An up to thirty-year retrospective study on the success and survival of single unit and splinted implant-supported crowns in a dental school setting

Statement of problem

Studies investigating the survival of implant-supported crowns provided in a dental school setting are sparse.

Purpose

The purpose of this retrospective study was to evaluate the success and reasons for failure of single unit and splinted implant-supported crowns provided in a dental school.

Material and methods

Using the axiUm dental management software program and paper charts, all single unit and splinted implant-supported crowns provided between September 1989 and January 2020 were included for evaluation. Success, survival, and failure were recorded as well as reasons for failure. A Kaplan-Meier survival estimate with an associated P value, a life table analysis, and a log-rank test comparing the survival of single unit and splinted implant-supported crowns were performed.

Results

Over 30 years, 678 implant-supported crowns (586 single unit and 92 splinted) had been provided. Of these crowns, 17 (2.90%) single unit crowns and 5 (5.43%) splinted crowns failed, with most being prosthetic failures for both single units (64.7%) and splinted (80%), rather than biologic failures. A total of 371 single unit (63.3%) and 46 splinted (50.0%) implant crowns were a complete success, and 215 single unit (36.7%) and 46 splinted (50.0%) crowns survived but had some type of complication. The overall implant-supported crown survival rate was 96.8%. The survival distribution of the single unit and splinted implant-supported crowns was not statistically significantly different [χ2(2)=1.285, P=.257].

Conclusions

Both single unit and splinted implant-supported crowns had high success rates and showed similar survival rates. The most common causes of complications were also similar, with debonding and screw loosening of crowns being the most common complication for both single unit and splinted crowns.