bluuebunny/crossref_metadata_2025 huggingface dataset:
The Concomitant Deposition of Strontium and Fluoride in Dental Plaque
Authors: Pearce E.I.F. , Sissons C.H.
Published: November 2010

We have investigated the feasibility of incorporating Sr into dental plaque by means of an enzyme-dependent system known to increase Ca, P, and F levels in plaque. A solution containing Ca (20 mmoll L), P (12 mmol/L), MFP (4.7 mmol/L), F (0.3 mmol/L), and urea (500 mmol/L) was modified by equimolar replacement of Ca with 1, 2, 5, and 10 mmol/L Sr. Thin films of human salivary sediment incubated in these solutions showed increasing levels of acid-extractable Sr as the solution Sr increased. When the concentration exceeded 2 mmol/L, deposition of Ca, P, and F was reduced. In artificial plaque, grown on bovine enamel, from mixed human salivary organisms and treated with the solution containing 2 mmol Sr/L, there was a slightly smaller uptake of Ca, P, and Sr, but a greater uptake of F than in sediment treated with the same solution. Natural human plaque treated 12 times in vivo over three days with this solution (in the form of a mouthrinse) also showed substantial increases (from five- to 26-fold) in the concentrations of all four ions. Absolute levels of Ca, P, F, and especially Sr were, however, lower than those in the artificial plaque samples. (Ca + Sr)/P ratios suggested apatite deposition, and the correlation between amounts of Ca and Sr deposited in natural plaque samples suggested that Sr, like F, is structurally incorporated into this apatite. Fluctuations in the pH of natural plaque may promote apatite crystal maturation, causing a slow loss of Sr. The substituted apatite should act as a plaque reservoir, releasing Sr and F as well as Ca and P to inhibit caries during low pH episodes that might otherwise threaten the adjacent enamel or root surfaces.
Microbial Aspects of Preventive Regimes in Patients with Overdentures
Authors: Keltjens H.M.A.M. , Schaeken M.J.M. , Van der Hoeven J.S.
Published: November 2010

The aim of this study was to test effects of preventive regimes using fZuoride and chlorhexidine to prevent caries and periodontal diseases in 34 patients with overdentures. The patients, who were treated with immediate overdentures, were distributed at random into three experimental groups. In these groups, different gels — a placebo, a fluoride, and a chlorhexidine-fluoride gel — were tested by daily application. Supragingival plaque samples from selected surfaces of two abutment teeth were taken at one week, and at one, three, and six months after initial insertion of the overdenture. The placebo and fluoride gel influenced neither total CFU nor S. sanguis and A. viscosus/naeslundii counts. In the placebo group, but not in the fluoride group, S. mutans levels increased significantly, indicating the caries risk involved in overdentures. The use of chlorhexidine-fluoride gel resulted in a long-term suppression of total CFU. Further, S. mutans was found to be selectively suppressed to below detection level. A. viscosus/naeslundii was initially strongly suppressed, but after three months a partial return of the population was noticed. S. sanguis was relatively insensitive to the chlorhexidine-fluoride gel. It is concluded that a daily application of a chlorhexidine-fluoride gel is effective against plaque formation and S. mutans on abutment teeth in overdentures.
Root Surface Caries Subsequent to Gingivectomy in Rats Inoculated with Streptococcus sobrinus (mutans) and Actinomyces viscosus
Authors: Firestone A.R. , Graves C. , Caufield P.W. , Feagin F.F.
Published: November 2010

We studied the effect of oral infection with cariogenic micro-organisms on alveolar bone loss and root surface caries subsequent to gingivectomy in rats. Thirty-six rats were fed diet MIT 200 (67% sucrose); one-half, the controls, had antibiotics added to the diet. At ages 18, 19, and 21 days, the experimental group was orally infected with streptomycin-resistant Streptococcus sobrinus (mutans) 6715 and Actinomyces viscosus M-100. At age 30 days, all animals were subjected to a gingivectomy on maxillary and mandibular left quadrants. The experimental group was re-inoculated at age 36 days. Animals were killed seven weeks after surgery. Jaws were stained, and planimetric measurements of exposed root surface area and caries on lingual/palatal surfaces of 1st and 2nd molars were made from video images with a computer/digitizer. Compared with the non-operated contralateral quadrants, gingivectomy significantly increased exposed root surface area in the maxilla and in the mandible in both the control and experimental groups. Oral inoculation significantly increased exposed root surface in mandibular (but not maxillary) quadrants which had received a gingivectomy, but had no effect on non-gingivectomized quadrants. There was no caries in the control group, whereas ten rats in the experimental group had root surface caries lesions, all in quadrants which had received a gingivectomy. This rat model should prove useful in further studies of root surface caries.
Effects of pH on Expression of Sodium Fluoride Resistance in Streptococcus mutans
Authors: Brussock S.M. , Kral T.A.
Published: November 2010

Stable fluoride-resistant mutants of Streptococcus mutans GS-5 were isolated on Todd-Hewitt agar by a step-wise selection procedure. Resistance is defined here as the ability to form colonies in 48 hr. First-step mutants demonstrated six different levels of resistance, ranging from 400 to 1000 μg/mL sodium fluoride. Second-step mutants demonstrated two levels of resistance, one at 1600 and the highest at 3000 μg/mL sodium fluoride. All mutants (originally isolated at pH 7.2) were tested for fluoride resistance at pH 5 and 6. At these lower pH values, all of the mutants demonstrated resistance to fluoride when compared with the parent strain, but at much-reduced levels.
Developmental Changes of Esteroprotease and Androgen Receptors in the Mouse Submandibular Gland
Authors: Baba R. , Kurokawa R. , Ota M.
Published: November 2010

