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Implant splinting in mandibular overdentures: a systematic review with meta-analysis of randomized clinical trials
Abstract
Objectives:
To evaluate the influence of implant splinting on peri-implant marginal bone level and implant failures in completely edentulous patients who have been rehabilitated with mandibular implant overdentures.
Method and materials:
A literature search of electronic databases (PubMed and Cochrane Central Register of Controlled Trials [CENTRAL]) was performed, with the last search conducted in July 2019. Randomized controlled trials with at least a 12-month follow-up period were selected. The review and meta-analysis were performed in accordance with PRISMA guidelines. Two comparisons were included in the meta-analysis: (1) Two-implant supported ball versus two-implant supported bar mandibular overdenture; (2): Two- versus four-implant supported bar mandibular overdenture.
Results:
Six randomized controlled trials fulfilled the inclusion criteria and were included in a quality assessment and meta-analysis. Pooled data revealed a nonsignificant difference in marginal bone level (I2 = 0%; P = 1; mean difference = 0.00; 95% CI -0.37 to 0.37) and implant failures (P = .24; risk ratio = 6.07; 95% CI 0.30 to 121.33) when two-implant ball overdentures were compared to two-implant bar overdentures. Similarly, there was no significant difference in marginal bone level (I2 = 59%; P = .59; mean difference = -0.16; 95% CI -0.73 to 0.41) or implant failures (I2 = 0%; P = .36; risk ratio = 2.03; 95% CI 0.45 to 9.16) when two- versus four-implant bar overdentures were compared.
Conclusion:
Based on the findings of the meta-analysis, there is no influence of implant splinting on peri-implant marginal bone level and implant failures for completely edentulous patients rehabilitated with mandibular implant overdentures. However, this result should be interpreted with caution due to the limited number of analyzed studies, most of them considered at unclear risk of bias. Well-designed randomized controlled trials with follow-up periods of at least 5 years are highly recommended to establish evidence with regard to the influence of implant splinting on mandibular overdentures.
... Implant-supported overdentures incorporating splinted or nonsplinted attachment systems have been reported to be effective restorative options with high implant survival rates and patient satisfaction levels. [1][2][3][4] Bar attachments, although effective, come with drawbacks such as high cost, gingival hyperplasia, and encroachment on the prosthetic space. 5 Bar attachments require additional clinical and laboratory steps to achieve a passive fit. ...
... 8 Furthermore, it is important to achieve minimal divergence between the abutments to avoid excessive wear. 1,2 Despite the use of digital technologies in overdenture fabrication, certain issues still need to be addressed conventionally. This includes transferring the resin teeth to the metal framework, which requires accurate transfer using a silicone guide. ...
... Fixed implant-supported maxillary prostheses reduce the issues the patient encounters with removable complete dentures; they have high success rates, and increase the patient's self-esteem 3,4 . Furthermore, implant splinting a metal framework provides a firm connection for better stress distribution and stability for the overlying prosthesis; indeed, the incidence of implant failures in splinted implants supporting prostheses is lower than in non-splinted ones [5][6][7] . ...
... Moreover, because the beam is restricted to a small area, temperature fluctuations do not induce deformities or stress to implants or the surrounding structures. It has been reported that the laser-welded titanium approach displays superior passive fit, reducing the stresses on the implant-bone interface and resulting in less peri-implant bone resorption 7 . A recent systematic review revealed that the laser-welded framework has greater stress distribution properties than cast ones. ...
PURPOSE. To compare the clinical outcomes of electrically welded versus cast frameworks for screw-retained implant-supported maxillary prostheses.
MATERIALS AND METHODS. Twelve patients with edentulous maxillae received six implants each. After four months of unloaded healing, shaping abutments were connected to the implants on one randomly selected side, and titanium wire was bent and attached to the implants by intraoral electric welding (EWF). A cast metal framework (CMF) was constructed on the other side. The fit between the implant abutments and their respective prosthetic abutments was assessed at the framework try-in stage. Then, both cast and welded frameworks were picked up in the complete maxillary denture after modification. Patients were followed up to one year after loading. Outcome measures were: prosthesis and implant failures, complications, peri-implant bone loss, and passive prothesis fit.
RESULTS. No patient dropped out and no prosthesis or implant failed. CMF was associated with a higher rate of complications (P = 0.16); RD: -0.25; 95% CI: -0.60 to 0.10) than EWF, but the difference was not statistically significant. One year after loading, the CMF group had lost an average of 0.97±0.15 mm of peri-implant bone vs. 0.43±0.28 mm in the EWF group. This difference was statistically significant (mean difference = -0.54 mm, 95%CI -1.03, -0.31, P = 0.005). All 12 EWF prostheses were passive, while eight CMF (67.3%) prostheses were passive, and 4 were not (33.3%). The difference was statistically significant (P = 0.02; risk difference -0.33, CI 95% -0.05 to -0.61).
CONCLUSIONS. Electrically welded implant-supported framework could be a superior treatment option compared to conventional cast framework as it seems to be associated with less peri-implant bone loss and better passive prosthesis fit.
... 17 However, mechanical stress applied to implants during the healing period may result in micromotions at the implant-to-bone interface, thus interfering with the healing process. 18 Meta-analyses [19][20][21] and clinical studies 22,23 have compared splinted and unsplinted overdenture attachments. In addition, the effects of immediate and delayed loading protocols on peri-implant health have been analyzed. ...
... The authors are unaware of a previous NMA that summarized the available evidence regarding the effect of different overdenture attachments with delayed or immediate loading mandibular 2-implanteretained overdentures on peri-implant tissue health. From the present NMA, the null hypothesis that no difference in the MBL among different overdenture attachments with different loading protocols was accepted, a finding consistent with those of Leao et al, 19 Alqutaibi and Elawady, 21 Helmy et al, 45 and Kawai and Taylor. 24 The lack of difference in MBL among the different attachments could be attributed to the high bone density in the interforamina area together with the same biomechanical situation created by the 2-implant overdentures. ...
Statement of problem
A systematic review of the effect of different overdenture attachments with different loading protocols on peri-implant health is lacking.
Purpose
The purpose of this systematic review and network meta-analysis was to evaluate the effect of different overdenture attachments with delayed or immediately loaded 2-implant–retained mandibular overdentures on peri-implant tissue health.
Material and methods
A comprehensive search of the PubMed, EMBASE, and Cochrane library was conducted to identify eligible randomized controlled trials (RCTs). The outcomes were marginal bone loss, probing depth, plaque index, bleeding on probing, implant survival rate, and prosthetic complications. The Bayesian network meta-analysis accompanied by a random effect model and 95% credible intervals was calculated.
Results
Sixteen RCT (n=599 participants receiving 1198 dental implants) were included. Five common overdenture attachment systems with delayed or immediate loading were compared. The difference in marginal bone loss and probing depth was not statistically significant when comparing different overdenture attachments with different loading protocols. The rank probability test showed that bar+ immediate loading ranked highest (63.8%) in terms of marginal bone loss, whereas ball+ delayed loading (73.3%) ranked highest in terms of probing depth. The implant survival rate was 100% for the LOCATOR+ delayed loading, resilient telescopic+ delayed loading, and magnet+ immediate loading; however, bar+ delayed loading, ball+ delayed loading, magnet+ delayed loading, LOCATOR+ immediate loading, ball+ immediate loading, and bar+ immediate loading had survival rates of 99.1%, 98.8%, 96.0%, 94.7%, 93.1%, and 91.2%, respectively.
Conclusions
All types of overdenture attachment with immediate loading or delayed loading had a similar effect on peri-implant health. Bar+ immediate loading was associated with the least marginal bone loss, whereas ball+ delayed loading showed the least probing depth.
... According to Al Qutaibi et al. 2020 [48] meta-analysis comparing marginal bone loss in two versus fourimplants bars overdentures, no significant difference was detected in the marginal bone loss of the selected studies [5,38,49,50] between both groups. However, three [5,49,50] of the included articles had the same study using a round shaped bar with no distal extension and a mucosabar distance higher than 2 mm. ...
Different characteristics of bars (cross-sectional shape, diameter, distal extension etc.) lead to different biomechanical behavior (retention and stress) with implants and peri-implant tissues.
