Atomic layer deposition SiO2 films over dental ZrO2 towards strong adhesive to resin

Shear Bond Strength to Enamel, Mechanical Properties and Cellular Studies of Fiber-Reinforced Composites Modified by Depositing SiO2 Nanofilms on Quartz Fibers via Atomic Layer Deposition

Introduction

Poor interfacial bonding between the fibers and resin matrix in fiber-reinforced composites (FRCs) is a significant drawback of the composites. To enhance the mechanical properties of FRC, fibers were modified by depositing SiO2 nanofilms via the atomic layer deposition (ALD) technique. This study aims to evaluate the effect of ALD treatment of the fibers on the mechanical properties of the FRCs.

Methods

The quartz fibers were modified by depositing different cycles (50, 100, 200, and 400) of SiO2 nanofilms via the ALD technique and FRCs were proposed from the modified fibers. The morphologies, surface characterizations of nanofilms, mechanical properties, and cytocompatibility of FRCs were systematically investigated. Moreover, the shear bond strength (SBS) of FRCs to human enamel was also evaluated.

Results

The SEM and SE results showed that the ALD-deposited SiO2 nanofilms have good conformality and homogeneity. According to the results of FTIR and TGA, SiO2 nanofilms and quartz fiber surfaces had good chemical combinations. Three-point bending tests with FRCs showed that the deposited SiO2 nanofilms effectively improved FRCs' strength and Group D underwent 100 deposition cycles and had the highest flexural strength before and after aging. Furthermore, the strength of the FRCs demonstrated a crescendo-decrescendo tendency with SiO2 nanofilm thickness increasing. The SBS results also showed that Group D had outstanding performance. Moreover, the results of cytotoxicity experiments such as cck8, LDH and Elisa, etc., showed that the FRCs have good cytocompatibility.

Conclusion

Changing the number of ALD reaction cycles affects the mechanical properties of FRCs, which may be related to the stress relaxation and fracture between SiO2 nanofilm layers and the built-up internal stresses in the nanofilms. Eventually, the SiO2 nanofilms could enhance the FRCs' mechanical properties and performance to enamel by improving the interfacial bonding strength, and have good cytocompatibility.

Construction of Nanostructured Glass-Zirconia to Improve the Interface Stability of Dental Bilayer Zirconia

Bilayer zirconia restoration is one of the most commonly used restorations in dental practice, but the high frequency of the cohesive/adhesive fracture of veneered porcelain is still a problem. This paper focuses on the development of nanostructured glass-zirconia to improve the interface stability of dental zirconia substrate and veneered porcelain. A novel SiO₂-Li₂O-Al₂O₃ (SLA) glass was prepared and infiltrated into the surface of fully sintered dental zirconia to obtain nanostructured glass-zirconia structure. The prepared glass-zirconia was analyzed with scanning electron microscopes (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction spectroscopy (XRD). The wettability, roughness and 3D morphology of zirconia were altered, and shear bonding strength (SBS) test demonstrated almost double increase in SBS values of the nanostructured glass-zirconia structure. The failure modes and microstructure characteristics also verified the improved interfacial stability. This investigation provides a promising method for enhancing the structural stability of bilayer zirconia restorations.