others have supported having dentin-like mechanical properties for the posts. 1,17 While fiber posts with a modulus of elasticity approximating that of dentin could reduce stress at the post-dentin interface, they might also increase stresses at the margin of the restoration, as the relatively elastic posts are placed in the neutral axis of stressed ETT 18 ; evidence for a final recommendation on the post material is lacking. 19 However, recently published clinical studies [20][21][22] reporting higher failure rates with glass fiber posts than with zirconia ceramic posts have caused the validity of this concept to be questioned. ...
... 5 Few studies reported that teeth restored with dentin as post material have shown the greatest fracture resistance and reparability compared to fiber-reinforced glass post systems. 8,9 Among the various factors affecting the retention of a post, the post length is still controversial. The root's resistance to fracture is influenced by the stress distribution caused by the length of the post. ...
... Dentin posts with two-thirds length showed higher fracture resistance than other tested groups; different results have been reported by Ghazawy and Badran, who discovered that compared to fiber posts, long biological dentin posts had statistically significant lower fracture resistance. 9 This might be explained by the histological variation between the permanent teeth utilized in the current investigation and the primary teeth used in their study. ...
Abstract
This study aims to evaluate the resistance to fracture of endodontically treated anterior permanent teeth restored with dentin posts of 3 different lengths and compare it with fiber posts
with two-thirds of the length of the root canal.
Thirty-six extracted mandibular premolars were used for the preparation of the dentin posts, while forty-eight extracted maxillary central incisors were endodontically treated and radicular post preparations were performed, then the teeth were randomly divided into four groups (n=12); group A (comparative group): restored with fiber-reinforced posts two-third of the canal length, group B, C and D were restored with dentin posts of two-third, half-length, and one-third of the intra-canal length respectively. The resistance to fracture of the samples was tested using a Universal Testing Machine, and the location of the fracture was examined under a stereomicroscope (x10).
One–way ANOVA showed that dentin posts of two-thirds length had a statistically significant higher fracture resistance than fiber posts of two-thirds length, with favorable fracture patterns.
Dentin posts with two-thirds of the root canal length can be a promising substitute for conventional glass fiber posts by acting as a micro-mechanical homogenous unit along with the root dentin.
... Endodontically treated teeth (ETT) present a greater risk of biomechanical failure than vital teeth, [1][2][3] and the longevity of a restored tooth thus depends on the amount of tooth structure remaining and on the efficiency of the restorative procedure used to replace lost structural integrity. 3,4 Posts should only be placed to retain a core within the remaining tooth structure and do not strengthen the tooth. ...
... 16 Although the impact of a low modulus of elasticity is controversial, some have argued that stiff posts are necessary, 4,8,9 while others have supported having dentin-like mechanical properties for the posts. 1,17 While fiber posts with a modulus of elasticity approximating that of dentin could reduce stress at the post-dentin interface, they might also increase stresses at the margin of the restoration, as the relatively elastic posts are placed in the neutral axis of stressed ETT 18 ; evidence for a final recommendation on the post material is lacking. 19 However, recently published clinical studies [20][21][22] reporting higher failure rates with glass fiber posts than with zirconia ceramic posts have caused the validity of this concept to be questioned. ...
STATEMENT OF PROBLEM: The influence of the ferrule thickness and post materials on the fracture resistance of endodontically treated teeth remains unclear. PURPOSE: The purpose of this laboratory study was to evaluate the influence of post material and ferrule thickness on the fracture resistance of endodontically treated mandibular premolars. MATERIAL AND METHODS: Sixty-four extracted and endodontically treated mandibular first premolars were used and divided into 4 test groups (n=16) depending on the ferrule thickness: F-0: without a ferrule, F-0.5: with a 0.5-mm ferrule thickness, F-1: with a 1-mm ferrule thickness, and F-1.5: with a 1.5-mm ferrule thickness. In groups with ferrules, the height ranged from 2 mm buccally/lingually to 1 mm proximally. Teeth in subgroups (n=8) were restored with either prefabricated glass fiber (FF) or titanium posts (FT) (ISO size 70 and length of 7.5 mm) and then adhesively restored with composite resin foundation materials. After foundation procedures, each specimen was restored with a cobalt chromium crown which was cemented with glass-ionomer cement. All specimens were subjected to dynamic loading in a masticatory simulator for 1 200 000 loading cycles with a nominal load of 5 Kg at 1.2 Hz and simultaneous thermocycling (5 to 55 degrees C). Specimens were then quasistatically loaded at 30 degrees in a universal testing machine until fracture. Fracture loads were analyzed by using 2-way ANOVA followed by the Tukey honestly significant difference test (alpha=.05). RESULTS: Fracture loads ranged from 610 +/-45 N (no ferrule - glass fiber post) to 1216 +/-169 N (1.5 mm ferrule thickness - glass fiber post). A statistically significant increase in fracture resistance was observed with increasing ferrule thickness (P<.001). However, post materials did not show a statistically significant influence (P=.977). CONCLUSIONS: Under the conditions of this laboratory study, increasing the ferrule thickness had a significant effect on the fracture resistance of endodontically treated teeth after thermomechanical fatigue, irrespective of post materials.
... (11) . The application of resin cement for post-to-canal preparation gained significant attention in the past year (12,13) . In certain laboratory, it has been discovered that resin cement considerably improves post retention (14,15,16) . ...
... In several clinical applications, such as orthodontic retention and the reinforcement of resin provisional fixed prosthodontic restorations, a leno-woven polyethylene ribbon known as Ribbond Bondable Reinforcement Ribbon has shown effective (23) In addition, it was used to splint teeth, manage dental emergencies, and replace missing teeth. The use of resin cement to connect a post into a prepared canal has garnered a lot of attention in the past year (12,13) . Resin cement has been demonstrated in several laboratory studies to significantly improve post retention (14,16) . ...
... The amount of tooth structure remaining, shape, size, and anatomical variations are a few important aspects for deciding which type of post system is to be used, either a cast post or a prefabricated one. 1 When a root canal requires a greater amount of preparation and the internal anatomy is too wide, a post system such as a cast post that fits nicely into the canal is preferred over prefabricated posts that do not adapt to the canal's internal shape. 2,3 In this method, the insertion of a custom-made metallic post into the root canal facilitates a well-fitting final prosthesis. ...
... Restoration of teeth with more rigid material produce a high incidence of un-restorable fracture compared to intact teeth (Oliveira et al. 1987;Mohammadi et al. 2009;Göktürk et al. 2018). Also, more unfavorable fracture was reported with tapered post design due to unequal distribution of force and stress concentration at the coronal shoulder and wedging effect and stress concentration of the tapered design (Fernandes & Dessai 2001;Madfa et al. 2014;Revathi et al. 2019). This could explain the high prevalence of unfavorable fracture in the group of DT post. ...
... Geniş kanal enstrümantasyonu, sekonder çürükler ve büyük post yuvaları dentin kaybını artırarak dişi zayıflatabilir (de C. Oliveira, Denehy, & Boyer, 1987). Kalan diş dokusunun miktarı, kırılma direncini doğrudan etkilediğinden, minimal invaziv yaklaşımlar benimsenerek mine ve dentinin korunması büyük önem taşımaktadır (A S Fernandes & Dessai, 2001). Büyük madde kaybına uğramış dişlerde post-kor restorasyonları, kök kanalından destek alarak fonksiyonel ve yapısal stabiliteyi sağlamaktadır (CHEUNG, 2005). ...
... Geniş kanal enstrümantasyonu, sekonder çürükler ve büyük post yuvaları dentin kaybını artırarak dişi zayıflatabilir (de C. Oliveira, Denehy, & Boyer, 1987). Kalan diş dokusunun miktarı, kırılma direncini doğrudan etkilediğinden, minimal invaziv yaklaşımlar benimsenerek mine ve dentinin korunması büyük önem taşımaktadır (A S Fernandes & Dessai, 2001). Büyük madde kaybına uğramış dişlerde post-kor restorasyonları, kök kanalından destek alarak fonksiyonel ve yapısal stabiliteyi sağlamaktadır (CHEUNG, 2005). ...
... When there is inadequate dentin to support the restoration, a post-core is required to provide retention and stability. 1 While posts are intended to strengthen teeth, studies indicate that posts lacking sufficient resistance to rotational forces may weaken teeth, increasing the risk of root fractures. 2,3 To mitigate this risk, posts should possess an modulus of elasticity similar to dentin, enabling uniform stress distribution under occlusal loads. ...
Cast metal post and core systems have been reliably used for decades due to their excellent physical properties. However, the increasing demand for aesthetically pleasing and biocompatible restorations has spurred the development of tooth-colored post and core systems. Among these, zirconia post systems have gained popularity, offering a solution that combines strength with enhanced esthetics. The translucency of zirconia allows for seamless integration with all-ceramic crowns, maintaining a natural appearance and meeting patient expectations for visually appealing restorations.
In light of the growing interest in zirconia ceramic post systems, numerous in vitro studies have been conducted over the past 15 years to evaluate their performance. These studies have examined critical aspects such as retention, fracture resistance, and aesthetic advantages. Zirconia posts are celebrated for their ability to improve esthetics while providing sufficient strength and long-term durability.
Nevertheless, zirconia posts are not without limitations. Issues like achieving proper cementation and optimal adhesion remain active areas of research and clinical focus. This review article aims to consolidate existing data on zirconia posts, highlighting their retention, fracture resistance, aesthetic benefits, challenges, and cementation techniques to aid clinicians in their effective application.
... However, in cases where the tooth structure is substantially compromised owing to caries, failed restorations, or fractures, ET is imperative. The preservation and restoration of root-filled teeth present a great challenge in contemporary dentistry, especially when faced with compromised clinical crowns [1]. Moreover, extensive loss of tooth structure makes the retention of restorations or crowns unfeasible [2,3]. ...
