Measurement of Enamel Loss Following Recontouring and Polishing of Iatrogenic Proximal Tooth Damage

Objectives: Little is known about the amount of enamel loss from recontouring and polishing proximal tooth damage. This study measured enamel loss due to iatrogenic bur damage on adjacent teeth during approximal preparation and after the subsequent recontouring and polishing process. Methods and Materials: Eighteen extracted third molars were fit into the first molar positions of a typodont, placed between adjacent teeth with Class II preparations. The extracted teeth were scanned at baseline. Three operators, using an A-dec Simulator, created two types of tooth damage on the proximal surfaces with a 245 carbide bur: a “nick” using the bur tip, and “flat” damage using the side of the bur. Severity of damage was varied but was not deemed to require restoration. After the damage was scanned, the operators recontoured and polished the damaged lesions to clinical acceptability before a final scan. Enamel loss from damage and recontouring/polishing steps was determined with image analysis software and statistically analyzed with the Mann-Whitney U test. Results: Maximum depth after polishing correlated strongly with maximum depth of the initial damage (nicks, R 2 = 0.86; flat lesions, R 2 = 0.73). After recontouring and polishing, maximum depth increased minimally, 0.03 (± 0.04) mm for nicks and 0.03 (± 0.05) mm for flat lesions. Surface area of enamel loss after recontouring/polishing increased substantially, 7.0 (± 3.3) mm 2 for nicks and 4.8 (± 2.9) mm 2 for flat lesions. Volume loss after recontouring/polishing correlated strongly with the initial damage for flat lesions (R 2 = 0.74), but not for nicks (R 2 = 0.14). Nicks significantly increased volume loss compared to flat damage ( p = 0.023). Conclusions: Recontouring/polishing did not deepen the damage, but increased the area and volume of tooth structure loss. Nicks caused more tooth loss after recontouring/polishing than flat damage.