bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of pH on the Sensitivity of Species of Lactobacillus to Chlorhexidine and the Antibiotics Minocycline and Spiramycin
Authors: Cleghorn B. , Bowden G.H.
Published: November 2010

The purpose of this study was to determine the sensitivity of a range of Lactobacillus species to chlorhexidine, Minocycline, and Spiramycin, at a range of pH from 5.0 to 7.4. Strains of Streptococcus were also tested for their sensitivity to chlorhexidine, as a comparison between the genera. There were both inter- and intra-species variations in the sensitivity of these strains to chlorhexidine. The strains tested were sensitive at pH 6. 7 to the following levels of chlorhexidine (μg/mL) : L. casei (6 strains), 10-60; L. plantarum (4 strains), 40; L. fermentum (13 strains), 2-20; L. brevis (1 strain), 10; and L. acidophilus (3 strains), 10-60. The Streptococcus species were sensitive to 1-4 μ/mL (13 strains); 4-10 μg/mL (3 strains); and 10-20 μg/mL (2 strains). One strain was able to survive 20 μg/mL. Chlorhexidine was found to be less effective at lower pH levels. The following examples show sensitivity (μg/mL) at pH 6.5 followed by sensitivity at pH 5.0 : L. casei (ATCC 15008), 40,60 ; L. plantarum (CH 374), 40,100 ; L. fermentum (CH 324) 10,40 ; L. acidophilus (ATCC 4356), 10,40 ; and S. mutans (BM 52), 2,2.

All of the strains of Lactobacillus tested with Spiramycin were resistant at pH 5.0. Minocycline was less affected by changes in pH, but at pH 7.4 Lactobacillus strains were more resistant to Minocycline as compared with Spiramycin. Both of these antibiotics are bacteriostatic, and therefore may have a more limited effect than a bactericidal agent such as chlorhexidine.

The Lactobacillus strains tested required higher concentrations of chlorhexidine than did the strains of Streptococcus for a killing effect in vitro.
Possible Function of Matrix Proteins in Fluoride Incorporation into Enamel Mineral during Porcine Amelogenesis
Authors: Aoba T. , Collins J. , Moreno E.C.
Published: November 2010

The present study was undertaken to elucidate the mechanism of fluoride incorporation into secretory enamel mineral, with porcine enamel used as a model. Although the fluoride content in the enamel varied greatly among the animals, we observed that the fluoride-to-calcium ratio in the enamel tissue was maximal at the beginning of the secretory stage; the F/Ca ratio decreased (and leveled off) with the advancement of mineralization. In vitro work showed that some of the fluoride in the secretory enamel tissue was removed with the extraction of organic matter, mostly amelogenins. Furthermore, coating hydroxyapatite crystals with enamel matrix proteins resulted in a retardation of fluoride incorporation into the crystals when exposed to fluoride solutions, as a result of an inhibition of apatite reprecipitation. We also confirmed that the growth kinetics of fluoridated apatite onto HA seeds decreased with increasing coverage of the seed surface with the enamel proteins_ All the results of the present study strongly suggest that the fluoride incorporation into enamel mineral during the secretory stage may be regulated by the kinetics of mineralization, which is highly dependent on the driving force for precipitation and the presence of proteinaceous inhibitors, mainly amelogenins.
Surface Tension and Contact Angle on Enamel of Surfactant Solutions for Caries Diagnosis with Dyes
Authors: Van de Rijke J.W. , Busscher H.J. , Ten Bosch J.J. , Perdok J.F.
Published: November 2010

We measured the surface tension of solutions of five surfactants in water, ethanol, and a 50% water/ethanol mixture at 25°C, as well as the contact angle of these solutions on ground and polished bovine enamel in vitro and on intact pellicle-covered human enamel in vivo.

All surfactants lowered the surface tension of water. In ethanol, no reduction of the surface tension was achieved by any of the five surfactants. In the water/ethanol mixture, only Fluorad® lowered the surface tension from 29.2 to 19.7 mJ.m-2 at 25°C.

On bovine dental enamel, all surfactant solutions showed a significantly lower contact angle than did distilled water.

On pellicle-covered human enamel, Rewoteric® in distilled water showed no significantly lower contact angle than did pure distilled water, but all other solutions did.

Both in vitro and in vivo, ethanol spread instantaneously over the enamel surface.

Based on these measurements, we concluded that several surfactants may be used to spread ayueous dye solutions. In a 50% mixture of water and ethanol and in pure ethanol, no surfactant is necessary for enhanced spreading of the solution, but surfactants may be considered for adhesive properties.
A Clinical Trial of Intraligamentary Anesthesia
Authors: Edwards R.W. , Head T.W.
Published: November 2010

The effectiveness of the periodontal ligament injection in providing anesthesia for routine extractions and the possible mechanisms of action of the periodontal ligament injection in producing dental anesthesia were investigated in a clinical trial.

Periodontal ligament injections were administered under strong pressure with lidocaine on 14 teeth, with epinephrine on seven teeth, and with normal saline on another seven teeth. The anesthesia attained was evaluated by: response of the teeth to an electric pulp tester, gingival probing around the teeth, and the ability for teeth to be extracted without pain.

The results demonstrated that periodontal ligament injections with lidocaine were effective in providing adequate anesthesia for the performance of dental extractions. Lidocaine periodontal ligament injections were statistically and clinically more effective in attaining anesthesia than were epinephrine or saline injections.