The activities of p-tosyl-L-arginine methyl ester (TAMEase) and cytosolic and nuclear androgen receptors in the submandibular glands of male and female mice were determined at various developmental stages. In males, the activity of TAMEase was detectable at four weeks after birth, and thereafter it increased rapidly. Cytosolic androgen receptor increased gradually with age, whereas nuclear androgen receptor, which was minimal one week after birth, increased remarkably four weeks after birth. In females, the minimal activity of TAMEase was detectable at five weeks after birth and increased very slowly with age. Cytosolic receptor increased with age, but nuclear receptor level was unchanged. These findings suggest that the appearance of TAMEase was in accordance with an elevation of nuclear androgen receptor in mice submandibular glands.
Intracrystalline Structure of Enamel Crystals Affected by Caries
Authors: Tohda H. , Takuma S. , Tanaka N.
Published: November 2010

Enamel crystals in the demineralized zones in early caries lesions of human teeth were observed by high-resolution electron microscopy. The enamel crystals frequently exhibited perforations in their centers and defects of various sizes on their lateral surfaces. There were a number of small electron-lucent spots, suggesting that the dissolution of crystals had taken place there. These spots were in especially large numbers near the central dark line. The central perforations, the lateral defects, and the small spots had a common habit which formed regularly along the crystalline a- and b-axes. In many cases, when the central dark line was seen, the perforations were located a few unit cells away from the line. The perforations seem to result from a fusion of small spots, which enlarge by involving other small spots. The lateral defect seemed to enlarge by removal of unit cells and progression along the a- and b-axes. In the regions where the small spots were present, however, the enlargement of the defects also progressed involving the spots. The central dark line seems to be rather resistant to dissolution. One of the main factors for the central perforation of the crystals is thought to be the presence there of especially large numbers of defective sites.
Cross-inhibition Between Black-pigmented Bacteroides Species
Authors: Van Winkelhoff A.J. , Kippuw N. , De Graaff J.
Published: November 2010

Cross-inhibition within the group of black-pigmented Bacteroides, including both oral and non-oral strains, was studied by means of a membrane filter technique. It was found that B . gingivalis possessed the most extended inhibitory capacity among all species tested. B . gingivalis showed inhibitory activity against B . intermedius, B. endodontalis, B . loescheii, and B . melaninogenicus. B . endodontalis was active against some B . intermedius strains. Among the saccharolytic species, some B . melaninogenicus strains were inhibitory for some B . endodontalis strains, some B. gingivalis strains, and some B . intermedius strains. These inhibitory activities observed in vitro may play a role in the colonization of the periodontal pocket.
Micro-electrode Techniques for the Analysis of Oral Fluids
Authors: Vogel G.L. , Carey C.M. , Chow L.C. , Brown W.E.
Published: November 2010

This paper describes the use of micro-electrodes for the analysis of small fluid volumes recovered from the oral environment. The analysis has several advantages: (1) It directly measures the activity of ions, a quantity more relevant to mineral saturation than the conventionally measured concentration, (2) minimum fluid volume for analysis is usually less than 0.005 μL, small enough to avoid sample pooling in most analyses, (3) numerous ions can be measured simultaneously, (4) the analysis time is very short, and (5) the use of mineral oil to isolate specimens provides a simple method for controlling the CO2 tension and humidity over the specimens.
The Influence of Vanadate on Calcium Uptake in Maturing Enamel of the Rat Incisor
Authors: Takano Y. , Matsuo S. , Wakisaka S. , Ichikawa H. , Nishikawa S. , Akai M.
Published: November 2010

The influence of vanadate, a potent inhibitor of Ca2+-ATPase and Na+-K+-ATPase, on 45Ca uptake in maturing enamel of the rat incisor was investigated by a vascular perfusion method combined with 45Ca autoradiography. The morphological integrity of the maturation-stage enamel organ was well-retained during vascular perfusion under all the experimental conditions. Distinct patterns of 45Ca labeling, comparable with those found in previous in vivo 45Ca autoradiographic studies, appeared in the maturing enamel after vascular perfusion with a standard perfusate. One mmol/L vanadate added to the standard perfusate caused a drastic decrease in 45Ca uptake in the maturing enamel, corresponding to the ruffle-ended ameloblasts, leaving narrow peaks of moderate intensity corresponding to the bands of the overlying smooth-ended ameloblasts. The in vitro labeling of exposed enamel surfaces with 45Ca revealed blackening of autoradiographic emulsion in wide bands separated by unlabeled or slightly labeled narrow ones resembling the distribution of smooth-ended ameloblasts in both control and vanadate-treated incisors.

Our observations indicate that the ruffle-ended ameloblasts of the rat incisor serve as an efficient diffusion barrier to calcium ions and regulate transcellular calcium transport to the maturing enamel, at least in part, by a vanadate-sensitive mechanism.
Stiffness Increase During the Setting of Dental Composite Resins
Authors: Braem M. , Lambrechts P. , Vanherle G. , Davidson C.L.
Published: November 2010

Changes in the dynamic Young's modulus under flexure of self-cured and light-cured composite resins during setting were demonstrated to reflect accurately the condition of the curing composite resins. The rate of stiffness increase during setting varied considerably with the product, and the light-cured composite resins generally showed a faster rate of increase of stiffness.

