bluuebunny/crossref_metadata_2025 huggingface dataset:
A Survey of the Publication History of Randomly Selected IADR/AADR Abstracts Presented in 1983 and 1984
Authors: Corry A.M.
Published: November 2010

IADR/AADR abstracts of research projects to be presented at the Annual Meeting are published each year in the Journal of Dental Research. An assumption often made is that the material in these abstracts is subsequently published as journal articles. The validity of this assumption was assessed in this study. Following a review of the literature to establish study criteria, the specific objectives of this study were to determine: (1) the percentage of IADR/AADR abstracts subsequently published as articles, (2) the length of time from abstract to publication, and (3) the amount of discrepancy between abstract and article. Ten percent of the IADR/AADR abstracts from the years 1983 (n = 125) and 1984 (n = 150) were randomly selected and surveyed for their publication history. Major reference sources were checked for determination of whether articles had resulted from the abstracts. Of the 1983-1984 abstracts surveyed, the results indicated that more abstracts were not published (78.5% in 1983/76.0% in 1984) than were published (21.6% in 1983/24.0% in 1984). Of those articles previously published as abstracts, the greatest number (44.4% in 1983/ 47.2% in 1984) were published within ten to 21 months following presentation. The greatest amount of discrepancy between the abstract and the article involved names and numbers of authors, titles, purpose statements, and results/conclusions. In other health disciplines, the percentage of abstracts subsequently published as articles ranged from 31.1% to 53.9%. Since a smaller percentage of the IADR/AADR abstracts surveyed in this study were ultimately published (21.6% to 24%), IADR/AADR should consider various strategies to improve the quality of abstracts and their accessibility.
The Effects of Sucralose on Coronal and Root-surface Caries
Authors: Bowen W.H. , Young D.A. , Pearson S.K.
Published: November 2010

Sucralose is an intensely sweet, chlorinated carbohydrate structurally similar to sucrose; thus, its cariogenic potential is of great interest. Four groups of 12 Sprague-Dawley rats were infected with Streptococcus mutans (sobrinus), caged in a Konig-Höfer programmed feeding machine, and fed diet 2000 or modified diet to contain sucralose at various concentrations instead of sucrose. Rats fed sucralose diet developed significantly fewer lesions than did the rats fed regular diet 2000. Animals fed diet 2000 also harbored more S. mutans (sobrinus) than did the other groups of animals.

In a concurrent study, desalivated rats were inoculated with S. mutans (sobrinus) and Actinomyces viscosus. They were fed (ad libitum) either diet 2000 (contains 56% sucrose) or diet 2000 minus sucrose plus 93 mg% sucralose. The severity of caries lesions in the sucralose-fed rats after 35 days was significantly less than those in the sucrose-fed rats. The amount of root exposure was the same in both groups. However, root-surface caries did not develop in the sucralose-fed rats. These results show that sucralose is non-cariogenic in rats.
Cytotoxicity of Experimental Casting Alloys Evaluated by Cell Culture Tests
Authors: Craig R.G. , Hanks C.T.
Published: November 2010

The cytotoxicity of a series of 29 experimental alloys and six pure metals was determined with cell culture techniques and succinic dehydrogenase histochemistry. The width of any ring of inhibition, optical density of the histochemically stained cells, and a visual ranking of the intensity of the blue color of the stained cells were compared for determination of cytotoxicity. Twenty-four of the 35 metals and alloys (-70%) had the same rankings by the three methods. Of the pure metals, Au, Pd, and Ti were the least cytotoxic, followed by Ag, then Ni, and finally, Cu. Single-phase alloys with moderately high Cu and without high Pd and Au concentrations had high cytotoxicity, as did multiphase alloys, even when they were high in Au and Ag. High Pd was more effective in maintaining the biocompatibility of alloys containing Cu than was Au. Single-phase alloys with compositions typical of those to be used for porcelain-fused-to-metal restorations showed good biocompatibility, as did those base metal alloys that formed adherent oxide surface layers.
Mechanism of Endotoxin Inhibition of Human Gingival Fibroblast Attachment to Type I Collagen
Authors: Pitaru S. , Madgar D. , Metzger Z. , Hekmati H.
Published: November 2010

Bacterial endotoxin inhibits the attachment of human gingival fibroblasts to collagen. The present study attempted to elucidate the possible mechanism of this inhibition. Two mechanisms were considered: direct toxicity to the cells and steric interference. Collagen substrates were prepared by rat type I collagen being air-dried in the wells of 24 multi-well plates. Experimental collagen substrates were treated with 50 μg of endotoxin/well, while untreated collagen substrates served as controls. Two mL of cell suspension (104 cells/mL) was added to each well, and these were incubated at 37°C for two h. The average cell number/mm2 attached to experimental and control substrates was determined. Cell attachment to endotoxin-treated collagen was inhibited by 78%, compared with that to untreated collagen. The washing of the endotoxin-treated collagen for two h did not affect the inhibition of cell attachment, whereas after 24 h of washing, cell attachment was inhibited by 54%, compared with that to untreated collagen. Pre-incubation of the cells in endotoxin for two h did not affect their attachment to collagen. The addition of fetal calf serum (15%) to the experimental system completely reversed the inhibition of fibroblast attachment to endotoxin-treated collagen. These findings suggest that endotoxin interferes with fibroblast attachment to collagen through a steric phenomenon, possibly by blocking the binding sites on the collagen molecule recognized by the membrane receptor for collagen.
Effect of Solution Composition on Morphological and Structural Features of Carbonated Calcium Apatites
Authors: Shimoda S. , Aoba T. , Moreno E.C. , Miake Y.
Published: November 2010

