This review assessed the 5- and 10-year survival and complication rates of implant-supported fixed partial dentures (FPDs). The authors concluded that survival rates for FPDs were high but biological and technical complications were common, and that more long-term studies are required. This was generally a well-conducted review and the authors' conclusions are likely to be reliable.

To assess the 5- and 10-year survival and complication rates of implant-supported fixed partial dentures (FPDs).

MEDLINE was searched from 1966 to April 2004 for studies published in English in the dental literature; the search terms were reported. The bibliographies of related reviews and identified full-text articles were also screened. Eight named relevant dental journals were searched (2001 to 2003).

Study designs of evaluations included in the review

In the absence of randomised controlled trials, prospective and retrospective cohort studies with a mean follow-up period of at least 5 years were eligible for inclusion. The included studies had follow-up times of either an average of 5 years (range: 1 to 14) or 10 years (range: 7 to 16).

Specific interventions included in the review

Studies of any type of implant-supported FPD were included. Studies using FPDs and single crowns had to use FPDs in at least two thirds of cases. The included studies used five different commercially available implant systems (details were reported). Most of the FPDs (90%) were retained by screws and most studies using bridges were of metal ceramic design FPDs; others were of gold-acrylic design.

Participants included in the review

Inclusion criteria were not specified in terms of the participants. The patients in the included studies were aged from 15 to 86 years.

Outcomes assessed in the review

The studies had to clinically examine all patients at follow-up. Studies that assessed outcomes using patient records, questionnaires or interviews were excluded. The review assessed survival of implant, survival of FPD, success, biological (peri-implantitis and soft tissue) complications and technical complications. Survival was defined as FPD still in situ with or without modification during follow-up, while success was defined as FPD free of all complications during follow-up. The outcomes were assessed at 5 and 10 years.

How were decisions on the relevance of primary studies made?

Two reviewers independently selected studies and any disagreements were resolved through discussion. Inter-reviewer agreement was assessed.

The authors did not state that they assessed validity, but they did extract data on drop-outs.

Two reviewers independently extracted the data using a data extraction form. Any disagreements were resolved through consensus. For each study, the numbers of events were extracted and the total exposure time calculated using various methods (details reported). The reviewers then estimated survival, success and complication rates, with 95% confidence intervals (CIs), after 5 and 10 years. Survival and success outcomes were calculated on a per-implant basis. For complications, the patient was the unit of analysis.

How were the studies combined?

Pooled 5- and 10-year event rates were calculated using a Poisson regression model, and 95% CIs were calculated from robust standard errors. Random-effects models were used where significant heterogeneity (P<0.05) was found. Survival proportions were calculated assuming constant event rates.

How were differences between studies investigated?

Heterogeneity was tested using the Spearman goodness-of-fit statistic. Multivariable Poisson regression was used to assess the influence of study design (retrospective or prospective), year of publication (1990 or before versus 2000 and after) and veneer material (ceramic versus gold-acrylic).

Twenty-one studies with sixteen different cohorts (five reported results separately for 5- and 10-year follow-up) were included (n=1,123 patients, with 1,336 FPDs supported by 3,578 oral implants). There were 16 prospective and 5 retrospective studies.

Implant survival.

Estimated survival at 5 years was 95.4% (95% CI: 93.9, 96.5; based on 15 studies). This was calculated from the pooled implant failure rate from a random-effects model as significant heterogeneity was found (P=0.0007). There was no significant difference in implant failure rates between prospective and retrospective studies (P=0.64). More recent studies had significantly lower failure rates than studies published before 2000 (failure rate 48% lower, P=0.006). Survival at 10 years was 92.8% (95% CI: 90, 94.8; based on 6 studies). No significant heterogeneity was found (P=0.081).

FPD survival.

