Effects of Occlusal and Brushing Forces on Wear of Composite Resins

Abstract

INTRODUCTIONWear of restorative materials is a very complex phenomenon that is affected by several extrinsic and intrinsic factors. Wear of restorative materials in the oral environment results from direct contact between the tooth and the restoration during mastication, oral parafunctions, toothbrushing with abrasive particles, as well as chemical effects caused by dietary and regurgitated acids 1） . To date, many studies 2-9） have attempted to evaluate the wear behavior of restorative materials using several testing methods. However, these methods evaluated only a part of the wear process of restorative materials. It is absolutely necessary to integrate main wear processes such as abrasion and fatigue for a thorough and holistic evaluation of the wear behavior of restorative dental materials. To this end, a combined wear test system -which carried out two different types of wear test -was developed 10） . In the combined wear test, a simulated occlusal wear test and a toothbrush wear test repeated alternately on the same position of one specimen. This testing system provided a means for clinical simulation and a basic wear model which consisted of different wear mechanisms induced in the oral environment. Occlusal force and brushing force are important factors for characterizing the wear behavior of restorative dental materials, especially when the two different wear processes are combined.The purpose of this study was to investigate the effects of different occlusal forces and brushing forces on the wear of composite resins in the combined wear test as well as in the simulated occlusal wear test and toothbrush wear test. Table 1 shows four commercially available light curing composite resins used in this study. APX （KURARAY, Okayama, Japan）and Z100（3M, MN, USA）were intended for both anterior and posterior restorations, while SRE （GC, Tokyo, Japan） and SDX（Shofu, Kyoto, Japan）were for posterior restorations. Preparation of the wear specimens and wear tests were carried out following the procedure reported in a previous study 11） . Wear specimens were prepared using a metal mold （diameter: 15 mm, depth: 8 mm） . Thickness of the specimens was adjusted to 2 mm using a spacer in the mold. Each composite resin was injected into the mold and pressed with a glass plate（1.4 mm thickness） . The specimen was polymerized using a curing light MATERIALS AND METHODS Specimen preparation and wear testEffects of occlusal and brushing forces on the wear of composite resins were investigated using three different wear tests: simulated occlusal wear test, toothbrush wear test, and combined wear test which carried out toothbrush wear test and occlusal wear test alternately. Test specimens were prepared from four commercial composite resins. Worn volume and maximum worn depth were measured under different occlusal forces（40 N and 80 N）and brushing forces（1.5 N and 3 N） in the three wear tests. Worn surfaces were observed using a SEM.In all the three wear tests, both higher occlusal and brushing forces resulted in significantly ...

Toothbrushing alters the surface roughness and gloss of composite resin CAD/CAM blocks

“…The bristles of the toothbrush act as an antagonist while the toothpaste slurry is used as the medium. Many investigations have shown the effects of toothbrushing on the surface roughness and gloss of composite resins, in terms of brushing time [9][10][11] , brushing force 12,13) , and abrasivity of the particles contained in the toothpaste 14) . An increase in toothbrushing cycles was shown to deteriorate the smoothness and glossy appearance of conventional composite resins 15) .…”

Surface textures of composite resins after combined wear test simulating both occlusal wear and brushing wear

“…Rough surface caused by brushing wear increased friction between the worn surface and antagonist for every subsequent time of occlusal wear. Kon et al 6) showed that wear after a combined wear test tended to be higher than the sum of brushing wear and occlusal wear when performed singly.…”

“…Details of the combined wear test were given in previous reports [4][5][6] . A combined wear test, which simulated occlusal wear and brushing wear alternately, was carried out on the surfaces of the composite resin specimens.…”

“…Specimen preparation details were given in previous reports [4][5][6] . Briefly, each wear specimen was prepared using a metal mold (diameter: 15 mm, depth: 8 mm).…”

Effects of Occlusal and Brushing Cycles on Wear of Composite Resins in Combined Wear Test

“…Various types of wear tests have been used to evaluate the wear behavior of composite resins [6][7][8][9] . Of late, studies by Wakamatsu et al 10) , Kato et al 11) , and Kon et al 12) proposed a combined wear test which alternately carries out simulated occlusal wear test and toothbrush wear test. This test method simulates our daily routine of alternately repeating toothbrushing and mastication.…”