In the initial stage, the Young's moduli were very low, especially for the self-cured composite resins. This accounts for the damage (adhesion disruption and cross-linking interruption) that can be inflicted on a freshly placed composite resin filling that is not yet mechanically stabilized. Therefore, such fillings are vulnerable to aggressive distortion for at least 10 to 15 minutes after placement.
The Influence of Incorporated and Adsorbed Fluoride on the Dissolution of Powdered and Pelletized Hydroxyapatite in Fluoridated and Non-fluoridated Acid Buffers
Authors: Wong L. , Cutress T.W. , Duncan J.F.
Published: November 2010

The effects of fluoride (F) incorporated into hydroxyapatite (HA), adsorbed onto the HA surface, and fluoride in solution were studied during HA dissolution. Dissolution rates at pH 5. and 25°C were determined in fluoridated (0.1, 5.0 μg/mL) and non-fluoridated buffers for the following powdered and pelletized synthesized HAs: non-fluoridated HA, partially-fluoridated (100, 1000, 37,000 μglg) HA, and surface-adsorbed fluoridated (100, 1000 μg/g) HA. The dissolution rate curves were used to derive two components we have called 'diffusion' and 'surface chemical reactivity'. With powders, the rate-determining factor was surface chemical reactivity during the first 60 min. Diffusion was reduced by increasing the F levels in the apatite or buffer. In non-fluoridated buffers, diffusion was reduced 29% for apatite with 100 μg/g incorporated F and 99% with 37,000 μg/g-Diffusion was reduced by 37% and 81 % by 0.1 and 5.0 μg/mL F, respectively, in the buffer. With pelletized HA, the rate-determining factor during the first 10 min was surface chemical reactivity. Diffusion then became relatively more important, but the diffusion rate was independent of F content. During the dissolution of powdered apatites, F was taken up by the remaining apatite solid, as evidenced by the lower F concentration in solution than that calculated to be released during dissolution. There was also a decrease in the F concentration of the 0.1 μg/mL buffer as reaction progressed. Pelletized apatites did not release enough F to influence dissolution significantly. Surface-adsorbed F was more effective than incorporated F in reducing HA dissolution. However, solution F present at the apatite surface in small concentrations (<5.0 μg/mL) was more effective than much higher concentrations (1000 μg/g) of adsorbed or incorporated F in reducing dissolution.
Resorption of Residual Ridges (RRR) in Rats
Authors: Nishimura I. , Damiani P.J. , Atwood D.A.
Published: November 2010

The post-extraction resorption of residual ridges (RRR) is a major and largely unsolved health problem, probably of multifactorial etiology. In order for one to study the role of specific factors in the pathophysiology of RRR, the use of animal models is desirable. The purpose of this study was to establish a reliable animal model and a standardized assay system to measure RRR for future experiments.

A new oblique cephalometric device was designed to take pairs of xeroradiographs on the right and left sides of the rat skull and mandible at a 45-degree angle to the horizontal plane. Preliminary studies confirmed the reproducibility of the technique.

All molars were extracted with minimal trauma from the right maxilla and mandible in five male Sprague-Dawley rats (40 days old). Longitudinal cephalographic examinations were performed before and immediately after extraction and at two, four, eight, and 12 weeks after extraction. Alveolar bone resorption was measured on enlarged cephalographs (5. 7X) at a point mesial to the mandibular first molar. Sequential mean bone resorption was 0.8 ± 0.2 mm (S.D.), 1.0 ± 0.3, 1.3 ± 0.3, and 1.5 ± 0.4, respectively. Graphically, these findings produced bone loss curves similar to those observed in man.

These results indicate that the rat model may be utilized in longitudinal studies of the resorption of the residual ridge.
Mechanism for Erosion of Glass-ionomer Cements in an Acidic Buffer Solution
Authors: Fukazawa M. , Matsuya S. , Yamane M.
Published: November 2010

In order to clarify the mechanism for erosion of glass-ionomer cements, we immersed two commercial luting cements in an acidic buffer solution under various conditions. The amounts of F, Al, Si, and Ca eluted from the cement were (1) in proportion to the square root of immersion time, (2) unrelated to shape or volume of the sample, (3) dependent on its surface area, and (4) not affected by shaking of the solution. It was concluded that the dissolution was controlled by the diffusion of those species in the cement matrix, which was influenced by the structure of the matrix and the concentration of H+ ion at the cement surface. The unreacted glass particles near the cement surface were dissolved by the long immersion, and many pores were left in the surface region.
Analysis of Photo-initiators in Visible-light-cured Dental Composite Resins
Authors: Taira M. , Urabe H. , Hirose T. , Wakasa K. , Yamaki M.
Published: November 2010

Seven commercial visible-light-cured (VL) dental composite resins were analytically studied for identification of the photo-initiator consisting of photo-sensitizer and reducing agent. Gas-liquid chromatography (GC) was used for the determination of the dilute components extracted from the composite resin. Mass spectroscopy (GC-MS) was used for confirmation of the qualitative data obtained by GC.

The results showed that all composite resins examined included camphorquinone (CQ) as a photo-sensitizer. The concentration of CQ in the resin phase, however, ranged from 0.17 to 1.03% w/w. The composite resin with hybrid-sized filler tended to have a higher concentration of CQ than did the micro-filled composite resin.

