bluuebunny/crossref_metadata_2025 huggingface dataset:
Materials Science The Relationship Between Hardness and Structure of Pd-Cu-Ga Alloys
Authors: Oden A. , Hero H.
Published: November 2010

Most Pd-Cu-Ga alloys on the market have a yield strength of the order of 1000 MPa, which is too high for an adequate adjustment of the margins of a crown and may promote wear of an opposing natural tooth. In the present work, the structure of a commercial Pd - 10 wt% Cu - 9 wt% Ga alloy has been shown by means of TEM to consist of thin (5-25 nm) laths with two ordered fct phases with the composition Pd 3GaxCu1-x. The c/a ratios in these fct phases are, alternatingly, >1 and <1. The transformation of an fcc structure by short atomic movements into the fct structures occurs rapidly below 500°C, as judged by thermal expansion measurements. Such fct structures are likely to provide substantial resistance to dislocation movement and thus a high yield stress and hardness. By adding 6 wt% Ag to the Pd-Cu-Ga alloy and reducing the Ga and Cu content correspondingly, a predominantly fcc structure occurred with nearly no fct laths. At the same time, the hardness was reduced to approximately half the value for the initial Pd-Cu-Ga alloy.
Incidence and Characterization of Anti-microbial Effects Produced by Actinomyces viscosus and Actinomyces naeslundii
Authors: Tompkins G.R. , Tagg J.R.
Published: November 2010

Sixty-two facultative Actinomyces strains isolated from dental plaque were tested for the production of bacteriocin-like inhibitory effects by a deferred antagonism method. When incubated anaerobically, all isolates produced identical inhibitory patterns against 15 indicator organisms, but under microaerophilic conditions, little inhibitory activity was observed. Activity was not evident after anaerobic incubation on a medium buffered by 0.5% (wlv) calcium carbonate. Gas-liquid chromatographic analyses of agar blocks removed from the inhibitory zones indicated that, compared with microaerophilic conditions, anaerobic incubation encouraged production of high concentrations of lactic and succinic acids, and the concomitant fall in the pH was probably responsible for the inhibitory effects.
Inorganic Pyrophosphatase Activity of Purified Bovine Pulp Alkaline Phosphatase at Physiological pH
Authors: Harada M. , Udagawa N. , Fukasawa K. , Hiraoka B.Y. , Mogi M.
Published: November 2010

At physiological pH, the hydrolytic activity of purified bovine pulp alkaline phosphatase toward phosphorus compounds was observed to be in the order of inorganic pyrophosphate > β-glycerophosphate > phosphorylcholine > p-nitrophenylphosphate > glucose-6-phosphate. Optimum pH of the enzyme toward inorganic pyrophosphate was shown to be 8.5, with around 60% of the activity at pH 7.5. The activity was increased by the addition of Mg2+, but a different pattern of activation was observed between pH 7.5 and 8.5.
Percent Agreement, Pearson's Correlation, and Kappa as Measures of Inter-examiner Reliability
Authors: Hunt R.J.
Published: November 2010

Percent agreement and Pearson's correlation coefficient are frequently used to represent inter-examiner reliability, but these measures can be misleading. The use of percent agreement to measure inter-examiner agreement should be discouraged, because it does not take into account the agreement due solely to chance. Caution must be used in the interpretation of Pearson's correlation, because it is unaffected by the presence of any systematic biases. Analyses of data from a reliability study show that even though percent agreement and kappa were consistently high among three examiners, the reliability measured by Pearson's correlation was inconsistent. This study shows that correlation and kappa can be used together to uncover non-random examiner error.
Variables Affecting Measurements of Vertical Occlusal Force
Authors: Fields H.W. , Proffit W.R. , Case J.C. , Vig K.W.L.
Published: November 2010

Previous studies of occlusal force have provided conflicting results. The purpose of these studies was to determine whether the extent of vertical opening, contralateral occlusal support, or head posture influenced vertical occlusal forces during swallowing, simulated chewing, and maximum biting effort.

Three samples of subjects with normal vertical facial proportions - one each of children, adolescents, and young adults - were evaluated to determine the effects of changes in small (2.5 vs. 6.0 mm) vertical separation of the first molars. A sample of young adults was used to evaluate changes in large (10-40 mm) vertical openings, and a sample of adolescents was used to investigate the effect of contralateral support and head posture. All between-group comparisons were evaluated using non-parametric statistics.

For the small vertical openings, there was significantly more vertical occlusal force at 6.0 than 2.5 mm in children during swallowing and chewing but not during maximum biting effort. In adults, there was significantly more force during swallowing at 6.0 than at 2.5 mm separation, but no differences in chewing or maximum biting. Increasingly large vertical openings resulted in a progressive increase in maximum bite force to a maximum at about 20 mm, followed by a decrease and then a second increase to near-maximum force at about 40 mm for young adults. There were no significant differences in vertical force with or without contralateral support or between flexed, normal, and extended head postures at either of the small openings.
Relationship Between Jaw Movement and Food Breakdown in Human Mastication
Authors: Lucas P.W. , Ow R.K.K. , Ritchie G.M. , Chew C.L. , Keng S.B.
Published: November 2010