Aim: To evaluate the impact of implant-supported removable prostheses bar designs in fully edentulous arch (in the maxilla and/or mandibula), with 4 implants or more, on the peri-implant soft and hard tissues.
Two reviewers searched for observational studies, RCT and in vitro studies, published on five main databases and three from the grey literature, without restrictions on November 2023.
Of the 3049 selected articles, four met the inclusion criteria. Four RCT evaluated peri-implant health tissues in full edentulous arches with 4 or 6 implants rehabilitated with implant bar overdentures. One prospective study with 5 years follow-up evaluated the success/survival rate of implants and implant bar overdentures. Overall, 261 subjects were enrolled in our systematic review with 1176 implants. Overdentures’ survival rate was 100%. There was a trend that plaque indices and gingival indices were low in all of the studies, however no statistical analysis was done due to the lack of information.
Due to the lack of information in the included studies, we cannot confirm if bar characteristics affect the peri-implant tissues health.
... These issues, including problems with prosthesis retention, stability, and comfort, can significantly impact functional abilities such as speech, aesthetics, and chewing. Dental implants have revolutionized the treatment options for completely edentulous patients, providing solutions through either fixed [6][7][8] or removable implant-supported prostheses [9][10][11][12][13][14]. Even in cases where patients have systemic conditions [15,16] or require bone grafting prior to implant placement, dental implants have been shown to yield effective outcomes [17][18][19][20][21][22]. ...
The absence of teeth, known as edentulism, poses considerable obstacles in prosthodontic care and greatly affects a person's well-being. Conventional complete dentures frequently lead to problems like instability and insufficient retention, especially in the lower jaw. Fortunately, the introduction of dental implants has transformed the way we approach edentulous patients, as they now offer support and enhanced retention for removable prostheses, thus revolutionizing their treatment. While a consensus exists on using two implants for retaining mandibular overdentures, the associated cost may be prohibitive for economically disadvantaged individuals. As a solution, the concept of single implant-retained mandibular overdentures has emerged, catering to individuals with limited financial resources and complete tooth loss. This review explores the efficacy and suitability of the single implant overdenture approach, along with an overview of treatment options for edentulous patients, including traditional dentures, tooth-supported overdentures, and implant-supported overdentures. The preservation of bone, improvements in functional abilities, and psychological benefits associated with overdentures are discussed. Moreover, various classifications and prosthetic options for implant overdentures, specifically for mandibular cases, are presented. This literature review aims to provide a comprehensive understanding of possible treatment options and focus on the single implant-retained mandibular overdenture approach and its implications in prosthodontic rehabilitation for edentulous patients.
... Mandibular overdentures supported by two implants are well-known for their long-term effectiveness and are frequently recommended for the treatment of edentulous patients. Their relative simplicity, minimal invasiveness, good performance, and affordability make them an alternative treatment solution [3]. ...
... Es comúnmente aceptado que los implantes múltiples adyacentes en pacientes desdentados deben estar necesariamente unidos, por lo que la confección de una barra que los ferulice cuando se planifica una sobredentadura surge como una opción, más que obvia y necesaria ante tal preconcepto. Al respecto, es importante destacar que la evidencia es contundente al demostrar que no existe diferencia en el éxito a largo plazo de los implantes individuales frente a los ferulizados cuando se realizan sobredentaduras en maxilar inferior, aunque si en el superior 18,21 . ...
p>El aumento de la edad de la población y el número relevante de pacientes edéntulos obligan a pensar su tratamiento como una necesidad actual y progresiva. El uso de implantes dentales deviene en alternativas de tratamiento de probada eficacia. Las sobredentaduras como nueva alternativa terapéutica están indicadas siempre en la mandíbula, mientras en el maxilar superior solo si existen piezas dentarias viables en el maxilar inferior. Se buscó literatura relacionada con el tema planteado, para desarrollar esta revisión narrativa, con el fin de estudiar las bases que indican las sobredentaduras implantoasistidas en el paciente desdentado total. La literatura científica internacional sugiere que el tratamiento de un desdentado total con prótesis completa convencional inferior no es actualmente el tratamiento más adecuado. Existe evidencia científica significativa que soporta la elección a priori de una sobredentadura inferior soportada por dos implantes, es vista como primera opción de tratamiento en un desdentado total.</p
... Alquataibi et al. konnten im Rahmen einer systematischen Literaturübersicht bei Unterkieferdeckprothesen, die auf 1 oder 2 Implantaten verankert waren, nach einer Beobachtungszeit von 5 Jahren keinen Unterschied in der Überlebensrate der Implantate und der prothetischen Gesamtkonstruktion feststellen 8 . Weiterhin konnte bei der Verwendung von 2-4 Implantaten gezeigt werden, dass die Art der Verblockung der Implantate oder die Auswahl der Verankerungselemente (Stege, Locatoren, Kugelkopf, Magnete) keinen Einfluss auf den periimplantären Knochenabbau oder auf das Risiko des Implantatverlustes hatten 9 . ...
The use of CAD/CAM-fabricated elements in bar constructions for the retention of mandibular overdentures on 2 to 4 implants has increased over the last 10 years. An application of these constructions made from titanium or chromium-cobalt alloys has in the meantime been supported by several clinical studies with observational periods of up to 7 years. CAD/CAM fabrication leads to a decrease in technical complications. However, the manufacturers’ recommendations regarding the maximum length of extensions must be followed in order to avoid fractures. Sufficient retention of the overdenture by activatable or easy-to-replace retention elements is recommended in order to maintain long-term functioning of the restoration. Sufficient accessibility for home oral hygiene procedures must be considered from the start of treatment through bar fabrication to avoid peri-implant inflammation.
... The reason 4 bar was ranked the best and associated with the least MBL can be attributed to the splinting effect of the bar, which can evenly distribute the occlusal forces over a wide area on the four implants, resulting in an improvement in retention, stability, and masticatory efficiency [40]. According to a systematic review conducted by Alqutaibi et al. [53], the authors stated that no matter two or four dental implants along with bar attachment, no statistically significant differences were observed regarding MBL, which was in accordance with the results of our NMA. ...
Purpose: To evaluate the effect of overdenture (OD) attachment type and the number of implants supporting mandibular ODs on peri-implant health.
Study selection: From inception to October 2020, electronic databases (Medline/PubMed, Embase, Cochrane Library, and Scopus) were systematically searched. The outcomes of interest were marginal bone loss (MBL), pocket probing depth (PPD), plaque index, bleeding index, and implant survival rate. Bayesian network meta-analysis was performed using the GeMTC package supported by R. The weighted mean difference and 95% credible interval were estimated.
Results: Twenty-eight studies with a total of 1166 participants who received 2666 dental implants were included. Except for 4 bar and 4 telescopic, which showed a statistically lower MBL than the 2 locator, all other interventions showed insignificant differences in MBL (P > 0.05). The difference in periodontal probing depth was not statistically significant when comparing the different groups. The pooled implant survival rates of the different interventions ranged from 88.9% to 100%. The rank probability test showed that 4 bar and 4 telescopic had the lowest MBL, 2 magnet and 2 bar had the highest PI, whereas 4 locator showed the least PPD.
Conclusions: Except for 4 implants+bar, or telescopic, and 4 locator that, respectively, showed less MBL and PPD compared to some interventions, it seemed that different attachment types and number of implants supporting mandibular ODs have no clear superiority over the other in terms of peri-implant health outcomes.
... Alquataibi et al. konnten im Rahmen einer systematischen Literaturübersicht bei Unterkieferdeckprothesen, die auf 1 oder 2 Implantaten verankert waren, nach einer Beobachtungszeit von 5 Jahren keinen Unterschied in der Überlebensrate der Implantate und der prothetischen Gesamtkonstruktion feststellen 8 . Weiterhin konnte bei der Verwendung von 2-4 Implantaten gezeigt werden, dass die Art der Verblockung der Implantate oder die Auswahl der Verankerungselemente (Stege, Locatoren, Kugelkopf, Magnete) keinen Einfluss auf den periimplantären Knochenabbau oder auf das Risiko des Implantatverlustes hatten 9 . ...
