bluuebunny/crossref_metadata_2025 huggingface dataset:
Water-borne Fluoride and Cortical Bone Mass: A Comparison of Two Communities
Authors: Phipps K.R. , Burt B.A.
Published: November 2010

This study investigated the relationship between cortical bone mass in an older female population and their ingestion of fluoride from community water supplies. The study was conducted among lifelong female residents in Lordsburg (3.5 ppm fluoride) and Deming (0.7 ppm fluoride), NM. A total of 151 postmenopausal women ranging in age from 39 to 87 years took part; 69 were residents of the optimal-fluoride community, while the remaining 82 were residents of the high-fluoride community. Although bivariate analyses showed no difference in cortical bone mass between women in the two communities, with multiple regression analyses, significant predictors of bone mass (p < 0.05) were weight, years since menopause, current estrogen supplementation, diabetes, and fluoride exposure status. Based on a model containing all of these variables, women living in the high-fluoride community had a bone mass ranging from 0.004 to 0.039 g/cm 2 less than that of similar women living in the optimum-fluoride community. These results suggest that lifelong ingestion of water containing 3.5 ppm fluoride, compared with water containing 0.7 ppm fluoride, does not increase cortical bone mass in women of similar age, weight, and menopausal status. Under the conditions of this study, cortical bone mass might be reduced in a high-fluoride area.
Prevalence and Need for Replacement of Amalgam and Composite Restorations in Dutch Adults
Authors: Kroeze H.J.P. , Plasschaert A.J.M. , van 't Hof M.A. , Truin G.J.
Published: November 2010

In 1986, the'first nationwide epidemiological survey of adult oral health and attitudes to oral health care was carried out in The Netherlands. One of the aims of this study was to evaluate the prevalence and the quality (in terms of need for replacement) of amalgam and composite restorations in the Dutch adult population.

A group of 600 dentate individuals, 20-44 years of age, was examined. Stratified cluster sampling included as factors age, gender, socio-economic status, and area of residence. Two additional parameters were studied: frequency of visiting a dentist and type of health insurance. Oral examinations consisted of direct (mirror and explorer) and indirect (color slides and bite-wing radiographs) observations with use of well-defined criteria.

On average, 13.4 restorations per individual were present, of which 23.3% were classified as unsatisfactory. A great difference in prevalence and quality data was found among several types of restorations. Test results (ANOVA) for effects of age, gender, socio-economic status, area of residence, frequency of visiting a dentist, and insurance on the prevalence of (un)satisfactory restorations resulted nearly always in significant effects of only age and frequency of visits to a dentist. There was a tendency (p<0.05) for the prevalence of (un)satisfactory restorations to be higher with increasing age. For individuals visiting a dentist infrequently (once or not at all in the past two years), the prevalence of restorations was lower, and the percentage of unsatisfactory restorations was higher, in comparison with individuals visiting a dentist frequently. The two major reasons for the scoring of restorations as clinically unacceptable were approximal ledges (43%) in class II restorations and marginal (secondary) caries (57%) in all other types of restorations.
The Effect of Sucrose and Fat in Cookies on Salivation and Oral Retention in Humans
Authors: Brudevold F. , Kashket S. , Kent R.L.
Published: November 2010

Six adults were served accurately weighed portions (about 5 g) of cookies varying in sucrose and fat content. The cookies were chewed and spat out at the time the subjects were ready to swallow. Additional spittings were collected at intervals up to two, three, and four min. Chewing time decreased with increase in sucrose, or with increase in fat. The volume of saliva in each spitting was calculated from its wet and dry weights, and it was assumed either (a) that saliva produced during chewing was not carried over in the retained food, or (b) that saliva was incorporated in the retained food in the same proportion as in the first spitting. Both approaches revealed that salivary flow rates were independent of cookie formulation, with two exceptions: (1) The cookie highest in sucrose produced a significantly higher flow rate during chewing, and (2) the fat-free cookie, which was hard to chew, elicited an elevated flow rate up to two min. The total volume of saliva for the entire experimental period was similar for all formulations, except the latter. Masticatory effects, therefore, appeared to predominate over sweetness stimulation, unless sugar content was very high.

The volume of saliva in the food bolus at the time of swallowing correlated with chewing time. Oral clearance of the cookies did not give straight lines when logarithms of retained material were plotted against time. Initial clearance rates appeared to diminish with increasing sucrose and fat content of the cookies. Effects of sugars and fat on all parameters may reflect changes in cookie texture and the sizes of particles produced within the mouth.
Transmission Electron Microscopic Characterization of Hypersensitive Human Radicular Dentin
Authors: Yoshiyama M. , Noiri Y. , Ozaki K. , Uchida A. , Ishikawa Y. , Ishida H.
Published: November 2010

Transmission electron microscopy (TEM) and x-ray microanalysis (XMA) were used for the study of the ultrastructure of the lumens of dentinal tubules in superficial layers of dentin specimens obtained by use of a new biopsy technique from both hypersensitive and naturally desensitized areas of exposed root surfaces, in vivo. The TEM images showed clearly that the lumens of most of the tubules were occluded with mineral crystals in naturally desensitized areas, but such lumens were empty and surrounded with peritubular and intertubular dentin in hypersensitive areas. Moreover, electron-dense structures that lined peritubular dentin were observed in the empty lumens of dentinal tubules.
Association of the Microbial Flora of Dental Plaque and Saliva with Human Root-surface Caries
Authors: Van Houte J. , Jordan H.V. , Laraway R. , Kent R. , Soparkar P.M. , Depaola P.F.
Published: November 2010

