Application of polyetheretherketone (PEEK) posts: evaluation of fracture resistance and stress distribution in the root: in vitro and finite element analyses

Abstract To evaluate the feasibility of using a milled polyetheretherketone (PEEK) post and core in endodontically treated teeth with or without a ferrule. Sixty bovine tooth roots were endodontically treated followed by cementation of intraradicular retainers (IR), according to each experimental group: a) non-ferrule glass fiber post (f0FP); b) 2-mm-ferrule glass fiber post (f2FP); c) non-ferrule resized glass fiber post (f0PR); d) 2-mm-ferrule resized glass fiber post (f2PR); e) non-ferrule PEEK post and core (f0PPC); and f) 2-mm-ferrule PEEK post and core (f2PPC). Metal crowns were made and cemented. A periodontal ligament was simulated using polyether. A force was applied to the palatine portion of each sample at 45°, until fracture. Fracture resistance data were submitted to two-way ANOVA and Tukey's test (α = 0.05). Three-dimensional digital models were developed to calculate the tensions formed in the root using finite element analysis. Models of glass fiber posts and PEEK posts and cores were evaluated with or without a ferrule. The results were analyzed by the Mohr-Coulomb criterion. The type of IR was not influenced by fracture strength (p = 0.243). There were significant statistical differences among the remaining factors. Ferrule groups had greater fracture resistance, and the failure mode of teeth with a ferrule was more catastrophic than the non-ferrule group. A ferrule increases fracture resistance and influences failure mode; the PEEK post and core did not modify the biomechanics of endodontically treated teeth, and resembled the glass fiber post results. The crack initiation point differed between the ferrule and non-ferrule groups.

Dental displacement in complete dentures influenced by different flask types and polymerization cycles

Abstract This study evaluated the dental displacement in dentures included in different flasks and processed by the Australian cycle modified or by microwave. Metal pins were placed on the teeth as reference for measurements: a) Incisal edge of maxillary and mandibular central incisors, buccal cusp of maxillary and mandibular vestibular first premolars, and mesiobuccal maxillary and mandibular cusps of second molars; b) Incisor to incisor, premolar to premolar and molar to molar; c) Left incisor to left molar and right incisor to right molar, and d) Vertical. Dentures were divided according to flasks (n=10): G1- Metal; G2- HH bimaxillary metal; G3-Microwaves; G4- HH bimaxillary microwaves. For G1 and G2, polymerization at 65ºC/30 min, flame quenched for 30 min, heating at 65ºC/30 min, boiling water for 1 h. For G3 and G4, microwave (20 min/140 W and 5 min/560 W). Comparator microscope with digital camera and analytical unit assessed the measurements before and after denture polymerization. The final distance was made subtracting the distance before the denture processing from the distance of the dental displacement after processing. The value of the difference was submitted to 2-way ANOVA, considering the flask type and denture type. Maxillary denture showed greater displacement when compared to mandibular denture. Flask types and interaction with denture types showed similar difference between before and after polymerization. In conclusion, displacement promoted by flask types in dentures cured by polymerization cycles promoted similar effect on the distance between teeth. Greater value for distance between teeth occurred for maxillary denture.

Resumo O objetivo neste estudo foi avaliar o deslocamento dental em próteses totais incluídas em diferentes tipos de muflas e polimerizadas pelo ciclo australiano ou por micro ondas. Pinos metálicos foram colocados nos dentes como pontos de referência para as medidas: a) Borda incisal dos incisivos centrais maxilares e mandibulares, cúspide vestibular dos primeiros pré molares maxilares e mandibulares e cúspides mésiovestibulares dos segundos molares maxilares e mandibulares; b) Distâncias látero-laterais incisivo a incisivo, pré-molar a pré-molar e molar a molar; c) Distâncias horizontais anteroposterior incisivo esquerdo a molar esquerdo e incisivo direito a molar direito, e d) Vertical. As próteses foram separadas de acordo com o tipo de mufla (n=20): G1- Metálica; G2-HH bi-maxilar metálica; G3- Micro-ondas; G4- HH bi-maxilar micro ondas. Ciclo de polimerização para G1 e G2, água a 65ºC por 30 minutos, aquecimento interrompido por 30 minutos, reaquecimento a 65ºC por 30 minutos, seguido de água fervente por 1 hora. Para G3 e G4, micro ondas (20 minutos a 140 W e 5 minutos a 560 W). As medidas foram avaliadas com microscópio comparador linear. A distância final entre os dentes foi obtida subtraindo o valor da distância antes do processamento da prótese do valor da distância resultante do deslocamento dentário após o processamento. A diferença obtida entre essas distâncias foi submetida à ANOVA de 2 fatores, considerando como variáveis tipo de mufla e tipo de prótese. A prótese maxilar apresentou maior deslocamento dental quando comparada à mandibular. Os tipos de muflas e a interação com os tipos de próteses mostraram movimentos dentais similares antes e depois da polimerização. Em conclusão, o deslocamento dental promovido por diferentes tipos de frascos em próteses curadas por diferentes ciclos de polimerização promoveu efeito semelhante na alteração da distância entre os dentes. Maior valor para a mudança de distância entre os dentes ocorreu na prótese maxilar.

