bluuebunny/crossref_metadata_2025 huggingface dataset:
Dentin-Polymer Bond in Resin Fillings Tested in vitro by Thermo- and Load-cycling
Authors: Munksgaard E.C. , Itoh K. , Jorgensen K.D.
Published: November 2010

The effect of stress applied by thermo- and load-cycling to the bond between composite- and bonding-agent-treated dentin was tested. Cylindrical cavities in extracted human teeth, approximately one-half of the margins in dentin, were etched and treated with two bonding agents - Gluma and Clearfil Bond - before being filled with Silux composite. Forty specimens, some provided with cavity floor lining, were cycled several hundred times between 15° and 50°C, either immediately after light-curing or upon 24 hr of water storage. In all cases, microscopic inspection revealed unchanged adaptation at the dentin margins. Teeth with Class 3 and Class 5 cavities, ten of each and with the gingival margins entirely in dentin, were pre-treated and filled as above. The teeth were covered with a dye during loading and unloading in a manner simulating biting and chewing. Inspection of the cavity margins revealed absence of percolation at the dentin margins.

It is concluded that effective bonding agents are necessary to prevent contraction gaps in resin-filled cavities where the margins are partly or entirely located in dentin.
Effect of NaF and pH on the Growth and Glycolytic Rate of Recently Isolated Strains of Oral Lactobacillus Species
Authors: Milnes A.R. , Bowden G.H. , Hamilton I.R.
Published: November 2010

Twenty-eight fresh and seven type strains of Lactobacillus species were tested for their ability to grow and metabolize glucose in the presence of fluoride. While there was variation between the test organisms, freshly isolated strains were generally more fluoride-tolerant than were the type strains, and a group of seven strains would grow well at pH 4.5 with 5.3 mm NaF. Glucose metabolism by representative strains of this latter group required average fluoride concentrations of 204, 64, and 9.3 mM to inhibit glycolysis completely at pH 7.0, 6.0, and 5.0, respectively. These values are ten times higher than those required to inhibit glucose metabolism by Streptococcus mutans.
Polyamines of Dental Plaque in Caries-resistant vs. Caries-susceptible Adults
Authors: Vratsanos S.M. , Mandel I.D.
Published: November 2010

Utilizing a sensitive liquid chromatographic system, polyamines were quantitated in three-day plaque from 13 caries-resistant (CR) and 35 caries-susceptible (CS) adults after they had fasted for 12 hours. The values for putrescine and cadaverine were significantly higher in the CR group. This may be attributed to a greater availability of salivary substrate precursors of polyamines and/or higher levels of biosynthetic decarboxylase activities in the CR subjects, or both.
Cyclic Adenosine 3', 5'-monophosphate Levels in Human Parotid Saliva at Different Secretion Rates
Authors: Mornstad H. , Van Dijken J.
Published: November 2010

Seventy-four samples of unstimulated and stimulated parotid saliva were collected from 12 healthy male volunteers. The secretion rates and cAMP concentrations were determined. The secretory rate ranged from 0.01 to 1.03 ml/min/gland. The concentration of cyclic AMP varied from 1.6 to 31.9 pmol/ml. The concentration of cAMP was 10.0 ± 6.5 pmol/ml in unstimulated saliva and 3.8 ± 1.6 pmol/ ml in stimulated saliva. A curvi-linear relationship existed between secretory rate and cyclic AMP concentrations, and the best-fitting regression equation was y = 2.06 + 0.5/x, where y = concentration of cyclic AMP and x = secretory rate.
Intercuspal Distances of Maxillary Pre-molar Teeth in Australian Aboriginals
Authors: Townsend G.C.
Published: November 2010

Intercuspal distances and mesiodistal and buccolingual crown diameters of maxillary pre-molars were recorded from dental casts of 262 Australian Aboriginals. Although mesiodistal and buccolingual dimensions showed sexual dimorphism, no significant differences were noted between the sexes for intercuspal distances. Intercuspal dimensions showed greater variability and fluctuating asymmetry than did either of the traditional measures. No significant differences in heritability were noted among the three dimensions. Correlations between mesiodistal and buccolingual dimensions were higher than those between buccolingual and intercuspal measures.

It appears that the sex differences, which are observed in overall crown dimensions, are established after the cusp tips are localized. Intercuspal distances appear to have a strong genetic component of variability, although they show high phenotypic variability and fluctuating asymmetry. Total tooth size may be subject to more intense selective pressures than the sites of initial calcification.
pH Change in Artificial Dental Plaque Formed by Glucosyltransferase and Some Oral Bacteria During Batch and Continuous Culture
Authors: Takehara T. , Itoh M. , Hanada N. , Saeki E.
Published: November 2010

Streptococcus mutans alone or cell-free glucosyltrarisferase (GTase) - together with either Streptococcus sanguis, Streptococcus salivarius, Actinomyces viscosus, or Lactobacillus casei cells-formed artificial dental plaque that firmly adhered to glass electrodes in a continuous culture system containing sucrose. The pH in these artificial plaque samples decreased more than did that of the surrounding medium. In the absence of GTase, the bacteria other than S. mutans did not form firmly-adhering plaque on glass electrodes. The pH of the plaque formed with GTase alone did not show the pH decrease seen when the plaque contained bacteria, but, because it catalyzed the synthesis of glucan, it is suggested that the glucan acts as a diffusion barrier to retard acid loss from plaque containing acid-producing bacteria.
Clinical Science
Authors: Torstenson B. , Brannstrom M. , Mattsson B.
Published: November 2010

Composite resin restorations are often applied in cavities where cervical margins are left unetched, resulting in poorer adaptation in this area. Recent experiments have indicated the possibility of impregnating with resin the gap caused by polymerization contraction.