Background
The literature has reported contradictory findings regarding the association of Intra-radicular posts (IRPs) presence and periapical radiolucent lesions (PRLs) prevalence in endodontically treated teeth (ETT). Considering this, the study aimed to investigate the association between IRPs presence and PRLs prevalence.
Methods
A cross-sectional study was conducted to compare PRLs prevalence in ETT with and without IRPs. CBCT images were utilized, and the teeth with at least 2 mm of remaining gutta-percha apical to the post-end were included. Two calibrated assessors assessed the PRLs presence. A stepwise backward binomial logistic regression was conducted to evaluate the effect of age, post presence, gender, tooth position (anterior/posterior), and arch location (maxillary/mandibular) on the likelihood of periapical radiolucency presence. The null hypothesis is that the presence of IRPs does not influence the prevalence of PRLs.
Results
Teeth with IRPs showed significantly higher PRLs prevalence. However, there were insignificant differences in PRLs prevalence with respect to IRPs type or remaining gutta-percha length. The model, including all five predictors, demonstrated significant fit (χ²(7) = 22.528,p = .002), explaining 14.5% of the variance in the presence of radiolucency (Nagelkerke R²). The Hosmer-Lemeshow test showed no evidence of a lack of fit (χ²(8) = 11.550,p = .172), supporting the model’s adequacy. The model correctly classified 67.3% of cases, with a sensitivity of 54.5%, specificity of 75.4%, positive predictive value (PPV) of 58.3%, and negative predictive value (NPV) of 72.4%. Among the predictors, post presence was the only statistically significant variable (B = 1.300,p < .001,]OR = 3.670,95%CI[1.985–6.785]).
Conclusions
A higher prevalence of PRLs was noted among the ETT with IRPs. Within the limitations of this study, we recommend that clinicians should carefully weigh the risks and benefits of using IRPs during the restoration of ETT.
... According to a study using finite element analysis, increasing the post diameter resulted in less stress formation in the dentin [75]. There appears to be general agreement that the root canal shouldn't be unnecessarily enlarged because doing so weakens the tooth and lowers its resistance to fracture [75][76][77]. ...
... Tis age restriction was implemented due to the acknowledged infuence of tooth age on the nature of dentin and dentinal tubules. So, samples were selected depending on similar canal confguration and dentin hardness [19]. An inclusion criterion for the study encompassed teeth with straight and mature roots. ...
A layer of smear that coats the walls of root canals is produced by root canal instrumentation, which could be unfavorable to endodontic therapy. The endodontic irrigant SmearOFF is designed to effectively remove both the smear layer and bacteria concurrently. The objective of this study was to evaluate and compare the efficacy of SmearOFF and 17% EDTA in removing the smear layer across the coronal, middle, and apical thirds of root canals. Sixty-four single-canal mandibular premolar roots were chosen. Two irrigant protocols were separated into two sets of thirty-two teeth, respectively, Group 1 (6% NaOCL/SmearOFF) and Group 2 (6% NaOCl/17% EDTA.) Until X2, the ProtaperNext rotary system (Dentsply, Maillefer, Switzerland), with a COXO C-SMART Endomotor (Foshan COXO Medical instrument Co., Ltd., China) was utilized for the shaping of all teeth, the equipment settings were tuned to 300 revolutions per minute (rpm) and a torque of 3 Newton-centimeters (Ncm). Before applying the final irrigants, an initial irrigation with 6% sodium hypochlorite (NaOCl) was performed using a 27-G side-vented needle. An ultrasonic gadget, EndoUltra, was utilized to activate the irrigation. After that, the determination of how well the proposed solutions worked on the prepared teeth was conducted by scanning electron microscopy. The mean smear layer scores were lower in all three regions (coronal, middle, and apical) using 17% EDTA in comparison with the samples treated with SmearOFF. Despite that, there were no significant differences between G1, 6% NaOCL/SmearOFF and G2, 6% NaOCL/17% EDTA in smear layer removal according to Kruskal–Wallis tests and Mann–Whitney U-tests (p<0.05). Considering the findings of this investigation, both 17% EDTA and SmearOFF serve as chelating agents, demonstrating the capability to effectively remove the smear layer. This process is facilitated with the assistance of passive ultrasonic irrigation at intervals of every third of the root canal.
... The Richmond crown has several benefits: it is custom-fitted to the root configuration, alleviates pressure at the cervical margin, delivers strong support, allows ample space for ceramic firing, and ensures sufficient clearance at the incisal edge. (9) However, the Richmond crown also has some drawbacks like it requires more time and multiple patient appointments, is more costly, and modulus of elasticity that is ten times greater than that of dentin, is less retentive compared to parallel-sided posts, and acts as a wedge when transferring occlusal loads. If the ceramic component fractures, it can be challenging to remove, potentially leading to tooth fracture. ...
Restoring severely compromised or damaged crown structures after endodontic therapy presents a significant challenge. Sometimes restoring a mutilated tooth with Post and core restoration is insufficient for a tooth with minimal overjet, and extensive structural damage, especially cervically. While the Richmond crown is frequently viewed as a historical technique, we illustrate a case involving a 24-years old patient whose maxillary right central incisor was horizontally fractured 1 month prior to reporting. Support, retention and aesthetic outcomes for the patient are crucial to be achieved optimally.
... The authors suggested that post placement on teeth with limited substance loss should be critically evaluated to prevent overuse [47]. Furthermore, a previous review highlighted the importance of preserving tooth structure to reduce fracture resistance in post-core reconstructed teeth [93] and indicated that the evidence shows that post placement may not help if the intention is to reinforce the tooth. Some clinical studies have suggested that ETT location is associated with long-term survival [94,95]. ...
Purpose: Non-vital teeth usually exhibit substantial loss of coronal and radicular tooth structure, and use of posts after root canal treatment is controversial. This review examined whether placement of posts influences clinical behavior and survival probability of endodontically treated teeth (ETT).
Methods: An electronic search, without time restrictions, for publications written in English was undertaken in PubMed, Scopus, and Web of Science. Terms related to four main components (endodontically treated teeth, fixed prosthesis, post restoration, and survival rate) were used for the database search strategies.
Results: 57 studies met the inclusion criteria and were included in the qualitative analysis. Of the publications chosen for qualitative analysis, 17 clinical studies (11 prospective and 6 retrospective studies) were found to be suitable for quantitative analysis. These studies included 7,278 patients (7,330 ETT), with a mean age ± standard deviation (SD) of 45.46 ± 12.1 years. There was a statistically significant difference in survival rate between ETT with or without posts (P < 0.001).
Conclusion: As compared with teeth with no posts, post placement on ETT may improve clinical performance and survival probability of endodontically treated teeth.
... 25,26 In contrast, prefabricated posts are not suitable for these situations as they cannot adequately adapt to the canal shape. 27,28 The enhanced flexibility of custom-cast post and core systems helps them better withstand torsional stress. 29,30 Moreover, in the case of single-rooted and premolar teeth, which tend to weaken due to the cumulative loss of dental structure during preparation, these specialized posts and cores serve as stabilizers for both the crown and root portions of the tooth. ...
Selecting the right post system and material to repair fractured teeth that have undergone endodontic treatment is a significant challenge for dental surgeons. Typically, cast metal posts and cores are used when there's extensive loss of tooth structure, especially if the plan involves metal-ceramic crowns. It's crucial to restore teeth effectively after endodontic treatment, with the post helping to retain the core needed to support the final prosthesis. When there's considerable loss of tooth structure or not enough ferrule left, it's recommended to use custom cast post and core systems. These systems not only help retain the core but also improve fracture resistance after root canal therapy. Often, an interdisciplinary approach is needed, considering both prosthetic and endodontic treatments, while meeting the patient's expectations and clinical needs. Using custom cast posts along with full veneer crowns has been successful in repairing severely damaged teeth, both functionally and aesthetically. These treatments strengthen weakened, endodontically treated teeth against the forces in the mouth, channeling torquing forces through the root dentin to supportive tissue along the roots. This approach ensures positive outcomes and patient satisfaction, especially in cases involving injured upper front (anterior) teeth. When anterior teeth are weakened or lost due to factors like decay, endodontic treatment, or trauma, extracoronal restoration becomes necessary. Custom cast post and core systems offer retention for core restorations, replacing lost coronal structure. This method has proven effective in restoring badly damaged anterior teeth, followed by porcelain-fused-to-metal restorations. Trauma-induced fractures in permanent anterior teeth are common, causing discomfort and aesthetic concerns for patients. Managing such cases endodontically may require post and core systems to reinforce coronal restorations. Despite the availability of various post systems, custom cast post and core remains a popular choice. The current case report discusses how dealing with severely damaged maxillary anterior teeth often requires using custom cast post and core systems followed by full coverage crowns. This approach effectively addresses both functional and aesthetic concerns.
... Dentes tratados endodonticamente requerem frequentemente retentores intrarradiculares para a realização de procedimentos restauradores, devido às grandes perdas de estrutura dental causadas por cárie ou acessos endodônticos à cavidade. 1,2 A preservação da estrutura dental remanescente constitui fator importante para prevenir complicações biomecânicas dos retentores intrarradiculares, [3][4][5][6] uma vez que, diante da perda da adesão à dentina intracanal, a resistência mecânica do dente é fragilizada, aumentando o risco de dano da estrutura dental remanescente. 7 A introdução dos pinos de fibra de vidro surgiu como alternativa aos pinos metálicos para restauração de dentes tratados endodonticamente. ...
