Comparison of the effect of gluconate, lactose, and xylitol on bone recalcification in calcium-deficient rats.

The therapeutic value of three calcium absorption promoting carbohydrates, lactose, gluconate and xylitol, in bone calcification was evaluated in 7-week-old male rats which were fed on a semisynthetic Ca-deficient diet for 3 weeks. Lactose + CaCO3, xylitol + CaCO3, Ca-gluconate, or CaCO3 alone were administered to the Ca-deficient rats for 2 weeks; the carbohydrate and Ca contents of the diets were 5% and 0.5%, respectively. The Ca-deficient rats showed a decrease in serum total Ca and ionized Ca2+ and in tibial Ca, Mg, P and density, with a concomitant increase in bone hydroxyproline concentration. Bone and serum tartrate-resistant acid phosphatase activities were increased 2-fold and the serum 1,25(OH)2D3 level 5-fold. Smaller increases were found in serum calcitonin, PTH, alkaline phosphatase and osteocalcin levels. These changes (except calcitonin) were reversed by the administration of Ca and the carbohydrates. It was observed that all three agents improved the recalcification of bones compared with the effect of CaCO3 alone. The effect of lactose and xylitol was superior to that of gluconate. These results suggest advantages in the use of xylitol in Ca-supplements.

Dietary xylitol supplementation prevents osteoporotic changes in streptozotocin-diabetic rats.

The effects of 10% and 20% dietary xylitol supplementation on the biomechanical properties, trabeculation, and mineral content of long bones were studied in streptozotocin-diabetic rats. Forty 3-month-old male Wistar rats were divided randomly into four groups of 10. Rats in three groups were administered a single injection of streptozotocin (50 mg/kg body weight) to induce type I diabetes, while animals in the fourth group were given a sham injection of physiological saline. The sham-injected group and one of the streptozotocin-diabetic groups were fed the basal diet, while the two diabetic groups were fed the same diet supplemented with 10% and 20% xylitol (wt/wt). After 3 months, the rats were killed and the long bones were prepared for analysis. The 10% and 20% dietary xylitol supplementation significantly prevented the type I diabetes-induced decrease in the mechanical stress resistance of the tibia in the three-point bending test, the shear stress of the femur in the torsion test, and the stress resistance of the femoral neck in the loading test. No statistically significant differences were found between any groups in the values for strain or Young's modulus in the three-point bending test, or in the values for the shear modulus of elasticity in the torsion test. These findings indicate that dietary xylitol protects against the weakening of the bone strength properties of both cortical and trabecular bone without affecting the elastic-plastic properties. Supplementation with 10% and 20% dietary xylitol significantly prevented the type I diabetes-induced decrease of humeral ash weight and tibial density. Histomorphometric data for the secondary spongiosa of the proximal tibia showed that 10% and 20% dietary xylitol supplementation also significantly prevented the type I diabetes-induced loss of trabecular bone volume. In conclusion, dietary xylitol supplementation protects against the weakening of bone biomechanical properties in streptozotocin-diabetic rats. This is related to the preserved bone mineral content and preserved trabecular bone volume.

Improved bone biomechanical properties in xylitol-fed aged rats.

Our previous studies have shown that dietary xylitol protects against weakening of bone biomechanical properties in experimental postmenopausal osteoporosis. To study whether xylitol preserves bone biomechanics also during aging, a long-term experimental study was performed with rats. Twenty-four male Sprague-Dawley rats were divided into 2 groups. The rats in the control group (NON-XYL group) were fed a basal rat and mouse no. 1 maintenance (RM1) diet, while the rats in the experimental group (XYL group) were continuously fed the same diet supplemented with 10% xylitol (wt/wt). The rats were killed after 20 months. Their femurs were prepared for biomechanical analyses and scanning analyses with peripheral quantitative computed tomography (pQCT). In 3-point bending of the femoral diaphysis, maximum load, maximum elastic load, stiffness, energy absorption, elastic energy absorption, ultimate stress, and yield stress were significantly greater in the XYL group than in the NON-XYL group. This indicates a xylitol-induced improvement of both structural and material strength properties of cortical bone. Accordingly, the maximum load of femoral neck was significantly greater in the XYL group. In the pQCT analysis of femoral diaphysis, cortical bone area, cortical thickness (CtTh) periosteal circumference, and cross-sectional moment of inertia were greater in the XYL group. The endosteal circumference was smaller in the XYL group. In the pQCT analysis of the femoral neck cortical area of the midneck was significantly greater in the XYL group. This data indicates that xylitol exerted beneficial effects on the cross-sectional architecture of the bones. In conclusion, continuous moderate dietary xylitol supplementation leads to improved bone biomechanical properties in aged rats concerning both bone structural and material strength properties.

Quantitative analysis of the effect of xylitol on pneumococcal nasal colonisation in rats.

