bluuebunny/crossref_metadata_2025 huggingface dataset:
Root Caries in an Optimally Fluoridated and a High-fluoride Community
Authors: Burt B.A. , Ismail A.I. , Eklund S.A.
Published: November 2010

The purpose of this study was to measure the prevalence and distribution of root caries in two New Mexico communities. One community, Deming, had a natural fluoride concentration of 0.7 mglL in its drinking water, optimum for its climate. The other, Lordsburg, was naturally fluoridated at 3.5 mg/L, five times the optimum. Dental examinations were carried out on 151 adults in Deming (mean age, 39.8 years) and 164 in Lordsburg (mean age, 43.2 years); only persons born in the communities were included. Prevalence of root caries was 23.8% in Deming and 7.3% in Lordsburg; mean number of lesions was 0.69 in Deming and 0.08 in Lordsburg (p < 0.0001). Although there was more gingival recession in Lordsburg, Root Caries Index scores were five times greater in Deming. Root caries was more prevalent in older age groups, and was correlated with coronal caries experience in both communities. Root caries was correlated with plaque and calculus scores in Deming only. Logistic regression showed that city of residence was the major predictor of root caries, with other significant predictors being age, education, gingival recession, and loss of periodontal attachment. When combined with previous research, these results confirm that root caries experience is directly related to the fluoride concentration in the drinking water.
Effects of Photoinitiators for the Visible-light Resin System on Hemolysis of Dog Erythrocytes and Lipid Peroxidation of Their Components
Authors: Fujisawa S. , Kadoma Y. , Masuhara E.
Published: November 2010

The visible-light (VL) polymerizing resin system with photoinitiators (photosensitizer and reducing agent) is widely used in modern dentistry. In this system, polymerization is initiated by photochemical reactions between the photosensitizers (aromatic or aliphatic ketones) and reducing agents (tertiary amines) during VL irradiation.

In order to simulate the VL resin-induced toxicity in dental pulps, the present investigation was conducted to determine whether hemolysis of dog erythrocytes and lipid peroxidation of their components occur on exposure to a VL resin system containing aromatic (9-fluorenone, benzil) or aliphatic ketones (camphoroquinone) plus tertiary amine [2-(dimethylamino) ethyl methacrylate].

It was demonstrated that the hemolysis and lipid peroxidation with aromatic ketones were markedly higher than with those of aliphatic ketones, even when the latter were used at higher concentrations. It was clear that peroxidation-induced hemolysis occurred and, further, that surface-active complexes between photosensitizers and reducing agents, which are formed by irradiation, promote hemolytic activity due to their hydrophobic interactions. VL resin-induced responses to dental pulps are probably promoted due to the double effects of unpolymerized monomers and of both radicals and surface-active complexes formed during irradiation.
Dental Benefits of Limited Exposure to Fluoridated Water in Childhood
Authors: Burt B.A. , Eklund S.A. , Loesche W.J.
Published: November 2010

The effect of limited exposure to fluoridated water in childhood is of potential importance in highly-mobile modern society, but the subject has not been well-studied. This longitudinal study assessed caries experience and S. mutans proportions from fissure plaque in school-children who lived for at least the three years of the study in a non-fluoridated community (0.2 mg/L). Residence histories permitted division of the cohort into those who had lived all their lives in non-fluoridated communities, and those who had lived for some time previously in a fluoridated community. The children were aged 6-7 years at the beginning of the three-year study. Children with previous residence in the fluoridated communities developed 26.8% less caries in their permanent teeth during the study than did the children who had lived in non-fluoridated communities all their lives (p = 0.04), and had 29.8% less caries after three years (p = 0.02). Differences between the groups in S. mutans proportions from fissure plaque, sampled at six-monthly intervals throughout the study, could not be demonstrated. The dental benefits observed could not be attributed to socio-economic differences between the groups. Despite evidence that the benefits of limited ingestion of fluoridated water are topical in nature, the fact that many of the affected teeth in this study were unerupted at the time of the fluoride exposure means that pre-eruptive benefits cannot be ruled out.
The Effects of the Availability of Diet on the Levels of Exoglycosidases in the Supragingival Plaque of Macaque Monkeys
Authors: Smith K. , Beighton D.
Published: November 2010

Supragingival plaque from macaque monkeys was assayed for 13 exoglycosidase enzymes, with appropriate p-nitrophenylglycosides and N-acetylneuramin-lactose used as substrates. Protein in each plaque sample was quantitated with a Coomassie Brilliant Blue dye binding assay, and the specific activity of each enzyme was calculated. In monkeys fed a starch-based diet, fasting resulted in significant increases in the levels of a-L-fucosidase, β-N-acetyl-D-glucosaminidase, β-N-acetyl-D-galactosaminidase, and neuraminidase. Such changes are consistent with the hypothesis that plaque bacteria degrade salivary glycoproteins for their growth and maintenance in both the presence and especially the absence of dietary food. In contrast, fasting monkeys previously fed a sucrose-rich diet showed no significant alterations in the specific activities of those enzymes whose levels were increased in the starch-based diet group. It is considered likely that, under the conditions prevailing when the sucrose-rich diet is fed, the effective and maximal utilization of sucrose by plaque bacteria necessitates the increased mobilization of nitrogen sources, including the amino sugars of glycoproteins.
Tight Genetic Linkage of a Glucosyltransferase and Dextranase of Streptococcus mutans GS-5
Authors: Burne R.A. , Rubinfeld B. , Bowen W.H. , Yasbin R.E.
Published: November 2010

