Gingival and alveolar bone reaction to marginal fit of subgingival crown margins

Interproximal subgingival marginal discrepancies of full coverage restorations were compared with adjacent crevicular fluid flow and percentage radiographic periodontal bone loss. A total of 88 patients with 116 premolar crowns were evaluated. Patients were selected at random from student treatment records, Institute of Dental Prosthetics, Royal Dental College, Copenhagen, Denmark. Crevicular fluid collected on filter paper strips from the interproximal area was stained with 0.2% ninhydrin solution and the length of the area measured. Marginal fit was determined by measuring the marginal excess or deficit recorded in a polyether impression. The amount of bone around each crowned tooth was measured on five times magnified prints of radiographs. Percentage bone loss was calculated by dividing the distance from the alveolar crest to the most coronal level at which the periodontal space retained its normal width by the distance from the alveolar crest to the root apex. Correlating marginal fit with crevicular fluid within gingival index scores showed r = 0.32 (G.I.1) and r = 0.42 (G.I.2). Fit vs percentage bone loss showed r = 0.68 and r = 0.59, respectively (P less than or equal to 0.001). Differentiation was further made within the 0.0-0.2 mm range discrepancy by categorizing the data in four groups. Comparing fit relative to crevicular fluid and bone loss, most of these groups were significantly different when analyzed statistically using the Mann-Whitney U-Test. Small defects less than or equal to 0.050 mm were associated with significantly less fluid flow and bone loss than defects exceeding this value.