A mouse caries model and evaluation of aqp5-/- knockout mice.

Current techniques to alter gene expression in mice allow direct analysis of the net role of a host factor in caries development. Towards this goal we first established protocols to induce and score caries in NFS/N mice and determined caries susceptibility in mice with targeted deletion of the gene encoding aquaporin-5 (Aqp5-/-), a water channel involved in the production of saliva. In the NFS/N strain of mice total sulcal caries and severity scores were consistent between experiments, whereas smooth surface caries scores were lower, more variable but distributed fairly evenly among the buccal, lingual and sulcal surfaces. In Black Swiss/129SvJ mice (genetic background of Aqp5-/- mice) caries scores were 50-75% lower compared to NFS/N mice, suggesting strain variation in caries susceptibility under our experimental conditions. In Aqp5-/- mice, in which the volume of total salivary secretion is reduced by 60-65%, there was a significant increase in caries, primarily on the buccal and sulcal surfaces. Results indicate that caries susceptibility increases with a reduced salivary flow that is associated with decreased water content of saliva.

Frequency and causes of hospitalization in HIV-negative children and adolescents with haemophilia A or B and its effect on academic achievement.

The aim of the study is to determine the causes and frequency of hospitalization in HIV-negative boys and adolescents with haemophilia and evaluate their impact on academic achievement. One hundred and twenty-six HIV-negative boys and adolescents were followed prospectively from 1989-96, at 14 comprehensive haemophilia treatment centres. One hundred and fifteen participants with haemophilia A or B were included in the investigation. These participants contributed an average of 57.8 months of follow-up. There were 203 hospitalizations in 65 participants and 50 participants were never hospitalized. Haemarthroses and soft tissue bleeds accounted for 46 and 44 causes of hospitalization. Central line infection was the third most common cause. Participants with inhibitor had the majority of central line infections and hospitalizations. Intracranial haemorrhage resulted in five hospitalizations in two participants. Other causes of bleeding accounted for 22% of hospitalizations. The median number of hospitalizations per year was 0.18. Duration of hospital stay was significantly related to lower spelling scores. Acute and chronic joint problems and soft tissue bleeds still account for the majority of hospitalizations. Positive inhibitor status was associated with higher numbers of hospitalizations and central line infections. Academic achievement was affected, to some degree, by length of hospital stay.

The effects of egg-derived antibodies to glucosyltransferases on dental caries in rats.

The role of Streptococcus mutans in the development of dental caries is well recognized. Important virulence factors include the glucosyltransferases (gtf), essential for production of glucans. We evaluated the anticariogenic effects of orally administered chicken anti-cell-associated (CA) Gtf antibodies in desalivated rats. The animals were infected with S. mutans MT8148R and treated with chicken anti-CA-Gtf egg yolk antibodies (IgY) or nonimmune egg yolk powder. Smooth surface lesions were significantly lower in the anti-CA-Gtf-treated group in comparison to the control groups. Sulcal surface caries was also decreased and of less severity. Our study suggests that chicken anti-CA-Gtf antibodies may have promise as a prophylaxis for high caries risk patients.

Rescue of the autoimmune scurfy mouse by partial bone marrow transplantation or by injection with T-enriched splenocytes.

The scurfy mutant mouse is the genetic and phenotypic equivalent of the single-gene human autoimmune disease immunodysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX). The scurfy mutation disrupts the Foxp3 gene, a putative master switch for T regulatory cell development. Bone marrow transplant without conditioning was previously reported to be ineffective in scurfy mice, yet clinical remission occurs in transplanted human IPEX patients despite limited donor engraftment. In view of this contradiction, we sought to validate scurfy as a model for studying the pathogenesis and treatment of human IPEX, in particular the phenomenon of dominant immune regulation. One half of scurfy mice given bone marrow transplants after sublethal irradiation recovered and survived long-term with donor chimerism ranging from 1.7% to 50%. Early transfer of 2 x 107 normal T cell-enriched splenocytes also prevented or limited disease and permitted long-term survival. Donor T cells in rescued mice made up 3-5% of lymphocytes and became highly enriched for CD25+ T cells over time. Transfer of 106 CD4+ CD25+ sorted T cells showed some beneficial effect, while CD4+ CD25- cells did not. Thus, both partial bone marrow transplant and T-enriched splenocyte transfer are effective treatments for scurfy. These results indicate that scurfy results from a lack of cells with dominant immune regulatory capacity, possibly T regulatory cells. The potency of small numbers of normal cells indicates that IPEX may be a feasible target for gene therapy.