A genetic library consisting of over 5000 clones with an average insert size of 6.9 kilobasepairs (kbp) of Streptococcus mutans GS-5 has been constructed in a bivalent plasmid vector pMK3, which is capable of replicating in Escherichia coli and Bacillus subtilis. The recombinant plasmid pSUCRI, containing a 6.0 kbp fragment of S. mutans GS-5 DNA, was the focus of this study. Using Southern hybridization, in vitro and in vivo gene expression techniques, and biochemical analysis, this clone was shown to encode the 55 kiloDalton (kDal) GS-5 gtfA gene product, as well as a 38 and a 66 kDal polypeptide. In addition to the gtfA gene, pSUCRI encodes a dextranase activity with specificity for α(1→6)-linked glucans, and with no detectable activity on mutan. The dextranase enzyme had an apparent molecular weight of 66 kDal as demonstrated by SDS-PAGE analysis of the proteins produced by a dextranase-negative deletion derivative. The pH optimum of the enzyme was approximately 6.0, and there was no detectable activity below pH 5.0. By subcloning various combinations of DNA fragments from pSUCRI, it was demonstrated that the dextranase gene (designated dexB) can be separated from the gtfA gene and still be efficiently expressed in both E. coli and B. subtilis. The dexB gene contained its own promoter and ribosome-binding site. The genetic linkage of the gtfA and dexB genes in the S. mutans GS-5 chromosome was confirmed by Southern hybridization and by the independent isolation of four distinct clones containing the gtfA gene and common flanking sequences. In addition to a glucosyltransferase and dextranase, an invertase-like activity is also encoded on pSUCRI, indicating that there is a cluster of genes on the S. mutans GS-5 chromosome which is devoted to the dissimilation of sucrose and concomitant synthesis or modification of glucans into a water-insoluble form, perhaps constituting an operon for glucan modification which can be coordinately regulated in response to environmental alterations.
Interleukin-1 Modulates T6 Expression on a Putative Intra-epithelial Langerhans Cell Precursor Population
Authors: Walsh L.J. , Seymour G.J. , Powell R.N.
Published: November 2010

T6 is an antigen which is a highly specific marker for Langerhans cells. Previous studies have demonstrated that Interleukin-1 (IL-1 ) and an IL-1 inhibitor (ILS) modulate T6 expression (T6E) in explant culture. The present study examined the effects of IL-1 and ILS on T6E in dispersed gingival epithelial cell (EC) cultures. EC were obtained by trypsinization of gingival fragments obtained during periodontal surgery. T6E by EC was demonstrated using OKT6 monoclonal antibody in an immuno-peroxidase technique. In both unseparated and T6-depleted EC, IL-1 (0.5 U/mL) stimulated T6E, and this effect was abrogated by ILS (1 :30). ILS alone depressed T6E in unseparated EC cultures. All effects were consistent between four- and 24-hour culture periods, and no treatment affected EC viability, thus excluding cell proliferation or necrosis as a vector for the action of IL-1 and ILS. These results indicate that a population of epithelial cells exists which is induced to express T6 under the influence of IL-1. IL-1 and ILS act in combination to regulate T6E on these precursor cells and on DR(—) Langerhans cells in gingival epithelium.
Mandibular Growth and Histologic Changes in Condylar Cartilage of Rats Intoxicated with Vitamin D3 or 1,25(OH)2D3 and Pair-fed (Undernourished) Rats
Authors: Weinreb M. , Gazit E. , Weinreb M.M.
Published: November 2010

The mandibular condyles of 1,25(OH)2D3or Vitamin D3intoxicated rats were studied and compared with those of normal as well as pair-fed controls. Experimental animals were injected with either Vitamin D3(2 mg/kg/day ) or 1,25(OH)2D3(400 ngl/kg/day) for 19 days. Controls were given the solvent only, while pair-fed animals were restricted in their food intake for the same period of time, so that they exhibited a weight-curve similar to that of the experimental rats. The length of the mandibular ramus was measured in lateral radiographs of all mandibles. Demineralized coronal sections were obtained from all mandibular condyles and were stained with Mallory's connective tissue stain. The width of each zone within the condylar cartilage was measured.

Experimental animals showed significant reduction in width of all layers within the condylar cartilage, with total lack of distinction between the maturation and hypertrophic zones. They also exhibited a significant retardation in growth of the mandible.

Pair-fed animals had a normal width of the chondroprogenitor layer but significantly smaller maturation + hypertrophic zones (vs. controls). They also exhibited a significant retardation in mandibular growth but not to the same degree as did the intoxicated animals.

