Resistance of Hydraulic Calcium Silicate Cements to Dislodgment in Short- and Long-term Assessment.

PURPOSE: To investigate the resistance to dislodgment produced by Biodentine (Septodont) and White-MTA (Angelus) after immersion in phosphate-buffered saline (PBS) for different durations. MATERIALS AND METHODS: Dentin disks 1 ± 0.1 mm thick were obtained from the middle third of the roots of 6 human maxillary canines. On the coronal surface of each dentin disk, four 0.8-mm-diameter holes were drilled. Then the slices were halved using a low-speed saw diamond disk, and the two holes in each half were filled with one of the two tested materials. Each filled half was immersed in PBS solution (pH 7.2) either for 7 days (short term) or 60 days (long term) at 37°C. The push-out test was performed after both time periods. A general linear model (GLM) for repeated measures ANOVA was used to verify the effect of the material and duration of contact with PBS on the push-out strength. The material was considered as the within-subject contrast and the contact duration as the between-subjects effect (p < 0.05). RESULTS: Repeated measures GLM indicated a significant impact of material and time on the push-out strength of the samples (p = 0.000 and p = 0.033, respectively). Biodentine significantly improved the push-out strength compared to MTA at both times (p = 0.000). The lack of significance in the interaction between material and time indicates that PBS immersion positively influenced the push-out values of both tested materials. CONCLUSION: Long-term PBS immersion positively influenced the resistance to dislodgement from dentin of all cements tested. The Biodentine cement provided greater resistance to push-out force than did the MTA.

Distribuição das tensões relacionadas ao uso de retentores em dentes tratados endodonticamente utilizando o método dos elementos finitos / Stress distribution related to the use of retainers in endodontically treated teeth using the finite element method

A restauração dos dentes tratados endodonticamente, com grande fragilidade de suas estruturas, traz dúvidas ao clínico quanto à melhor forma de atuar nesses elementos. Os retentores intrarradiculares, sejam núcleos metálicos fundidos ou pré-fabricados, são geralmente necessários para a restauração destes elementos. Cada um desses materiais imprime uma força diferente nas estruturas adjacentes, sendo o entendimento destas uma necessidade para a melhor escolha e aplicação clínica do retentor. Objetivo: A proposta do presente trabalho é analisar e avaliar a distribuição de tensões no complexo dente-periodonto pelo método dos elementos finitos bidimensional com a utilização de diferentes tipos de retentores. Método: Este estudo tem por base modelos matemáticos de um canino superior tratado endodonticamente com a utilização de retentores intrarradiculares metálicos fundidos em NiCr, metálicos pré-fabricados em titânio. Os modelos foram submetidos a uma carga de 100 N por palatina em um ângulo de 45º. A análise e avaliação das tensões foram realizadas para cada um dos modelos e seus diferentes tipos de pinos. Resultados: A maior concentração de tensões se deu com o uso do pino metálico pré-fabricado de titânio, com valores de tração que oscilam entre 1.207 MPa a 4.878 MPa e de compressão entre -9.806 MPa a -2.464 MPa. O pino metálico fundido imprimiu tensões de menores valores, mais homogêneas e uniformes, tendo seus valores de tração variando de 1.287 MPa a 4.919 Mpa e seus valores de compressão variando de -9.607 MPa a 2.344 Mpa. Conclusão: Os pinos intrarradiculares metálicos pré-fabricados de titânio geram forte estresse no sistema dente-periodonto, sendo o menos indicado clinicamente. O mais indicado para uso clínico foi o pino metálico fundido, cuja tensão se manifestou de maneira mais uniforme no elemento dentário.

The restoration of endodontically treated teeth with great structure fragility challenges the clinician about the best way to proceed on these elements. The use of intracanal retainers, either post and core systems of prefabricated posts, is usually necessary to restore this kind of teeth. Each one of these materials exerts a different force on the adjacent structures and understanding these forces is mandatory for a better choice and clinical application of intracanal retainers. Objective: The purpose of this study was to analyze and evaluate the stress distribution in the tooth-periodontium complex by the two-dimensional finite element method, using different types of retainers. Methods: This study was based on mathematical models of an endodontically treated maxillary canine, using a NiCr cast intracanal posts and a prefabricated titanium post. The models were subjected to a 100 N load directed palatally at a 45º angle. The strains for each of the models and different types of post were analyzed and evaluated. Results: The highest stress concentration occurred with the use of the prefabricated titanium post, with traction values ranging from 1207 MPa to 4878 MPa and compression values between -9806 and -2464 MPa. The NiCr cast post exhibited lower tension values, with a more homogeneous and uniform distribution, traction values ranging from 1287 MPa to 4919 MPa and compression values ranging from -9607 MPa to 2344 MPa. Conclusion: Prefabricated titanium intraradicular posts induced strong stress to the tooth-periodontium complex and is less indicated clinically. The metal cast post appears more adequate cast for clinical use, as the resulting tension was distributed more uniformly along the tooth.