Influence of diameter on mechanical behavior of morse taper narrow implants

Dental implants could give back function, esthetics and quality of life to patients. The correct choice of the implant, especially in borderline cases, is essential for a satisfactory result. Aim: Thus, the objective of this study was to evaluate the mechanical behavior of Morse taper implants with two different prosthetic interfaces. Methods: Twenty self-locking Morse taper implants, 2.9 mm in diameter (FAC), and 20 Morse taper implants, 3.5 mm in diameter (CM) were divided into two groups (n=10), and submitted to strength to failure test, optical microscopic evaluation of fracture, metallographic analysis of the alloy, finite element analysis (FEA) and strain gauge test. A Student's t test (α = 0.05) was made for a statistical analysis. Results: For the strength to failure test, a statistically difference was observed (p <0.001) between FAC (225.0 ± 19.8 N) and CM (397.3 ± 12.5 N). The optical microscopic evaluation demonstrated a fracture pattern that corroborated with FEA ́s results. The metallographic analysis determined that the implants of the FAC group have titanium-aluminum-vanadium alloy in their composition. In the strain gauge test, there was no statistical difference (p = 0.833) between CM (1064.8 ± 575.04 µS) and FAC (1002.2 ± 657.6 µS) groups. Conclusion: Based on the results obtained in this study, ultra-narrow implants (FAC) should ideally be restricted to areas with low masticatory effort

Microstructural and mechanical analysis of two CAD-CAM lithium disilicate glass-reinforced ceramics

Abstract The aim of this study was to analyze the structural, morphological and mechanical properties of two different lithium disilicate glass-reinforced ceramics for CAD-CAM systems (IPS e.max CAD and Rosetta SM). Five methodologies were used for both ceramics: microstructure (n = 2) was analyzed using x-ray diffraction (XRD); morphological properties (n = 2) were analyzed by scanning electron microscopy (SEM), with and without hydrofluoric etching; porosity (n = 3) was assessed using 3D micro-computed tomography (micro-CT); flexural strength was measured (n =1 0) using the three-point bending test; and bond strength was determined with self-adhesive resin cement (n = 10), using a microshear bond test. After performing all the tests, the data were analyzed using t-Student test and two-way ANOVA. All the tests used a significance level of α = 0.05. High peak positions corresponding to standard lithium metasilicate and lithium disilicate with similar intensities were observed for both ceramics in the XRD analysis. Morphological analysis showed that the crystalline structure of the two ceramics studied showed no statistical difference after acid etching. Additionally, no significant differences were recorded in the number or size of the pores for the ceramics evaluated. Moreover, no differences in flexural strength were found for the ceramic materials tested, or in the bond strength to ceramic substrates for the resin cements. Based on the study results, no significant differences were found between the two CAD-CAM lithium disilicate glass-reinforced ceramics tested, since they presented similar crystalline structures with comparable intensities, and similar total porosity, flexural strength and bond strength.

Influence of furnace type in the crystallization of lithium disilicate on bond strength and flexural strength

Aim: The crystallization step is required for lithium disilicate ceramics to change color, improve the mechanical properties and yield material to support mouth loading. Several furnaces could complete the crystallization process. This study evaluated the flexural and bond strength of lithium disilicate ceramics crystallized by different furnaces with the presence or not of vacum and different holding time. Methods: Forty lithium disilicate samples were divided into two groups: Programat P300 - control group with vacuum and holding time 7 minutes (CG) and FVPlus- experimental group and without vacuum and holding time 25 minutes (EG) and submitted to 2 experimental tests: 3-point flexural strength test and micro shear bond strength test (µSBS). For this test, the surface of the samples was treated and 1mm² of resin cement was applied on the surface. The samples were stored in artificial saliva over 2 time periods (24 hours: T0; 1-month storage: T1). To analyze the morphologic crystals of the ceramics tested, one representative specimen from each group were analyzed by using Scanning Electron Microscopy (SEM). Results: There was no significant difference in 3-point flexural strength test between groups CG and EG (p= 0.984). The µSBS results showed no statistical difference between groups, considering different storage time. There was no difference in the 3-point flexural strength and µSBS for lithium disilicate samples regardless of heat treatment of furnace type. The storage time had no influence on the µSBS. No differences were noted in the shape and size of these crystals when comparing the furnace analyzed by SEM images. Conclusion: Different furnaces did not influence the flexural and bond strength of lithium disilicate ceramics

