Jennifer Kuracina D.D.S.
Implant-supported single crowns demonstrate high survival rates at 5 and 10 years, but technical, biological and esthetic complications can arise.
An update that includes longer-term evidence (at least five years) than that included in a 2006 systematic review  suggests that single missing teeth restored with implant-supported crowns demonstrate high survival, but biological, technical and esthetic complications may affect treatment success.
What are the 5- and 10-year survival rates of single crowns on implants in adults? What is the incidence of complications associated with this restoration?
The authors searched one database for clinical studies involving at least 10 patients published between 2006 and 2011 that reported survival data for implant-supported single crowns (SC) with a mean follow-up of at least 5 years. They hand searched relevant systematic reviews and references of all included studies, and included 24 studies from a previous systematic review . The authors considered inclusion of randomized controlled trials (RCTs), controlled clinical trials, prospective case series, cohort studies and retrospective studies in English or German. Two authors independently selected articles based on title and abstract and obtained, in full text, those articles agreed on by both authors. They resolved disagreements by discussion and calculated Cohen's Kappa-coefficient to assess agreement, which was 0.88 ± 0.87. Studies needed to demonstrate clinical follow-up, and details about the restoration needed to be provided. The authors excluded studies that did not meet all inclusion criteria. Three authors selected studies based on inclusion criteria and extracted additional data about implant type, reconstruction material, methods of fixation, follow up, implant and crown survival, complications, and esthetic outcome. They calculated 5- and 10-year failure and complication rates, and related event rates with reconstruction material or fixation method using used multivariable Poisson regression.
Forty- six studies met all inclusion criteria. Twenty-seven studies were prospective evaluating survival of 1,436 implants, while 19 were retrospective (1,758 implants); all were published between 1996 and 2012. When considered together, the studies evaluated a total of 3,223 implants from 10 commercially available implant systems. Patients were treated at universities, specialist clinics, or in private practice. The authors used meta-analysis to calculate 5-year implant survival as 97.2 percent (95 percent CI: 96.3-97.9 percent). At 10 years, implant survival was 95.2 percent (95 percent CI: 91.8-97.2 percent.) Five-year SC survival was 96.3 percent (95 percent CI: 94.2-97.6 percent), and 10-years SC survival was 89.4 percent (95 percent CI: 82.8-93.6 percent). Complication rates were calculated at 5 years. Soft tissue complications occurred at a rate of 7.1 percent (95 percent CI: 4.4-11.3 percent) and bone loss >2mm at 5.2 percent (95 percent CI: 3.1-8.6 percent.) The esthetic complication rate was 7.1 percent (95 percent CI: 3.6-13.6 percent.) The most reported technical complications were screw loosening at 8.8 percent (95 percent CI: 5.1-15.0 percent,) cement failure at 4.1 percent (95 percent CI: 2.2-7.5 percent,) and fracture of veneering material at 3.5 percent (95 percent CI: 2.4-5.2 percent.)
The outcomes of the meta-analyses in this review demonstrate high survival rates for both single-tooth implants and crowns over 5 and 10 years, but not without complications.
Source of Funding:
Authors reported no conflict of interest.
Importance and Context:
Using implants to replace single missing teeth has become mainstream; therefore, it is important to know how the prognosis of this restoration compares with conventional treatment with fixed dental prostheses (FDPs). A previous systematic review examined the survival of SCs on implants after 5 years in function, analyzing studies published up to 2006 . Reviewing longer-term studies that are more current provides us with clearer evidence on which to base treatment decisions.
Strengths and Weaknesses of the Systematic Review:
The authors used only one electronic database to select studies, and hand searched related reviews for references. They clearly identified inclusion criteria. Independent reviewers selected studies, and agreement was statistically evaluated. The authors listed included and excluded studies and stated reasons for exclusion. They extracted data from selected papers by multiple reviewers and reviewed them for consistency. They did not, however, discuss risk of bias in studies. Heterogeneity of the results was noted and managed statistically.
Strengths and Weaknesses of the Evidence:
The 5-year evidence for implant survival is based on 35 studies, with 23 being prospective in nature. The authors did not find any RCTs. Evidence for 5-year SC survival is more limited, based on 20 studies of which 14 were prospective. The 10-year data for implant and SC survival is limited, based on 10 and seven studies, respectively. Biological complications are reported inconsistently. Strong heterogeneity exists in the esthetic outcome data, partly due to non-standardized evaluation criteria. Technical failure rates may be skewed by changes in implant and abutment design over time. Older data associated with designs infrequently used today may be less relevant.
Implications for Dental Practice:
This review is an update of an earlier systematic review and presents stronger evidence for the 5-year survival of SCs on implants. Design improvements in implants and prosthetic components may explain the trend in improved survival rates in the more current literature. The limited 10-year data implies this treatment modality to be comparable in survival to conventional FDPs, whose survival rate approaches 90 percent according to another systematic review. This review demonstrated the need for evaluating biological and esthetic complications based on standardized criteria. An accurate assessment of these complications is important, as they detract from the patient-oriented outcome of restoration success.
1. Jung RE, Pjetursson BE, Glauser R, et al. A systematic review of the 5-year survival and complication rates of implant-supported single crowns. Clin Oral Implants Res 2008; 19(2):119-30
2. Tan K, Pjetursson BE, Lang NP, Chan ES. A systematic review of the survival and complication rates of fixed partial dentures (FPDs) after an observation period of at least 5 years. Clin Oral Implants Res 2004; 15(6): 654-66.