A Novel in vitro Microbial-Based Model for Studying Caries Formation – Development and Initial Testing

We report on the development and the initial testing of a new microbial-based caries model. Specimens were fixed on a rotating mount within a reaction chamber hermetically surrounded by a sterilised glove box. A cariogenic environment was obtained by inoculation with Streptococcus mutans (ATCC 25175) combined with a continuously repeating supply of sucrose solution, trypticase soy broth and artificial saliva applied by dripping. Twenty-five caries-free upper premolars were used. The mesial parts of the occlusal fissures had been sealed with a resin-based fissure sealant (test group 1). To produce marginal gaps, the distal parts had been moistened with saliva before resin application (test group 2). Five teeth served as control and were exposed to all fluids under sterile conditions before being removed from the system after 7 days. Test specimens were infected with S. mutans and were incubated for another 14 days. No unintentional contamination occurred during the 3-week period of operation. Demineralizations were evaluated by using confocal laser scanning microscopy. Only the test specimens showed clearly visible signs of biofilm formation and caries-like lesions. The mean primary lesion depth did not differ significantly between test groups. Wall lesion depths and surface areas of demineralizations underneath the fissure sealants were significantly higher in test group 2. Thus, our model allows the simultaneous production of primary and secondary caries-like enamel lesions in a considerable number of specimens and facilitates the possibility to manipulate and transfer them without necessarily terminating the experiment, opening new possibilities for in vitro caries research.

Methamphetamine abuse: medical and dental considerations

Amphetamines are central nervous system stimulants with high abuse potential and intense physiological and psychological effects. Abuse of methamphetamine--a methyl derivative of amphetamine--has grown to epidemic proportions across the United States. Due to the characteristic signs of methamphetamine abuse that appear in the oral cavity dentists should have a heightened awareness of the medical and dental issues surrounding this dangerous behavior. Moreover, recognition and proper referral to treatment should be a part of every provider's plan for preventing the devastating psychological, oral, and overall systemic effects of methamphetamine abuse.

Bonding of resin to artificially carious dentin

PURPOSE

To evaluate the bond strength of adhesive resins to artificially carious dentin specimens which were previously exposed to an acid buffer solution for various periods.

MATERIALS AND METHODS

Flat dentin disks were obtained from superficial occlusal dentin of extracted human third molars and polished with wet silicon carbide paper. Dentin disks were immersed in acid buffer solution for different periods to create the demineralized dentin layer. The first group of demineralized specimens was used for the evaluation of demineralization depth under SEM and the second group was used for the bond strength measurement. Shear bond strengths mediated by three dentin adhesives (Clearfil SE Bond, OptiBond Solo Plus Total-Etch, and OptiBond Solo Plus Self-Etch) were examined. A 0.75-mm-diameter area of dentin was bonded according to the manufacturers' instructions before placing a 0.5-mm-high resin composite cylinder. The bonds were stressed in shear at a crosshead speed of 1 mm/min. All data were analyzed using ANOVA and LSD multiple comparison test.

RESULTS

Depth of demineralization increased with the prolongation of demineralizing time. After dentin specimens were demineralized for up to 24 h, bond strengths of the self-etching adhesives were significantly higher than those of the total-etch adhesive. However, for longer demineralization periods, no statistical differences in bond strengths were observed. SEM photographs showed that resins cannot thoroughly infiltrate through the whole depth of the demineralized dentin layer.

CONCLUSION

Bond strengths to demineralized, artificially carious dentin were affected by the depth of demineralization and adhesive resins used.

[Lead level, enamel defects and dental caries in deciduous teeth]

OBJECTIVE

To verify the relationship between lead concentration in the enamel of deciduous teeth and the presence of enamel defects and, consequently, with dental caries among preschool children.

METHODS

The sample consisted of 329 preschool children in Piracicaba, State of São Paulo: 132 attending municipal kindergartens close to industrial plants and 197 attending kindergartens in non-industrial areas. This sample belonged to an initial study made between 2000 and 2001, in which the lead concentration was obtained by means of enamel biopsy. Oral clinical examination of the children from both regions was performed to verify the prevalence of enamel defects, using the Developmental Defects of Enamel (DDE) Index of the World Dental Federation (FDI), and of dental caries, using the decayed, missing and filled surfaces (dmfs) index of the World Health Organization. The chi-squared test and relative risk calculation were utilized in relation to a significance level of 5%, considering each region separately.

