bluuebunny/crossref_metadata_2025 huggingface dataset:
High-resolution Electron Microscopy of Hydroxyapatite Grown in Dilute Solutions
Authors: Aoba T. , Yoshioka C. , Yagi T. , Moreno E.C.
Published: November 2010

High-resolution electron microscopy (HREM) was applied to the study of seeded crystal growth of hydroxyapatite (HA) in supersaturated solutions. The HA seed crystals were rod-shaped, elongated along the c-axis, and showed smooth contours. The seed crystals exhibited hexagonal prism facets, and one end was rhombohedrally terminated, whereas the opposite end was blunt. Growth experiments were carried out at 37°C, and solution compositions were carefully selected to avoid the involvement of precursor phases during the HA growth. After five-hour growth, the total amount of precipitation was from 3 to 7% of the initial crystal mass added to the solutions; examination of the crystals by HREM disclosed the formation of projections on the end surfaces of the HA crystals. High-resolution TEM clearly showed lattice fringes with predictable spacings over the entire crystal specimen, including the formed projections. Analysis of selected regions by optical diffraction of the HRTEM fringe negatives showed that the nature and orientation of the projections were similar to those of the underlying seed crystal. High-resolution SEM of the HA crystal after five-hour growth disclosed step-like structures on the prism faces, as well as the projections localized on the ends. These results strongly suggest that more than one growth process may be involved, perhaps related to the distinct faces of the HA seed crystals.
Human Gingival Fibroblast Production of Interferon
Authors: Rose G.G. , Pinero G.J. , O'Neill P.A. , Nikai H. , Mahan C.J.
Published: November 2010

Three human gingival fibroblast cell lines were used to determine whether they could be induced by a synthetic RNA and super-induced by metabolic inhibitors to produce interferon (IFN-β). When established procedures were followed for human fetal or newborn skin fibroblast cell lines, the adult gingival fibroblasts produced comparable amounts of IFN-β. It was shown that the superinducers alone would not cause an IFN-β production response, and that the absence of serum in the production medium also inhibited the production of IFN-β. The effect of IFN-β on cell growth was carried out in T-flasks seeded with 105 HEp-2 cells. After one and two wk, the cells of triplicate control flasks and triplicate flasks containing various dilutions of the production media were enumerated to determine a cell multiplication inhibition (CMI) value. A correlation between the IFN-β content and the CMI effect, however, was not obtained, and it was concluded that other CMI agents, possibly more potent than the IFN-β, were being produced by the stimulated human gingival fibroblasts. Cell protein assays which gave a high ng/ cell protein content correlated with TEM micrographs which showed clusters of complex lysosomes, primarily in cells cultured in the IFN-β-containing nutrient. However, since commercial IFN-β initiated no such lysosomal response, it was further concluded that the complex lysosomes were due to CMI agent(s) other than IFN-β.
A Comparison of S. mutans Prevalence in Relation to Caries Experience in Norwegian and Immigrant Vietnamese Children
Authors: Scheie A.A. , Selikowitz H.S. , Arneberg P.
Published: November 2010

Vietnamese immigrant and Norwegian children, matched according to caries experience, age, and sex, were compared with respect to S. mutans in dental plaque and in saliva. Regardless of ethnic group, S. mutans prevalence was highest in plaque over caries lesions and from fissures, and lowest in plaque from smooth surfaces. The S. mutans distribution appeared very similar in the two groups. Only in untreated Vietnamese children were the S. mutans saliva levels higher, probably refTecting the numerous untreated caries lesions present in this group. After caries treatment, we observed significant reductions in S. mutans levels in both saliva and smooth surface plaque.
Basic Biological Sciences Hydrolysis of Dicalcium Phosphate Dihydrate in the Presence or Absence of Calcium Fluoride
Authors: Tung M.S. , Chow L.C. , Brown W.E.
Published: November 2010

Effects of temperature (25 and 37°C), pH (4.9-10.5), and CaF2 on CaHPO4·2H2O (DCPD) hydrolysis were studied in a pH-stat. Octacalcium phosphate (OCP) was the product at pH 6.2-6.8 and 25-37°C; thermodynamically stable apatitic compounds were formed at higher pH and/or higher temperature. In the presence of CaF2, apatite was the product, its crystallinity improved, and the fluoride content increased as pH of the reaction decreased. The results demonstrate the remarkable ability of fluoride to promote the hydrolysis of an acidic calcium phosphate, DCPD, to apatite.
Oligosaccharide Structures of the Low-molecular-weight Salivary Mucin from a Normal Individual and one with Cystic Fibrosis
Authors: Reddy M.S. , Levine M.J. , Prakobphol A.
Published: November 2010

Studies were begun to compare the oligosaccharide structures of the low-molecular-weight mucin purified from the submandibular-sublingual saliva of a normal individual with that from one with cystic fibrosis. Following alkaline/borotritide cleavage, neutral and sialic acid-containing chains were purified by a combination of gel filtration, paper chromatography, and high-voltage paper electrophoresis. Oligosaccharides ranged in size from a disaccharide to a heptasaccharide. Approximately 80% of the oligosaccharides were GalB1, 3 GalNAc; Fucα1,2GalB1,3GalNAc; and NeuAcα2,3GalB1, 3GalNAc. The other structures were Fucα1,2GalB1,4(Fucα1,3)GlcNAcB1,6 (GalB1,3)GalNAc or GalB1,4(Fucα1,3)GlcNAcB1,6(Fucα1,2GalB1, 3)GalNAc; GalB1,4(Fucα1,3)GlcNAcB1,6(NeuAcα2,3GalB1,3)GalNAc; and Fucα1,2GalB1,4(Fucα1,3)GlcNAcB1,6 (NeuAcα2,3Gal-B1,3)GalNAc. There were no apparent qualitative differences in the neutral and sialic acid-containing units recovered from the normal and cystic fibrosis samples.
Alternative Interpretations of Water Sorption Values of Composite Resins
Authors: Fan P.L. , Edahl A. , Leung R.L. , Stanford J.W.
Published: November 2010