The composition of enamel mineral corresponds to that of a calcium carbonato-apatite. For insight to be gained into the precipitation of carbonato-apatites having specific properties (crystal size, morphology, and carbonate incorporation into the crystal lattice), apatites were prepared at 80°C in aqueous systems having various CO3 concentrations and pH values of around 7.5 or 10.5 (± 0.5). The various preparations had a wide range (0.005 to 0.19) of CO3/Ca molar ratios that bracket the ratios found in porcine enamel mineral at various developmental stages. Fourier transform infrared spectroscopy (FTIR) and x-ray diffraction analyses showed that the calcium apatites precipitating at neutral pH incorporated the carbonate into both the hydroxyl and phosphate ion sites in their lattices (A,B-types), whereas the preparations made at the alkaline pH (high OH-CO32- competition) or in the presence of fluoride (F--CO32- competition) yielded only the B-type carbonato-apatite. It was also ascertained that the size and morphology of the carbonato-apatites, assessed by specific surface area determination and high-resolution electron microscopy, were highly dependent on the driving force for precipitation and the presence of regulators (CO 32- and F-) in solution. In neutral media, early precipitates were thin-ribbon in appearance, but grew into crystals having flattened-hexagonal cross-sections. In the presence of fluoride or in alkaline media, acicular apatite crystals, precipitated initially, grew into large rod-like carbonato-apatites having a symmetric-hexagonal cross-section. In both neutral and alkaline solutions, carbonate inhibited the growth of apatite crystals along their c axis, leading to the formation of bulkier crystals. The formation of carbonato-apatites at the neutral pH and their properties are consistent with observations made on enamel minerals formed in the early developmental stages.
Characterization of the α-amylase Receptor of Streptococcus gordonii NCTC 7868
Authors: Douglas C.W.I.
Published: November 2010

The purpose of the work described here was to investigate the mechanisms involved in the binding of salivary α-amylase to Streptococcus gordonii NCTC 7868 (Challis). Of six types of a-amylase studied, only mammalian forms of the enzyme were found to bind to S. gordonii cells. Salivary a-amylase binding was inhibited by treatment of cells with trypsin and pronase, but not with pepsin or sodium periodate. Presence of starch, dextrin, or maltoheptaose partially inhibited binding of the enzyme to S. gordonii. Both mutanolysin extracts of cells and culture supernatants contained α-amylase-binding activity, which was partially purified by Sepharose CL-6B and DEAE-ionexchange chromatography. Western blotting detected four putative receptor bands-65 kDa, 15 kDa, 12.5 kDa, and one with a very high molecular weight; the lower-molecular-weight components may be products of proteolytic degradation of the high-molecular-weight material, but their true relationship has yet to be determined. Pre-treatment of salivary α-amylase with these putative receptors partially inhibited subsequent binding of the enzyme to S. gordonii cells. When bound to cells, only 19% of the salivary α-amylase activity was detectable, suggesting that α-amylase binds to the receptor at or near the active site of the enzyme.
Development of Horizontal Tooth Wear in Maxillary Anterior Teeth from Five to 18 Years of Age
Authors: Nystrom M. , Könönen M. , Alaluusua S. , Evalahti M. , Vartiovaara J.
Published: November 2010

Sizes of horizontal wear facets of maxillary anterior teeth were studied longitudinally from the primary dentition at age five to the young adult dentition at the age of 18 years. By a planimetric method, we calculated the wear areas on dental casts taken at the ages of five, ten, 14, and 18 years from the dentition of 39 healthy, orthodontically untreated subjects with good morphological occlusion. For young adults, we also studied the association between the amount of wear and reported parafunctions, maximal bite force, salivary buffer capacity, salivary flow rate, and some cephalometric variables.

Size of wear facets on all anterior teeth increased with age. Significant correlations were found between the total wear areas of the six anterior primary teeth at five years of age and those of their permanent successors at age 14 (r = 0.44) and 18 (r = 0.39). For an individual, tooth wear at five years of age was, however, of low predictive value for tooth wear in young adulthood, whereas tooth wear at 14 years of age predicted it well (r = 0.89). Highest correlations between tooth wear and background factors at 18 years of age were found for maximal anterior bite force (r = 0.44) and for the size of the gonial angle (r = -0.31). Wear of anterior teeth was not associated with reported parafunctions in young adulthood.
Influence of Test Method on Failure Stress of Brittle Dental Materials
Authors: Ban S. , Anusavice K.J.
Published: November 2010