Reduction in growth attributed to 1,25(OH)2D3or Vitamin D3intoxication is partly caused by undernutrition, which is a by-product of this condition. A further kinetic study is indicated to elucidate the mechanism of growth retardation and the differential effect on the various cartilage layers.
Patterns of Dental Fluorosis in a European Country in Relation to the Fluoride Concentration of Drinking Water
Authors: Larsen M.J. , Kirkegaard E. , Poulsen S.
Published: November 2010

Dental fluorosis among 456 14-16-year-old schoolchildren who had resided continuously since birth in their respective study areas was recorded using the Thylstrup and Fejerskov classification system. The children fell into four groups according to fluoride concentration of their drinking water: (1) less than or equal to 0.1 ppm; (2) 0.3-0.5 ppm; (3) 0.5-1.25 ppm; and (4) 1.26-2.0 ppm. It was found that the later in childhood the tooth was formed, the higher was the prevalence of dental fluorosis. The fluoride concentration in the drinking water affected the prevalence of dental fluorosis in all teeth except the lower incisors, which are formed very early in life. Apart from these teeth, the proportionate increase of dental fluorosis with increasing water fluoride concentration was almost the same for all tooth types. However, the actual amount of increase in the prevalence and degree of fluorosis was greatest among those teeth that formed later during childhood.

The observed fluorosis is presumed to result from and reflect the drinking water habits in the population as well as the patterns of use of fluoride prophylactics.
Invited Review: Possible Mechanisms Involved in the Immunoregulation of Chronic Inflammatory Periodontal Disease
Authors: Seymour G.J.
Published: November 2010

It is generally agreed that immunological mechanisms are involved in the pathogenesis of periodontal disease; however, regulation of these mechanisms has hitherto received scant attention. Regulatory net works exist at both a cellular and a molecular level. At the cellular level, the existence of helper (T4-positive) and suppressor (T8-positive) T lymphocytes, the expression of Class II major histocompatibility complex antigens, and the heterogeneity of macrophage subpopulations are central to an understanding of the regulatory mechanisms involved. It is only recently that studies of these separate components, in both humans and experimental animals, have begun to provide a basis for understanding the complex interactions occurring in periodontal disease.

Studies using the human experimental gingivitis model have shown an immunoregulatory picture consistent with a controlled immunological reaction with an essentially normal T4:T8 ratio of 2.0. In con trast, studies utilizing cells extracted from adult periodontitis lesions have shown a reduced T4:T8 ratio (approximately 1.0) and an inability to respond in, or to stimulate, an autologous mixed lymphocyte reaction. Animal studies using athymic nude rats have supported the concept of a central role for T-cell control in periodontal disease and the possibility of an imbalance in this control with disease progression. These results are reviewed and areas of future research explored.
A Bacteriological Study of Rampant Caries in Children
Authors: Boue D. , Armau E. , Tiraby G.
Published: November 2010

We undertook a microbiological study, in children, of dental plaque from sound surfaces or associated with rampant caries, both black-colored and unstained. Improved selective media allowed for the enumeration of bacteria belonging to specific genera or species present in plaque samples. A nearly similar bacterial distribution was found in both types of rampant caries. Aciduric flora, Streptococcus mutans, Veillonella, and Lactobacillus predominated in plaque over the lesions, whereas extracellular polysaccharide-producing streptococci other than S. mutans, as well as Actinomyces, were more abundant in plaque from sound surfaces. However, more lactobacilli and Actinomyces were recovered from pigmented lesions than from the unstained ones.

These findings suggest that the microbial flora associated with black-pigmented lesions did not strongly differ from that observed over unstained caries lesions.
Modification of Food Cariogenicity in Rats by Mineral-rich Concentrates from Milk
Authors: Harper D.S. , Osborn J.C. , Clayton R. , Hefferren J.J.
Published: November 2010

Dairy products, including milk, cheese, and casein, can reduce the caries-causing potential of cariogenic substrates as measured in various animal, plaque acidity, and in vitro systems. Although the mechanisms responsible for protection are not completely identified, substances containing Ca and P may contribute to the protective potential by reducing demineralization and/or promoting remineralization of enamel. Casein may reduce demineralization by forming a protective coat on the enamel surface. By means of a rat model, this study evaluated the ability of three casein-free milk mineral concentrates with various levels of whey protein, calcium, and phosphate to modify the cariogenicity of a powdered diet containing 20% sucrose. Analysis of these data indicates that there were no significant differences among groups for weight gain, total food consumption, or feeding frequency, as monitored by a computer-based infrared activity monitor. All three mineral concentrates significantly reduced buccal caries, and two of the three reduced sulcal caries by from 10 to 30%. The analysis further shows that casein-free milk mineral fractions can modify the cariogenicity of sucrose-containing foods in a rat model.
Morphometric Analysis of Teeth with Inflamed Pulp
Authors: Warfvinge J.
Published: November 2010

The most common method of evaluating pulp tissue reactions to injury is by a qualitative assessment of pulp tissue alterations. This evaluation method is subjective and difficult to quantify; stereological methods are more suitable, for they can quantify important tissue components, and so more objectively describe pulp tissues.

This study compares a morphometric and a descriptive method of classification for pulp tissue analysis by using 15 teeth with inflamed pulp tissue, and 12 teeth experimentally pulp-capped with calcium hydroxide. Morphometric analysis allowed for volumes of remaining dentin, pulp tissue, inflamed pulp tissue, and reparative dentin to be calculated. In addition, volume densities of polymorphonuclear and mononuclear leukocytes, odontoblasts, fibroblasts, erythrocytes, vessels, and residual tissue were calculated for comparison among different experimental teeth.

The morphometric method provided a quantitative description of tissue reactions. The descriptive method of classification was adequate when inflamed tissue subjacent to the cavity was evaluated, but was less precise than the morphometric method in describing reactions deeper in the tissue. The descriptive method could delineate the amounts and types of inflammatory cells only in non-quantified terms, while the morphometric method could quantify and locate them. It also yielded a quantified evaluation of the healing sequence of experimentally pulp-capped teeth.

