Biomechanical behavior of overdentures supported by different implant position and angulation using Micro ERA® system: a finite element analysis study

Aim: The aim of this study was to investigate the biomechanical behavior of implant-retained mandibular overdentures using Micro ERA® system with different implant position and angulation by finite element analysis (FEA). Methods: Four 3D finite element models of simplified mandibular overdentures were constructed, using one Bränemark implant with a Micro ERA® attachment. The implant was positioned on the canine or lateral incisor area with an angulation of either 0º (C-0º; LI-0º) or 17º (C-17º, LI-17º) to the vertical axis. A 100 N axial load was applied in one side simultaneously, from first premolar to second molar. In all models it was analyzed the overdenture displacement, compressive/tensile stress in the bone-implant interface, and also the von Mises equivalent stress for the nylon component of the housing. The stresses were obtained (numerically and color-coded) for further comparison among all the groups. Results: The displacement on the overdenture was higher at the posterior surface for all groups, especially in the C-17º group. When comparing the compressive/tensile stress in the bone-implant interface, the lateral-incisor groups (LI-0º and LI-17º) had the highest compressive and lowest tensile stress compared to the canine groups (C-0º and C-17º). The von Mises stress on the nylon component generated higher stress value for the LI-0º among all groups. Conclusions: The inclination and positioning of the implant in mandibular overdenture interferes directly in the stress distribution. The results showed that angulated implants had the highest displacement. While the implants placed in the lateral incisor position presented lower compressive and higher tensile stress respectively. For the attachment the canine groups had the lowest stress

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

Effect of thermocycling in a hard denture liner and acrylic resin after different chemical and mechanical polishing / Efeito da termociclagem em reembasador rígido para prótese e resina acrílica após polimento químico e mecânico

Objective: To evaluate the effect of aging in a hard denture reline (New Truliner) and an acrylic resin (Classic) after chemical and mechanical polishing. Methods: Eighty specimens were made, divided randomly between 8 groups: G1.Acrylic Resin Classic (RAC)/Mechanical Polishing (PM); G2.RAC/PM + thermocycling (TR); G3) RAC/Chemical Polishing (PQ); G4.RAC/PQ + TR; G5.New Truliner (NT)/PM; G6.NT/PM + TR; G7. NT/PQ; G8.NT/PQ + TR. The surface hardness was measured before and after polishing, and after TR. The impact resistance tests were measured after all applied treatments. The data were submitted to ANOVA and Tukey test (a=5%). Results: Regardless of the polishing, it was noted that RAC presented significantly higher surface hardness than NT; PM had higher hardness in both materials compared with PQ; on both polishing, the impact resistance of the RAC was higher than NT. Independently of TR test, the impact resistance of the materials that received PQ was higher than received PM. The PQ caused greater changes in properties than the PM. Conclusion: Aging and chemical and mechanical polishing influenced the physical and mechanical properties of hard denture reline and acrylic resin.

Objetivo: Avaliar o efeito da termociclagem em reembasador rígido para próteses totais (New Truliner) e resina acrílica (Clássico) após polimento químico e mecânico. Métodos: Foram confeccionados 80 corpos de prova, divididos de forma randomizada entre 8 grupos: G1. Resina Acrílica Clássico (RAC)/Polimento mecânico (PM); G2. RAC/PM + termociclagem (TR); G3.RAC/Polimento químico (PQ); G4.RAC/PQ + TR; G5.New Truliner (NT)/PM; G6.NT/PM + TR; G7. NT/PQ; G8. NT/PQ + TR. A dureza superficial foi mensurada antes e após os polimentos, e após a TR. Os ensaios de resistência ao impacto foram mensurados após todos os tratamentos. Os dados foram submetidos à análise de variância e Tukey (a=0,05). Resultados: Independente do polimento verificou-se que RAC apresentou resultados de dureza superficial significativamente mais altos que NT; PM gerou superfícies mais duras em ambos os materiais quando comparado ao PQ; em ambos os polimentos, os valores de resistência ao impacto da RAC foram maiores que os do NT. Independentemente da realização da TR, a resistência ao impacto dos materiais que receberam PQ foi maior que a dos que receberam PM. PQ causou maior alteração nas propriedades do que PM. Conclusão: A termociclagem e os polimentos químico e mecânico influenciam as propriedades físicas e mecânicas do reembasador rígido e da resina acrílica.

