A variety of pathologies exist which increase the likelihood of bone fracture. Present methods for determining the fracture risk of a specific patient are based exclusively on the amount of bone present. While the quantity of bone tissue is correlated with strength, it neglects to account for bone’s intricate microarchitecture. To assess the effect of bone quality on strength, a methodology was developed for the structural analysis of cancellous bone biopsies. Thirty biopsies were selected from a pre-existing biopsy bank, and scanned using a SCANCO µCT-40 at a resolution of 30 microns. Cortical bone was removed from the resulting three-dimensional geometry, and the remaining cancellous bone was meshed with solid tetrahedral elements. A linear static uniaxial compression test was performed using ANSYS v14.0 to determine the apparent-level Young’s modulus. The maximum von Mises stress was also investigated, but showed poor convergence with increased mesh density. Consistent with the methodology of Pistoia et al., the failure load was assumed to occur when 2% of the bone volume exceeded 7000 µstrain. The results of the finite element analysis compared favorably with known values for cancellous bone strength.

Aims Preservation of peri-cervical dentin during the preparation of endodontic access is important to prevent fractures and improve the long-term prognosis. The purpose of this study was to evaluate the impact of rotary file instrumentation (TruNatomy and XP-Endo Shaper) on peri-cervical dentin removal, depending on access size. Materials and Methods Forty 3D printed mandibular first molars, with either a small or large access design, were instrumented using TruNatomy or XP-endo Shaper file systems. Canal volumes were calculated based on micro-computed tomography data obtained pre- and post-operatively. Digital sectioning of each reconstructed volume was performed 90-degrees to the long axis at the floor of the pulp chamber at 5 levels, at the pulp chamber floor (Level 0) as well as 1 and 2mm coronally and apically of Level 0. Linear measurements were taken from the inner wall of the access cavity or canal to the outer surface of the tooth for both instrumentation techniques and compared to the unprepared control dataset. These measurements served as an approximation of remaining peri-cervical dentin after root canal instrumentation. Results Some of the coronal measurements were not reportable for the control group due to incomplete capture of the crown during the microCT scan. The remaining peri-cervical dentin thickness at the level of the pulpal floor and coronally were significantly (p<0.01) affected by the access cavity size, with the smaller access preserving more dentin in all samples. Apical to the pulpal floor, there was no significant difference between instrumentation groups at the data points evaluated. Remaining dentin thickness was largest at coronal section 1 and smallest at apical section 6 with 3.81mm (p = 0.05) and 1.84mm (p = 0.06), respectively. Conclusion Access cavity size had a significant impact on remaining dentin thickness at the level of the pulpal floor and coronally, with more remaining dentin in the conservative access group, irrespective of instrumentation technique. Future studies will evaluate dentin thickness in the furcation and mid root level, as well as apical canal transportation, and procedural errors.

No description available.

