Effect of miniscrew placement height on the distribution of biological forces produced by clear aligner for mandibular molar distalization / 口腔疾病防治

Objective@#To explore the effect of different miniscrew placement heights on the distribution of biological forces produced by clear aligner combined with intramaxillary traction for mandibular molar distalization, to identify the miniscrew location that is conducive to the protection of lower anterior tooth anchorage and to provide a reference that can be used when designing clinical treatments.@*Methods@#Mimics, GeomagicStudio 2017, SolidWorks 2016, and Ansys workbench were used to establish finite element analysis models and perform mechanical analysis under the following six working conditions: working condition 1 was the control group without miniscrews; working conditions 2 to 5 had miniscrew in the buccal bone cortex between the first and second molars of the lower jaw 10 mm, 7 mm, 4 mm, and 1 mm from the top of the alveolar crest, respectively; working condition 6 had the miniscrew in the center of the buccal tongue at the anterior edge of the ascending branch of the lower jaw 5 mm above the occlusal plane.@*Results@#On the sagittal axis, miniscrew anchorage caused distal displacement of all teeth. Compared to the control group, in the miniscrew group, the displacement of the anterior molars exceeded that of the second molars. On the vertical axis, the result in the control group was similar to backward bending; the results in the miniscrew groups resembled the effect of a lever, lowering the lateral incisors and canines and raising the central incisors and first premolars. On the coronal axis, the second premolars and the first molars showed lingual displacement in the control group, and only the premolars and first molars showed lingual displacementin the miniscrew groups. The canines were the teeth that were most strongly affected by the change in miniscrew placement height.@*Conclusion@#The higher the miniscrew position is, the stronger the protective effect on the anterior anchorage. According to the miniscrew placement height, the mandibular arch should be properly narrowed, the central incisors and first premolars should be lowered, and the lateral incisors and canines should be raised when designing clinical treatments.

The effect of different framework's material on strain induced in distal abutment in mandibular Kennedy's class II: an in-vitro study / O efeito de diferentes materiais de estrutura na deformação induzida na distal do pilar da classe II de Kennedy mandibular: um estudo in vitro

Objective: This study aims to compare the strain induced in the supporting structures of unilateral mandibular removable partial denture frameworks retained by extra-coronal attachments fabricated with three different materials. Material and Methods: Three mandibular class II digitally designed and printed acrylic models with detachable abutments were used to fabricate three removable partial denture framework with extra coronal attachments from three different materials. A total of 33 models were prepared for strain testing (n=11). Models were divided into three groups according to framework's material: porcelain fused to cobalt chromium (PFM), polyetherketoneketone (PEKK) and polyetheretherketone (PEEK) group. Unilateral load of 60 N was applied in the three groups and strains were measured around the main abutment and saddle area using strain gauge. Results: Statistical analysis was performed using Shapiro-Wilk's test and by checking data distribution. Data were found to be non-parametric and were analysed using Kruskal-Wallis test followed by Dunn's post hoc test with Bonferroni correction. PFM group showed significantly the highest strain values around abutment, slot 1 (1mm distal to the socket of the last abutment) and slot 2 (1 cm away from slot 1) respectively (843.00±23.08, 91.00±6.52 and 1274.00±65.71) than the other tested groups (p<0.05) at same tested sites respectively followed by PEKK group (384.00±37.48, 81.00±2.24 and 135.00±0.00) and PEEK group (29.00±4.18, 63.00±4.47 and 52.00±5.70). Conclusions: PEEK and PEKK for partial denture framework with extra coronal attachments are adequate alternative to PFM due to their good mechanical response applying less strain on supportive structures in free-end cases. PEEK induces lower strain magnitude on the supporting structures when compared to PEKK. (AU)

Objetivo: Este estudo tem como objetivo comparar a tensão induzida nas estruturas de suporte de estruturas de próteses parciais removíveis mandibulares unilateraisretidas por encaixes extracoronários fabricados com três materiais diferentes. Material e Métodos: Três modelos mandibulares de classe II digitalmente projetados e impressos em acrílico com pilares destacáveis foram usados para fabricar três estruturas de próteses parciais removíveis com encaixes extracoronários de três materiais diferentes. Um total de 33 modelos foram preparados para testes de deformação (n=11). Os modelos foram divididos em três grupos de acordo com o material da estrutura: porcelana fundida com cobalto-cromo (PFM), poliétercetonacetona (PEKK) e polieteretercetona (PEEK). Carga unilateral de 60 N foi aplicada nos três grupos e as deformações foram medidas em torno do pilar principal e área de sela usando medido de tensão. Resultados: A análise estatística foi realizada por meio do teste de Shapiro-Wilk e com a verificação da distribuição dos dados. Os dados mostraram-se não paramétricos e foram analisados pelo teste de Kruskal-Wallis seguido pelo de Dunn com correção de Bonferroni. O grupo PFM mostrou significativamente os maiores valores de tensão ao redor do pilar, slot 1 (1mm distal do último pilar) e slot 2 (1 cm de distância do slot 1) respectivamente (843,00±23,08, 91,00±6,52 e 1274,00±65,71) do que os outros grupos testados (p<0,05) nos mesmos locais testados, respectivamente, seguido pelo grupo PEKK (384,00±37,48, 81,00±2,24 e 135,00±0,00) e grupo PEEK (29,00±4,18, 63,00±4,47 e 52,00±5,70). Conclusão: PEEK e PEKK para estrutura de prótese parcial com encaixes extracoronários são alternativas adequadas ao PFM devido à sua boa resposta mecânica aplicando menos tensão nas estruturas de suporte em casos de extremidade livre. O PEEK induz menor magnitude de deformação nas estruturas de suporte quando comparado ao PEKK (AU)