Water sorption values for direct filling resins and an unfilled resin were much more similar at 30 days when expressed as mg/g organic matrix than as mg/cm2 or weight percent. This interpretation is indicative of the water sorption characteristics of resin matrices. The values are even more indicative when solubility or leaching is taken into consideration. With the specimen sizes used in this study, the effect of the kinetics of water sorption could be minimized by using values obtained after immersion in water for 30 days.
Analysis of Dental Hard Tissue by Computerized Microdensitometry
Authors: Mallon D.E. , Mellberg J.R.
Published: November 2010

One method of quantitating mineral content in thin sections of dental hard tissue is microdensitometry of contact radiographs. This method is often applied to analysis of artificial caries lesions. Because there is great inter- and intra-tooth variability, a single microdensitometric scan will not accurately reflect the content or distribution of mineral within an individual lesion, or within a group of lesions. To increase the number of replicates that can be handled routinely, a computer-driven microdensitometer has been used with a step series of aluminum and enamel to quantitate mineral content values at approximately 1-μm intervals. Accurate assessment of an individual lesion was made possible by averaging multiple scans of the lesion on each of several thin sections prepared from the lesion. Mean mineral profiles of treatment groups were then made from the profiles of the individual lesion. These data reduction techniques allowed for a large number of replicates to be used in the measurement of remineralization. The computerized microdensitometric system described here was developed to allow for an objective, quantitative analysis of the mineral content of dental hard tissue.
A Technique for Characterizing Casting Behavior of Dental Alloys
Authors: Hinman R.W. , Tesk J.A. , Whitlock R.P. , Parry E.E. , Durkowski J.S.
Published: November 2010

A technique for characterizing casting behavior of dental alloys has been developed and tested. The method employs easily reproducible specimen patterns and uses equipment and procedures generally available in dental prosthetic laboratories. A castability value is arrived at by counting complete segments of a cast alloy grid.

Test results indicate that the castability evaluation procedure described can be a valuable aid in the laboratory for both selecting and using dental materials for producing cast restorations. The test method would also appear useful for the evaluation of products and techniques during research and development.

An absolute minimum for the castability value determined relative to clinical and laboratory efficacy has yet to be established.
The Effect of Five-year Storage Prior to Bonding on Enamel/Composite Bond Strength
Authors: Williams V.D. , Svare C.W.
Published: November 2010

The purpose of this study was to examine the effect of pre-bonding storage durations on the shear strength of light-cured composite bonded to enamel. Thirty whole extracted human molars - 12 with a storage time of five years, 12 with a storage time of three or fewer months, and six with a storage time of 24 hours or less - were mounted in improved dental stone in copper tubing. The molars were faced 90° to the horizontal with a milling device to produce 120 surfaces, 48 each for two groups, and 24 for one group. Composite buttons 2.3 mm in diameter were bonded to the enamel using the acid-etch light-curing system. The samples were tested in shear utilizing a cross-head speed of 0.5 cm/min with a 500-kg load cell. The results showed that: (1) there was no significant difference, at the 0.05 confidence level, in compositelenamel bond strength between teeth stored for 24 hours, three months, and five years prior to bonding; (2) the lingual surface developed the highest composite/enamel bond strength in all three groups; and (3) enamel fracture occurred 29% of the time on de-bonding.
Contribution of Stereochemical Interactions in the Adhesion of Streptococcus sanguis C5 to Experimental Pellicles
Authors: Gibbons R.J. , Etherden I. , Moreno E.C.
Published: November 2010

Parameters for the adsorption of Streptococcus sanguis C5 to experimental salivary pellicles were determined to assess the relative contributions of stereochemical and less specific hydrophobic-electrostatic interactions in this process. S. sanguis C5 cells possess hydrophobic surfaces and also an adhesin which exhibits stereochemical binding to sialic acid-containing salivary receptors. The adsorption of S. sanguis C5 to untreated pellicles was significantly better described by a two-site adsorption model than by a one-site model (p<0.001). One class of binding sites had an affinity for the organism that was more than 400 times that of the second class of binding sites. However, adsorption of the organism was better described by a one-site model to asialo pellicles prepared by neuraminidase treatment which destroyed the receptors for the organism's adhesin.