Cavities were prepared in vitro and in vivo. A thin liner was applied inside and outside the cavity. Except for the cervical wall, enamel margins were bevelled and acid-etched, and the cavities restored with Concise Enamel Bond and Composite.

In another series, cavities with unetched enamel were restored-Since the liner was placed outside the cavity margins, excess material could be removed without blockage of the air-filled gap.

Enamel Bond with a fluorescent additive was applied to various margins. Ground sections were prepared, and the penetration of this resin into the gap was examined with a microscope.

In most teeth, the resin penetrated from 0.5 to 2 mm from the cervical margins. Similar penetration was seen from unetched margins, except for the occlusal one. No penetration was seen at acid-etched margins. By impregnating gaps with low-viscous resin after the filling has cured, one can obtain an improved seal at unetched margins.
Immediate and Delayed Effects of an Enzyme-dependent Mineralizing Mouthrinse on Dental Plaque
Authors: Schamschula R.G. , Pearce E.I.F. , Un P.S.H. , Cooper M.H.
Published: November 2010

Twenty-two children aged 13 to 14 years rinsed for 3 x 1 min periods with a supersaturated cadcium phosphate solution containing urea and monofluorophosphate. Plaque sampled one min after the last rinse showed a marked increase in water-extractable F and a smaller increase in Ca but no increase in water-extractable P. Water-insoluble forms of all three ions were elevated, however. The mean pdaque pH was 8.28. Plaque sampled 24 hr after the last rinse showed significant increases in water-insoluble F and Ca only, and no increase in pH. The prompt pH rise and disappearance of watersoluble P suggest that, on exposure to the mineralizing solution, urea and monofluorophosphate are rapidly hydrolyzed by plaque enzymes to provide catabolites which cause the immediate precipitation of fluoridated calcium phosphate.
Systematic Assessment of Color Removal Following Vital Bleaching of Intrinsically Stained Teeth
Authors: Seale N.S. , Thrash W.J.
Published: November 2010

Various treatment variables associated with a standard bleaching technique were systematically recorded in 53 individuals exhibiting intrinsic discoloration of permanent teeth. These variables (predictors) included: (1) etiology (fluoride or tetracycline) ; (2) age of the patient; (3) the presented color of the stain; (4) the intensity of that color; (5) a long versus short bleaching time technique; and (6) the number of bleaching sessions. These were assessed as to their relationship with the results of treatment (dependent variable). The findings of a multiple regression analysis revealed that the contributions of the individual predictors were significantly different between those stains caused by tetracycline ingestion (N = 27) and those stains due to fluoride ingestion (N = 20). The analysis also revealed that those variables contributing to a significant proportion of the variance in results of treatment when tetracycline was the cause were: (1) the color of the stain and (2) the number of bleaching sessions. When fluoride was apparently the causal agent: (1) the bleaching time technique; (2) age of the patient; (3) color of the stain; and (4) the number of bleaching sessions contributed to a significant proportion of the variance in the results of treatment.
Rapid Identification of Periodontal Pathogens in Subgingival Plaque: Comparison of Indirect Immunofluorescence Microscopy with Bacterial Culture for Detection of Actinobacillus actinomycetemcomitans
Authors: Bonta Y. , Zambon J.J. , Genco R.J. , Neiders M.E.
Published: November 2010

The sensitivity of indirect immunofluorescence microscopy using specific polyclonal or monoclonal serodiagnostic reagents for Actinobacillus actinomycetemcomitans in subgingival dental plaque ranged from 82-100% as compared with culture on selective or non-selective media. This bacterium was found in 100% of the periodontally diseased sites examined in localized juvenile periodontitis patients and was statistically related to clinical indices of periodontal disease including the Gingival Index, Plaque Index, and Pocket Depth. Indirect immunofluorescence microscopy is a useful technique for the rapid and reliable determination of A. actinomycetemcomitans in human subgingival dental plaque which may be applied to the clinical diagnosis, treatment, and monitoring of periodontitis associated with A. actinomycetemcomitans.
In vitro Attachment, Salivary Agglutination, and Surface Fibril Density of Fresh Actinomyces Isolates from Two Distinct Oral Surfaces
Authors: Ellen R.P. , Sivendra R.
Published: November 2010

Whereas attachment specificity among bacterial species is well recognized, the question of specificity among strains of the same species isolated from distinct oral surfaces has not been studied. Twenty strains of Actinomyces, freshly isolated as they re-populated the cleaned teeth and tongues of a male twin pair, were compared for: (1) their ability to attach to saliva-coated hydroxyapatite (SHA), (2) the density of their surface fibrils, (3) their agglutination in saliva, and (4) their ability to agglutinate human erythrocytes. Differences among the strains were mostly along species rather than tissue source lines. The A. naeslundii strains were the least efficient in SHA attachment and had the least number of fibrils, but they were the most strongly agglutinated strains in saliva. The A. viscosus strains, while showing some tissue source differences in hemagglutination, were consistently alike in SHA attachment and fibril density. Salivary agglutination did not correspond with the ability to attach to SHA. Considering the surface characteristics of the Actinomyces species studied, strains of the same species isolated from distinct oral surfaces are apparently more alike than strains of the two closely-related species isolated from the same surface.
Factors Relating to Dental Stain Formation in the Rat
Authors: McDonald J.L. , Schemehorn B.R. , Stookey G.K.
Published: November 2010

