Objective: To evaluate the application effect of the platform switching implants in maxillary anterior region, to explore the effect of platform switching technology on the surrounding tissues. Methods: 55 patients with 60 single maxillary anterior implants were divided into two groups: platform-switching implants group (Ankylos), 25 patients with 28 implants; butt-joint implants group (Nobel Replace), 30 patients with 32 implants. The patients received follow-up care more than 1 and 2 year after the final setting of the prosthesis, at which time periapical radiographs were taken. The marginal bone level around the implant and Pink Esthetic Score (PES) were measured for comparison. Results : The average marginal bone changes of platform-switching implants after 1 year and 2 year were (-0.41 ± 0.36) mm and (-0.55 ± 0.33) mm respectively; and the ones of butt-joint implants were (-1.77 ± 0.54) mm and (-1.82 ± 0.61) mm. The average PES of platform- switched implants after 1 year and 2 year were 10.43 ± 1.37 and 10.32 ± 1.21 respectively; the ones of butt-joint implants were 9.21 ± 0.97 and 9.16 ± 0.95. There were significantly differences of marginal bone changes and PES between both groups (P < 0.05). Conclusion Platform switching implant in the maxillary aesthetics area is more effective in preserving the surrounding bone tissue and aesthetic effect.

Objective : To compare and analyze the effects of thermal etching on the shear strength of zirconia substrates and decorative ceramics. Methods: A total of 20 specimens made with zirconia ceramics were randomly divided into an observation group and a control group with 10 cases in each group. The control group was treated with sandblasting, while the observation group was treated with sandblasting and thermal etching. The surface characteristics were examined by scanning electron microscope (SEM) and phase analysis of X-ray diffraction (XRD), and the shear strength was tested using a universal testing machine. The characteristics of surface destruction were examined by SEM. Results : SEM showed that the peak structure was observed in both groups. The observation group exhibited deep fissures, and the control group exhibited small fissures. The diffraction peaks of the two groups are similar. The T (101) peak is the main peak, and both groups exhibit an M (111) peak. However, the peak intensity is relatively small. The relative levels of monoclinic zirconia were 15.16% in the observation group and 16.22% in the control group. The shear bond strength of the observation group was 24.74 ± 3.02 MPa, which was significantly higher than that of the control group at 21.09 ± 2.58 MPa. The difference was statistically significant (t=2.599, P=0.021). In the control group, the porcelain residue on the zirconia surface was minimal at low magnification, and the zirconia substrate was obviously exposed. The zirconia surface was similar to cristae obliqua at high magnification, and the porcelain exhibited a scattered distribution. In the observation group, a large amount of residual veneer porcelain remained on the zirconia surface at low magnification, but considerable porcelain was observed at high magnification. Conclusion Thermal etching and sandblasting treatment can improve the shear strength of zirconia substrate.