ABSTRACT
PURPOSE: To analyze the stress distribution and the direction of force in external hexagonal implant with crown in three different angulations. MATERIALS AND METHODS: A total of 60 samples of geometric models were used to analyze von Mises stress and direction of force with 0-, 5-, and 10-degree lingual tilt. Von Mises stress and force distribution were evaluated at nodes of hard bone, and finite element analysis was performed using ANSYS 12.1 software. For calculating stress distribution and force, we categorized and labeled the groups as Implant A1, Implant A2, and Implant A3, and Implant B1, Implant B2, and Implant B3 with 0-, 5-, and 10-degree lingual inclinations, respectively. Inter- and intra-group comparisons were performed using ANOVA test. A p-value of ≤0.05 was considered statistically significant. RESULTS: In all the three models, overall maximum stress was found in implant model A3 on the implant surface (86.61), and minimum was found on model A1 in hard bone (26.21). In all the three models, the direction of force along three planes was maximum in DX (0.01025) and minimum along DZ (0.002) direction with model B1. CONCLUSION: Maximum von Mises stress and the direction of force in axial direction was found at the maximum with the implant of 10 degrees angulation. Thus, it was evident that tilting of an implant influences the stress concentration and force in external hex implants.
Subject(s)
Crowns , Software , Finite Element Analysis , Stress, MechanicalABSTRACT
PURPOSE: The purpose of this study is to evaluate the stability of interface between Co-Cr-Mo (CCM) UCLA abutment and external hex implant. MATERIALS AND METHODS: Sixteen external hex implant fixtures were assigned to two groups (CCM and Gold group) and were embedded in molds using clear acrylic resin. Screw-retained prostheses were constructed using CCM UCLA abutment and Gold UCLA abutment. The external implant fixture and screw-retained prostheses were connected using abutment screws. After the abutments were tightened to 30 Ncm torque, 5 kg thermocyclic functional loading was applied by chewing simulator. A target of 1.0 × 106 cycles was applied. After cyclic loading, removal torque values were recorded using a driving torque tester, and the interface between implant fixture and abutment was evaluated by scanning electronic microscope (SEM). The means and standard deviations (SD) between the CCM and Gold groups were analyzed with independent t-test at the significance level of 0.05. RESULTS: Fractures of crowns, abutments, abutment screws, and fixtures and loosening of abutment screws were not observed after thermocyclic loading. There were no statistically significant differences at the recorded removal torque values between CCM and Gold groups (P>.05). SEM analysis revealed that remarkable wear patterns were observed at the abutment interface only for Gold UCLA abutments. Those patterns were not observed for other specimens. CONCLUSION: Within the limit of this study, CCM UCLA abutment has no statistically significant difference in the stability of interface with external hex implant, compared with Gold UCLA abutment.
ABSTRACT
PURPOSE: The purpose of this study is to evaluate the stability of interface between Co-Cr-Mo (CCM) UCLA abutment and external hex implant. MATERIALS AND METHODS: Sixteen external hex implant fixtures were assigned to two groups (CCM and Gold group) and were embedded in molds using clear acrylic resin. Screw-retained prostheses were constructed using CCM UCLA abutment and Gold UCLA abutment. The external implant fixture and screw-retained prostheses were connected using abutment screws. After the abutments were tightened to 30 Ncm torque, 5 kg thermocyclic functional loading was applied by chewing simulator. A target of 1.0 × 10⁶ cycles was applied. After cyclic loading, removal torque values were recorded using a driving torque tester, and the interface between implant fixture and abutment was evaluated by scanning electronic microscope (SEM). The means and standard deviations (SD) between the CCM and Gold groups were analyzed with independent t-test at the significance level of 0.05. RESULTS: Fractures of crowns, abutments, abutment screws, and fixtures and loosening of abutment screws were not observed after thermocyclic loading. There were no statistically significant differences at the recorded removal torque values between CCM and Gold groups (P>.05). SEM analysis revealed that remarkable wear patterns were observed at the abutment interface only for Gold UCLA abutments. Those patterns were not observed for other specimens. CONCLUSION: Within the limit of this study, CCM UCLA abutment has no statistically significant difference in the stability of interface with external hex implant, compared with Gold UCLA abutment.