A series of studies was conducted to investigate the use of the rat as an in vivo model for studies of dental stain and to identify dietary factors which influence stain formation in this model. It was determined that appreciable amounts of stain formed on the molar teeth of rats provided a synthetic diet containing lactalbumin, and the amount of stain increased throughout a four-week test period. Stain formation was also observed when rats were provided their diet by gastric intubation. Topical applications of chlorhexidine generally resulted in an increase in stain formation, as did the presence of tea in the drinking water. These studies support the use of the rat for investigations of dental stain.
Clinical Science Age-dependent Decreases in Human Submandibular Gland Flow Rates as Measured Under Resting and Post-stimulation Conditions
Authors: Pedersen W. , Schubert M. , Izutsu K. , Mersai T. , Truelove E.
Published: November 2010

Submandibular saliva samples were obtained with a new collection device, under resting and post-stimulation conditions, from 28 healthy individuals between 70 and 91 years of age, and from 30 healthy individuals between 18 and 39 years of age. The salivary flow rates were significantly decreased in the aged group compared with the control group. The mean resting and post-stimulation flow rates for the aged group averaged 22% and 39%, respectively, of control values.
Comparisons of Various Salivary Parameters in Smokers Before and After the Use of a Nicotine-containing Chewing Gum
Authors: Olson B.L. , McDonald J.L. , Gleason M.J. , Stookey G.K. , Schemehorn B.R. , Drook C.A. , Beiswanger B.B. , Christen A.G.
Published: November 2010

This study was designed to compare various salivary parameters between smokers and non-smokers and to determine the influence of a nicotine-containing chewing gum (used to aid in quit-smoking efforts) upon these same parameters. At the baseline examination, subjects were assigned to one of three groups: non-smokers who did not utilize any gum, smokers provided a nicotine-containing gum, and smokers provided a placebo gum. Saliva was collected from all subjects and analyzed for acidogenicity and buffer pH as well as for levels of thiocyanate, lactoperoxidase, lysozyme, lactoferrin, and secretory IgA. After 15 weeks of gum usage, saliva was again collected from each subject and the identical analyses performed. Significant differences were observed between smokers and non-smokers with regard to three parameters: The saliva of smokers contained greater concentrations of thiocyanate and lower concentrations of lactoferrin, at the baseline examination and after the 15-week test period. In addition, the CO content of alveolar air was higher in smokers at both examination periods. In contrast, the use of the nicotine gum per se had no effect on any of the test parameters.
Oral Mucosal Lesions Among Elderly in Israel
Authors: Fleishman R. , Peles D.B. , Pisanti S.
Published: November 2010

The prevalence of ulcerative or proliferative oral mucosal lesions (OML) is an important parameter in evaluating the oral health of an elderly population. This paper relates the prevalence of OML in an elderly population to possible risk factors and defined high-risk groups. The second objective was to examine whether effective prediction of OML was possible from interview data alone. The elderly population of a Jerusalem neighborhood was surveyed in 1981: 456 elderly were interviewed by trained interviewers, and their oral cavities were examined by an oral epidemiologist. Specific diagnoses were confirmed by an independent senior clinician. Almost 40% of the elderly presented ulcerative or proliferative oral mucosal lesions. The prevalence of these OML was strongly related to the condition and age of dentures. The association between these OML and oral hygiene disappeared after controlling for the condition of the denture. Two variables ascertained by interview - age of denture and self-reported suitability of denture - turned out to be strong predictors of denture condition.
Tarnish Evaluation of Gold-based Dental Alloys
Authors: Corso P.P. , German R.M. , Simmons H.D.
Published: November 2010

Three commercial gold dental alloys and three ternary (Au-Ag-Cu) alloys of constant nobility were subjected to a standardized test battery for tarnish. The tests included sodium sulfide and artificial saliva solutions, both at 37°C, in sealed containers. Quantitative measurements of tarnish were made from the alloy color change during a three-day exposure. Alloy nobility is a relatively important factor in determining tarnish resistance; however, microstructure can have a negative effect on tarnish resistance. Alloys with a two-phase microstructure produce microgalvanic conditions which lead to either silver chloride or silver sulfide tarnish products. A solution heat treatment improves tarnish resistance by eliminating microstructural inhomogeneities.
Enamel Fluoride in Nursing Rats with Mothers Drinking Water with High Fluoride Concentrations
Authors: Drinkard C.R. , Deaton T.G. , Bawden J.W.
Published: November 2010

The purpose of this study was to determine the F levels in plasma and molar enamel from rat pups whose mothers had received various levels of F during pregnancy and/or lactation. Rats were started on water containing 0 (Group I), 50 (Group II), or 100 (Group III) ppm F at the beginning of pregnancy or on the day of delivery. The mothers and pups were killed 13 days after delivery, and plasma F levels, milk Flevels, and pup molar enamel F levels were determined.