Efeito do lubrificante no torque de afrouxamento de parafusos protéticos sob dois níveis de adaptação de próteses implantossuportadas / Lubrication effect on loosening torque of prosthetic screw under two levels of implant-supported prostheses fit

A literatura sugere que a utilização de lubrificante poderia aumentar a estabilidade das conexões parafusadas. Este estudo avaliou a influência do uso de lubrificante líquido no torque de afrouxamento de parafusos protéticos em próteses mandibulares implantossuportadas sob diferentes níveis de adaptação. Foram criadas duas condições de adaptação (adaptação passiva e desajuste), confeccionando 2 modelos de gesso a partir de cada prótese. Foram utilizados 20 conjuntos de parafusos protéticos de titânio (5 parafusos cada conjunto) divididos aleatoriamente em 4 grupos: 1) sem lubrificante + adaptação passiva (grupo controle); 2) sem lubrificante + esajuste; 3) com lubrificante + adaptação passiva e 4) com lubrificante + desajuste. O torque de afrouxamento dos parafusos foi mensurado 10 minutos após aplicação do torque de aperto (10 Ncm), utilizando torquímetro digital. Os resultados foram submetidos à ANOVA (2 fatores) e teste de Tukey (a=0,05). Os valores médios (desvio padrão) de torque de afrouxamento (Ncm) foram: G1 = 7,6 (0,4); G2 = 6,6 (0,3); G3 = 7,5 (0,2) e G4 = 6,9 (0,8). O fator ‘adaptação’ apresentou diferença estatisticamente significante (p=0,003). Porém, o fator ‘lubrificante’ e a interação entre os fatores não foram significantes (p=0,537 e p=0,311, respectivamente). O desajuste diminuiu o torque de afrouxamento dos parafusos protéticos, enquanto que o lubrificante líquido não apresentou efeito considerável.

The literature suggests that the use of lubricant may increase the screw joint stability. This study has evaluated the influence of the use of liquid lubricant on loosening torque of prosthetic screws in implant-supported mandibular dentures under different fit levels. Two conditions were created (passive fit and misfit) making 2 cast models from each denture. Twenty set of titanium prosthetic screws (5 screws each set) were randomly divided in 4 groups: 1) without lubricant + passive fit (control group); 2) without lubricant + misfit; 3) with lubricant + passive fit; and 4) with lubricant + misfit. The loosening torque of the screws was measured 10 minutes after applied torque (10 Ncm) using digital torque meter. The data were submitted to the ANOVA (two-way) and Tukey’s test (a;=0.05). The mean values (standard deviation) of loosening torque (Ncm) were: G1 = 7.6 (0.4); G2 = 6.6 (0.3); G3 = 7.5 (0.2); and G4 = 6.9 (0.8). The factor ‘fit’ presented significant statistically difference (p=0.003). However, the factor ‘lubricant’ and the factors interaction were not significant (p=0.537 and p=0.311, respectively). The misfit decreased the loosening torque of the prosthetic screws, whereas the liquid lubricant did not present considerable effect

Stress Distribution in Co-Cr Implant Frameworks after Laser or TIG Welding

Lack of passivity has been associated with biomechanical problems in implant-supported prosthesis. The aim of this study was to evaluate the passivity of three techniques to fabricate an implant framework from a Co-Cr alloy by photoelasticity. The model was obtained from a steel die simulating an edentulous mandible with 4 external hexagon analog implants with a standard platform. On this model, five frameworks were fabricated for each group: a monoblock framework (control), laser and TIG welding frameworks. The photoelastic model was made from a flexible epoxy resin. On the photoelastic analysis, the frameworks were bolted onto the model for the verification of maximum shear stress at 34 selected points around the implants and 5 points in the middle of the model. The stresses were compared all over the photoelastic model, between the right, left, and center regions and between the cervical and apical regions. The values were subjected to two-way ANOVA, and Tukey's test (α=0.05). There was no significant difference among the groups and studied areas (p>0.05). It was concluded that the stresses generated around the implants were similar for all techniques.