Effect of cavity preparation design and ceramic type on the stress distribution, strain and fracture resistance of CAD/CAM onlays in molars

Abstract Objective This study aimed to evaluate the effect of the cavity preparation and ceramic type on the stress distribution, tooth strain, fracture resistance and fracture mode of human molar teeth restored with onlays. Material and Methods Forty-eight molars were divided into four groups (n=12) with assorted combinations of two study factors: BL- conventional onlay preparation with boxes made from leucite ceramic (IPS-Empress CAD, Ivoclar Vivadent); NBL- conservative onlay preparation without boxes made from leucite ceramic; BD- conventional onlay preparation with boxes made from lithium disilicate glass ceramic (IPS e.max CAD, Ivoclar Vivadent); NBL- conservative onlay preparation with boxes made from lithium disilicate glass ceramic cuspal deformation (µS) was measured at 100 N and at maximum fracture load using strain gauge. Fracture resistance (N) was measured using a compression test, and the fracture mode was recorded. Finite element analysis was used to evaluate the stress distribution by modified von Mises stress criteria. The tooth strain and fracture resistance data were analyzed using the Tukey test and two-way ANOVA, and the fracture mode was analyzed by the chi-square test (α=0.05). Results The leucite ceramic resulted in higher tooth deformation at 100 N and lower tooth deformation at the maximum fracture load than the lithium disilicate ceramic (P<0.001). The lithium disilicate ceramic exhibited higher fracture resistance than the leucite ceramic (P<0.001). The conservative onlay resulted in higher fracture strength for lithium disilicate ceramic. Finite element analysis results showed the conventional cavity preparation resulted in higher stress concentration in the ceramic restoration and remaining tooth than the conservative onlay preparation. The conservative onlays exhibited increased fracture resistance, reduced stress concentration and more favorable fracture modes. Conclusion Molars restored with lithium disilicate CAD-CAM ceramic onlays exhibited higher fracture resistance than molars restored with leucite CAD-CAM ceramic onlays.

Comparative analysis of optical microscopy, scanning electron microscopy, and micro-computed tomography on measurements

Abstract: Microscopic measurements are widely used in scientific research and the correct equipment to perform these evaluations could be critical to determine study results. Regarding microscopic measurements, three of the most used methods are: Optical Microscopy (OM), Scanning Electron Microscopy (SEM), and Micro-computed Tomography (MCT). It is important to select the best method for assessing diverse parameters, considering operational characteristics of the method, the equipment efficiency, and the machinery cost. Aim: Therefore, the main objective of this study was to define which is the most useful measurement method for assessing magnitudes below 0.4 mm. Methods: Ten dental implants, with known dimensions as defined by the manufacturer were randomly distributed. Two blinded observers assessed the distance between the second and the third screw vortex of the implants using three suggested methods. The true distance was defined to be 0.5 mm. Results: The assessed distances were: 0.597±0.007mm for OM, 0.578±0.017mm for SEM, and 0.613±0.006mm for MCT. The assessed distances were significantly different when the methods were compared (P>0.01). All measurements were into the CAD tolerances. Conclusion: It was possible to conclude that linear easurements between 595 and 605 µm could be performed by any of the described technologies (AU)

Reabilitação maxilar após radioterapia utilizando implante unitário e prótese obturadora tipo overdenture: acompanhamento clínico de um ano / Maxillary rehabilitation after radiotherapy using a single-tooth dental implant and the obturator-type overdenture: one-year clinical follow-up

Este caso clínico relata o uso de uma prótese obturadora tipo overdenture para compensar a deficiência estética em um paciente previamente irradiado. Um indivíduo do sexo masculino, 73 anos de idade, que possuía uma prótese sobre três implantes dentários foi acometido de câncer no seio maxilar e assoalho da órbita. Seis doses de cisplatina e 35 sessões de radioterapia (dose diária 1,8 Gy) foram executadas. Após a maxilectomia, apenas um implante restou na região anterior. O tratamento consistiu de uma prótese obturadora tipo overdenture com encaixe tipo Equator. O paciente retornou um ano depois, sem alterações estéticas e com nível de satisfação melhorado. Entretanto, o anel borrachoide do encaixe foi trocado. Reabilitações implantossuportadas e mucorretidas que recebem carregamento tardio pode melhorar o prognóstico de implantes dentais em pacientes irradiados. Este cuidado mostra que este cenário ainda requer maior atenção da comunidade científica, na busca por meios de prevenir e minimizar os danos causados pela radioterapia, por inovações tecnológicas e protocolos regenerativos que potencializem a osseointegração. Com isso, a Odontologia poderá contribuir ainda mais com a melhora da qualidade de vida de pacientes, devolvendo satisfação pessoal e autoestima.

