Comparison of two methods of measuring dye penetration in restoration microleakage studies

This study compared the slice method of measuring microleakage to the whole-wall method. Forty-eight Class V direct metal restorations were placed in the buccal and lingual surfaces of 24 human molars. Following thermocycling and storage in 2% methylene blue stain for 12 hours, the teeth were sectioned and the restorations removed to expose the intact occlusal and gingival cavity walls. Maximum dye penetration axially was determined along either one or two imaginary slices or over the whole wall. Data were statistically evaluated by ANOVA and Tukey's test. Non-uniform staining occurred with 38 of the 96 walls available for evaluation. The average maximum dye penetration depth of the 38 walls was 0.61 mm and 0.70 mm for the slice method using one slice or two, respectively, and 1.29 mm for the whole-wall method. About half of these walls had leakage depths that were more than twice as great as when measured by the slice methods. All 12 of the 38 walls with no leakage when measured by the slice method, showed leakage at least somewhere along the margin when measured by the whole-wall method. This study shows that the whole-wall method detects significantly more leakage than does the slice method (p < 0.0001) and that using two rather than one slice does not improve the detection of leakage (p < 0.1534). Slicing the tooth restoration interface into only two or three sections may seriously underestimate the degree of leakage.