The purpose of this study was to evaluate the lento-craniofacial morphology and the occlusal characteristics in the Central American Indians from the dental-anthropological point of view. The sample consisted of cephalograms, pantomograms, dental casts, photos and records (anthropometric measurements and oral examinations) which were taken from 210 modern Central American Indians and 212 ancient Central American Indians. The results were summarized as follows: 1. Craniofacial morphology: The modern Central American Indians showed; (1) smaller facial height and shorter depth of the cranial base and jaws than those of the Caucasians. (2) posterior position of peri-orbital structures, and smaller values of anterior facial height in comparison with the Japanese, which were similar to the Peruvian Indians. (3) shorter depth of the jaws and prominence of the chin than the ancient Central American Indians. 2. Dental arch form and tooth size: The modern Central American Indians had; (1) wider dental arches than the Caucasians, while sharing similar values with the Peruvian Indians and the Japanese. (2) smaller incisors, larger premolars and molars in the mesio-distal crown diameter compared with the Caucasians. (3) smaller teeth in the mesio-distal crown diameter than the ancient Central American Indians. 3.Occlusal conditions: The modern Central American Indians showed a good mesio-distal relationship between the upper and lower first molars in 70 percent.
The adaptability of the upper complete denture base made from superplastic alloy 90Ti-6Al-4V was investigated by measuring the space between the master model and the denture base. The denture bases showed a high adaptability with the space less than 0.1 mm, whereas after curing resin for denture, it became worse especially with the heat-curing resin. In addition, the thinnest area of the denture base was observed at the middle of the plate with 38% reduction in thickness, and distortion of the base plate of 0.55mm thickness by curing resin was found to be nearly the same as that of type 304 stainless steel plate of 0.50 mm thickness.
The aim of the study was to evaluate the effect of the subgingival plaque control by direct irrigation. Twelve adult patients with periodontal pockets of 4 mm or more received an initial treatment. The patients were followed by irrigation using the device called Pocket Irrigator PT-01 with 0.05% acrinol solution or 0.025% benzalkonium chloride solution. The clinical and microbiological parameters were recorded prior to the irrigation and immediately after, at 1 hour, 1 day and 1 week after the irrigation. The Plaque Index, Gingival Index, gingival crevicular fluid and probing depth were used as clinical parameters. Samples of the subgingival plaque were collected with sterilized paper points from the periodontal pockets. The samples were examined by dark field microscopy with the Petroff-Hauser counting chamber with a magnification of 1, 500×. The total number of bacteria and the proportion of the motile rods and spirochetes of the pockets were examined. All clinical parameters showed no significant changes after the irrigation. Intracrevicular irrigation by both acrinol and benzalkonium chloride solution significantly reduced the relative number of bacteria and the percentage of spirochetes/motile rods, when compared to those before the irrigation on day 1, though the differences did not persist on day 7. Thus, only by the single irrigation of the deep pockets with acrinol or benzalkonium chloride, the beneficial effects did not appear to continue clinically and microbiologically for a week.