Prosthetic design and restorative material effect on the biomechanical behavior of dental implants: strain gauge analysis / Efeito do desenho protético e do material restaurador no comportamento biomecânico de implantes dentários: análise de extensometria

Objective: The purpose of this in vitro study was to evaluate the effect of different implant prosthetic designs with two restorative materials on biomechanical behaviour using strain gauge analysis. Material and Methods:6 different screw-retained implant restorations were designed and fabricated using a CAD/CAM system. These implants were divided into three main groups according to each design: group FB (fixed bridge); CB (cantilever bridge); SC (separate crowns). Each group was divided into two subgroups according to their restorative material: subgroup I ­ ultra translucent multi-layered zirconia (Kuraray Noritake Dental Inc, Japan); subgroup II ­ a combination of PEEK framework (BioHPP, Bredent, GmbH & Co.KG, Germany) and zirconia crowns (ultra-translucent multi-layered zirconia, Kuraray Noritake Dental Inc, Japan). Each subgroup was subjected to a vertical load of 100 N and their biomechanical behaviour was evaluated using a strain gauge (Kyowa, Japan) with a resistance of 120 Ω, length of 1 mm and width of 2.4 mm. For the implants, two strain gauges were positioned buccally and lingually, parallel to the long axis of the implant. For the restoration, two strain gauges were positioned buccally and lingually in the middle of it. The results were analyzed using three-way analysis of variance (ANOVA), followed by serial two-way and one-way ANOVAs at each level of the study, followed by Tukey's post hoc test P-values were adjusted for multiple comparisons using BENFORRONI correction and the significance level was set at P ≤ 0.05 for all tests. Results: FB showed the lowest strain values out of all 3 design groups. Moreover, the combination of PEEK and zirconia showed strain values smaller than full zirconia. The highest mean strain value was recorded in CB at 299.50 while the lowest mean strain peak value was recorded in group FB (74.50). The highest strain peak was recorded in CB subgroup I (3901.0 ± 195.91) and the difference had statistical significance (P-value < 0.01). Conclusion: the fixed bridge designed with PEEK framework and zirconia crowns was found to be more favorable in restoring the posterior edentulous area regarding strain measurements on the level of prosthetic components, implant and bone level. (AU)

Objetivo: O objetivo deste estudo in vitro foi avaliar o comportamento biomecânico de diferentes desenhos protéticos com dois materiais restauradores em implantes dentários usando análise por extensometria. Material e Métodos: 6 diferentes restaurações parafusadas em implantes foram projetadas e fabricadas usando um sistema CAD/CAM. Esses implantes foram divididos em três grupos principais de acordo com cada desenho: grupo PF (ponte fixa); PC (ponte cantilever); CI (coroas individuais). Cada grupo foi dividido em dois subgrupos de acordo com o material restaurador: subgrupo I ­ zircônia multicamada ultra translúcida (Kuraray Noritake Dental Inc, Japão); subgrupo II ­ uma combinação de estrutura PEEK (BioHPP, Bredent, GmbH & Co.KG, Alemanha) e coroas de zircônia (zircônia multicamada ultra translúcida, Kuraray Noritake Dental Inc, Japão). Cada subgrupo foi submetido a uma carga vertical de 100 N e seu comportamento biomecânico foi avaliado usando um extensômetro (Kyowa, Japão) com resistência elétrica de 120 Ω, comprimento de 1 mm e largura de 2,4 mm. Para os implantes, dois extensômetros foram posicionados pela vestibular e lingual, paralelos ao longo eixo do implante. Para a restauração, dois extensômetros foram posicionados no centro da estrutura, pela vestibular e lingual. Os resultados foram analisados usando análise de variância de três fatores (ANOVA), seguida de ANOVA dois fatores e um fator em cada estágio do estudo, seguidas pelo teste de Tukey. Os valores P foram ajustados para comparações múltiplas usando a correção de BENFORRONI e o nível de significância foi estabelecido em P ≤ 0,05 para todos os testes. Resultados: PF apresentou os menores valores de deformação de todos os 3 grupos de desenho. Além disso, a combinação de PEEK e zircônia apresentou valores de deformação menores do que a zircônia total. O maior valor médio de deformação foi registrado no PC em 299,50, enquanto o menor valor médio de pico de deformação foi registrado no grupo PF (74,50). O maior pico de deformação foi registrado no subgrupo PC I (3901,0 ± 195,91) e a diferença teve significância estatística (P-valor < 0,01). Conclusão: a ponte fixa projetada com estrutura de PEEK e coroas de zircônia mostrou-se mais favorável na restauração da área edêntula posterior em relação às medidas de deformação dos componentes protéticos, implante e nível ósseo (AU)

