In vitro analysis of durability of S-PRG filler-containing composite crowns for primary molar restoration

Optimizing restorative procedure and material selection for pulpotomized primary molars: Mechanical characterization by 3D finite element analysis

Purpose

This study aimed to assess the stress distribution in pulpotomized primary molars with different types of restorative materials using 3D-finite element analysis (FEA), and provide valuable insights into the selection and application of restorative materials, with the ultimate goal of reducing the risk of pulpotomy failure and protecting residual dental tissue.

Methods

Four 3D models of pulpotomized primary molars with different restorative materials according to the material and its elastic modulus were analysed: resin composite, stainless steel crowns (SSCs), prefabricated zirconia crowns and endocrowns. The food layer was also designed before vertical and bucco-lingual forces were applied to simulate physiological masticatory conditions. The results were obtained by colorimetric graphs of the von Mises stresses (VMS) in the restoration and tooth remnant. The maximum shear stress on the bonding interfaces and pressure stress on the Mineral trioxide aggregate (MTA)-pulp interfaces were recorded.

Results

The results of the 3D-FEA showed that all restorative materials generated stresses and strains on the tooth structure after pulpotomy. In the resin composite group, the marginal enamel exhibited the highest stress peaks. In the zirconia crown and SSC groups, there was a concentration of stress at the dentin-restoration margin. The shear stress concentrations were mainly at the adhesive margins, with lower levels around endocrowns compared to other groups. MTA in the resin composite group experienced more VMS than in the other group. The resin composite group also generated relatively higher pressure stress values at the MTA-pulp interface compared to the other groups.

Significance

In the model of primary teeth following pulpotomy, the three types of restorations covering the occlusal surface can effectively reduce the stress on pulp capping materials under occlusal loads, thereby potentially decreasing the risk of pulpotomy failure. In addition, the group of endocrowns demonstrated reduced stress at the bonding interface and in the stress concentration zone near the dentist-restoration edge, making them more effective at protecting residual dental tissue.

CAD-CAM resin composites: Effective components for further development

OBJECTIVE

This paper summarizes the effective components of computer-aided design and computer-aided manufacturing (CAD-CAM) resin composites that contribute to achieving greater mechanical properties and further development.

METHODS

In silico multi-scale analysis, in silico nonlinear dynamic finite element analysis (FEA), and artificial intelligence (AI) were used to explore the effective components of CAD-CAM resin composites. The effects of the filler diameter and silane coupling ratio on the mechanical properties of CAD-CAM resin composites have been clarified through multi-scale analysis. The effects of the filler contents, and filler and monomer compositions have been investigated by AI algorithms. The fracture behavior of CAD-CAM composite crown was analyzed using in silico non-linear dynamic FEA. The longevity of CAD-CAM composite crown was assessed through step-stress accelerating life testing (SSALT).

RESULTS

As the filler diameter decreases, there is an increase in elastic moduli and compressive strengths at the macroscale. At the nanoscale, a decrease in the filler diameter results in a decrease in the maximum value of the maximum principal strain. When the silane coupling ratio decreases, there is a decrease in the elastic modulus and compressive strength. According to the exhaustive search and feature importance analysis based on the AI algorithm, the combination of certain components was narrowed down to achieve a flexural strength of 269.5 MPa. The in silico non-linear FEA successfully detected the sign of the initial crack of the CAD-CAM composite molar crown. The SSALT revealed that CAD-CAM resin composite molar crowns containing nanofillers with a high fraction of resin matrix demonstrated great longevity.

SIGNIFICANCE

This paper summarized the effective components of CAD-CAM resin composites for their further development. The integration of in vitro and in silico approaches will expedite the advancement of CAD-CAM resin composites, offering benefits such as time efficiency and reduction of material waste for researchers and manufacturers.