Effect of hydrofluoric acid etching time on the resin bond durability of glass ceramic / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To analyze the effect of hydrofluoric acid (HFA) etching time on the resin bond durability of glass ceramic.</p><p><b>METHODS</b>Three groups of samples of machinable glass ceramic (ProCAD) were etched by 4.8% HFA for 0, 30 and 60 s respectively. The roughness parameters (Ra, Sm, S) and surface area of the samples, were measured with a 3D-laser scanning microscope. Then the ceramic surfaces were bonded with four resin cements (silane coupler/resin cement), which were Monobond S/Variolink II, Clearfil Ceramic Primer/Clearfil Esthetic Cement, GC Ceramic Primer/Linkmax HV, and Porcelain Liner M/SuperBond. The micro-bond strengths between the ceramic and the resin were tested at baseline and after the samples had been treated in 30000 thermal cycles.</p><p><b>RESULTS</b>The Ra [(3.89+/-1.94), (12.53+/-0.80), (13.58+/-1.10) microm] and surface area [(7.81+/-2.96), (30.18+/-2.05), (34.16+/-1.97) mm2] of ceramic increased with the increase of HFA etching time. The thermal cycling test reduced the bond strength of all test groups. The bond strength of Monobond S/Variolink II group [(3.59+/-3.51), (16.18+/-2.62), (20.33+/-2.45) MPa] and Clearfil Ceramic Primer/Clearfil Esthetic Cement group [(4.74+/-2.08), (7.77+/-1.55), (13.45+/-3.75) MPa] increased with the increase of HFA etching time; 30 s HFA etching group of Porcelain Liner M/SuperBond had higher bond strength [(22.00+/-1.64) MPa] than its 0 s HFA etching group [(12.96+/-4.17) MPa], and no significant difference was found between the 30 s and 60 s HFA etching groups of Porcelain Liner M/SuperBond [(20.42+/-3.01) MPa]. HFA etching time had no effect on the bond strength of GC Ceramic Primer/Linkmax HV.</p><p><b>CONCLUSIONS</b>HFA etching can improve the resin bond durability of glass ceramic, and the etching time is not only related to the change of ceramic surface roughness and area, but also to the characteristics of resins.</p>

A comparison of color space of Vitapan 3D-Master shade guides to nature teeth from Nanjing population / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To study the fitness of color dimension between Vitapan 3D-Master shade guides and nature teeth.</p><p><b>METHODS</b>2,159 nature teeth from Nanjing population and Vitapan 3D-Master shade guides were analyzed by dental chromameter ShadeEye NCC on CIE L*a*b* color system.</p><p><b>RESULTS</b>1) The color dimension of natural teeth displayed a broader range than those from Vitapan 3D-Master shade guides. Comparing with incisor group, canine-premolar group had better fitness with Vitapan 3D-Master shade guides. 2) In color space, incisor values a* shifted toward green (-a*), while the shade guide values a* located toward red (+a*). The shade guide lacked tabs of values L* 71-78 and a* -1.5-(-)0.2 for natural incisor. 3) According to the perceptibility threshold AE*ab<1.4, the match rates with Vitapan 3D-Master shade guides was 33% in incisor group and 50% in canine-premolar group.</p><p><b>CONCLUSION</b>Vitapan 3D-Master shade guides had inferior match with nature teeth from Nanjing population, especially in incisor.</p>