A preservação da estrutura dental constitui fator decisivo para a longevidade de procedimentos restauradores de dentes tratados endodonticamente. Geralmente esses dentes se en- contram enfraquecidos devido à perda de estrutura dentária, sendo necessária a utilização de pinos intrarradiculares para gerar estabilidade e retenção à reconstrução coronária. Este trabalho tem por objetivo relatar um caso clínico de reabilitação estética do sorriso, em que se associa pino de fibra de vidro e coroa em cerâmica pura CAD/CAM à base de dissilicato de lítio, o que demostra que, para a finalização de casos estéticos, se deve integrar tanto a estética dental quanto a estética gengival. São destacados os passos clínicos associados a uma revisão de aspectos biomecânicos e estéticos dessa alternativa reabili- tadora.
ABSTRACT
The preservation of tooth structure is an important factor for the longevity of the restoration of endodontically treated teeth. Usually these teeth are weakened due to tooth structure loss, requiring the intraradicular posts to perform restorative procedures for stability and retention for the coronal reconstruction. The aim of this paper is to present a clinical case of a CAD/CAM ceramic crown rehabilitation associated with fiberglass post showing that integration of both restoration and gingival health should be considered for the completion of aesthetic cases. The clinical steps and a brief review of biomechanical and aesthetic rehabilitation of this alternative are highlighted.
... 9 Two factors that influence the choice between a cast post and a prefabricated post are the canal's geometry and the amount of remaining tooth structure. 10 It has been argued that for a canal requiring extensive preparation, a well-fitted cast post and core offer greater retention compared to a prefabricated post that does not align with the canal pattern. 11,12 The custom-made cast post and core, engineered to endure torsional forces, are placed into the prepared root canal space. ...
Posts are recommended to fortify weak, endodontically treated teeth against intra-oral forces by channeling torquing forces through the radicular dentin to supportive tissue along the roots. The subsequent case studies demonstrate an interdisciplinary approach that employed custom cast posts and complete veneer crowns to repair severely damaged treated teeth, restoring both their appearance and functionality. Coordinating prosthetic and endodontic treatments, while carefully considering the patient's expectations and requirements, played a pivotal role in achieving positive outcomes and ensuring patient satisfaction. Traditionally, the cast metal post and core system has been widely used as the foundational restoration for a prosthetic crown, benefiting from a natural extension of the post within the core. The post's function is to bolster the core restoration, which rebuilds the compromised coronal structure. This article explores the utilization of cast post and core systems alongside porcelain-fused-to-metal restorations for addressing injured maxillary central incisors.
... Cast metal post-core systems have long history of successful clinical 4,5,6,7 use due to superior physical properties . Successful outcomes may be compromised in these cases as the low elastic modulus of cast metal post-cores can cause stress concentrations in the surrounding radicular 8,9 dentin, leading to root fractures . ...
Background: Methodology: To investigate impact of novel inner ferrule preparation around cervical part of root canal. A case report featuring endodontically treated tooth restored with newly designed zirconia ceramic post. Special drills were used for horizontal root canal preparation around cervical part and post spaces in canal, leaving at least 3 mm gutta-percha apical seal. Zirconia ceramic posts were cemented with Multilink Automix, upgraded with Multi-Core and zirconia crowns. IF preparation design and new post-core desi Results: gn with retentive rings in the coronal part showed stronger retentive coronal design. IF preparation and retentive rings of the zir Conclusion: conia post contribute to increased fracture strength. Rehabilitation signicantly reduced the severity of root fracture for excellent function and aesthetics.
... In addition, it is difficult to imitate the soft tissue that supports the tooth and standardization problems may be experienced in extracted tooth samples due to physical and anatomical differences (13). Variables such as the age of the teeth and the storage conditions after extraction may cause high standard deviations in evaluating the results (14). For these reasons, using virtual models, simulation modeling and finite element analysis (FEA) has ...
The aim was to evaluate the effect of stress distribution on vertical, horizontal, and oblique forces on the tooth model after reattaching the fragments of the maxillary incisor with vertical root fracture (VRF) using different materials, by 3D finite element analysis (FEA). Tooth with a root canal, spongious, and cortical bone models were designed. VRF was modeled on a tooth with 4 different re-attachment models: Group 1: dual-cure cement (DC)+fiber reinforced composite (FRC), Group 2: DC+polyethylene fiber, Group 3: DC+glass fiber, and Group 4:DC. 100 N force was applied in 3 different directions. Maximum principal stresses (σmax) of dentin, and re-attachment materials were evaluated on colored images. The highest σmax values were on the repair materials under vertical forces for Groups 1 and 4, respectively; Groups 2 and 3 showed similarity. The highest σmax values in repair materials under horizontal and oblique forces were observed in Group 3 however the lowest σmax values in repair materials under oblique and horizontal forces were observed in Group 1. The stress values on repair materials gradually increased respectively starting from horizontal to vertical. As the elasticity modulus of the repair materials increased, the stress values on root dentin increased. Through all force directions, except vertical forces, lower stress values were observed with FRC. The fracture resistance was bigger when using solely FRC or dual-cure resin cement in comparison to fiber-supported designs. Adding polyethylene fiber to re-restorations decreased stress values compared to glass fiber addition. Therefore, when adding fibers, polyethylene fiber will be advantageous.
... During the preparatory phase, the objective is to furnish molars with a broad, robust surface capable of withstanding daily compressive forces [11]. By ensuring that the prepared surface and the occlusal plane are parallel, stress resistance on the central axis can be achieved [12]. ...
This case report explores the innovative application of the endocrown technique for restoring a severely damaged mandibular molar (tooth #46) in a 28-year-old male patient. With a recent root canal treatment history, the patient presented with a dislodged prosthesis. Due to financial constraints, a base metal alloy was chosen for the endocrown restoration. The unique preparation process involved reducing the occlusal surface by 2 mm, creating a shoulder cervical margin, and preserving enamel walls. The endocrown, crafted from a base metal alloy, demonstrated a semi-conservative approach, providing cost-effectiveness and minimal tooth preparation. The case adheres to the 2013 CAse REport (CARE) guidelines. The discussion highlights the biomechanical benefits of the endocrown, emphasizing stress resistance, stability, and superior performance compared to traditional treatments. Materials like ceramic, resin nanoceramic, and polyetheretherketone are briefly discussed, focusing on the promising success rates of endocrowns, mainly through computer-aided designing/computer-aided manufacturing systems. The report provides valuable insights for clinicians considering this endocrown technique in reconstructing severely damaged molars and premolars.
... However, they have debonding problems, especially in cases with an insufficient ferrule [6,13]. In addition to these problems, a significant amount of root dentin is removed during the preparation of the teeth for all types of post systems, which further increases the risk of root perforation, root fracture, and endodontic system contamination [14][15][16][17][18]. As a result, choosing the right restoration type and material that fortifies and reinforces the residual tooth structures against fracture is just as crucial for the long-term prognosis of endodontically treated teeth as choosing an effective endodontic procedure [19,20]. ...
This in-vitro study aimed to evaluate the fracture strength (FS; N) of composite, feldspathic, and glass–ceramic computer-aided design/computer-aided manufacturing (CAD/CAM) endocrowns after thermomechanical aging. Seventy non-carious human molars were randomly divided into seven groups, according to the CAD/CAM material used for endocrown fabrication. Intact molars without cavity preparations were used as control (n = 10). Following endodontic treatment, standardized endocrown cavities were prepared and endocrowns were fabricated using composite (Cerasmart270, CS and Grandio Blocs, GB), fired and milled zirconia-reinforced lithium silicate (Celtra Duo, CD), leucite-reinforced feldspar ceramic (LRF Initial, LRF), and feldspathic (Cerec Blocks, CE) materials which were luted with universal adhesive (Futurabond U; Voco) and dual-cure resin cement (Bifix QM). Following thermocycling for 20,000 cycles and 480,000 load cycles in a chewing simulator (CS-4.2, SD Mechatronik), FS was evaluated (Instron). Data were analyzed with one-way ANOVA and post hoc Tukey’s tests (p < 0.05). FS was significantly influenced by the tested material (p = 0.00). CS had the highest FS, which was not significantly different from intact molars and fired CD (p > 0.05). There were no significant differences in FS between LRF, GB, and CD, which were significantly higher than CE. Most of the failure modes of CS, CD, and GB were repairable, whereas those of CE were irreparable. All the tested materials withstood clinically relevant axial forces. Composite endocrowns exhibited more favorable fracture pattern, whereas feldspathic and leucite-reinforced feldspar ceramic endocrowns exhibited mostly irreparable fractures.
... Since the root canals don't need to be any certain form, drilling doesn't make them more fragile, and using post won't put stress on them either. The walls of the pulp chamber and the cervical butt joint get a greater distribution of the lowered compressive forces [15,[19][20][21]. The pulp chamber and endodontic access cavity of ETTs with low coronal tooth structure loss, in particular those with endodontic access cavities and marginally expanded pulp chambers, may be filled with adhesive restorative materials, such as composite resin, or covered with amalgam. ...
Endocrown restorations are single prostheses that are made of reinforced ceramics and may be acid etched; they are recommended for endodontically treated molar teeth that have suffered a considerable loss of coronal structure. In order to provide a strong foundation for the restoration and strengthen the restored tooth structurally, the quality and integrity of the residual tooth structure should be carefully preserved. For this reason, Endocrown is used as a minimally invasive technique. Endocrowns are particularly recommended for molars with short, destroyed, dilacerated, or unstable roots. They may also be utilized when it is unable to achieve an acceptable thickness of the ceramic coating on the metal or ceramic substructures due to significant coronal dental tissue loss and constrained interocclusal space. Endocrowns provide a more beneficial choice than conventional and post- and core-retained restorations because of the little and simple preparation required. This favorable outcome can be attributable to a number of variables, including the preparation method, occlusal thickness, and elastic moduli. When it comes to material selection it is impossible to create what is called the material of choice since new material is constantly being introduced.
... 28 Consequently, the root canals do not require specific shaping, and they remain resilient, avoiding the stresses associated with post usage. 29 As a result, compressive stresses are effectively distributed over the cervical butt joint and the walls of the pulp chamber. [30][31][32] In 2018, Dartora et al. conducted a biomechanical evaluation of endodontically treated teeth restored using different extensions of endocrowns within the pulp chamber. ...
