bluuebunny/crossref_metadata_2025 huggingface dataset:
Clinical Science An SEM Study of Posts Cemented with an Unfilled Resin
Authors: Goldman M. , DeVitre R. , White R. , Nathanson D.
Published: November 2010

Post preparations in two groups of endodontically treated anterior teeth were completed. In Group I, the preparation was rinsed with 2 ml of 5.25% NaOCL. In Group II, the preparation was rinsed with 1 ml of 17% EDTA, followed by 1 ml of 5.25% NaOCl. A plastic post was fitted and cemented with an unfilled resin. After polymerization, the teeth were decalcified in 5% nitric acid. The decalcified structure was dissolved away with 5.25% NaOCl, leaving a model of the cemented post. This was examined by SEM to determine the extent of resin penetration into the dentinal tubules. In Group I, most of the post was smooth, and there was penetration only in small, random areas. In Group II, there was penetration into the tubules the full length and circumference of the post. Such penetration provides a very strong mechanical lock that enhances the tensile strength of the cemented post. Removing the smeared layer and then cementing a post with a Bis-GMA resin results in greatly increased tensile strength, even with shorter posts.
The Effect of Chronic Isoproterenol Administration on the Plasma Membrane of Acinar Cells in Rat Submandibular Gland
Authors: Sahara N. , Araki N. , Fukasawa K. , Harada M. , Suzuki K.
Published: November 2010

The effect of chronic administration of isoproterenol on the plasma membrane of acinar cells in the rat submandibular gland was studied by biochemical and immunohistochemical methods, using dipeptidyl peptidase (DPP) IV as a marker enzyme. Chronic isoproterenol treatment led to a marked reduction of DPP IV activity as well as of its immunoreactivity in the gland. Its effect progressively increased with the age of the animals. The present study showed that chronic treatment with isoproterenol caused a qualitative alteration of the plasma membrane of the luminal surface in acinar cells of the rat submandibular gland, and that the effect of the drug on the plasma membrane was dependent on the developmental stage of the acinar cells of the gland.
Relatedness and Classification of Streptococcus mutans and "Mutans-like" Streptococci
Authors: Schleifer K.H. , Kilpper-Bälz R. , Kraus J. , Gehring F.
Published: November 2010

The "mutans-like" streptococci can be separated into five species (Streptococcus mutans, S. rattus, S. sobrinus, S. cricetus, and S. ferus ) that belong to the same rRNA homology cluster. New valuable chemical characters for differentiation of the five species - such as peptidoglycan type, presence of cell wall teichoic acid, and cell wall sugar composition - are described. The peptidoglycan type and the cell wall sugar composition can be determined by rapid procedures.
Fissure Removal and Needle Scraping for Evaluation of the Bacteria in Occlusal Fissures of Human Teeth
Authors: Meiers J.C. , Schachtele C.F.
Published: November 2010

The bacterial counts obtained with a needle-scrape method for collecting plaque samples from human occlusal fissures with incipient caries were compared with the microflora remaining in the fissures as determined with a fissure removal method. Scraping of six fissures with a sterile needle recovered only 18.2% of the total recovered fissure flora. The needle-scrape method failed to detect specific cariogenic bacteria which were present in four of the fissures. Treatment of nine fissures with an antibacterial solution demonstrated that the needle method failed to detect viable bacteria in eight of the fissures which were subsequently shown to contain bacteria by fissure removal. The commonly used needle-scraping method does not appear adequate for studies on the effect of antimicrobial agents on fissure plaque.
The Lamina Limitans of Human Dentinal Tubules
Authors: Thomas H.F.
Published: November 2010

Fractured coronal surfaces of both fixed and unfixed human teeth were examined by scanning electron microscopy following HCl demineralization and collagenase digestion. This treatment removed a considerable amount of matrix from the surface of dentin. Tubular structures, termed lamina limitans, were not affected by this treatment and remained on the surface of the tissue. The lamina limitans extended from the pre-dentin-dentin junction to the dentin-enamel junction. Further enzymatic digestion of unfixed specimens with hyaluronidase resulted in the complete removal of the lamina limitans. The susceptibility of the lamina limitans to hyaluronidase digestion indicates a high content of glycosaminoglycan, suggesting that they are extracellular in nature. These data provide further evidence that lamina limitans are not odontoblast processes.
Properties of Kininase in Rat Dental Pulp
Authors: Maita E. , Endo Y. , Ogura Y.
Published: November 2010

A kininase, capable of degrading bradykinin, was partially purified from the dental pulp of rats, and its properties were investigated. Chromatography on both Sephadex G-200 and DEAE Sephadex A-50 columns gave a single peak of kininase activity. The molecular weight of the enzyme, estimated by gel filtration, was about 67,000, and the optimum pH for the enzymatic reaction was about 7.5. The enzyme appears to contain a labile SH group(s) that is essential for its activity, because CdCl2, HgCl2(0.1 mM each), and p-chloromercuric benzoate (0.05 mM) inhibited the enzyme completely, while dithiothreitol retarded the loss of activity during storage. Of various peptides tested, bradykinin was the substrate most sensitive for the enzyme. The enzyme released several amino acids located in the C-terminal regions of bradykinin - angiotensin I and neurotensin - but only one C-terminal amino acid from des-Arg9- bradykinin and angiotensin II. In contrast, the enzyme did not release any amino acids from substance P, of which only the two amino acids in the N-terminal region are the same as those of bradykinin, but its C-terminal is blocked by an amino group. Although the enzyme was not so highly purified as to rule out the contribution of other peptidases, these results suggest that the dental pulp of rats may contain a single enzyme that degrades bradykinin, and the enzyme may be a type of carboxypeptidase, differing from known kininases from other animal sources.
Influence of Serum on Cultured Murine Tooth Organ Allotransplants
Authors: Riviere G.R.
Published: November 2010

