ABSTRACT
Aim: In dental implant treatment, there is a demand for mechanically stronger implants. Despite the existence of several studies showing the clinical success of narrow diameter implants, most of them are based on pure titanium (cpTi) alloys. There is a few clinical evidences of the success rate of titanium-zirconium (TiZr) narrow diameter implants. The aim of this study was to evaluate the stress distribution in the peri-implant area of narrow diameter cpTi and TiZr implants under axial and oblique loads. Methods: Photoelastic models were produced using epoxy resin (PL2, Vishay Precision Group) from a master model. The implants (cpTi and TiZr; Straumann AG) had 3.3 mm in diameter and 12 mm in height. Loads of 100 N and 200 N were applied to the abutment at angles of 0° (axial), 10°, 20°, and 30° (oblique). A circular polariscope (Eikonal) was used under dark field white-light configuration. The isochromatic fringes were analyzed in the peri-implant region in 5 areas, using ASTM table with isochromatic fringes; cervical-mesial, cervical-distal, mid-mesial, mid-distal and apical. Results: In general, under axial and oblique loads, the stress in the TiZr implant was lower than in the cpTi implant. The load of 200 N produced the highest stress values in cpTi and TiZr implants. In both implants and loads, the fringes were located more in apical area at all angles evaluated. Conclusion: It can be concluded that for small implants, the load inclination and intensity change the pattern of stress distribution and the cpTi implant exhibited the highest peri-implant stress
Subject(s)
Stress, Mechanical , Titanium , Dental Implants , Dental Stress AnalysisABSTRACT
Se forças oclusais excederem a capacidade de absorção do sistema implante/osso, o implante tende a fracassar. O objetivo deste estudo foi avaliar a tensão peri-implantar com e sem utilização de placa oclusal plana sob carregamentos diferentes. Materiais e Métodos: Foram confeccionados cinco modelos fotoelásticos, com um implante em cada. Sobre estes implantes foram instaladas coroas unitárias e construída uma placa oclusal plana. Foram aplicadas cargas axiais de 100N, 200N e 300N, com e sem a presença da placa oclusal plana, por meio da máquina universal de ensaio conjugada ao polariscópio. O teste de Mann-Whitney foi utilizado para comparar os grupos com e sem placa, em todas as condições de carregamento. O teste de Kruskal-Wallis foi utilizado para comparar as tensões decorrentes das cargas de 100, 200 e 300N e também para comparar as tensões nas seis áreas periimplantares analisadas. Resultados: Os resultados dos testes de Mann-Whitney não identificaram diferenças estatísticas (p>0,05) ao comparar as ordens de franjas com e sem a utilização de aparelho oclusal plano, em todas as áreas periimplantares analisadas, sob cargas verticais de 100, 200 e 300N. Os resultados dos testes de Kruskal-Wallis indicaram tensões significativamente maiores nas regiões apicais (p<0,05) e que nas áreas apicais as tensões foram maiores com o carregamento de 300N (p<0,05). Conclusões: A utilização da placa oclusal plana sobre a prótese unitária não reduziu significativamente as tensões nas regiões periimplantares; as tensões tendem a se concentrarem na região periapical e nestas áreas a maior magnitude de força implicou em maior tensão...
Introduction: If occlusal forces exceed the capacity of the implant/bone system, the implant tends to fail. The aim of this study was to evaluate the peri-implant stress with and without use of flat occlusal splint under various loads. Materials and Methods: Five photoelastic models were made with an implant in each. About these implants crowns were installed and built a flat occlusal splint. Axial loads of 100N, 200N and 300N, with and without the presence of the occlusal plane plate, were applied by universal testing machine conjugate to the polariscope. The Mann-Whitney test was used to compare the groups with and without plate, in all conditions of loading. The Kruskal-Wallis test was used to compare the stresses resulting from loads of 100, 200 and 300N and also to compare the peri-implant stresses in the six areas analyzed. Results: The results of Mann-Whitney tests identify no significant differences (p> 0.05) comparing fringe orders with and without the use of flat occlusal appliance, in all peri-implant areas examined under vertical loads 100, 200 and 300N. The results of Kruskal-Wallis tests indicated significantly higher stress in the apical regions (p <0.05) and in the apical areas stresses were higher with the loading of 300N (p <0.05). Conclusions: The use of flat occlusal splint on the unitary prosthesis did not significantly reduce the stress in the peri-implant regions; stress tend to concentrate on the periapical region and in these areas the largest magnitude of force resulted in higher stress...