Measurement of Maximum Occlusal Force Using Digital Occlusal Force Measurement Device: A Scoping Review

@#The aim of this review was to provide an update on the current status of digital occlusal force measurement devices, as well as clinical and research applications in complete arch maximum occlusal force measurement. SCOPUS, ScienceDirect, and PubMed databases were used to conduct a literature search from January 2001 to January 2021. Identification and screening of literature were done independently according to published guidelines and selection criteria. The electronic searches turned up 394 articles, 16 of which met the inclusion and exclusion criteria and were selected for study analysis. All of these studies used T-scan and Dental Prescale digital occlusal analysis system with pressure-sensitive foils as occlusal force measurement devices. The devices showed a promising potential for identifying and comprehending maximum occlusal forces objectively. According to the current review, maximum occlusal force measured with digital occlusal force devices can be used as a prosthodontic adjunct to address issues that arise during the treatment of occlusal disorders, temporomandibular disorders, and complete dentures. It is also useful in predicting cognitive and functional decline in the elderly.

Vulnerabilidad al estrés en adolescentes de instituciones deportivas / Vulnerability to stress in teenagers in sports institutions

Fundamento: Los trastornos temporomandibulares tienen origen multifactorial y el factor psicológico ocupa un papel importante en su desencadenamiento. Objetivo: Determinar la vulnerabilidad al estrés en adolescentes de instituciones deportivas. Metodología: Se realizó un estudio observacional descriptivo de corte transversal, en la EIDE provincial de Sancti Spíritus "Lino Salabarría Pupo" entre octubre de 2020 y marzo de 2021. Se seleccionaron 70 escolares de décimo, onceno y duodécimo grados mediante muestreo aleatorio simple. Se midió la variable: rango de vulnerabilidad al estrés. Se utilizaron métodos del nivel teórico, empírico y estadístico. Resultados: El 51.4 %.de los estudiantes fueron clasificados con vulnerabilidad al estrés, el 40 % no vulnerables, el 8.6 % seriamente vulnerables y ninguno extremadamente vulnerables. Conclusiones: Existe un predominio de adolescentes de instituciones deportivas con vulnerabilidad al estrés.

Background: Temporomandibular disorders have a multifactorial origin and the psychological factor plays an important role in their triggering. Objective: To determine the vulnerability to stress in teenagers from sports institutions. Methodology: A cross-sectional descriptive observational study was conducted at the Sancti Spíritus provincial EIDE "Lino Salabarría Pupo" between October 2020 and March 2021. Seventy schoolchildren from tenth, eleventh and twelfth grades were selected by simple random sampling. The variable range of vulnerability to stress was measured. Theoretical, empirical and statistical methods were used. Results: 51.4 % of the students were classified with vulnerability to stress, 40 % not vulnerable, 8.6 % seriously vulnerable and none extremely vulnerable. Conclusions: There is a predominance of teenagers from sports institutions with vulnerability to stress.

THE POST TRANSFIXED IN THE CORONAL CAVITY INCREASES THE FRACTURE RESISTANCE OF WEAKENED AND DIRECTLY RESTORED TEETH? A SYSTEMATIC REVIEW

Introduction: The objective of this systematic review was to answer the question: Does the intraradicular post transfixed in the dental crown increases the fracture resistance of weakened and directly restored teeth? Methods: Electronic databases (MEDLINE/PubMed, LILACS, SCOPUS, EMBASE, Scientific Electronic Library Online - SCIELO, and Central Register of Controlled Trials - CENTRAL) were searched until March 2021, without language or year restriction. Grey literature was also searched through Google scholar and OpenGrey repository. Only in vitro stud-ies were included that evaluated the influence of the use of intraradicular post trans-fixed in the crown in the buccopalatal/lingual direction in the fracture resistance of the dental crown. Relevant results were summarized and evaluated. The risk of bias was also assessed in the studies. Results: Initial screening of databases resulted in 249 studies, of which 109 were excluded for being duplicates. Of 140 eligible pa-pers, fourteen studies met the inclusion criteria and were selected for full-text read-ing. Of these, two studies were excluded for not having access to the full article. All selected articles were classified as low risk of bias. Conclusion: Based on the studies, it is possible to conclude that the use of a transfixed post in the crown increases the fracture resistance of weakened and directly restored teeth.

Evaluación de zonas de esfuerzo entre implante personalizado sinterizado e implante prefabricado mediante fotoelasticidad / Evaluation of effort zones between custom implant sinterized and the prefabricated implant though photoelasticity

Resumen Introducción: el uso de implantes personalizados es un tratamiento utilizado con mayor frecuencia, valorando y comparando su comportamiento frente a implantes convencionales. Este estudio tuvo como objetivo analizar si las zonas de esfuerzo del implante personalizado son diferentes a las que presenta el implante prefabricado convencional mediante fotoelasticidad. Métodos: muestra n=10 dientes premolares superiores, n=10 implantes personalizados sinterizados y n=10 implantes prefabricados convencionales, sometidos a 3 presiones fijas y controladas, observados a través de un polariscopio para analizar la distribución del esfuerzo generados. Resultados: zonas de esfuerzo presentes en las diferentes muestras analizadas aplicando 3 presiones. La cantidad de esfuerzo en la presión 1 (test de Chi-cuadrado, p=0,596) es diferente entre los dos tipos de implantes al igual que con la presión 2 (test de Chi-cuadrado, p=0,407), al aplicar la presión 3 (test de Levene, p=0,899) no hay diferencia en la distribución de fuerzas entre los dos tipos de implantes. Conclusiones: se determinó que el implante prefabricado convencional distribuye y concentra mejor el esfuerzo generado bajo diferentes presiones en comparación con el implante personalizado sinterizado.

