bluuebunny/crossref_metadata_2025 huggingface dataset:
An Intra-oral Appliance Study of the Plaque Microflora Associated with Early Enamel Demineralization
Authors: Macpherson L.M.D. , MacFarlane T.W. , Stephen K.W.
Published: November 2010

An intra-oral appliance model was used to investigate the composition of the plaque microflora associated with early enamel demineralization. Enamel sections, with exposed windows, were mounted on lower removable appliances, and the devices were worn by volunteers for three-week periods under three experimental conditions. These were: (1) "normal" plaque conditions, (2) extra-oral sucrose applications nine times daily, and (3) inoculation of each volunteer's own mutans streptococci onto the test sites and sucrose applications as described for (2). After 21 days, the plaque overlying each window was removed, and the bacterial composition was determined. Changes in mineral content of the associated enamel were measured by microradiography and microdensitometry, and the total mineral loss (Az) that had occurred at each site was calculated. The 144 sites studied were divided into four demineralization groups by Az value, with an increase in mineral loss from group 1 to group 4.

A progressive and significant increase in the isolation frequency of mutans streptococci occurred from Az group 1 to group 4 sites. These organisms were isolated from the plaque of every location with enamel mineral loss of over 1000 Az units, but were not detected in 27% of the group 3 sites. Lactobacilli comprised 2% to 3% of the total cultivable microflora in groups 1-3 sites, but were found in significantly higher proportions (18%) at those enamel sites experiencing the most extensive mineral loss (group 4). No significant relationship was found between demineralization and the levels of Actinomyces species or Veillonella.

This model allows plaque bacterial composition to be related to the very early stages of enamel demineralization, and the results support the view that lactobacilli are associated with the more established lesions.
Primary Structure and Anticandidal Activity of the Major Histatin from Parotid Secretion of the Subhuman Primate, Macaca fascicularis
Authors: Xu T. , Telser E. , Troxler R.F. , Oppenheim F.G.
Published: November 2010

A major macaque histatin (M-histatin 1) from the parotid secretion of the subhuman primate, Macaca fascicularis, was isolated by gel filtration on Bio-Gel P-2 and purified to homogeneity by reversed-phase high-performance liquid chromatography on a TSK-ODS C18 column. The complete amino acid sequence of M-histatin 1, determined by automated Edman degradation, is: 1 10 20 Asp-Pse-His-Glu-Glu-Arg-His-His-Gly-Arg-His-Gly-His-His-Lys-Tyr-Gly-Arg-Lys-Phe 21 30 38 His-Glu-Lys-His-His-Ser-His-Arg-Gly-Tyr-Arg-Ser-Asn-Tyr-Leu-Tyr-Asp-Asn M-histatin 1 contains 38 amino acid residues, a phosphoserine at residue 2, has a molecular weight of 4881.8, a calculated pI of 8.5, and histidine forms 26.3% of the mass. The hydropathicity plot of M-histatin 1 predicts that the molecule is entirely hydrophilic, and Chou-Fasman secondary prediction indicates that the polypeptide is devoid of alpha-helix and beta-sheet conformation in aqueous solutions but contains a series of beta turns. M-histatin 1 includes a six-amino-acid insert (residue 10-15) not present in human histatins and, with the introduction of gaps to maximize homology, it displays 89% and 91% sequence similarity with human histatins 1 and 3, respectively. M-histatin 1 exhibited fungicidal and fungistatic effects against the dimorphic pathogen, Candida albicans, in three separate bioassays. Its anticandidal effects were comparable with or greater than those of human histatins 1, 3, and 5. M-histatins 2, 3, and 4 were not sequenced directly because insufficient materials were available, but the amino acid composition of M-histatin 3 was nearly identical to that of the N-terminal 20 amino acid residues of M-histatin 1. There appears to be only one major histatin in macaque parotid secretion in contrast to the family of histatins in human parotid and submandibular secretions, and the significance of this in the context of evolution and mechanism of action in anticandidal assays is discussed.
mRNAs for PRPs, Statherin, and Histatins in von Ebner's Gland Tissues
Authors: Azen E.A. , Hellekant G. , Sabatini L.M. , Warner T.F.
Published: November 2010

A search was made for expression of genes for proline-rich proteins (PRPs) and other salivary-type proteins, including statherin and histatins, in taste-bud tissues of mice and primates because of previous genetic findings in mice (Azen et al., 1986) that Prp and taste genes for certain bitter substances are either the same or closely linked. Taste-bud tissues and other tissues were tested for specific mRNAs with labeled DNA probes by Northern blotting and in situ hybridization. It was found that PRP mRNAs were present in von Ebner's glands of mice and macaques, and that there was a much greater degree of PRP mRNA induction in mouse parotid (16-fold) than in von Ebner's gland (two-fold) after in vivo isoproterenol stimulation. This difference may be due, in part, to differences in autonomic nerve innervation. Statherin and histatin mRNAs were found in macaque taste-bud tissues containing von Ebner's gland, and statherin protein was found in human von Ebner's gland by immunohistochemistry. The finding of PRP gene expression in von Ebner's gland, whose secretions have been suggested to play a role in taste stimulation, adds further support to a possible function of PRPs in bitter tasting. The possible functions of statherin and histatins in von Ebner's gland secretions may be related to statherin's regulation of salivary calcium and histatins' antibacterial and antifungal properties.
Phenotypic Changes of Rabbit Mandibular Condylar Cartilage Cells in Culture
Authors: Engel F.E. , Khare A.G. , Boyan B.D.
Published: November 2010