A bi-axial flexure test (piston-on-three-balls), a four-point flexure test, and a diametral tensile test were used to measure the failure stress of four brittle dental materials: zinc phosphate cement, body porcelain, opaque porcelain, and visible light-cured resin composite. Furthermore, the fracture probability of the bi-axial test specimens was predicted from the results of the four-point flexure test, with use of statistical fracture theory. Bi-axial failure stresses calculated from an equation developed by Marshall (1980) exhibited no significant difference for zinc phosphate cement as a function of piston size, specimen thickness, presence or absence of a stress-distributing film, and loading rate. The four-point flexure strength values of zinc phosphate cement and opaque porcelain were significantly lower (p<0.05) than the corresponding mean biaxial strength values, while the mean four-point flexure strength values of body porcelain and resin composite were not significantly lower (p>0.05) than the corresponding mean bi-axial strength values. The diametral tensile strength of all materials was significantly lower than the bi-axial flexure strength. The mean bi-axial flexure strengths of zinc phosphate cement and opaque porcelain were much higher than the theoretical values predicted from surface flaw theory, while the strength values for body porcelain and resin composite were comparable with those determined from the four-point flexure test. These results demonstrate that the strength of zinc phosphate cement depends not only upon the geometric factors, but also upon sample preparation conditions.
Expression of Integrins in Human Gingiva
Authors: Hormia M. , Ylänne J. , Virtanen I.
Published: November 2010

The distribution of the α 1-α6 subunits of β1 integrins was studied by using a panel of monoclonal antibodies in indirect immunofluorescence microscopy. The results showed that the β1 subunit was expressed at the cell membrane of basal cells of gingival epithelium, throughout the cells of junctional epithelium (JE), and in cells of connective tissue, including endothelial cells. The α1 subunit was expressed in vascular endothelial cells and, more faintly, in inflammatory cells in gingival connective tissue. The α4 subunit was expressed selectively in inflammatory cells, and the α5 subunit was expressed in cells throughout gingival connective tissue. An overall cell membrane immunoreactivity for the α2 and α3 subunits was shown in basal cells of gingival epithelium and in cells of JE, corresponding to the epithelial localization of the β1 subunit. The α6 subunit was polarized to the basal aspects of basal epithelial cells, but was also present in an overall cell surface distribution in basal cells and in cells of JE. The β4 integrin subunit was mainly expressed at the basal aspects of basal cells in gingival epithelium and JE. The results indicate that the α2/β1, α3/β 1, α6/β1, and α6/β 4 integrins are all expressed in human gingival epithelium. Of these, the α6/β4 integrin complex is the major candidate for mediation of the attachment of epithelial cells to the basement membrane facing the connective tissue and probably also the tooth.
Fluoride Intake of Infants in New Zealand
Authors: Chowdhury N.G. , Brown R.H. , Shepherd M.G.
Published: November 2010

Since the fluoride (F-) intake of New Zealand infants and young children is not known, a study was designed to determine and compare the F- intake of infants, aged 11 to 13 months, residing in fluoridated (F) and non-fluoridated (NF) areas. Parents of 60 infants duplicated quantitatively and qualitatively all food and drink that the infants ingested during a three-day period. The acid-diffusible F- content in the liquid homogenate was isolated by the HMDS-HCl diffusion technique (Taves, 1968) and measured by a fluoride electrode. The ionic F- in samples of breast milk was measured directly by the electrode. In the F area, the F- content of the food and drinks of 31 subjects ranged from 0.130 to 0.679 mg/kg (mean, 0.320; SD, 0.168); in the NF areas, the F- content of the food and drinks of 29 subjects ranged from 0.036 to 0.281 mg/kg (mean, 0.095; SD, 0.053). The dietary intake ranged from 0.089 to 0.549 mg F/day (0.009-0.056 mg F/kg bw) in the F area, and from 0.038 to 0.314 mg F/day (0.004-0.038 mg F/kg bw) in the NF area. Including F- from tablets and toothpastes, total intake ranged from 0.093 to 1.299 mg F/day (0.009-0.150 mg F/kg bw) and from 0.039 to 0.720 mg F/day (0.004-0.061 mg F/kg bw) in F and NF areas, respectively.

The mean dietary intake of infants in the F area was about half the recommended "optimal" range; in the NF areas, the dietary intake was five to seven times less than the optimal. Sources of high fluoride intake such as soy-milk formulae and tea, however, raised the fluoride content of the diet to near optimal levels. The use of F toothpastes and tablets raised the intake to near optimal levels. The optimal intake was exceeded by one child in the F area as a result of excessive toothpaste use. It was calculated that, if a child on soy formula in the non-fluoridated areas were to ingest fluoride supplements and large amounts of toothpaste as well, the total fluoride intake of this infant could exceed optimal levels. This finding stresses the need for identification of potential sources of high fluoride intake in a child's diet before any form of fluoride supplementation is recommended.
Activation of Complement by Treponema denticola
Authors: Schenkein H.A. , Berry C.R.
Published: November 2010

Oral spirochetes have been shown to be associated with periodontal diseases and are present in increased numbers in lesions of greater severity. In this study, the interaction of Treponema denticola with human complement, a major antibacterial defense system, was examined. For each of two strains of T. denticola, it was found that both the classical and alternative pathways of human complement were activated in human serum upon incubation at 37°C. C3 fragments were deposited on the surface of this organism following complement activation; the fragments bound included both of the major C3-derived op-sonic fragments C3b and iC3b. Under incubation conditions identical to those carried out for complement activation in serum, T. denticola failed to degrade purified, hemolytically-active C3, although it readily degraded inactivated C3. Thus, despite the documented proteolytic activity of this organism, complement activation and deposition of complement-derived opsonins may be important defense mechanisms in the control of infections with T. denticola.
Power and Sample Size Calculations for Clinical Trials of Myofascial Pain of Jaw Muscles
Authors: Dao T.T.T. , Lavigne G.J. , Feine J.S. , Tanguay R. , Lund J.P.
Published: November 2010

When a clinical trial is planned, the approximate number of subjects needed for significant differences between/among groups to be detected must be estimated. Sample-size calculations provide the investigator with this information.