Dental plaque was obtained from one or two sound root surfaces of subjects with different degrees of root-surface caries experience. From subjects with root-surface caries, plaque samples were also obtained from either one incipient or one more advanced lesion. Proportions of the total flora were determined for total streptococci and different streptococcal species, total and different Actinomyces species, and lactobacilli. A sample of saliva was obtained from about one-third of the subjects for determination of the concentrations of mutans streptococci and lactobacilli. The main observations were: (1) Subjects without root-surface caries or restorations (group I), as compared with subjects with root-surface caries with or without restorations (group II), were characterized by having a lower prevalence and proportion of mutans streptococci and a higher prevalence and proportion of A. naeslundii in plaque on sound root surfaces; (2) subjects in group I also tended to have a lower salivary concentration of mutans streptococci and lactobacilli than subjects in group II; (3) dental plaque on sound surfaces in group II subjects contained a lower proportion of mutans streptococci than plaque associated with incipient or advanced lesions; and (4) the prevalence and proportion of lactobacilli in plaque associated with sound as well as carious root surfaces were very low. The data reinforce findings from other studies and indicate that, as for coronal caries, the plaque and saliva populations of mutans streptococci specifically are correlated positively with the presence of root-surface caries.
Genetic Heterogeneity of Porphyromonas (Bacteroides) gingivalis by Genomic DNA Fingerprinting
Authors: Loos B.G. , Mayrand D. , Genco R.J. , Dickinson D.P.
Published: November 2010

This study describes the use of total genomic DNA fingerprinting with the use of restriction endonucleases to characterize clinical isolates of Porphyromonas gingivalis (Bacteroides gingivalis) obtained from patients with periodontitis or with root-canal infections. The majority of independent isolates had a unique DNA fingerprint, indicating extensive genetic heterogeneity within this species. Twenty-nine distinct DNA fingerprints were found among the 33 isolates investigated. This is in contrast to biotyping and serotyping, where only one type and three types, respectively, have been reported. The observed heterogeneity indicates that DNA fingerprinting is a sensitive measure of genetic dissimilarity between P. gingivalis isolates and is able to characterize individual isolates. These results have ecological implications, indicating that there is considerable natural diversity in the global population of P. gingivalis, and that there are likely to be relatively large numbers of genetically distinct clonal lines. Furthermore, DNA fingerprinting is a sensitive and powerful tool for longitudinal and cross-sectional epidemiological studies. This technique provides far greater discrimination between isolates than either biotyping or serotyping, and will be most helpful in, for example, the analysis of distribution of clonal lines within one periodontal patient, or the analysis of the transmission to and turnover of strain populations within a patient population, since the probability of two strains with the same DNA fingerprint being found by chance is small.
Relative Cariostatic Effects of KOH-soluble and KOH-insoluble Fluoride in situ
Authors: Ogaard B. , Rølla G. , Ruben J. , Arends J.
Published: November 2010

The relative cariostatic effects of fluoride as fluorapatite, CaF2, loosely-bound fluoride, or KOH-soluble fluoride are debated. The present study was carried out to investigate this further in an intra-oral caries model. Pairs of premolars extracted for orthodontic reasons were used. Enamel from one tooth of each pair was used as control (untreated). Two slabs were cut from the enamel of the other contralateral premolar. These slabs were treated with 2% NaF for 24 h. One slab was then treated with 1 mol/L KOH twice for 24 h for removal of all loosely-bound fluoride. The slabs treated with 2% NaF and then with 1 mol/L KOH would contain the KOH-insoluble fluoride. Those treated with only 2% NaF would, in addition, contain KOH-soluble fluoride. Each slab, control, KOH-insoluble F, and KOH-soluble and insoluble F was mounted on different upper removable appliances. The slabs were covered with orthodontic banding material, thus allowing space for plaque accumulation. Five individuals wore the appliance in three separate four-week periods. The slabs were analyzed by quantitative microradiography. The average mineral loss (ΔZ) was 1680 ± 1000 vol% x μm in the control teeth, 620 ± 76 vol% x μm in the KOH-soluble and -insoluble F teeth, and 2167 ± 1278 vol% x μm in the KOH-insoluble F teeth. The average lesion depths were 90 ± 41 μm in the control teeth, 35.3 ± 5.5 μm in the KOH-soluble F teeth, and 88 ± 35 μm in the KOH-insoluble F teeth. It was concluded that only KOH-soluble fluoride reduced mineral loss and lesion depths significantly, compared with the untreated teeth.
Wavelength-independent Microradiography: A Method for Non-destructive Quantification of Enamel and Dentin Mineral Concentrations using Polychromatic X-rays
Authors: Herkströter F.M. , Ten Bosch J.J.
Published: November 2010

