bluuebunny/crossref_metadata_2025 huggingface dataset:
An Autoradiographic Study of Periodontal Development in the Mouse
Authors: Osborn J.W. , Price D.G.
Published: November 2010

Tritiated thymidine was injected into 10- and 13-day-old mice because at this age the third molar is at the appropriate stage of development. At set intervals, the mice were killed and the distribution of labeled cells within the dental papilla and follicle examined. The change in labeling index with time was measured for defined areas in the papilla and follicle. It was shown that, during the late bell stage of development, cells moved from the papilla into the follicle. It was concluded that the pulp, rather than the investing layer of the follicle, is the source of the periodontium and that growth of the pulp and periodontal tissues could generate an important force contributing to tooth eruption.
Comments on the Clinical Application of Fibronectin in Dentistry
Authors: Pearson B.S. , Klebe R.J. , Boyan B.D. , Moskowicz D.
Published: November 2010

Several studies have demonstrated that citric acid demineralization of the root surface promotes tissue attachment. Since demineralization exposes collagen to which fibronectin binds, the role of fibronectin in the attachment of cells to the tooth surface has been of considerable interest. It is clear that fibronectin and other cell adhesion proteins can promote cell attachment to the tooth surface; therefore, attempts have been made to utilize these findings in a clinical setting.

Using a quantitative ELISA procedure to measure the binding of fibronectin to demineralized bone and tooth, we have found that I μg fibronectin can saturate approximately 1 mg of either demineralized bone or demineralized tooth powder. Since serum contains 300 μg fibronectin per mL, the bleeding that occurs during oral surgery should saturate exposed tooth surfaces with amounts of fibronectin adequate for cell adhesion. Thus, exogenous fibronectin would appear to be of little clinical benefit.
Production and Characterization of Monoclonal Antibodies Against Bacteroides forsythus and Wolinella recta
Authors: Werner-Felmayer G. , Guggenheim B. , Gmür R.
Published: November 2010

Hybrid cell lines producing monoclonal antibodies against Bacteroides forsythus or Wolinella recta were generated by fusion of SP2/0 or FO myeloma cells with splenocytes from Balb/c mice immunized with formalinized cells of B. forsythus FDC 331 or W. recta D13a-g, respectively. Enzyme-linked immunosorbent assays and indirect immunofluorescence tests were used to analyze the distribution of the recognized antigens on a panel of 70 strains representing 35 taxa, most of which are members of the oral flora. All monoclonal antibodies-eight against B. forsythus and six against W. recta-proved specific for the immunizing species. Four of the monoclonal antibodies against W. recta recognized antigens expressed by only some of the tested W. recta strains, thus confirming the earlier noted antigenic heterogeneity of this species. Antibody binding patterns consistent with those previously described or distinct for new serogroups could not, however, be observed. Four of the eight anti-B. forsythus monoclonal antibodies bound to only two of the three tested B. forsythus strains. All the remaining monoclonal antibodies detected every strain tested of the respective species against which they were raised. Preliminary results indicated that several of these antibodies should be very useful for the direct identification and quantification of these organisms in subgingival plaque.
Wear and Microhardness of a Silver-sintered Glass-Ionomer Cement
Authors: McKinney J.E. , Antonucci J.M. , Rupp N.W.
Published: November 2010

Knoop Hardness and pin-and-disc-wear measurements were made on a commercial silver-sintered glass-ionomer cement. The objective was to determine whether the incorporation of a bonded-metal-to-glass filler would enhance durability as determined by the above measurements. As with the previous work on conventional (non-metalized) glass-ionomer cements, the specimens were preconditioned at 37°C in air, water, 0.02 mol/L lactic acid (pH 2.67), and heptane. The influence of these media on the microhardness of the silver-sintered material was about the same as that on the conventional materials. Storing in air produced dehydration, which increased the hardness considerably. Heptane storage increased the hardness less, but this increase is attributed to continued curing during storage. After storage in water, the hardness was essentially unchanged; the influence of increased cure is believed to be offset by softening or plasticization from water uptake. Lactic acid produced a decrease in hardness from chemical dissolution as seen from the SEM observations. In most cases, in particular for the air-stored specimens, the wear resistance was enhanced markedly over that of the conventional materials evaluated previously. The exception was the lactic acid-stored specimens for which little, or no, improvement was observed during early periods of wear. The incorporation of silver appeared to provide lubrication, thus reducing wear. However, catastrophic failure from brittle fracture was still a problem, but its occurrence was less frequent.
Influence of Filler Type and Water Exposure on Flexural Strength of Experimental Composite Resins
Authors: Calais J.G. , Soderholm K.-J.M.
Published: November 2010

The objective of this investigation was to determine the influence of water exposure on the flexural strength of three experimental composite materials. The composites consisted of an experimental resin system which contained silane-treated filler particles of quartz, barium glass, and porous silica. The amorphous silica particles were spheres approximately 5 μm in diameter. In addition to the different composites, pure resin samples were investigated as a control group.