In conclusion, a morphometric method can yield more quantitative data on pulp tissue reactions than can a descriptive method of classification.
The Proper Role of Nerves in Salivary Secretion: A Review
Authors: Garrett J.R.
Published: November 2010

Consideration of the history of this subject has created a perspective which helps one to appreciate how errors in thinking have occurred and why some have persisted, despite subsequent improvements in information. The most enduring misconception has been that the drying of the mouth under stress is due to sympathetic inhibitory fibers, a view that must be eradicated, for such fibers do not exist. The inhibition is due to central influences from higher centers acting on the salivary centers and thereby suppressing reflex activity. Wide variations exist in the neuro-effector arrangements and in the cellular responses in different glands from different species. Myoepithelial cells are usually contracted by both parasympathetic and sympathetic nerves. The blood vessels also receive a dual innervation, but parasympathetic impulses cause vasodilatation as part of secretion, whereas the sympathetic vasoconstrictor fibers are part of a more generalized vascular control system and not a direct part of the reflex secretory sympathetic pathway. Parasympathetic drive usually provides the main stimulus for fluid formation by parenchymal cells, whereas sympathetic nerves tend to increase the output of pre-formed components from certain cells. Absence of nerve impulses causes variable atrophic and other metabolic effects on the parenchymal cells. Evidence is beginning to accrue that certain nerve impulses may influence resynthetic activities. Vacuolation, often found experimentally after strong stimulation, also occurs to a variable extent in certain cells as a normal part of reflex secretion and may therefore have an effect on the components entering the saliva. If rupture of vacuoles occurs, then this may contribute to the salivary amylase that is present in the blood. Recent evidence points to the possibility that, even in a monomorphic gland, not all of the components necessarily enter nerve-induced saliva in "parallel" proportions. Consideration of current information has enabled some provisional generalizations about the roles of the secretory nerves to be suggested in the summary, but they must not be considered immutable.
Current Diagnostic Uses of Saliva
Authors: Ferguson D.B.
Published: November 2010

Most of the information which has been collected on salivary composition in different disease states (with the notable exception of that in digitalis intoxication) has proved of little practical diagnostic value. Diagnostic use of saliva has become more extensive in recent years, particularly in relation to estimation of systemic levels of lipid-soluble drugs and hormones. Thiocyanate levels have been used to validate self-reported frequency of tobacco-smoking, and nitrate levels have been assayed to estimate dietary nitrate intakes. The estimation of steroid hormone concentrations in saliva is now generally recognized as a means of determining systemic steroid levels which offers many advantages over estimation in serum or urine samples. Immunoassay methods now permit measurement of very small concentrations of biologically active substances in saliva.
Ontogeny and Senescence of Salivary Immunity
Authors: Smith D.J. , Taubman M.A. , Ebersole J.L.
Published: November 2010

The objective of the present study was to evaluate the capacity for secretory immune responses throughout life. This was done by measuring, by single radial immunodiffusion, the concentrations of IgA and IgAI subclass in saliva samples of subjects who ranged in age from two months to 91 years. The presence of salivary IgA antibodies to two nearly ubiquitous mucosal antigens, Streptococcus mutans glucosyltransferase (GTF) and killed poliovirus (Types 1, 2, and 3), was measured in an enzyme-linked immunosorbent assay in this population. Whole saliva from 2-5-month-old infants contained significantly less IgA than did parotid saliva of any adult group. Also, a significantly higher proportion of the total salivary IgA was IgAI in infants' saliva than was found in parotid saliva of adults. Salivary IgA and IgAl subclass levels in parotid saliva of young and old (70-91 years) adults did not differ. Salivary IgA antibody levels to GTF were negligible in most saliva samples of children less than five years old, while 40% of children older than one year had detectable levels of salivary antibody to poliovirus (PV). This difference between response to GTF and PV antigens may reflect differences in antigenic challenge. Parotid saliva of the oldest group (70-91 years) had narrowly distributed and uniformly low levels of IgA antibody to both antigens. Since their IgA immunoglobulin levels were the same as in younger adults, the low antibody levels in this oldest group may be associated with changes in the number or function of T or B lymphocytes or antigen-processing cells, and/or may result from diminished levels of challenge with these antigens.
Characterization of Lactoferrin Interaction with Streptococcus mutans
Authors: Lassiter M.O. , Newsome A.L. , Sams L.D. , Arnold R.R.
Published: November 2010

Lactoferrin (LF) is an iron-binding glycoprotein common to exocrine secretions and the specific granules of neutrophils. Each molecule is capable of high-affinity coordinate-binding of two ferric ions with two bicarbonate or carbonic anions. The initial aspect of the present study was directed at determining the nature of anion involvement in LF bactericidal activity. It was found that selective anions were capable of inhibiting the expression of bactericidal activity by LF on S. mutans 10449. The ability to block LF expression was directly related to the capacity of the anion to serve as a coordinate ion in iron-binding by the transferrin molecules. These data support the hypothesis that the LF target site on the bacterial surface is anionic. There has been controversy in the literature regarding LF involvement in hydroxy radical generation. The second phase of these studies indicated that treatment of S. mutans with LF under anaerobic conditions abrogated the bactericidal effect of this molecule. LF-killing could be enhanced by the presence of thiocyanate and inhibited by catalase and lactoperoxidase; however, bovine serum albumin was equally effective as an inhibitor. The apparent requirement for oxygen in LF bactericidal effect on S. mutans is not inconsistent with a hydroxy radical mechanism.
Effects of Variations in pH and Hypothiocyanite Concentrations on S. mutans Glucose Metabolism
Authors: Mansson-Rahemtulla B. , Baldone D.C. , Pruitt K.M. , Rahemtulla F.
Published: November 2010