Die CAD/CAM-Fertigung von Stegkonstruktionen zur Verankerung oder Retention von Unterkieferdeckprothesen auf 2–4 Implantaten hat in den letzten 10 Jahren zunehmend Verbreitung gefunden. Die Anwendung derartiger Konstruktionen aus Titan- oder Kobalt-Chrom-Legierungen ist mittlerweile durch mehrere klinische Studien mit einer Beobachtungszeit von bis zu 7 Jahren abgesichert. Durch die CAD/CAM-Fertigung ässt sich eine Reduktion technischer Komplikationen nachweisen. Dennoch sollten vor allem die Herstellerempfehlungen hinsichtlich der maximalen Länge von Extensionen
berücksichtigt werden, um Frakturen zu vermeiden. Zum langfristigen Funktionserhalt ist die ausreichende Retention der Deckprothese durch die Einbeziehung aktivierbarer oder einfach austauschbarer Retentionselemente zu empfehlen. Bei der Indikationsstellung und Ausführung von Stegkonstruktionen ist zur Vermeidung
periimplantärer Entzündungsprozesse eine ausreichende Zugänglichkeit für Maßnahmen der häuslichen Mundhygiene sicherzustellen.
Objective:
To estimate the prevalence of spin and completeness of reporting of systematic reviews with metanalysis (SRMAs) in implant dentistry.
Study design and setting:
Inclusion criteria were SRMAs of randomized clinical trials of implant dentistry on survival, success, or failure rates in humans, with no language restriction. Three databases were searched from inception to May 2021. Main outcomes were prevalence of spin (primary outcome) and completeness of reporting (secondary outcome) in abstracts and full texts.
Results:
We identified 2481 SRMAs and 45 unique manuscripts were included. There was a low presence of spin in the abstracts and full text, except for adverse events, in which 51.1% (in the abstract) failed to mention any adverse event for summarized interventions. There was an adequate report of SRMAs in the full text except for prospective register (33.3% not reported). However, there was an incomplete report for most items in the abstract considering PRISMA-A checklist.
Conclusion:
In general, the included SRMAs presented a (a) low prevalence of spin (except for adverse events in the abstract); (b) adequate completeness of reporting in the full text (except for prospective register); and (c) incomplete report for most items in the abstracts.
Purpose:
To compare prosthesis and implant failures and marginal bone loss (MBL) resulting from submerged vs nonsubmerged dental implant protocols.
Materials and methods:
Electronic and manual searches of two databases (MEDLINE [PubMed] and Cochrane) were conducted to identify randomized controlled trials (RCTs) comparing submerged to nonsubmerged dental implant protocols. Data were independently extracted by two reviewers, and meta-analyses were performed for the included RCTs. The Cochrane Risk of Bias tool was used to assess the quality of included studies.
Results:
Eight RCTs were identified, and six were included. Four of the included studies were considered to be at high risk of bias, one at unclear risk, and one at low risk. The meta-analysis for studies reporting MBL revealed significantly more bone loss around submerged implants (I2 = 0%, P = .04; mean difference: 0.12; 95% confidence interval: 0.00, 0.24); however, there were no differences in implant or prosthesis failures between the two interventions.
Conclusion:
Two conclusions were made: (1) There were no differences between the two interventions regarding implant or prosthesis failures, and (2) submerged implants exhibited statistically significantly more MBL, but this difference was not clinically relevant. These conclusions should be interpreted with caution, since the present review is underpowered and the included RCTs were considered to be at high risk of bias.
The aim of this study was to compare implant failure and radiographic bone level changes with different loading protocols for unsplinted two-implant-supported mandibular overdentures. An electronic search of two databases (PubMed, Cochrane Library) was performed, without language restriction, to identify randomized controlled trials (RCTs) comparing immediate or early versus conventional dental implant loading protocols for unsplinted two-implant-supported mandibular overdentures. Data were extracted independently by two reviewers. The Cochrane tool was used to assess the quality of included studies. A meta-analysis was performed. Eight RCTs were identified, seven of which were included; one trial was excluded because related outcomes were not measured. Four of the seven studies were considered to have a high risk of bias and three an unclear risk. Meta-analysis revealed no difference between immediate versus conventional or early versus conventional implant loading protocols regarding implant failure (risk difference (RD) -0.02, 95% confidence interval (CI) -0.13 to 0.10; RD 0.09, 95% CI -0.03 to 0.20) or marginal bone loss (mean difference (MD) 0.09, 95% CI -0.10 to 0.28; MD -0.05, 95% CI -0.12 to 0.02) for implants supporting mandibular overdentures. These findings should be interpreted with great caution given the serious numerical limitations of the studies included.
Purpose:
To compare prosthesis and implant failure, patient satisfaction, prosthetic complications and peri-implant marginal bone loss of mandibular overdentures (IOD) supported by a single or two implants.
Materials and methods:
Manual and electronic database (PubMed and Cochrane) searches were performed to identify randomised controlled trials, without language restriction, comparing single vs two implant supported mandibular overdentures. Two investigators extracted data independently. The Cochrane tool was used for assessing the quality of included studies. Meta-analyses were performed for the included RCTs.
Results:
Six publications corresponding to four RCTs were identified. Three RCTs (corresponding to five publications) were included and one trial was excluded. Follow-ups in function were 1, 3 and 5 years after loading. All included studies were considered to be at a high risk of bias. The pooled result revealed more prosthesis failures at overdentures supported by two implants at 1 year (three trials) (P = 0.02; Risk Difference: -0.12, 95% CI: -0.22, -0.02), however, there were non-significant differences at 3 years (two trials) (P = 0.22; Risk Difference: -0.32, 95% CI: -0.83, 0.19) and at 5 years (one trial) (P = 0.95; Risk Difference: 0.01, 95% CI: -0.22, 0.24). Regarding implant failures, there were more implant losses in overdentures supported by two implants at 1 year (three trials) (P = 0.02; Risk Difference: -0.12, 95% CI: -0.22, -0.02) and at 5 years (one trial) (P = 0.95; Risk Difference: -0.15, 95% CI: -0.28, -0.02), however, there were non-significant difference at 3 years (two trials) (P = 0.2; Risk Difference: -0.33, 95% CI: -0.84, 0.18). After 5 years in function, meta-analyses revealed that there were non-significant differences regarding overall prosthetic complications when mandibular overdentures supported by a single implant were compared with overdentures supported by two implants (P = 0.43; RD: 0.04, 95% CI: -0.06, 0.15).
Conclusion:
Mandibular overdentures retained by a single implant have comparable results to those retained by two implants. However, this should be interpreted with caution as all the included studies were considered at a high risk of bias.
The objective was to evaluate and compare single- and two-implant retained overdentures for the rehabilitation of the edentulous mandible. Fifty-six edentulous subjects were eligible for inclusion. Using a random sampling system, a single implant or two implants were placed in the mandible. After 3 months, locator attachments were connected to the implants and the denture delivered with the retentive components incorporated in the denture base. Implant failure and muscle activity were evaluated at the 3-, 6-, and 12-month follow-up examinations. The study sample comprised 56 patients (32 male, 24 female), with a mean age of 58.2 years. A total of 84 implants were placed (28 in the single-implant group and 56 in the two-implant group). All patients completed the 12 months of follow-up. No significant differences were found between subjects in the two groups with respect to implant failure. With regard to improvements in muscle activity, the two-implant group showed statistically significant but perhaps not clinically important differences. Single-implant mandibular overdentures may be suggested as an alternative treatment modality for the rehabilitation of edentulous patients who cannot afford the cost of a two-implant overdenture.
The aim of the present study was to evaluate the periimplant conditions and the maintenance requirements for implant-supported overdentures in the mandible retained with ball or bar attachments during a 5-year period.
Twenty-six completely edentulous patients had two Astra Tech dental implants placed in the anterior part of the mandible. The denture attachment system for the patients was chosen randomly by drawing lots. Eleven patients drew the bar attachment system and fifteen patients drew the ball attachment system. Plaque Index, Gingival Index, and probing pocket depth were assessed around each implant. Periotest values were recorded, and periodically identical intraoral radiographs were obtained with a specially designed film-holding device.
No implants were lost from baseline to the 5-year registration. The periimplant conditions were very healthy after 5 years. No significant differences of the periimplant variables were recorded between the bar and the ball groups. During the first year of function, significantly more complications/repairs were registered in the bar group than in the ball group. In the following years, no significant differences were registered. The mean frequency of complications/repairs per patient per year was 1.0 in the bar group and 0.6 in the ball group during the 5-year observation period.