Effect of prosthetic design and restorative material on the stress distribution of implant-supported 3-unit fixed partial dentures: 3D-FEA / Efeito do desenho protético e do material restaurador na distribuição de tensão de próteses parciais fixas de 3 elementos suportada por implante: FEA 3D

Objective: Evaluate the effect of Implant prosthetic designs and restorative material on the stress concentration of 3-unit implant-supported restoration with two restorative materials. Material and Methods: Six different screw-retained prostheses models were virtually designed and divided according to design: fixed bridge (FB), cantilever bridge (CB), and separate crowns (SC). Then, each model was also divided into two subgroups according to the material: Ultra-translucent multi-layered zirconia (Kuraray Noritake Dental Inc., Japan); or a combination of PEEK (Polyetheretherketone) framework (BioHPP, Bredent, GmbH & Co., KG, Germany) and zirconia (ZR) crowns (ultra-translucent multi-layered zirconia, Kuraray Noritake Dental Inc., Japan). A vertical load of 100 N was applied statically perpendicular to the central fossa of each crown. The von-Mises stress was computed using Solidworks software (SolidWorks Corp, Massachusetts, USA), based on the physical parameters of the materials. Results: FB showed the lowest von Mises stress values out of all 3 design models. Moreover, the combination of PEEK and zirconia showed strain values smaller than full zirconia. The highest von Mises stress value was recorded in CB with the zirconia subgroup at (1098 MPa) while the lowest von Mises stress value was recorded in FB with combined PEEK and zirconia subgroup at (190 MPa). Conclusion: For three-unit implant supported restorations, the use of PEEK framework and zirconia crowns was found to be more favorable biomechanically regarding the prosthetic components, implant and bone stresses. (AU)

Objetivo: Avaliar o efeito do desenho da prótese sobre implantes e do material restaurador na concentração de tensão de próteses fixas de 3 elementos implantossuportada, com dois materiais restauradores. Material e Métodos: Seis diferentes modelos de próteses aparafusadas foram virtualmente projetados e divididos de acordo com o desenho: ponte fixa (PF), ponte cantilever (PC) e coroas individuais (CI). Em seguida, cada modelo também foi dividido em dois subgrupos de acordo com o material: Zircônia multicamada ultra translúcida (Kuraray Noritake Dental Inc., Japão); ou associada a uma estrutura de PEEK (Polyetheretherketone) (BioHPP, Bredent, GmbH & Co., KG, Alemanha) e coroas de zircônia (CZ) (zircônia multicamada ultra translúcida, Kuraray Noritake Dental Inc., Japão). Uma carga vertical estática de 100 N foi aplicada perpendicular à fossa central de cada coroa. A tensão de von-Mises foi calculada usando o software Solidworks (SolidWorks Corp, Massachusetts, EUA), com base nos parâmetros físicos dos materiais. Resultados:PF apresentou os menores valores de tensão de von Mises de todos os 3 modelos propostos. Além disso, a combinação de PEEK e zircônia apresentou valores de deformação menores do que a zircônia pura. O maior valor de tensão de von Mises foi registrado em PC com o subgrupo de zircônia em (1098 MPa), enquanto o menor valor de tensão de von Mises foi registrado em PF com PEEK combinado e subgrupo de zircônia em (190 MPa). Conclusão: Para ponte fixa de 3 elementos implantossuportadas, o uso de estrutura PEEK e coroas de zircônia mostrou-se mais favorável biomecanicamente em relação aos componentes protéticos, implante e tensão sobre o osso. (AU)

Correlation between Demographic and Socio-Economic Factors among Undergraduate Medical Students in Taif University, Saudi Arabia

