Comparison of physical properties of the various 3D printing temporary crown and bridge resin / 대한치과재료학회지

Conventional dental resins for crown and bridge fulfill ISO 10477 and ISO 10993 before clinical application. Although 3D printing or rapid prototyping (RP) for the fabrication of temporary crown and bridge have been proposed, a little studies were reported for 3D printing resin for temporary crown and bridge. The purpose of this study was to evaluate the physical properties (such as water sorption and solubility, color stability and flexural strength) of the various 3D printing temporary crown and bridge resin following the ISO 10477:2018 and estimate the effect of chemical composition of resin on the physical properties. Four resins approved by KFDA and 4 experimental resins developed by different manufacturer were tested in this study. Samples were prepared with DLP typed 3D Printer (G-Printer) and post-cured using UV-light Cure Unit (Cure M). Proper 3D printing and post-curing conditions were selected for different 3D printing resins. Each test was performed according to the ISO 10477 and results were statistically analyzed using Tukey-multiple comparison test (p=0.05). Only group-B did not satisfied the ISO requirement ( 60 MPa). Resin components may affect the flexural strength, then user should check the components of 3D printing resin. Deficient degree of polymerization may lead to large water sorption, water solubility and color changes. Further study should be done comparison between specimens printed with specific 3D printer recommended by manufacturer and specimens used in this study.

Effects of acid-treatment conditions on the surface properties of the RBM treated titanium implants / 대한치과재료학회지

The purpose of this study was to evaluate the effect of acid-treatment conditions on the surface properties of the RBM (Resorbable Blast Media) treated titanium. Disk typed cp-titanium specimens were prepared and RBM treatments was performed with calcium phosphate ceramic powder. Acid solution was mixed using HCl, H2SO4 and deionized water with 4 different volume fraction. The RBM treated titanium was acid treated with different acid solutions at 3 different temperatures and for 3 different periods. After acid-treatments, samples were cleaned with 1 % Solujet solution for 30 min and deionized water for 30 min using ultrasonic cleanser, then dried in the electrical oven (37℃). Weight of samples before and after acid-treatment were measured using electric balance. Surface roughness was estimated using a confocal laser scanning microscopy, crystal phase in the surface of sample was analyzed using X-ray diffractometer. Surface morphology and components were evaluated using Scanning Electron Microscope (SEM) with Energy Dispersive X-ray spectroscopy (EDX) and X-ray Photoemission Spectroscopy (XPS). Values of the weight changes and surface roughness were statistically analyzed using Tukey-multiple comparison test (p=0.05). Weight change after acid treatments were significantly increased with increasing the concentration of H₂SO₄ and temperature of acid-solution. Acid-treatment conditions (concentration of H₂SO₄, temperature and time) did not produce consistent effects on the surface roughness, it showed the scattered results. From XRD analysis, formation of titanium hydrides in the titanium surface were observed in all specimens treated with acid-solutions. From XPS analysis, thin titanium oxide layer in the acid-treated specimens could be evaluated. Acid solution with 90℃ showed the strong effect on the titanium surface, it should be treated with caution to avoid the over-etching process.