Epinephrine periodontal ligament injections resulted in a slight but statistically significant increase in the stimulus necessary to produce a patient response, when the teeth were stimulated with an electric pulp-tester. Saline injections produced no change in response to the stimulus tested. It appears, based on the results of the saline and epinephrine injections, that hydrostatic pressure had no direct effect on the production of anesthesia with the periodontal ligament injection.
Associations between Salivary Levels of Streptococcus mutans, Streptococcus sobrinus, Lactobacilli, and Caries Experience in Kenyan Adolescents
Authors: Beighton D. , Manji F. , Baelum V. , Fejerskov O. , Johnson N.W. , Wilton J.M.A.
Published: November 2010

Salivary levels of mutans streptococci (S. mutans and S. sobrinus) and lactobacilli were determined in a random sample of rural Kenyans between 15 and 19 years of age (n = 149). It is possible for the natural history of dental caries in this population to be studied since it is characterized by a limited access to conventional dental treatment. Using a short set of biochemical tests, we identified from seven to ten presumptive mutans streptococcus colonies-cultured from the saliva of each individual-to differentiate between S. mutans and S. sobrinus. No colonies resembling S. rattus (S. mutans serotype b) were isolated. Lactobacilli were identified as Gram-positive, catalase-negative rods. The mean D1-4MFS and D3-4MFS were 7.03 ± 6.43 and 1.46 ± 3.44, respectively. The mean mutans streptococcus and lactobacillus levels were 8. 7 x 104 and 6. 7 x 104, respectively. The salivary mutans streptococcus and lactobacillus levels were significantly correlated (p<0.01). Of the subjects, 64% harbored only S. mutans, 4% only S. sobrinus, 30% both species, and 2% neither. Lactobacilli were ubiquitous. The caries experience of the group was significantly (p<0.001) correlated with both the total salivary level of mutans streptococci and the salivary S. mutans levels, but not with the salivary S. sobrinus level.
Development and in vitro Evaluation of an Intra-oral Controlled-release Delivery System for Chlorhexidine
Authors: Mirth D.B. , Bartkiewicz A. , Shern R.J. , Little W.A.
Published: November 2010

Copolymers of hydroxyethyl methacrylate (HEMA) and methyl methacrylate (MMA) were prepared and used to fabricate a membrane-controlled reservoir-type controlled-release delivery system for chlorhexidine that should be suitable for intra-oral use. The reservoir of the system was prepared bys softening an 80:20 mixture of chlorhexidine diacetate and 50:50 HEMA:MMA copolymer with methyl ethyl ketone (MEK), and pressing standard amounts of the resulting dough-like mixture into silicone rubber molds. A membrane was applied to the reservoirs by rotating them through a solution of 30:70 HEMA:MMA copolymer in MEK. The finished oval-shaped controlled-release pellets were approximately 4. 7 mm wide, 3.3 mm high, and 7.4 mm long, and contained 45.0 ± 3.7 mg of chlorhexidine diacetate. The mean in vitro release rate of chlorhexidine diacetate from the pellets into 37°C water was 608 ± 55 μg/24 h for days 2 through 11, and 389 ± 50 μg/24 h for days 15 to 30 of the test period. The chlorhexidine released on day 30 was biologically active, as determined by a serial dilution assay against Streptococcus mutans. The extended release of biologically active chlorhexidine at a controlled rate from this system suggests that it is worthy of further evaluation for the intra-oral therapy of chlorhexidine-treatable oral infections in non-compliant and physically or mentally compromised individuals.
A Rapid Heating and Cooling Rate Dilatometer for Measuring Thermal Expansion in Dental Porcelain
Authors: Twiggs S.W. , Searle J.R. , Ringle R.D. , Fairhurst C.W.
Published: November 2010

Herein we describe a dilatometer that consists of a low-mass infrared furnace for rapid heating or cooling, an optical pyrometer, and a laser interferometer. The dilatometer facilitates observations of thermal expansion at rates comparable with those in dental laboratory practice over the temperature range necessary for comparison of thermal expansion of dental porcelain and alloy. Examples of thermal expansion data obtained at a 600°Clmin heating rate on NIST SRM 710 glass and dental porcelain are reported. To a limited extent, thermal expansion data above the glass-transition temperature range of dental porcelain were obtained. A shift of the glass-transition temperature range to higher temperatures was observed for both materials, compared with data obtained at 20°Clmin.
The Colors of Mixtures of Dental Opaque Porcelains
Authors: White J.M. , O'Brien W.J.
Published: November 2010

The colors of mixtures of dental opaque porcelains and modifiers were measured with use of the CIE L*a * b* uniform color space. Mixtures of dental porcelains were tested to duplicate the range of human tooth colors. Vertical movements in the yellow and blue directions were obtained. Horizontal movements in the red and green directions were achieved. Reflectance measurements were made with use of a spectrophotometer with an integrating sphere. Spectrophotometer measurements were converted to absolute reflectance and then used to calculate CIE a* b* values for a 2° standard observer and for illuminant C. Movements in the yellow, red, blue, and green directions for adequate simulation of the tooth color range can be demonstrated with use of dental opaque and modifier porcelains.
The Interpretation of CO2 Equilibration Data to Obtain Plaque Fluid Buffer Capacities, and Comparison with Results Obtained by Titration
Authors: Dibdin G.H. , Shellis R.P.
Published: November 2010