Resumo A falta de passividade tem sido associada a problemas biomecânicos em próteses implantossuportadas. A proposta deste estudo foi avaliar, por meio da fotoelasticidade, a influência de três diferentes de fabricação de infraestrutura em liga de Co-Cr na passividade destas. O modelo foi obtido a partir de uma matriz de aço simulando uma mandíbula edêntula com 4 análogos de implantes de hexágono externo com plataforma padrão. Neste modelo, foram confeccionados cinco amostras para cada grupo: infraestruturas em monobloco, infraestruturas soldadas a laser e soldadas a TIG. O modelo fotoelástico foi feito com uma resina epóxi flexível (GIII, Polipox Industria e Comercio Ltda.). Na análise fotoelástica, as infraestruturas foram aparafusadas no modelo para a verificação da tensão de cisalhante máxima em 34 pontos selecionados ao redor dos implantes e 5 pontos na região média do modelo. Foram comparadas as tensões em todo o modelo fotoelástico, entre as regiões direita, esquerda e centro e também entre as regiões cervical e apical. Os valores foram submetidos à análise de variância a dois critérios, seguido pelo teste de Tukey (α=0,05). Os resultados não mostraram diferença significativa entre as tensões presentes nos grupos e nas áreas estudadas. Conclui-seque as tensões geradas ao redor dos implantes foram semelhantes entre as diferentes técnicas de confecção e entre todas as regiões analisadas. .

Linear dimensional change, compressive strength and detail reproduction in type IV dental stone dried at room temperature and in a microwave oven

The type IV dental stone is widely used for the fabrication of dyes and master casts for fixed and removable partial prostheses. It is typically normal to wait at least 24 hours for the casts to dry prior to beginning the laboratory procedures. The waiting time has been shown to be greatly reduced by using microwave drying. OBJECTIVE: This study evaluated the influence of drying techniques at room temperature and microwave oven on the linear dimensional change, compressive strength and detail reproduction in type IV dental stones. MATERIAL AND METHODS: Three type IV dental stone brands were selected; elite Rock, Shera Premium and Durone IV. Two different drying protocols were tested in 4 groups (n=10); G1 - room temperature (25±4ºC) dried for 2 hours; G2 - room temperature dried for 24 hours; G3 - room temperature dried for 7 days and G4 - microwave oven dried at 800 W for 5 minutes and after 2 hours at room temperature. After drying, the samples were assayed for dimensional charges. The sample surface was submitted to the ImageTool 3.0 software for compressive strength in a universal testing machine with a cell load of 50 KN at a crosshead speed of 0.5 mm/minutes and the detail reproduction was analyzed with a stereomicroscope at 25x magnification. The statistical analysis of the linear dimensional change and compressive strength data were conducted by the ANOVA test followed by the Tukey test (p<0.05). Detailed reproduction values were reported in percentages. RESULTS: For the compressive strength test, Elite Rock and Durone IV did not present significant differences between G2 and G4, while Shera Premium did not present differences between G3 and G4. The best reproduction levels were observed for G3. CONCLUSIONS: Dental stone microwave oven drying showed a linear dimensional change similar to after room temperature drying for 24 hours and 7 days. The compressive strength of the stone dried in the microwave oven was similar to those dried at room temperature for 24 hours, with the exception of Shera Premium, which had similar results for microwave and room temperature drying for 7 days. For the microwave drying method the detail reproduction levels for samples dried at room temperature for 24 hours and 7 days were similar, except for the Durone IV.

Evaluation of resistance to displacement of metal posts with different lengths.

