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The significance of systemic dietary effects on the response of the pulpo-dentinal complex to dentinal caries was examined. Weanling rats were divided into high sucrose or control diet groups both with and without cariogenic bacterial inoculation. At the onset, tetracycline was injected to mark the dentin formation during the experiment. After 5-6 week, mandibular molars were sectioned sagittally. The areas of dentin formed during the experiment and those of dentinal caries were quantified separately in the first and second molars. In the control diet groups the area of dentin was significantly greater under carious fissures, whereas in the high sucrose diet groups the area of dentin formed did not differ between intact and carious fissures. The high sucrose diet resulted in a significantly smaller area of dentin formation than did the control diet. The high sucrose diet with cariogenic bacterial inoculation resulted in the greatest area of dentinal caries. With the control diet a positive response against dentinal caries occurs, but the high dietary sucrose content impairs the defensive reactions of pulpo-dentinal complex against dentinal caries. These findings add further evidence of the importance of the local endogenous factors of caries progression.

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Previous studies show that a high sucrose diet reduces the rate of primary dentinogenesis and increases dental caries, although their cause-effect relationship is still obscure. The purpose of this study was to explore whether the effect of sucrose load on the dentinogenesis and dental caries of young rat molars is mediated by systemic (intragastric) or by systemic and local (dietary) factors. At weaning (19 days), animals were randomized into the control, intragastric sucrose, and dietary sucrose groups for 4 weeks. The areas of dentin appositions and dentinal caries lesions were measured planimetrically. Caries was also determined with Shiffs staining and the width of predentin by histology. Urinary Ca, K, and Na levels were measured by flame photometry, urinary P levels using an UV method, and serum insulin levels using radioimmunoassay. Systemic and local sucrose load reduced dentin appositions and intragastric sucrose increased urinary Ca excretion. No differences in the width of predentin were noticed. Only dietary sucrose enhanced the occurrence and progression of caries. The present findings show that sucrose load reduces dentinogenesis by impairing the synthesis of dentin matrix, but also point out the crucial importance of the local sucrose challenge in the initiation of dental caries.

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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.

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A high sucrose diet reduces dentin apposition of growing rats. The mechanisms of reduction are unclear, but disturbances in calcium balance or in mineralization of predentin may explain them. In this experiment, 29 Sprague-Dawley rats, 21 days old, were weaned and randomized into calcium-deficient, high-sucrose or standard-diet groups for 3 weeks. They were given food and water ad libitum. During the experiment, animals were individually housed in metabolic cages where urine samples were collected. At ages of 21 and 40 days mineralizing dentin was marked using I.P. injections of oxytetracycline hydrochloride. At 42 days of age, the animals were anesthetized and their blood was collected by cardiac puncture. Right hemimandibles were sectioned sagittally and left hemimandibles were fixed, decalcified, and cut into histological sections. Dentin appositions were measured planimetrically, predentin width, from histological sections. Ca, K, and Na levels of serum and urine were measured flame photimetrically and P levels were measured by the UV method. Statistical analyses were done using one-way analysis of variation (ANOVA) Tuckey's HSD t test. In the calcium-deficient group, hypocalcemia, reduced dentin apposition, and increased predentin width were noticed when compared with the control group (P<0.05). Also, the increase in predentin width, caused by calcium deficiency, was significant compared with sucrose-fed animals (P<0.05). Sucrose diet reduced dentinogenesis, increased Ca excretion to urine, but also reduced urinary levels of P, K, and Na, and the differences were significant for the controls (P<0.05). In conclusion, despite the same kind of reduced dentinogenesis in calcium-deficient and high-sucrose groups, calcium imbalance or reduced mineralization of predentin does not explain reduced dentinogenesis in sucrose-fed animals.