Titration measurements of pooled plaque fluid buffering capacity (Shellis and Dibdin, 1988), which showed a broadly defined minimum at pH 7 were compared with recent curves published by Carey et al. (1988a), which they obtained by an ultra-micro CO 2-equilibration technique and which suggested a quite different profile, peaking sharply at pH 7.1. When analyzed in a different, more conventional way, the raw measurements in the latter study become more consistent with our own results and with earlier findings of Tatevossian (1977). In particular, we conclude that the peak at pH 7.1 is an artifact, and that Carey et al. underestimated buffer capacities below pH 6.4 and above pH 7. 4. Rationales for the two modes of analysis are compared, and possible reasons for the remaining differences between the re-analyzed CO2-equilibration results and the titration results are discussed. Suggestions for the improvement of the accuracy of the CO2-equilibration technique are put forward.
Vasoactive Intestinal Peptide Interacts with Alpha-adrenergic-, Cholinergic-, and Substance-P-mediated Responses in Rat Parotid and Submandibular Glands
Authors: Bobyock E. , Chernick W.S.
Published: November 2010

Secretory dose-response curves were obtained with both acetylcholine and phenylephrine treatment in rat parotid and submandibular glands. Vasoactive intestinal peptide (VIP), which produced relatively low volumes of protein-rich saliva in rat salivary glands, also enhanced acetylcholine-, phenylephrine-, and substance-P-mediated fluid and protein secretion when administered in combination with these agents. The specific mechanisms involved in the synergistic actions of VIP with substances such as acetylcholine, phenylephrine, and substance P, which are primarily linked to the production of fluid secretion in rat salivary glands, have yet to be determined.
Effect of Exercise on Salivary Composition and Cortisol in Serum and Saliva in Man
Authors: Ben-Aryeh H. , Roll N. , Lahav M. , Dlin R. , Hanne-Paparo N. , Szargel R. , Shein-Orr C. , Laufer D.
Published: November 2010

The effect of exercise on electrolytes and cortisol levels in serum and saliva was examined in 27 young, healthy male volunteers who performed graded submaximal cycle exercise for nine min at up to 85% of their age-predicted maximal heart rate. Seventeen men performed the Wingate anaerobic test for 30 s. A significant increase in pulse rate and systolic blood pressure and a decrease in diastolic blood pressure were found, and serum concentrations of Na+, K+, and lactate were significantly elevated immediately after exercise. A non-significant increase in saliva and serum cortisol levels was found. Significantly lowered salivary flow rate and elevated salivary K*, protein, and lactate concentrations were found within ten min after exercise. Salivary Mg2+ was significantly elevated after anaerobic exercise only.
Genotoxic Evaluation of Chronic Fluoride Exposure: Micronucleus and Sperm Morphology Studies
Authors: Dunipace A.J. , Zhang W. , Noblitt T.W. , Li Y. , Stookey G.K.
Published: November 2010

The purpose of this study was to investigate the genotoxic effects of chronic fluoride exposure on mammalian cells in vivo by use of the mouse bone-marrow micronucleus test and the sperm morphology methodology. Mice of genotype B6C 3F1 were obtained at weaning and maintained on a low-fluoride diet (<0.2 ppm F) ad libitum throughout the experiment. The animals were randomly assigned to seven groups and given fluoride (as sodium fluoride) in concentrations ranging from 1.0 to 75 ppm in the drinking water. Negative (distilled water) and positive (cyclophosphamide) controls were included. After a 21-week treatment period, the animals were killed by cervical dislocation, and blood was obtained by cardiac puncture. Slides of femur marrow cells were prepared and blindly examined for the frequency of micronucleated polychromatic erythrocytes (MN-PCE). Slides of sperm from the cauda epididymides of the male mice were also prepared and similarly examined for morphological abnormalities. Weight of the testes was recorded, and the plasma, humeri, testes, and carcasses were saved for fluoride analyses. Analyses of bone and plasma fluoride confirmed the effective absorption of fluoride following ingestion. The frequency of MN-PCE, the count of abnormal sperm, and the weight of the testes for mice chronically exposed to fluoride, in doses ranging from approximately 0.3 to 23 mg/kg/day, were not significantly different from those of the negative control animals. The results of this study support the view that fluoride has no genotoxic effects.
Stiffness of Endodontically-treated Teeth Related to Restoration Technique
Authors: Reeh E.S. , Douglas W.H. , Messer H.H.
Published: November 2010

Endodontically-treated posterior teeth are susceptible to fracture; consequently, full-occlusal-coverage restorations are recommended. We designed this study to examine the potential for alternative restorative techniques for pulpless teeth, using strain gauges mounted on extracted maxillary second premolars to measure strains generated by nondestructive occlusal loading. Cuspal stiffness was evaluated on the following sequentially performed procedures: unaltered tooth, completion of all endodontic procedures, appropriate restorative preparation, and restoration. The restorative procedures evaluated were: (1) amalgam, (2) cast gold onlay, (3) composite restoration with enamel etch, and (4) composite restoration with enamel and dentin etch. Finally, all teeth were loaded to fracture. Cast gold was the strongest restorative material tested (2.11 relative stiffness, compared with that of the unaltered tooth at 1.00), and amalgam was the weakest (0.35 relative stiffness). Composite restoration and enamel plus dentin etch were almost as strong as the unaltered tooth (0.87 relative stiffness), while enamel-etch-only yielded lower stiffness (0.51).
Effect of Force Level on Synthesis of Type III and Type I Collagen in Mouse Interparietal Suture
Authors: Yen E.H.K. , Yue C.S. , Suga D.M.
Published: November 2010

Nine-week-old Swiss male white mice were divided into groups killed after time intervals of force application of six h, and one, three, five, seven, ten, 14, 21, and 28 days. Each group had 45 animals: three control, three sham-operated, and three experimental animals for each of the five force levels: 50 g, 35 g, 25 g, 15 g, and 5 g. The experimental animals had helical springs placed surgically in their calvaria for expansion of the interparietal suture. The sham-operated animals received inactive springs. Control animals were at the same age as the experimental and sham-operated animals.