Two implants with ball or bar attachment supported an overdenture in the mandible for 5 years with a 100% survival rate. No differences in marginal bone loss or health of the periimplant mucosa were observed between bar and ball attachment, but the frequency of technical complications/repairs per patient was higher around bar than ball attachments.
Two treatment concepts for implant-supported bar retention of mandibular overdentures-2 intramobile cylinder (IMZ) implants and a Dolder bar and 4 titanium plasma-sprayed (TPS) screw implants and an angulated bar-were compared in a randomized controlled clinical trial with respect to postprosthetic efficacy and safety.
Four hundred twenty-five patients with edentulous mandibles were enrolled; 212 were randomized to TPS implants (control group) and 213 to IMZ implants (test group). Endpoints were occurrences of postprosthetic integration deficiency (ID), functional deficiency (FD), and complications. The trial was sized to detect a 10% difference in 5-year ID-free postprosthetic system lifetime with a power of 80%.
With 340 protocol-completed cases, the trial achieved its predetermined power. The 2 systems did not show statistically significant differences in occurrences of postprosthetic ID and FD; 5-year occurrence-free postprosthetic system lifetime probabilities were estimated as 42.5% with IMZ and 42.8% with TPS, for ID; and as 82.6% with IMZ and 87.2% with TPS, for FD. However, at 3 to 6 months after surgery, mean Periotest values were significantly higher (P = .0001 without adjustment) with IMZ implants (5.6, SD 4.2) than with TPS implants (0.8, SD 4.3). TPS implants showed a higher incidence of inflammation and recession, while IMZ implants had a higher incidence of implant fracture after functional loading.
The system-wise approach overcomes potential bias with implant-wise analyses. A combination of radiographic and clinical criteria distinguishes between desirable integration and functional anchorage. The in situ survival rates at 5 years in this study (95% for IMZ, 92% for TPS) match rates reported in the literature.
This study demonstrated equivalent efficacy of 2 IMZ cylinders and 4 TPS screws in implant-supported, bar-retained mandibular overdentures and indicated a higher rate of complications with the TPS screw implants.
The type of attachment that is used in oral rehabilitation by means of implant-retained mandibular overdentures may influence the retention and the stability of the denture. In this study, we examined the hypothesis that a better retention and stability of the denture improve the oral function. Eighteen edentulous subjects received 2 permucosal implants, a new denture, and, successively, 3 suprastructure modalities. Maximum bite force and electrical activity of the masseter and temporalis muscles were measured. The maximum bite force nearly doubled after treatment for each of the 3 attachments. However, the average bite force after treatment was still only two-thirds of the value obtained for dentate subjects. No large differences in maximum bite force and muscle activity were found among the 3 attachment types. Temporalis activity was significantly lower than masseter activity when subjects clenched without implant support. There was no difference in activity when subjects clenched with implant support.
Article Title and Bibliographic Information
What is the optimal number of implants for removable reconstructions? A systematic review on implant-supported overdentures. Roccuzzo M, Bonino F, Gaudioso L, Zwahlen M, Meijer HJ. Clin Oral Implant Res 2012;23.s6:229-37.
Type of Study/Design
Systematic review with meta-analysis of data
Background: Different attachment systems for mandibular two-implant overdentures could influence levels of patient satisfaction. Positive consensus of the majority of patients being satisfied does not preclude the possibility of dissatisfaction for some.
Purpose: To evaluate patient satisfaction before and after 5 years of wearing mandibular two-implant overdentures using different attachment systems.
Materials and Methods: A total of 106 edentulous participants enrolled in a clinical trial completed a preliminary self-report inventory of their original complete denture complaints. New complete maxillary dentures and mandibular two-implant overdentures were provided to each participant using one of six different attachment systems. Patient satisfaction was determined at pretreatment; at baseline with mandibular two-implant overdenture insertion; and then annually for 5 years, using visual analogue and Likert-type scales.
Results: Patient satisfaction with mandibular two-implant overdentures at baseline was significantly improved in all domains compared to pretreatment (old dentures) and sustained up to the 5-year recall. The level of satisfaction with Straumann gold alloy matrices at 5 years was significantly lower than that with other attachment systems. Highly significant differences were found with some social and psychological aspects by the fifth year compared to baseline. Diagnostic and prognostic indicators from a pretreatment inventory identified 12 participants (13.5%) who were dissatisfied. These indicators revealed a maladaptive predisposition to mandibular two-implant overdentures.
Conclusions: A mandibular two-implant overdenture (opposing a conventional complete maxillary denture) will improve patient satisfaction, regardless of the attachment system. Careful evaluation of pretreatment complaints with conventional dentures can possibly identify patient dissatisfaction with mandibular two-implant overdentures.
In a randomized controlled clinical trial carried out at the Ignatius teaching hospital in Breda, The Netherlands, I10 edentulous patients with severe mandibular bone loss were treated with implants of the ITI® Dental Implant System using 3 different treatment strategies: a mandibular overdenture supported by either 2 implants with ball attachments, 2 implants with an interconliecting bar, or by 4 interconnected implants. In this study, results of clinical and radiographic parameters were evaluated and compared over a period of 19 months after implant placement. A total of 283 ITP Dental Implants were placed. Six implants (2%) were lost during the osseointegration period. No further implant losses occurred after that, At the 19 month evaluation mean values and standard deviations for bleeding index were 0.51±0.5 (bleeding incidence=70%) and for plaque index they were 0.46±0.5 (plaque incidence=45%). The mean values and standard deviations for probing depth and loss of attachment were 2.7±1.1 mm and 0.26±O.6 mm respectively. The radiographic evaluation showed a mean bone loss of 1.5 mm± 0.26 after 19 months for all the implants. In cases with 4 interconnected implants there was significantly more bone loss around the central 2 implants (2.1±0.31 mm) in comparison with the lateral 2 (1.4±0.25 mm). No significant correlations were found between plaque and bleeding indices and bone loss.
Purpose: The aim of this study was to compare the retention characteristics of various overdenture attachment systems commonly used to retain overdentures to dental implants.
Materials and Methods: An edentulous mandibular model was constructed incorporating 2 parallel 4.0 mm × 13 mm Branemark implants placed in the canine regions. Attachments were embedded in a metal-reinforced experimental overdenture designed to be dislodged from the model by a universal testing machine. Tensile dislodging force was applied to the overdenture at a cross-head speed of 50 mm/min. Five overdentures were constructed for each of the attachment systems. The attachments evaluated were the Hader bar & metal clip, Locator LR pink, Locator LR white, Spheroflex ball, Shiner magnet, Maxi magnet, Magnedisc magnet, ERA white, and ERA gray. Each apparatus was tested with 5 specimens per attachment system. Peak load-to-dislodgement was measured. Analysis of variance and Scheffé multiple comparison tests were applied to the data with α≤ 0.05 level of significance.
Results: Peak load-to-dislodgement for all attachment systems ranged from 3.68 ± 1.32 N to 35.24 ± 1.99 N. Strain-at-dislodgement, calculated from stress-strain curves, ranged from 0.78 ± 0.20% to 2.78 ± 0.5%. The ERA gray attachment demonstrated the greatest retention, with a peak load-to-dislodgement of 35.24 ± 1.99 N, and a relatively low strain-at-dislodgement of 1.64 ± 0.09%. Less retention was recorded for the Locator LR white, Spheroflex ball, Hader bar & metal clip, and ERA white systems. The Locator LR pink attachment demonstrated still less retention with a load-to-dislodgement of 12.33 ± 1.28 N. Significantly high strain-at-dislodgement was recorded for the Hader bar & metal clip and Locator nylon attachment systems. The lowest dislodging loads and strains were recorded for the Shiner magnet, Maxi magnet, and Magnedisc magnet attachments.
Conclusions: Results suggest that the attachment systems evaluated may be grouped into high (ERA gray), medium (Locator LR white, Spheroflex ball, Hader bar & metal clip, ERA white), low (Locator LR pink), and very low (Shiner magnet, Maxi magnet, Magnedisc magnet) retention characteristics.
