During growth and development of the gnathic bone in infants, it is not possible to observe the processes of resorption of the bone and deciduous tooth root, bone formation and calcification of the permanent teeth separately. In the gnathic bone of infants where a normal balance exists between formation of new tissue and resorption, the formative bone tissue is closely related to the cells which give rise to the deciduous and the permanent teeth. We used a scanning electron microscope to observe the fine structure of the root resoption of the deciduous teeth, using root deciduous teeth extracted from humans. Large and small plateshaped absorbed fossula were found together with projecting dentinal fiber tubuli in the dentinal resorption cavity of the deciduous tooth root. Odontoclasts with a round form supported and covered by fibrous connective tissue were also observed.
Furthermore, when the fibrous tissue was removed washed out, an arrangement of calcified collagen fibers (similar to stromal tissue) was found in the cavity. On the absorbed cementum surface a plate-like resorption cavity had formed. The surface was covered by fibrous connective tissue with a regular pattern. The round and oval odontoclasts were surrounded by thick vascular-like connective tissue.

View full abstract

Accurate investigation of the position of the mandibular foramen is important in anatomical and clinical studies, and there are a number of reports about such measurements.
In this study,140 Indian dry skulls, whose dental stages ranged from the stage before deciduous occlusion to the later phase of third molar eruption, were reproduced and the position of the mandibular foramen was measured using laser beams and three-direction photography.
The position of the mandibular foramen was defined by the tip of the lingula mandibulae.

View full abstract

The purpose of the present epidemiological study was to clarify the influence of regular dental health examination practiced as school dental health care on the caries situation. The data analyzed were the result of dental examinations for 272 1 st year pupils attending a junior high school which was attached to a private educational institution with pupils and students ranging from the kindergarten to university level. The institution is conducting regular dental health examination for all but the primary school. We analyzed the differences in the situation of caries between pupils who had graduated from the primary school which was attached to the institution and pupils from other primary schools. The former group was composed of the pupils who had not received regular dental health examination in primary school and the latter was composed of the pupils who had received it.
Then, including the factor of the dental health care in kindergarten, we obtained the following results.

View full abstract

Using the X-ray films, plastic models and pathological photograph of 4824patients seen at the Department of Pedodontics of Iwate Medical University, the patterns of ectopic eruptions of permanent incisors and first molars (restricted to these teeth in this study) were classified into 4 groups (I-IV) to investigate the conditions of its incidence, size of the teeth and dental arch, and conditions at the stage of the mixed and permanent dentitions.

View full abstract

In the previous report we showed the conversion of calcium hydroxide contained in root canal filling materials to calcium carbonate by means of 4 weeks of subcutaneous implantation in rats. The purpose of this study was to discover if this reaction would take place in vitro as a chemical reaction and also to find out the rate of the conversion. The alteration of three materials, Vitapex, Calvital, calcium hydroxide, when in serum, was checked and the alteration of the latter two, when in the air, was checked. The solubility of calcium hydroxide in serum or distilled water was also determined. The results showed that calcium hydroxide was neutralized to calcium carbonate after several weeks in the serum. The conversion in the air was much slower than that in the serum. This means that calcium hydroxide will not change while in storage and when it has no contact with the tissue fluid. Calcium hydroxide was dissolved in both the serum and distilled water, but calcium carbonate was not. This fact suggests that calcium hydroxide neutralized to calcium carbonate by serum will cause little or no chemical irritation.

View full abstract

The present study was so designed to evaluate the change of topesthesia based on the degree of resorption of deciduous teeth and the grade of root formation of permanent teeth. A total 12315 teeth (6140 deciduous teeth and 6175 permanent teeth) from 311 boys and 364 girls, whose ages ranged from 3.9 to 17.2 years (average 8.3 years) were examined. After taking dental X-rays,20 g of pressure was applied on the axially direction on each tooth, and then the child was requested with his index finger to identify which tooth was perceived to be pressed. A specially designed tooth pressing device was used. For reference, the measurement of the root surface was made on an extracted tooth using a degital image analyzer (MAGISCAN-IIA). The followings were the results obtained in the present study.

View full abstract

There are no reports with regard to fluctuation of signs concerning the TMJ dysfunction syndorome in adolescents. Concerning this problems, we examinated 145 children (70 boys and 75 girls) of junior high school age and 429 children (202boys and 227 girls) of senior high school age for 2-years (total 3-years) longitudinally.