As for the reducing agent, two out of seven brands contained dimethylaminoethyl methacrylate (DMAEMA), and one included dimethyl-p-toluidine (DMPTI). The mixing ratio between CQ and the amine in these three composite resins also varied. Another four brands did not contain either DMAEMA or DMPTI, and would utilize different reducing agents.
The Effect of Long-term Use of a Dentifrice Containing Zinc Citrate and a Non-ionic Agent on the Oral Flora
Authors: Jones C.L. , Ritchie J.A. , Marsh P.D. , Van Der Ouderaa F.
Published: November 2010

The effect on the oral ecology of daily use, for seven months, of a dentifrice containing 0.5% (w/w) zinc citrate and a non-ionic agent, i.e., 0.2% (wlw) Triclosan (2,4,4' -trichloro-2' -hydroxydiphenyl ether), has been monitored on 13 adult volunteers. Plaque and saliva were sampled monthly and the bacterial flora analyzed. Twenty-six volunteers used a placebo dentifrice as part of their normal oral hygiene for four months to establish the baseline microbial flora. The volunteers were then split into two equal groups: One group continued to use the placebo dentifrice; the other used the dentifrice containing zinc citrate and Triclosan. There was no evidence that seven months' use of a dentifrice containing 0.5% zinc citrate and 0.2% Triclosan caused shifts in the oral microbial ecology, nor was there any evidence of developing bacterial resistance to Triclosan.
Influence of Contraction Mismatch and Cooling Rate on Flexural Failure of PFM Systems
Authors: Coffey J.P. , Anusavice K.J. , Dehoff P.H. , Lee R.B. , Hojjatie B.
Published: November 2010

The interactive influence of cooling rate and the sign and magnitude of thermal contraction difference between metals and ceramic veneers on bond strength have not been extensively analyzed, although numerous bond-test studies have been reported during the past two decades. A previous analytical study of residual incompatibility stress in bond-test specimens indicated that bond strength values may be of relatively little value if the residual stress state of the metal-ceramic specimens is not considered. The objective of this study was to determine the influence of cooling rate and contraction mismatch on the flexural failure resistance of metal opaque-porcelain strips.

Specimens were subjected to four-point loading in an Instron testing machine until crack initiation occurred at the metal-ceramic interface. The residual stress states in the ceramic region were estimated from finite element stress analyses of the bond-test specimens by use of dilatometry data obtained at the cooling rate of 3°Clmin. The total stress induced from the residual stress and the applied flexural load was also determined for these specimens. Statistical analyses of the experimental data revealed that the slowly cooled specimens exhibited a significantly lower (p < 0.05) flexural strength compared with rapidly cooled specimens. Regardless of the cooling technique, metal-ceramic specimens with a negative thermal contraction difference (αm - αp < 0) failed at significantly lower (p < 0.05) flexural loads than did specimens with a positive thermal contraction difference.
The Influence of Aging on Lysosomal Acid DNase of the Rat Submandibular Gland
Authors: Yaegak K. , Ogura R. , Kameyama T. , Sujaku C. , Tonzetich J.
Published: November 2010

Lysosomal and cytoplasmic fractions were prepared from rat submandibular glands for investigation of the release of lysosomal acid DNase in relation to aging. It was found that the acid DNase activity ratio for cytoplasmic/lysosomal fractions in rats aged 27 months was higher than that in three-month-old rats. The release of acid DNase from the lysosomal fraction by shaking was markedly increased in the fraction from the older animals.
Effect of NaF on cAMP Accumulation, cAMP-dependent Protein Kinase Activity in, and Amylase Secretion from, Rat Parotid Gland Cells
Authors: Shahed A.R. , Allmann D.W.
Published: November 2010

Stimulation of amylase secretion from parotid glands by beta-adrenergic agonists is mediated by the activation of adenylate cyclase and the resultant increase in cellular cAMP. Since NaF is known to increase adenylate cyclase activity and cAMP accumulation in intact cells, we investigated whether it would stimulate amylase secretion from isolated rat parotid gland cells. The results provide evidence that the addition of NaF (0.01 - 10 mmol/L) increased cAMP concentration (1.5-2.8-fold) in, and amylase secretion (16-93%) from, isolated parotid gland acinar cells. NaF was found to increase cAMP-dependent protein kinase activity ratios (51-84%) in a concentration-and time-dependent manner. The data suggest that the stimulation of amylase secretion from parotid gland cells by NaF may be mediated by an increase in the cellular cAMP concentration, which exerts its effect, at least in part, by increasing the activity of cAMP-dependent protein kinase.
Effect of Chewing Gum Containing Sodium Bicarbonate on Human Interproximal Plaque pH
Authors: Igarashi K. , Lee I.K. , Schachtele C.F.
Published: November 2010

The effect of chewing sorbitol gum containing sodium bicarbonate on interproximal plaque pH was determined by use of an ion-sensitive field-effect transistor (ISFET) electrode system with four human volunteers. Plaque pH was lowered by 2 min of chewing of a sucrose-containing toffee. After 20 min, either sodium bicarbonate or control gum was chewed for 10 min, and the pH was followed for an additional 20 min. The minimum pH after toffee chewing was elevated by both the control gum (4.5 ± 0.3 to 5.2 ± 0.5) and the sodium-bicarbonate-containing product (4.3 ± 0.3 to 6.1 ± 0.6) to levels which were significantly different (p<0.01). The rate of rise in pH was 2.6 times faster with the gum containing buffer compared with the control gum. In comparison with the control gum, the sodium bicarbonate gum caused the pH to remain at a higher level, approximately 0.5 pH units, for 20 min after gum chewing. The addition of sodium bicarbonate to gum containing sorbitol markedly enhanced its capacity to cause and maintain an elevation of interproximal plaque pH previously lowered by exposure to fermentable carbohydrate. Sodium bicarbonate may be useful in products designed to reduce the acidogenic challenge to the teeth following food ingestion.
A Comparison of Different Treatments for Nocturnal Bruxism
Authors: Pierce C.J. , Gale E.N.
Published: November 2010

