DOES RESECTION OF THE NERVES SUPPLYING THE MANDIBLE AFFECT TOOTH DEVELOPMENT?

¹ Department of Anatomy and College of Dentistry, The Ohio State University, Columbus, Ohio

1. The objective in the present study was to determine whether or not unilateral resection of the nerves supplying the mandible of the kitten affects the development of the permanent tooth-germs. 2. Three series of unilateral operations were performed, 2 animals of the same age being used in each series. The first involved resection of the superior cervical ganglion, the second resection of the superior cervical ganglion including the inferior alveolar nerve and the third involving the inferior alveolar nerve only. 3. The methods employed to determine the effect of these operations on the development of the permanent tooth-germs were (1) measurement of the length of the tooth-germs on roentgenographs by means of a vernier caliper, (2) repeating the same procedure by using photographic enlargements of the roentgenographs in order to verify the results obtained with the first method and (3) determining the amount of growth exhibited by the molar tooth-germs in photographic enlargements by measuring the distance from the apex of the highest cusp to the inferior border of the mandible. 4. The unoperated side or half of each mandible was used as a control for each series of operations and in addition the mandible from an unoperated kitten of the same age as 45 and 46 served as a normal control. 5. In all cases where the superior cervical ganglion was resected 100 per cent of the tooth-germs which were measured on the operated side exhibited acceleration of growth, the average percentile difference in size of the tooth-germs being 6.1 per cent. 6. In the 2 animals in which the inferior alveolar nerve alone was resected only 60 per cent of the tooth-germs on the operated side exhibited acceleration of growth, the average percentile difference in size of the tooth-germs being only 3.2 per cent. 7. Measurements of the molar tooth-germs as well-as the distance from the tip of the cusps to the inferior border of the mandible on photographic enlargements of the roentgenographs verify in general the results obtained from the roentgenographs. 8. The suggestion is offered that acceleration of growth of the tooth-germs on the operated side following resection of the superior cervical ganglion is due to increased vascularity resulting from vasodilation of the vessels which nourish the future teeth and surrounding tissues. 9. Failure to obtain consistent results following resection of the inferior alveolar nerve may be explained on the basis that few if any sympathetic, vaso-constrictor fibers are present in this nerve. It is suggested, moreover, that the apparent acceleration of growth in 60 per cent of the tooth-germs on the operated side following this operation may be attributed to a normal variation in growth rate since 60 per cent of the mandibular tooth-germs of a normal kitten are larger on one side than on the other.