The Influence of C-factor, Flexural Modulus and Viscous Flow on Gap Formation in Resin Composite Restorations

Abstract

SUMMARYThis study analyzed the influence of C-factor, flexural modulus and viscous flow on gap formation in resin composite restorations. Two resin composites, a mini-filled hybrid (P 60) and a nanofilled (Supreme), were used. The flexural modulus was obtained from bar-shaped specimens submitted to three-point bending. Viscous flow was obtained from the difference between the initial and final diameter of resin composite disks submitted to a load of 10 N for 120 seconds. Gap analysis was conducted in three types of cylindrical cavities (C-factor of 1.8, 2.6 and 3.4) that were prepared on the occlusal surfaces of human molars. The gap width at the dentin-resin composite interface was measured using a 3D scanning system (Talyscan 150). The data were analyzed by ANOVA and Student-Newman-Keuls' test, t-test and linear regression analysis (α=0.05). The cavities with C-factor 3.4 presented the highest Gap formation (p<0.0001). The lowest Gap formation was found in cavities restored with Supreme resin composite (p<0.0001). P 60 presented significantly higher flexural modulus and lower viscous flow than Supreme (p<0.0001). Regression analyses detected a significant influence of flexural modulus and viscous flow on gap formation (p<0.05).

Effect of Aging on Coronal Microleakage in Access Cavities through Metal Ceramic Crowns Restored with Resin Composites

“…34,35 In this study, the results demonstrated that water storage could significantly affect the mean coronal microleakage at the metal-ceramic/composite interface; there was a slight decrease in mean coronal microleakage in 7-day water storage compared to 1-day water storage. These slight differences could be explained by the slightly more water at 7 days than 1 day with more hygroscopic expansion, thereby agreeing with other studies that showed that the degree of hygroscopic expansion in resin-based composites had an inverse relationship between filler loading and water sorption, 45 thus compensating for resin composite shrinkage.…”

The Evaluation of Various Restoration Techniques on Internal Adaptation of Composites in Class V Cavities

“…The flow characteristics of a restorative material affect its ability to adapt to the walls of a cavity preparation. Thus, a composite resin with a higher flow might adapt more easily the walls of a cavity preparation than one with lower flow values [ 25 ]. Many studies have recommended preheating of conventional composites instead of the use of a flowable composite liner.…”

A resin composite material containing an eugenol derivative for intracanal post cementation and core build-up restoration

“…A low viscosity of these composites during the working period is also desirable as it can facilitate their injection into the root canal through the delivery devices, and for effective impregnation of dentinal substrates and post surface [25]. It also reduces the polymerisation shrinkage stress within the material during early setting [26,27] and the stress relief via resin flow relaxation can reduce the possibility of gap formation [14] and marginal leakage [28,29], which can enhance the longevity of the restorations. It has also been reported that the lower viscosity resin composites provide significantly higher adhesion to post surface attributed to higher intrusion on the substrates [8].…”

“…The higher viscosity that is associated with higher filler load [11] also impedes the injection of the material into the root canal producing gaps and voids that may provide a site for recurrent caries to develop. The composition of the matrix [12] also has an effect on both viscoelastic and rheological properties, which influence the contraction stress and microleakage of the direct restoration [13,14].…”