Objective. To determine the translucency of human and bovine enamel and dentin using reflection spectrophotometers. Material and Methods. The color of intact human and bovine enamel and dentin specimens was measured over a white and a black plasticine backing using two spectrophotometers with different aperture sizes; translucency parameter (TP) and contrast ratio (CR) were calculated. Plasticine was used as backing because the specimens were not uniform. The TP values of five composite resins measured over the backings of plasticine and reflectance standards were also determined. Results. There were no significant differences between the TP values of the composite resins measured over the backings of plasticine and reflectance standards (p>0.05). Mean TP values of 1 mm thick bovine enamel, bovine dentin, human enamel and human dentin were 14.7, 15.2, 18.7, and 16.4, respectively, based on the 3 mm round aperture. There were significant correlations between the TP values measured by the two apertures; the bigger the aperture size, the higher the TP value (r=0.87–0.91, p<0.01). The translucency of enamel and dentin increased in direct proportion to wavelength and in inverse proportion to thickness (r=0.87–0.91). Mean CR values were negatively correlated with the TP values (r = −0.93 to −0.78). Conclusions. These data could be used as references in the development of esthetic restorative materials and clinical shade-matching.

Kim MJ, et al. J Adv Prosthodont. 2013 May;5(2):161-166. http://dx.doi.org/10.4047/jap.2013.5.2.161

Jung YS, et al. J Adv Prosthodont. 2010 Sep;2(3):111-115. http://dx.doi.org/10.4047/jap.2010.2.3.111

3D printing of denture artificial teeth with resin materials is worthy of study in a novel way. This study evaluated chipping and indirect tensile fracture resistance of 3D printing resin material (Dentca 3D printing denture teeth resin) compared with conventionally prefabricated resin denture teeth (Premium-8, Surpass, SR-Orthosit-PE, and Preference). One hundred tooth specimens were prepared for testing. The 3D printed tooth specimens were printed at a 50 µm layer thickness with methacrylate-based photopolymerized resin by stereolithography 3D printing. Chipping and indirect tensile fracture tests were conducted at a speed of 1 mm/min until fracture. The indirect tensile fracture loads of the 3D printed resin teeth were higher than those of Premium-8, Surpass, and SR-Orthosit-PE, and lower than those of Preference teeth. Regarding chipping resistance, the 3D printed resin teeth were not different from Surpass and SR-Orthosit-PE, and were lower than Premium-8 and Preference teeth. The 3D printed resin teeth exhibited vertical fracture of the loaded cusp without deformation in chipping. The 3D printed resin teeth showed simultaneous fracture of two cusps in indirect tensile fracture, unlike other teeth. The results of this study suggest that 3D printing technology using resin materials provides adequate fracture resistance for denture artificial tooth use.