bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Calcium in Model Plaque on the Anticaries Activity of Fluoride in vitro
Authors: Blake-Haskins J.C. , Mellberg J.R. , Snyder C.
Published: November 2010

The uptake of calcium by a polysaccharide (agarose) gel used as a model for plaque from a two-step treatment (consisting of a calcium rinse followed by a fluoride treatment) and the effect ofthe deposited calcium in model plaque on caries lesion formation in enamel were determined. Calcium uptake was measured by treatment of the model plaques with [45Ca]-CaCl2 solutions with or without NaF. A two-step treatment consisting of calcium followed by fluoride produced a 100% increase in calcium content of model plaque, presumably due to the formation of CaF2, compared with a treatment with artificial saliva followed by calcium alone. The effects of these increased plaque minerals on caries lesion formation were studied by subjecting model-plaque-covered enamel blocks to a cyclic demineralization-remineralization treatment. Artificial-plaque-covered enamel blocks were treated daily with 180 ppm calcium for ten min, then 100 ppm fluoride for ten min, followed by demineralization for 16 h, and finally, remineralization for seven h and 40 min. After five days, the blocks were sectioned, and lesion formation was determined by microradiography-microdensitometry. Artificial plaque treated with a calcium rinse followed by a fluoride rinse reduced lesion size by 90%, compared with a 68% reduction by a fluoride rinse alone. When the experiment was repeated with a simulated pre-brush calcium rinse (180 ppm calcium) followed by a fluoride dentifrice suspension (110 ppm fluoride), lesion size was reduced by 46%, compared with a 32% reduction by the fluoride dentifrice suspension alone.
Studies of Fluoride Retention by Oral Soft Tissues after the Application of Home-use Topical Fluorides
Authors: Zero D.T. , Raubertas R.F. , Pedersen A.M. , Fu J. , Hayes A.L. , Featherstone J.D.B.
Published: November 2010

Previous studies have focused on enamel and plaque as the primary sites of fluoride (F) retention in the mouth. The present study was undertaken to evaluate the role of oral soft tissue as a site of F retention by comparing an edentulous subject panel (n = 9) with a fully dentate panel (n = 10). Unstimulated whole saliva samples were collected by having subjects pool saliva for two min. Samples were collected over a 24-hour period after application of a placebo dentifrice (PD; 0.4 ppm F), fluoride dentifrice (FD; 1100 ppm F), fluoride rinse (FR; 226 ppm F), or fluoride gel (FG; 5000 ppm F) delivered in custom trays. There was no statistically significant difference in salivary flow rate between the two panels for any of the treatments. The edentulous panel had higher salivary F levels than the dentate panel, which reached statistical significance (p < 0.05) for the FD and FG treatments. In a separate study involving the same treatments, F levels at specific soft-tissue sites were measured over a one-hour period by use of absorbent discs placed in different soft-tissue areas of the mouth. The tongue and lower posterior vestibule retained the highest F levels, followed by the upper posterior buccal vestibule and upper anterior labial vestibule, with the lowest F levels retained in the lower anterior vestibule and the floor of the mouth. There was a strong-to-moderate correlation between whole saliva F concentration and F levels at specific soft-tissue sites. This study establishes the importance of oral soft tissue as the major site of F retention in the mouth.
Distribution of Fluoride in Saliva and Plaque Fluid after a 0.048 mol/L NaF Rinse
Authors: Vogel G.L. , Carey C.M. , Ekstrand J.
Published: November 2010

An ultramicro method has recently been described for measurement of plaque-fluid fluoride concentration (Vogel et al., 1990a). This method was used: (1) for exploration of the variation in fluoride concentration of plaque fluid collected from the same buccal tooth sites following a 0.048 mol/L NaF (0.2%) rinse, and (2) for examination of the distribution of fluoride in plaque fluid and saliva within one hour after this rinse. Results indicated an average coefficient of variation (CV) of 31% for plaque-fluid fluoride in triplicate samples recovered simultaneously from the buccal-proximal region of two teeth after the rinse. This was similar to the CV found for plaque-fluid fluoride from the same sites after separate administrations of the rinse. A strong linear correlation was found between salivary and plaque-fluid fluoride at 30 and 60 min after rinse administration, showing that plaque-fluid fluoride is influenced by the concentration of salivary fluoride after administration of this rinse. Plaque-fluid fluoride concentrations were higher than that in saliva at baseline, 30, and 60 min. Very large inter-site and inter-subject variations in plaque-fluid distribution were observed, with the central incisors showingthe slowest clearance. These variations suggest that an examination of plaque-fluid fluoride from specific tooth regions may be essential for understanding the effects of fluoride on the site-specificity of caries.
Identification and Analysis of the Gap Region in the 23S Ribosomal RNA from Actinobacillus actinomycetemcomitans
Authors: Haraszthy V.I. , Sunday G.J. , Bobek L.A. , Motley T.S. , Preus H. , Zambon J.J.
Published: November 2010