Aims and Objectives: to evaluate the resistance to displacement of metal intraradicular retainers of different lengths by means of the shear test. Material and Methods: Thirty-six maxillary central incisors were cross-sectioned at 16 mm from the root apex, endodontically treated and randomly divided into three groups that were treated as follows: G1 (control) preparation of 2/3 (10.6 mm) of the total root length; G2: preparation of 1/2 (8 mm) of the total root length and G3: preparation of 1/3 (5.3 mm) of the total root length. After canal preparation, a matrix was made of the coronal and radicular portions using Duralay to obtain metal intraradicular retainers. These retainers were cemented with zinc phosphate cement and subjected to the compression shear test in a Universal Test Machine (EMIC DL 2000) at a crosshead speed of 0.5 mm/minute. The results were subjected to statistical analysis by analysis of variance (ANOVA) and Newman- Keuls, which showed statistically significant difference (P < 0.01). Results: The means in Newtons and their respective standard deviations were: G1 = 972.05 (±81.36); G2 = 921.15 (±112.25); G3 = 686.66 (±113.02). Conclusion: It could be concluded that metal retainers of 2/3 and 1/2 the length of the root portion showed higher resistance to displacement values when compared with the group that had been prepared for 1/3 of the root length.

Manutenção longitudinal do tratamento de peri-implantite / Long term clinical outcome of peri-implantitis treatment: a clinical report

O alto número de reabilitações orais com implantes, associadas à ausênciade uma correta terapia de manutenção, tem contribuído para o aparecimentode diversos casos de peri-implantite. Juntamente com este fato, odiagnóstico das doenças peri-implantares parece ser dificultado pelo desconhecimento,ou medo, dos cirurgiões-dentistas no exame das estruturasperi-implantares. O objetivo deste relato de caso clínico foi apresentaruma situação em que diagnóstico e tratamento da peri-implantite permitirama continuação e o sucesso da reabilitação oral com implantes. Dentrodas limitações do caso clínico apresentado concluiu-se que uma vez diagnosticadaa peri-implantite, a aplicação não cirúrgica de iodo povidine 10%,associado à abordagem cirúrgica, para a descontaminação da superfíciedos implantes e correção tecidual peri-implantar, por meio de enxerto detecido conjuntivo, e uma rigorosa terapia de suporte periodontal tornaramo resultado clínico satisfatório após 18 meses de acompanhamento, em setratando de estabilização do processo patológico.

Efeitos da plataforma switching em reabilitações implantossuportadas - revisão de literatura / Effects of platform switching in implant-supported rehabilitations - a literature review

Objetivo: o objetivo deste estudo foi avaliar os efeitos do uso da plataforma switching em reabilitações implantossuportadas. Esse tipo de sistema consiste em utilizar um componente protético de menor diâmetro, conectado à plataforma de implante com maior diâmetro, portanto, não combinados como de maneira convencional. Revisão de literatura: foram selecionados 13 artigos publicados no período de 2006 a 2011 abrangendo as consequências do uso da plataforma switching em relação aos fatores biológicos e biomecânicos das reabilitações implantossuportadas. Considerações finais: ficaram claros os benefícios e a indicação do uso de tal sistema, destacando-se a redução na reabsorção inicial da crista óssea peri-implantar e manutenção desse nível ósseo ao longo dos anos, bem como a diminuição nas forças sobre o tecido ósseo adjacente à região cervical do implante. Sendo assim, mesmo na presença de possíveis inconvenientes causados por este sistema, como o aumento das tensões na região do parafuso e componente protético, o uso da plataforma switching torna-se um atrativo para as reabilitações protéticas implantossuportadas.

Solução protética para implantes mal posicionados: relato de caso clínico / Prosthetic solution for misplaced implants: a case report

Reabilitações protéticas sobre implantes ainda é um desafio para Odontologia. Existem situações em que os implantes são colocados em locais não compatíveis com o posicionamento dos dentes no arco, sendo necessário utilizar compensações protéticas capazes de corrigir essa dificuldade. Este trabalho tem como objetivo, relatar um caso clínico que apresenta uma opção protética para compensar o mau posicionamento dos implantes, pelo uso de uma mesoestrutura metálica. O paciente apresentava uma deformação óssea na região anterior de maxila onde foram instalados quatro implantes, posicionados de tal forma que os acessos aos parafusos protéticos ocorriam em áreas estética e biomecanicamente desfavoráveis. Portanto, foi planejado a confecção de uma mesoestrutura metálica, alterando a região de acesso aos parafusos protéticos, o que proporcionou ótimo resultado estético e satisfação do paciente.

