Evaluation of Seven Commercial Composites Using New In Vitro Wear Simulator

Objective: The OHSU Oral Wear Simulator has been successful at modeling the major wear mechanisms of dental composite, which include three body abrasion, attrition, and wear of opposing dentition. However, operators found it to be time-consuming and technique sensitive. An improved version of the OHSU Oral Wear Simulator was developed which uses roller slides and solenoids to reproduce the oral mechanisms with similar precision while being easier to operate. Methods: The wear tester applied a 20N load through a polished enamel stylus while sliding across the composite specimen in the presence of a food simulating slurry to produce three-body abrasion. As the stylus reversed direction, a higher load of 90N was triggered to produce attrition wear. After 100,000 cycles, the average depth in each region was measured with a contact profiler. The wear of the enamel antagonist was measured with digital image analysis. Seven commercial composites were tested and the results were compared to published clinical wear results to validate the system. Six bar-shaped specimens of each composite were prepared using a steel mold in a light-curing oven (Triad II). The results were compared by ANOVA/Tukey's Test (p≤0.05). Results: ave(s.d.):

           Clearfil   Fulfil  Heliomolar Herculite   Prisma    Silux Plus     Z100

Abrasion,mm   7(3)^a     61(10)^d   12(5)^a      19(5)^a,b      45(9)^c    24(10)^b            9(2)^a

Attrition,mm    20(4)¹    77(7)⁵    61(8)^3,4     47(12)^2,3   61(11)^3,4,5 65(12)^4,5     34(8)^1,2

Enamel,mm²       2.5(.1)^B 3.1(.4)^C 1.3(.3)^A    2.6(.4)^B,C    4.1(.3)^D   1.6(.4)^A      2.4(.3)^B

Conclusions:The microfilled (Heliomolar and Silux) and mini-filled (Z100, Herculite and Clearfil) composites demonstrated low abrasive wear but were sensitive to attrition wear (except Clearfil). The midi-filled composites (Fulfil and Prisma) had high abrasion, attrition and enamel wear. A comparison of abrasion values with contact-free-wear values from three clinical studies produced an average correlation coefficient of r²=0.98. The improved wear simulator provides meaningful, consistent results. Supported by NIH/NIDCR grant #DE07079.