Actinobacillus actinomycetemcomitans is a Gram-negative coccobacillus which can cause certain severe extra-oral infections as well as forms of human periodontal disease such as localized juvenile periodontitis. In contrast to many prokaryotic and eukaryotic species which exhibit an intact 23S ribosomal RNA (rRNA) molecule, examination of six A. actinomycetemcomitans strains-including three serogroup representative strains and two strains from non-human primates-revealed that this micro-organism does not produce an intact 23S ribosomal RNA (rRNA) molecule but, rather, two smaller forms of 1.8 kb and 1.2 kb designated as 23Sa and 23Sβ fragments. On the other hand, 14 other strains of Actinobacillus, Haemophilus, and Pasteurella species demonstrated intact 23S rRNA. The sequence of the region of the 23S rRNA gene in A. actinomycetemcomitans strain ATCC 43718 containing the cleavage site was determined by dideoxynucleotide sequencing, while the location of the 3' and 5' termini of the 23Sa and 23Sβ fragments was resolved by S1 nuclease mapping and cDNA primer-extension. A deletion of 112 bases was noted in comparisons of base sequences from A. actinomycetemcomitans rRNA and rDNA. The DNA intervening sequence was localized to nucleotide 1180 of the Escherichia coli 23S rRNA map. While the primary structure of the gap region showed little homology with the gap regions described in other organisms, the secondary structure was similar to that previously described in the parasitic helminth Schistosoma japonicum. Restriction enzyme and nucleotide sequence analysis of the gap region in eight other A. actinomycetemcomitans strains showed it to be highly conserved.
Adsorption of Human Salivary Proteins to Hydroxyapatite: A Comparison Between Whole Saliva and Glandular Salivary Secretions
Authors: Jensen J.L. , Lamkin M.S. , Oppenheim F.G.
Published: November 2010

The protein compositions of in vitro pellicles formed from whole saliva and parotid and submandibular secretions were determined by use of synthetic hydroxyapatite as a model for dental enamel. The adsorbed and unadsorbed protein fractions were analyzed by amino acid analysis and both anionic and cationic discontinuous polyacrylamide gel electrophoresis. For further characterization of the in vitro pellicle, the adsorbed fractions were subjected to gel filtration on Sephadex G-100 and reversed-phase chromatography on C18 columns.

Amylase, acidic and glycosylated proline-rich proteins, statherins, and histatins were identified in the parotid-derived pellicle. Detailed analysis of the statherin-containing fractions resulted in the observation of several statherin-like proteins. The use of cationic gel electrophoresis allowed for the identification of histatin 3 and histatin 5, which have not been previously detected in pellicle formed in vitro. The protein composition of submandibular-derived pellicle was similar to that of parotid-derived pellicle except for the presence of cystatins and the absence of glycosylated proline-rich proteins. In contrast, in vitro pellicle derived from whole saliva exhibited a vastly different composition, consisting primarily of amylase, acidic proline-rich proteins, cystatins, and proteolytically-derived peptides. The results indicate that acidic phosphoproteins as well as neutral and basic histatins from pure secretions selectively adsorb to hydroxyapatite, whereas in whole saliva some of these proteins are proteolytically degraded, dramatically changing its adsorption pattern.
Distribution of Chondroitin Sulfate and Dermatan Sulfate in Normal and Inflamed Human Gingivae
Authors: Bartold P.M.
Published: November 2010

The effect of inflammation on the distribution of chondroitin sulfate and dermatan sulfate proteoglycans was assessed after normal and inflamed human gingivae were stained with monoclonal antibodies against these extracellular matrix macromolecules. The tissues were obtained following periodontal surgery and reacted with specific antibodies after pre-treatment with chondroitinase ACII or chondroitinase ABC, and staining was visualized by the immunoperoxidase technique. The results indicated that these two proteoglycans were present in both the 4-sulfated and 6-sulfated isomeric forms. While chondroitin sulfate appeared to be uniformly distributed throughout the connective tissue, dermatan sulfate showed greater intensity of staining in the areas immediately subjacent to the epithelium. Positive staining for chondroitin sulfate was noted in the intercellular spaces of the epithelium. In inflamed tissues, there was significant staining associated with 4-sulfated dermatan sulfate and chondroitin sulfate, but this had lost the structured pattern of staining noted in normal sections. The 6-sulfated isomeric forms were greatly reduced in inflamed tissues and tended to show a predilection to be localized within the perivascular tissues. In the inflamed tissues, there was intense staining for chondroitin sulfate associated with the infiltrating inflammatory cells. These findings corroborate earlier biochemical studies on normal and inflamed gingival tissues. The specific tissue localization of dermatan sulfate and chondroitin sulfate in tissues damaged by inflammation indicates that, as opposed to the large loss of collagenous material noted during inflammation, there is not a corresponding large loss of proteoglycan. Indeed, at specific inflammatory foci, the intensity of staining for these macromolecules may intensify.
Interactions of Delmopinol with Constituents of Experimental Pellicle
Authors: Steinberg D. , Beeman D. , Bowen W.H.
Published: November 2010

