Since the introduction of temporary skeletal anchorage in orthodontics during the eighties, osteosynthesis miniplates, modified with orthodontic attachments, have been increasingly used. However, no quantitative data about bone reactions around loaded miniplates, and only few prospective clinical studies with small numbers of patients, were found in the literature. Therefore, this project was set up to scientifically emphasize the use of miniplates for orthodontic anchorage with combined experimental and clinical approaches. The specific objectives of the experimental chapters of this thesis were to evaluate if orthodontic loading has an impact on bone reactions around screws supporting miniplates, and to describe the histological components of the bone-screw interface. The clinical chapters aimed to determine patients’, orthodontists’ and surgeons’ perceptions about miniplates, to assess their success rate and to describe the surgical techniques of placement and removal. The experimental study involved eighty miniplates, placed in the jaws of 10 dogs : 2 miniplates per jaw quadrant. After 2 weeks, coil springs applying a 125 g force were placed between the miniplates of an upper quadrant and the controlateral lower quadrant of each dog. The other miniplates were not loaded and were considered controls. Five dogs were sacrificed 7 weeks after implantation and 5 dogs after 29 weeks. Fluorochromes were injected at implantation and at sacrifice. Jaw quadrants were scanned with peripheral Quantitative Computed Tomography. Undecalcified sections were carried out and submitted to microradiographic analysis to assess bone-implant contact and bone volume/total volume. The sections were finally observed under UV light, stained and examined under ordinary light. The success rate in this animal study was 53 % and the proportion of stable miniplates was significantly higher in the maxilla than in the mandible. No significant difference in success rate was found between loaded and nonloaded miniplates. Mobility occurred on average 5 weeks after placement. Bone mineral density was higher around mandibular than around maxillary miniplates, but was not significantly different around loaded and nonloaded miniplates. Bone implant contact and bone volume/total volume did not differ significantly neither between the loaded and the nonloaded screws, nor according to the direction of load, whereas they increased with time. Fifty-six percent of the screws were osseointegrated. Healing reactions showed mainly limited remodelling of lamellar bone. The remaining screws were fibro-integrated. Stability and osseointegration of titanium orthodontic miniplates were thus influenced by the recipient site anatomy, but not by loading. The clinical study focused on ninety-seven consecutive patients treated with miniplates, who completed questionnaires. A total of 200 miniplates were placed by nine oral surgeons, who filled out questionnaires after placement and removal surgeries. The 30 orthodontists treating these patients also completed questionnaires concerning miniplate success, handling complexity, and effectiveness. The success rate obtained in this clinical survey was 92.5 %. Placement surgery, generally performed under local anesthesia, lasted on average 15-30 minutes per plate, and was considered by the surgeons to be very to moderately easy. Patients tolerated the miniplates well : 72 % of patients said they did not mind having the implant and 82 % reported that the surgical experience was better than expected, with little or no pain. The chief complaints were post-surgical swelling, lasting 5 days on average, and cheek irritation. The orthodontists rated these devices as easy to use and simplifying treatment. The removal surgery was shorter and considered easier than the placement surgery. Miniplates were thus well accepted by patients and providers, and were considered a useful tool especially for difficult treatments.

Objetivo. O objetivo deste trabalho é avaliar o resultado da protração ortopédica da maxila em pacientes com fissura labiopalatina por meio de elásticos intermaxilares ancorados em miniplacas tipo Bollard. Material e métodos. Foram instaladas 92 miniplacas em 23 indivíduos (grupo experimental- GE), 17 do sexo masculino (73,91%) e 6 do sexo feminino (26,09%) com idade média de 11 anos e 9 meses (10,3 anos a 13,2 anos). Após três semanas da instalação das miniplacas, iniciou-se o uso de elásticos intermaxilares 24horas por dia por 18 meses. Tomografias computadorizadas de feixe cônico foram realizadas no início e no final do tratamento. O grupo-controle (GC) foi formado por 23 pacientes com o mesmo tipo de fissura não tratados ortopedicamente, pareados por sexo, idade e tempo entre os exames de imagem com o GE. As comparações intergrupos e intragrupos foram realizadas, respectivamente, por meio do teste t independente e pareado (p<0.05) Resultados. A comparação intergrupos apontou que o grupo experimental demonstrou maior movimento anterior da maxila que o grupo-controle, com capacidade de impressionar o perfil facial. O comprimento mandibular alongou menos no grupo experimental comparativamente ao controle. As alterações na relação ântero-posterior entre as bases ósseas e