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To show that the rate and the rate of reduction of dentin apposition are about the same in mandibular and maxillary molars, 23 Sprague-Dawley rat pups were randomized into 2 groups on the day of birth. During lactation half of their dams received a standard rodent diet; the other half, a diet containing 41% sucrose. At the age of 3 weeks the pups were weaned, weighed, given an intraperitoneal injection of oxytetracycline hydrochloride, and inoculated with oral Streptococcus sobrinus. During the experiment the pups received the same diet as their dams during lactation. After 5 weeks the pups were decapitated, their jaws sectioned sagittally, the first and second molars photographed, and the areas of dentin apposition and dentinal caries measured planimetrically. The area of dentin formation was about the same in maxilla and mandible in the first molars, but slightly smaller in the mandibular second molars of the control group. The sucrose diet reduced dentin apposition significantly in both jaws, although the areas were significantly smaller in the mandibles than in the maxillae. Caries did not affect the rate of dentin apposition. The areas of caries lesions were smaller in the maxillary molars of both diet groups. The results show that the hypothesis of equal rate of dentin apposition in mandible and maxilla was not valid because the reduction, caused by sucrose, was more prominent in mandibular molars for unknown reasons. The reduction of dentin apposition was reflected as acceleration of caries progression among the diet groups and the jaws. It was concluded that the response of the pulpodentinal complex to sucrose and dentinal caries during the primary dentinogenesis cannot be seen as a formation of reactionary or reparative dentin, as with adult rats.

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Estrogen receptors have been demonstrated in many osteogenic cell lines. Recently, we showed that estrogen deficiency induced by ovariectomy caused enhanced dentin formation in adult rats, suggesting that estrogen receptors may be present in dental tissues. Nothing is known about estrogen receptors in human teeth. We used immunohistochemical staining and immuno-blotting to demonstrate the presence of estrogen receptors in human pulp and/or the pulpo-dentinal border. Unerupted human wisdom teeth were surgically removed, frozen in liquid nitrogen, and prepared for immunological studies. Western blot analysis with monoclonal antibodies specific for human estrogen-receptor-related antigens demonstrated an approximately 29-kDa clear double band in the material scraped from the predentin-odontoblast border and in the fluid that emerged into the pulpal chamber, evidently from the odontoblasts. A weaker double band was also present in pulpal tissue samples. By immunohistochemical staining, estrogen-receptor-related antigens were visualized in the predentinal-odontoblast region and in the pulpal blood vessels. Our results suggest the presence of estrogen receptors in human teeth, and thus the previously reported enhancement of the dentin formation in rats after ovariectomy may be mediated via these receptors.

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The effect of two high-sucrose diets on dentinal caries, dentin formation, and the predentin width was studied in Sprague-Dawley rats. Rats were weaned at the age of 3 weeks and for 4 weeks fed a non-cariogenic commercial rat food (R36) for control, a high-sucrose Stephan-Harris (S-H) diet, or a new high-sucrose (sR36) diet in which most of the barley and wheat flour of the control R36 diet were replaced by sucrose. The areas of dentinal caries, the areas of dentin formation, and the width of predentin and dentin were quantified. Both high-sucrose diets induced dentinal caries, and both reduced dentin formation and increased the width of predentin compared with the control diet. Moreover, rats fed the S-H high-sucrose diet showed significantly greater progression of caries and reduction of dentin formation relative to rats fed the new high-sucrose diet, sR36. The high-sucrose diet thus was a substrate for caries-inducing microbes and a significant, but possibly not the exclusive, substrate for host modulation of odontoblast function.

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The effect of early weaning on caries progression, dentin formation, and dentin mineralization was examined in four groups of rats. Two groups received a normal diet and were weaned on day 18 or 21, and another two received a sucrose-rich diet and were weaned on day 18 or 21. At age 35 days the lower molars were sectioned sagittally, and the areas of dentin formation and of the dentinal caries were quantified. The width of the predentin zone was measured from histologically stained sections of maxillary molars. Early weaning reduced dentin formation in the group on the high-sucrose diet only the first days; later this effect was partially caught up with. A high-sucrose diet significantly increased caries frequency and extension of caries lesions compared with a normal diet in both early weaned and normally weaned groups. The effect of early weaning on caries frequency and extension in the high-sucrose group was insignificant compared with the normally weaned group on a high-sucrose diet. The predentin zone was wider in the sucrose groups than in the control groups at the end of the experiment. These results indicate that the effect of sucrose on dentin formation was dependent on the stage of physiologic dentin formation, but early weaning as such did not affect this.

