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Push-out Bond Strength of Fiber Posts Luted with Unfilled Resin Cement
Abstract
The study evaluates the behavior of different adhesive systems and resin cements in fiber post placement, with the intent to clarify the possible role of unfilled resin as a luting material for fiber posts.
Two luting agents (Dual-Link and Unfilled Resin) for cementing fiber posts into root canals were applied either with All-Bond 2 or One-Step Plus, or without an adhesive system, and challenged with the push-out test. Slices of roots restored with posts were loaded until post segment extrusion in the apical-coronal direction. Failure modes were analyzed under SEM.
Push-out strength was significantly influenced by the luting agent (p < 0.05), but not by the bonding strategy (p > 0.05). The best results were obtained in combination with Unfilled Resin with One-Step Plus. Dual-Link groups failed mainly cohesively within the cement, while Unfilled Resin demonstrated more adhesive fracture at the post interface.
The results of this study support the hypothesis that adhesive unfilled resin application is essential for achieving high bond strength to radicular dentin.
... Ethanol solution is a dehydrating agent 10 that has been tested to improve dentine wettability and to increase sealer penetration along the root canal walls 8 . Some authors suggest there is a higher compatibility between ethanol-saturated dentine and hydrophobic resin monomers, preventing collagen shrinkage and allowing for higher impregnation 11 , infiltrating hydrophobic monomers into the demineralised dentine collagen matrix [12][13][14] . The use of 70% or 100% ethanol increased dentine wettability and improved the interaction between resin-based endodontic sealer and dentine root canal walls 15 . ...
... Rhodamine must be incorporated with cement at a ratio of 0.1%. It did not interfere with the physicochemical properties of endodontic sealers 13,16 . Autofit gutta-percha cones were coated with sealer and placed 2 mm short of the working length. ...
Aim: The aim of this study was to evaluate the effect of ethanol-conditioned dentin on endodontic sealer penetration into dentinal tubules by confocal laser scanning microscopy (CLSM). Methods: Forty human maxillary anterior teeth were instrumented and divided into four groups (n = 10) according to the drying methods: 1) wet: vacuum only, 2) paper points: vacuum + absorbent paper points, (3) 70% ethanol: 70% ethanol (1 min) + vacuum + absorbent paper points, and (4) 100% ethanol: 100% ethanol (1 min) + vacuum + absorbent paper points. All root canals were filled with resin-based endodontic sealer. Four sections from each third (cervical, middle, and apical) were examined by CLSM. Root canal wall perimeter infiltrated by sealer, maximum depth of sealer penetration, percentage of penetrated area, and fluorescence intensity of rhodamine B were measured. Statistical analysis was performed by analysis of variance and Tukey’s tests (α = 0.05). Results: No statistical difference was found when percentage of root canal wall coverage infiltrated by sealer were compared. The groups in which ethanol solutions were used presented greater depth of sealer penetration, higher percentage of penetrated area, and higher fluorescence intensity of rhodamine B (p< 0.05) when compared with the wet and paper point groups. Overall, 100% ethanol produced better results than 70% ethanol, except for rhodamine B intensity (cervical third). In addition, the absorbent paper points drying method behaved better than did vacuum only group, except for rhodamine B intensity (apical third). Conclusion: Ethanol-conditioned dentin improved the penetration of resin-based sealer into dentinal tubules, especially at the concentration of 100%.
... The adhesive cementation procedure is generally based on either the use of the acid etching of the tooth structure followed by the bonding agent application [4][5][6][7][8][9] or the utilization of self-etching adhesive systems [4,8,10,11]. These latter imply in a smaller technique sensibility and greater usage easiness because of the elimination of the acid etching step thus not compromising the adhesion inside the root canal because of either the incomplete removal of the acid or inefficient drying [12] prior to the application of the resin cement. ...
... The punch diameter (0.85 mm) was selected up to the luted fiber post cross-section diameter for each slice, without stressing the surrounding root canal walls. Post diameters were measured on each surface of the post-dentin sections using a digital caliper (Starrett; Itu, São Paulo, Brazil), and the total bonding area for each post segment was calculated using the formula of a conical frustum: A = π(R1+R2)(h2 + [R1-R2]2)1/2 ( Figure 2) [6,11]. Push-out strength data were converted to MPa by dividing the maximum failure load value (in Newton) by the bonded surface area in mm 2 . ...
Objective: This study evaluated the effect of rootperforations on the bond strength of fiberglassposts cemented to the root canal with two adhesivesystems and resin cement. Material and Methods:Forty single-rooted human teeth received endodontictreatment and were prepared for the cementationof fiberglass posts (Exacto Mini, Angelus). Theteeth were divided into four experimental groups(n = 10) according to the root condition (with orwithout perforation) and the adhesive system used:G1: without perforation + Adper Single Bond 2(3M ESPE), G2: without perforation + Clearfil SEBond (Kuraray), G3: with perforation + AdperSingle Bond 2, G4: with perforation + Clearfil SEBond. The perforation was executed on the rootsurface with a diamond bur and sealed with whitemineral trioxide aggregate (MTA). The specimenswere sectioned and a push-out test was carriedout (1 mm/min speed and 50 kgf). The data werestatistically analyzed by ANOVA and Tukey Test(5%). Results: Adper Single Bond 2 promoted thegreatest values of bond strength to the roots withoutroot perforation. The presence of root perforation ledto the reduction in bond strength values regardlessof the bonding system used (p < 0.05). Conclusion:The root perforations caused a direct effect on thebond strength of the fiberglass posts cemented byreducing the bond strength values to the root dentinregardless of the adhesive system used.