Effects of apigenin and tt-farnesol on glucosyltransferase activity, biofilm viability and caries development in rats.

Propolis, a resinous hive product secreted by Apis mellifera bees, has been shown to reduce the incidence of dental caries in rats. Several compounds, mainly polyphenolics, have been identified in propolis. Apigenin and tt-farnesol demonstrated biological activity against mutans streptococci. We determined here their effects, alone or in combination, on glucosyltransferase activity, biofilm viability, and development of caries in rats. Sprague-Dawley rats were infected with Streptococcus sobrinus 6715 and treated topically twice daily as follows: (1) tt-farnesol, (2) apigenin, (3) vehicle control, (4) fluoride, (5) apigenin +tt-farnesol, and (6) chlorhexidine. Apigenin (1.33 mM) inhibited the activity of glucosyltransferases in solution (90-95%) and on the surface of saliva-coated hydroxyapatite beads (35-58%); it was devoid of antibacterial activity. tt-Farnesol (1.33 mM) showed modest antibacterial activity against biofilms and its effects on glucosyltransferases were minimal. The incidence of smooth-surface caries was significantly reduced by apigenin +tt-farnesol (60%), fluoride (70%), and chlorhexidine (72%) treatments compared to control (P < 0.05).

The effects of benzoate and fluoride on dental caries in intact and desalivated rats.

The decline in prevalence of dental caries in some segments of the population has been attributed mainly to extensive exposure to fluoride. Over the past decades, the use of fluoridated products has increased. During the same period, the consumption of food preservatives such as benzoates and sorbates has also increased substantially. Benzoates, in vitro, possess antibacterial properties similar to those of fluoride and in combination with fluoride could affect caries development. In the present study we explored the effects of sodium benzoate and fluoride in combination and alone on dental caries in our animal model. The results showed a combination of benzoate and fluoride reduced caries activity more effectively in rodents fed a cariogenic diet ad libitum than fluoride alone (p = 0.038).

The effect of plasma human immunodeficiency virus RNA and CD4(+) T lymphocytes on growth measurements of hemophilic boys and adolescents.

OBJECTIVE: The investigation examined the associations of plasma human immunodeficiency virus (HIV) RNA and CD4(+) T lymphocytes with height, weight, skeletal maturation, testosterone levels, and height velocity for hemophilic children and adolescents with HIV infection in the Hemophilia Growth and Development Study. STUDY DESIGN: Two hundred seven participants were evaluated over 7 years. RESULTS: A threefold increment in baseline plasma HIV RNA was associated with a 0.98-cm decrease in height and a 1.67-kg decrease in weight; 100-cells/microL decrements in baseline CD4(+) were associated with a 2.51-cm decrease in height and a 3.83-kg decrease in weight. Participants with high plasma HIV RNA (>3125 copies/mL) experienced significant delay in achieving maximum height velocity and lower maximum velocity compared with those with low viral load. The high CD4(+) (>243)/low plasma HIV RNA group had earlier age at maximum height velocity compared with the other 3 groups and higher maximum height velocity compared with the low CD4(+)/high plasma HIV RNA and low CD4(+)/low plasma HIV RNA groups. Decrements in CD4(+) were associated with decreases in bone age and testosterone level. CONCLUSIONS: CD4(+) and HIV RNA were important in predicting growth outcomes.

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.

Influence of (S)-ketoprofen and fluoride on caries in rats.

OBJECTIVE: Non-steroidal anti-inflammatory agents (e.g., ketoprofen) used topically appear to be effective in reducing bone loss in the ligature model of periodontitis. Ketoprofen, in common with some food preservatives, e.g., benzoate and sorbate, is a weak acid. Fluoride, too, may behave as a weak acid and, similar to the other agents, may exert antibacterial effects. The purpose of the present study was to determine whether a combination of (S)-ketoprofen, an enantiomer of ketoprofen, alone or in combination with fluoride, would suppress Streptococcus sobrinus populations and reduce the incidence of dental caries in rats. MATERIALS AND METHODS: Toothpastes containing ketoprofen and/or monofluorophosphate were applied to the teeth of six groups of 20 rats twice daily for 5 weeks. RESULTS: Fewest S. sobrinus were found in the group treated with a paste containing 3% (S)-ketoprofen + 0.1% F. This group also displayed the lowest incidence of smooth surface caries of all groups. Severity of sulcal surface caries was also lowest in this group. CONCLUSIONS: Results from this study show that the (S) enantiomer of ketoprofen enhances the caries protective effect of fluoride. It is conceivable that this combination could be effective in combating the two most common maladies of the mouth; periodontal disease and dental caries.