Osteoarthritis is the most common form of arthritis. Genetic models have been developed to determine if and how a targeted gene may influence cartilage degenerative changes. The itga1-null mouse model has an inhibited integrin α1B1 through a ubiquitous integrin α1 subunit knockout, which leads to fibrosis in articular cartilage through excessive signalling from transforming growth factor beta (TGFB). Depleting this TGFB signalling is proposed to have a protective effect on cartilage. This project is part of a foregoing study where a cartilage-specific knockout of TGFB receptor type II (TBRII) was used to deplete TGFB signalling in articular cartilage of the itga1-null mice to reduce the severity of cartilage degradation. This project continues the analysis of the genetic model into bone architecture at the knee. Mouse hindlimbs were scanned at a 13μm resolution using micro-computed tomography and segmented into 3D datasets containing calcified tissues and bone of the knee and surroundings. Quantification methods for trabecular bone parameters (bone volume fraction, trabecular separation, and trabecular thickness) and ectopic calcification of soft tissues were developed. Loss of trabecular bone around the involved joint is a hallmark of post-traumatic osteoarthritis. However, the results from this study showed no significant changes in trabecular bone of itga1-null mouse knees despite observing severe osteoarthritic changes in the adjacent cartilage. There were no significant effects in peri-articular trabecular bone when the TBRII knockout in cartilage was activated, but there were significant increases in ectopic calcifications of the menisci and collateral ligaments. These ectopic calcifications were also seen in tamoxifen control mice, suggesting that tamoxifen, along with TBRII depletion in cartilage, had a role in increased abnormal calcifications. Although integrin α1B1 inhibition appears to have an important role in cartilage degeneration, it does not appear to influence the bony changes that normally accompany post-traumatic arthritis. / Thesis / Master of Applied Science (MASc) / Osteoarthritis is a common joint disorder, associated mainly with cartilage degradation. Some genes have been identified that cause or prevent osteoarthritis. A previous study used two of these genes in a genetic mouse model to explore how osteoarthritis may develop. Removing the integrin α1 subunit from mice caused osteoarthritic changes in the cartilage of the mouse knee. When the transforming growth factor beta gene was removed from the cartilage, these changes were less severe. This project continued the study by exploring changes in bone around the mouse knee. We quantified bone changes around the mouse knee using high-resolution micro-computed tomography scans. Contrary to common findings in post-traumatic osteoarthritis, we found that there were no significant changes in the bone around the knees even where severe cartilage changes had been identified. However, there were significant increases in calcifications of soft tissues including the meniscus and ligaments around the knee.

Multimodal image registration is essential when combining functional and structural imaging modalities. Among the most common combinations, numerous methods have been developed for co-registration of CT and PET, typically validated on human size scanners. However, only a few registration studies have been performed for the combination of small animal miniPET and microCT imaging. The Jonasson Center for Medical Imaging at KTH possesses an integrated miniPET/ microCT for pre-clinical research purposes. The motivation for this work is the need for the development of fusion method(s) for combining the data of these two modalities. In this work, a novel pipeline registration method, employing image processing and Mutual Information (MI) is proposed and implemented. The method starts with a pre-alignment step before acquisition of the miniPET/microCT volumes, followed by scaling, binarization and processing of the two volumes and finally, a registration procedure by Maximization of Mutual Information (MIM) as a voxel-based similarity metric. A established intrinsic landmarks based method is also implemented for comparison. For the validation of the methods, volumes acquired by in-house designed 3D printed Polyethylene (PE) phantoms, filled with multiple concentrations of FDG were used. The misalignment between corresponding points volumes after registration, is analyzed and compared in terms of absolute spatial distance. The proposed method based on 3D processed volumes outperformed the Landmarks based registration method, showing average misalignments of 0.5 mm. The registered volumes were also successfully visualized together using Alpha blending. By so, an automatic fusion method for miniPET/microCT has thus been implemented, presented and evaluated, raising prospects for multimodal imaging research at the Jonasson Center for Medical Imaging. / Kombinationen av funktionell och strukturell avbildning är vanlig inom medicinsk bildgivning, och koregistrering av bildvolymerna utgör en essentiell del i den multimodala framställningen. PET/CT-avbildning hör till de vanligast förekommande multimodala avbildningskombinationerna, och till följd av detta har ett antal koregistreringsmetoder utvecklats för just detta. Vad gäller pre-klinisk avbildning är dock validerade koregisteringsmetoder inte lika vanliga, och framförallt inom forskningsbaserad avbildning (där egendesignade scanners förekommer) är behovet av effektiva metoder tydligt. Inom Jonassons centrum för medicinsk avbildning på KTH har ett multimodalt miniPET/ microCT-system utvecklats, och det är just behovet av koregistering som utgjort basen för följande examensarbete. I följande arbete har en koregistreringsmetod baserad på fördefinierad bildbehandling och analys av gemensam information (mutual information, MI) implementerats och testats. Metoden bygger på ett initialt upplinjeringssteg innan microCT/ miniPET bildtagning. Efter detta genomförs en rad bildbehandlingssteg (skalning, binärisering) innan en slutgiltig koregistrering genomförs med hjälp av s.k. maximering av gemensam information (Maximization of Mutual Information, MIM). En etablerad landmärkesbaserad metod implementerades även som jämförelse. Metoderna testades sedan genom multimodal avbildning av egendesignade 3D-printade fantomer, fyllda med varierande aktivitet av FDG. Den föreslagna MI-metoden överträffade den etablerade landmärkesmetoden, med ett genomsnittligt koregistreringsfel på 0.5 mm. Visualisering av de koregistrerade volymerna genomfördes även genom så kallad alpha blending. Genom detta har en koregistreringsmetod för miniPET/microCT:n på Jonassons center för medicinsk avbildning implementerats och testats, vilket möjliggör för framtida studier av multimodal avbilning på KTH.