Previous investigations indicated that in vitro culture of fetal tooth germs before allotransplantation prolonged graft survival. This study assessed the influence of different sources of serum in culture medium on post-transplant development of neonatal tooth organs. The results indicate that recipient-strain serum, but not donor-strain serum or calf serum, increased tooth survival compared with that of uncultured controls, which were rejected by the fourteenth post-transplant day. The survival curve for cultured tooth organs was shifted to the right by two days. No tooth transplant survived beyond three wk.
Effect of Daily Rinsing with Stannous Fluoride on Plaque and Gingivitis: Final Report
Authors: Leverett D.H. , McHugh W.D. , Jensen Ø.E.
Published: November 2010

Two groups of children, ages 12 to 15, rinsed daily for 28 mo with aqueous fluoride solutions, one group using 0.05% sodium fluoride (NaF) and the other group using 0.1% stannous fluoride (SnF2). The SnF2 group had less plaque accumulation after four mo, but no difference was apparent at 16 and 28 mo. Gingivitis was less severe in the SnF2 group throughout the study, although the difference did not reach statistical significance. The 0.1% SnF2 solution, used daily as a mouthrinse, inhibits plaque formation, although this inhibitory effect is not apparent after 16 mo of rinsing.
Materials Science Bond Strength Between Dentin and Restorative Resins Mediated by Mixtures of HEMA and Glutaraldehyde
Authors: Munksgaard E.C. , Asmussen E.
Published: November 2010

We investigated the bond strength between restorative resin and dentin pre-treated with mixtures of HEMA and glutaraldehyde. It is suggested that the mixture acts by forming a chemical bond of HEMA molecules to a collagen-glutaraldehyde reaction complex. Subsequently applied resin will then co-polymerize with the collagen-linked methacrylate groups. Statistical analysis of the results from varying mixtures of HEMA and glutaraldehyde revealed that the bond strength was highly dependent on the HEMA concentration, with a maximum at 35%, and nearly independent of the glutaraldehyde concentration when greater than 3%. The highest mean bond strength was about 1.8 kg/mm2, and bond strength of this order of size may be attractive for clinical use.
Experimental Marginal Leakage Around Dental Amalgams Placed in Artificial Cavities
Authors: Jodaikin A. , Grossman E.S.
Published: November 2010

Experimental marginal leakage of high- and low-Cu amalgam restorations placed in acrylic teeth, where the cavities were untreated or painted with denatured collagen and/or a CaP slurry, was assessed after specimens were stored in a 1% NaCl solution for ten days and for one yr. All specimens stored for ten days showed severe marginal leakage. High- and low-Cu amalgam restorations placed in untreated acrylic teeth cavities formed seals after a storage period of one yr, indicating that these materials are able to form a seal without interacting with a natural tooth cavity interface. Cavities treated with denatured collagen also formed seals in the long-term group. It was apparent that, when the CaP slurry was used, generally more leakage resulted after the year's storage period than when amalgam restorations were placed in uncoated acrylic cavity surfaces or in those painted with denatured collagen.
The Influence of Restorative Dental Materials on Heat Transmission in Human Teeth
Authors: Spierings Th.A.M. , De Vree J.H.P. , Peters M.C.R.B. , Plasschaert A.J.M.
Published: November 2010

Using the finite element method, we analyzed the temperature distribution and heat flow patterns in an axisymmetric tooth model. The models of an unrestored tooth and three teeth restored with different restorative materials were evaluated comparatively.

The insulating ability of a calcium hydroxide cement base (Ca(OH)2) is low, which is inherent in its insufficient thermal and poor mechanical properties. In the given conditions, the Ca(OH)2-base reduces the temperature increase at the cement-dentin interface by 12.5% with respect to a restoration of amalgam only. By using a double base (Ca(OH)2 + polymer-modified zinc oxideeugenol), the reduction is 21.9%. With respect to a sound tooth model, the presence of a double base in the restored tooth caused a temperature increase of only 0.1°C at the pulpo-dentinal junction.

The thermal conductivity coefficient (λ) of amalgam does not have any influence on the results of the calculations. The heat transfer coefficient (α) turned out to be an essential parameter in this mathematical model.
Ultrastructural Changes in the Cementoblasts of Rat Molars after Injection of Vincristine
Authors: Takuma S. , Sawada T. , Yama S. , Yanagisawa T.
Published: November 2010

Cytological changes in the cementoblasts of rats treated with vincristine were investigated. Accumulation of secretion granules indicated a disturbed secretory mechanism in the cells. Conspicuous dilation of the endoplasmic reticulum suggested disturbance in the transport of substances from the rough endoplasmic reticulum to the Golgi elements. These disturbances were interpreted to be a result of disruption of microtubules.
In vivo Remineralization of Human Enamel and Dental Calculus Formation
Authors: Hoyer I. , Gaengler P. , Bimberg R.
Published: November 2010

The aim of this investigation was to determine the inorganic composition and the surface morphology of remineralized enamel areas and of dental calculus in heavy-calculus-formers (five subjects) and to compare these results with those of non-calculus-formers (two subjects). Electron probe micro-analysis (EPMA) was carried out on sound, acid-etched, and in vivo remineralized enamel samples from heavy- and non-calculus-formers. The mean values of Ca, P, Na, Mg, Al, Si, S, Cl, and K were compared with the SEM morphology.