da convexidade facial mostraram uma melhora no grupo experimental e a mandíbula girou no sentido antihorário contrariamente ao grupo-controle. O ângulo goníaco fechou mais no grupo experimental. Das 92 miniplacas instaladas, somente três delas precisaram ser substituídas por apresentarem mobilidade. Conclusão. Os resultados encontrados permitem concluir que esta modalidade de tratamento mostra-se viável para a correção das discrepâncias maxilomandibulares causadas por deficiência da maxila em pacientes com fissura labiopalatina. Essa técnica pode contribuir para evitar a cirurgia ortognática ou pelo menos diminuir a magnitude do avanço necessário, permitindo ao indivíduo tratado melhor padrão facial durante sua adolescência e início da juventude / Objective. This study evaluated the outcome of orthopedic maxillary protraction in individuals with cleft lip and palate, by intermaxillary elastics anchored on Bollard miniplates. Material and methods. A total of 92 miniplates were placed in 23 individuals (study group - SG), being 17 males (73.91%) and 6 females (26.09%) with mean age of 11 years and 9 months (10.3 years to 13.2 years). Three weeks after miniplate placement, the utilization of intermaxillary elastics was initiated 24 hours a day for 18 months. Cone beam computed tomographies were obtained at treatment onset and completion. The control group (CG) consisted of 23 individuals with the same type of cleft not submitted to orthopedic treatment, matched with the SG for gender, age and time between imagining examinations. Intergroup and intragroup comparisons were performed by the independent and paired t tests, respectively (p<0.05) Results. Intergroup comparison revealed that the study group presented greater forward maxillary movement compared to the control group, with influence on the facial profile. The mandibular length exhibited smaller elongation in the study group compared to the control group. Changes in anteroposterior relationship between the bone bases and in facial convexity evidenced improvement in the study group. The mandible exhibited counterclockwise rotation in the study group, different from the control group. The gonial angle was more closed in the study group compared to the control group. Among the 94 plates placed, only three required replacement because of mobility. Conclusion. The results revealed that this treatment option is feasible for correction of maxillomandibular discrepancies caused by maxillary deficiency in individuals with cleft lip and palate. This technique may contribute to avoid the need of orthognathic surgery or at least reduce the magnitude of advancement required, providing the treated individual with a better facial pattern during adolescence and early youth

Objetivo. O objetivo deste trabalho é avaliar o resultado da protração ortopédica da maxila em pacientes com fissura labiopalatina por meio de elásticos intermaxilares ancorados em miniplacas tipo Bollard. Material e métodos. Foram instaladas 92 miniplacas em 23 indivíduos (grupo experimental- GE), 17 do sexo masculino (73,91%) e 6 do sexo feminino (26,09%) com idade média de 11 anos e 9 meses (10,3 anos a 13,2 anos). Após três semanas da instalação das miniplacas, iniciou-se o uso de elásticos intermaxilares 24horas por dia por 18 meses. Tomografias computadorizadas de feixe cônico foram realizadas no início e no final do tratamento. O grupo-controle (GC) foi formado por 23 pacientes com o mesmo tipo de fissura não tratados ortopedicamente, pareados por sexo, idade e tempo entre os exames de imagem com o GE. As comparações intergrupos e intragrupos foram realizadas, respectivamente, por meio do teste t independente e pareado (p<0.05) Resultados. A comparação intergrupos apontou que o grupo experimental demonstrou maior movimento anterior da maxila que o grupo-controle, com capacidade de impressionar o perfil facial. O comprimento mandibular alongou menos no grupo experimental comparativamente ao controle. As alterações na relação ântero-posterior entre as bases ósseas e da convexidade facial mostraram uma melhora no grupo experimental e a mandíbula girou no sentido antihorário contrariamente ao grupo-controle. O ângulo goníaco fechou mais no grupo experimental. Das 92 miniplacas instaladas, somente três delas precisaram ser substituídas por apresentarem mobilidade. Conclusão. Os resultados encontrados permitem concluir que esta modalidade de tratamento mostra-se viável para a correção das discrepâncias maxilomandibulares causadas por deficiência da maxila em pacientes com fissura labiopalatina. Essa técnica pode contribuir para evitar a cirurgia ortognática ou pelo menos diminuir a magnitude do avanço necessário, permitindo ao indivíduo tratado melhor padrão facial durante sua adolescência e início da juventude / Objective. This study evaluated the outcome of orthopedic maxillary protraction in individuals with cleft lip and palate, by intermaxillary elastics anchored on Bollard miniplates. Material and methods. A total of 92 miniplates were placed in 23 individuals (study group - SG), being 17 males (73.91%) and 6 females (26.09%) with mean age of 11 years and 9 months (10.3 years to 13.2 years). Three weeks after miniplate placement, the utilization of