Keywords
Adhesion; Cementation; Dental adhesives; Dental cements; Fiberglass pins.
... Irrigation solutions used during endodontic therapy, which have the main objective of cleaning the root canal [55,56], can facilitate the reduction and removal of the smear-layer [43,57] due to their antimicrobial, solvent and chelating actions [44]. However, the use of irrigation solutions can have an impact on the physicochemical properties of dentin, including wettability, roughness, penetrability of cement into dentin and microhardness [58,59]. ...
Adhesion science is one of the greatest contributions to restorative dentistry. Adhesion not only established the current principles of tissue preservation, but also allowed for the production of more hermetic and long-lasting restorations. Although adhesive strategies are routinely used in most clinical situations, adhesion to root dentin is still a major challenge. The presence of humidity together with less intertubular dentin are factors that limit the adhesive potential of root dentin. This situation is more unfavorable in endodontically treated teeth prepared for prefabricated or custom-made intraradicular posts; these procedures may alter the mechanical properties of teeth by modifying the viable dentin surface for adhesion. Also, contaminants deposited on the dentin surface are difficult to remove through conventional techniques. Moreover, root canal morphology has a very unfavorable C-factor, bringing undesirable effects resulting from polymerization contraction of resin-based materials. However, the differences between coronal and root dentin are not a barrier for dentin adhesion. Standardization of procedures and care during clinical steps are fundamental to the success of adhesion to coronal or intraradicular dentin. Thus, it is essential to know the anatomy of the root structure, the factors that interfere with intraradicular adhesion, as well as the current adhesive materials and techniques.
... 18,19 There is a higher compatibility between ethanolsaturated dentin and hydrophobic resin monomers, preventing collagen shrinkage and allowing for higher impregnation. 20 This technique has been shown to produce adhesive interfaces with higher bond strength, reduced interface nanoleakage, and increased stability over time when compared to the "water-wet bonding technique." 21,22 In endodontics, it is suggested that a final rinse of dentin walls with different substances 23 or with ethanol may alter root dentin properties, enhancing endodontic sealer penetration into dentinal tubules. ...
This study aimed to evaluate the influence of different ethanol concentrations on dentin roughness, surface free energy, and contact angle between AH Plus and the root canal dentin. One hundred human maxillary anterior teeth were split longitudinally and 200 dentin specimens were polished to make the surface flatter and smoother. An acrylic bar was positioned between two dentin specimens and impression material was added to create a block, simulating an instrumented root canal space. Specimens were removed from the mold and cleaned in an ultrasonic bath for 10 min. Thereafter, dentin specimens were divided into four groups (n = 50) according to the drying methods used: a) wet: vacuum only, b) paper points: vacuum + absorbent paper points, c) 70% alcohol: 70% alcohol (1 min) + vacuum + absorbent paper points, and d) 100% alcohol: 100% alcohol (1 min) + vacuum + absorbent paper points. A rugosimeter and a goniometer were used to verify the roughness (Ra) and to measure the surface free energy and the contact angle between the AH Plus sealer and the root canal dentin. ANOVA and Tukey tests (α = 0.05) were used for statistical analysis. The 70% and 100% ethanol groups showed significantly decreased roughness as well as increased surface free energy in the root canal dentin when compared to the wet and paper point groups. In addition, ethanol significantly reduced the contact angle between the AH Plus sealer and the root canal dentin. Ethanol solutions (70% and 100%) provide better wettability of AH Plus sealer on dentin surfaces.
... Carvalho CA. y col. (44), utilizando adhesivos de tres pasos-All Bond 2 y de dos pasos, One ...
In 90th decade the Prefabricated Fiber Posts (PFP) were introduced in the market as an alternative to metallic systems (casted, prefabricated and ceramics). They are nowadays in use and in continued modification of their commercials presentations and fixation strategies. Their mechanical qualities, low Elastic Modulus (EM), similar to dentine.rsquo;s, introduce a new paradigm in Endodontically Treated Tooth Rehabilitation: when .ldquo;the post must go along supportively, the banding of dental tissues against the loads.rdquo;. Their esthetic qualities, ease removal, and the possibility of adhesive cementation, have converted them in a proven alternative to the traditional solutions. However, some contradictories results in addition to important difficult of achieving hybridation in root dentine maintain issues to be answered in the future. The PFP are indicated in those a case in which retreatment is foreseen, in young patients with of a high esthetic demand, and each and every time the costs of noble alloys can be avoided. In the present paper clinic and the experimental fundamental of several authors are analyzed, establishing practical arguments for their use. A clinical case in a young patient with a preceding injury record and high esthetic requirements in presented as an example
... These results in an acid-base reaction between the adhesive system and the resin cement, which in turn prevents appropriate copolymerization and, as a result, the bonding between the adhesive and the luting agent is weak. (30) The results are in contrary with Carlos et al, (31) whom found that the push-out strength for cementing fiber posts into root canals was not significantly influenced by the bonding strategy (etch and rinse adhesive system and self etch adhesive system). ...