The present study describes the behavior of mandibular condylar cartilage (MCC) cells as a function of time in primary culture, since it is not yet clear whether these cells maintain their phenotype in culture. MCC cells from New Zealand white rabbits were seeded at high density and cultured in DMEM containing 50 μg/mL ascorbic acid and 10% fetal bovine serum. These cells appeared as a heterogeneous population and changed their shape, size, and refractivity as cultures aged. Cartilage-like cells, which always dominated the culture, were infiltrated with a minority of fibroblast-like cells. Cell number increased progressively, and cultures reached confluence at nine days. Antibody activity for cartilage-specific glycosaminoglycan was determined by ELISA assay. This reaction reached a maximum at six days and decreased thereafter. Cultures stained with Alcian blue (pH 1.0) supported these results. Cytoplasmic mRNA analysis indicated that the transcription of type II collagen gene was present at all time points. Type I collagen and alkaline phosphatase mRNA levels showed progressive increases from 12 h to nine days, with significantly higher values in cells cultured for six, nine, and 12 days than in cells collected from earlier time points. These results suggest that in our present culture system, MCC cells undergo phenotypic changes that resemble their maturation processes in vivo.
A New, Small-color-difference Equation for Dental Shades
Authors: O'Brien W.J. , Groh C.L. , Boenke K.M.
Published: November 2010

Traditionally, dental-shade-guide standards are designated in terms of Munsell hue (H), value (V), and chroma (C). However, ΔE color differences proposed as ADA tolerances for shade guides are in the CIE L*a*b* system. The purpose of this study was to evaluate a new color-difference equation, for estimation of small color differences by Munsell parameters. The published values of the Bioform shade-guide tooth colors determined with a Beckman spectrophotometer were used. Color differences among 276 combinations of the 24 Bioform shade-guide colors were calculated with Eq. 1, with use of the Munsell notation, and also with the CIE L*a*b* equation for ΔE. An estimate of the accuracy of Eq. 1 was 0.41 ΔE units when ΔE CIE was below 4.0. The Vita shade-guide colors were determined with a Beckman spectrophotometer. This data set contained 16 samples, and 120 combinations were used for calculation of color difference. An estimate of the accuracy for this set of data was 0.35 ΔE units when ΔE CIE was less than 4.0. The new color-difference equation provides a means for estimation of AE CIE L*a*b* color difference between dental shades with Munsell notation. This equation will be useful for estimation of small AE CIE L*a*b* values for shade-guide teeth that are designated in terms of Munsell notation.
A 24-month Clinical Study of the Incidence and Progression of Dental Caries in Relation to Consumption of Chewing Gum Containing Xylitol in School Preventive Programs
Authors: Kandelman D. , Gagnon G.
Published: November 2010

The effect of chewing gum containing xylitol on the incidence and progression of dental caries was tested in a sample of 274 children, aged eight and nine years, of low socio-economic status and high caries rate. They were divided into two experimental groups (15% and 65% xylitol chewing gum distributed three times a day at school) and one control group (without chewing gum). The three groups were exposed to the same basic preventive program.

Children who chewed gum had a significantly lower net progression of decay (progressions-reversals) over a 24-month period than did the controls. Results for the two groups chewing gum were similar. Chewing xylitol gum had a beneficial effect on the caries process for all types of tooth surfaces, and especially for bucco-lingual surfaces.

The two experimental groups had a DMF(S) increment of 2.24 surfaces, compared with 6.06 surfaces for the control group. For this indicator, there was no difference between the two experimental groups.

Results for the plaque index were in agreement with those of the DMF(S) increment and the net progression of decay.
Variation of Approximal Tooth Contact Tightness with Postural Change
Authors: Southard T.E. , Southard K.A. , Tolley E.A.
Published: November 2010

In order to investigate the role played by posture in determining posterior dental contact tightness, we measured contact tightness of maxillary and mandibular posterior teeth in ten adult subjects, while each was initially seated upright, after each had assumed a supine posture for two h, and finally after each had returned to an upright posture for two h. The technique used for measurement of contact tightness was based on frictional force concepts and consisted of the recording of the force required to withdraw a 0.038-mm-thick stainless-steel strip that had been slipped into each contact. A decreased mean tightness of all maxillary and mandibular contacts followed the change from an upright to a supine posture. The most significant decrease (-32%) occurred at the mandibular first molar-second premolar contact, and the smallest decrease (-10%) occurred at the mandibular first premolar-canine contact. An increased mean tightness of all maxillary and mandibular contacts followed a return to an upright posture. The most significant increase (20%) occurred at the maxillary first molar-second premolar contact, and the smallest increase (8%) occurred at the maxillary first premolar-canine contact. We conclude that posterior dental contact tightness, generally regarded by dentists as a static feature of occlusion, varies significantly as a function of posture.
Wavelength-independent Microradiography Used for Quantification of Mineral Changes in Thin Enamel and Dentin Samples with Natural Surfaces, Pseudo-thick Tooth Sections, and Whole Teeth
Authors: Herkstroter F.M. , Noordmans J. , Ten Bosch J.J.
Published: November 2010