The prolonged retention of an effective chemotherapeutic agent on oral surfaces and in dental plaque aids in plaque control. The objective of this study was to investigate interactions between delmopinol, a morpholinoethanol derivative, and experimental pellicle. Hydroxyapatite beads were coated with different constituents of pellicle (e.g., saliva, carbohydrates, cell-free enzymes, and bacteria). Delmopinol demonstrated a higher affinity for saliva-coated hydroxyapatite (sHA) and for experimental pellicle coated with in situ-synthesized glucans than for untreated hydroxyapatite. High-molecular-weight (MW) dextran but not low-MW dextran interfered with the adsorption of delmopinol to sHA. Delmopinol did not compete with dextran for the same binding sites on sHA, nor did it compete with saliva for the same binding sites on untreated hydroxyapatite. Delmopinol inhibited the activity of cell-free fructosyltransferase adsorbed onto sHA. In addition, synthesis of glucans by Streptococcus mutans adsorbed onto sHA was significantly reduced in the presence of delmopinol.
The Influence of Growth Hormone on Cell Proliferation in Odontogenic Epithelia by Bromodeoxyuridine Immunocytochemistry and Morphometry in the Lewis Dwarf Rat
Authors: Young W.G. , Zhang C.Z. , Li H. , Osborne P. , Waters M.J.
Published: November 2010

For investigation of how growth hormone affects tooth development, bromodeoxyuridine immunocytochemistry and morphometry were used for the study of cell proliferation in odontogenic epithelial cell layers. The number of cells in the S phase, as revealed by this technique, and in mitosis, were counted in Bouin's-perfused and paraffin-embedded undecalcified maxillary incisor enamel organs of normal rats, in growth-hormone-deficient dwarf rats, and in dwarf rats treated with growth hormone (66 μg/100 g body wt) twice daily for six days. Significantly fewer labeled nuclei, unlabeled nuclei, and total nuclei of various odontogenic epithelia were found in dwarf rats, but in dwarf rats treated with growth hormone, numbers of labeled nuclei equivalent to normal were found in the internal enamel epithelium, stratum intermedium, and Hertwig root sheath. Moreover, the mitotic index for pre-ameloblasts was 1.64 in normal rats, 0.92 for dwarf rats, and 1.66 for growth-hormone-treated dwarf rats (SD, 0.10). Other parameters-such as the labeling index and the ratio of positive to negative nuclei-were similarly related to GH status. Thus, growth hormone may play a role in the proliferation of the odontogenic epithelia in the rat.
The Relationship Between Level of Mandibular Pain and Dysfunction and Stage of Temporomandibular Joint Internal Derangement
Authors: Schiffman E.L. , Anderson G.C. , Fricton J.R. , Lindgren B.R.
Published: November 2010

Temporomandibular joint internal derangement (TMJ ID) is the most common intra-articular TM disorder and can progress from TMJ ID with reduction to TMJ ID without reduction. It is not known whether this anatomical progression is associated with increasing levels of mandibular dysfunction. The objective of this study was to determine whether the level of clinically detectable mandibular dysfunction was related to the stage of TMJ ID. Two clinicians examined 42 subjects prior to bilateral TMJ arthrographic evaluation. The level of mandibular dysfunction was calculated by Helkimo's Clinical Dysfunction Index (Di) and the Craniomandibular Index (CMI). Statistical analysis revealed that the level of mandibular dysfunction as determined by the Di and CMI was not related to the arthrographic presence or absence of TMJ ID. Therefore, the clinician cannot assume that the level of mandibular dysfunction is directly related to the absence or presence of TMJ ID. Epidemiologically, the CMI and Di can be used only for estimation of the degree of mandibular dysfunction, since they do not provide direct information on a specific TM disorder.
The Relationship of Undifferentiated Mesenchymal Cells to TMJ Articular Tissue Thickness
Authors: Bibb C.A. , Pullinger A.G. , Baldioceda F.
Published: November 2010

Undifferentiated mesenchymal (UM) cells, the progenitor cells of the cartilage layer, have been assigned a significant role in TMJ articular tissue maintenance. This was based on reports of UM cell reduction with increased soft-tissue thickness for the condyle and temporal component. However, the strength of this inverse relationship was not presented and remained unclear. The purpose of the present study was to assess the strength of the correlation between UM cell presence and soft-tissue thickness in young adult TMJs at autopsy. Sagittal histological sections from the central thirds of 50 joints were evaluated with respect to articular soft-tissue thickness, histological character, and UM cell presence in the condyle and temporal component. The superior sector ofthe condyle and the articular eminence showed the greatest variability in soft-tissue thickness and were the only areas to show localized UM cell absence. The eminence was the only location to show an inverse relationship between soft-tissue thickness and UM cell presence, and this was consistent in both an ANOVA (p = 0.0016) and a Spearman correlation analysis. However, the strength of this correlation was only moderate (rho = -0.52), and no such relationship was observed in any other location. This study suggests that the relationship between UM cell presence and soft-tissue thickness is more complex than previously hypothesized and that the contribution of UM cells to articular tissue maintenance has been overstated, while other biological processes were overlooked.
A Seven-and-a-half-year Survival Study of Resin-bonded Bridges
Authors: Creugers N.H.J. , Kayser A.F. , Van't Hof M.A.
Published: November 2010

A clinical trial, concerning 203 resin-bonded bridges (RBBs), was performed for investigation of the influence of retainer-type and cementation materials on the survival of these restorations. The survival rates after a 7.5-year follow-up were 75% for anterior RBBs and 44% for posterior bridges. Etched metal RBBs (E-bridges) were significantly more retentive than perforated RBBs (P-bridges); the survival rates were 78% and 63%, respectively. With respect to the cementation materials, Clearfil F, in combination with E-bridges, had the best overall survival (89%, anterior and posterior). Maxillary anterior RBBs were more susceptible to failure than mandibular anterior RBBs.
Labile or Surface Pools of Magnesium, Sodium, and Potassium in Developing Porcine Enamel Mineral
Authors: Aoba T. , Shimoda S. , Moreno E.C.
Published: November 2010