Purpose: To evaluate the push out bond strength of three glass fiber composite posts bonded to radicular dentin using either etch and rinse or self etch adhesive systems. methods: Forty-two single rooted extracted mandibular first premolars were decoronated. The roots were endodontically prepared and randomly divided into three main groups according to the type of glass fiber post (n=14): group I; electrical-glass (everStick, ES); group II, alkaline resistance-glass (RelyX, RX); group III, quartz-glass (Peerless, PL). Each group was further subdivided into two subgroups (n=7) according to the adhesive system used; in the first subgroup; Adper Single Bond 2 (ASB2) was used while in the second subgroup; Adper Easy Bond (AEB) was employed. Posts were cemented with dual cure resin cement (Rely X ARC). The roots were perpendicularly sectioned to obtain two discs from the coronal half of each root. In each subgroup 10 discs were submitted to a push-out test, while the remaining 4 discs for scanning electron microscopic examination (SEM). Data was analyzed using two way ANOVA and Tukeys post hoc test. results: Groups; PL/ASB2 (17.1±1.4 MPa) and RX/ ASB2 (14.59±5.9 MPa) yielded significantly the highest mean push-out bond strength values. Meanwhile, there was no statistically significant difference between the other groups; ES/ASB2 (8.28 ± 1.9 MPa), RX/AEB (9.36±1.5 MPa), PL/AEB (8.04±0.2 MPa) and ES/AEB (7.03 ± 2.9 MPa), respectively. Conclusion: Alkaline resistance (RX) and quartz glass (PL) fiber posts in conjunction with etch and rinse adhesive system (ASB2) showed prompt bonding to radicular dentin. Key wOrds: Composite glass fiber posts, etch and rinse adhesive system, self etch adhesive system, push out bond strength test.
... 11 The application of adhesive resin to root canal dentin to bond the fiber posts is a mandatory step to effectively seal the cement/dentin interface. 3 Due to their simplicity, one-step self-etching adhesives are now widely used to bond fiber post to root canal dentin. As the self-etching adhesives contain solvent and water in their compositions, effective removal of both during the air-drying step is crucial to improve the adhesive performance. ...
Purpose:
To evaluate the effect of solvent removal and light-curing methods on the push-out bond strength of fiber posts to root canal dentin using a one-step self-etching adhesive.
Materials and methods:
Eighty single-rooted, single-canal human mandibular premolars were used in this study. After removal of the crown, the pulp was extirpated and the post space was prepared. The teeth were divided into two main groups according to the solvent removal method, either using the paper point or the air-drying method. Each of the above main groups was further subdivided into 4 subgroups according to the light-curing method: group 1: both adhesive and resin cement were cured from the top of the post in the same step (cocuring) for 40 s; group 2: the adhesive was light cured for 20 s and the resin cement for 40 s; group 3: the adhesive was light cured for 40 s as was the resin cement; group 4: an intracanal tip was used to cure the adhesive inside the post space for 20 s. In groups 1 to 4, the solvent was evaporated using oil-free compressed air for 5 s from the root surface and excess adhesive was removed from inside the canal using a paper point. In groups 5 to 8, the adhesive and cement were applied and light cured as in groups 1 to 4, except the solvent was evaporated (air dried) from inside the post space using an intra-canal disposable plastic tip attached to the tip of a 3-way syringe. After 24 hours, three 2-mm-thick root slices were obtained from each root. Each slice was subjected to the push-out bond strength test at a crosshead speed of 0.5 mm/min. Factorial analysis (two-way ANOVA) was run to test the effect of solvent evaporation method, light-curing method, and their interactions on bond strength. One-way ANOVA followed by Duncan's Multiple Range Test were used to test the effect of lightcuring method on bond strength within each solvent evaporation method. Student's t-test was performed to compare the effect of solvent evaporation method on bond strength within each light-curing method.
Results:
Two-way ANOVA revealed that the solvent removal method had a significant effect on the bond strength of fiber post to root canal dentin. Neither the light-curing method nor the interaction between the two independent variables had a significant effect on the push-out bond strength.
Conclusions:
Only air drying the one-step self-etching adhesive could influence the bond strength of the fiber post to root canal dentin.
... In this study, the analysis of the failure modes demonstrated that most failures occurred at the post/luting material interface, and this is in accordance with the results of a recently published investigation 6 . This type of fracture could be due to the lack of chemical union between the cured epoxy resin matrix fiber-post and the unfilled resin (HeMA, Bis-GMA; Figure 2). ...
Objective:
This study evaluated the performance of different adhesive systems in fiber post placement aiming to clarify the influence of different hydrophobic experimental blend adhesives, and of one commercially available adhesive on the frictional retention during a luting procedure.
Material and methods:
One luting agent (70 Wt% BisGMA, 28.5% TEGDMA; 1.5% p-tolyldiethanolamine) to cement fiber posts into root canals was applied with 4 different adhesive combinations: group 1: The etched roots were rinsed with water for 30 s to remove the phosphoric acid, then rinsed with 99.6% ethanol for 30 s, and blotdried. A trial adhesive (base to catalyst on a 1:1 ratio) was used with an experimental luting agent (35% Bis-GMA, 14.37% TeGDMA, 0.5% eDMAB, 0.13% CQ); group 2: A trial adhesive (base to catalyst on a 1:2 ratio) was luted as in group 1; group 3: One-Step Plus (OSP, Bisco Inc.) following the ethanol bonding technique in combination with the luting agent as in group 1; group 4: OSP strictly following the manufacturer's instructions using the luting agent as in group 1. The groups were challenged with push-out tests. Posted root slices were loaded until post segment extrusion in the apical-coronal direction. Failure modes were analyzed under scanning electron microscopy.