Tests of the efficacy of therapeutic agents for caries repair or prevention in vitro or in situ should be performed as realistically as possible. This implies the non-destructive assessment of mineral changes in whole teeth. In this study, Wavelength-independent Microradiography (WIM), a non-destructive form of microradiography that uses polychromatic x-rays, was tested for its use in following mineral changes during demineralization of whole teeth. Since the method was, in a previous paper, only tested on flat samples of about 0.3 mm in thickness, the present study aimed to adapt and test WIM for use on thicker samples. This was done in three steps: In the first step, natural surfaces were introduced. The mineral content of enamel and dentin samples about 0.3 mm in thickness and with natural (curved) surfaces was determined by WIM, and the result was compared with mineral measurements performed with Longitudinal Microradiography (LMR). A correlation of 0.98 was found for both the enamel and the dentin samples. In the second step, the thickness of whole teeth was added. Thick tooth sections were simulated by addition of a 5-mm block of dentin to such thin enamel and dentin samples. Mineral measurements with WIM of the samples plus the dentin block were compared with mineral measurements of the thin samples (without block). A correlation of 0.97 was found for enamel, and one of 0.90 was found for dentin. Finally, in a third step, the demineralization of whole premolars was followed as a function of time.
Human Salivary Peroxidase and Bovine Lactoperoxidase are Cross-reactive
Authors: Mansson-Rahemtulla B. , Rahemtulla F. , Humphreys-Beher M.G.
Published: November 2010

Peroxidases are abundant in nature, and the primary function of mammalian peroxidases is to catalyze the peroxidation of halides and pseudohalides. Previous studies have shown that antibodies raised against bovine lactoperoxidase moderately cross-react with human salivary peroxidase, a feature that has been used in the present study to examine epitopes common to the antigen and human salivary peroxidase. Polyclonal antibodies against a highly purified preparation of bovine lactoperoxidase were raised in rabbits, and their properties were examined. In double-immunodiffusion experiments, the two enzymes showed partial identity, and in competitive radioimmunoassay and enzyme-linked immunosorbent assay, lactoperoxidase replaced the labeled and coated antigen, while salivary peroxidase did not. However, salivary peroxidase from human and rat saliva samples and the purified enzyme in its non-reduced, reduced, and de-glycosylated forms were recognized by these antibodies, as analyzed by Western blot analysis and immunodetection. The major activity of these antibodies was directed against the protein core of the antigen. Immunodetection of the peptide fragments of bovine lactoperoxidase and human salivary peroxidase revealed structural differences in the two enzymes. These antibodies also precipitated an in vitro translation product from rat-parotid-gland cell lysate that, on SDS-PAGE, compared favorably with the expected molecular weight of a de-glycosylated peroxidase. The antibodies partly inhibited the enzyme activity of salivary peroxidase and the peroxidase in rat parotid gland lysate, but the enzyme activity of lactoperoxidase was not affected by addition of anti-lactoperoxidase IgG between 25 and 400 wg/mL. The enzyme activity remained unchanged in all samples when pre-immune IgG was used.
Immunohistochemical Localization of the Matrix Glycoproteins-Tenascin and the ED-sequence-containing Form of Cellular Fibronectin—in Human Permanent Teeth and Periodontal Ligament
Authors: Lukinmaa P.-L. , Mackie E.J. , Thesleff I.
Published: November 2010

The expression of two matrix glycoproteins, tenascin and cellular fibronectin (cFN), has been studied in fully developed human permanent teeth, periodontal ligament, and alveolar bone, in both frozen and paraffin-processed material. Polyclonal antibodies to tenascin and a monoclonal antibody recognizing the ED sequence specific to at least some forms of cFN were used

Staining for both tenascin and cFN was positive in the dental pulp, odontoblastic layer, cementoblast-pre-cementum zone, and on the periosteal as well as endosteal surfaces of the alveolar bone. In the periodontal ligament, cFN was evenly distributed, whereas tenascin was accumulated in the attachment zones. Pre-dentin stained for tenascin but not for cFN. Mineralized dentin and cementum were tenascin- and cFN-nega- tive. The relative staining intensity for tenascin was greater than that for cFN in the cementoblast-pre-cementum layer and in the attachment zones of the periodontal ligament, whereas cFN stained more intensely in the pulp. In frozen material, antigenicities were well-preserved. Paraffin processing facilitated precise recognition of tissue morphology, but the antigenicity of cFN was lost

The co-expression of tenascin and cFN in the dental pulp, cementogenic zone, and on the surfaces of the alveolar bone may reflect the ability of the cells to deposit mineralized tissue matrices. The pronounced expression of tenascin in the interfaces between mineralized and non-mineralized tissues suggests that it is functionally associated with mechanical stress and may thus have at least two distinct functions. The relative amounts of the two matrix glycoproteins may contribute to regulation of tissue structure.
Enhancing the Virulence of Streptococcus sobrinus in Rats
Authors: Madison K.M. , Bowen W.H. , Pearson S.K. , Falany J.L.
Published: November 2010

