Greater concentration of dietary sucrose decreases dentin formation and increases the area of dentinal caries in growing rats

Effects of protein deficiency induced by raw soy with and without sucrose on dentine formation and dentinal caries in young rats

OBJECTIVES

The effects of protein deficiency and sucrose on formation and mineralization of dentine and dental caries in the molars of young rats were investigated.

MATERIALS AND METHODS

Two groups of weaning Wistar rats received raw soy flour to induce protein deficiency with sucrose or starch as the carbohydrate source; the other two groups received skim milk powder as the protein source with sucrose or starch as the carbohydrate source. At the onset, tetracycline was injected to mark the dentine formed at that moment. After 6 weeks, lower molars were sectioned sagittally, and the areas of dentine formation and dentinal caries developed during the experiment were quantified separately in the first and second molars. Dental caries was also classified according to Schiff's reaction. Calcium (Ca), phosphorus (P) and total mineral elements were analyzed using an electron probe microanalyzer.

RESULTS

Rats in both protein-deficient groups and normal protein sucrose group had significantly larger areas of dentine formed compared with rats fed with normal protein starch diet. Ca, P and total mineral elements in dentine were significantly reduced by normal protein sucrose diet. P content was significantly reduced in dentine of rats in protein-deficient sucrose group. Rats in normal protein sucrose group had significantly more and larger dentinal caries lesions than in any other group.

CONCLUSION

This study suggests that protein deficiency induced by soy prevents the progression of dental caries even in highly cariogenic environment.

The effect of fluorine and homeopathic medicines in rats fed cariogenic diet

Although some sectors of dentistry have benefited from technological advances, dental caries is still a major problem. Prevention and treatment of dental caries by fluorine is considered a major advance in public health. Nevertheless fluorosis, caused by ingestion of excessive amounts of fluorine during the period of teeth formation, is of great concern. In accordance with the homeopathic doctrine, minimum doses of fluorine and other substances could prevent and/or treat caries. In this experiment, we compared the preventive action of fluorine and evaluated the effect of homeopathic medicines on the teeth of rats fed a cariogenic diet. None of the groups included in this study developed caries. However, microscopy revealed the presence of precipitate and/or deposit in the groups treated with homeopathic medicines. This phenomenon might be due to deposit in the dental surface or precipitation of bacterial plaque or calcium salts. It was not possible to identify the composition of the deposit/precipitate due for technical reasons. In one of the groups treated with homeopathic medicines fur loss was observed in 40% of animals. These reactions might be caused due to the action of the homeopathic medicines.

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.

Parotid gland function and dentin apposition in rat molars

Previous studies have clearly established the down-regulating effect of a sucrose-rich diet on primary dentinogenesis in rat molars. Earlier observation of the negative effect of a high-sucrose diet on a parotid function involved in the control of intradentinal solute movement led us to hypothesize that parotid gland function(s) may have a role in regulating dentinogenesis. Dentin apposition in 1st and 2nd molars of young rats was measured by planimetry in sagittal sections. The following experimental variables were tested: standard and high-sucrose diets, removal of the parotid or the submandibular/sublingual glands, and diets in powder or pellet form. Removal of the submandibular/sublingual glands and changes in diet consistency did not significantly affect dentin apposition. Dentin apposition was significantly depressed by the high-sucrose diet or following parotidectomy. A further decrease followed the combination of the two treatments. Parotid glands appeared to exert a positive effect on dentin apposition in rat molars.

Effect of dietary carbamyl phosphate on dentine apposition in rat molars

In rats, sucrose increases dental caries and impairs odontoblastic function by reducing dentine apposition during primary dentinogenesis. A high-sucrose diet also affects negatively a pulp or dentine function that appears to regulate solute or fluid movement within rat dentinal tissue. In earlier work it was found that carbamyl phosphate could significantly reverse sucrose-induced cariogenesis and also stimulate sucrose-depressed movement of dentinal fluid through a mechanism involving parotid function(s). In the current study, the possibility that carbamyl phosphate could overcome the sucrose-induced reduction in dentine apposition was examined. Weanling rats were fed a high-sucrose diet supplemented or not with carbamyl phosphate for 5 weeks. Dentine apposition was measured planimetrically in sagittal sections of the molars. The effect of carbamyl phosphate was similarly tested in parotidectomized animals. Carbamyl phosphate significantly reduced the deleterious effect of sucrose on dentine apposition by 58% in the first molars. However, the reduction in dentine apposition that followed parotidectomy was not altered by carbamyl phosphate supplementation. The possibility that the beneficial effect of carbamyl phosphate on dentinogenesis involves a parotid function is entertained.

