Shika gakuho. Dental science reports最新文献

The following results were obtained from the experiment on the five different blocks (HAP, HAP.diopside, diopside, HAP.anorthite and anorthite) which were created as a material of dental implant for in rabbit mandible. Implantation was done on those five blocks under the same condition using pathologic histology, SEM and TEM to see and examine about the changes in the inner surface of each block, the joint condition of new bone and the block, and new bone created around each block and follow its maturing procedure. 1. Much resorption was not seen HAP block even after 48 weeks, with HAP.diopside block, beta-TCP of HAP was resolved, and with HAP.anorthite block, its inner surface was either broken or resolved. Diopside was resolved only in the inner surface, but it was limited only in the Si-rich area. 2. HAP block was created in the long term, and with HAP.anorthite and anorthite block, their inner surface tended to brake apart. In comparison, neither cracking on parting was seen with diopside and HAP.diopside. 3. In two weeks after operation, direct bone was created and attached to diopside with HAP and HAP.diopside, this kind of bone formation was seen in the part of it, and in the rest of the part, the fiber was created. HAP.anorthite and anorthite did not seem to have new bone attached to the direct block. 4. By 4 weeks after the operation, diopside block was surrounded and stabilized by the completed new bone. It took more than 12 weeks for HAP, HAP.diopside, HAP.anorthite and anorthite block to have osteon in the new bone. 5. Crystal lattice created by HAP crystal which appeared in the diopside block, and apatite crystal in the new bone is continuous and arranged in one direction. 6. From above mentioned study results, we can say that diopside is mechanically strong, and because of new bone created along the block surface at an early stage, it is stabilized in the bone soon after the implantation and is the most suitable as a material of dental implant in all the blocks used in this study case.

A number of factors, including, for example, patient jawbone condition, influence prognosis of dental implants. At present, X-ray and intraosseous punctures are employed as means of examining bone quality. But lack of definite criteria makes objective evaluation difficult. In order to develop a more reliable method for making objective evaluations of bone quality for dental implant, this study quantitatively measured the cutting force at an intraosseous puncture and investigated its relation to bone mineral content, a parameter of bone condition. Methods One side of each of 4 mandibles obtained from adult Japanese cadavers was fixed with formalin. The mandibles were free of deformity and injury to the jaw or face but lacked molars (these materials were the property of the Department of Anatomy, the Tokyo Dental College). Drilling tests were made in 5 samples taken from each of the 4 mandibles (20 in all), and bone mineral content was measured. Prior to the drilling test, the dental engine was remodeled to produce an experimental test machine permitting quantitative measurement of the cutting force (cutting torque) exerted on cutting instrument in the direction of rotation. The device was fitted to a universal testing machine and constant-feed-speed drilling tests were performed. Cutting force on the cutting instrument produced during drilling was divided into cutting torque (cm-g) in the direction of rotation and cutting load (gf) in the direction of feeding. Densitometry and image analysis were used to measure bone mineral content. X-ray photograph were taken from each sample with an aluminum reference, the density of which was digitalized and measured. The density value was then image analyzed, and bone mineral content of the drilled site was obtained as relative value calculated in aluminum equivalent (mmAl). Comparative examinations of cutting torque, cutting load, and bone mineral content were made through the same drilled site at every 1.0 mm-depth from surface. Results and Conclusions 1. The experimental test machine permitted quantitative measurements of the cutting force exerted on the cutting instrument in the direction of rotation (cutting torque). 2. Quantitative measurements on the cutting force during drilling produced the following values: cutting torque--0.4 to 56.5 cm-g with an average of 8.7 cm-g; cutting load--1.7 to 1419.7 gf with an average of 169.3 gf. 3. Bone mineral content at the drilled site ranged from 0 to 0.67 mmAl and averaged 0.19 mmAl.(ABSTRACT TRUNCATED AT 400 WORDS)