... Nevertheless, it is crucial to acknowledge that the efficacy of a root canal procedure is contingent upon not only the specific sealer employed but also on a multitude of factors. These factors encompass a thorough biomechanical preparation of the root canal system, the removal of pulp tissue and bacteria completely, and the appropriate filling of the canals [19]. Furthermore, the total strength and FR of a tooth that has undergone endodontic therapy can be influenced by various factors, including the residual dental structure, the extent of the carious lesion or damage, and the kind of restorative materials applied to the tooth subsequent to the endodontic procedure. ...
Introduction
The utilization of endodontic sealers is of paramount importance in ensuring the sustained efficacy and resilience of endodontic treatment. The primary objective of the research was to appraise and contrast the fracture resistance (FR) of three distinct categories of endodontic sealing materials that are frequently employed in the context of endodontic therapy.
Materials and methods
This research used an in vitro experimental design. Sixty single-rooted human teeth indicated for extraction were utilized according to established protocols. These teeth were then arbitrarily divided into four piles, one for each of the four possible sealants. All specimens were put through a standardized thermal cycling procedure to simulate clinical conditions after the root canals were obturated. The subsequent step involved testing the FR of each group by utilizing a universal testing machine up until failure. Any statistically significant difference in FR among the three sealing materials was identified through appropriate statistical analysis.
Results
Group 1, which utilized a particular sealing material, exhibited the highest mean fracture resistance, measuring at an impressive 1198.33 ± 321.4 Newtons (N). A post hoc analysis was done to see the exact differences between each group and statistically significant differences between Groups 1 and 2 (p<0.05), Groups 1 and 4 (p<0.05), and Groups 3 and 4 (p<0.001) were observed.
Conclusion
The FR of Group 1 specimens were noticeably greater than those of Group 2 and Group 4 while the FR of Group 3 specimens was more than that of the Group 4 specimens. This study provides important insights into the fracture resistance of various endodontic sealing materials.
... A III A IV A I ----A II 1 The fracture resistance of endodontically treated teeth was affected by various factors. A review analyzed factors affecting the fracture resistance of post-core reconstructed teeth which included post length, diameter, material, adaptability, design, amount of remaining dentin, cement, and biocompatibility of post material [22]. Another review on ferrule effect and biomechanical stability of teeth restored with cores, posts, and crowns revealed that the ferrule tooth structure was the most vital factor that resisted fracture and reduced forces compared to post, core, cement or resin bond materials [23]. ...
In this in vitro study, fracture resistance was evaluated according to the post-diameter and -length in zirconia crown restorations on three-dimensional printed primary incisors undergone pulpectomy. One hundred-and-sixty primary incisor abutments were used which were artificially fabricated through 3D-printing. Each group was divided into two subgroups based on the zirconia post-diameter (1.5 mm and 2.0 mm) employed for post setting after pulpectomy. Furthermore, each group was divided into four subgroups based on the zirconia post-height (3.0, 4.0, 5.0 and 6.0 mm). Zirconia post setting was made by applying flowable resin after filling the pulp cavity with calcium hydroxide up to 3.0 mm below cemento-enamel junction (CEJ). Finally, a preformed zirconia crown of size #1 was cemented to the abutment through resin cement. A compressive load was applied to the middle palatal surface of incisors restored with zirconia crowns by using a universal testing machine at 145° angle which is the normal interincisal angle of children. The root fracture specimens were excluded and the samples fractured within crown and core parts were included in the final fracture resistance analysis. The group with 1.5-mm post-diameter and 5.0-mm post-height had the highest fracture resistance strength (130.63 ± 55.75 N) under masticatory pressure condition. Fracture resistance was statistically greater in 5.0-mm than in 4.0-mm and 3.0-mm post-height groups for 1.5-mm post-diameter subgroup. Moreover, 5.0-mm post-height subgroup had a statistically greater fracture resistance than that of 3.0-mm post-height subgroup for 2.0-mm post-diameter group. The 2.0-mm post-diameter subgroup had a statistically greater fracture resistance than that of 1.5-mm post-diameter subgroup for 3.0-mm and 4.0-mm post-heights. If zirconia post incorporation is required for deciduous incisor restoration, a post-length equal to facial CEJ level is recommended for gaining additional retention against masticatory pressure.
... Proper post placement can help to distribute forces during biting and chewing. An optimal post length is affected by various factors, such as the remaining root structure and morphology, the type and location of an existing fracture, bite forces and occlusion, restorations, and the crown-to-root ratio 5,22 . Post materials can also influence potential reinforcement and fracture prevention. ...
The objectives of this study were to evaluate the stress distribution and risk of fracture of a non-vital immature maxillary central incisor subjected to various clinical procedures using finite element analysis (FEA). A three-dimensional model of an immature central incisor was developed, from which six main models were designed: untreated immature tooth (C), standard apical plug (AP), resin composite (RC), glass-fibre post (GFP), regeneration procedure (RET), and regeneration with induced root maturation (RRM). Mineral trioxide aggregate (MTA) or Biodentine® were used as an apical or coronal plug. All models simulated masticatory forces in a quasi–static approach with an oblique force of 240 Newton at a 120° to the longitudinal tooth axis. The maximum principal stress, maximum shear stress, risk of fracture, and the strengthening percentage were evaluated. The mean maximum principal stress values were highest in model C [90.3 MPa (SD = 4.4)] and lowest in the GFP models treated with either MTA and Biodentine®; 64.1 (SD = 1.7) and 64.0 (SD = 1.6) MPa, respectively. Regarding the shear stress values, the dentine tooth structure in model C [14.4 MPa (SD = 0.8)] and GFP models [15.4 MPa (SD = 1.1)] reported significantly higher maximum shear stress values compared to other tested models (p < 0.001), while no significant differences were reported between the other models (p > 0.05). No significant differences between MTA and Biodentine® regarding maximum principal stress and maximum shear stress values for each tested model (p > 0.05). A maximum strain value of 4.07E−03 and maximum displacement magnitude of 0.128 mm was recorded in model C. In terms of strengthening percentage, the GFP models were associated with the highest increase (22%). The use of a GFP improved the biomechanical performance and resulted in a lower risk of fracture of a non-vital immature maxillary central incisor in a FEA model.
... Além disso, em casos de canais calcificados ou com dilacerações, o uso de retentores intrarradiculares pode não ser indicado 8 . No que se refere ao preparo mecânico dos condutos, para utilização dos retentores intrarradiculares, além da perda de estrutura dentinária 10 , existem riscos associados à técnica, os quais incluem: alteração da obturação remanescente devido ao aquecimento dos instrumentais rotatórios e manuais utilizados para desobturação parcial dos condutos 11 , e perfurações radiculares 12 . ...
Introdução: Visando introduzir restaurações mais conservadoras, surgiram as endocrowns, coroas monolíticas cujo preparo envolve às margens da cavidade, retidas pela câmara pulpar sem necessitar do envolvimento dos canais radiculares. Objetivo: Revisar a literatura acerca das endocrowns, de forma a esclarecer suas indicações, vantagens, desvantagens e como elas podem ser utilizadas como alternativa na prática clínica. Métodos: Trata-se de uma revisão integrativa da literatura que consultou à base de dados National Library of Medicine (PubMed), usando-se como descritores: “Endocrowns”, “Endodonticallly treated teeth” e “monoblock”. Os critérios de inclusão para a seleção da amostra foram: artigos publicados e indexados de forma gratuita no período de janeiro de 2012 a janeiro de 2022 (últimos 10 anos). Resultados: Incluiu-se vinte artigos que se enquadraram nos critérios previamente estabelecidos. Os estudos revisados apontam que esta é uma restauração com estética satisfatória e mais conservadora para dentes tratados endodonticamente, sendo uma opção com menor custo e rapidez em suas etapas clínicas, fortemente indicadas para molares, nos casos em que há espaço interoclusal mínimo, bem como a presença de canais radiculares curvos ou estreitos, o que impossibilita a realização do tratamento convencional utilizando pinos radiculares. Conclusões: Endocrowns apresentam-se como opção restauradora viável para molares tratados endodonticamente. Contudo, para pré-molares e dentes anteriores, não há estudos que demonstram efetividade que justifique sua indicação. Estas restaurações podem ser confeccionadas em polímeros e cerâmicas, principalmente as cerâmicas vítreas que favorecem a adesão. Entretanto, mais estudos clínicos precisam ser realizados para melhor compreensão da longevidade desse tipo de restauração
... This helps in replacing any lost coronal tooth structure after root canal treatment. The shape of the residual coronal tooth structure, combined with the core, should result in an ideal shape for the preparation [7,8]. Endodontic posts can be casted with metals such as gold and nickel-chromium posts, or it is also available as prefabricated, such as titanium and stainless steel posts. ...
Post-retained crowns are indicated for endodontically restored teeth with severely damaged coronal tooth structure. Endodontic posts may be cast with the metals, but these noble metal alloys have shown certain limitations over the years and hence fibre reinforced fibre post and core came into use in recent times. The ability to predict its prevalence may pave the way towards better coping strategies and help dentists in proper treatment decisions.
... Obtaining samples that resemble each other regarding cross-section, anatomy, storage duration and environment after extraction, age, and the forces (chewing or traumatic) to which the teeth are subjected before or during extraction is a really difficult task. All these variables may affect the results of the study and are especially important for mechanical testing (37). Premolars were extracted for periodontal reasons without cracks, and caries was included in the current study. ...
... Other advantages of endocrowns are: the minimal amount of dental tissue required to be removed and the reduced working time by eliminating certain clinical and technical steps. Due to their configuration and pattern of contact with the remaining dental structures, after cementation, the endocrowns ensure the distribution of the occlusal forces that mimic the natural tooth [13,14]. ...
