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Title: Periodontal and pulpal connections from the teeth to the trigeminal mesencephalic nucleus and ganglion in the vervet monkey and olive baboon
Author: Hassanali, Jameela
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1990
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1. The quantitative and somatotopic aspects of periodontal/gingival and pulpal afferent connections of the mandibular and maxillary incisors, canines and molar teeth to the mesencephalic nucleus of trigeminal nerve and the trigeminal ganglion have been investigated in the vervet monkey and olive baboon using horseradish peroxidase (HRP) retrograde axonal tracing method. 2. It has been demonstrated that the periodontal proprioceptive afferent neurons of incisors, canines and molars are found predominantly in the ipsilateral caudal part of the trigeminal mesencephalic nucleus extending from the level of inferior colliculi to the trigeminal motor nucleus in pons. The incisors have significantly more mesencephalic neural connections than canines and molars. No HRP labelled pulpal mesencephalic neurons have been observed. Faintly labelled neurons have been observed bilaterally, presumably in the supratrigeminal nuclei. 3. It has been shown that the incisors and canines have a large and preponderantly ipsilateral representation in the trigeminal ganglion compared to the molars which have a sparse ipsilateral representation. The discrete periodontal/gingival and pulpal HRP labelled afferent neurons innervating mandibular teeth are found in the postero-lateral aspect of the ganglion and those of the maxillary teeth are found in the middle, along the dorso-ventral extent of the ganglion. 4. Present study shows that about 10% to 15% of the mesencephalic neurons (unilaterally) and 0.32% to 0.58&37 of trigeminal ganglion neurons have afferent connections with the periodontium of incisors, canines and molars in the monkey and baboon. The stereological analysis and cell counts in stratified serial paraffin wax sections has shown that there are bilaterally 1379-2674 and 1620-2816 mesencephalic neurons; 98073-10178 and 137250-153555 ganglion neurons in the monkey and baboon respectively. 5. The periodontal proprioceptive mesencephalic afferent connections of the anterior and posterior teeth suggest that they are involved in the modulation of the reflex effects on the jaw-opening and jaw-closing motor neurons and are thus important in the regulation of masticatory jaw movements. Moreover, a cluster of mesencephalic neurons may form a functional unit for synchronizing jaw movements during mastication. The numerous trigeminal ganglion afferent connections of the anterior teeth suggest that they have a major sensory role particularly in perception of the food bolus. Furthermore, the afferent connections of the anterior teeth may serve to regulate the jaw movement by providing anterior guidance during the occlusal phase of chewing. It is concluded that the connections of teeth to the ipsilateral trigeminal mesencephalic nucleus and ganglion; the connections to the interneurons of the supratrigeminal and the sensory nuclei are involved in the reflex modulation and bilateral control of jaw movements and the perception of stimulation of the teeth.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (D.D.S.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available