A movimentação dentária induzida é um processo biológico complexo mediado por estímulos mecânicos, levando a um subsequente processo de remodelação óssea, podendo haver reabsorção indesejada da raiz dentária provocada pelo excesso de força. Uma vez que a movimentação ortodôntica se baseia em um processo inflamatório localizado, o propósito deste estudo foi avaliar os efeitos do laser de baixa potência no processo de remodelação óssea e reabsorção radicular, buscando correlacionar as mudanças metabólicas observadas a nível celular ocorridas nos dias iniciais da movimentação dentária às alterações teciduais observadas microscopicamente e à arquitetura e morfologia do trabeculado e cortical ósseo. Primeiros molares de sessenta e oito ratos machos Wistar foram submetidos à movimentação induzida, divididos em 3 grupos: controle negativo (nenhuma movimentação), não irradiado (movimentação sem irradiação) e laser (movimentação e irradiação com laser de baixa potência de comprimento de onda de 810 nm, potência de 100 mW, área de 0,02cm2 e energia de 1,5 J/ponto) e eutanasiados nos dias 3, 6, 9, 14 e 21. Mensurações da movimentação dentária e análises histomorfométricas foram realizadas em todos os dias estudados. Análise imunoistoquímica dos marcadores RANKL, OPG e TRAP e avaliações por microscopia eletrônica de varredura (MEV) foram feitas nos dias 3, 6 e 9 e o ensaio Western Blotting para proteínas RANKL e SOFAT e imagens de microtomografia computadorizada (MicroCT) nos dias 14 e 21. Os resultados deste estudo mostraram que a movimentação dentária foi significantemente maior no grupo Laser (aumento em média de 40%) em todos os dias avaliados. O lado de compressão mostrou maior expressão de RANKL e osteoclastos TRAP-positivos nos dias 3, 6 e 9 (p<0,05), promovendo significativa redução na área de osso alveolar presente no lado de compressão nos dias 6, 9 e 14 (p<0,05), e alterações microestruturais, como menor fração de volume ósseo/volume total, menor densidade óssea mineral aos 14 dias. A irradiação com laser também aumentou a expressão de RANKL e a citocina SOFAT no dia 14. No lado de tensão, houve maior expressão de OPG especialmente aos 9 dias (p<0,001) e significativo aumento na área de osso alveolar presente nos dias 14 (p<0,01) e 21 (p<0,05) histomorfometricamente e maior densidade óssea mineral e espessura das trabéculas aos 21 dias (p<0,01). Com relação às áreas de hialinização presentes, os resultados mostraram áreas significantemente reduzidas nos dias 3, 6 e 9 nos grupos irradiados, o que explica o menor número de odontoclastos na superfície radicular nestes dias e a redução significante das áreas de reabsorção radicular observadas nas lâminas histológicas nos dias 9, 14 e 21 e nas imagens de MEV nos dias 3 e 9. Os grupos irradiados também mostraram menor volume das lacunas de reabsorção radicular medidas no MicroCT nos dias 14 e 21, especialmente nos lados de compressão. O estudo concluiu que o laser de baixa potência influenciou a remodelação óssea, aumentou a atividade dos osteoclastos no lado da compressão, e estimulou a formação óssea no de tensão, acelerando significativamente o movimento dentário e