The mean maternal plasma F concentrations were 0.02 ± 0.005 ppm in Group I, 0.10 ± 0.031 ppm in Group II, and 0.21 ± 0.057 ppm in Group III. The milk F values were about twice as high as the respective plasma concentrations. The plasma F concentration in control pups was 0.003 ± 0.0002 ppm, and there was a rise to 0.006 ± 0.0002 ppm in Group III. Enamel F concentrations were 0.62 ± 0.13 ppm, 4.72 ± 0.79 ppm, and 8.80 ± 1.74 ppm, respectively. The plasma and enamel F values obtained from pups were not significantly different between the pre-natal/post-natal, and the post-natal-only groups. It was concluded that: (1) fluoride levels in the plasma and enamel of control rat pups were much lower than those found in adult rats, (2) such values could be increased only slightly when high doses of F were given to the mother, and (3) unlike values reported for other species, rat milk fluoride concentrations were higher than the respective plasma values.
Effects of the Selective β2-Adrenergic Agonists, Procaterole and Terbutaline, on Protein Secretion by Rat Submandibular Glands
Authors: Abe K. , Inoue H. , Yokota Y.
Published: November 2010

We examined the secretory effects of two β2-adrenergic agonists, procaterole and terbutaline, on the submandibular glands of anesthetized rats. After stimulation with these agents with and without a range of antagonists (non-specific α- and β-adrenergic blockers), submandibular saliva was collected. The flow rate, protein concentration, the electrophoretic patterns, and amino acid composition of saliva were examined. These parameters were compared with their counterparts in saliva stimulated with isoproterenol (IPR), with and without antagonists. Assessed by these criteria, secreted proteins were classified as the α- or β-type. In addition, IPR-stimulated proteins were compared in submandibular saliva of rats chronically treated with IPR or procaterole.

Both β2-agonists were potent secretagogues for the submandibular glands of rats. All β-antagonists completely abolished the secretory effects elicited by both β2-agonists, with the exceptions of carteolol and propranolol. However, no blocking agent abolished the secretory effects of IPR (60 mg/kg). The types of proteins in all submandibular saliva samples elicited by both β2-agonists with and without antagonists were the β-type. Enlargement of the submandibular glands was not observed in rats subjected to chronic administration of procaterole, nor were abnormal and additional proteins observed, as confirmed by electrophoresis and by the amino acid analyses.
Erythema Multiforme and Herpes Simplex Virus
Authors: Lozada-Nur F. , Shillitoe E.J.
Published: November 2010

It has been suggested that herpes simplex virus (HSV) can trigger erythema multiforme (EM) at different times. One recent study showed HSV antigen in immune complexes of patients with EM. The purpose of our study was to assess a possible association between EM and HSV. Sixteen patients and 16 matched controls were studied using an enzyme-linked immunosorbent assay (ELISA) to measure antibody of the IgG, IgA, and IgM classes against HSV-1. From our study on patients with oral erythema multiforme, we found no evidence to correlate the occurrence and/or severity of EM and the HSV-1.
Effect of Anti-oxidants on Growth and Lactic Acid Production by Streptococcus mutans
Authors: Kupp L.I. , Rosen S. , Beck F.M.
Published: November 2010

The effects of three anti-oxidants — tertiary butylhydroquinone (TBHQ), butylated hydroxyanisole (BHA), and butylated hydroxytoluene (BHT) - on both growth and lactic acid production by eight cariogenic strains of Streptococcus mutans were investigated. Synergistic inhibitory effects of potassium sorbate on lactic acid production were also determined. All three anti-oxidants are phenolic derivatives and are commonly used in food systems due to their excellent "carry-through" properties during processing. Growth inhibition was determined by turbidity measurements at 600 nm. Lactic acid was assayed by gas chromatography, and bacterial DNA was assayed by the diphenylamine reaction. There were reduced growth levels of S. mutans due to the anti-oxidants and potassium sorbate for at least 12 hr, with TBHQ and BHA still inhibiting growth at 24 hr. Nearly all concentrations of anti-oxidants and potassium sorbate reduced lactic acid production by S. mutans, but only TBHQ significantly inhibited lactic acid production when the amount of acid per μ g DNA was calculated. A synergistic reduction of lactic acid production by S. mutans does occur in most combinations of potassium sorbate with anti-oxidants.
Mitosis and Hypertrophy of Intercalated Duct Cells and Endothelial Cells in the Isoproterenol-treated Rat Parotid Gland
Authors: Hand A.R. , Ho B.
Published: November 2010

Chronic treatment of rats with isoproterenol (IPR) induces mitosis and differentiation of intercalated duct cells, and mitosis and hypertrophy of endothelial cells of the microvasculature in the parotid gland. Mitoses occurred in duct cells situated at or near the acinar-intercalated duct junction, and were most numerous after six IPR injections. These cells increased in size, contained numerous electronlucent granules, and were incorporated into the hypertrophic acini. The granules contained branching filamentous or finely reticulated material, and did not react with histochemical stains for carbohydrate. Capillary and venule endothelial cell mitoses were frequently seen after four to six IPR injections. The endothelial cells increased in thickness, contained abundant cytoplasmic organelles, lacked fenestrations, and had few pinocytotic vesicles. These results demonstrate the extensive nature of the response to chronic IPR treatment, and are consistent with the concept that the intercalated ducts have an important role in salivary gland physiology.
Serial Measurements of Intra-oral Air Mercury: Estimation of Daily Dose from Dental Amalgam
Authors: Vimy M.J. , Lorscheider F.L.
Published: November 2010

