bluuebunny/crossref_metadata_2025 huggingface dataset:
Urinary Excretion of Fluoride Following Ingestion of MFP Toothpastes by Infants Aged Two to Six Years
Authors: Drummond B.K. , Curzon M.E.J.
Published: November 2010

The absorption and excretion of fluoride in a group of 25 infants (<6 years of age) were followed for up to seven hours after the ingestion of a known quantity of either sodium monofluorophosphate alone in solution, or toothpastes with sodium monofluorophosphate and an abrasive of either hydrated silica or dicalcium phosphate dihydrate. Fluoride appeared to be well-absorbed based on the excretion patterns found. From the results, it was concluded that parents of pre-school-aged children should now be given appropriate advice regarding their children's use of fluoride toothpaste. Such use of fluoride toothpaste should be closely supervised by the parents, and only a smear of paste, about the size of a pea, should be used, particularly where fluoride supplements are used. Because of the likelihood of toothpastes with even higher amounts of fluoride being marketed, it would also appear that toothpaste manufacturers and researchers in caries prevention should look further at the problem of fluoride absorption from toothpastes in infants.
Influence of Soluble Pyrophosphate on Calculus Formation in Adults
Authors: Mallatt M.E. , Beiswanger B.B. , Stookey G.K. , Swancar J.R. , Hennon D.K.
Published: November 2010

The purpose of this double-blind, longitudinal clinical study was to assess the efficacy of a dentifrice containing 3.3% soluble pyrophosphate in inhibiting calculus formation and its effect upon the oral soft tissues. A total of 265 adult volunteers was given a dental prophylaxis. Each was examined for dental calculus and oral soft tissue pathology. The volunteers were then randomly assigned to use either a dentifrice containing soluble pyrophosphate and sodium fluoride or a placebo sodium fluoride formulation for ad libitum home usage. At the two-month completion of the study, 217 subjects were available for examination. The results showed that the group using the dentifrice containing soluble pyrophosphate experienced a significant 26% decrease in calculus formation as compared with the placebo group, with both dentifrices being equally well-tolerated by the oral soft tissues.
The 'C'-Test for the Evaluation of Dental Porcelain
Authors: Edwards M.R. , Jacobsen P.H.
Published: November 2010

The 'C'-test, which has been employed in the testing of industrial porcelain, offers several advantages when used with dental porcelain. In particular, specimens are similar in size and geometry to porcelain jacket crowns. This study evaluates the application of the 'C'-test for dental porcelain. The results showed good consistency and reproducibility, and those specimens constructed using a tin-oxide-coated foil did not display any greater strength than did those in which the platinum foil was not plated.
Streptococcus mutans and Lactobacillus Detection in the Assessment of Dental Root Surface Caries Risk
Authors: Ellen R.P. , Banting D.W. , Fillery E.D.
Published: November 2010

Forty-five subjects contributing 150 root surfaces with gingival recession were sampled seven times over a 32-month period. We calculated isolation frequencies of lactobacilli on selective Rogosa SL agar and S. mutans in a sensitive enrichment broth and on mitis salivarius agar. Both S. mutans and lactobacilli were isolated more frequently from surfaces which became carious than from those remaining caries-free. Isolation frequencies were also higher for caries-free surfaces in caries-active subjects than for caries-free surfaces in caries-inactive subjects. The presence or absence of S. mutans and lactobacilli in samples taken at baseline could discriminate between subjects who were to be root-caries-active and those who were to remain root-caries-inactive during the subsequent observation period. Moreover, if both bacteria were detected or only S. mutans was detected on a root surface at its entry into the study, that surface had a greater risk for developing a root lesion. However, the tests could not predict which root surfaces within the mouths of caries-active subjects were to become carious. Analysis of the data suggests that simple microbiological detection tests may be useful in identifying patients at high risk of root caries.
Changes in Oral Health from 1973 to 1982 of 13-15-year-old Schoolchildren Residing in Three Different Fluoride Areas in Finland
Authors: Parviainen K. , Ainamo J. , Nordling H.
Published: November 2010

The aim of the present study was to analyze the change from 1973 to 1982 in the oral health conditions of 13-, 14-, and 15-year-old schoolchildren residing in three different fluoride areas in Finland. Oral hygiene, as measured with the Visible Plaque Index (Ainamo and Bay, 1975), had improved significantly both among 13-year-old girls (P<0.01) and among boys of the same age (P<0.05). A highly significant improvement (P<0.001) of gingival health, as measured with the Gingival Bleeding Index (Ainamo and Bay, 1975), was observed for boys but not for girls. The striking change was for the DFST (T= total) and FSAA (A = approximal) scores for the totals of 180 girls and 180 boys. This improvement in dental health was mainly due to a dramatic decline of caries in the low-fluoride (0.2 ppm F) area, whereas in the high-fluoride area (2.5 ppm F), the improvement in oral hygiene and gingival health was the greatest. The results support earlier assumptions that caries and gingivitis are separate and mutually independent disease entities. The study further suggests that local fluoride treatments can provide caries-preventive benefits similar to those achieved by community water fluoridation, although at greater cost. The comparison in time revealed that most of the differences in oral health, observed in 1973 both between sexes and between the different fluoride areas, had disappeared by the time of the 1982 examination.
Anaerobic and Aerobic Metabolism of Sorbitol in Streptococcus sanguis and Streptococcus mitior
Authors: Svensater G. , Takahashi-Abbe S. , Abbe K. , Birkhed D. , Yamada T. , Edwardsson S.
Published: November 2010

