Prevalence of caries in teeth adjacent to implant-supported prostheses and relationship with implant location and the manner of restoration placement: a retrospective cohort study

The primary objective of this study was to analyze the overall prevalence of caries in teeth adjacent to implant-supported protheses (ISPs). Secondary objectives were to determine how different implant restoration placement options (direct to implant, intermediate abutment, or Ti-Base) and/or ISP location influence the occurrence of caries. This retrospective cohort study was performed at the University Clinic of King Juan Carlos University (URJC, Madrid, Spain), between January 2018 and December 2023, following strict inclusion and exclusion criteria. Both single crowns and fixed partial dentures supported by implants were included. Descriptive statistics were calculated for the relevant variables. Associations between different groups (direct to implant, Ti-base, and intermediate abutment) were analyzed. The study evaluated 445 implant-supported protheses in 359 patients. The overall prevalence of caries in teeth adjacent to ISPs at patient level was 8.9% (95% CI: 5.95% to 11.84%) and 8.1% (95% CI: 5.56% to 10.63%) at prothesis level. Prevalence was higher in the molar region (9.6%; 95% CI: 5.7% to 13.4%), followed by premolar sites (8.6%; 95% CI: 4.2% to 12.9%). The highest prevalence of caries was found in teeth adjacent to ISPs placed direct to implant (11.4%; 95% CI: 7.3% to 15.4%); followed by teeth adjacent to implants restored with Ti-Base (10.5%; 95% CI: 0.0% to 24.2%). Those teeth adjacent to implants restored using intermediate abutments had the lowest prevalence (3.7%; 95% CI: 1% to 6.3%). Statistically significant differences between restoration groups were observed (p = 0.013). Moreover, the odds of caries increased by 3.37 times in teeth adjacent to ISPs placed direct to implant compared with those restored with intermediate abutments. The prevalence of caries in teeth adjacent to ISPs is significantly higher in implants restored direct to implant compared with those restored with intermediate abutments. Selecting the appropriate implant-supported restoration placement option may reduce caries in teeth adjacent to an ISP. Intermediate abutments would appear to reduce the risk of caries compared with direct implant restorations.