Hypothiocyanous acid (HOSCN) and hypothiocyanite (OSCN-) were generated by the antibody-independent salivary peroxidase (SP) system. The metabolism of Streptococcus mutans NCTC 10449 was examined by uniformly labeled glucose incorporation studies. We found that the SP-system causes a pH-dependent inhibition of 14C-labeled glucose uptake, and that the effects of HOSCN/OSCN- are bacteriostatic. The results also showed that, at low pH, bacteria required more time to recover fully from HOSCN/OSCN- inhibition. When control experiments were performed in the absence of HOSCN/OSCN-, but the pH was varied, we found a positive correlation between pH and the rate of 14C-glucose incorporation. The results also showed that pH did not affect the maximum incorporation of 14C-glucose, demonstrating that S. mutans can adapt to pH changes in the environment. Based on the data obtained, we postulate that the antibody-independent SP system plays an important role in the regulation of the metabolism of oral streptococci.
Effects of Ion Transport Inhibition on Rat Mandibular Gland Secretion
Authors: Young J.A. , Cook D.I. , Evans L.A.R. , Pirani D.
Published: November 2010

The effects of substituting gluconate for extracellular Cl, and of treatment with various ion transport blockers, on cytosol pH (pHi) and secretion by the acetylcholine stimulated rat mandibular gland were studied in vitro. Gluconate replacement increased pHi from 7.12 ± 0.02 to 7.27 ± 0.04, caused secretory rate to fall by 75%, and increased salivary HC03 from 14 ± 0.9 mmollL to 67 ± 1.5 mmoll L. Furosemide (I mmol/L), which blocks Na-K-2Cl symports and Cl-HCO 3 antiports, had effects similar to those of gluconate replacement, except that secretion was reduced only by 59%. Bumetanide (1 mmoll L), which blocks only Na-K-2Cl symports, caused a 67% reduction in secretion rate, but it had little effect on pHi and caused only a small rise in salivary HCO3 concentration. SITS (1 mmol/L), which blocks Cl-HCO3 antiports, increased pHi to 7.26 ± 0.03 and induced a small rise in the secretory rate. Methazolamide and acetazolamide (1 mmol/L), both of which inhibit carbonic anhydrase and may also block anion channels, increased pHi to 7.43 ± 0.02 and 7.20 ± 0.03, respectively, but had no effect on secretory rate, and reduced salivary HC03 slightly. Ba (3 mmol/L), tetraethylammonium (10 mmoll L), and decamethonium (5 mmol/L) all caused marked but reversible reductions in secretory rate, consistent with the known actions of these agents on K channels. Ba, however, also appeared to act as a Ca antagonist, an action that it seemed to share with Mn ions (5 mmoll L). The results are interpreted in terms of a secretion model based on the presence, in the baso-lateral plasma membranes of the secretory cells, not only of a Na-K-2Cl symport, but also of Na-H and Cl-HC03 antiports, contributing, respectively, to secretion in the proportions 8:5:3.
Cholinergic Receptor-regulation of Potassium Channels and Potassium Transport in Human Submandibular Acinar Cells
Authors: Morris A.P. , Gallacher D.V. , Fuller C.M. , Scott J.
Published: November 2010

The cholinergic receptor-regulation of K+transport was studied in human submandibular glands. Acetylcholine stimulation 10 μmol/L results in an increase in membrane permeability (86Rb+efflux) for, and a net efflux of, K+ions from the glandular tissue. In the post-stimulus period, there is a net re-uptake of K+ions into the tissue. Patch-clamp electrophysiological techniques were employed to demonstrate the presence of a large conductance K+selective ion channel in the basolateral membranes of isolated human submandibular acinar cells. The patch-clamp results indicate that this voltage- and calcium-activated K+channel operates to regulate the K+permeability in both the resting and acetylcholine-stimulated acinar cells. We discuss the role of the K+channel, K+efflux, and K+re-uptake in relation to stimulus-secretion coupling.
A Comparison of Four Modes of Evaluating Depth of Cure of Light-activated Composites
Authors: DeWald J.P. , Ferracane J.L.
Published: November 2010

Four commonly used methods for evaluating depth of cure in light-activated composites were compared. Optical and scraping methods correlate well, but severely overestimate depth of cure as compared with hardness testing or degree of conversion analysis. Degree of conversion appears to be the most sensitive test of depth of cure.
Potential Retinal Hazards of Visible-light Photopolymerization Units
Authors: Satrom K.D. , Morris M.A. , Crigger L.P.
Published: November 2010