The results of this investigation did not support the hypothesis that use of porous amorphous silica filler particles reduced the hydrolytic degradation effect of composites containing such silica particles. Instead, the results indicated that water may have a more detrimental effect on the strength of the matrix than on the filler-matrix interface. However, the relatively high frequency of fracture lines in the porous silica particles after storage in water indicate that water had a weakening effect on this type of filler.
A Case-Control Study of Plasma Ascorbate and Acute Necrotizing Ulcerative Gingivitis
Authors: Melnick S.L. , Alvarez J.O. , Navia J.M. , Cogen R.B. , Roseman J.M.
Published: November 2010

Data from animal studies and from studies of patients with acute necrotizing ulcerative gingivitis (ANUG) have provided suggestive evidence for an association between ascorbate deficiency and disease risk. Further, there is biological plausibility for such an association, due to the role of ascorbate in collagen synthesis and leukocyte function. A case-control study of plasma ascorbate and ANUG was performed on 60 patients with a history of ANUG infection and 60 age-race-sex-matched controls. No cases had had active lesions for at least two months prior to their vitamin assay to avoid any potential reduction of dietary intake of ascorbic acid due to the presence of painful mouth lesions. According to results obtained by use of a modification of the 2,4-dinitrophenylhydrazine method for determination of total plasma ascorbate, the mean and standard error of the mean of plasma ascorbate for all ANUG cases was 0.07 ± 0.006 mmol/L; the mean for all controls was 0.10 ± 0.006 mmol/L. Paired differences in plasma ascorbic acid concentrations between cases and controls were significantly different from zero (p < 0. 001). The unadjusted relative risk (RR) of ANUG as obtained by conditional logistic regression for subjects whose plasma ascorbic acid concentration was at or below the median value for controls, relative to subjects with higher values, was 7.3 (90% confidence interval, 3.0 - 17.4; one-sided p value < 0.001). Patients with a history of ANUG ingested a daily average of 1.2 ± 0.2 servings of dietary ascorbic acid, as compared with a daily average of 1.9 ± 0.2 servings for healthy controls. The significant RR of ANUG for decreased plasma ascorbate persisted after data were adjusted for dietary intake (RR = 6.6 ; 2.7 - 16.1; p = 0.016). Similarly, smoking status only partly explained ascorbate differences, with a RR of ANUG of 4.4 (0.9 - 20.2 ; p = 0.057) adjusted for smoking. Adjusting for social class differences between cases and controls, however, explained the observed differences (RR = 1.00). We conclude that the significant association between decreased plasma ascorbate and ANUG even after healing of initial lesions was as hypothesized, although a causal interpretation of the findings was obscured by social class differences between cases and controls.
Quantification of Free Water in Human Dental Enamel
Authors: Bonte E. , Deschamps N. , Goldberg M. , Vernois V.
Published: November 2010

The amount of free water in 50 samples of air-dried enamel from permanent and deciduous teeth was measured by the Karl Fischer method. Samples included both contemporary and burial specimens. The mean values obtained showed that free water constituted about 1% of enamel mass. However, the range of individual values varied considerably, from 0.56 to 1.48%. The proportion of free water did not seem to depend on the patient's age, the type of tooth, or the relationship between the tooth and its oral environment. On the other hand, the deciduous enamel tested displayed a mean free water content that was three times the mean for the permanent teeth (3.01 vs. 1.00%) and the five burial teeth, a mean content of 1.68%.
Eminence Development of the Postnatal Human Temporomandibular Joint
Authors: Nickel J.C. , McLachlan K.R. , Smith D.M.
Published: November 2010

The objective of this study was to analyze postnatal eminence development quantitatively, as a first step in defining the relationship between loading of the TMJ and eminence development.

A sample of human osteological remains provided the temporal bones of forty-nine (49) individuals of ages between birth and twenty years. An angular measurement technique permitted quantification of the degree of eminence development of each individual. It was concluded that: (i) the TMJ eminence reaches more than 50% of mature size, and exhibits mature morphology, by the time of completion of eruption of the primary dentition; (ii) the maximum velocity of development of the eminence takes place before three years of age; and (iii) the velocity of development of the eminence is reduced at about five years of age, and slowly diminishes to zero by the middle to late teens.
Fracture Mechanics Parameters for Failure Prediction of Composite Resins
Authors: De Groot R. , Van Elst H.C. , Peters M.C.R.B.
Published: November 2010

This study contains the first part of a research project in which the applicability of fracture mechanics parameters to predict failure of a restored tooth was investigated. Fracture mechanics parameters have been used in dental research before, but were restricted to comparative studies between various brands of composites. The critical values of the opening mode stress intensity factor (KI), its equivalents, the strain energy release rate (GI), and the J integral (J I), were measured with single-edge notched-bend (SENB) specimens of dental composite in a three-point bend test. The measured values of K Ic for Silux (KIc = 0.99 ± 0.03 MNm-3/2) and P-30 (KIc = 1.88 ± 0.12 MNm-3/2), compared with values from the literature, show quantitative agreement. The J integral was computed by means of finite element analysis (FEA) on a two-dimensional model of the SENB specimens.