Sorbitol-fermenting strains of Streptococcus sanguis and Streptococcus mitior were grown both anaerobically and in the presence of oxygen in a sorbitol-containing complex medium. Washed-cell suspensions were incubated with an excess of sorbitol, and the production of lactate, formate, ethanol, and acetate was analyzed. Moreover, we determined the lactate dehydrogenase and pyruvate formate-lyase activities in cell-free extracts of anaerobically grown cells. The anaerobically grown cells produced lactate, formate, ethanol, and acetate under anaerobic conditions. When these cells were exposed to air, the amounts of formate, ethanol, and acetate were reduced in comparison with those of the strictly anaerobic cells. Cells grown in the presence of oxygen only produced detectable levels of lactate and acetate. Anaerobically grown cells possessed lactate dehydrogenase and pyruvate formate-lyase activities under strictly anaerobic conditions. The level of pyruvate formate-lyase was dramatically reduced when cells were exposed to air, while the level of lactate dehydrogenase was about the same as that under strictly anaerobic conditions. Thus, the results indicate that S. sanguis and S. mitior both metabolize sorbitol differently under anaerobic and aerobic conditions. This difference may depend on the oxygen-sensitivity of the pyruvate formate-lyase of these micro-organisms.
Chemical Softening and Wear of Dental Composites
Authors: McKinney J.E. , Wu W.
Published: November 2010

The purpose of this work was to determine the influence of chemical food-simulating liquids on the wear of various commercial dental composite restoratives. In many cases, pre-conditioning the restoratives in these liquids for one week produced swelling of the polymer matrix and considerable surface damage. The resulting degradation reduced the hardness and enhanced the wear as measured by a pin-and-disc apparatus. Four kinds of commercial composites were investigated: a conventional quartz-filled, a strontium-glass-filled, a visible-light-activated, and a micro filled composite. The liquids employed were heptane and several aqueous solutions of ethanol with solubility parameters, 8, ranging from δ = 1.5 to 4.8 × 104 J1/2m-3/2. With all restoratives, the decline in hardness during pre-conditioning maximized at about δ = 3 × 104, which corresponds to a 75% ethanol solution. The wear behavior was considerably more complicated and variable, as discussed in the text. For the most part, the increase in wear rate from pre-conditioning corresponded to the fall in hardness. A notable exception was for the strontium-glass-filled composite preconditioned in pure water. Here the wear was enhanced considerably, with no decrease in hardness. In this case, the degradation mode is assumed to be different from the others in that it is attributed to stress corrosion of the glass filler.
An Immunocytochemical Study of the Human Odontoblast Process using Antibodies against Tubulin, Actin, and Vimentin
Authors: Sigal M.J. , Aubin J.E. , Ten Cate A.R.
Published: November 2010

An immunofluorescence technique was applied at the light microscope level to human third molar coronal dentin in order to localize the intracellular components tubulin, vimentin, and actin. Third molars were split immediately upon extraction, and immersed in periodate-lysine-paraformaldehyde fixative. The crowns were demineralized, dehydrated, and wax-embedded, and 6-μm sections were prepared. The sections were post-fixed in -20°C acetone, and then incubated with monoclonal mouse anti-tubulin, anti-vimentin, or anti-actin antibodies, followed by fluorescein-conjugated sheep anti-mouse immunoglobulins. Intratubular immunofluorescence labeling for tubulin and vimentin was very similar in pattern and intensity and extended to the dentino-enamel junction. In contrast, the actin labeling appeared less intense and more punctate, and was located primarily in the pulpal half of the crown, although some labeling was detectable up to the dentino-enamel junction. The presence of tubulin-, vimentin-, and actin-containing structures extending to the dentino-enamel junction supports the hypothesis that the odontoblast process does extend to the dentino-enamel junction in the human, and is in agreement with earlier studies of rat molars.
Genetic Variance in Dental Dimensions of Punjabi Twins
Authors: Sharma K. , Corruccini R.S. , Henderson A.M.
Published: November 2010

Genetic variance analysis of 56 tooth size traits was based on a sample of 58 pairs of twins (23 MZ and 35 DZ) from Chandigarh, India. Results of a t -test for equality of means showed no association of zygosity with any of the traits. Heterogeneity of total variance was found in 18 traits, which invalidates conventional genetic variance estimates and reveals considerable hidden environmental determinance. In contrast to other studies, Indian MZ twins had higher variance than did DZ twins, in most instances. There was also evidence of stronger environmental covariance for MZ and DZ twins. The study revealed substantial, complex environmental determination for some dental dimensions, especially of incisors and second molars.
Inhibition of Acid Production from Oral Bacteria by Fluorapatite-derived Fluoride
Authors: Harper D.S. , Loesche W.J.
Published: November 2010

