Effect of glass-fiber post on the biomechanical behavior of teeth with direct veneers / Efeito do pino de fibra de vidro no comportamento biomecânico de dentes com facetas diretas

Objective: This study aimed to evaluate the biomechanical behaviour of endodontically treated teeth with direct veneer that received or not intra-radicular glass fiber post by finite elements analysis. Material and methods: Six models were designed, varying the presence or absence of glass fiber post and the thickness of direct veneer (0.5, 0.7 and 1 mm). Tridimensional models of maxillary central incisors were obtained with CAD software, Rhinoceros 4.0, and transferred to CAE software, ANSYS 17.2, which a 100N load was applied in a 45° on the lingual surface to simulate functional movements. Geometry contacts were bonded, and the structures were isotropic, linear, elastics, and homogeneous. After coherence and convergence analysis of mashes, the chosen fail criterion was the maximum principal stresses. Results: For cement, glass fiber post, the stress distribution was similar independently of glass fiber post presence or veneer thickness. Models with glass fiber post had better stress distribution and lower values of maximum stress for inner dentin and veneers. Veneers with 0.5 and 1 mm had higher stress concentration areas. Conclusions: It can be concluded that glass fiber post is favorable for restored teeth with direct veneers, and very thin or very thick preparations can damage the biomechanical behavior of restorations.(AU)

Objetivo: Este estudo teve como objetivo avaliar o comportamento biomecânico de dentes tratados endodonticamente com faceta direta que receberam ou não pinos de fibra de vidro intrarradicular através de análise de elementos finitos. Material e métodos: Foram desenhados seis modelos, variando a presença ou ausência do pino de fibra de vidro e a espessura da faceta direta (0,5, 0,7 e 1 mm). Modelos tridimensionais de incisivos centrais superiores foram obtidos com o software CAD, Rhinoceros 4.0, e transferidos para o software CAE, ANSYS 17.2, cuja carga de 100N foi aplicada a 45° na superfície lingual para simular movimentos funcionais. Os contatos geométricos foram colados e as estruturas eram isotrópicas, lineares, elásticas e homogêneas. Após análise de coerência e convergência de malhas, o critério de falha escolhido foi a tensão principal máxima. Resultados: Para cimento e pino de fibra de vidro, a distribuição de tensões foi semelhante independentemente da presença do pino de fibra de vidro ou da espessura da faceta. Os modelos com pinos de fibra de vidro apresentaram melhor distribuição de tensão e menores valores de tensão máxima para dentina interna e facetas. Facetas com 0,5 e 1mm apresentaram maiores áreas de concentração de estresse. Conclusões: Pode-se concluir que o pino de fibra de vidro é favorável para dentes restaurados com facetas diretas, e preparações muito finas ou muito espessas podem prejudicar o comportamento biomecânico das restaurações.(AU)

Restauração de dentes tratados endodonticamente com resinas bulk-fill: revisão integrativa / Endodontically treated teeth restored with bulk-fill resins: integrative review

Objetivo: realizar uma revisão de literatura sobre o uso de resinas bulk-fill para restaurar dentes tratados endodonticamente. Materiais e método: a busca dos estudos, clínicos ou laboratoriais, foi realizada no portal PubMed, utilizando os descritores "bulk fill" e "endodontically treated". Os dados extraídos da literatura foram agrupados em um quadro, que apresenta as características metodológicas e os principais resultados de cada estudo. Resultados: Sete estudos foram incluídos na revisão. Dentre eles, cinco avaliaram a resistência à fratura dos dentes após a restauração, um avaliou a adaptação da resina ao assoalho da câmara pulpar, e um realizou um ensaio clínico com acompanhamento de três anos, comparando o uso de resina bulk-fill com resina convencional. Considerações finais: o desempenho das resinas bulk-fill mostrou-se semelhante ao das resinas convencionais nas características de resistência à fratura dos dentes (in vitro) e longevidade (in vivo). A economia de tempo clínico proporcionada pelas resinas bulk-fill pode justificar o seu emprego para a restauração de dentes tratados endodonticamente. (AU)