Different quantities and sizes of peanuts were offered to six human subjects for mastication at two or three experimental sessions during which jaw movements and chewing cycle duration were measured. The amplitude of vertical movement and cycle duration depended on the position of a chew in a sequence of chews (masticatory sequence). Cycle duration also depended on the position of a given masticatory sequence during the first experimental session, the earlier sequences tending to be longer. Lateral jaw movements fluctuated about a reasonably constant value during a sequence and were unaffected by different food inputs. The amplitude of vertical movements increased markedly with an increase in food weight but was unaffected by change in the initial food particle size. These results were analyzed in the light of previous reports on the comminution of peanuts. It is hypothesized that observed jaw movements were unrelated to food particle size but that the amplitude of each vertical movement depended on the volume of food that was broken by the teeth during the next closing stroke. This food volume was provided and selected by bulk movements of the tongue during the preceding jaw opening.
Dental Caries Prevalence in Texas Schoolchildren Using Water Supplies with High and Low Lithium and Fluoride
Authors: Curzon M.E.J. , Richardson D.S. , Featherstone J.D.B.
Published: November 2010

The effect of lithium (Li) in drinking water on caries prevalence in seven Texas towns was investigated. Children (life-long residents) aged 12-14 years were examined for caries prevalence, as DMFS, in towns with drinking water Li concentrations ranging from 0.0 to 165μg/L and fluoride (F) concentrations ranging from 0.20 to 1.94mgl L. A significant negative relationship was found between F in drinking water and DMFS. When corrected for the F contribution, Li in water supplies showed a positive correlation with DMFS.
A Comparison of Some of the Permeability Characteristics of Intact and Tape-stripped Hamster Cheek Pouches in vitro
Authors: Reid C.O. , Hardcastle J. , Smith C.J.
Published: November 2010

Cheek pouches were removed from anesthetized hamsters and were either tape-stripped or left intact and then mounted in Ussing chambers, where they were bathed in Krebs-Ringer bicarbonate saline.

A potential difference could be measured across all pouches and was stable for over an hour across the unstripped pouches. The electrical resistance across the unstripped pouches was high (8960 Ω.cm2), whereas the resistance across the tape-stripped pouches was significantly lower (p<0.01), suggesting that these pouches are likely to be more permeable than the unstripped pouches.

Reflection coefficients of urea, ethanol, and glycerol were derived by means of streaming potentials. Values for intact pouches were all close to 1 and for tape-stripped pouches were 0.938, 0.822, and 0.509, respectively.

Permeability coefficients for urea and ethanol across intact and tape-stripped pouches were, respectively, 12.5 × 10-9 cm/min; 27.6 x 10-9 cm/min; 2325 × 10 -9 cmlmin ; and 28471 × 10-9 cmlmin.

The hamster cheek pouch has a high electrical resistance; it is an impermeable structure in which the keratin layer appears to provide a major barrier to the passage of water, ions, and certain solutes.
Root Surface Caries and Periodontal Disease in Long-term Alloxan Diabetic Rats
Authors: Reuterving C.-O. , Haggz E. , Gustafson G.T.
Published: November 2010

Caries, periodontal disease, and occlusal wear were studied in rats with short-term (one month) and long-term (12 months) untreated alloxan diabetes and in age-matched control rats. Standard laboratory diet and water were given ad libitum. Streptococcus mutans and lactobacilli were naturally occurring inhabitants of the oral bacterial flora. In short-term diabetic rats, there was less dental plaque in the gingival region of the first mandibular molar than in control rats, but the density of leukocytes in the junctional epithelium was increased. Interdentally, the gingival papillae were intact, and the prevalence of foreign material was as low as for the controls. No caries lesions were seen. The proportion of the oral flora which was lactobacilli was positively correlated with the blood glucose level. In long-term diabetic rats, there was more periodontal breakdown than in the age-matched control rats. The periodontal breakdown was always associated with large interdental impactions of foreign material. Caries was seen only in the diabetic rats and in sites with interdental impactions. The decay was shown to start in the cementurn at the cemento-enamel junction. The amount of alveolar bone loss, but not the amount of dental caries, was related to the degree of hyperglycemia. Occlusal wear of the molars in long-term diabetic rats was significantly increased as compared with that in the controls.
Effect of Antimicrobial Agents on Root Surface Caries, Alveolar Bone Loss, and Microflora in Rice Rats
Authors: Toth A. , Beck F.M. , Beck E.X. , Flaxman N. , Rosen S.
Published: November 2010

Two antimicrobial agents, 9-aminoacridine (0.2%) and minocycline (0.2%), were evaluated for their efficacy in inhibiting root surface caries, bone loss, and microflora in rice rats. A solution of 5000 ppm fluoride was used as a positive control for the inhibition of root surface caries, and double-distilled water was used as a negative control group. Each rat was treated by having its molar teeth swabbed 2 x per day with the prescribed agent in its group for nine weeks. Root caries reduction in the minocycline and fluoride groups was not significantly different, but the reduction was significantly greater than in the 9-aminoacridine group, with the caries score in all three groups being significantly less than that in the water control. Bone loss reduction for the minocycline group was significantly greater than that for any other group.
Long-term Effects of Two Different Treatments for Dental Fear and Avoidance
Authors: Berggren U.
Published: November 2010