The affinity of the organism to sites in asialo pellicles was low, and approximated that to the low-affinity sites in untreated pellicles. These observations suggest that, in the absence of stereochemical interactions involving the organism's adhesin and specific salivary receptors, S. sanguis C5 cells only exhibit low-affinity binding to experimental pellicles. This was substantiated by studies which showed that adsorption of the organism to albumin-coated hydroxyapatite and to polystyrene beads was also better described by a one-site model, and it occurred with only low affinity.
Remineralization of Softened Bovine Enamel following Treatment of Overlying Plaque with a Mineral-enriching Solution
Authors: Pearce E.I.F. , Moore A.J.
Published: November 2010

Pre-softened, gauze-covered bovine enamel blocks were worn in the buccal sulcus of five subjects for seven days. Artificial plaque enmeshed in the gauze was treated four times per day for four days with an enzyme-dependent mineralizing solution, resulting in 20-, 10-, and 200-fold increases in Ca, P, and F, respectively. Enamel beneath this mineral-enriched plaque recovered 37% of the hardness lost from pre-softening, while control enamel beneath untreated plaque recovered only 14%. Test enamel contained from five to 13 times as much F as did control enamel in the outer four layers sampled. Even though direct use of the mineralizing solution without the interposition of plaque caused a hardness recovery and F uptake similar to those in test enamel in vivo, a direct solution effect on enamel is not thought to explain the in vivo effects. Plaque treated with the urea-containing solution rapidly reaches a pH > 8, when a precipitate develops, leaving much-reduced ion concentrations in solution. Direct exposure of softened enamel to such a supernatant resulted in reduced hardness recovery and F uptake. It is concluded that the in vivo enamel remineralization was due mainly to the presence of a mineral phase in the overlying plaque. This mineral could have promoted remineralization by creating mildly supersaturated conditions during normal plaque pH cycles.
Pharmacokinetics of Chronic Fluoride Ingestion in Growing Pigs
Authors: Richards A. , Kragstrup J. , Nielsen-Kudsk F.
Published: November 2010

The present study was undertaken to estimate bio-availability and biological half-life of fluoride and accumulation of fluoride in bone in the domestic pig. Eight animals receiving 2 mg F-/kg b.w. per day from age 8 to 14 months were compared with eight controls.

Plasma fluoride concentrations just prior to the daily oral dose were measured at regular intervals. After 112 days post-dose, plasma fluoride levels were measured over a 48-hour period following the daily oral dose or a single intravenous dose. Mean bio-availability factor for the oral dose was 0.3 (range 0.2-0.4), and mean biological half-life was 59 days (range 49- 72). Bone fluoride content calculated from the pharmacokinetic parameters derived from plasma data was similar to the content of fluoride measured in the bone at slaughter.

The study showed that accumulation of fluoride in bone influences plasma fluoride levels during chronic administration of fluoride to growing pigs. The long biological half-life found showed that it was not possible to achieve steady-state plasma levels within the six-month experimental period used. This means that, for dose-response studies of dental fluorosis in this animal, it is not possible to achieve steady-state plasma concentrations as a basis for correlations to the degrees of pathological change observed in the teeth.
Dissolution Studies of Human Enamel Treated with Aluminum Solutions
Authors: Putt M.S. , Kleber C.J.
Published: November 2010

Dissolution tests using human enamel were conducted after treatment with aqueous solutions of various aluminum (Al) salts. All Al compounds, except those which formed stable Al-complexes, greatly decreased enamel dissolution in a pH 4 acetate buffer. A comparison with fluoride compounds demonstrated that Al was equivalent to SnF2 and more effective than NaF and Na2PO3F. Furthermore, the reduction in enamel dissolution produced by Al persisted after more than three hr of successive demineralization, which was twice as long as that observed with a pH 4.5 SnF2 solution.
Creep-fatigue as a Possible Cause of Dental Amalgam Margin Failure
Authors: Williams P.T. , Hedge G.L.
Published: November 2010

Fracture of the margins is the most common cause of failure of dental amalgam restorations. Both corrosion and creep have been identified as possible contributors to this type of failure. The stresses that induce creep may arise from the continued setting expansion of the amalgam, the formation of corrosion products, mastication, or from the thermal expansion of the amalgam during ingestion of hot foods. The latter two are low-frequency cyclic stresses. The amalgams used in dentistry have fusion temperatures only about 40°C above mouth temperature, and they experience grain boundary sliding during creep deformation. Since grain boundary sliding, low-frequency cyclic stresses, and a temperature near the fusion temperature of the alloy are prerequisites for so-called "creep-fatigue fracture", this type of fracture may contribute to amalgam margin failure. Amalgam made from seven different alloys was condensed into stainless steel dies. After being allowed to set for seven days, the specimens were thermally cycled between 4°C and 50°C for 500 and 1000 cycles. Amalgam margin integrity was evaluated by scanning electron microscopy both before and after each cycling period. The amount of margin fracture was calculated after 1000 cycles. Thermal cycling of amalgam restorations placed in stainless steel dies resulted in predominantly intergranular fracturing of the amalgam margins, indicating that creep-fatigue failure may be a significant contributor to in vivo margin fracturing.
Thermal Stress Failure of Porcelain Bonded to a Palladium-Silver Alloy
Authors: Walton T.R. , O'Brien W.J.
Published: November 2010

Cracking or rupturing, due to thermal stress, of porcelain bonded to a palladium-silver alloy indicated that porcelain-metal thermal compatibility was dependent on: the difference in thermal expansion coefficients of the porcelain and metal; the geometry and dimensions of the samples; and the porcelain-metal thickness ratio. A spherical configuration was more sensitive to thermal expansion coefficient differences than was a disc configuration. A higher incidence of cracking resulted from an increase in both specimen size and porcelain-metal thickness ratio.
A Comparison of the Antibacterial and Cytotoxic Effects of Parachlorophenoll
Authors: Messer H.H. , Feigal R.J.
Published: November 2010