One hundred bruxers were evaluated for bruxing activity before, during, and after treatment with a portable electromyograph (EMG). A six-month post-treatment follow-up of bruxing activity was obtained. Experimental treatment groups consisted of diurnal biofeedback, nocturnal biofeedback, massed negative practice, and splint therapy. A no-treatment control group was included. The comparative efficacy of treatments was determined by analyses of variance.

Both EMG-measured frequency of bruxing episodes and duration of bruxing activity decreased significantly for nocturnal biofeedback and splint therapy treatments but not for massed negative practice, diurnal biofeedback (relaxation), or the no-treatment control group. The two-week treatment effects were transient, and bruxing activity generally returned to baseline levels when treatment was withdrawn. These findings are consistent with the findings of previous researchers with regard to nocturnal biofeedback and splint therapy but differ from previous findings for massed negative practice therapy.
Protective Efficacy of Active and Passive Immunizations against Experimental Infection with Bacteroides gingivalis in Ligated Hamsters
Authors: Okuda K. , Kato T. , Naito Y. , Takazoe I. , Kikuchi Y. , Nakamura T. , Kiyoshige T. , Sasaki S.
Published: November 2010

The protective efficacy of immunization against Bacteroides gingivalis infection was examined in hamsters. Whole cells or extracted hemagglutinin of B. gingivalis 381 was injected with incomplete Freund adjuvant into the inguinal regions of hamsters. Two weeks after the rats received a booster injection, cotton threads were tied coronally to the gingival margins of the mandibular first molars, and then a streptomycin-resistant B. gingivalis 381R' strain was inoculated into the rats' oral cavities. The subcutaneous immunizations resulted in slight reductions in the numbers of B. gingivalis on the ligature threads compared with the sham-immunized group. Peroral administration of whole cells of B. gingivalis to hamsters elicited salivary immunoglobulin responses, but no reduction of B. gingivalis 381R' colonization was found in this group. Repeated passive immunizations with rabbit antiserum to B. gingivalis into the oral cavities of the hamsters resulted in a reduction in the number of organisms in the periodontal region.
Influence of Thyroxine in the Regulation of Rat Parotid Salivary Protein Composition
Authors: Johnson D.A. , Kalu D.N.
Published: November 2010

This study tested the role of thyroxine in the regulation of the protein composition of rat parotid saliva. Thyro-parathyroidectomy was performed on two groups of rats, one of which subsequently received thyroxine replacement; the third group was sham-operated. Parotid saliva was collected on the eighth day after surgery, with pilocarpine and isoproterenol used as a secretory stimulus. The volume of saliva collected in 30 min from the thyro-parathyroidectomized rats was 55% less than that collected from sham-operated rats. In the thyro-parathyroidectomized rats, the protein concentration as measured by absorption at 215 nm was unaltered, but that measured by the Lowry procedure was 43% higher. Spectrophotometric scans of Coomassie Blue-stained gels following sodium dodecylsulfate polyacrylamide gel electrophoresis of the secreted proteins showed an18% reduction in the proportion of protein attributable to amylase and a 43% reduction in proportion of acidic and basic proline-rich proteins following thyro-parathyroidectomy ; deoxyribonuclease and two other major secretory proteins (Fraction I and Fraction V) were increased (38%, 20%, and 46%, respectively). These changes in flow rate, protein concentration by the Lowry assay, and protein composition were prevented by treatment of thyro-parathyroidectomized rats with thyroxine replacement and are in opposition to those changes we reported earlier for hyperthyroid rats. The results indicate that the flow of saliva as well as the synthesis of the various salivary proteins are influenced by thyroxine.
Artificial Caries around Restorations in Roots
Authors: Purton D.G. , Rodda J.C.
Published: November 2010

An artificial caries technique was used to produce caries-like lesions in the cavity walls adjacent to micro filled resin restorations with and without dentin bonding agent, and glass-ionomer cement restorations, in the roots of extracted teeth. The lesions had histological characteristics similar to those of natural lesions and to those of the lesions produced by other experimental methods. The zonal pattern of the lesions was examined by means of polarized light microscopy and microradiography, and the depth of the lesions was measured for assessment of the microleakage around the restorations. Three cavity cleaning regimes — water spray alone, 50% citric acid, and a proprietary cleaner — were compared in conjunction with the three restorative methods.

Cavity cleaning with the citric acid or the proprietary cleaner, and the use of a fluoride-releasing restorative material, acted to reduce the depths of the lesions. Glass-ionomer cement restorations in cavities cleaned with citric acid showed lesions significantly shallower than those treated with other restorations. The glass-ionomer cement was soluble in the acidic environment but promoted the precipitation of minerals in the lesions.

