Since an excellent magnetic attachment had been developed, it have been conducted an opportunity to aware of the importance of utilizing the remaining root, tooth-supported complete dentures with or without mechanical attachments, which are increasingly a part of the routine dental services offer to patients in recent years. Conserving the remaining natural root has several advantages which include less bone loss in the mandible and maxilla, improvement of proprioceptive guidance, maintenance of the vertical dimension of occlusion, psycologic benefit to the patient, and improvement of stability and retention of dentures. Since the designs of abutment tooth are controversal, although the tooth-supported dentures are benefical, this study was initiated to determine the most excellent abutment design by comparing the horizontal movement of lower canine root abutment with ten different desings for tooth-supported dentures. The ten designs of abutment tooth for tooth-supported complete denture tested were (1) the short coping of 4mm in vertical height above the crest of the ridge, (2) the long coping of 8mm in vertical height above the crest of the ridge, (3) the short coping with a magnetic attachment, (4) the long coping with a magnetic attachment, (5) the short coping with OP Anchor attachment, and the others were designs which were given the relief chamber to each of the above designs. All the dentures, however, were constructed to rest directly on the coping or the coping with mechanical attachment. The tooth movement was measured in horizontal plane by two laser displacement sensors on a simulation model. The obtained results were as follows : 1) The abutment tooth with the various coping designs tested by this experiment tipped not only to distolingual direction, but also to mesiobuccal direction under load. 2) Different positions of applying load generated different amount of movement and direction of the abutment tooth. 3) When the relief chamber was prepared around the coping, it tended to produce a great deal of torque on the abutment. Above results would facilitate the use of tooth-supported dentures with clinical success.

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Whether or not accumulation of retrogradely transported horseradish peroxidase (HRP) in the neuronal cell bodies affects their metabolic profiles was studied by examining the effects on the synthesis of acetylcholinesterase (AChE) in the rat masseter motoneurons. HRP was injected into the left masseter muscle in the experimental animals, but not injected in the control group. Sixteen hours later all rats were administered diisopropyl fluorophosphate to inactivate the existing AChE and then given an additional 1 hour for the synthesis of new AChE. Serial frozen 60 μm sections of brainstems were processed for AChE activity. The amount of AChE reaction products in the masseter motoneurons was measured by using an image processing system and ratios between the amounts in the right and left masseter motoneurons were calculated. There was no significant difference in the values between the control and experimental groups, suggesting that HRP accumulation in the cell bodies of motoneurons does not affect their synthesis of AChE.

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The mechanism of action of physical exercise and calcium intake on the jaw bones at the growth and development stage has not yet been clarified. Four-week-old male rats of Wistar strain, therefore, were used, and running exercise and food of different calcium contents were given at the same time. Their effects on the jaw bones were then investigated. The results were as follows : I. Body weight In the normal diet group, no significant differences were found from the first week through the fourth week, the calcium deficient diet group with physical exercise showed lower values (p<0.01) than the calcium deficient diet group with no physical exercise. II. Bone density findings Bone density was measured to determine degrees of bone calcifiction. No significant differences were found in the normal diet group and in the calcium deficient diet groups. Significant differences were found between the normal diet group and calcium deficient diet groups and the normal diet group showed higher values (p<0.01). III. Histopathological findings In the normal diet group, no particular changes were found in the internal structure of jaw bones from the lingual alveolar bone, central alveolar bone, buccal alveolar bone, to the labial alveolar bone. In the calcium deficient diet groups, the lingual alveolar bone, central alveolar bone, buccal alveolar bone, and labial alveolar bone showed about the same findings. In the comparison between the normal diet group and calcium deficient groups, the whole lower jaw showed extensive decrease in bone quantity for the calcium deficient groups. IV. Scanning electron microscope findings In the normal diet group and calcium deficient diet groups, no morphological changes were found in the jaw bones from the lingual alveolar bone, central aleolar bone, buccal alveolar bone, to labial alveolar bone. V. Findings in physical strength of the lower jaw bone by compression In the normal diet group and the calcium deficient diet groups, significant differences were found and the normal diet group showed higher values (p<0.01). On the basis of the foregoing findings, it was found clearly that physical exercise given to rats at the growth and development stage did not affect the jaw bones. The nutrient have an effect on the jaw bones of the rats at the growth and development stage.

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In dental clinic, dentists usually use the needles of 27G (diameter : 0.41 mm) for regional anesthesia and 30G (diameter : 0.32 mm) for infiltration anesthesia. The new needle made for infiltration is 31G (diameter : 0.28 mm) to alleviate needle penetration pain. The effects of needle diameter on penetration pain was assessed at the canine or first molar mucobuccal region by using visual analog scale (VAS). There were significant differences between the group given topical anesthesia and the groups not given in 27G and 30G needle diameters at the cainine region. Topical anesthesia is effective for the needle diameter of 30G and larger. For 31G, however, topical anesthesia is not involved in penetration pain at the canine region or at the molar region.

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In dental treatment, patients hate infiltration anesthesia which is intended to alleviate pain because of its accompanying pain. This pain accompanying infiltration anesthesia may also caused genera complication such as cerebral anemia and hyperventiration. Topical anesthesia is frequently used to prevent injection pain. The effects of lidocain concentration in topical anesthesia were assessed at canine mucobuccal region by using visual analog scale (VAS). There are no significant differences between 4% and 10% lidocaine. in penetration of 30G needle and in injection of 0.9 ml in 30 seconds. The findings indicate that 4% lidocaine is sufficient to prevent the infiltration pain at the mucobuccal region.

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[in Japanese]

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It has often been said that success in any sphere of dental minor surgery depends upon a sound knowledge of fundamental principles of surgical techniques for dental surgeon. A study of this paper will provide an excellent refresher course for any dentist wishing to improve his knowledge of this subject.

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