Ceramics are very important in the science of dental biomaterials. Among all dental ceramics, zirconia is in evidence as a dental biomaterial and it is the material of choice in contemporary restorative dentistry. Zirconia has been applied as structural material for dental bridges, crowns, inserts, and implants, mostly because of its biocompatibility, high fracture toughness, and radiopacity. However, the clinical success of restorative dentistry has to consider the adhesion to different substrates, which has offered a great challenge to dental zirconia research and development. This study characterizes zirconia as a dental biomaterial, presenting the current consensus and challenges to its dental applications.

To evaluate the substrate masking ability of different ceramic systems used for complete crowns and assess the influence of their association with an opaque resin-based luting agent (OLA). Eleven ceramic groups were tested (n=10). Bilayer groups were: ZrPc - zirconia+porcelain; CAD-onHT - zirconia+high translucent lithium disilitace; CAD-onLT - zirconia+low translucent lithium disilicate; LDPc - high opaque lithium disilicate+porcelain. Monolithic groups were: TZ - high translucent zirconia; TLS - translucent, zirconia-reinforced lithium silicate; HTLS - high translucent, zirconia-reinforced lithium silicate; LTLD - low translucent lithium disilicate; HTLD - high translucent lithium disilitace; LGC - leucite-reinforced glass ceramic; FC - feldsphatic ceramic. The substrates adopted were resin composites shaded A1 (control), A3.5 and C4; coppery and silvery metals. Color differences (ΔE00) and translucency parameter (TP00) were assessed with the CIEDE2000 formula. ΔE00 was obtained assessing the ceramic influence only and in association with OLA. Zirconia groups presented lower ΔE00 and TP00. CAD-on structures associated to OLA led to the lower ΔE00 when tested over metals. ΔE00 for LDPc were similar to zirconia when associated to OLA. Monolithic groups presented significant higher ΔE00 and TP00 compared to bilayers, with ΔE00 below the acceptability threshold only when associated to OLA over substrate shade A3.5. Ceramic type and the white-opaque resin-based luting agent presented a significant effect on the substrate masking ability. All the discolored substrates tested are adequately masked with veneered zirconia or with LDPc (preferably associated to OLA). The CAD-on technique associated with OLA improved the masking ability over metallic substrates.

Bacchi A, et al. J Adv Prosthodont. 2015 Oct;7(5):375-379. http://dx.doi.org/10.4047/jap.2015.7.5.375