bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of Casting Ring Liners on the Potential Expansion of a Gypsum-bonded Investment
Authors: Earnshaw R. 
Published: November 2010

Cellulose paper (used wet) and ceramic paper (used dry) are replacing asbestos paper as cushioning ring liners in dental casting. A study was made of the effects of all three of these materials on the setting and subsequent thermal expansion of a gypsum-bonded cristobalite casting investment (W/P = 0.40). Thermal expansion measurements were made on the same specimens that were produced during the setting expansion tests. Control specimens setting against a smooth dry surface showed a total expansion of 1.7%. Specimens setting against dry ceramic liners had similar total expansions, in the range 1. 6 to 1.7%. Specimens setting against either of the wet lining materials showed an increased total expansion (in the range 2.2 to 2.3%), by virtue mainly of a large increase in setting expansion. In order for reproducible setting expansion results to be obtained with wet liners, it was necessary to control the amount of absorbed water carefully. Dry asbestos and dry cellulose liners gave higher expansions than pre-wetted ones, since they abstracted water from the mix, reducing its effective WlP ratio (giving a thicker mix), and then functioned as wet liners. These results suggest that, at least as far as potential investment expansion is concerned, wet cellulose liners have an effect similar to that of the traditional wet asbestos liners. Dry ceramic liners give a much lower investment expansion, and when these liners are used, an investment with an increased measured expansion could be an advantage.
Adsorption of 4-Methacryloxyethyl Trimellitate Anhydride (4-META) on Hydroxyapatite and its Role in Composite Bonding
Authors: Misra D.N. 
Published: November 2010

The adsorption of 4-methacryloxyethyl trimellitate anhydride (4-META) was studied from ethanol and dichloromethane onto synthetic hydroxyapatite (containing about 1.5 monolayers of physisorbed water) in order to study its role in restorative composite bonding to teeth. The adsorption lsotherm of 4-META was S-shaped and reversible from ethanol, and followed the Langmuir plot at lower concentrations. The isotherm was irreversible from dichloromethane, and a constant amount of adsorbate was removed from the solutions above a certain concentration. The irreversibly adsorbed compound was completely removed by washing with ethanol. Therefore, the bonding between teeth and the restorative resin containing 4-META as a coupling agent is micromechanical and not chemical in nature. An analysis of isotherms showed that the benzene rings of the adsorbate molecules lie flat on the surface for both solvents. The molecules adsorbed from ethanol rotate about the solvent-modified (esterified) or unmodified carboxylic anhydride moieties with methacrylate hydrocarbon groups which are folded upward. However, the molecules adsorbed from dichloromethane remain fixed to the surface without rotation, and their methacryloxyethyl groups are folded over the rings. The diametral tensile strength of a BIS-GMA polymer with adsorbate-covered apatite was approximately equal to that of the composite filled with untreated apatite.
National Survey of Caries Prevalence in 6-15-year-old Children in France
Authors: Cahen P.M. , Turlot J.C. , Frank R.M. , Obry-Musset A.M. 
Published: November 2010

The prevalence of dental caries in France is not known on a nationwide basis, despite the fact that a number of epidemiological studies have been conducted in various parts of the country. The aim of the present study was to provide a national baseline examination of the dental health of children in 1987 since, beginning in November, 1986, the sale of fluoridated salt began in France. A multi-stage probability sample of 19,366 children was selected as representative of the 6-to-15-year-old population. The sample covered all the 95 departments of France. Teams of well-calibrated examiners were constituted in each of the sixteen Faculties of Dental Surgery of France. The prevalence of caries for each age group was determined by means of DMFT, DMFS, dft, and dfs indices. Periodontal conditions were assessed by means of the Plaque Index (Silness and Löe, 1964), the Calculus Index (Marthaler, 1966), and the Gingival Index (Löe and Silness, 1963). Calculation of the mean DMFT index showed, respectively, 0.5 and 1.0 new carious teeth per year under and over the age of 11. The mean values of the DMFT index at ages 6, 12, and 15 were, respectively, 0.5, 4.2, and 6.9. Under the age of 11, the mean DMFS index increased by one between each successive age group and by nearly two over the age of 11. The mean values of the DMFS index at ages 6, 12, and 15 were, respectively, 0.8, 7.6, and 13.0. The percentage of caries-free children decreased from 32.2% at age 6 to 7.9% at age 15.
A Survey of Reference Accuracy in Five National Dental Journals
Authors: Doms C.A. 
Published: November 2010