Results:
Push-out strength was not significantly influenced by the luting agent (p>0.05). No statistically significant differences among the tested groups were found as group 1 (exp 1--ethanol-wet bonding technique)=group 2 (exp 2--ethanol-wet bonding technique)=Group 3 (OSP--ethanol-wet bonding technique)=group 4 (control, OSP--water-wet bonding technique) (p>0.05). The dominating failure modes in all the groups were cohesive/adhesive failures, which were predominantly observed on the post/luting agent interface.
Conclusions:
The results of this study support the hypothesis that the proposal to replace water with ethanol to bond fiber posts to the root canal using highly hydrophobic resin is plausible, but this seems to be more the proof of a concept than a clinically applicable procedure.
Objetivo: O presente estudo relata um caso clínico de reabilitação do incisivo central superior esquerdo com uso de retentor intrarradicular pino de fibra de vidro, utilizando a técnica do pino anatômico com resina composta. Metodologia: Trara-se de um relato de caso clínico de cunho analítico descritivo (Pereira et al., 2018), realizado na clínica odontológica do CEUNI-Fametro, na disciplina de estágio supervisionado em Clínica Integrada II. Relato de caso clínico: A paciente melanoderma, R. R, de 43 anos, procurou atendimento, tendo como queixa principal o comprometimento da aparência estética do dente 21; relatou que comprometia seu sorriso e o incomodo. Nos exames clínico e radiográfico observou-se extensa destruição coronária e tratamento endodôntico insatisfatório. Foi planejado e realizado o retratamento endodôntico e a reabilitação com uso de retentor pré-fabricado pino de fibra de vidro. O pino de fibra de vidro foi condicionado com ácido fosfórico para limpeza da superfície, lavado com spray de ar e água, feito a secagem, preparado com silano, sistema adesivo e fotopolimerização. A resina composta foi depositada sobre o pino, levando ao conduto este lubrificado com gel hidrossolúvel, fazendo movimento de inserção e remoção, modelando o formato do conduto radicular. O cimento resinoso utilizado foi autoadesivo dual. A restauração da coroa clínica com resina composta com a técnica direta utilizando o protocolo de preparo para faceta e estratificação de cor. Considerações finais: O uso do pino de fibra de vidro mostrou-se uma alternativa eficaz na reabilitação do dente, favorecendo a estética da paciente, obtendo um resultado satisfatório.
Amaç: Bu çalışmanın amacı, farklı çözücü buharlaşma stratejilerinin fiber postların kök kanal dentinine bağlanma dayanımına etkisini değerlendirmektir.Gereç ve Yöntem: Otuz adet çekilmiş insan üst santral kesici dişlerin kök kanalları TF Adaptive eğe sistemi (SybronEndo, CA, ABD) kullanılarak genişletildi. Kök kanal dolgusu yapıldıktan sonra post boşlukları 8 mm derinliğinde hazırlandı. Adeziv sistemi (ED Primer A + ED Primer B; Kuraray, Tokyo, Japonya) uygulamasının ardından örnekler rastgele iki gruba ayrıldı. Grup 1 (APA Grubu): 10 sn hava ile kurutmayı takiben kâğıt kon ile kurutma yapıldı, sonrasında ek olarak 10 sn daha hava uygulandı. Grup 2 (EV Grubu): 10 sn hava kurutmayı takiben EndoVac (Discus Dental, CA, ABD) ile 40 sn apikal negatif basınç ile kurutma yapıldı ardından da ek olarak 10 sn daha hava uygulandı. Fiber postlar (E Hahnenkratt GmbH) rezin siman ile yapıştırıldıktan sonra 40 sn boyunca her yönden ışınlandı. Bütün örnekler 48 saat boyunca %95 nemlilikte 37 °C’de saklandı. Daha sonar Push-out testi uygulandı.Bulgular: Fiber postların kök kanal dentinine bağlanma dayanım değerleri koronal ve apikal kısımda istatistiksel olarak anlamlı bir farklılık göstermemiştir. Ancak, orta üçlüde APA grubu EV grubuna göre istatistiksel olarak daha yüksek bağlanma dayanımı göstermiştir.Sonuç: EndoVac uygulanarak yapılan çözücü buharlaştırma yönteminin fiber postların kök kanal dentinine bağlanma dayanımına olumlu bir etkisi olmamıştır.
This in vitro study investigates the bonding capacity of resin cements to dowels, using the push-out bonding strength of four different dowel systems, namely, stainless steel dowels (SSD), resin-supported polyethylene fiber dowels (RSPFD), zirconia dowels (ZD), and superpost glass fiber dowels (GFD), luted in root canals, using two different resin cements, namely, Multilink Automix Cement and Clearfil Esthetic Cement. Ninety-six maxillary central incisor teeth were sectioned below the cementoenamel junction, and the roots were treated endodontically. Then the roots were placed into four groups, based on the dowel systems used. The roots were further placed into two subgroups, based on the cement type used as subgroup A and subgroup B. Push-out bonding tests were performed on the bonded specimens, which were cut into 1mm thick sections. A two-way ANOVA test and Tukey's HSD tests were performed. The push-out bonding strength values for SSD, ZD, and RSPFD were not significantly different (p>0.05). The means for GFD were significantly higher than the means for ZD (p<0.05) when Multilink Automix Cement was used. However, when Clearfil Esthetic Cement was used, the means for RSPFD were significantly higher (p<0.001) than the means for the other systems. When Clearfil Esthetic Cement was used, the RSPF dowel system provided significantly higher bonding strength values than the other systems.