The antibacterial and cytotoxic effects of para chlorophenol (as 35% camphorated PCP and 2% aqueous PCP) were compared directly, using the agar overlay technique. Human pulp fibroblasts and L929 cells were grown to confluence in 60-mm petri dishes. Bacterial suspensions (S. aureus, E. coli ) in agar were poured as a thin layer in 60-mm petri dishes. All were overlaid with agar. Cells were exposed to medicament via filter paper discs placed on the agar surface. After 24 hours, the zone of cell lysis (fibroblasts) or inhibition of bacterial growth was measured as diameter in mm. A dose-response relationship was observed for both fibroblasts and bacteria. The zone of inhibition for fibroblasts was larger than that for bacteria, indicating that the cytotoxicity of parachlorophenol exceeds its antibacterial activity.
A New Method for Matching Tooth Colors with Color Standards
Authors: Van Der Burgt T.P. , Ten Bosch J.J. , Borsboom P.C.F. , Plasschaert A.J.M.
Published: November 2010

A new method for quantitative intra-oral tooth color determination is presented. Basically, the tooth color is assessed by visual comparison with opaque color standards, which are logically arranged according to three visual color dimensions. The standards were analyzed spectrophotometrically, and the C.I.E. color coordinates were computed. Illumination and observation were standardized during the matching procedure. Two distinct situations, method 1 and method 2, were investigated. The situation in method 1 is to be considered as large window illumination and small window collection of the reflected light. For method 2, the same small window was used for both illumination and observation.

Using both methods, the color of a tooth could be quantified into three separate color dimensions. Using method 1, the consistency among 25 examiners was high in determining the color of ten teeth; using method 2, the inter-examiner agreement was low. For the same tooth, different color standards were selected with method 1 or method 2. The standard selected with method 2 often appeared to be in disagreement within clinical expectations. The differences in results between method 1 and method 2 are explained by the optical properties of the translucent dental enamel (e.g., volume reflection).

Method 1 allows for reproducible quantification of clinical tooth discoloration according to C.I.E. color specifications and can possibly be applied in prosthetic dentistry.
Basic Biological Sciences Application of an X-ray Image Magnifier to the Microradiography of Dental Specimens
Authors: Takagi S. , Chow L.C. , Brown W.E. , Dobbyn R.C. , Kuriyama M.
Published: November 2010

A highly parallel incident x-ray beam combined with x-ray image magnification was used to obtain high-resolution microradiographs of dental specimens. Preliminary results obtained using a rotating anode x-ray generator show that limitations associated with conventional contact microradiography regarding (1) spatial resolution, (2) sample thickness, and (3) sample orientation, relative to the film, were significantly reduced.
Differences in Permeability of Microperoxidase and Horseradish Peroxidase into the Alveolar Bone of Developing Rats
Authors: Tanaka T. , Sakano A.
Published: November 2010

Microperoxidase (small m.wt tracer) and horseradish peroxidase (large m.wt tracer) were used to investigate the existence of extracellular (between blood vessels and bone cells) and intracellular transport pathways in the alveolar bone cells of five-day-old rats. HRP directly penetrated the cytoplasm and nucleus of the osteocytes and osteoblasts, but MP did not. These findings suggest that HRP at high dosages is more toxic to bone cells than is MP, since the direct penetration of HRP probably results from alteration of plasma membrane permeability. If so, MP seems to be a more suitable tracer than HRP. The findings from MP tracing suggest that a main transport pathway of bone fluid exists between the external part of the unmineralized zone, which is located in the lacunar and canalicular spaces around bone cells, and the innermost edge of the mineralized matrix, which constitutes the lacunar and canalicular walls; in addition, minor pathways as accessory routes might diverge from the main pathway to go around the bone cells.
Depth of Penetration of in vitro Root Surface Lesions
Authors: Phankosol P. , Ettinger R.L. , Hicks M.J. , Wefel J.S.
Published: November 2010

An acidified gel system was used to produce artificial caries lesions in root surfaces and in enamel. The teeth were exposed to the gel system for two weeks and four weeks, after which the lesions were examined by polarized light microscopy and photographed by standardized techniques. The depths of penetration of the lesions were measured from these standardized photomicrographs.

The lesions in root surfaces were deeper than those in enamel for all teeth. After two but not four weeks of exposure in the gel system, the lesions in the root surfaces of anterior teeth were deeper than those in pre-molars.
Inhibition of Root Surface Caries in Rice Rats: Use of a Sodium Fluoride Dentifrice
Authors: Rosen S. , Beck F.M. , Beck E.X.
Published: November 2010

A sodium fluoride-containing dentifrice (Gleem) was evaluated for its efficacy to inhibit root surface caries in the rice rat. The dentifrice was diluted 50/50 with water so that the slurry contained 500 ppm fluoride. This slurry, a solution of 5000 ppm fluoride, and demineralized water were applied to the molar teeth twice daily for 10 weeks. Another group of rats was given 50 ppm fluoride in the drinking water. There was significantly less root surface caries in all groups of rats which received fluoride than in the demineralized water control animals. However, none of the fluoride preparations inhibited the loss of alveolar bone.
Clinical Science
Authors: Tal H.
Published: November 2010