RESULTS

Among the children from the non-industrial area, there was a higher proportion with dental caries among those with higher lead concentrations in deciduous teeth (p=0.02). This was not, however, observed among the children from the industrial area (p=0.89). There was an increased relative risk (RR) of caries among the children from the non-industrial area, but this was not seen among the children from the industrial area. No relationship was observed between the presence of lead and enamel defects.

CONCLUSIONS

No data was found that would give evidence of a relationship between lead concentration and enamel defects in either of the areas studied. No relationship was found between lead and dental caries in the industrial area, thus emphasizing that more studies of such relationships are needed.

[Clinical aspects of the evolution of dental caries and periodontal disease in patients treated with corticosteroids]

Patients treated with adrenal glucocorticoids may run a higher risk of dental caries, both as a result of their medical condition and of the physical and physiological effects of their pharmacotherapy. Our clinical study reports about patients treated with glucocorticoids who were also having an odonto-periodontal condition. They were examined and we found rampant caries and periodontal diseases. The slow evolution of asymptomatic periodontal disease encouraged destruction of teeth in root caries. The rampant caries were correlated with immunodeficiency and treatment of these caries must take into account the general treatment.

Fluoride releasing materials: their anti-cariogenic properties tested in in vitro caries models

The anti-cariogenic properties of three fluoride-releasing materials on root surfaces were evaluated using two different caries models. Standardized cavities were prepared in dentin specimens and restored with either glass-ionomer, resin-modified glass-ionomer, polyacid-modified resin composite or resin composite material. Two groups of 56 specimens were demineralized using a microbial caries model for three days, while another 56 specimens were demineralized using a chemical demineralization model for three days. Lesions around the restorations were measured with a confocal laser scanning microscope. Glass ionomers demonstrated significant anti-cariogenic properties when exposed to the chemical model. However, no significant anti-cariogenic properties were observed with the microbial caries model. In conclusion, the fluoride releasing materials showed different anti-cariogenic properties in root surfaces under the different caries models, suggesting that caution should be exercised when trying to extrapolate the results of in vitro studies to the clinical situation.

Relationship between S. mutans and the autofluorescence of carious dentin

PURPOSE

To investigate the relationship between the presence of S. mutans and the autofluorescent signal detected in carious dentin, using confocal laser-scanning microscopy.

METHODS

Experiment 1:15 visually caries-free freshly extracted premolars were coated with varnish except for two 2 mm x 2 mm windows; five were subjected to a 15-day bacterial artificial caries system using Streptococcus mutans while 10 underwent a 7-day controlled, lactic acid (0.5 M, pH 2.7) demineralization protocol. At the end of both periods, all teeth were longitudinally sectioned and the 20 bacterial and 40 acid-induced artificial lesions were examined by confocal laser-scanning microscopy. The media containing the S. mutans was also examined for autofluorescence. Experiment 2: 20 750 microm-thick caries-free coronal dentin disks were prepared from 10 healthy premolars. Ten underwent a demineralization protocol using 0.1 M EDTA (pH 4.8) for 21 days. All 20 were finally subjected to the same artificial bacterial caries system as above for 15 days and then examined for autofluorescence using confocal laser-scanning microscopy.

RESULTS

Experiment 1 results showed that acid-demineralized lesions did not generate any autofluorescence. Lesions created by the bacterial system did exhibit autofluorescence. The media with or without S. mutans did not exhibit autofluorescence. Experiment 2: bacteria-induced lesions on dentin that had previously been acid-demineralized generated a visibly stronger autofluorescence signal than those lesions grown on sound dentin. It is hypothesized that dentin demineralization during the carious process exposes more matrix to a bacteria-matrix interaction, thus generating or refining the matrix chromophore responsible for the autofluorescence signal detected in carious dentin.

