Fracture resistance and stress distribution of weakened teeth reinforced with a bundled glass fiber-reinforced resin post.

OBJECTIVES: To make an in vitro assessment of fracture resistance of weakened and non-weakened teeth receiving intraradicular reinforcement using Rebilda bundled glass fiber-reinforced composite posts (GT), Rebilda conventional glass fiber posts (RP), or both systems combined (GT + RP). MATERIALS AND METHODS: Eighty sound bovine incisors were prepared and divided randomly into eight groups as follows: (a) nWnR: without simulating weakness, and without intraradicular reinforcement; (b) WnR: simulating weakness, but without intraradicular reinforcement; (c) nWGT: without simulating weakness, but with GT; (d) WGT: simulating weakness, and with GT; (e) nWRP: without simulating weakness, but with RP; (f) WRP: simulating weakness, and with RP; (g) nWGTRP: without simulating weakness, but with GT + RP; (h) WGTRP: simulating weakness, and with GT + RP. The specimens were subjected to the load-to-fracture test using the DL-2000MF universal testing machine. The finite element method assessed the mechanical behavior and stress distribution in endodontically treated teeth. RESULTS: The groups nWGTRP and WGTRP presented the best results in the load-to-fracture test, with the former being better than the latter, but with no statistically significant difference (P > 0.05). However, there was a significant difference between these and the other groups (P < 0.05), except for nWRP. Stress distribution inside the canal wall was different among the groups, with promising mechanical behavior for nWGTRP and nWRP. CONCLUSIONS: The Rebilda conventional fiber post (RP), combined with the Rebilda bundled glass fiber-reinforced composite post (GT) improves the resistance and stress distribution of immature teeth. CLINICAL RELEVANCE: Longitudinal fracture is less frequent in teeth restored with GT and RP posts.

Effect of Passive Ultrasonic Irrigation over Organic Tissue of Simulated Internal Root Resorption.

This study aimed to evaluate the efficacy of passive ultrasonic irrigation (PUI) on dissolving the organic tissue inside simulated internal root resorption (IRR) using sodium hypochlorite (NaOCl) or chlorhexidine (CHX). A total of 40 human lower premolars were collected based on dimensional and morphological similarities. The roots were embedded in cylinders (3 cm diameter; 2.5 cm height) of self-cured acrylic resin, and then an IRR was simulated. The specimens were divided into 4 groups (n = 10) according to irrigation protocols: group 1: CHX + PUI; group 2: CHX; group 3: NaOCl + PUI; group 4: NaOCl. The total irrigation time was 150 s at a flow rate of 5 mL/min. A tissue mass of porcine palatine mucosa was used to simulate the organic tissue, it was weighed before and after the irrigation using an analytic balance, and the difference between both readings was calculated and transferred to percentage values. Data were submitted to statistical analysis using two-way ANOVA (factors: irrigant type and with/without PUI) and Tukey's test for multiple comparisons among the experimental groups (α = 0.05). There was a significant difference in both factors (irrigant: p=0.04; PUI: p ≤ 0.001). The groups that used PUI were more effective in dissolving the organic tissue of the IRR simulation than the groups without PUI. PUI is more effective than the syringe and needle irrigation in organic tissue dissolution.

Bond strength of cemented fiber posts to teeth with simulated internal root resorption.

BACKGROUND: Teeth with internal root resorption (IRR) have guarded prognosis, considering that IRR defect could influence on the post bond strength. The aim of this study was to evaluate the bond strength and the bond interface between different glass fiber-reinforced posts (FRP) after cementation in teeth with simulated internal root resorption (IRR). MATERIAL AND METHODS: Forty-five (45) human premolar roots with simulated IRR were embedded in acrylic resin blocks and cross-sectioned into two segments, enabling them to be re-approximated by screws. Intracanal medication was inserted for 15-days, removed by passive ultrasonic irrigation (PUI) and examined by stereomicroscopy. The push-out bond strength of two fiber reinforced composite posts (Rebilda Post - RP) and Rebilda Post GT - GT, (VOCO) were evaluated at the cervical and IRR regions (n = 20). And, the bonded interface between resin cement and root dentine was analysed by scanning electron microscopy (SEM). RESULTS: 62.5% of IRR were not completely cleaned by PUI. Bond strength values at the cervical region (9.8 and 14.6 MPa) were higher than the IRR region (6.3 and 4.2 MPa). Micrographies showed bubbles in the cement and spaces in the bonded interface. CONCLUSIONS: RP post showed better bond strength at the cervical region while GT had better bond strength at the IRR region. Key words:Endodontics, root canal filling materials, root resorption, X-Ray microtomography.