Periodontal bone loss associated with periodontitis results in increase in the distance between the cemento-enamel junction (CEJ) and the alveolar bone crest (ABC). This study analyzed periodontal bone loss in 100 mandibles of South African blacks who were never exposed to preventive or restorative dental treatment. Specimens were equally distributed over the third to the seventh decade of adult life. CEJ to-ABC (CA) distances were measured along 4904 surfaces of 1076 teeth. Analysis of the measurements showed that, generally, CA distances increased with age; differences were substantial between the first and fifth age groups. The incisors were most severely affected in all age groups, and bone loss was less severe around posterior teeth. Pre-molars and second molars lost the least bone. No significant differences between measurements on the buccal, lingual, mesial, or distal surfaces for these teeth were found. Measurements on the right and left sides of the mandible did not differ significantly. These observations may, in part, have been influenced by mid-life loss of teeth caused by severe periodontitis; their absence from the sample may have masked the true extent of periodontal bone loss. The difference in age of eruption and, therefore, the difference in period of exposure to the oral environment may account for the more severe bone loss in the anterior teeth, especially in specimens from younger individuals (21-30 years).
Smoking and Periodontal Disease in the Finnish Population Aged 30 Years and Over
Authors: Markkanen H. , Paunio I. , Tuominen R. , Rajala M.
Published: November 2010

The aim of this study, which was part of the Mini-Finland Oral Health Survey, was to evaluate the effect of smoking on periodontal condition in the Finnish adult population. A representative sample was drawn from the population aged 30 years and over. The total number of subjects was 8000, 90% of whom participated in the clinical examination. Periodontal diagnoses were made according to the modified Periodontal Treatment Need System (PTNS). Information about age, toothbrushing, and smoking habits was collected by personal interviews. When the sample was divided into two groups (with and without periodontal pockets), the overall risk ratio (RR) was 1.39 and was slightly higher for men than for women. A log-linear model was used to study simultaneous associations and interactions between smoking, periodontal disease, and some background factors. In this model, smoking had not significantly affected the periodontal condition.
Effects of Extracellular Plaque Components on the Chlorhexidine Sensitivity of Strains of Streptococcus mutans and Human Dental Plaque
Authors: Wolinsky L, E. , Hume W.R.
Published: November 2010

An in vitro study was undertaken to determine the effects of sucrose-derived extracellular plaque components on the sensitivity of selected oral bacteria to chlorhexidine (CX). Cultures of Streptococcus mutans HS-6, OMZ-176, Ingbritt C, 6715-wtl3, and pooled human plaque were grown in trypticase soy media with or without 1 % sucrose. The sensitivity to CX of bacteria grown in each medium was determined by fixed-time exposure to CX and subsequent measurement of 3H-thymidine uptake. One-hour exposure to CX at concentrations of 10-4 M (0.01% w/v) or greater substantially inhibited subsequent cellular division among all the S. mutans strains and human plaque samples tested. An IC50 (the CX concentration which depressed 3H-thymidine incorporation to 50% of control level) of close to 10-4 M was noted for S. mutans strains HS- 6, OMZ-176, and 6715-wt13 when grown in the presence of sucrose. The same strains grown in cultures without added sucrose showed about a ten-fold greater sensitivity to CX (IC50 close to 10 -5 M). A three-fold difference was noted for S. mutans Ingbritt C. Only a slight increase in the IC50 was noted for the plaque samples cultured in sucrose-containing media, but their threshold for depression of 3H-thymidine uptake by CX was lower than that for the sucrose-free plaque samples. The study showed that extracellular products confer some protection against CX to the bacteria examined, and provided an explanation for the disparity between clinically-recommended concentrations for plaque suppression and data on in vitro susceptibility. Also, when compared with similarly-derived indices of susceptibility of mammalian cells to CX, the data obtained give rise to new possibilities for therapeutic use of CX or other bisguanides in dentistry.
Correlation of Apical and Lateral Membrane Modulations of Maturation Ameloblasts
Authors: Skobe Z. , LaFrazia F. , Prostak K.
Published: November 2010

Maturation ameloblasts of rat incisor teeth have smooth-ended and ruffle-ended apical membrane configurations. It has also been reported that maturation ameloblasts have several lateral membrane configurations. The purpose of this study was to determine the correlation between the modulations of lateral and apical cell membranes of murine incisor ameloblasts in the maturation stage of amelogenesis. Maxillary and mandibular incisors were dissected, demineralized, embedded in paraffin, sectioned and then de-paraffinized, and the enamel organs were prepared for scanning electron microscopy. Additional mouse and rat incisor enamel organs were fixed and teased apart during dehydration, then observed in the SEM. The lengths of smooth- and ruffle-ended ameloblast segments were measured, and the site, length, and frequency of each lateral membrane configuration were determined within each segment. The lateral membrane configuration with folds forming from 12 to 14 channels around the periphery of the cells was most predominant in both smooth- and ruffle-ended cells. Cells surrounded by from six to eight channels were the only other lateral membrane configuration observed in ruffle-ended ameloblasts. Smooth-ended ameloblasts had lateral membrane configurations with either dense or sparse microvillous projections in addition to both types of channel cells. The observation that channelled extracellular spaces are always associated with ruffle-ended cells suggests that channels somehow function in conjunction with the ruffled apical membrane in resorption and removal of enamel matrix proteins. The smooth-ended ameloblasts lack tight apical junctions, and their microvillous lateral membranes permit the passage of plasma fluids around cells to the maturing enamel surface. Analysis of our data indicates that specific lateral membrane configurations are related to the type of apical membrane present.
Clinical Science
Authors: Vimy M.J. , Lorscheider F.L.
Published: November 2010

