In vitro wear resistance of three types of composite resin denture teeth

Statement of problem

The wear resistance of artificial teeth is important to the life of the removable prosthesis for the edentulous patient. The ability of artificial teeth to maintain a stable occlusal relationship over time may be influenced by this property.

Purpose

The purpose of this in vitro study was to evaluate the wear resistance of artificial teeth based on composite resin filler content when opposed by a denture tooth antagonist.

Material and methods

The right first molars (both maxillary and mandibular) of 3 composite resin denture teeth (Endura, 47% organic filler; Duradent, 42% organic and inorganic filler; and Duracross, 68% organic filler) were secured in an in vitro 2-body wear-testing apparatus that simulated masticatory function (60 strokes/min, grinding distance of 2 mm, under 37°C flowing water). Wear resistance was assessed as volume loss (mm³) and height loss (mm) at 5 kgf (grinding force) after 50,000 strokes (6 pairs for each type). The Vickers microhardness (VHN) of the occlusal surfaces was measured with a load of 50 g and a loading time of 30 seconds. After testing, the worn surfaces were observed with a scanning electron microscope (SEM). Mean values were analyzed using a 1-way analysis of variance followed by the Fisher test (α=.05).

Results

The volume loss of Duradent teeth (0.87 ± 0.03 mm³) was significantly higher than of the 2 other types of teeth tested (P<.001). The Duracross teeth (0.22 ± 0.08 mm³ and 0.11 ± 0.04 mm) exhibited the best wear resistance of the denture teeth tested. The wear resistance of the materials tested was consistent with their hardness (Endura 27.54 ± 0.67 VHN, Duradent 24.00 ± 0.60 VHN, Duracross 39.64 ± 3.11 VHN). SEM observation showed that many filler particles were missing from the matrix of Duradent.

Conclusion

The wear resistance among the 3 types of teeth was significantly different; Duracross and Endura were more wear resistant than Duradent. Although the densities as reported by the manufacturer were similar, hardness and microstructure were the primary factors affecting the wear resistance of artificial teeth. Hardness appears to correlate with wear resistance since the wear resistance of Duradent with a lower VHN of 24 was greater than the other 2 types of teeth with greater hardness.