Fracture of upper incisors: a three-year follow-up of a multidisciplinary approach / Fratura em incisivos centrais superiores: tratamento multidisciplinar com acompanhamento clínico de três anos

ABSTRACT Multiple clinical specialties are usually needed for a successful long-term treatment in buccal cavity. The aim of this article is to report a clinical case of multi-disciplinary rehabilitation of fracture upper incisors without pulp exposure, concerning about endodontics, periodontics and restorative dentistry comments or procedures. A case of a patient reporting trauma that resulted in fracture and substantial loss of hard tissue, in mesial angle of both upper central incisors (11 and 21). In palatal side, fracture extended beyond cingulum up to subgingival region. Periodontal surgery was performed in order to reestablish biological space. Clinical and radiographic assessments demonstrated no need for endodontic treatment, since pulp was vital and non-altered. Preparations for restorative procedures were minimally invasive, followed by composite direct. A three-year follow-up was performed, consisting in re-assessment of clinical and radiographic aspects, re-polishing of the restorations and photographic documentation. No pulp tissue alteration was observed after the follow-up period. Restorative procedures, adjacent tissues and pulp vitality were considered adequate, and the patient was satisfied with the treatment.

RESUMO O objetivo deste artigo é relatar um caso clínico de reabilitação de incisivos superiores fraturados sem exposição pulpar, com considerações na área de endodontia, periodontia e dentística restauradora. O caso relata um trauma que resultou em perda substancial de tecido dentário em ângulo mesial de ambos os incisivos centrais superiores. Na parede palatina, a fratura se estendeu além do cíngulo até a região subgengival. A cirurgia periodontal foi realizada para restabelecer o espaço biológico. As avaliações clínicas e radiográficas não demonstraram necessidade de tratamento endodôntico, pois a polpa se apresentava vital e sem alterações. Os procedimentos restauradores foram minimamente invasivos através da realização de restauração direta com resina composta. Foi realizado acompanhamento de três anos, consistindo em reavaliação dos aspectos clínicos e radiográficos, polimento das restaurações e documentação fotográfica. Nenhuma alteração do tecido pulpar foi observada após o período de acompanhamento. Os procedimentos restauradores, tecidos adjacentes e vitalidade pulpar foram considerados adequados e a paciente demonstrou satisfação com o tratamento.

Implant volume loss, misfit, screw loosening, and stress in custom titanium and zirconia abutments

Abstract The aim of this study was to verify the effect of the implant volume loss, vertical misfit between abutment and prosthetic platform, prosthetic screw loosening torque, and screw stress distribution in titanium and zirconia abutments. Ten CAD/CAM system custom abutments of each material were milled and attached to the titanium implants. The implant volume loss was evaluated by microtomography, the vertical misfit with optical microscopy, and digital torque wrench measured the prosthetic screw loosening. All experimental analyses were performed before and after mechanical cycle (1,000,000 cycles, 100 N/2 Hz). Virtual models of the structures were created for finite element analysis, and the stress on the screw obtained with von Mises procedure. Data were analyzed using an independent t-test, two-way ANOVA for repeated measures, and Tukey's HSD test (a=0.05). There was no significant difference in the implant volume loss for the two abutment materials (p=0.662). Titanium abutments provided higher loosening torque values after mechanical cycling (p<0.001). Lesser marginal misfit was obtained with titanium abutments before and after mechanical cycling (p<0.001). The stress distribution on the screw was similar between abutment materials. In conclusion, CAD/CAM custom titanium abutment reduced the marginal misfit and increased the torque maintenance of prosthetic screws when compared to CAD/CAM custom zirconia abutment.

