Mechanobiological analysis of rat root tissue with occlusal trauma

Orientador: Felippe Bevilacqua PradoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de PiracicabaResumo: O dente e o periodonto são continuamente submetidos a forças mecânicas capazes de estimular processos de remodelação óssea. Entretanto, sobrecargas mecânicas direcionadas aos tecidos periodontais podem promover alterações patológicas, como perda óssea e reabsorção radicular. Com o objetivo de avaliar a resposta mecanobiológica do tecido dental radicular, em primeiro molar inferior de ratos, submetidos à condição experimental de trauma oclusal dental, foram utilizados quinze ratos machos Wistar, aleatoriamente, divididos em dois grupos, sendo um grupo experimental (n=10) e outro o controle (n=5). O grupo experimental recebeu um dispositivo de resina e fragmento de fio ortodôntico em primeiro molar superior direito, para estabelecer condição de trauma oclusal. O grupo experimental foi divido em dois subgrupos, conforme a data da eutanásia, que foi de 7 dias (n=5) e de 14 dias (n=5), após a instalação do dispositivo de trauma. O grupo controle não foi submetido à trauma oclusal e seus indivíduos foram eutanasiados no 14º dia, juntamente com um subgrupo experimental. Foram obtidas amostras histológicas dos primeiros molares inferiores direitos e do periodonto dos ratos. Foi construído o modelo de elementos finitos para simulação de sobrecarga oclusal (40 N) e para simulação de oclusão normal (20 N). Os resultados demonstraram compatibilidade no padrão de reabsorção radicular externa da análise histológica e a análise com elementos finitos. As áreas de cemento mais afetadas foram em região de furca e de raiz distal de primeiros molares inferiores direitos, no grupo experimental. No grupo controle não houve alteração significativa. A presente avaliação mecanobiológica comparativa entre os achados da análise de elementos finitos e os achados histológicos mostram semelhanças entre áreas afetadas pelas deformações, computacionalmente, simuladas e as áreas de reabsorção radicular externa. Além das sobrecargas oclusais, outras variáveis como a morfologia raiz do dente e os movimentos mandibulares parecem interferir nas respostas biomecânicasAbstract: Tooth and periodontium are continuously subjected to mechanical forces capable of stimulating processes of bone remodeling. However, mechanical overloads directed to the periodontal tissues can promote pathological alterations, such as bone loss and root resorption. In order to evaluate the mechanobiological response of dental root tissue in the first molar of rats submitted to the experimental condition of occlusal dental trauma, fifteen male Wistar rats were randomly divided into two groups, an experimental group (n=10) and the control group (n=5). A set of resin and fragment of orthodontic wire was placed in the upper right first molar of each rat of the experimental group, in order to establish occlusal trauma condition. The experimental group was divided into two subgroups, according to the date of euthanasia, which was 7 days (n=5) and 14 days (n=5), after the installation of the traumatic device. The control group was not submitted to occlusal trauma and their subjects were euthanized on the 14th day, together with an experimental subgroup. Histological samples were obtained from the lower right first molars and the periodontium of the rats. The finite element model was used to simulate occlusal overload (40 N) and to simulate normal occlusion (20 N). The results demonstrated compatibility between the pattern of histological external root resorption and the finite element analysis. The most affected areas were furcation region and distal root cementum of lower right first molars, in the experimental group. There was no significant change in the control group. The present comparative mechanobiological evaluation between the findings of the finite element analysis and the histological findings shows similarities between areas affected by high compressive strains, computationally, simulated and the areas of external root resorption. In addition to occlusal overloads, other variables such as tooth root morphology and mandibular movements may interfere with biomechanical responsesDoutoradoAnatomiaDoutor em Biologia Buco-Dental1443261CAPE

Comparison of gunshot entrance morphologies caused by .40-caliber Smith & Wesson, .380-caliber, and 9-mm Luger bullets: a finite element analysis study.

Firearms can cause fatal wounds, which can be identified by traces on or around the body. However, there are cases where neither the bullet nor gun is found at the crime scene. Ballistic research involving finite element models can reproduce computational biomechanical conditions, without compromising bioethics, as they involve no direct tests on animals or humans. This study aims to compare the morphologies of gunshot entrance holes caused by.40-caliber Smith & Wesson (S&W), .380-caliber, and 9×19-mm Luger bullets. A fully metal-jacketed.40 S&W projectile, a fully metal-jacketed.380 projectile, and a fully metal-jacketed 9×19-mm Luger projectile were computationally fired at the glabellar region of the finite element model from a distance of 10 cm, at perpendicular incidence. The results show different morphologies in the entrance holes produced by the three bullets, using the same skull at the same shot distance. The results and traits of the entrance holes are discussed. Finite element models allow feasible computational ballistic research, which may be useful to forensic experts when comparing and analyzing data related to gunshot wounds in the forehead

The finite element skull model: (A) FE model meshed with small tetrahedral elements particularly in the glabellar region.

<p>(B) Right view of the 3D-FE model.</p

Morphologies of the entrance holes caused by the three computational gunshots.

<p>(A) Irregular round entrance hole (FMJ FP.40 S&W); (B) Irregular triangular entrance hole (FMJ RN 9×19-mm Luger); (C) Irregular triangular entrance hole (FMJ RN.380). Note that the wound seen in B exhibits an intermediate shape between those seen in A and C.</p

Properties of the materials used in the finite element models.

<p>Properties of the materials used in the finite element models.</p

von Mises stress values in the glabellar region for each shot.

<p>(A) FMJ FP.40 S (B) FMJ RN 9×19-mm Luger; (C) FMJ RN.380.</p

Number and average size of elements used in the finite element models (skull, ballistic impact area and bullets).

<p>Number and average size of elements used in the finite element models (skull, ballistic impact area and bullets).</p

Refined mesh of the skull model.

<p>(A) Frontal view of the refined mesh in the ballistic impact area (glabellar region). (B) Internal view of the anterior cranial fossa with refined mesh in frontal bone and ethmoid bone (yellow arrow points to ethmoidal crest and red arrow points to cribiform plate).</p

Values of von Mises stress (MPa) for each shooting simulation.

<p>Values of von Mises stress (MPa) for each shooting simulation.</p