EPMA measurements showed no significant differences in the Ca/P ratio of the surface layers of prism-oriented and/or homogeneous enamel remineralization. The variations of remineralization pattern after acid-etching are similar in teeth from heavy dental-calculus-forming patients and in teeth from non-calculus-formers. The SEM appearances of remineralized areas and of the inner surface of mature dental calculus must be considered to be totally different. The experiments carried out suggest that the remineralization of enamel is not related to the formation of calculus.
Larval vs. Adult Pharyngeal Dentition in Some Japanese Cyprinid Fishes
Authors: Nakajima T.
Published: November 2010

The development of the pharyngeal dentition was examined in 13 species of five subfamilies of the family Cyprinidae. A previously described difference between the larval and adult dentition in Gnathopogon caemlescens was observed in 11 species of Gobioinae, Cyprininae, Leuciscinae, and Danioinae, but was not seen in two species of Acheilognathinae. The adult dentition is usually complete by the later larval or juvenile period. In the adult dentition, the functioning teeth are generally shed at each position, when the replacement tooth has been ankylosed to the bone, or when the germ of that tooth has grown sufficiently. In the larval dentition, however, the replacement tooth is ankylosed medial to the functioning tooth, so the older functioning tooth is retained after ankylosis of the replacement tooth. That is why the dentigerous surface of the bone grows rapidly during the larval period. Each tooth row represents a single replacement wave. The distribution and pattern of the central teeth are exactly the same in all types of the larval dentition. However, those of the anterior teeth vary between and within different species. The larval dentition develops into the major row of the adult dentition through tooth replacements. The number of tooth families in the larval dentition is completely consistent with the tooth number of the major row in the adult dentition. Therefore, the number of major row teeth owes its variation to that in the appearance pattern of the anterior teeth.
Dental Disease and Work Loss
Authors: Reisine S.T.
Published: November 2010

Few studies have analyzed dental diseases in terms of their social impact. This study explored the feasibility of a social outcome measure, work absence. 2600 employed people in the Hartford (CT) area were interviewed by 'phone using Random Digit Dialing methodology. While dental disability did not affect the majority (75%) of those workers interviewed, 25% reported an episode of work loss in the past 12 months related to dental problems and dental treatment visits. Workers lost an average of 1.7 hours. The prevalence and magnitude of work loss were sensitive to several sociodemographic, access, and health-related factors.
An International Collaborative Study of Laboratory Methods for Assessing Abrasivity to Dentin
Authors: Hefferren J.J. , Kingman A. , Stookey G.K. , Lehnhoff R. , Muller T.
Published: November 2010

An International Collaborative Study was conducted in which one surface profile and two radio tracer methods for assessing abrasivity of dentifrices on human dentin were compared. The study consisted of two phases: an open phase in which participating laboratories used the method they routinely practiced; and a controlled phase in which an expert team for each method performed the abrasion tests using all three methods. Four test pastes of known abrasivity were evaluated by each method. Similar abrasivity values for the test pastes were obtained with the radio tracer methods, whereas the surface profile method produced significantly different values. The precision levels of the radio tracer methods were similar, and both were superior to those obtained by the surface profile method. The time needed to perform the tests by the ADA radio tracer method was significantly less than that needed by the other methods. These findings suggest that the ADA radiotracer method will be useful in assessing abrasivity of dentifrices.
Dental Fear and Avoidance: A Comparison of Two Modes of Treatment
Authors: Berggren U. , Linde A.
Published: November 2010

Ninety-nine individuals, all of whom had long avoided dental treatment due to severe dental fear, received therapy according to one of two treatment modalities - behavioral therapy from a psychologist (BT) and treatment under general anesthesia (GA) - both of which were followed by clinical training and dental test treatments. These treatment programs were followed by referring the individuals to community dental clinics for complete oral rehabilitation.

Among BT patients, significantly more (92%) completed the treatment program, compared with the GA patients (69%). Complete oral rehabilitation in community dental clinics was achieved by 78 and 53%, respectively. BT patients also had a significantly lower frequency of cancellations. The reduction in dental anxiety according to the Corah Dental Anxiety Scale was substantial in both groups, but the anxiety was significantly more reduced for BT patients, who reached a level equivalent to that of average dental patients. Patients' self-reported tension and the dentists' ratings of patient behavior during treatment were also significantly more positive for the BT groups.
Inhibition of Marginal Leakage with a Dentin Bonding Agent
Authors: Dumsha T. , Biron G.
Published: November 2010

Class V cavity preparations were treated in vitro with dentin bonding agents and composite. The teeth were thermally cycled, stained, and scored for marginal leakage, by a silver stain technique. The composite-only control group leaked significantly more than did the dentin-bonding-treated experimental groups. The coating of pre-treated dentinal walls with unfilled bonding resin offered no advantage with this dentin bonding system.
Topical Fluoride Application and Lesion Progression in vitro
Authors: Wefel J.S. , Harless J.D.
Published: November 2010

The objectives of this investigation were to study the effects of topical fluoride application on white spot enamel and the effect that this application would have on a second acid exposure (lesion progression).