Caries inhibition efficacy of an antiplaque/antigingivitis dentifrice.

PURPOSE: To evaluate the efficacy of a fluoride dentifrice containing a fixed combination of essential oils (Thymol, Menthol, Eucalyptol, and Methyl Salicylate) in preventing caries in Sprague Dawley rats. MATERIALS AND METHODS: The dentifrice contains 0.76% sodium monofluorophosphate (SMFP) as the fluoride source and a silica abrasive system. A fluoride-free placebo and a clinically proven USP dentifrice reference standard for SMFP/silica were included as controls. Three groups of 45 SDV-free Sprague Dawley weanlings were infected by a cariogenic strain of Streptococcus sobrinus and fed cariogenic diet NIH 2000 ad libitum. Animals were treated twice daily (once on weekends) with the assigned dentifrice using a cotton-tipped applicator, for 5 wks, after which they were terminated and caries scored using Larson's modification of the Keyes method. RESULTS: Analyses of variance were used to compare inter-group means, the total E lesion score was the primary efficacy variable. Compared with the fluoride-free vehicle control, the experimental dentifrice and USP reference standard dentifrice produced a statistically significant reductions of 18.3% and 12.2% respectively for total caries score (P<0.001). Compared with the clinically tested USP positive control dentifrice, the experimental dentifrice produced a statistically significant reduction in the total caries score of 6.9% (P=0.028). The results of this study show that 1) both the new dentifrice containing essential oils and USP dentifrice are statistically significantly effective in reducing caries in the rat model, 2) the anticaries activity of the SMFP dentifrice is not adversely affected with the addition of essential oils.

Influence of lead on the cariostatic effect of fluoride co-crystallized with sucrose in desalivated rats.

OBJECTIVE: Results from previous studies have shown that pre- and perinatal exposure to lead enhances susceptibility of rats to development of dental caries. A possible explanation for this phenomenon may be that lead complexes with fluoride and renders F insoluble and unable to exert its cariostatic effects. MATERIALS AND METHODS: Thus, to explore this hypothesis, 48 desalivated Sprague-Dawley rats were placed in a König-Höfer programmed feeder and received 17 meals of powdered sucrose daily, and water ad libitum as follows: group (1) plain sucrose and sterile distilled water (SDW); (2) sucrose containing 15 ppm F and SDW; (3) sucrose containing 15 ppm F and 10 ppm Pb water; (4) sucrose containing 15 ppm F and 25 ppm Pb water. RESULTS: The highest smooth-surface, sulcal surface caries and severity scores were observed in group I. Animals that were exposed to fluoride showed reduced smooth-surface caries and severity scores. S. sobrinus counts did not differ among the groups. CONCLUSION: Lead did not interfere with the protective effect of fluoride in the conditions of the present study.

Litter effects on caries in rats and implications for experimental design.

The purpose of this study was to obtain quantitative estimates of litter effects on caries development in rats and to examine the implications for design of rat caries experiments. Twelve female Sprague-Dawley rats, aged 60 days, were bred with 4 male rats. Nine of the 12 dams had litters in close proximity. The litters were culled to 10 pups. One pup from each litter was placed with each of the other dams for nursing, leaving 2 pups from each litter with the birth dam. This design allowed the litter effect to be separated into a prenatal component, reflecting the shared genetic makeup and in utero environment of littermates, and a postnatal component reflecting a shared environment from shortly after birth to weaning. Pups were infected with Streptococcus sobrinus and fed Diet 2000 and 10% (w/v) sucrose water for 5 weeks. There was no significant evidence of a postnatal litter effect for smooth surface caries (p = 0.37) or sulcal caries (p = 0.43). The prenatal litter effect was significant for both smooth surface caries and sulcal caries (p<0. 01). When litter effects are present, the statistical power of caries studies is improved if animals from the same litter are divided evenly among experimental groups. In addition, if litter effects are present but not allowed for in data analysis, incorrect statistical inferences may be drawn. Based on our results and other reports of litter effects, we recommend planning for litter effects in the design and analysis of rat caries studies.

Comparability of absolute/percent CD4+ T-lymphocytes completed locally and centrally. Hemophilia Growth and Development Study.

