bluuebunny/crossref_metadata_2025_split huggingface dataset:
Clinical Science The Prevalence and Significance of Yeasts in Persons Wearing Complete Dentures with Soft-lining Materials
Authors: Wright P.S. , Clark P. , Hardie J.M. 
Published: November 2010

Fifty-three persons wearing soft-lined mandibular dentures and heat-cured acrylic-resin maxillary dentures were studied, using imprint cultures, to determine the isolation frequency and density of colonization of denture and mucosal surfaces by yeasts. Yeasts were isolated from 35 (66%) of the persons studied. Nine species of Candida and one each of Trichosporon and Saccharomyces were identified. Candida albicans, occurring either alone or together with another strain, was identified in 66% of the isolates and was associated with a higher mean density/cm 2 than that of other strains. An association between the method of denture cleaning, denture hygiene, and smoking habits and the isolation of yeasts was demonstrated, but a similar association could not be demonstrated with the sex of the person, denture-wearing habits, type and condition of the soft lining, or the clinical appearance of the mandibular denture-bearing mucosa. Although yeasts are more likely to colonize soft-lining materials than the fitting surface of conventional lower dentures, their presence did not significantly affect the soft-lining material. Further, the increased isolation of yeasts on the fitting surface of the soft-lined mandibular denture was not associated with an increased incidence of inflammatory changes in the mandibular denture-bearing mucosa.
Malocclusion, Masticatory Muscle, and Temporomandibular Joint Tenderness
Authors: Bush F.M. 
Published: November 2010

The Angle classification of occlusion, as well as occlusal contacts determined at retrusion, mediotrusion, laterotrusion, and protrusion were recorded from 298 dental students. Various masticatory muscles and the TM joints were palpated simultaneously for tenderness. No significant relationships were observed between (1) tenderness and Angle class or (2) tenderness and any occlusal contact. In relation to a slide between retruded contact position and intercuspal position: measurements for (a) vertical and (b) horizontal displacements, but not (c) lateral deflection, were greater in Class I students without tenderness than in Class I students with tenderness.
Reduction of Acidurance of Streptococcal Growth and Glycolysis by Fluoride and Gramicidin
Authors: Bender G.R. , Thibodeau E.A. , Marquis R.E. 
Published: November 2010

The acidurance of glycolysis by intact cells of Streptococcus mutans GS-5, Streptococcus salivarius ATCC 25925, and Streptococcus sanguis NCTC 10904 was found to be highly dependent on membrane functions affected by gramicidin, which increases the proton permeability of cell membranes. Plots of % glucose utilized during two hours against suspension pH values for cells suspended in 100 mM phosphate buffer plus 1 mM MgCl 2 plus 13.9 mM glucose indicated, for 50% glucose utilization, pH values of 5.0 for S. mutans, 5.7 for S. salivarius, and 6.2 for S. sanguis. Gramicidin treatment shifted these values to 6.0, 6.3, and 6.9, respectively. Growth of S. mutans and S. salivarius in complex media proved to be more acid-sensitive than was glycolysis, and in batch cultures, there was a well-defined, post-growth phase of glycolysis. Minimum pH values for growth and for glycolysis in medium with excess glucose were approximately 4.8 and 4.4, respectively, for S. mutans, and 4.9 and 4.3 for S. salivarius. S. sanguis was less aciduric and showed little differential acid sensitivity, with minimum pH values of about 5.2 for both growth and glycolysis. Fluoride acted to eliminate the differences in acidurance of growth and glycolysis for S. mutans or S. salivarius and to render both processes more acid-sensitive. Thus, glycolysis was more fluoride-sensitive than was growth. Growth was found to be acid- limited in media with initial glucose levels greater than 0.2, 0.3, and 0.5% (weight/volume) for S. sanguis, S. mutans, and S. salivarius, respectively, and to be glucose-limited at lower levels. When 1.0 mM NaF was added to the media, the acid-sensitizing effect of fluoride was evident in major shifts in the initial glucose levels for transition from glucose-limited to acid-limited growth to 0.1 and 0.2% for S. mutans and S. salivarius, respectively. S. sanguis was less severely affected by fluoride. Fluoride treatment of glycolyzing cells of S. mutans at a pH value of 5 resulted in little change in intracellular levels of phosphoenolpyruvate but increased levels of 2-phosphoglycerate, indicative of inhibition of intracellular enolase. However, there were also large decreases in levels of early glycolytic intermediates, to about the levels found in starved cells, presumably due to fluoride inhibition of glucose uptake.
The Effects of Different Concentrations of Sucrose, Fructose, and Glucose on pH Changes by Streptococcus mitior in an Artificial Mouth
Authors: Lagerlof F. , Dawes R. , Dawes C. 
Published: November 2010