Abstract Introduction: the use of custom implants is a very common treatment; we assess and compare their behavior against that of conventional implants. This study aimed to make sure that the stress zones of the custom implant are different from those presented by the conventional prefabricated implant by photoelasticity. Methods: we subjected samples of n=10 bicuspid teeth, n=10 sintered custom implants, and n=10 conventional prefabricated implants to 3 fixed and controlled forces and observed the samples through a polariscope to analyze the distributions of effort generated. The effort zones present in the different samples were analyzed under 3 different forces. Results: the amounts of effort in the two types of implants under force 1 (chi-square test, p=0.596) are different, as is also the case under force 2 (chi-square test, p=0.407). Under force 3 (Levene test, p=0.899), there is no difference in the distributions of effort between the two types of implants. Conclusions: it was determined that the conventional prefabricated implant distributes and concentrates the effort generated under different forces better than the sintered custom implant.

Relationship between extrinsic factors and non-carious cervical lesions in patients of the National Hospital "Hipólito Unánue"

Non-carious cervical lesions cause destructive dental disorders that actively contribute to the progressive loss of dental structure and the immediate need for dental treatment, due to their multiple symptoms and factors that produce them. Aim: The purpose of the study was to determine the relationship between extrinsic factors and non-carious cervical lesions in patients of the National Hospital Hipólito Unánue. Methods: The research was of a descriptive correlative type. The sample consisted of male and female patients between 18 and 65 years old, who attended the carielogy service of this hospital. For data collection, 2 questionnaires were used to estimate the values of the extrinsic factors that allowed us to obtain the necessary information on the variables to be studied. Spearman's Rho was applied to determine the relationship between the variable's study. Results: According to Spearman's Rho of 0.622, compared to p-0.000 <0.01. Between the variables studied; extrinsic factors and noncarious cervical lesions there is a moderate and significant positive correlation. Conclusion: Through this section it was possible to demonstrate the existing relationship between extrinsic variable factors and non-carious cervical lesions, therefore it was concluded that there is a moderate and significant positive correlation in the sample comprised by the patients of the Hospital in mention

3D finite element model based on CT images of tooth: a simplified method of modeling

Aim: This study aimed the description of a protocol to acquire a 3D finite element (FE) model of a human maxillary central incisor tooth restored with ceramic crowns with enhanced geometric detail through an easy-to-use and low-cost concept and validate it through finite element analysis (FEA). Methods: A human maxillary central incisor was digitalized using a Cone Beam Computer Tomography (CBCT) scanner. The resulted tooth CBCT DICOM files were imported into a free medical imaging software (Invesalius) for 3D surface/geometric reconstruction in stereolithographic file format (STL). The STL file was exported to a computer-aided-design (CAD) software (SolidWorks), converted into a 3D solid model and edited to simulate different materials for full crown restorations. The obtained model was exported into a FEA software to evaluate the influence of different core materials (zirconia - Zr, lithium disilicate - Ds or palladium/silver - Ps) on the mechanical behavior of the restorations under a 100 N applied to the palatal surface at 135 degrees to the long axis of the tooth, followed by a load of 25.5 N perpendicular to the incisal edge of the crown. The quantitative and qualitative analysis of maximum principal stress (ceramic veneer) and maximum principal strain (core) were obtained. Results: The Zr model presented lower stress and strain concentration in the ceramic veneer and core than Ds and Ps models. For all models, the stresses were concentrated in the external surface of the veneering ceramic and strains in the internal surface of core, both near to the loading area. Conclusion: The described procedure is a quick, inexpensive and feasible protocol to obtain a highly detailed 3D FE model, and thus could be considered for future 3D FE analysis. The results of numerical simulation confirm that stiffer core materials result in a reduced stress concentration in ceramic veneer

Effect of glazing application side and mechanical cycling on the biaxial flexural strength and Weibull characteristics of a Y-TZP ceramic

Abstract Glaze application on monolithic zirconia (Y-TZP) can be a practical approach to improve the mechanical properties of this material. Objective Our study evaluated the effect of glazing side and mechanical cycling on the biaxial flexure strength (BFS) of a Y-TZP. Methodology Eighty sintered Y-TZP discs (Ø:12 mm; thickness: 1.2 mm - ISO 6872) were produced and randomly assigned into eight groups (n=10), according to the factors "glazing side" (control - no glazing; GT - glaze on tensile side; GC - glaze on compression side; GTC - glaze on both sides) and "mechanical aging" (non-aged and aged, A - mechanical cycling: 1.2×106, 84 N, 3 Hz, under water at 37°C). Specimens were subjected to BFS test (1 mm/min; 1,000 Kgf load cell) and fractured surfaces were analyzed by stereomicroscopy and SEM. Hsueh's rigorous solutions were used to estimate the stress at failure of glazed specimens. Two-way ANOVA, Tukey's test (5%), and Weibull analysis were performed. Results The "glazing side", "mechanical aging" and the interaction of the factors were significant (p<0.05). Groups GC (1157.9±146.9 MPa), GT (1156.1±195.3 MPa), GTC (986.0±187.4 MPa) and GTC-A (1131.9±128.9 MPa) presented higher BFS than control groups (Tukey, 5%). Hsueh's rigorous solutions showed that the maximum tensile stress was presented in the bottom of zirconia layer, at the zirconia/glaze interface. Weibull characteristic strength (σo) of the GC was higher than all groups (p<0.05), except to GT, GTC-A and GTC, which were similar among them. The fractography showed initiation of failures from zirconia the tensile side regardless of the side of glaze application and fatigue. Conclusion Glazing zirconia applied on both tensile and compression sides improves the flexural strength of Y-TZP, regardless the mechanical aging.