Serial measurements of Hg concentration in intra-oral air were made during and after chewing stimulation in 35 subjects with occlusal amalgam restorations. Hg concentrations remained elevated during 30 min of continuous chewing and declined slowly over 90 min after cessation of chewing. By curve-fitting and integration analysis of data during these time periods (including corrections for respiratory volume, retention rate of inspired Hg, oral-to-nasal breathing ratios, and consumption of three meals and three snacks per day), we calculated that all subjects received an average daily Hg dose of approximately 20 μ g. Subjects with 12 or more occlusal amalgam surfaces were estimated to receive a daily Hg dose of 29 μ g, whereas in subjects with four or fewer occlusal amalgam surfaces, the dose was 8 μ g. These Hg dosages from dental amalgam were as much as 18-fold the allowable daily limits established by some countries for Hg exposure from all sources in the environment. The results demonstrate that the amount of elemental Hg released from dental amalgam exceeds or comprises a major percentage of internationally accepted threshold limit values for environmental Hg exposure. It is concluded that dental amalgam Hg makes a major contribution to total daily dose.
Dental Development in Precocious Puberty
Authors: Roberts M.W. , Li S.H. , Comite F. , Hench K.D. , Pescovitz O.H. , Cutler G.B. , Loriaux D.L.
Published: November 2010

One hundred and one children with precocious puberty were given an oral examination. Dental root development was assessed using panoramic radiographs. All mandibular canines, pre-molars, and molars which could be visualized without apparent distortion were included. The patients were grouped for analysis according to the etiology of their precocity, e.g., McCune-Albright syndrome, familial male, congenital adrenal hyperplasia, central nervous system lesions, and idiopathic precocious puberty. Dental development was significantly retarded relative to their chronological age in patients with idiopathic precocious puberty. However, no significant abnormal dental development was detected in any of the other groups. Individual oral-facial growth and development remain the primary considerations for timing orthodontic treatment.
Basic Biological Sciences
Authors: Lowenberg B.F. , Aubin J.E. , Deporter D.A. , Sodek J. , Melcher A.H.
Published: November 2010

Initial attachment and longer-term cell migration, attachment, and orientation of cultured human gingival fibroblasts to untreated, collagen-coated, and demineralized root slices were measured. Cells prelabeled with 51chromium were used to measure initial attachment. Refractile material in relation to the root slices, observed using phase contrast optics and known to result from orientation of cell sheets, was measured to assess cell migration, attachment, and orientation. No significant difference in initial cell attachment of51Cr-labeled cells to demineralized, collagen-coated, or untreated root slices was detected up to one hr of incubation. However, after 72 hr of culture, cell attachment, migration, and orientation were significantly greater in relation to demineralized and collagen-coated root slices than to untreated root slices. Analysis of the data suggests that collagen-coating could enhance cell migration, attachment, and orientation, but not initial attachment, to surfaces that cannot be demineralized.
The Mouse Parotid Gland Preparation: An in vivo Pharmacological Tool
Authors: Bobyock E. , Chernick W.S. , Digregorio G.J.
Published: November 2010

The effects of several autonomic agents on total protein, amylase, RNase, calcium, potassium, and sodium levels and also on flow rate of mouse parotid saliva were investigated during the process of evaluating the in vivo mouse parotid gland preparation as a pharmacological tool. Acetylcholine and pilocarpine were used as secretagogues and produced different sequential patterns of sodium and enzyme levels secreted in mouse parotid saliva. Additionally, propranolol treatment was able to alter amylase and sodium levels produced by pilocarpine stimulation significantly, as well as alter calcium levels produced by both acetylcholine and pilocarpine stimulation. Phentolamine treatment resulted in higher amylase levels with both acetylcholine and pilocarpine stimulation. The use of acetylcholine as a secretagogue allows one to perform in vivo anticholinergic experiments which alter flow rates without significantly altering protein or ion levels secreted in mouse parotid saliva.
Failure of PTH, Calcitonin, or Vitamin D Metabolites to Influence Calcium Transport in the Maturation Stage Enamel Organ
Authors: Bawden J.W. , Deaton T.G. , Timko D.A. , Crenshaw M.A.
Published: November 2010

Eleven-day-old rat maxillary first molar explants were removed by microdissection and incubated in vitro to determine the direct effects of parathyroid hormone (PTH), calcitonin (CT), 1,25(OH)2 D3 , 24.25(OH) 2 D3, and a combination of PTH and vitamin D 3 metabolites on calcium uptake in the mineralizing enamel of the explants. None of the agents had a statistically significant effect. These results are in contrast to those observed on explants from six-day-old rats, where PTH + 24,25(OH)2 D3 caused a significant increase in net calcium transport. The findings are consistent with the hypothesis that the transcellular transport of calcium through the secretory stage and the maturation stage ameloblasts occurs by different mechanisms.
Accuracy of Localization of Pulpal Pain on Cold Stimulation
Authors: Abdel Wahab M.H. , Kennedy J.G.
Published: November 2010