Artificial white spot lesions of approximately 200 μm were created with an acidified gel technique, central control sections were removed, and the remaining tooth halves were randomly paired, with one half serving as an untreated control while the other received a single four-minute application of 1.23% (w/v) fluoride solution of either NH4F, Na2SnF6, APF, or TiF4. Both tooth halves were sectioned following progression and examined with polarized light microscopy. Lesion depth, internal pore volume, and presence, size and shape of dark zones were determined. The considerable variation among progressed lesions revealed no significant benefit from any topical fluoride treatment.
Fracture Properties of Human Teeth in Proximity to the Dentinoenamel Junction
Authors: Rasmussen S.T.
Published: November 2010

Under conditions of controlled failure, the fracture properties of dentin at and in proximity to the dentinoenamel junction (DEJ) were studied with a work-of-fracture (Wf) technique and by scanning electron microscropy (SEM). In 37°C distilled water, fracture of normal human teeth at the DEJ was a difficult failure mode to investigate. Even with high stress concentration at the DEJ, only a few specimens showed apparent DEJ failure at localized regions. SEM fractography of these localized regions revealed surfaces similar in some respects to surfaces found in other studies of the DEJ of diseased teeth and decalcified or desiccated teeth. SEM fractographs varied depending upon the distance of the fractured surface from the DEJ. The results of this research suggest that the work of fracture of dentin increases for failure in the near vicinity of the DEJ, probably reaching a maximum at the DEJ.
Intermediate Restoratives from n-Hexyl Vanillate-EBA-ZnO-Glass Composites
Authors: Brauer G.M. , Stansbury J.W.
Published: November 2010

Vanillate esters such as n-hexyl vanillate (HV) dissolved in a suitable chelating agent - e.g., o-ethoxybenzoic acid (EBA) - react with zinc oxide, aluminum oxide, and hydrogenated rosin powder to yield non-eugenol-containing cements that do not inhibit polymerization and are compatible with acrylic monomers. These cements can be modified by adding methyl methacrylate, or the less-volatile, higher-molecular-weight dicyclopentenyloxyethyl, or cyclohexyl methacrylate to the HV-EBA liquid, and silanized glass to the powder. On incorporating a suitable initiator-accelerator system, one can prepare powder-liquid mixes that have good working properties and harden in five to 10 min. The cured materials containing monomethacrylate ingredients have compressive and tensile strength one and one-half to three times that of eugenol-based intermediate restoratives. Cements with even better mechanical properties are obtained using dimethacrylates as monomeric components. Storage stability of the liquids comprising vanillates-EBA and monomethacrylates is excellent. The vanillate-EBA-dimethacrylate liquid containing amine accelerators polymerizes within days when left standing at 45°C The cement composites adhere strongly to composites, non-precious metals, or porcelains. Rupture of the bond occurs cohesively within the cement. Because of their high strength, low solubility, and excellent adhesion, these cements, subject to their biocompatibility with dental tissues, show great promise as intermediate restorative resins and in the repair of fractured porcelain or porcelain-to-metal crowns and bridges.
Oxide Compounds on Ni-Cr Alloys
Authors: Baran G.R.
Published: November 2010

Five Ni-Cr alloys were studied in order to identify the compounds formed on the alloy surface during oxidation under conditions similar to those encountered during dental laboratory procedures prior to application of porcelain. After the alloys were oxidized, the films covering the surfaces were removed with the aid of a Brmethanol solution. X-ray diffraction was used to analyze the compounds formed.

Oxides of nearly all elements contained by the alloys were found after low-temperature (650°C) oxidation, while NiO and particularly Cr203 were predominant after oxidation at high temperatures (1000°C).
Measurement of Oxide Adherence to PFM Alloys
Authors: Mackert J.R. , Parry E.E. , Hashinger D.T. , Fairhurst C.W.
Published: November 2010

A method has been reported for evaluating adherence of an oxide to its substrate metal to a maximum value of about 40 MPa. Oxidized alloy plates were cemented between two aluminum cylinders with a high-strength cyanoacrylate cement and loaded in tension until failure occurred either at the oxide/metal interface, within the oxide layer, or in the cement itself. Significant differences were found among the oxide adherence values obtained from different PFM alloys. The oxides formed on five of the alloys exhibited adherence strengths in excess of the published value for cohesive strength of dental opaque porcelain, indicating that they possess sufficient adherence to act as the transition zone between the porcelain and the alloy. In addition, a correspondence was found between the quality of porcelain bond for a given alloy and its oxide adherence strength. These results remove the principal objection to the oxide-layer theory of porcelain bonding in dental alloy systems and emphasize the importance of oxide adherence in the establishment of a bond. It is therefore suggested that future work devoted to porcelain-metal bonding should seek to elucidate the mechanism of oxide adherence to PFM alloys and explore the development of new alloys which form adherent oxides.
Effects of Sequential Calcium Phosphate-Fluoride Rinses on Dental Plaque, Staining, Fluoride Uptake, and Caries in Rats
Authors: Shern R.J. , Chow L.C. , Couet K.M. , Kingman A. , Brown W.E.
Published: November 2010

