title: Effect of contact area size on enamel and composite wear.
abstract: 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)
authors.affiliation: Department of Preventive Dentistry, Periodontology and Cardiology, Zürich University, Switzerland.
authors.forename: I
authors.initials: I
authors.lastname: Krejci
authors.forename: F
authors.initials: F
authors.lastname: Lutz
authors.forename: C
authors.initials: C
authors.lastname: Zedler
mesh_terms: D003080:Cold Temperature; D003188:Composite Resins / Q000737:chemistry*; D003743:Dental Enamel / Q000473:pathology*; D003764:Dental Materials / Q000737:chemistry; D003775:Dental Polishing; D006358:Hot Temperature; D006801:Humans; D008422:Materials Testing; D013314:Stress, Mechanical; D013499:Surface Properties; D014072:Tooth Abrasion / Q000473:pathology*; D014099:Toothbrushing
chemical_list: C075707:Brilliant Enamel; D003188:Composite Resins; D003764:Dental Materials