The accuracy of localization of pulpal pain was determined on cold stimulation of upper and lower anterior teeth, both without and with the use of occlusal splints to reduce the possibility of simultaneous stimulation of the periodontal receptors. The results indicated that it is difficult to localize pulpal pain and that pain can be referred across the midline as well as between the mandible and the maxilla. Moreover, the ability of the subjects to identify the stimulated tooth varied according to whether the tooth was a central incisor, lateral incisor, or canine and also whether it was in the upper or lower jaw. It was also found that the reaction time to cold stimulation was significantly longer when the tests were performed with the occlusal splints rather than without them.
Compressive Creep of Dental Composites
Authors: Bapna M.S. , Mueller H.J. , Knoeppel R.
Published: November 2010

The creep compliance curves for P-10, Adaptic, and Silar composite materials were obtained at 23°C, 37°C, and 50°C and at a number of initial stress levels ranging from 5 to 75% of their compressive strengths. The creep compliance curves were characterized by large instantaneous compliances, followed by retarded strain compliances with very minimal viscous flow. Rupturing occurred only at the higher stresses and temperatures, and was characterized by a sharp upsurge in the compliance just before failure. Empirical curve-fitting of the data indicated that the creep compliances exhibited a very good representation when plotted against log t.

Both isochronous stress-strain and isochronous compliance-stress diagrams indicated that linear visco-elasticity was followed below the stress of about 70-100, 50-70, and 120-<240 MPa for Silar, Adaptic, and P-10, respectively. The combined Voight-Maxwell linear viscoelastic model was used to describe the compliance curves. At higher stresses, where compliance was dependent upon stress, a nonlinear visco-elastic model based upon Eyring's thermally activated process was considered.
Basic Biological Sciences
Authors: Wells B.R. , Birkedal-Hansen H.
Published: November 2010

A large body of evidence suggests that retinoids modulate the phenotypic expression of epithelial cells of skin and mucous membranes. The purpose of this study was to investigate the effect of retinoic acid on keratinocyte-mediated collagen breakdown. Keratinocytes derived from the ventral surfaces of the tongues of 4-6-week-old male Wistar rats were established in culture under conditions which are restrictive to growth of fibroblasts, and they were eventually cloned by limiting dilution. The cells were seeded (100,000 cells/cm2 ) in dishes coated with 3H-labeled, reconstituted type I collagen fibrils and incubated in serum-free medium over a 3-5-day period. Dissolution of the collagen fibrils was monitored by the release of radioactivity to the culture medium. Unstimulated cells metabolized the collagen rather slowly, but addition of retinoic acid in concentrations from 10-6M to 10-8M resulted in marked acceleration of the degradative process, with complete solubilization of the collagen fibrils in four or five days. The effect of 10-6 M retinoic acid was of the same order of magnitude as that obtained by addition of a proteolytic activating system either in the form of plasmin or of plasminogen, which is converted to catalytic plasmin by endogenous activators. The effects of retinoic acid and plasminogen/plasmin, however, were not additive. Keratinocytes rendered vitamin A-deficient by cultivation in sera from deficient rats were clearly less effective in degrading the collagen substrate than were "sufficient" cells. Addition of retinoic acid (10-7 M) enhanced collagen breakdown in both sets of cultures and partially restored the collagenolytic activity of the deficient cells.
Comparison of Cyclic AMP-dependent Protein Kinases from Salivary Glands of Four Species
Authors: Dowd F. , Cheung P. , Warren J. , Faerber T. , Traub D.
Published: November 2010

Cyclic AMP-dependent protein kinase activity, subcellular distribution, and isozyme profile were compared in rabbit, rat, guinea pig, and mouse in both parotid and submandibular glands. Glands were homogenized under hypotonic conditions and the following fractions isolated: 600 g pellet, 27,000 g pellet, and 27,000 g supernatant. The specific activity of the enzyme was similar in the eight glands and was highest in the 27,000 g supernatant. The average activity in the 27,000 g supernatant was approximately 75% of the total gland activity, although there was considerable variability between tissues and species. After being washed with isotonic buffer, this percentage was increased to an average of 84%. When isozyme patterns of the kinase were examined, the rabbit parotid was unique in that it contained a high percentage of isozyme I as isolated on DEAE cellulose columns.
The Surface Free Energy of Oral Streptococci after being Coated with Saliva and its Relation to Adhesion in the Mouth
Authors: Weerkamp A.H. , Van der Mei H.C. , Busscher H.J.
Published: November 2010

Contact angle measurements on layers of bacteria were used to determine the bacterial surface free energy (γb) of a variety of oral streptococcal strains, both without and after being coated with human whole saliva. At least four isolates of each species, either freshly isolated or laboratory strains, were used.

The species Streptococcus mutans, S. sanguis, and S. salivarius were homogeneous, having high surface free energies, and were not affected by saliva treatment (γb = 106 ± 12 and 107 ± 10 erg·cm-2 in the absence and presence of saliva coating, respectively; n = 20). S. mitis had a very low surface free energy (46 ± 15; n = 5), which was significantly increased after salivary adsorption (71 ± 14 erg·cm-2; p<0.002). The species S. milleri contained strains with both high and low γ b.