After death, the amount of sutural expansion was measured, and the calvaria with the implanted springs were explanted into Trowelltype organ culture dishes. [ 14C]-glycine was added for two h after 60 min of culture for all explants. The rate of suture expansion was directly proportional to the force value of the tensile stress, and a maximum 2.0-mm expansion was achieved for all force levels by the 28th day. Sutural collagen was solubilized by limited pepsin digestion, and radiolabeled types I and III a-chains were separated by SDS-PAGE, visualized fluorographically, and measured densitometrically. All the experimental and sham-operated animals responded with a rapid rise followed by an almost equally rapid fall in the proportion of newly-synthesized type III collagen before becoming stabilized for the rest of the experimental period at a level that was significantly higher than that of the control and sham-treated animals of the same age. The increase in the proportion of type III collagen was directly related to force level and rate of suture expansion. The peak value of the proportion of type III collagen due to the lightest force was much closer to the proportions that occur naturally in the suture during normal rapid growth and development than to those caused by the heavier forces. Thus, it appeared that light forces tended to initiate a more physiological response than heavy forces, with respect to the proportion of newly-synthesized type III collagen.
Quantitative in vivo Wear of Human Enamel
Authors: Lambrechts P. , Braem M. , Vuylsteke-Wauters M. , Vanherle G.
Published: November 2010

In this study, the attrition wear, also called occlusal-contact-area wear, of human enamel was measured quantitatively with a computerized three-dimensional measuring technique over a period of four years. Tooth replicas from a clinical trial were used. A running-in wearperiod after restorative treatment, followed by steady-state wear, was suggested. The average steady-wear rate on occlusal contact areas was about 29 μm per year for molars and about 15 μm per year for premolars.
Comparative Microbiological and Immunological Studies of Subgingival Dental Plaque from Man and Baboons
Authors: McMahon K.T. , Wasfy M.O. , Yonushonis W.P. , Minah G.E. , Falkler W.A.
Published: November 2010

Baboons may be useful as animal models for the study of human oral diseases and infections. They are closely related to man anatomically, physiologically, and phylogenetically. Plaque and gingival indices were relatively low in 18 baboons (Papio anubis). The mean scores ranged between 0.62 ± 0.29 and 0.37 ± 0.20, respectively. Gram-positive and Gram-negative cocci comprised 27.0 ± 32.4 and 3.1 ± 7.5% of the total viable counts in the dental plaque samples. Black-pigmented Bacteroides formed about 1.9 ± 5.9% of the bacterial population in the samples. Anaerobic Gram-negative bacilli were found in 73.2% of the samples and averaged 19.2 t 26.3% of the total recovered flora. Species of the oral Actinomyces and other Gram-positive rods found in humans were not isolated. The composition of the oral flora in baboons appeared to be significantly different from that of man. Isolates of F. nucleatum, L. buccalis, and B. intermedius from the two mammals were biochemically similar, but were distinguishable by analysis with antibody, both by precipitin lines and/or differences between homologous and heterologous titers.
Changes in Protein Secretion by Rat Submandibular Glands in Response to Isoproterenol, a-Methylnoradrenaline, and Clonidine during Post-natal Development
Authors: Tanaka E. , Habu T. , Letić-Gavrilović A. , Abe K.
Published: November 2010

We studied developmental changes in salivary volumes and proteins secreted by the submandibular glands of male rats at weekly intervals from two to ten weeks of age in response to the β1-, α1-, and α2- adrenoceptor agonists, isoproterenol (IPR), a-methylnoradrenaline (a-mNA), and clonidine (Clonid). The types of proteins in saliva samples were determined and compared by isoelectric-focusing electrophoresis with the Phast system in both the gradient pH -3.5-to-5 and pH-3.5-to-9 gels by means of silver staining. Salivary volume and protein concentration in saliva samples elicited by IPR and a-mNA were positively related to the weight of the submandibular glands up to six or seven weeks of age, whereas in saliva elicited by Clonid, no relation was found. The isoelectric-focusing electrophoretic patterns of proteins secreted by the glands in response to three stimuli were different from each other during post-natal development. Within one stimulation, differences were also observed at two and three weeks of age for Clonid, and from seven weeks of age for the three stimuli, respectively. The a-type proteins, but not the β-type proteins, were very similar to those in extracts from glands of rats at seven weeks of age. Almost all of the a-type proteins, but not the β-type proteins, reacted with antibodies to two proteases. We conclude that functional maturation precedes morphological maturation in the submandibular glands of rats.
Transient and Residual Stress in a Porcelain-Metal Strip
Authors: Asaoka K. , Tesk J.A.
Published: November 2010

Porcelain-fused-to-metal (PFM) restorations may develop cracks during processing or in-mouth service if the relative physico-mechanical properties of the porcelain and metal are highly mismatched. Precise conditions when this might occur are not known. Many processing and property variations can affect the stresses developed throughout a porcelain-metal system. To understand this, we conducted a computer simulation of stress developed in a PFM beam. The simulation considers cooling from temperatures higher than the porcelain sag-point. The following temperature-dependent factors were incorporated: the elastic modulus, shear viscosity (porcelain), and coefficients of thermal expansion. The cooling rate dependencies of the glass transition temperature, (Tg), and the temperature distribution during cooling were also included.

