Mouthguard Use Effect on the Biomechanical Response of an Ankylosed Maxillary Central Incisor during a Traumatic Impact: A 3-Dimensional Finite Element Analysis.

(1) Background: Trauma is a very common experience in contact sports; however, there is an absence of data regarding the effect of athletes wearing mouthguards (MG) associated with ankylosed maxillary central incisor during a traumatic impact. (2) Methods: To evaluate the stress distribution in the bone and teeth in this situation, models of maxillary central incisor were created containing cortical bone, trabecular bone, soft tissue, root dentin, enamel, periodontal ligament, and antagonist teeth were modeled. One model received a MG with 4-mm thickness. Both models were subdivided into finite elements. The frictionless contacts were used and a nonlinear dynamic impact analysis was performed in which a rigid object hit the model at 1 m·s-1. For each model, an ankylosed periodontal ligament was simulated totaling 4 different situations. The results were presented in von-Mises stress maps. (3) Results: A higher stress concentration in teeth and bone was observed for the model without a MG and with ankylosed tooth (19.5 and 37.3 MPa, respectively); the most promising mechanical response was calculated for patients with healthy periodontal ligament and MG in position (1.8 and 7.8 MPa, respectively). (4) Conclusions: The MG's use is beneficial for healthy and ankylosed teeth, since it acts by dampening the generated stresses in bone, dentin, enamel and periodontal ligament. However, patients with ankylosed tooth are more prone to root fracture even when the MG is in position compared to a healthy tooth.

Influence of Surface Treatment and Resin Cements on the Bond Strength between the Y-TZP Zirconia and Composite Resin Interface / Influência do Tratamento de Superfície e dos Cimentos Resinosos na Resistência de União Entre a Interface Zircônia Y-TZP e Resina Composta

The evolution of dental materials and the improvement of ceramic systems stimulated the increased use of Y-TZP zirconia-based ceramics. Despite the excellent mechanical performance, this material has low adhesion potential. The objective of this work was to evaluate the surface treatments and resin cements influence on bond strength between Y-TZP zirconia and composite resin interface. A total of 60 blocks of Y-TZP zirconia (3x8x8mm) were prepared and divided into 3 groups according to the surface treatments: (C) control - extra fine diamond bur, (J) sandblasting with Al2O3 and (JP) sandblasting with Al2O3 + ceramic primer. Each group was subdivided into two groups according to type of resin cement used for cementing composite resin discs (2mm thick x 5mm diameter): self-adhesive and conventional (n=10). The samples were stored in distilled water for 24 hours at 37±1°C in a incubator and subsequently submitted to the shear bond test to determine the bond strength (RU). There was no significant difference in RU among the surface treatments when using conventional resin cement. For the self-adhesive resin cement, Al2O3 blasting and Al2O3 + primer blasting increased the RU but did not present significant differences between them (p<0.05). Comparing the cements, it was observed that regardless of the surface treatment, the highest values were for the self-adhesive resin cement (p<0.05). Application of the primer after blasting with Al2O3 did not increase RU. (AU)

A evolução dos materiais odontológicos e o aprimoramento dos sistemas cerâmicos impulsionaram o aumento da utilização da cerâmica a base de zircônia Y-TZP. Apesar do excelente desempenho mecânico, este material apresenta baixo potencial de adesão. O objetivo deste trabalho foi avaliar a influência dos tratamentos de superfícies e dos cimentos resinosos na resistência de união entre a interface zircônia Y-TZP e resina composta. Foram confeccionados 60 blocos de zircônia Y-TZP (3x8x8 mm) e divididos em 03 grupos de acordo com os tratamentos de superfícies que receberam: (C) controle - ponta diamantada extrafina, (J) jateamento com Al2O3 e (JP) jateamento com Al2O3 + primer cerâmico. Cada grupo foi subdividido em dois novos grupos de acordo com tipo de cimento resinoso utilizado para cimentação de discos de resina composta (2mm de espessura x 5mm de diâmetro): autoadesivo e resinoso convencional (n=10). As amostras foram armazenadas em água destilada por 24 horas a 37±1°C em estufa e posteriormente submetidas ao teste de cisalhamento para averiguar a resistência de união (RU). Não houve diferença significativa na RU entre os tratamentos de superfície quando utilizado o cimento resinoso convencional. Para o cimento resinoso autoadesivo o jateamento com Al2O3 e o jateamento de Al2O3 + primer aumentaram a RU porém não apresentaram diferenças significativas entre si (p<0,05). Comparando os cimentos observou-se que, independente do tratamento de superfície, os maiores valores foram para o cimento resinoso autoadesivo (p<0,05). A aplicação do primer após o jateamento com Al2O3 não proporcionou aumento da RU. (AU)

Influence of polishing systems on roughness and color change of two dental ceramics.

