根未完成歯不完全脱臼後の歯髄および歯周組織の変化に関する実験的研究

Abstract

Experimental subluxation was conducted on the bilateral upper lateral incisors with incomplete root in 39 young dogs (3 in control group) and pathohistologic and neuropathohistologic investigations were made. The results were as follows : 1. In the subluxated teeth with incomplete root, the periodontal fibers were restored to the former state on 20th day. 2. None of the cases showed ankylosis between the alveolar bone and subluxated teeth. 3. Revascularization was found in the dental pulp of the subluxated teeth with incomplete root. It was confirmed that a large number of new blood vessel extended from the periodontium to the root pulp from 7th day and reached the coronal pulp on and after 20th day. 4. The dental pulp showed edema immediately after the experimental subluxation and necrosed in places. However organization of the pulp progressed and fibrosis extended to the whole pulp on 30th day. 5. Odontoblasts disappeared in places after the experimental subluxation of the teeth but were recovered on 30th day. Predentin was formed and the pulp was strictured by the deposited dentin. 6. The existence of the epithelial sheath of Hertwig was greatly related to growth of the root. Dentin-like hard tissues began to extend along the epithelial sheath of Hertwig in the root apex on 7th day and apparent growth of the root was noted thereafter with time. 7. In the subluxated teeth with incomplete root, neurotomesis and Wallerian degeneration occurred concurrently in the intraperiodontal nerve tissues. Immediately after experimental subluxation of the teeth, the intraperiodontal nerve fibers and nerve fascicle were severed at the ruptures of the periodontium and degeneration of nerve fibers proceeded with time centering on the ruptures of the periodotium, and ranged over the whole periodontium. These findings were noted until 10th day. 8. In the subluxated teeth with incomplete root, only Wallerian degeneration occurred in the intrapulpal nerve tissues. The nerve tissues invading into the pulp were severed at the ruptures of the periodontium in the apex regions immediately after experimental subluxation of the tooth. The nerve fibers remaining in the pulp decreased with time and the nerve fibers exhibiting degenerative findings disappeared on 15th day. 9. As to regeneration of nerve in the periodontium of the subluxated teeth with incomplete root, marked proliferation of Schwann cells occurred on 7th day from the tip of nerve fascicles on the gingival side and in vasoneural space of the alveolar bone, and fine nerve fibers appeared along that arrangement. On 10th day, the nerve fascicle consisting of fine nerve fibers extended on the side of the alveolar bone up to the midlevel of the root and reached the periodontium in the alveolar crest regions on 20th day. On 30th day, the nerve distribution was approximately completed in the periodontium. 10. As to regeneration of nerve in the pulp of the subluxated teeth with incomplete root, a large number of fine nerve fibers and nerve fascicle invaded through the opened apical foramen on 10th day. The nerve distribution appeared to be restored with the peak on 20th day. However the nerve tissues in the pulp decreased slightly after 30th day. On the basis of the foregoing, the subluxated teeth with incomplete root keep the normal positions in the alveolar bone and mature as complete teeth supported by the periodontium which recovered morphologically and functionally. But the pulp is strictured and fibrosed and the sense response of the pulp is thought to be lowered slightly.