The inhibitory effect of fluorapatite (FAP)-derived fluoride upon resting cell suspensions of Streptococcus mutans incubated at pH 4.5 and 6.5 was studied using lactic acid production from 0.1% sucrose as an indicator of fermentation activity. Cells incubated with FAP produced significantly less lactic acid than did cells incubated with hydroxyapatite (HAP). Addition of HAP to cell suspensions containing FAP reduced this inhibition, suggesting that dissolution of the FAP was necessary for inhibition. Incubation with low concentrations of NaF showed significant inhibition in cell suspensions incubated with as little as 0.45 μg/mL F at pH 5.0. These results provide further support to the hypothesis that fluoride levels in plaque and enamel, achievable through use of fluoridated water and/or fluoride dentifrices, may produce appreciable inhibition of glycolysis at the acidic pH levels which are readily achieved in plaque. Thus, bacterial acid production may activate plaque and enamel-bound fluoride, resulting in inhibition of further acid production, and thereby contribute substantially to the other cariostatic mechanisms of fluoride.
Aryl Hydrocarbon Hydroxylase Activity in Rat Submandibular Glands
Authors: Murakami K. , Ishikawa T. , Shimosato T. , Noshiro M. , Hayashi S. , Okuda K.
Published: November 2010

The activities of aryl hydrocarbon hydroxylase and 7-ethoxycoumarin O-de-ethylase in the rat submandibular gland, both of which are normally very low, were increased about 10- and 25-fold, respectively, by administration of 3-methylcholanthrene. The increased activity of aryl hydrocarbon hydroxylase was inhibited by 7,8-benzoflavone but little if any by metyrapone and SKF-525A. The submandibular gland aryl hydrocarbon hydroxylase was also inhibited by antibodies elicited against rat liver cytochrome P-448 and NADPH-cytochrome P-450 reductase, respectively, and slightly by anti-cytochrome b5antibody, suggesting that submandibular gland aryl hydrocarbon hydroxylase resembles that of the liver, not only in the immunochemical properties of cytochrome P-450 involved, but also in the entire enzyme complex, including the electron transferring system. Cofactor(s) required by aryl hydrocarbon hydroxylase in submandibular gland was NADPH, whereas NADH sustained the reaction at a much slower rate (about 20%). NADH showed some additive action when added with NADPH.
In vivo Measurements of Sulcal Plaque pH in Rats After Topical Applications of Xylitol, Sorbitol, Glucose, Sucrose, and Sucrose Plus 53 mM Sodium Fluoride
Authors: Firestone A.R. , Navia J.M.
Published: November 2010

In two series of experiments, Sprague-Dawley-derived rats were infected orally with cariogenic micro-organisms and fed caries-promoting diets. By means of an antimony electrode, resting pH values were measured in the mesial sulcus of the maxillary left first molar. 100 or 200 μL of the test solutions were applied, and the change in pH (Δ pH) was recorded for three min. Test solutions were: (a) 10% sucrose, 10% glucose, 10% sorbitol, or 10% xylitol; (b) 0%, 10%, 20%, or 40% sucrose; (c) 0%, 3%, 7%, or 10% sucrose; and (d) 10% sucrose, 10% sucrose + 53 mmol/L NaF (1000 ppmF-), or 10% sucrose + 53 mmol/L NaCl. Experimental design was a 4 × 4 Latin square (a, b, c) or a cross-over design (d). Solutions of sucrose and glucose gave significantly greater decreases in pH than did sorbitol or xylitol. pH fall was maximal for 10% sucrose and significantly less for 40% sucrose during the three-minute experimental period. For sucrose solutions ranging in concentration from 3 to 10%, pH fall was highest after application of 10% sucrose when plaque was previously rinsed with water, but this pH fall did not differ significantly from that obtained using a 7% sucrose solution. Adding 1000 ppmF- to a 10% sucrose solution caused an increase in pH. Rinsing the teeth to remove saliva resulted in significantly lower resting pH values. The results of these experiments are in agreement with the results of human plaque pH measurements.
Clinical Science Effects of Highly Concentrated Stannous Fluoride and Chlorhexidine Regimes on Human Dental Plaque Flora
Authors: Schaeken M.J.M. , De Jong M.H. , Franken H.C.M. , Van Der Hoeven J.S.
Published: November 2010

The aim of this study was to determine the effect of an intensive antimicrobial treatment on the number of Streptococcus mutans, Streptococcus sanguis, Actinomyces viscosus/Actinomyces naeslundii, and the total Colony-forming Units (CFU) in plaque.

The dentition of human volunteers was treated in a dental office with either chlorhexidine (5%) or stannous fluoride (8%). Following the office treatment with chlorhexidine, selected volunteers rinsed daily at home for seven or 49 days with chlorhexidine solution (0.2%), while another group flossed daily at home for seven days with dental floss impregnated with chlorhexidine. On days one, seven, 21, 35, and 49 after the local applications, we took saliva samples and plaque samples from fissures, smooth surfaces, and approximal areas.

Chlorhexidine and stannous fluoride suppressed S. mutans and the Actinomyces species on all surfaces and in saliva. S. mutans on tooth surfaces was suppressed for approximately seven days and returned to the baseline level at day 21. A. viscosus/naeslundii was suppressed for more than seven days on the teeth. S. sanguis and the total CFU returned to the baseline level within seven days on all surfaces and in saliva. Rinsing or flossing with chlorhexidine suppressed S. mutans during the period of time that these supplements were used.