The critical value of the J integral (measured with SENB specimens, notch depth-to-width ratio (a/W) = 1/2) was used to predict failure of specimens having an arbitrary geometry. In this study, failure was predicted for SENB specimens with notch depth-to-width ratio (a/W) = 1/4 and 3/4. The predicted deflection and load at failure correspond well with the measured deflection and load.
DICOR® Surface Treatments for Enhanced Bonding
Authors: Bailey L.F. , Bennett R.J.
Published: November 2010

Treatments for preparing castable ceramic surfaces for enhanced bonding to specially formulated resin-based cements were examined. An ammonium bifluoride etch combined with y-methacryloxypropyltrimethoxysilane produced shear bond strengths higher than when an ammonium bifluoride treatment was used alone. The method of curing the silane was highly significant in the contribution to the cement/ substrate bond strength, with the heat-cure producing the highest values. Long-term water storage tests indicated that the cement bond with etch plus silane-treated castable ceramic surfaces (whether heat or chemically cured silane was used) demonstrated no significant decrease in strength after a one-year period.
Time-dependent Changes of Collagen Crosslinks in the Socket after Tooth Extraction in Rabbits
Authors: Kuboki Y. , Hashimoto F. , Ishibashi K.
Published: November 2010

Time-dependent changes of the reducible collagen crosslinks in the healing tissue of rabbit tooth extraction wounds were analyzed chromatographically. The ratio of dihydroxylysinonorleucine to hydroxylysinonorleucine in the collagen from normal alveolar bone was 4.4. This value increased about four times, on the 10th day after tooth extraction, coinciding with the phase of active woven bone formation, and then decreased rapidly toward a normal value on the 14th day after tooth extraction. The data suggest that active biosynthesis and fibrillogenesis of bone collagen precede the morphological completion of lamellar bone formation.
Dentifrice Usage Among Danish Children
Authors: Bruun C. , Thylstrup A.
Published: November 2010

The usage of dentifrice was studied in 179 Danish children of approximate ages 3, 7, 9, and 16 years. The usage was assessed by measurement of the aggregated quantities used at home during a two-week period. Information was also obtained on toothbrushing habits. The mean daily usage with the same brand of dentifrice increased from 1.1 g among 3-year-olds to 1.5, 2.3, and 3.4 g among 7-, 9-, and 16-year-olds, respectively. The amount used showed a significant, positive relationship to the orifice diameter of the tube. However, the lengths of ribbon of paste squeezed out per brushing were quite similar, regardless of tube orifice diameter. When the usage data were considered in light of the fact that young children swallow an average of 15 to 30% of the dentifrice used for brushing, it became obvious that a notable number of the 3- and 7-year-olds can be expected to ingest fluoride from 1000- and 1500-ppm-F dentifrices in quantities exceeding recommended daily doses.
The Effects of Treatment on Masticatory Muscle Activity and Mandibular Posture in Myofascial Pain-dysfunction Patients
Authors: Burdette B.H. , Gale E.N.
Published: November 2010

The purpose of this study was to evaluate tonic masticatory muscle activity and the postural rest position of the mandible, pre- and posttreatment, in patients with TM disorders.

Forty-one patients diagnosed as suffering from myofascial pain-dysfunction (MPD) were evaluated, with electromyography (EMG) used to measure the muscle activity of the masseteric and anterior temporal areas at rest. Postural rest position was assessed by measurement of interocclusal distance. Twenty-three asymptomatic subjects were also tested as controls.

Treatment for the pain group emphasized cognitive awareness of dysfunctional orofacial behavior and biofeedback training of the masseteric area to teach masticatory muscle relaxation.

The pre-treatment EMG values of both the masseteric and anterior temporal areas were significantly higher for the pain group than for the control group. Post-hoc division of the pain group into successful and unsuccessful subgroups was made on the basis of the degree of symptom improvement. EMG activity decreased significantly in the masseters of both subgroups, but only the unsuccessful subgroup showed a significant decrease in anterior temporal activity following therapy. Interocclusal distance was significantly increased in both subgroups.

These results suggest that tonic masticatory muscle activity may be elevated in MPD patients. They also suggest that a decrease in EMG activity in the masseter and anterior temporalis muscles and an opening of the postural rest position of the mandible may accompany completion of psychophysiological therapy, but these changes do not correspond directly with the outcome of that therapy.
Production of Interleukin-1 and Tumor Necrosis Factor by Human Peripheral Monocytes Activated by Periodontal Bacteria and Extracted Lipopolysaccharides
Authors: Lindemann R.A. , Economou J.S. , Rothermel H.
Published: November 2010

Whole Gram-negative bacteria associated with juvenile and adult periodontitis, and their respective extracted lipopolysaccharides (LPS), were tested for the ability to activate quiescent human peripheral blood monocytes. All pathogenic Gram-negative bacteria and all LPS tested were able to induce the production of significant amounts of IL-1 and TNF, monokines known to induce osteoclastic bone resorption. Haemophilus segnis, which has not been associated with any form of periodontal disease, did not activate monocytes. Purified LPS from Actinobacillus actinomycetemcomitans Y4 was able to elicit IL-1 and TNF release at a threshold concentration of 1-10 ng/mL. To examine the mechanism whereby whole bacteria activated monocytes, we added polymixin B in culture with glutaraldehyde-fixed bacteria to bind LPS. This resulted in the abrogation of IL-1 and TNF production. To compare the effects of Gram-positive oral bacteria on monocytes, we also tested Staphylococcus epidermidis and the Gram-positive amphipathic equivalent of LPS, lipoteichoic acid (LTA) extracted from Staphylococcus aureus bacteria. Whereas whole Gram-positive bacteria had no stimulatory effect on monocytes, LTA induced IL-1 and TNF production at a concentration range equivalent to that of the LPS. These results indicate that monocytes are activated by free LPS or LPS bound to Gram-negative pathogenic periodontal bacteria to produce monokines which may contribute to the destruction of periodontal bone.
A Genetic Contribution to Dental Caries, Occlusion, and Morphology as Demonstrated by Twins Reared Apart
Authors: Boraas J.C. , Messer L.B. , Till M.J.
Published: November 2010