Sugars and dental caries

A dynamic relation exists between sugars and oral health. Diet affects the integrity of the teeth; quantity, pH, and composition of the saliva; and plaque pH. Sugars and other fermentable carbohydrates, after being hydrolyzed by salivary amylase, provide substrate for the actions of oral bacteria, which in turn lower plaque and salivary pH. The resultant action is the beginning of tooth demineralization. Consumed sugars are naturally occurring or are added. Many factors in addition to sugars affect the caries process, including the form of food or fluid, the duration of exposure, nutrient composition, sequence of eating, salivary flow, presence of buffers, and oral hygiene. Studies have confirmed the direct relation between intake of dietary sugars and dental caries across the life span. Since the introduction of fluoride, the incidence of caries worldwide has decreased, despite increases in sugars consumption. Other dietary factors (eg, the presence of buffers in dairy products; the use of sugarless chewing gum, particularly gum containing xylitol; and the consumption of sugars as part of meals rather than between meals) may reduce the risk of caries. The primary public health measures for reducing caries risk, from a nutrition perspective, are the consumption of a balanced diet and adherence to dietary guidelines and the dietary reference intakes; from a dental perspective, the primary public health measures are the use of topical fluorides and consumption of fluoridated water.

[Structural disorder of dental enamel caused by antineoplastic agents--case report]

Cancer is the second most common cause of mortality in childhood. Complex therapy decreases the rate of mortality, but chemotherapy and irradiation may, however, create acute and long-term side effects. Although immuno- and myelo-suppressive side effects of anti-neoplastic therapy are unavoidable, their detrimental impact on oral health can and should be avoided contributing to a better quality of life of these children.

Medications: impact on dental diagnosis and treatment planning

Today, many patients regularly take prescription and over-the-counter medications that may be a risk factor for periodontal disease and caries. The sugar in many medications presents a serious caries challenge, which, in some cases, is compounded by an acidic pH. Attitude-altering medications may inhibit compliance with oral hygiene. Many medications cause xerostomia, which can lead to root surface caries and candidiasis. In many cases, these drugs cannot be substituted and dosages cannot be reduced, so it is essential to detect adverse conditions early and begin oral hygiene treatment planning to prevent more severe dental conditions from developing. This article discusses the impact of medications on treatment planning for patients who have clinical manifestations of dental problems that are attributed to medications.

[Dental changes in patients treated with calcium antagonists]

For a period of 7 years the dental status of 160 patients has been investigated and followed. These patients have been treated with calcium channel blockers and selected in age between 22 and 50 years. Their diagnoses are: m. hypertonicus I-II stage--106, WPW-syndrome--10, stenocardia--18, atrial extrasystolia--26. Duration of treatment--from 1 to 7 years (corinfar, nifedipin, adalat--tabl. 40 mg, taken peroral or chewed, respectively suck; isoptin, verapamil--tabl. 40 mg, diltiazem--tabl. 30 mg, taken peroral. A control group of 60 clinically well people at age from 20 to 48 years was investigated. Under continuous treatment with calcium antagonist (> 1 year) the examined patients are found to have considerable decalcination of the dental enamel and caries more frequent (87.5%) compared to the group of clinically healthy people (65%), also increased number of caries in the same patient in comparison to his dental status before starting the therapy in 108 of 160 (67.5%). The differences in the results are statistically significant (p < 0.001). The number of the discovered caries in patients treated with calcium channel blockers and in the studied groups is also large (4 to 2 on average, i.e. two times more). The results allow to recommend a continuous stomatological control for patients treated with calcium antagonists.

