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KMID : 0376319930050010049
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Dental Journal of CNU
1993 Volume.5 No. 1 p.49 ~ p.69
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A HISTOMORPHOLOGIC STUDY OF MASSETER MUSCLE AND TEMPOROMANDIBULAR JOINT TO MASSETERIC NERVE RESECTION AND LOSS OF INCISAL FUNCTION IN THE RAT
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Kim Dong-Min
Yang Kyu-Ho
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Abstract
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This study was performed to evaluate, in growing rats, the changes of the masseter muscle and mandibular joint to loss of incisal function and/or unilateral resection of the masseteric nerve. The animals were divided into two groups. The group Ⅰ was received unilateral masseteric nerve resection only. The group Ⅱ was received unilateral masseteric nerve resection and loss of incisal function with soft diet.
The results were as follows :
1. Denervated atrophy was identified in the first week after denervation. Nuclear migration into central portion of sarcoplasm, angulation of muscle fiber and ring fiber formation were also observed. The degree of denervation atrophy was more marked in group Ⅱ than in group Ⅰ.
2. The proportion of muscle fiber types was variable, but type Ⅰ fiber was increased in group Ⅰ at SDH stain and group Ⅱ showed the largest proportion of type Ⅰ fiber at myosin-ATPase stain.
3. The cross sectional area of masseter muscle after denervation was significantly reduced. The area of group Ⅰ was reduced in about 1/2 size than the control side, and group Ⅱ was reduced in about 1/3 size.
4. The cartilage capping of the surface of the mandibular condyle was composed of five layers at the first week after denervation. But the thickness of prechondroblastic layer was reduced in the second week after denervation in both groups, and at the fourth week prechondroblastic and proliferative layer were reduced in group Ⅱ.
The denervation of masseteric nerve altered the morphology of masseter muscle, and active changes in muscle function influenced on temporomandibular joint morphology. It suggested that continuous adjustment between the soft and hard tissue is preserved for balancing.
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