The present study was undertaken to assess the labile or surface pools of Mg, Na, and K ions in porcine enamel tissues at various developmental stages. The enamel samples, corresponding to the outer and the inner secretory, the early maturing, and the mature hard enamel, were dissected from the labial sides of permanent incisors of 6- to 8-month-old piglets. Each enamel sample was extracted successively with solutions of de-ionized water and 50 mmol/L Tris-4 mol/L guanidine buffer (for removal of organic matrix proteins, mainly amelogenins). The labile (free or organically bound) pools of Mg, Na, and K were assessed by the total amounts of these ionic species extracted by the water and Tris-guanidine buffer. The surface (adsorbed onto enamel mineral) pool of Mg was assessed directly by determination of the adsorption of Mg onto enamel mineral at various developmental stages. The results showed that: (i) 30-40% of the Mg in the secretory and early maturation enamel was in the surface pool (adsorbed onto the enamel mineral); (ii) 25 to 40% of the total sodium in the enamel samples was in labile forms; and (iii) most (around 70-80%) of the total potassium was readily extracted in water and appeared to originate from the enamel fluid; only marginal portions remained in the solids. The present adsorption studies also indicated that the maximum uptake of magnesium in the early maturation enamel was due mostly to an increase of the occupancy by Mg ions of adsorption sites on the crystal surfaces, which become accessible with a massive removal of enamel matrix proteins. The observation that the surface pool of Mg (and the total Mg content) decreased markedly with the advancement of mineralization is explained by the displacement of the adsorbed Mg from the crystal surfaces by Ca2+ having a higher adsorption affinity for the same adsorption sites and by changes in the properties of the mineral surfaces. The overall results support the contention that incorporation of Mg into developing enamel upon resorption of the organic matrix may play a key role in regulating enamel crystal growth.
Correlates of Success and Failure in Behavior Therapy for Dental Fear
Authors: Kleinhauz M. , Eli I. , Baht R. , Shamay D.
Published: November 2010

Extreme dental fear and avoidance are universal problems, with severe adverse effects on the patient's oral health. Although behavior modification techniques were shown to be effective in the treatment of this problem, their success is by no means absolute. In the present article, the SCL-90 questionnaire was used for development of possible predictive measures for success and failure of behavior modification as a treatment for dental fear. Patients who failed in treatment through behavior modification were found to score significantly higher on the global score of Positive Symptom Distress Index (p < 0.01) and on individual subscales of somatization (p < 0.02) and psychoticism (p < 0.05) than patients who were treated successfully. The predictive value of chosen SCL-90 scales was 71%. The results suggest that use of SCL-90 may be valuable for the prediction of success and failure of behavior modification as a treatment for dental fear and avoidance.
The Fit of Gold-alloy Full-crown Castings Made with Ceramic Casting Ring Liners
Authors: Earnshaw R. , Morey E.F.
Published: November 2010

Measurements were made of the fit of gold-alloy full-crown castings produced with dry ceramic ring liners. When used with vacuum investing, these liners absorb relatively large amounts of water from the investment mix (thereby reducing its original W/P ratio) and then function as wet liners, thus increasing the investment's potential expansion and giving castings which are consistently larger than when air investing is used.

With four of the five liners tested, investing in air produced many castings which were unacceptably undersized (inaccuracy worse than -0.2%). The fifth liner, an industrial material 2 mm thick, gave only one casting out of 12 which was outside this limit, although all castings were undersized to a lesser extent. Vacuum investing gave improved casting accuracy; with four of the five liners, the improvement was highly significant (p < 0.001), and with the fifth, probably significant (p < 0.05). Even with vacuum investing, however, with only two of the liners did all castings show inaccuracies within ± 0.2%. With the other three liners, some castings (ranging from 2/10 to 7/9) had inaccuracies worse than -0.2%.

With both air and vacuum investing, changing from one liner to another caused changes in relative casting accuracy which were often significant (p < 0.01) or highly significant (p < 0.001). In casting techniques where a ceramic ring liner is used, the choice of specific lining material and the choice between investing in air or under vacuum are important factors which can have a major effect on the fit of castings.
The Effect of Chewing Gum Use on in situ Enamel Lesion Remineralization
Authors: Creanor S.L. , Strang R. , Gilmour W.H. , Foye R.H. , Brown J. , Geddes D.A.M. , Hall A.F.
Published: November 2010