Wavelength-independent Microradiography (WIM), described in this paper, used polychromatic, high-energy (≤ 60 kV) x-rays for determination of mineral concentrations in tooth material non-destructively. This was done with the aid of a reference step-wedge made of 94% aluminum, 6% zinc. The mass attenuation coefficient of this material has a wavelength-independent ratio to the mass attenuation coefficients of enamel and dentin. With this method, mineral concentrations of enamel and dentin samples, with a thickness up to 500 μm, were determined at 20- and at 60-kV tube voltage. The samples were demineralized for 72 and 144 h and measured again. Comparison of the data showed that mineral quantification was within 1.5%, independent of the x-rays used. Finally, these mineral concentrations-obtained from the Wavelength-independent Microradiography-were compared with measurements of the same samples by Longitudinal Microradiography. A correlation of 0.99 was found for enamel and one of 0.96 for dentin.
Twin Half-sibs: A Research Design for Genetic Epidemiology of Common Dental Disorders
Authors: Potter R.H.
Published: November 2010

Dental caries and the chronic type of periodontal disease are classic examples of common familial diseases that are complex and multifactorial in etiology. Due to previous methodological limitations, there is no information at present on the genetic and shared environmental risks within families that account for familial aggregation of these diseases. Such information, however, is needed in the long run to help specify modifiable family environments that affect the frequency and/or severity of the disease, and thereby to aid in the planning of prevention strategies to be targeted at the family level. Recently, an innovative genetic model has been described to test the genetic and environmental basis of chronic familial diseases in identical (monozygotic) twins, their spouses, and their offspring, who are genetically half-sibs. In this paper, the method is detailed and shown to be appropriate not only for partitioning shared genetic and environmental risks within families, but also for delineating maternal effects and assortative mating as two non-genetic mechanisms that may ultimately be found to affect the incidence of disease.
A Confocal Microscopic Study of Some Factors Affecting the Adaptation of a Light-cured Glass Ionomer to Tooth Tissue
Authors: Watson T.F.
Published: November 2010

Vitrabond consists of a conventional glass ionomer, in conjunction with a light-curing resin and hydroxy-ethylmethacrylate. This study, which used a tandem scanning reflected light microscope for confocal imaging, looked at factors affecting the adaptation of this material to tooth tissue. Wedge-shaped cervical cavities were cut and restored in three ways: (1) Vitrabond was applied as a thin sub-base and either extended onto the enamel margin or kept clear of it. P50 resin composite was then placed, following phosphoric-acid-etching of the enamel margins. (2) The dentin surfaces were conditioned with Scotchprep (maleic acid), then with the Vitrabond, the enamel was etched, and the Scotchbond 2 adhesive applied prior to addition of the P50. (3) Vitrabond was applied alone in bulk, with and without Scotchprep acid-dentin conditioning with a 1:1 (normal) and 3:1 powder:liquid ratio (P:L). Adaptation of the Vitrabond was excellent when maleic acid was used for conditioning of the dentin. When the Vitrabond was used with P50 but extended onto the enamel, the enamel margin occasionally failed. Enamel invariably fractured when the Vitrabond was used alone in bulk. An increase in the P:L ratio decreased contraction gaps when the dentin was not conditioned, but Vitrabond failed cohesively when the dentin was conditioned. The Vitrabond was very susceptible to shrinkage on dehydration. This study suggests that Vitrabond should only be applied to dentin in thin layers, should not be extended onto enamel margins, and should not be allowed to dehydrate. Maleic acid conditioning of the dentin improved adaptation.
Textural Properties of Food Used in Studies of Mastication
Authors: Wang J.-S. , Stohler C.S.
Published: November 2010

Foods are known to influence jaw elevator muscle activity in chewing. With the long-range goal of gaining insight into force control and modeling muscle recruitment, these initial experiments were performed to determine the textural properties of commonly used test food.

Experiments were carried out by means of a standard Instron instrument, equipped with a compression cell. A stylus with 45-degree cuspal angulation and an opposing copper-plated lower arch was used for approximation of the natural situation. The breakage force characteristics of a single peanut, a carrot cube, beefstick, and monkey chow were determined.

The peanut demonstrated the steepest and beefstick the least steep force build-up, with breaking forces of 104 N (Newtons) for monkey chow, 66 N for the carrot, and 52 N for the peanut. No clear breakage point was found with beefstick; the force build-up showed an initial plateau at 25 N, which was followed by a significantly steeper force increase to peak.

We conclude that each of the test foods commonly used in studies of mastication had particular breakage characteristics in terms of its force-time curve.
The RNA Polymerases of Porphyromonas gingivalis and Fusobacterium nucleatum are Unrelated to the RNA Polymerase of Escherichia coli
Authors: Klimpel K.W. , Clark V.L.
Published: November 2010

Western blot analysis that used antisera to the E. coli core enzyme and sigma factors was used for examination of the RNA polymerase of Actinobacillus actinomycetemcomitans, Streptococcus mutans, Fusobacterium nucleatum, and Porphyromonas gingivalis. Both antisera reacted with proteins in A. actinomycetemcomitans and S. mutans whole-cell extracts. Reactions were seen with some F. nucleatum proteins when the anti-core RNA polymerase antisera were used, but the cross-reacting proteins were not of an expected molecular weight for β or β'. No reaction with F. nucleatum proteins was seen when extracts were reacted with antisera to E. coli sigma factor. There were no cross-reacting proteins detected in P. gingivalis extracts with either antisera. These results suggest that E. coli RNA polymerase may not be sufficiently similar to P. gingivalis and F. nucleatum RNA polymerase for E. coli RNA polymerase to recognize P. gingivalis or F. nucleatum promoters. Partially purified P. gingivalis and F. nucleatum RNA polymerase exhibited a specificity for a P. gingivalis DNA template, while having a decreased activity from an E. coli DNA template. The antibiotic sensitivity profile of P. gingivalis and F. nucleatum RNA polymerase activity was shown to differ from that of E. coli, with these activities not being affected by rifampicin, streptovaricin, or streptolydigin. We conclude that the efficient cloning and expression of P. gingivalis and F. nucleatum genes in E. coli will require the use of promoter-containing expression vectors.
Relationship of Restoration Width, Tooth Position, and Alloy to Fracture at the Margins of 13- to 14-year-old Amalgams
Authors: Osborne J.W. , Gale E.N.
Published: November 2010

