The Study On Wear Behavior Of Six Composite Resins And The Influencing Factors

Composite resins are widely used in dentistry because of their superior aesthetic appearance,good handling properties,better adhesive effect and so on.Though there are some methods of measuring degree of conversion,the measurement of surface hardness is an indirect and effective method.Polymerization shrinkage is a major disadvantage of dimethacrylate composite resins and might lead to adverse effects,such as microleakage,discoloration,secondary caries,postoperative sensitivity and pulp pathological status.Many kinds of methods have been used to reduce the shrinkage,such as the use of monomers of high weight,increasing the content of inorganic fillers,using new types of monomers such as silorane and ormocer(organically modified ceramic)and ring-opening monomers such as spiroorthocarbonate and so on.Resistance to wear represents an important factor in determining the clinical success of resin composite restoratives.In recent years,scholars did a lot of work to improve the wear resistance performance of composite resin,but new research about the wear resistance of lowshrinkage composite resin is very few.Four low-shrinkage commercial composite resins including CLEARFIL MAJESTY Posterior(CMP),Filtek LS(LS),Admira(AD),Kalore(KA)and two traditional composite resins including Filtek Z350XT(Z350),Solitaire2(S2)were chosen.After surface microhardness test the bar-shaped specimens were fabricated and mounted in a UMT-2 wear testing machine and abraded with the two-body media(distilled water)with a Si3N4 ball as antagonist.The maximum wear depth was determined after 14.4K cycles.The friction coefficient was determined during the test.The worn surfaces were examined with SEM.CMP showed the lowest maximum wear depth and KA presented the highest maximum wear depth.The maximum wear depth ranked as follows: CMP < S2≈LS < Z350≈AD < KA(P<0.05),and the hardness ranked as follows: CMP > Z350 > LS ≈ AD > S2 > KA(P<0.05).The wear loss of the composite resins were negatively relevant to their hardness(P<0.05).The wearing surfaces of Z350,S2,AD and KA were flatter and smoother,showing attrition wear and adhesive wear,whereas the wearing surfaces of CMP and LS were rougher,showing fatigue wear.The wear resistance of composite resins correlated to their type of filler,filler content and filler-resin matrix bonding.Improving the hardness of composite resin helps to the wear resistance of composite resin.