Abstract: BACKGROUND: The selection of appropriate ceramic material is crucial for esthetic all-ceramic restorations. In studies of the esthetic performance of dental restorations, color difference and light transmittance are often used as evaluation indicators. Factors influencing the color difference and light transmittance of all-ceramic restorations primarily include the type of ceramic material, hue, thickness, processing technique, abutment color, and adhesive.
OBJECTIVE: To investigate the impact of material type and thickness on the esthetic performance of all-ceramic restorations.
METHODS: Six representative machinable ceramic materials (conventional zirconia ZR-ST, resin-based ceramic RC, high-transmittance zirconia ZR-TT, leucite-reinforced glass-ceramic LE, lithium disilicate glass-ceramic LD, and feldspathic ceramic FP) were selected. Rectangular ceramic specimens (10.0 mm × 12.5 mm) with thicknesses of 0.8, 1.0, and 1.5 mm were prepared from each material. After corresponding surface treatments, the specimens were bonded to resin specimens (representing abutments) to create ceramic-resin composite specimens. CIE L*a*b* values, color difference ΔE, and light transmittance were measured before and after bonding.
RESULTS AND CONCLUSION: (1) When the abutment thickness does not reach infinite optical thickness, the type and thickness of ceramic material jointly influence the color and transmittance of the restoration. When the ceramic specimen thickness does not exceed 1.0 mm, the color after bonding to the resin sheet generally approaches blue-red. When the ceramic specimen thickness is 1.5 mm, the color after bonding to the resin sheet generally approaches blue-green, suggesting that color pre-compensation can be used to optimize esthetic matching when comparing all-ceramic restorations. (2) With the exception of the 1.5 mm thick ZR-ST ceramic, the color difference ΔE between the ceramic specimens and the resin sheet after bonding in all groups was less than 5. The color difference ΔE between the 0.8 mm ZR-ST ceramic specimen and the resin sheet was close to 3, and the color difference ΔE between the 1.0 mm ZR-TT ceramic specimen and the resin sheet was less than 3. This suggests that ZR-TT and ZR-ST ceramics may be potential options for minimally invasive restorations when the light transmittance of the affected tooth is low, the esthetic restoration space is limited, and high material strength is required. (3) The light transmittance of the ceramic specimen decreased after bonding and diminished significantly with increasing ceramic thickness. The RC ceramic specimen had a high light transmittance, and the color difference ΔE between the specimen and the resin sheet after bonding was close to 3, indicating excellent optical performance.

Key words: esthetic dental restoration, ceramic material;, esthetic performance, color difference, transmittance, minimally invasive prosthodontic procedure, CIE L*a*b*, color compensation