Introduction
The opportunity of using Endocrown-type restorations in the current prosthetic dentistry practice as an alternative to other, well-established methods of corono-radicular restorations and the evolving palette of adhesive materials has made these restorations more popular in the last few years.
Objective
The purpose is to review the available literature about Endocrown restorations regarding mechanical properties – fracture strength and resistance, survival rate, the preparation design – marginal and internal adaptation, and esthetics.
Method
The search was carried out on four databases: PubMed, Scopus (ScienceDirect), Web of Science, and Scielo using the following terms: ”endocrowns”, ”endodontic crown”, and” no buildup crown”. Initially, a total of 163 articles published between 2015 and May 2021 were selected. After the duplicates, papers presented only as abstracts, articles in any other languages except English, and review articles were eliminated; a total of 72 articles remained to be considered for this review.
After assessing the 72 considered articles, 37 were chosen as fit for this review. The reasons for the elimination of the other 35 articles were: their main focus was other than endocrowns, e.g., direct restorations, indirect restorations of vital teeth; case reports; study protocols.
Results
From the 37 articles selected, 34 were focused on mechanical properties, including the influence of the preparation design, and three on survival rate, of which one also had a point of view regarding esthetics.
Conclusions
The literature included in this review shows that endocrowns perform similarly or even better in some cases than other coronal restorations. However, this statement must be interpreted cautiously, given that most articles were in vitro or finite element analysis studies. Given the high degree of conflicting results found in the articles included in this review, the authors consider as reasonable to conclude that further studies are needed to confirm the feasibility of endocrowns and the best choice of material.
... There are several factors that determine the success of endodontic treatment such as preoperative apical status, obturation techniques, materials, and the quality of coronal seal [1][2][3]. The fracture resistance of an endodontically treated tooth with post is influenced by post length, post diameter, remaining dentin, post material, post adaptability, post design, cement, core material, biocompatibility of the post material and load experienced by the restored tooth [4]. During post and core treatment, gutta-percha material may not provide an adequate seal in the root canal, compromising the coronal seal. ...
The coronal seal in root canal-treated teeth may be compromised depending on the accuracy of post space preparation and post cementation along with remaining gutta-percha. Root canal treatment can be compromised by endotoxins released by the coronal bacteria as a result of microleakage. The study was conducted by undergraduate students to measure the gap between the cemented post and residual gutta-percha. In total, 217 endodontically treated teeth were evaluated with intraoral peri-apical radiographs. Based on the intraoral periapical radiographic examination in the CS-R4 program, Group I had no gap, Group II had a gap of >0 to 2 mm, and Group III had a gap of more than 2 mm between the end of the cemented post and the remaining gutta-percha. In total, 40% (n = 87) of the teeth had no gap, 59% (127) had a gap of >0 to 2 mm, and 1% (n = 3) had a gap of more than 2 mm between the cemented post end and remaining gutta. Chi square test revealed a significant difference in the gap between the post and remaining gutta-percha between males and females students (p < 0.001). In terms of the gap between the cemented post end and the residual gutta-percha, the root canal treated teeth with post and core by undergraduates were clinically acceptable.
This study aims to evaluate the stress distribution of polyetheretherketone (PEEK) and high noble alloy materials in a detailed 3D model of a central incisor using finite element analysis (FEA). A comprehensive 3D model incorporated the crown, crown cement, post and core, post cement, central incisor root, periodontal ligament (PDL), and bone. The PEEK and high noble alloy material properties were input into the model, and the FEA was performed using ABAQUS software. The results showed that while the stresses on the bone, root, and crown increased slightly with the PEEK compared to the high noble alloy, the difference was minimal and attributed to the PEEK’s reduced stiffness. This led to a higher load transfer to surrounding regions around the post. The factor of safety decreased from 16 to 10 when using PEEK, but this reduction was still within acceptable limits and reduced stress-shielding effects. In conclusion, while there was no significant difference in stress magnitudes and distributions between the PEEK and high noble alloys, the PEEK exhibited superior stress-shielding properties, which may offer an advantage in preserving the underlying tooth structure in post and core restorations.
A BSTRACT
Aim
To analyze the fracture resistance of three post systems and their mechanism of failure.
Materials and Procedures
Forty-five newly excised human mandibular single-rooted pre-molar, for periodontal or orthodontic reasons, were used. The teeth were separated into three groups (n = 15) based on the post system utilized. Group A had teeth restored with custom cast post; Group B had prefabricated glass fiber posts (Angelus post); and Group C with edelweiss composite post (Edelweiss Post).
Results
The custom cast posts provided the highest fracture resistance but exhibited more unfavorable fractures. The edelweiss posts exhibited the least fracture resistance.
Conclusion
Further investigations should be targeted at elucidating the force dynamics of this newer post system.
Introduction: Endodontic treatment aims to keep the tooth in proper shape and function, but it may fail, requiring retreatment. This involves the complete removal of the contents of the root canal for disinfection and refilling. The aesthetics and function of the endodontically treated tooth depend on the choice of restorative material, with fiberglass pins being an option that offers superior aesthetics and mechanical properties similar to dentin, providing greater retention and stability of the restoration. Case report: A female patient came to the clinic complaining of loss of restoration of the maxillary canine (13). Radiographic examination revealed an inadequate filling, exposed to the oral environment for a long period. Endodontic retreatment was performed in three sessions, with removal of the previous filling, disinfection of the root canal, and new filling with resin cement. Subsequently, a fiberglass pin was installed, followed by composite resin restoration. The steps included anamnesis, clinical and radiographic examinations, absolute isolation, use of files and solvents to remove the old filling, and application of intracanal medication. After the final filling, the canal was prepared to receive the fiberglass post, followed by the coronary restoration with composite resin. Conclusion: Endodontic retreatment is essential to eliminate bacteria from the root canal, especially in cases of previous failure. The choice of the fiberglass post, due to its biomechanical and aesthetic properties, in combination with the composite resin, proved to be effective in the rehabilitation of teeth with compromised coronary structure, resulting in a functional and aesthetically satisfactory restoration.
Background
The aim of this study was to calculate the stress distribution of fiberglass post associated with resin composite crown restoration and fiberglass posts with zirconia restorations in mature and immature endodontically treated central maxillary incisor under various loading conditions.
Materials and Methods
The study created six different study models in a virtual environment: healthy mature maxillary central teeth, intact immature maxillary central teeth, mature maxillary central teeth with fiberglass post associated with resin composite crown restoration, immature maxillary central teeth with fiberglass post associated with resin composite crown restoration, mature maxillary central teeth with fiberglass posts and zirconia restoration, and immature maxillary central teeth with fiberglass posts and zirconia restoration. Loading conditions simulating mastication, trauma, and bruxism were applied to each of the models at different angles and amounts. The von Mises and the maximum and minimum principal stress values in tooth structures (dentin) and support structures (bone, PDL) and materials were observed using finite element stress analysis.
Background
Endodontically treated teeth (ETT) are considered structurally compromised due to significant changes in their biomechanics.The purpose of this in vitro study was to evaluate fracture resistance using three computer-aided design/computer-aided manufacturing (CAD/CAM) customized post systems.
Methods
Forty extracted intact maxillary central incisors were used in the study, and the teeth were endodontically treated and randomly divided into four equal groups ( n = 10): control group without any post and accessed cavity was restored with direct composite restoration. Test groups were prepared for a post and restored according to the material type. The posts and cores were fabricated with computer-aided design/computer-aided manufacturing technology using titanium, vita enamic, and biological dentin materials. The posts were luted using self-adhesive resin cement, and then, zirconia crowns were fabricated, cemented, teeth in all groups were mounted to universal testing machine and subjected to compressive load in Newton at crosshead speed 0.5 mm/min.
Results
Control group exhibited the highest fracture resistance (727 ± 172.05) followed by biological dentin posts with mean value (712.29 ± 298.58) then group titanium posts with mean value (678.59 ± 132.83) and the least fracture resistance was for group vita enamic with mean value 331.84 ± 74.27. Regarding to fracture favorable it was significantly higher in vita post group than titanium post group (70% vs. 30%) and control group (70% vs. 10%) but it was significantly higher in biological dentin group than titanium group (80% vs. 70%).
Conclusion
According to type of material, teeth restored with the biological dentin posts showed highest fracture resistance followed by titanium posts, the least fracture resistance was vita enami posts.
Purpose
This study investigated the fracture resistance and failure modes of custom-fabricated post- and core dental restorations using various CAD/CAM materials.
Materials and Methods
Seventy-five mandibular second premolars were allocated to five groups (n = 15) and prepared for standardized post and core restorations. The groups included a control group comprising cast metal and four CAD/CAM materials: Vita Enamic, Shofu HC, Trilor, and PEKK. Fracture resistance was assessed using a compressive force at a crosshead speed of 1 mm/min until failure occurred. Data were analyzed using one-way analysis of variance (ANOVA) and chi-square tests.
Results
The metal group had the highest fracture resistance (244.41 ± 75.20 N), with a significant variance compared to that in the CAD/CAM groups (p < 0.001). No significant differences were observed among the non-metallic groups.
Conclusions
While several CAD/CAM materials displayed satisfactory flexural properties, cast metal posts showed superior fracture resistance in endodontically treated teeth but were mostly associated with catastrophic failure. The clinical application of CAD/CAM materials for post-core restorations presents a viable alternative to traditional metal posts, potentially reducing the risk of unfavorable fractures.
Background
Dental post and core is one of the common procedures performed after endodontic treatment. The aim of this study was to radiographically assess the quality of post and core procedures performed by dental students at different education levels in addition to determining the most critical errors encountered during their clinical practice.