Two independent cross-over studies investigated the possibility of enhanced early enamel lesion remineralization with the use of chewing gum. The first study involved a sorbitol-containing chewing gum, and the second, which had an identical protocol, tested a sucrose-containing chewing gum. In each study, 12 volunteers wore in situ appliances on which were mounted enamel sections containing artificial caries lesions. Subjects brushed twice daily for two min with a 1100-ppm-F (NaF) dentifrice (control and test) and in the test phase chewed five sticks of gum per day for 20 min after meals and snacks. Microradiographs of the enamel lesions were made at baseline and at the end of the seven-week experimental period. In the sugar-free gum study, the weighted mean total mineral loss (Az) difference [(wk7 - wk0) x (-1)] was 788 vol.% min. x μm for the gum, corresponding to remineralization of 18.2%, vs. the control value of 526 vol.% min. x μm, 12.1% remineralization (p = 0.07). There were no significant differences for the surface-zone (p = 0.20) and lesion-body (p = 0.28) values. In the sucrose-containing gum study, the Az difference was 743 vol.% min. x μm for the gum, corresponding to a remineralization of 18.3%, vs. the control value of 438 vol.% min. x μm, 10.8% remineralization (p = 0.08). The surface-zone values were not significantly different (p = 0.55). For the lesion body, however, the sucrose-containing gum value of 6.11 vol.% min. was significantly different (p = 0.01) from that of the control (2.81 vol.% min.).
Distribution and Isolation Frequency of Eight Streptococcal Species in Saliva from Predentate and Dentate Children and Adults
Authors: Tappuni A.R. , Challacombe S.J.
Published: November 2010

The isolation frequency and distribution of eight recently defined streptococcal species have been investigated in the saliva of adults and that of both predentate and dentate children. The effects of frequency of sugar intake and tooth presence on the distribution of streptococcal species were also analyzed. Saliva samples were collected from 121 subjects divided into three study groups: (a) 56 predentate children (predentate group), (b) 37 dentate children (dentate group), and (c) 28 adults (adult group). Up to 17 biochemical and enzymatic tests were used to categorize streptococcal isolates into S. mitis, S. oralis, S. salivarius, S. anginosus, S. sanguis, S. vestibularis, S. mutans, and S. gordonii.

The mean total and streptococcal salivary colony-forming units (CFU) were lowest in the predentate group and highest in the adult group. Streptococci were found in all the study subjects, and there was no obvious relationship between the total or streptococcal CFU and the number of teeth or the frequency of sugar intake. There was a wide variation in the isolation frequency of streptococcal species in the three study groups. S. mitis, S. oralis, and S. salivarius were the most frequent species isolated, and together they comprised 83% of the total streptococcal isolates. In contrast to studies using older classifications, S. sanguis was a minor species in the saliva though found more often in adults than in children (p < 0.04). S. anginosus was a minor species found in about 10% of adults and children. S. gordonii was detected rarely and only in dentate subjects. S. mutans was detected only in dentate subjects, significantly greater in adults (57.1%) than in children (5.4%, p < 0.001). In contrast, S. vestibularis was found in both dentate and predentate children but not in adults. No relationship between the isolation frequency of any of the species and sugar intake in children was demonstrated. The new classification of streptococci has revealed major differences in isolation frequency and distribution of the individual species and should prove useful in future studies of ecological factors affecting oral flora.
Effect of Jaw Opening on Masticatory Muscle EMG-Force Characteristics
Authors: Lindauer S.J. , Gay T. , Rendell J.
Published: November 2010

This study was designed to evaluate the way in which changes in vertical jaw opening affected the relative contributions of various masticatory muscles to bite force production. EMG activity was recorded simultaneously from the masseter, and anterior, middle, and posterior temporalis muscles, during controlled isometric biting at different force levels and vertical jaw openings. EMG-force characteristics were compared between muscles and bite openings. All but the posterior temporalis muscle displayed significant increases in muscle activity with increased bite force production; the masseter muscle demonstrated the largest activity increments. Statistically significant changes in muscle function due to jaw opening were demonstrated only for the masseter muscle, though similar trends were observed for the anterior and middle temporalis muscles. Minimum increases in muscle activity associated with increases in bite force occurred between 9 and 11 mm of opening, measured at the first molar, for all three muscle groups. The results of this study suggest that changes in masticatory muscle length resulting from vertical jaw opening cause alterations in muscle contractile properties, but the relative contributions of various masticatory muscles toward bite force production may also be affected by biomechanical factors and neural control adaptations.
Influence of Shearing Action of Food on Contact Stress and Subsequent Wear of Stress-bearing Composites
Authors: Pallav P. , De Gee A.J. , Werner A. , Davidson C.L.
Published: November 2010

The influence of sliding action of the antagonist on occlusal three-body wear of composites and an amalgam was investigated in vitro by gradual change in the distance between the opposing substrates. When the distance was decreased from 10 μm to approximately 3 μm, wear increased significantly by a factor of two to three and was exclusively of erosive nature. At a slurry-film thickness of approximately 1 μm, direct contacts between the antagonist and protruding composite filler particles started to occur. This consequently slowed the erosive wear. Ultimately, direct contact phenomena predominated, decreasing the wear rate of the various materials to different degrees. Loss of material due to subsurface fatigue could not be demonstrated with a contact pressure of 45 MPa at which the experiments were performed. From this study, it can be concluded that minor alterations of the food-film thickness at the contact areas result in considerable changes in wear rates and wear-rate ranking of composite materials, which may partly explain inconsistencies among clinical trials.
The Effects of Etching, Micro-abrasion, and Bleaching on Surface Enamel
Authors: Tong L.S.M. , Pang M.K.M. , Mok N.Y.C. , King N.M. , Wei S.H.Y.
Published: November 2010