Xylitol possesses anti-bacterial effects on pneumococci in vitro. To study the effect in vivo, the nostrils of 80 rats were inoculated with pneumococci. Intervention groups (n = 20) received either a xylitol diet or xylitol nasal sprays. The control groups were on a normal diet or had saline sprays. After 3 days, a quantitative bacterial culture and a PCR were done from the mucosal suspension. Neither the mean colony-forming unit counts nor the PCR counts differed statistically significant between the xylitol and control groups. Thus, we found that xylitol had no significant effect on pneumococcal mucosal colonisation.

Mutans streptococci in plaque from margins of amalgam, composite, and glass-ionomer restorations.

Levels of mutans streptococci in plaque samples from margins of Class II amalgam (Dispersalloy), composite (P-10), and glass-ionomer (Ketac Silver) restorations were compared. Fifty-one children, each having one of the restorations in a permanent first molar, were part of an inter-individual comparison, giving 17 restorations of each material. The age of the children, the age of the restorations, and the salivary levels of mutans streptococci were comparable in the three groups. Another seven children--each having both a composite and a glass-ionomer restoration of the same age placed on contralateral premolar or molar teeth--were part of an intra-individual comparison. The percentage mutans streptococci of total CFU count in plaque was higher on composite (mean 13.7) and amalgam (mean 4.3) than on glass-ionomer (mean 1.1) restorations in the inter-individual comparison, and higher on composite (mean 4.2) than on glass-ionomer (mean 0.4) restorations in the intra-individual comparison. In both comparisons, the differences in values between samples from glass-ionomer restorations and samples from composite or amalgam restorations were statistically significant (p less than 0.05).

Intraoral transmission of Streptococcus mutans by a dental explorer.

A streptomycin-resistant strain of S. mutans was introduced into the mouth as adherent growth on an artificial fissure (AF). A second AF, which was initially sterile, was placed in a crown on the opposite side of the dentition. The labeled strain was not found in 8 initially-sterile AFs which were left in vivo for 2 to 6 days and were not examined with a dental explorer. The labeled strain was detected in 7 of 9 initially-sterile AFs which were probed with the dental explorer.

Effects of dietary xylitol on collagen content and glycosylation in healthy and diabetic rats.

The effects of three-month dietary xylitol supplementation on the amounts and hexose contents of acid-soluble collagen as well as on the amounts and fluorescence of collagenase-soluble collagen were studied in healthy and streptozotocin-diabetic male rats. Collagen was extracted from skin samples. In the healthy rats, supplementation with xylitol (10%) increased the hydroxyproline content of the acid-soluble fraction and skin thickness. In diabetic rats receiving and not receiving xylitol, the acid-soluble collagen fraction was markedly lower than in healthy rats. However, its amount was significantly elevated when xylitol had been added to the diet. Supplementation with xylitol caused no changes in the amounts of collagenase-soluble fraction in either healthy or diabetic rats. Supplementation with xylitol (10%) significantly decreased the hexose content of acid-soluble collagen and the fluorescence of the collagenase-soluble fraction in both healthy and diabetic rats. The results indicate that dietary xylitol affects collagen synthesis and collagen glycosylation.

Implantation of transformant strains of the bacterium Streptococcus sanguis into adult human mouths.

Streptococcus sanguis strains isolated from dental plaque of 12 subjects were screened for their ability to undergo genetic transformation using a streptomycin-resistance marker. All subjects harboured at least one transformable strain. Eight of the subjects were implanted with transformant strains originally isolated from their own mouth, whereas four subjects received bacteria from other donors. The Strep. sanguis transformants became successfully implanted; their oral levels remained virtually unchanged during the 3-month experimental period. Their oral establishment did not seem to be related to whether the subjects were implanted with their own transformant strains or not. The implanted Strep. sanguis could be recovered both from teeth, oral soft tissues and throat.

Persistence and spread of the orally-implanted bacterium Streptococcus sanguis between persons.

Transformant strains of streptomycin-resistant Streptococcus sanguis persisted 2.5 years after oral implantation in 6 out of 11 subjects. Natural transmission of these bacteria to spouses had occurred in 5 of the 6 infected subjects. At follow-up examinations, the median value of streptomycin-resistant Strep. sanguis per ml saliva was 226,000 c.f.u. in the infected subjects and 352,000 c.f.u. in their spouses. The median values of streptomycin-resistant Strep. sanguis as a percentage of the total Strep. sanguis c.f.u. count were 3.6 and 4.8 per cent in samples from vestibular mucosa, and 18.2 and 7.8 per cent in samples from the teeth of the infected subjects and their spouses, respectively.

Morphological analysis of dentine formation in young rat molars during the recovery phase with calcium alone or combined with xylitol following a low-calcium dietary regimen.