Oral rinses which included (1) an acidic calcium phosphate solution containing 0.7 M Ca, 1.9 M PO4, and saturated with respect to CaHPO4 · 2H 2O, and with a pH of 2.0, followed by (2) a 0.52 M fluoride solution, from NaF or SnF2, were provided to rats once daily for seven days. The investigation consisted of two studies: In the first study, the amounts of dental plaque on the tooth surfaces and fluoride concentrations in the outer enamel were assessed seven days after the last treatment; in the second study, the extent of dental caries was evaluated seven weeks after the last treatment. All rinse sequences containing fluoride provided significant caries protection. The acidic calcium phosphate treatment markedly enhanced the ability of the enamel to acquire fluoride without change of surface morphology. Only the rinse sequences that included stannous fluoride showed significant plaque suppression.
An in vivo Investigation of the Fluoride Uptake in Partially Demineralized Human Enamel from Several Different Dentifrices
Authors: Reintsema H. , Schuthof J. , Arends J.
Published: November 2010

In this study, the total fluoride uptake in partially demineralized enamel from in situ brushing with six dentifrice systems was investigated in vivo among 22 panelists. Five dentifrices with different fluoride systems were compared with a placebo control. Two demineralized enamel discs were placed in proximal positions on specially fabricated dentures worn by each participant. Each treatment involved use of the placebo dentifrice for one week, followed by two weeks of twice-daily use of the test dentifrice.

The F- contents of the dentifrices were: A = 1000 ppm F as Na2P03F + 450 ppm F as NaF; B = 1100 ppm F as NaF; C = 1000 ppm F as Na 2PO3F; D = 1000 ppm F as SnF2; E = 1500 ppm F as Na2PO3F; and P = 0 ppm F (placebo). The F- uptakes from A, C, D, and E were not significantly different from each other but were all significantly higher than the placebo. Statistical analysis showed a significantly higher F- level from the NaF-based paste B than that from all other systems. No differences existed between mesial-distal specimens; there was no correlation between F- uptake and age. Significant uptake differences were found between panelists with full and partial prostheses.
Lysozyme-mediated De-chaining of Streptococcus mutans and Its Antibacterial Significance in an Acidic Environment
Authors: Iacono V.J. , Byrnes T.P. , Crawford I.T. , Grossbard B.L. , Pollock J.J. , MacKay B.J.
Published: November 2010

The ability of physiological amounts of lysozyme to de-chain two serotype c strains of Streptococcus mutans was determined. Both human and hen lysozymes were equally effective in chain breakage of S. mutans DPR and S. mutans DJR. De-chaining did not affect growth of cultures, but resulted in finely dispersed suspensions, at stationary phase, which were visibly different from untreated cultures. Less than 50 μg lysozyme per ml culture medium reduced chain length to virtually all diplococci and single cells, and this chain disruption increased total viable cell count. De-chaining required an active enzyme indicating that a degree of hydrolysis of the peptidoglycan occurred at the septae of the streptococci. Dechained S. mutans did not survive as well as streptococci of normal chain length when incubated under acidic conditions (pH 5.5), but gross cellular lysis was not apparent. The reduced aciduric property of the disrupted chains may have been due to a participation of autolysins or to a lethal reaction triggered by the lysozyme-damaged peptidoglycan. De-chaining may be a mechanism by which lysozyme could regulate the levels of S. mutans in acidogenic plaque samples.
Materials Science
Authors: Sutow E.J. , Jones D.W. , Hall G.C. , Milne E.L.
Published: November 2010

A conventional (γ 2-containing) dental amalgam was fatigue-tested at 1800 and 80 cycleslmin, employing uni-axial, sinusoidal loading, with R = -8. Compressive, tensile, and creep tests were conducted to characterize the alloy's static mechanical behavior. Tests were performed at 37°C on specimens which were aged for seven days, at 37°C. Fatigue-tested specimens were microscopically examined for fracture surface appearance and crack path. The amalgam demonstrated a frequency dependence and a significant reduction in fracture strength due to fatigue loading. The fatigue crack path was primarily intergranular in the γ 1 phase and inclined at approximately 45° to the principal stress axis. These observations are characteristic of some metals when subjected to low-frequency, elevated temperature testing where significant grain boundary sliding occurs, and therefore suggest a creep-fatigue interaction for this alloy.
Glycylprolyl Dipeptidylaminopeptidase from Bacteroides gingivalis
Authors: Abiko Y. , Hayakawa M. , Murai S. , Takiguchi H.
Published: November 2010

Dipeptidyl aminopeptidase activity was found in the culture medium of Bacteroides gingivalis 381. The enzyme, hydrolyzing glycylprolyl-4-methylcoumaryl-7-amide, was purified 750-fold from culture medium by ammonium sulfate precipitation, Sephadex G-200 gel filtration, and DEAE Bio Gel A column chromatography. The molecular weight, determined by gel filtration, was approximately 160,000. The isoelectric point of the enzyme, estimated by isoelectric focusing using polyacrylamide disk gel electrophoresis, was about pH 6.2. The optimum pH of the enzyme was about 8.0, and the Km value was 0.05 mM. The enzyme activity was strongly inhibited by phenylmethylsulfonylfluoride and diisopropylfluorophosphate. The purified enzyme specifically cleaved glycylprolyl dipeptide from partially digested type I collagen.
Clinical Science The Prevalence and Significance of Yeasts in Persons Wearing Complete Dentures with Soft-lining Materials
Authors: Wright P.S. , Clark P. , Hardie J.M.
Published: November 2010

