Impact of Quantity of Resin, C-factor, and Geometry on Resin Composite Polymerization Shrinkage Stress in Class V Restorations

Abstract

Adhesive dentistry allows for the simple removal of decayed tissue to guide preparation design. Knowledge about differences in stress concentration within cavities can help in understanding the impact of shape and cavosurface angle of the cavity, optimizing the distribution of stress during the cure of the restorative material and improving the expected lifetime of the restoration. SUMMARYObjective: This study evaluated the effect of quantity of resin composite, C-factor, and geometry in Class V restorations on shrinkage stress after bulk fill insertion of resin using two-dimensional finite element analysis.Methods: An image of a buccolingual longitudinal plane in the middle of an upper first premolar and supporting tissues was used for modeling 10 groups: cylindrical cavity, erosion, and abfraction lesions with the same Cfactor (1.57), a second cylindrical cavity and abfraction lesion with the same quantity of resin (QR) as the erosion lesion, and then all repeated with a bevel on the occlusal cavosurface angle. The 10 groups were imported into Ansys 13.0 for two-dimensional finite element analysis. The mesh was built with 30,000 triangle and square elements of 0.1 mm in length for all the models. All materials were considered isotropic, homogeneous, elastic, and linear, and the resin composite shrinkage was simulated by thermal analogy. The maximum principal (MPS) and von Mises stresses (VMS) were analyzed for comparing the behavior of the groups.Results: Different values of angles for the cavosurface margin in enamel and dentin were obtained for all groups and the higher the angle, the lower the stress concentration. When the groups with the same C-factor and QR were compared, the erosion shape cavity showed the highest MPS and VMS values, and abfraction shape, the lowest. A cavosurface bevel decreased the stress values on the occlusal margin. The geometry factor overcame the effects of C-factor and QR in some situations.Conclusion: Within the limitations of the current methodology, it is possible to conclude that the combination of all variables studied influences the stress, but the geometry is the most important factor to be considered by the operator.

Polymerization shrinkage stresses in different restorative techniques for non-carious cervical lesions

“…The marginal adaptation of composite resin restorations can be influenced by the type of adhesive system and factors related to the development of stress during the polymerization process of the restorative material [1][2][3][4]. The stress is influenced by factors such as elastic modulus [5], quantity of restorative material, cavity geometry [6], restorative technique, and light-curing protocol [7,8]. In addition, the composite resin polymerization shrinkage is an important source of interfacial stress [5].…”

“…However, shrinkage stresses and microleakage are higher in restorations with larger diameters and depths and seem to be related to the volume of the restoration, but not to its C-factor [21]. Therefore, the geometry and cavity shape are the most critical factors to be considered [6,24].…”

“…For large and/or deep restorations, incremental placement with oblique layers is recommended to decrease the effects of polymerization shrinkage and the thickness of a resin composite compared to other techniques [19]. However, this technique increases the possibility of incorporating voids between resin layers, as well as the time associated with placing and curing each layer of the material [6,25].…”

Direct‐Indirect Class V Restorations: A Novel Approach for Treating Noncarious Cervical Lesions

“…The composite resin quantity, cavity geometry, and C‐factor are reported to influence the shrinkage stress exerted on the tooth in class V restorations . Layering techniques have been advocated to minimize the undesired consequences of composite shrinkage (i.e., post‐operative sensitivity, microleakage), but there are divergent findings regarding the efficacy of incremental layering versus bulk filling .…”

“…The composite resin quantity, cavity geometry, and C-factor are reported to influence the shrinkage stress exerted on the tooth in class V restorations. 38,39 Layering techniques have been advocated to minimize the undesired consequences of composite shrinkage (i.e., post-operative sensitivity, microleakage), [40][41][42] but there are divergent findings regarding the efficacy of incremental layering versus bulk filling. [43][44][45] The benefits of bulk filling class V defects, however, make it more attractive to operators, because they frequently include use of a single shade, thus minimizing the number of steps and reducing operative time.…”