The results suggest that transient tensile stress at the porcelain alloy interface may result in cracks in the porcelain during cooling. Occlusal forces may set up stresses to cause cracking at the surface of the porcelain if the compressive residual stress is not high enough. PFM restorations with an alloy of high thermal expansion coefficient require rapid cooling; on the contrary, PFM restorations with the alloys of lower coefficients require slow cooling. A high cooling rate can make up for thermal expansion mismatches between the alloy and the porcelain up to 2 × 10-6/°C. Finally, the results indicated that curvature was not a sensitive indication of stress for a multimaterial beam when visco-elastic relaxation and high cooling rates are involved. For the case modeled here, curvature varied inversely with a 1/2 to 1/7th power of the stress.
Hysteresis in Jaw Positioning Following Lateral Stretches
Authors: Rugh J.D. , Lemke R.R. , Dal Santo F.B.
Published: November 2010

The purpose of this study was to examine hysteresis of the masticatory system following brief voluntary lateral positioning of the mandible. Hysteresis was studied in ten healthy subjects, as a function of both time and distance that the mandible was held laterally off the midline. So that the effects of distance of lateral stretch on hysteresis could be studied, subjects positioned their jaws to the left or right of the midline distances of 2, 4, 6, 8, and 10 mm for ten s. So that the effects of time could be studied, the distance of lateral stretch was held a constant 8 mm for durations of two, four, six, 12, 16, and 20 s. Following each voluntary lateral stretch, subjects relaxed the muscles using EMG biofeedback and allowed the mandible to reposition itself passively. Hysteresis was defined as the difference in the mandibular resting position between pre- and post-stretch recordings. Mean hysteresis effects ranged from 0.7 mm to 1.8 mm. Hysteresis effects were found to increase with both distance and time; after eight s, however, no additional effect of time was noted.
Characterization of Monoclonal Antibodies against Glucosyltransferase Synthesizing Water-insoluble Glucan from Streptococcus sobrinus B13
Authors: Ochiai K. , Fukushima K. , Shiota T. , Ikeda T.
Published: November 2010

Four hybrid cell lines secreting monoclonal antibodies (McAbs) against glucosyltransferase synthesizing water-insoluble glucan (GTase-I) were generated by fusion of myeloma cells (P3U1) with splenocytes from mice immunized with GTase-I from Streptococcus sobrinus B13-N. Cell lines 29E7, 21GC7, and 42HB8 were found to secrete an IgG2a-type immunoglobulin, and 29EG, an IgM-type immunoglobulin. These two isotypes of McAbs were used for the determination of the binding sites on the GTase molecule, with use of an enzyme-linked immunosorbent assay. The binding site for McAb 29EG was different from the site that bound other McAbs. McAb 29EG was found to inhibit water-insoluble glucan synthesis by GTase-I by 50%, and 29E7 was found to inhibit it weakly. However, other McAbs did not show any inhibitory effect in spite of binding to GTase-I. McAb 42HB8 strongly inhibited GTase-I-mediated adherence of heat-killed cells of S. sobrinus B-13N to glass surfaces. When the McAbs were tested for their cross-reactivity among GTase preparations from different mutans streptococci, McAb 29EG reacted with S. cricetus and S. sobrinus, but not with other mutans streptococci. Three other McAbs, 21GC7, 29E7 and 42HB8, were found to react only with the enzyme from S. sobrinus. These findings indicated that the specificity of the McAbs studied varied with respect to the antigenic sites on the GTase-I molecule, and that some of the sites differed in their functions.
Colonization Resistance of Defined Bacterial Plaques to Streptococcus mutans Implantation on Teeth in a Model Mouth
Authors: Perrons C.J. , Donoghue H.D.
Published: November 2010

We investigated the ability of Streptococcus mutans C67-1 to colonize simple bacterial plaques and the effects of age and stability of the pre-formed plaque on colonization resistance. Mixed plaques of Actinomyces viscosus WVU627, 'Streptococcus mitior' LPA-1, and Veillonella dispar OMZ193 were grown on tcoth segments, mounted back to back for simulation of approximal sites in a model mouth for 66 h. S. mutans C67-1 was either included in the original inoculum or super-inoculated onto the developing plaque. Inclusion of S. mutans C67-1 did not alter the total viable counts, but the proportional composition changed due to inter-species interactions. Colonization resistance of the mixed-plaque samples developed within 24 h, although S. mutans C67-1 was always able to colonize these stagnation sites. Colonization resistance of 24-hour plaque against a fresh isolate, S. mutans CP3, was also studied. There was greater colonization resistance by the basic plaque to this organism, compared with S. mutans C67-1, although the reasons for this were not clear. These initial experiments demonstrate the way in which the factors involved in bacterial colonization resistance in microbial films on teeth can be studied under controlled conditions.
Hearing-damage Risk and Communication Interference in Dental Practice
Authors: Wilson C.E. , Vaidyanathan T.K. , Cinotti W.R. , Cohen S.M. , Wang S.J.
Published: November 2010

The use of high-speed air-turbine handpieces, operated at 300, 000 to 400, 000 revolutions per minute, has led to concern over the possibility of noise-induced hearing loss. Sound levels were measured in clinical settings and in a pre-clinical laboratory for estimation of hearing-damage risk among dentists, and the extent of communication interference. Octave-band sound pressure levels were obtained with use of a Fast-Fourier-Transform analyzer and associated instrumentation.