The purpose of this study was to explore the virulence of strains of Streptococcus sobrinus that had been re-isolated from a desalivated rat. Furthermore, we wished to determine the influence of desalivation on the acidogenicity of fasting and sucrose-pulsed dental plaque in rats infected by strains of S. sobrinus. Experimental groups were formed and infected as follows: Group 1, desalivated animals, S. sobrinus ATCC 27352; Group 2, intact animals, infected as in Group 1; Group 3, desalivated animals, S. sobrinus re-isolated from a desalivated animal that had been infected with the ATCC 27352 strain for five weeks; Group 4, intact animals, infected as in Group 3; Group 5, desalivated animals, S. sobrinus re-isolated from a desalivated animal that had been infected with the ATCC 27352 strain for ten weeks; Group 6, intact animals, infected as in Group 5; Group 7, intact animals, no infection. All animals were fed cariogenic diet 2000 and sucrose-sweetened drinking water ad libitum. After five weeks, desalivated and intact animals that had been infected with isolates obtained from desalivated animals had significantly higher (p<0.05) smooth-surface-caries scores than did intact and desalivated animals infected with cultures of the original stock ATCC strain. Moreover, fasting plaque pH values were statistically lower in desalivated animals (Groups 1 and 3) than in intact animals (Groups 2, 6, and 7) (Tukey analysis, p<0.05). These data support the hypothesis that the pH values of plaque in desalivated animals are highly acidic and that lack of saliva may influence cariogenicity in at least two ways: the loss of inherent protective effects of saliva and the selection of cariogenic micro-organisms that exhibit enhanced virulence.
Tandem-scanning Microscopy of Slow-speed Enamel Cutting Interactions
Authors: Watson T.F.
Published: November 2010

The aim of this study was to observe the subsurface microstructure of dental enamel during cutting procedures. Real-time confocal scanning optical microscopy, with a tandem-scanning reflected-light microscope, is suitable for making high-resolution images of enamel prisms in intact teeth under near-normal conditions. Blocks of enamel were held on a micropositioning stage and advanced toward the tip of a diamond knife. The orientation of the samples was varied to simulate common clinical cutting conditions. Oil immersion objectives were used with the knife rigidly mounted in a specially made carrier. This was attached to the objective below its end-lens. The images were recorded with a sensitive video camera and cassette recorder for analysis of the cutting interactions at a slow playback speed. The presence of decussating enamel prisms was particularly effective at slowing crack propagation when loading was applied in an appropriate direction. Residual subsurface cracking was seen when the blade had finished cutting. This was most pronounced in regions where the enamel prisms were cut transverse to their long axis; this was equivalent to the preparation of the cervical margin of an approximal cavity. Where there is surface adhesion to enamel (e.g., glass-ionomer cements), residual subsurface cracking will produce a weakened substrate for bonding that could have important implications for restoration longevity.
In vitro Fluoride Release from a Light-cured Glass-ionomer Liner/Base
Authors: Mitra S.B.
Published: November 2010

This paper reports the results of an in vitro study of fluoride release from Vitrabond™ Light-Cure Glass Ionomer Liner/Base. The material released fluoride ions into the surrounding medium for up to 740 days. The rate of release of fluoride ions was independent of the cure time in the range studied. Combining a conventional polyalkenoic acid solution with the powder portion of Vitrabond Liner/Base did not significantly alter the release profile, thus indicating that light curing did not hinder the rate of fluoride release in this system. Secondary ion mass spectrometry studies of the dentin underlying the cured glass ionomer revealed that there was considerable incorporation of fluoride ions. There was no significant change in the mechanical properties of the cured cement aged in water at 37°C for prolonged periods, thus indicating that long-term fluoride release did not adversely affect the strength of this material.
Analysis of Neutrophil Chemotaxis and CD11b Expression in Pre-pubertal Periodontitis
Authors: Watanabe K. , Lambert L.A. , Niederman L.G. , Punwani I. , Andersen B.R.
Published: November 2010

The objectives of this study were to (1) determine chemotaxis (CX) response by neutrophils (PMNs) isolated from patients with the localized form of pre-pubertal periodontitis (L-PP) and compare these responses with those of age-matched and adult controls, (2) determine the level and up-regulation of CDllb expression upon stimulation with fMLP by peripheral blood PMNs (PB-PMNs) isolated from patients with L-PP and compare these levels with those of age-matched and adult controls, and (3) determine whether there is a correlation between CX and CDllb expression (up-regulation) by PB-PMNs. PB-PMNs from a total of seven patients with L-PP, seven age-matched pediatric controls, and 11 adult controls (four adults for both CDllb and CX assays, and seven adults for CX assays only) were analyzed for CX and CDllb expression. Direct immunofluorescence staining of CDllb was performed with FITC-conjugated monoclonal antibody. Flow cytometry was used to analyze stained cells for their fluorescence intensity. Chemotaxis activity in response to 10-8 mol/L fMLP was examined in micro-well chemotaxis chambers. The results indicated that CX of PMNs from both L-PP patients and pediatric control subjects was significantly decreased, compared with that of normal adult control subjects (p<0.001). There was no significant difference between CX of PMNs from L-PP patients and that from normal pediatric controls (p>0.7). CDllb expression did not significantly differ among L-PP patients, normal pediatric controls, and adult controls. Analysis of the data indicates that there was no statistically significant correlation between CX and CDllb expression by PMNs isolated from L-PP and pediatric control subjects.
Enhanced Replication of Herpes Simplex Virus Type 1 in Human Cells
Authors: Miller C.S. , Smith K.O.
Published: November 2010

