Development of Powder Jet Deposition Technique and New Treatment for Discolored Teeth

The powder jet deposition (PJD) process is for creation of a hydroxyapatite (HA) layer on human teeth. To develop the PJD device, the layer-forming properties have improved. Created HA layers with a new handpiece-type PJD device demonstrate excellent material properties in vitro. Titanium dioxide (TiO2) is known to cause whitening because of the selective reflection of the light. Therefore, we assessed the possibility of using the creation of TiO2-HA layers with the new PJD device as a new treatment for discolored teeth. In this study, the microstructural and mechanical properties of TiO2-HA layers were evaluated under the same conditions of the previous study. These properties were evaluated before and after 500 cycles of thermal cycling (5–55 °C). Furthermore, the CIE L*a*b* color system was used for color measurement and ⊿E* values for color differences were calculated. The maximum thickness of the TiO2-HA layers was about 60 μm. There were no significant differences in thickness, hardness, or bonding strength before and after thermal cycling. The layers showed an increased L* parameter and a decreased b* parameter, and the color difference ⊿E* was approximately 6.7 units. Creation of TiO2-HA layers by PJD might be a valuable new treatment for discolored teeth.