Morphological studies of the altered pulps of the New Zealand white rabbit after resection of the inferior alveolar nerve and/or the superior cervical ganglion

Abstract

This study was carried out to determine the effects of denervation of the pulp organs of teeth, particularly on the odontoblasts and their processes. Therefore, resection of the inferior alveolar, cervical sympathetic, or a combination of both types of nerves supplying the mandibular incisor teeth of New Zealand white rabbits was performed and the results compared to adjacent, unaltered teeth. Neural stains were used to evaluate the presence or absence of nerve elements, while histochemical and titrametric methods were employed to determine the presence, location and concentration of cholinesterase enzymes in these teeth. Dilation of blood vessels was noted after cervical sympathetic resection and larger nerve trunks as well as peripherally located fine fibers were absent in the pulps following inferior alveolar nerve resection. Further, irregular dentin formation and associated small openings in the tips of the teeth were observed after nerve resection. Titrametric analysis indicated a significant decrease in the concentration of cholinesterase in the pulp organ of incisors 15-19 days after resection of either the inferior alveolar nerve or both inferior alveolar and cervical sympathetic nerves. Only a slight decrease in the concentration of cholinesterase was noted after removal of the cervical sympathetic nerve alone. Histochemical results confirmed a decrease in cholinesterase after resection of the inferior alveolar, cervical Sympathetic or both nerves. The concentration of the oxidative enzyme, succinic dehydrogenase, however, increased after all three types of nerve resection. This increase was apparent particularly in the odontoblastic cells underlying the predentin.

Vasodilatation in the dental pulp produced by electrical stimulation of the inferior alveolar nerve in the cat

“…It is not clear if there are cholinergic vasodilator fibres in the dental pulp. Functional studies in dogs (Weiss et al 1972) and the histochemical demonstration of specific cholinesterase activity related to nerve fibres in the rabbit, cat and dog pulp (Avery et al 1971, Pohto & Antila 1972 lend some support to the hypothesis that there is an autonomic vasodilator mechanism in the pulp. The results of the present experiments with atropine show, however, that acetylcholine is not involved in vasodilatation produced by inferior alveolar nerve stimulation and they do not support the idea of a role for cholinergic vasomotor fibres in the cat dental pulp: Histamine-like fluorescence has been found in human, cat and rabbit pulps (Pohto & Anti1 1972) and mast cell histamine has been suggested to play a part in vasodilatation following electrical stimulation of cutaneous nerves in rats (Kiernan 1975).…”

Pulpal healing after luxation injuries and root fracture in the permanent dentition

“…Experimental investigations suggest that PCO may be caused by an uncontrolled sympathetic nervous response to trauma (a result of loss of parasympathetic inhibition) (107)(108)(109)(110)(111)(112). This could be caused by a diminished blood flow in pulpal vessels, which can be observed during sympathetic nerve stimulation (110,(113)(114)(115)(116)(117)(118).…”

Occurrence of pulp canal obliteration after luxation injuries in the permanent dentition

“…While experimental studies have attempted to explain aeeelerated hard tissue apposition, it has not been possible to arrive at any definite conclusions concerning the actual mechanism (12)(13)(14). Furthermore, few elinieal studies to date exist whieh do more than present the frequency of PCO after traumatic dental injuries.…”