Intra-oral air was analyzed for mercury (Hg) vapor concentration in 46 subjects, 35 of whom had dental amalgam restorations. Measurements were made with a Jerome Hg detector both before and ten min after chewing stimulation. Subjects with dental amalgams had unstimulated Hg vapor concentrations that were nine times greater than basal levels in control subjects with no amalgams. Chewing stimulation in subjects with amalgams increased their Hg concentration six-fold over unstimulated Hg levels, or a 54-fold increase over levels observed in control subjects. Concentrations of Hg measured in intra-oral air larger than those reported in expired air were attributed to the rate and direction of air passage across amalgam surfaces. There were significant correlations between Hg vapor released into intra-oral air after chewing stimulation and the numbers and types of amalgam restorations. It is concluded that intra-oral air is a reliable physiological indicator of Hg released from dental amalgam that may reflect a major source of chronic Hg exposure,
A Survey of the Reasons for Dental Extractions in France
Authors: Cahen P.M. , Frank R.M. , Turlot J.C.
Published: November 2010

3516 French dentists, selected at random, were asked to record every tooth they extracted during January, 1984. They were also asked to give the reason for extraction in each case. These were assigned to eight groups: caries, periodontal diseases, eruption problems, prosthetics, trauma, orthodontics, occlusal problems, and other reasons. Data were received from 910 dentists (25.3%) relating to a total of 14,621 extractions. Overall, caries was the most frequent cause for extraction (49%), followed by periodontal diseases (32.4%) and orthodontics (8.4%). In the age group under 50, dental caries was the main reason for extraction. However, in the age group over 50, periodontal diseases became the principal reason for extraction. Orthodontic extractions were most prominent in the 6-12 and 13-20 age groups, with respective frequencies of 72.6% and 24.8% of all extractions. Eruption problems contributed most frequently in the 13-20 and 21-30 age groups, their respective percentages being 8.7% and 12.3%. Extractions resulting from trauma were most frequently noted in the under-6 age group (frequency of 8.8%).

As far as the type of tooth was concerned, first and second molars taken together made up 29.6% of extractions These were followed by pre-molars, anterior teeth, and third molars at levels of 25.8%, 29.9%, and 14.7%, respectively.

The teeth most frequently extracted because of caries were the molars (40.9%); because of periodontal disease, the anteriors (49.1%); and, for prosthetic reasons, again the anteriors (57.5%). Extractions from the various regions of France showed important variations. Percentage frequencies for caries and periodontal extractions were inversely linked.
Interactive Effect of Stress and Temperature on Creep of PFM Alloys
Authors: Anusavice K.J. , Shen C. , Hashinger D. , Twiggs S.W.
Published: November 2010

The creep rates of six alloys for porcelain-fused-to-metal (PFM) restorations were determined as a function of flexural stress and temperature. Although two Pd-Cu alloys demonstrated excellent resistance to creep at low-stress, high-temperature conditions, they were especially susceptible to deformation at high stresses and temperatures near the glass transition temperature of dental porcelains. In comparison, a Ni-Cr alloy and a Pd-Co alloy demonstrated superior creep resistance at high-stress, low-temperature conditions. This indicates a relatively low potential for deformation due to stresses which may result from a thermal contraction differential between these two alloys and incompatible dental porcelains.
Clinical Science A Longitudinal Study of Root Caries: Baseline and Incidence Data
Authors: Banting D.W. , Ellen R.P. , Fillery E.D.
Published: November 2010

A 34-month clinical investigation of root caries was conducted using a hospitalized, chronically-ill population. Forty-five subjects with 150 caries-free surfaces were observed for at least 12 consecutive months. Clinical measurements included diagnosis of new root and coronal caries, gingival inflammation, pocket depth, recession, and distance of new lesions from the gingival margin. The overall root caries attack rate was 1.90 lesions per 100 person-months at risk, with the greatest rate occurring during the first year of study. Mesial and facial surfaces accounted for 84% of all new lesions. Sixteen subjects accounted for 26 new lesions; nine subjects had two or more new lesions. Subjects with new root lesions were found to have lower enamel caries experience but higher root caries experience at baseline and higher scores for gingival inflammation, pocket depth, and recession compared with those who did not develop root caries.
Age-related Salivary Flow Rate Changes in Controls and Patients with Oral Lichen Planus
Authors: Gandara B.K. , Izutsu K.T. , Truelove E.L. , Ensign W.Y. , Sommers E.E.
Published: November 2010

Unstimulated whole saliva and stimulated whole, parotid, and labial minor gland saliva samples were collected from 25 patients with oral lichen planus and from 25 age- and sex-matched controls between the ages of 25 and 87 years. All subjects did not smoke or chew tobacco, had no serious illnesses, and were unmedicated. There were no significant differences in flow rates between the two groups. However, a significant age-related decrease in labial minor gland saliva flow rate was found in both the lichen planus group and the controls. Flow rates of unstimulated and stimulated whole saliva and stimulated parotid saliva were not related to age in either group.
Materials Science Structure, Corrosion, and Tarnishing of Ag-Pd-Cu Alloys
Authors: Niemi L. , Herø H.
Published: November 2010

The structure of Ag-Pd-Cu-Au-Zn alloys can be expected to have an influence on their corrosion and tarnish resistance. Four experimental Ag-based alloys (I-IV) with varying PdlAg ratios were studied by scanning electron microscopy (SEM), microprobe analyses, and x-ray diffraction analyses. Both as-cast and in the annealed state, they contain a Pd-Cu-Zn-enriched compound A and a Ag-rich matrix (compound B) with a fcc structure, α2. X-ray diffraction data indicated that compound A consisted of two fcc phases (α1 and α 2) in addition to a bcc PdCuxZnx-1 phase. The phases of compound A were too small to be distinguishable by SEM. Alloys I-IV could not be solid-solution-annealed to a single phase.