The McGill consensus statement on overdentures (14) was published following a symposium held at McGill University in Montreal, Canada in 2002. A panel of relevant experts in the field stated that: The evidence currently available suggests that the restoration of the edentulous mandible with a conventional denture is no longer the most appropriate first choice prosthodontic treatment. There is now overwhelming evidence that a two-implant overdenture should become the first choice of treatment for the edentulous mandible (14). In 2009, a further consensus statement was released as a support and follow-up to the McGill consensus statement. This report was jointly created by members of the BSSPD (British Society for the Study of Prosthetic Dentistry) Council and the panel of presenters at the BSSPD conference in York, UK in April 2009 (15). This report also highlighted that since the McGill statement in 2002, uptake by dentists of implant technology for complete denture wearers has been slow. The York statement concluded that 'a substantial body of evidence is now available demonstrating that patients' satisfaction and quality of life with ISOD mandibular overdentures is significantly greater than for conventional dentures. Much of this data comes from randomised controlled trials (15). Whilst it is accepted that the two-implant overdenture is not the gold standard of implant therapy it is the minimum standard that should be sufficient for most people, taking into account performance, patient satisfaction, cost and clinical time.
Mandibular implant overdentures provide improved treatment outcome than conventional denture therapy, but there is controversy as to which overdenture treatment is the best choice.
This study evaluated 3 different mandibular implant overdenture treatments with respect to prosthesis retention and stability, tissue response, patient satisfaction and preference, and complications to determine treatment outcomes.
In a prospective, randomized clinical trial, using a crossover design, 30 subjects (mean age, 58.9; 63% male) received 4 implants in the anterior mandible. For each subject, 3 different overdenture attachment types were fabricated and/or fitted to the implants. These included a 4-implant bar attachment fitted to all 4 implants, a 2-implant bar attachment, and 2 independent ball attachments. Subjects were randomly assigned to 1 of 6 possible treatment sequences and received all 3 attachment types each for approximately 1 year. Data were collected at baseline, and at 6 and 12 months for treatment types. Denture retention and stability and parameters of soft tissue response were recorded. Complications were documented and questionnaires were used to identify subject masticatory ability, denture complaints, and preferences. Data were analyzed to determine statistical equivalence among the 3 different treatments using the Schuirmann's two one-sided test (TOST) procedure, and the Wilcoxon-Mann-Whitney TOST procedure (α=.05).
Force gauge prosthesis retention measurements showed that the 3 treatment types were not statistically equivalent, with the 4-implant bar demonstrating the greatest retention. Criterion-based retention scores were statistically equivalent for all treatments. Both the force gauge and criterion-based prosthesis stability measurements were statistically equivalent among all 3 treatment types. Analysis of all other multiple criterion-based scoring systems indicated the majority of these variables demonstrated equivalence. Where equivalence was not identified, the most favorable responses were typically found with the O-ring treatment, and the least favorable with the 4-implant bar treatment. From the small percentage of treatment visits demonstrating minor complications, no single treatment presented with greater complications than the others. For the treatment preference among subjects, 52% selected the independent ball attachment, 32% the 4-implant bar, and 16% the 2-implant bar (P=.10).
The 2-implant independent treatment used in this study provided equivalent or more favorable treatment outcomes for most measured parameters relative to the more complex and costly 2- and 4-implant bar attachments. The 4-implant bar treatment provided greater prosthesis retention than the other treatment types in this study, but after experience with all systems, subjects were more satisfied with and preferred the independent implant treatment.
The aim of the study was to compare the differences in the long-term clinical and radiologic effects for three different treatment strategies with implant-supported overdentures in the edentulous mandible, with a special emphasis on smoking.
In a randomized- controlled clinical trial, 110 edentulous patients participated. Thirty-six patients were treated with an overdenture supported by two implants with ball attachments (2IBA), 37 patients with an overdenture supported by two implants with a bar (2ISB) and 37 patients with an overdenture supported by four implants with a triple bar (4ITB). After a mean evaluation period of 8.3 years, the clinical and radiographic parameters were evaluated.
Ninety-four out of the original 110 patients (=85%) were evaluated. In the 2IBA group, the plaque index was significantly lower (vs. 2ISB, P=0.013; vs. 4ITB, P=0.001) than in the other groups, but there was no correlation with the other peri-implant parameters. In the 4ITB group, the marginal bone loss was significantly higher than that in the two implant groups. The maximal probing depth was correlated with peri-implant bone loss (P=0.011). Smoking almost doubled marginal bone loss irrespective of the treatment strategy chosen.
Patients with two implants show less marginal bone loss than those with four implants. Smoking is a risk factor for the survival of dental implants in the long run.
The use of two implants for mandibular overdenture stabilization improves the patients' comfort and well-being. This treatment could be more cost-effective if surgery and prosthetic treatment could be performed by one clinician in the normal setting of a dental clinic.
The aim of this retrospective clinical study was to describe implant success, restorative outcome, and the patients' opinion of mandibular overdenture treatment on two early-loaded, nonsplinted Astra Tech TiOblast Microthread (Astra Tech Dental, Mölndal, Sweden) implants.
Thirty-seven consecutive patients treated with implant-supported mandibular overdentures were invited for a clinical examination. Implant survival, marginal bone level, quality of implant and prosthetic treatment, and the patients' opinion by means of questionnaires were scored.
Thirty-four patients attended the examination. Two implants were lost in one patient and the failure rate for the total group of patients was 3%. As 8 of the 33 remaining patients were still in the provisional loading stage, they were not included in the final clinical and radiographic examination. Based on 25 patients and 50 implants with a mean follow-up of 18.8 months (range 4-33), implant positioning and occlusion/articulation scored perfect in 74 to 80% of the cases. Retention of the dentures was rated perfect in 80%, but 20% needed minor activation of the attachments, 20% showed signs of abrasion, and 20% had already been repaired. The average marginal bone level was 0.8 mm below the reference point. The mean pocket depth was 2.1 mm, and 54% of the peri-implant tissues were free of bleeding. The patients were appreciative of the work carried out by their dentist and they indicated a significant improvement in their well-being and quality of life.
It can be concluded that the Astra Tech implant system was successfully used by the general dentist both surgically and prosthetically with minimal implant failures and prosthetic complications and that this led to high levels of patient appreciation and overall satisfaction.
The objective of this systematic review was to assess the influence of splinted and unsplinted oral implants in the mandibular and maxillary implant-supported overdenture therapy, concerning the implant survival, the peri-implant parameters, the prosthetic complications and the patient satisfaction. An electronic MEDLINE search complemented by manual searching was conducted to identify randomized clinical trials, prospective and retrospective cohort studies on implant-supported overdentures with a mean follow-up of at least 3 years. Twelve studies from an initial yield of 1022 titles were finally selected and data were extracted. After an observation period of more than 3 years, there was no difference in implant survival rates between splinted and unsplinted design. From most of the investigations included in this study, it was mentioned that the unsplinted design needs more prosthetic maintenance. In more of the studies that were dealing with the satisfaction of the patients wearing implant-supported overdentures, no significant difference in the preference of the patients was reported. No significant difference in the peri-implant outcome between splinted and unsplinted design was found. Within the limits of this systematic review, it is concluded that there was no significant difference between the two different designs of implant-supported overdentures with respect to the soft tissue health status or patient satisfaction, although the bar-supported overdentures have been shown to need less prosthetic maintenance.
The aim of this study was to evaluate the effect of treatment with either two or four mandibular endosseous implants with an overdenture on mandibular posterior residual ridge resorption over a 10-year period.
Sixty edentulous patients with residual mandibular height between 12 and 18 mm participated. Thirty patients were treated with an overdenture supported by two IMZ implants (group A) and 30 patients were treated with an overdenture with four IMZ implants (group B). Before treatment and 10 years after treatment, panoramic radiographs were taken and compared to ascertain possible bone loss. Proportional area measurements were used to determine changes in the mandibular posterior residual ridge bilaterally.
There was a statistically significant difference in mandibular posterior residual ridge resorption between the two treatment protocols. The posterior bone area index was reduced by a mean of 10% for group A and 6% for group B over 10 years.
There was a significant difference in mandibular posterior residual ridge resorption between patients treated with either two or four implants to stabilize an overdenture. No correlation was shown between mandibular posterior residual ridge resorption and peri-implant marginal bone loss. The confounding factors of marginal bone loss around the implants, age, gender, initial mandibular height, and the number of years the patient had been edentulous failed to show a significant effect on posterior ridge resorption.
