백서에서 신경절단과 절치부 기능 상실에 따른 교근 및 악관절의 변화에 관한 연구 = A HISTOMORPHOLOGIC STUDY OF MASSETER MUSCLE AND TEMPOROMANDIBULAR JOINT TO MASSETERIC NERVE RESECTION AND LOSS OF INCISAL FUNTION IN THE RAT

다국어 초록 (Multilingual Abstract)

This study was performed to evaluate, in growing rats, the changes of the masseter muscle and medibular 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 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 mtosin-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 the fourth week prechondroblastic and proliferative layer were reduced in group Ⅱ.
The denervation of masseteric nerve altered the morphology of masseter, and active changes in muscle function influenced on temporomandibular jointmorphology.
It suggested that continuous adjustment between the soft and hard tissue is preserved for balancing.