Resumo O objetivo neste estudo foi verificar o efeito da diminuição de volume do implante, desajuste vertical entre o pilar e plataforma protética, torque de afrouxamento do parafuso protético e distribuição da tensão no parafuso em pilares de titânio e zircônia. Dez pilares personalizados de cada material foram fresados e conectados aos implantes de titânio. A diminuição de volume do implante foi avaliada com microtomografia, o desajuste vertical com microscopia óptica e o torque de afrouxamento do parafuso protético com chave de torque digital. Todas as análises experimentais foram realizadas antes e após aplicação do ciclo mecânico (1.000.000 ciclos, 100 N/2 Hz). Modelos virtuais das estruturas foram criados para análise por elementos finitos e a tensão no parafuso obtida com valores de von Mises. Os dados foram analisados usando teste t independente, análise de varância dois fatores para medidas repetidas e teste de Tukey HSD (a=0,05). Não houve diferença significativa na diminuição de volume do implante para os dois materiais do pilar (p= 0,662). Os pilares de titânio proporcionaram maiores valores de torque de afrouxamento após o ciclo mecânico (p<0,001). O menor desajuste marginal foi obtido com os pilares de titânio antes e após o ciclo mecânico (p<0,001). A distribuição da tensão no parafuso foi similar entre os materiais. Em conclusão, os pilares personalizados de titânio reduziram o desajuste marginal e aumentaram a manutenção do torque dos parafusos protéticos quando comparados aos pilares de zircônia.

Propriedades mecânicas e ópticas das cerâmicas feldspáticas e dissilicato de lítio: Revisão de literatura / Mechanical and optical properties of feldspathic ceramics and lithium disilicate: literature review

Objetivo: o objetivo dessa revisão de literatura é apresentar os dados existentes sobre capacidade estética e resistência à fratura das cerâmicas feldspáticas e dissilicato de lítio confeccionadas para o uso em CAD/CAM. Material e Métodos: para realizar o estudo foram levantados artigos originais sobre as cerâmicas feldspáticas e dissilicato de lítio em periódicos na base de dados PubMed e ScienceDirect, desde 2015 até 2020 utilizando como termos de busca "lithium disilicate AND esthetic AND CAD/CAM", "lithium disilicate AND fadigue AND CAD/CAM", "lithium disilicate AND fracture AND CAD/CAM", "feldspathic AND esthetic AND CAD/CAM", "feldspathic AND fadigue AND CAD/CAM", "feldspathic AND fracture AND CAD/CAM". Ainda, foram selecionados artigos de relevância publicados em datas anteriores selecionados pelos autores. Constam trabalhos longitudinais, de revisão de literatura, casos clínicos e pesquisas in vitro. Resultados: no total, 209 artigos foram encontrados e somente 16 foram incluídos para comparação. Os dados apresentaram boa capacidade estética para ambos materiais, sendo o dissilicato com maior resistência à fratura. Conclusão: concluiu-se que cerâmicas feldspáticas e dissilicato de lítio para CAD/CAM apresentam capacidade ópticas satisfatórias para restaurações estéticas quando utilizado os blocos multicores, devendo-se optar pelo dissilicato de lítio em situações de maior esforço mastigatório ou menor espessura da peça protética

Objective: this literature review presents the existing data on the esthetic capacity and fracture resistance of feldspathic and lithium disilicate ceramics made for CAD/CAM. Material and Methods: original articles on feldspathic ceramics and lithium disilicate were collected in journals in the PubMed and ScienceDirect databases from 2015 to 2020 using the search terms "lithium disilicate AND esthetic AND CAD/CAM," "lithium disilicate AND fatigue AND CAD/CAM," "lithium disilicate AND fracture AND CAD/CAM," "feldspathic AND esthetic AND CAD/CAM," "feldspathic AND fatigue AND CAD/CAM," "feldspathic AND fracture AND CAD/CAM." relevant articles published previously to 2015 were also selected by the authors. Longitudinal studies, literature reviews, clinical cases and in vitro studies were included. Results: in total, 209 articles were selected and 16 included for comparison. Data presented good esthetic capability for both materials, disilicate presented higher fracture strength. Conclusion: the study concluded that feldspathic ceramics and lithium disilicate for CAD/CAM have satisfactory optical capacity for esthetics restorations when multicolor blocks are used. Lithium disilicate should be chosen in situations of greater masticatory effort or thinness of the prosthetic piece

How many implants are needed for mandibular full-arch rehabilitation?

