Bond strength and quality of bond interface of multifilament fiberglass posts luted onto flat-oval root canals without additional dentin wear after biomechanical preparation.

STATEMENT OF PROBLEM: An intraradicular retainer formed by multiple independent glass fiber filaments was developed aiming to allow better adaptation in flattened root canals; however, the performance of the new posts is unclear. PURPOSE: The purpose of this in vitro study was to compare the bond strength (BS) and adhesive interface quality achieved in flattened root canals restored with conventional glass fiber posts (CFPs) and multifilament glass fiber posts (MFPs). MATERIAL AND METHODS: The distal roots of mandibular molars with long oval root canals were endodontically treated, and the obturation material was removed and assigned to 2 groups (n=11) according to the type of retainer used: CFP (WhitePostDC#0.5; FGM) or MFP (CometTail#4; Synca). The posts were cemented with self-adhesive resin cement. The specimens were sectioned (2 slices per third). The most cervical slice in each third was used to evaluate the BS, while the adhesive interface in the apical slices was analyzed by scanning electron microscopy. BS data were analyzed by using a multilevel generalized linear model, and adhesive interface SEM data were analyzed by using a multilevel ordinal logistic regression model (α=.05). RESULTS: Multilevel regression showed a statistically significant difference for the "type of retainer" factor (P=.001; CFP 2.61 ±1.30>MFP 1.59 ±1.54). No statistically significant differences were found for the "root thirds" factor (P=.346) or for the interaction of both factors (P=.114). The failure pattern was predominantly mixed or adhesive for CFP and adhesive to dentin for MFP. A better adaptation of the restorative material was observed in the cervical third for CFP and in the apical third for MFP (P<.001). CONCLUSIONS: MFP resulted in lower BS values than CFP, with a higher prevalence of adhesive failures to dentin and better adaptation of the adhesive interface in the apical third.

Effect of Intracoronal Depth of Teeth Restored with Endocrowns on Fracture Resistance: In Vitro and 3-dimensional Finite Element Analysis.

INTRODUCTION: Endodontically treated teeth have an increased risk of biomechanical failure because of significant loss of tooth structure. The biomechanical behavior of endodontically treated teeth restored was evaluated using different extensions of endocrowns inside the pulp chamber by in vitro and 3-dimensional finite element analysis (FEA). METHODS: Thirty mandibular human molars were endodontically treated. Standardized endocrown preparations were performed, and the teeth were randomly divided into 3 groups (n = 10) according to different endocrown extensions inside the pulp chamber: G-5 mm, a 5-mm extension; G-3 mm, a 3-mm extension; and G-1 mm, a 1-mm extension. After adhesive cementation, all specimens were subjected to thermocycling and dynamic loading. The survival specimens were subjected to fracture resistance testing at a crosshead speed of 1 mm/min in a universal testing machine. All fractured specimens were subjected to fractography. Data were analyzed by 1-way analysis of variance and the Tukey post hoc test (P < .05). Stress distribution patterns in each group were analyzed using FEA. Qualitative analyses were performed according to the von Mises criterion. RESULTS: After dynamic loading, a survival rate of 100% was observed in all groups. For static loading, statistically significant differences among the groups were observed (P < .05) (G-5 mm = 2008.61 N, G-3 mm = 1795.41 N, and G-1 mm = 1268.12 N). Fractography showed a higher frequency of compression curls for G-5 mm and G-3 mm than for G-1 mm. FEA explained the results of fracture strength testing and fractography. CONCLUSIONS: Greater extension of endocrowns inside the pulp chamber provided better mechanical performance.

Comparative study about generation methods of geometric models by finite element analysis / Estudo comparativo sobre métodos de geração de modelos geométricos por análise de elementos finitos

The aim of this study was to assess the influence of different methods for generating geometric models on stress values and distributions of endodontically treated teeth using a three-dimensional finite element analysis (3D-FEA). An endodontically treated human maxillary canine restored with glass fiber post and ceramic-fused-to-metal crown was scanned by microcomputed tomography and three-dimensionally reconstructed. Based on the microcomputed tomography images, 2 geometric models were generated and divided into the following groups: Group GCAD - only the root dentine was reconstructed based on a microcomputed tomography image while the remaining structures were generated by GCAD software simulation, and Group GTC - the whole assembly was obtained from scanning and rehabilitated by microcomputed tomography. Loading of 180N at 45° of the tooth long axis was applied on the lingual surface of the incisal third and the models were supported by a periodontal ligament fixed into the 3 axes of the Cartesian system (x=y=z=0). von Mises stress (VMS) were calculated. Differences in stress value and distribution between the generation methods of the geometric models were found. The lowest ratio difference in GTC/GCAD was for resin cement and core. Thus, the method for generation of the geometric model in finite element analysis was found to influence the research results, suggesting better results for GCAD method(AU)

O objetivo deste estudo foi avaliar a influência de diferentes métodos para a geração de modelos geométricos em valores de tensões e distrubuições de dentes tratados endodônticamente, utilizando-se uma análise tridimensional de elementos finitos (3D-FEA). Canino superior humano tratado endodonticamente, restaurado com pino de fibra de vidro e coroa metalocerâmica foi escaneado por meio de microtomografia computadorizada e reconstruído tridimensionalmente. Baseadas nas imagens de microtomografia computadorizada, foram gerados 2 modelos geométricos e divididos nos seguintes grupos: grupo GCAD-apenas a dentina radicular foi reconstruída baseada na imagem obtida por meio de microtomografia computadorizada, enquanto as estruturas remanescentes foram geradas por simulação de software de CAD, e grupo GTC-todo conjunto inteiro foi obtido do escaneamento e reabilitado pela microtomografia computadorizada. O carregamento de 180N em 45° do longo eixo do dente foi aplicado na superfície lingual do terço incisal e os modelos foram suportados por um ligamento periodontal fixado nos 3 eixos do sistema cartesiano (x = y = z = 0). Tensões equivalents de von Mises (VMS) foram calculados. Foram encontradas diferenças no valor de tensões e distribuição entre os métodos de geração dos modelos geométricos. A menor razão entre GTC/GCAD foi para o cimento de resinoso e núcleo. Assim, verificou-se que o método de geração do modelo geométrico na análise de elementos finitos influenciou os resultados da pesquisa, sugerindo melhores resultados para o método GCAD(AU)