The Long-Term Impact of Single Implant-Supported Crowns on Adjacent Natural Teeth: A Retrospective Longitudinal Study

To evaluate the long-term impact of single implant-supported crowns on the health status of adjacent natural teeth.

Clinical and radiographic data from 456 subjects with single implants were analyzed. Complication rates (caries, new restorations, tooth loss) of adjacent teeth were compared against three intra-patient control groups (other quadrants) using data at restoration delivery as the baseline. Multivariate models assessed risk over short-term (1-5 years) and long-term (5-15 years) periods.

Mean follow-ups were 3.88 ± 1.75 years for the short-term (n = 456) and 8.90 ± 2.10 years for the long-term (n = 180) cohorts. Adjacent teeth showed significantly higher overall complication rates compared to all control groups in both the short-term (8.0% vs. 2.2%-2.7%; ORs: 2.92-3.65) and long-term follow-ups (15.0% vs. 6.4%-7.8%; ORs: 2.16-2.57). A clear positional dichotomy emerged: mesial teeth showed pronounced short-term caries susceptibility, while distal teeth drove a short-term risk of tooth loss. Restoration needs remained consistently elevated. Bone-level implants (short-term OR: 0.44; long-term OR: 0.38), narrow-diameter implants (OR: 0.23), and pre-existing orthodontic alignment (OR: 0.20) were associated with a lower incidence of complications, whereas patient-level factors such as bruxism (OR: 5.78) and male gender (OR: 10.88) correlated with increased complication rates.

Single implant-supported restorations significantly elevate the incidence of caries, new restorations, and tooth loss in adjacent teeth relative to controls. While adjacent tooth loss is predominantly an acute short-term risk localized to distal teeth, susceptibility to carious lesions and restorative interventions represents a persistent, long-term morbidity.