On the Innervation, Especially, the Sensory Innervation of the Peridental Membrane, the Dental Pulp and the Periosteum of the Lower Alveolus in Dog

Abstract

The courses run by the nerves distributed in the dental pulp and the peridental membrane in dog are little different from those in man.The distribution of the sensory terminations found in a number in the peridental membrane, however, is somewhat different from man (YAMAZAKI) to dog. In dog, they show little dissimilarity by position but are proportionate in size and structure to the development of the membrane. Thus, around the roots of the canines and the incisors, where the membrane is well developed, the sensory terminations are also well developed, but in the membrane around the premolars and the molars, they are much poorer in development.The sensory terminations found in the peridental membrane represent a quite unique type not to be found in any other place of the body.These terminations comprise simple and complex branched types and as their specific characteristics, we may mention that their nerve elements show abrupt change in size in their courses, that the terminal fibres show widely varied terminal modes and that the general outlines of these terminations are also much diversified. Such peculiarities are common to those in man, as reported by YAMAZAKI. In dog, however, the development of these terminations is inferior to that in man. This finding is in agreement with the results of many past studies in this laboratory, and is one of the proofs that show the highest perfection of sensory terminations in the human body.So, no such terminations showing a high degree of differentiation, as the glomerular terminations and specific terminations (YAMAZAKI), reported as forthcoming in the human peridental membrane, were found in that of dog.In this membrane, fibres were often found to ramify several times without losing their myelin. This shows that single sensory fibres can end in plural endings.Sometimes in simple branched terminations their nerve branches are found to end in a few very fien short terminal fibres. Some of the terminations may also consist of nerve branches showing frequent changes in size, and of terminal fibres ending in club-like, brush-like or blunt tips. The general form of such simple branched terminations is always quite non-typical.Of the complex branched terminations, the classification into typical forms is somewhat more feasible. For example, we often find terminations formed by stem fibres sending out many primary and secondary branches at frequent intervals in their courses and in general outline arranged in arborized form. In many cases, the branches in such terminations are slender at their origine but abruptly gain in size later on, and their terminal fibres end in very fine size in sharp points. Complex branched terminations formed by thick nerve fibres showing frequent changes in size are also not rarely found. The terminal fibres of these terminations also frequently show changes in size and their ends are in various forms. The arrangement of the nerve fibres is always irregular, sometimes to a mild extent, but otherwise also to total amorphousness.In the pulp of dog, no such glomerular and perivascular terminations as found in the human pulp are to be found. The sensory fibres there come beneath the odontoblast layer and losing their myelin, end in branched terminations. Their terminal fibres are as fine as in the human counterpart and end sharply. A part of the terminal fibres run further into the odontoblast layer. A part of the sensory fibres, upon losing their myelin, run directly into the odontoblast layer and in similar branched terminations. The terminal fibres of these terminations run between or through the odontoblasts to the margin of the odontoblast layer but never go further into the predentine.The periosteum lining the outer surface of the alveoli of dog is also provided with sensoy terminations, though in a limited quantity.