Estimated survival at 5 years was 95% (95% CI: 92.2, 96.8; based on 14 studies with 1,289 FPDs). This was calculated from the pooled implant failure rate from a random-effects model as significant heterogeneity was found (P<0.0001). Significantly more metal ceramic FPDs survived compared with gold-acrylic FPDs (96.6% versus 90.4%, P=0.014). Survival at 10 years was 86.7% (95% CI: 82.8, 89.8; based on 3 studies with 219 FPDs). Statistically significant heterogeneity was found (P=0.035).

Success.

Estimated success (FPD with no complications) at 5 years was 61.3% (95% CI: 55.3, 66.8; based on 4 studies with 266 patients). No significant heterogeneity was found (P=0.12).

Biological complications.

The estimated cumulative biological complication rate at 5 years was 8.6% (95% CI: 5.1, 14.1; based on 9 studies with 751 FPDs). Significant heterogeneity was found (P<0.0001) and a random-effects model was used.

Technical complications.

The most common technical complication was fracture of a veneer, with an estimated rate at 5 years of 13.2% (95% CI: 8.3, 20.6). The next most common technical complications were due to loss of screw access (8.2% of anchors at 5 years), abutments or occlusal screw loosening (5.8% at 5 years), fracture of abutments and occlusal screws (1.5% at 5 years and 2.5% at 10 years), and fracture of luting cement (2.9% at 5 years and 16% at 10 years). Fractures of implants were rare (0.4% at 5 years and 1.8% at 10 years).

Survival rates for FPDs were high, but biological and technical complications were common. More studies with long-term follow-up (at least 10 years) are required.

The review addressed a clear question in terms of the intervention, outcomes and study design, although criteria were only explicit for study design. The search of one electronic database was supplemented by handsearches of several relevant journals. However, limiting the search to English language publications might have resulted in the omission of some relevant studies and raises the possibility of language bias. No attempts were made to locate unpublished studies, thus raising the possibility of publication bias. Methods were used to minimise errors and bias in the study selection and data extraction processes. Validity was not formally assessed, although the authors stated that they used stringent inclusion criteria to ensure that only studies with a clinical follow-up examination were included.

The studies were combined using a meta-analysis, with random-effects models used when there was statistically significant heterogeneity. However, forest plots were only presented for two outcomes; for other outcomes (e.g. complications) there appeared to be considerable variation between studies, therefore summarising the data by meta-analysis might not have been appropriate. Survival was calculated from the estimated implant failure rates in each study, but it was not reported whether any of the studies had actually reported survival; this would have been useful information to include alongside the authors' calculations. Some potential reasons for heterogeneity were examined, including if the study was retrospective or prospective in design. However, overall, this was a well-conducted review and the authors' conclusions are likely to be reliable.

Practice: The authors did not state any implications for practice.

Research: The authors stated that there is a need for long-term (at least 10 years), prospective cohort studies of implant-supported FPDs that report complete follow-up information. They stated that authors should report the following: implant survival in combination with incidence rates for complications; implant loss prior to loading and during function; use of well-defined criteria for biological and technical complications; frequency distributions for clinical and radiographic assessments; clinical assessments including pocket probing depth, clinical attachment level and bleeding on probing; and major, medium and minor technical complications, as well as the time and cost of repair.

Clinical Research Foundation for the Promotion of Oral Health.

1. Tan K, Pjetursson BE, Lang NP, Chin ES. Systematic review of the survival and complication rates of fixed partial dentures (FPDs) after an observation period of at least 5 years - III. Conventional FPDs. Clin Oral Impl Res 2004;15:654-66. 2. Pjetursson BE, Tan K, Lang NP, Bragger U, Egger M, Zwahlen M. A systematic review of the survival and complication rates of fixed partial dentures (FPDs) after an observation period of at least 5 years - IV: cantilever or extension FPDs. Clin Oral Impl Res 2004;15:667-76. 3. Lang NP, Pjetursson BE, Tan K, Bragger U, Egger M, Zwahlen M. A systematic review of the survival and complication rates of fixed partial dentures (FPDs) after an observation period of at least 5 years - II: combined tooth-implant-supported FPDs. Clin Oral Impl Res 2004;15:643-53.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.