The effect of width of the restoration, tooth position, and amalgam type on the fracture of the margins of 13- to 14-year-old, high-copper, amalgam restorations was evaluated. The evaluation assessed 193 photographs of restorations by use of ridit analysis and a rank-ordering test. The results indicated that the width of the restoration was the predominant factor and that tooth position and the different high-copper alloys were less significant. Interactions between tooth position and width indicated that lower premolars with conservative restorations exhibited the least fracture at the margins, and upper premolars with a wide preparation exhibited the most. It is postulated that tooth deflection under mastication may play a role in long-term fracture at the margins of amalgams.
Estimation by a 24-hour Study of the Daily Dose of Intra-oral Mercury Vapor Inhaled after Release from Dental Amalgam
Authors: Berglund A.
Published: November 2010

The difficulties associated with estimations of daily doses of inhaled mercury vapor released from dental amalgam are considerable. Existing data are often unreliable, especially if they are based on a single or a small series of samples of intra-oral concentrations of mercury vapor before, during, and after chewing stimulation. In the present paper, the aim was to obtain a more representative estimation of the daily dose of mercury vapor inhaled from amalgam fillings by measurement of amounts of mercury vapor released in the oral cavity during 24 h, under conditions that were as normal as possible. A series of measurements was carried out on each of 15 subjects, with at least nine occlusal surfaces restored with dental amalgam, and on five subjects without any amalgam restorations. The subjects had to follow a standardized schedule for 24 h, whereby they ate, drank, and brushed their teeth at pre-determined time periods. The amount of mercury vapor released per time unit was measured at intervals of 30-45 min by means of a measuring system based on atomic absorption spectrophotometry. None of the subjects was professionally exposed to mercury, and all of their amalgam fillings were more than one year old. Study casts were made for each subject, and the area of the amalgam surfaces was measured. Samples of urine and saliva were analyzed so that values for the mercury concentrations and the rate of release of mercury into saliva could be obtained. The average frequency of fish meals per month was noted. The daily release of elemental mercury from dental amalgam was corrected for retention of inspired mercury vapor and for oral-to-nasal breathing ratio. The estimated average daily dose of mercury vapor inhaled from the amalgam restorations was 1.7 μg, i.e., about 1% of the dose obtained from a TLV exposure of 50 μg Hg/m3 air. The threshold limit value (TLV) of a substance is the airborne concentration to which nearly all workers can be exposed eight hours a day, five days a week for prolonged periods without suffering adverse health effects (American Conference of Government Industrial Hygienists: Threshold Limit Values and Biological Exposure Indices for 1985-86, Cincinnati, 1985).
Influence of Chronic Ethanol Exposure on Nitrous Oxide Analgesia in Mice
Authors: Henry R.J. , Ishii M.M. , Quock R.M.
Published: November 2010

The purpose of this study was to determine whether sensitivity to nitrous oxide analgesia was altered by chronic ethanol exposure. Control mice exposed to 25%, 50%, and 75% nitrous oxide in oxygen demonstrated a concentration-related analgesic effect, as measured by the acetic acid abdominal constriction test. Other mice previously exposed to ethanol vapors for 72 h exhibited a significantly reduced sensitivity to nitrous oxide analgesia. The dose-response curve of the chronic ethanol-exposed group was shifted to the right of that of the control mice. These findings suggest the possibility that subjects with a history of alcohol abuse might have reduced responsiveness to nitrous oxide in a clinical setting.
Polymorphism of Submandibular-Sublingual Salivary Proteins which Promote Adhesion of Streptococcus mutans Serotype-c Strains to Hydroxyapatite
Authors: Kishimoto E. , Hay D.I. , Kent R.
Published: November 2010

Previously, we showed that human submandibular-sublingual (SMSL) salivas contain one or more proteins, Mr circa 300,000 daltons, which specifically promote adhesion of Streptococcus mutans serotype-c strains to hydroxyapatite. Also, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed that the adhesion-promoting proteins (APPs) exhibit heterogeneity. The aims of the present study were to determine whether APPs are generally present in human SMSL salivary secretions and to characterize the noted heterogeneity. Acid-stimulated SMSL saliva samples were obtained from 54 Japanese subjects, and M, values were obtained by SDS-PAGE. APPs were present in all saliva samples examined, though at significantly different concentrations. The APPs occurred as either single (20 subjects) or double bands (34 subjects), with a mean Mr (88 bands) of 297 kD and a range of 248-338 kD. A plot of the frequency distribution of the APPs according to Mr showed a trimodal distribution, with mean Mr values, standard deviations, and ranges for the three groups being 265 (S.D., 6.9; range, 248-278), 293 (S.D., 6.7; range, 280-305), and 320 (S.D., 7.0; range, 310-338) kD. Variations of Mr within groups may be attributed to experimental variation, although microheterogeneity cannot be excluded. Differences between groups can best be explained in terms of three polymorphic proteins, with low (L), intermediate (I), and high (H) Mr values. Six phenotypes were detected with L, I, H, LI, LH, and IH M r bands. A Hardy-Weinberg analysis showed that the phenotype data fit a single-gene, three-alleles model. The widespread occurrence of the APPs and their potential to modulate colonization of teeth by an oral pathogen suggest that the noted variations in concentrations and phenotypes may be of biological significance.
Casting Pure Titanium into Commercial Phosphate-bonded SiO2 Investment Molds
Authors: Takahashi J. , Kimura H. , Lautenschlager E.P. , Chern Lin J.H. , Moser J.B. , Greener E.H.
Published: November 2010

