Quantitative examination of factors influencing the colour reproduction ability of lithium disilicate glass-ceramics.

BACKGROUND: Effects of ceramic translucency, layer thickness, and substrate colour on the shade of lithium disilicate glass-ceramic restorations proved to be significant in several studies, however, quantitative, numerical results on the relationship between the colour difference and these parameters are still lacking. The purpose of this in vitro study was to quantitatively determine how the colour reproduction ability of a lithium disilicate glass-ceramic is affected by its translucency, layer thickness, and substrate colour. METHODS: Ceramic samples were prepared from A2 shade IPS e.max CAD blocks with high and low translucencies (HT and LT) in a thickness range of 0.5-2.5 mm (+/- 0.05 mm). Layered samples were acquired utilizing composite substrates in 9 shades; transparent try-in paste was used. The spectral reflectance of the specimens was assessed under D65 standard illumination with a Konica Minolta CM-3720d spectrophotometer. The CIEDE2000 colour difference (ΔE00) between two samples was analysed using perceptibility and acceptability thresholds set at 50:50%. Statistical analysis involved linear regression analysis and the Kruskal-Wallis test. RESULTS: An increase in the thickness of 0.5 mm reduced the ΔE00 of the HT samples to 72.8%, and that of the T samples to 71.1% (p < 0.0001). 7 substrates with HT and LT specimens had significantly different results from the mean (p < 0.05). A thickness of 0.5 mm is not sufficient to achieve an acceptable result at any level of translucency, while the low translucency ceramic at a thickness of 1.5 mm gave acceptable results, except for severely discoloured substrates (ND8 and ND9). CONCLUSIONS: The colour reproduction ability of lithium disilicate glass-ceramics is significantly affected by their translucency, layer thickness, and 7 substrates out of 9 substrates examined.

Effect of thickness, translucency, and substrates on the masking ability of a polymer-infiltrated ceramic-network material.

OBJECTIVE: The aim of this in vitro study is to evaluate the masking ability of polymer-infiltrated ceramic-network materials (PICN) with different translucencies and thicknesses on multiple types of substrates. MATERIALS AND METHODS: Ceramic samples were prepared of VITA ENAMIC blocks in two different translucencies (2M2-T, 2M2-HT) in a thickness range of 0.5-2.5 mm (±0.05 mm). Layered specimens were obtained using composite substrates in nine shades and transparent try-in paste. Spectral reflectance of specimens was measured using a Konica Minolta CM-3720d spectrophotometer and D65 standard illumination. CIEDE2000 color difference (ΔE00 ) between two samples was evaluated using 50%:50% perceptibility and acceptability thresholds. Specular component of the reflection was examined with Specular Component Excluded (SCE) and Included (SCI) settings. Statistical evaluation was performed by linear regression analysis, Kruskal-Wallis test, and multiplicative effect analysis. RESULTS: An increase in thickness of 0.5 mm reduces ΔE00 of HT samples to 73.5%, of T samples to 60.5% (p < 0.0001). Five substrates with HT specimens, and three substrates with T specimens had significantly different results from average (p < 0.05). There is a significant difference between SCE and SCI data depending on the wavelength (p < 0.0001). CONCLUSIONS: Masking ability of PICN materials is influenced by the thickness and translucency of the ceramic, and by the substrate. Reflection of the examined PICN material is characterized by both diffuse and specular reflection. CLINICAL SIGNIFICANCE: Although PICN materials have been available on the market for 10 years now, there is a lack of information regarding their masking ability. Acquiring in-depth data and thereby practical experience of the factors affecting the esthetics of PICN materials is essential for creating perfectly lifelike restorations.

Prosthetic rehabilitation of a patient with ectrodactyly-ectodermal dysplasia-cleft lip/palate syndrome through a hybrid workflow: A case report with 2-year follow-up.

AIM: Ectrodactyly-ectodermal dysplasia-cleft lip/palate (EEC) syndrome is a rare genetic disorder that affects ectodermal derived structures, including teeth, nails, hair, and sweat glands. Prosthetic rehabilitation of patients with EEC syndrome is essential towards improving their overall quality of life. METHODS AND RESULTS: In the case shown, a telescopic retained overdenture was made on the lower jaw based on digital impression of a patient with EEC syndrome associated with cleft lip and cleft palate. Due to the congenital anomalies and limited mouth opening, the impression was taken with intraoral scanner, and after designing the telescopes on the digital model, the primary and secondary telescopes were confectioned by selective laser sintering. CONCLUSION: Combining digital dental technology and conventional clinical prosthetic treatment methods, results in a well-functioning overdenture even in such complicated situations. The prosthodontic rehabilitation of patients with ECC helps to restore the masticatory and phonetic functions, increases the patient's self-esteem, and prevents further psychological trauma caused by hypodontia.