Fracture strength of teeth with access cavity preparation with operating microscope or on buccal surfaces / Resistência à fratura de dentes submetidos a cavidade de acesso endodôntico com microscópio operatório ou nas faces vestibulares

Objective: The present study assessed the fracture strength of teeth subjected to endodontic access cavity preparation on buccal surfaces, or with the aid of operating microscopy when compared to the conventional technique. Material and methods: Sixty mandibular incisors were split into four groups (n=15): conventional access cavity preparation (CCP); conservative (C); buccal surface (BS); and control. The canals were prepared and filled and the cavities were restored. A static compressive strength test was conducted until crown fracture. The force data were compiled and assessed statistically. Kolmogorov-Smirnov and ShapiroWilk tests were performed to assess normality, Levene's test to assess variance homogeneity, the one-way ANOVA to compare fracture strength in the assessed groups. Tukey's HSD test was used to determine whether the differences in the means were significant between the groups. Results: The experimental groups did not show any statistically significant differences in mean fracture strength (CCP = 585.65 N±107.64 N)(BS = 530.52 N±129.35 N) (C = 517.83 N±114.68 N). Conclusion: Therefore, the selection of surface or size of access cavity proposed did not influence the fracture strength of mandibular incisors when compared to conventional cavity preparation (AU)

Objetivo: O presente estudo avaliou a resistência à fratura compressiva de dentes submetidos as cavidades de acesso endodôntico nas faces vestibulares, ou com o auxílio de microscópio operatório quando comparados à técnica convencional. Material e métodos: Sessenta incisivos inferiores foram divididos em quarto grupos (n=15): cavidade de acesso convencional (CAC); conservadora (C); na face vestibular (FV); e controle. Os canais foram preparados e obturados, e as cavidades restauradas. O teste estático de resistência compressiva foi procedido até a fratura coronária. Os dados de força foram compilados e analisados estatisticamente. Os testes de KolmogorovSmirnov e Shapiro-Wilk foram realizados com o intuito de avaliar a normalidade. O teste de Levene para verificar a homogeneidade de variâncias. O teste de análise de variância a um critério (ANOVA) para comparar a resistência à fratura entre os grupos. O teste de Tukey HSD foi realizado para determinar se as diferenças entre as médias dos grupos apresentava significância. Resultados: Os grupos experimentais não apresentaram diferenças estatisticamente significantes com relação a média de resistência à fratura. (CAC = 585.65 N±107.64 N)(FV = 530.52 N±129.35 N) (C = 517.83 N±114.68 N). Conclusão: Portanto, a variação da face ou do tamanho da cavidade de acesso endodôntico não exerceram influência na resistência à fratura de incisivos inferiores quando comparados a tradicional cavidade de acesso endodôntico. (AU)

Stress distribution in the peri-implant area of pure titanium and titanium-zirconium small implants

Aim: In dental implant treatment, there is a demand for mechanically stronger implants. Despite the existence of several studies showing the clinical success of narrow diameter implants, most of them are based on pure titanium (cpTi) alloys. There is a few clinical evidences of the success rate of titanium-zirconium (TiZr) narrow diameter implants. The aim of this study was to evaluate the stress distribution in the peri-implant area of narrow diameter cpTi and TiZr implants under axial and oblique loads. Methods: Photoelastic models were produced using epoxy resin (PL2, Vishay Precision Group) from a master model. The implants (cpTi and TiZr; Straumann AG) had 3.3 mm in diameter and 12 mm in height. Loads of 100 N and 200 N were applied to the abutment at angles of 0° (axial), 10°, 20°, and 30° (oblique). A circular polariscope (Eikonal) was used under dark field white-light configuration. The isochromatic fringes were analyzed in the peri-implant region in 5 areas, using ASTM table with isochromatic fringes; cervical-mesial, cervical-distal, mid-mesial, mid-distal and apical. Results: In general, under axial and oblique loads, the stress in the TiZr implant was lower than in the cpTi implant. The load of 200 N produced the highest stress values in cpTi and TiZr implants. In both implants and loads, the fringes were located more in apical area at all angles evaluated. Conclusion: It can be concluded that for small implants, the load inclination and intensity change the pattern of stress distribution and the cpTi implant exhibited the highest peri-implant stress

Three-dimensional finite element analysis of cantilever fixed bridge supported by implants with mandibular central incisor / 中华口腔医学杂志