The aim of this study was to determine the effects of the initial sucrose (S) concentration, as well as those of fructose (F), glucose (G), and invert sugar (F/G), on the pH developed by a layer of S. mitior, to represent dental plaque, in an artificial mouth which simulates the process of oral sugar clearance. At S, F. G, and F/G concentrations of 2% and with normal oral sugar clearance rates, the bacteria produced a smaller pH fall from S than from the other sugars; at initial concentrations of 20%, however, the differences were not significant. With constant S concentrations of 0.5 - 35%, the minimum pH reached was 4.03 ± 0.14 (S.D.); with S concentrations of 50% and above, slightly but significantly higher values (4.41 ± 0.34) occurred. However, with normal sugar clearance, the pH fall was much less than with a constant concentration and was dependent on the S concentration over the range of 0 - 10%, but was independent at higher concentrations. Exposure of the bacteria to S for as short a period as two min during normal sugar clearance gave a nearly maximum pH fall. This suggests that rinsing the mouth with water more than two min after consumption of sucrose in liquid form will have very little effect in reducing the pH fall in dental plaque. A more appropriate method for reducing acid formation by dental plaque would be consumption of a salivary stimulant which would increase the flow rate and buffer capacity of the saliva.
Materials Science Photo-oxidation of Tetracycline Adsorbed on Hydroxyapatite in Relation to the Light-induced Staining of Teeth
Authors: Davies A.K. , Cundall R.B. , Dandiker Y. , Slifkin M.A. 
Published: November 2010

In an attempt to understand the chemistry of the light-induced staining of children's teeth by tetracycline, we studied the photochemical behavior of tetracycline adsorbed on hydroxyapatite, as a simple model of enamel. Tetracycline was strongly bound by hydroxyapatite to give a pale yellow material which, under ultraviolet light, showed a bright yellow fluorescence (λmax 525 nm). On exposure of this material to the radiation from a medium-pressure mercury lamp, the fluorescence gradually disappeared, and a red-purple product was formed. Photo-acoustic spectroscopy was employed to follow the disappearance of tetracycline and the concomitant formation of the red-purple product, the spectrum of which (λmax 530 nm) led to the conclusion that it was 4α, 12α-anhydro-4-oxo-4-dedimethylaminotetracycline (AODTC). This assignment was supported by the observation that 1 mole of oxygen was absorbed per mole of adsorbed tetracycline converted to the red-purple product. It is suggested that the formation of AODTC on hydroxyapatite probably takes place by a mechanism of photo-oxidation similar to that already proposed for solutions of tetracycline, and that the formation of AODTC in children's teeth is responsible for the light-induced staining caused by tetracycline.
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.
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.
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.
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.
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.
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.
Effects of Photoinitiators for the Visible-light Resin System on Hemolysis of Dog Erythrocytes and Lipid Peroxidation of Their Components
Authors: Fujisawa S. , Kadoma Y. , Masuhara E. 
Published: November 2010

The visible-light (VL) polymerizing resin system with photoinitiators (photosensitizer and reducing agent) is widely used in modern dentistry. In this system, polymerization is initiated by photochemical reactions between the photosensitizers (aromatic or aliphatic ketones) and reducing agents (tertiary amines) during VL irradiation. In order to simulate the VL resin-induced toxicity in dental pulps, the present investigation was conducted to determine whether hemolysis of dog erythrocytes and lipid peroxidation of their components occur on exposure to a VL resin system containing aromatic (9-fluorenone, benzil) or aliphatic ketones (camphoroquinone) plus tertiary amine [2-(dimethylamino) ethyl methacrylate]. It was demonstrated that the hemolysis and lipid peroxidation with aromatic ketones were markedly higher than with those of aliphatic ketones, even when the latter were used at higher concentrations. It was clear that peroxidation-induced hemolysis occurred and, further, that surface-active complexes between photosensitizers and reducing agents, which are formed by irradiation, promote hemolytic activity due to their hydrophobic interactions. VL resin-induced responses to dental pulps are probably promoted due to the double effects of unpolymerized monomers and of both radicals and surface-active complexes formed during irradiation.
Mandibular Growth and Histologic Changes in Condylar Cartilage of Rats Intoxicated with Vitamin D3 or 1,25(OH)2D3 and Pair-fed (Undernourished) Rats
Authors: Weinreb M. , Gazit E. , Weinreb M.M. 
Published: November 2010

The mandibular condyles of 1,25(OH)2D3or Vitamin D3intoxicated rats were studied and compared with those of normal as well as pair-fed controls. Experimental animals were injected with either Vitamin D3(2 mg/kg/day ) or 1,25(OH)2D3(400 ngl/kg/day) for 19 days. Controls were given the solvent only, while pair-fed animals were restricted in their food intake for the same period of time, so that they exhibited a weight-curve similar to that of the experimental rats. The length of the mandibular ramus was measured in lateral radiographs of all mandibles. Demineralized coronal sections were obtained from all mandibular condyles and were stained with Mallory's connective tissue stain. The width of each zone within the condylar cartilage was measured.Experimental animals showed significant reduction in width of all layers within the condylar cartilage, with total lack of distinction between the maturation and hypertrophic zones. They also exhibited a significant retardation in growth of the mandible.Pair-fed animals had a normal width of the chondroprogenitor layer but significantly smaller maturation + hypertrophic zones (vs. controls). They also exhibited a significant retardation in mandibular growth but not to the same degree as did the intoxicated animals.Reduction in growth attributed to 1,25(OH)2D3or Vitamin D3intoxication is partly caused by undernutrition, which is a by-product of this condition. A further kinetic study is indicated to elucidate the mechanism of growth retardation and the differential effect on the various cartilage layers.