The heritability of dental characteristics has been systematically studied in animals, human populations, families, and twins, but not in twins reared apart. Under the assumption that environmental factors are no different for monozygotic twins reared apart than for dizygotic twins reared apart, the present study measured the genetic variance of several dental characteristics in twins reared apart. Ninety-seven subjects (44 twin pairs, three triplet sets) of mean age 40.6 years (S. D. 11. 7) were examined over a six year period by means of clinical and radiographic examinations, study models, and dental history questionnaires. Characteristics assessed retrospectively were: dentate status, treatment status, treatment/caries status, tooth size, malalignment, occlusion, and morphology. Data were analyzed by two-way ANOVA, intraclass correlations, heritability estimates, and concordance. There was statistically significant resemblance within monozygotic but not dizygotic pairs in the number of teeth present (p<0.001), percentage of teeth and surfaces restored (p<0.001), percentage of teeth and surfaces restored or carious (p< 0. 001), tooth size (p < 0. 001), and malalignment (p <0. 009). Intercanine and intermolar arch width showed significant resemblance within both monozygotic (p<0.001) and dizygotic (p <0. 01, p<0.05) pairs, whereas overjet and overbite showed no significant resemblance within pairs. Morphological features (Carabelli's trait and mandibular first premolar groove configuration) were more highly concordant in monozygous than in dizygous twins. This study provides new evidence for a marked genetic component to dentate status and dental caries experience and confirms previous reports of acknowledged inherited contributions to tooth size, malalignment, occlusion, and morphology.
Composition of Human Plaque Fluid
Authors: Moreno E.C. , Margolis H.C.
Published: November 2010

The composition of pooled resting plaque fluid was determined in four groups of college-age students (18-22 years), each composed of 50 individuals, who abstained from oral hygiene for 36 hours and did not eat or drink for at least one hour prior to plaque collection. Plaque samples from each group were pooled under mineral oil in small centrifuge tubes and centrifuged at 37,000 g for one hour at 4°C. Supernatants were then combined under mineral oil and centrifuged at 5000 g (4°C) for 15 minutes. In general, the inorganic composition of plaque fluid in the four groups was quite similar and in agreement with values reported by other investigators, but quite different from those of saliva or serum. The mean composition was: Ca, 7.07 ± 0.51 mmol/L; P, 23.2 ± 5.3 mmol/L; Na, 18.6 ± 2 mmol/L; K, 85.1 ± 5.3 mmol/L; Mg, 3.9 mmol/L; Cl, 42.8 ± 9 mmol/L ; F, -0.004 mmol/L; pH, 5.69 (5.63-6.01). Acetate, propionate, succinate, butyrate, lactate, and formate were determined in two samples analyzed, with acetate and propionate being the predominant acids found. It was also demonstrated, through the titration of one of the plaque fluid samples, that the observed buffer capacity in plaque fluid was mostly related to its organic acid composition. It was noted, however, that when the initial pH in plaque fluid exceeded 6.5, phosphate contributed significantly to the buffer capacity. The contribution of other soluble species (proteins, peptides, amino acids) to the observed buffering in plaque fluid appeared to be small. Calculated ion activity products suggest that plaque fluid is saturated with respect to enamel mineral and dicalcium phosphate dihydrate. This finding is consistent with noted observations of the presence of dicalcium phosphate dihydrate in young calculus.
A Histological Evaluation of a Functional Endosseous, Porous-surfaced, Titanium Alloy Dental Implant System in the Dog
Authors: Deporter D.A. , Watson P.A. , Pilliar R.M. , Howley T.P. , Winslow J.
Published: November 2010

We have previously reported the clinical and radiographic findings of a trial in dogs of a new dental implant system after a functional period of eight months. The present report consists of the corresponding qualitative and quantitative histological data.

The implant system was fabricated from Ti-6A1-4V and employed a porous-surfaced configuration to achieve implant fixation by bone ingrowth. A similar porous surface was used on the apical 1/3 of the transgingival collar in an attempt to gain ingrowth and attachment of gingival connective tissue. The qualitative histological data confirmed that white such attachment to the collar did occur for some implants, in the majority of implants (22 of 32) the parous region of the collar became contaminated with bacterial plaque, resulting in implant failure (four implants) or suggesting future implant failure (18 implants).

