The content of fluorides in experimental animal diets has been discussed and reported by several researchers. In studies on the metabolism of fluoride and dental caries experiments, low fluoride diets have been used with specially prepared formulas. However, data on fluoride content in commercially available diets for animals have not been reported with accurate analysis for total fluoride.
The purpose of this study was to examine fluoride contents in various experimental animal diets commercially available and also to ascertain fluoride analysis for the diets, especially for total fluoride in the sample. This information will be useful for designing animal experiments and evaluating the results.
Samples of 9 experimental animal diets obtained from 3 manufacturers for fluoride analysis were the diets for mice, hamsters and rats (CA-1, MF and CE-2); the diet for rabbits and guinea pigs (Labo RG-RO and RC-4); the diets for rabbits (CR-3); the diet for dogs (CD-5); the diet for cats (CFE-2); and the cariogenic diet for rats and hamsters (Diet #2000). Each sample was powdered and Ca (OH) ₂ (F free) added as a fixative for fluoride during ashing at 550°C. The distillate of fluoride from samples with perchloric acid (F free) was obtained approximately 200mlfrom each sample and also the distillate was analyzed by ion-specific fluoride electrode.
Samples were classified by fluoride contents as follows: (1) low-fluoride diet (4-5ppm F^-; sample codes: RC-4, CR-3 and Diet #2000); (2) medium-fluoride diet (approx. 20ppm F^-; sample codes: Labo RG-RO, CD-5 and CFE-2), and (3) high-fluoride diet (40-80ppm F^-; sample codes: CE-2, MF and CA-1). From these results, we found that high-fluoride diets contained fish-meal and low-fluoride diets contained soybean-meal as the major protein source. In order to ascertain analysis procedure for total fluoride in the sample, the distillation rate of fluoride and the ashing time for decomposition of powdered sample included organic and inorganic substances were analyzed statistically by two-way layout of the experimental design. Statistical findings suggested that more than 10 hours of ashing is advisable for each of the distillation rates (30ml/10min, 50ml/10min and 100ml/10min) and also the results obtained in this study revealed relatively high fluoride content in the commercially available diets for experimental animal.
We suggest the establishment of guideline for fluoride content in diets for experimental animals, such as AIN-76^TMproposed by American Institute of Nutrition Ad Hoc committee for experimental animal diets.

View full abstract

We examined 483 pharmaceutical college students and 337 dental college students in an oral health survey, and discussed the relationship between their dental disease status and oral health behavior obtained by the questionnaire. The results were as follows.
1) The percentage of students with caries teeth treated completely was 24.84% in the pharmaceutical students, and 32.84% in the dental students. The former percentage was significantly lower than the latter (P<0.01).
2) The pharmaceutical students had 11.96 DMF teeth, 2.86D teeth, and 8.68F teeth, and the dental students had 11.89 DMF teeth, 2.53D teeth, and 8.76F teeth.
3) The percentage of subjects with gingival inflammation was not significantly different between pharmaceutical students and dental students.
4) From the questionnaire about oral health behavior, dental students had more dental health awareness than pharmaceutical students. This result was consistent with the good caries treatment status in dental students.

View full abstract

The purpose of this study was to investigate the effect of ammonium titanium fluoride solution on rat caries. Eighteen-day-old male Sprague-Dawley rats were infected with Streptococcus mutans GS-5 for three days and fed a cariogenic diet (Diet 2000 No. 3) during the experimental period. The rats were divided into three groups; 2 experimental groups were given topical application of the solution of APF (0.9% of F, pH 3.4) or (NH₄) ₂TiF₆ (0.9% of F, pH 3.4), twice a week without anaesthesia, and the third group served as a control. Caries prevalence was examined using a standardized photograph (×50) of the rat jaw, and then caries scores (caries incidence and caries extent) were calculated from these data. The distributions of calcium, phosphorous, fluoride, and titanium in the enamel were determined by electron probe microanalysis. The enamel surface was observed by scanning electron microscope.
Both caries incidence and caries extent were clearly reduced, and significantly lower values were found in the fluoride groups than in the control group. The fluoride groups had very few serious grades of lesion, whereas the control group had many collapsible lesions at 33 days of age.
In the electron probe microanalysis, an enriched zone of fluoride and titanium was observed at the entrance of enamel fissures in the group treated with (NH₄) ₂TiF₆. The scanning electron microscopic study showed that there was glaze formation on enamel surfaces caused by titanium uptake.
It is concluded that the topical application of (NH₄) ₂TiF₆ leads to uptake of fluoride and titanium into the enamel surface in vivo, and is effective in reducing caries incidence and inhibiting caries progression in rat experimental caries.