Pure titanium was cast into five different phosphate-bonded SiO2 investment mold materials (at 350°C) with an argon-arc melting and pressure casting machine. The mesh castability, the fit of the MOD inlay castings, and the Knoop hardness and the micro-structure in cross-sections of castings were examined. The setting and thermal expansion, the compressive strength, and the x-ray diffraction analysis of the investments were also measured. The castability, the fit, and the thickness of the reacted layer differed in degree among these investments, in spite of the same phosphate-bonded SiO2-type investment. A significant correlation was obtained between the thermal expansion (at 350°C) and the casting accuracy.
Influence of Water Exposure on the Tensile Strength of Composites
Authors: Soderholm K.-J.M. , Roberts M.J.
Published: November 2010

The objective of this study was to investigate whether water storage causes permanent damage to composites by determining how the tensile strength of nine different composite materials changes with both water storage and water storage followed by dehydration. Eighteen samples (ASTM-D Specification 1708-66) of each of the nine materials were prepared and divided into three groups of six samples each. Group I was stored dry at 60°C, while Groups II and III were stored in distilled water at 60°C. After six months, Groups I and II were subjected to tensile testing, while Group III was transferred to a desiccator and dehydrated for two weeks at 60°C before this group was tested in tension. Mean values, pooled by storage group independent of material, revealed a significant (p<0.05) reduction in strength for both Groups II and III relative to Group I. These findings prove that water has an irreversible effect on most dental composites. A comparison of Group II with Group III data revealed that the samples which were aged in water and tested (Group II) were significantly (p<0.05) weaker than the dehydrated samples (Group III). However, some products within Group III did not show any tendency to recover their strength after dehydration.
Long-term Effects of Orthodontic Forces on the Morphology of the Rat-incisor Socket and its Location in the Mandible
Authors: Brin I. , Michaeli Y. , Steigman S.
Published: November 2010

The effect of orthodontic force application on the rat-incisor socket and mandible was studied on roentgenograms. A mean linguo-intrusive force of 19 ± 0.6 g was applied continuously to the shortened left lower incisor for a period of two (group A) and four weeks (group B). A third group of rats, subjected to shortening of the left mandibular incisor only, served as a hypofunctional control (group C). A fourth group of normal rats constituted the intact control (group D). After a recovery period of three months, the animals were killed, and standardized roentgenograms of the cleaned mandibles were taken. Socket and mandibular dimensions were measured on magnified tracings of the roentgenograms. Comparison of groups A and B with the control groups, on the one hand, and of group C with group D, on the other, facilitated isolation of the hypofunctional factor. In groups A and B, the orthodontic forces caused changes in the parameters affected ( i.e., socket area, alveolar bone thickness, mandibular dimensions) and not affected by hypofunction ( i.e., socket angulation and location, anterior-socket length). The former finding implies modification of the adaptive capability of dental structures to functional demands. It is concluded that mechanical loading of the incisor for two to four weeks causes long-lasting changes in the socket and its surrounding bone.
The Crown Odontoblasts of Rat Molars from Primary Dentinogenesis to Complete Eruption
Authors: Romagnoli P. , Mancini G. , Galeotti F. , Francini E. , Pierleoni P.
Published: November 2010

The involution of crown odontoblasts after primary dentinogenesis in teeth of limited eruption is discussed. The odontoblasts of rat first lower molars were analyzed morphometrically from the tenth day to the 40th day of age, i.e., from the late phase of primary dentinogenesis to complete eruption. All the organelles underwent atrophy, but at different rates. In particular, the membranes of the endoplasmic reticulum decreased progressively in surface area from day 10 to day 40, whereas those of the Golgi apparatus decreased significantly between day 10 and day 14, and then remained practically unchanged in size. The volume of the lysosome compartment never increased beyond that during primary dentinogenesis. The profile length of the endoplasmic reticulum in each observed cell section was taken as an estimate of secretory activity. At day 40, this organelle was smaller in ~95% of the cells than it had been in any cell at day 10. These results suggest that cell atrophy may occur without any increase in the degradation processes of the cytoplasmic components and that the organelles along the secretory pathway may have independent regulatory systems. In the odontoblasts, as in several types of secretory epithelial cells, only a small fraction of the cells is engaged in appreciable secretory activity. This occurs, however, when the overall activity of the same cell population is relatively low.
Involvement of PGE Synthesis in the Effect of Intermittent Pressure and Interleukin-1β on Bone Resorption
Authors: Saito S. , Ngan P. , Rosol T. , Saito M. , Shimizu H. , Shinjo N. , Shanfeld J. , Davidovitch Z.
Published: November 2010