Análise da cimentação e da resistência de união de dois diferentes tipos de pinos de fibra de vidro em dentes com reabsorções radiculares internas simuladas / Analyses of cementation and bond strength of two different type of glass fiber post in teeth with simulated internal root resorption

Este estudo analisou a interface de união e a força de adesão dos pinos de fibra de vidro Rebilda Post (RP) (VOCO) e Rebilda Post GT (GT) (VOCO) após cimentação em dentes com Reabsorção Radicular Interna (RRI) simulada. Quarenta e cinco raízes de pré-molares inferiores humanos foram padronizadas em 16 mm e incluídas em resina acrílica. Os canais radiculares (CR) foram preparados biomecanicamente, as raízes foram seccionadas em sua metade e a RRI foi simulada. Os segmentos foram retornados à posição original com auxílio de parafusos. Uma pasta de Ca(OH)2 permaneceu como MIC por 15 dias. A remoção foi feita por PUI e a qualidade da limpeza foi avaliada por estereomicroscopia. Os CR das amostras foram obturados e o preparo foi feito de forma padronizada. Os espécimes foram divididos em 2 grupos (n=20), de acordo com o tipo de pino cimentado. A resistência de união foi avaliada aos níveis cervical e da RRI pelo teste push-out. Para a análise estatística só foram incluídas falhas adesivas e predominantemente adesivas. Os resultados foram submetidos ao teste de Kruskal-Wallis, Mann Whitney e teste de Dunn (α = 0,05). Foi realizada MEV para análise da interface de união entre cimento e dentina radicular (n=1) e análise por microtomografia computadorizada (microCT) do pino GT (n=3). PUI não foi capaz de limpar completamente a maioria das RRI (62,5%). Houve alteração da resistência adesiva entre todos os grupos (p <0,05). Os valores de resistência de união para ambos os grupos na região cervical foram maiores em relação aos grupos na região de RRI. A MEV mostrou formação de tags resinosas na interface de união entre cimento resinoso e dentina radicular para ambos os grupos. Em análise por micro-CT, presença de bolhas no cimento e espaços na interface de união entre cimento são visíveis. A adesão de ambos os pinos foi afetada negativamente pelo nível da cimentação, adaptação do pino no canal radicular e presença de RRI. Rebilda Post apresentou melhores resultados de resistência adesiva no nível cervical enquanto que no Rebilda Post GT apresentou melhores resultados a nível de RRI(AU)

This study analyzed the adhesion interface and bond strength of Rebilda Post (RP) (VOCO) and Rebilda Post GT (GT) (VOCO) glass fibers after cementation in teeth with simulated Internal Root Resorption (IRR). Forty-five roots of lower human premolars were standardized at 16 mm and included in acrylic resin.The root canals (RC) were prepared biomechanically, the roots were sectioned and the IRR was simulated.The segments were returned to original position with the aid of screws. A Ca(OH)2 paste remained as MIC for 15 days.The removal was done by PUI and the quality of the cleaning was evaluated by stereomicroscopy. The RC of the samples were filled and the preparation was done in standardized way. The specimens were divided into 2 groups (n=20), according to the type of cemented post. The bond strength was evaluated at the cervical and RRI levels by the push-out test. For the statistical analysis only adhesive and predominantly adhesive failures were included. The results were submitted to Kruskal-Wallis test, Mann Whitney test and Dunn test (α =.05). SEM was used to analyze the bond interface between cement and dentin root (n=1) and Microcomputed tomography (micro-CT) analysis of the GT post (n=3). PUI was not able to clear completely the majority of RRI (62.5%). There was alteration of the adhesive resistance between all groups (p <.05). The values of bond strength for both groups in the cervical region were higher in relation to the groups in the RRI region.The SEM showed formation of resin tags at the bond interface between resin cement and root dentin for both groups. In micro-CT analysis, the presence of bubbles in the cement and spaces in the bond interface between cement are visible. The adhesion of both posts was affected negatively by the level of cementation, post adaptation in the root canal and presence of IRR. Rebilda Post presented better results of adhesive resistance at the cervical level while that Rebilda Post GT presented better results at RRI level(AU)

Effect of shear bond strength of metallic orthodontic brackets bonded with and without dental adhesive / Efeito da resistência ao cisalhamento de braquetes ortodônticos unidos com e sem adesivo dentário