The effects of DNA-damaging agents on the replication of herpes simplex virus type 1 (HSV-1) were assessed in vitro. Monolayers of human lung fibroblast cell lines were exposed to DNA-damaging agents (methyl methanesulfonate [MMS], methyl methanethiosulfonate [MMTS], ultraviolet light [UV], or gamma radiation [GR]) at specific intervals, before or after inoculation with low levels of HSV-1. The ability of cell monolayers to support HSV-1 replication was measured by direct plaque assay and was compared with that of untreated control samples. In this system, monolayers of different cell lines infected with identical HSV-1 strains demonstrated dissimilar levels of recovery of the infectious virus. Exposure of DNA-repair-competent cell cultures to DNA-damaging agents produced time-dependent enhanced virus replication. Treatment with agent before virus inoculation significantly (p < 0.025) increased the number of plaques by 10 to 68%, compared with untreated control cultures, while treatment with agent after virus adsorption significantly increased (p<0.025) the number of plaques by 7 to 15%. In a parallel series of experiments, cells deficient in DNA repair (xeroderma pigmentosum) failed to support enhanced virus replication. These results suggest that after exposure to DNA-damaging agents, fibroblasts competent in DNA repair amplify the replication of HSV-1, and that DNA-repair mechanisms that act on a variety of chromosomal lesions may be involved in the repair and biological activation of HSV-1 eenomes.
Application of the MTT Colorimetric Assay to Measure Cytotoxic Effects of Phenolic Compounds on Established Rat Dental Pulp Cells
Authors: Kasugai S. , Hasegawa N. , Ogura H.
Published: November 2010

The cytotoxicities of various phenolic compounds were examined using the 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) colorimetric assay and established rat dental pulp cells (RPC-C2A). The ID50 (50% inhibition concentration) of the phenolic compounds ranged from 0.1 to 10 mmol/L, and the cytotoxicities of the phenolic compounds were related to their phenolic coefficients. The therapeutic index of each phenolic compound was calculated from the ID 50 results and from the 50% inhibition concentration for prostaglandin synthesis that has been reported previously. Eugenol, guaiacol, and creosol had therapeutic indices much higher than those of other phenolic compounds examined. This experimental system could be used as a simple preliminary assay to test for toxicity of dental drugs and materials.
Photo-activation of Resin Cements through Porcelain Veneers
Authors: Linden J.J. , Swift E.J. , Boyer D.B. , Davis B.K.
Published: November 2010

The purpose of this study was to determine the effects of porcelain opacity, chemical catalyst, and exposure time on polymerization of light-activated resin-composite cements. Samples of microfill and hybrid composites, with and without catalyst (i.e., dual-cure and visible-light-activated), were polymerized by exposure to visible light through porcelain discs of different opacities. Microhardness testing (KHN) was used to compare degree of cure for each material at various exposure times. Porcelain opacity did not significantly affect hardness. However, the results indicated that a chemical catalyst and prolonged curing times might be essential for clinical success.
Immunocytochemical Evidence for the Presence of Somatostatin-like Immunoreactive Nerves in Human Dental Pulp
Authors: Casasco A. , Calligaro A. , Casasco M. , Springall D.R. , Polak J.M. , Marchetti C.
Published: November 2010

Specific antiserum to somatostatin was used for the immunocytochemical detection of this neuropeptide in human dental pulp. Immunoreactive axon varicosities were observed in the radicular as well as coronal pulp. Fibers displaying somatostatin-like immunoreactivity were detectable within radicular nerve trunks and were found to be associated mainly with blood vessels. Nevertheless, positive fibers with no apparent relation to blood vessels were also observed. No pulp cell was found to be immunoreactive. Previous physiological studies demonstrated that somatostatin may function as a regulatory peptide in feline dental pulp via a pre-synaptic inhibition of substance P release from sensory nerve terminals. It is tempting to speculate that such a mechanism may also be effective in human teeth and may be of value in the regulation of pulpal blood flow and in situations when sensory nerve fibers are activated, e.g., during pulpal inflammation.
Therapeutic Mineral Enrichment of Dental Plaque Visualized by Transmission Electron Microscopy
Authors: Pearce E.I.F. , Wakefield J.ST.J. , Sissons C.H.
Published: November 2010