Fifty-three persons wearing soft-lined mandibular dentures and heat-cured acrylic-resin maxillary dentures were studied, using imprint cultures, to determine the isolation frequency and density of colonization of denture and mucosal surfaces by yeasts. Yeasts were isolated from 35 (66%) of the persons studied. Nine species of Candida and one each of Trichosporon and Saccharomyces were identified. Candida albicans, occurring either alone or together with another strain, was identified in 66% of the isolates and was associated with a higher mean density/cm 2 than that of other strains. An association between the method of denture cleaning, denture hygiene, and smoking habits and the isolation of yeasts was demonstrated, but a similar association could not be demonstrated with the sex of the person, denture-wearing habits, type and condition of the soft lining, or the clinical appearance of the mandibular denture-bearing mucosa.

Although yeasts are more likely to colonize soft-lining materials than the fitting surface of conventional lower dentures, their presence did not significantly affect the soft-lining material. Further, the increased isolation of yeasts on the fitting surface of the soft-lined mandibular denture was not associated with an increased incidence of inflammatory changes in the mandibular denture-bearing mucosa.
Malocclusion, Masticatory Muscle, and Temporomandibular Joint Tenderness
Authors: Bush F.M.
Published: November 2010

The Angle classification of occlusion, as well as occlusal contacts determined at retrusion, mediotrusion, laterotrusion, and protrusion were recorded from 298 dental students. Various masticatory muscles and the TM joints were palpated simultaneously for tenderness.

No significant relationships were observed between (1) tenderness and Angle class or (2) tenderness and any occlusal contact.

In relation to a slide between retruded contact position and intercuspal position: measurements for (a) vertical and (b) horizontal displacements, but not (c) lateral deflection, were greater in Class I students without tenderness than in Class I students with tenderness.
Time-dependent Deformation of Composite Restorative Materials in Compression
Authors: Cock D.J. , Watts D.C.
Published: November 2010

The strain of six composite resins, including microfine and conventional types, has been measured in compression as a function of time. Compressive loads have been used in separate experiments to produce a wide range of applied stress in samples of clinically-appropriate size. The magnitude of visco-elastic response generally decreases with increasing % of filler in the composite. Additionally, the very substantial linear strain, up to 20%, observed in some microfine composites suggests the visco-elastic deformation of both organic filler, as well as resin matrix, at high stress levels. Caution is therefore indicated with regard to the clinical use of microfine restorative materials in high-stress-bearing situations.
Reduction of Acidurance of Streptococcal Growth and Glycolysis by Fluoride and Gramicidin
Authors: Bender G.R. , Thibodeau E.A. , Marquis R.E.
Published: November 2010

The acidurance of glycolysis by intact cells of Streptococcus mutans GS-5, Streptococcus salivarius ATCC 25925, and Streptococcus sanguis NCTC 10904 was found to be highly dependent on membrane functions affected by gramicidin, which increases the proton permeability of cell membranes. Plots of % glucose utilized during two hours against suspension pH values for cells suspended in 100 mM phosphate buffer plus 1 mM MgCl 2 plus 13.9 mM glucose indicated, for 50% glucose utilization, pH values of 5.0 for S. mutans, 5.7 for S. salivarius, and 6.2 for S. sanguis. Gramicidin treatment shifted these values to 6.0, 6.3, and 6.9, respectively.

Growth of S. mutans and S. salivarius in complex media proved to be more acid-sensitive than was glycolysis, and in batch cultures, there was a well-defined, post-growth phase of glycolysis. Minimum pH values for growth and for glycolysis in medium with excess glucose were approximately 4.8 and 4.4, respectively, for S. mutans, and 4.9 and 4.3 for S. salivarius. S. sanguis was less aciduric and showed little differential acid sensitivity, with minimum pH values of about 5.2 for both growth and glycolysis.

Fluoride acted to eliminate the differences in acidurance of growth and glycolysis for S. mutans or S. salivarius and to render both processes more acid-sensitive. Thus, glycolysis was more fluoride-sensitive than was growth. Growth was found to be acid- limited in media with initial glucose levels greater than 0.2, 0.3, and 0.5% (weight/volume) for S. sanguis, S. mutans, and S. salivarius, respectively, and to be glucose-limited at lower levels. When 1.0 mM NaF was added to the media, the acid-sensitizing effect of fluoride was evident in major shifts in the initial glucose levels for transition from glucose-limited to acid-limited growth to 0.1 and 0.2% for S. mutans and S. salivarius, respectively. S. sanguis was less severely affected by fluoride.

Fluoride treatment of glycolyzing cells of S. mutans at a pH value of 5 resulted in little change in intracellular levels of phosphoenolpyruvate but increased levels of 2-phosphoglycerate, indicative of inhibition of intracellular enolase. However, there were also large decreases in levels of early glycolytic intermediates, to about the levels found in starved cells, presumably due to fluoride inhibition of glucose uptake.
The Effects of Different Concentrations of Sucrose, Fructose, and Glucose on pH Changes by Streptococcus mitior in an Artificial Mouth
Authors: Lagerlof F. , Dawes R. , Dawes C.
Published: November 2010

The aim of this study was to determine the effects of the initial sucrose (S) concentration, as well as those of fructose (F), glucose (G), and invert sugar (F/G), on the pH developed by a layer of S. mitior, to represent dental plaque, in an artificial mouth which simulates the process of oral sugar clearance.

