Objective To evaluate the influence of the substrate and the cement on the final color of ceramic crowns. Methods Prosthetic crowns (framework + porcelain) were fabricated using two all‐ceramic systems (YZ, 3 mol% yttria‐stabilized tetragonal zirconia; IZ, alumina‐based zirconia‐reinforced glass‐infiltrated ceramic) and a metal‐ceramic system (MC; n = 8). Metal (M) and resin (R) were used as substrate abutments. For R substrate, crowns were evaluated as seated (R) and after cementation (R‐C). CIELAB color coordinates were obtained using a dental spectrophotometer with D65 light illumination. CIELAB, CIEDE2000 (1:1:1) and CIEDE2000 (2:1:1) color difference metrics were used. Data were analyzed using 95% confidence intervals and compared to perceptibility (PT) and acceptability (AT) thresholds. Results The ∆Eab*, ∆E00(1 : 1 : 1), and ∆E00(2 : 1 : 1) values of the restorative systems evaluated using different substrates (M.R) were similar to the AT values of each metric. When non‐cemented and cemented crowns were evaluated (R.R‐C), MC had color difference values at PT and below AT; while YZ and IZ showed similar values to AT, for ∆Eab* and ∆E00(1 : 1 : 1) metrics. Conclusion The substrate and cement affected the final color of zirconia‐based all‐ceramic crowns, but the color differences corresponded to an acceptable match. Clinical Significance As both substrate and cement influence the final color of multi‐layered ceramic prosthesis, dentists and dental technicians should understand the optical properties of dental ceramics to reproduce the natural appearance of dental structures and maximize the chance for excellent color matches.

ResumoA zircônia tetragonal policristalina estabilizada por ítria (Y-TZP) vem sendo amplamente empregada na Odontologia como material de infraestrutura (IE) de coroas e próteses parciais fi xas devido às suas características mecânicas como alta resistência e tenacidade à fratura. O objetivo desta revisão de literatura é buscar evidências em estudos in vitro e in vivo a respeito do comportamento mecânico, adesão e longevidade clínica de próteses fi xas confeccionadas com IE de Y-TZP. Foram obtidos artigos, na base de dados online Medline/Pubmed, seguindo a seguinte combinação de palavras-chaves: zircônia tetragonal estabilizada por ítria ("Y-TZP"), adesão ("adhesion"; "bonding"), propriedades mecânicas ("mechanical properties"), estudos clínicos ("long-term clinical trials"), longevidade ("longevity"). A busca abrangeu os anos de 1990 a 2012. De acordo com a literatura, a Y-TZP apresenta propriedades mecânicas superiores às demais cerâmicas odontológicas devido a um mecanismo de tenacifi cação associado à transformação de fase cristalina (transformation toughening). Ainda, a silicatização associada a silanização tem sido indicada como o tratamento de superfície mais adequado para cimentação adesiva de IE em Y-TZP, além do uso de um cimento resinoso contendo monômeros fosfatados (MDP). Nos estudos clínicos, a Y-TZP tem mostrado altas taxas de sucesso como IE de coroas unitárias e PPFs. Apesar do comportamento mecânico e de união da Y-TZP não estarem completamente esclarecidos, estudos apontam resultados promissores em relação à aplicação clínica deste material. Palavras-chave: zircônia, cerâmicas dentais. Abstract Yttrium stabilized tetragonal zirconia polycrystal (Y-TZP) has been widely used in Dentistry as

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OBJECTIVES: to evaluate the effect of the type of ceramic framework material on the final color of all-ceramic restorations. The hypotheses tested were: (1) the final color of the restoration is different than the porcelain shade selected initially to veneer the framework and (2) different framework materials result in different colors of all-ceramic restorations. METHODS: Steel models simulating abutment teeth were used to design all-ceramic fixed partial dentures (FPDs). The FPDs were produced using three different framework materials (n=8): (YZ) yttria partially stabilized tetragonal zirconia polycrystal (LAVA, 3M); (IZ) glass-infiltrated alumina/zirconia (Vita In-Ceram Zirconia); (AL) polycrystalline alumina (Vita In-Ceram AL). Each framework was veneered with the recommended porcelain, VM9 for YZ and VM7 for IZ and AL groups (Vita). The porcelain shade used was 2M2. A uniform thickness of 1.2 mm of porcelain was applied around the retainers. The color difference (ΔE) and lightness difference (ΔL) between the selected porcelain shade (2M2) and the color of the final restoration were obtained using a clinical spectrophotometer (VITA Easyshade). Statistical analysis was performed using One-Way ANOVA and Tukey’s test (α=0.05). RESULTS: The ΔE mean values, standard deviation and statistical ranking for the experimental groups were: (YZ) 2.38 ± 0.44b; (IZ) 2.92 ± 0.67ab; (AL) 3.43 ± 0.84a. AL group showed the highest ΔE and ΔL mean values. IZ showed an intermediate ΔE value and statistically similar to AL and YZ groups. There was no significant difference between ΔL values for YZ and IZ groups. CONCLUSION:  Although the color difference between all experimental groups and the porcelain shade selected to veneer the restorations could be visually detected (ΔE>1.0), only AL showed a difference above the clinical threshold (ΔE>3.0). Thus, the first study hypothesis was partially accepted. In addition, the type of framework ceramic influenced the final restoration color, accepting the second study hypothesis.

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