Methods
A retrospective cross-sectional study design was conducted in the College of Dentistry, Imam Abdulrahman Bin Faisal University. A total of 550 periapical radiographs (PAs) of cemented posts were retrieved from the records of patients treated by dental students. Parameters and guidelines for assessing the quality of post treatment have been determined and statistically analyzed. A P value <0.05 was considered statistically significant.
Results
The study included 502 students and most of them were females (66.5%). Data were obtained from 502 patients (62% females) with fiber posts used in 98.2% of the cases. About 50% of the posts were inserted in premolars, 62.9% in the upper arch, and 66.7% were restored with crowns as a final restoration. Regarding the quality of posts, 98.4% showed good preparation quality and 98% showed good radiographic quality. The post diameter was equal to 1/3 of the root diameter in 31.9% of the cases; post length was equal to 2/3 of root length in 5% of the cases and equal to or more than crown height in all cases (100%). Length of the remaining gutta percha (GP) was between 3–5 mm in 38.8%, and there was no gap between the post and remaining GP in 95.6% of the cases. There were no statistically significant differences between dental students at different clinical educational levels regarding the quality of post placement.
Conclusions
The quality of post and core procedures performed by students showed acceptable radiographic quality and were within the recommended standards.
This clinical case report aimed to investigate impact of a novel inner ferrule (IF) preparation around root canal on the subsequent esthetic restoration. Material and Methods: This clinical research involved a case report featuring endodontically treated teeth (ETT) restored using a newly developed ceramic post. Special drills (Edenta AG GmbH, Switzerland) were utilized for root canal preparation, involving horizontal preparation around the cervical portion of the root canals and post spaces. Experimental samples (ETT) were prepared with and without a 2mm IF preparation. The newly designed zirconia ceramic posts (TZ-3Y-SBE, Tosoh, Japan) were cemented with Multilink Automix (Ivoclar), upgraded with MultiCore (Ivoclar), and crowned with an all-ceramic zirconia crown (Zirkonzahn, Italy). Results: Our clinical case provided insights into a new type of all-ceramic aesthetic restoration of prepared teeth (ETT) with a new IF preparation design and a new zirconia post-core design. Conclusion: The novel horizontal IF preparation around the root canal was developed to accommodate the initial retentive coronal ring of the newly designed zirconia posts. The incorporation of IF preparation and coronal retentive rings within the zirconia post structure effectively enhances the fracture resistance of ETT. This new modern aesthetic rehabilitation in all restored teeth significantly reduces the severity of root fractures for excellent function and aesthetic restoration of ETT.
BACKGROUND: Endocrowns (ECs) are alternatives for rebuilding severely damaged teeth and show superior efficacy in molars over premolars. OBJECTIVE: The objective of this in vitro study is to evaluate the effects of different preparation designs with short pulp chambers on the mean color change (ΔE), fracture resistance, and failure types of mandibular molar ECs. METHOD: A total of 40 extracted mandibular molars were treated endodontically and divided into four groups. Samples in groups 1, 2, 3, and 4 had occlusal preparation depths of 5 mm, 3 mm, 3 mm with ferrule, and 3 mm with boxes, respectively. The samples were immersed in coffee and their ΔE values were measured by using the Commission Internationale de l’Eclairage color system. They were also subjected to a fracture test. Next, all specimens were examined visually under a stereomicroscope to evaluate their failure modes and identify their fracture origins. Data were entered and analyzed by using Statistical Package for Social Sciences. RESULTS: Among all groups, group 4 (3 mm + boxes) presented the highest ΔE (4.15) after immersion in coffee. Moreover, ANOVA revealed that the ΔE of group 4 (occlusal preparation depth of 3 mm with boxes) was significantly different (p< 0.05) from that of group 2 (3 mm + ferrule, 3.07). The EC with a 3 mm chamfer and ferrule showed the highest maximum load of 2847.68 ± 693.27 N, whereas that with a 5 mm chamfer finish line had a marginally reduced load at fracture of 2831.52 ± 881.83 N. The EC with a 3 mm chamber and boxes had a slightly increased maximum load of 2700.75 ± 436.40 N, whereas that with the 3 mm chamber had the lowest maximum load at fracture of 2385.97 ± 465.61 N. One-way ANOVA showed that different EC preparation designs had no effect on maximum fracture load (F [3,16] = 0.550, p= 0.6). CONCLUSION: The recorded ΔE values of ECs in all groups were equal or marginally higher than the acceptable values. The EC with a 3 mm chamfer and ferrule displayed the highest mean maximum load. The EC with a 5 mm chamfer finish line had a marginally lower maximum load at fracture than other ECs. Failures, such as ceramic fracture, split fracture, and ceramic and tooth splitting above the cemento–enamel junction (CEJ) or vertically were predominant in samples with occlusal preparation depths of 3 mm with ferrule and 5 mm.
A Comparative Evaluation of Root Fracture Resistance of Endodontically Treated Teeth using Two Fiber Posts with Two Ferrule Heights
Aim: To compare fracture resistance of severely destructed mandibular canine under oblique loading restored with Richmond crown verses zirconia endocrown. Materials and method: 10 mandibular canine were endodontically treated and divided into 2 group of 5 each both the group were cut 2mm above the cement enamel junction one group received endo crown and second group received cast metal post and core, both the group were subjected shear force on UTM at cross head speed of 1 mm/min the results obtained were calculated in newton’s and statistical analysis was carried out. Results: Cast metal post and core (972.4±217.51N) showed better resistance to fracture than Richmond crown group (1180.6±168.87N).statistical analysis done using unpaired t test (P value =0.1818) which was which was statistically insignificant. Conclusion: endocrown showed better resistance to fracture from shear forces than cast metal post and core.
The maximal bite force and the strength of the finger-thumb grip of 125 Skolt Lapps, aged 15 to 65, was measured with a specially devised apparatus. The bite force was measured with the biting fork placed between the first molars and between the incisors, respectively. The finger-thumb grip was measured by letting the subject press the prongs of the fork between the thumb and forefinger of each hand as hard as possible. The range of inter-individual variation of the maximal bite force and finger-thumb grip was great. The mean values were higher for the males than for the females. In the males the maximal bite force thus measured in the molar region was 39 kg (382 N) and 18 kg (176 N) in the incisor region. The corresponding values for the females were 22 kg (216 N) and 11 kg (108 N). The finger-thumb grip strength for males was, on the average, 10 kg (98 N); that of the females, 7 KG (69 N). The average difference in bite force between the men and the women was larger in the group with natural teeth than in the one with complete dentures. The values found for the bite force decreased with increasing age, especially for the females. Most of this reduction with increasing age was probably due to the age-dependent deterioration of the dentition. In both sexes the bite force was notably smaller among the denture wearers than among the dentate persons. The number of natural teeth varied closely with the bite force, i.e. the greater number of natural teeth the greater the bite force.
The effect of a metal collar on stress distribution with cast post and cores was studied by using three-dimensional photoelastic models of maxillary canine teeth of average dimensions. Standardized parallel post and cores were cemented into the models, with half of the samples incorporating a 1.5 mm metal collar. A 400 gm load was applied to the cingulum of the cores and stresses were frozen in the models. The posts were removed, the teeth were sectioned, and stresses were measured with a circular polariscope. In both groups the greatest stress concentration was found at the lingual apex of the post. On a point by point basis, stresses were higher in the collared specimens. Variation in stress magnitude among five preselected points was greater within the noncollared group.
Three healthy subjects with neighboring or contralateral vital and root-filled teeth requiring crown therapy were selected as test persons. All teeth had optimal alveolar bone support. The root-filled teeth were furnished with individual cast posts and cores, and veneer crowns were made on both the vital and non-vital teeth. Buccal extension bars were then soldered to the occlusal surfaces of these crowns, and weights were applied in different positions along the bars until the test persons experienced pain. The experiments were repeated under local anesthesia. The results showed that non-vital teeth had mean pain threshold levels that, on cantilever loading, were more than twice as high as those of their neighboring or contralateral vital teeth. The positions of the centers of rotational deformations of the loaded teeth, which were assumed to be mainly rotational, were calculated and found to be located inside the peripheries of the crowns for the vital teeth but extracoronally in markedly more peripheral positions for the non-vital teeth.
An idealized axisymmetric finite element model of a second premolar restored with a post and core was used to study the distribution and magnitude of stresses as a function of the following parameters: the diameter of the post, the length and the shape of the post, and finally the interface characteristics between post and cement. Emphasis was directed toward the cement layer interposed between the post and the tooth. Bonding between the post and the cement appeared to be the most important parameter to achieve optimal mechanical behavior of the tooth-prosthesis combination.
Statement of problem. The main factor that determines the prognosis of restored pulpless teeth is preservation of sound dentin. Purpose. This study evaluated the residual dentinal thickness (RDT) of mandibular premolars after preparation of post space with Gates Glidden and ParaPost drills. Material and methods. Twelve extracted single canal mandibular premolars were embedded in clear polyester resin to the cementoenamel junction (CEJ) in a muffle device. Three horizontal sections were made 1, 3, and 5 mm apical to the GET. Mesiodistal (MD) and faciolingual (FL) axes were carefully marked and the RDT was measured for each slice. Each tooth slice was reassembled in the muffle device with orientation pins, then secured with stabilizing pins. This procedure was repeated after enlarging the root canal to K-40 file and preparing the coronal root canal space with Gates Glidden drills and ParaPost drills Nos. 3, 4, and 5. Results. Residual dentinal thickness in a MD direction was 3.77 +/- 0.51 mm in the unprepared upper slice and 2.23 +/- 0.31 mm in the No. 5 ParaPost drill prepared lower slice, for a difference of 41%. The corresponding values for the FL direction were 4.35 +/- 0.51 mm and 4.08 +/- 0.46 mm, respectively (6%). Conclusion. The average dentinal thickness 5 mm below the CEJ in the mesial and distal directions after post space preparation approached the accepted minimal 1 mm. A conservative approach to post space preparation was advocated.
