Changes of TMJ Following Mandibular Distraction Osteogenesis in Growing Mini-pigs

• Main Authors: Chi-Ying Huang, 黃繼瑩
• Other Authors: 姚宗珍
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/88324348163729442698

碩士 === 國立臺灣大學 === 臨床牙醫學研究所 === 94 === Distraction osteogenesis has been widely used in congenital anomalies to correct craniofacial deficiency. Clinically it is frequently conducted on growing patients for early establishment of normal physiological functions. However, the effects on temporomandibular joints due to mandibular distraction are still controversial, and the influence of growth was not taken into consideration in most of the research. In this study, we investigated the effects on TMJs in growing mini-pigs in which unilateral mandibular distraction osteogenesis was performed. Fourteen (5~12 weeks, 6~15kg weight) Lee-Sung genus of mini-pigs were divided into 4 groups: 1) Experimental group A (n=5), received osteotomy and the distractor device (Leibinger intraoral distractor) was fixed on one side of the mandible. After one-week latency period, the mandible was distracted for 2 weeks with the velocity of 0.9 mm/day. At the end of distraction, the animals were sacrificed immediately. 2) Experimental group B (n=2), the animals received the similar treatment as Experimental group A, except that they were sacrificed after a consolidation period of 4 weeks for the long-term observation. 3) Control group (n=5), received osteotomy but the distractor device was placed without distraction. And 4) Normal group, 2 healthy mini-pigs without any operation were used to provide information of normal structures. Changes of temporomandibular joints in the experimental groups were detected from 4 different approaches. 1) Using three-dimensional reconstruction using MRI image data, to observe morphological changes of mandibular condyle and relative position between temporal fossa and condyle. 2) From the H & E staining of different portion of the condyles, to observe histological characteristics and changes of thickness of condylar cartilage. 3) Via immunohistochemical analysis, to observe the distribution of MMP9 in cartilage. 4) Using TUNEL staining method, to detect apoptosis in chondrocytes in the sections of condylar cartilage. There were detectable changes in morphology, position and histological characteristics of condyle after unilateral mandibular distraction and the extent of changes was more obvious at the distraction side than control side. Increased activities of subchondrol ossification and matrix degradation after distraction were noticed. After a 4-week consolidation, these changes returned to the normal level; however, the thickness of cartilage decreased. These findings revealed the enormous adaptive capacity of condyle in growing animals. Changes in the position of condyle and thickness of cartilage also suggested that the lateral and middle third of condylar head were under higher degree of loading. Additionally, the number of apoptotic chondrocytes did not obviously increase under distraction. In conclusion, distraction osteogenesis is an effective way to lengthen the mandible with minimal and transient changes of TMJ. A more long-term observation is required to follow the morphological change of condyle and its consequences on the mandibular movement and function if it is not a reversible process.