Human periodontal ligament (PDL) fibroblasts, cultured from extracted healthy premolars, and a cloned osteogenic cell line (MC3T3-E1) were used in this study to determine the effect of intermittent pressure on bone resorption. Cells (1 x 105) were incubated with BGJb medium in the presence or absence of the following factors: intermittent negative ( - 30 g/cm2) or positive (30 g/cm2) hydrostatic pressure and interleukin-lp (IL-1β, 1 ng/mL), for 24 h. Conditioned media (CM) generated from cultures of either cell types were used for prostaglandin E (PGE) assay, bone resorption assay, and assessment of osteoclast (OC)-like cell formation. Unstimulated PDL fibroblasts or MC3T3-E1 cells produced measurable amounts of PGE and bone-resorbing activity as measured by 45Ca released from mouse calvaria and OC-like cells. IL-1β-treated cells showed significantly elevated levels of PGE, bone resorption, and OC-like cell formation, as compared with unstimulated cells. Intermittent positive pressure (IPP) alone stimulated PGE production, but the resultant CM did not stimulate bone resorption or OC-like cell formation when IPP was applied to either cell type. The application of IPP, together with IL-1β in CM, caused a slight increase in the number of a-like cells, as compared with that of IL-1β-treated CM in both cell types. On the other hand, direct application of IPP on mouse bone-marrow cultures significantly increased the number of OC-like cells. This effect was additive in combination with either CM from unstimulated cells or exogenous addition of PGE2. These results suggest that locally produced autocrines or paracrines can modify the effect of mechanical stress on periodontal and bone cells via PGE synthesis. One of the roles of PGE elaboration in response to mechanical or chemical stimuli is osteoclast recruitment.
The Role of Leukotriene B4 in Neutrophil Infiltration in Experimentally-induced Inflammation of Rat Tooth Pulp
Authors: Okiji T. , Morita I. , Sunada I. , Murota S.
Published: November 2010

Inflammation was induced in rat dental pulp by applying bacterial lipopolysaccharide (LPS). Extirpated tissue samples from inflamed pulps were incubated in vitro in a Krebs buffer containing Ca2+ ionophore A23187, and leukotriene (LT) B4 released into the medium was determined by radio-immunoassay. Production of LTB4 could be detected three to 24 h after the application of LPS and showed a maximum at 12 h. Histologically, marked infiltration of neutrophils, but not other leukocytes, was characteristically observed in the LPS-applied pulps, and the temporal change in neutrophil infiltration was almost parallel, but somewhat more delayed than LTB4 production. When BW755C, a dual inhibitor of cyclo-oxygenase and lipoxygenase, was given to the animals before the application of LPS, both the production of LTB4 and the number of infiltrated neutrophils were significantly decreased, whereas administration of indomethacin had no effect. These results suggest that LTB4 may be involved in neutrophil infiltration in pulpal inflammation. It was also suggested that a major early source of LTB4 in experimental pulpitis was leukocytes, primary neutrophils, because the synthesis of LTB4 in the inflamed pulp was diminished by depletion of circulating leukocytes with cyclophosphamide prior to the application of LPS.
An Analysis of Clinical Studies on Resin-bonded Bridges
Authors: Creugers N.H.J. , Van 't Hof M.A.
Published: November 2010

Many clinical data on resin-bonded bridges (RBBs) have been published in the last ten years. The survival rates vary widely, and the conclusions are sometimes conflicting. A method of combining the results of different studies in order to draw conclusions about the effectiveness of therapeutic concepts is meta-analysis. The aims of the meta-analysis in this study were: (1) to assess an "overall" survival ratio for RBBs and (2) to explore relationships between potential success factors and reported survival times.

About 60 publications with clinical data on RBBs were reviewed. Following a number of inclusion criteria (information adequate to calculate or assess survival rates, as well as adequate information about the patients, the designs, and types of RBBs), 16 different samples were used for this meta-analysis. A weighted multiple-regression analysis revealed no significant effects of "type of retention" and "location" on the survival percentages. Kaplan-Meier estimates were used to assess overall survival in a secondary analysis with the data from all 16 samples (n = 1598). The overall survivals were: one year, 89 ± 1%; two years, 84 ± 1%; three years, 80 ± 1%; and four years, 74 ± 2%.
Human Dentin-matrix-derived Bone Morphogenetic Protein
Authors: Bessho K. , Tanaka N. , Matsumoto J. , Tagawa T. , Murata M.
Published: November 2010

Bone morphogenetic protein (BMP) was extracted from human dentin matrix with 4 mol/L guanidine-HCl and was purified by liquid chromatography. SDS-PAGE and IEF showed that the purified BMP was homogeneous and induced new bone formation in situ after three weeks when implanted into muscle pouches in Wistar rats. The molecular weight of BMP was estimated to be about 20.0 kDa by SDS-PAGE, and the pI value was 8.8 by IEF. Amino acid analysis suggested that BMP is a protein containing 191 amino acids. A partial amino acid sequence was obtained from the final purified BMP. Dentin-matrix-derived BMP is probably not identical to, but is similar to, bone-matrix-derived BMP, though both types of BMP have the same action in vivo.
Correlates of Dental Anxiety Among Older Adults
Authors: Locker D. , Liddell A.M.
Published: November 2010