potencialmente reduzindo as áreas de necrose no ligamento periodontal e, consequentemente, a reabsorção radicular. / Tooth movement is a complex biological process induced by mechanical stimulation, leading to a subsequent process of bone remodeling, concomitantly unwanted root resorption may occur caused by excessive force. Since orthodontic movement is based on a localized inflammatory process, the purpose of this study was to evaluate the effects of low-level laser therapy on the process of bone remodeling and root resorption, searching to correlate metabolic changes observed at cellular level in the initial days of tooth movement to tissue changes observed microscopically and both architecture and morphology of trabecular and cortical bone. Upper first molars of sixtyeight male Wistar rats were submitted to induced movement, divided into 3 groups: negative control (no movement), non-irradiated (movement without irradiation) and Laser (movement and irradiation using low level laser of 810 nm wavelength, 100 mW power, 0.02cm2 area, energy of 1.5J/point) and euthanized on days 3, 6, 9, 14 and 21. Measurements of tooth movement and histomorphometric analysis were performed at all days. Immunohistochemistry analysis of RANKL, OPG and TRAP markers and scanning electron microscopy (SEM) were made on days 3, 6 and 9. Western Blotting method to evaluate RANKL and SOFAT proteins and MicroCT images were performed on days 14 and 21. The results of this study showed that tooth movement was significantly greater in the irradiated side (increased in average of 40%) in all evaluated days. The compression side showed higher expression of RANKL and TRAP-positive osteoclasts on days 3, 6 and 9 (p <0.05), promoting significant reduction in alveolar bone area in the compression side on days 6, 9 and 14 ( p <0.05), and leading to microstructural changes such as decrease of the fraction of bone volume / total volume (BV/TV) and the bone mineral density (BMD) at 14 days. The laser also increased RANKL expression and SOFAT on day 14. On the tension side there was an increased expression of OPG especially after 9 days (p <0.001), a significant increase in alveolar bone area on days 14 (p < 0.01) and 21 (p <0.05) histomorphometrically and increase in bone mineral density and trabecular thickness after 21 days (p <0.01). Regarding hyalinized areas, the results showed significant reduced areas on days 3, 6 and 9 in irradiated groups, which explains the lower number of clastic cells on the root surface in these days, and a significant reduction of areas of root resorption observed in histology on days 9, 14 and 21 and on days 3 and 9 by SEM images. Irradiated groups also showed less volume of root resorption lacunaes measured by MicroCT on days 14 and 21, especially in the compression side. The study concludes that the low-level laser therapy had an effect on bone remodeling, increasing osteoclast activity on the compression side, and stimulating bone formation in tension side, resulting in significant tooth movement acceleration and potentially reducing the areas of necrosis in the periodontal ligament and consequently the root resorption process.