Statistical analyses of the quantitative histological data indicated that there were no significant differences in surface contact of bone with the middle third of the porous implant surface (CLF) when initial healing interval (four or eight weeks), implant location, or aspect of implant (buccal vs. lingual vs. mesial vs. distal) were compared. However, comparison of the current group of functional implants with an earlier group of similarly implanted non-functional implants indicated that function produced a highly significant increase in CLF.
Cytotoxicity of Amalgams
Authors: Kaga M. , Seale N.S. , Hanawa T. , Ferracane J.L. , Okabe T.
Published: November 2010

The purpose of this study was to compare the relative cytotoxicity of amalgams and to determine whether their toxicity depends upon composition and aging time, by means of a rapid and sensitive in vitro cell culture test. Zinc-containing amalgams showed higher cytotoxicity than did any other amalgams. High-copper amalgams had the same cytotoxicity as did the low-copper amalgam. The addition of selenium did not reduce the cytotoxicity of amalgam. Moreover, excessive additions of selenium increased the cytotoxicity of amalgam compared with that of a similar selenium-free material. The cytotoxicity of amalgam was decreased with aging time, possibly due to the combined effects of surface oxidation and further amalgamation.
Changes in Bovine Dentin Mineral with Sodium Hypochlorite Treatment
Authors: Sakae T. , Mishima H. , Kozawa Y.
Published: November 2010

Dentin powders from bovine incisors were treated with 10% NaClO solution. Differential thermal analysis (DTA) indicated the removal of organic material from the dentin sample following the treatment, since the exothermic reaction at 320°C had disappeared. X-ray diffraction studies revealed a change in the crystallinity of the dentin crystals and the formation of calcite after the treatment. Infrared absorption analysis showed that the band due to carbonate ions was weakened after the treatment, while atomic absorption spectroscopic analysis showed that magnesium ions had been dissolved from the dentin sample. The a-axis lengths of treated and heated dentin samples differed from those of untreated and heated samples. Whitlockite was always found in the untreated/heated samples, whereas it was absent in the treated/heated samples. The unit cell dimensions of the whitlockite indicated the partial substitution of magnesium for calcium. Magnesium ions seemed to be more effective than carbonate ions in forming whitlockite. These results showed that some magnesium and carbonate ions were removed from the dentin crystal structure upon NaClO treatment, while at the same time organic materials were removed from the dentin sample. It was suggested that crystals in the NaClO-treated dentin were similar to enamel crystals from a crystallographic viewpoint.
Improvement of the Caries Resistance of Human Dental Roots by a Two-step Conversion of the Root Mineral into Fluoridated Hydroxylapatite
Authors: Hoppenbrouwers P.M.M. , Groenendijk E. , Ramlochan Tewarie N. , Driessens F.C.M.
Published: November 2010

Roots of extracted human molars were treated for both 10 and 30 min with a saturated solution of dicalcium phosphate dihydrate (DCPD) of pH 2.4 and subsequently with a 5.3 mmol.L -1 solution of sodium fluoride of pH 7.0. The objective of these combined treatments was to convert the highly-soluble root mineral into the less-soluble fluoridated hydroxylapatite, with DCPD as an intermediate, to improve caries resistance. The mineral content of the surface layer was not affected in a significant way.

Roots treated in this way were subjected to 50 mmol.L-1 acetate buffer solutions of pH 5.5 and with pIOHA-values of 112, 116, and 122. The proportional reduction of the rate of demineralization (Vdem) of similarly treated roots subjected to buffer solutions of pIOHA 112 and 116 appeared to be equal initially. Since fluoridated hydroxylapatite is insoluble under these conditions, these findings are in agreement with expectations. The reduction of Vdem amounted to about 45 and 70% for roots treated for 10 and 30 min, respectively.

When roots were treated for 10 and 30 min and then exposed to buffer solutions with a pIOHA 122, reductions of Vdem of about 30 and 55%, respectively, were found.

Conversion of the root mineral into fluoridated hydroxylapatite can eliminate, in principle, the existing difference in caries susceptibility of the root and of the dental enamel.
Loci and Characteristics of EMG Silent Periods During Masticatory Mandibular Movements in Rats
Authors: Byrd K.E.
Published: November 2010

Frontal plane mandibular movements and the associated superficial masseter EMG signals of six 39-day-old rats were simultaneously recorded and digitized at a rate of 1 kHz by the optoelectronic method in order to investigate the loci and attributes of masseteric silent periods during mastication of hard (pellets) and soft (sluny) food items. The marked silent periods, defined as cessations of EMG activity during the slow-close (SC) phase of single chewing cycles, were analyzed for their (1) onset and offset durations relative to physiological centric occlusion (PCO), (2) frontal vertical (FV) and frontal horizontal (FH) loci relative to PCO, and (3) FV and FH velocities and accelerations of masticatory mandibular movements in relation to PCO. The start (SSP) and end (ESP) of silent period loci relative to PCO moved superiorly as sequences of pellet mastication progressed. All silent period attributes during slurry consumption were significantly different (p ≤ 0.01) from pellet attributes: Sluny SSP and ESP loci were closer to PCO than were pellet loci; durations of silent period loci during pellet mastication were more variable than were slurry durations. FV distance and velocity values for pellets were greater than slurry values; FV accelerations during slurry mastication were greater than with pellets. Although FV velocities during both pellet and slurry mastication decreased at ESP relative to SSP values, their FH velocities at ESP actually increased relative to SSP velocities. Loci attributes of EMG silent periods appeared largely dependent on the consistency of the food item being masticated.
Release of Formaldehyde from Dental Composites
Authors: Øysæd H. , Ruyter I.E. , Sjøvik Kleven I.J.
Published: November 2010