A sensory unit with one or two Pacinian corpuscles was isolated from cat mesentery and square wave mechanical stimulation (duration 5-10 sec), sinusoidal frequency stimulation (duration 4-130 sec, frequency 0.06-300 Hz) and ramp mechanical stimulation (duration 5-10 sec) were applied to the Pacinian corpuscles. When the temperature exceeded 27 degrees C, the sensory unit caused a sustained discharge after on-response to the square wave stimulation. The sustained discharge lasted until the off-response. The sustained discharge was considered to be generated by an oscillation of the receptor potential in the Pacinian corpuscles. The results were as follows: 1. Sensory units with two Pacini corpuscles of cats from young (20 days after birth) to adult were found to respond with both fast-adapting and apparent slow-adapting responses at room temperature (27 degrees C). 2. The two Pacini corpuscles showed the characteristics of fast-adapting mechanoreceptor and vibrator. It was confirmed that the apparent slow-adapting responses from the sensory units were not artifacts induced by vibration from the stimulating bar or experimental table or experimental room, but were originated by an unknown mechanism in the corpuscles. 3. Some sensory units with two Pacinian corpuscles also responded with both fast-adapting and apparent slow-adapting responses in the range of 27-29 degrees C. The apparent slow-adapting responses were caused by pressure and vibratory stimulations above a strength level, but not by dumping of the stimulating bar. 4. The sensory unit evoked only the fast-adapting discharges near the threshold level of stimulus strength at less than 27 degrees C. In the temperature range of 27-40 degrees C, the sensory unit showed an increase in frequency of the apparent slow-adapting discharge by increased displacement and velocity of the stimulus. 5. The sensory unit responded with repeated firing to low-frequency stimulation (0.1-0.06 Hz) at the temperature range and the impulse number was increased by increased strength of the low-frequency stimulation. 6. At the 27-40 degrees C, the sensory units with Pacinian corpuscles evoked after discharge and spontaneous discharges and the impulse number was increased by increased displacement, velocity and frequency of the mechanical stimulus. Thus it is difficult to call the response of Pacinian corpuscles observed at more than 27 degrees C a slow-adapting one, judging from the duration of the receptor potential. We considered that these discharge responses resulted from an electrical oscillation of the receptor potential in the corpuscles.(ABSTRACT TRUNCATED AT 400 WORDS)

The purpose of this study was to determine the stimulus response properties of fast and slow adapting units in the fungiform papillae of the frog tongue. Secondly, fast- and slow- adapting generator potentials were recorded from fast and slow-adapting mechanoreceptors in the single fungiform papilla glossopharyngeal nerve preparations, respectively. Results I. Impulse response properties of fast- and slow-adapting units 1) Most of the fungiform papillae were innervated by both fast- and slow-adapting units. Fast-adapting units evoked 1-4 impulses to each stimulus and the adaptation time was less than 17.5 msec. Slow-adapting units evoked 27.8 +/- 8.0 impulses (range: 11-49 impulses n = 18) during a pressure stimulation of 3 sec, and the adaptation time was 1.64 +/- 0.73 sec (range: 0.53-2.86 sec, n = 18). 2) Threshold, latency and absolute refractory period for fast-adapting units were 7.0 +/- 1.9 microns (range: 3.0-11.8 microns, n = 189), 2.31 +/- 1.29 msec (range: 0.85-6.80 msec, n = 31) and 2.9 +/- 1.0 msec (range: 1.8-5.6 msec, n = 33), respectively. Those for slow-adapting units were 4.6 +/- 1.8 microns (range: 2.0-11.8 microns, n = 152), 13.54 +/- 11.29 msec (range: 2.00-54.00 msec, n = 35) and 6.5 +/- 3.6 msec (range: 1.9-19.6 msec, n = 35), respectively. 3) A fast-adapting unit innervated 5.1 +/- 2.5 fungiform papillae (range: 1-13 fungiform papillae, n = 58) and the receptive area was 0.342 +/- 0.312 mm2 (range: 0.005-1.548 mm2, n = 55). A slow-adapting unit innervated 3.3 +/- 2.0 fungiform papillae (range: 1-12 fungiform papillae, n = 50) and the receptive area was 0.158 +/- 0.144 mm2 (range: 0.006-0.616 mm2, n = 29). 4) Conduction velocity of the fast-adapting unit was 23.0 +/- 3.1 m/sec (range: 15.0-30.6 m/sec, n = 528) and that of the slow-adapting unit was 12.8 +/- 2.2 m/sec (range: 4.4-21.1 m/sec, n = 495). The conduction velocity was calculated from the time necessary to conduct at two different points of the nerve fiber. 5) The upper limits of fast- and slow-adapting units for vibratory stimulation were 62.7 +/- 10.5 Hz (range: 50-80 Hz, n = 15) and 34.5 +/- 9.6 Hz (range: 15-45 Hz, n = 10), respectively. II.(ABSTRACT TRUNCATED AT 400 WORDS)

