Physical properties and wear behavior of CAD/CAM resin composite blocks containing S-PRG filler for restoring primary molar teeth

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.

Wear characteristics of esthetic resin matrix and zirconia reinforced lithium disilicate CAD/CAM materials: two-body wear and surface topography analysis

BACKGROUND

This in vitro study assessed the wear behavior of different CAD-CAM blocks and the abrasion of the enamel antagonist against these materials.

METHODS

64 disk-shaped specimens were prepared from 8 different CAD/CAM blocks as follow: one lithium disilicate glass ceramics block "IPS Emax CAD" as control group, two zirconia reinforced lithium silicate "Vita Suprinity & Celtra DUO," one interpenetrating network ceramic block "Vita Enamic," Three resin-based block composites "Lava Ultimate, Cerasmart & Brilliant-crios" as well as one hybrid nanoceramic "Shofu block HC". All specimens were mounted against canine and tested for two body wear analysis using a chewing simulating loading machine (100,000 cycles, 50 N, 5/55 °C). The amount of wear loss was measured for each specimen using a digital precise scale. Wear area before and after the chewing simulation were evaluated using an optical profilometer. Data analysed using one-way ANOVA test followed by Tukey's post hoc.

RESULTS

The results showed a significantly higher wear loss in resin matrix ceramics in comparison to glass ceramics. However, for tooth wear glass ceramics had significantly higher value than hybrid ceramics.

CONCLUSIONS

Resin based CAD/CAM Blocks gives a superior result when evaluating the wear behavior and its effect on the opposing tooth surface.

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

OBJECTIVE

To evaluate the reliability, maximum principal stress, shear stress, and crack initiation of a computer-aided design/computer-aided manufacturing (CAD/CAM) resin composite (RC) incorporating surface pre-reacted glass (S-PRG) filler for primary molar teeth.

METHODS

Mandibular primary molar crowns fabricated by experimental (EB) or commercially available CAD/CAM RCs (HC) were prepared and cemented to a resinous abutment tooth using an adhesive resin cement (Cem) or a conventional glass-ionomer cement (CX). These specimens were subjected to a single compressive test (n = 5/each) and the step-stress accelerated life testing (SSALT) (n = 12/each). Data was evaluated using Weibull analyses and reliability was calculated. Afterwards, the maximum principal stress and crack initiation point of each crown was analyzed by finite element analysis. To evaluate bonding of EB and HC to dentin, microtensile bond strength (μTBS) testing was conducted using primary molar teeth (n = 10/each).

RESULTS

There was no significant difference between the fracture loads of EB and HC for either cement (p > 0.05). The fracture loads of EB-CX and HC-CX were significantly lower than EB-Cem and HC-Cem (p < 0.05). The reliability at 600 N for EB-Cem was greater than that for EB-CX, HC-Cem, and HC-CX. The maximum principal stress concentrated on EB was lower than that on HC. The shear stress concentrated in the cement layer for EB-CX was higher than that for HC-CX. There was no significant difference among the μTBSs of EB-Cem, EB-CX, HC-Cem, and HC-CX (p > 0.05).

SIGNIFICANCE

The crowns fabricated with the experimental CAD/CAM RC incorporating S-PRG filler yielded greater fracture loads and reliability than the crowns manufactured with commercially available CAD/CAM RC regardless of the luting materials. These findings suggest that the experimental CAD/CAM RC crown may be clinically useful for the restoration of primary molars.

Multiple-Ion Releasing Bioactive Surface Pre-Reacted Glass-Ionomer (S-PRG) Filler: Innovative Technology for Dental Treatment and Care

Surface Pre-Reacted Glass-ionomer (S-PRG) filler, which releases strontium (Sr²⁺), borate (BO₃^3-), fluoride (F^-), sodium (Na⁺), silicate (SiO₃^2-), and aluminum (Al³⁺) ions at high concentrations, is a unique glass filler that are utilized in dentistry. Because of its multiple-ion releasing characteristics, S-PRG filler exhibits several bioactivities such as tooth strengthening, acid neutralization, promotion of mineralization, inhibition of bacteria and fungi, inhibition of matrix metalloproteinases, and enhancement of cell activity. Therefore, S-PRG filler per se and S-PRG filler-containing materials have the potential to be beneficial for various dental treatments and care. Those include restorative treatment, caries prevention/management, vital pulp therapy, endodontic treatment, prevention/treatment of periodontal disease, prevention of denture stomatitis, and perforation repair/root end filling. This review summarizes bioactive functions exhibited by S-PRG filler and its possible contribution to oral health.

In Silico Finite Element Analysis of Implant-Supported CAD-CAM Resin Composite Crowns

PURPOSE

The aim of this study was to evaluate the mechanical behavior of an implant-supported crown made using computer-aided design and computer-aided manufacturing (CAD-CAM) resin composite (RC) blocks in the posterior region.

MATERIAL AND METHODS

Four commercially available CAD-CAM RC blocks were used in this study: Cerasmart 300 (CS300; GC, Tokyo, Japan), Katana Avencia P Block (KAP; Kuraray Noritake Dental, Niigata, Japan); KZR HR3 Gamma Theta (HR3; Yamakin, Osaka, Japan), and Estelite P block (ESP; Tokuyama Dental, Tokyo, Japan). Katana Zirconia STML (ST; Kuraray Noritake Dental) was used as the control group. The elastic moduli of each material were determined by a three-point bending test. After the CAD models were designed, two different loading scenarios (oblique, vertical) were created. 3D finite element analysis was conducted with the prepared models.

RESULTS

The elastic modulus of the material utilized for the implant restorations did not cause any change in the stresses transmitted to the implant or peripheral bone. An important difference was detected in the abutment-crown junction area. The minimum von Mises value at the abutment-crown interface was obtained in ST, which has the closest elastic modulus to the titanium abutment.

CONCLUSIONS

The 3D finite element model designed in this study was used to demonstrate that implant-supported crowns fabricated with four different CAD-CAM RCs showed no critical stress concentrations in the bone or implant under all loading conditions. These results suggest that CAD-CAM RC blocks could be used as an alternative material for implant-supported restorations in the posterior region in terms of stress distribution.