Aim: To analyze the stress distribution at the peri-implant bone tissue of mandible in full-arch implant-supported rehabilitation using a different number of implants as support. Methods: Three-dimensional finite element models of full-arch prosthesis with 3, 4 and 5 implants and those respective mandibular bone, screws and structure were built. ANSYS Workbench software was used to analyze the maximum and minimum principal stresses (quantitative analysis) and modified von Mises stress (qualitative analysis) in peri-implant bone tissue after vertical and oblique forces (100N) applied to the structure at the cantilever site (region of the first molars). Results: The peak of tensile stress values were at the bone tissue around to the distal implant in all models. The model with 3 implants presented the maximum principal stress, in the surrounding bone tissue, higher (~14%) than the other models. The difference of maximum principal stress for model with 4 and 5 implants was not relevant (~1%). The first medial implant of the model with 5 implants presented the lower (17%) stress values in bone than model with 3 implants. It was also not different from model with 4 implants. Conclusion: Three regular implants might present a slight higher chance of failure than rehabilitations with four or five implants. The use of four implants showed to be an adequate alternative to the use of classical five implants

Extruded upper first molar intrusion: Comparison between unilateral and bilateral miniscrew anchorage

ABSTRACT Objective: The aim of his study was to evaluate the stress on tooth and alveolar bone caused by orthodontic intrusion forces in a supraerupted upper molar, by using a three-dimensional Finite Element Method (FEM). Methods: A superior maxillary segment was modeled in the software SolidWorks 2010 (SolidWorks Corporation, Waltham, MA, USA) containing: cortical and cancellous bone, supraerupted first molar, periodontal tissue and orthodontic components. A finite element model has simulated intrusion forces of 4N onto a tooth, directed to different mini-screw locations. Three different intrusion mechanics vectors were simulated: anchoring on a buccal mini-implant; anchoring on a palatal mini-implant and the association of both anchorage systems. All analyses were performed considering the minimum principal stress and total deformation. Qualitative analyses exhibited stress distribution by color maps. Quantitative analysis was performed with a specific software for reading and solving numerical equations (ANSYS Workbench 14, Ansys, Canonsburg, Pennsylvania, USA). Results: Intrusion forces applied from both sides (buccal and palatal) resulted in a more homogeneous stress distribution; no high peak of stress was detected and it has allowed a vertical resultant movement. Buccal or palatal single-sided forces resulted in concentrated stress zones with higher values and tooth tipping to respective force side. Conclusion: Unilateral forces promoted higher stress in root apex and higher dental tipping. The bilateral forces promoted better distribution without evidence of dental tipping. Bilateral intrusion technique suggested lower probability of root apex resorption.

RESUMO Objetivos: o presente estudo teve como objetivo avaliar, por meio da Análise de Elementos Finitos, as tensões geradas por forças ortodônticas intrusivas em um molar superior e no osso alveolar circundante. Métodos: um segmento maxilar foi modelado no software SolidWorks 2010 (SolidWorks Corporation, Waltham, MA, EUA), contendo: osso cortical e medular, primeiro molar extruído, tecido periodontal e acessórios ortodônticos. Um modelo de elementos finitos simulou forças intrusivas de 4 N no elemento dentário, aplicadas a partir de mini-implantes em localizações distintas. Três diferentes vetores para mecânica de intrusão foram simulados: ancoragem em mini-implante vestibular, ancoragem em mini-implante palatino ou a associação de ambas. Todas as análises foram realizadas em termos de tensão mínima principal e deformação total. A análise qualitativa foi feita por meio do mapeamento da distribuição das tensões em gradiente de cores. A análise quantitativa foi feita em software específico para leitura e resolução de equações numéricas (ANSYS Workbench 14, Ansys, Canonsburg, Pennsylvania, EUA). Resultados: as forças intrusivas aplicadas simultaneamente nos dois lados (vestibular e palatino) resultaram em uma distribuição mais homogênea das tensões geradas, sem zonas de acúmulo de tensão e com uma resultante vertical para a movimentação intrusiva. As forças aplicadas somente em um lado, vestibular ou palatino, resultaram em zonas de concentração de tensão, com maiores valores, e na inclinação do elemento dentário para o lado em que a força foi aplicada. Conclusão: as forças unilaterais promoveram maior tensão no ápice radicular e maiores inclinações do elemento dentário. Já as forças bilaterais promoveram melhor distribuição das tensões e não resultaram em inclinação do elemento dentário. Assim, as forças intrusivas ancoradas bilateralmente apresentam menor probabilidade de reabsorção do ápice radicular.

