Interactory effect between marginal plaque and subgingival proximal restorations on periodontal pocket depth

The purpose of the present study was to investigate the influence of plaque on periodontal pocket depth adjacent to proximal amalgam restorations after non-surgical periodontal treatment. From 120 randomly selected patients 200 proximal premolar- or molar sites with subgingival restorations (test sites) and 200 contralateral unrestored sites within the same patient (control sites) were included if plaque was present on test as well as on control sites. At baseline the periodontal mean pocket depth adjacent to subgingival restorations were found to be significantly deeper (0.25 mm) than for control sites. After treatment, 24% of the initially subgingivally located restorations were registered as supragingival restorations. The differences according to mean pocket depth between supragingival restorations and corresponding control sites after treatment were found to be statistically non-significant. At reexamination mean pocket depth adjacent to proximal restorations with plaque were significantly deeper than their contralateral unrestored sites (mean difference 0.34 mm), while a non-significant difference was calculated for subgingival restorations without plaque. Subgingival restorations with their apical borders still located subgingivally after periodontal treatment should be regarded as a risk factor in periodontitis progression. Consequently, placement of the restoration margin supragingivally is recommended, especially in periodontitis-prone patients with an insufficient plaque control.