PURPOSE: To evaluate the polishing effect on roughness and color change of pressed and layering ceramics after immersion in coffee solution. MATERIALS AND METHODS: 88 ceramic discs (1.0 mm × 10.0 mm) were manufactured - 44 nano-fluorapatite layering ceramics (IPS e.max Ceram. Group C) and 44 pressed lithium disilicate ceramic discs (IPS e. max Press - Group P). Each group was divided into 4 subgroups according to surface treatments: (G) Glaze, (S) Shofu polishing system (Shofu Inc.), (E) Edenta AG polishing System, (KG) 30-µm diamond granulation tip. Surface roughness (Ra) and color change (ΔE) measurings after the surface treatments were performed, before and 12 days after the immersion in coffee solution. A samples' qualitative analysis was conducted with a scanning electron microscopy (SEM). Data were statistically-treated with one-way-ANOVA and Duncan's tests, apart from paired t-test and Pearson's correlation test (α=5%). RESULTS: The decrescent order, both for surface roughness (Ra) and ΔE for both ceramics were: KG > E > S > G (P<.05). With exception for PG and CG subgroups, which did not present statistical difference between them, all other pressed ceramics subgroups presented smaller Ra values and greater ΔE values than the layering ceramics subgroups (P<.05). CONCLUSION: Although mechanical polishing systems presented intermediate Ra values, their colors were considered clinically acceptable. There is a strong correlation between the surface roughness and the color change of tested ceramics.

Influence of bone loss and inclination of incisor on periradicular stresses due to simulated bite force / Influência da perda óssea e da inclinação do incisivo na distribuição de tensões perirradiculares decorrentes da simulação de forças oclusais

Introduction: Adults with sequelae of periodontal disease tend to have bone loss, with consequent flaring of the maxillary incisors. Objective: The influence of bone loss and the inclination of the maxillary incisor in the distribution of stresses due to simulated bite forces was studied. Material and method: Models in epoxy resin were made in three conditions (without bone loss and with bone loss of 5mm and 8mm). Increases in the labial inclination of the maxillary incisor of 10° and 20° were obtained with a beveled metallic block. Loads of 100N were applied five times in each condition using a universal test machine. The models were observed and filmed with a circular polariscope. Orders of isochromatic fringes (stresses) on the labial, lingual, and apex surfaces were recorded. The agreement of the data was evaluated using the weighted kappa test, and the results were 0.89 and 0.82 for intra- and inter-examiners, respectively. Result: The results of the Kruskal-Wallis and SNK tests indicated higher stresses (2.0) with increased labial inclination in the labial surface; higher stresses (2.67) with increased bone loss; higher greater stresses with the association of bone loss and labial-inclination (3.6); and the highest stresses tended to concentrate on the labial surfaces, except in cases of normal inclination and without bone loss (0.45). Conclusion: It was concluded that increases in both the labial inclination of the maxillary incisors and bone loss increase periradicular stresses, and the combination of these factors further increases the stresses due to bite forces, with the highest concentration on the labial side.

Introdução: Adultos com sequelas de doenças periodontais tendem a apresentar perda óssea, com consequente vestibularização dos incisivos superiores. Objetivo: A influência da perda óssea e da inclinação do incisivo superior na distribuição de tensões devido a forças mastigatórias simuladas foram avaliadas nesse estudo. Material e método: Modelos em resina epóxi foram confeccionados em três condições (sem perda óssea e com perda óssea de 5mm e 8mm). Aumentos na inclinação vestibular do incisivo superior de 10° e 20° foram obtidos com um bloco metálico chanfrado. Cargas de 100N foram aplicadas cinco vezes em cada condição usando uma máquina de ensaio universal. Os modelos foram observados e filmados com um polariscópio circular. Ordens de franjas isocromáticas (tensões) nas faces vestibular, lingual e apical foram registradas. A concordância dos dados foi avaliada pelo teste kappa ponderado e os resultados foram 0,89 e 0,82 para intra e interexaminadores, respectivamente. Resultado: Os resultados dos testes de Kruskal-Wallis e SNK indicaram maiores tensões (2,0) com aumento da inclinação vestibular na face vestibular; maiores tensões (2,67) com aumento da perda óssea; maior tensão com a associação de perda óssea e inclinação vestibular (3,6); e as maiores tensões tenderam a concentrar-se na face vestibular, exceto em casos de inclinação normal e sem perda óssea (0,45). Conclusão: Concluiu-se que aumentos tanto da inclinação vestibular dos incisivos superiores quanto da perda óssea aumentam as tensões perirradiculares, e a combinação desses fatores aumenta ainda mais as tensões devido às forças mastigatórias, com a maior concentração na face vestibular.

