The effects of cement space thickness and material type on marginal discrepancy of restoration / Efeitos da espessura do cimento e do tipo de material na discrepância marginal da restauração

Objetivo: Estudos demostraram que a zircônia monolítica um dos materiais restauradores desenvolvidos recentemente, resolveu vários problemas de restauração de zircônia. Portanto, a precisão marginal e o ajuste interno são necessários para o sucesso clinico e para a qualidade da restauração, e o espaço do cimento pode influenciar o ajuste marginal. Assim, o presente estudo teve como objetivo investigar os efeitos da espessura do cimento e o tipo de restauração na discrepância marginal. Material e métodos: foram usadas para fabricação de coroa total. Dois tipos de materiais incluindo Zirconia monolítica (Zolid) e Sintron foram usadas para produzir a coroa total. As amostras de cada grupo foram digitalizadas em laboratório dentário por um scanner 3D, projetadas e acessadas usando CAD-CAM. As amostras foram divididas em quatro grupos de cinco com espaço de 30 e 50 mícrons de cimento. Para avaliar a discrepância marginal, as coroas foram colocadas em seus respectivos dentes sem o uso de qualquer intermediário e examinados em micro-CT. Os dados foram avaliados pelo software SPSS. Resultados: Descobriu-se que a discrepância marginal do Sintron é maior que a discrepância da zircônia monolítica. Na verdade, a zircônia monolítica com espaço de 50 µm de cimento exibiu uma menor discrepância marginal, e o espaço de cimento do Sintron não influenciou significantemente na discrepância marginal. Conclusão: Concluiu-se que os tipos de material e o espaço do cimento influencia na discrepância marginal da restauração construída pelo fluxo digital (AU)

Objective: Studies demonstrated that as one of then ewly developed restorative materials, monolithic zirconia resolved several issues of zirconia restoration. Therefore, marginal accuracy and internal fit are necessary for clinical success and quality of restorations, and cement space may influence the marginal fit. Thus, the present research aimed to investigate the effects of the cement thickness and kind of restoration on the marginal discrepancy. Material and methods: In this study, 20 maxillary left first molars, prepared by DRSK Co., were used to fabricate a full crown. Two types of material included monolithic zirconia (Zolid) and Sintron were used to make a full crown. Samples from each group were scanned by dental laboratory 3D scanner and designed and processed using CAD-CAM. The samples were divided into four groups of five with 30-and 50- µm cement spaces. In order to assess the vertical marginal discrepancy, the crowns were fittedon their respective teeth without using any mediator and examined by a micro-CT scanner. Data were analyzed by SPSS software. Results: It has been found that marginal discrepancy in Sintron is higher than the discrepancy of monolithic zirconia. In fact, monolithic zirconia with 50-micron cement space exhibited the least marginal discrepancy and the cement space in Sintron did not significantly influence the marginal discrepancy. Conclusion: It has been concluded that the material kinds and cement space influence the restoration marginal discrepancy constructed by digital workflow (AU)

Occlusal morphology of mandibular second molars in Iranian adolescents.

Context: During human evolution, the morphology of mandibular molar occlusal surface has changed from pattern "y" to pattern "+". Six types of occlusal patterns were classified as: +4, 4-y,+5, 5-y,+6 and 6-y. Aims: To determine the prevalence of these six types of mandibular second molars in Iranian adolescents. Settings and Design: This descriptive investigation was undertaken in the high schools of Isfahan city, Iran. The students were selected by cluster sampling method, and then they were screened and only those with erupted mandibular second molars bilaterally were selected. Materials and Methods: A total of 794 cases were randomly selected and the number of cusps and groove pattern of mandibular second molar were examined intra-orally and by studying dental casts. Statistical Analysis Used: Descriptive statistics and chi-square test were used for data analysis. Results: The most frequent occlusal configuration was the "+4" form (76.9%). A total of 683 cases (86%) were found to have four-cusp form, 104 cases (13.1%) were five-cusp form and 7 cases (0.9%) were six-cusp form. Conclusion: The most frequent occlusal configuration was the "+4" form; thus, there is a high evolutionary trend in Iranian mandibular second molars.