Three Body in-Vitro Wear Test Method

Objective: This study describes the development of a soft, three-body in-vitro wear test method that simulates oral wear by a mechanism similar to chewing.

Method: Uses a slurry of PMMA beads, 50% in water, to simulate the food bolus and a Macor ceramic stylus, 1 cm dia., to simulate the opposing tooth.  The stylus is aligned in a jig that allows periodical vertical motion, 0.3 Hz, and application of a 50 psi normal force onto the sample.  Resin samples (3-5) were cured according to manuf. instr. into disks 50 mm dia. x 2 mm thick and stored 2 wks. in 37 ºC water.   The samples were inserted into a chamber mounted normal to the stylus in a lathe that rotated at 2.6 Hz, for accelerated wear.  The samples were tested in 10K cycles with fresh slurry for a total of 250K cycles; air dried and weighed to the nearest 0.0001 g.   The mean vol. loss/cycle and s.d. were calculated and analyzed by Anova (p<0.05). 

Results:  The table compares the wear rates of first generation and current composites (superscripts indicate differences between the means).   The wear rates of earlier composites were several orders of magnitude higher than current generation composites. 

Conclusion:  The wear test method produced a range of wear rates with rankings similar to that observed clinically (research funded by Kerr Corp.).