[in Japanese]

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Streptococcus sobrinus and Streptococcus downei are closely related cariogenic species. A DNA fragment (1.2 kb) of a central region of the S. sobrinus dextranase gene (dex) was amplified by polymerase chain reaction and utilized for a DNA probe to differentiate S. sobrinus and S. downei. The dex probe was dot-hybridized to the reference strains (17 strains of 5 species) of mutans streptococci and other related strains (13 strains of 9 species). The probe hybridized only to both S. sobrinus and S. downei at a highly stringent condition, but to none of the other mutans streptococci nor other gram-positive cocci. To differentiate S. sobrinus and S. downei, Southern blot hybridization was carried out against restriction fragments of chromosomal DNAs with the dex probe. The probe showed species-specific hybridization patterns to the EcoRI, EcoRV, HindIII and PvuII-fragments. This result suggests that hybridization analysis with the dex DNA probe is useful for the detection and differentiation of S. sobrinus and S. downei.

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The transverse cut and polished surfaces of a cow longbone were observed by backscattered electron (BSE) imaging, and then they were treated with a combined treatment of sodium hypochlorite (NaOCl) and ethylenediamine tetra-acetic acid (EDTA). The samples were observed again by BSE or by scanning electron microscopy (SEM). The combined treatment strongly eroded young hypocalcified osteons, and they were compared with older osteons. Some young osteons before treatment contained hypocalcified lines along the Haversian lamellas. The hypocalcified lines were more strongly eroded than the neighboring lines in the NaOCl-EDTA/ BSE method. In addition, a developing small osteon or a Haversian lamella showed a loose structure in the NaOCl-EDTA/SEM method. Thus, it was revealed that hypocalcified osteons and incremental lines, containing either a large or a smaller amount of collagen fibers, were strongly eroded by the combined treatment of NaOCl and EDTA. From such findings, it is suggested that the hypocalcified lines of spherical and linear laminate structures in human dentin are more strongly eroded than the hypercalcified lines in the NaOCl-EDTA/SEM method. Though we have previously suggested the positive correlation between the concentration of collagen fibers and the degree of calcification in the dentin, the correlation may be negative if the lower the concentration of collagen fibers is, the higher the degree of calcification as suggested by an author. On this correlation, further investigations will be necessary.

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This study was carried out to determine statistical information concerning the crowns and the fixed partial dentures (total number, types and rate of crowns, number of vital or non-vital abutment teeth, etc.) which were placed in the outpatients in the Department of Fixed Prosthodontics at Showa University Dental Hospital from April 1995 to March 1996. The following results were obtained :
(1) The total number of crowns and fixed partial dentures produced were 1,135; among them, crowns totaled 922 (81.2%) and the fixed partial dentures, 213 (18.8%).
(2) Most of the crowns were full cast crowns (550, 59.7%); the second most commonly produced was porcelain fused to metal crowns (166, 18.0%), the third was resin faced cast crowns (149, 16.2%).
(3) Porcelain fused to metal crowns and resin faced cast crowns were most commonly used for the anterior teeth; full cast crowns and porcelain fused to metal crowns, for the premolar teeth; full cast crowns, for the molar teeth.
(4) Fixed partial dentures located in the posterior region were about 60%; those in the anterior and the antero-posterior regions were about 20% each.
(5) With regard to the relationship between the missing teeth and the abutment teeth of the fixed partial denture, the three-unit fixed partial dentures (one missing tooth with two abutmentteeth) were most frequently treated in all regions.
(6) The crowns covered by the insurance dental service were 75.7%; the fixed partial dentures were 68.1%.
(7) Concerning the abutment teeth of the crowns, non-vital teeth were 88.5%, implant abutments were 2.2%; non-vital teeth of the fixed partial dentures were 67.3%, implant abutments were used this year for the first time to make the fixed partial dentures; concerning the bridges, implant abutments were 2.3%.