Conservative techniques for improving the appearance of discolored teeth have become popular in the past decade. These include: in-office bleaching with 30% hydrogen peroxide, which is applied on etched enamel with a gauze pad and then exposed to a bleaching light; home bleaching with a mild form of peroxide, such as 10% carbamide peroxide, which is applied on the tooth surface with custom-made mouthguards; and enamel micro-abrasion with 18% hydrochloric acid, which is applied in a pumice slurry. In this study, the in-office bleaching and enamel micro-abrasion techniques were performed on extracted teeth for investigation of their microscopic effects on the surface enamel. Specimens treated only with 37% phosphoric acid showed an enamel loss of 5.7 ± 1.8 μm. The specimens treated with 37% phosphoric acid followed by 30% hydrogen peroxide showed enamel loss of 5.3 ± 1.6 μm; this loss was probably not caused by the hydrogen peroxide, but rather by the etching with 37% phosphoric acid which preceded the hydrogen peroxide application. A direct application of 18% hydrochloric acid for 100 s resulted in a loss of 100 ± 47 μm. The extent of enamel loss was much greater when the 18% hydrochloric acid was applied in a pumice slurry for the same period of time (360 ± 130 μm), and the effect was time-dependent. Thus, the pumice and rotary prophy cup used in conjunction with the 18% hydrochloric acid contributed markedly to the loss of surface enamel, enhancing the non-selective stain-removing action of the hydrochloric acid. Therefore, the hydrochloric acid-pumice technique must be used clinically with caution.
The Determination of Ionic Bonding Interactions of N-Phenyl Glycine and N-(2-hydroxy-3-methacryloxypropyl)-N-Phenyl Glycine as Measured by Carbon-13 NMR Analysis
Authors: Wolinsky L.E. , Armstrong R.W. , Seghi R.R.
Published: November 2010

The purpose of the present investigation was to determine whether high-resolution carbon-13 nuclear magnetic resonance could be utilized for detection of ionic bonding interactions of NPG and NPG-GMA with selected inorganic cations. The C1-carbonyl carbon of NPG and NPG-GMA were labeled with 13C to help magnify the spectral response signal. The labeled monomers were allowed to react with Ca(OH)2 and LiOH. The C-13 carbonyl resonance was observed by solution- and solid-state NMR. The interaction of the cations in solution and on a powdered glass support resulted in a downfield chemical shift of about 2-5 ppm, indicating the presence of a chemical interaction between the monomer and the cations. The reaction of the monomers with the solid substrates of hydroxyapatite, and bovine dentin did not result in a significant downfield shift in the carbonyl resonance. The results provide evidence that high-resolution nuclear magnetic resonance can be used for evaluation of chemical bonding interactions of dental adhesives with inorganic ions.
Influence of Dentinal Fluid and Stress on Marginal Adaptation of Resin Composites
Authors: Krejci I. , Kuster M. , Lutz F.
Published: November 2010

The influence of dentinal fluid and of a number of stress procedures on the quality of the margins of class V restorations located in both enamel and dentin was quantitatively assessed in vitro with the aid of a scanning electron microscope. The materials tested were GLUMA 2000 experimental, Prisma Universal Bond 3, and Syntac, together with the fine hybrid composites supplied by the respective manufacturers (Pekafill, AP.H, and Tetric). All materials achieved over 95% of "continuous margin" in enamel before and after stressing. In dentin, the initial values, with as well as without dentinal fluid simulation, were situated between 93.2 and 98.2%. With GLUMA 2000 experimental after stressing, a "continuous margin" occurred in only 50.2%, but with Prisma Universal Bond 3 and Syntac, the value was 79.0%. The influence of dentinal fluid simulation was dependent on the dentinal adhesive used. The effects of the various stress procedures were not significantly different.
The Association of Mutans Streptococci and Non-Mutans Streptococci Capable of Acidogenesis at a Low pH with Dental Caries on Enamel and Root Surfaces
Authors: Sansone C. , Van Houte J. , Joshipura K. , Kent R. , Margolis H.C.
Published: November 2010

Coronal dental plaque from each of 12 caries-positive subjects (Group I) was pooled from "white spot" tooth surface areas and, separately, from sound surface areas; sound surface areas in each of 18 caries-free subjects (Group II) were sampled similarly. Two samples, one consisting of material from a root-surface lesion and another of plaque from a sound root-surface area, were obtained from each of another 10 subjects (Group III). The samples from Groups I and II were evaluated for: (1) pH-lowering potential in vitro with dispersed plaque suspensions, excess glucose supply, and a 60-minute test; (2) the levels of mutans streptococci (MS) and lactobacilli; and (3) the distribution of the predominant non-mutans streptococci (non-MS) according to their final pH in glucose broth; only microbial analysis was done for the Group III samples. The levels of the MS were generally positively associated with caries. A weaker positive association was found for the levels of those non-MS capable of acidogenesis at low pH (final pH < 4.4). The latter generally far outnumbered the MS in all types of samples. The levels of lactobacilli were nearly always very low. The pH-lowering potential (final pH and pH drop rate) was higher for plaque from "white spot" areas than for plaque from sound surface areas (Group I). The samples from caries-free subjects (Group II), however, exhibited a pH-lowering potential which was not significantly different from that of both types of samples from the caries-active subjects (Group I). Collectively, the findings suggest that the role of non-MS capable of acidogenesis at low pH in caries development merits further study.
Familial Aggregation of Periodontal Indices
Authors: Beaty T.H. , Colyer C.R. , Chang Y.C. , Liang K.Y. , Graybeal J.C. , Muhammad N.K. , Levin L.S.
Published: November 2010