The Hemophilia Growth and Development Study (HGDS) is a multicenter longitudinal study of 333 male children and adolescents with moderate or severe hemophilia, ranging in age from 6 to 19 at entry. Sixty-two percent of the cohort was infected with human immunodeficiency virus (HIV) in the late 1970s and early 1980s through exposure to contaminated clotting factor concentrates. The HGDS has followed this cohort since 1989. HGDS subjects have blood drawn twice each year for t-lymphocyte subsets, with fresh blood shipped overnight to a central laboratory. T-lymphocyte subsets from the same blood draw are often determined locally as well. To evaluate interlaboratory variation, we examined the comparability of pairs of local and central results for CD4+ absolute counts and percents. Ninety-four pairs of absolute counts and 73 pairs of percent CD4 + results were available. We calculated concordance correlation coefficients, which evaluate the agreement between two readings from the sample by measuring the variation from the 45 degrees line through the origin. Absolute counts were square root transformed. Comparability of the pairs was high for both absolute counts and percents (0.93 and 0.92, respectively). Agreement was high whether we determined the CD4+ counts and percents centrally, using fresh samples received the day after the examination (0.95, 0.95), or from specimens that were frozen upon receipt and batched for later testing (0.90, 0.87). We conclude that when a centrally processed CD4+ result is unavailable because of shipping problems or loss of specimens, a study may reasonably accept a CD4+ result completed locally, if validity checks indicate good comparability. In the HGDS, the data provided by the local laboratories were of comparable quality to those provided by the central laboratories.

The effects of fluoride concentration and the level of cariogenic challenge on caries development in desalivated rats.

Dental caries is an infectious and transmissible disease that continues to affect the majority of people. The presence of carbohydrate, mainly sucrose in the diet, is an important factor in its occurrence. The amount of fluoride required for optimal protective effect where there is a high caries challenge is unclear. Differences in the intensity of cariogenic challenge, for whatever reason, may play a part in determining fluctuations in the effectiveness of fluoride. The purpose of this study was to evaluate the effect of different concentrations of fluoride on the development of caries and explore the cariostatic effect of fluoride under various levels of cariogenic challenge. The study comprises two experiments. In experiment I, 60 desalivated Sprague Dawley rats infected with Streptococcus sobrinus were offered the following to drink for 21 days: group (1), sterile distilled water (SDW); (2) 10 parts/10(6) F SDW; (3) 20 parts/10(6) F SDW; (4) 30 parts/10(6) F SDW; (5) 40 parts/10(6) F SDW. In experiment II, eight groups of 9 rats were placed in a König Höfer programmed feeder and were exposed to different levels of cariogenic challenge through varying frequency of eating and offered water containing 10 parts/10(6) F. In experiment I, exposure to 20, 30 and 40 parts/10(6) F reduced caries development significantly: fluoride, at 10 parts/10(6), reduced the severity of the carious lesions. In this model of severe cariogenic challenge, the results suggest that elevated concentrations of fluoride might be effective in patients at high caries risk. In experiment II, fluoride reduced the incidence and severity of smooth-surface caries in all groups. The protective effect of fluoride decreased as the number of exposures to sugar increased. It is concluded that the effectiveness of fluoride is influenced by the level of cariogenic challenge and that consideration should be given to adjusting the level of fluoride exposure based on perceived caries risk, and that there is a maximum therapeutic effect of fluoride beyond which no additional protection can be expected.

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.

Assessing the cariogenic potential of some infant formulas, milk and sugar solutions.

Using a desalivated rat model, the authors found that several commonly used infant formulas had significant cariogenic potential. Sucrose was by far the most cariogenic and cows' milk the least cariogenic of all the products examined. The data show that dental practitioners and other health care professionals should discourage the use of sugar in baby bottles and provide information on which formulas are least likely to induce caries when continuous bottle feeding is unavoidable.

Effects of iron salts in sucrose on dental caries and plaque in rats.

Anaemia caused by iron deficiency and dental caries are still among the most prevalent diseases in some developing countries. Anaemia can be prevented by iron fortification of food. Previous studies demonstrated that iron-sucrose, which has been used for prevention of anaemia, reduces the incidence of caries in rats. The aim of the present study was to compare the influence of ferrous sulphate and ferric glycerophosphate co-crystallized with sucrose on the incidence of dental caries in rats. Forty-eight desalivated rats were caged in a programmed feeder and received their essential nutrition by gavage. The animals were fed 17 meals per day at hourly intervals of 88 parts/10(6) Fe++ or Fe co-crystallized with sucrose. Plain sucrose and calcium glycerophosphate with sucrose were used as control groups. Both ferric- and ferrous-sucrose meals reduced the incidence of smooth-surface and sulcal caries in rats. Stain formation, organic acid production and acidogenic activity of dental plaque in animals receiving iron-sucrose meals were also investigated. Ferric glycerophosphate did not induce extrinsic staining on the tooth surface. The concentration of organic acids did not differ significantly among the groups. The acidogenic activity of plaque in animals receiving either of the iron-sucrose meals tended to be lower than that of the control groups. The possibility that iron-sucrose might reduce the prevalence of two major public health problems, dental caries and anaemia, makes this preventive approach extremely attractive for additional investigation.

