Efeito de fatores combinados na tensão e perda óssea peri-implantar: análise de elementos finitos e estudo observacional longitudinal.

Abstract

The dental implants have often been used for the prosthetic rehabilitation of edentulous areas due to the excellent esthetic, biologic, and functional results associated with the high success rate for this treatment. However, the maintenance of initial stability obtained with osseointegration depends on factors acting synergistically and include the occlusal, peri-implant, and implant-prosthetic characteristics. The present study was divided into two chapters. In Chapter 1 the finite element analysis (FEA) assessed the influence of the antagonist occlusal material (teeth; occlusal splint), implant length and insertion depth (9mm at equicrestal; 11mm at 2mm subcrestal) on stress distribution in peri-implant bone tissues and implant-abutment connection for normal and parafunctional occlusal forces. The Chapter 2 reports an observational longitudinal study that assessed the influence of occlusal, peri-implant and implantprosthetic factors on implant marginal bone loss (MBL). Considering the 3 described variables, 8 models were constructed for the FEA. Each model was composed of a mandibular bone section including the second premolar, first and second molar. At the first molar, equicrestal and 2-mm subcrestal implant insertion depths were simulated. The antagonist arch was simulated based on three natural maxillary teeth crowns with and without the occlusal splint interposition. Normal (200N) and parafunctional occlusal forces (1000N) were applied, increasing 10% of the full loading per second, until 10 seconds. von Mises stresses and maximum principal stresses were analyzed for titanium components and peri-implant bone tissues, respectively. Stress was mainly concentrated in the abutment-implant and implant-bone interfaces. Models loaded with parafunctional forces and without acrylic resin occlusal splint showed the highest stresses values. Occlusal splint changed the pattern of stress distribution and decreased stress levels for all structures assessed, except in the trabecular bone. Subcrestal insertion of the 9-mm implant provided reduced stress in the implant-abutment interface and coronal bone crest, while increased the stress in the implant-bone interface. In the observational study, 33 individuals with 109 cone morse implants were evaluated. Implants were radiographically examined at surgery and 12 months after prosthesis loading. Implant-prosthetic, peri-implant, and occlusal factors were assessed clinically at one month and 12 months after prosthesis loading. Independent variables were analyzed by decision tree analysis using the classification and regression tree and Chi-squared automatic interaction detection. Two-levels multilevel mixed effect analysis was used to estimate predictive values of each analytical model (α= 0.05). Highest levels of MBL were found for cement-retained prosthesis, platform diameter of 3.5mm, papilla sizes up to 2mm, keratinized gingival width up to 3mm, implant lengths above 8.5mm, inadequate occlusal pattern, presence of bleeding on probing and deeper pocket. Even though implant-related data appeared more frequently associated with MBL in the first level, peri-implant and occlusal-related factors also influenced.