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The present study was carried out by fabrication of microcorrosive resin cast to investigate the vascular changes of periodontium of dogs' mandibular incisors with severe mobility and deep pocket formation concomitant with suppuration and alveolar bone loss. With aid of the dissolution of soft tissues by protease, alveolar bone remained left with resin cast of specimen, which then was referred for scanning electron microscopic examination. Results were as follows: 1. The vasculature of inner gingival epithelium which originally appeared as a flat, mesh-like network underwent a conformational change and turned out to be a vasculature with glomerulus-like loops due to chronic inflammation. 2. No remarkable change was ever identified in vasculature of periodontal ligament surrounding cervix of tooth. 3. Certain parts of vasculature of periodontal ligament disappeared, which combining with the occlusion indicated the occurrence of occlusal trauma. 4. Exposed alveolar bone surface where the periodontal vasculature disappeared showed an amorphous, flat surface. Quite contrast to this, the surface of alveolar bone on which the vasculature is located appeared undergoing a resorptive process. 5. Accordingly, the damage occurred in periodontium was not merely due to chronic inflammation but to the accompanying occlusal trauma which was supposed to be a predominant factor.

This study was designed to examine the relationship between frequency of silent period and initial occlusal sliding time. The subjects consisted of three volunteers with normal occlusal contacts and three patients with premature contacts. Electromyograms of the bilateral masseter muscles, initial occlusal contacts and jaw movements during the habitual tapping (20-25) were synchronously recorded and replayed using Takamatsu's technique. Results were as follows: 1. The frequency of silent period in the bilateral masseter muscles was 95-100% in subjects with normal occlusal contacts and 34-53% in patients with premature contacts. 2. The silent period latency in three normal subjects was 8.9 +/- 1.3 msec in the left masseter and 13.9 +/- 2.2 msec in the right masseter. The silent period latency in three patients with premature contacts was 12.4 +/- 2.6 msec in the left masseter and 13.9 +/- 8.2 msec in the right masseter. 3. The duration of silent period in three normal subjects was 12.4 +/- 2.6 msec in the left masseter and 11.1 +/- 3.7 msec in the right masseter. The duration of silent period in three patients with premature contacts was 9.1 +/- 1.7 msec in the left masseter and 11.1 +/- 5.6 msec in the right masseter. 4. Initial occlusal sliding time in three subjects with normal occlusal contacts was less than 30 msec, and 98% of all slidings lasted for less than 15 msec. Initial occlusal sliding times in patients with premature contacts were distributed between 6 and 80 msec (40%: 6 to 15 msec, 60%: greater than 15 to 80 msec).(ABSTRACT TRUNCATED AT 250 WORDS)

Of the researches on periodontal diseases, the changes occurred in the vasculature of peridontal membrane and the surrounding alveolar bone there-to-fore attracts much attention. In order to induce an experimental occlusal trauma, composite resin was added on the occlusal surfaces of mandibular second and third premolars of dogs to raise the bite for a period of time, followed by injection of methacrylate resin (MERCOX) into inferior alveolar artery and dissolution of soft tissues by protainase and examined under the scanning electron microscope (SEM, JEOL 35 C). The results are as follows: After 14 days, a wide range of avascularized area was observed on resin cast of periodontal membrane. The surface of alveolar bone on which the vasculature disappeared did not show resorption process. However, the surface of alveolar bone next to the periodontal vasculature showed undergoing a direct bone resorption. After 30 days, the vasculature of periodontal membrane underwent a morphological change and turned out to appear as a mesh-like vascular network. Certain avascularized regions was observed over the alveolar bone on margin region and cervical region, and it was circumscribed by a vasculature with glomerule-like loops. This vasculature was suspected originating from underlying alveolar bone marrow and connected with the residual vasculature of periodontal membrane. After 60 days, vasculature of periodontal membrane facing teeth appeared quite resemblance with that of health periodontal membrane. Those next to the alveolar bone, however, showed enlargement. In this period, avascularized area was not observed. After 90 days, the vasculature in periodontal membrane lost its original two-layered arrangement and replaced by the irregular arrayed bundle-like vasculature. Longitudinally arrayed mesh like vasculature was observed in certain region of periodontal vasculature. After 180 days, bundle-like vessels arrayed as an ellipse pattern. Also, resorption process could be observed on the surface of alveolar bone and interradicular septum. Experimental study of occlusal trauma on dentition clearly indicated that teeth were showed a mobility in vertical direction and that the vasculature of periodontal membrane were showed depression and elongation for a period of time. It could not show an apposition where were showed by the experimental depression and elongation, so it was only showed the expansible periodontal membrane space by resorption of alveolar bone.