Effects of detachment and repositioning of the medial pterygoid muscle on the growth of the maxilla and mandible of young rats

Abstract

Purpose:To analyze the effects of detachment and repositioning of the medial pterygoid muscle on the growth of the maxilla and mandible of young rats through cephalometry. Methods: Thirty one-month-old Wistar rats were used, distributed into three groups: experimental, sham-operated and control. In the experimental group, unilateral detachment and repositioning of the medial pterygoid muscle was performed. The sham-operated group only underwent surgical access, and the control group did not undergo any procedure. The animals were sacrificed at the age of three months. Their soft tissues were removed and the mandible was disarticulated. Radiographs of the skull in axial projection and the hemimandibles in lateral projection were obtained, and cephalometry was performed. The values obtained were subjected to statistical analyses among the groups and between the sides in each group. Results: There were significant differences in the length of the mandible relative to the angular process in the experimental group and in the height of the mandibular body in the sham-operated group. Conclusion: The experimental detachment and repositioning of the medial pterygoid muscle during the growth period in rats affected the growth of the angle region, resulting in asymmetry of the mandible. Key words: Pterygoid muscle. Maxillofacial development. Growth and development. Rats. RESUMOObjetivo: Avaliar os efeitos do descolamento e reposicionamento do músculo pterigoideo medial no crescimento da maxila e mandíbula em ratos jovens por meio de cefalometria. Métodos: Foram utilizados 30 ratos Wistar com um mês de idade, distribuídos em três grupos: experimental, controle-operado e controle. No grupo experimental, o descolamento unilateral e reposicionamento do músculo pterigoideo medial foi realizado. O grupo controle-operado foi submetido somente ao acesso cirúrgico e para o grupo controle nenhum procedimento foi realizado. Os animais foram sacrificados aos três meses de idade. Os tecidos moles foram removidos e a mandíbula foi desarticulada. Radiografias axiais do crânio e laterais das hemimandíbulas foram obtidas e a cefalometria foi realizada. Os valores obtidos foram submetidos a análises estatísticas entre os grupos e entre os lados em cada grupo. Resultados: Houve diferenças significantes no comprimento da mandíbula relativo ao processo angular no grupo experimental e na altura do corpo mandibular no grupo controle operado. Conclusão: O descolamento e reposicionamento experimental do músculo pterigoideo medial durante o período de crescimento em ratos comprometeu o crescimento na região de ângulo, resultando em assimetria da mandíbula. Descritores: Músculo pterigoideo. Desenvolvimento maxilo facial. Crescimento e desenvolvimento. Ratos.

Facial symmetry evaluation after experimentally displaced condylar process fracture in methotrexate treated rats

“…Cephalometric evaluations from radiographs of specimens using a computer system, as in this study, lead to reliable measurements, reducing technical difficulties 5,9,28 . Distances found were similar to those noted in other experiments 5,28,29 . In the cephalometric evaluation it was possible to measure linear distances, and also the mandibular deviation, by measuring the angles α and  3,5,9,30,31 .…”

Effects of temporal muscle detachment and coronoidotomy on facial growth in young rats

“…1 An injury to these structures may have adverse effects on mandibular growth. 2,3 Experimental studies have demonstrated that temporal muscle detachment during a growth period leads to a reduction in the size of the coronoid process itself. 4 The anatomy of the coronoid process reflects the relative development of the temporal muscle.…”

Muscle insulin-like growth factor-I modulates murine craniofacial bone growth

“…3f), this was attributed to the actions of IGF-I from multiple craniofacial muscle groups. Despite the fact that masseter thickness positively correlates to mandibular ramus height in a human model (Kubota et al, 1998), rodents rely on the posterior temporal muscle and anterior digastric muscle to alter the mandibular ramus (Cruz et al, 2009;Lifshitz, 1976). Thus, data with IGF-I overexpression recapitulated the human model where mIgf1 +/+ mice captured the vertical effect due to IGF-I action from muscle groups, while the AAV-IGF-I experiment captured the horizontal effect indicating a specific role of the masseter.…”