Photoelastic and finite element stress analysis reliability for implant-supported system stress investigation

Aim: To compare the reliability between photoelastic and finite element (FE) analyses by evaluating the effect of different marginal misfit levels on the stresses generated on two different implant-supported systems using conventional and short implants. Methods: Two photoelastic models were obtained: model C with two conventional implants (4.1×11 mm); and model S with a conventional and a short implant (5×6 mm). Three-unit CoCr frameworks were fabricated simulating a superior first pre-molar (P) to first molar (M) fixed dental prosthesis. Different levels of misfit (µm) were selected based on the misfit average of 10 frameworks obtained by the single-screw test protocol: low (<20), medium (>20 and <40) and high (>40). Stress levels and distribution were measured by photoelastic analysis. A similar situation of the in vitro assay was designed and simulated by the in silico analysis. Maximum and minimum principal strain were recorded numerically and color-coded for the models. Von Mises Stress was obtained for the metallic components. Results: Photoelasticity and FE analyses showed similar tendency where the increase of misfit generates higher stress levels despite of the implant design. The short implant showed lower von Mises stress values; however, it presented stresses around its full length for the in vitro and in silico analysis. Also, model S showed higher µstrain values for all simulated misfit levels. The type of implant did not affect the stresses around pillar P. Conclusions: Photoelasticity and FEA are reliable methodologies presenting similarity for the investigation of the biomechanical behavior of implant-supported rehabilitations

Repair Strength in Simulated Restorations of Methacrylate- or Silorane-Based Composite Resins

Abstract The study verified the bond strength in simulated dental restorations of silorane- or methacrylate-based composites repaired with methacrylate-based composite. Methacrylate- (P60) or silorane-based (P90) composites were used associated with adhesive (Adper Single Bond 2). Twenty-four hemi-hourglass-shaped samples were repaired with each composite (n=12). Samples were divided according to groups: G1= P60 + Adper Single Bond 2+ P60; G2= P60 + Adper Single Bond 2 + P60 + thermocycling; G3= P90 + Adper Single Bond 2 + P60; and G4= P90 + Adper Single Bond 2 + P60 + thermocycling. G1 and G3 were submitted to tensile test 24 h after repair procedure, and G2 and G4 after submitted to 5,000 thermocycles at 5 and 55 ?#61616;C for 30 s in each bath. Tensile bond strength test was accomplished in an universal testing machine at crosshead speed of 0.5 mm/min. Data (MPa) were analyzed by two-way ANOVA and Tukey's test (5%). Sample failure pattern (adhesive, cohesive in resin or mixed) was evaluated by stereomicroscope at 30?#61655; and images were obtained in SEM. Bond strength values of methacrylate-based composite samples repaired with methacrylate-based composite (G1 and G2) were greater than for silorane-based samples (G3 and G4). Thermocycling decreased the bond strength values for both composites. All groups showed predominance of adhesive failures and no cohesive failure in composite resin was observed. In conclusion, higher bond strength values were observed in methacrylate-based resin samples and greater percentage of adhesive failures in silorane-based resin samples, both composites repaired with methacrylate-based resin.

