To understand the development of oral function and the growth and development of dentition and occlusion, it is important to know the characteristic growth-related changes of the alveolar arch and palate in infants. The purpose of this study was to investigate the morphological characteristics of the palate before teething in infants and how palatal form changes are influenced by the feeding methods during the first three months after birth. Thirty-seven upper jaw cast models from infants were used in the study. Subjects' ages ranged from 1.3 to 9.3 months and were divided into three groups by age in months (i.e., 1 and 2 months, 3 and 4 months, and 5 months and older). Three-dimensional measurements of the palate were performed on each cast model using a semiconductor laser.Results were as follows : A three-dimensional image of the palate could be precisely rebuilt on a computer, and it was used for performing detailed measurements. In addition, three-dimensional models for each group were created in a synthetic resin by applying CAD-CAM technology. The length in the front part of the palate (A−CC') significantly increased with age, whereas no changes were found in the rear part of the palate. As to the width of the palate, three items (B−B', M−M', C−C') out of four significantly increased. Palate depth and surface area did not differ among the three groups. The curve of the palatal medial plane could be expressed significantly with the sixth-order approximation. Frequency of a sucking fossa was 70.3% altogether, and no differences were found in either the frequency or the width of the sucking fossa among age groups. Palatal form in infants was also not related to feeding methods.In conclusion, significant changes of palatal and alveolar form due to growth were found in the predental period in infants, i.e., increases in both length and width of the front part of the palate. Because these characteristic changes occurred after two months of age, it suggests that growth of the anterior primary teeth and intraosseous eruption could be related to changes of palatal and alveolar form.

View full abstract

It is very difficult for dental professionals to objectively assess brushing skill of patients. Although oral health is one of the most important factors for general health, dental professionals cannot provide clear guidance on tooth brushing to patients. To perform the appropriate instruction of brushing to patients and the progress of brushing skill, dental professionals need a method of quantitative evaluation and a clear step-by-step index of brushing skill in patients.In this study, we focused on the reciprocatory motions of the toothbrush during brushing. Toothbrush motion performed by a dental hygienist for 15 seconds was captured using a motion-capture system that could continuously calculate the three-dimensional coordinates of an object's motion relative to floor. The dental hygienist performed the tooth brushing on the buccal side of the right and left upper molars. The frequency and power spectrum of the toothbrush motion were calculated and analyzed statistically.Study conclusions :1)The motion capture system accurately and continuously captured the three-dimensional coordinates of the motion of the toothbrush and was an effective method for acquiring the motion during tooth brushing.2)Although the movement for the right side of the upper molars was more unstable than that of left side, it was confirmed quantitatively that the dental hygienist had an individual distinctive rhythm during tooth brushing.We suggest that an individual's frequency during tooth brushing might provide a numerical index to assess the brushing skill of patients.

View full abstract

Dental caries are caused when acid, produced by bacteria found in plaque, demineralizes the teeth. However, caries can be prevented by a low concentration of fluoride in dental plaque. One way in which fluoride acts to prevent dental caries is through its anti-enzyme activity that inhibits the glucose metabolism of plaque bacteria, thereby reducing their production of organic acids, such as lactic acid. To clarify the actual effects of fluoride, we investigated the effects of fluoride on dental plaque bacteria by rinsing the mouth with either a 250 ppmF sodium fluoride (NaF) solution (experimental group,n＝10) or distilled water (control group, n＝10), followed 10 min later by a 10% glucose solution rinse and measurement of the lactic acid produced during bacterial metabolism. Dental plaque was collected 5 min after the glucose rinsing, and the fluoride, lactate, and glucose concentrations in the collected plaque were measured. The following results were obtained :・The fluoride concentration was significantly increased in the experimental group compared to the control group.・The experimental group showed a significantly decreased concentration of lactate production after glucose rinsing compared to the control group.・The experimental group tended to have a large concentration of residual glucose.The results of this study indicate that fluoride ions are incorporated into the plaque during NaF mouth rinsing, thereby inhibiting the production of lactic acid by plaque bacteria. However, because rinsing with NaF only temporarily increased fluoride concentration in dental plaque, in the future, it will be necessary to consider how to maintain a high concentration of fluoride in dental plaque over the long term.

View full abstract

In clinical pediatric dentistry, there are many cases of maxillary impacted supernumerary teeth. We report two rare cases in which an inverted impacted supernumerary tooth moved backward along the palate in the maxilla. Neither inverted impacted supernumerary tooth influenced the dentition or occlusion. CT images showed that each supernumerary tooth had erupted into the nasal mucous membrane. Each supernumerary tooth was surgically extracted. The postoperative course was uneventful,without any symptoms.In conclusion, it is possible to extract an inverted impacted supernumerary tooth without clinical influence by understanding the condition in detail. This case report suggests that CT images are effective for understanding the condition of impacted supernumerary teeth.

View full abstract

Ectopic eruption of permanent first molars occurs infrequently and causes some resorption of the adjacent primary second molar. Early treatment of ectopically erupting permanent first molars was considered in order to prevent space loss. The purpose of these two case reports is to describe and document correction of moderately impacted both permanent maxillary right first molars and both maxillary and mandibular left first molars in the mixed dentition. Using both a Halterman and a modified appliance as correcting appliances, the ectopically erupting permanent first molars were successfully uprighted and repositioned. The Halterman appliance is a band and loop appliance with a bonded button on the permanent molar and an elastic chain for disimpaction. The modified appliance was a combination of a Halterman and Nance holding arch or lingual arch. The results of these cases were as follows :1.By using the Halterman and the modified appliance, ectopic eruption of permanent first molars was improved in a short period of 2 to 3 months, and patients accepted the appliance without showing pain or discomfort.2.It was shown that the modified appliance can be applied to the mandibular first molar.Finally, it was suggested that the Halterman and the modified appliance are sufficiently effective treatment for ectopic eruption of permanent first molars.

View full abstract