Within-mouth spillover of dental restorations on periodontal status

Abstract Aim: To test whether neighbouring-tooth restorations affect a focal tooths periodontal status (within-mouth spillover), and whether accounting for them alters the established association at the restored surface. Materials and methods: Prospective tooth-surface data from the Study of Health in Pomerania (SHIP): SHIP-START (N=2,715/1,982/1,397, follow-ups 1-3) and SHIP-TREND (N=2,123). Own and neighbouring-tooth restoration were defined at baseline; probing depth (PD), clinical attachment level (CAL), bleeding on probing (BOP) and deep pockets (PD >=4 mm) at follow-up. A neighbourhood-exposure mixed model with generalized propensity-score adjustment estimated both effects, with two corroborating estimators. Results: Own restoration was associated with worse periodontal status at that surface (crown PD exp(beta) up to 1.10). Neighbouring-tooth restorations raised focal-tooth PD (spillover exp(beta) 1.03-1.05) and deep-pocket risk (risk ratio up to 1.25); CAL and BOP showed none consistently. It attenuated with tooth-lag, nearing the null by two to three teeth in most estimators. Ignoring interference modestly inflated the direct effect; an opposing-tooth negative control showed none; untreated caries reproduced it. Conclusions: Dental restorations exert a within-mouth spillover on neighbouring-tooth PD: their periodontal footprint extends beyond the restored tooth. The direct association persists, modestly attenuated, after accounting for the neighbourhood.