Motivated by the need to standardize preclinical imaging for image-guided radiation therapy (IGRT), we examine the parameters that influence microcomputed tomography (microCT) scans in the realm of image quality and absorbed dose to tissue, including therapy beam measurements of small fields. Preclinical radiation research aims to understand radiation-induced effects in living tissues to improve quality of life. Small targets and low kilovoltage x-rays create challenges that do not arise in clinical radiation therapy. Evidence based on our multi-institutional study reveals a considerable aberration in microCT image quality from one institution to the next. We propose the adoption of recommended tolerance levels to provide a baseline for producing satisfactory and reproducible microCT image quality scans for accurate dose delivery in preclinical IGRT. Absorbed dose imparted by these microCT images may produce deterministic effects that can negatively influence a radiobiological study. Through Monte Carlo (MC) methods we establish absorbed microCT imaging dose to a variety of tissues and murine sizes for a comprehensive combination of imaging parameters. Radiation beam quality in the small confines of a preclinical irradiator is also established to quantify the effects of beam scatter on half-value layer measurements. MicroCT scans of varying imaging protocols are also compared for murine subjects. Absorbed imaging dose to tissues are established and presented alongside their respective microCT images, providing a visual bridge to systematically link image quality and imaging dose. We then characterize a novel small plastic scintillating dosimeter to experimentally measure microCT imaging and therapy beams in real-time. The presented scintillating dosimeter is specifically characterized for the low energies and small fields found in preclinical research. Beam output is measured for small fields previously only achievable using film. Finally, quality assurance tests are recommended for a preclinical IGRT unit. Within this dissertation, a narrative is presented for guiding preclinical radiotherapy towards producing high quality microCT images with an understanding of the absorbed imaging dose deposited to tissues, including providing a tool to measure small radiation fields. / Graduate

Depuis une dizaine d’années, l’essor des minivis d’ancrage orthodontique a été grandissant jusqu’à devenir, aujourd’hui, un outil incontournable dans l’arsenal thérapeutique de l’orthodontiste. Très peu d’études ont été publiées quant à la nature de la réponse tissulaire face à l’insertion et la mise en charge de ces minivis. De plus, une partie des patients concernés par l’orthodontie étant des adolescents, il serait intéressant de savoir si le tissu osseux en croissance est propice à l’utilisation de ces dispositifs. L’influence de la nature du matériau sur cette réaction tissulaire reste également à définir. L’objectif de cette étude a été d’évaluer la biointégration de deux systèmes de minivis orthodontiques présents sur le marché, l’un en acier chirurgical et l’autre en titane-aluminium-vanadium, en conduisant une analyse clinique, histomorphométrique et microtomographique chez le porc en croissance. Les résultats ont montré que la réponse osseuse se caractérise, dans un os en croissance peu compact, par un épaississement des travées osseuses au contact des dispositifs, probablement pour résister à la contrainte locale. Le tissu osseux en croissance permet la biointégration des minivis d’ancrage orthodontique, mais le taux de succès relativement faible observé implique l’adaptation des protocoles cliniques par une analyse préalable du ratio os trabéculaire/os cortical, une augmentation du délai avant mise en charge, et l’application de forces légères. La réponse tissulaire est similaire, quel que soit le système étudié. L’acier chirurgical, grandement utilisé en orthopédie, présente donc un intérêt en orthopédie dento-faciale, dans une indication temporaire / The miniscrew implants are increasingly used over the last decade in orthodontics and gradually replacing the use of extraoral forces because of their greater efficiency and because their effectiveness is not subject to patient compliance. Few studies seeking to understand the response to orthodontic anchorage devices at bone-tissue interface have been published over the last ten years. Despite the large use of miniscrews in teenagers, very few have included young subjects in their protocol. Furthermore, despite the use of stainless steel miniscrew implants, no studies have investigated biointegration of such devices. The aim of the present study was to evaluate tissue response to immediately loaded miniscrew