Previous studies have examined the bibliographic accuracy of citations in medical journals. The purpose of this study was to assess reference accuracy in five national dental journals. One hundred references were randomly selected from the March, 1987, issue of each of five dental journals (a total of 500 references). Each reference was verified either from the original source or from other indexing tools if the original was unavailable. References were divided into two categories: incorrect and correct. The number of incorrect references was counted and subdivided into major and minor errors. The errors were grouped by types of error: author, article title, citation (which included errors in journal title, volume, issue, and page numbers), and "unable to verify". This survey found 211 (42%) inaccuracies out of 500 references reviewed, with a total of 248 errors within the incorrect group. Out of the latter, 173 (70%) were minor errors, and 75 (30%) were major errors. Types of minor errors ranked as follows: minor article title errors, 86 (35%); minor author errors, 61 (25%); and minor citation errors, 26 (10%). Types of major errors were ranked as follows: incorrect journal citation, 32 (13%); "unable to verify", 25 (10%); incorrect author, 10 (4%); and incorrect article title, 8 (3%). The results of this survey showed that nearly half of the references reviewed were inaccurate.
The Effect of Daily Gum-chewing on Salivary Flow Rates in Man
Authors: Jenkins G.N. , Edgar W.M. 
Published: November 2010

Following reports of increased salivary gland size and increased function, induced by increased mastication in animals, the effects of long-term, frequent gum-chewing on resting and stimulated flow rates were studied in human volunteers in separate experiments in Newcastle upon Tyne and in Toronto. In both experiments, unstimulated and stimulated saliva flow rates were measured in student volunteers at intervals of one or two weeks over a baseline period. Approximately half of the subjects were then given sugarless gum to be chewed (four pieces per day) over the experimental period; controls refrained from vigorous mastication. During (and, in Newcastle, after) the experimental period, salivary flow rates were measured at intervals, as before. In Newcastle unstimulated, but not stimulated, flow rates increased in the gum-chewing group and were still elevated (compared with controls) eight weeks following the experiment. In Toronto, the mean results showed no effect of gum-chewing, but the seven gum-chewers among the 11 subjects with low baseline flow rates (< 0.3 mLlmin) showed a 43% rise in unstimulated flow rate (p ∼ 0.05). The results suggest that increased mastication, in the form of gum-chewing, can increase unstimulated flow rates, especially in those with low salivary function. In addition to short-term beneficial effects of sugarless gum, these long-term effects indicate the possibility of a beneficial effect in caries prevention.
Effect of Firing Temperature and Water Exposure on Crack Propagation in Unglazed Porcelain
Authors: Anusavice K.J. , Lee R.B. 
Published: November 2010

Static fatigue of dental ceramics results from the interaction of residual tensile stress and an aqueous environment. This phenomenon is a potential cause of delayed crack formation and propagation in ceramic or metal-ceramic restorations. For dental ceramics, the influence of microstructural defects such as porosity or fissures caused by incomplete sintering is not known. The objectives of this study were to characterize the influence of porosity (produced by underfiring) on the crack propagation resistance of two feldspathic porcelains and to determine whether lower stress corrosion susceptibility or higher fracture toughness accounts for the superior thermal shock resistance of one of these ceramics. We underfired bars of each porcelain, 25 mm × 4 mm × 4 mm, by as much as 84°C below their recommended firing temperatures. After polishing the specimens through 0.05 μm alumina, we induced cracks in their surfaces with a Vickers microhardness indenter. Semicircular cracks, which were produced under an applied indenter load of 19.6 N, grew with time during storage in distilled water at 37°C. Underfiring of both ceramics caused a slight increase in fracture toughness and a relatively small change in pore volume fraction until we underfired the ceramics at 30°C or more. The crack propagation data indicate that the higher thermal shock resistance of one of the ceramics-as measured previously by a water-quench technique-may be due to its greater resistance to stress corrosion at the initial stage of crack propagation.
Scanning Electron Microscopy of Monkey Secretory-and Transitional-stage Enamel Organ Cells
Authors: Skobe Z. , Prostak K.S. , Stern D.N. 
Published: November 2010

