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Evaluation of toothbrush and generalized wear of luting materials.

PURPOSE
To evaluate (1) the wear rates of various types of luting materials by means of toothbrush and generalized wear tests, and (2) the relationship between interfacial gap and luting material wear.


METHODS
NiCr inlays were cemented into cylindrical Class I cavities prepared on flattened extracted molars with various luting materials (composite, compomer, hybrid and conventional glass-ionomers, and zinc phosphate). They were stored in 37 degrees C water for 24 hours and then resurfaced with a 600 grit Si-C paper. Half the specimens were subjected to 100 minutes of toothbrushing with a 1.47 N load using an automated brushing device, and the rest of the specimens were subjected to three-body generalized wear test with a 75 N load and 1.2 Hertz for 133,333 cycles. Eight specimens were evaluated for each cement by both wear modes. Wear depths of the luting materials were measured with a profilometer. The data were statistically analyzed by two-way ANOVA, and differences between wear modes and among luting materials were analyzed by a Bonferroni test (P< 0.05).


RESULTS
There were significant differences between the luting materials (P< 0.0001) and wear mode (P= 0.015) for wear depth but no significant interaction between luting material and wear mode (P= 0.1059). The wear values of the resin-based composite (6.4 +/- 3.1 microm) and compomer (6.2 +/- 2.4 microm) were significantly lower than those of the hybrid glass-ionomer (11.3 +/- 2.8 microm), the conventional glass-ionomer (11.1 +/- 4.4 microm), and the zinc phosphate (12.1 micro 1.7 microm) in the toothbrush wear. The wear value of the resin-based composite (6.5 +/- 3.1 microm) was significantly lower (P< 0.0001) than those of zinc phosphate (15.0 +/- 2.7 microm) and hybrid glass-ionomer (13.5 +/- 1.5 microm), but not significantly different from conventional glass-ionomer (10.1 +/- 3.9 microm) and compomer (10.2 +/- 2.5 microm) in the generalized wear.