Prosthetic rehabilitation on implants is still a challenge for Dentistry. There are situations where the implants are placed in locations that are not compatible with the positioning of the teeth in the arch, prosthetic compensation is necessary to be able to fix this problem. This study aims, report a clinical case that presents a prosthetic option to compensate the poor positioning of implants, by using a metallic mesostructure.The patient had a bone deformation in the anterior maxilla where four implants were installed, positioned so that access to prosthetic screws occurred in areas aesthetics and biomechanically unfavorable. So it was planned the construction of a metallic mesostructure, changing the area of access to prosthetic screws, which provided excellent aesthetic results and patient satisfaction.

Radiographic inspection of porosity in Ti-6Al-4V laser-welded joints

Widely used in dentistry, Ti-6Al-4V alloy is difficult to cast and solder, as it frequently exhibits pores inside the structure. This study was conducted to evaluate the effect of joint openings and diameters of laser-welded joints executed in Ti-6Al-4V structures on the presence of pores as checked by radiographic procedures. Sixty dumbbell rods with central diameters of 1.5, 2.0 and 3.5 mm were created from Ti-6Al-4V-wrought bars. Specimens were sectioned and welded using two joint openings (0.0 and 0.6 mm). The combination of variables created six groups (n = 10). Laser welding was executed using 360V/8ms (1.5 and 2.0 mm) and 380V/9ms (3.5 mm), with the focus and frequency set to zero. The joints were finished, polished and submitted to radiographic examination. The radiographs were visually examined for the presence of pores in the joints, qualitatively. The percentage of radiographic presence of pores was calculated without counting pores per joint. Data were analyzed using a chi-square test (α = 0.05). For the 1.5-mm specimens, the incidence of pore presence was significantly higher (p = 0.0001) when using 0.6-mm joint openings (40 percent) compared to 0.0-mm openings (0 percent). For the 2.0-mm specimens, there was no significant difference between groups (p = 0.2008). However, for the 3.5-mm specimens, the incidence of pore presence was lower (p = 0.0061) for 0.6-mm openings (50 percent) compared to 0.0-mm openings (70 percent). Therefore, laser welding of Ti-6Al-4V structures with thin diameters provides the best condition for the juxtaposition of the parts.

Análise da influência de diferentes técnicas de preenchimento do molde com gesso na precisão de modelos de próteses fixas implanto-retidas / Evaluation of master cast techniques influence of implant fixed prostheses cast precision

Objetivo: Este estudo teve por objetivo avaliar a precisão de três técnicas de preenchimento do molde com gesso para obtenção de modelos de trabalho a partir de um modelo mestre simulando uma situação clínica de uma prótese fixa implanto-retida de três elementos. Materiais e métodos: Foram obtidos trinta modelos (n = 10) a partir do modelo mestre, por meio de três técnicas de preenchimento do molde com gesso. Assim, o Grupo 1 foi obtido pela técnica de preenchimento único (PU); o Grupo 2, pelo preenchimento do molde com gesso em duas porções (DP); o Grupo 3, utilizando-se a técnica do cilindro de latex (CL). Sobre a matriz metálica foi obtida uma infraestrutura fundida em titânio comer-cialmente puro simulando uma prótese fixa implanto-retida de três elementos, utilizada como referência para a avaliação de desajustes verticais em cada modelo. O desajuste vertical foi avaliado segundo a técnica do parafuso único. Para a análise dos resultados foi aplicada a análise de variância, seguida do teste de Tukey. Resultados: De acordo com os resultados obtidos, observou-se maior valor médio entre as amostras do grupo em que o molde foi preenchido com gesso pela técnica do preenchimento único (média = 0,14), ao passo que as amostras dos grupos 2 e 3 apresentaram os mesmos valores médios (média = 0,10). Porém, de acordo com o teste de Tukey, não houve diferença estatística entre os três diferentes grupos de tratamento. Conclusão: Assim, pode-se afirmar que as três técnicas foram eficientes, sendo, de acordo com a praticidade, a mais indicada a técnica de preenchimento único.