View full abstract

With a view to classifying. foods on the basis of the amount of masticatory acrequired, an attempt was made to correlate the properties ot different foods as shown by mechanical measurements with the amount of masticatory action involved as determined by means of an electromyogram.
We obtained the following results:
1) We found an extremely high correlation (r =0.924) between the amount of masticatory action involved and the mechanical properties of our samples when these were expressed as values given by the formula: 1og (firmncss×cohcsiveness×strainess×10)We refer to this parameter as toughness.
2) We were then able to estimate the amount of activity necessary in actual mastication of various foods from our toughness values and other values obtained through texturometer readings, a procedure which we carriedout for 144 types of foods.
3) We were thus able to classify foods into ten levels according to masticatory action.

View full abstract

[in Japanese]

View full abstract

The resorption of the roots of deciduous teeth is a physiological phenomenon. Many morphological and histological investigations of the root resorption have been reported. However little biochemical data concerning systemic factors in it are available.
In this study, cell culture derived from the root resorbing tissue of human deciduous teeth was tried and the effect of EGF on that cell was examined.
The dissected root resorbing tissue from human deciduous teeth was cultured in a medium containing 10% fetal calf serum in a humidified incubator at an atomosphere of 5% CO₂ in air at 37°C.
The outgrowing cells from root resorbing tissue were a mixed population of mesenchymal cells and epithelial cells during the early stage of cultivation, but at the later stage they changed to morphologically single population. The mesenchymal cells seemed to be derived from the dental sac and the epithelial cells from the enamel organ or the oral mucoepithelium. These cells seemed to be useful for analysis of the systemic factors in the root resorption.
The effect of EGF on the proliferation of cells obtained as stated above was examined.

View full abstract

The aim of this report was to establish a method for objective examination of TMJ sounds which is required for preventive care of the TMJ dysfunction, and to confirm its clinical importance by means of analysis of mandibular border movement and EMG.
The subjects for the acoustical analysis of TMJ sounds consisted of 13 temporomandibular joints as the clicking group,4 as the crepitus group, and 11 as the control group. The subjects for the analysis of the mandibular movement and EMG consisted of 8 adults with clicking as the clicking group and 11 without TMJ sounds as the control.

View full abstract

To examine the effect of iodoform, widely used as a component of filling sealer for root canals, on differentiation and development of tooth-germs, toothgerms of second molars from newborn Syrian hamsters were cultivated overnight and treated with various concentrations of iodoform for 48 hours.
They were subsequently transplanted into the cheek pouch of Syrian hamsters and were subjected to histo chemical examinations three weeks later.86% of the seven tooth germs examined survived treatment with 1.0μg/ml iodoform, as determined by morphology of tooth-germs. The ratio of survival decreased with increasing doses of iodoform, e. g.63%,37%, and 13% for 3.3μg/ml,6.6μg/ml and 10.0g/ml iodoform, respectively. In untreated tooth-germs, a similar level of survival was obtained with treatment using 1.0μg/ml iodoform. Although treatment with 1.0μg/ml iodoform showed a survival similar to untreated tooth-germs, the treatment induced a considerale level of aplasia of enamel and dentin in the dental crowns. Meanwhite, higher dose of iodoform was reguired for induction of aplasia or depression of the dental pulp or root dentain.
These results indicate that iodofbrm over the dose of 1.0μg/ml is toxic to cultured tooth-germs of Syrian hamsters and inhibits ditteretiation or development of the tooth-germs with tissue specificity.

View full abstract

The value and change with time of the impedance of surface EMG electrodes and the effects of their difference between the bipolar electrodes on the electromyographic activity from the anterior temporal muscle and the masseter muscle in six adult male subjects with normal occlusion were studied. The results were as follows: 1. In the anterior temporal muscle, if the impedance of theelectrode was under 20 kΩ it was stable from just after the electrode disc was applied to the skin. In the masseter muscle, if the impedance was under 30kΩ it became stable within two minutes after the electrode was applied.2. The difference of impedance between the bipolar EMG electrodes did not correlate with EMG activity.

View full abstract

Growing human offsprings are creatures that communicate by language. If rapidly growing children lose their deciduous teeth very early in life, their language and pronunciation functions may be seriously affected. The authors conducted a series of tests to find how the voice changes when deciduous teeth are extracted. The results may be summarized as follows.
1. There was no significant difference in the formants of vowels on “a-gyo”, the first line of the Japanese syllabary, but an appreciable difference was recognized between children (four to six years old) with missing anterior teeth and posterior teeth when there were consonants before and after these vowels.
2. In the formants of the vowels, there was a marked difference in the vowel “i”when children were fitted with no appliance.
3. The strength of voice components in each frequency range was ccmpared between children with missing anterior teeth and posterior teeth. It differed widely in “o ka a sa n” (which means “Mother”) and“a-gyo”, when children were fitted with no appliance.