Objective: the aim of this study was to review the literature regarding the use of bulk-fill resin to restore endodontically treated teeth. Materials and method: the search was performed at PubMed, using the descriptors "bulk fill" AND "endodontically treated". Clinical and laboratorial studies were included. The extracted data was presented on a table showing the methodological features and results of each study. Results: seven studies evaluated the bulk-fill resin on direct restoration. Five of these seven evaluated the resistance to fracture, one assessed the resin adaptation to the floor chamber, and one was a randomized clinical trial comparing the bulkfill resin to conventional resin. Final considerations: the performance of bulk-fill resins was similar to the conventional resins when compared to the in vitro studies on tooth fracture resistance and in vivo study on longevity of restorations. The economy of clinical time may justify its use to restore endodontically treated teeth. (AU)

Diferencia entre las medidas radiográficas y anatómicas de conductos, posterior a la preparación para la colocación de postes / Difference between radiographic and anatomical measurements of canals, after preparation for the placement of a post

Antecedentes: Las radiografías periapicales presentan distorsiones que podrían conducir a un mayor desgaste de la estructura dental aumentando el riesgo de debilitamiento y de perforación o fractura vertical cuando se realiza la preparación del conducto radicular para la colocación de postes. Objetivo: El objetivo de la presente investigación es determinar la diferencia entre las medidas del espesor radiográfi co y el espesor anatómico mediante un calibrador de la dentina residual, luego de la preparación para poste en conductos ovales de premolares. Material y métodos: 50 premolares fueron tratados endodóncicamente y posteriormente fueron desobturados con fresas Pesso #1 y 2 dejando 4 mm de sellado apical, se realizó la toma radiográfi ca y se comparó con medidas realizadas con un calibrador digital. Las medidas fueron comparadas con una t de Student. Resultados: Las medidas radiográfi cas fueron 24.63% más grandes en comparación con las medidas del calibrador. Las medidas radiográfi cas no fueron signifi cativamente mayores en comparación con las del calibrador digital. Conclusiones: La radiografía periapical presenta una sobrestimación de la medida de la dentina residual, por lo tanto se debe escoger el protocolo más conservador para obtener resultados predecibles y exitosos (AU)

Background: Periapical radiographs have distortions that lead to greater wear of the dental structure, increasing the risk of weakening, perforation or vertical fracture when the root canal is preparation for post placement. Objective: The investigation is to determine the diff erence between the measurements of the radiographic thickness and the anatomical thickness by means of a calibrator of the residual dentine after the preparation for post placement. Material and methods: Root canal treatment was performed in 50 premolars and was unsealed with Pesso #1 and 2 leaving 4 mm of the apical seal, the radiographic was made and compared with measurements made with a digital calibrator. The measurements were compared with a Student t. Results: The radiographic measurements were 24.63% larger than the caliper measurements. The radiographic measurements were signifi cantly higher in comparison with the digital calibrators. Conclusions: The periapical radiography presents an overestimation residual dentin measurement, therefore the most conservative protocol should be chosen to obtain predictable and successful results (AU)

Influence of remaining coronal thickness and height on biomechanical behavior of endodontically treated teeth: survival rates, load to fracture and finite element analysis

Abstract Objective To evaluate the effect of restorative strategy (fiber post vs cast post and core), coronal height (0 mm vs 2 mm) and thickness (higher than 1 mm vs lower than 1 mm) on survival rate, fracture resistance and stress distribution. Material and Methods Seventy-two bovine teeth were cleaned and allocated in six groups (n = 12). Twenty-four teeth were sectioned at 13 mm length (no remaining coronal structure) and forty-eight were sectioned at 15 mm (2 mm remaining coronal structure). Half of the forty-eight had remaining coronal thickness lower than 1 mm and the other half had thickness higher than 1 mm. All root canals were prepared at 10 mm (luting length), fiber posts were cemented in thirty-six specimens and cast post and core in other thirty-six. All teeth were restored with metallic crowns. Specimens were submitted to 1.5 million cycles (100 N, 45°, 10 Hz at 2 mm below incisal edge) and evaluated at each 500,000 cycles to detect failures. Specimens that survived were submitted to load to fracture test. Bidimensional (Rhinoceros® 4.0) models were obteined survival data submitted to Kaplan-Meier (α=0.05) analysis and load to fracture values submitted to ANOVA and Tukey tests (α=0.05). Results Groups without remaining coronal structure showed survival rates lower than other groups (p=0.001). ANOVA showed higher values of load to fracture for groups with coronal thickness higher than 1 mm (p=0.0043). Finite element analysis showed better stress distribution in groups with remaining coronal structure and restored with fiber post. Conclusion Specimens without remaining coronal structure have lower survival rates. Specimens with remaining structure lower than 1 mm and without coronal structure support the same load to fracture value independently of the restorative strategy.