Effect of monomer content in the monomer-polymer ratio on complete denture teeth displacement

The purpose of the study was to verify the linear displacement of teeth in maxillary complete dentures influenced by different monomer-polymer ratios - according to the manufacturer's instructions, with 25 percent excess or 25 percent less monomer content - in the conventional and microwaved polymerization techniques. Wax base plates and wax planes were made on edentulous maxillary stone casts according to traditional method. The set was assembled in semi-adjustable articulator with a lower toothed stone cast as guide to mounting of the maxillary artificial teeth. Impressions were taken from this tooth arrangement with silicone and the mold was used to standardize the mounting of the teeth of all dentures. Referential points were made on the artificial teeth for linear measurements with optical microscope before processing of the dentures and after deflasking. Denture bases were conventionally packed with acrylic resin according to the monomer-polymer ratio protocol. Tooth displacement data were submitted to ANOVA and Tukey test (α=0.05). There were no statistically significant differences (p>0.05) between the group with monomer content recommended by the manufacturer and groups with 25 percent more and 25 percent less monomer, in both conventional and microwaved polymerizations. Excess or less monomer in the monomer-polymer ratio and polymerization types did not change the linear distance between teeth.

O propósito neste estudo foi verificar a movimentação linear de dentes em prótese total superior confeccionada com resina acrílica, proporcionada com conteúdo de monômero indicado pelo fabricante, com 25 por cento de excesso ou com 25 por cento a menos de monômero, nas técnicas de polimerização convencional e por microondas. Foram confeccionados 30 modelos, representando uma arcada maxilar desdentada com rebordo normal. As bases de prova e os planos de orientação foram confeccionados em cera e o conjunto montado em articulador semi-ajustável relacionado com um modelo inferior dentado. Depois da montagem dos dentes artificiais, a prótese foi moldada com silicone para duplicação das demais próteses. Foram confeccionados pontos referenciais para mensurações das distâncias entre os dentes, as quais foram analisadas com microscópio comparador linear antes e depois da desinclusão das próteses. As resinas acrílicas foram prensadas de modo convencional, alterando somente o conteúdo de monômero na proporção monômero-polímero recomendada pelo fabricante. Os dados da distância entre os dentes foram submetidos à análise de variância e ao teste de Tukey (5 por cento). Não houve diferença estatística entre os grupos com quantidade de monômero recomendada pelo fabricante e os grupos com 25 por cento a mais ou 25 por cento a menos de monômero, tanto na polimerização convencional como por microondas. A alteração do conteúdo de monômero e o tipo de polimerização (convencional ou por microondas) não exerceram influência na movimentação dental nas distâncias transversal e ântero-posterior.

Análise radiográfica de uniões soldadas a laser executadas no titânio comercialmente puro fundido, em diversas situações clínicas simuladas / Radiographic analysis in casting titanium laser-joints in diverse clinical situations

Esse estudo foi conduzido para avaliar a possibilidade de visualização de porosidade interna em radiografias periapicais de uniões soldadas a laser, confeccionadas em estruturas de titânio (Ti) comercialmente puro (cp), em diferentes situações de soldagem. Foram confeccionados halteres em resina acrílica, com diâmetros centrais de 1,5; 2,0; e 3,5 mm, por meio de uma matriz metálica bipartida. Os halteres em resina foram fundidos em Ti cp e após acabamento e polimento, seccionados em duas partes iguais. As partes foram alinhadas e fixadas de tal forma que as distâncias entre elas fossem 0,0 e 0,6 mm. A combinação entre as variáveis (distância de soldagem e diâmetro dos halteres) gerou seis grupos (n=10). A soldagem a laser foi realizada com as seguintes especificações: 360V/8ms (1,5 e 2,0 mm) e 380V/9ms (3,5 mm), com foco e freqüência regulados em zero, em um aparelho de soldagem a laser Desktop-F. As uniões obtidas receberam acabamento, polimento e foram submetidas à análise radiográfica com exposição à radiação (90 KV, 15 mA, 0,6 seg e 10 a 13 mm de distância) utilizando filme periapical. As radiografias foram analisadas visualmente quanto à presença de porosidade nas uniões soldadas, e os dados obtidos, submetidos ao teste Qui-Quadrado (5%). Com isso, verificou-se ser possível visualizar porosidade interna nessas uniões. Em corpos de prova de menores diâmetros, 1,5 e 2,0 mm, a incidência é maior quando a distância é 0,6 mm. Entretanto, em corpos de prova de 3,5 mm, a incidência é alta para ambas as uniões, não diferindo estatisticamente entre si.