This case describes the use of an obturator-type overdenture prosthesis to compensate for the aesthetic defi ciency in a previously irradiated patient. A 73 years-old male, who had a prosthesis on three dental implants was diagnosed with cancer in the maxillary sinus and orbital floor. Six doses of cisplatin and 35 radiotherapy sessions (daily doses of 1.8 Gy) were performed. After maxillectomy, only one implant survived in the anterior region. The treatment consisted of an obturator overdenture with the Equator attachment. The patient returned one year later without cosmetic changes and demonstrated an enhanced satisfaction level. However, the o-ring rubber was replaced. Implant-supported, mucosa-retained restorations receiving delayed loading can improve the prognosis of dental implants in irradiated patients. Also, this scenario still requires more attention from the scientific community seeking for new ways to prevent and minimize damages caused by radiation, technological innovations, and regenerative protocols that enhance osseointegration. Thus, dentistry can further contribute to improving the quality of life of patients, returning their personal satisfaction and self-esteem.

Influence of dentistry procedures on masticatory function of dentate patients

Aim: Evaluate the masticatory performance in patients with different clinical situations: patients with natural dentition without restorative and/or orthodontic intervention (Group CG) and patients with restorations and/or orthodontic intervention (Group TG). Subjects received instruction before the experiment, related to masticatory movements. Methods: Three capsules containing the granules were delivered separately to chew for 20 seconds each, controlled by the examiner. One capsule was chewed for 20 seconds only on the left side; the second capsule was chewed for 20 seconds only on the right side; and the third capsule was chewed for 20 seconds to simulate each patient's mastication. The mean data and standard deviation of masticatory function of each patient was calculated. Results: The results obtained in this study showed that there were no statistically significant differences (P < 0.05) between both tested groups (0.0320 ± 0.00716, 0.0436 ± 0.00974). Conclusions: Patients who were submitted to orthodontic and/or restorative procedures, with balanced occlusion could be used as a control group, making easier the patient recruitment. Clinicians and researchers on masticatory performance evaluation could apply the colorimetric method. The colorimetric method was a standardize method, effective and easy to execute. (AU)

Reabilitação protética com componentes dinâmicos ­ relato de caso / Prosthetic rehabilitation with dynamic components ­ case report

Os componentes dinâmicos surgiram como alternativa para reabilitar implantes inclinados em até 20°, possibilitando o restabelecimento da estética, função e reduzindo os custos do procedimento. Sendo assim, o objetivo deste trabalho é apresentar um relato de caso utilizando esses componentes. Durante o exame clínico foi diagnosticado que os implantes apresentavam profundidade gengival rasa, inclinação e paralelismo desfavoráveis. Dessa forma, foi optado pela utilização de pilares retos com componentes dinâmicos, que irão corrigir a inclinação do orifício de acesso do parafuso da prótese definitiva.

Dynamic components were created as an alternative to rehabilitate tilted implants until 20º angled. This component allows aesthetic and function rehabilitation with lower cost comparing to angled abutments. The aim of this study was to present a case report us-ing these dynamic components. The patient presented tilted implants with gingival shallow depth, with unfavourable parallelism. Thus, straight abutment and dynamic components were concomitantly used to correct the access screw hole inclination of final the prosthesis.

Sistema Cone Morse e utilização de pilares com plataforma switching / Morse Taper System and platform switching abutment application

Os implantes cone morse associados a pilares com plataforma switching têm proporcionado resultados promissores com relação à estabilidade dos tecidos peri-implantares. Isso se deve ao perfil cônico do componente protético, à íntima adaptação na interface implante/pilar e ao menor acúmulo de biofilme bacteriano. Para isso, deve-se levar em consideração o posicionamento infraósseo do implante. Essa configuração implante/pilar possui resistência à fratura superior em relação aos sistemas convencionais e, além disso, devido à manutenção da crista óssea e da diversidade de pilares e componentes protéticos, possibilita reabilitações orais estéticas e biocompatíveis.