Post preparations in two groups of endodontically treated anterior teeth were completed. In Group I, the preparation was rinsed with 2 ml of 5.25% NaOCL. In Group II, the preparation was rinsed with 1 ml of 17% EDTA, followed by 1 ml of 5.25% NaOCl. A plastic post was fitted and cemented with an unfilled resin. After polymerization, the teeth were decalcified in 5% nitric acid. The decalcified structure was dissolved away with 5.25% NaOCl, leaving a model of the cemented post. This was examined by SEM to determine the extent of resin penetration into the dentinal tubules. In Group I, most of the post was smooth, and there was penetration only in small, random areas. In Group II, there was penetration into the tubules the full length and circumference of the post. Such penetration provides a very strong mechanical lock that enhances the tensile strength of the cemented post. Removing the smeared layer and then cementing a post with a Bis-GMA resin results in greatly increased tensile strength, even with shorter posts.
Little attention has been given to the resistance to fracture of teeth that have been endodontically treated and subsequently restored. This study investigates the impact resistance of maxillary central incisors to simulated trauma. Untreated teeth, teeth treated endodontically, and teeth restored with the use of parallel stainless steel posts were subjected to identical impacts. The absorbed energy values recorded for each group were compared with changes in the size of the endodontic preparation and the post diameter. Results of the study show that preservation of internal tooth structure and the use of smaller posts in teeth that have been endodontically treated provide maximum resistance to fracture.
Posted teeth were evaluated to determine the reinforcement capabilities of various post lengths. The results suggest that as internal tooth structure is removed from the tooth the tooth becomes weaker, that teeth with posts do show more reinforcement than nonposted teeth with the same manipulation characteristics, and that some load transfer appears to exist with cemented posts.
Corrosion of base metal alloys was studied by placing the alloys in artificial saliva for 2 months and then determining the concentration of metal ions in the saliva. The distribution of the attack on the surface was examined. The results indicated that the amount of metal ions in the artificial saliva could be related to the Cr content of the alloy. When the Cr content exceeded 16% very little corrosion was observed. The corrosive attack was located at Cr depleted areas, grain boundaries. The Cr depletion probably resulted from coring during solidification.
Oral function was evaluated in complete denture wearers by using a questionnaire, clinical examination and bite force measurements. Ten patients with satisfactory and ten with unsatisfactory dentures were studied and six of the latter patients were reexamined 1 year after the insertion of new dentures. The bite force values were compared with those obtained in ten dentate controls.
No significant differences in bite force were found between the satisfactory and unsatisfactory denture groups. Individual values varied much in both groups. The six patients re-examined were satisfied with their new dentures and thought they had improved chewing but no significant increase of bite force was found. The maximal bite force was 5–6 times greater in the dentate subjects than in the denture wearers. Edentulous persons are very handicapped in masticatory function and even clinically satisfactory complete dentures are poor substitutes for natural teeth.
The principal stress distribution in a root with a loaded post was analyzed in model experiments, in which emphasis was directed to the cervical boundary of the root where the stresses are greatest. Maximum stresses were found in the inner proximal sides, and were stronger when the prepared root canal walls were parallel. When contact between post and root was reduced, stresses decreased. These findings point to the importance of sparing tooth substance in the proximal parts of the canal in order to reduce the risk of breaking the cement layer and loosening the post.
Fifteen hundred permanent teeth were examined for mesiodistal widths of roots at the cervical, middle third, and apical third areas of the root. One hundred twenty-five teeth of each unit of the dentition, except second and third molars, were observed. These observations were recorded, and the means, standard deviations, 95% confidence intervals, and ranges were calculated. By use of the confidence interval, the optimal dowel size was selected.
There has been an increase in the use of prefabricated post systems to restore endodontically treated teeth. Various restorative materials are being used as core buildups on these posts. The purpose of this study was to compare three core materials that are used with prefabricated stainless steel posts. Two types of prefabricated posts were placed in extracted teeth, followed by core buildups in amalgam, composite resin, or glass ionomer. The teeth were prepared for full cast crowns with the margins of the crown preparation extending 0.5 to 1.0 mm below the margins of the core buildup. Crowns were fabricated and cemented with zinc phosphate cement. A custom-designed chewing machine was used to cyclically load the teeth with vertical and horizontal forces for one million cycles or until failure occurred. Results indicated highly significant differences in the survival of the post-core-crown restorations depending on which core buildup material was used. Amalgam cores had the lowest failure rate, followed by composite resin cores. All teeth restored with crowns over glass-ionomer core buildup failed. The type of prefabricated post used had no effect on the survival of the post-core-crown restorations regardless of the core buildup used.
A finite element analysis was carried out to study the roles of posts in reducing dentin stress in pulpless teeth. Two-dimensional plane strain models of the midlabiolingual section of a human maxillary central incisor were first analyzed. The results showed that the gold alloy post reduced maximal dentin stress by as much as 30%. However, the integrity of the dentin was compromised and the effects of the post were likely to be exaggerated in such models. In an effort to correct for these problems, plane stress models with side plates and axisymmetric models were analyzed. Posts were found to reduce maximal dentin stress by only 3% to 8% when the teeth were subjected to masticatory and traumatic loadings in these latter models. Although posts reduced maximal dentin stress by as much as 20% when the teeth were loaded vertically, teeth such as incisors and canines normally are not subjected to vertical loadings. Thus the reinforcement effects of posts seem to be doubtful in these teeth.
Severely damaged endodontically treated teeth require the use of a post and core for the retention of the restoration. The choice of material for a post and core and their stress-producing characteristics must be considered by the clinician. Two-dimensional photoelastic analysis of birefringent models was used to investigate the influence of different core materials on the stress distribution of nonthreaded cylindrical posts. Cast posts and cores and prefabricated posts with amalgam and composite resin cores were compared with posts without cores at installation and under two loading conditions. The findings indicate a significant difference between posts with and without cores. It appears that the stiffer core materials can shift the load from the apex to the coronal region.
Tissue reaction and stability of partially stabilized zirconia ceramic in vivo was evaluated with the use of the subcutaneous implantation test. During the experimental period, zirconia ceramic was completely encapsulated by a thin fibrous connective tissue with less than 80 μm thickness. No changes of weight and 3-point bending strength were detected after 12 months of implantation. The result suggests that zirconia ceramic is biocompatible and no degradation of zirconia ceramic occurred. © 1992 The Editorial Council of The Journal of Prosthetic Dentistry.
Fabrication of posts and cores for fixed partial denture (FPD) and removable partial denture (RPD) abutment restorations is common in dentistry. The biocompatibility of various post and core techniques with the restorations was clinically evaluated according to location and function. In this study, 154 post and core constructions for 150 patients were observed for a 3-year period to determine if the function of the original restorations remained unsatisfactory. The following techniques were included: (1) screw post and light-curing composite resins, (2) cemented post with parallel sides and light-curing composite resins, and (3) a cast and core technique. Seventeen of the 154 restorations failed; four failures were attributed to root fractures, three to radicular caries, and five to crown dislodgement, while five failures were from detachment of the post and core from the root. The statistical analysis revealed that only the factor "type of abutment" (RPDs and FPDs) had some effect on the failure of the restorations.
This study evaluated the fracture resistance of pulpless teeth with various ferrule designs and amounts of coronal tooth structure. One millimeter of coronal tooth structure above the crown margin substantially increased the fracture resistance of endodontically treated teeth, whereas a contrabevel at either the tooth-core junction or the crown margin was ineffective. The thickness of axial tooth structure at the crown margin did not appreciably improve resistance to fracture.
Heat treatment during the burnout procedure may cause corrosion of the stainless steel post. This study was undertaken to determine whether alteration of the corrosion resistance of stainless steel posts occurs as a result of various simulated burnout procedures. Stainless steel posts were divided into five groups of five posts: group 1, control; 2, gypsum-bonded investment, bench cooled; 3, gypsum-bonded investment, quenched; 4, phosphate-bonded investment, bench cooled; and 5, phosphate-bonded investment, quenched. The posts were placed in individual containers of Ringer's solution and observed at 30, 180, and 600 days. Scanning electron microscopy, energy dispersive x-ray spectroscopy, optical emission spectroscopy, and optical microscopy were used to evaluate the posts qualitatively and quantitatively. Investment and heat treatment altered the metallic structure of stainless steel posts. Prefabricated posts submitted to simulated burnout procedures had a noticeable reduction in corrosion resistance. Direct casting to stainless steel posts is contraindicated.
This study determined the effect of different post designs and varying amounts of post-to-canal adaptation on the fracture resistance of endodontically treated teeth. Forty freshly extracted maxillary central incisors were endodontically treated. Groups of 10 teeth were prepared according to four experimental designs. Cast post and cores and crowns were waxed, cast, and luted with zinc phosphate cement on a static loading device. The teeth were embedded in acrylic resin and the crowns were loaded on a universal testing machine at 130 degrees to the long axis of the tooth until failure. Maximum adaptation of the residual root structure with a tapered post significantly increases the fracture resistance of endodontically treated teeth, but upon failure renders the tooth nonrestorable. Tapered posts resulted in fractures that were directed more apically and lingually. Parallel-sided posts had a lower frequency of fracture upon failure, involving less tooth structure. Parallel-sided posts surrounded by large amounts of cement had no significant effect on failure loads.
This study compared the stress distribution during insertion and function of three prefabricated endodontic posts with different designs using the criteria of post length and diameter. Test blocks of photoelastic material were prepared with simulated endodontic canals. Three posts for each design, diameter, and depth were cemented. Each specimen was examined and photographed without load, with 135 Newton (N) compressive force, and with 90 N and/or 135 N oblique force applied at 26 degrees by use of a circular polariscope. Para-Post and Para-Post Plus posts produced similar, evenly distributed patterns of stress using the criteria of diameter, depth, and load. Flexi-Post posts produced asymmetric stress patterns with concentration of stress at each thread. During compressive loading and after cementation alone, Flexi-Post posts displayed significantly higher shoulder stresses and substantially greater stresses along the coronal surface of the post's length than Para-Post and Para-Post Plus posts. Apical stresses were similar for Flexi-Post, Para-Post, and Para-Post Plus posts during compressive loading.