This paper reports on a study of dental anxiety among adults aged 50 years and over living independently in two communities in Ontario, Canada. Subjects were identified by means of a telephone survey based on random-digit dialing. Data on dental anxiety were collected from 580 subjects by means of a self-completed questionnaire and were measured by the Dental Anxiety Scale (DAS) (Corah, 1969). The mean DAS score was 7.8, and 8.4% of subjects were classified as dentally anxious. Age was the only demographic factor associated with dental anxiety. Older individuals had lower DAS scores than younger individuals (p<0.0001). There was also a significant association between dental anxiety and general fearfulness measured by the Fear Survey Schedule II (Geer, 1965) (r = 0.31; p<0.001). A series of regression analyses revealed that dental anxiety was a significant predictor of a number of behavioral and oral health outcomes. While these results confirm that dental anxiety is less prevalent among older adults than in younger populations, it has a number of important consequences with respect to dental care provision.
Staining of in vivo Subsurface Degradation in Dental Composites with Silver Nitrate
Authors: Mair L.H.
Published: November 2010

A previously reported technique for staining areas of degradation in dental composite restorations was evaluated in 51 removed restorations. The staining reagent was silver nitrate, which penetrated the degraded subsurface as ionic silver and was subsequently developed into colored deposits of metallic silver. Several artefacts were recognized that resulted in an apparent image of subsurface stain. Most importantly, the presence of a layer of adsorbed silver on the edge of the specimen exaggerated the extent of staining. In order for the true depth of stain to be determined, thin sections of the materials should first be examined with a stereomicroscope to distinguish any contribution from adsorbed silver on the specimen edge. With this regimen, no stain was present in 41% of the restorations, and in a further 30%, the depth of stain was less than 50 μm. In two composites, the depth of stain was greater than 900 μm, and in a number of specimens, localized stain was found in association with attrition scars. Energy-dispersive x-ray analysis indicated that the amount of silver present in the degraded layers was very small. Overall, the results indicated that the staining technique is useful in the study of composite degradation.
An in vivo and in vitro Study of the Loss of Plasticizer from Soft Polymer-gel Materials
Authors: Graham B.S. , Jones D.W. , Sutow E.J.
Published: November 2010

Polymer-gel materials used as short-term denture soft linings are blended with plasticizers to lower the glass transition temperature (Tg). A lower Tg allows for greater polymer chain mobility, thus producing a more flexible material. The present work evaluated the loss of plasticizers due to leaching both in vivo and in vitro. Two commercial denture soft-lining materials (A and B) were tested. These were both poly(ethyl methacrylate) polymers, blended with alcohol and phthalate esters. A clinical study was conducted in which patients wore, sequentially, dentures bearing (on separate occasions) each of the two soft-polymer lining materials. The two materials A and B were randomly assigned for each of ten patients and were worn for 14 and 30 days, respectively. With one exception, patients wore dentures with both lining materials, for a total of 19 clinical evaluations. The plasticizer loss occurring during the clinical trial was determined by GC analysis from the initial and terminal day sampling of plasticizer content of the soft polymer-gel materials. The results of this analysis were compared with results obtained from an in vitro leachability study by use of sink conditions in water at 37°C for the same two commercial soft polymers conducted over the same time periods of 14 and 30 days. The results indicated that a higher loss of plasticizer occurred in vivo, compared with the in vitro tests for 17 of the 19 clinical evaluations. The average plasticizer lost in vivo from material A at 14 days was 122 ± 58 mg/g, and for material B at 30 days it was 33 ± 27 mg/g. This can be compared with the in vitro loss that was 13.41 ± 1.11 mg/g for material A at 14 days, and 8.47 ± 0.73 mg/g for material B at 30 days. It is not known how much of the plasticizer lost from the denture soft lining in the in vivo trial was ingested by the patient. Patients were cautioned against soaking the denture in any liquid; however, it is not known how much was lost due to cleaning of the denture by the patients.
Cellular Sources of Transforming Growth Factor-Alpha in Human Oral Cancer
Authors: Todd R. , Chou M.Y. , Matossian K. , Gallagher G.T. , Donoff R.B. , Wong D.T.W.
Published: November 2010

Aberrant expression of TGF-a is associated with human malignant oral epithelium. Experiments were initiated to determine the cellular sources of transforming growth factor-alpha (TGF-a) in human oral cancer. Ten freshly resected human oral cancers and four specimens of normal human oral epithelium were studied by in situ hybridization and immunohistochemistry. Tissues were probed with 35S-labeled sense and antisense riboprobes to (i) human TGF-a (hTGF-a), (ii) human epidermal growth factor receptor (EGFR) to determine the distribution of TGF-a responsive cells, and (iii) histone H3 to examine TGF-a and/or EGFR's possible contribution to altered proliferation in transformed epithelium. Results of our experiments showed that TGF-a mRNA could be detected in normal and transformed human oral epithelium. More surprising, we have identified the major source of TGF-a mRNA to be the infiltrating eosinophils. A monoclonal antibody to the mature human TGF-a peptide stained similar areas in normal and malignant specimens. Eosinophils associated with tumors exhibited positive cytoplasmic immunostaining for TGF-a protein. Labeling of EGFR mRNA in human oral epithelium demonstrated uniform labeling of basal layers in normal, hyperplastic, and mildly dysplastic epithelium. In severely dysplastic epithelium and carcinomas (particularly moderate to poorly differentiated types), cellular levels of EGFR mRNA were significantly higher. The profile of altered cellular levels of EGFR mRNA correlated well with the profile of altered proliferation as indicated by H3 mRNA labeling. We hypothesize that the overproduction of EGFR mRNA in tumor epithelium-together with the localized delivery of high amounts of TGF-a by eosinophils at tumor-developing sites-is responsible for the increased proliferation of the tumor epithelium.
The Effect of Particle Size Reduction on the Jaw Gape in Human Mastication
Authors: Van Der Bilt A. , Van Der Glas H.W. , Olthoff L.W. , Bosman F.
Published: November 2010

