Association between apical periodontitis and retrograde peri-implantitis: a 10-year retrospective study

Retrograde peri-implantitis (RPI) has been hypothesized to be associated with apical periodontitis (AP). This retrospective study evaluated whether adjacent AP was associated with RPI and whether implant-to-lesion distance modified this association.

A total of 1,047 patients with 1,819 implants were included; 56 implants in 56 patients were placed near teeth with AP. RPI was diagnosed during follow-up using radiographic and clinical examinations. Firth's penalized logistic regression was first used to assess the association between adjacent AP and RPI development. Implant-to-lesion distance was then analyzed as a continuous variable using Firth's penalized logistic regression and restricted cubic splines to determine whether RPI risk increased as distance decreased. Based on the linear relationship, previous literature, and clinical feasibility, distance was subsequently dichotomized at 3 mm (<3 mm vs. ≥3 mm). Potential risk factors for RPI, including this distance category and other covariates, were examined using a multivariable Firth model. The manifestations and management of RPI were also summarized.

The incidence of RPI was 10.71% among implants placed adjacent to teeth with AP (odds ratio [OR], 26.51, P<0.01). In the continuous-distance model, shorter implant-to-lesion distance was associated with a higher risk of RPI (β=0.541; OR per 1-mm change, 0.58; 95% confidence interval, 0.25-0.96; P=0.030). Using the statistically and clinically meaningful 3-mm threshold, an implant-to-lesion distance <3 mm was significantly associated with RPI occurrence (OR, 6.48; P=0.03). Five of the 6 AP-related RPI cases received relevant treatment and showed an 83% survival rate at the last follow-up.

Within the limitations of this retrospective study, AP in adjacent teeth was associated with RPI. Maintaining a clearance of at least 3 mm from adjacent AP may help reduce the risk of RPI.