The use of a dentin bonding agent did not affect the depth of demineralization around the micro filled resin restorations.
Marginal Sealing of Curing Contraction Gaps in Class V Composite Resin Restorations
Authors: Kemp-Scholte C.M. , Davidson C.L.
Published: November 2010

When one uses composite resins, the curing contraction, the stiffness of the material, and the strength of the vulnerable dentinal bond are important factors in determining the marginal adaptation of the restoration. Calculations based on these intrinsic material properties have indicated that both bulk placement and incremental placement of the restorative material in the cervical cavity inevitably lead to marginal gap formation. Sealing of this gap with an unfilled low-viscosity resin, directly after the composite resin is cured, may lead to perfectly closed restoration margins, provided that composites with low linear curing contraction and low Young's modulus are used. These conditions were ezperimentally shown to be valid for laboratory and clinical situations.
Induction of Activated Lymphocyte Killing by Bacteria Associated with Periodontal Disease
Authors: Lindemann R.A. , Miyasaki K.T. , Wolinsky L.E.
Published: November 2010

Complex interactions occur among host defense cells during bacterial infection. Bacteria and bacterial products may enhance or inhibit the effector and regulatory activity of human lymphocytes. Accordingly, we tested the ability of human periodontal pathogens to activate peripheral blood lymphocytes using standard 51chromium-release assays to measure lymphocyte-mediated cytolysis. Human adherent-cell depleted peripheral blood lymphocytes (PBL) with the addition of glutaraldehyde-fixed bacteria at a 5:1 bacteria:lymphocyte ratio were incubated at 37°C for 24 hr in RPMI 1640 medium. Six of eight bacteria tested significantly augmented lymphocyte killing of the natural killer (NK) cell-sensitive human erythroleukemia cell line K562. E. corrodens, representing activating bacteria, was also able to induce the killing of NK-resistant targets (M14, Raji), comparable with induction by interleukin-2. Lipopolysaccharides extracted from A. actinomycetemcomitans strains, when incubated with PBL, were able to enhance cytotoxicity without the presence of whole bacteria. A majority of cytotoxicity was mediated by NK cells bearing Leu-11 and NKH-1 markers.
Aspiration and Characterization of Predentin Fluid in Developing Rat Teeth by means of a Micropuncture and Micro-analytical Technique
Authors: Larsson P.A. , Howell D.S. , Pita J.C. , Blanco L.N.
Published: November 2010

A fluid phase was aspirated in vivo and in vitro from predentin or pulp of developing rat teeth by means of a micropuncture technique. Pooled aspirates (approx. 2 nL) were analyzed for P, Na, K, Ca, Mg, and S by electron probe microtechniques (Lechene and Warner, 1979). Compared with pulp fluid, currently and previously studied cartilage fluids, as well as serum, predentin fluid showed elevated K, depressed Na, Cl, and Ca, as well as increased P. Statistical analysis was possible for only a few groups of comparisons among the elemental profiles. Ultrastructural examination of the aspiration site and of the aspirates showed no evidence of contamination with cell organelles or other formed elements. The micropuncture technique used was a critically precise and laborious procedure; possible contamination with intracellular fluid could not be avoided. The consistently low Mg concentration found in the aspirates, however, supports our view that the samples were primarily extracellular.
Assessing Composite Resin Wear in Primary Molars: Four-year Findings
Authors: Vann W.F. , Barkmeier W.W. , Mahler D.B.
Published: November 2010

Many investigators have reported minimal wear of resin restorations in primary molars. Until recently, quantitative wear assessments have not been reported. The purpose of this investigation was (1) to present and contrast data from two 48-month clinical trials wherein quantitative wear assessments were used to evaluate wear of resin restorations in primary molars, and (2) to compare these results with those using the USPHS method of wear assessment.

The data were collected from two different clinical trials. One was conducted at the University of California in San Francisco by Tonn and Ryge (TR Trial). The other was conducted at the University of North Carolina at Chapel Hill by Oldenburg, Vann, and Dilley (OVD Trial). The OVD Trial had a sample size of 45 patients with 106 restorations; the TR Trial had 44 patients with 96 restorations. The restorations in both trials were Class I and II restorations in occlusion. They were placed with the experimental light-cured posterior composite resin F-70, later marketed as Ful-Fill®. At baseline, six, 12, 24, 36, and 48 months, restorations were evaluated by two evaluators trained in USPHS criteria as well as by a quantitative method of wear assessment, the standard cast technique as described by Leinfelder. Interstudy comparisons were made by Chi-square tests (USPHS evaluations) and ANOVA (quantitative assessments).

The results showed that resin restorations in primary molars exhibited progressive wear with time in service. The rate and quantity of wear were very similar to those seen in permanent posterior teeth over 36 months. Findings agree with previous reports that the USPHS evaluation criteria are insensitive in detecting early wear in primary molars.
A Theoretical Model of Loading and Eminence Development of the Postnatal Human Temporomandibular Joint
Authors: Nickel J.C. , McLachlan K.R. , Smith D.M.
Published: November 2010

The objectives of the present study were to characterize the loading of the immature TMJ, and to develop a theoretical model to explain the relationship between joint loading and development of the eminence of the human TMJ.

The osteological remains of forty individuals, ages ranging from birth to twenty years, were used to provide metric coordinates of the three-dimensional relationships of the anatomy of the biting apparatus. The data were used, in a numerical model of TMJ loading (Smith et al., 1986), to calculate the magnitudes and directions of condylar loading.