Static anodic polarization testing was carried out in an artificial saliva containing Na2S (pS=5). It was found that an alloy made as a duplicate of the Pd-Cu-Zn-rich compound A for a given potential had current density clearly lower than that of the Ag-rich alloys. Furthermore, cathodic reduction of oxygen took place at a considerably higher rate on this Pd-Cu-Zn-rich duplicate alloy than on the Ag-based alloys. It is suggested that micro-galvanic cells are created between the Pd-Cu-Zn-rich compounds A and the Ag-rich matrix in alloys I-IV. Immersion tests in aqueous Na2S solutions (pS=1.6) showed tarnishing to take place only on the Ag-rich matrix. However, increasing the Pd content of an Ag-rich single-phase alloy increased its tarnish resistance.
Clinical Science
Authors: Lagerlöf F. , Dawes C.
Published: November 2010

A theoretical study of oral sugar clearance (Caries Res 17:321-334, 1983) suggested that the unstimulated salivary flow rate (UNSTFR) and the volume of saliva present in the mouth before swallowing (VMAX) can greatly affect the rate of sugar clearance. The object of this study was to determine whether variations in UNSTFR, by water infusion into the mouth, and in VMAX, which can be altered by varying the swallowing frequency, would influence sugar clearance and whether changes in VMAX would affect the extent of the pH fall produced by S. mitior in vivo after sucrose consumption.

In three experiments on each of ten adult subjects, UNSTFR was measured initially (mean value = 0.55 mllmin), and a swallowing schedule was calculated so that the volumes swallowed were either 0.3 ml or 1.0 ml. After a 10-second rinse with 20 ml of a 10% sucrose solution, the subjects maintained a swallowing frequency such that the volumes swallowed were either 0.3 ml or 1.0 ml at normal UNSTFR or were 0.3 ml when UNSTFR was increased by infusing water at 0.5 mllmin. In all subjects, clearance of sugar was faster at the higher swallowing frequency and at the higher flow rate, as predicted by the theoretical model.

Small acrylic splints were made to fit over the lower incisors of ten subjects and to hold in the floor of the mouth an antimony microelectrode covered by a 0.5-mm layer of S. mitior, which was held in place by a dialysis membrane. On two occasions, and in random order, the subjects rinsed with a 25% sucrose solution for 10 sec. Then, with the bacteria-covered electrode in the floor of the mouth, pH changes were followed for 30 min while the subjects swallowed either once each 15 sec or once each 120 sec. In all subjects, the pH fall from an initial mean value of 6.6 was less at all time points at the high swallowing frequency (min. mean pH = 6.05) than at the low (min. mean pH = 5.56).

The results confirm the predictions of the theoretical model that, with larger values of UNSTFR and smaller values of VMAX, less time is required for sugar clearance. In addition, they show that, with larger values of VMAX, a greater pH fall is produced by oral bacteria. Thus, VMAX may be an important determinant of caries susceptibility.
Plasma Fluoride Levels in Man Following Intake of SnF2 in Solution or Toothpaste
Authors: Ellingsen J.E. , Ekstrand J.
Published: November 2010

The degree and rate of fluoride absorption in five volunteers were studied after ingestion of SnF2 and NaF solutions or SnF2 toothpaste. The fluoride concentration in plasma was followed for eight hours. The relative bio-availability of fluoride was calculated and was similar for both the NaF and SnF2 solutions, although the latter solution showed a somewhat faster absorption rate. The bio-availability of fluoride from the SnF2 dentifrice was 85%.
Serotype c Streptococcus mutans Mutatable to Lactate Dehydrogenase Deficiency
Authors: Abhyankar S. , Sandham H.J. , Chan K.H.
Published: November 2010

Three lactate-dehydrogenase-deficient mutants of serotype c S. mutans were made by using, as parents, two serotype c strains that produced unusually large amounts of ethanol, acetic acid, and acetoin, and very little lactic acid, when grown in broth containing a limiting amount of glucose. The mutants, obtained with N-methyl-N'nitro-N-nitrosoguanidine, were stable during 12 weeks of daily subculture in broth. Crude cell-free extracts of the mutants had less than 1% of the LDH-specific activity of their parent strains. The serotype c mutants resembled serotype g mutants in having molar growth yields at least as high as those of their parents. However, in contrast to the g mutants, the c mutants produced cell crops (cell mass per ml medium) that were as high as those of their parent strains.
Dental Attrition and Craniofacial Morphology in Two Australian Aboriginal Populations
Authors: Richards L.C.
Published: November 2010

This study considers the craniofacial morphology of two Australian Aboriginal populations with different patterns of tooth wear. Evidence of regional variation in cranial and facial morphology is provided by significant differences in a number of variables. In addition, the inter-group differences in the correlations between attrition and facial variables provide evidence of different adaptive and compensatory changes occurring in each group in response to the different patterns of tooth wear.
Analysis of Alloy-Porcelain Compatibility Using a Multi-component Material Strip Equation
Authors: Dehoff P.H. , Anusavice K.J.
Published: November 2010

An analytical model has been developed to calculate residual stresses and curvature changes due to thermal contraction differences in metal-porcelain strips consisting of any number (n) of component materials. This model was also used to analyze transient and residual stresses due to solidification of a semicircular arch casting. Results obtained from this model were in close agreement with those obtained from finite element calculations for the cases studied.