Morse taper implants associated with platform switching abutments have provided promising results with respect to the stability of peri-implant tissues. This is due to the conical profile of the abutment, the intimate adaptation at the implant/abutment interface, and to the lower accumulation of bacterial biofilm. For this, it has been proposed the insertion of the implants below the crestal bone level. This implant/ abutment configuration presents higher fracture strength compared to the conventional systems and, in addition, because of the maintenance of crestal bone and the diversity of abutments and prosthetic components, provides aesthetic and biocompatible oral rehabilitations.

Strain analysis of different diameter Morse taper implants under overloading compressive conditions

The aim of this study was to evaluate the amount of deformation from compression caused by different diameters of Morse taper implants and the residual deformation after load removal. Thirty Morse taper implants lacking external threads were divided into 3 groups (n = 10) according to their diameter as follows: 3.5 mm, 4.0 mm and 5.0 mm. Two-piece abutments were fixed into the implants, and the samples were subjected to compressive axial loading up to 1500 N of force. During the test, one strain gauge remained fixed to the cervical portion of each implant to measure the strain variation. The strain values were recorded at two different time points: at the maximum load (1500 N) and 60 seconds after load removal. To calculate the strain at the implant/abutment interface, a mathematical formula was applied. Data were analyzed using a one-way Anova and Tukey’s test (α = 0.05). The 5.0 mm diameter implant showed a significantly lower strain (650.5 μS ± 170.0) than the 4.0 mm group (1170.2 μS ± 374.7) and the 3.5 mm group (1388.1 μS ± 326.6) (p < 0.001), regardless of the load presence. The strain values decreased by approximately 50% after removal of the load, regardless of the implant diameter. The 5.0 mm implant showed a significantly lower strain at the implant/abutment interface (943.4 μS ± 504.5) than the 4.0 mm group (1057.4 μS ± 681.3) and the 3.5 mm group (1159.6 μS ± 425.9) (p < 0.001). According to the results of this study, the diameter influenced the strain around the internal and external walls of the cervical region of Morse taper implants; all diameters demonstrated clinically acceptable values of strain.

Bacterial microleakage at the implant-abutment interface in Morse taper implants

AIM: To evaluate the microleakage at the implant-abutment (I-A) interface of Morse tapered implants inoculated with different volumes of bacterial suspension. METHODS: Morse tapered I-A sets were selected and divided in two groups depending on the type of abutment: passing screw (PS) and solid (S), and then subdivided into four subgroups (n=6) according to the suspension volume: PS1: 0.1 µL; PS3: 0.3 µL; PS5: 0.5 µL; PS7: 0.7 µL; S1: 0.1 µL; S3: 0.>3 µL; S5: 0.5 µL and S7: 0.7 µL. A control test was performed to verify the presence of external contamination during the inoculation and the implants were incubated for microbiological analysis. The microleakage was evaluated every 24 h for 7 days by the clarity of solution. After this period, the implants were disassembled for confirmation of bacterial viability. RESULTS: All the specimens with 0.7 µL and one sample of S5 presented turbidity in the control test indicating external contamination, and were excluded from the study. After 7 days of observation, none of the specimens presented positive results for microleakage and the bacterial viability was confirmed in all specimens. The 0.1 µL and 0.3 µL volumes did not present bacterial microleakage, meaning that these volumes may be inadequate for analysis. CONCLUSIONS: None of the sets evaluated showed bacterial microleakage at the I-A interface and the volume of 0.7 µL exceeded the internal capacity of the implants...

Stress analysis of different configurations of 3 implants to support a fixed prosthesis in an edentulous jaw

This study's aims was to evaluate the stress distribution in a mandibular implant-supported prosthesis and peri-implant bone considering implant quantity, diameter and position using linear 3-D finite element analysis. Models of an anterior jaw comprised 4 groups according to implant quantity, diameter, and position: control group C, 5 regular implants; R, 3 regular implants; W, 3 wide implants; and DTR, 3 regular implants with the distal ones tilted 30º distally. The cantilever was loaded with an axial load of 50 N. Data was evaluated using von Mises stress on implants and maximum principal stress and microstrain on the bone. The W group showed the lowest value of maximum principal stress in peri-implant bone of the loaded side (4.64 MPa) when compared to C (5.27 MPa), DTR (5.94 MPa), and R (11.12 MPa). Lower stress values in the loaded implants were observed in the experimental groups when compared to the C group. However, the unloaded implants presented opposite results. All the screws of the W group presented lower stress values when compared to the C group. However, the R and DTR groups presented an increase in stress values with the exception of the loaded screw. A reduction in the number of implants associated with wider implants reduced the stress in the bone and prosthetic components.