Aims
The aim of this study was to investigate, by means of the push-out test, the bond of Prime & Bond NT at various post-space dentin locations and the influence of time of water storage on bond strength values.
Methods
30 single-rooted teeth were used for the bond strength measurement. In each tooth fiber posts were cemented with the commercial bonding system “Prime & Bond NT” in combination with the resin-based filling material “Opticore Cure Core Composite”. After 24 h (group A: 10 roots), 1 month (group B: 10 roots), and 6 months (group C: 10 roots) of water storage, the specimens were sectioned in 1 mm-thick slices for the push-out test. The data were divided into three regions (coronal/middle/apical) and analyzed using Kruskal-Wallis Test and Mann-Whitney U Test (p<0.05).
Results
The bond strength values registered did not show statistically significant differences within group A and C; within group B statistically significant differences were found between the coronal and the middle thirds and between the coronal and the apical third. The apical bond strength values did not show any statistically significant difference among the three groups (Kruskal-Wallis test); in the middle thirds a statistically significant difference was found at 6 months when compared with the 24 h and 1-month samples. In the coronal thirds was found a statistically significant difference between 1 month and 6 months. Analysis of the specimens under optical microscope revealed a prevalence of adhesive failures between fiber post and root dentin.
Conclusions
Bond strength values are lower at the apical third. Over time the adhesion of the fiberpost/luting cement/post-space dentin does not remain stable.
Luting fiber posts to intraradicular dentin remains an unpredictable goal due to various clinical factors influencing the clinical procedure. Primarily differences can be found between bonding to coronal or to intraradicular dentin due to the different histological characteristics of the substrates, the high C-factor of the endodontic space, the presence of smear layer due to the post preparation technique, incompatibility between some adhesive systems and resin-based cements, and finally the limited access of the post space that may lead the clinician to different mistakes. Thus this article critically evaluates all aspects that may jeopardize the adhesion of luted fiber posts within the endodontic space, suggesting the use of standardized techniques that improve immediate adhesion and stabilize the adhesive interface over time. The review of the data currently available in peer-reviewed journals suggests that a strict following of a step-by-step clinical standardized technique allows the clinician to minimize bond failure and obtain a clinically reliable durable bond.
This study examined the immediate bond strength of etch-and-rinse adhesives to demineralized dentin saturated with either water or absolute ethanol. The research hypothesis was that there would be no difference in bond strength to dentin between water or ethanol wet-bonding techniques. The medium dentin of 20 third molars was exposed (n = 5). The dentin surface was then acid-etched, left moist and randomly assigned to be saturated via either water wet-bonding (WBT) or absolute ethanol wet-bonding (EBT). The specimens were then treated with one of the following etch-and-rinse adhesive systems: a 3-step, water-based system (Adper Scotchbond Multipurpose, or SBMP) or a 2-step, ethanol/water-based system (Adper Single Bond 2, or SB). Resin composite build-ups were then incrementally constructed. After water storage for 24 h at 37°C, the tensile strength of the specimens was tested in a universal testing machine (0.5 mm/min). Data were analyzed by two-way ANOVA and Tukey's test (a = 5%). The failure modes were verified using a stereomicroscope (40'). For both adhesives, no significant difference in bond strength was observed between WBT and EBT (p > 0.05). The highest bond strength was observed for SB, regardless of the bonding technique (p < 0.05). No significant interaction between adhesives and bonding techniques was noticed (p = 0.597). There was a predominance of adhesive failures for all tested groups. The EBT and WBT displayed similar immediate bond strength means for both adhesives. The SB adhesive exhibited higher means for all conditions tested. Further investigations are needed to evaluate long-term bonding to dentin mediated by commercial etch-and-rinse adhesives using the EBT approach.
This articles concerns itself with the testing of adhesion between direct restoratives and dental hard tissue, ie, enamel and dentin. The aim is to survey available methods for adhesion testing and influential parameters affecting experimental outcome. The testing of adhesion to indirect restorative materials, eg, ceramics and metals, is beyond the scope of this article and shall be discussed elsewhere. The longevity and success of modern dental restorations very often relies on potent dental adhesives to provide durable bonds between the dental hard substance and the restorative composite. To predict the clinical outcome of such restorative treatment, a large variety of in vitro laboratory tests and clinical in vivo experiments have been devised, analyzed, and published. The purpose of this review is to provide a current overview of bond strength testing methods and their applicability to the characterization of dental adhesives. Regardless of the method employed, subtle variations in sample preparation may already severely impact test results, usually necessitating at least co-testing of a well-known internal reference to allow conclusive interpretation. This article attempts to list and discuss the most influential parameters, such as substrate nature, age, health status, storage, clinically relevant pre-treatment, and sample preparation. Special attention is devoted to the last aspect, as numerous publications have stressed the tremendous influence of preparatory parameters on the validity and scope of obtained data. Added to the large variety of such factors, an equally large diversity of load-applying procedures exists to actually quantify adhesion between composites and dental hard substance. This article summarizes the basics of macro and micro approaches to shear and tensile bond strength testing, as well as push- and pull-out tests. The strengths and weaknesses inherent to each method and influential test parameters are reviewed and methods for accelerated sample aging and simulation of clinical conditions presented. Alternatively to shear or tensile bond strength tests, fracture toughness is introduced together with its application to dental adhesives and an overview of its physical background.