Objective@#To investigate effect of the contact surface between the bridge and the adjacent teeth on the stress distribution of the implant and bone tissue and the displacement of the prosthesis in the cantilever fixed implant bridge restoring missing mandibular central incisors.@*Methods@#Two-dimensional images of the mandible and dentition in healthy adults were obtained using CT data. A three-dimensional finite element model of cantilever fixed bridge supported by implants with mandibular central incisor was established by computer reconstruction technique.The contact surface between the bridge and the adjacent natural tooth was designed as "oval" and "trapezoid". The "trapezoid" has a slightly smaller median diameter on the labial side and a slightly larger medial diameter on the lingual side. Loading of 120 N was applied on the tangential margin of the middle line of the long axis of the bridge 41. The direction was set at 0°, which was parallel to the long axis of the tooth and downward. The buccal to lingual and downward angles were 30°, 45° and 60°, respectively, perpendicular to the long axis of the tooth and 90° to the lingual side.The stress distribution of the implant and surrounding bone tissue and the displacement of the prosthesis were compared between the two models.@*Results@#Under axial and buccolingual loading, the maximum equivalent stress peak in the implant and surrounding bone tissue in the cantilever with trapezoidal contact surface design and the maximum displacement of the prosthesis were lower. Moreover, the distribution of stress was more balanced and the concentration range of stress was smaller. With the loading angle increasing, this trend was more obvious. When loading angle increased to 90°, the maximum equivalent stress and the maximum displacement of the elliptic contact surface model implant and surrounding bone tissue were 196 and 101 MPa and 0.196 mm, respectively, while the trapezoidal contact surface model were 157 and 72 MPa and 0.164 mm, respectively.@*Conclusions@#The trapezoidal contact surface of the bridge and the adjacent teeth in the cantilever fixed bridge supported by implants with mandibular central incisor is beneficial to reduce the impact of the leverage on the implant and surrounding bone tissue.

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.

Effect of a sonic device on bonding of fiberglass posts to root canals

Aim: This study evaluated the effect of a sonic device on the bonding of fiberglass posts cemented with a self-etching adhesive combined with conventional cement or a self-adhesive cement to root dentin. Methods: Forty single-rooted bovine incisors were endodontically prepared using a step-back technique. Gutta-percha and AH Plus sealer were used for root canal filling, combined with a thermoplasticization technique. After 1 week, the post space was prepared and the roots were divided into four groups according to the following factors: adhesive system/resin cement (Ambar/ AllCem Core [FGM] and RelyX U200 [3M]) and application mode (manual or sonic). The posts were cemented and the roots were cut into discs and submitted to push-out bond strength (POBS) test. The failure mode was evaluated using a stereoscope at 25x magnification. The data were analyzed statistically using ANOVA and Tukey's post-hoc test (α = 0.05). Results: The sonically activated RelyX U200 group was superior to the other groups. RelyX U200 manually applicated showed similar results to those of sonically activated Âmbar/AllCem. These three groups outperformed the Âmbar/AllCem manually applicated group. Adhesive failure between dentin and resin cement was the most predominant pattern. Conclusion: Sonic application of self-etching adhesive and self-adhesive cement improved the POBS of fiber posts to the root canal

Photoelastic analysis of the influence of prosthetic material on the stress distribution in bone around implant / 中华口腔医学杂志

Objective@#To provide a reference for a suitable alternative treatment choice for implant-supported prostheses, and to explore the influence of 3 types of prosthetic material on the stress distribution around implant.@*Methods@#The implant-abutment analogs were embedded individually into photoelastic resin blocks, which were medical pure titanium castings reproducing the surface and outline of implant (diameter 4.3 mm, length 11.5 mm) and esthetic abutment (regular profile, 1 mm). The prostheses were divided into 3 groups according to the type of prosthetic material. Each group consisted of 5 samples. The samples of composite resin ceramic and zirconia group were milled by chair-side computer aided design and computer aided manufacture (CAD/CAM) system. The samples of porcelain-fused-to-metal crown group were made manually and a pre-arranged silicone rubber impression of CAD/CAM crown would guide to shape the veneer porcelain. Each set was submitted to a 300 N compressive load axially or obliquely (75°). The stress value in the peri-implant bone at the level of the neck, neck1/3, middle1/3 and root1/3 of the sections (0.5, 1.5, 2.5, 3.5 mm) from implant was analyzed by digital photoelasticity, and the stress cushioning effect of 3 types of prosthetic material was comprehensively evaluated.@*Results@#The time spent reaching the stress peak of composite resin ceramic group [(1.58±0.08) s, axially; (2.75±0.21) s, obliquely] was larger than that of the zirconia group [(1.40±0.12) s, axially; (2.30±0.25) s, obliquely] (P<0.05) under the same download mode. Although there were no significant differences in equivalent stress values of the measurement points among the three groups (P>0.05), a downward trend of equivalent stress values of composite resin ceramic group was observed compared to zirconia group, regardless of load type. When loaded obliquely, the highest degree of stress concentration at the level of the neck of implant were found in the porcelain-fused-to-metal crown group.@*Conclusions@#Within the limitations of this study, composite resin ceramic was more beneficial to the biomechanical behavior of implant in stress buffer compared to zirconia.