Some experimental evidence exists to suggest that thermal contraction coefficients of certain body porcelains progressively increase with the number of firing cycles. Therefore, a parametric study was conducted to determine the effects of variations in the thermal contraction coefficient of each porcelain layer on residual stresses and gap changes produced in porcelainized semicircular arch specimens. Based on the analytical model developed in this study, we found that calculated residual stresses near interfacial areas of adjacent layers of porcelain are most sensitive to variations in thermal contraction coefficients of the material layers.
CLINICAL SCIENCE Longitudinal Microbiological Investigation of a Hospitalized Population of Older Adults with a High Root Surface Caries Risk
Authors: Ellen R.P. , Banting D.W. , Fillery E.D.
Published: November 2010

Intact root surfaces of chronically hospitalized subjects were sampled periodically to enumerate bacterial species believed to be associated with root caries. Bacteria were cultivated and enumerated using a series of selective and enriched media. Microbial counts, isolation frequencies, and percent cultivable flora data were analyzed for caries-active and caries-free surfaces and subjects. S. mutans, S. sanguis, A. viscosus, A. naeslundii, total lactobacilli, and Veillonella accounted for a mean of less than 20% of the cultivated flora, with mitis salivarius agar cultivable streptococci averaging less than 5%. The microbial count data were highly variable, precluding the finding of significant differences in caries association for either subjects or sites. Streptococci, especially S. mutans, correlated highly with lactobacilli in the samples.
Temporomandibular Joint Sounds Related to Orthodontic Therapy
Authors: Sadowsky C. , Muhl Z.F. , Sakols E.I. , Sommerville J.M.
Published: November 2010

A cross-sectional survey for temporomandibular joint (TMJ) sounds was conducted on 347 orthodontic patients before, during, and after treatment. Those patients who reported joint sounds, or in whom sounds were noted on clinical examination, were subjected to an audiovisual evaluation which was recorded on videotape to identify more precisely the character of the sounds during jaw opening and closing. TMJ sounds were quite common before, during, and after orthodontic treatment. There was a significant association among three variables: joint sounds, age, and treatment. It is not clear, however, whether joint sounds increased due to orthodontic treatment, age, or both. No significant associations were found between TMJ sounds and functional occlusal factors. Significantly more sounds were noted by the examiners than were reported by the patients. Medium or high amplitude sounds were evident in 32.6% of the 135 subjects who underwent the audiovisual examination.
Effect of Low Levels of Fluoride in Solution on Enamel Demineralization in vitro
Authors: Margolis H.C. , Moreno E.C. , Murphy B.J.
Published: November 2010

The effect of low levels of fluoride in solution on in vitro enamel demineralization has been studied. Extracted human teeth were exposed to 0.1 M lactate solutions (at pH 4.3) which were partially saturated with respect to enamel mineral and which contained between 0.004 and 1 ppm fluoride. Enamel demineralization was monitored using SEM and polarized light microscopy. It was observed that, in the absence of fluoride, rapid enamel demineralization occurred, resulting in the formation of cavitations within 72 hours. Using the same demineralizing medium containing as little as 0.024 and 0.054 ppm fluoride, we observed a remarkable protection of the enamel surface. Subsurface enamel demineralization was, however, observed under these conditions as well as in a solution containing 0.154 ppm fluoride. When the demineralizing solution containing 1 ppm fluoride was used, no mineral loss was detected. The observed inhibition of enamel demineralization was also shown to be associated with a significant uptake of fluoride by the enamel mineral. These observations have been noted to correlate with an increase in solution supersaturation with respect to fluoridated apatitic species. The results obtained were found to be consistent with a proposed hypothesis that the net rate of enamel demineralization will be reduced in a demineralizing medium supersaturated with respect to less soluble fluoridated phases, due to the enhancement of the precipitation rate offluoridated apatitic phases relative to the rate of dissolution of the original enamel surface.
Immunoglobulins and Innate Antimicrobial Factors in Whole Saliva of Patients with Insulin-dependent Diabetes Mellitus
Authors: Tenovuo J. , Lehtonen O.-P. , Vkari J. , Larjava H. , Vilja P. , Tuohimaa P.
Published: November 2010

We analyzed the flow rate and composition of paraffin-stimulated whole saliva samples from 35 adult diabetic patients and their age- and sex-matched, non-diabetic, clinically healthy controls. All patients had insulin-dependent diabetes (IDDM) with a mean (± S.D.) duration of 14.0 ± 9.1 years. The saliva analysis included the quantitation of total protein, amylase, immunoglobulins (isotypes A, G, and M), and the non-antibody, innate antimicrobial factors (lysozyme, lactoferrin, salivary peroxidase, myeloperoxidase, thiocyanate, and hypothiocyanite). The whole saliva samples from diabetic patients had significantly higher amounts of IgA (p < 0.001) and IgG (p < 0.05) than did the controls. No differences between the study groups were observed in flow rate, protein content, amylase activity, or IgM. The levels of innate defense factors were similar in both study groups except for salivary peroxidase, which was higher (p < 0.02) among diabetics than among controls. Our results indicate that the antimicrobial defense capacity of whole saliva is not impaired in diabetic patients.