Subject(s)
Crowns , Fungi , Mastication , Prostheses and Implants , TorqueABSTRACT
O afrouxamento dos parafusos protéticos é descrito na literatura como uma das complicações mais frequentes das próteses sobre implantes. Durante sua confecção, os profissionais sentem necessidade de remover várias vezes as próteses e/ou componentes protéticos, soltando e re-apertando os parafusos repetidamente. O principal objetivo deste trabalho foi avaliar a variação do torque de remoção de parafusos de fixação de pilares protéticos a implantes osteointegráveis após sucessivos ciclos de parafusamento e desparafusamento. Outro objetivo foi avaliar a influência do hexágono da base do pilar no torque de remoção dos parafusos. Para isso, foram utilizados 20 implantes de plataforma regular com hexágono externo e 20 pilares protéticos sextavados, que foram parafusados aos implantes com um parafuso de titânio, aplicando-se a este um torque de 32Ncm, por meio de um torquímetro digital. Os conjuntos implante/pilar/parafuso foram divididos em dois grupos: (1) pilares cujo hexágono da base foram removidos e (2) pilares convencionais, com hexágono na base. Cada conjunto recebeu uma restauração provisória e foi submetido a ciclagem mecânica por 15 minutos. Depois, os parafusos foram removidos, medindo-se o torque de remoção. Esta sequência foi repetida dez vezes e então o parafuso foi trocado por outro sem uso, e mais um ciclo foi realizado. Uma análise de regressão linear demonstrou nos dois grupos uma queda do torque de remoção do parafuso ao longo dos repetidos ciclos de inserção/remoção. A comparação entre os coeficientes da regressão nos dois grupos não revelou diferença entre eles. Também não houve diferença entre as médias das 5 últimas repetições e o 11° ciclo, com o parafuso novo. Concluiu-se que (1) repetidos parafusamentos e desparafusamentos promoveram a diminuição progressiva do torque de remoção dos parafusos, (2) a troca do parafuso por outro sem uso após dez ciclos de inserção/remoção não aumentou sua resistência ao afrouxamento, e (3) a remoção ...
Screw loosening is one of the most common problems of implant-retained prostheses. During their confection, dentists need to remove and re-install them several times, loosening and re-tightening the screws repeatedly. The first purpose of this study was to evaluate the effects of repeated insertion/removal cycles on the removal torque of retaining prosthetic screws. The second purpose was to evaluate the influence of the hexagon of the abutment on the removal torque. For that, 20 regular external hex implants were used and 20 hexagonal abutments were tightened to the implants with a titanium alloy screw, with an insertion torque of 32Ncm, given by a digital torque gauge. The implant/abutment/screw assemblies were divided into two groups: (1) abutments with no hexagon on the base and (2) abutments with an hexagon on the base. Each assembly received a provisional restoration and was submitted to mechanical loading cycles for 15 minutes. After this, the screws were removed and the removal torque measured. This sequence was repeated ten times and then, the screw was changed for a new one, and another cycle was done. Linear regression analysis was performed and showed that removal torque values tended to decrease as the number of insertion/removal cycles increased, for both groups. Comparisons of the slopes and the intercepts between the two groups showed no statistic difference between them. There was also no difference between the mean values of last 5 cycles and the 11th cycle. It was concluded that (1) repeated insertion/removal cycles promoted gradual reduction in removal torque of screws, (2) changing screw by a new one after ten insertion/removal cycles did not increase resistance to loosening, and (3) removal of the hexagon of the abutment base had no effect on the removal torque of the screw.
Subject(s)
Dental Prosthesis, Implant-Supported , Torque , Linear Models , TitaniumABSTRACT
O sucesso da osseointegração está intimamente relacionado ao ajuste passivo entre os componentes utilizados e à precisão de adaptação da prótese instalada sobre os implantes. Quando os sistemas de implantes possuem um bom grau de padronização de usinagem existe a possibilidade de intercambiar seus componentes, de acordo com a necessidade, sem prejuízo para a conexão protética. O objetivo desta investigação foi avaliar o grau de liberdade entre os hexágonos dos implantes e abutments das empresas 3i, Implamed e Nobel Biocare, analisando: 1) as diferenças entre as medidas lineares das faces opostas dos implantes e abutments; 2) as diferenças entre as medidas lineares dos ângulos opostos dos implantes e abutments nos sistemas avaliados. A metodologia envolveu imagens obtidas através da microscopia eletrônica de varredura analisadas por um programa computadorizado específico. Através da análise de variância com nível de significância de 5% e teste de Tuckey para comparações múltiplas pôde-se observar que: 1) para as diferenças entre as medidas lineares das faces opostas dos hexágonos dos implantes e dos abutments houve diferença estatisticamente significante entre os grupos Nobel e Implamed, tendo o grupo Nobel os melhores resultados; 2) para as diferenças entre as medidas lineares dos ângulos opostos dos hexágonos dos implantes e dos abutments, o grupo Implamed diferiu dos demais, com os piores resultados.
The success of osseointegration is closely related to passive fit among the components employed and accurate fit of the implant-supported prosthesis. Implant systems with good machining standardization allow exchange of components according to the needs, without damage to the prosthetic connection. This study aimed to evaluate the degree of freedom among hexagons of implants and abutments fabricated by 3i, Implamed and Nobel Biocare, by analysis of: 1)differences among linear measurements of opposite aspects of implants and abutments 2) differences among linear measurements of opposite angles of implants and abutments in these systems. The metodology comprised analysis of scanning electron microscopy images by a specific computer software. Analysis of variance and the Tukey test for multiple comparisons at a significance level of 5% revealed the following: 1) there were statistically significant differences in linear measurements of opposite aspects of hexagons of implants and abutments between Nobel and implamed, with better results for the Nobel system; 2) concerning the differences among linear measurements of opposite angles of hexagons of implants and abutments, the Implamed system was different from the others, presenting the worst results.