Efficacy of sterilisation methods and their effect on enamel demineralisation

The aim of this project was to determine the effectiveness of sterilisation methods for dental enamel for use in intra-oral cariogenicity tests, and their possible effect on the degree of demineralisation of enamel. Bovine incisors were cut vertically into five portions and each assigned to one of five groups. Group 1 was used as a control while the other four groups were subjected, respectively, to gamma irradiation ( congruent with 25kGy), steam autoclaving (121 degrees C for 15 min), sodium hypochlorite (12% w/v for 24h) and povidone-iodine (7.5% w/v for 24h). Total viable counts of microorganisms remaining following sterilisation of the specimens were performed following incubation of the specimens for 24h at 37 degrees C. Caries-like lesions were produced in each specimen using an acidic buffer solution (pH4.5). Sections were cut from each specimen, ground to 80-microgram thickness, and microradiographed. Mineral loss and lesion depth were quantified using transverse microradiography. Statistical analysis was by ANOVA. Dunnett's and Tukey's tests. Microbial growth (Staphylococcus aureus and bacilli) was observed only in control specimens in both brain heart infusion broth and on blood agar plates. The sterilisation methods affected the enamel surface as follows: gamma irradiation (cream discolouration), NaOCl (bleaching), and povidone-iodine (white spot-like lesion). Compared with the control, there was no significant difference in mineral loss and lesion depth with any of the groups, but the numerical values of mineral loss and lesion depth in groups can be ranked as follows: gamma irradiation <povidone-iodine <control <autoclave <NaOCl. In conclusion, the four sterilisation methods were all effective to sterilise enamel, but gamma irradiation proved the most acceptable method for enamel to be used in cariogenicity tests having the least adverse effect.

The effect of chronic clonidine administration on salivary glands and caries in the rat

Clonidine is a widely prescribed, centrally acting antihypertensive with proposed pharmacologic mechanisms of stimulation of central postsynaptic alpha(2)-adrenergic receptors and agonist activity at presynaptic alpha(2)-adrenergic receptors, interfering with peripheral regulation of norepinephrine and acetylcholine release. Both of these mechanisms are capable of adversely influencing salivary output and composition, potentially leaving an individual with increased caries risk. The purpose of the present study was to determine the effect of chronic administration of clonidine on saliva, salivary glands, and caries in rats. Sprague-Dawley rat pups were infected with Streptococcus sobrinus, given Diet 2000 and 10% sucrose water ad libitum, and either desalivated, or treated with clonidine HCl (125 or 250 microg/kg administered daily for 28 days by means of osmotic minipumps), or assigned as controls. There were no statistical differences in stimulated parotid or submandibular gland salivary output or sublingual gland weights among the groups. The weight of the submandibular glands as a percent of total body weight was significantly decreased in animals that received clonidine when compared with controls. Sulcal caries scores in both clonidine groups and smooth surface caries scores in the high clonidine group were increased when compared with control animals. Positive control animals (desalivated) had significantly higher caries scores than all other groups. These data show that chronic administration of clonidine significantly decreases submandibular gland weight and increases susceptibility to dental caries.

Reproducibility of quantitative measurement of white enamel demineralisation by image analysis

The reproducibility of measuring artificial enamel white spot lesions from captured photographic images using computerised image analysis was assessed. Enamel lesions were induced on the buccal surface of 22 human teeth over periods of 3, 7 and 14 days. Standardised photographs were taken from above and below the occlusal plane. These were repeated after 2 weeks. The photographs were converted into TIFF images and mean grey scale levels of the areas of etched enamel were measured using computerised image analysis. Assessment of repeat readings of the same slide showed good reproducibility for photographs taken below the occlusal plane. The limits of agreement showed reasonable agreement between readings carried out on two slides of the same tooth. Capturing TIFF images via 35-mm film and measuring grey scale levels by computerised image analysis is a useful method of quantitative study of early enamel demineralisation. This may be developed for application in the clinical setting.

Effects of caffeine and theophylline on the development of dental caries in rats

The purpose of this study was to evaluate the influence of caffeine and theophylline on the development of dental caries in rats. Six Wistar dams (spf), mutans streptococci free, were obtained, each with six male pups. The dams were infected by Streptococcus sobrinus 6715 and divided into three groups which received during the lactating period: (1) diet 2000; (2) diet 2000 plus caffeine (2 mg/100 g) and (3) diet 2000 plus theophylline (0.57 mg/100 g). After weaning, the pups were infected by S. sobrinus, placed in a König-Höfer programmed feeder machine, and received 17 meals daily at hourly intervals, for five weeks. During this time the pups were fed with the same diet that their dams were. The percentage of S. sobrinus relative to total flora was significantly higher in the theophylline group. The results for slight (Ds) and moderate (Dm) dentine lesions, for smooth-surface and sulcal scores were statistically higher for the theophylline group than the other groups. Salivary assays did not demonstrate significant inorganic alterations in salivary composition. Caffeine and theophylline groups showed the highest ulcer score. It is concluded that caffeine does not affect the cariogenic potential of the diet, however theophylline can increase the development of dental caries, and this effect may be related to organic alterations of salivary composition.

