Journal of Dental Research, Vol 71, 1413-1416, Copyright © 1992 by International & American Associations for Dental Research Online Journals
Effect of contact area size on enamel and composite wear
I. Krejci, F. Lutz and C. Zedler
Department of Preventive Dentistry, Periodontology and Cardiology, Zurich University, Switzerland.
The effect of contact area dimensions on the wear of composite specimens
and their opposing enamel cusps was evaluated in vitro. Thirty-six
standardized cylindrical composite specimens were placed into metal
cavities (8 mm x 2 mm) and divided randomly into five groups. The composite
used was a fine-particle hybrid and was stressed as follows: storage in 75%
aqueous ethanol solution for 24 h, toothbrush/toothpaste-abrasion for 30
min, followed by 300 thermal cycles in water ranging from 5 degrees to 55
degrees C and simultaneous 120,000 occlusal chewing loads at a frequency of
1.7 Hz at 53 N maximum force. In group 1 (n = 12), the occlusal chewing
loads were applied by palatal cusps of extracted human maxillary molars
with natural morphology. In groups 2 to 5 (n = 6), the cusp tips had
standardized contact area dimensions of 0.26, 0.38, 1.18, and 4.10 mm2,
respectively. Wear of composite specimens and antagonistic enamel cusps
(means +/- SD) was assessed in microns by means of a 3-D scanner.
Additionally, the contact surfaces of the restorations and of the
antagonistic enamel cusps were evaluated by SEM. Increases in enamel
contact areas after being loaded were measured by means of a digitizer and
expressed in percent of the initial size before stress exposure. The wear
of the composite specimens varied from 69.8 +/- 19.9 to 9.5 +/- 3.6
microns, and that of antagonistic enamel cusps from 31.3 +/- 3.4 to 8.8 +/-
1.5 microns. The increase in contact area varied between 27.8 and
0.1%.(ABSTRACT TRUNCATED AT 250 WORDS)