Influence of fluoride co-cystallized with sugar on caries development in desalivated rats.

Previous studies have shown that fluoride (F) administered concomitantly with sucrose in drinking water, in the diet, or alone is an effective cariostatic agent. The purpose of the present study was to determine the minimum concentration of F co-crystallized with sugar that may be used to prevent dental caries in rats subjected to a severe cariogenic challenge. Desalivated Sprague-Dawley rats, infected with Streptococcus sobrinus, were placed in a König-Höfer programmed feeder. The rats received 17 meals daily for 21 days as follows: group (1) sucrose and sterile distilled water (s.d.w.); (2) sucrose and 1 part/10(6) F-water; (3) 1 part/10(6) F-sucrose and s.d.w.; (4) 4 parts/10(6) F-sucrose and s.d.w.; (5) 8 parts/10(6) F-sucrose and s.d.w.; (6) sucrose and 10 parts/10(6) F-water. Essential nutrition was administered by gavage. At death, blood was collected from each animal and one-half of the lower jaw was sonicated in 0.9% saline solution for microbial assessment and F analysis. Keyes smooth-surface and sulcal caries scores were significantly lower in the groups that received 10 parts/10(6) F-water and 8 parts/10(6) F-sucrose than in all other groups. The F concentration in the jaw suspension and plasma were significantly higher in the 10 parts/10(6) F-water and the 8 parts/10(6) F-sucrose groups than in all other groups. The total cultivable flora and Strep. sobrinus populations were lowest in F groups but this did not reach statistical significance. It is concluded that 8 parts/10(6) F co-crystallized with sucrose reduces the cariogenic potential of sugar as effectively as 10 parts/10(6) F in water, that is as little as 1 part/10(6) in sucrose has a significant effect, and that this cariostatic action is related to the amount of F in the oral environment.

Effects of frequency of exposure to iron-sucrose on the incidence of dental caries in desalivated rats.

World Health Organization (WHO) estimates that 2.5 billion people have anemia caused by iron deficiency that could be prevented by fortification of food; sugar, for example, has been used successfully as a vehicle for dietary iron fortification. The inclusion of 88 ppm of iron (as FeSO4) co-crystallized with sugar has been shown to reduce the incidence of caries by more than 30% when rats are fed 17 meals daily at hourly intervals. The purpose of the present study was to determine the influence of varying the number of daily exposures to iron on caries in desalivated rats. Four litters of 12 Sprague-Dawley rats were desalivated when aged 25 days and caged in a programmed feeder. All animals received their essential nutrition by gavage and 17 meals of sucrose daily. In Group A, 6 meals contained 88 ppm Fe; in Group B, 3 meals continued iron: Group C had 2 meals, and in Group D, no iron was added. The investigation continued for 3 weeks. Smooth-surface and sulcal (in parentheses) caries scores were: Group A 60.8 (39.4); Group B 72.4 (41.3); Group C 73.1 (41.3), and Group D 92.9 (49.2). Caries scores in all the iron groups were statistically lower than in the control group. Severity scores followed a similar pattern. Thus, as few as 2 daily exposures to iron-sucrose had a significant effect on caries development; therefore the use of iron as a cariostatic agent is worthy of further exploration. The concept that two major public health problems could be alleviated by the addition of iron to sucrose is indeed attractive.

Influence of iron alone or with fluoride on caries development in desalivated and intact rats.

Sugar is used as a vehicle for iron fortification in communities where anemia is prevalent. The purpose of the present study was to investigate the relationship between caries experience and iron concentration in sugar fed to rats subjected to a severe cariogenic challenge. Desalivated and intact animals were assigned to 4 different diet subgroups, 3 receiving iron sucrose (350, 175 and 88 ppm Fe) and a control group. The influence of iron sugar combined with 10 ppm F in drinking water was explored in an additional study. Iron reduces the incidence of smooth-surface carries in desalivated rats at concentrations as low as 88 ppm Fe. In addition, a combination of iron and fluoride reduced the incidence of dental caries in our rats.