Purpose: Zirconium silicate (ZrSiO₄) particles were employed for the air abrasion of dental zirconia surfaces, with the aim of utilizing the residual silicon on the surface to enhance adhesion through silane coupling.

Methods: For the surface treatment of yttria-stabilized zirconia test specimens, zirconium silicate particles were used as an abrasive medium for air abrasion. For comparison, commonly used alumina particles were also used for air abrasion. For bonding, a resin-based luting agent and primer were used following the manufacturer’s instructions. To investigate the silane coupling effect induced by air abrasion, bonding tests were conducted using a different resin-based luting agent and a primer containing a silane coupling agent. Comparative analysis was performed to evaluate the influence of the silane coupling agent on the bonding strength.

Results: The bonding strength of specimens treated with zirconium silicate air abrasion and a porcelain primer containing a silane coupling agent was 8.4 ± 1.9 MPa, which was significantly higher than those of unprimed specimens (5.9 ± 1.2 MPa) and a control group (5.2 ± 1.6 MPa). However, the bonding strength was lower than that of zirconia treated by alumina air abrasion at pressures of 0.2 and 0.4 MPa (12.1 ± 2.1 and 12.2 ± 2.1 MPa, respectively).

Conclusion: The use of zirconium silicate as an air abrasion medium improves the bonding strength of yttria-stabilized zirconia when combined with silane coupling.

Purpose: This study investigated whether or not cervical vertebral morphology could be automatically classified using a deep-learning system.

Methods: Nine hundred and ninety-nine cephalometric radiographs obtained for orthodontic diagnoses were used in the present study. Segmented rectangular images between the second and fourth cervical vertebrae were resized with a patch size of 300 × 300 pixels (resized images) or padded with black images on the right and left sides, keeping their aspect ratio unchanged (padded images). Seven hundred and ninety-nine and 200 images were defined as the training and test data, respectively. Le Net and Alex Net Neural Network Console architectures were used to classify the images into two groups based on cervical vertebral maturation (CVM). The classifications of resized images using Le Net and Alex Net were designated Le Net Resizing and Alex Net Resizing, respectively. The classifications of the padded images using Le Net and Alex Net were designated Le Net Padding and Alex Net Padding, respectively. The accuracy of the classification using deep learning was evaluated.

Results: The average accuracies of the classification of CVM using Le Net Resizing and Le Net Padding were 59.0% and 89.5%, respectively. The average accuracy of classification of CVM using Alex Net Resizing and Alex Net Padding was 90.5% and 93.0%, respectively.

Conclusion: The deep-learning system using Le Net Padding, Alex Net Resizing, and Alex Net Padding showed high accuracy in classifying images into two groups based on CVM.

Purpose: Nickel-titanium (Ni-Ti) orthodontic archwire corrodes under the application of oral fluoride products. This study aimed to develop a thin-film coating for Ni-Ti archwire to prevent surface corrosion by fluoride attack while maintaining its superelasticity and without increasing friction with the bracket.

Methods: A thin yttria (Y₂O₃) film was deposited onto Ni-Ti archwire using a molecular precursor method. The surface of Y₂O₃-coated Ti disk was observed by scanning electron microscope (SEM) and its hardness was measured and was analyzed by X-ray photoelectron spectroscopy (XPS). Y₂O₃-coated Ni-Ti archwires were immersed in acidulated phosphate fluoride (APF) for 30 min, and their corrosion resistance was observed using SEM. Static friction between the archwire and orthodontic bracket was measured using a custom-made apparatus. Three-point bending tests were performed using an original three-point bending apparatus.

Results: The entire archwire surface was coated with Y₂O₃ without visible peeling or cracks. XPS revealed the presence of the Y₂O₃ coating. There were no significant differences in micro-Vickers hardness before and after coating. There was no remarkable corrosion of the Y₂O₃-coated Ni-Ti surface, and the presence of the coated layer was still observed after immersion in APF. There were no significant differences in static friction between Ni-Ti and Y₂O₃-coated Ni-Ti archwire. Three-point bending tests indicated that Y₂O₃-coated Ni-Ti archwire can maintain the same superelastic properties as Ni-Ti archwire.

Conclusion: Y₂O₃-coated Ni-Ti archwire can be applied to orthodontic treatment because of its corrosion resistance to fluoride attack, whilst maintaining the same friction ability and superelasticity as Ni-Ti archwire.