View full abstract

Using Tokyo primary school children in grades 2-4 as subjects, a dental examination together with 3 caries activity tests, Snyder test (ST media, simplified method), Cariostat and the Buffer Test were carried out. In addition, the plaque adherence test, DI-S, and the primary molar test, DHC, were conducted. The patients were then followed for 2 years and the relationship with the increased DMF index (ΔDMFT) was investigated.
An attempt was then made to determine which test was the most effective for caries screening. The results are as follows:
1) No significant correlation between the DMFT obtained at the initial examination and the ΔDMFT during the observation period was observed.
2) Among the caries activity tests, the Snyder test at all observation periods showed a significant correlation with respect to ΔDMFT. In addition, there was a strong correlation between the results of the Snyder test and the average ΔDMFT value.
3) The Snyder test was found to be relatively superior to the other caries activity tests as judged by the ROC Map and Odds Ratio. When the Snyder test was used in combination with the Cariostat or Buffer test, the accuracy of the positive reactions was increased. However, in practical terms, the Snyder test by iteself was judged to be the best.
4) For screening tests conducted using DI-S and DHC, from the point of view of the DMFT, the results of the former were poor, while it can be said that DHC was more sensitive and specific and the positive reaction more accurate. Therefore, it appears to be useful for short term estimates.
5) Summarizing the above, for predicting caries outbreak in primary school children, the Snyder test alone was best at predicting risk, with DHC also being relatively good. Using combined resulted in omission of the high risk groups, so their use is probably not wise.

View full abstract

Total fluoride (F) determination in dental plaque is rather complicated because of its small quantities and low F concentration smapled from the individual. Full dissociation of the bound F in dental plaque is also required for the assay by F sensitive electrode.
Recently, AlF (aluminum monofluoride) molecular absorption spectrometry was developed for the ultratrace analysis of F. An application of this method to the determination of total F in dental plaque was investigated.
The results were as follows:
1) The AIF absorbance was linearly increased by increase of F (5-50ng/ml) added to sample solutions (0.5-2.1mgdry plaque/ml). The regression coefficients of sample solutions were almost equal to that of the standard solution. The sensitivity was 0.066ng F per 20μl standard solution at the 1% absorption level, and the relative detection limit was 0.0036ppm (3.6ppb).
2) The variations of absorbance increased with the plaque amounts, but the recovery of fluorine from sample solution was not affected by the amounts of plaque contained.
3) The coefficient of variation of F concentration in small plaque samples (approximately 1mg dry weight) ranged from 8.6 to 15.9%, and F concentrations of five pooled plaque samples ranged from 8.0 to 12.3ppm (dry weight).
These experiments suggest that AlF molecular absorption spectrometry is useful for analysis of total F in dental plaque, especially in small samples and at low F concentrations.

View full abstract

A comparison was made between the scrub method and the roll method of brushing teeth.
It has been reported that when the roll method of brushing is used, plaque removal, as indicated by the decrease in plaque score, is proportional to the product of the brushing force and the frequency of brushing strokes, and that the largest plaque removal is obtained by brushing with a force of 800g at 30 strokes per twenty seconds. The manual dexterity for manipulating toothbrushes was evaluated by means of a tri-axial strain gauge on the handle of the toothbrush.
In this study of plaque removal using the scrub method, the brushing force was determined by a cathode-ray tube oscilloscope attached to a tri-axial strain gauge on the handle of the toothbrush. The frequency of brushing strokes was determined by synchronization with a metronome. It was concluded that the largest plaque removal was obtained by the scrub method with a force of 400g and 80 strokes per twenty seconds. Plaque removal with the scrub method was proportional to the product of the brushing force (100-400g) and the frequency of brushing strokes (40-80times/20sec).
The better the manual dexterity of handling the toothbrush, the more plaque was removed. The dexterity was evaluated by the direction and magnitude of the strain in the handle and the motions of the brush.
It was found that, for those subjects who showed a 100% decrease in plaque, there was an inverse relationship between brushing force and the frequency of strokes. This was not necessarily the case when the decrease in plaque was less than 100%. This was also a common phenomenon with the roll method.

View full abstract

[in Japanese]

View full abstract

[in Japanese]

View full abstract

The purpose of this investigation is to evaluate the validity of TPI in the assessment of malocclusion in Japanese. Plaster models obtained from 163 females of 18 to 24years of age were examined according to TPI, and ranked for severity of malocclusion by three orthodontists. The following results were obtained after the comparison between the order of TPI value and the orthodontic ranking. TPI showed a reasonable validity because the Spearman rank correlation coefficient was 0.806. There were some overestimated cases in TPI, such as maxillary incisal crowding, mandibular incisal crowding, deep bite, molar malocclusion, and ectopic eruption.
There were several underestimated cases in TPI, such as inversion of incisors, maxillary protrusion, edge to edge, diastema, midline displacement, and mandibular incisor aplasia. These were thought to be unacceptable faults.
Therefore it is concluded that some modification must be considered to the weighting of TPI in order to apply it for epidemiological survey in Japanese.

View full abstract

In vitro and in vivo effects of mutanase on the release of reducing sugar from human dental plaque were examined.
In vitro, release of reducing sugar was detected with 2.8 units of mutanase, and linearly increased to about 11 units.
In vivo, after rinsing for 1 minute with mouthwash containing 11 units of mutanase, the amount of released reducing sugar was significantly higher (p<0.01) than that after rinsing with placebo (heatinactivated mutanase solution). However, mouthwash containing 2.8 units of mutanase had no effect.
These results suggest that mutanase degrades human dental plaque, and that the lowest clinically effective level of mutanase is between 2.8 and 11 units.

View full abstract