Calculation of the interfacial free energy of adhesion (ΔF adh) for bacteria from a saliva suspension to solid surfaces with various arbitrary surface free energies (γs) showed that, theoretically, most strains will encounter thermodynamically favorable conditions for adhesion to surfaces with a γs above 62 erg·cm-2. However, S. mitis strains not coated with saliva would only be able to adhere to surfaces with γs lower than this value. Saliva-coating reverses the calculated relationship with γs for these strains.

The results indicate that an enamel surface with a low γs value would be thermodynamically unfavorable for adhesion of most oral streptococci.
Toxicological Assessment of Lidocaine in the Pregnant Rat
Authors: Ramazzotto L.J. , Curro F.A. , Paterson J.A. , Tanner P. , Coleman M.
Published: November 2010

Teratogenic and toxicological effects of lidocaine administered during pregnancy were evaluated in the Sprague Dawley rat. High doses of lidocaine administered during specific periods of gestation were shown to produce no apparent adverse toxicological or teratogenic effects. Histological, enzymological, and physical features of the fetuses, utilizing conventional toxicological parameters, were all found to be normal following maternal administration of lidocaine. Analysis of these data suggests that the administration of lidocaine during pregnancy had no detectable adverse effects on the fetus.
Acid-Base Properties of Human Gingival Crevicular Fluid
Authors: Bickel M. , Munoz J.L. , Giovannini P.
Published: November 2010

The pH of human gingival crevicular fluid (GCF) has been reported by many authors to be very alkaline (pH 7.5 - 8.7). This alkalinity could be explained, at least partially, by the fact that all measurements were performed either at low Pco, or in the absence of CO2. Therefore, we set up a procedure which allows for measurement of the pH of GCF samples from single inflamed sites at controlled Pco2. At a Pco2 of 4.7 kPa (= 35 mmHg) and at 37 °C, the pH was 7.96 ± 0.10 (SEM, n = 9), a value which differs significantly from the value of 8.38 ± 0.09 measured in the absence of CO2 in the same samples. The non-bicarbonate buffer value of the sample determined by CO2 titration was 6.0 slykes. It is because this value is low that pH varies so greatly with Pco 2. At physiological Pco 2, the total buffering power becomes very high above pH 8.0, because of the high bicarbonate concentration.
Reproducibility of Computer-aided Image-analysis-derived Estimates of the Depth and Area of Radiolucencies in Approximal Enamel
Authors: Pitts N.B. , Renson C.E.
Published: November 2010

In vivo studies of caries progression from serial bite-wing radiographs require the reproducible detection and measurement of approximal radiolucencies in enamel; the aim of this study was to evaluate the reproducibility of a new computer-aided image analysis method. Three series of radiographs depicting natural caries lesions were employed: films of 11-12-year-old (Hounslow) schoolchildren, dental students from Hong Kong (HKDS), and extracted Hong Kong teeth (EXT). Each surface was "searched" three times, resulting in data from 450, 600, and 180 searches, respectively. Lesion detection was consistent for all but two of the 1230 searches. Average values for the standard error of the mean (SEM) of triple determinations of depth % were between 2.0 and 3.5%, while the mean SEM for area was from 0.03 to 0.04 mm2 . Average testlre-test correlations ranged from 0.963 to 0.871 for depth and from 0.963 to 0.884 for area, while average reliability coefficients ranged from 0.937 to 0.821 for depth and 0.963 to 0.886 for area. There was a significant difference (P<0.001) between the reproducibility of the two clinical series, with measurements of the Hounslow lesions being more consistent. When compared with the reproducibility of attempts to grade radiolucency size visually, the image analysis method appears to offer considerable advantages, in that consistent estimates of radiolucency size are now possible. This method may facilitate more sensitive assessments of the behavior of lesions over time than has hitherto been possible.
The Effect of Alternatives to Formocresol on Antigenicity of Proteins
Authors: Ranly D.M. , Horn D. , Zislis T.
Published: November 2010

As part of an overall evaluation of possible substitutes for the pulpotomy agent formocresol, this study was initiated to compare the antigenicity of the reaction products of protein with formaldehyde, glutaraldehyde, or dimethylsuberimidate (DMS).

Rabbits were injected with rabbit serum albumin (RSA) which had been treated with one of the following solutions: phosphate-buffered saline, 2% glutaraldehyde, 4% formaldehyde, or 2% DMS. The antisera from the rabbits were analyzed for elicited antibodies by the enzyme-linked immunosorbent assay (ELISA) and in a horseradish peroxidase (HRP) assay using a spot technique on nitrocellulose paper.

These assays demonstrated that DMS-treated RSA was the most antigenic of the reaction products tested. The least provocative was the glutaraldehyde-treated RSA; the reaction product of formaldehyde was intermediate.