The form, location, and distribution of fluorhydroxyapatite deposited in dental plaque by a urease-mediated mineral enrichment process have been studied by transmission electron microscopy. Artificial plaque was formed in terylene gauze in the mouth of one subject and immersed for five min four times per day in a mineral-enriching solution. Contralateral control plaque remained untreated. The effect on natural plaque was studied in two subjects who withheld oral hygiene for four days and mouthrinsed with this solution for two min four times per day during the last two days. Mineral deposits were seen in all plaque samples exposed to the test solution. None was detected in any control sample. The deposits were scattered in the interbacterial matrix as needle-shaped crystals, the size and shape of apatite, together with amorphous material. The crystals appeared larger and more perfect, and the amorphous material less conspicuous, with longer in vivo rinsing periods. Platelet-shaped crystals of octacalcium phosphate were never seen. Mineral was also seen within the remnants of dead bacterial cells and within degenerating epithelial cells. Crystals were never seen within intact bacterial cells, as in calculus formation. The presence of a single crystal type and the relative absence of densely-mineralized foci are other differences between this mineral-enrichment process and supra-gingival calculus formation. A longer-term study is necessary to determine whether the solution promotes calculus by providing nucleation seeds.
Biosynthesis and Secretion of Rat Salivary Proteins by Xenopus laevis Oocytes
Authors: Apekin V. , Goldberger G. , Oppenheim F.G. , Paz M.A.
Published: November 2010

Xenopus laevis oocytes injected with poly (A+) RNA isolated from rat parotid and submandibular glands synthesize and secrete salivary proteins. Amylase was identified in the media of cultured oocytes injected with rat parotid mRNA by size and immunoprecipitation with anti-human amylase serum. Secretion of the salivary proteins was detectable in the medium eight h following the parotid mRNA injection and continued in a time-dependent fashion for up to 96 h.

In contrast to rat parotid slices in culture, which demonstrate a regulated pathway of secretion highly responsive to the secretagogue isoproterenol, secretion of salivary proteins by oocytes did not respond to the stimulation by isoproterenol. Though parotid mRNA is presumed to contain the templates encoding the regulated pathway of secretion, reconstitution of this pathway of secretion in oocytes was not observed in our experiments.

Since Xenopus laevis oocytes secrete constitutively significant amounts of proteins when injected with salivary gland mRNA, they are a useful biological system for the analysis of secretion, processing, and function of salivary proteins.
Alkaline Phosphatase Induces the Deposition of Calcified Layers in Relation to Dentin: An in vitro Study to Mimic the Formation of Afibrillar Acellular Cementum
Authors: Beertsen W. , Van Den Bos T.
Published: November 2010

An attempt was made to test the hypothesis that alkaline phosphatase, an enzyme which is abundant in periodontal ligament, plays a role in the formation of acellular root cementum. Thin slices of bovine dentin were incubated in Iscove Modified Dulbecco's Medium supplemented with 10% normal rabbit serum and 10 mmol/L (3-glycerophosphate (P-GP) or folded into pericardial explants. Intestinal bovine alkaline phosphatase (APase), covalently linked to agarose beads, was added to the cultures. In the presence of the enzyme, the dentin slices were covered with thin layers of mineralized material. Such layers were not observed in cultures not provided with APase-beads or β-GP. They also did not form in relation to demineralized dentin. The layers of calcified material appeared to consist of crystallites embedded in a granular matrix of moderate electron density, which often exhibited the presence of incremental lines and resembled the matrix of afibrillar acellular cementum formed under in vivo conditions. When pericardial explants were interposed between the enzyme-containing beads and the dentin, mineral deposition in relation to the dentin was retarded. This finding lends support to the view that soft connective tissues interfere with the free diffusion of phosphate.
Tensile Fatigue Limits of Prosthodontic Adhesives
Authors: Aquilino S.A. , Diaz-Arnold A.M. , Piotrowskp T.J.
Published: November 2010

Tensile fatigue limits and ultimate tensile strengths of some prosthodontic adhesive systems were determined. Ni-Cr-Be cylinders were: electro-etched, chemically etched, and sandblasted prior to being bonded end-to-end with BIS-GMA and 4-META adhesives. Bonded specimens were stored in distilled de-ionized water for three days prior to being tested. Fifteen paired specimens per group were subjected to a cyclic tensile load for 1000 cycles. Tensile fatigue limits were determined by the staircase method. Five specimens per group were tested for ultimate tensile strength. In addition, those specimens which survived the 1000 cycles during fatigue testing were also tested for ultimate tensile strength. Statistical evaluations to compare tensile fatigue limits and ultimate tensile strengths for fatigued and non-fatigued specimens were then performed.

The results indicated that the tensile fatigue limit and the ratio of fatigue limit to ultimate tensile strength of the sandblasted, 4-META adhesive system were significantly lower than those of the other systems tested. The application of a cyclic load significantly decreased the ultimate tensile bond strength of the 4-META adhesive. Application of a cyclic load had no significant effect on the ultimate tensile bond strengths of the BIS-GMA systems tested.
Draft Results of a Workshop to Develop Guidelines for Studies Involving Microbial Incidence or Populations in the Oral Cavity
Authors: Krichevsky M.I.
Published: November 2010

The following five outlines are the results to date of the Workshop held in Rockville, Maryland, in January, 1990. The topics considered in these outlines are: (1) validation of immunological and/or nucleic acid identification probes, (2) cross-calibration of methods and/or laboratories for multi-laboratory cooperative studies, (3) choosing methods for identifying or describing microbial populations appropriate to the scientific question asked, (4) microbial ecology methods (e.g., population dynamics) for the oral cavity studies, and (5) epidemiological methods (e.g., incidence, risk factor analysis) for oral microbial studies.