This study aimed at evaluating the post-root dentin push-out bond strength of circular and oval posts luted in oval-shaped canals with two different resin cements. Twenty extracted premolars with oval-shaped canals were selected, endodontically instrumented and obturated. The teeth were divided into two groups according to the drill used for post-space preparation and to the post shape (Ellipson oval tip + post and MTwoPF + DT Light-Post). Each group was then subdivided into two subgroups according to the cement (Gradia Core and Corecem Automix). The post-dentin bond strength was evaluated with the thin-slice push-out test. The bonded surface area was calculated for each post shape with an appropriate geometric formula in order to express the retentive strength in megapascal. Push-out strength data were analyzed with the Kruskal-Wallis ANOVA. The results showed that neither the drill-post system nor the cement significantly affected the push-out strength. The means (SD) of the push-out bond strengths in the experimental subgroups were the following: 11.79 MPa (4.77) for Gradia Core/Ellipson tip and post, 13.36 MPa (5.16) for Gradia Core/MtwoPF and DT Light-Post, 11.18 MPa (2.58) for Corecem Automix/Ellipson tip and post, and 10.91 MPa (3.89) for Corecem Automix/MtwoPF and DT Light-Post. In conclusion, circular and oval posts achieved similar retentive strengths in oval canals.
Tribology is the study of adhesion, friction, lubrication and wear of surfaces in relative motion. It remains as important today as it was in ancient times, arising in the fields of physics, chemistry, geology, biology and engineering. The more we learn about tribology the more complex it appears. Nevertheless, recent experiments coupled to theoretical modelling have made great advances in unifying apparently diverse phenomena and revealed many subtle and often non-intuitive aspects of matter in motion, which stem from the nonlinear nature of the problem.
Rubber exhibits unusual sliding friction. When rubber is slid on a hard, rough substrate, the surface asperities of the substrate exert oscillating forces on the rubber surface leading to energy “dissipation” via the internal friction of the rubber. I estimate this contribution to the friction force and compare the results with the experimental data of Grosch. Because of its low elastic modulus, the adhesion of the rubber to the substrate is very important. I show that the adhesion force will deform the rubber at the rubber–substrate interface, in such a manner that, at low sliding velocities, the rubber completely follows the short-wavelength surface roughness profile. This gives an additional contribution to the friction force, which is estimated and compared with experimental data.
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.
Adhesion between solid materials results from intermolecular interactions. The fracture resistance of an adhesive joint is, however, determined jointly by the mechanical deformation in the bulk material and the strength of the interfacial bond. The force needed to break an interfacial bond does not have a fixed value; it depends on the thermal state of the system and the rate at which the force is transmitted to the bond. The concomitant energy dissipation arising from the extension and the relaxation of the interfacial bonds contributes a significant resistance to fracture, which is clearly evident in elastomeric polymers. This issue of interfacial dissipation and its relationship to the length of the interfacial bridges and the rate of crack propagation are addressed with the kinetic theory of bond rupture in the tradition of the models developed by Eyring, Tobolsky, Zhurkov, Bueche, Schallamach, Kausch, and more recently, by Evans and Ritchie. Next, the method is extended to address the velocity-dependent sliding friction of elastomers against low energy solid surfaces. The theme of this article is to point out that certain aspects of adhesion, friction, and fracture may be described under a generalized framework of interfacial kinetics.
Adhesion and friction experiments were carried out with a variety of surfactant monolayer-coated surfaces using the surface forces apparatus technique. The equilibrium and time-dependent adhesion and the interfacial or'boundary friction of these surfaces were measured as a function of monolayer density and phase state, load, temperature, contact time, sliding speed, and relative humidity. The aim was to investigate the correlations between the friction and adhesion of these fairly ideal, molecularly smooth, and chemically homogeneous surfaces. The results show that friction and adhesion are not generally related if one only compares the magnitude of the friction force (or coefficient of friction) with the adhesion force (or adhesion energy). However, since friction is an energy-dissipating process, one might expect to find a relation between friction and adhesion hysteresis. This was confirmed by comparing the adhesion energy hysteresis during loading-unloading cycles with the friction forces measured under similar conditions. The authors find that -- in spite of its great complexity and dependence on many parameters -- the boundary friction force varies with temperature, sliding velocity, load, and relative humidity in highly systematic ways, which can be represented by a dynamic friction phase diagram. 53 refs., 17 figs., 1 tab.
The use of fiber-reinforced composite resin posts in endodontically treated teeth has increased. However, selecting an adhesive system that provides reliable and long-lasting bonding to root canal dentin remains difficult.
This study evaluated the microtensile bond strength of 2 adhesive systems to root dentin and 2 different fiber-reinforced composite resin posts.
Forty single-rooted teeth were instrumented, and root canals were prepared for translucent (Light Post [LP]) or opaque (Aestheti Post [AP]) quartz fiber-reinforced composite resin posts. Two adhesive systems were used: Scotchbond Multi-Purpose Plus (SBMP) (autopolymerized) as a control group, and Single Bond (SB) (photoactivated). Teeth were assigned to 4 groups (n=10): SBMP+LP, SBMP+AP, SB+LP, SB+AP. After post cementation, roots were perpendicularly sectioned into 1-mm-thick slices, which were trimmed to obtain dumbbell-shaped specimens. The specimens were divided into 3 regions: cervical (C), middle (M), and apical (A). To determine the bond strength, the bonding area of each specimen was calculated, and specimens were attached to a device to test microtensile strength at a crosshead speed of 1 mm/min. Data were analyzed using 3-way analysis of variance and the Tukey test (alpha=.05). Fractured specimens were examined under a x 25 stereomicroscope to determine the mode of fracture.