This paper discusses the choice of outcome measures and describes the steps used to estimate the numbers of subjects necessary for a study that compares treatments for patients with chronic myofascial pain of jaw muscles. Within- and between-subject variances were estimated for the chosen variables, the subjects' pain ratings on visual analogue scales. Sample sizes were then calculated for theoretical differences between groups by pre-treatment means and overall standard deviations (Cohen, 1977).

The results of this analysis can be used by other researchers when planning studies involving these types of patients.
The Effect of EHDP Concentration on Enamel Demineralization in vitro
Authors: Christoffersen J. , Christoffersen M.R. , Ruben J. , Arends J.
Published: November 2010

The depth of caries lesions produced in bovine enamel situated in an unstirred 0.1 mol/L lactic acid buffer at pH 4.5 has been studied as a function of time and of concentration of the inhibitor ethane-1-hydroxy-1, 1-diphosphonate, EHDP. At concentrations of EHDP up to 5 mmol/L, the lesion progress decreased with increasing concentration of inhibitor. At higher concentrations, the opposite effect was observed. At low inhibitor concentration (0.1 mmol/L), the lesion depth to the third power varied linearly with time. At intermediate concentrations (0.25-5 mmol/L), the square of the lesion depth varied linearly with time. At high inhibitor concentrations (25-100 mmol/L), the lesion depth varied linearly with time. It was also shown that the rate of dissolution of calcium hydroxyapatite crystals was retarded by low concentrations of EHDP, but accelerated by high concentrations of EHDP. The results are related to a physico-chemical model describing lesion formation.
Influence of Initial Flaw Size on Crack Growth in Air-tempered Porcelain
Authors: Anusavice K.J. , Gray A. , Shen C.
Published: November 2010

Tempering of dental porcelain by forced convective cooling in air has been shown previously to inhibit the sizes of cracks induced in porcelain surfaces. However, the depth of compressive stress that is produced by tempering of feldspathic porcelain has not been determined. It can be assumed that the potential of tempered specimens to inhibit crack formation is reduced as the flaw size exceeds some critical value, since the compressive stress decreases with distance from the surface.

The objective of this study was to test the hypothesis that the effectiveness of tempering stress in porcelain decreases with the increasing size of initial surface flaws. Body porcelain discs, 16 mm in diameter and 2 mm in thickness, were tempered (T) by forced convective cooling in air from an initial temperature of 982°C at a pressure of 0.34 MPa for 90 s. Non-tempered control discs (NT) were slowly cooled by termination of power to the furnace. The half crack-lengths (c) of surface cracks induced by a Vickers microhardness indenter at loads ranging from 2.0 to 39.2 N were determined initially and over a period of 24 h. The initial half crack-lengths, co, for the tempered specimens were significantly smaller (p < 0.05) than the corresponding values for the slow-cooled specimens. The mean value of the stress corrosion susceptibility coefficient (n), which is inversely related to the slope of log crack size vs. log time, was only slightly smaller for the NT specimen groups (15.3), compared with the mean value for the T groups (17.1).

These results indicate that tempering stress can effectively inhibit the initial sizes of half-penny cracks with initial depths of at least 100 μm. However, in tempered specimens, the growth rate of initial cracks, which varied in length from 21.4 μm to 76.1 μm, was relatively insensitive to the compressive stress (78.1 MPa) produced by tempering.
Effect of Cooling Rate on Leucite Volume Fraction in Dental Porcelains
Authors: Mackert J.R. , Evans A.L.
Published: November 2010

Prasad et al. (1988) have shown that slow cooling of dental porcelain produces increases in thermal expansion sufficient to make a compatible metal-porcelain system incompatible. The present study was undertaken to determine whether the increase in porcelain thermal expansion might be attributable to crystallization of additional leucite during slow cooling of the porcelain. Eight x-ray diffraction specimens for each of six commercial dental porcelains and for the Component No. 1 frit of the Weinstein and Weinstein (1962) and Weinstein et al. (1962) patents were fabricated and divided into two groups. Specimens in the first group (termed fast-cooled) were cooled in the conventional manner by removing them from the furnace at the maximum firing temperature immediately into room air. Specimens in the second group (termed slow-cooled) were cooled slowly by interrupting power to the furnace muffle and allowing them to cool inside the closed furnace. Quantitative x-ray diffraction was performed on the fast- and slow-cooled porcelain specimens with standards containing leucite volume fractions of 0.111, 0.223, 0.334, and 0.445. Unpaired, one-tailed t tests were performed on the fast- and slow-cool data, and a significant increase (p<0.05) in the amount of leucite (as a function of the slow cooling) was found for each of the porcelains. The increases in the leucite volume fractions resulting from the slow cooling ranged from a low of 8.5% to a high of 55.8%, with an average increase of 26.9%. Because of the strong dependence of the coefficient of thermal expansion of dental porcelain on its leucite content, slow cooling of porcelain-metal dental restorations would be capable of producing severe porcelain-metal thermal incompatibilities.
Association of Proteases of Porphyromonas (Bacteroides) gingivalis with its Adhesion to Actinomyces viscosus
Authors: Li J. , Ellen R.P. , Hoover C.I. , Felton J.R.
Published: November 2010