Objective: The aim of this study was to evaluate the shear bond strength (SBS) of two materials for bonding orthodontic brackets on dental enamel before and after thermocycling. Material and Methods: Forty bovine incisors were divided into four groups (n=10). All teeth were etched with 35% phosphoric acid (3M Espe). For bonding of the brackets, G1 and G2 received orthodontic composite resin (Fill Magic Ortodôntico) and G3 and G4, an adhesive (ScotchBond) was used before the orthodontic resin Transbond XT (3M Unitek). G1 and G3 were kept at 37ºC for 24h and G2 and G4 were submitted to thermocycling (5000 cycles, at 5ºC - 55ºC) prior to SBS testing, performed by a universal machine (EMIC) at 1 mm/min, with a 50kgf load cell. Results were analyzed with two-way ANOVA, followed by Tukey's test (p=0.05). Adhesive surfaces were evaluated through stereomicroscopy and classified according to the type of failure presented. Results: Surface treatment with dental adhesive presented higher SBS values, regardless thermocycling (G3: 12.01 MPa; G4: 12.36 MPa) and the lowest values occurred in G2 (8.89 MPa). For groups without adhesive and with thermocycling, a higher number of completely adhesive failures between composite and enamel were present. For groups in which dental adhesive was used, regardless thermocycling, the failures were mainly adhesive between composite and the bracket. Conclusion: Surface etching of enamel with 35% phosphoric acid with or without adhesive showed a positive effect on SBS. The application of adhesive on enamel surface contributed to the maintenance of SBS values after thermocycling (AU)

Objetivo: O objetivo desse estudo foi avaliar a resistência ao cisalhamento de dois materiais para fixação de braquetes ortodônticos ao esmalte dentário antes e após a termociclagem. Material e Métodos: Quarenta incisivos bovinos foram divididos em quatro grupos (n=10). Todos os dentes foram condicionados com ácido fosfórico a 35% (3M Espe). Para a fixação dos braquetes, G1 e G2 receberam a resina composta ortodôntica (Fill Magic Ortodôntico) e G3 e G4, um adesivo dentário (ScotchBond) foi usado antes da resina ortodôntica Transbond XT (3M Unitek). G1 e G3 foram mantidos a 37ºC por 24h e G2 e G4 foram submetidos à ciclagem térmica (5000 ciclos, de 5ºC - 55ºC) anterior ao teste de resistência ao cisalhamento, realizado por máquina universal (EMIC) a 1 mm/min, com célula de carga de 50kgf. Os resultados foram analisados com ANOVA 2-fatores, seguida do teste de Tukey (p=0,05). As superfícies adesivas foram avaliadas através de estereomicroscopia e classificadas de acordo com o tipo de falha presente. Resultados: O tratamento de superfície com adesivo dentário apresentou maiores valores de resistência ao cisalhamento, independente da termociclagem (G3: 12,01 MPa; G4: 12,36 MPa) e os menores valores ocorreram para G2 (8,89 MPa). Para os grupos sem adesivo e com termociclagem, o maior número de falhas predominantemente adesivas entre resina composta e esmalte estava presente. Para os grupos em que o adesivo dentário foi utilizado, independente da termociclagem, as falhas foram principalmente adesivas entre resina composta e o braquete. Conclusão: O condicionamento superficial do esmalte com ácido fosfórico a 35% com ou sem adesivo mostrou um efeito positivo sobre a resistência ao cisalhamento. A aplicação de adesivo na superfície do esmalte contribuiu para a manutenção dos valores de resistência ao cisalhamento após a termociclagem. (AU)

A opção pelo retratamento não cirúrgico na presença de pinos intrarradiculares: riscos e benefícios / The option for nonsurgical retreatment in the presence of intraradicular posts: risks and benefits

Introdução: O retratamento não cirúrgico é uma opção de tratamento quando ocorre o insucesso no tratamento endodôntico, porém, em muitos casos, há necessidade da remoção prévia de pinos intrarradiculares. Objetivo: Esta revisão de literatura tem como objetivo citar os riscos e os benefícios da opção pelo retratamento endodôntico não cirúrgico na presença de pinos intrarradiculares, bem como citar materiais e técnicas para a remoção de diferentes tipos de pinos. Conclusão: A opção pelo retratamento endodôntico não cirúrgico, em casos em que há necessidade de remoção de pinos, é segura e de índice de sucesso considerável, por isso, deve-se levar em conta o conhecimento de técnicas e os fatores que podem influenciar durante o processo, a fim de prevenir acidentes, bem como saber que apenas a presença do pino intrarradicular não é indicação para o tratamento cirúrgico.

Introduction: Nonsurgical retreatment is a treatment option when the failure happens in the endodontic treatment, but in many cases, there is need for prior removal intrarradicular posts. Objectives: This literature review aims to cite the risks and benefits of option for nonsurgical endodontic retreatment in the presence of intraradicular posts and cite materials and techniques for removing different types of posts. Conclusion: The option for nonsurgical endodontic retreatment in cases where removal the posts there need, is safe and considerable success rate, therefore, one should take into account the knowledge of techniques and factors that may influence during the process, in order to prevent accidents, as well as to know that only the presence of intraradicular post is no indication for surgical treatment.