implants (of Ti6Al4V and of stainless steel) in growing pigs in order to answer to the following questions: Is it possible to implant and load miniscrew implants in a growing bone? Does stainless steel devices present the same biointegration than titanium devices? A clinical evaluation, and histomorphometrical and micro-CT analyses were performed. Results showed that the growing bone seems compatible with the orthodontic anchorage. In the growing pig with low bone density areas, the trabecular thickness increase appears as the bone response to withstand the local strains induced by loaded orthodontic miniscrews. Stainless steel devices presented similar behavior to the Ti6Al4V devices in pigs. This study showed the possibility to place stainless steel miniscrew implants for orthodontic anchorage in growing models

A movimentação dentária induzida é um processo biológico complexo mediado por estímulos mecânicos, levando a um subsequente processo de remodelação óssea, podendo haver reabsorção indesejada da raiz dentária provocada pelo excesso de força. Uma vez que a movimentação ortodôntica se baseia em um processo inflamatório localizado, o propósito deste estudo foi avaliar os efeitos do laser de baixa potência no processo de remodelação óssea e reabsorção radicular, buscando correlacionar as mudanças metabólicas observadas a nível celular ocorridas nos dias iniciais da movimentação dentária às alterações teciduais observadas microscopicamente e à arquitetura e morfologia do trabeculado e cortical ósseo. Primeiros molares de sessenta e oito ratos machos Wistar foram submetidos à movimentação induzida, divididos em 3 grupos: controle negativo (nenhuma movimentação), não irradiado (movimentação sem irradiação) e laser (movimentação e irradiação com laser de baixa potência de comprimento de onda de 810 nm, potência de 100 mW, área de 0,02cm2 e energia de 1,5 J/ponto) e eutanasiados nos dias 3, 6, 9, 14 e 21. Mensurações da movimentação dentária e análises histomorfométricas foram realizadas em todos os dias estudados. Análise imunoistoquímica dos marcadores RANKL, OPG e TRAP e avaliações por microscopia eletrônica de varredura (MEV) foram feitas nos dias 3, 6 e 9 e o ensaio Western Blotting para proteínas RANKL e SOFAT e imagens de microtomografia computadorizada (MicroCT) nos dias 14 e 21. Os resultados deste estudo mostraram que a movimentação dentária foi significantemente maior no grupo Laser (aumento em média de 40%) em todos os dias avaliados. O lado de compressão mostrou maior expressão de RANKL e osteoclastos TRAP-positivos nos dias 3, 6 e 9 (p<0,05), promovendo significativa redução na área de osso alveolar presente no lado de compressão nos dias 6, 9 e 14 (p<0,05), e alterações microestruturais, como menor fração de volume ósseo/volume total, menor densidade óssea mineral aos 14 dias. A irradiação com laser também aumentou a expressão de RANKL e a citocina SOFAT no dia 14. No lado de tensão, houve maior expressão de OPG especialmente aos 9 dias (p<0,001) e significativo aumento na área de osso alveolar presente nos dias 14 (p<0,01) e 21 (p<0,05) histomorfometricamente e maior densidade óssea mineral e espessura das trabéculas aos 21 dias (p<0,01). Com relação às áreas de hialinização presentes, os resultados mostraram áreas significantemente reduzidas nos dias 3, 6 e 9 nos grupos irradiados, o que explica o menor número de odontoclastos na superfície radicular nestes dias e a redução significante das áreas de reabsorção radicular observadas nas lâminas histológicas nos dias 9, 14 e 21 e nas imagens de MEV nos dias 3 e 9. Os grupos irradiados também mostraram menor volume das lacunas de reabsorção radicular medidas no MicroCT nos dias 14 e 21, especialmente nos lados de compressão. O estudo concluiu que o laser de baixa potência influenciou a remodelação óssea, aumentou a atividade dos osteoclastos no lado da compressão, e estimulou a formação óssea no de tensão, acelerando significativamente o movimento dentário e potencialmente reduzindo as áreas de necrose no ligamento periodontal e, consequentemente, a reabsorção radicular. / Tooth movement is a complex biological process induced by mechanical stimulation, leading to a subsequent process of bone remodeling, concomitantly unwanted root resorption may occur caused by excessive force. Since orthodontic movement is based on a localized inflammatory process, the purpose of this study was to evaluate the effects of low-level laser therapy on the process of bone remodeling and root resorption, searching to correlate metabolic changes observed at cellular level in the initial days of tooth movement to tissue changes observed microscopically and both architecture and morphology of trabecular