We evaluated the potential for retinal damage, both thermal and photochemical, from commercially available visible-light photopolymerization units. The spectral radiance profiles of 11 visible-light photopolymerization units were measured by means of a spectroradiometer and the results weighted according to the American Conference of Governmental Industrial Hygienists (ACGIH) Blue Light Hazard Function and Thermal Hazard Function. The values were then integrated by means of the proposed ACGIH hazard formulae, so that we could determine the maximum permissible exposure (t MAX) duration for each light. This calculation assumed a worst-case condition of direct vision of the light source from a distance of 25 cm. The results indicate that there is no thermal hazard to the retina. The t MAX duration values for the photochemical (blue light) hazard to the retina ranged from 2.4 minutes per day (for the most hazardous unit) to 16.0 minutes per day (for the least hazardous). None of these hazard times is short enough to be of concern unless the individual operator elects to focus on the light source or the reflected output from these visible-light photopolymerization units for an extended period of time.
Effects of Eugenol on Polymorphonuclear Cell Migration and Chemiluminescence
Authors: Fotos P.G. , Woolverton C.J. , Van Dyke K. , Powell R.L.
Published: November 2010

In this study, the effects of eugenol on human polymorphonuclear (PMN) cell migration and chemiluminescence were examined in vitro. Utilizing zymosan-activated serum or crude Bacteroides sonicate fractions as chemotractants, we found that eugenol inhibits PMN migration at 6.6 x 10-2 to 6.6 x 10-5 mol/L (P<0.05). Also, similar effects were observed in PMNs pre-incubated in eugenol. Regardless of concentration, eugenol was not found to induce chemotaxis of PMNs. An examination of PMN membrane activation through chemiluminescence gave results consistent with the chemotaxis data, demonstrating a decrease in light emission at concentrations as low as 6.6 x 10-6 mol/L (P<0.05). In view of these data, the potential effect of eugenol on in vivo (sulcular or periapical) PMN function deserves further study.
Migration, Attachment, and Orientation of Human Gingival Fibroblasts to Root Slices, Naked and Porous-surfaced Titanium Alloy Discs, and Zircalloy 2 Discs in vitro
Authors: Lowenberg B.F. , Pilliar R.M. , Aubin J.E. , Fernie G.R. , Melcher A.H.
Published: November 2010

Cell migration, attachment, and orientation of cultured human gingival fibroblasts (HGF) were measured in relation to four types of specimens: Ti-6Al-4V alloy discs with either ground surfaces or porous structured surfaces, and Zr alloy discs (Zircalloy 2) with either ground surfaces or surfaces modified by being heated to form a thicker oxide cover. Surface-demineralized and non-demineralized root slices were used as controls. Initial cell attachment was measured by means of a 51Cr assay, and cell attachment and orientation following migration by an assay that measures development of the resulting refractile material in relation to the specimen. No significant difference between initial cell attachment to Ti alloy and control demineralized root slices could be detected after one hr using the 51Cr assay. However, with the second assay, cell attachment and orientation at three, seven, 10, and 14 days were significantly higher in relation to surface-demineralized root slices than to all of the metal discs and the non-demineralized root slices. While cell attachment to the surface-ground Ti alloy discs appeared to be higher than that to the porous-surfaced Ti alloy discs at three days and seven days, cell orientation to the porous-surfaced Ti alloy discs and the non-demineralized root slices at days 7, 10, and 14 was greater than that to all of the other metal discs. These data suggest that surface geometry could affect attachment and orientation of cells in vitro.
The Effects of Various Secretagogues on the Mucin Content of Pure Submandibular Salivas
Authors: Denny P.C. , Denny P.A. , Yim M.S.
Published: November 2010

The concentrations of a specific mucin and total protein were compared in pure submandibular saliva samples elicited by pilocarpine (PILO), epinephrine (EPI), and isoproterenol (IPR) in mice. At the dosages employed, IPR-stimulated samples contained, on the average, the highest concentrations of protein and mucin. EPI samples contained intermediate levels, and PILO the lowest concentrations. The average mucin-to-protein ratio in the PILO saliva samples was intermediate between the IPR and EPI samples. Non-stimulated saliva samples showed a broader range of mucin to total protein than did the stimulated saliva sets. Within the PILO saliva samples, there was a very strong positive correlation between the mucin content of saliva and the mucin content in the pre-secretory gland prior to stimulation. The mucin content of EPI and IPR samples also showed strong positive relationships with the content of mucin in the gland. The mucin and protein in EPI saliva samples were significantly correlated in at least one of the collections, whereas in the IPR samples, there was a much weaker relationship. With the exception of the third sequential collection of EPI saliva, all nine of the other EPI, IPR, and PILO collection sets showed only a weakly negative or no correlation between flow rate and saliva mucin or protein content. This is in sharp contrast with the strongly negative correlalion which was noted between saliva protein or mucin contents and flow rate when all of the data were combined. These observations suggest that the nature of the stimulant is a very important determinant of overall flow rates, saliva protein, and mucin concentrations. However, at the individual level, factors which control each are often not strongly coordinated.
The Relationship Between Test Methodology and Elastic Behavior of Composites
Authors: Braem M. , Davidson C.L. , Vanherle G. , Van Doren V. , Lambrechts P.
Published: November 2010

Comparisons were made of the Young's moduli obtained with tests that impose static, low-frequency, or high-frequency elastic deformations on dental composite systems.