P. gingivalis adheres to A. viscosus on mineral surfaces mimicking teeth. To study whether P. gingivalis proteases contribute to its binding, mutants of P. gingivalis deficient in proteases were compared with their parent strain and a P. gingivalis-type strain for their adherence to A. viscosus on saliva-coated hydroxyapatite by manipulating a radio-isotope binding assay. Adherence of P. gingivalis 2561 to A. viscosus was studied by tests of the effects of incubation temperature and known inhibitors or promoters of proteases. Controls were handled by the assay run in PBS buffer at 22°C. Two mutants deficient in trypsin-like protease were found to be deficient in adherence (% attachment relative to control: 3.2 ± 0.1% and 11.2 ± 0.4%), while a collagenase-deficient mutant had an adherence score (51.6 ± 8.4) closer to that of the parent strain (75.6 ± 7.2%). Heating P. gingivalis at 70°C decreased its subsequent adherence at 22°C by 80%. Adherence decreased by 60% when the assay was run at 4°C, but increased by 70% at 37°C. Reducing agents (dithiothreitol, cysteine, and mercaptoethanol) enhanced P. gingivalis adherence by 50 to 60%. Protease inhibitors (BZMD, SBTI, TPCK, TLCK, CMPS, PMSF) decreased adherence by 10 to 50%. Also, Hg2+ and Zn2+ decreased adherence by 30 to 50%, and arginine decreased it by 50%. Most of these effects on P. gingivalis adherence were statistically significant (p<0.05). Analysis of these data suggests that P. gingivalis proteases may contribute to the cohesion of P. gingivalis and A. viscosus.
A Human Periodontal Ligament Fibroblast Clone Releases a Bone Resorption Inhibition Factor in vitro
Authors: Giniger M.S. , Norton L. , Sousa S. , Lorenzo J.A. , Bronner F.
Published: November 2010

The conditioned media (CM) obtained from three lines of cloned human periodontal ligament (PDL) cells were analyzed to determine whether they altered the parathyroid hormone (PTH)-stimulated resorption rates (45Ca release) in 48-hour cultures of 45Ca-labeled rat long bones. One PDL cell line, PDL-5, produced a heat-resistant factor in its CM that inhibited the PTH-stimulated resorption by 43.8 ± 9.7 (SE) percent (p < 0.02), whereas the CM from the other cell lines were without statistically significant effect. The CM from the PDL-5 line did not diminish organ culture viability, as determined by 3H-thymidine incorporation, and did not enhance or diminish the resorption-inhibiting activity of calcitonin added to the PTH-stimulated cultures. The addition of CM from PDL-5 did not alter the bone-resorbing effect of interleukin-1 (IL-1). These results indicate that CM from PDL-5 inhibits only the PTHinduced and not the IL-1-mediated resorption processes, whose mechanisms are therefore likely to differ.
Immunoglobulin Isotypes in Human Minor Gland Saliva
Authors: Smith D.J. , Taubman M.A. , Ali-Salaam P.
Published: November 2010

Lower labial, upper labial, palatine (minor), and parotid (major) gland saliva samples from 18 young adult males were quantitatively assayed for the presence of IgAl, IgA2, IgM, and IgG. The mean (± standard deviation) concentrations of IgA (sum of IgAl + IgA2) were 79 ± 42 μg/mL (parotid), 111 ± 42 μg/mL (lower labial), 69 ± 72 μg/mL (upper labial), and 88 ± 68 μg/mL (palatine). Total IgA concentrations were positively correlated among different minor-gland samples from the same subject, although these correlations did not reach significance. Upper-labial-gland saliva samples contained significantly (at least p<0.05) lower concentrations of IgAl than those found in parotid or lower-labial minor-gland secretions. All three minor-gland sources of saliva contained significantly (p<0.002) higher levels of IgG than did parotid saliva. Upper-labial fluids had significantly (p<0.02) higher IgG concentrations than lower-labial saliva. IgM could be detected in 89% of parotid saliva samples and 75% of the palatine saliva samples. Palatine IgM concentrations (8.2 ± 17.8 μg/ mL) were significantly (p<0.05) higher than parotid IgM concentrations (0.6 ± 0.4 μg/mL). IgM was detected much less frequently and at lower concentrations in lower- and upper-labial-gland saliva. These data reveal that minor-gland saliva from different oral sites may contain distinctive immunoglobulin isotype patterns, and expressions of host defense may vary within each micro-environment.
The Distribution of Magnesium in Developing Rat Incisor Dentin
Authors: Steinfort J. , Driessens F.C.M. , Heijligers H.J.M. , Beertsen W.
Published: November 2010

Previous studies have shown that rat incisor dentin contains a considerable amount of magnesium that is distributed heterogeneously. The cementum-related dentin, especially its incisal portion, is richest in magnesium. It was the purpose of the present study to investigate the changes that occur in the magnesium content during dentin maturation.