Brushing for seven days with chlorhexidine gel (1%) without a preceding intensive chlorhexidine treatment had virtually no effect on S. mutans in approximal areas and in saliva, but suppressed S. mutans in fissures and on smooth surfaces.
A Theoretical Analysis of the Effects of Plaque Thickness and Initial Salivary Sucrose Concentration on Diffusion of Sucrose into Dental Plaque and its Conversion to Acid During Salivary Clearance
Authors: Dawes C. , Dibdin G.H.
Published: November 2010

A mathematical model, written in FORTRAN, has been developed to simulate the interrelated processes of salivary sucrose clearance from the mouth, diffusion of sucrose into dental plaque, and conversion of sucrose to acid and glucan. Reaction of acid with enamel is not included in the model. A total of 28 parameters can be varied by the user, and the relative importance of the different factors affecting acid formation can be assessed. The output of the program gives sucrose and acid concentrations and pH at different depths within the plaque. The initial variables studied were plaque thickness, the salivary sucrose concentration, and the duration of exposure of the plaque to sucrose.

Stephan curves typical of those recorded in vivo were generated by the model. With any particular salivary sucrose concentration, there was an optimum plaque thickness at which a minimum pH was achieved at the enamel surface, with very thin or thick plaque samples producing a smaller pH fall. With thick plaque, the minimum pH was often not achieved at the inner surface but at some intermediate depth, which may explain the location of early caries lesions in fissures. The extent of the pH fall at the inner surface and the duration of the pHminimum region of the Stephan curve were directly related to the initial salivary sucrose concentration and to the duration of exposure to sucrose prior to normal salivary clearance. Simulation of a water rinse at as short a time as two min after the beginning of normal salivary sugar clearance showed that this procedure had only a very small effect on the shape of the Stephan curve. Thus, the maximum salivary sucrose concentration achieved prior to normal salivary clearance appears to be a major factor which determines the extent of the pH fall at the enamel surface of the plaque.
The Effects of Calcium Hydroxide on Dentin Permeability
Authors: Pashley D.H. , Kalathoor S. , Burnham D.
Published: November 2010

Calcium hydroxide paste was applied to human dentin in vitro to determine its effects on dentin permeability. Discs of dentin were acid-etched on both sides to permit determination of their maximum permeability. Smear layers were then applied to the enamel sides of the discs, thereby reducing dentin permeability 99%. Topical application of Ca(OH)2 paste to the smear layer reduced dentin permeability further, to levels 48% below that of untreated smear layers. When the Ca(OH) 2-treated smear layers were exposed to 6% citric acid for two min, dentin permeability returned to the initial acid-etched value, demonstrating that Ca(OH)2 offers little protection to acid challenge. Treatment of acid-etched dentin with Ca(OH)2 produced a similar reduction in dentin permeability, which was restored to normal following acid challenge. Thus, Ca(OH)2 is effective at reducing the permeability of both the smear layer and of acid-etched dentin, in vitro.
Comparison of the Reproducibility of EMG Signals Recorded from Human Masseter and Lateral Pterygoid Muscles
Authors: Dahan J. , Boitte C.
Published: November 2010

EMG recordings of the left and right masseter and lateral pterygoid muscles were repeated three times in 15 young adults to test the reproducibility of the signals. Two tests were made on the same day (morning and afternoon) and one test three days later (morning). Needle and hook electrodes were used for the masseter muscle and needle electrodes for the lateral pterygoid muscle. The superficial areas of recording were tattooed on the skin. An intra-oral approach was selected for the lateral pterygoid muscle. The subjects were asked to perform three definite tasks for the masseter muscle (intercuspid occlusion, maximum protrusion, and centric relation with a bite opening of 3mm) and two for the pterygoid muscle (maximum opening and maximum protrusion). The EMG signals were directly integrated, and root mean squares of the AC components were computed. The selection of the signals to discard possible artefacts was performed by displaying EMG and RMS outputs on a six-channel UV oscillograph. The selected RMS values were submitted to different analyses of variance to define additive and non-additive models of effects. The results may be summarized as follows: The between-day sessions showed more variation than the within-day sessions. The variations related to the method accounted for a very high percentage of the total variance (48.9%). The recordings with needle electrodes displayed a large percentage of the individual variation (masseter, 31.2%; lateral pterygoid muscle, 65.9%) and significantly lower values for the variations related to the session or the side of recording. The one-side recordings were more suitable for distinguishing the biological variations than were the bilateral ones. The right side was less sensitive to variations than the left side. The study of the lateral pterygoid muscle was less dependent on "session", "side", or "task" effects than was that of the masseter muscle. The lack of significant variation resulting from the performed tasks suggested that only the lower bundle was recorded with a similar activity in protrusion and opening. The reproducibility of the superficial recordings of the masseter muscle may be improved if non-significant interactions between "task" and "area" or "side" factors, as well as between "task" and "session", are taken into consideration. A direct comparison of the different tasks performed in one "session" will help reduce the undesirable effects due to the random selection of the recording "side" or "site".
Characterization of Human Dental Plaque Formed on Hydrogen-ion-sensitive Field-effect Transistor Electrodes
Authors: Chida R. , Igarashi K. , Kamiyama K. , Hoshino E. , Esashi M.
Published: November 2010