The aim of this 10-year clinical trial was to evaluate the treatment outcome (condition of hard and soft peri-implant tissues, patient satisfaction, surgical and prosthetic aftercare) of mandibular overdentures supported by two or four implants.
Sixty edentulous patients with a mandibular height between 12 and 18 mm participated. Thirty patients were treated with an overdenture supported by two IMZ implants (group A) and 30 patients were treated with an overdenture supported by four IMZ implants (group B). Standardised clinical and radiographic parameters were evaluated 6 weeks after completion of the prosthetic treatment and after 1, 5 and 10 years of functional loading. Prosthetic and surgical aftercare was scored during the evaluation period, as well as patient satisfaction.
There were no statistically significant differences with regard to any of the studied clinical or radiographic parameters of the peri-implant tissues between the groups. In addition, no differences in satisfaction and aftercare were observed between the groups.
There is no difference in the clinical and radiographical state of patients treated with an overdenture on two or four implants during a 10-year evaluation period. Patients of both groups were evenly satisfied with their overdentures and received the same amount of aftercare. For reasons of cost-effectiveness, a two-implant overdenture is advised for patients with a Cawood classes IV-VI resorption of the mandible and complaints concerning retention and stability of the lower denture.
This study presents data related to 136 patients who were treated with 300 implants in the edentulous mandible anterior to the mental foramina. Two implant systems were used: the titanium plasma-sprayed screw implant (TPS) and the intramobile cylinder implant (IMZ) in three different modifications. The longest observation time was 11 years, with a mean of 5.7 years. Patients were recalled for regular clinical examinations once every 6 months. After prosthesis placement, only a few implant losses were recorded, although critical states could be found according to periodontal standards. This led to the definition of success criteria according to clinically tolerable bone loss or pocket-probing depths. The 5-year survival rate considering the implant loss was greater than 90% for all implant systems and was lowest for the new type IMZ 3.3. Selecting a vertical bone loss of 4 mm or more as failure criterion reduced the survival rates, which then ranged from 83% to 97% (according to the implant system) for the 5-year interval. The mean annual bone-level change was identified individually for each implant using a linear-regression model.
In the past, fixed prostheses were believed to be more efficient implant-supported devices than removable types for edentulous patients. However, this hypothesis was never properly tested. Therefore, a within-subject crossover clinical trial was designed in which 145 completely edentulous subjects were tested wearing implant-supported mandibular fixed prostheses and long-bar overdentures. Eight subjects received the fixed appliance first and seven the removable type. The patients' perceptions of various characteristics of the implant-supported prostheses were measured after a minimum of two months' adaptation. Mandibular movements and jaw muscle electromyographic activity were recorded while the patients chewed five standard-sized test foods: bread, apple, hard cheese, sausage, and raw carrot. The prostheses were then changed, worn for the same period of adaptation, and the procedures repeated. There were three test sessions per prosthesis, and each included five trials per food. The measurements were repeated three times at one-week intervals. Mastication time was found to be shorter for three foods (bread, cheese, and sausage) when subjects wore the long-bar overdenture. The vertical amplitude of the masticatory strokes was significantly less with the overdenture for all foods except carrot. Cycle duration was significantly longer with the overdenture for sausage and carrot. Contrary to what might be expected, the long-bar overdenture appears to be no less efficient than the fixed prosthesis. Furthermore, these data suggest that patients are capable of adapting their masticatory movements to the characteristics of the two prostheses.
In a randomized controlled clinical trial 110 edentulous patients with severe mandibular bone loss have been treated with ITI-dental implants using three different treatment strategies: (1) a mandibular overdenture supported by two implants with ball attachments, (2) two implants with an interconnecting bar or (3) by four interconnected implants. As implant surgery involves elevation of the mucoperiosteum, bone remodelling at the implant site and insertion of implants close to the mental foramen, altered sensations of the mental nerve caused by the surgery are to be expected. An altered sensation of the lower lip can also be caused by pressure of an ill-fitting lower denture on the mental foramen, or in the case of severe bone loss of the alveolar ridge, on the alveolar nerve itself. This article presents the results of the patients' perception of the sensation of their lower lip before, 10 days after and 16 months after implant surgery in the mandible. It shows that 25% of the patients describe a sensory disturbance before treatment. This 25% also showed high scores on the Hopkins Symptoms Check List indicating a tendency to somatize complaints. Eleven percent of the patients report a sensory disturbance in the lower lip 10 days after surgery. Ten percent report a sensory disturbance 16 months after surgery of which one third also reported a disturbance before the treatment. This implies the risk of a sensory disturbance of the lower lip to be a possible complication after implant surgery. Therefore patients must be informed about this phenomenon before treatment.
The aim of this study was to evaluate the clinical function and long-term prognosis of overdentures retained by a small number of implants in the maxilla and mandible using one of two different attachment systems. Included in the study were all patients referred to specialty clinics in Jönköping and Linköping, Sweden, during the treatment period who needed an overdenture and could be provided with a minimum number of two bilaterally-placed implants. Excluded were patients with bone-grafted jaws, irradiated cancer patients, heavy bruxers, and patients who had lost a fixed prosthesis because of implant losses. The patients were randomly assigned to receive one retentive system, either a round 2-mm-diameter bar with clips or ball attachments (Nobel Biocare). Eighteen overdentures were placed in maxillae and 32 in mandibles, supported by a total of 115 Brånemark implants. Of the implants placed, 86.1% were continuously osseointegrated. The cumulative implant survival rates after 7 years of loading were 75.4% in the maxillae and 100% in the mandibles. There was no difference in implant survival rate between the attachment systems. Patients with implant losses were characterized by severely resorbed maxillary ridges and inferior bone quality, together with unfavorable loading circumstances such as short implants combined with long leverages. Complications and prosthetic adjustments were mostly resolved early and easily.
The aim of this prospective study was to evaluate the effect of the number of implants supporting a mandibular overdenture on the condition of the peri-implant tissues. Sixty edentulous patients (Cawood class V VI) participated in this study. After randomization, thirty patients were treated with an overdenture supported by two IMZ implants (group A) and thirty patients with an overdenture on four IMZ implants (group B). The implants were inserted in the anterior region of the mandible. After three months overdentures were constructed, supported by round bar and clip attachments. A standardized clinical and radiographic evaluation was performed 0, 6 and 12 months after insertion of the denture. One implant was lost (group A) during the healing period. There were no significant differences with regard to any of the studied clinical or radiographic parameters of the peri-implant tissues, neither were significant differences found between the lateral and central implants in group B. None of the patients reported a sensory change in lip or chin region. From this study it is concluded that there seems to be no need to insert more than two endosteal implants to support an overdenture, however, long-term prospective studies are needed to support this notion.
Prosthetic outcome and patient satisfaction were evaluated in order to investigate whether there is a need or advantage to splint two implants in the mandible retaining a hinging overdenture. This study included 36 fully edentulous patients randomly divided into three groups according to the attachment system they received: magnets, ball attachments or straight bars (reference group). None of the implants failed during the whole observation period in any of the groups. After 5 years of observation, the Bar group presented the highest retention capacity and the least prosthetic complications but revealed more mucositis and gingival hyperplasia. Patient satisfaction rated similar for all groups although the Magnet group showed lower retention forces. All patients would repeat the same treatment even though the majority of the Magnet group would prefer a more retentive solution because of limited denture stability.
Sixteen edentulous subjects participated in a within-subject crossover clinical trial to test the hypotheses that a long-bar overdenture attached to 4 implants gives greater patient satisfaction and masticatory efficiency than a two-implant hybrid overdenture. All subjects were given a new maxillary conventional denture. Ten received mandibular long-bar overdentures first and six the hybrid overdentures. Two months later, psychometric assessments and functional tests were repeated 3 times at one-week intervals. The mandibular prosthesis was then changed, and recordings were repeated after another 2 months. Mandibular movements and electromyographic activity of jaw muscles were recorded while subjects chewed standard-sized pieces of 5 foods: bread, cheese, apple, sausage, and carrot. Measurements included masticatory time, cleaning time (the time between the end of mastication and the last swallow), and duration and amplitude of masticatory cycles and phases. Multilevel analyses were performed. No significant differences in masticatory time were found between prostheses for any test food. However, cleaning time for carrot [estimated mean of difference (delta) +/- SE: 1.6 sec +/- 0.7] and bread (delta = 1.0 sec +/- 0.4) was slightly but significantly longer for subjects wearing long-bar overdentures. Cycle duration was longer with the long-bar overdenture only for subjects chewing carrot. The opening phase was shorter and the closing phase longer with the long-bar overdenture for almost all test foods. Vertical amplitude was significantly less with the long-bar overdenture for cheese (delta = -2.6 mm +/- 1.1), apple (delta = -2.6 mm +/- 1.0), and sausage (delta = -2.9 mm +/- 1.3). These results suggest that mastication with the 2 prostheses is equally efficient, although clearance of some foods from the mouth is longer with the long-bar overdentures. They also indicate that patients adapt their masticatory movements to the characteristics of different prostheses.