The results of this study indicate that the sound energy contribution of a typical dental practice is about 8% to 12% of the dentist's average 24-hour noise exposure. However, noise levels during dental procedures result in an articulation index of 0.21 to 0.37, corresponding to understanding of about 18% to 48% of nonsense syllables and 52% to 90% of sentences. It appears that hearing-damage risk is slight among dentists using modern equipment. However, further noise control in handpieces is necessary so that error-free communication during dental procedures can be ensured.
Taurodontism in 45,X Females
Authors: Varrela J. , Alvesalo L. , Mayhall J.
Published: November 2010

Orthopantomograms of 87 45, X females, 61 first-degree female relatives of these females, and a population sample of 113 normal females and 44 normal males were examined for the occurrence of taurodontism in mandibular molars. In the sample of 45, X females, two showed taurodont lower molars. In one of them, a hypotaurodont second molar was detected, while hypotaurodont third molars were found in the other. Three of the females' relatives and four of the population control females showed taurodontism, three unilaterally and four bilaterally. In all cases, the affected teeth were hypotaurodont. The results suggest that taurodontism occurs in 45, X females with a frequency similar to that in normal females. This result is not in accordance with the hypothesis that low mitotic activity of the chromosomally abnormal cells is an etiological factor in the development of taurodontism. The present findings, together with earlier results, suggest that the gene content of the X chromosome, rather than the amount of heterochromatin, is the cause of taurodontism in individuals with chromosome aneuploidy.
Interaction of Saliva and Taste
Authors: Spielman A.I.
Published: November 2010

In spite of the coexistence of saliva and taste in the oral cavity, an understanding of their interactions is still incomplete.

Saliva has modulating effects on sour, salt, and the monosodium-glutamate-induced savory or umami taste. It has a diminishing effect on sour taste as a result of the buffering by salivary bicarbonate. It probably also contributes to the umami taste with endogenous salivary glutamate levels. Salt taste is detected only when above salivary sodium-chloride concentrations; thus saliva influences salt taste threshold levels. It also provides the ionic environment for taste cells, probably critical in signal transduction.

Salivary flow rate and composition are influenced by the type of taste stimuli. In general, sour taste, elicited by citric acid or sour food, induces the highest flow rate and Na+ concentrations, while salt gives rise to high protein and Ca2+ concentrations. Stimulation with the four basic taste modalities (sour, sweet, salty, and bitter), however, does not increase the relative proportion of any of the salivary proteins.

This review examines the literature on the interactions of saliva with taste, and the effect of taste on salivary composition. The possible role of the von Ebner's salivary glands and the role of saliva as a chemical cue are also discussed.
Cyclopolymerizable Monomers for Use in Dental Resin Composites
Authors: Stansbury J.W.
Published: November 2010

The simple reaction of conventional monofunctional acrylate monomers with paraformaldehyde has yielded a new class of difunctional monomers. The unique proximity of the double bonds within these compounds allows a facile cyclopolymerization to incorporate a cyclic ether structure into the polymer backbone. The external position of the acrylate esters means that these pendant groups can be varied for alteration of the physical properties of the monomers and the corresponding polymers. A series of the new monomers has been prepared and polymerized under dilute solution and bulk conditions to yield non-crosslinked and crosslinked polymers, respectively. The polymers exhibited high degrees of conversion and significantly reduced polymerization shrinkage, compared with polymers obtained from conventional diacrylate or dimethacrylate monomers. These properties appear to be a direct result of an efficient cyclopolymerization process. The combination of improved conversion to polymer with less contraction makes these monomers ideal candidates for use in dental resin composites. A preliminary evaluation of their potential in this application has shown that with suitable ester functionality, they can be formulated to provide composites with excellent mechanical strength properties.
In vitro Virucidal Effectiveness of a 0.12%-Chlorhexidine Gluconate Mouthrinse
Authors: Bernstein D. , Schiff G. , Echler G. , Prince A. , Feller M. , Briner W.
Published: November 2010

The purpose of this work was to assess the in vitro antiviral effectiveness of a mouthrinse (Peridex) containing 0.12% chlorhexidine gluconate (CH) on several viruses that are associated with the oral cavity. These included herpes simplex virus (HSV), cytomegalovirus (CMV), influenza A, parainfluenza, polio, and hepatitis B (HBV). Virucidal assays in tissue cultures were performed on all viruses except HBV. The virucidal effect on HBV was assessed by inactivation of the DNA polymerase contained within the Dane particle of HBV. The CH mouthrinse had virucidal activity against all of the viruses, except polio, in as little as 30 s. The virucidal activity increased with time. However, there were differences in the responses of these viruses to the challenge of the CH mouthrinse, probably due to subtle differences in the physical/chemical structures of the virus envelopes. Results on DNA polymerase of the HBV virus were similar to those on the other viruses, except polio, suggesting a common mechanism. With respect to this mechanism, it was proposed that CH exerted its antiviral effect on the envelopes of these viruses, and that the absence of an envelope on polio precluded effectiveness against this virus.
Evaluation of Alveolar Bone in Relation to Nutritional Status During Pregnancy
Authors: Clark D.E. , Navia J.M. , Manson-Hing L.R. , Duncan H.E.
Published: November 2010

Demand for nutrients necessary for the formation of mineralized tissues increases dramatically during pregnancy to meet fetal requirements. The purpose of this clinical study was to identify short-term effects of pregnancy and dietary intakes of calcium, phosphorus, protein, and vitamin C on radiographic density and alveolar crest morphology of the mandible.