In the treatment of removable dentures including mucosa born, it is essential to secure the occlusion based on adequate consideration of deformation of mucous membrane. This means that it is necessary to clarify the plastic deformation of underlying soft tissues after denture insertion. With the objective of assessing the influence of the difference in the supporting pressure of the underlying soft tissues, the longitudinal changes of the tissue surface after insertion of denture were observed. The non-pressure areas with special conditions were established between the basal surface of the dentures and the surface of the underlying soft tissues. Removable free end dentures with cylindrical non-pressure cavity (3 mm in diameter and 2 mm in depth) in the basal surface were prepared for 20 subjects having a missing of lower posterior region. Such three non-pressure cavities were positioned in the following locations: in a mesio-distal location corresponding to the distal region of the first molar, at the alveolar crest, at a location halfway between the alveolar crest and the buccal denture border, and a location halfway between the alveolar crest and the lingual denture border. Impressions were taken from the subjects' jaws after the fixed numbers of days following initiation of denture wearing. Contours of the non-pressure areas were measured in 100 jaw models. Results. 1. Swelling of the mucous membrane of the non-pressure area 1) Subjects are classified into the following 5 types on the bases of longitudinal changes in the swelling height of the mucous membrane in the non-pressure area. Type S-1: Marked increase in swelling height observed within the first 3 days after insertion of dentures, but practically no change in swelling height until the 30th post installation day. Type S-2: Marked increase in swelling height observed within the first 3 days after insertion of dentures, and swelling height increased continuously until the 30th post installation day. Type S-3: Marked increase in swelling height observed within the first 3 days after insertion of dentures, but swelling height decreased continuously until the 30th post-installation day. Type G: Increase in swelling height comparatively small within the first 3 days after insertion of dentures, but swelling height increased until the 30th post-installation day. Type N: No increase in swelling height observed until the 30th post-installation day. 2) Swelling height and frequency in each location according to type.(ABSTRACT TRUNCATED AT 400 WORDS)

In dental clinic for children, criteria for growth and developmental changes related to increases in the width and length of the dental arch at the primary, mixed, and permanent dentition stages are essential. This study was carried out to measure the width and the length of normal dental arch and to make detailed observations of growth and developmental processes in the dental arch at each dentition stage. Materials were serial study casts of the maxilla and the mandible taken every 2 month from 127 children (74 boys and 54 girls). The casts were made from 6 months after birth until the age of 15. Measurements of the width of the dental arch were made between bilateral teeth of the same tooth type, both deciduous and permanent. The length of the dental arch was measured on the basis of the perpendicular distance from the contact point of mesial surfaces of central incisors to a line between bilateral teeth of the same tooth type. Measured values were categorized according to either chronological age or tooth age on the basis of the eruption of the central permanent incisors. The indices of the dental arch with relation to the width and the length at each dentition stage were calculated for the sake of partial and total observations of alterations in dental arch form. The results were as follows: 1) In terms of chronological age, until 1 year before the eruption of permanent replacements, the width of the dental arch gradually decreased in both the maxilla and the mandible in the regions of the deciduous central and lateral incisors. Increasing slightly from about the age of 6 years and the period of mixed dentition, the width of the dental arch remained stable until the permanent dentition stage. From the primary dentition stage, the width of the dental arch in the region of the maxillary and mandibular canines and first and second molars gradually increased. Therefore it remained stable until the eruption of permanent dentition. The width in the region of the permanent maxillary and mandibular first molars gradually increased and attained a stable condition at about 12 years of age. In males, the width in the area of the maxillary secondary molars decreased slightly and tended to decrease in the mandible. In females, on the other hand, the width showed a tendency to increase with advancing ages. With the exception of the second permanent molars, the width between the distance of bilateral teeth were consistently larger in males than in females.(ABSTRACT TRUNCATED AT 400 WORDS)