Infiltration of Rhodamin B into three materials used as cervical barrier / Infiltração da Rodamina B em três materiais utilizados como tampão cervical

OBJECTIVE: To evaluate in vitro the sealing ability of three materials used as cervical barrier for internal dental bleaching. METHODS: Thirty-three canines were selected, and after biomechanical root canal preparation, the canals were filled by lateral condensation technique. After the filling material setting reaction, the teeth were randomly divided into three groups of ten teeth each, according to the following materials for constructing the cervical barrier: X Temp LC; Vitro Fil; Coltosol. The control group consisted of three teeth, without placement of the cervical cap. Sodium perborate /distilled water associated with 2% Rhodamin B were used as bleaching substance. After placing the bleaching agent in the pulp chamber, access cavities were sealed with temporary cement IRM and samples were stored at 37 ° for 7 days. After this period, the samples were cleaved longitudinally, and leakage was evaluated by the visual method. The data were submitted to Pearson test with a 5% level of significance. RESULTS: No statistically significant difference was found between the study groups, however, the largest number of specimens with a lower degree of leakage were found in the Coltosol group. CONCLUSION: All the materials evaluated for making the cervical cap allowed some level of leakage. .

OBJETIVO: Avaliar in vitro a capacidade seladora de três materiais utilizados como barreira cervical durante o clareamento interno. MÉTODOS: Foram selecionados trinta e três caninos humanos, que após o preparo biomecânico dos canais radiculares, foram obturados pela técnica da condensação lateral ativa. Após a reação de presa do material obturador os dentes foram divididos aleatoriamente em três grupos de dez dentes cada, de acordo com os seguintes materiais para confecção da barreira cervical: X Temp LC; Vitro Fil; Coltosol. O grupo controle constituiu de três dentes sem a confecção do tampão cervical. Utilizou-se como substância clareadora o Perborato de Sódio/ água destilada associado à Rodamina B 2%. Após a colocação do agente clareador na câmara pulpar, as aberturas coronárias foram seladas com cimento provisório IRM e as amostras foram armazenadas em estufa a 37° por 7 dias. Após esse período, as amostras foram clivadas no sentido longitudinal, e a avaliação da infiltração foi realizada pelo método visual. Os dados foram submetidos ao teste estatístico de Kruskal-Wallis, com nível de significância de 5%. RESULTADOS: Não houve diferença estatisticamente significante entre os grupos de estudo, embora o Coltosol tenha obtido maior número de espécimes com menor grau de infiltração. ...

Resistance to compression of weakened roots subjected to different root reconstruction protocols

OBJECTIVE: This study evaluated, in vitro, the fracture resistance of human non-vital teeth restored with different reconstruction protocols. MATERIAL AND METHODS: Forty human anterior roots of similar shape and dimensions were assigned to four groups (n=10), according to the root reconstruction protocol: Group I (control): non-weakened roots with glass fiber post; Group II: roots with composite resin by incremental technique and glass fiber post; Group III: roots with accessory glass fiber posts and glass fiber post; and Group IV: roots with anatomic glass fiber post technique. Following post cementation and core reconstruction, the roots were embedded in chemically activated acrylic resin and submitted to fracture resistance testing, with a compressive load at an angle of 45º in relation to the long axis of the root at a speed of 0.5 mm/min until fracture. All data were statistically analyzed with bilateral Dunnett's test (α=0.05). RESULTS: Group I presented higher mean values of fracture resistance when compared with the three experimental groups, which, in turn, presented similar resistance to fracture among each other. None of the techniques of root reconstruction with intraradicular posts improved root strength, and the incremental technique was suggested as being the most recommendable, since the type of fracture that occurred allowed the remaining dental structure to be repaired. CONCLUSION: The results of this in vitro study suggest that the healthy remaining radicular dentin is more important to increase fracture resistance than the root reconstruction protocol.

