Correlation between 2D and 3D measurements of cement space in CAD-CAM crowns.

STATEMENT OF PROBLEM: Although the 2D analysis of prosthesis cementation space has been popular, its correlation with volumetric comparison (3D data) of cement space is unclear. PURPOSE: The purpose of this in vitro study was to evaluate the cement space in computer-aided design and computer-aided manufacturing (CAD-CAM) crowns of different materials and correlate 2D measurements of cement space with their corresponding 3D values (volume of cement space) by using microcomputed tomography (µCT) analysis of regions of interest. MATERIAL AND METHODS: Ten molar crowns were milled in lithium disilicate (LD), resin nanoceramic (RN), and zirconia (Z) ceramics. Silicone replicas were produced and used as the analog cement layer and scanned with a desktop X-ray microfocus CT scanner. Twenty-eight slices were evaluated in 3 regions: marginal, axial, and occlusal (n=84 measurement points/specimen). After 3D reconstruction of the cement space, the volume was calculated. Data were statistically evaluated through 2-way ANOVA and Bonferroni test (α=.05). The Pearson correlation test was used to investigate the correlation between the 2D and 3D data. RESULTS: The volumes of the occlusal (LD 10 ±1 mm3; RN 9 ±1 mm3) and axial regions (LD 9 ±2 mm3; RN 8 ±1 mm3) were significantly higher than the volume of the marginal region for LD and RN specimens (LD 6 ±2 mm3; RN 4 ±1 mm3) (both P<.001). For the Z group, the axial region had the highest volume (19 ±2 mm3), followed by the volumes of the occlusal (15 ±1 mm3) and marginal regions (12 ±1 mm3). The Pearson correlation test determined a moderate positive correlation of the marginal area (r=0.606, P<.001) and of the axial region (r=0.588, P<.001). However, a moderate negative correlation was found between volume and thickness of the occlusal area (r=-0.437, P=.016). CONCLUSIONS: Z showed more volume of cement space, as well as thicker cement space than LD and RN. The µCT analysis is an efficient method of analyzing cement thickness and volume in ceramic crowns at the selected regions of interest. A moderate positive correlation was found between the 2D and 3D analyses for the axial and marginal regions of ceramic crowns.

Comparison of marginal adaptation and internal fit of monolithic lithium disilicate crowns produced by 4 different CAD/CAM systems.

OBJECTIVES: To evaluate the marginal adaptation and internal space of crowns produced by 4 CAD/CAM systems using microcomputed tomography (µCT) and replica technique (RT). MATERIALS AND METHODS: Monolithic lithium disilicate crowns were milled (Ceramill, Cerec, EDG, and Zirkonzahn) (n = 10). The cement film obtained with low viscosity silicone was scanned by the µCT system and captured by a stereomicroscope, according to RT. Two-way ANOVA followed by Tukey's test were used for statistical analysis (α = 0.05). A uniformity index (UI) was idealized to describe the distribution of crowns' internal space and submitted to the Kruskal-Wallis and Tukey's test (α = 0.05). The correlation between µCT and RT was performed by Pearson's Correlation Coeficient (α = 0.05). RESULTS: Marginal adaptation and internal space were statistically significant different between the experimental groups for the µCT and RT (p < 0.05). The medians of the 4 systems tested were within clinically acceptable range and the mean (± SD) highest marginal discrepancy was recorded in the Ceramill group at 133.0 ± 71.5 µm (µCT) and 90.6 ± 38.5 µm (RT). For internal fit, the UI disclosed a better distribution of the internal space for the Zirkonzahn group (p < 0.001). There was a strong correlation between the methods (p = 0.01 and r = 0.69). CLINICAL RELEVANCE: Because of the variability of the CAD/CAM systems available, evaluating their accuracy is of clinical interest. The 4 systems are capable to produce restorations adaptated within clinically appropriate levels. The µCT and RT are efficient adaptation methodologies.

Analysis of correlation between optical and microtomography measurements of cementation space in CAD-CAM ceramic crowns.

STATEMENT OF PROBLEM: Identical computer-aided design (CAD) parameters may be used to mill a variety of ceramic materials for computer-aided design and computer-aided manufacture (CAD-CAM) crowns. Whether milled crown spacing matches the designed parameters when more than a single evaluation method is applied is unknown. PURPOSE: The purpose of this in vitro study was to correlate the stereomicroscope and the microcomputer tomography (µCT) 2-dimensional analysis of the cementation space with the replica technique in assessing 3 different ceramic materials. MATERIAL AND METHODS: The specimens were milled in lithium disilicate, resin nanoceramic, and zirconia (n=30). The cement space was measured at the marginal, axial, and occlusal regions. One hundred twenty measurements of each material were used to correlate the methodologies. Data were statistically evaluated with 2-way repeated measures ANOVA and the Tukey test (α=.05). The Pearson correlation coefficient was used for each region for both methodologies (µCT and optical microscopy) separately. RESULTS: For the µCT analysis, no differences were observed (P>.05) among the materials, but the axial region showed a positive correlation with the marginal (r=0.957) and occlusal regions (r=0.349); the same was observed between the occlusal and marginal regions (r=0.338). However, for stereomicroscope evaluation, resin nanoceramic and zirconia present similar cementation space (P=960), both being different from lithium disilicate (P<.05). The marginal region presented a positive correlation with axial (r=0.149) and occlusal regions (r=0.344), but the axial region showed negative correlation with the occlusal surface (r=-0.205). CONCLUSIONS: The measurements of the scanned replicas were accurate when thinner sections were under measurement. Although the same space parameters were set in the CAD software program, definitive internal dimensions varied among the milled crowns.

Esthetic rehabilitation with zirconia on tooth and morse taper implant: case report / Reabilitação estética em zircônia sobre dente e implante cone morse: caso clínico

Among the ceramic materials used in dentistry, Zirconia presents the ideal opacity for cases where the clinical challenge is to neutralize the difference in the colors of the substrates. The "ceramic steel", so called by some authors, guarantees to Zirconia resistance and hardness similar to a metal, but with aesthetic advantages superior to the metal-ceramic restorations, which can exhibit exposure of the metal band over time. This article describes a complex rehabilitation treatment involving dental elements with different substrates: 11 - vital tooth with large crown damage; 21 ­ endodontically treated tooth and cast metal core; 22 - Morse taper implant. The selection of a completely zirconia-based ceramic system allowed masking the different conditions of substrates, so achieving the esthetic expectations. Moreover, considering the patient's high smile line, excellent gingival esthetics was obtained with an internal connection Morse taper implant associated with an individualized anatomic abutment.

Dentre os materiais cerâmicos utilizados na Odontologia, a Zircônia apresenta a opacidade ideal para os casos em que o desafio clinico é neutralizar a diferença nas cores dos substratos. O "aço cerâmico", assim chamado por alguns autores, garante à Zircônia resistência e dureza semelhantes a um metal, mas com vantagens estéticas superiores às restaurações metalocerâmicas, as quais podem apresentar exposição da cinta metálica ao longo do tempo. Este artigo descreve um tratamento reabilitador complexo, envolvendo elementos dentários com diferentes substratos: 11 - dente vital com ampla destruição coronária; 21 - dente com tratamento endodôntico e núcleo metálico fundido; 22 ­ ausente, reabilitado com implante do tipo cone morse. A seleção do sistema totalmente cerâmico à base de zircônia, permitiu mascarar as diferentes condições dos substratos atingindo as expectativas estéticas. Além disso, diante do sorriso alto gengivoso presente neste caso, a excelência na estética gengival foi obtida utilizando implante com conexão interna do tipo cone morse associado a um pilar anatômico individualizado.