Changes caused by attrition in interocclusal contact were investigated in 11 subjects with natural dentition showing no or only slight attrition and 6 subjects with natural dentition showing moderate attrition. Interocclusal spaces in the molar region in the maximally intercuspidated position of each subject were recorded in White Silicone impression material. Light-transmittance measurements of interocclusal records were made to determine differences in interocclusal spaces. Results 1. Mean values of the most closely occluding area in the upper molar region Tooth kind I B II B I M II M Slight-attrition group 0.6 0.9 3.2 2.5 (mm2) Moderate-attrition group 7.2 11.0 30.4 26.8 (mm2) 2. Mean values of ratios between most closely occluding areas and occlusal-surface projecting areas in the upper molar region Tooth kind I B II B I M II M Slight-attrition group 1.1 1.7 3.1 2.7 (%) Moderate-attrition group 13.1 21.0 28.4 27.5 (%) Conclusions 1. Differences in interocclusal spaces between the slight- and moderate-attrition groups were apparent only in the most closely occluding areas. 2. When load on supporting tissues is proportionate to the size of the closely occluding area, the supporting load probably increases as attrition progresses, although the ratio of increasing load changes little among different kinds of teeth.

After treating the infected canals, we investigated to determine the influence of autogenous dentin chips accidentally applied as filling in the root apexes. Materials were 15 mandibular premolars and molars obtained from healthy, mature dogs. According to standard procedures, after pulp extirpation, canals were temporarily filled with sandarac cotton pellets and left otherwise untreated for 4 weeks. At this time, the degree of infection was ascertained. After root-canal enlargement, root canals were filled with No. 55 gutta-percha points; and a sealer (Neotriozinc Paste, AH26, or Sealapex) was applied. The animals were sacrificed at the conclusion of either a short term (2 weeks) or a long term (16 weeks), and histological studies were performed. Conclusions In short-term specimens, no formation of new hard tissue was observed at the apical dentino-cemental junction; and inflammatory changes in the periapical soft tissue were remarkable. In long-term specimens, hard-tissue formation had resulted in apical closure in 6 out of 8 instances; and periapical inflammatory changes had decreased. Relations between dentin-chip density and histopathological conditions were as follows: In most of the specimens that were evaluated as good, dentin chips were very densely applied. Insufficient numbers of dentin chips produced poor results. In other words, dense applications of dentin chips result in good prognoses. Consequently, when root-canal enlargement has been adequately performed, application of dentin chips to the apex of infected canals stimulates hard-tissue formation resulting in biological apical closure. In infected canals, however, the degree to which dentin chips are infected can be a major factor.

Visual observations were made of 3,202 maxillary first premolars and 3,365 maxillary second premolars from subjects of known sex, age, and side attributes. The material belongs to the Okamoto Research Laboratory of Dentistry. Items observed for each donor included number of dental roots, shapes of root apexes, root grooves, root orientation and curvature, and conditions of the maxillary first and second premolars. Results 1) In 65.7% of all materials (55.4% in males and 76.1% in females), maxillary first premolars had primary single roots. Complete branched roots accounted for 25.5% of the male and 17.6% of the female materials. In both cases, there was significant distinction between the sexes. Triple root teeth were extremely rare in both male- and female-donor teeth, as were double rooted maxillary second premolars. 2) Protruding, circular, and flat root apex types occurred in both maxillary first and second premolars. Circular and flat types were common among males. Branched and double-root maxillary first and second premolars were of either the complete or the incomplete type, both of which were more common in males. 3) About half of the mesial surface grooves in single-root maxillary first premolars were deeper than distal surface grooves in the same teeth: In 1/4-branch double teeth, 28.8% of the mesial surface grooves were deeper than the distal-surface grooves. The corresponding percentage for 1/3-branch double teeth was 38.8%. In 7.6% of 1/4-branch and 17.4% of 1/3-branch double teeth, distal-surface grooves were deeper than mesial-surface grooves. In 36.4% of 1/4-branch double teeth and 28.9% of 1/3-branch double teeth, the lower portion of the root was web shaped. In maxillary first premolars, lingual roots of 1/3-branch double-root teeth were cylindrical, as were 28.9% of buccal roots. Root grooves occurred on the lingual sides of 61.7% of all specimens. For 1/2-branch double root teeth, 18.4% were cylindrical: and 62.7% had grooves on the lingual side. Results are essentially the same in both cases. 4) Straight dental roots occurred in 37.4% of maxillary first and 35.4% of maxillary second premolars. Roots inclined distally in 36.7% of maxillary first premolars and in 18.8% of maxillary second premolars. A variety of inclinations and curvatures was observed. Booth roots were straight in 47.5% of 2-branch maxillary first premolars, whereas 35.1% had 1 straight and 1 inclined root and 84.4% had 2 distally inclined roots.(ABSTRACT TRUNCATED AT 400 WORDS)