The purpose of this study was to evaluate (with scanning electron microscopy and microbiological characterization) the bacterial deposits which accumulate on hydrogen-ion-sensitive field-effect transistor electrodes (pH-ISFET) under conditions normally employed for telemetric monitoring of changes in human dental plaque pH. Electrodes were mounted in a carrier appliance which was worn for two, four, and six days. The plaque pH response to a sucrose solution increased with the age of the plaque, as expected from previous studies. After two days, the electrode was shown to be almost completely covered with cocci. At days 4 and 6 there was a dramatic increase in the number of rods present in the plaque. Adjacent enamel surfaces showed similar accumulations of bacteria. The total number of bacteria which had accumulated per unit area by day 4 was very similar for the electrode and enamel surfaces. On both surfaces the plaque contained approximately 25% streptococci, and the dominant species was Streptococcus sanguis (approximately 75%). The plaque which accumulated on pH-ISFET electrodes could not be distinguished visually or microbiologically from that which formed on control enamel surfaces.
Effects of Certain Salts on Glucosyltransferase Synthesis by Streptococcus mutans Strain PS-14
Authors: Takada K. , Fukushima K.
Published: November 2010

We investigated the effects of various salts on the synthesis of extracellular glucosyltransferase in a partially defined medium (M4) by Streptococcus mutans strain PS-14 and by certain other selected strains. The levels of glucosyltransferase produced by S. mutans strain PS-14 were found to increase to a maximum of seven-fold with increasing (NH4)2SO4 concentrations. However, at a 2% concentration of the salt, the level was stimulated 2.5-fold, and the growth was inhibited by 75%. A 1% concentration of MgS04 or NaCl also caused an increase of glucosyltransferase of six-fold or 2.4-fold, respectively. However, for S. mutans strain B-13N, the enzyme production was not stimulated by (NH4)2SO4, MgSO4, or NaCl. Moreover, the enzyme production by serotypes c, e, and f was found to be stimulated by 1% (NH4)2SO4, whereas the enzyme production by serotypes d and g was not affected.
Effect of Abrasion Medium on Wear of Stress-bearing Composites and Amalgam in vitro
Authors: Degee A.J. , Pallav P. , Davidson C.L.
Published: November 2010

Measurements of in vitro wear for several composite materials and an amalgam were conducted using a new device in which contact stress, moving speed, mutual slip, and third-body composition could be set. This preliminary study reports the results obtained with a fixed choice of contact stress, speed, and slip, but with different third-body media. With a Millet-seedIPMMA-beads mixture as a medium, the various types of restoratives showed a wear pattern and relative ranking comparable with that reported in clinical studies.
The Kinetics of Dissolution of Tooth Enamel — A Constant Composition Study
Authors: Chen W.C. , Nancollas G.H.
Published: November 2010

The kinetics of dissolution of powdered bovine enamel and of human enamel, both untreated and extracted with either hypochlorite or chloroform, has been studied using a constant solution composition technique in undersaturated solutions of calcium phosphate (total molar calcium concentration, TCa = 0.3 to 13.1 × 10-3 mol L-1, total molar phosphate, Tp = 0.18 to 7.9 x 10-3 mol L-1) at an ionic strength of 0.15 mol L-1, and pH = 4.5. The kinetic equations describing the dissolution reactions suggest a surface dislocation mechanism, and the presence of fluoride ion markedly retarded the reaction. For human enamel, a fluoride level of only 0.5 ppm reduced the rate of dissolution ten-fold. In contrast, the dissolution of hydroxyapatite, HAP, is best interpreted in terms of a polynucleation process.
Correlated Observations and Analysis of Maturation-ameloblast Morphology and Enamel Mineralization
Authors: Debari K. , Takiguchi R. , Higashi S. , Sasaki T. , Garant P.R.
Published: November 2010

A combined HCI-collagenase digestion technique and scanning electron microscopy were used to isolate the enamel organ and to confirm the presence of maturation ameloblasts of both ruffle-ended (RA) and smooth-ended (SA) types on maturing enamel in kitten permanent tooth germs. EDTA perfusion of animals fixed with aldehyde produced two or three belt-like shallow grooves (from 30 to 100 μ m wide) running horizontally through the maturing enamel surface, coinciding closely with the SA distribution pattern. In animals that had been perfusion-fixed with unbuffered osmium tetroxide containing 2.5% potassium pyroantimonate, SEM-EDX analysis detected K in a superficial enamel layer overlaid by the SA layer. Potassium concentration decreased gradually toward the deeper layers. Very little K penetrated the enamel under the RA layer. Energy-dispersive x-ray analysis of Ca and P concentrations in the enamel revealed an even distribution of these elements throughout the superficial layer of maturing enamel. These results suggest that the SA layer forms an access route for K and EDTA and that, in spite of the obvious morphological and functional differences between RA and SA, the maturing enamel surfaces overlaid by these two cell types show similar degrees of mineralization.
Fracture Toughness of Human Dentin
Authors: El Mowafy O.M. , Watts D.C.
Published: November 2010

Plane strain fracture toughness (KIC) was determined for coronal dentin using compact tension test-pieces obtained from recently extracted permanent lower molar teeth. Specimens were prepared and tested such that the moving crack front was aligned parallel to the tubule orientation. The fracture toughness (K IC) was temperature-invariant in the range 0-60°C, and the mean value obtained was 3.08 MN.(m)-1.5 (SD: 0.33). The critical strain energy release rate (GIC) of dentin was also calculated utilizing modulus data and was found to increase slightly with temperature, possibly as a consequence of significant temperature-dependence of the modulus:

The fracture toughness of dentin is midway in the range (0.23- 6.56) observed for cortical bone and is a factor of two greater than that exhibited by most current restorative materials.
Relation Between the Presence of Supragingival Calculus and Protease Activity in Dental Plaque
Authors: Morita M. , Watanabe T.
Published: November 2010

Protease activity was measured in dental plaque collected from patients with or without supragingival calculus. Plaque specimens from the calculus group showed significantly greater protease activity in the presence of 0.05% sodium thioglycollate than did those from the non-calculus group. No significant difference between the two groups was observed in the protease activity without sodium thioglycollate. There was no significant correlation between the age of the patients and the protease activity.
Adsorption of Benzoic Acid on Pure and Cupric Ion-modified Hydroxyapatite: Implications for Design of a Coupling Agent to Dental Polymer Composites
Authors: Misra D.N.
Published: November 2010

The adsorption isotherms of benzoic acid on synthetic hydroxyapatite (containing about 1.5 monolayers of physisorbed water) were studied from ethanol, dimethylsulfoxide, p-dioxane, methylene chloride, and benzene to discern the role of solvent in the process. The adsorption is reversible from the first three solvents and follows the Langmuir plots. It is irreversible from the last two, and a constant amount of absorbent is removed from solutions above a certain concentration. The isotherms of potassium benzoate on the apatite from ethanol and dimethyl sulfoxide were reversible.

The isotherms of the acid on cupric ion-modified apatite surfaces from ethanol and benzene were identical with those obtained on the pure hydroxyapatite. This may demonstrate that any "surface chelation" with the cation may not be a significant factor for adsorption to occur.

The adsorptive behavior seems to depend upon the interplay of hydrogen-bonding among the solute, the solvent, and the hydrated apatite surface. The capability of a solvent to hydrogen-bond may determine whether adsorption from it will be reversible or irreversible. Based upon its compatibility with a solvent, the benzene ring is upright or lies flat on the surface. The adsorbed molecules rotate about the center of the carboxylate groups which are hydrogen-bonded to the surface. These factors should be considered in designing or selecting a suitable surface-active moiety for a coupling agent between tooth mineral and a restorative resin.
Adhesion of Polycarboxylate-based Dental Cements to Enamel: An in vivo Study
Authors: Jemt T. , Stålblad P.A. , Øilo G.
Published: November 2010

The bond strength of two polycarboxylate and two glass ionomer cements to enamel in vivo has been measured by a tensile test method. The four cements were used to cement small stainless steel cylinders onto the facial surfaces of 11 and 21. The cylinders were removed by a tensile force applied by a handpiece containing a semi-conductor sensory unit.

The results showed that all cements gave two sets of bond strength values, either a good bond corresponding to a cohesive failure, or a weak bond corresponding to an adhesive failure. The mean bond strength values were lower than those recorded in vitro, and differences among the cements were limited.
Production and Degradation of Formate by Veillonella dispar ATCC 17745
Authors: Hoshino E. , Sato M.
Published: November 2010

Under strictly anaerobic conditions, the resting cells of V. dispar ATCC 17745 produced formate as well as acetate and propionate from pyruvate or from lactate. Pyruvate formate-lyase activity was found when the activity was assayed under strictly anaerobic conditions. Under aerobic conditions, however, the resting cells did not produce formate from pyruvate or from lactate, though the cells actively metabolized pyruvate or lactate (mainly to acetate). This was ascribed to pyruvate formate-lyase activity being easily lost when the cell-free extract was exposed to the air. A part of the produced formate was further degraded to CO2 by the resting cells.
Comparative Recovery of Streptococcus mutans on Five Isolation Media, Including a New Simple Selective Medium
Authors: Schaeken M.J.M. , Van der Hoeven J.S. , Franken H.C.M.
Published: November 2010

For the isolation of Streptococcus mutans, several selective media have been developed, of which Mitis-Salivarius Sucrose Bacitracin agar (MSB) is the most widely used (Gold et al., 1973). Recently, the Trypticase Yeast-Extract Cystine agar medium (TYC, de Stoppelaar et al., 1967) was modified into a selective medium for S. mutans , called Trypticase Yeast-Extract Cystine Sucrose Bacitracin (TYCSB, van Palenstein Helderman et al., 1983). The aim of this study was to compare the recovery of S. mutans from clinical samples on Mitis-Salivarius agar (MS), MSB, TYC, and TYCSB. Further, a new simple selective medium for S. mutans was introduced. This medium, called TSY20B, was supposed to have the same qualities as TYCSB, but its preparation is less laborious.

One hundred eighty-five plaque and saliva samples from 37 subjects were plated on MS, MSB, TYC, and TYCSB, and 285 samples from 23 subjects were plated on TYCSB and TSY20B. All plates were incubated at 37°C in a 91% N2, 5% CO2, 4% H2 atmosphere for five days. The S. mutans counts on TYC and TYCSB were significantly higher than on MS or MSB by almost a factor of 10. Seventy-seven percent of the samples gave higher S. mutans counts on TYCSB than on MSB. Especially, samples with high S. mutans dlg numbers gave lower S. mutans counts on MSB. These data clearly indicate that MSB agar is inhibitory for S. mutans and should not be used. An additional advantage of TYCSB over MSB agar is the possibility of distinguishing S. mutans serotypes dlg from other serotypes. No significant difference was found between the recovery of S. mutans on TYCSB and its simplified version, TSY20B.
Dental Caries Prevalence in Early Polynesians from the Hawaiian Islands
Authors: Keene H.J.
Published: November 2010