Micro-leakage at the implant-abutment interface with different tightening torques in vitro

OBJECTIVES: This study evaluated the microleakage at the implant/abutment interface of external hexagon (eH) implants and abutments with different amounts of bacteria and tightening torques. MATERIAL AND METHODS: A bacterial suspension was prepared to inoculate the implants. The first phase of this study used nine EH implants and abutments that were divided into three groups with different amounts of bacterial suspension (n=3): V0.5: 0.5 µL; V1.0: 1.0 µL e V1.5: 1.5 µL, and tightened to the manufacturer's recommended torque. The second phase of this experiment used 27 assemblies that were similar to those used in the first phase. These samples were inoculated with 0.5 µL of bacterial suspension and divided into three groups (n=9). T10: 10 Ncm; T20: 20 Ncm and T32: 32 Ncm. The samples were evaluated according to the turbidity of the broth every 24 hours for 14 days, and the bacteria viability was tested after that period. The statistical evaluation was conducted by Kruskal-Wallis testing (p<.05). RESULTS: During the first phase, groups V1.0 and V1.5 was presented with bacterial contamination in all samples after 24 h. During the second phase, two samples from group T10 and one from T20 presented positive results for bacterial contamination. Different amounts of bacterial solution led to overflow and contamination during the first 24 h of the experiment. The tightening torques did not statistically affect the microleakage in the assemblies. However, the group that was tightened to 32 Ncm torque did not show any bacterial contamination. CONCLUSION: After 14 days of experimentation, the bacteria were proven to remain viable inside the implant internal cavity.

Para reconstruções de dentes tratados endodonticamente, utilizo pino intrarradicular de fibra de vidro ou metálico?

Mostra o ponto de vista de dois profissionais da área de Odontologia, sobre a utilização de pino intrarradicular de fibra de vidro ou metálico para reconstruções de dentes tratados endodonticamente. Para os dois profissionais não existe o pior, ou o melhor método, pois deve-se analisar cuidadosamente a técnica que melhor se adequa à situação do paciente.

Evaluation of screw loosening on new abutment screws and after successive tightening

This study evaluated the loss of the torque applied after use of new screws and after successive tightening. Four infrastructures (IE), using UCLA castable abutment type, were cast in cobalt-chromium alloy and new abutment screws (G1) were used in a first moment. Subsequently, the same abutment screws were used a second time (G2) and more than two times (G3). The values of the torques applied and detorques were measured with a digital torque wrench to obtain the values of initial tightening loss ( percent). Data were analyzed by ANOVA and Tukey's test (?=0.05). Significant differences were observed between the G1 (50.71 percent ± 11.36) and G2 (24.01 percent ± 3.33) (p=0.000) and between G1 (50.71 percent ± 11.36) and G3 (25.60 percent ± 4.64) (p=0.000). There was no significant difference between G2 and G3 (p=0.774). Within the limitations of the study, it may be concluded that the percentage of the initial torque loss is lower when screws that already suffered the application of an initial torque were used, remaining stable after application of successive torques.

O objetivo deste estudo foi avaliar a perda do torque inicial, quando usados novos parafusos de pilares e após sucessivos apertos. Quatro infra-estruturas (IE), utilizando pilares calcináveis tipo UCLA, foram fundidas em liga de cobalto-cromo, onde novos parafusos de pilares foram utilizados (G1) em um primeiro momento. Posteriormente os mesmos parafusos de pilares foram utilizados em um segundo momento (G2), e depois por mais duas vezes (G3). Os valores de torque e detorque aplicados foram mensurados a partir de um torquímetro digital para obtenção dos valores de perda do torque inicial ( por cento). Os dados foram coletados e submetidos à análise de variância e teste de Tukey (p<0,05). Foram observadas diferenças estatisticamente significantes entre os grupos G1 (50,71 por cento ± 11,36) and G2 (24,01 por cento ± 3,33) (p=0,000) and the groups G1 (50,71 por cento ± 11,36) and G3 (25,60 por cento ± 4,64) (p=0,000). Os maiores valores foram encontrados para o grupo G1. Não houve diferença estaticamente significante entre os grupos G2 e G3 (p=0,774). Dentro das limitações deste estudo, pôde-se observar que a porcentagem de perda de torque inicial foi menor quando os parafusos já haviam sofrido a aplicação do primeiro torque, se mantendo estáveis após os demais torques.