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To assess the effects of early ovariectomy on whole bone density and several morphometric and serum markers of bone metabolism, female Wistar rats were ovariectomized or sham-operated upon weaning. The animals were fed ad libitum. After 8 weeks, the increase in the weight gains of ovariectomized rats was minute when compared with the control animals. The whole bone densities of the femorae of ovariectomized rats were slightly reduced when compared with the sham-operated animals. The proximal cross section of the femorae of the ovariectomized rats exhibited enhanced periosteal bone apposition and increased cortical area when compared with the sham-operated animals, but the differences were not statistically significant. The cancellous bone of the femora and the proportional areas of trabeculae of the proximal tibia were reduced in ovariectomized rats. It is concluded that ovariectomy upon weaning caused a clear tendency toward osteopenia. Cancellous bone was clearly affected after ovariectomy, indicating its relation to gonadal hormone regulation even during growth.

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Female Wistar rats were weaned at the age of 3 weeks and fed for 7 weeks either a high-sucrose diet, a non-cariogenic raw potato-starch diet, a high-sucrose diet with 5% xylitol supplement, a raw potato-starch diet with 5% xylitol supplement or a non-cariogenic, commercial, powdered rat food (Ewos R3) for reference. A low xylitol concentration reduced the progression and severity of carious lesions but did not affect dentine apposition or the width of predentine in rats fed high-carbohydrate diets. Widening of the predentine zone in rats fed a high-sucrose diet might reflect disturbed mineralization, which could not be explained by serum ionized calcium or phosphate ion levels and which could not be corrected by low xylitol concentrations. It is concluded that the reduced area of dentinal carious lesions after low xylitol supplementation is not dependent on dentine formation or mineralization, but rather on direct effects in the mouth.

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In addition to its caries-promoting effect, a high-sucrose diet reduces the apposition of mineralized dentin in young rats. This study was undertaken to test whether it has a similar effect on the width of the as-yet-uncalcified matrix, predentin. Female Wistar rats were weaned at the age of 3 weeks and fed for 7 weeks with either a high-sucrose diet, a non-cariogenic raw potato starch diet, or a non-cariogenic commercial powdered rat food (for reference). The sucrose diet induced the greatest number of caries lesions. Dentin formation was smaller and the predentin zone wider in rats fed a sucrose diet when compared with rats fed the reference diet. In rats fed a starch diet, dentin formation was smaller than in rats fed a reference diet, but no alterations in the areas of caries lesions or predentin width were observed. Widening of the predentin zone in rats fed a high-sucrose diet may reflect changes in odontoblast function, such as reduced matrix synthesis and possibly disturbed mineralization. Dentinal caries progression may thus be modulated by odontoblast function, not as much by matrix formation but rather by mineralization.

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We recently demonstrated the advantages of back-scattered electron images (COMPO) in the visualization of dentinal caries, and the relationship of the change in the dentin fluorescence pattern in caries lesions. However, the exact nature of these changes is not known. In this paper, the nature of the changes in the areas with reduced mineral content in COMPO images was investigated. We examined the relation of changes in mineral elements and the appearance of soft carious and sound dentin in COMPO images using a scanning electron microscope (SEM) equipped with an electron probe microanalyzer (EPMA). Rat molars with small dentinal caries lesions just under the DEJ were chosen for the study. The Ca, P, Na, Mg, Zn, F, and total contents were determined by EPMA from five different dentin sites, and the Ca/P and Mg/Ca ratios were calculated. Generally, the lowest contents were found in caries lesions and highest in mantle dentin, with the exceptions of Mg and Zn. The Ca/P ratio was lowest in mantle dentin and highest in carious dentin. The results confirm that the change in fluorescence in the dentinal caries lesion is correlated with the very initial changes in mineral content, and that EPMA used in combination with COMPO images is a useful tool for determining small changes in mineral elements in the carious and adjacent areas of dentin.

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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.

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In this retrospective study the effects of different kinds of emergency treatments on flare-ups and other complications were examined. A total of 197 teeth received emergency treatment after diagnosis at the beginning of the root canal therapy; in 103 the pulp chamber was left open for drainage of pus, 35 were treated with dexamethasone sodium phosphate, and 59 with various other medicaments, followed by routine root canal treatment. In all, 404 teeth received root canal treatment without emergency treatment. If symptoms occurred during treatment, flare-up was said to be present. If a periapical radiolucency was found, long-term calcium hydroxide treatment was used: no sign of periapical healing radiographically after 6 months was described as a complication. The percentage of teeth with no complications varied from 72.2% (dexamethasone) to 78.9% (other modification) and the results showed no differences between the groups in the teeth with no complications, flare-ups or other complications. The number of bacteria detected with Gram's staining was higher in the teeth which were left open. In conclusion, leaving the pulp chamber open for drainage had no effect on the incidence of flare-ups or other complications.