The frequency of the imposed stress was reflected in the absolute value of Young's modulus. However, the values obtained at different test frequencies could be compared and understood by taking into account this frequency dependence. It was thus found that the composite structure largely determined the type of reaction to the imposed stress. The fundamental period test permitted the greatest differentiation in the elastic behavior of the investigated composites.
Thermal Diffusivity of Glass-ionomer Cements
Authors: Tay W.M. , Braden M.
Published: November 2010

Thermal diffusivity, a property related to the thermal insulative efficiency of a material, was measured in nine glass-ionomer cements and compared with results from a silicate and a polycarboxylate cement. Each cement was mixed at various powder-liquid ratios (P/L) and moulded into a rectangular prism of approximate dimensions 2 cm cube with a thermocouple embedded in it. The prism was immersed in a constant-temperature bath at 1°C, and the fall in temperature was observed over a period of three min. Except for the initial and later stages, the plot of the logarithmic difference between external and internal temperatures of each block of cement against time showed a straight line in accord with theoretical prediction. From the slope, the thermal diffusivity of the material was calculated. The values for the silicate, polycarboxylate, and glass-ionomer-metal (cermet) showed a marked rise with increasing P/L, whereas at higher P/L, glass ionomer cements showed gradual change, with values being only slightly higher than the thermal diffusivity of dentin. Glass-ionomer cements are good thermal insulators over a wide range of PIL, and close agreement between experimental and theoretical data shows that glass-ionomer cements are homogeneous isotropic materials.
Clinical Application of Topical Fluoride Products- Risks, Benefits, and Recommendations
Authors: Lecompte E.J.
Published: November 2010

This portion of the symposium discusses the various methods of professionally applying high-concentration topical fluoride products and their risks and benefits. Numerous recent investigations in this area of research are reviewed and discussed. Data from these research investigations point to the need for care when high-potency F products are used, especially in young children. Oral-retained F doses following four-minute topical application procedures ranged from 10 to 31 mg when no suction devices or patient expectoration was utilized. Following the use of suctioning devices, oral-retained F doses ranged from 6 to 12 mg, a clinically unacceptable level. Following the use of suctioning devices plus patient expectoration, the oral-retained F doses were reduced to from 2 to 7.5 mg, depending on type of F product and application system.

The following recommendations for topical application of high-potency F products are made:

(I) No more than 2 g of gel per tray or approximately 40% of tray capacity should be dispensed. Even more conservative amounts should be considered for small children.

(2) Because patients may have the need to swallow during a four-minute topical application procedure, the use of a saliva ejector during the procedure is recommended.

(3) Following the four-minute application procedure, the patient should be instructed to expectorate thoroughly for from 30 sec to one min, regardless of whether high-speed suction is utilized. Expectoration is probably the single most effective way of reducing orally retained fluoride.

(4) When utilizing custom individually fitted trays for patients requiring daily or weekly application of a high-F-concentration product, utilize only 5 to 10 drops of product per tray.
Topical Fluorides: Effects on Physiologic and Biochemical Processes
Authors: Whitford G.M. , Allmann D.W. , Shahed A.R.
Published: November 2010

The ingestion of fluoride from dentifrices or mouthrinses can contribute substantially to the total daily intake of the ion, even in communities that provide optimally fluoridated drinking water. It is concluded that the frequent and unsupervised use of these products by children six years of age or younger, especially those living in areas with water fluoridation, places them at risk of dental fluorosis. Recommendations to reduce the risk are presented. The use of 1.23% (12,300 ppm) APF gels, particularly in the absence of suctioning during the application and expectoration after the application, is associated with the swallowing of relatively large quantities of fluoride. The resulting increases in plasma fluoride levels may be sufficient to cause dental fluorosis, as judged by studies with laboratory animals, and a reduction in the kidney's ability to concentrate the urine, as judged by studies with both laboratory animals and humans. The epigastric distress experienced by some patients during or after APF gel applications appears to be due, at least in part, to a direct toxic effect of fluoride on the gastric mucosa. Data from studies with humans and laboratory animals indicate that there may also be associated changes in plasma and tissue cAMP levels, glucose metabolism, and salivary amylase secretion. There is an immediate need for the dissemination to the dental profession of standardized methods for gel application that will minimize the quantities of fluoride available for ingestion and systemic absorption.
Topical Fluorides: A Discussion of Risks and Benefits
Authors: Ripa L.W.
Published: November 2010

Inadvertent ingestion of fluoride from topical procedures poses the risk of dental fluorosis in age-susceptible users. This risk can be minimized for mouthrinsing by restricting it to those above the age-susceptible limit. Operators administering topical fluoride treatments can take practical precautions that have been shown to reduce the amount of fluoride retained and, thus, reduce ingestion. Clinical and epidemiological studies have failed to establish that dentifrice ingestion by young children constitutes a serious fluorosis risk. Discussion of risk must consider the effect of perceived risks upon the public.
Selection for Streptococcus mutans with an Altered Xylitol Transport Capacity in Chronic Xylitol Consumers
Authors: Trahan L. , Mouton C.
Published: November 2010