In this study, the effect of various materials used in fabricating superstructures for implant-retained fixed partial dentures on stress distribution around implant tissues was investigated. Five different mathematical models consisting of 11,361 nodes and 54,598 elements were constructed to study porcelain, gold alloy, composite resin, reinforced composite resin, and acrylic resin veneering materials using the 3-dimensional finite element analysis method. MARC K7.2/Mentat 3.2 software was used for the analysis. Reference points were determined on the cortical bone, where perpendicular, oblique, and horizontal forces were applied. Stress values created by oblique and horizontal forces appeared to be higher than those created by vertical forces. Stress seemed to be concentrated at the cortical bone around the cervical region of the implant. Gold alloy and porcelain produced the highest stress values in this region. Stresses created by acrylic resin and reinforced composite resin were 25% and 15% less, respectively, than porcelain or gold alloy. Porcelain and gold alloy produced stress values at the lingual implant sites that reached the ultimate strength values of the cortical bone.
The purpose of this retrospective study was to evaluate the clinical performance of and patients' satisfaction with maxillary overdentures retained by splinted and unsplinted implants. Patients who had been treated with maxillary implant-retained overdentures because of functional problems with conventional complete dentures were identified and invited to participate in the study. A total of 16 patients fulfilled the enrollment criteria and agreed to participate. Eleven patients were treated with bar-retained overdentures with 3 to 6 clips (mean follow-up 32 months), and 5 patients wore overdentures retained by 2 to 6 ball attachments (mean follow-up 54 months). All subjects were satisfied with their prostheses, and most subjects experienced improvement in their oral function after treatment with implant-retained overdentures. At the time of clinical examination, 92% (n = 77) of the 84 implants placed were functioning satisfactorily. The cumulative survival rate for the implants after 72 months was 90%. Loss of bone support correlated with peri-implant probing depth (r = 0.29; P < .02). No differences in mean bone loss between the subjects with ball-retained or bar-retained overdentures were found. The presence of plaque or peri-implant bleeding was not associated with the type of attachment.
The implant-retained overdenture for the mandible has been shown to be a highly successful prosthetic treatment similar to the fixed implant denture. However, controversy persists as to its design and indications. Few literature reviews have been published on the topic. This article critically analyzes the existing mandibular implant overdenture literature relative to bone preservation, effect on antagonist jaw, number of implants required, anchorage systems, maintenance, and patient satisfaction. A MEDLINE search was completed (from 1987 to 2001), along with a manual search, to locate relevant English-language articles on mandibular implant overdentures. Twelve treatment concepts are elucidated from a distillation of the literature review.
The aim of this study was to evaluate the prosthetic complications with implant-supported overdentures in the maxilla.
Forty-one patients (mean age 61 years) were consecutively admitted for treatment from 1991 to 1998. A total of 173 ITI implants were placed. Four to six implants either connected with a bar (34 overdentures) or with single anchors (seven overdentures) supported the denture, and only a few parties had fewer than four implants. The overdentures had a horseshoe design and were reinforced by a cast-metal framework. The mean observation time was 3.2 years. Oral hygiene and periimplant parameters were regularly assessed, and records were kept of prosthetic maintenance service. All prosthetic complications encountered were classified related to (1) implant components and anchorage devices, (2) mechanical and structural failures of dentures, or (3) denture-related adjustments.
Three implants did not osseointegrate, and five implants were lost after loading. Thus, the overall survival rate of the implants was 95.5%. Altogether, 85 prosthetic complications were encountered. The most frequent finding was retightening of the bar screw and adjustments of the bar retainers. Repair of dentures was not frequent and was mostly related to broken teeth. No fracture of dentures was observed. Renewal of dentures occurred twice, once after loss of all implants in one patient. Thirty-nine overdentures had been continuously worn; thus, the overall denture stability was 95%. Mucosal irritation and need for occlusal adjustment were the most frequent findings in the first year. Over time, a decrease of complications was observed.
Planned maxillary overdentures supported by implants are a successful treatment modality on a short-term basis.
The aim of this 5-year longitudinal study was to investigate the influence of the retention mechanism for overdenture fixation on the periimplant parameters of mandibular implants.
Ninety edentulous patients, each with two interforaminal implants supporting an overdenture, participated in the study. They had received either a straight or slightly bent round clip bar, a U-shaped rigid bar with or without distal extensions, or single-ball anchors. Anatomic-morphologic and prosthetic variables were assessed related to the implant position and the type of overdenture retention. The degree of mandibular atrophy was determined using cephalometric radiographs. The angle beta between the virtual axis connecting both implants and the mandibular hinge axis was measured on mounted casts. A supporting surface was identified between bent clip bars and U-shaped extension bars. Clinical periimplant parameters were recorded, and changes of the probing attachment level after 5 years were analyzed in 70 patients with respect to the retention device and anatomic-morphologic and prosthetic variables.
A significant increase of the Plaque Index was observed after 5 years. The mean clinical attachment loss after 5 years was about 0.2 mm. In more than 50%, beta was small, i.e., < or = 5 degrees. For these implants, loss of clinical attachment was significantly lower. The correlation between attachment loss and beta was weak, while no significant correlation was found with regard to the degree of atrophy and surface.
In view of the long observation period, it was concluded that the position and retention mechanism of mandibular implants supporting an overdenture have little influence on the long-term stability of the clinical parameters.
The aim of the present study was to compare the peri-implant soft tissue health status of implants supporting overdentures with bar attachments or ball attachments in the mandible, as well as patient satisfaction with these attachment types.
The study included a Dolder bar group with 18 cases (43 implants) and a ball attachment group with 18 cases (51 implants). The mean function period in the Dolder bar group was 49 months (range: 12 to 72 months) and in the ball attachment group, the mean was 23 months (range: 12 to 40 months). Implants were clinically evaluated by using a modified plaque index (mPI), modified sulcus bleeding index (mSBI), and probing depths. Patient satisfaction with the treatment was recorded using a questionnaire.
mPI, probing depth, and mSBI did not statistically differ between groups (Mann-Whitney U test, P > 0.05). Patient satisfaction was similar with both retentive systems.
Within the limits of this study, we concluded that there was no significant difference between the 2 attachment types used for implant-supported overdentures with respect to the soft tissue health status or patient satisfaction.
This clinical trial tested the null hypothesis that there would be no difference in prosthetic maintenance for two-implant mandibular overdentures retained by either a bar-clip mechanism or ball attachments. Prosthetic outcomes are reported over 3 years using a six-field protocol.
One hundred edentulous participants received new maxillary complete dentures and a mandibular two-implant overdenture (IOD), with random assignment to either a bar and metal clip or two ball attachments (titanium alloy matrix and spring) for retention. Eighty-seven subjects were available for follow-up after 3 years.
Almost three times as many bar-clip dentures (63%) were rated successful compared to the ball attachment design. Two percent of the participants in each group died over the course of the study, while 15% of the bar-clip and 8% of the ball IOD subjects were lost to follow-up. More than three times as many ball attachment IODs (60%) required retreatment in the form of excessive repairs, and twice as many of the ball attachment design (8%) required replacement. The ball attachment IOD was significantly more likely to require patrix tightening or matrix replacement, while the bar-clip design was more likely to require activation of the matrix.
Using the criteria of a six-field protocol for implant overdenture outcomes, the bar-clip IOD was a significantly more successful prosthesis, requiring less maintenance than the titanium alloy matrix and spring ball attachment IOD employed in this study. The null hypothesis was therefore defeated.