Each topic was considered by two independent groups of participants and later rationalized into one. These outlines are meant to be working outlines for evolution of a set of guidelines to advise on designing studies with microbial incidence and/or population components. We are publishing this preliminary version to elicit comment and criticism from people who did not attend the Workshop. (Attendance at the Workshop was necessarily limited by both space and funds.) Some of the topic outlines have been condensed to save Journal space. The full document is available on request.

The next stage will be an open forum to gather and discuss further amplification of the "Guidelines", planned for April 17, 1991, Acapulco, Mexico, in conjunction with the IADR/ AADR Meeting.

Written comments and requests for further information should be sent to the Workshop organizer (MIK) at the above address. Within each topic, the editing was done in two phases. The basic outlines were prepared by the "break-out" groups during the Workshop. The second stage was to annotate the outlines with the organizer's editorial comments and suggestions. The annotations are set off by brackets. In the main, these consist of requests for amplification and clarification. In a few cases, there may well need to be a fresh look at some of the concepts presented. Three come to mind immediately: (1) the use of diversity measures, (2) "gold standards", and (3) the use of community structure analysis as presented herein. Others may occur to the reader.

You are invited to make any and all comments on the material presented in these outlines. Please let your comments range from syntax and format through detailed and broad observations on content and omission. Especially welcome will be your comments on the annotated remarks and any annotations you feel should be added. For example, should reprints be attached to the guidelines, or should the contents of relevant papers be synthesized (or some combination thereof)?
Quantitative Immunohistochemical Analysis of Keratins and Desmoplakins in Human Gingiva and Peri-implant Mucosa
Authors: Carmichael R.P. , McCulloch C.A.G. , Zarb G.A.
Published: November 2010

Quantitative immunohistochemistry was used to compare the distributions of keratins and desmoplakins in human gingiva and peri-implant mucosa (three specimens each). In gingiva, keratin 1 (a marker of cornification) and desmoplakins I & II (markers of desmosomes) stained most heavily in granular strata followed by corneal strata; keratin 13, a marker of non-cornifying stratified squamous cells, stained most heavily in suprabasal strata of oral sulcular epithelium. Keratin 19, a marker for junctional epithelium, stained the basal stratum of oral sulcular epithelium most heavily. In peri-implant mucosa, the patterns of staining were similar, except that staining for desmoplakins I & II was generally significantly reduced compared with gingiva, and junctional epithelium co-expressed keratins 13 and 19. Peri-implant junctional epithelial cells attached to titanium implant abutments were removed by trypsin/EDTA digestion, and also exhibited co-expression of keratins 13 and 19. Inflammatory cell infiltration was associated with reduction of keratin 1 staining in gingiva. The data indicate that the epithelia of gingiva and peri-implant mucosa are not composed of identical cell populations.
Carbonate Content in Developing Human and Bovine Enamel
Authors: Sydney-Zax M. , Mayer I. , Deutsch D.
Published: November 2010

The present study describes the detailed changes in carbonate distribution throughout the different stages of development in human and bovine enamel, from early formation to maturation. Twenty-two human maxillary and mandibular deciduous anterior teeth and 46 bovine teeth were studied. The major mineral ions, calcium and phosphorus, were also analyzed to facilitate comparison of carbonate content with progressing mineralization. The results showed that as enamel matured and mineral concentration increased, carbonate concentration decreased. The observed decrease in percent carbonate per weight enamel mineral may be due to dilution by an influx of relatively carbonate-free mineral, and could, in part, explain the observed increase in crystallinity of enamel mineral as the tissue matures.
Effect of Thermal Tempering on Strength and Crack Propagation Behavior of Feldspathic Porcelains
Authors: Anusavice K.J. , Hojjatie B.
Published: November 2010

The objective of this study was to test the hypothesis that tempering stress can retard the growth of surface cracks in layered porcelain discs with variable levels of contraction mismatch. Porcelain discs, 16 mm in diameter and 2 mm thick, were prepared with a 0.5-mm-thick layer of opaque porcelain (0) and a 1.5-mm-thick layer of body porcelain (B). The materials were selected to produce contraction coefficient differences, ao-aB, of +3.2, +0.7, -0.9, and -1.5 ppm/°C. Body porcelain discs with a thickness of 2 mm were used as the thermally compatible control specimens (Δα=0). The discs were fired to the maturing temperature of body porcelain (982°C) and were then subjected to three cooling procedures: slow cooling (SC) in a furnace, fast cooling (FC) in air, and tempering (T) by blasting the surface of the body porcelain with compressed and dried air for 90 s. The dimensions of cracks induced by a Vickers microhardness indenter under a load of 4.9 N were measured at baseline and six months after indentation at 80 points along diametral lines within the surface of body porcelain. In addition, biaxial flexure tests were performed to determine the influence of mismatch and tempering on flexure strength. The results of ANOVA indicate that crack dimensions were influenced significantly by the interaction of cooling rate and contraction mismatch (p<0.0001). Multiple contrast analysis by the Tukey's HSD Test indicated that the crack lengths of tempered specimens at baseline and six months were significantly smaller (p<0.05) than the corresponding values for the FC and SC specimens. For tempered specimens with contraction differences of + 3.2, 0, and -1.5 ppm/°C, the mean crack lengths during the six-month period increased by 10.8%, 8.3%, and 9.7%, respectively, compared with increases of 13.8%, 20.1%, and 15.9%, respectively, for the SC specimens. Tempering treatment of the compatible discs (Δα=0) resulted in the highest mean flexure-strength value of 116.2 MPa. This value was 2.6 times greater than the corresponding value for the slow-cooled specimens. These results indicate that tempering by forced convective cooling in air significantly strengthened bilayered discs and reduced the initial size of induced surface cracks. However, tempering stress was less effective in reducing the propagation rate of induced cracks.
The Release of Elements of Dental Casting Alloys into Cell-culture Medium
Authors: Wataha J.C. , Craig R.G. , Hanks C.T.
Published: November 2010