and cortical bone. Upper first molars of sixtyeight male Wistar rats were submitted to induced movement, divided into 3 groups: negative control (no movement), non-irradiated (movement without irradiation) and Laser (movement and irradiation using low level laser of 810 nm wavelength, 100 mW power, 0.02cm2 area, energy of 1.5J/point) and euthanized on days 3, 6, 9, 14 and 21. Measurements of tooth movement and histomorphometric analysis were performed at all days. Immunohistochemistry analysis of RANKL, OPG and TRAP markers and scanning electron microscopy (SEM) were made on days 3, 6 and 9. Western Blotting method to evaluate RANKL and SOFAT proteins and MicroCT images were performed on days 14 and 21. The results of this study showed that tooth movement was significantly greater in the irradiated side (increased in average of 40%) in all evaluated days. The compression side showed higher expression of RANKL and TRAP-positive osteoclasts on days 3, 6 and 9 (p <0.05), promoting significant reduction in alveolar bone area in the compression side on days 6, 9 and 14 ( p <0.05), and leading to microstructural changes such as decrease of the fraction of bone volume / total volume (BV/TV) and the bone mineral density (BMD) at 14 days. The laser also increased RANKL expression and SOFAT on day 14. On the tension side there was an increased expression of OPG especially after 9 days (p <0.001), a significant increase in alveolar bone area on days 14 (p < 0.01) and 21 (p <0.05) histomorphometrically and increase in bone mineral density and trabecular thickness after 21 days (p <0.01). Regarding hyalinized areas, the results showed significant reduced areas on days 3, 6 and 9 in irradiated groups, which explains the lower number of clastic cells on the root surface in these days, and a significant reduction of areas of root resorption observed in histology on days 9, 14 and 21 and on days 3 and 9 by SEM images. Irradiated groups also showed less volume of root resorption lacunaes measured by MicroCT on days 14 and 21, especially in the compression side. The study concludes that the low-level laser therapy had an effect on bone remodeling, increasing osteoclast activity on the compression side, and stimulating bone formation in tension side, resulting in significant tooth movement acceleration and potentially reducing the areas of necrosis in the periodontal ligament and consequently the root resorption process.

Nos últimos anos, o corpo de evidência científica a respeito da relação entre as doenças periodontais e desordens metabólicas - como a obesidade e a síndrome metabólica - vem aumentando consideravelmente. Entretanto, estudos avaliando os mecanismos biológicos que permeiam esta associação ainda são escassos. A presente tese teve como objetivo principal avaliar, em ratos Wistar, o efeito da obesidade e da síndrome metabólica (MetS) sobre a patogênese da perda óssea alveolar. Nesse sentido, foram produzidos 4 artigos científicos, sendo 2 revisões de literatura e 2 estudos experimentais. A primeira revisão de literatura buscou avaliar a literatura disponível acerca da relação MetS e doença periodontal. Pode-se observar que poucos estudos foram localizados e, dentre aqueles avaliados, a maioria tratouse de estudos de natureza epidemiológica transversal. Não foram localizados estudos de natureza longitudinal e apenas um estudo de intervenção piloto foi avaliado. A análise desta evidência permitiu concluir que o tópico é de interesse, porém ainda não foi explorado na perspectiva dos fatores de risco. Para o segundo e terceiro artigos, foi utilizado um modelo animal que reproduz as características de obesidade (artigo 2) e MetS (artigo 3). Para o segundo artigo, foram utilizados 28 ratos Wistar machos divididos em 2 grupos experimentais. O grupo controle recebeu ração padrão e água e o grupo teste além da ração padrão/água foi exposto a uma dieta de cafeteria (CAF) para indução de obesidade. Foi definido um ponto de corte para ocorrência de doença periodontal, sendo essa considerada positiva quando da presença de perda óssea alveolar ≥0.51mm em fotografias padronizadas. Diferenças significativas para o peso e índice de Lee foram observadas no grupo exposto a dieta CAF indicando presença de obesidade neste grupo. Observou-se que os animais obesos apresentaram significativamente mais sítios positivos para doença periodontal. Portanto, pode se concluir que a obesidade aumenta a perda óssea alveolar espontânea em ratos Wistar. Para o terceiro artigo, 60 ratos Wistar foram divididos em 4 grupos: Controle (ração padrão e água), Doença Periodontal (DP) (ração padrão e ligadura no semana 12), MetS (dieta CAF por 17 semanas) e MetS+DP (ligadura na semana 12 e dieta