Polymeric composite materials may contain releasable degradation products or unreacted constituents. Release of formaldehyde from nine different composites was investigated by means of HCHO-hydrazone derivative analyzed with high-performance liquid chromatography. Formation of formaldehyde was found in all the investigated materials. The highest concentrations were observed in specimens polymerized in contact with air. A correlation coefficient, r = 0.83, was found between released formaldehyde and the thickness of the unpolymerized surface inhibition layer. The formaldehyde concentrations were reduced when the inhibition layer was removed prior to testing. A continuous release of formaldehyde was evident during the first ten days. The release decreased with time, but was still detectable after 115 days.
Differential Modulation of Adherence of Oral Streptococci by Human Neutrophil Myeloperoxidase
Authors: Miyasaki K.T. , de Camargo P.M. , Wolinsky L.E.
Published: November 2010

In this study, the modulation of adherence of hydrogen peroxide (H2O2)-producing and non-H2O2-producing strains of oral streptococci by the host leukocyte enzyme myeloperoxidase (MPO) was examined. It was found that exposure to MPO decreased adherence of many strains of oral streptococci to saliva-coated hydroxyapatite beads in the presence of exogenous H2O 2 and chloride. The MPO-H2O2-Cl- system increased the adherence of one strain. In the absence of exogenous H 2O2, the MPO-H2O2-Cl- system decreased the adherence of H2O2producing strains only. Glucose increased streptococcal H2O2 production and also increased the anti-adhesive activity of MPO in the absence of exogenous H2O2. We conclude that: (1) host leukocytes can modulate the adherence of oral streptococci via MPO; (2) endogenous production of H 2O2 by the oral streptococci can provide sufficient substrate H2O2 to drive this system; and (3) MPO will exert differential modulatory effects on the adherence of oral streptococci, based in part upon the level of endogenous H2O2 production and in part upon the particular characteristics of the adhesins of the bacteria.
A Scanning Electron Microscope Study of Monkey Maturation-stage Ameloblasts
Authors: Skobe Z. , Prostak K.S. , Stern D.N.
Published: November 2010

The maturation-stage enamel organs of Macaca arctoides and Macaca mulatta were examined in order to determine whether the cells were similar to those of the continuously erupting rat incisor. Tooth buds of the permanent dentition were fixed in fonnaldehyde-glutaraidehyde and post-fixed in OsO4. The enamel organs were separated from the enamel during dehydration, critical-point-dried, metal-coated, and examined in a scanning electron microscope.

The results showed that there were few differences in the morphology of maturation-stage ameloblasts of these primates compared with those of other species reported in the literature. The apical plasma membranes were either smooth- or ruffle-ended, while the later mem branes had maze, microvillous, or ridge configurations, also seen in rats, and an additional configuration of interdigitating bulbous extensions. The blood vessels of the papillaiy layer in monkeys were about 7 μm in diameter, considerably larger than those of the rat.
Bisphosphonate Effects on Alveolar Bone During Rat Molar Drifting
Authors: Hardt A.B.
Published: November 2010

The remodeling of bone during molar drifting and cortical growth in the rat maxilla and the effects of dichloromethylene bisphosphonate (Cl2MBP) on these processes were investigated in 30 age-matched rats. A control group of six rats was killed at 10 weeks of age. Beginning at 10 weeks of age, 12 rats were treated with daily subcutaneous injections of Cl2MBP (10 mg/kg), and 12 control rats were injected daily with normal saline. Six rats of each group were killed at 12 and at 20 weeks of age. All rats were injected with fluorescent bone labels eight and one days before termination. Calcified and decalcified vertical sections through the lingual roots of maxillary molars were prepared for histomorphometry. Bone apposition rates, remodeling activity, and bone cell populations were quantified by image analysis on depository and resorptive surfaces of alveolar bone and on cortical bone surfaces. The drift rates of the first and second molars were calculated.

Results showed that in control animals the drift rate of the first molar exceeded that of the second molar (p < 0.05), supporting a previously proposed mechanism for age-dependent narrowing of interdental bone. Cl2MBP treatment decreased remodeling activity on resorptive surfaces of alveolar bone, despite a transient increase in osteoclasts. Cl2MBP also decreased the osteoblast number and bone apposition rate on depository surfaces of alveolar bone, and reduced the rate of molar drifting (p < 0.05). However, Cl2MBP treatment had no detectable effect on osteoblast number or bone apposition on cortical bone surfaces. These results support the concept that bisphosphonates influence bone formation indirectly through a coupling mechanism which links formation with resorption.
A Rheological Study of the Role of Additives on the Setting of Glass-ionomer Cements
Authors: Hill R.G. , Wilson A.D.
Published: November 2010

The effects of various additives on the setting of the glass-ionomer cement system was studied by means of cone and plate viscometry. The action of (+)-tartaric acid, the most important additive, on the setting reaction depended on its concentration. Low concentrations accelerated the development of viscosity of the cement paste, while high concentrations retarded it. At intermediate concentrations, (+)-tartaric acid had an interesting, uniquely favorable effect on setting characteristics. First, it induced a lag period in the setting process during which the viscosity of the cement paste remained constant. This lag period was followed by a sharp, almost exponential, increase in viscosity. Thus, (+)-tartaric acid was found to have a dual effect on setting, first inhibiting gelation and then accelerating it. The practical effect is to prolong working time and sharpen setting. No other hydroxyacid, not even meso-tartaric acid, combined these advantageous effects. Meso-tartaric acid, for example, repressed the development of viscosity at all stages of the reaction. Other hydroxyacids either accelerated or retarded the development of viscosity throughout the course of the reaction.
The Effects of 1% Pyrophosphate and 0.02% Sodium Fluoride on Artificial Caries Lesions in vivo
Authors: Mellberg J.R. , Petrou I.D. , Deutchman M. , Grote N.
Published: November 2010