The following conclusions were drawn: (i) static equilibrium cannot be satisfied unless the immature TMJ is loaded; (ii) in the neonate, the direction of condylar loading is approximately vertical but, as the child matures, the angle of condylar loading becomes more oblique; and (iii) evidence is given in support of the hypothesis that early development of the eminence is consequent upon the stimulation of bone growth by the appropriate position and timing of loading of the immature condyle on the temporal component of the joint.
Correlation of Parameters used to Estimate Monomer Conversion in a Light-cured Composite
Authors: Rueggeberg F.A. , Craig R.G.
Published: November 2010

The sensitivities of Fourier transform infrared spectroscopy, Knoop hardness, water sorption, and resin leaching were compared for their ability to distinguish differences between composite samples cured through different thicknesses of overlying resin. The method developed allowed samples of light-cured composite to be made with controlled conversion for parameter testing, and eliminated effects of resin lost to slurry during polishing or an increase in conversion as a result of heat generated during grinding. Sensitivity to differences was greatest and equal for FTIR spectroscopy and Knoop hardness, while resin leaching proved to have moderate sensitivity, and water sorption none. The ability of these parameters to predict monomer conversion as measured by FTIR spectroscopy was also determined. Knoop hardness proved the best conversion predictor, resin leaching the next best, and water sorption the worst. Water sorption values did not vary with changes in specimen conversion.
The Effects of Experimental Variations in Dietary Sugar Intake and Oral Hygiene on the Biochemical Composition and pH of Free Smooth-surface and Approximal Plaque
Authors: Wilson R.F. , Ashley F.P.
Published: November 2010

The biochemical compositions of free smooth-surface and approximal plaque were compared after 48 hours in the presence and absence of twice-daily toothbrushing and during ingestion of either high- or low-sugar diets in ten young adults. In addition, the effect of a single sugar intake on the pH of both types of plaque was investigated. The results confirmed previously reported differences in biochemical composition between free smooth-surface and approximal plaque, the concentrations of inorganic ions and carbohydrate fractions being generally lower in the approximal sample after all experimental regimens. The concentrations of calcium and phosphorus were doubled on the low-sugar diet compared with the high-sugar diet in both types of plaque. A significant decrease in carbohydrate concentrations was observed in free smooth-surface plaque in subjects on the low-sugar diet, but not in approximal plaque. Little variation was observed in the biochemical composition which could be attributed to the presence or absence of toothbrushing. The pH in free smooth-surface plaque was lower than that in approximal plaque five minutes after a sugar intake, but the situation was reversed two hours later. The results indicate that differences in composition and pH between free smooth-surface and approximal plaque are associated with reduced access to salivary and dietary influences due to diffusion limitation in the deeper layers of plaque.
Comparison of the Effects of Two Topical Fluoride Regimens on Demineralized Enamel in vivo
Authors: Clark J.W. , Corpron R.E. , More F.G. , Easton J.W. , Merrill D.F. , Kowalski C.J.
Published: November 2010

The purpose of this investigation was to study the intra-oral remineralization of acid-softened enamel by a NaF dentifrice compared with that from a combination of topical F agents. Bovine enamel slabs were demineralized with 0.1 mol/L lactic acid at pH 4.0 for 14 hr and then mounted in a removable mandibular appliance. Control slabs were worn for 96 hr by seven adult males who brushed daily with a F-free dentifrice. Test slabs were brushed with a NaF dentifrice 4 x / day or with the same dentifrice 4 x /day and a 0.02% APF mouthrinse and a 0.4% SnF2 gel which were applied oncelday for three days. The natural dentition was also brushed with the NaF dentifrice during both test periods. Microhardness testing was performed on sound enamel, and after acid-softening, intra-oral exposure (IOE), and acid resistance testing (ART) in 0.01 mol/L lactic acid at pH 4.0 for 24 hr. Control and test slabs were etched with 0.5 mol/L HClO4 for from 15 to 60 sec. The F content was measured with a F electrode and PO4 by spectrophotometry. Contact microradiography and image analyses were performed on control and test slabs so that changes in mineral content resulting from treatment could be assessed. Both test groups were significantly harder after both IOE and ART than were controls, but no differences appeared between the effects of the two test groups. The F content of control slabs was significantly less than that of both test groups, and the combination-treated slabs showed greater F than did the dentifrice-treated slabs. Microradiographs revealed a higher mineral content in the basal 2/3 of combination-treated lesions, while diffuse mineral deposition occurred, especially subjacent to the surface in the dentifrice-treated lesions. Control lesions showed little added mineral.
Effect of Inoculum Size and Frequency on the Establishment of Streptococcus mutans in the Oral Cavities of Experimental Animals
Authors: Ooshima T. , Sumi N. , Izumitani A. , Sobue S.
Published: November 2010

SPF Sprague-Dawley rats and ICR mice were inoculated with either Streptococcus mutans MT8148R (serotype c) or 6715 (g), and the influence of inoculum size, inoculum frequency, and sucrose on the establishment of S. mutans in the oral cavity was examined. Successful colonization of S. mutans in the experimental animals was absolutely dependent on the number of the cells introduced orally. Furthermore, inoculum frequency and sucrose seemed to act as secondary factors to modify the establishment of S. mutans, and it is suggested that high inoculum frequency may decrease the inoculum size necessary for the colonization of S. mutans in the oral cavity.
Chronic Treatment with Beta Adrenergic Agonists and Antagonists Alters the Composition of Proteins in Rat Parotid Saliva
Authors: Johnson D.A. , Cortez J.E.
Published: November 2010