Histological features of artificial secondary caries adjacent to amalgam restorations

Artificially induced carious lesions on either side of in vitro un/restored amalgam cavities were examined to establish the degree of randomness of caries development. Class I cavities were cut in 132 extracted premolars: twelve teeth were not restored, and 120 teeth were restored with one of 20 different restoration combinations of silver amalgam, base and varnish. After ageing for periods of 3 months and 1 year, the 12 unrestored teeth and 80 of the restored teeth were subjected to an in vitro bacterial challenge for 36 days, while the other 40 specimens were challenged in acidified broth (pH 4.0). Sections were then prepared for polarized light microscopy. Carious lesion configuration on either side of the cavity was noted, and outer, wall and dentine lesions measured. Data underwent Fisher's exact test, a chi-squared goodness of fit test and a Student's paired t-test with P<0.05. Except for dentine lesions, acid broth and unrestored specimens showed carious lesions having similar size and occurrence on either side of the cavity. Two unrestored cavities showed caries resistance. Restored, bacterially challenged specimens were significantly different regarding total and wall lesion distribution and wall lesion width and area on either side of the cut cavity. Acid broth challenge will promote regular caries development at the tooth-restoration interface. The random caries pattern which developed in restored bacterially challenged specimens indicates that the tooth-restoration interface forms a diverse environment providing sites of varying susceptibility to caries.

Risks for oral health with the use of antidepressants

In this article, attention is focused on oral pathology, particularly dental caries, caused by hyposalivation as a consequence of (long-term) use of antidepressants. Changes in clinical psychiatric practice and increasing numbers of prescriptions of antidepressants in primary care and specialty care settings have made awareness of this risk even more relevant than in the past. Normal physiology of salivary glands and changes in the secretion of saliva during use of antidepressants are described. Monitoring, prevention, and treatment of hyposalivation induced by antidepressants are encouraged as an adjunct in the clinical management of depression.

Medications as a risk factor for caries and periodontal disease

Since our population is aging, patients will present to our offices with more medications than in the past. Although these medications may benefit their general health, they may adversely affect their dental health. Although most medications discussed increase the risk for caries and periodontal disease, a few may actually decrease the risk.

Influence of maternal lead ingestion on caries in rat pups

Lead is one of the most toxic and pervasive pollutants in society, and although there has been some lowering of blood lead levels in recent years, the levels continue to be of concern for African Americans, central city residents, residents in the Northeast region of the United States, persons with low income, and those with low educational attainment. Notably, these are the persons and the region where the highest prevalence of dental caries is observed. Information relating lead toxicity to oral health is sparse, but the preponderance of epidemiological data shows a relation between lead in the environment and the prevalence of dental caries. Using our well-defined rat caries model we found that pre- and perinatal exposure to lead results in an almost 40% increase in the prevalence of caries and a decrease in stimulated parotid function of nearly 30%. Levels of lead in milk from lead-treated dams were approximately 10 times as high as the corresponding blood lead levels, suggesting that lead is being concentrated by mammary glands. These findings may help in part to explain the comparatively high levels of dental caries observed in the inner cities of the United States where exposure to lead is common. Environmental sources of lead include drinking water, lead-based paint and, to a lesser extent, automobile and industrial emissions. In humans lead is accumulated and stored in bones (half-life of approximately 62 years), and even maternal exposure to lead decades before pregnancy can subsequently result in exposure of the developing fetus to elevated levels of lead. Moreover, lead concentration in maternal blood has been shown to increase during pregnancy and lactation because of mobilization of stored lead from bone, and typically, lead is found in milk at a higher concentration than the level found in maternal plasma at the same time point.