Subject(s)
Biomechanical Phenomena , Dental Implants , Dental Implantation/methods , Occlusal Splints , Materials Testing , Reference Values , Reproducibility of Results , Statistics, Nonparametric , Weight-BearingABSTRACT
OBJECTIVE: To compare dental and skeletal anchorages in mandibular canine retraction by means of a stress distribution analysis. METHODS: A photoelastic model was produced from second molar to canine, without the first premolar, and mandibular canine retraction was simulated by a rubber band tied to two types of anchorage: dental anchorage, in the first molar attached to adjacent teeth, and skeletal anchorage with a hook simulating the mini-implant. The forces were applied 10 times and observed in a circular polariscope. The stresses located in the mandibular canine were recorded in 7 regions. The Mann-Whitney test was employed to compare the stress in each region and between both anchorage systems. The stresses in the mandibular canine periradicular regions were compared by the Kruskal-Wallis test. RESULTS: Stresses were similar in the cervical region and the middle third. In the apical third, the stresses associated with skeletal anchorage were higher than the stresses associated with dental anchorage. The results of the Kruskal-Wallis test showed that the highest stresses were identified in the cervical-distal, apical-distal, and apex regions with the use of dental anchorage, and in the apical-distal, apical-mesial, cervical-distal, and apex regions with the use of skeletal anchorage. CONCLUSIONS: The use of skeletal anchorage in canine retraction caused greater stress in the apical third than the use of dental anchorage, which indicates an intrusive component resulting from the direction of the force due to the position of the mini-implant and the bracket hook of the canine. .
OBJETIVO: comparar as ancoragens dentária e esquelética na retração do canino inferior, por meio do estudo da distribuição de tensões. MÉTODOS: foi confeccionado um modelo fotoelástico de segundo molar a canino, sem o primeiro pré-molar, e simulada a retração do canino inferior com elástico preso a dois tipos de ancoragem: dentária, no primeiro molar conjugado aos dentes adjacentes; e ancoragem esquelética, em gancho simulando o mini-implante. As forças foram aplicadas 10 vezes e observadas no polariscópio circular. As tensões no canino inferior foram registradas em 7 regiões. O teste de Mann-Whitney foi aplicado para comparar as tensões em cada região, considerando os dois sistemas de ancoragem. As tensões nas regiões perirradiculares do canino foram comparadas pelo teste de Kruskal-Wallis. RESULTADOS: as tensões foram similares tanto na região cervical quanto no terço médio. No terço apical, as tensões associadas à ancoragem esquelética foram maiores que as tensões associadas à ancoragem dentária. Os resultados do teste de Kruskal-Wallis mostraram que as maiores tensões foram identificadas nas regiões cervicodistal, apicodistal e na região do ápice com o uso da ancoragem dentária; e com o uso da ancoragem esquelética, as maiores tensões se localizaram nas regiões apicodistal, apicomesial, cervicodistal e no ápice. CONCLUSÃO: o uso de ancoragem esquelética na retração promoveu maior tensão no terço apical do que o uso da ancoragem dentária, indicando um componente intrusivo devido à direção da força decorrente da posição do mini-implante e do gancho do braquete do canino. .
Subject(s)
Humans , Cuspid/pathology , Orthodontic Appliance Design , Orthodontic Anchorage Procedures/instrumentation , Tooth Movement Techniques/instrumentation , Biomechanical Phenomena , Dental Implants , Models, Dental , Mandible , Molar/pathology , Orthodontic Brackets , Orthodontic Wires , Orthodontic Anchorage Procedures/methods , Orthodontic Space Closure/instrumentation , Stress, Mechanical , Tooth Apex/pathology , Tooth Cervix/pathology , Tooth Root/pathologyABSTRACT
The aim of this study was to evaluate the effect of different curing methods on the stress generated by the polymerization shrinkage of a restorative composite in two moments: immediately after light exposure and after 5 min. Photoactivation was performed using two different light sources: (1) xenon plasma arc (PAC) light (1,500 mW/cm2 - 3s) and (2) a quartz-tungsten-halogen (QTH) light with three light-curing regimens: continuous exposure (40 s at 800 mW/cm2 - CL); soft-start (10 s at 150 mW/cm2 and 30 s at 800 mW/cm2 - SS) and intermittent light [cycles of 4 s (2 s with light on at 600 mW/cm2 and 2 s of light off), for 80s - IL]. The composite resin was applied between two 5-mm diameter metallic rods, mounted in a servohydraulic machine. The maximum stress was recorded immediately after light exposure (FF) and after 5 min (5F). The results were submitted to ANOVA and Tukey's test (5 percent). For each method, the results obtained in FF and 5F were, respectively: CL (3.58 and 4.46 MPa); SS (2.99 and 4.36 MPa); IL (3.11 and 4.32 MPa) and PAC (0.72 and 3.27 MPa). The stress generated by the polymerization shrinkage during light exposure can be associated with the photoactivation method used. A significant increase in the stress level was observed during the post-curing period up to 5 min, for all evaluated methods.