Seventy-six subjects between ten and 20 weeks' gestational age were recruited from the Jefferson County, Alabama, Department of Health maternity clinic. Initially, an evaluation of their diet was done, and a single periapical radiograph was taken in the canine-premolar region of the mandible. A final evaluation of the diet and a periapical radiograph of the same teeth were obtained at a time as close to the expected date of delivery as possible.

Dietary evaluation consisted of a 24-hour recall history and a food-frequency history at the two visits. Radiographs were made with a bite-block film-holding system with occlusal registration in acrylic for reproduction of projection geometry at the two visits. An aluminum stepwedge was incorporated for densitometric standardization. Measurements of plaque, and bleeding and pocket-depth probing were recorded for control of local effects on alveolar change.

Standard statistical procedures of regression determined correlation of 12 nutrients and periodontal variables with bone density change and with alveolar crest morphology change. Vitamin C intakes (24-hour recall) showed a positive correlation (p = 0.033) with bone density change, and calcium intakes (24-hour recall) showed a negative, but not significant, correlation (p = 0.058) with bone density change, contributed particularly by subjects with the highest calcium intakes. The strongest relation with alveolar crest morphology change was the interproximal pocket-depth change (p = 0.086).
Properties of Alkaline Phosphatase of the Human Dental Pulp
Authors: Goseki M. , Oida S. , Nifuji A. , Sasaki S.
Published: November 2010

Enzymatic and immunological properties of alkaline phosphatase [ALP; orthophosphoric monoester phosphohydrolase, alkaline optimum, EC 3.1.3.1.] in the human dental pulp were investigated. In inhibition and thermal inactivation studies, dental pulp ALP showed properties of universal-type ALP (kidney/bone/liver type). Dental pulp ALP cross-reacted with polyclonal and monoclonal antibodies against purified swine-kidney ALP, and with monoclonal antibody against ALP of human osteoblast-like cells in the same manner as ALPs of human bone and kidney. The sodium dodecyl sulfate-gel electrophoretic pattern showed a 140, 000-Mr native protein band.

These data suggest that dental pulp ALP can be classified as a universal-type ALP having antigenic determinants common to ALP of the kidney and bone.
An Ultrastructural Study of Bacterial Invasion and Tissue Breakdown in Human Experimental Root-surface Caries
Authors: Nyvad B. , Fejerskov O.
Published: November 2010

This study describes the structural features of the interface between microbial deposits and root cementum in actively progressing root-surface caries lesions developed experimentally in six elderly individuals. A total of 18 specimens was examined by microradiography, and a further 18 by light and transmission electron microscopy after intra-oral periods of one, two, and three months. All specimens showed various degrees of subsurface dissolution of mineral and bacterial invasion of the cementum. Although the microradiographic pattern of mineral loss was subsurface in nature, transmission electron microscopy showed dissolution of crystals in the outermost layers of the cementum, with a distinct gradient inward. Bacterial invasion occurred along the borders between bundles of relatively well-mineralized extrinsic collagen fibers in which the characteristic cross-banding remained intact. The pattern of bacterial invasion was influenced by the incremental lines and the cemento-dentinal junction. The invading bacteria were almost exclusively Gram-positive, of various shapes, and possessed thick, moderately electron-dense cell walls and electronlucent "vacuoles" in the cytoplasm. It is concluded that because of pronounced mineral loss of the outermost cementum, accompanied by bacterial invasion, the surface of an active cementum caries lesion, as observed by transmission electron microscopy, is not identical to that seen in micro-radiograms.
pH Regulation of Urease Levels in Streptococcus salivarius
Authors: Sissons C.H. , Perinpanayagam H.E.R. , Hancock E.M. , Cutress T.W.
Published: November 2010

Potential mechanisms for regulation of urease levels in Streptococcus salivarius were examined, including: induction by urea, nitrogen or carbon source repression, and effects of pH and CO2 (because CO2 enrichment enhanced urease detection on urea agar plates). Regulation by either pH or CO2 was confirmed by comparison of the urease accumulation pattern during anaerobic growth under CO2 with that under N2. Under CO2, there was an initial buffering plateau at pH 6.2 and a rate of Streptococcus salivarius urease accumulation three-fold that under N2, with a pH 7.6 plateau. With both gas phases there was also an increase in the rate of urease appearance coincident with the decrease in medium pH following the pH plateau. The effects of pH, CO2, and HCO3- on urease levels and on growth were separately assessed by culture in media containing 0, 25, 100 mmol/L KHCO3 buffered at different pH levels. There was an inverse relationship between the logarithm of the urease level after 24-hour growth and the pH during growth-the urease specific activity was 100-fold higher at pH 5.5, compared with pH 7.0 and above. HCO3-/CO2 (100 mmol/L) had little effect on urease levels, but was essential for growth at pH 5.5. There was no significant urease induction by urea, or repression by ammonia or glucose. There was also evidence of pH regulation of urease levels in some staphylococci, Klebsiella pneumonia, and Corynebacterium renale, but not in Actinomyces naeslundii and several other species. We conclude that the external pH is a major factor regulating urease levels in S. salivarius and possibly some other species-a mechanism equivalent to urease repression by OH-.
A Method for Measuring the Flow of Saliva from the Minor Salivary Glands
Authors: Shern R.J. , Fox P.C. , Cain J.L. , Li S.-H.
Published: November 2010