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Ovariectomized (Ovx) or sham-operated (Cnt) and tetracycline-labelled growing rats were fed either a commercial powdered standard rat diet (Ovx and Cnt) or a high-sucrose diet (Ovxsuc and Cntsuc). All animals were inoculated in the mouth with Streptococcus sobrinus. At 11 weeks of age the areas of caries lesions and dentinal apposition of the first and second molars and the areas of the pulpal cross-section of the incisors were determined. The area of dentinal apposition was largest in Cnt animals, the difference being statistically significant only in comparison with the Cntsuc animals. No such difference between the diets was found among the Ovx animals. The cross-section of the pulpal chamber was smallest in the Ovxsuc rats and largest in the Cnt animals, but no statistically significant differences were found between the groups. The caries lesions were significantly larger in Ovx, Ovxsuc and Cntsuc animals than in Cnt ones. Ovariectomy thus increased caries progression in growing rats, but the effect on dentine formation remained negligible. In this respect there is a difference between primary and secondary dentinogenesis.

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The effects of high-sucrose and high-starch diets on dentine apposition were examined. One group of young Wistar rats (20 rats) received a high-sucrose (43%) diet; for the high-starch group (16 rats), sucrose was replaced with potato flour. The control group (18 rats) received standard laboratory rat food. The onset of dentine formation was marked with tetracycline. After 5 weeks lower molars were sectioned sagittally, and the areas of the dentine apposition and those of the dentinal caries were quantified. Dentine apposition was independent of sex. The high-sucrose diet reduced dentine apposition and induced caries progression. A negative correlation between dentine apposition and caries progression in the molars was found. This study suggests that a high-sucrose diet itself reduces primary dentine apposition.

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Twenty-nine 3-month-old female Wistar rats were labeled by means of a single intraperitoneal tetracycline injection. Nineteen animals were subsequently ovariectomized, whereas a control group of 10 animals underwent sham operations. All the animals received the basal diet, and 10 of the ovariectomized animals were given an additional dietary xylitol supplementation (5%). Three months later the animals were killed by decapitation, and dentinal apposition on the molars was measured. The results indicate that supplementation of the diet with 5% xylitol had an attenuating effect on the enhanced dentin formation caused by ovariectomy, but the mechanism remains unsolved.

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After being weaned, the Wistar rats (12) were fed on a sucrose diet for five weeks to induce dental caries. Tetracycline was injected intraperitoneally into 7 of them to label the mineralizing dentin front. Five rats without tetracycline injection were used to verify spontaneous fluorescence. The evidently carious area under one prominent fissure from each mandibular molar hemisected sagittally in the midline was photographed under ultraviolet light so that autofluorescence would be revealed. The jaws were then stained with Schiff's reagent and photographed under normal light and again under ultraviolet light. The areas of all the lesions were quantified planimetrically as they appeared on the photographs. The mineral contents of the areas were verified with the back-scattered electron images. The caries lesions revealed with Schiff's reagent also exhibited a change in the color of the dentin fluorescence regardless of the tetracycline labeling. The areas of these lesions followed the shapes of the lesions stained by Schiff's reagent but they were greater. Staining with Schiff's reagent was repeatable after the specimen was washed with ethanol for a few weeks. The loss of minerals was seen in the areas stained with Schiff's reaction but was also related to the change in dentin fluorescence, which seems to be a more sensitive indicator of the caries progression than Schiff's reagent, especially in the early phase of the carious process.

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An evaluation of Gram's method of staining of 601 nonvital dental pulps was performed. It gave positive results in 60.1% of the cases, the most frequent finding was gram-positive cocci. Preoperative x-ray status correlated significantly with the staining results but the size of the radiolucency did not. Previously treated teeth gave less positive staining results than other teeth. There was an obvious correlation between presence of bacteria and various complications (p < 0.001), but no differences were noted between the combinations of bacteria. The teeth that were the most resistant to complications seemed to be the lower canines. The staining results did not correlate with sex, systemic diseases, or preoperative symptoms. We believe that Gram's method of staining is a useful, rapid aid in root canal therapy, especially in complicated cases.

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