This study was conducted to evaluate the possibility of porosity inspection in laser-weld joints executed in cp titanium structures, by radiographic analyses. Sixty acrylic dumbbells rods with 1.5, 2.0 and 3.5 mm central diameter were prepared by lost-wax casting procedure. The casted specimens were finished, polished and sectioned in two halves. The parts were lined up in a metal matrix and fixed according two welding distances (0.0 and 0.6 mm). The combination between diameter and welding distance created a total of six groups (n = 10). The laser welding was executed as follows: 360V/8ms (1.5 and 2.0 mm) and 380V/9ms (3.5 mm) with focus and frequency regulated to zero. The achieved joints were finished, polished and submitted to radiographic examination (90 KV, 15 mA, 0.6 second and 10 to 13 mm of distance) with periapical film. The radiographies were visually analyzed for the presence of internal porosity in the joints. The data was submitted to Chi-Square test (5%). Herewith, it was possible to visualize internal porosity in the analyzed joints. In thin specimens, 1.5 and 2.0 mm, the porosity incidence was higher when the joint distance was 0.6 mm. However, in 3.5 mm specimens, this incidence was high for both joint openings.

Porcelain application and simulation of firing cycle: effect on marginal misfit of implant-supported frameworks

Aim: Success of implant-supported prostheses is related to the frameworks’ passive fit, henceinaccuracies can generate stress, leading to bone resorption and rehabilitation failure. This study evaluated misfit levels of implant-supported frameworks after different coverage treatments.Methods: Twenty commercially pure titanium (CP Ti) frameworks were manufactured with 5Branemark type multi-unit abutments. Frameworks were distributed in two groups as follows: G1- porcelain application (n=10); G2 - porcelain firing cycle simulation (n=10). Using a traveling microscope, marginal misfit was measured before and after undertaking the techniques, following the single-screw test protocol. All data were submitted to ANOVA and Tukey’s test (p<0.05).Results: Initial marginal misfit values were not significantly different, but both groups presented significantly higher misfit values after treatment: G1: 233.99 ìm (p=0.0003); G2: 119.75 ìm(p<0.0001). In addition, G1 presented higher misfit than G2 (p<0.0001). Conclusions: Porcelain application promoted significantly higher increase of misfit, which indicates that such procedure should be considered on misfit analysis of implant-supported prostheses.

Dimensional stability of distances between teeth in complete dentures comparing microwave polymerization and conventional cycles

Aim: This study investigated the tooth movement of complete dentures processed by micro wave activation and conventional processing method in water bath. Methods: Twenty maxillary complete dentures were fabricated and randomly assigned to 4 groups (n=5): Group I: Classico convention alheat-curing acrylic resin processed by microwave polymerization; Group II: Classico resinprocessed in water bath at 74°C for 9 h (control-group); Group III: QC-20 fast heat-curing acrylic resin processed in boiling water for 20 min; Group IV: Onda-Cryl microwave acrylic resin processed at the same conditions of Group 1. Metallic referential pins were placed on the incisal border of the central incisors, buccal cusp of the first premolars, and the mesiobuccal cusp of the second molars.Transversal and anteroposterior distances were measured before and after the complete dentures processing with a linear optical microscope (Olympus Optical Co., Tokyo, Japan) accurate to0.0005 mm. Data were subjected to A NOVA and Tukey’s test at 5% significance levels. Results:Inside each group, dentures showed some tooth movement but without statistical difference before and after the polymerization. Conclusions: Dentures processed by microwave energy presented similar performance to those subjected to conventional cycles in water bath for most of distances evaluated.

