Effect Of Preoxidation On Strength Of Pure Titanium Porcelain Crown

Objective: To investigate the effect of the temperature of preoxidationtechnique on the strength of pure titanium porcelain crown, and whether thestrength is related to the different brands of pure titanium, expecting forexperimental reference for clinical application of pure titanium porcelaincrown.Materials and Methods：1Porcelain crowns preparation: a metal die of simulating crown core ofpremolars was produced by precision instrument. The impression of the metaldie was taken by silicon rubber and the ultra hard plaster was perfused. Totallywax models of72titanium substrate crowns were fabricated by wax dippedmethod. The three brands of titanium substrate crowns with0.3mm thicknesswere conventionally fabricated, each group had24samples. According to thepure titanium brands and the preoxidation temperature all crowns weredivided into12groups, each group included six samples: group A1(domestictitaniumⅠ, non-preoxidation), group A2(domestic titaniumⅠ, preoxidationat500℃),group A3(domestic titaniumⅠ, preoxidation at600℃),group A4(domestic titaniumⅠ, preoxidation at700℃),group B1(domestic titaniumⅡ,non-preoxidation), group B2(domestic titaniumⅡ, preoxidation at500℃),group B3(domestic titaniumⅡ, preoxidation at600℃),group B4(domestictitaniumⅡ, preoxidation at700℃),C1(Japan titanium, non-preoxidation),group C2(Japan titanium, preoxidation at500℃),group C3(Japan titanium,preoxidation at600℃),group C4(Japan titanium, preoxidation at700℃).According to the requirements of Duceratin Kiss porcelain system, a uniformthickness of1.2mm of porcelain was veneered on the crowns.2Strength test: five crowns of each group were tested for fracturestrength by universal load-testing machine. Data of fracture strength were recorded just samples fracture occurred, and the features of the fracturesurface were observed.3The feature of the titanium-porcelain bonding surface were observed byscanning electron microscope (SEM).Results:1Macroscopic observation, a large area of porcelain layer stripped fromthe crowns. The fracture location mostly appeared between the titanium oxidefilm and the substrate. The substrate of the titanium had no remains ofporcelain, and the dropped porcelain surface presented a uniform layer ofsilver film. Also, small part of the titanium substrate surface showed a tinyamount of bonder porcelain. The fracture of the titanium porcelain appeared inporcelain layer.2The strength values of porcelain crowns were as follows: group A11563.38±27.04N, group A21668.50±13.80N, group A31647.22±17.81N,group A41558.08±40.64N, group B11335.74±24.67N, group B21424.92±31.82N, group B31311.14±27.11N, group B41346.46±26.93N, groupC11341.78±26.18N, group C21438.46±32.40N, group C31315.68±26.39N, group C41350.38±29.62N.Factorial analysis was used to determine significant differences in thestrength values of porcelain crowns among different groups. The resultsshowed the difference was significant with different preoxidation temperaturefactor(P<0.05); and the difference was also significant with the differentbrands of pure titanium material factor(P<0.05), suggesting an interactiverelationship between the two factors．The multiple comparisons of the two factors were as follows:The results of different preoxidation temperature at the same brand oftitanium material were as follows. In the group of domestic titanium Ⅰ, therewere no significant differences in the strength values betweennon-preoxidation and preoxidation at700℃, preoxidation at500℃andpreoxidation at600℃(P>0.05). There were significant difference in thestrength values between preoxidation at500℃,preoxidation at600℃and non-preoxidation, preoxidation at700℃(P<0.05). In the group of domestictitaniumⅡ, there were no significant differences in the strength valuesbetween non-preoxidation, preoxidation at600℃and preoxidation at700℃(P>0.05). There were significant difference in the strength valuesbetween preoxidation at500℃and non-preoxidation, preoxidation at600℃,preoxidation at700℃(P<0.05). In the group of Japan titanium, there were nosignificant differences in the strength values between non-preoxidation,preoxidation at600℃and preoxidation at700℃(P>0.05). There weresignificant difference in the strength values between preoxidation at500℃andnon-preoxidation, preoxidation at600℃, preoxidation at700℃(P<0.05).The results of different brands of titanium material at the samepreoxidation temperature technique were as follows. There were significantdifference in the strength values between group domestic titaniumⅠand groupdomestic titaniumⅡ, group Japan titanium(P<0.05). There were no significantdifference in the strength values between group domestic titaniumⅡand groupJapan titanium(P>0.05).3Under the SEM, the titanium-porcelain interface feature of group A2,A3, B2, C2were clear, and the combination between titanium and porcelainwas tight. No obvious cracks and bubbles were observed. A continuousreaction thin layer at the interface showed better infiltration between titaniumand porcelain. For other groups, some holes or cracks were observed. Thetitanium-porcelain interface was not combined closely, which indicated thatthe infiltration between titanium and porcelain is worse.Conclusions：1The strength of pure titanium porcelain crown was related to thepreoxidation temperature. The pure titanium had the highest strength whenpreoxidation temperature was set500℃.2Different brands of pure titanium material also had certain effect on thestrength of pure titanium porcelain crown. Appropriate pure titanium material should be chosen for higher strength of porcelain crown.