Efecto de un tratamiento experimental de una superficie sobre la resistencia flexural en una zirconia Y-TZP / Effect of an experimental surface treatment on Y-TZP zirconia flexural strength

RESUMEN Objetivo: Analizar el efecto del microgranallado superficial como tratamiento experimental de regeneración, en la resistencia flexural y esfuerzos residuales de una Zirconia Y-TZP, una vez ha sido alterada con otros tratamientos mecánicos como microarenado y fresado. Métodos: Un total de 75 probetas de Zirconia Y-TZP fueron divididas en cinco grupos n=15 y sometidas a tratamientos de superficie así: fresado y microarenado (Grupos 2 y 4) microarenado + microgranallado y fresado + microgranallado (Grupos 3 y 5), y comparadas con un grupo control (Grupo 1), mediante Difracción de Rayos X (DRX), Microscopía electrónica de barrido (SEM), Microscopía confocal (CLSM) y sometida a falla en máquina universal de ensayos. Resultados: Los grupos de microgranallado y microarenado presentaron un aumento significativo de la resistencia flexural p=0.0082 con relación al grupo de fresado. Las mediciones mediante DRX no mostraron relación estadística con los cambios en la resistencia flexural. Significancia: Es posible que el microgranallado se considere un tratamiento para regenerar las propiedades mecánicas reducidas por fresado o arenado en la Zirconia Y-TZP.

ABSTRACT Objective: To analyze the effect of surface micro shot peening as an experimental regeneration treatment on the flexural strength and residual stresses of a Y-TZP Zirconia, once it has been altered with other mechanical treatments such as micro sandblasting and milling. Methods: A total of 75 Zirconia Y-TZP specimens were divided into five n = 15 groups and subjected to surface treatments such as: milling and micro sandblasting (Groups 2 and 4) micro sandblasting + micro shot peening; and milling + micro shot peening (Groups 3 and 5), compared to a control group (Group 1), by X-ray diffraction (XRD), scanning electron microscopy (SEM), confocal microscopy (CLSM) and subjected to failure in a universal testing machine. All the results were compared to find a statistical relationship between them using a mixed linear model and Tuckey. Results: The groups of micro shot peening and micro sandblasting presented a significant increase of the flexural strength p = 0.0082 vs the milling group. The XRD technique is not related to flexural strength measurements. Significance: It is possible that the micro shot peening be considered a treatment to regenerate the mechanical properties reduced by milling or sandblasting in Zirconia Y-TZP.

Trastornos temporomandibulares en pacientes bruxópatas, trabajadores de estomatología de Mayarí / Temporomandibular Disorders in Patients with Bruxism, Dentistry Workers of Mayarí

Introducción: el estrés es una enfermedad omnipresente en la sociedad industrial actual. El aparato estomatognático sufre, con frecuencia, los impactos nocivos de la vida moderna. Numerosos estudios tratan de dilucidar la relación existente entre el bruxismo y los trastornos temporomandibulares. Objetivo: determinar la frecuencia de trastornos temporomandibulares a un grupo de pacientes bruxópatas, trabajadores de estomatología del municipio Mayarí en Holguín. Método: se realizó, desde octubre 2014 a enero 2015, un estudio de serie de casos en 70 trabajadores de estomatología, se diagnosticaron 49 pacientes bruxópatas entre 19 y 59 años, de ambos sexos en Policlínico Universitario "26 de Julio". Los resultados se presentaron en tablas de análisis de frecuencia simple, las cifras se dieron en valores absolutos y porcentaje. Para procesar los datos se utilizó procesador Microsoft Excel XP. Resultados: de 49 pacientes bruxópatas diagnosticados, 30 presentaron trastornos temporomandibulares para el 61,2%. Predominó el grado de disfunción leve con 20 pacientes para el 66,7% seguido del moderado y severo en orden decreciente con menor número de casos. La presencia de ruidos articulares fue la manifestación clínica más frecuente en este estudio en el 83,3% de los pacientes con trastornos temporomandibulares, seguido del dolor muscular en el 63,3% y la limitación de los movimientos en el 33,3%. Se evidenció una prevalencia de pacientes del sexo femenino para el 67%, con relación al masculino para el 33% y el grupo de edad con mayor representación de afectados fue de 40 a 49 años para el 60%. Conclusiones: los resultados del estudio indicaron que la frecuencia de trastornos temporomandibulares en los pacientes bruxópatas estudiados fue alta, con más de la mitad de los afectados.

Introduction: stress is an universal condition in the industrial society of our days. The estomatognatic device usually suffers the harmful impacts of modern life. Several studies try to explain the current relationship between the bruxism and the temporomandibular disorders. Objective: to estimate the frequency of temporomandibular disorders in a group of bruxer patients, of dentistry workers of Mayarí, Holguín. Method: a case series study, was carried out from October 2014 to January 2015 in 70 stomatology workers, 49 patients with bruxism between 19 and 59 years old, of both sexes, were diagnosed at 26 de Julio Teaching Polyclinic. Results: of 49 patients, 30 had temporomandibular disorders for 61.2%. There was a slight degree of dysfunction that predominated in 20 patients for 66.7%, followed by a declining moderate and severe order with lower number of cases. The presence of articular noises was the most frequent clinical manifestation showed study with 83.3% of the patients with temporomandibular disorders, followed by the muscular pain in 63.3% and the limitation of the movements in 33.3%. The female sex was the prevailing one 67% in relation with the male ones for 33% and the age group was from 40 to 49 years was the most representative for 60%. Conclusions: the results of the study showed that the frequency of temporomandibular disorders in the studied bruxer patients was high, with more than half of the affected ones.