CAF por 17 semanas). Dois animais foram perdidos ao longo do período experimental por razões não relacionadas ao protocolo do estudo. Diferenças significativas foram observadas para o peso, índice de Lee colesterol total e triglicerídeos, indicando presença de MetS. Foram realizadas análises do percentual de perda óssea alveolar através de micro-tomografias e os níveis séricos de IL1- e TNF- foram avaliados por ELISA. Observou-se que os animais portadores de MetS exibiram maiores percentuais de perda óssea alveolar induzida e espontânea. Não foram observadas diferenças significativas para os níveis séricos das citocinas avaliadas. Nesse sentido, pode ser concluído que a presença de MetS modula a resposta do hospedeiro, provavelmente pela quebra da homeostase do periodonto. O artigo 4 tratou-se de uma revisão de literatura com caráter informativo alertando aos profissionais da odontologia a responsabilidade da transcender as abordagens odontológicas tradicionais colocando a profissão como parte importante e integrantes da equipe de saúde. A partir dos resultados obtidos nos artigos constituintes da presente tese e frente às reflexões realizadas, pode-se concluir que a doença periodontal é influenciada por desordens metabólicas. Recomenda-se, portanto, a inclusão de questionamentos e análises dessas condições e suas potenciais inter-relações pelos profissionais da saúde / between periodontal diseases and metabolic disorders – like obesity and metabolic syndrome – has considerably increased. However, studies evaluating the biological mechanisms related to this association are still scarce. The present thesis had as main objective to evaluate, in Wistar rats, the effect of obesity and metabolic syndrome (MetS) on the pathogenesis of alveolar bone loss. In this respect, 4 scientific articles were written, being 2 literature reviews and 2 experimental studies. The first literature review evaluated the available literature relating MetS and periodontal disease. It can be observed that few studies were retrieved and, among thos evaluated, the majority were of cross-sectional epidemiological nature. Longitudinal studies were not found and only one pilot intervention study was evaluated. The analysis of this evidence lead to the conclusion that the topic is of interest, however still has not been explored in the perspective of risk factors. For the second and third articles, an animal model was used, that mimics obesity (article 2 and MetS (article 3). For the second article, 28 male Wistar rats were divided in 2 experimental groups. The control group received chow and water and the test group, besides the standard chow/water was exposed to cafeteria diet (CAF) in order to induce obesity. A cut-off point was defined for the occurrence of periodontal disease, being this considered positive when alveolar bone loss ≥0.51mm was present in standardized pictures. Significant differences for body weight and Lee Index were observed in the group exposed to CAF diet, indicating obesity. Obese animals presented significantly more sites positive for periodontal disease. Thus, it may be concluded that obesity increases spontaneous alveolar bone loss in Wistar rats. For the third article, 60 male Wistar rats were divided in 4 groups: Control (standard chow and water), Periodontal disease (PD) (standard rat chow and ligature on week 12, MetS (CAF diet for 17 weeks and MetS+PD (ligature on week 12 and CAF diet for 17 weeks). Two animals were lost during the experimental period for reasons not related to the study protocol. Significant differences were observed in body weight, Lee Index, total cholesterol and triglycerides, indicating the presence of MetS. Analyses of percent alveolar bone loss were performed by microcomputer tomography and the serum levels of IL1- and TNF- were performed by ELISA. Animals with MetS exhibited higher percentage of spontaneous and induced alveolar bone loss. No significant differences were observed for the serum levels of the evaluated cytokines. Thus, it may be concluded that the presence of MetS modulates the host response, probably breaking the periodontium homeostasis. Article 4 is a literature review with informative characteristics alerting the dental professionals about the responsibility of going beyond the traditional dental practices, making the profession an important component of the health team. Taking into consideration the obtained results in the articles in this thesis, and the thoughts coming from them, it may be concluded that periodontal disease is influenced by metabolic disorders. It is recommended that questions and analyzes are made about these conditions and their potential interrelationships by the health personnel.