This investigation was undertaken to determine the role of β-adrenergic receptors in the regulation of the protein composition of rat parotid saliva. Chronic treatment of rats with dobutamine, a β1-adrenergic agonist, resulted in changes in parotid saliva volume, protein concentration, and composition which were essentially the same as those changes which occurred following chronic treatment with isoproterenol, a non-specific β-adrenergic agonist. Chronic treatment with the β2-adrenergic agonist, terbutaline, had no effect on parotid saliva volume, protein concentration, or composition. Chronic treatment of rats with a β1-adrenergic antagonist, metoprolol, had different effects on saliva dependent on the manner by which the drug was delivered. Twice-daily injections of metoprolol led to a decrease in flow rate, but protein concentration and composition were unaltered. When metoprolol was delivered by surgically implanted osmotic mini pumps, neither the flow of parotid saliva nor its concentration of protein was altered; however, there was a reduction in the proportion of proline-rich proteins in saliva. Comparable changes in parotid saliva protein composition occurred when the mini pumps delivered propranolol, a non-specific β-adrenergic antagonist. Chronic treatment of rats with an α2-adrenergic agonist (clonidine) or antagonist (yohimbine) was without effect on parotid saliva flow rate, protein concentration, or composition. These findings suggest that the synthesis of proline-rich proteins is regulated, in part, by β-adrenergic receptor stimulation, and primarily by the β1-receptor subtype.
Gene Regulation in the Development of Oral Tissues
Authors: Slavkin H.C.
Published: November 2010

The regulatory processes associated with tooth formation are being investigated by the identification of when, where, and how cell adhesion molecules (CAMs), substrate adhesion molecules (SAMs), dentin phosphoprotein, enamel gene products, and intermediate cementum products are expressed during sequential developmental stages of morphogenesis, cytodifferentiation, dentin, enamel and cementum extracellular matrix (ECM) formation, and biomineralization. Instructive and permissive signaling is required for both morphogenesis and cytodifferentiation based upon in vitro organotypic culture studies in serumless, chemically-defined medium. Intrinsic developmental instructions, independent of exogenous growth factors, mediate tooth morphogenesis from the initiation of the dental lamina through crown and initial root development. Recent progress using recombinant DNA methods has advanced descriptions of several dental structural genes. The complete nucleic acid sequence for mouse amelogenin has been defined. This sequence is located on the mouse X chromosome and on the human X and Y chromosomes. This discussion summarizes recent results using experimental embryology, recombinant DNA technology, and immunocytology in the context of instructive epithelial-mesenchymal interactions associated with epithelial differentiation into ameloblasts, ectomesenchyme differentiation into odontoblasts, and dentin and enamel ECM biomineralization. The tooth organ provides opportunities at several levels of biological organization to investigate cellular, molecular, and developmental processes.
Micro-analysis of Mineral Saturation Within Enamel During Lactic Acid Demineralization
Authors: Vogel G.L. , Carey C.M. , Chow L.C. , Gregory T.M. , Brown W.E.
Published: November 2010

In this study, the physicochemical factors responsible for caries-like lesion propagation were investigated by means of a micro-analytical system used to study the fluid within a lesion during a simulation of the decay process. Four 500-μm-thick serial sections prepared from a single human molar were mounted between glass plates with only the natural surface of the tooth exposed. Microwells were then drilled into sound and pre-existing carious regions of the section through one of the plates. These microwells were then filled with fluid under mineral oil, and after a week of equilibration, the natural surface of the section was exposed to a lesion-producing fluid. The concentrations of calcium, phosphate, and hydrogen ions of the fluid in the wells were then followed as a function of time as the lesion advanced.

The results of this study, in which lactic acid was used to demineralize enamel, were consistent with those previously reported (Vogel et aL, 1987a): The solution within the lesion remained saturated during the acid attack. Differences in initial mobilities of the calcium and phosphate and other ions, a result of the permselectivity of the enamel, increased the concentrations within the lesion and permanently changed the ratio of these ions in the lesion solution. Based on these results, we suggest that the ionic permselectivity of tooth enamel can have a profound effect on the transport of mineral from a caries lesion.
Determination of the Rate of Release of Intra-oral Mercury Vapor from Amalgam
Authors: Berglund A. , Pohl L. , Olsson S. , Bergman M.
Published: November 2010

The experimental and analytical difficulties associated with the measurement of mercury vapor in the oral cavity are considerable. In the present paper, the objective was to measure the amount of intra-oral mercury vapor in subjects with amalgams, by means of two sets of equipment based on different functional principles. In addition, it was found that the type of mercury source prevalent in the oral cavity had to be evaluated. The measuring technique used to obtain correct results is discussed, and an evaluation of the conditions for the application of the measuring equipment available was made. It was found that the amount of mercury released from the oral cavity was time-dependent. Furthermore, the amount of mercury released with the time kept constant was almost independent of the pumping flow rate up to 8 L/min. It was found that the tissue, saliva, and the amalgam restorations were not depleted of mercury during the measuring time. The results of the Mercollector-Mercometer measurements carried out on seven subjects with nine or more occlusal surfaces restored with dental amalgam and on three subjects without any amalgam restorations revealed that the rate of mercury release was in the range 0.03-0.34 ng/sec in the former group and < 0.01 nglsec in the latter. Based on the experimental results and on theoretical considerations, it was concluded that the amount of mercury released per time unit is the only quantity measurable.