At S, F. G, and F/G concentrations of 2% and with normal oral sugar clearance rates, the bacteria produced a smaller pH fall from S than from the other sugars; at initial concentrations of 20%, however, the differences were not significant. With constant S concentrations of 0.5 - 35%, the minimum pH reached was 4.03 ± 0.14 (S.D.); with S concentrations of 50% and above, slightly but significantly higher values (4.41 ± 0.34) occurred. However, with normal sugar clearance, the pH fall was much less than with a constant concentration and was dependent on the S concentration over the range of 0 - 10%, but was independent at higher concentrations.

Exposure of the bacteria to S for as short a period as two min during normal sugar clearance gave a nearly maximum pH fall. This suggests that rinsing the mouth with water more than two min after consumption of sucrose in liquid form will have very little effect in reducing the pH fall in dental plaque. A more appropriate method for reducing acid formation by dental plaque would be consumption of a salivary stimulant which would increase the flow rate and buffer capacity of the saliva.
Some Physico-chemical Properties of Deciduous Enamel of Children with and Without Pre-natal Fluoride Supplementation (PNF)
Authors: LeGeros R.Z. , Glenn F.B. , Lee D.D. , Glenn W.D.
Published: November 2010

Physico-chemical investigations of enamel from deciduous teeth of a small number of children with and without pre-natal fluoride supplementation (PNF) exhibited the following differences between the PNF and non-PNF enamel, with the former showing: (a) more homogeneous and less extensive patterns of acid-etching; (b) denser crystal populations in intra-prismatic regions; (c) larger prism dimensions; (d) greater total mineral density (wt% ash); (e) higher degree of crystallinity; (f) smaller a-axis dimensions; and (g) more fluoride and less carbonate contents. On the basis of these preliminary findings, further studies with larger numbers of samples would seem appropriate.
Effect of Oral Nutrient Limitation of Gnotobiotic Rats on Acidogenic Properties of Dental Plaque Formed by Oral Streptococci
Authors: Van Houte J. , Russo J.
Published: November 2010

The acid production rate of dental plaque, formed by different streptococci in gnotobiotic rats fed a high sucrose diet or starved for seven or eight days, was determined in vitro. Starvation had no appreciable effect on acid production. This supports the idea that the small pH-lowering ability of plaque of caries-free or stomach tube-fed people in whom exposure of the teeth to fermentable carbohydrate is relatively low or negligible results from a change in the bacterial population rather than a change in the rate of acid production by an unaltered flora.
Corrosion Evaluation of Gold-based Dental Alloys
Authors: Corso P.P. , German R.M. , Simmons H.D.
Published: November 2010

Three commercial gold-based dental alloys and three constant-nobility ternary alloys (Au-Ag-Cu) were evaluated for corrosion using a quantitative test battery. Integration of the current density, in a de-aerated solution of 1% NaCl along the approximate potential range found in the mouth (-300 m V to +300 m V vs. SCE), yields a quantitative rank ordering of the test alloys. The results are combined with prior findings on other commercial alloys to demonstrate the interaction of nobility and microstructure. Nobility determines the overall corrosion resistance for gold-based alloys. However, because of mutual insolubility, alloying with copper induces silver segregation, resulting in a higher corrosion rate at a given nobility. Thus, microstructure has an influence on corrosion, but heat treatments are largely ineffective in altering the basic corrosion characteristics. The test techniques, in combination with tarnish evaluations, provide a quantitative battery for alloy evaluation. The results indicate the combinations of nobility, microstructure, and environment most likely to avoid corrosion difficulties.
Contribution of Extracellular and Intracellular Calcium to the Enhanced Effect of an a-Adrenergic Agonist on Amylase Release from Dispersed Rat Parotid Cells
Authors: Takemura H. , Ohshika H.
Published: November 2010

The role of calcium in the potentiation of amylase release by the α-adrenergic agonist methoxamine (MTX) was examined using dispersed rat parotid acinar cells. The stimulatory effect of MTX (10 μM) on the β-adrenergic agonist isoproterenol (ISP, 1 μM)-induced amylase release was blocked by the α-adrenergic antagonist phentolamine (10 μM). In Ca-free (1 mM EGTA) medium, the increment of amylase release by MTX in normal medium was decreased by about 70%, but MTX still potentiated ISP-induced amylase release, MTX did not affect the cyclic AMP accumulation activated by ISP in either normal or Ca-free medium. MTX enhanced the ISP-stimulated uptake and efflux of45Ca2+. These results suggest that both extracellular Ca2+and intracellular stored Ca2+may play an important role in the potentiation of amylase release from rat parotid acinar cells.
Identification and Characterization of Rabbit Buccal Mucosal Hyaluronidase
Authors: Bertolami C.N. , Ellis D.G.
Published: November 2010

This study establishes the existence of a mammalian buccal mucosal hyaluronidase having properties typical of a lysosomal enzyme. Mucosal hyaluronidase exhibited a distinct substrate preference for hyaluronic acid, generated saturated de-polymerization products by endoglycosidic hydrolysis, and possessed a pH optimum of 3.5 and an isoelectric point of 5.9.
Economic Specification of Cost Estimates in Dental Programs
Authors: Doherty N.J.G. , Crakes G.M.
Published: November 2010