Residual stress within the porcelain veneer of 3-unit zirconia fixed dental prostheses with different framework designs measured by nanoindentation / Estresse residual na porcelana de revestimento de próteses parciais fixas de 3 elementos com diferentes desenhos de infraestrutura mensurado por nanoendentação

The present study aimed to identify different concentrations of residual stress of surfaces of porcelain veneer (PV) fused to zirconia 3-unit fixed dental prostheses (FDPs) with even thickness and modified (lingual collar connected to proximal struts presenting 12 mm2 connector area) framework designs by nanoindentation method. Twenty-three FDPs replacing second premolar (PM) were fabricated and the cyclic loading was applied on twenty FDPs. Fractured, suspended and non-fatigued FDPs were selected and divided (n=3/each) into: 1) Fractured even thickness (ZrEvenF); 2) Suspended even thickness (ZrEvenS); 3) Fractured with modified framework (ZrModF); 4) Suspended with modified framework (ZrModS); 5) Non-fatigued even thickness (Control). Moreover, the control group surfaces could be divided (n=3/each) into: 6) Mesial PM abutment (MPMa); 7) Distal PM abutment (DPMa); 8) Buccal PM abutment (BPMa); 9) Lingual PM abutment (LPMa); 10) Mesial PM pontic (MPMp); 11) Distal PM pontic (DPMp); 12) Buccal PM pontic (BPMp); 13) Lingual PM pontic (LPMp); 14) Mesial molar abutment (MMa); 15) Distal molar abutment (DMa); 16) Buccal molar abutment (BMa); 17) Lingual molar abutment (LMa). The PV surfaces were nanoindented in regions of interest (ROI) 1, 2 and 3, which were 0.03 mm, 0.35 mm and 1.05 mm from outer PV surface surface towards the PV/framework interface, respectively. Each ROI received 5 nanoindentations with 10 µm of minimum separation loaded to a peak load 4 µN. The Linear Mixed Model test and Least Significant Difference (95%) were used. The statistical analysis among ZrEvenF, ZrEvenS, ZrModF, ZrModS, and Control groups showed differences (p=0.000) except for the comparison between ZrModS and Control group (p=0.371). Also, ROI 1, 2, and 3 were different (p<0.001) with higher residual stresses in outer PV regions relative to those closer to the framework. The comparison among crowns showed that pontic was different from premolar (p=0,001) and molar (p=0,007) abutments, always showing higher residual stress levels. When marginal ridges groups (MPMa, DPMa, MPMp, DPMp, MMa, DMa) were compared, the DMa group was different from DPMp (p=0,004) and MPMa (p=0,00) group, whereas MPMa was different among all groups. The residual stress of porcelain veneer FDPs was different between: fractured and suspended FDPs regardless of the framework design; ROI 1, 2 and 3; and pontic and abutment crowns. Moreover, the proximal areas presented the highest concentration of residual stress. (AU)

O presente estudo teve como objetivo identificar diferentes concentrações de tensão residual de superfícies da cerâmica de revestimento (CR) de próteses parciais fixas de zircônia de 3 elementos (PPFs) com desenho da infraestrutura de espessura mínima e modificada (cinta lingual conectada aos postes proximais com 12 mm2 de área de conector) pelo método de nanoindentação. Vinte e três PPFs repondo segundo premolar (PM) foram confeccionados e o carregamento dinâmico foi aplicado em vinte PPFs. As PPFs fraturadas, suspensas e não fadigadas foram selecionadas e divididas (n=3/cada) nos seguintes grupos: 1) Fraturadas com espessura mínima (ZrEvenF); 2) Suspensas com espessura mínima (ZrEvenS); 3) Fraturadas com infraestrutura modificada (ZrModF); 4) Suspensas com infraestrutura modificada (ZrModS); 5) Não fadigadas com espessura mínima (Controle). Além disso, as superfícies do grupo controle foram divididas (n=3/cada) nos seguintes grupos: 6) Mesial do pilar PM (MPMa); 7) Distal do pilar PM (DPMa); 8) Vestibular do pilar PM (BPMa); 9) Lingual do pilar PM (LPMa); 10) Mesial do pôntico PM (MPMp); 11) Distal do pôntico PM (DPMp); 12) Vestibular do pôntico PM (BPMp); 13) Lingual do pôntico PM (LPMp); 14) Mesial do pilar molar (MMa); 15) Distal do pilar molar (DMa); 16) Vestibular do pilar molar (BMa); 17) Lingual do pilar molar (LMa). As superfícies da CR foram nanoendentadas nas regiões de interesse (ROI) 1, 2 e 3, a qual a distância da superfície externa da CR no sentido da interface CR/infraestrutura era de 0,03 mm, 0,35 mm e 1,05 mm, respectivamente. Cada ROI recebeu 5 nanoendentações com espaço mínimo de 10 µm para carregar até 4 µN. O teste modelo linear misto com diferença estatística mínima (95%) foi executado usando os valores de dureza. A análise estatística entre os grupos ZrEvenF, ZrEvenS, ZrModF, ZrModS, e Control apresentou diferenças (p=0.000) exceto para a comparação entre os grupos ZrModS e Control (p=0.371). Também, ROI 1, 2 e 3 foram diferentes (p<0.001). A comparação entre coroas mostrou que o pôntico foi diferente dos pilares pré-molar (p=0,001) e molar (p=0,007), sempre apresentando os maiores níveis de tensão. Quando os grupos das cristas marginais (MPMa, DPMa, MPMp, DPMp, MMa, DMa) foram comparadas, o grupo DMa foi diferente dos grupos DPMp (p=0,004) and MPMa (p=0,00), enquanto que o grupo MPMa foi diferente de todos os grupos. A tensão residual da cerâmica de revestimento foi diferente entre: PPFs fraturadas e suspensas independente do desenho da infraestrutura; ROI 1, 2 e 3; e pônticos e pilares. Além disso, as áreas proximais apresentaram a maior concentração de tensão residual. (AU)