Cross-sections were prepared from rat incisors at the apical, middle, and incisal levels. By means of an electron microprobe, tracings were made of the Ca-, Mg-, and P- signal frequencies. Comparison of corresponding dentin layers within and between the cross-sections showed that the Mg/P molar ratio was always higher in the cementum-related dentin (CRD) than in the enamel-related dentin (ERD) and increased from the apex toward the incisal edge. Especially in the incisal cross-section, an increase in Mg/P was found from the older (peripheral) toward the younger (central) dentin layers. As the Mg/P ratio varied from 0.07 to 0.33, the Ca/P ratio was found to fluctuate from 1.48 to 1.15. The two ratios appeared to be highly correlated (r = -0.97; p<0.001), suggesting that Mg replaces Ca and is bound to phosphate.
Dentin-bonding Molar Efficiency Using N-Phenylglycine, N-Phenyl-beta-Alanine, or N-Methyl-N-Phenylglycine
Authors: Webb R.E. , Johnston A.D.
Published: November 2010

Three structurally related substituted amino acids (N-compounds) were studied in a three-step dentin-bonding protocol. The first step of an acidic ferric oxalate solution and the third step of a surface-active comonomer were held constant throughout the study. In the second step, the amount of the N-compound-either N-phenylglycine (NPG), N-methyl-N-phenylglycine (NMNPG), or N-phenyl-p-alanine (NPBA)-was varied in acetone from 0 mol/L through 5 x 10-1 mol/L in seven steps. At 1 x 10-3 mol/L for NPG and NMNPG, average bond strength values were 7.4 ± 2.2 and 10.5 ± 2.7 MPa. The highest bond strength value for NMNPG was at 1 x 10-2 mol/L, with 13.2 ± 4.0 MPa. The highest value for NPG was at 1 x 10-1 mol/L, with a value of 11.8 ± 2.5 MPa. The average bond strength for NPBA did not differ from zero across the entire range of concentrations. Molar efficiency was defined as the bond strength per mole of these applied N-compounds. For the two N-compounds that did provide adhesion to dentin, NPG and NMNPG, the average bond strengths rose, peaked, and fell as the amounts of applied N-compound were increased. The molar efficiency dropped off as the concentration of applied N-compound rose. The least operator-sensitive and most efficient N-compound, NMNPG, delivered a bond strength equivalent to that of NPG, with 10% of the applied NPG amount.
Abrasion of Human Enamel by Different Dental Ceramics in vitro
Authors: Seghi R.R. , Rosenstiel S.F. , Bauer P.
Published: November 2010

Manufacturers generally quote indentation hardness values when predicting the clinical wear potential of newly introduced ceramic restoratives. The objective of this study was to determine whether in vitro two-body wear correlated well with hardness. A modified polisher was used to abrade enamel cylinders against polished disks of commercially available dental porcelains and glass. Enamel loss after four h was measured with a micrometer. Five ceramic materials were tested, and enamel abrasion rates were correlated with Knoop hardness values. Dicor and Dicor coated with a shading porcelain were found to cause the lowest wear of enamel. These rates were statistically significantly lower than those obtained with Optec, the most abrasive material. These findings may be due to microstructural differences between the materials. Knoop hardness showed poor correlation with the results of the abrasive testing.
Destructive Stresses in Adhesive Luting Cements
Authors: Davidson C.L. , Van Zeghbroeck L. , Feilzer A.J.
Published: November 2010

In this study, curing shrinkage stress development was monitored in a glass-ionomer and a BisGMA composite luting cement adhesively placed at film thicknesses ranging from 30 to 200 μm. The nature and magnitude of the stress development depended greatly on the formulation and film thicknesses of the lute. The thicker the layer, the faster the stress development in the glass ionomer and the slower in the composite. The contraction stress had a detrimental effect on the cohesive strength of the glass ionomer and on the adhesive strength of the composite cement.
The Effect of Local Interfacial Geometry on the Measurement of the Tensile Bond Strength to Dentin
Authors: Van Noort R. , Cardew G.E. , Howard I.C. , Noroozi S.
Published: November 2010

The local detail of the geometry of the adhesive interface can have a significant effect on the measurement of dentin bond strengths and may be a contributory factor in the discrepancies among data in the published literature. The potential effect on the dentin bond strength due to modifications of the local stress distribution at the adhesive/dentin interface has been assessed. Tensile bond strength measurements for specimens with and without an adhesive flash were carried out and compared with the stress distribution at the adhesive interface determined by finite element stress analysis.

The results showed that when the adhesive was constrained to the interface only, the tensile bond strength was 3.10 MPa, which increased to 6.90 MPa when a flash of adhesive was present. For a realistic measurement of dentin bond strength, the adhesive should be constrained to the interface only. Extension of the adhesive beyond the interface will result in an artificially high value for the dentin bond strength. A standardized method for the measurement of dentin bond strength is urgently needed, but must take these as well as all other known factors into account if results from different testing centers are to be directly comparable.
Use of an Intra-oral Model to Evaluate 0.05% Sodium Fluoride Mouthrinse in Radiation-induced Hyposalivation
Authors: Meyerowitz C. , Featherstone J.D.B. , Billings R.J. , Eisenberg A.D. , Fu J. , Shariati M. , Zero D.T.
Published: November 2010