This investigation evaluated a procedure to measure the quantity of secretion by the minor salivary glands from various locations in the mouth before and after citric acid stimulation. Fourteen healthy non-medicated adults were assessed on each of two morning visits at the same specific areas of the mucosa (labial, buccal, and palatal). During each assessment, an absorbent paper strip was placed on each designated location for 30 s, removed, and its moisture content determined with a calibrated Periotron™. Calibration procedures indicated that readings were linearly associated with known saliva volumes and were negligibly influenced by differences in salt concentration and viscosity. At each visit, the buccal flow was significantly greater than those from the lip and palate. The flow from glands in each area was unaffected by a single application of the gustatory stimulant. The mean flow rates at each specified site were similar during the two visits.
Salivary Flow Rates and Salivary Film Thickness in Five-year-old Children
Authors: Watanabe S. , Dawes C.
Published: November 2010

The flow rate of unstimulated whole saliva, the volume of saliva in the mouth before (VMAX) and after (RESID) swallowing, and the surface area of the mouth were measured for determination of the average thickness of the salivary film in five-year-old children with primary dentitions.

In 30 subjects of each gender, RESID was calculated from the potassium concentration in unstimulated saliva by a dilution technique. VMAX was calculated as the total of RESID plus the volume normally swallowed (the unstimulated salivary flow rate divided by the swallowing frequency). From these children, ten subjects of each gender who had no missing teeth were selected, and impressions were taken for determination of the surface area of the mouth. Aluminum foil, of known weight per unit area, was adapted to the stone models of different regions of the mouth, and the surface areas were calculated from the weights of foil.

The unstimulated salivary flow rate was 0.22 ± 0.14 mL/min, the mean values of RESID and VMAX were 0.38 ± 0.11 mL and 0.50 ± 0.15 mL, respectively, and the mean total surface area of the mouth was 117.6 ± 7.6 cm2. There were no significant differences in these values due to gender. The average thickness of the salivary film in the mouth was calculated to vary between 0.06 and 0.09 mm. Although the values of salivary flow rate, RESID, and VMAX were much lower than those reported for adults, the average thickness of the salivary film was very similar to that in adults.
The Mechanism for Erosion of Glass-ionomer Cements in Organic-Acid Buffer Solutions
Authors: Fukazawa M. , Matsuya S. , Yamane M.
Published: November 2010

The behavior and mechanism for erosion of glass-ionomer cements in organic-acid buffer solutions were studied as a function of time, pH, and citric-acid concentration. In acidic solutions, the dissolution of the cement was controlled by the diffusion of the eluted species in the cement matrix, which depended on H+ ion concentration. In citric-acid solutions, the dissolution of the cement was controlled by both the diffusion and the surface reaction between the acid anion and the eluted species. Contribution of the latter reaction was larger with the increase in the acid concentration.
Effects of Instrument-measuring Geometry on Colorimetric Assessments of Dental Porcelains
Authors: Seghi R.R.
Published: November 2010

Recent developments in optical electronic instrumentation for color control have made the potential use of clinical photometric analysis a future possibility for dental materials selection and custom restoration design. The development of such instrumentation will require a more complete understanding of the performance of current technologies on translucent materials. This study was designed to evaluate the effects of instrument-measuring geometry on color-difference assessments made on dental porcelains. The results indicate that a high degree of correlation can exist between color-difference measurements regardless of the design of the instrument-measuring geometry. This work suggests that the development of clinically useful devices need not be restricted to more traditional integrating-sphere-type designs and that more photometrically efficient alternative designs should be explored.
The Epidemiology of Root Surface Caries
Authors: Beck J.
Published: November 2010

Although a secular decline is being seen in coronal caries in children in industrialized countries, there appears to be a relatively high prevalence of root caries, with chronologically older adults exhibiting the highest prevalences. This paper reviews the descriptive and analytical epidemiology of root caries as found in recent national, regional, and local studies.

A review of the variety of study designs, populations surveyed, and epidemiologic criteria for root caries comprising recent studies is presented as a background for comparison of prevalence rates which range from 7.3% to 69.7% of the population with root decay. In the few incidence studies reported, attack rates range from 1.6 surfaces per 100 surfaces at risk to 6.3 per 1000 surface-months at risk.

Risk indicators for root caries are also reviewed with studies applying multivariate techniques implicating age, fluoride, educational level, use of dental services, coronal caries, loss of attachment, and number of teeth as possible risk factors. Although incidence studies have isolated risk factors, the small number of studies result in little agreement. Risk factor models from the Iowa 65 + Oral Health Study and a Risk Indicator model from the Piedmont 65 + Dental Study are presented to illustrate the variety of factors that may be involved in the expression of root surface caries in human populations.