We examined the skeletal remains of 1338 early Hawaiians (preserved in the Bishop Museum, Honolulu) to determine total caries and root surface caries prevalence. Specimens from seven islands were represented in the collection. Estimation of age at death was made by a combination of dental developmental staging for younger individuals and occlusal attrition and/or alveolar bone loss in adults. Museum records were also consulted for age estimation of adults which was primarily based on osteological criteria. The material was divided into six age groups. Predentate infants and edentulous adults were not included. A total of 19,425 teeth was examined. Caries lesions were observed in 462 individuals (34.5%) and 1895 teeth (9.8%). Coronal caries lesions in children and adolescents tended to be small and not particularly destructive of tooth structure. Root surface lesions in young adults were also small but increased progressively in size in the older groups, resulting in pulp exposure and coronal amputation. Although coronal caries was apparently not a significant dental health problem in children and young adults (compared with contemporary Hawaiians), root surface caries was an increasingly important source of tooth morbidity and tooth mortality in the older population groups. This age-related caries pattern was similar for all of the islands.
A Histologic Study of the Width and Nature of Inter-radicular Spaces in Human Adult Pre-molars and Molars
Authors: Heins P.J. , Wieder S.M.
Published: November 2010

Serial sections of jaw segments from a human post mortem population of 29 individuals providing 116 posterior interproximal sites were examined at the light microscopic level. Minimum inter-root distances at the locale of closest proximity ranged from more than 4 mm to less than 0.1 mm. They were located in the coronal third of pre-molars and mandibular first and second molars and the middle third of maxillary first molars and second molar interproximal spaces.

Cancellous bone flanked by lamina dura was found between 89.6% of the teeth examined and was observed where inter-root distances exceeded 0.5 mm. At sites of less than 0.5 mm, cancellous bone was not observed, and, instead, adjacent laminae durae appeared fused (7.7%). Bone was not observed between root surfaces which were less than 0.3 mm apart, but in these instances the roots were con nected by a periodontal ligament.
Susceptibility of Bacteroides gingivalis to Bactericidal Activity of Human Serum
Authors: Okuda K. , Kato T. , Naito Y. , Ono M. , Kikuchi Y. , Takazoe I.
Published: November 2010

Susceptibility of Bacteroides gingivalis strains to the complement-mediated bactericidal activity of human serum was examined under anaerobic conditions. Serum containing high concentrations of IgG antibody to B. gingivalis enhanced the bactericidal activity. No enhancement was found in serum which did not contain the specific antibody or in serum absorbed with intact cells. The sensitivity to the killing by pooled serum differed among B. gingivalis strains. Cells of B. gingivalis activated the pooled human serum complement not only through the classic pathway but also through an alternative pathway. It was found that the susceptibility of B. gingivalis to the bactericidal activity was classic-pathway-dependent.
Effect of X-ray Irradiation on Lipid Peroxide Levels in the Rat Submandibular Gland
Authors: Nishi M. , Takashima H. , Oka T. , Ohishi N. , Yagi K.
Published: November 2010

We examined the effect of local x-ray irradiation on the changes in the lipid peroxide level in submandibular gland, liver, and blood plasma. Rats five weeks of age received a single low dose of 3 Gy x-ray irradiation to their neck regions. The lipid peroxide level in the submandibular gland was significantly enhanced at seven days after irradiation, as was the level in the blood plasma at two hours, seven and 14 days after irradiation. The lipid peroxide level in the liver decreased, as compared with levels in the controls. There was a slight tendency for acinar cells of the submandibular gland to show pyknosis and anomalous nuclei within three days after irradiation. These results suggest that radiation injury results in an elevation of the lipid peroxides in the submandibular gland, and an increased level in the blood.
The Vulnerability of Unexposed Human Dental Roots to Demineralization
Authors: Hoppenbrouwers P.M.M. , Driessens F.C.M. , Borggreven J.M.P.M.
Published: November 2010

Crowns and roots of human molars, the roots from which had not been exposed to the oral environment, were exposed for 0, 3.5, 7, and 14 days to buffer solutions which were undersaturated or supersaturated with respect to hydroxyapatite. Densitometric measurements on contact-microradiograms of transverse sections of the crowns and of the cervical parts of the roots yielded plots of the mineral content as a function of the distance to the outer surface. From these plots, the rate of demineralization was calculated. It was found that the mineral of the roots dissolved even in buffer solutions which were supersaturated with respect to hydroxyapatite. Comparison of the results obtained from the crowns with those from the roots showed that the root hard tissues were more vulnerable to demineralization than was the dental enamel.
An Explanation for the "Two Fiber Axes" Problem in Human Enamel by X-ray Diffraction
Authors: Hirota F.
Published: November 2010

Since Thewlis found the "two fiber axes" patterns on x-ray diffractograms of human enamel in 1934, many investigators have studied this problem. However, a definite answer has not yet been obtained. The present detailed x-ray diffraction study showed that the 'two fiber axes" patterns in human enamel were caused by reflections from the two zones of the Hunter-Schreger bands being recorded simultaneously on x-ray film, because we used an x-ray beam far larger in size than the width of the Hunter-Schreger bands.
Exocytosis in Rat Parotid Acini After in vitro Treatment with Forskolin is Accompanied by Cellular Redistribution of Regulatory Subunits of Cyclic AMP-dependent Protein Kinase
Authors: Mednieks M.I. , Cheng L.F. , Hand A.R.
Published: November 2010