Follow-up clinical studies of treatment for dental fear and avoidance behavior are infrequent in the literature. The present investigation reports follow-up results over more than two years from 84 out of 99 patients treated for dental fear in a Swedish community-based dental fear clinic. Broad-based behavioral therapy (BT) or general anesthesia (GA), both in combination with adjusted conventional dental treatment, were used. The frequency of patients' attendance for regular dental care after two years was unchanged or even somewhat increased and was significantly higher in those who had received the BT therapy. Most patients stated that they had no problems after leaving the dental fear clinic. Among patients reporting such problems, the change of dentist was most frequently reported. The level of dental anxiety as measured by Corah's DAS was still at a low level, in spite of a slight increase over the two years since initial therapy.
Glycogen Synthetic Abilities of Actinomyces viscosus and Actinomyces naeslundii Freshly Isolated from Dental Plaque over Root Surface Caries Lesions and Non-carious Sites
Authors: Komiyamai K. , Khandelwal R.L. , Duncan D.E.
Published: November 2010

Relative glycogen synthetic abilities of resting cells of fresh clinical isolates of Actinomyces viscosus and Actinomyces naeslundii originating from dental plaque samples over root surface caries lesions and non-carious sites were studied under anaerobic conditions at a constant pH of 7.0, with U-(14C)-glucose used as the carbon source. Although the rates of glucose utilization and total acid formation were essentially the same, A. viscosus strains isolated from root surface caries lesions showed glycogen synthetic abilities approximately two to seven times higher than did A. viscosus strains originating from non-carious sites, and also two to four times higher than did A. naeslundii strains originating from both carious and non-carious sites.
Desulfuration of Cysteine and Methionine by Fusobacterium nucleatum
Authors: Pianotti R. , Lachette S. , Dills S.
Published: November 2010

Fusobacterium nucleatum is a Gram-negative anaerobic rod-shaped bacterium frequently isolated from human dental plaque. It is capable of the desulfuration of cysteine and methionine, resulting in the formation of sulfide and thiol volatiles, respectively. Intact cells, as well as cell-free extracts produced by French pressure cell lysis of F. nucleatum, hydrolyzed radiolabeled cysteine to produce sulfide, pyruvic acid, and ammonia. The hydrolysis products of radiolabeled methionine were a volatile thiol, ketobutyrate, and ammonia. Both activities were associated with the cytoplasmic component, not the membrane. The desulfuration mechanisms are heat-labile, inhibited by the presence of excess substrate, and rates are dependent upon substrate concentration. These dissimilar pathways by F. nucleatum can account in part for the presence of sulfur-containing volatile products that occur in the mouth.
Demonstration of Structural Variation in Rat Incisor Dentin as Determined by the X-ray Laue Method
Authors: Mishima H. , Sakae T.
Published: November 2010

Rat incisor dentin was studied by an x-ray micro-Laue method to investigate the relationship between crystal orientation and structural variation in the dentin.

The results showed that crystal orientation was very poor in the labial dentin, but that the crystals were well-oriented in the lingual dentin. In the lingual dentin, the axis of crystal orientation was parallel to the tooth axis. It is suggested that the difference in crystal orientation between the lingual and labial dentin is due to the different mode of calcification between the two.
Distribution and Retention of Salivary Fluoride from a Sodium Fluoride Tablet Following Various Intra-oral Dissolution Methods
Authors: Primosch R.E. , Weatherell J.A. , Strong M.
Published: November 2010

The distribution and retention of salivary fluoride were investigated according to the following intra-oral dissolution methods of a sodium fluoride tablet: active chewing/swishing, active sucking/swishing, and passive dissolution in the maxillary and mandibular labial vestibule. The results suggested that the oral cavity was somewhat compartmentalized, in that homogeneous distribution of a dissolved fluoride tablet did not occur throughout the mouth, but rather each site sampled was influenced by various rates of clearance and retention. Tablet chewing may have an advantage over tablet sucking in terms of salivary fluoride retention, and there was a tendency for fluoride to be preferentially retained in the maxillary labial vestibule following swishing. The passive tablet dissolution methods resulted in a less homogeneous distribution of fluoride. Although the fluoride retention values for passive dissolution were impressively superior to either active dissolution method, the alarmingly high salivary fluoride concentrations (4000 ppm F) recorded at the passive dissolution sites should discourage its use until the potential cytotoxicity of this approach is thoroughly investigated.
Quantitative Diameter Analysis of Lingual Nerve Axons in Man
Authors: Heasman P.A. , Beynon A.D.G.
Published: November 2010

Previous studies on axon counts and fiber-diameter spectra in lingual nerves have been carried out only on animal models. This study reports an histological investigation on a series of 20 lingual nerves removed post mortem from human subjects. The results show wide variation in the myelinated fiber counts — a variation which does not appear to be related to the ages of the subjects. When the results are compared with those of a previous study (Heasman and Beynon, 1983), it is seen that the lingual nerve:inferior dental nerve ratio of axon counts is not a consistent index. The fiber-diameter spectrum for the human lingual nerve is characterized by a bimodal curve with the more pronounced peak in the small-diameter fiber range.
The Appearance of Tooth in Children Ingesting Water a High Fluoride Content for a Limited Period during Early Tooth Development
Authors: Ish T. , Suckling G.
Published: November 2010