View full abstract

This paper is a report regarding a dermaerosion case dealing with a leakage of a chemically irrigable solution in a 3 year old boy. We are continuing to observe the dermal changes during as he grows. Also, we carried out a pathological experiment on a rabbit and a patch test of the derm of seven people. The following conclusions were obtained.

View full abstract

Practice at Shimonoseki city We encountered three patients with TMJ dysfunction syndrome in adolescents whose mandibulars were asymmetrical. In two cases, we tried to treat with EMG Biofeedback therapy in order to improve a form and function. The following results were obtained from the progress and result of the treatment.
Asymmetry of mandibular causes the functional disharmony of masticatory muscle and it is probable that its asymmetry causes TMJ symptoms. These symptoms are improved with an occlusal splint, occlusal adjustment and occlusal reconstruction. The form does not change with the EMG Biofeedback therapy which is used in order to activate the masseter muscle. The function changed but was not stable.

View full abstract

This report concerned 2 cases (1-month and 8-day-old boy and 5-month and 27-day-old boy) of Riga-Fede's disease. The cases were treated with photopolymerized resin coverage of the incisal edges. Generally, the treatment methods for Riga-Fede's disease are discing and extraction of the traumatized teeth. The photopolymerized resin coverage proved to help in the rapid healing of the ulcerations. This method is useful because it is easy and is able to avoid a false pulp exposure of the hypoplastic natal and neonatal teeth by discing.
7 cases of natal and neonatal teeth were encountered at the Pedodontic Clinic of Niigata University Dental Hospital during 8 years from September 1979 to August 1987.

View full abstract

This paper reports on a rare case of horizontal impaction of the mandibular left and right deciduous central incisors.
The patient was a 4 year and 7-month-old-girl at the time of first visit to our clinic. She had no previous history, and there was no family history or anomaly in her general physical condition. All the deciduous teeth except the mandibular left and right deciduous central incisors had already erupted. The right deciduous central incisor was impacted completely and the left one erupted with its incisal edge about 2 mm at the lingual gingiva. In the X-ray examination, the horizontal impaction of the mandibular left and right deciduous incisors were noted. There were no cysts, odontoma or tumors. Both of them were extracted to prevent loss of space for the permanent central incisors. Each root of both teeth was curved 90 degrees in the lingual direction at half of length of the root. There was no anomaly of figure and color in their crowns. In the histopathologic examination, there was no anomaly except for the small root resorption at the labial and lingual sides.

View full abstract

The present paper describes ten children with eleven cases of dentigerous cysts which were treated by extraction of the primary teeth, cyst wall enucleation and lingual-arch spacemaintainer.
The patients were seven boys and three girls, with a mean age of nine years two months, in Hellman's Dental Age IIIA and IIIB. In eight of the cases, the mandibular second premolar was involved, and of the remainder, two cases involved the first premolar, and one case, a maxillary lateral incisor.

View full abstract

Ehlers-Danlos syndrome, an inherited connective tissue disorder, is characterized by skin hyperextensibility, joint hypermobility and skin fragility. The disease is at least classified into 10 types, I to X, based on clinical features, biochemical abnormalities of the connective tissue and the mode of inheritance.
A case is reported of a 6-year,8-month-old girl who showed the features of the Ehlers-Danlos syndrome type VII.

View full abstract

As the oral psychosomatic diseases of infants appear connected with a predisposition of their environment, environmental adjustment and psychotherapy on the basis of psychosomatic dentistry are necessary in the treatment.
We encountered a 9-year-old boy who seemed to be suffering from a facial tic caused by psychological factors. An attempt of therapy on the basis of psychosomatic dentistry was made in this case. The results as follows were obtained

View full abstract

The purpose of this study is to discover the actual condition and the state of the recall visit of the patients who appeared at the Pediatric Dentistry Clinic of Nagasaki University Dental Hospital, and to compare the results of 1987 and 1985.
Concerning the making of appointments for the recall visit, we sent cards to patients in 1987 though, in 1985 we did not send cards to the patients so the patients themselves had to make a telephone call to arrange an appointment.

View full abstract