The effects of dietary calcium deficiency and subsequent replenishment of the diet with calcium alone or with xylitol were studied. Thirty 3-week-old Wistar rats were labelled with an i.p. tetracycline injection. Twenty rats were fed a diet with 0.026% calcium (Ca-deficient); 10 received a 0.5% Ca diet (controls). After 3 weeks the tetracycline labelling was repeated. Replenishment of the diet was introduced for Ca-deficient rats, and 10 received additional 5% xylitol in the diet. After 4 weeks the labelling was repeated and the animals were decapitated. Dentine formation was measured by the tetracycline stripes in the lower first and second molars. Calcium deficiency during the first 3 weeks reduced dentine formation. In the control and xylitol groups, a much smaller amount of dentine was formed during the recovery period. With Ca alone, dentine formation was faster than in the controls or Ca-xylitol group and did not differ from the Ca-deficient period. These results indicate that in rat molars the odontoblasts can accelerate the rate of dentine formation when calcium is restored to the diet, at least during primary dentinogenesis. This effect was not seen when 5% xylitol was added to the replenishment diet.

Dental caries, mutans streptococci, lactobacilli, and saliva secretion rate in adults.

In 718 Swedish patients, equally divided into four age groups (19-25, 26-45, 46-60, greater than 60 yr), salivary levels of mutans streptococci and lactobacilli, saliva secretion rate, and DMFS were registered. No significant differences were found between the various age groups either in salivary factors or in caries (D). Number of missing (M) and filled (F) surfaces increased with age. Prevalence of root caries, which increased with age, was significantly correlated to number of exposed root surfaces independent of age. Of the total study group, 50% had greater than or equal to 10(6) mutans streptococci and 40% had greater than or equal to 10(5) lactobacilli per mL saliva. Three percent had a saliva secretion rate of less than or equal to 0.5 mL/min. Correlation analyses showed that both mutans streptococci and lactobacilli significantly correlated to the caries prevalence but the r-value never exceeded 0.34.

Asymmetrical dental caries and Streptococcus mutans infection.

A 27-year-old woman chewed unilaterally and had restorations and caries only on the right side of the dentition. The left side had a greater amount of soft and hard deposits and more severe periodontal disease. Plaque samples from occlusal and interproximal tooth surfaces were collected and cultured. The proportion of Streptococcus mutans of the total anaerobic count in the plaque samples from the right side was 1,000 to 10,000 times as high as from the left side. The proportion of S mutans of the total streptococcus was 6% to 20% on the right and less than 1% on the left side.

Class II amalgam restorations, glass-ionomer tunnel restorations, and caries development on adjacent tooth surfaces: a 3-year clinical study.

Eighteen caries-active adolescents, each having both a class II conventional amalgam (Dispersalloy) and a glass-ionomer (Ketac Silver) tunnel restoration of the same age placed on a contralateral tooth, were part of a 3-year clinical study. At the 1- and 2-year examinations all test restorations were assessed as acceptable in all patients. At the 3-year assessment three amalgam restorations failed due to recurrent caries, and one glass-ionomer restoration failed due to marginal ridge fracture. During the entire study period, the requirement of restorative therapy because of primary proximal caries was significantly reduced (p < 0.05) on tooth surfaces adjacent to the glass-ionomer restorations as compared with that on tooth surfaces adjacent to the amalgam restorations.

Streptococcus mutans in plaque after mouth-rinsing with buffers of varying pH value.

After a period of mouthrinsing with a phosphoric buffer solution with low pH the proportional distribution of Streptococcus mutans in plaque from occlusal retention sites was significantly higher than after a control period. This indicates that colonization with S. mutans may be favored or that other microorganisms competing with S. mutans are inhibited under these circumstances.

Contamination of toothpaste and toothbrush by Streptococcus mutans.

Toothbrushes and toothpaste tubes used by persons infected with S. mutans were examined for the presence of this microorganism. Fifteen minutes after brushing greater than 10(6) S. mutans were isolated from the toothbrushes and after ordinary storage for 24 h 10(4) were recovered. From two out of 10 toothpaste tubes S. mutans was isolated from the orifice of the tube. The implications of these findings for the spread of the microorganism are discussed.

Dietary xylitol retards bone resorption in rats.

Dietary xylitol has previously been found to promote the content of calcium and minerals of the bone during rehabilitation following dietary calcium deficiency and during a normocalcemic diet in rats. This in vivo experiment was performed in order to study whether a short-term dietary xylitol supplementation affects bone resorption and calcium incorporation into bone during two different experiments utilizing either calcium-deficient or normocalcemic diets. Xylitol reduced bone resorption measured by the urinary excretion of 3H radioactivity both during calcium-deficient and normocalcemic diets. However xylitol reduced vitamin D levels only during calcium deficiency, indicating that the decreased bone dissolution was not associated with changes in 1,25(OH)2D3 concentration alone. Dietary xylitol did not alter 45Ca incorporation into bone, although this does not exclude the possibility that xylitol may have caused alterations in bone apposition. These results suggest that a short-term xylitol ingestion retards bone resorption in the rat.