Influência de diferentes aplicaçõesde cargas e interposição de aparelhooclusal plano em implantes dentais:análise fotoelástica / Influence of different loads and interposing of plane occlusalappliance in dental implants: photoelastic analysis

Se forças oclusais excederem a capacidade de absorção do sistema implante/osso, o implante tende a fracassar. O objetivo deste estudo foi avaliar a tensão peri-implantar com e sem utilização de placa oclusal plana sob carregamentos diferentes. Materiais e Métodos: Foram confeccionados cinco modelos fotoelásticos, com um implante em cada. Sobre estes implantes foram instaladas coroas unitárias e construída uma placa oclusal plana. Foram aplicadas cargas axiais de 100N, 200N e 300N, com e sem a presença da placa oclusal plana, por meio da máquina universal de ensaio conjugada ao polariscópio. O teste de Mann-Whitney foi utilizado para comparar os grupos com e sem placa, em todas as condições de carregamento. O teste de Kruskal-Wallis foi utilizado para comparar as tensões decorrentes das cargas de 100, 200 e 300N e também para comparar as tensões nas seis áreas periimplantares analisadas. Resultados: Os resultados dos testes de Mann-Whitney não identificaram diferenças estatísticas (p>0,05) ao comparar as ordens de franjas com e sem a utilização de aparelho oclusal plano, em todas as áreas periimplantares analisadas, sob cargas verticais de 100, 200 e 300N. Os resultados dos testes de Kruskal-Wallis indicaram tensões significativamente maiores nas regiões apicais (p<0,05) e que nas áreas apicais as tensões foram maiores com o carregamento de 300N (p<0,05). Conclusões: A utilização da placa oclusal plana sobre a prótese unitária não reduziu significativamente as tensões nas regiões periimplantares; as tensões tendem a se concentrarem na região periapical e nestas áreas a maior magnitude de força implicou em maior tensão...

Introduction: If occlusal forces exceed the capacity of the implant/bone system, the implant tends to fail. The aim of this study was to evaluate the peri-implant stress with and without use of flat occlusal splint under various loads. Materials and Methods: Five photoelastic models were made with an implant in each. About these implants crowns were installed and built a flat occlusal splint. Axial loads of 100N, 200N and 300N, with and without the presence of the occlusal plane plate, were applied by universal testing machine conjugate to the polariscope. The Mann-Whitney test was used to compare the groups with and without plate, in all conditions of loading. The Kruskal-Wallis test was used to compare the stresses resulting from loads of 100, 200 and 300N and also to compare the peri-implant stresses in the six areas analyzed. Results: The results of Mann-Whitney tests identify no significant differences (p> 0.05) comparing fringe orders with and without the use of flat occlusal appliance, in all peri-implant areas examined under vertical loads 100, 200 and 300N. The results of Kruskal-Wallis tests indicated significantly higher stress in the apical regions (p <0.05) and in the apical areas stresses were higher with the loading of 300N (p <0.05). Conclusions: The use of flat occlusal splint on the unitary prosthesis did not significantly reduce the stress in the peri-implant regions; stress tend to concentrate on the periapical region and in these areas the largest magnitude of force resulted in higher stress...

Influence of chemical and mechanical polishing on water sorption of acrylic resin polymerized by water bath and microwave irradiation

Previous studies have investigated the possible influences to different types of polymerization and polishing procedures in some properties of acrylic resins. Water sorption is an important property, which may be induced by these factors. The aim of this work was to evaluate water sorption in acrylic resin processed in microwave energy or water bath, after chemical and mechanical polishing. Forty heatpolymerized acrylic resin (Vipi-Cril, Dental VIPI Ltd, Pirassununga, São Paulo, Brazil) specimens were made according to ADA Specification No.12 for Denture Base Polymers and divided into 4 groups: Groups I and II were processed in microwave energy (500 W for 3 minutes); Groups III and IV, in water bath (73ºC ± 1ºC for 9 hours). Groups I and III were polished chemically; Groups II and IV were polished mecahnically. The specimens were submitted to water sorption test. The water sorption values (mg/cm2) were calculated and submitted to ANOVA and Tukeyïs test (5% significance level). The obtained results were: Group I: 0.000953, Group II: 0.001069, Group III: 0.000958 and Group IV: 0.001491. No statistical difference were found among the groups (p>.05). Polymerization by microwave energy or water bath associated with chemical or mechanical polishing did not influence the water sorption of the heat polymerized acrylic resin evaluated.