Avaliação da influência do tratamento endodôntico na resistência de união de pinos de fibra reforçados por um compósito restaurador / Evaluation of the endodontic treatment influence on the bond strength of fiber posts reinforced by a restorative composite

INTRODUÇÃO E OBJETIVO: Pinos de fibra de vidro são largamente utilizados para aumentar a resistência mecânica das restaurações. O objetivo deste estudo foi avaliar a resistência de união de pinos de fibra de vidro reforçados por um compósito restaurador à dentina radicular nas regiões cervical, média e apical quanto ao preparo do espaço para pino posterior ou prévio ao tratamento endodôntico. MATERIAL E MÉTODOS: Foram utilizados 30 incisivos bovinos, que tiveram seus detritos removidos, lavados em água corrente e mantidos congelados. As amostras foram distribuídas aleatoriamente em dois grupos (n = 15), segundo o tratamento já aplicado para a instalação dos pinos: grupo 1 - com preparo do espaço para o pino posterior ao tratamento endodôntico; grupo 2 - com preparo do espaço para o pino prévio ao tratamento endodôntico. Os pinos foram cimentados nos espaços intrarradiculares e cortes de 2 mm foram realizados nas regiões cervical (C), média (M) e apical (A) para a aplicação do ensaio push out. A resistência de união foi calculada em MPa, e os dados foram analisados estatisticamente pela Anova e pelo teste de Tukey (p < 0,05). RESULTADOS: As médias obtidas foram (MPa ± DP): G1C -4,0 ± 6,0; G1M -3,5 ± 2,9; G1A -7,2 ± 6,3; G2C -12,7 ± 8,1; G2M -11,6 ± 10,2; G2A -6,5 ± 8,1. Os terços cervical e médio do grupo 2 tiveram as maiores médias, com diferença estatística em relação ao grupo 1. Para o terço apical, não houve diferença significativa entre os grupos. Eles também não apresentaram individualmente diferença estatística acerca de seus terços cervical, médio e apical. CONCLUSÃO: O preparo do espaço para o pino prévio ao tratamento endodôntico resultou em maior resistência de união dos pinos de fibra de vidro reforçados por um compósito restaurador.

INTRODUCTION AND OBJECTIVE: Fiber posts are widely used to increase the mechanical strength of the restorations. The aim of this study was to evaluate the bond strength of fiber posts reinforced by a restorative composite to radicular dentin on its cervical, middle and apical thirds, regarding to post preparation prior or posterior to the endodontic treatment. MATERIALS AND METHODS: Thirty bovine incisors were used, which had their debris removed, washed in tap water, and stored frozen. The samples were divided into two groups (n = 15) - according to the treatment applied previously to the installation of the posts: Group 1 - root canal obturation followed by root canal preparation for fiber posts bonding; and Group 2 fiber posts preparation followed by root canal obturation. The posts were cemented and the roots were cut on their cervical (C), medium (M) and apical (A) thirds - for push out test application. Bond strength was calculated in MPa and data were statistically analyzed by Anova and Tukey test (p < 0.05). RESULTS: The mean values were (MPa ± SD): G1C - 4.0 ± 6.0; G1M - 3.5 ± 2.9; G1A 7.2 ± 6.3; G2C - 12.7 ± 8.1; G2M - 11.6 ± 10.2; G2A - 6.5 ± 8.1. The cervical and middle thirds of group 2 had the highest mean values, showing significant statistically difference compared to group 1. For apical third, no significant statistically differences were found among groups. When the cervical, middle and apical thirds were analysed separately, no significant statistically differences were found. CONCLUSION: The post preparation prior to root canal obturation increased the bond strength of fiber posts reinforced by a restorative composite.

Fracture resistance of weakened teeth restored with condensable resin with and without cusp coverage

OBJECTIVES: This in vitro study evaluated the fracture resistance of weakened human premolars (MOD cavity preparation and pulp chamber roof removal) restored with condensable resin composite with and without cusp coverage. MATERIAL AND METHODS: Thirty human maxillary premolars were divided into three groups: Group A (control), sound teeth; Group B, wide MOD cavities prepared and the pulp chamber roof removed and restored with resin composite without cusp coverage; Group C, same as Group B with 2.0 mm of buccal and palatal cusps reduced and restored with the same resin. The teeth were included in metal rings with self-curing acrylic resin, stored in water for 24 h and thereafter subjected to a compressive axial load in a universal testing machine at 0.5 mm/min. RESULTS: The mean fracture resistance values ± standart deviation (kgf) were: group A: 151.40 ± 55.32, group B: 60.54 ± 12.61, group C: 141.90 ± 30.82. Statistically significant differences were found only between Group B and the other groups (p<0.05). The condensable resin restoration of weakened human premolars with cusp coverage significantly increased the fracture resistance of the teeth as compared to teeth restored without cusp coverage. CONCLUSION: The results showed that cusp coverage with condensable resin might be a safe option for restoring weakened endodontically treated teeth.