Analysis of three measures of periodontal health (plaque index, gingival index, and attachment loss) was carried out on 178 individuals in 75 families examined as part of a family study of periodontal health. Original participants in this study were volunteers recruited from the University of Maryland Dental Clinic, and were selected independently of any specific dental disease or condition. Relatives were invited to participate in the family study so that the extent of familial aggregation of indices of periodontal health could be assessed. By means of an analysis of variance model for persons nested within families, evidence for familial aggregation of plaque index was found both before and after adjustment for covariates such as age, gender, race, and reported oral hygiene habits. While a substantial fraction of variance in gingival index and attachment loss was also due to differences among families, neither attained statistical significance in these data. Examination of familial correlations (e.g., parent-offspring, sib-sib, spouse correlations) confirmed that plaque index showed greater familial resemblance compared with other measures of periodontal health. Both mean gingival index and mean attachment loss showed a stronger correlation between mothers and offspring compared with fathers and offspring. This suggests that further analysis of models for separating genetic and environmental effects may be appropriate for plaque index, but complete analysis of other periodontal indices will require more flexible statistical models for separation of genetic and cultural inheritance while considering gender-specific expression and transmission, as well as incorporation of information from covariates.
The Short-term Fluoride Release of a Hand-mixed vs. Capsulated System of a Restorative Glass-ionomer Cement
Authors: Verbeeck R.M.H. , De Moor R.J.G. , Van Even D.F.J. , Martens L.C.
Published: November 2010

The present study investigated whether variability in fluoride release was reduced by use of a capsulated system as compared with a hand-mixed system based on the same qualitative and quantitative glass-ionomer formulation. Five operators independently prepared five disks of each type of glass-ionomer restorative filling material. The amount of fluoride released in water by each specimen after 1, 2, 3, 7, and 14 days was determined. The variance and the mean value of the fluoride release at a given time were independent of the operator, regardless of the glass-ionomer system considered. However, the variance and the mean value of the fluoride release at a given time were considerably greater for the capsulated system than for the hand-mixed system. A regression analysis further showed that the cumulative amount of fluoride released, [F], as a function of the time t conformed to [F] = a[1- exp (-bt)] + ct0.5 for each glass-ionomer specimen, suggesting the simultaneous occurrence of two processes. Whereas the parameter b was the same for the hand-mixed and capsulated system and was independent of both a and c, the latter parameters were positively correlated. Moreover, the values for a and c were significantly greater for the capsulated system. On the basis of these results, it is concluded that the mixing process drastically influences the short-term as well as the long-term fluoride release.
Segregation in Precious-metal Dental-casting Alloys
Authors: Drapal S. , Pomajbik J.
Published: November 2010

The aim of this study was to conduct a theoretical analysis of segregation in Au-Ag-Cu and Ag-Pd-Au-Cu dental-casting alloys, and to confirm and extend the results experimentally. Both theoretical and experimental data showed greater segregation in the Ag-Pd-Au-Cu alloy than in the Au-Ag-Cu alloy. There was very little segregation of gold, zinc, and platinum, while between the dendrites copper increased and silver and palladium decreased.
Distribution of Substance P and Calcitonin Gene-related Peptide-like lmmunoreactive Nerve Fibers in the Rat Temporomandibular Joint
Authors: Kido M.A. , Kiyoshima T. , Kondo T. , Ayasaka N. , Moroi R. , Terada Y. , Tanaka T.
Published: November 2010

The density and distribution of substance P-like immunoreactive (SP-LI) and calcitonin gene-related peptide-like immunoreactive (CGRP-LI) nerve fibers in rat temperomandibular joint (TMJ) were investigated in whole-mount preparations and frozen sections by immunohistochemistry with the avidin-biotin-peroxidase complex method. Both types of immunoreactive nerves were observed primarily in the joint capsule, the peripheral articular disc, the synovial membrane, and the periosteum. The distribution of CGRP-LI nerves was similar to that of SP-LI nerves. The anterior portion of the joint capsule and disc was most densely innervated, followed by the posterior, lateral, and medial portions. In addition, CGRP-LI nerves were more numerous and more dense in immunointensity than SP-LI nerves. In the synovial membrane, many SP- and CGRP-LI nerves terminated in the subsynovial layer, but some branches extended into the superficial synovial lining layer close to the joint cavity. Immunolabeled nerves were prominently located in the disc attachment and peripheral portion of the disc, and occasional nerves were located in the dense collagenous disc band as an actual disc. However, no fibers were detected in the central disc band. Thus, most of the disc was not innervated by any nerves.