The effect of long-term consumption of refined xylitol on the natural populations of S. mutans in the human oral cavity has been investigated. Fifty four S. mutans strains were isolated from adults and children who had been consuming commercial food products containing xylitol for a period of from 1½ to 10 years. Twenty isolates were also obtained from control subjects who had never consumed xylitol-containing commercial food products. The inhibitory effect of xylitol on the isolated strains was determined by monitoring growth on glucose in the presence or absence of xylitol. This was used to define the sensitivity of each isolate to xylitol. Phosphoenolpyruvate:sugar phosphotransferase (PEP-PTS) activities were measured by means of the soluble and membrane fractions prepared from strains from both study populations. It was found that 87% of the fresh isolates from xylitol consumers were xylitol-resistant (XR), compared with only 10% of the strains isolated from the control subjects. The XR strains had low constitutive fructose PTS activity and very low xylitol-phosphorylating capacity. The xylitol-sensitive (Xs) strains, however, had much higher levels of constitutive fructose PTS activity and phosphorylated xylitol 16 times more rapidly than did the XR strains. Evidence for the phosphorylation of xylitol by a fructose PEP-PTS in the Xs strains was obtained. The growth inhibition by the intracellular accumulation of non-metabolizable toxic xylitol phosphate and its prevention by the presence of fructose are discussed.
Variables Affecting the Fracture Toughness of Dental Composites
Authors: Ferracane J.L. , Antonio R.C. , Matsumoto H.
Published: November 2010

The fracture toughness of a variety of dental composites was evaluated using notched bending specimens, with and without pre-cracks. The pre-crack simulates more accurately a sharp, natural flaw in a material than does a notch, and is standard procedure in fracture-toughness evaluation. The fracture toughness was related to the filler composition and degree of conversion in the composite resins. In general, fracture toughness was highest in the more heavily filled resins, independent of degree of conversion in the matrix. The results also show that producing a pre-crack in certain composites reduced the value of their fracture toughness compared with notched-only specimens.
Time-dependent Dissolution of Amalgams into Saline Solution
Authors: Ferracane J.L. , Mafiana P. , Cooper C. , Okabe T.
Published: November 2010

The dissolution of mercury, silver, and copper from polished and unpolished surfaces of low- and high-copper amalgams into saline was investigated with respect to time via atomic absorption spectrophotometry. Greater amounts of mercury and silver were released from unpolished than from polished surfaces. Ion release was greatest during the first three hours after trituration of all amalgams.

The rate of dissolution of ions from amalgams into saline is considered to be very low once the amalgam has set, and is probably inhibited by the formation of a surface film formed during immersion.
Timing of Temporomandibular Joint Sounds in Orthodontic Patients
Authors: Muhl Z.F. , Sadowsky C. , Sakols E.I.
Published: November 2010

The consistency of occurrence and also the timing of TMJ sounds during jaw opening and closing were studied by means of an audiovisual sound recording system in an attempt to address the possible causes of temporomandibular joint (TMJ) sounds. From a group of 347 orthodontic patients, 104 were found to have medium- or high-amplitude TMJ sounds during jaw opening or closing. Most patients (53%) had reciprocal clicking — that is, a single sound on opening and on closing; another 12% had multiple sounds on opening or closing; 22% had a single closing sound; and 13% had a single opening sound. Sounds occurred at all degrees of jaw opening throughout this sample, but in most patients opening sounds tended to be closer to maximum opening, whereas closing sounds tended to occur in the middle of the closing movement. No statistically significant association was found between the timing of the opening and closing sounds. In 42.3% of patients, the sound was inconsistent in its occurrence on successive opening and closing cycles. Twenty-three percent of patients reported pain, jaw locking, or limitation of movement, but these were not associated with the timing of the opening sound. The findings suggest that the reciprocal click, widely associated with anterior disc displacement with reduction, was relatively common, but that other explanations for the joint sounds should also be considered. Conversely, a large variation may exist in the timing and the occurrence of sounds in patients with anterior disc displacement in the absence of pain and limitation of movement.
Phenytoin and 5-(p-hydroxyphenyl)-5-phenylhydantoin do not Alter the Effects of Bacterial and Amplified Plaque Extracts on Cultures of Fibroblasts from Normal and Overgrown Gingivae
Authors: Smith Q.T. , Hinrichs J.E.
Published: November 2010

Local irritation of gingival tissue by plaque is among the factors which affect development of gingival overgrowth in patients undergoing chronic phenytoin (PHT) therapy. Variability in the cytotoxicity of plaque components or of plaque substances plus PHT and/or its metabolites toward gingival fibroblasts may relate to whether gingival overgrowth forms in a particular patient. Fibroblasts from healthy and overgrown gingivae were incubated with (a) PHT and its major human metabolite, 5-(p-hydroxyphenyl)-5-phenylhydantoin (HPPH), (b) microbial and "amplified" plaque extracts, and (c) microbial and "amplified" plaque extracts plus PHT and HPPH. Cell numbers and cell-associated protein were determined for each incubation preparation. A wide range in cytotoxic response to a particular microbial or plaque extract occurred among cell strains. Plaque extracts from different subjects had variable cytotoxicity toward a cell strain. The differences among fibroblast strains in response to an extract and the variability in cytotoxicity of different plaque extracts toward a cell strain were not related to their source from normal or overgrown gingivae. Cell numbers and cell-associated protein were similar for incubation mixtures containing extracts with and without PHT and HPPH. These data do not show differences among cytotoxicity levels of plaque extracts, the response of particular gingival fibroblast strains to plaque components, or interaction between drugs and certain plaque samples which explain development of gingival overgrowth in some subjects receiving chronic PHT therapy.