There were significant differences only among root dentin regions (P<.001). The cervical third (9.16 +/- 1.18 MPa) presented higher mean bond strength values, especially for SBMP. Middle and apical regions demonstrated lower values (7.08 +/- 0.92 and 7.31 +/- 0.60 MPa, respectively). Adhesive and post main factors did not demonstrate significance. Also, no interaction was significant. No cohesive fractures within resin cement, fiber-reinforced composite resin post, or root dentin were identified.
Both adhesive systems tested demonstrated reliable bonding when used with translucent and opaque fiber-reinforced composite posts.
The setting stress in composite resins was studied as a function of restoration shape. The shape is described by the configuration factor, C, the ratio of the restoration's bonded to unbonded (free) surfaces. In an experimental set-up, the shape of the restoration was simulated by cylindrical forms of various dimensions. The shrinkage stress was measured continuously. It was shown that in most of the clinically relevant cavity configurations, the stress-relieving flow is not sufficient to preserve adhesion to dentin by dentin-bonding agents.
Teeth, adhesively restored with resin-based materials, were modeled by 3D-finite elements analysis that showed a premature failure during polymerization shrinkage and occlusal loading.
Simulation of Class II MOD composite restorations with a resin bonding system revealed a complex biomechanical behavior arising from the simultaneous effects of polymerization shrinkage, composite stiffness and adhesive interface strain. Due to a polymerization contraction, shrinkage stress increases with the rigidity of the composites utilised in the restoration, while the cusp movements under occlusal loading are inversely proportional to the rigidity of the composites. The adhesive layer's strain also plays a relevant role in the attenuation of the polymerization and occlusal loading stresses.
The choice of an appropriately compliant adhesive layer, able to partially absorb the composite deformation, limits the intensity of the stress transmitted to the remaining natural tooth tissues. For adhesives and composites of different rigidities, FEM analysis allows the determination of the optimal adhesive layer thickness leading to maximum stress release while preserving the interface integrity. Application of a thin layer of a more flexible adhesive (lower elastic modulus) leads to the same stress relief as thick layers of less flexible adhesive (higher elastic modulus).
The restoration of endodontically treated teeth is a topic that is extensively studied and yet remains controversial from many perspectives. This article reviews the major pertinent literature on this topic, with an emphasis on major decision-making elements in post placement and restoration of endodontically treated teeth. Recommendations are made for treatment planning, materials, and clinical practices from restorative and endodontic perspectives.
To evaluate the resin-dentine interface of different adhesive systems and corresponding luting cements proposed for bonding fibre posts to root canal dentine.
Fifty extracted maxillary canines and central incisors were used. After root canal treatment the teeth were randomly divided into five groups of 10 teeth each. Fibre posts were inserted with five different adhesive systems and corresponding luting cements. Group 1: Clearfil Core/New Bond (Kuraray), group 2: Multilink (Vivadent), group 3: Panavia 21/ED Primer (Kuraray), group 4: PermaFlo DC (Ultradent), and group 5: Variolink II/Excite DSC (Vivadent). The primer was labelled in each case with 0.1% Rhodamine B isothiocyanate (RITC). Each root was sectioned into 2 mm thick slices at 1, 4 and 7 mm below the cementoenamel junction. The resin-dentine interface was evaluated using a Confocal Laser Scanning Microscope; the thickness of the hybrid layer and the number of resin tags were measured. The statistical analysis was performed using nonparametrical tests for comparisons between groups; for overall comparisons the Kruskal-Wallis test was used. Intraindividual analysis within teeth was performed using a linear model.
The thickness (microm) of the hybrid layer of group 1 (5.45; SD 1.21), group 4 (3.36; SD 1.59), and group 5 (4.33; SD 1.19) was significantly higher than in the other groups (P < or = 0.05). The number of resin tags observed in group 1 was significantly higher than in groups 2-4 (P < 0.05), but did not differ from group 5. Each group showed significantly more resin tags in the coronal and in the central part of the root canal than in the apical part (P < 0.001).
Conditioning of the root canal dentine with phosphoric acid and the use of one- and two-bottle-bonding systems gave a thicker and more uniform hybrid layer with considerably more resin tags than observed after the use of 'self-etching' adhesives. This might provide a more durable bond of the post to root canal dentine.
This study tested the null hypothesis that the use of dentin adhesives produces no improvement on the fixation of fiber posts with resin cements in endodontically treated teeth. Post spaces were prepared in 36 single-rooted root-filled teeth. Silanized glass fiber posts were cemented to the post spaces using a self-etch (ED primer/Panavia 21) and a total etch resin cement (Excite DSC/Variolink II), with or without the accompanying dentin adhesives. Fixation strengths and interfacial ultrastructure were evaluated using a "thin slice" push-out test and transmission electron microscopy. For both resin cements, the fixation strengths obtained from specimens luted with resin cement only did not differ significantly from those in which the intraradicular dentin was first bonded with a dentin adhesive. In the presence of incomplete smear layer removal and interfacial gaps, the dislocation resistance of bonded fiber posts was contributed largely by sliding friction.