Sixteen Japanese children, inadvertently exposed to drinking water containing 7.8 ppm fluoride (F) from birth, were tiged 11 to 42 months when a low-F water supply was substituted. The appearance of the enamel of their permanent teeth was assessed 11 years later (children aged 12-15 years) and recorded using Dean's and the FDI indices. All grades of Dean's classification were seen. The enamel lesions were more severe in the older than in the younger children, in the incisal compared with the gingiva l halves of the teeth, and in the early- compared with the late-forming teeth. Small, localized, chalky-white areas of enamel were found at or close to the incisal margins of the anterior teeth of six children. The characteristics and the distribution, of the lesions in this study add to our knowledge of the mechanism by which fluoride produces dental fluorosis.
Elements in Marginal Seals at Amalgam-Tooth Interfaces
Authors: Grossman E.S. , Witcomb M.J. , Jodaikin A.
Published: November 2010

X-ray micro-analysis was used to determine the elemental composition of the tooth, amalgam, and base material of ten aged, amalgam-restored, posterior teeth after they had been fractured across the amalgam-tooth interface, Subsequently, replicas were used to remove marginal seal material from each interface for examination by x-ray micro-analysis , The results show that P and Sn were present in all marginal seal material analyzed. Ca, Cl, Cu, Fe, S, and Zn were present in the marginal seals of various numbers of specimens.
A Numerical Model of Temporomandibular Joint Loading
Authors: Smith D.M. , McLachlan K.R. , McCall W.D.
Published: November 2010

A numerical model of the mandible, its articulating surfaces, and the forces exerted by the primary masticatory muscles has been developed for the purpose of investigating loading of the temporomandibular joint. Evidence is presented which shows that the temporomandibular joint is a load-bearing joint over the normal functional range of bite-force positions and angles. In this investigation, temporomandibular joint loads were found to vary from a maximum appositional force of 60% of the bite force (when bite forces were applied to the incisors) to a distracting force of about 5% of the bite force (when applied to the distal surfaces of the third molars).

TMJ loads tended to reach a minimum as a result of vertically directed bite forces positioned at the second molars. A range of conditions in which bite forces were directed parallel to or within approximately 20° of the mid-sagittal plane was found to be conducive to stability of the temporomandibular joint. This stability included symmetry in the direction and in the magnitude of condylar loads as well as the presence of small forces tending to appose the condyle and articular eminence.

TMJ loads tended to reach a maximum in response to mediolaterally directed bite forces. This result is consistent with the fact that no muscle of mastication exhibits a spatial orientation in which the muscle fibers are predominantly mediolateral in direction.
Antimicrobial Properties of Hydrogen Peroxide and Sodium Bicarbonate Individually and in Combination Against Selected Oral, Gram-negative, Facultative Bacteria
Authors: Miyasaki K.T. , Genco R.J. , Wilson M.E.
Published: November 2010

The topical application of hydrogen peroxide (H2O2) and sodium bicarbonate (NaHC03), individually and in combination, has been used empirically in the treatment of periodontal diseases. In this study, we examined both minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) of these disinfectants individually and in combination against selected facultative, Gram-negative oral bacteria in a microtiter dilution assay. The bacteria studied included Actinobacillus actinomycetemcomitans, Haemophilus aphrophilus, Eikenella corrodens, and Capnocytophaga gingivalis. These bacteria exhibited MBC (one hr) values ranging from 75 μ mol/L to greater than 10 mmol/L and MIC from <5 to 500 μ mol/L for H2O2. The tested bacteria exhibited MIC values for NaHCO3 of from 23 to 182 mmol/L, and the MBC (one hr) exceeded 728 mmol/L for most of the strains examined. At sublethal (sub-MIC) concentrations, sodium bicarbonate antagonized the ability of H2O2 to inhibit bacterial growth in MIC assays, but sublethal concentrations of H2O 2 had no effect on the MIC values of NaHCO3. Lethal concentrations of H2O2 and NaHC03 exhibited synergistic antimicrobial activity in combination in one-hour bactericidal assays. Since the bactericidal properties of these antimicrobial agents are synergistic, we conclude that it may be rational to use them in combination to treat certain forms of periodontal disease. Also, lower and perhaps safer concentrations of H2O2 can be used in combination with NaHC03 when oxidative antimicrobial chemotherapy is indicated.
In vitro Studies of Growth and Competition between S. salivarius TOVE-R and Mutans Streptococci
Authors: Kurasz A.B. , Tanzer J.M. , Bazer L. , Savoldi E.
Published: November 2010

Streptococcus salivarius TOVE-R has previously been reported as a successful competitor with Streptococcus mutans 10449S and Streptococcus sobrinus 6715-13 WT on the teeth of rats. We studied, in vitro, some possible bases for this competition, including hydrogen peroxide or catalase production, bacteriocin or enocin production, and growth rates. Growth rates were measured spectrophotometrically in both complex and defined media. We studied conditions of (i) aerobic and anaerobic incubation; (ii) glucose and sucrose medium supplementation at three concentrations each; (iii) various initial pH's; (iv) singly- or doubly-inoculated cultures; and (v) half-strength, normal, or double-strength broth used both fresh and as culture filtrates. TOVE-R grew as well as did mutans streptococci at acid pH, decidedly better at alkaline pH, and nearly twice as fast near neutral pH. The average doubling time for TOVE-R was about 0.5 hr, while that for the mutans streptococci was about 1.0 hr. When TOVE-R was grown together with a mutans streptococcus, the growth rate observed for the doubly-inoculated culture was equal to or less than that of TOVE-R alone, never greater. The presence and proportions of both organisms in mixed cultures were confirmed by plate counts, direct specific immunofluorescence, and Nomarski interference microscopy. There was no evidence, by any of the methods employed, to indicate the production of an inhibitory substance against mutans streptococci by TOVE-R, or vice versa. Also, there was no evidence that the faster growth rate of TOVE-R could be attributed to nutrient limitation of the mutans streptococci. TOVE-R's ability to compete successfully with mutans streptococci in vivo may be attributable to its inherent ability to grow faster over a wide range of environmental conditions, as observed in vitro.
Modulation of the Kinetics of Induced Neutrophil Superoxide Generation by Fluoride
Authors: Gabler W.L. , Creamer H.R. , Bullock W.W.
Published: November 2010