Análise da distribuição das tensões em maxila submetida à expansão cirurgicamente assistida com aparelho ósseo-suportado / Analysis of the distribution of maxillary stresses submitted to surgically assisted maxillary expansion with a bone-supported device

A expansão de maxila cirurgicamente assistida (EMCA) é a modalidade de tratamento que tem como objetivo romper as regiões de reforço maxilar permitindo seu movimento expansivo gradativamente. Tal movimento pode ser realizado às custas de aparelhos dento-suportado, dento-muco-suportado, implanto-suportados ou ósseo-suportado. Os efeitos produzidos pelo tratamento vão desde alterações esqueléticas (aumento da base, cavidade e do espaço aéreo nasais) até inclinações dentárias (principalmente nos dentes de suporte do aparelho expansor), dentre outras. O objetivo desta pesquisa foi avaliar, por meio do Método de Elementos Finitos (MEF), a distribuição das tensões produzidas pela EMCA nas estruturas maxilares utilizando-se aparelho expansor ósseo-suportado. Material e métodos: Foi confeccionado um modelo tridimensional de maxila para simulação da EMCA com osteotomia tipo LeFort I descendente sem degrau, com disjunção pterigomaxilar utilizando um modelo de aparelho ósseo-suportado para o teste com a simulação de abertura de 1mm. Os resultados mostraram maior abertura da maxila na região anterior de incisivos a pré-molar (1 mm) e em menor quantidade (0,6mm) na região de molares. A tensão máxima principal (TMXP) mostrou a concentração de tensões principalmente em toda face palatina da maxila de pré-molar ao túber maxilar. Pela face lateral, ficou mais evidente a TMXP nas região de osso alveolar posterior ao pré-molar, molares e túber, assim como na região de pilar zigomático acima da osteotomia. Pelo plano transversal foi possível observar a transmissão de tensões ao longo das estruturas ósseas mostrando pouca dissipação para as raízes do molar. Enquanto que as forças de compressão (Tensão Mínima Principal), evidenciadas pela tensão mínima principal, se manifestaram nas áreas de pilar zigomático e adjacentes as osteotomias, assim como na áreas de contato do apoio do aparelho com o osso palatino. Tensões de tração e compressão também foram evidenciadas na região de processo pterigoide. A análise de tensão de Von Mises mostrou que a parte que mais sofre estresse é a haste que liga o módulo do aparelho com a plataforma de apoio. Conclusão: Houve maior abertura da maxila na região anterior e as tensões resultantes de forças transmitidas ao osso alveolar dos dentes adjacentes ao aparelho, parecem não ser suficientes para deslocar os dentes.(AU)

Surgically assisted maxillary expansion (SARME) is the modality of treatment that aims to weaken the points of maxillary reinforcement allowing its gradual expansion. Such movement can be performed at the expense of dento-supported, dento-muco-supported, implanto-supported or bony-backed devices. The effects produced by the treatment range from skeletal changes (increase of nasal base, cavity and nasal air space) to dental inclinations (mainly in the supporting teeth of the expander apparatus), among others. The objective of the present research was to evaluate the distribution of stress produced by SARME in the maxillary structures using the bone-supported expander apparatus by the Finite Element Method (FEM). Material and methods: A three-dimensional hemi-maxilla model was simulated for SARME with a non-step descending LeFort I osteotomy with pterygomaxillary disjunction using a bone-supported device model for the 1mm aperture simulation test. The results showed a greater opening of the maxilla in the anterior region of the incisors to the premolar (1 mm) and smaller (0.6 mm) in the molar region. The principal maximal stress (TMXP) showed the concentration of the tension forces mainly in all the palatine face of the pre-molar maxilla to the maxillary tuft. Due to the lateral aspect, the TMXP was more evident in the posterior alveolar bone region, the molars and tuber, as well as in the epilating zygomatic region above the osteotomy. From the transversal plane, it was possible to observe the transmission of stress along the bony structures showing little dissipation for the roots of the molar. Meanwhile, the forces of compression (Principal Minimum Tension) evidenced by the principal minimal stress, were manifested in the areas of the zygomatic pillar adjacent to the osteotomies, as well as in the areas of contact of the support of the apparatus with the palatine bone. Tension and compression forces were also evidenced in the pterygoid process region. Von Mises' stress analysis showed that the most stressed part is the rod connecting the device module to the support platform. Conclusion: There was a greater opening of the maxilla in the anterior region and the resulting forces of tension transmitted to the alveolar bone of the teeth adjacent to the appliance did not seem to be sufficient to displace the teeth.(AU)

Considerations for the Survival of Complete Arch Implant-Supported Zirconia Restorations; Status of Antagonistic Arches and Stress Distribution on Frameworks: A Case Report

This report describes two cases of complete arch implant-supported restorations. The first patient had seven dental implants in each arch with monolithic zirconia frameworks. At four weeks' follow-up, the one-piece maxillary framework was fractured, which was re-designed and re-fabricated using laser-sintered cobalt-chrome alloy. The second patient had four implants in the mandible only. A mandibular monolithic zirconia framework and a maxillary conventional complete denture were fabricated and delivered. At five years' follow-up, the patient reported no significant discomfort. Careful consideration and monitoring of the status of antagonistic arches and stress distribution on zirconia frameworks were suggested for complete arch implant-supported fixed restorations