Dietary influences on the formation of dental calculus in rats

Eleven diets were evaluated for their ability to produce dental calculus in albino rats. A diet containing 50 % cornstarch, 32 % nonfat dry milk, 3 % liver powder, 5 % celluflour, 1 % cottonseed oil, 5 % powdered sucrose, 1 % calcium chloride dihydrate, 2.7 % sodium dihydrogen phosphate monohydrate, and 0.3 % magnesium sulfate (Francis and Briner 1969) was remarkably effective. On the basis of a 0–3 calculus scoring system, an average score of 2.36 (S.D. = 0.65) resulted after 4 weeks' exposure to the above diet and, after 8 weeks, the average score was 2.59 (S.D. = 0.56).
While it was found that, in general, high cornstarch and milk powder diets were associated with higher calculus scores, no other diet remotely approached the above diet in calculogenicity.     

Inhibitory effect of a bisphosphonate (risedronate) on experimental periodontities in rats

The present study was designed to examine whether systemic administration of a bisphosphonate, risedronate, could prevent alveolar bone resorption in rats with experimental periodontitis. On Day 1, an elastic ring was placed around the neck of the right mandibular 1st molar to induce inflammatory periodontitis. The animals were given daily injections of either 0.9% NaCl (control group), or 0.8, 1.6 or 3.2 Öoles/kg (s.c.) of risedronate (experimental groups) from Days 1 to 7, and were killed on Day 8. Histological examinations and determination of bone mineral density in the interdental area between the 1st and 2nd molars with an image analyzer revealed that the presence of the elastic ring induced a loss of attachment and bone resorption in the control group. Vigorous bone resorption, with appearance of a large number of osteoclasts, was observed in the interdental and bifurcation areas. In the experimental groups, however, the resorption of alveolar bone and the loss of bone mineral content in these areas were prevented in a dose-dependent fashion, especially at doses of 1.6 and 3.2 Ömoles/kg. Many osteoclasts were detached from the surface of the alveolar bone and had degenerated appearances, such as rounded shapes, loss of polarity and pyknosis. These results suggest that administration of risedronate is effective in preventing bone resorption in periodontitis.     

Inhibitory effect of barium on caries formation in rats

The aim of this investigation was to study the effect of barium and fluoride in drinking water on caries formation in rats. Sprague-Dawley rats were fed a cariogenic diet (MIT-200) 17 times daily in a K?nig-Hofer programmed feeding machine for 37 days. Drinking water containing barium (0, 50 or 100 ppm) and fluoride (0 or 10 ppm) was available ad libitum. Rats to whose water was added 50 ppm barium had significant reductions in the mean severity of both buccolingual lesions and sulcal lesions compared with those rats whose water contained no barium. As expected, F at 10 ppm in the drinking water significantly reduced caries severity but this F effect was independent of the barium effect. This suggests that the inhibitory effects of barium and fluoride at these levels are additive and operate by separate mechanisms.     

Inhibitory effect of PVDF tubes on biofilm formation in dental unit waterlines.

OBJECTIVES: It has been reported that dental unit waterlines (DUWLs) are contaminated with bacterial biofilm, and that water discharged from a DUWL contains bacteria that might be opportunistic pathogens. This study aimed to investigate the ability of polyvinylidene fluoride (PVDF) tubing to inhibit bacterial contamination in DUWLs. METHODS: Newly installed dental units were equipped with either a conventional polyurethane tube (unit A) or a PVDF tube (unit B), and the numbers of bacteria discharged from high- and low-speed handpiece lines were counted using R2A agar plates. Bacterial attachment on surfaces was observed with a scanning electron microscope (SEM) up to 185 days. Bacterial outflow during 1-day clinical service from a DUWL after 1-year usage was also examined. The surface free energy of each tube was determined based on the measurement of contact angles. RESULTS: The number of bacteria discharged from unit B was lower than from unit A at 80 days and thereafter. SEM examination demonstrated that the unit A tube was covered by biofilm constituting rods and filaments after 94 days, while no biofilm was observed in the unit B tube even after 185 days. After 1-year of usage, the unit B released significantly less bacteria than the unit A at every sampling period of 1-day clinic work. Surface free energies, calculated from contact angles measured, of PVDF and polyurethane tubes were 37.7 and 77.8, respectively. SIGNIFICANCE: The present results indicate that PVDF tubes, which have lower surface free energy than the conventional tubes, were effective in inhibiting biofilm formation and reducing bacterial outflow from DUWLs.     

The effect of soluble pyrophosphates on dental calculus in adults

A sodium fluoride dentifrice, containing a mixture of soluble pyrophosphates, was used ad libitum in an adult population for 6 months after receiving a dental prophylaxis. In comparison with the control group, who used the sodium fluoride formula without the pyrophosphates, the test group had significantly less calculus by occurrence and severity. Thus, a significant reduction in newly forming calculus was obtained with the experimental dentifrice when used as an adjunct to regular professional care and personal oral hygiene procedures.     

The effect of a high-sucrose diet on dentin formation and dental caries in hyperinsulinemic rats

A high-sucrose diet decreases dentin formation and its minerals, but the mechanisms behind the effect are largely unknown. We studied the combined and separate effects of sucrose and insulin on dentin formation and mineral metabolism in growing rats. At weaning, animals were randomized into 4 groups: control/sucrose diets both with and without external insulin (1 U/x 100 g body weight daily). After 4 weeks, we measured areas of dentin formation, numbers and areas of dentinal caries lesions, and serum and urine glucose, insulin, Ca, Na, K, and P. Exogenous insulin increased serum and urine insulin levels and decreased serum glucose level, but did not affect dentin formation or dentinal caries lesion formation or progression. A high-sucrose diet decreased dentin formation independently of insulin. The differences in serum and urine minerals between the groups were minor. The findings confirm that sucrose-diet-induced reduction in dentinogenesis is independent of insulin and loss of minerals in urine.     

A case report of unusual dental calculus formation.

A case is presented in which an unusual amount of intraoral calculus was seen in a 59-year-old woman. The deposits completely covered all surfaces of most teeth and extended over the facial and lingual gingivae. The relationship between certain chemical salivary parameters and heavy calculus formers is briefly described.     

Study on mercury in dental calculus

It has been reported that dental calculus contains trace elements of mercury besides lead, cadmium and zinc. The mercury is one of the hazardous metal elements from the environmental point of view. The purpose of this study was to clarify the mechanism of the accumulation of mercury in the dental calculus. The results were as follows: 1. The concentration of mercury was 1.6 ppm in the dental calculus collected from the subjects with no amalgam fillings. 2. The most of the mercury was found in the organic fraction of the dental calculus. 3. In the culture study of Bacterionema matruchotii in vitro, with the increase of Bacterionema matruchotii the uptake of mercury by the bacteria increased. And the maximum uptake of mercury was seen between 7 to 14 days of the culture period. 4. After 7 days of culture, the bacterial cells were destroyed into several fractions and the quantity of the mercury in the respective fractions was assayed. About 90% of mercury was found in the cell wall. From these results, it was suggested that the uptake of mercury by the bacteria was the cause of mercury accumulation in the dental calculus.