Material effects on the long-term survival and complication rate of cemented implant-supported single crowns: A retrospective clinical study.

Statement of problem: Despite high survival rates of implant-supported single crowns, retention loss remains common and decementation of crowns can compromise long-term stability, patient satisfaction, and treatment costs. Limited long-term evidence on cement type, abutment design, and materials requires further research to optimize clinical outcomes.

Purpose: The aim of this retrospective clinical study was to analyze the survival and decementation rates of zirconia and metal-ceramic implant-supported crowns in combination with different abutments (prefabricated or custom and unabraded or airborne-particle abraded).

Material and methods: A total of 639 implant-supported single crowns placed in 395 patients (mean age: 67.2 years; 195 men) were evaluated for up to 18 years. The frameworks were made from Au alloys (n=153) or zirconia (n=486) and were cemented with glass-ionomer cement (GIC) (n=568) or eugenol-free interim cement (n=71). A total of 416 crowns were cemented on prefabricated abutments and 223 on custom abutments. Of the abutments, 445 were unabraded, while 194 were airborne-particle abraded before cementation. The variables crown framework, abutment type, abutments surface treatment, and cement type were analyzed using Kaplan-Meier analysis, log-rank tests, and Cox regression analysis (α=.05).

Results: A total of 18 crowns failed and required replacement because of veneer chipping (n=9), abutment loosening (n=3), or implant loss (n=6). In addition to the failures, 38 crown decementations were documented. The decementation rate for airborne-particle abraded abutments after 18 years was 10% while unabraded abutments showed a 5% risk of decementation (P=.252). Prefabricated abutments showed a higher decementation rate of 8% after 10 years compared to custom abutments (2%, P=.031). For zirconia single crowns, the decementation rate was significantly lower at 4% compared to Au frameworks at 14% (P=.011). The type of cement had a significant influence: interim cement led to a decementation rate of 25%, while glass-ionomer cement only led to a loss of retention in 3.5% of the crowns (P<.001).

Conclusions: Zirconia crowns can be successfully used with glass-ionomer cement in the long term. Interim cements cannot be recommended because of the high decementation rate.