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We cloned DNA fragments of cysteine proteinases (CPs) genes of Trichomonas tenax (T. tenax) and analyzed their nucleotide sequences in order to develope DNA probes. Initially, we constructed a pair primers (a and b) to amplify the CP genes of T. tenax, and obtained approximately 550-bp fragments by PCR. We then cloned the PCR fragments into pGEM-T vector and then isolated 150 clones. The inserts were sequenced and they were 498 to 513 by long. From the DNA sequences, amino acid sequences were deduced and 26 out of 150 DNA fragments were suggested to be CP gene. The 26 clones were divided into three groups, based on the amino acid sequences, and were designated CP-6, CP-8 and CP-25. By comparing the amino acid sequences with those of CPs, papain, cathepsin B and L, CPs of other protozoa, it was suggested that CPs of T tenax are more closely related to those of T. vaginalis (75-79%).

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The dynamics of the maxillofacial bone formation during postnatal growth has a complex process and the morphological characteristics in several patients has affect to the treatment planning. The growth pattern of the mandible and the facial type have been assessed by the application of various methods developed for the cephalometric measurement of the skeletal size or positions.
However, these conventional methods cannot evaluate the changes of growth sites in lives and the differences among each skeletal shapes. The purpose of this study was to develop a new method of mathematical way of superpose technique for comparison of the different shapes. In this article, new method for morphological analysis was introduced and 16 cleft palate patients with longitudinal cephalometric data and their parents were compared to clarify the hereditary effect in the madibular growth.
New analysis was described following equations :
Fv=∑(abs (Vs-Vh)×Dl)
Vs : Transforming velocity
Vh : average velocity
D1 : Distance between neighborning two points on same shapes
Gn=∑(abs (S))
abs (S) : changes of area
H=Fv+Gn
Superposed position was defined where H presented the minimum value. The application of thid new method using mathematical coordinate transformation technique was assessed to quantify and to visualize the difference of two shapes.
From the comparison of cleft patient and their parents, the possibility of hereditary effect was suggested in madibular growth.

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The mandibular condylar cartilage, which provides an important growth center during the period of mandibular growth, works essentially as an articular cartilage. With a failure in growth activity, the condylar cartilage may adapt its matrix organization to circumferential change. The adaptability has been a subject of considerable speculation ever since. The purpose of this study is to elucidate histological features and ultrastructural changes of collagen fibril arrangement in the condylar cartilage of the rats aged from 80 to 120 weeks, by light microscopy, transmission and scanning electron microscopy. The condylar cartilage was classified into three distinct zones : fibrous, proliferative, and cartilaginous zones. The condylar cartilage decreased in thickness with advancing age. In the fibrous zone the fibrils were organized into closely arrayed bundles running parallel to the articular surface, but became longitudinally arranged in the deeper fibrous zone. The chondrocytes in the cartilaginous zone, most of which is occupied by mature chondrocytes in 80-week-old rats, changed into fibrocartilage cells in the rats over the age of 90 weeks. The fibrils were mainly organized into longitudinally or obliquely arranged bundles in almost all the cartilaginous zone. The fibril bundles were more complexly interlaced in 120-week old rats. Thick fibrils whose existence cover a wide range in the cartilaginous zone of aged rats increased with advancing age. The condylar cartilage infrequently showed a quite structural difference from the other condylar cartilages. A partial thickening of the fibrous and cartilaginous zones in this cartilage appears to show occurrence of temporomandibular joint remodeling. The age-related changes of the diameter and organization in the cartilaginous fibrils may offer sufficient strength to enable to resist the long-term influence of compressive, abrasive, and tensile stress.

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In recent years, osteoporosis has been one of remarkable diseases due to the increase of patient numbers. Sufficient care is necessary to apply dental implants for the patients with osteoporosis in whom bone resorption exceeds bone formation.
The report describing here is a case with osteoporosis with displacement of dental implant into maxillary sinus. After the implants of upper jaw had been removed, wide alveolar bone loss from premolar to molar area at both sides was brought out. As it was judged to be difficult to recover occlusal function by full removal denture, the implants utilyzed magnetic attachment were applied to the regions at both canines. The sites of implant fixation were decided by measuring the height of alveolar bone with Dent-Scan. At 12 months later after final treatment, the patient could obtain satisfactory stability of the denture.

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