Implant/abutment vertical misfit of one-piece cast frameworks made with different materials

This study compared vertical and passive fit of one-piece cast frameworks made with 3 different materials: commercially pure titanium (CP Ti - G1), cobalt-chromium alloy (Co-Cr - G2) and nickel-chromium-titanium alloy (Ni-Cr-Ti - G3). Fifteen frameworks were obtained simulating bars for fixed prosthesis in a model with 5 implants. The passive and vertical fit of the framework interface was measured using an optical microscope at ×30 magnification. Data were statistically analyzed by ANOVA and LSD tests (α=0.05). Mean and standard deviation values for passive fit and vertical fit were, respectively: G1 [472.49 (109.88) µm and 29.9 (13.24) µm], G2 [584.84 (120.20) µm and 27.05 (10.30) µm], and G3 [462.70 (179.18) µm and 24.95 (11.14) µm]. For vertical fit, there were no significant differences among G1, G2 and G3 (p=0.285). There were no significant differences for passive fit between G1 and G3 (p=0.844), but both differed significantly from G2 (p=0.028 and p=0.035, respectively), which showed the highest misfit values. It may be concluded that the vertical fit of frameworks was not affected by the tested materials, and that one-piece cast frameworks resulted in inadequate passive fit. The Co-Cr alloy presented the worst values for passive fit.

Este estudo tem como objetivo comparar o ajuste vertical e a passividade de infraestruturas em monobloco confeccionadas em 3 diferentes materiais: titânio comercialmente puro (Ti cp - G1), cobalto-cromo (Co-Cr - G2) e níquel-cromo-titânio (Ni-Cr-Ti - G3). Quinze infraestruturas foram obtidas simulando barras para próteses fixas em um modelo com 5 implantes. O ajuste vertical e a passividade da interface da infraestrutura foram medidos usando um microscópio óptico (30×). Os dados foram analisados estatisticamente por meio da ANOVA e teste LSD (α=0,05). A média dos valores e o desvio-padrão da passividade e do ajuste vertical estão apresentados respectivamente: Ti cp [472,49 (109,88) μm e 29,9 (13,24) μm], Co-Cr [584,84 (120,20) μm e 27,05 (10,30) μm], Ni-Cr-Ti [462,70 (179,18) μm e 24,95 (11,14) μm]. Para o desajuste vertical, não houve diferença significante entre o Ti cp e as ligas Co-Cr e Ni-Cr-Ti (p=0,285). Para passividade, não houve diferença significante entre Ti cp e Ni-Cr-Ti (p=0,844), mas ambos foram estatisticamente diferentes do Co-Cr (p=0,028 e p=0,035, respectivamente), o qual apresentou os piores resultados. Pode-se concluir que os materiais utilizados para confecção das infraestruturas não influenciaram o ajuste vertical e que infraestruturas fundidas em monobloco resultaram em inadequados ajustes passivos. A liga de Co-Cr apresentou os piores resultados para a passividade.

Relation between implant/abutment vertical misfit and torque loss of abutment screws

This study investigated whether there is a direct correlation between the level of vertical misfit at the abutment/implant interface and torque losses (detorque) in abutment screws. A work model was obtained from a metal matrix with five 3.75 x 9 mm external hex implants with standard platform (4.1 mm). Four frameworks were waxed using UCLA type abutments and one-piece cast in commercially pure titanium. The misfit was analyzed with a comparator microscope after 20 Ncm torque. The highest value of misfit observed per abutment was used. The torque required to loose the screw was evaluated using a digital torque meter. The torque loss values, measured by the torque meter, were assumed as percentage of initial torque (100 percent) given to abutment screws. Pearson's correlation (α=0.05) between the misfit values (29.08 ± 8.78 µm) and the percentage of detorque (50.71 ± 11.37 percent) showed no statistically significant correlation (p=0.295). Within the limitations of this study, it may be concluded that great vertical misfits dot not necessarily implies in higher detorque values.