The present study was undertaken to evaluate the effect of a twice-daily topical application of a 0.05% NaF mouthrinse on de- and remineralization in the oral cavities of subjects suffering from radiation-induced hyposalivation. Six subjects each wore a bonded intra-oral appliance containing a sound and a demineralized human enamel slab for four weeks. During that period, the subjects used 0.05% NaF rinses, twice daily, instead of the 1.1% NaF gel that had previously been a part of their preventive regimen. Salivary flow rates, plaque pH profiles following a 10% sucrose rinse, S. mutans and lactobacillus counts, fluoride clearance, and enamel microhardness were determined during the study. Sound enamel samples displayed no evidence of demineralization, and the previously demineralized enamel showed remineralization in the outer 50 μm in three of the six subjects. The results suggest that a twice-daily oral rinse with 0.05% NaF can prevent demineralization and enhance remineralization in subjects with radiation-induced hyposalivation.
Effects of Topical and Systemic Nicotine on Gingival Blood Flow in Dogs
Authors: Johnson G.K. , Todd G.L. , Johnson W.T. , Fung Y.K. , Dubois L.M.
Published: November 2010

It has been suggested that due to its vasoconstrictive action, nicotine may have a deleterious effect on the periodontium. This study examined the effects of topical and systemic nicotine administration on gingival blood flow. Eighteen young adult dogs were divided into three groups receiving the following treatments for 28 days: topical nicotine in orabase, systemic nicotine via osmotic mini-pumps, and topical orabase or systemic saline via osmotic mini-pumps. Blood flow to the gingiva was measured (at days 0 and 28) by the radiolabeled microsphere method. Blood flow was consistently increased from day 0 to day 28 in the nicotine-treated animals. Comparison of days 0 and 28 blood-flow values demonstrated a statistically significant change (p<0.05) in the anterior regions of the topical-nicotine group as compared with the control group. The increased flow may be a reflection of the mode of nicotine delivery and timing of the blood-flow determination procedures.
The Effects of Autonomic Drugs on the Concentration of Kallikrein-like Proteases and Cysteine-proteinase Inhibitor (Cystatin) in Rat Whole Saliva
Authors: Bedi G.S.
Published: November 2010

The influence of isoproterenol, phenylephrine, propranolol, and reserpine on the salivary concentration of kallikrein-like proteases and cysteine-proteinase inhibitor (cystatin) was investigated. The protease activities in saliva from treated rats were studied by means of five different chromogenic substrates. In the isoproterenol- and phenylephrine-treated groups, a significant decrease in protease activity was found, compared with the control group. The protease activity of saliva was found to be elevated by about 25-50% after chronic administration of reserpine (0.5 mg/kg). Specific polyclonal antibodies to rat glandular kallikrein and cystatin were utilized to determine the salivary concentrations of these proteins. Results from the use of anti-kallikrein antibodies in Western blot analysis and crossed immuno-electrophoresis indicated that differences observed in the kallikrein-like protease levels of saliva from treated animals were due to altered immunoreactive protein levels. The salivary concentrations of kallikrein and cystatin were measured by direct radio-immunoassays with specific antibodies. The concentration of cystatin in the saliva of normal animals or animals treated with reserpine or propranolol was very low, but was increased about 100-fold in phenylephrine-treated animals and more than 5000-fold in isoproterenol-treated animals. Western blot analysis with antibodies to submandibular gland mucin, glutamine/glutamic-acid-rich protein (GRP), and proline-rich proteins (PRP) were also utilized to compare the effects of autonomic drugs on these salivary proteins. The salivary mucin showed an increase in reactivity and increased mobility in saliva from both isoproterenol- and phenylephrine-treated animals. The PRP-antibody-immunoreactive bands were significantly prominent in saliva from isoproterenol- or phenylephrine-treated rats, whereas GRP-immunoreactive bands of 55 and 43 kDa showed a marked decrease in saliva from isoproterenol-treated animals.
Adhesion to Bovine Dentin-Surface Characterization
Authors: Ruse N.D. , Smith D.C.
Published: November 2010

X-ray photo-electron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) were used to characterize the dentin surface, to determine the effects of different pre-conditioning procedures on the elemental composition of the dentin surface, and to investigate the interaction between dentin and a dentin bonding agent (ScotchBond) by studying the changes in the elemental composition of dentin as a result of the interaction. Scanning electron microscopy (SEM) was used to characterize sample surface morphology, which was then correlated with surface elemental composition.

The results showed that: (a) the elemental composition of the smear layer was similar to that of the underlying dentin; (b) cleaning with hydrogen-peroxide did not produce any modification in the elemental composition of the dentin surface; and (c) acid-etching led to an almost complete demineralization of the dentin, leaving behind an organic-rich surface. The results suggest that bonding systems that use acid-etching as a pre-conditioning procedure should be based on agents able to interact with the organic components of dentin, since bonding agents that rely on a chelation-to-calcium reaction are unlikely to be successful.

The investigation of the interaction between the bonding agent and dentin led to a postulated adhesive-bonding reaction mechanism and suggested a partially cohesive failure in the bonding agent during fracturing of a dentin-bonding-agent-bonded assembly.
The Severity of Dental Fluorosis in Children Exposed to Water with a High Fluoride Content for Various Periods of Time
Authors: Ish T. , Suckling G.
Published: November 2010

Inhabitants of the Ikeno district of Japan were accidentally exposed to drinking water containing 7.8 ppm fluoride (F) for 12 years, after which water with 0.2 ppm F was substituted. Dental examinations of local inhabitants revealed that only children aged seven years or less at the introduction or aged 11 months or more at the removal of the high-F water had fluorosis.

