Clinical Evaluation And Wear Resistance Research Of A Universal And A Posterior Composite Resin For Posterior Restorations

Composite resin is a widely used direct restorative material in clinic, with the advantages of beautiful color and the capability of adhesion to tooth hard tissue etc. With the development of composite resin, more and more cavities in posterior have been restored with composite resin due to its improved performance. Currently, two type composite resins are available for posterior restoration, universal and posterior composite resins. Recent year, universal composite resin Z350 XT and posterior composite resin P60, both are the products of 3M Company, are widely used for posterior restorations in China. However, the reports on their clinical performance used for posterior restoration are few, especially the studies involving both qualitative and quantitative method. Therefore, in this study, a one-year observation on the clinical performance and wear resistance of these two resins used in posterior restoration were performed using a modified USPHS evaluation system and 3D scanning method. At the same time, the micro-morphology on the occlusal contact area of the restorations were observed and compared under the SEM to explore the wear mechanism, hoping for providing suggestions for the selection of composite resin in clinical and the improvement of composite resin fillings.AIM:1 To evaluate the clinical performances of Z350 XT and P60 in posterior restoration;2 To measure the surface wear loss of posterior restorations of Z350 XT and P60 composite resin quantitatively;3. To explore the wear mechanism of occlusal contact areas of Z350 XT and P60 in posterior restorations.METHODS:1. The evaluation of the clinical performance of the two composite resins Composite resin Z350 XT and P60 were filled in 54 Class I and 12 Class II cavities. After 1-, 6-, 12- month, all restorations were observed and evaluated according to a modified USPHS criteria, which included anatomy form, color matching, marginal adaptation and discoloration, surface smoothness and secondary caries.2. Quantitative measurement of wear loss Fine impressions of the occlusal surface of each restored teeth were taken using a polyvinyl siloxane impression material in two-step and stone model were made, followed by the scanning of the surface of the model by a 3D scanner. The 3D data was transmitted into software Geomagic and a 3D digital model was rebuilt for each restoration. The digital model of the restorations of the same resin at 6- and 12- months were matched and the average wear depth and volume loss of each restoration were calculated using Geomagic software.3 SEM observations An epoxy resin copy was made for each restored tooth and the micro-morphology of the restoration was observed under SEM.RESULTS:1. At 1 and 6- months Z350 XT restorations showed better color matching and surface smoothness than P60 restorations(P<0.05). With the time passed, surface smoothness and marginal adaptation in Z350 XT restorations decreased significantly(P<0.05).But for the anatomy form, marginal staining and secondary caries, no significant difference was showed between the two resins(P> 0.05).2 At 6-and 12 months, the mean vertical loss was 39.33±14.25μm and 52.74±30.65μm for Z350 XT respectively, 39.16±19.11μm and 54.18±21.47μm for P60, the volume loss was 1.03±0.6mm3 and 1.40±1.13mm3 for Z350 XT, 0.85±0.54mm3 and 1.62±1.03mm3 for P60. No statistical difference was observed between the two resins(P> 0.05).3. SEM results showed that more and more small abrasion pits and marginal fracture were observed on the two resin restorations as time went on, with much more in number and size at 6 months than at 12 months.CONCLUSION:The 12 months findings from this study showed that universal composite resin Z350 XT and posterior composite resin P60 presented satisfactory and similar clinical performances when used to restore Class I and Class II cavities. Comparatively, Z350 XT showed better polishability and color match than P60. The two composite resins presented similar surface wear loss, and the main cause for wear of the two resins is surface abrasion and marginal fracture.