The present study provides a morphological basis for the possible roles of neuropeptides in endocytosis by synoviocytes, regulation of blood flow in the synovial membrane, nociception mechanisms of the TMJ, and modulation of the inflammatory response in the TMJ.
Influence of Gastric Acidity on Fluoride Absorption in Rats
Authors: Messer H.H. , Ophaug R.H.
Published: November 2010

The rate of F absorption from the stomach is pH-dependent, with greater absorption at low pH. Since the rate of absorption is also strongly influenced by the rapidity of gastric emptying, we have compared the relative importance of gastric acidity and gastric emptying in overall F absorption. Male rats (350 g, n = 85) were pre-treated with cimetidine (to inhibit gastric acid secretion) or pentagastrin (to stimulate gastric acid secretion) or were untreated controls, and given 50 μg F by stomach intubation. The pH of the F-containing solution was varied in the cimetidine-pre-treated group (pH 1.5, 5.5, 8.5), and was 5.5 for the control and pentagastrin-pre-treated groups. Gastric emptying was measured by addition of 14C polyethylene glycol to the F solution as an unabsorbed marker of fluid movement. F absorption was measured after 10, 20, and 40 min. The rate of gastric emptying was unaffected by pre-treatment or pH of the intubating solution. Initially, F absorption was greatest at low pH. After 40 min, absorption was comparable in all groups, averaging approximately 70% of the initial dose. The extent of absorption from the stomach was inversely related to pH, but increased absorption from the small intestine compensated for the low gastric absorption at high pH.
The Effect of an Occlusal Stabilization Splint and the Mode of Visual Feedback on the Activity Balance Between Jaw-Elevator Muscles During Isometric Contraction
Authors: Lobbezoo F. , Van Der Glas H.W. , Van Kampen F.M.C. , Bosman F.
Published: November 2010

The aim of the present study was to gain an insight into the influence of a vertical bite-rise (clenching in intercuspal occlusion vs. clenching on an occlusal stabilization splint), the mode of visual feedback (VF; obtained from the compound masseter signal, from the compound anterior temporalis signal, or from the compound signal of both masseter and anterior temporalis muscles) and the EMG clenching level (10% MVC and 50% MVC) on the muscle balance between the masseter and the anterior temporalis muscles. The muscle balance was quantified as the logarithmic value of the ratio between the summated mean rectified EMG activity of the masseter muscles and this activity of the anterior temporalis muscles. The muscle balance was influenced significantly by the mode of VF (p < 0.01), the muscle balance shifting toward the group of muscles from which VF was obtained. When VF was obtained from the masseter muscles, a decrease in the anterior temporalis EMG activity was observed when the vertical dimension was increased (p < 0.05-0.01). When VF was obtained from the anterior temporalis muscles, the activity of the masseter muscles was raised with respect to that of the anterior temporalis muscles during clenching with a vertical bite-rise (p < 0.05-0.01). When VF was obtained from both groups of muscles, the masseteric EMG activity increased, whereas the anterior temporalis EMG activity decreased. Hence, regardless of the mode of VF, a relatively lower activity level of the anterior temporalis muscles was achieved after insertion of an occlusal stabilization splint. The therapeutic effect of a stabilization splint may therefore, at least in part, be related to a reduced activity in the anterior temporalis muscles.
Fluoride and Iron Concentrations in the Enameloid of Lower Teleostean Fish
Authors: Sugat S. , Taki Y. , Ogawa M.
Published: November 2010

Our quantitative elemental analyses with the electron microprobe indicated that the fluoride and iron concentrations in the enameloid of bony fish are related to the phylogeny of fish. The enameloid of some bony fish with high F also contained high Fe. In order to clarify the phylogenetic significance of such a peculiar dual deposition of F and Fe into developing enameloid, quantitative electron microprobe analyses of these elements were made on the teeth of taxonomically lower teleosts. There were significantly different trends of F and Fe concentrations in the enameloid among various forms of lower teleosts. In the Osteoglossiformes, the enameloid of the osteoglossid species contained very low levels of F and Fe, whereas in the single representative of the Mormyroidei, the F was very low but Fe was very high. In the Elopomorpha, the enameloid of the elopiform species contained a medium level of F and high Fe, and that of the anguilliform high levels of F and Fe. In the Salmoiformes, the salmonid species had medium F and high Fe, and in a species of the Esocidae, high F and high Fe levels were found. The stomiiform fish exhibited levels of medium and high F and high Fe. The results of the present study and our previous investigations made on archaic non-teleostean and various teleostean fish indicate that the mechanisms of F and Fe concentrations into developing enameloid are independent of each other, and that the mechanisms of Fe concentration appeared earlier and disappeared later than, or concurrently with, that of the F concentration, in the course of fish evolution.
Scanning Microradlographic Study of the Kinetics of Subsurface Demineralization In Tooth Sections under Constant-composition and Small Constant-volume Conditions
Authors: Gao X.J. , Elliott J.C. , Anderson P.
Published: November 2010

The kinetics of subsurface demineralization of tooth sections has been studied in real-time by scanning microradiography (SMR). Demineralization was carried out: (1) with a large volume of solution buffered to pH = 4 to maintain a constant composition; and (2) in a small constant volume (~ 3 mL), buffered initially at pH = 4, so that the degree of saturation at the tooth surface increased as the tooth dissolved. At constant composition, the change in lesion depth, Y, with time, T, followed a linear relation, Y= α + bT, for T> 44± 5 h. Before this time, the relation could be approximated by a linear one with different a and b constants. At constant volume, Y= q(1-e-r(T+8)) for all T, where q, r, and s are constants. Similar relations, with different constants, were found for the mineral loss per unit area of lesion exposed to acid. These results showed that the process of demineralization under the rather severe conditions used was essentially a surface-controlled process. The change of slope at ~ 44 h and the presence of the constant s in the exponential function were attributed to a change in kinetics after formation of the surface layer.