This research was carried out in the College of Medicine at the University of Taif, Kingdom of Saudi Arabia. It included arandom sample of medical students in 4th, 5th and 6th years (males and females). Data were collected using a semistructured, self-administered questionnaire, including comprehensive, anonymous demographic and socioeconomic data,lifestyle factors, health related quality of life using the WHOQOL-BREF questionnaire, other health-related data, socialsupport, as assessed using the Multidimensional scale of perceived social support (MSPSS), student’s academic motivation,using self-efficacy and active learning strategies scales from MSPSS questionnaire an the past year grade point average(GPA). The results showed that their GPA ranged between 1.30 and 3.90 out of 4 with a mean of 3.04 and SD of 0.52. It wasabnormally distributed as evidenced by significant Shapiro-Wilk test, p<0.001. Multiple linear regression analysis revealedthat, after control for confounding, only gender of the students (females), non-smokers, membership in charity association,having higher score of psychological domain of quality of life, better overall QOL, and higher learning strategies score weresignificantly associated with GPA score and they are responsible for 21.5% variability of the score (r-square=0.215). Fromthe results it could be concluded that Academic performance of senior medical students in Taif University, manifested byGPA score is influenced by many factors (multi-factorial) that are responsible for only 21.5% of variability in grade pointaverage (GPA).

Factors of Academic Success Among Undergraduate Medical Students in Taif University, Saudi Arabia: A Cross-Sectional Study

This cross-sectional research was carried out in the College of Medicine at the University of Taif, Kingdom of Saudi Arabia.It included a random sample of medical students in 4th, 5th and 6th years (males and females). Data were collected using asemi-structured, self-administered questionnaire, including comprehensive, anonymous demographic and socioeconomicdata, lifestyle factors, health related quality of life, social support, student’s academic motivation, the past year grade pointaverage (GPA). The study included 261 students. The age ranged between 21 and 27 years (22.8±1.1 years). Malesrepresented 55.9% of the participants. Moreover, non-smokers, membership in charity association, having higher score ofpsychological domain of quality of life, and higher learning strategies score were significantly associated with grade pointaverage (GPA) score and they are responsible for 21.5% variability of the score. From the results it could be concluded thatAcademic performance of senior medical students in Taif University, manifested by GPA score is influenced by many factors(multi-factorial) that are responsible for only 21.5% of variability in grade point average (GPA).

role of arthroscopic acromioplasty in the treatment of chronic impingement syndrome in elderly age group

Twenty five cases of chronic impingement syndrome above 50 years of age whether associated with partial thickness rotator cuff tears or not are included in this study. The most common presenting symptoms are night pain and weakness. The most important signs are impingement sign and impingement injection test. Radiological examination shows Type III and Type II acromion in almost all cases. All these cases had at least three months course of conservative treatment but with no improvement. All cases were assessed using UCLA scoring system. All cases were treated by arthroscopic technique starting with arthroscopic subacromial bursectomy, then release of coracoacromial ligament and then excision of the anterior acromion. Most cases showed marked improvement as regard pain and function score. Twenty one cases had satisfactory results while four cases unsatisfactory results, Thus, arthroscopic acromioplasty proved to be as effective as open technique with better cosmesis, shorter hospital stay and preservation of deltoid attachments

Crystal induced osteoarthritis

Microscopical study using regular, polarized and electron microscopy, were done in 40 patients with 1ry osteoathritis, for detection of crystals in their synovial fluid and to correlate their presence especially apatite crystals with markers of inflammation detected in their serum and synovial fluids. Eight cases [20%] had negative findings to all types of crystals, 16 cases had calcium pyrophosphate dihydrate [40%] and ten cases [25%] showed Hydroxyapatite crystals. Five cases showed ureate crystals [12. 5%] three of them were accompanied by calcium pyrophosphate dihydrate crystals. Seven cases contained oxalate [17. 5%] three of them were accompanied by other types of crystals [one with hydroxyapatite and 2 with calcium pyrophosphate]. Patients with hydroxyapatite crystals had a significantly higher mean of TLC in their synovial fluids compared to other groups, they also had high mean tenderness score, denoting a possible inflammatory arthritis. It is concluded that [Apatite Associated Arthropathy] detected by electron microscopy was found in a significant number of patients with 1ry osteoarthiritis and their presence could be linked to inflammatory flares in such patients