OBJECTIVE: To evaluate the effect of repeated sintering on the color and translucency of dental lithium disilicate-based glass ceramic. METHODS: Thirty disc specimens (10 mm in diameter, and 1.00 mm ± 0.01 mm in thickness) were fabricated using an IPS e.max Press HT A2 ingot and then randomly divided into six groups (SO, S1, S2, S3, S4, and S5) (n = 5). Each group was sintered 0, 1, 2, 3, 4, and 5 times individually according to the manufacturer's recommendation. After polishing, ultrasonic cleaning, and drying, the color parameters (L*, a*, and b* values) and transmittance (τ) of all the specimens were measured using a ShadeEye NCC dental colorimeter and a TM-2 spectrophotometer, respectively. Subsequently, C*ab and ΔE were calculated. The results were statistically analyzed using SPSS 17.0 software for ANOVA and LSD. RESULTS: After repeated sintering, the L* value significantly decreased (P < 0.05), and the a*, b*, and C*ab values initially increased and then decreased (P < 0.05). The color parameters (L*, a*, and b*) and the C*ab values of group S3 were higher than those of the other groups. The τ values initially increased and then decreased (P < 0.05), and these values were optimal when sintered twice. In terms of transmittance (τ), statistical differences existed between the following groups: S0 and S2, S0 and S3,.S2 and S5, and S3 and S5 (P < 0.05). Compared with group S0, the color differences ΔE were 0.89 minimally and 2.01 maximally after different sintering times, which can be clinically acceptable. CONCLUSION: Repeated sintering can affect the color and translucency of the IPS e.max Press lithium disilicate-based glass ceramic, but the color difference can be clinically acceptable.
OBJECTIVE: To evaluate the effect of repeated sintering on the color and translucency of dental lithium disilicate-based glass ceramic. METHODS: Thirty disc specimens (10 mm in diameter, and 1.00 mm ± 0.01 mm in thickness) were fabricated using an IPS e.max Press HT A2 ingot and then randomly divided into six groups (SO, S1, S2, S3, S4, and S5) (n = 5). Each group was sintered 0, 1, 2, 3, 4, and 5 times individually according to the manufacturer's recommendation. After polishing, ultrasonic cleaning, and drying, the color parameters (L*, a*, and b* values) and transmittance (τ) of all the specimens were measured using a ShadeEye NCC dental colorimeter and a TM-2 spectrophotometer, respectively. Subsequently, C*ab and ΔE were calculated. The results were statistically analyzed using SPSS 17.0 software for ANOVA and LSD. RESULTS: After repeated sintering, the L* value significantly decreased (P < 0.05), and the a*, b*, and C*ab values initially increased and then decreased (P < 0.05). The color parameters (L*, a*, and b*) and the C*ab values of group S3 were higher than those of the other groups. The τ values initially increased and then decreased (P < 0.05), and these values were optimal when sintered twice. In terms of transmittance (τ), statistical differences existed between the following groups: S0 and S2, S0 and S3,.S2 and S5, and S3 and S5 (P < 0.05). Compared with group S0, the color differences ΔE were 0.89 minimally and 2.01 maximally after different sintering times, which can be clinically acceptable. CONCLUSION: Repeated sintering can affect the color and translucency of the IPS e.max Press lithium disilicate-based glass ceramic, but the color difference can be clinically acceptable.