Effect of Air-Abraded Versus Laser-Fused Fluorapatite Glass-Ceramics on Shear Bond Strength of Repair Materials to Zirconia

Biomechanical reinforcement by CAD-CAM materials affects stress distributions of posterior composite bridges: 3D finite element analysis

OBJECTIVES

This 3D finite element analysis study aimed to investigate the effect of reinforcing CAD-CAM bars on stress distribution in various components of a posterior composite bridge.

METHODS

A virtual model mimicking the absence of an upper second premolar was created, featuring class II cavity preparations on the proximal surfaces of the adjacent abutment teeth surrounding the edentulous space. Five distinct finite element analysis (FEA) models were generated, each representing a CAD-CAM reinforcing bar material: 3-YTZP (IPS. emax ZirCAD MO; Zr), lithium disilicate (IPS e.max CAD; EX), nano-hybrid resin composite (Grandio Blocs; GB), Fibre-reinforced composite (Trilor; Tri), and polyetheretherketone (PEEK). A veneering resin composite was employed to simulate the replacement of the missing premolar (pontic). In the FEA, an axial force of 600 N and a transverse load of 20 N were applied at the center of the pontic. Subsequently, maximum von Mises (mvM) and maximum principal stresses (σmax) were computed across various components of the generated models. Additionally, shear stresses at the interface between the CAD-CAM bars and the veneering resin composite were determined.

RESULTS

CAD-CAM materials with high modulus of elasticity, such as Zr and EX, exhibited the highest mvM stresses and shear stresses while transferring the lowest stress to the veneering resin composite in comparison to other materials. Conversely, PEEK demonstrated the lowest mvM stresses but produced the highest stresses within the veneering resin composite. There was a uniform distribution of mvM stresses in the remaining tooth structure among all groups, except for a noticeable elevation in the molar region of Zr and EX groups.

SIGNIFICANCE

Reinforcing CAD-CAM bar materials with a high modulus of elasticity, such as Zr and EX, may result in debonding failures at the connector sites of posterior composite bridges. Conversely, GB, PEEK, and Tri have the potential to cause fracture failures at the connectors rather than debonding.

Indirect restorative systems-A narrative review

OBJECTIVE

The background and clinical understanding of the properties of currently available indirect restorative systems and fabrication methods is, along with manufacturer and evidence-based literature, an important starting point to guide the clinical selection of materials for tooth and/or implant supported reconstructions. Therefore, this review explores most indirect restorative systems available in the market, especially all-ceramic, along with aspects of manufacturing process, clinical survival rates, and esthetic outcomes.

OVERVIEW

Progressive incorporation of new technologies in the dental field and advancements in materials science have enabled the development/improvement of indirect restorative systems and treatment concepts in oral rehabilitation, resulting in reliable and predictable workflows and successful esthetic and functional outcomes. Indirect restorative systems have evolved from metal ceramics and polymers to glass ceramics, polycrystalline ceramics, and resin-matrix ceramics, aiming to improve not only biological and mechanical properties, but especially the optical properties and esthetic quality of the reconstructions, in attempt to mimic natural teeth.

CONCLUSIONS

Based on several clinical research, materials, and patient-related parameters, a decision tree for the selection of indirect restorative materials was suggested to guide clinicians in the rehabilitation process.

CLINICAL SIGNIFICANCE

The pace of materials development is faster than that of clinical research aimed to support their use. Since no single material provides an ideal solution to every case, professionals must continuously seek information from well designed, long-term clinical trials in order to incorporate or not new materials and technological advancements.

Current Protocols for Resin-Bonded Dental Ceramics

Resin-bonded ceramic restorations are common treatment options. Clinical longevity of resin-bonded ceramic restorations depends on the quality and durability of the resin-ceramic bond. The type and composition of the specific ceramic determines the selection of the most effective bonding protocol. Such protocol typically includes a surface pretreatment step followed by application of a priming agent. Understanding of fundamental ceramic properties and chemical compositions enables the clinician to make proper material selection decisions for clinically successful and long-lasting restorations. Based on research accrued over the past decades, this article reviews and discusses current resin-bonding protocols to most commonly used dental ceramics.

Indirect repair of saliva-contaminated materials using veneering ceramics

PURPOSE

To analyze the in vitro efficacy of a surface conditioning liquid facilitating ceramic repairs of saliva-contaminated metal-ceramic and all-ceramic restorations.

MATERIALS AND METHODS

Specimens constructed from non-precious alloy (NPA), precious alloy (PA), lithium-disilicate (LD), zirconia (ZI), veneering ceramics for zirconia (VZI), veneering ceramics for lithium-disilicate (VLD), and veneering ceramics for metal alloys (VM) were manufactured (total: n = 168; each material n = 24). Veneering ceramic cylinders (thickness: 2mm) were hand-layered on top of the specimens. Shear bond strength (SBS) tests were performed, measuring the maximum bond strength (MBS) of the cylinders on the specimens. Following this, the specimens were artificially aged and stored in artificial saliva for 30 days at 37°C. After physical cleaning using aluminum oxide air abrasion, a new surface conditioning liquid was applied (test, n = 84) or not (control, n = 84). New ceramic cylinders were hand-layered followed by a second SBS test. Descriptive statistics, linear regression analyses, and a one-sample t-test (α = 0.05) were used to ascertain the differences within (pre- vs. post-repair) and between the groups.

RESULTS

All specimens in the test group could be repaired, whereas 18 repairs in the control group failed. After the repairs, an MBS decrease was observed for the NPA specimens of the control group (-15.5MPa, p = 0.004) but not among any of the test groups. Comparing the change in MBS between the test and control groups, the reduction was significantly higher in the repaired NPA specimens of the control group (mean difference 11.8 MPa, p = 0.017).

CONCLUSIONS

Using the analyzed surface conditioning liquid, metal-ceramic and all-ceramic materials can be repaired, while some repairs failed without the liquid. The initial bond strengths between core and veneering materials could be restored in all specimens when the new surface conditioning liquid was applied. This article is protected by copyright. All rights reserved.