Carbon fibre reinforced carbon (CFRC) in the form of a prefabricated post has recently been developed and is theoretically acceptable for consideration in an endodontic post-retained crown system. This study compared four different types of postcore system cemented into 40 extracted anterior human teeth. The test groups consisted of CFRC posts cemented with a composite resin luting agent, and used with either a cast gold alloy core (Group B) or a composite resin core (Group C). Two existing post-core techniques were used as controls for comparison with the CFRC groups. One control was a prefabricated wrought precious alloy post having a cast gold alloy core, and cemented with zinc phosphate cement (Group A). The other was a prefabricated stainless steel post with a composite resin core, and cemented with a composite resin luting agent (Group D). All specimens were restored with a gold alloy crown and tested to failure with an obliquely applied compressive load at 130 degrees in an Instron using a cross-head speed of 5 cm min-1. The results showed that post-retained crowns using a prefabricated CFRC post exhibited properties comparable with, and in some cases better than, those of existing prefabricated posts. The mode of failure of specimens restored with a CFRC post was more favourable to the remaining tooth tissue than was that of specimens restored with a metallic post.
This study compared a new parallel-tapering, threaded, split-shank post with a well-accepted parallel serrated post under applied compressive-shear loads. The posts were placed in paired, contralateral human teeth to attempt to minimize variation in the tooth model. Both initial and ultimate failure modes were observed, and the clinical significance reported. The Flexi-post system compared favorably with the Para-Post system under the conditions of this research.
Sixty-nine patients who received cast posts and cores in 1978 at the Students' Clinic at the Faculty of Odontology, University of Umeå were recalled for examination in 1984. Fifty-three or 76.8% of the patients with 96 posts and cores or 73.3% of the original 131 attended. Of the 96 posts and cores, nine, corresponding to a failure rate of 1.56% per year, were classified as unsuccessful, which compared favorably with previous studies. Various criteria parameters were reviewed for possible correlations to the failures but the only common factor was that the nine failures were located in jaws occluding against a natural dentition. The endodontic failures noted could not be related to the prosthodontic treatment. Another conclusion from this study is that the conventional design of the cast post and core can be strongly recommended.
Fractures of restored pulpless teeth without reinforcement are a familiar dilemma to the dentist. This study examined the effect of a metal collar with approximate 3 degrees of taper on the resistance of endodontically treated roots to fracture. Teeth without copings failed at a load of 49.6 kg whereas teeth with metal collars failed at a load of 65.29 kg. Our findings indicated that reinforcement with a metal collar is necessary to enhance resistance to root fracture.
A photoelastic model was used to examine the influence of different types of restorations placed following endodontic therapy, emphasizing the way in which forces applied to the occlusal surface were dispersed to the supporting structures of the teeth. Stresses were photographed in the polarized light field. Findings indicate that distribution and patterns of stresses vary depending on the direction of the loads and the nature of the involved restorative procedures.
The effect of endodontic therapy, post-hole preparation, and post placement on tooth models of maxillary central incisors was investigated. Two-dimensional photoelastic analysis of birefringent models, under load in a polariscope, indicated the relative stress magnitudes and concentrations at the cervical and apical regions. Within the limits of the method, the results suggest that enlargement of the canal increases cervical stresses and that post placement will decrease stresses in this region. Nevertheless, conservative enlargement of the root canal may render post placement unnecessary for largely intact teeth. Post length appeared more important than post diameter in determining relative stresses at the cervical region. However, short wide posts led to elevated stress concentrations in this region. Post placement beyond two thirds of the root depth did not further decrease cervical stresses but usually increased stresses in the apical region.
In the spectrum of treatment modes of endodontically treated molars, composite dowel and core systems are considered an alternative to the widely used cast dowel and core method. In a laboratory setting under oblique loading with a slowly increasing force, no significant differences between the tested composite dowel and core systems could be detected. All systems could resist forces of more ythan 2,000 N. Long-term clinical evaluations should give the ultimate answer about their durability and the influence of other possible destructive factors.
Para-Post dowels were cemented by using combinations of cement, cleansing agents, and dentinal treatments. The comparative retentive strengths were as follows: 1. Para-Post posts cemented with composite into mechanically corrugated post spaces recorded the greatest retention. 2. The retention of the posts cemented with composite into post spaces rinsed with 1 ml of 17% EDTA with a pH of 7.5 and followed immediately by 1 ml of 5.25% NaOCl was lowest. 3. The retention of the posts secured with zinc phosphate into mechanically corrugated post spaces was significantly higher than with untapped post spaces. 4. The retentive strength of the posts placed with glass-ionomer cement into post spaces, irrigated with 1 ml of 40% polyacrylic acid solution, and rinsed with distilled water was comparable to that of posts secured with zinc phosphate cement without roughened post spaces.
An in vitro study of 45 teeth compared the failure loads of endodontically treated teeth restored with pin and amalgams, Para-Post dowel and composite, and glass ionomer/amalgam alloy coronal-radicular buildups. The following conclusions were made. The Para-Post and composite buildups exhibited the highest mean failure load, 35.3 kg. The mean failure load for pin and amalgam buildups was 27.9 kg. Glass ionomer/amalgam alloy coronal-radicular buildups exhibited the lowest mean failure load, 14.1 kg. Restoration of endodontically treated anterior teeth with glass ionomer/amalgam alloy coronal-radicular buildups is contraindicated.
Four techniques for the cementation of cast post restorations were compared in extracted single-rooted teeth. The techniques used were the lentula spiral, endodontic explorer, paper point, and direct post application. Evaluation was based on the presence of voids in the cement and retention of the post. The lentula spiral technique was performed without voids. The other techniques produced voids in increasing numbers in the following order: the endodontic explorer, direct application, and the paper point. The voids were commonly located along the shaft of the post, but there was no correlation between the number of voids and the retention of the posts.
Fifty Flexi-Posts were cemented in extracted teeth and tested for tensile strength. The Flexi-Post was the most retentive post tested when compared with posts used in a similar study. The retention of the Flexi-Post became greater as the size of the post increased.
Thirty-one dentists were tested relative to the optimal and maximum amount of torque they could deliver to posts in teeth. The mean for the optimal amount of torque was 15.55 ounce-inches, and the mean for the maximum amount of torque was 35.29 ounce-inches. Female dentists showed a statistically significantly lower mean difference of 24.5 ounce-inches on the maximum torque test.
The significance of the amount of remaining buccal dentin plate of the dowel channel in resisting root fracture under horizontally directed load was investigated. Forty cast gold dowels and cores were made for four groups of dowel channels that had, respectively, 1 mm, 2 mm, 3 mm, and 1 mm with a 60-degree bevel (collar) of the remaining buccal dentin at the entrance of the canal. An Instron tester in compressive mode was used to produce the horizontal force. Although significant differences in the failure loads for the four groups were not found, dowel channels with 1 mm of remaining buccal dentin walls were apparently more prone to fracture under horizontal impact than those that had 2 or 3 mm of buccal dentin walls. Contrary to popular belief, the addition of a metal collar did not enhance the resistance to root fracture.
Three commonly used endodontic post designs, their lengths, their methods of insertion, and their abilities to transmit occlusal forces to supporting structures were compared. According to this photoelastic stress analysis, post design affects stress distribution. Stresses tended to concentrate under the post shoulder, especially if sharp angles were present. Also ascertained was the fact that the post length should approximate the length of the anatomic crown.
The dowel and core should possess a positive seat to prevent a wedge-like action of the post. The transverse and vertical shape of the prepared root canal should follow the contour of the exterior root surface. The dowel length should be determined by the bone support of the involved root.
Post preparations in two groups of endodontically treated anterior teeth were completed. In Group I, the preparation was rinsed with 2 ml of 5.25% NaOCL. In Group II, the preparation was rinsed with 1 ml of 17% EDTA, followed by 1 ml of 5.25% NaOCl. A plastic post was fitted and cemented with an unfilled resin. After polymerization, the teeth were decalcified in 5% nitric acid. The decalcified structured was dissolved away with 5.25% NaOCl, leaving a model of the cemented post. This was examined by SEM to determine the extent of resin penetration into the dentinal tubules. In Group I, most of the post was smooth, and there was penetration only in small, random areas. In Group II, there was penetration into the tubules the full length and circumference of the post. Such penetration provides a very strong mechanical lock that enhances the tensile strength of the cemented post. Removing the smeared layer and then cementing a post with a Bis-GMA resin results in greatly increased tensile strength, even with shorter posts.
Dentin stresses from simulated functional loads to post-reinforced tooth models with four levels of periodontal support were calculated using finite element analysis. As bone levels diminished, stresses were found to increase dramatically and to concentrate in the small amount of dentin remaining near the post apex.
Twenty-five extracted maxillary central incisors were instrumented to a #50 file 0.5 to 1.0 mm from the apex and obturated with gutta-percha using lateral condensation. All specimens had an experimental 18-gauge hollow stainless steel post. A group of five teeth had a standard gold core cast to the post. A second group of 20 had a customized gold core cast to the post. Six crimps were placed in each post to provide additional retention. The two groups were subjected to retention failure loads. The standard post and core group failed at a mean load of 14.44 kg. The customized post and core group failed at a mean load of 23.24 kg. There was a statistically significant difference (p<0.0001) between the two groups. A correlation coefficient of 0.63 was computed between the length of post customized and failure load. This factor was statistically significant (p<0.01).