This paper compares two approaches to the estimation of costs in dental care programs: a conventional approach and an approach based on theoretical expectations. The conventional approach typically uses a linear extrapolation of an average figure - e.g., cost per visit - over various program sizes and thus predicts constant costs. Constant costs are, however, theoretically implausible, and it should be anticipated that their use in program planning or analysis would generate biased estimates. This hypothesis is examined using annual costs and visits from a group of uniform clinics over a five-year period. Results show that costs calculated by the conventional method are underestimated at low volumes and increasingly overestimated at higher volumes. The findings, which illustrate how inefficiency can inadvertently be incorporated into program design, have implications for cost-effectiveness of dental care delivery in the public sector.
Materials Science Photo-oxidation of Tetracycline Adsorbed on Hydroxyapatite in Relation to the Light-induced Staining of Teeth
Authors: Davies A.K. , Cundall R.B. , Dandiker Y. , Slifkin M.A.
Published: November 2010

In an attempt to understand the chemistry of the light-induced staining of children's teeth by tetracycline, we studied the photochemical behavior of tetracycline adsorbed on hydroxyapatite, as a simple model of enamel. Tetracycline was strongly bound by hydroxyapatite to give a pale yellow material which, under ultraviolet light, showed a bright yellow fluorescence (λmax 525 nm). On exposure of this material to the radiation from a medium-pressure mercury lamp, the fluorescence gradually disappeared, and a red-purple product was formed. Photo-acoustic spectroscopy was employed to follow the disappearance of tetracycline and the concomitant formation of the red-purple product, the spectrum of which (λmax 530 nm) led to the conclusion that it was 4α, 12α-anhydro-4-oxo-4-dedimethylaminotetracycline (AODTC). This assignment was supported by the observation that 1 mole of oxygen was absorbed per mole of adsorbed tetracycline converted to the red-purple product.

It is suggested that the formation of AODTC on hydroxyapatite probably takes place by a mechanism of photo-oxidation similar to that already proposed for solutions of tetracycline, and that the formation of AODTC in children's teeth is responsible for the light-induced staining caused by tetracycline.
Antigenic Variation of Indigenous Streptococci
Authors: Beem J.E. , Clark W.B. , Bleiweis A.S.
Published: November 2010

Isolates of Group D streptococci indigenous to the murine oral cavity were studied to detect the occurrence of antigenic variation. Group D streptococci cultured from molar homogenates of Balb/c mice were randomly selected for study on the basis of distinctive colony morphology. Isolates obtained over a 12-week period were biotyped using the API 20S system, and subjected to Lancefield extraction and rocket immunoelectrophoresis for serotyping. All isolates were compared with an arbitrarily selected standard test strain (W1S-1) isolated the first week of the first experimental series. Four biotypes were encountered during the first week of two experimental series. Two very unusual biotypes detected during the first experimental series persisted throughout that series, as did two more common biotypes throughout the second experimental series. Anti-W1S-1 serum produced three precipitin bands (antigens O, D, and K) against WIS-1 Lancefield extract and against the respective biotypes detected during the first week of the two series. Of the three antigens detected, only the group antigen (D) did not vary during either experimental series. Antigenic variants lacking the O or K antigen and bearing these distinctive phenotypes were repeatedly isolated in subsequent weeks. Ultimately, 16% of 190 strains isolated during the first series and 26% of 167 strains isolated during the second series proved to be antigenic variants of the predominant biotypes detected in both series.
Prevalence of Dental Fluorosis after Fluoride-gel Treatments in a Low-fluoride Area
Authors: Joost Larsen M. , Kirkegård E. , Fejerskov O. , Poulsen S.
Published: November 2010

The goal of the present investigation was to study whether periodic use of fluoride-gel treatments resulted in an increased prevalence of dental fluorosis. 269 children, from 14 to 16 years of age, who had received semi-annual or quarterly fluoride-gel treatments were examined for possible fluoride-induced enamel changes. Further, in order to determine the amount of fluoride retained during the gel treatment, the expectorate was analyzed in 18 younger children presently participating in the prophylaxis program. It was found that the retention of fluoride averaged 7.3 mg per treatment (up to 0.5 mg fluoride per kg body weight). An increased prevalence of dental fluorosis was not observed, even after up to five yearly treatments were given during tooth formation periods. The background prevalence of dental fluorosis in a low-fluoride area in Denmark is described.
Fluoride Uptake in Plaque-Covered Enamel after Treatment with the Fluoride Lacquer Duraphat®
Authors: Hellwig E. , Klimek J. , Schmidt H.F.M. , Egerer R.
Published: November 2010

The amount of alkali-soluble and alkali-insoluble fluoride was determined in human enamel after one- and six-hour treatments with Duraphat®. The application was carried out on: (1) slightly demineralized enamel covered with artificial plague. (2) cleaned, slightly demineralized enamel, and (3) sound enamel without pre-treatment. After a single Duraphat® treatment lasting six hours, fluoride uptake was higher than after Duraphat® treatment for just one hour in all experimental groups. More fluoride was acquired in both slightly demineralized, plaque-covered and slightly demineralized, cleaned enamel than in sound enamel. Plaque significantly hampered the formation of alkali-soluble fluoride precipitation on demineralized enamel, but its influence on the amount of fluoride taken up by the enamel was minor.