Fluoride (F-) is unique in that, depending upon concentration, it can either stimulate or inhibit the synthesis of the neutrophil's major intracellular microbicidal product, superoxide anion (O-2). While a number of studies have delved into F- induction of O-2 generation, little has been reported on the effect of F- on the synthesis of O-2 induced by other agents. In this report, we show that F- inhibits the activation and activity of neutrophils induced either by formyl-methionyl-leucylphenylalanine (FMLP) or by phorbol myristate acetate (PMA). The extent of increase in lag period and decrease in velocity of O-2 synthesis was found to be directly related to the concentrations of F-and of hydrogen ion in the medium and to the length of contact time between the neutrophil and F-. Decreasing the pH of the medium, while maintaining a constant concentration of F-, disproportionately increased the inhibitory effect of the anion over the effect of pH alone. Fluoride inhibited the responsiveness of neutrophils to FMLP more than it did their responsiveness to PMA. A gradual but partial reversal of F -'s inhibition of O-2 synthesis could be achieved by transferring inhibited cells to F--free medium. Our study shows that the suppression of both FMLP- and PMA-induced synthesis of O- 2 by neutrophils is most dramatic at a reduced pH and is probably related to the intracellular accumulation of F-. On the other hand, at pH 7.2, the kinetics of the time-dependent decline in responsiveness to FMLP in the presence of F- was similar to that seen in the absence of Ca2+ . This suggests that the activation of neutrophils may also be influenced by the effect of F- on extracellular levels of Ca2+. Reduction in extracellular levels of Ca2+ could subsequently affect intracellular stores of membrane-associated Ca2+ and thus inhibit the Ca2+-dependent activation of neutrophils by FMLP.
A Theoretical Study of in vivo Lesion Repair Using a Controlled-release Device
Authors: Greene W.M. , Newbrun E.
Published: November 2010

A theoretical model of lesion remineralization predicts that in vivo caries repair can be effected in a five-day period by means of a controlled- and sustained-release device containing calcium, phosphate, and fluoride. The calculations detail an 80% repair before the remineralization process stops. However, the fluoridated hydroxyapatite formed is calculated to be about 20% more resistant to future attack than is hydroxyapatite, making effective repair complete. Optimal flux (W) conditions for repair of 100 μm lesions are WCa = 1.0 x 10-6 kglm2s, stoichiometric phosphate, and WF = 2.0 × 10-9 kg/ m2s.
Effects of Fluoride on Protein Secretion and Removal During Enamel Development in the Rat
Authors: Den Besten P.K.
Published: November 2010

Enamel maturation consists of a loss of the early secreted matrix proteins and an increase in mineralization. This study investigated the changes in enamel proteins of the rat incisor, caused by the ingestion of fluoride at various stages of enamel formation. Rats were given 0, 10, 25, 50, or 100 ppm fluoride in drinking water for five weeks. Changes in the protein composition of the secretory, early-maturation, and late-maturation enamel were investigated by means of gel filtration chromatography and polyacrylamide gel electrophoresis. No differences were found between fluorosed and control enamel proteins in secretory enamel. In fluorosed early-maturation enamel, amelogenins were retained in larger quantities than in control enamel in animals ingesting 25 ppm fluoride or greater. At the late-maturation stage of enamel formation, only enamel from animals ingesting 100 ppm fluoride in drinking water contained more protein, when compared with control enamel. This study suggests that fluoride ingestion levels resulting in enamel fluorosis inhibit the mechanisms involved in the removal of proteins during enamel maturation.
Kinetic Analysis of Streptococcus sanguis Adhesion to Artificial Pellicle
Authors: Cowan M.M. , Taylor K.G. , Doyle R.J.
Published: November 2010

Studies of equilibria between Streptococcus sanguis and artificial pellicle have suggested that there are multiple binding sites for the organism. In the present study, adhesion of S. sanguis to saliva-coated hydroxylapatite was examined by means of kinetic methods. Cell-pellicle complex formation was measured from initiation of binding to equilibrium. Rate constants were calculated for forward reactions (adsorption) and reverse reactions (desorption). Initial binding obeyed reversible, first-order kinetics, whereas desorption of bound cells followed biphasic kinetics. Initial desorption proceeded approximately ten times faster than the slower second rate. The results are consistent with the mechanism in which CP* represents the reversible equilibrium that shifts at a discrete rate to the high-affinity CP state. Thus, the biphasic binding behavior that has been previously deduced from equilibrium studies may be attributed to a time-dependent shift from close apposition to pellicle, stabilized by low-specificity forces, to a higher-affinity binding.
The Effect of Dentinal Stimulation on Pulp Nerve Function and Pulp Morphology in the Dog
Authors: Hirvonen T.J. , Narhi M.V.O.
Published: November 2010