Our findings suggest that if non-immunogenicity of a pulpotomy agent is a desirable property, then DMS does not meet the criteria of an alternative pulp fixative. In contrast, the relatively low antigenicity of glutaraldehyde reinforces other favorable findings which support its use clinically.
Antibiotic Susceptibility of Anaerobic Bacteria from the Human Oral Cavity
Authors: Baker P.J. , Evans R.T. , Slots J. , Genco R.J.
Published: November 2010

Anaerobic, agar-dilution, minimal inhibitory concentrations (MICs) of 18 antibiotics are given for the numerically important bacterial groups from the human oral cavity. Strains are divided into susceptibility categories using the guidelines for interpretation of MICs suggested by the National Committee for Clinical Laboratory Standards. These guidelines are based on data on antibiotic concentrations attainable in serum following various dosage regimens. MICs are also compared with attainable gingival fluid levels where these are known. The highest percentages of strains were susceptible to tetracycline, with 89% of the 139 strains tested susceptible to serum levels and 97% conditionally susceptible to attainable gingival fluid levels. Ninety-eight percent of strains were conditionally susceptible to attainable gingival fluid levels of minocycline, but many strains, including Actinobacillus actinomycetemcomitans, were only moderately susceptible to attainable serum levels of this tetracycline analogue. Carbenicillin was effective against most groups of organisms, with the important exception of A. actinomycetemcomitans, at serum levels attainable with oral formulations of carbenicillin. Only 2% of the total strains tested were resistant to penicillin, while 33% of strains were categorized as moderately susceptible. Clindamycin was active against many strains of Gram-negative bacteria but was not active against A. actinomycetemcomitans, some Bacteroides, Eikenella corrodens, or the anaerobic vibrios. Metronidazole was active against A. actinomycetemcomitans, all five groups of oral Bacteroides tested, and against Capnocytophaga species. Chloramphenicol was active against A. actinomycetemcomitans, but not against most of the other groups of oral organisms. Nearly all groups contained strains non-susceptible to serum levels attainable with the usual doses of erythromycin, spiramycin, vancomycin, kanamycin, neomycin, streptomycin, doxycycline, oxytetracycline, or chlortetracycline; several strains were resistant to maximum attainable serum levels of each of these antibiotics except doxycycline.
Micro-analytical Determination of pH, Calcium, and Phosphate in Plaque Fluid
Authors: Rankine C.A.N. , Moreno E.C. , Vogel G.L. , Margolis H.C.
Published: November 2010

Micro-analytical techniques for the determination of calcium, phosphate, and pH in a small volume (<0.25 μl) of plaque fluid are described and evaluated. The accuracy and the precision of the techniques were compared with those for standard macrotechniques applied to a large pooled plaque fluid sample. The results obtained for the micro-analysis of pooled plaque fluid were in excellent agreement with those obtained by macromethods. The described techniques were also used to analyze plaque fluid obtained from single quadrants of the oral cavities of five individuals. In this fashion, it was determined that, although a significant variation in plaque fluid composition exists between the quadrants, a greater variation exists between subjects. Analyses of plaque fluid obtained from six individuals, following sucrose exposure, were also conducted. The pH value of the fluid changed with time, following a typical Stephan curve, with a minimum value occurring between 15 and 30 minutes;following this, the pH increased to a value near that for resting plaque. An inverse relationship between pH and calcium and phosphorus concentrations was observed. It is noted that the described techniques are sensitive enough to carry out the above analyses both accurately and precisely using plaque obtained from a single quadrant.
Effects of a Single Intravenous Dose of Sodium Fluoride on Plasma Electrolytes and Metabolites in Rats, Rabbits, and Cockerels
Authors: Monsour P.A. , Kruger B.J. , Smid J.R.
Published: November 2010

This study assessed the effect of a single intravenous dose of sodium fluoride (20 mglkg body wt.) on plasma ionic fluoride and on some other plasma electrolytes and metabolites in rats, rabbits, and cockerels. At any given time following sodium fluoride administration, the plasma ionic fluoride was highest in rabbits and lowest in cockerels. The rate of removal of fluoride from plasma was slower in rabbits as compared with that in the other two species. Plasma sodium, chloride, total protein, albumin, total globulins, and osmolality were not significantly altered by sodium fluoride in any of these three species. However, plasma phosphate (inorganic), urea, creatinine, and glucose were elevated, and plasma calcium was reduced in the rats and the rabbits, but none was significantly altered in the cockerels. The analyses indicated that species variability does exist in fluoride toxicity.
Internal Morphology of Surface Zones from Acid-etched Caries-like Lesions: A Scanning Electron Microscopic Study
Authors: Hicks M.J. , Silverstone L.M.
Published: November 2010

Using scanning electron microscopic techniques, we compared the surface topography and internal surface morphology of acid-etched caries-like lesions of enamel with those of sound enamel and caries-like lesions of enamel. The results indicated that acid-etching of caries-like lesions of enamel yielded etching patterns similar to those previously described for sound enamel. The internal morphology of the acid-etched lesion indicated that porosities were created which may allow access to the subsurface demineralized area of the lesion and could prove beneficial in facilitating remineralization.
Plaque Inhibition by Sustained Release of Chlorhexidine from Removable Appliances
Authors: Friedman M. , Harari D. , Raz H. , Golomb G. , Brayer L.
Published: November 2010

We studied the effectiveness of a sustained-release delivery system for chlorhexidine in plaque prevention. A clinical trial in a group of eight students wearing orthodontic appliances coated by ethyl cellulose polymer containing the drug demonstrated that plaque accumulation was decreased for a period of four days. All oral procedures had been withdrawn during the clinical study. No side-effects of chlorhexidine, such as tooth staining and unpleasant taste, were observed.