The effects of high levels of glucose and insulin on type I collagen synthesis in mature human odontoblasts and pulp tissue in vitro

High levels of dietary sucrose affect the metabolism of the pulp-dentin complex and enhance the caries process in dentin. The high-sucrose diet reduces dentin formation in young rats (Tjäderhane et al., 1994; Hietala and Larmas, 1995; Tjäderhane, 1996) and in pups of rat dams fed high-sucrose diet during lactation (Pekkala et al., 2000a). However, the mechanisms behind the effects are unknown. A direct effect of elevated blood glucose or an indirect effect via insulin has been suggested. We investigated the effects of high glucose and insulin on type I collagen synthesis in human odontoblasts and pulp tissue in vitro, using an organ culture method for functional post-mitotic odontoblasts. Odontoblasts and pulp tissue were cultured separately for 10 days in DMEM with 15% FBS containing additional glucose (G) (4.45 g/L) or insulin (I) (0.6 microgram/mL) or both together (GI). We evaluated type I collagen synthesis with RIA, measuring the level of N-terminal propeptide of type I collagen (PINP) secreted into the culture media. PINP secretion decreased in odontoblasts and pulp tissue in G and GI groups when compared with the control and insulin samples (p = 0.001 in both groups in the pulp samples). Insulin alone did not affect PINP secretion distinctly. The results indicate that high levels of glucose, but not insulin, directly down-regulate the type I collagen synthesis in young, differentiated human odontoblasts and pulp tissue. Insulin does not affect the inhibitory effect of high sucrose. These in vitro findings indicate that the high-sucrose diet may alter odontoblast function independently of insulin.

The effect of sucrose diet of rat dams on the dentine apposition and dental caries of their pups

The purpose was to examine whether a sucrose diet in rat dams reduces dentine apposition and enhances dental caries in their pups. Sprague-Dawley rat pups were randomized into four groups on the day of birth. During the lactation period three dams received a standard rodent diet and three a diet containing 41% sucrose. At the age of 3 weeks the pups were weaned and given an intraperitoneal injection of oxytetracycline hydrochloride. During the experimental period, half of the pups of control dams received a sucrose diet (Cnt-Suc pups) and half of the pups of sucrose dams received a standard diet (Suc-Cnt pups). The pups in the other halves received the same diet as given to their dams during lactation (Cnt-Cnt and Suc-Suc pups). Urine samples were collected from dams and pups during the test periods. After 4 weeks the pups were killed, their blood was collected and their jaws sectioned sagittally. Dentine apposition was determined planimetrically and dental caries using Schiffs staining. Ca, K and Na of serum and urine were measured flame photometrically and P using an ultraviolet method. The lactational sucrose diet was associated with decreased P and Na excretion in the dams, and also with reduced dentine apposition in their pups. Reduced dentine apposition and induced Ca excretion with decreased P, K and Na excretions were observed in Suc-Suc pups and Cnt-Suc pups during the experiment period. Fewer intact teeth with more enamel and dentinal caries lesions occurred in sucrose-exposed groups (Suc-Cnt, Cnt-Suc and Suc-Suc pups). It was concluded that the sucrose diet given to dams during lactation changed the function of the pulp dentine complex of their pups leading to reduced dentinogenesis, but also predisposed to a reduction of dentinogenesis in pups during the experimental period and enhanced the occurrence of dental caries.

A high sucrose diet decreases the mechanical strength of bones in growing rats

High sucrose diets alter mineral metabolism in humans and animals. We examined the effect of a high sucrose diet on bone growth, composition and mechanical strength in growing rats. Weanling Wistar rats received a high sucrose (43 g/100 g) diet (9 males, 11 females). In the control diet (8 males, 8 females), sucrose was replaced with potato starch, providing an equal energy value. At the onset of the experiment, bones were marked by tetracycline. After 5 wk, the tibias and femurs were weighed, and maximum breaking strengths were determined. Tibias were cut at the tibia-fibular junction; the widths of the bone at the start of the experiment, the periosteal bone formation during the experiment, the widths of the medullary cavity and the final bone width were determined from tetracycline lines. Bone ash weight, Ca and P contents were determined. The breaking strengths of both bones were significantly lower in the sucrose-fed groups of both sexes. In females, the weight of both bones and the final width of the tibias were significantly lower in the sucrose-fed group. The Ca concentration in both bones and the P concentration in tibias were significantly lower in the sucrose-fed group. It was concluded that the metabolic interference induced by sucrose was the reason for the differences. The alterations were more pronounced in females, but independent of body weight.