Studies have shown that mandibular implant overdentures significantly increase satisfaction and quality of life of edentulous elders. Improved chewing ability appears to have a positive impact on nutritional state. Therefore, it is important to determine the best design of this prosthesis over the long term. In this randomized controlled trial, three groups of edentulous participants with atrophic mandibles wore 3 types of implant overdentures. During an eight-year follow-up, only seven of the 110 participants had dropped out of this study. Almost all participants were still satisfied with their overdentures. Participant satisfaction concerning retention and stability of the mandibular overdenture had decreased significantly in the two-implant ball attachment group, whereas the opinion of participants in the single- and triple-bar groups was still at the same level. The long-term results suggest that a mandibular overdenture retained by 2 implants with a single bar may be the best treatment strategy for edentulous people with atrophic ridges.
This randomized controlled clinical trial aimed to evaluate the efficacy of splinted implants versus unsplinted implants in overdenture therapy over a 10-year period.
The study sample comprised 36 completely edentulous patients, 17 men and 19 women (mean age 63.7 years). In each patient, 2 implants (Brånemark System, Nobel Biocare, Göteborg, Sweden) were placed in the interforaminal area. Three to 5 months after placement, they were connected to standard abutments. The patients were then rehabilitated with ball-retained overdentures, magnet-retained overdentures, or bar-retained overdentures (the control group). Patients were followed for 4, 12, 60, and 120 months post-abutment connection. Group means as well as linear regression models were fitted with attachment type and time as classification variables and corrected for simultaneous testing (Tukey).
After 10 years, 9 patients had died and 1 was severely ill. Over 10 years, no implants failed. Mean Plaque Index, Bleeding Index, change in attachment level, Periotest values, and marginal bone level at the end of the follow-up period were not significantly different among the groups.
The annual marginal bone loss, excluding the first months of remodeling, was comparable with that found around healthy natural teeth.
The fact that no implants failed and that overall marginal bone loss after the first year of bone remodeling was limited suggested that implants in a 2-implant mandibular overdenture concept have an excellent prognosis in this patient population, irrespective of the attachment system used.
Few prospective trials of implant-retained mandibular dentures have evaluated the increase and duration of patient satisfaction, costs of denture maintenance in relation to different methods of attaching overdentures to implants, or the use of a reinforced framework.
This report evaluates subjects' satisfaction and prosthodontic maintenance during a 3-year randomized clinical trial of implant-retained mandibular complete dentures, whether reinforced or not with a cast framework, and attached by bar-clip or 2.25-mm ball-spring matrices to endosteal dental implants.
One hundred edentulous subjects, each having at least 1 year's experience with conventional complete dentures, were selected from respondents to a university dental clinic's request for volunteers. Candidates were examined to verify adequate mandibular bone and medical suitability for implants. Subjects then received 2 implants in the anterior mandible before being stratified by mandibular bone height and gender and assigned randomly to 1 of 4 treatment groups. Every subject received a new maxillary complete denture in addition to an implant-supported mandibular complete denture, with or without a reinforcing framework, connected to implants by either a bar-clip or a ball-spring patrix and matrix. The dentures were adjusted and repaired as needed. Subjects indicated on a visual analogue scale (VAS) satisfaction with conventional dentures prior to the study and then with new dentures at 1 month, 1 year, and 2 years. The results reported here are from the first 68 subjects observed for 3 years after receiving new dentures (19 subjects received new dentures less than 3 years before this analysis, and another 13 subjects were lost to follow-up). VAS scores are presented in simple tables and graphs, and results for different groups were compared using 2-sided nonparametric rank tests and repeated measures ANOVA. With respect to costs and maintenance, t tests were used to compare group means. Sample size and other design considerations used a .05 significance level.
After receiving new dentures with mandibular implant supports, improved satisfaction "within subject" was prompt, durable, substantial, and statistically significant, regardless of the attachment mechanism, and with or without a reinforcing framework. In contrast, there were no notable satisfaction differences between the 2 attachment mechanisms, or with the presence or absence of a reinforcing framework, either at specific intervals after receiving the new dentures, or in repeated measures ANOVA. For both attachment groups, most denture adjustments occurred during the first year. This accounted for 81% of total adjustments during 3 years, when the 34 subjects in the ball-spring group and the 34 in the bar-clip group were combined. The mean numbers of adjustments per subject and associated clinical times did not differ significantly between the 2 groups. Conversely, denture repairs declined more slowly than adjustments. Almost all repairs (90%) occurred in the ball-spring group to correct problems with the attachments, 39% in the first year, and tapering off only slightly in the following 2 years. Over 3 years of follow-up, mean numbers of repairs per subject differed significantly between groups: 6.7 repairs per person in the ball-spring group, compared to 0.8 in the bar-clip group ( P<.001), and mean time per appointment was greater for repairs in the ball-spring group: 18.9 minutes compared to 16.9 ( P<.01). The cast framework had no influence on the satisfaction expressed or on adjustments and repairs.
Subjects were very satisfied with the new dentures, although the ball-spring attachment tested in this trial required substantially more repairs.
The aim of this 5-year prospective comparative study was to evaluate treatment outcome (survival rate, condition of hard and soft peri-implant tissues, patient satisfaction, prosthetic and surgical aftercare) of mandibular overdentures supported by two or four implants.
Sixty edentulous patients with a mandibular height between 12 and 18 mm participated. Thirty patients were treated with an overdenture supported by two IMZ implants (group A) and 30 patients were treated with an overdenture supported by four IMZ implants (group B). Standardised clinical and radiographic parameters were evaluated 6 weeks after completion of the prosthetic treatment and after 1, 2, 3, 4 and 5 years of functional loading. Prosthetic and surgical aftercare was scored during the evaluation period.
One implant was lost (group A) during the healing period. There were no significant differences with regard to any of the studied clinical or radiographic parameters of the peri-implant tissues between the groups. None of the patients reported sensory disturbances in the lip or chin region. No differences in satisfaction were observed between the groups. With regard to aftercare, there was a tendency of a greater need of prosthetic interventions in group A, while correction of soft-tissue problems was restricted to patients of group B.
There is no difference in clinical and radiographical state of patients treated with an overdenture on two or four implants during a 5-year evaluation period. Patients of both groups were as satisfied with their overdentures.
Mandibular implant overdentures increase satisfaction and the quality of life of edentulous individuals. Long-term aftercare and costs may depend on the type of overdentures. One hundred and ten individuals received one of 3 types of implant-retained overdentures, randomly assigned, and were evaluated with respect to aftercare and costs. The follow-up time was 8 years, with only seven drop-outs. No significant differences (Kruskal-Wallis test) were observed for direct costs of aftercare (p = 0.94). The initial costs constituted 75% of the total costs and were significantly higher in the group with a bar on 4 implants, compared with the group with a bar on 2 implants and the group with ball attachments on 2 implants (p = 0.018). The last group needed a significantly higher number of prosthodontist-patient aftercare contacts, mostly for re-adjustment of the retentive system. It can be concluded that an overdenture with a bar on 2 implants might be the most efficient in the long term.
Clinical, microbiologic, and immunologic comparisons of the peri-implant health in edentulous volunteers wearing long-standing implant-supported ball- or Dolder bar-retained mandibular overdentures were performed.
Ten age- and gender-matched individuals (mean age, 71 years) with either ball- or bar-retained complete mandibular overdentures, scheduled for an annual implant recall examination, were investigated an average of 7 years after implant placement. Plaque and gingival crevicular fluid samples were obtained from the peri-implant sulcus. The groups were compared with regard to peri-implant probing depth; plaque and bleeding on probing scores; sulcular fluid flow rates; implant stability measurements (Periotest device); relative concentrations of Actinobacillus actinomycetemcomitans, Prevotella intermedia, Fusobacterium nucleatum, Porphyromonas gingivalis, Tannerella forsythensis, and Treponema denticola assessed by polymerase chain reaction analysis; and sulcular concentrations of interleukin-1beta and prostaglandin E2, assessed by enzyme-linked immunosorbent assay.
No statistically significant differences were found for any of the examined parameters between both study groups.
Within the limitations of this study, both ball attachments and Dolder bars can be recommended for overdenture retention, with either one showing satisfying clinical, microbiologic, and immunologic findings in the peri-implant tissues after several years of service in healthy recall patients with good oral hygiene habits.