Efeito da adição de citrato e termociclagem sobre a sorção, solubilidade e rugosidade superficial de um reembasador resiliente / Effect of citrate addition and termocycling on water sorption, solubility and surface roughness of a soft liner

Objetivo: As propriedades dos materiais resilientes são alteradas quando o produto está em meio aquoso, sejaem saliva, seja em água destilada ou agentes químicos de limpeza. O processo de lixiviação sofrido pelo material resulta em endurecimento progressivo, distorção e alteração de rugosidade, apresentando longevidadeinferior à da prótese. Assim, este estudo foi realizado para avaliar e comparar a sorção, solubilidade e rugosidade superficial de um material reembasadorresiliente a base de resina acrílica (Eversoft®) em sua composição química original e com adição de citrato(experimental). Métodos: Foram confeccionados vinte corpos-de-prova de cada material com dimensões de45 mm de diâmetro X 1 mm de espessura, distribuídos em quatro grupos (n = 10). G1): Eversoft® com selante; G2): Eversoft® sem selante; G3): Experimental sem selante; e G4): Experimental com selante. Os corpos-deprova foram armazenados em água destilada em estufa à temperatura de 37 C e submetidos à termociclagem,sendo avaliados em quatro tempos: T0 = 0 (Controle), T1 = 1000 ciclos, T2 = 2000 ciclos, T3 = 3000 ciclos. Resultados: A adição de citrato na fórmula do Eversoft influenciou na rugosidade superficial, sorção e solubilidade do material; entretanto, mediante a aplicação de selante houve redução da rugosidade superficial e sorção do Eversoft®, não havendo diferença entre os grupos. Os valores de solubilidade do Eversoft® com aplicação de selante foram significativamente inferiores aosdo citrato. Conclusão: O Eversoft®, quando manipulado de acordo com as indicações do fabricante, ou seja, utilizando o selante, apresentou propriedades semelhantes às do Grupo Experimental. A adição de citrato nãosubstituiu o uso de selante

Seal capability of interim post and core crown with temporary cements

The purpose of the present study was to evaluate the in vitro seal capability of interim post and core crown restorations. Eighty teeth were selected and divided into 8 groups. Four experimental groups received interim posts and core crowns. Half of each group was decoronated at the cementum-enamel junction, groups PCCH and PCZO. The other half was sectioned 2 mm coronal to the cementum-enamel junction, groups PCrZO and PCrCH. The interim post and core crowns were luted with Rely X Temp NE, groups PCrZO and PCZO; Hydro C was used for Groups PCrCH and PCCH. The control groups, PC and PCr, received uncoated post and core crowns; groups OTg and OT were left without interim post and core crowns and were totally open. Infiltration was accessed by dye exposure followed by demineralization of the teeth. The length of the infiltration was measured using digital images taken from the specimens. The images were inserted into the Image Tool 3.0 software. Kruskal-Wallis analysis of variance and Dunn's multiple comparison method were used to test for significant differences among test groups (P < .05). Groups PCrZO and PCrCH showed the least dye penetration, followed by groups PCZO and PCCH. Teeth restored with interim post and core crowns will be subject to leakage. Ethics Committee: 095/2008.

Implant-supported titanium framework: photoelastic analysis before and after spark erosion procedure

Aim: This study used a photoelastic analysis to evaluate the passive fit of titanium cast laserwelding frameworks before and after spark erosion procedure. Methods: A stainless steel castwas used in order to reproduce a human mandible. Five Multi-Unit abutment analogs wereattached to this cast and 6 frameworks were produced in commercial pure titanium. The cast wasmolded and a photoelastic matrix was produced incorporating 5 dental implants with Multi-Unitabutments. All samples were subjected to a laser welding. The precision of adjustments within arange of 0.5 ìm was evaluated under microscope observation. The best fitted framework wasselected and subjected to a photoelastic analysis (Group I). The tightening of the screws was in 3predetermined sequences (1,2,3,4,5/ 5,4,3,2,1/ 3,2,4,1,5). Then the same framework wassubjected to a refinement by spark erosion technique (Group II) and evaluated by photoelasticanalysis. Results: The sequence (3,2,4,1,5) achieved better results in both groups. A largernumber of fringes were observed around the median implants in all sequences in both groups.Conclusions: The titanium cast laser welded frameworks processes associated with spark erosionprocedure improves significantly the marginal framework adaptation and is effective for its passive fit.