Cavity configuration factor (C-factor) is the ratio of the bonded surface area in a cavity to the unbonded surface area. In a box-like class I cavity, there may be five times more bonded surface area than the unbonded surface area. During polymerization, the volume of monomers is reduced, which creates sufficient shrinkage stresses to debond the material from dentin, thereby decreasing retention and increasing leakage. The important variables influencing bonding adhesive root-filling materials to canals was examined using a truncated inverted cone model. C-factors in bonded root canals exhibit a negative correlation with sealer thickness. For a 20 mm-long canal prepared with a size 25 file, calculated C-factors ranged from 46 to 23,461 with decreasing sealer thickness (500-1 microm), compared to a C-factor of 32 when the canal was filled only with sealer. As the thickness of the adhesive is reduced, the volummetric shrinkage is reduced, which results in a reduction in shrinkage stress (S-factor). C-factors above 954 calculated with sealer thickness smaller than 25 microm are partially compensated by increases in bonding area and decreases in shrinkage volume. However, the interaction of these two geometrically related factors (C- and S-factors) predicts that bonding of adhesive root-filling materials to root canals is highly unfavorable when compared with indirect intracoronal restorations with a similar resin film thickness.
This study tested the hypothesis that hybridization of intraradicular dentin eliminates interfacial gaps, thereby improving the coronal seal and retention of teeth restored with fiber posts. Post spaces were bonded with two types of fiber posts, using the corresponding etch-and-rinse adhesives and dual-cured resin cements. Longitudinal sections of the interfaces were examined for dentin hybridization in the coronal- and middle-thirds of the root canals. Resin replicas of these sections were evaluated for interfacial gap formation. Although intraradicular dentin hybridization was not compromised irrespective of whether the adhesives were light-cured before cementation, the universal occurrence of interfacial gaps along the hybrid layer surface or the post-cement interface reflects the challenge in bonding to post spaces with low compliance and high C-factors. The clinical success associated with bonded fiber posts is probably due predominantly to frictional retention.
This study examined the contribution of hygroscopic expansion of glass-ionomer (GIC) and resin modified glass-ionomer (RMGIC) luting cements to the push-out resistance of fiber posts. Glass fiber posts were luted to post spaces using different cements. Experimental specimens were stored in water, while control specimens were desiccated and stored in mineral oil to eliminate water from intraradicular dentinal tubules and/or the external environment that could have contributed to hygroscopic expansion of the cements. Thin slice push-out tests revealed no difference in retention strengths of resin composite cements that were stored in water or oil. Conversely, GIC and RMGIC cements exhibited increased retention strengths after water sorption. As unfavorable cavity geometry is taxing to dentin bond integrity in root canals, a strategy that relies on increasing the frictional resistance to post dislodgement via delayed hygroscopic expansion of glass-ionomer based materials may be a more pragmatic approach to fiber post retention.
Forty extracted maxillary incisors were decoronated, prepared in a crown-down fashion and randomly divided into two groups of 16 roots each. Remaining roots served as controls. Smear layer was removed with 17% EDTA followed by 5.25% NaOCl, the canals in group N were again rinsed with NaOCl before obturation with laterally compacted gutta-percha and Roth's 801 sealer. The roots in group E were rinsed with 95% ethyl alcohol instead of NaOCl for the final rinse. Leakage was determined using a fluid-flow model. Roots were cleared, split, and sealer penetration into the dentinal tubules was measured under light-microscopy. Group E demonstrated significantly greater sealer penetration (p = 0.002) and significantly less leakage (p = 0.040), than group N. Leakage could not be significantly correlated with sealer penetration (p = 0.725). Under the conditions of this study, we found that a final rinse with 95% ethyl alcohol increased sealer penetration and decreased leakage.
The elastic modulus of the restorative material is important in restoring endodontically treated teeth. This study aimed to compare the fracture resistance and failure patterns of 90 mandibular molars restored using resin composites with or without fiber posts, with respect to the number of residual cavity walls. Five restoration types were performed corresponding to different wall defects (groups 1-5). Groups were divided in two subgroups corresponding to the use or absence of fiber posts. Teeth were loaded and resistance of specimens was measured as the axial compressive load to cause fracture and macroscopic fracture patterns were observed. One way ANOVA revealed a significant difference in fracture resistance (p < 0.001). Tukey post hoc test also revealed significant differences between groups as samples restored with fiber posts exhibited mostly restorable fractures. It was concluded that the resistance of endodontically treated mandibular molars restored with composite resins is mainly affected by the number of residual walls. Using fiber-reinforced posts optimized fracture patterns.
This study examined the contribution of testing time on the interfacial strengths of fiber posts to radicular dentin. Twenty-five fiber posts were luted to root segments with resin cements and a zinc phosphate cement. Immediately upon setting of the materials, the roots were sectioned into slices and randomly divided into two subgroups, depending on testing time (immediate vs. 24-hours), for push-out test. The results showed an improvement on the interfacial strength after 24 hours of storage. When data were pooled for each cement, the interfacial strengths (MPa) were: Optibond Solo Plus/Nexus: 10.3+/-3.8a; zinc phosphate cement: 10.1+/-2.7a; Multilink: 9.6+/-3.8ab; RelyX Unicem: 7.1+/-4.9bc; AllBond 2/Duolink: 6.7+/-3.5c (groups with same superscript letter were not statistically significant). It is concluded that bond strength can increase during the first 24 hours and that the interfacial strength is predominantly contributed by frictional retention.