We evaluated the potential of a pyrophosphate-fluoride solution to affect the remineralizing-demineralizing equilibrium, i.e., caries-inhibitingl-promoting effects on enamel in vivo. Fifteen subjects carried dentin blocks and enamel thin sections with artificial caries lesions in removable partial dentures for periods of two weeks, during which time they rinsed twice daily in a double-blind, randomized cross-over design with solutions containing (a) 90 ppm F, (b) 90 ppm F and 1% pyrophosphate, or (c) no active agents (placebo). A severe cariogenic challenge provided to the lesions by plaque under a stainless steel mesh cover resulted in the placebo-treated lesions losing 70.2% ± 72.1% mineral. The pyrophosphate rinse with fluoride held the mineral loss to only 28.1 ± 52.8%, while the fluoride rinse without pyrophosphate held the loss to 24.2 ± 50.1%. The differences between the fluoride and placebo results were significant (p < 0.01), but the difference between the two fluoride groups was not.

A large amount of fluoride was deposited in the dentin lesions. In the surface layer, the concentration was increased from 1000 ppm F to more than 2300 ppm F by both fluoride treatments. The concentration of fluoride in both groups of fluoride-treated lesions further increased to more than 3500 ppm F in the approximate center of the lesion before declining in deeper layers toward the level found in the placebo-treated group. The findings from both mineral change and fluoride uptake phases of this study show that in the presence of 90 ppm F, 1% pyrophosphate did not promote demineralization of artificial caries lesions.
Methods of Disinfection of the Water System of Dental Units by Water Chlorination
Authors: Fiehn N.-E. , Henriksen K.
Published: November 2010

The aim of the present study was to develop a simple disinfection method for reducing the content of bacteria in the water system of dental units to an acceptable level. The study was carried out at the Royal Dental College, Copenhagen, on 250 dental units. Samples of the cooling water supplying the ultrasonic scalers and of the water supplying the water glasses were obtained from eight different units representing different parts of the school. Disinfection of the water system was carried out by addition of chlorine to the pipe water near the institution's main water intake. The chlorination of the water was automatically regulated, and the installation was so flexible that the concentration of chlorine and the time and frequency of the chlorination could be varied. Different modes of chlorine dosage were examined. Before chlorination, the bacterial content in the water system of the units was about 104 - 105cfu/mL. It was found that an intermittent chlorination with 0.5-1 ppm chlorine for 10 minutes every day could reduce the normal bacterial counts in the water system to about a few hundred per mL.
Quantitative Study of Fluoride Transport During Subsurface Dissolution of Dental Enamel
Authors: Chu J.S. , Fox J.L. , Higuchi W.I.
Published: November 2010

Previous studies using bovine dental enamel as a model have shown that surface and subsurface dissolution of enamel may be governed by micro-environmental solution conditions. We have now investigated the demineralization phenomenon more rigorously with the primary objective of developing a method for deducing solution species concentration profiles as a function of time from appropriate experimental data. More specifically, in this report, a model-independent method is described for determination of the pore solution fluoride gradients in bovine enamel during subsurface demineralization. Microradiography was used to determine the mineral density profiles, and an electron microprobe technique to determine total fluoride (F) profiles associated with the enamel. In each case, matched sections of bovine enamel were exposed to partially saturated acetate buffers at pH = 4.5 containing 0.5 ppm F for various periods of time (from six to 24 hours). The treated enamel was found to have an intact surface layer and subsurface demineralization. The extent of the demineralization and the depths of the lesions increased with time in all cases. The data were farst used to calculate (a) the total F gradients in the enamel at various times, and (b) the local uptake rate of F as a function of time and position. Then, by manipulation of the equations describing the uptake and transport of F, we calculated the pore diffusion rate of F and the micro-environmental solution F concentration in the aqueous pores as a function of time and of distance from the enamel surface. It was also possible to calculate an intrinsic F diffusion coefficient in the pores, which was about 1.0 × 10-5 cm2/ sec, in good agreement with reported values. 14C-sucrose uptake and release experiments with identically prepared demineralized enamel sections were also conducted to provide an independent check on the assumed dependence of porosity on mineral density. The results of this investigation, especially the outcomes relative to this new method for determination of pore solution F gradients during acid attack of the dental enamel, should be valuable in future studies of the mechanism(s) of the action of F in inhibiting dental enamel demineralization.
Jaw Pain and Stiffness Levels After Repeated Maximum Voluntary Clenching
Authors: Clark G.T. , Jow R.W. , Lee J.J.
Published: November 2010

Ten normal male volunteers performed six maximum voluntary isometric jaw-closing muscle contractions within an 80-minute experimental period. Each individual contraction was sustained until maximum pain tolerance was reached. Before and one, two, three, and seven days after the experiment, the following measures were made: (1) superficial masseter and anterior temporalis muscle tenderness (pain threshold), (2) jaw movement (opening and lateral excursion), and (3) current pain level for the right and left sides of the jaw. In this study, measures of current jaw pain, muscle pain threshold, maximum active opening, and maximum lateral excursions showed no significant post-experimental changes. These results challenge the idea that sustained isometric clenching in healthy male subjects could be used as a model for chronic or even subacute muscle pain, as has been suggested by previous investigators.
Effects of Sustained-release Chlorhexidine Acetate on the Human Dental Plaque Flora
Authors: Schaeken M.J.M. , De Haan P.
Published: November 2010