Ten dental casting alloys were tested for alloy-element release into cell-culture medium, and this release was related to alloy composition, alloy microstructure, and alloy cytotoxicity (previously determined). Cell-culture medium was analyzed for alloy elements by flame atomic absorption. Concentrations of elements in the medium were normalized by dividing them by their atomic abundance in the alloy, giving element medium-alloy ratios (EMA ratios). Results showed that Au, In, and Pd generally did not dissolve into the medium, but that Ag, Cd, Cu, Ga, Ni, and Zn frequently dissolved. Comparison of EMA ratios for Ag, Cu, and Zn showed that each element retained a behavioral identity in diverse metallurgical environments, but that these environments influenced the release behavior to some degree. Some EMA ratios in multiphase alloys were greater than those in solid solutions, and EMA ratios showed great diversity within all the alloys. Nominal composition seemed to be of little value in the prediction of metal release unless the composition supported multiple-phase formation. In addition, release of alloy elements did not, in itself, completely predict alloy cytotoxicity measured previously. However, cytotoxicity was associated with metal release in each case. The commercial alloys used in this study exhibited more complex and less predictable release behavior than did the simpler ternary alloy systems used by previous investigators. It is believed that the use of commercial preparations is necessary for their in vivo behavior to be modeled.
Risk Factors in Dental Erosion
Authors: Jarvinen V.K. , Rytomaa I.I. , Heinonen O.P.
Published: November 2010

Dental erosion and factors affecting the risk of its occurrence were investigated with a case-control approach. One hundred and six cases with erosion and 100 randomly selected controls from the same source population were involved in the study. All cases and controls were evaluated by the recording of structured medical and dietary histories and by examination of the teeth and saliva. Erosion was classified according to pre-determined criteria. The relative importance of associations between factors and erosion was analyzed by a logistic multivariable model. Adjusted odds ratios (AOR) were estimated. There was considerable risk of erosion when citrus fruits were eaten more than twice a day (AOR 37), soft drinks were drunk daily (AOR 4), apple vinegar was ingested weekly (AOR 10), or sport drinks were drunk weekly (AOR 4). The risk of erosion was also high in individuals who vomited (AOR 31) or exhibited gastric symptoms (AOR 10), and in those with a low unstimulated salivary flow rate (AOR 5).
A Histomorphometric Analysis of the Effects of Fluoride on Experimental Ectopic Bone Formation in the Rat
Authors: Mohr H. , Kragstrup J.
Published: November 2010

Ectopic bone formation was induced in 14 rats receiving 100 ppm fluoride in drinking water and in 14 control animals. Sections from ossicles removed after 14 and 20 days were sampled for stereological analysis. Bone volume density and bone volume were reduced in experimental animals on day 14 (p < 0.05). This difference was no longer present after 20 days. On day 20, surface density and areas of formative surfaces were increased in the fluoride group (p<0.05). Osteoid seam thickness was higher in the fluoride group on both days (p<0.01). In conclusion, fluoride induced quantitative alterations in ectopic bone formation, and the presented model may prove a useful addendum to previous methods for investigation of fluoride effects on mineralization processes in vivo.
Influence of Fluoride and Carbonate on in vitro Remineralization of Bovine Enamel
Authors: Lammers P.C. , Borggreven J.M.P.M. , Driessens F.C.M. , Van Dijk J.W.E.
Published: November 2010

The influence of fluoride, carbonate, and fluoride in combination with carbonate on the in vitro remineralization of bovine enamel was investigated with the use of a sandwich technique. After demineralization, enamel slices were subjected for 610 h to remineralizing solutions with 0.03 or 1.0 ppm fluoride. At each fluoride level, either 0, 1, 10, 20, or 25 mmol/L carbonate was tested. After 0, 22, 62, 126, 192, 329, and 610 h of remineralization, contact microradiographs were made by Cu Kα-radiation. At 0.03 ppm fluoride, carbonate had an inhibiting influence on remineralization. At 1.0 ppm fluoride, the inhibiting influence of carbonate changed into a stimulation of remineralization at 20 and 25 mmol/L carbonate. At 0, 1, and 10 mmol/L carbonate, fluoride had an inhibiting influence on remineralization. The differences in remineralization between the groups were explained by events concerning crystal growth, i. e., different types of minerals might have precipitated with differences in precipitation rates, and retardation of a precipitation step might have occurred under the various remineralization conditions. There was a mutual influence of fluoride and carbonate on the remineralization process. We conclude that the composition of the remineralizing solution with respect to fluoride and carbonate concentrations is important for the remineralization process.