Surface degradation of glass ceramics after exposure to acidulated phosphate fluoride.
OBJECTIVE
This study evaluated the surface degradation effect of acidulated phosphate fluoride (APF) gel exposure on the glassy matrix ceramics as a function of time.


METHODS
Disc-shaped ceramic specimens (N = 120, 10/per ceramic material) were prepared in stainless steel molds (inner diameter: 5 mm, height: 2 mm) using 6 dental ceramics: 3 indicated for ceramic-fused-to-metal (Vita Omega 900, Carmen and Vita Titankeramik), 2 for all-ceramic (Vitadur Alpha and Finesse Low Fusing) and 1 for both types of restorations (IPS d.SIGN). The specimens were wet ground finished, ultrasonically cleaned and auto-glazed. All specimens were subjected to calculation of percentage of mass loss, surface roughness analysis and topographical description by scanning electron microscopy (SEM) before (0 min) and after exposure to 1.23 % APF gel for 4 min and 60 min representing short- and long-term etching effect, respectively. The data were analyzed using two-way ANOVA with repeated measures and Tukey's test (a=0.05).


RESULTS
Significant effect of the type of the ceramics (p=0.0000, p=0.0031) and exposure time (p=0.0000) was observed in both surface roughness and percentage of mass loss values, respectively. The interaction factor between both parameters was also significant for both parameters (p=0.0904, p=0.0258). Both 4 min (0.44+/-0.1 - 0.81+/-0.2 microm) and 60 min (0.66+/-0.1 - 1.04+/-0.3 microm) APF gel exposure created significantly more surface roughness for all groups when compared to the control groups (0.33+/-0.2 - 0.68+/-0.2 microm) (p<0.05). There were no significant differences in percentage of mass loss between the ceramics at 4 min (p>0.05) but at 60 min exposure, IPS d.SIGN showed the highest percentage of mass loss (0.1151+/-0.11). The mean surface roughness for Vita Titankeramik (0.84+/-0.2 microm) and Finesse Low Fusing (0.74.+/-0.2 microm) was significantly higher than those of the other ceramics (0.59+/-0.1 microm - 0.49+/-0.1 microm) and Vita Titankeramik (p<0.05) regardless of the exposure time. A positive correlation was found between surface roughness and percentage of mass loss for all ceramic materials [(r=0.518 (Vitadur Alpha), r=0.405 (Vita Omega 900), r=0.580 (Carmen), r=0.687 (IPS d.SIGN), r=0.442 (Finesse Low Fusing), r=0.572 (Vita Titankeramik), Pearson's correlation coefficient)]. The qualitative SEM analysis showed evidence of corrosive attack on all of ceramics at varying degrees.


CONCLUSIONS
The ceramics indicated for either metal-ceramic or all-ceramic restorations were all vulnerable to surface texture changes and mass loss after short-term and long-term APF gel exposure.
Ccahuana
Vanessa Zulema S
VZ
São José dos Campos Dental School, Department of Dental Materials and Prosthodontics, São Paulo State University, São José dos Campos, Brazil.
Ozcan
Mutlu
M
Mesquita
Alfredo Mikail Melo
AM
Nishioka
Renato Sussumo
RS
Kimpara
Estevão Tomomitsu
ET
Bottino
Marco Antonio
MA
D000149:Acidulated Phosphate Fluoride; D000538:Aluminum Silicates; D000704:Analysis of Variance; D002327:Cariostatic Agents; D002516:Ceramics; D003343:Corrosion; D045662:Dental Etching; D003776:Dental Porcelain / Q000737:chemistry; D005782:Gels; D006358:Hot Temperature; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D017680:Potassium Compounds; D018709:Statistics, Nonparametric; D013499:Surface Properties; D013997:Time Factors
D000538:Aluminum Silicates; D002327:Cariostatic Agents; D005782:Gels; D017680:Potassium Compounds; D003776:Dental Porcelain; C016447:feldspar; D000149:Acidulated Phosphate Fluoride; C023506:Glass ceramics