Avaliação das distribuições de tensões e deformações geradas por forças oclusais em implantes, abutments de base de titânio e no tecido ósseo, sob carga oclusal imediata e precoce

Abstract

The use of prostheses on implants with immediate occlusal loading has the advantages: only one surgical stage, no need for reopening surgery, the better conformation of the marginal gingival tissue and obtaining the most appropriate emergence profile, greater comfort for the patient due to the functional reestablishment of mastication and maintenance of the occlusal space. However, in single posterior regions, immediate occlusal loading has not been fully indicated due to the risks of bone loss and occasional dental implant failure. The aim of this study was to compare the distribution of stresses and strains generated in abutments and their retaining screws, in bone tissue and in dental implants under immediate (CI, up to two weeks after implant placement) and early (CP, between two weeks and three months after implant placement) occlusal loading. weeks to three months after implant placement), subjected to functional occlusal forces, of a lower first molar, using the Finite Element Method. Morse taper implant, 3.8 mm in diameter and 13 mm in height, and a titanium base-type abutment, 3.5 mm in diameter, 4 mm in height for cementation and 2 mm in transmucosal height were obtained by S.I.N. Implants. A computed tomography scan was performed to obtain the bone tissue and provisional crown, the latter considered of polymethylmethacrylate (PMMA), with 8.66 mm in occlusal-gingival height, 10.01 mm in mesio-occlusal width and 9.04 mm in buccal-occlusal width. The models were obtained after processing the images using the Mimics Innovation Suite software and its 3-Matic extension. To simulate the bone tissue, the Voigt method was used, and a surface of 0.55 mm of the alveolus around the dental implant had its modulus of elasticity altered according to the value obtained by this method, based on in vivo studies of the concentration of cells during the healing phases at the implant site. The healing process of the newly extracted socket also had its modulus altered through the law of mixtures by Voigt's method. The contact between the structures of the model was considered united. An occlusal load in an axial direction (at three points on the tooth, on the inner face of the mesiolingual and distobuccal cusp and on the outer face of the mesiobuccal cusp, for the CI-DA and CP-DA groups) and an oblique load (45o on the inner face of the lingual cusps, for the CI-DO and CP-DO groups) were simulated, through a functional load of 100 N, with a duration of 1 second. The risk of bone loss was assessed using Frost's mechanostat. There was a higher concentration of deformations in the regions of healing and osseointegration, alveolus, cortical bone tissue closes to the cervical region, with a higher concentration of deformations in the group that underwent DO loads. The risk of bone loss was higher in the CI-DA and CI-DO groups in the socket region and region of healing and osseointegration. Immediate occlusal loading on single implants in the posterior region may present a risk of bone loss, which may be related to physiological marginal bone loss.