| Objective:To study the effects of different thicknesses and optical properties of the porcelain veneer on the light intensity of LED-curing light,transmittance of porcelain veneers and the curing performance of light-cured resin cement under different light-curing protocols.Methods:Simulating clinical porcelain veneer restorations,lithium disilicate glass-ceramic blocks were first divided into two groups based on transparency HT and LT,and then into two subgroups based on shade A2 and BL2.They are HT A2;HT BL2;LT A2;LT BL2,respectively.According to the grouping,the ceramic blocks were cut,ground and polished into porcelain veneer specimens with thickness of 0.4 and 0.8 mm using automatic precision cutting machine and grinding and polishing machine.Divided into 8 groups,10 in each group,a total of 80 porcelain veneer specimens.The surface treatment of the porcelain veneers was measured by a portable radiometer under three different LED light curing units,and the surface morphology before and after the treatment was observed using a scanning electron microscope.A UV/Vis spectrophotometer measures the transmittance of porcelain veneers.According to the instructions,the light-curing resin cement was injected into a mold with a diameter of 5mm and a thickness of 500μm,and four different light-curing protocols were used(high light intensity mode 40s;low light intensity mode40s;high light intensity mode 20s;low light intensity mode 20s),the resin cement specimens under the porcelain veneer specimens with different optical properties(transparency and shade)were cured to prepare light-cured resin cement specimens.Divided into 16 groups,15 were prepared in each group,a total of 240 resin cement specimens.Fourier infrared spectrometer scanner was used to measure the degree of conversion of light-cured resin cement specimens.The microhardness tester measures the Vickers microhardness of light-cured resin cement specimens.Results:(1)The thickness(P＜0.05),transparency(P＜0.05)and shade(P＜0.05)of the porcelain veneer significantly affect the light intensity of the curing light.(2)The porcelain veneer before and after surface treatment(P>0.05)has no effect on the light intensity of the curing light.(3)The transparency of the porcelain veneer affects the transmittance of the porcelain veneer(P＜0.05).Porcelain veneer shade has no effect on transmittance(P>0.05).Porcelain veneers with high transparency have better transmittance.(4)The transparency(P＜0.05)of the porcelain veneer and light-curing protocol(P＜0.05)significantly affect the curing performance of the light-cured resin cement.Porcelain veneer shade(P>0.05)does not affect the polymerization properties of light-curing resin cement.When the optical property of the porcelain veneer is HT BL2 and the light-curing protocol is LCP1,the degree of conversion and Vickers microhardness value are the highest;while when the light-curing protocol is LCP4 and the optical property of the ceramic veneer is LT A2,the degree of conversion and Vickers microhardness value are the lowest.Conclusion:(1)The thickness,transparency and shade of the porcelain veneer have an impact on the light intensity of the LED light-curing unit,and the porcelain veneer before and after surface treatment has no effect on the light intensity of the light curing unit.Transparency significantly affects the transmittance of porcelain veneers,and the transmittance of porcelain veneers with high transparency is better than that of porcelain veneers with low transmittance.(2)The transparency of the porcelain veneers and light-curing protocol affect the curing properties of light-cured resin cement.Increasing the light intensity and exposure time can improve the curing performance of resin cement.Clinicians should consider a combination of porcelain veneer design and bonding to obtain the ideal bonded restoration. |
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