Eight subjects participated in chewing experiments to examine how the jaw gape in consecutive chewing cycles depends on the dimensions and the volume of the food bolus. Different volumes of chewing-gum and a silicone rubber (Optosil®) were used. The initial particle size of Optosil was also varied. With the aid of a sieving procedure, the size distribution of Optosil particles was determined after different numbers of chewing cycles. The maximum size of a chewing-gum bolus along three orthogonal axes was determined after a random number of chewing cycles for all the volumes of chewing-gum offered. The jaw gape was measured by means of an optical motion analysis system and calibrated at the level of the first molars. The maximum jaw gape and the gape at the first fall in mandibular velocity after the onset of jaw-closing were determined for different chewing cycles from the position signal and its time derivative. For each volume of chewing gum offered to the subject, the average of the maximum gapes attained in the subsequent cycles of jaw movement was related to the characteristic height of a bolus of that volume; maximum velocity of closing appeared to occur while the antagonistic teeth were already penetrating the gum bolus. The increase in the maximum jaw gape, the gape at the velocity maximum, and the height of the gum bolus, as a function of the volume of chewing-gum, could be well-described by a power function of the volume. The exponent of the power function for both jaw gapes was only slightly smaller than the exponent obtained for the bolus height. When a hard but comminutable test food (Optosil) was used with large initial particle sizes (> 4.8 mm), the gape at the first fall in velocity closely approached the calculated height of the largest particles in early chewing cycles, regardless of the volume of food offered. The maximum gape was correlated with the subsequent gape at the first fall in velocity and therefore was, indirectly, also related to the height of the largest Optosil particles. In a later phase of the chewing process, the gape at the velocity maximum was always larger than the height of the largest particles.
A Comparative Study of Fluoride Pharmacokinetics in Five Species
Authors: Whitford G.M. , Biles E.D. , Birdsong-Whitford N.L.
Published: November 2010

This study was designed to quantitate and compare the major features of the short-term pharmacokinetics of fluoride- i.e., the plasma (Cp), renal (Cr), and extra-renal (Cer) clearances-in young adult dogs, cats, rabbits, rats, and hamsters. Plasma and urine samples were collected for seven h after the iv administration of fluoride (0.5 mg F/kg). Cp ranged from 3.5 to 8.6 mL/min/kg in the dog and hamster, respectively. Cr ranged from less than 1.5 mL/min/kg in the dog and rabbit to about 3.5 mL/min/kg in the rat and hamster. Cer ranged from 2.1 mL/min/kg in the dog to over 4.5 mL/min/kg in the cat, rabbit, and hamster. It was concluded that (1) there are major quantitative differences in the metabolic handling of fluoride among the five species, and that (2) Cp, Cr, and Cer values of the young adult dog, when factored for body weight, resemble those of the young adult human most closely.
Immunocytochemical Evidence for the Site of O-methylation in Rat Dental Pulp
Authors: Inoue K. , Nishino T. , Creveling C.R.
Published: November 2010

Immunocytochemical observations by light and electron microscopy of catechol-O-methyltransferase (COMT) were conducted in dental pulp by use of a specific antibody to soluble rat-liver COMT and the peroxidase-antiperoxidase technique. Immunoreactive deposits were found in macrophages. The pattern of localization suggests that COMT may function in extraneuronal inactivation of catecholamines in dental pulp.
Effects of Calcium-phosphate-based Materials on Proliferation and Alkaline Phosphatase Activity of Newborn Rat Periosteal Cells in vitro
Authors: Teti A. , Tarquilio A. , Grano M. , Colucci S. , Laforgia A. , Mangini F. , Zambonin Zallone A.
Published: November 2010

The effects of dental materials, intended for bone substitution, on cell growth and alkaline phosphatase activity of newborn rat periosteal cells have been studied in vitro. Confluent periosteal cells were exposed to three apatite-based materials (400 μg/mL) with different physico-chemical properties. The materials were a β-tricalcium phosphate with a microporous granular structure obtained by sinterization (Synthograft, Johnson & Johnson, East Windsor, NY), a 40-60-mesh microporous durapatite ceramic (Periograf, Sterling Drug, Inc., Rensselaer, NY), and a 1-2-mm-diameter hydroxyapatite ceramic (Osprovit, Feldmuhle Aktiengeselschaft, Plochingen, Germany) with macropores larger than 100 μm. Cell proliferation and alkaline phosphatase activity were assessed by incorporation of 3H-thymidine into trichloroacetic-acid-precipitable material and by a fluorimetric method, respectively. Cell viability and compatibility with the materials were determined by morphology in phase-contrast microscopy. Periosteal cells showed increased proliferation following exposure to Synthograft, but were unaffected by Osprovit, whereas Periograf caused significantly reduced cell growth. Alkaline phosphatase activity was unaffected by Osprovit, but was decreased by both Synthograft and Periograf. The results indicated a differential response of periosteal cells to bone-substituting materials with heterogeneous physico-chemical characteristics.