The aim of this study was to determine the effect on the human dental plaque flora of a varnish containing chlorhexidine diacetate. The in vitro release of chlorhexidine acetate from the varnish preparation was relatively fast on the first day, followed by a substantial decline in the subsequent three days. In a clinical experiment, 26 volunteers were randomly distributed over four experimental groups. After a dental prophylaxis, the subjects were treated with a single application of a placebo varnish (group I), a fluoride varnish (group II), a chlorhexidine varnish (group III), or a fluoride-plus-chlorhexidine varnish (group IV). Saliva and pooled plaque samples from approximal surfaces were taken before (baseline) and one, two, three, four, and six weeks after the treatments.

No suppression was found of total cultivable flora or S. sanguis after the experimental treatments. Application of the fluoride varnish did not suppress the A. viscosus/naeslundii or S. mutans levels in the dental plaque. Chlorhexidine suppressed A. viscosus/naeslundii until two weeks after the treatment. S. mutans was significantly suppressed until four weeks after a single chlorhexidine application. While in some subjects S. mutans was effectively suppressed over the whole experimental period, in others S. mutans recovered quickly. In five subjects in whom S. mutans recovered quickly, the dentition was treated twice with chlorhexidine varnish, with an interval of one week between the treatments. After two chlorhexidine treatments, S. mutans in saliva and on the teeth was suppressed more strongly than after a single treatment. However, the second chlorhexidine treatment could not prevent the return of S. mutans in the approximal areas to its original level.
Protein Dissimilation by Human Salivary-sediment Bacteria
Authors: Reynolds E.C. , Riley P.F.
Published: November 2010

Proteins of known composition and structural characteristics were incubated (1.0 mglmL) with re-suspended salivary sediment (2.5% vl v) in a lactate-salt medium with an initial pH of 5.2 for two hr at 37°C. Hydrolysis of the proteins was monitored by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Hydrogen ion, amines, and ammonia were measured by use of a combined pH electrode, high performance liquid chromatography, and glutamate dehydrogenase, respectively. Of the proteins studied, the caseins αs1, β, and K and the histones H1 and H3 were extensively hydrolyzed by the salivary-sediment bacteria. The hydrolysis of these proteins was attributed to their relative lack of tertiary (folded) structure. The only amine detected was the polyamine putrescine arising from the catabolism of arginine following the hydrolysis of the arginine-rich histone H3. None of the other proteins extensively hydrolyzed by salivary sediment, although containing arginyl and lysyl residues, served as substrates for putrescine or cadaverine production. Pre-hydrolysis of the arginine-rich histone H3 and poly-L-arginine with trypsin resulted in a marked increase in putrescine produced, suggesting that the salivary-sediment proteolytic activity was not "trypsin-like". Incubation of salivary-sediment bacteria with the caseins and the histone H3 resulted in an increase in ammonium ion concentration and an associated decrease in hydrogen ion concentration. The increase in ammonium ion concentration not attributed to arginine hydrolysis was correlated with the content of glutaminyl plus asparaginyl residues of the proteins. The results suggest that amido nitrogen, in the form of glutaminyl and asparaginyl residues of salivary and dietary proteins, is a potential source of nitrogen for oral bacteria and may also play a role in plaque pH homeostasis.
Changes in the Tartrate-resistant Acid Phosphatase Cell Population in Dental Follicles and Bony Crypts of Rat Molars during Tooth Eruption
Authors: Wise G.E. , Fan W.
Published: November 2010

It was the aim of this study to determine the cellular changes that occur in the enamel organ, dental follicle, and surrounding bony crypt of the rat molar prior to and during tooth eruption. By use of light microscope histochemistry to detect cells containing tartrate-resistant acid phosphatase (TRAP), it was seen that TRAP-positive mononuclear cells were present in the dental follicle prior to the onset of eruption (e.g., three days postnatal age) and then declined in number during eruption. Concurrently, TRAP-positive osteoclasts were initially present in large numbers on the surface of the bony crypt surrounding the molars (three days postnatal age) and then declined in number as eruption progressed. Electron microscopy confirmed that these were mononuclear cells and osteoclasts. The results suggest that the mononuclear cells are either precursors of the osteoclasts or perhaps release cytokines that affect osteoclast formation or activity.

Staining for alkaline phosphatase (ALP) activity indicated that at an early postnatal age (secretory stage of amelogenesis), ALP was detected only in the stratum intermedium of the enamel organ, whereas at a later age (maturation phase of amelogenesis), it was present only in the ameloblasts. These results, combined with a survey of the literature, strongly suggest that ALP moves from the base of the enamel organ to the enamel itself over a period of time ranging from pre- to post-eruption.

Rat molars are teeth of limited eruption, and the cellular events that occur in eruption appear comparable with what is seen in dog and human dentition, especially in terms of the cellular events seen in the dental follicle prior to and during eruption. Thus, because rat molars are often more amenable to experimental protocol, they may be a suitable choice for answering questions pertaining to tooth eruption in the dog and in humans.