Influence of thickness and base material in class II restorations with nanofilled composites: finite element study.

Abstract

<h4>Statement of problem</h4>The selection of restorative and base materials in the restoration of large cavity preparations remains a debatable issue, and it is unclear how functional stresses affect Class II (MOD) restorations.<h4>Objective</h4>To evaluate the influence of base material type and thickness on stress distribution in Class II MOD restorations using various nanofilled packable composites.<h4>Material and methods</h4>Eight three-dimensional finite element models were developed: six experimental models combining three restorative composites (Filtek Supreme, Grandio and Admira Fusion) with two base materials [flowable resin composite [FR] and resin-modified glass ionomer [RMGI]] at thicknesses of 0.5 mm, 1.0 mm, and 1.5 mm; and two control models, including restorations without a base layer and a healthy, intact tooth. A static vertical load of 600 N was applied along the tooth's long axis, and Von Mises stress distribution was analyzed within the base, restoration, and dental structures.<h4>Results</h4>The sound tooth model exhibited the lowest stress concentration (20.777 MPa). Among the restored groups, models without a base layer showed higher stress values, with Filtek Supreme XTE reaching a maximum of 31.243 MPa. Overall, the incorporation of base materials improved stress distribution. The most favorable outcomes among the restored models were observed with the combination of Grandio and Fuji II GC glass ionomer, which yielded the lowest stress value (20.846 MPa). In contrast, the use of 1.5 mm-thick flowable resin bases tended to increase stress levels (up to 32.031 MPa in the Admira Fusion models) compared with thinner layers or glass ionomer alternatives.<h4>Conclusion</h4>Thicker resin-modified glass ionomer (RMGI) bases provide a more favorable stress distribution than flowable resin composite (FR) bases in Class II restorations.