intermaxillary elastics was initiated 24 hours a day for 18 months. Cone beam computed tomographies were obtained at treatment onset and completion. The control group (CG) consisted of 23 individuals with the same type of cleft not submitted to orthopedic treatment, matched with the SG for gender, age and time between imagining examinations. Intergroup and intragroup comparisons were performed by the independent and paired t tests, respectively (p<0.05) Results. Intergroup comparison revealed that the study group presented greater forward maxillary movement compared to the control group, with influence on the facial profile. The mandibular length exhibited smaller elongation in the study group compared to the control group. Changes in anteroposterior relationship between the bone bases and in facial convexity evidenced improvement in the study group. The mandible exhibited counterclockwise rotation in the study group, different from the control group. The gonial angle was more closed in the study group compared to the control group. Among the 94 plates placed, only three required replacement because of mobility. Conclusion. The results revealed that this treatment option is feasible for correction of maxillomandibular discrepancies caused by maxillary deficiency in individuals with cleft lip and palate. This technique may contribute to avoid the need of orthognathic surgery or at least reduce the magnitude of advancement required, providing the treated individual with a better facial pattern during adolescence and early youth

Fundação de Amparo a Pesquisa do Estado de Minas Gerais / The number of tumors in the oral cavity is increasing significantly, mainly, due to the use of tobacco. In general, resection is the treatment for these tumors. This process is made through the access to the oral cavity using the mandibulotomy technique. For that, different cuts can be made in the mandible, in function of tumor position and patient condition. The cuts fixation, in general, are made using miniplates and titanium screws or steel wires. In this aspect, many clinical doubts exist, under the biomechanics perspective, on which is the best surgical procedure would be. This work aims to evaluate two types of cuts in a mandible, midline and paramidline, using different fixation sets with miniplates. Simplified finite element models were used to verify which was the best configuration through analysis of the stability level and stress gradient. At the same time, a human jaw photoelastic model was used, where two types of cuts were analyzed: midline and paramidline, with two types of knotting for wires, parallel and opposite. The critical stress levels were evaluated for different cross sections. Additionally, a visual inspection of relative displacement was made between the cross sectional. It was observed that the number of bolts does not influence the stability when the same number of miniplates is used. Using only one miniplate, the medium cut presents better stability than the paramidline cut. Using two miniplates in the setting, despite the small difference, the paramidline presents better stability, while the best configuration is that with two miniplates and six screws. A significant increase in the obtained stress level was observed with two miniplates and six screws fastened. / O número de tumores na cavidade oral vem aumentando significativamente, principalmente, devido ao uso do fumo. Na maioria dos casos, a forma de tratamento destes tumores é a sua ressecção. Em várias situações isto é feito através do acesso oral utilizando a técnica de mandibulotomia. Para isto, podem ser feitos diferentes tipos de corte na mandíbula em função da localização do tumor e da condição do paciente. A fixação destes cortes, em geral, é feita através de miniplacas e parafusos de titânio ou fios de aço. Neste aspecto, existem muitas dúvidas clínicas, do ponto de vista biomecânico, sobre qual o melhor procedimento cirúrgico. O objetivo deste trabalho foi avaliar dois tipos de corte na mandíbula, mediano e paramediano, usando diferentes conjuntos de fixação com miniplacas. Modelos de elementos finitos simplificados foram utilizados para verificar qual a melhor configuração através dos níveis de estabilidade e gradiente de tensões. Paralelamente, foi utilizado um modelo fotoelástico de uma mandíbula humana, onde foram analisados dois tipos de cortes: mediano e paramediano com dois tipos de amarração por fios, paralela e cruzada. Através dos níveis de tensão gerados em cada tipo de corte foram avaliados os pontos críticos dos modelos. Paralelamente, foi feita uma inspeção visual sobre os efeitos do deslocamento relativo entre as faces dos cortes. Foi observado que o número de pinos não influencia na estabilidade quando for utilizada a mesma quantidade de miniplacas. Utilizando apenas uma miniplaca, o corte mediano apresenta melhor estabilidade que o corte paramediano. Utilizando duas miniplacas na fixação, apesar da pequena diferença, o paramediano apresenta estabilidade um pouco melhor, sendo a melhor configuração com duas miniplacas e 6 parafusos. Observou-se um aumento significativo no nível das tensões nos modelos fixados com duas miniplacas e seis parafusos. / Mestre em Engenharia Mecânica