The effect of repeated sintering on the color and light transmittance of glass ceramic restorations:
Sintering times ≤3, lightness increases slightly,
Sintering times ≥3, lightness gradually decreases.
2. Light transmittance:
Sintering times ≤2, the light transmittance increases,
Sintering times ≥2, the light transmittance decreases.
3. Hue and saturation:
Sintering times ≤3, shift to red-yellow phase,
Sintering times ≥3, shift to green-blue phase.
In order to ensure that the hue and saturation of the restoration are within the clinically acceptable range, the number of sintering should be ≤5.
——Effect of repeated sintering on the color and light transmittance of dental lithium disilicate glass ceramics [J]. West China Journal of Stomatology, 2015 (1).