Effects of extreme cooling methods on mechanical properties and shear bond strength of bilayered porcelain/3Y-TZP specimens.
OBJECTIVE
This study investigated the effect of extreme cooling methods on the flexural strength, reliability and shear bond strength of veneer porcelain for zirconia.


METHODS
Vita VM9 porcelain was sintered on zirconia bar specimens and cooled by one of the following methods: inside a switched-off furnace (slow), at room temperature (normal) or immediately by compressed air (fast). Three-point flexural strength tests (FS) were performed on specimens with porcelain under tension (PT, n=30) and zirconia under tension (ZT, n=30). Shear bond strength tests (SBS, n=15) were performed on cylindrical blocks of porcelain, which were applied on zirconia plates. Data were submitted to one-way ANOVA and Tukey's post hoc tests (p<0.05). Weibull analysis was performed on the PT and ZT configurations.


RESULTS
One-way ANOVA for the PT configuration was significant, and Tukey's test revealed that fast cooling leads to significantly higher values (p<0.01) than the other cooling methods. One-way ANOVA for the ZT configuration was not significant (p=0.06). Weibull analysis showed that normal cooling had slightly higher reliability for both the PT and ZT configurations. Statistical tests showed that slow cooling decreased the SBS value (p<0.01) and showed less adhesive fracture modes than the other cooling methods.


CONCLUSIONS
Slow cooling seems to affect the veneer resistance and adhesion to the zirconia core; however, the reliability of fast cooling was slightly lower than that of the other methods.
UNESP - Univ Estadual Paulista, Faculdade de Odontologia de Araraquara, R. Humaitá, 1680 Sala 415, Centro. Araraquara, SP 14801-903, Brazil.
Antonio A
AA
Almeida
Diogo
D
Longhini
Natália B
NB
Domingues
Claudinei
C
Santos
Gelson L
GL
Adabo
D000704:Analysis of Variance; D003080:Cold Temperature; D001840:Dental Bonding; D003776:Dental Porcelain; D003799:Dental Stress Analysis; D003801:Dental Veneers; D008422:Materials Testing; D055595:Mechanical Phenomena; D018583:Pliability; D033081:Shear Strength; D018709:Statistics, Nonparametric; D016019:Survival Analysis; D015019:Yttrium; D015040:Zirconium
C499362:yttria stabilized tetragonal zirconia; D003776:Dental Porcelain; D015019:Yttrium; D015040:Zirconium