Resumo O objetivo neste estudo foi verificar a resistência de união em restaurações simuladas de compósitos baseados em metacrilato ou silorano reparadas com compósito à base de metacrilato. Compósitos baseados em metacrilato (Filtek P60; 3M ESPE) ou silorano (Filtek P90; 3M ESPE) foram associados com adesivo (Adper Single Bond 2; 3M ESPE). Vinte e quatro amostras em forma de semi-ampulhetas foram reparadas com cada material (n=12), conforme os grupos experimentais: G1- P60 + Adper Single Bond 2 + P60; G2- P60 + Adper Single Bond 2 + P60 + termociclagem; G3- P90 + Adper Single Bond 2 + P60; e G4- P90 + Adper Single Bond 2 + P60 + termociclagem. Os grupos G1 e G3 foram submetidos ao ensaio de tração após 24 horas do procedimento de reparo e os grupos G2 e G4 depois de submetidos a 5.000 ciclos térmicos de 5 e 55 ?#61616;C por 30 s em cada banho. O teste de resistência à tração foi efetuado em máquina universal atuando numa velocidade de 0,5 mm/min. Os dados (MPa) foram submetidos a ANOVA a dois fatores e teste de Tukey (5%). O padrão de fratura das amostras (adesivo, coesivo em resina ou misto) foi avaliado em estereomicroscópio com aumento de 30x e imagens representativas foram obtidas em MEV. Os valores de resistência à tração das amostras feitas com compósito à base de metacrilato e reparadas com compósito à base de metacrilato (G1 e G2) foram maiores do que nas amostras feitas com compósito à base de silorano e reparadas nas mesmas condições (G3 e G4). A termociclagem diminuiu os valores de resistência à tração para ambos os compósitos. Todos os grupos mostraram predominância de fraturas adesivas e nenhuma falha coesiva foi observada em compósito. Em conclusão, valores maiores de resistência à tração foram observados em amostras de resina à base de metacrilato e maior porcentagem de fraturas adesivas nas amostras de resina à base de silorano, ambos os compósitos reparados com resina à base de metacrilato.

Piriform Aperture Morphometry and Nasal Bones Morphology in Brazilian Population by Postero-Anterior Caldwell Radiographys / Morfometría de la Apertura Piriforme y Morfología de los Huesos Nasales en la Población Brasileña por la Radiografía Postero-Anterior de Caldwell

Piriform aperture and nasal bone contribute to the formation of the nose. Its morphology varies according to ethnic group and gender. The piriform apertures and nasal bones of 97 individuals were examined radiographically through Caldwell radiographic technique and the types of nasal bones were classified according to Hwang et al. (2005). The width, height and area of piriform aperture were measured to demonstrate the difference according to gender. Statistical analysis was performed from the Student t test and analysis of variance (ANOVA). The most frequent type of nasal bone was A, and D was the most uncommon in both genders. In the Student t test significant differences between genders, height, width and area of the piriform aperture were obtained and were larger in males when compared to females. The dimensions of the piriform aperture were higher in males when compared to females, and therefore may be used as parameter for the distinction of gender in Brazilian population. The type A of nasal bone was the most frequent in the Brazilian population, contributing to ethnic differentiation in human identification.

La apertura piriforme y el hueso nasal contribuyen a la formación de la nariz. Su morfología varía de acuerdo a los grupos étnicos y al sexo. Este estudio evaluó la morfología de la apertura piriforme y el hueso nasal y su relación con el sexo. Las aperturas piriformes y los huesos nasales de 97 personas fueron examinados radiográficamente mediante la técnica radiográfica de Caldwell, y los tipos de huesos nasales se clasificaron de acuerdo con Hwang et al. (2005). Se midió el ancho, la altura y el área de la apertura piriforme para demostrar las diferencias por sexo. El análisis estadístico se realizó a partir de la prueba t de Student y análisis de varianza (ANOVA). El tipo más frecuente de hueso nasal fue la A, y la D fue la menos común, en ambos sexos. En la prueba t de Student se obtuvo diferencias significativas entre los sexos, altura, ancho y área de la apertura piriforme, las que fueron mayores en hombres en comparación a las mujeres. Las dimensiones de la apertura piriforme fueron mayores en los hombres que en las mujeres, por lo que se puede utilizar como parámetro para la distinción de sexo en la población brasileña. En la población brasileña el tipo A de hueso nasal fue el más frecuente, lo que contribuye para la diferenciación étnica en la identificación humana.