Regular inspections were made of the 86 children between those age limits. The severity of fluorosis in three tooth types (first permanent molars, upper central incisors, and first premolars) was assessed and related to the period of use of the high-F water. Continuous exposure throughout tooth development resulted in severe changes in all three tooth types. With limited exposure, the age at the beginning and at the end was an important factor in determining the severity of the fluorosis. The pattern of change from normal to severe fluorosis differed in the three tooth types, influenced by their respective times of formation. Two 'at-risk' periods for the production of moderate or severe fluorosis were evident. One started at birth and ended early in tooth development, while the other started later and ended at eruption.

The duration of F exposure, although determining the initial degree of fluorosis, did not influence the rate of post-eruptive enamel loss.
Atypical Structure of the 23S Ribosomal RNA Molecule in Certain Oral Bacteria
Authors: Sunday G.J. , Gillespie M.J. , Motley S.T. , Zambon J.J.
Published: November 2010

Ribosomal RNA (rRNA) isolated from Wolinella recta and seven related bacteria was examined by agarose gel electrophoresis. The 23S rRNA molecule could not be detected in W. recta, Wolinella curva, Bacteroides gracilis, or Bacteroides ureolyticus. In place of the 23S molecule, there were three smaller molecules of approximately 1700, 650, and 600 bases designated 23Sa, 23Sβ, and 23S∂, respectively. An intact 23S rRNA molecule could be isolated from Wolinella succinogenes, Campylobacter concisus, and Campylobacter sputorum. The cleavage sites of the W. recta 23S rRNA molecule were located by direct RNA sequence analysis and were found to be in similar locations, nucleotides 546 and 1180, as cleavage sites described in other prokaryotes. The presence or absence of the 23S rRNA molecule may be a useful marker for these micro-organisms.
Hamster Cheek-pouch Testing of Dental Soft Polymers
Authors: Harsanyi B.B. , Foong W.C. , Howell R.E. , Hidi P. , Jones D.W.
Published: November 2010

The hamster cheek pouch provides a suitable model system for the mucous-membrane irritation testing of dental materials. Poor retention of materials or difficulties in histopathological interpretation caused by surgical artifacts have been reported in published techniques. We describe a new "pouch-in-pouch" technique for mucous membrane irritation tests. The retention rate of polymer discs was 97% and 87% at 14 and 35 days, respectively. Clear differentiation was obtained between the tissue reaction to the test materials and the surgical procedure. Polymer discs containing dibutyltin diacetate (DBTD) or di-butyl phthalate (DBP) as plasticizer resulted in epithelial changes, including epithelial atypia, early papillomas, and areas resembling dysplasia. The potentially pre-malignant nature of these changes requires further investigation.
Alteration in Glutathione Level During Carcinogenesis of Hamster Buccal Pouch Mucosa
Authors: Zhang L. , Mock D.
Published: November 2010

This study examined the level of glutathione (GSH)-a tripeptide that may have an important role in detoxification of carcinogens-in the hamster buccal pouch mucosa (HBPM) by a 12-week regimen of tri-weekly topical application of 7,12-dimethylbenz[a]anthracene (DMBA) in mineral oil. GSH was quantified periodically and shown to be doubled in carcinogen-treated vs. control pouch mucosa. In the tumors that developed, the level of GSH was three times that of the controls. Previous studies showed that gamma-glutamyl transpeptidase (GGT), one of the enzymes that may be responsible for the detoxification of carcinogens, was increased in the hamster mucosa pre-neoplastic foci, but decreased with the formation of overt neoplasia. GGT and GSH are intimately related, since GGT is the only enzyme that can cleave the intact GSH molecule. The increase in both GSH and GGT levels may be responsible for the increased resistance of the pre-neoplastic pouch epithelium to the toxic effects of the carcinogen.
Effects of Salivary Bicarbonate Content and Film Velocity on pH Changes in an Artificial Plaque Containing Streptococcus oralis, After Exposure to Sucrose
Authors: Macpherson L.M.D. , Chen W.-Y. , Dawes C.
Published: November 2010

Chewing-gum stimulation of salivary flow (at the time of the pH minimum following exposure of plaque to carbohydrate) has been shown to cause a rapid increase in plaque pH. The objective of this study was to determine whether the rise in plaque pH is primarily due to the increased buffering capacity of stimulated saliva, or to the fact that an increased flow rate increases the concentration gradient for acid to diffuse from the plaque into the overlying salivary film, which will be moving at a higher velocity. This was investigated with an in vitro technique in which artificial plaque (0.5 or 1.5 mm deep) containing S. oralis cells was exposed to 10% sucrose for one min. The pH values at the proximal and distal undersurfaces of the plaque were then monitored during the passage of a 0.1-mm-thick film of a sucrose-free artificial saliva over the surface, at a range of film velocities (0.8-8 mm/min) that have been estimated to occur in vivo. When a minimum plaque pH had been achieved, the salivary film velocity was either (a) kept the same, with or without 15 mmol/L HC03 (the concentration measured in chewing-gum-stimulated saliva), (b) increased to 86.2 mm/min, or (c) increased to 86.2 mm/min with 15 mmol/L HC03 added to the artificial saliva. The findings suggest that after sucrose ingestion, the rapid rise from minimum plaque pH values, which can occur with gum-chewing stimulation of salivary flow, is due to the combined effects of the increase in salivary film velocity, and of a greater availability of bicarbonate. The former appeared to be more important in the thinner plaque (0.5 mm deep) than in the thicker one (1.5 mm deep).