The effect of dentinal stimulation on pulpal nerve responses and pulp morphology has been studied in the dog. Canine tooth (n = 25) dentin was stimulated by drilling, probing, and air-blasting for from two to five hours. Acid-etching was used to open dentinal tubules. All test teeth showed disruption of the odontoblast layer and its separation from the predentin; also, dislocation of odontoblast nuclei into dentinal tubules was found in most cases. Single-fiber (n = 14, conduction velocity = 24.3 ± 7.4 (SD) m/s) recordings of the responses of canine tooth pulpal nerves to dentinal stimulation were made in ten of the stimulated teeth. No changes in the sensitivity of the nerves to dentinal stimulation could be detected. It is concluded that pulpal nerve function and morphological changes of the pulp are not clearly correlated. The condition of the dentin surface seems to be the important factor.
Effect of pH, Concentration, and Treatment Time of Aluminum Solutions on Acid Dissolution of Enamel
Authors: Putt M.S. , Kleber C.J.
Published: November 2010

Dissolution tests were conducted with human enamel following treatment with aqueous aluminum (Al) solutions under conditions of varying pH, concentration, and treatment time. Al reduced enamel dissolution in a pH 4 acetate buffer most effectively when used in the pH range of 3 to 4, at concentrations above 0.005 mollL, and for treatment times of more than four minutes. However, significant activity was observed with concentrations as low as 0.0005 mol/L Al and treatment times as short as 15 seconds. The effects of Al solution pH and concentration on enamel dissolution were related to the hydrolysis of Al above pH 4 and to the accelerated dissolution of apatite below pH 3.
Reliability of a Craniomandibular Index
Authors: Fricton J.R. , Schiffman E.L.
Published: November 2010

The Craniomandibular Index (CMI) was developed to provide a standardized measure of severity of problems in mandibular movement, TMJ noise, and muscle and joint tenderness for use in epidemiological and clinical outcome studies. The instrument was designed to have clearly defined objective criteria, simple clinical methods, and ease in scoring; it is divided into the Dysfunction Index and the Palpation Index. Inter-rater reliability (three raters) and intra-rater reliability (19 patients examined twice by one rater) were tested to determine whether the instrument has operational definitions sufficiently precise to allow for consistency in use between different raters and with one rater over time. Intraclass Correlation Coefficient for inter-rater reliability was 0.84 for the Dysfunction Index, 0.87 for the Palpation Index, and 0.95 for the CMI. Correlation for intra-rater reliability was 0.92 for the Dysfunction Index, 0.86 for the Palpation Index, and 0.96 for the CMI. These results support the reliability of the CMI for use in epidemiological and clinical studies. Users are cautioned about the subjectivity of numerous items within the CMI and the strict methodological guidelines that must be followed in order to assure accuracy and reproducibility of results.
Establishment of an Improved Implantation Technique for Hamster Mucous Membrane Irritation Testing
Authors: Roy M. , Wishe H.I.
Published: November 2010

Biological evaluation procedures for the acceptance of new dental materials include testing for mucous membrane irritation and inflammation, with the hamster cheek pouch used as a model system. Previous reports have indicated both a low 14-day implant retention rate and poor differentiation between positive and negative controls, requiring the establishment of a new standard procedure for hamster cheek pouch implantations.

Groups of 10 female golden Syrian hamsters were implanted with uniform discs (6 mm in diameter and 1 mm thick) of white base-plate gutta percha (GP), gray welding-rod polyvinyl chloride (PVC), low-density polyethylene (LDPE), or test alloys, under Nembutal anesthesia. Each animal's right cheek pouch was everted and cleaned, and the implant was loosely placed at the bottom of the pouch. The pouch was closed by a double-suture technique. Contralateral (left) cheek pouches served as controls for the physical state of each animal. A collar (cable tie) was placed tightly around the animal's neck at a level between the sutures and the implant. Cheek pouches were assessed after 14 days.

Implants were kept in contact with oral mucosa longer using the double-suture-plus-collar technique than in hamsters without collars (14-day retention rates of 48.0% and 6.7%, respectively). Average severity indices (ASI) of 5.4 and 1.7 were obtained for PVC and GP, respectively, as compared with 1.6 for contralateral control pouches. LDPE was not a suitable negative control material (ASI = 2.6). Positive and negative controls were clearly delineated when PVC and GP were the control materials.
Triazine Monomers and Their Adhesion to Dentin
Authors: Lee C.H. , Liu X.Q. , Gong X.Q.
Published: November 2010