Este trabalho teve como objetivo correlacionar o nível de desajuste vertical pilar/implante a perda do torque aplicado (destorque). Um modelo de trabalho foi obtido a partir de uma matriz metálica com cinco implantes tipo hexágono externo (Titamax, Neodent, Curitiba, Brasil) com plataforma regular (4,1 mm). Sobre esta matriz, quatro infra-estruturas foram enceradas utilizando pilares tipo UCLA e fundidas em monobloco com titânio comercialmente puro (Tritan grau I, Dentaurum, Alemanha). Os desajustes foram analisados com um microscópio óptico comparador (Mytutoyo, Japão) após torque de 20 Ncm. O maior valor de desajuste observado por pilar foi utilizado. O valor do torque de desaperto, avaliado com um torquímetro digital (TQ-680, Instrutherm, Brasil), foi calculado em porcentagem do valor do torque inicial (100 por cento) dado aos parafusos protéticos. O teste de correlação de Pearson (p<0,05), entre os valores de desajuste (29,08 ± 8,78 µm) e as porcentagens da perda de torque (50,71 ± 11,37 por cento), não mostrou correlação estatisticamente significante (p=0,295) entre tais fatores. Dentro das limitações do estudo, pode ser concluído que não necessariamente grandes valores de desajustes verticais implicarão em grades perdas de torque.

Desajuste do pilar UCLA processado por diferentes laboratórios / UCLA abutment misfit machined by different laboratories

Objetivos: Avaliar o ajuste horizontal do pilar UCLA, após as etapas laboratoriais de fundição e solda, processado por três diferentes laboratórios de prótese dentária. Métodos: Quatro próteses fixas foram confeccionadas por cada laboratório, utilizando-se os pilares do tipo UCLA. A avaliação foi a partir de fotografias obtidas através do microscópio eletrônico de varredura. Resultados e Conclusão: As mudanças ocorridas no ajuste horizontal das infra-estruturas justificam análise cuidadosa, devido a um possível estresse mecânico estar sendo gerado nos parafusos de retenção. As etapas laboratoriais de fundição e solda podem alterar o ajuste entre pilar e implante, independente do laboratório utilizado, logo, estudos subseqüentes variando o tipo de união das infra-estruturas devem ser realizados, para verificar a ocorrência ou não de mudanças nos valores do ajuste/desajuste horizontal

Estudo comparativo dos métodos de avaliação do desajuste vertical na interface pilar/implante / Comparative study of evaluation methods of vertical misfit in abutment/implant interface

Alguns trabalhos avaliam o desajuste vertical na interface pilar/implante por meio do teste do parafuso único, enquanto outros aplicam torque nos parafusos antes da avaliação. Este trabalho objetiva avaliar se estas duas metodologias geram diferentes interpretações dos resultados quanto ao nível de ajuste vertical das infra-estruturas. Com a utilização depilares do tipo UCLA calcináveis (Neodent, Brasil), quatro infra-estruturas de cinco elementos foram confeccionadas sobre modelo de gesso obtido a partir de matriz metálica contendo cinco implantes do sistema Brånemark (3,75X9mm,Neodent, Brasil) e em seguida foram fundidas em monobloco em titânio comercialmente puro (grau I, Talladium, Brasil). Por meio de microscópio óptico comparador (Mytutoyo, Japão) sob aumento de 30x, avaliou-se o desajuste vertical na interface pilar/implante de cada pilar da infra-estrutura, inicialmente pelo teste do parafuso único e posteriormente aoaperto de todos os parafusos, com torque de 20Ncm obtido por meio de torquímetro manual (Neodent, Brasil). A partir do modelo de gesso, confeccionou-se modelo fotoelástico para avaliação de possíveis tensões geradas após os apertos dos parafusos. Submeteu-se os resultados à análise estatística (P<0,05). O teste t mostrou diferença estatisticamente significante (P=0,000) entre o desajuste no lado desapertado verificado após o teste do parafuso único (472,49±109,88μm)e após o aperto de todos os parafusos (29,09±13,24μm). A fotoelasticidade mostrou grande quantidade de tensão gerada ao redor dos implantes após o aperto dos parafusos (11,38±8,27KPa). Conclui-se que a metodologia utilizada na verificação dos desajustes verticais pode gerar diferentes interpretações quanto ao nível de desajuste vertical de infraestruturas para próteses sobre implantes.