OBJECTIVEThe purpose of this study was to investigate how different surface roughness of opaque porcelain influence reflectance and CIE L* value of porcelain fused to metal (PFM) restorations.

METHODS48 casted Ni-Cr alloy metal specimens (12.0 mm x 1.0 mm) were fabricated with ShoFu Vintage Halo porcelain and divided into six groups, eight pieces for each group. The specimens in the first group without polishing were used as control. Other groups were polished against 200-, 400-, 600-, 800-, and 1000-grit sandpaper after sintered, respectively. Surface roughness and color parameters of the specimens were measured with a Surface Roughometer EX2154-13 and a spectrocolorimeter, respectively. Ra (arithmetical mean deviation of the profile) was the main standard value to describe the surface roughness of many kinds of meatal or porcelain materials, and here we used it to express surface roughness of opaque porcelain. The data were statistically analyzed by one-way analysis of variance (alpha = 0.05) in SPSS 13.0.

RESULTSThe reflectance value increased from 72.386 +/- 3.953 to 78.671 +/- 3.408, and CIE L* value from 90.189 +/- 1.200 to 93.496 +/- 1.070 with the increasing of surface roughness (Ra) of opaque porcelain from (0.226 +/- 0.069) microm to (0.706 +/- 0.082) microm. The same magnitude were also observed after body porcelain and enamel porcelain were sintered on with reflectance increased from 76.301 +/- 3.097 to 81.529 +/- 4.028, and CIE L* value from 80.694 +/- 1.564 to 84.604 +/- 2.964.

CONCLUSIONThe surface roughness of opaque porcelain had effects on the reflectance and value of PFM restorations. Within the limitation of this study, the recommended Ra range of opaque porcelain was 0.23-0.50 microm.