A series of 4,6-dichloro-1,3,5-triazines [e.g., 2-allylamino-(ADT), diallylamino-(DADT), 2-N-p-allyloxyphenylamino-, 2-N-allyl-N-phenylamino-, and 2-N-allyl-N-p-tolylamino-4,6-dichloro-1,3,5-triazine] was synthesized and characterized by IR, NMR, and mass spectrometry. These monomers have chlorine atoms that can react with NH2 or OH groups and double bonds capable of copolymerization. Aniline reacted readily with ADT and DADT, ethanol reacted with ADT, but acetone, H2O, and DMF did not react with either triazine. It appears that ADT or DADT will react with dentinal collagen through NH2 or OH groups in the peptide side-chains. An aprotic solvent should be used for ADT or DADT, but absolute dryness in clinical usage is not essential because of the slow hydrolysis of ADT and DADT. Stability of the N-di-substituted amino derivative (DADT) is greater than that of the mono-substituted compound (ADT), which may isomerize. ADT and methyl methacrylate were copolymerized at 37°C with amine-peroxide. ADT solutions enhanced the adhesive strength of restorative resin to dentin. Thus, monomers such as ADT and DADT appear to be promising dentin-bonding agents.
Dental Fluorosis Developed in Post-secretory Enamel
Authors: Richards A. , Kragstrup J. , Josephsen K. , Fejerskov O.
Published: November 2010

The aim of this study was to test whether dental fluorosis can be produced by administration of chronic doses of fluoride during only the post-secretory stage of enamel mineralization. Eight control and eight experimental pigs matched by weight and litter were fed a low-fluoride diet (<0.05 mg F-/kg b.w. daily) from weaning to slaughter at 14 months. The test group received an oral dose of 2 mg F -/kg b.w. per day from 8 months of age. Lower fourth pre-molars were at the post-secretory stage at the start of fluoride administration (confirmed by tetracycline marker) and were just erupting at slaughter. All of the fourth pre-molar teeth from the test group developed diffuse enamel hypomineralization indistinguishable from human fluorosis. No such lesions were seen in any of the teeth from the control animals. It was concluded that enamel fluorosis may be caused by fluoride exposure in the maturation phase only. The pathogenic mechanism may be an effect either on the selective loss of protein or on the influx of mineral, both of which occur during the post-secretory or maturation stage of enamel formation.
Metronidazole Concentrations in Human Plasma, Saliva, and Gingival Crevice Fluid after a Single Dose
Authors: Van Oosten M.A.C. , Notten F.J.W. , Mikx F.H.M.
Published: November 2010

Metronidazole concentrations were estimated in four human volunteers after a single dose of 750 mg taken orally. Samples of blood, saliva, and gingival crevice fluid were collected before intake and during the following 24 hours.

The concentrations of metronidazole in plasma and saliva were measured by high-performance liquid chromatography (HPLC). The concentrations in gingival fluid were estimated by a capillary agar-diffusion assay. The results of the metronidazole measurements as obtained by both methods were significantly correlated. The peak concentrations of metronidazole in plasma and saliva were in the same range, 8.7-13.8 μ g/mL, and similar concentrations were found in the gingival fluid samples.

It is concluded that metronidazole taken orally has similar pharmacokinetics in both saliva and plasma, and that a single oral dose of 750 mg metronidazole leads to a concentration of the drug in the gingival crevice fluid that exceeds the minimal inhibitory concentration for most anaerobic oral micro-organisms.
Effects of Substance P and Substance P Antagonists on Rat Salivary Secretion
Authors: Bobyock E. , Barbieri E.J. , Chernick W.S.
Published: November 2010

The intra-arterial infusion of substance P produced dose-related responses of both parotid and submandibular salivary secretion in anesthetized rats. The substance P-induced secretion in both glands was inhibited by the substance P analogues [D-Arg1, D-Trp7,9, Leu11]-substance P and [D-Arg1, D-Pro2, D-Trp7,9, Leu11]-substance P, but not by [D-Pro2, D-Trp7,9]-substance P. The profiles of protein and calcium levels obtained with substance P-induced salivary secretion for both glands were similar to those produced by acetylcholine stimulation and were not altered by the substance P analogues.
Size of the Alveolar Arch of the Mandible in Relation to that of the Maxilla in 45,X Females
Authors: Laine T. , Alvesalo L.
Published: November 2010

Length and width of the alveolar arch of the mandible and maxilla were determined from hard stone casts of 45,X females (Turner syndrome), female first-degree relatives, and population control females. Adjusted mean values (covariance adjusted for age, previous orthodontic treatment, and number of lost permanent teeth) for mandibular arch width were larger in 45,Xfemales than in normal controls, both absolutely and, more clearly, in relation to the maxillary arch. The total absolute length of the mandibular arch was slightly reduced in 45,X females. The broader and shorter alveolar arch of the mandible in relation to the narrower but normal-length maxillary arch reflects imbalanced facial growth in subjects with one X-chromosome instead of the normal two.
A Comparison of the Effects of Continuous and Periodic Fluoride Delivery on Fluoride Levels in Plasma, Enamel, and Bones of Nursing Rats
Authors: Drinkard C.R. , Deaton T.G. , Bawden J.W.
Published: November 2010