Incubation of rat parotid acinar tissue with 1 μmol/L forskolin resulted in progressive exocytosis which was virtually complete after a 30-minute incubation period. Cyclic AMP binding to protein kinase (cA-PK) regulatory (R) subunits, determined by photo-affinity labeling with [32P]-8-azido cyclic AMP, was found to increase in a time-dependent manner in the 10,000-g supernatant fraction of a broken cell preparation. An apparent redistribution of protein kinase R subunits took place in the 600-g supernatant after in vitro treatment of cells with forskolin. In control cells, RI and RII subunits and a 35-to-40-kdal fragment were present in approximately equal amounts throughout the incubation. Azido labeling of RII appeared either to increase or to remain unchanged, while that of RI decreased in the 600-g pellet. Only type I isozyme R subunits were found in the 600-g pellet in either the absence or presence of forskolin. These findings indicate that a temporal relationship exists between stimulated protein exocytosis and cyclic AMP-dependent protein kinase activation. Forskolin stimulation of adenylate cyclase in salivary gland cells therefore provides a defined system for the study of cyclic AMP-mediated protein secretion.
In vivo Remineralization by a Monofluorophosphate Dentifrice as Determined with a Thin-section Sandwich Method
Authors: Mellberg J.R. , Castrovince L.A. , Rotsides I.D.
Published: November 2010

Artificial caries lesions were formed in thin sections of subsurface enamel sandwiched between protective sheets of plastic. Six lesions were placed into the buccal surfaces of lower partial dentures of seven subjects, covered with a stainless steel mesh to provide a plaque cover, and brushed with either a sodium monofluorophosphate or placebo dentifrice for four weeks, by means of a double-blind random cross-over design. Analysis of the lesions by quantitative microradiography revealed that significant remineralization (21%) occurred in the monofluorophosphate group and significant further demineralization (27%) in the placebo group. The difference between the active and placebo treatments was significant (p = 0.02), showing that the monofluorophosphate was effective not only in preventing lesion progression but also in promoting mineral deposition.

The simultaneous presence of remineralized lesions and lesions with increased demineralization showed the non-uniformity of conditions within a mouth.
Effects of Two Fluoride Gels on Fluoride Uptake and Phosphorus Loss During Artificial Caries Formation
Authors: Mellberg J.R. , Charig A. , Deutchman M. , O'Brien W. , Lass A.
Published: November 2010

Blocks of human enamel were cycled through a demineralization - F-treatment-remineralization procedure and then analyzed for fluoride and the presence of caries-like lesions. Treatments with a sodium fluoride gel (5000 ppm F) increased the enamel fluoride concentration to 6500 ppm F, whereas a stannous fluoride gel (1000 ppm F) increased enamel fluoride to about 1200 ppm F. Although a control treatment (water) allowed caries-like lesions to form, as observed by microradiography, no lesions were found in either of the fluoride-treated groups.

When the experiment was repeated with radioactive teeth, mineral loss, as determined by release of 32P, was again greatest in the water-treated control group, but some loss was observed in the fluoride treatment groups. The least loss was found in the sodium fluoride group.

It was concluded that the fluoride treatments not only increased enamel resistance but also enhanced remineralization so that calcium phosphate was replaced during the subsequent remineralization phase. Because of the probability that stannous ions were deposited during the stannous fluoride treatments, some of the apparent calcium phosphate re-deposition in this group was probably stannous compounds.
On the Non-existence of Compensatory Tooth Size Interaction in a Contemporary Human Population
Authors: Kieser J.A. , Groeneveld H.T. , Preston C.B.
Published: November 2010

Compensatory tooth size interactions between early and later developing teeth within the same tooth class were empirically evaluated in a sample of 125 study casts of Caucasoid children. Mean buccolingual and mesiodistal diameters for first and second molars, pre-molars, and incisors were calculated, and those first developing teeth that were either larger or smaller than the mean were identified. Pearsonian correlation coefficients and chi-square tests revealed highly significant positive correlations between smaller or larger early developing teeth and their later developing neighbors. This total lack of compensatory tooth size interaction was also confirmed when outsized teeth (larger or smaller than one standard deviation from the mean) were used. Similar results were obtained when tooth size was cor rected for arcade length, hence allowing for the rejection of Sofaer's model of compensatory tooth size interaction.
Wetting Properties of Human Saliva and Saliva Substitutes
Authors: Vissink A. , De Jong H.P. , Busscher H.J. , Arends J. , 's-Gravenmade E.J.
Published: November 2010

Contact angle measurements were employed so that we could study the wetting properties of human whole saliva and saliva substitutes containing mucins or carboxymethylcellulose (CMC) on human oral mucosa (in vivo) and on ground and polished human enamel (in vitro). A new approach was introduced for measuring contact angles on human oral mucosa in vivo. It was shown that the wetting properties of CMC- and mucin-containing saliva substitutes on human enamel were significantly better than those of human whole saliva. On human oral mucosa, the wetting properties of CMC-containing saliva substitutes and human whole saliva were comparable, but were surpassed by those of the mucin-containing saliva substitutes. Mucin-containing substitutes thus provide good wetting properties on ground and polished enamel as well as on oral mucosa.