Within-mouth spillover of dental restorations on periodontal status
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Aim
To test whether neighbouring-tooth restorations affect a focal tooth’s 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(β) up to 1.10). Neighbouring-tooth restorations raised focal-tooth PD (spillover exp(β) 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.
Clinical Relevance
Scientific rationale for the study
Conventional surface-level analyses treat teeth as independent (the no-interference assumption) and cannot detect whether a tooth’s restoration affects the periodontal status of neighbouring teeth.
Principal findings
Restorations on neighbouring teeth independently raised focal-tooth PD and deep-pocket risk; the spillover was local, specific to PD, and concordant for untreated caries. Ignoring interference inflated the direct own-restoration effect only modestly.
Practical implications
A restoration’s periodontal footprint extends modestly beyond the restored surface to the neighbouring tooth; the dominant effect nonetheless remains local, and own-surface estimates overstate the direct effect only modestly.