The purpose of this study was to determine and compare the F levels in plasma, enamel, and bones of nursing rat pups that received the same daily dose of F by continuous or periodic delivery during enamel development. The hypothesis was that F delivered continuously would result in enamel F levels higher than those attained when F was delivered periodically. For continuous delivery, copolymer devices (Southern Research Institute) that provide slow release of F were implanted in the backs of four-day-old rat pups. For periodic delivery, rat pups received F by intraperitoneal injection or gastric intubation. The doses were 0.01, 0.02, or 0.04 mg Flday. The rats were killed at 13 days of age, 24 hours after the last periodic delivery. Plasma was collected, femur and calvaria bones were removed, and enamel was scraped from developing first molars. Fluoride assay was by the microdiffusion method of Taves, with a F electrode. For the 0.02 mg Flday dose, plasma levels in control, implanted, injected, and gastric-intubated rats were 0.004, 0.020, 0.011, and 0.009 ppm, respectively. Enamel F levels were 1.1, 61.9, 54.0, and 42.3 ppm, respectively. Femur F levels were 2.2, 81.2, 84.8, and 68.1 ppm, respectively. Calvaria F levels were 2.5, 79.3, 80.1, and 67.9 ppm, respectively. The results showed that there was no significant difference in the enamel F levels or in the bone F levels in rat pups that received continuous or periodic, by injection, delivery of F at the same daily dose. The significance is that similar levels of F can be attained in developing enamel if the same total dose of F is delivered continuously or periodically once a day. Previous studies have shown that there is less chance of producing disturbances in enamel mineralization with continuous F delivery when compared with periodic F delivery at a lower daily dose.
Temperature-dependence of Compressive Properties of Human Dentin
Authors: Watts D.C. , El Mowafy O.M. , Grant A.A.
Published: November 2010

The effect of temperature on compressive stress/strain behavior of human dentin obtained from recently extracted permanent lower molar teeth has been determined over the range 0-80°C. Dentin specimens were loaded uni-axially in a direction perpendicular to the tubule orientation. A statistically significant, linear regression relationship was found between modulus (E) and temperature (T): The observed temperature coefficient of the modulus is in close agreement with that observed for cortical bone. Proportional limit, compressive strength, and resilience were also found to undergo a linear decrease with increasing temperature. Mechanical failure of specimens generally occurred along lines determined by maximum shear stresses, approximately 45° to the axial load direction.
Effects of Water-soluble Components of Cheese on Experimental Caries in Humans
Authors: Silva M.F. de A. , Burgess R.C. , Sandham H.J. , Jenkins G.N.
Published: November 2010

The effect of water-soluble components of extra-old Cheddar cheese on experimental caries was tested by means of the seven-day intraoral cariogenicity test (ICT). Two bovine enamel blocks were placed in each buccal flange of the dental appliances of five volunteers. One side of each appliance (experimental) was dipped in a 25% water extract of the cheese for five min, while the other side (control) was dipped in de-ionized water. Immediately thereafter, the appliance was returned to the subject's mouth, and two 60-second rinses with 10% sucrose were performed. These procedures were repeated six times per day.

The cheese-extract dippings reduced the cariogenicity of the sucrose by an average of 55.7% (p<0.01), as assessed by enamel microhardness. Neither the mean resting pH nor the mean minimum pH in response to sucrose was significantly different between the experimental and control sides.

The concentration of calcium was significantly higher in plaque from the experimental side (32.44 μg/mg) as compared with the control side (19.36 μg/mg, p<0.01). The concentration of plaque phosphorus was higher on the experimental side (12.90 μg/mg) than on the control side (9.61 μg/mg); however, the difference was not statistically significant. These results show that cheese has one or more water-soluble components which reduce experimental caries in human subjects.
The Influence of Plaque on Reaction Mechanism of MFP and NaF in vivo
Authors: Hellwig E. , Klimek J. , Wagner H.
Published: November 2010

A modified Intra-oral Cariogenicity Test was used to study the influence of plaque on the reaction mechanism of sodium monofluorophosphate (MFP) or sodium fluoride (NaF) in either sound or demineralized enamel in vivo. Volunteer students, wearing mouth appliances holding enamel blocks, rinsed their mouths with MFP or NaF solution (1000 ppm F-) three times a day. The amount of loosely-bound and acquired fluoride was determined after an experimental period of five days in plaque-covered, demineralized (PCD); clean, demineralized (CD); plaque-covered, sound (PCS); and clean sound enamel (CS). While no measurable loosely-bound fluoride could be found after MFP treatment, NaF caused deposition of a significant amount of alkali-soluble fluoride in all experimental groups. After MFP rinses, fluoride concentration in the enamel was increased in the following order: CS, PCS, CD, and PCD. After NaF treatment, demineralized enamel exhibited a higher fluoride acquisition when compared with sound enamel. Plaque had a minor effect on F- acquisition. It is concluded that demineralization of enamel enhances F- uptake from both NaF and MFP solutions. In the presence of plaque, F- acquisition was additionally increased only after MFP rinses in vivo.
Purification and Some Properties of Fucosyltransferase in Human Parotid Saliva
Authors: Tamagawa H. , Inoshita E. , Takeshita T. , Takagaki M. , Shizukuishi S. , Tsunemitsu A.
Published: November 2010

Fucosyltransferase was purified from human parotid saliva by affinity chromatography on GDP-hexanolamine Sepharose, followed by chromatofocusing on PBE 94 exchanger gel. The purified enzyme had the N-acetylglucosaminide α1→4, the N-acetylglucosaminide α1→3, and the glucoside α1→3 fucosyltransferase activities. The molecular weight of the purified enzyme was estimated to be approximately 20,000. These enzyme activities showed identical pH and divalent metal ion dependencies and identical rates of inactivation upon being heated. The paper chromatographic analysis of the fucosylated products by the purified enzyme and the susceptibility of these products to linkage-specific fucosidase digestion indicated that the transferase formed the Fuc α1→4GlcNAc, Fuc α1→3GlcNAc, and Fuc α1→3Glc linkages.