This scanning electron microscope (SEM) study of secretory- and transitional-stage enamel organ cells of the permanent dentition of Macaca mulatta and Macaca arctoides was undertaken because the topography of these cells in primates has not been described in the literature. Comparison of our results with murine enamel organ morphology reported previously revealed not only many similarities, but also some significant differences. Tooth buds of the permanent dentition were routinely prepared for SEM. Murine secretory-stage ameloblasts have been described to be 65-70 μm long, with smooth lateral membranes, but those of monkeys were only 30-35 μ m tall, with four different lateral plasma membrane configurations: smooth, filamentous, longitudinally ridged, and transversely ridged. The filamentous form was most common. Cells were seen with either transverse or longitudinal ridges in the basal half, and with filamentous ridges in the apical portion; this indicates modulation between these forms. Because of the extraordinary similarity between these lateral membrane modulations and those of rat incisor maturation ameloblasts, a comparable function is proposed — namely, that monkey secretory ameloblasts function, in part, in the resorption and mineralization of enamel matrix. There were several layers of rounded stratum intermedium cells basal to monkey secretory-stage ameloblasts, but only one layer of cuboidal stratum intermedium in rodents. The stellate rcticulum cells of rats and monkeys appeared attenuated, with large extracellular spaces. There was little or no reduction in cell length of monkey transitional-stage ameloblasls. The position of the nuclear bulge differentiated transitional- from secretory-stage ameloblasts. The lateral surfaces of monkey transitional ameloblasts had interdigitating bulbous extensions of cytoplasm, whereas those of mice were smooth, and became microvillous late in the transition stage. In this stage, monkey and murine stratum intermedium, stellate reticulum, and the outer enamel epithelium cells changed morphology to become papillary cells with microvillous surfaces. Clusters of papillaty cells were separated from each other by anastomosing blood vessels, with diameters ranging from 10 to 12 μ m in monkeys, but from only 5 to 8 μm in murine incisor teeth.
An in vitro Investigation of the Effects of Glass Inserts on the Effective Composite Resin Polymerization Shrinkage
Authors: Donly K.J. , Wild T.W. , Bowen R.L. , Jensen M.E. 
Published: November 2010

We placed an MOD preparation in each of 12 permanent molars, then restored each tooth with a posterior composite resin by means of six different application techniques (I-polymerization as one complete unit; II-polymerization as one complete unit with glass inserts; IIIpolymerization in gingivo-occlusal increments; IV-polymerization in gingivo-occlusal increments with glass inserts; V-polymerization in bucco-lingual increments; and VI-polymerization in a gingival increment with glass inserts, then bucco-lingual increments). A precision strain gauge was attached to the buccal surface of each tooth and balanced at zero. After each increment was polymerized, the strain appearing on the strain gauge indicator was recorded. Each tooth was restored by use of all techniques; two teeth started with each technique. Results demonstrated the average microstrain units to be 127-1, 102-11, 105-III, 86-IV, 72-V, and 66-VI. A randomized block design was the format used for data evaluation. Scheffé's Test indicated that composite resin placement and polymerization in bucco-lingual increments (V) created significantly less cuspal deflection than polymerization as one complete unit, with or without glass inserts (I and II), p<0.001, and gingivo-occlusal increments (III), p<0.05. Placement and polymerization in a gingival increment with glass inserts, then bucco-lingual increments (VI), also created significantly less internal deflection than polymerization as one complete unit, with or without glass inserts (I and II), p<0.001, and gingivo-occlusal increments (III), p < 0_ 005.
The Effects of Submandibularectomy on the Thymus and T-cell System of Mice
Authors: Letic-Gavrilovic A. , Radojičić Č. , Abe K. 
Published: November 2010

Functional changes of the T-cell immune system in submandibularectomized (SMx) male mice of CBA/H strain were analyzed three or four weeks after treatment. Thymuses and spleens were weighed and morphologically examined by light microscopy. We tested proliferation rates of thymocytes and splenocytes (stimulated by Con A and PHA) and cytotoxic activity of T lymphocytes in SMx, CBA/H (H-2k) mice by means of the rejection test of allogeneic skin graft (Balb/c, H-2d) and a microcytotoxicity to allo-antigens of EL-4 tumor cells (H-2b). Results showed a reduction of the weights of the thymus and spleen. However, there was increased functional capacity of the thymocytes - expressed as increased proliferation rates of the stimulated thymocytes, increased microcytotoxicity to allo-antigens of EL-4 tumor cells in vitro, and a reduction of the survival period of skin allografts in vivo. No morphological changes other than a reduction in both the cortex and medulla of the thymus were observed. The subpopulational changes within the T-cell system because of SMx indicate that the morphological atrophy could be just a consequence of SMx.
A New Method for Isolation of Salivary Neutrophils and Determination of Their Functional Activity
Authors: Ashkenazi M. , Dennison D.K. 
Published: November 2010

The purposes of this study were to develop a new method for isolating salivary neutrophils (SPMNs), and to determine their functional activity. Studies of neutrophils in the oral cavity have been largely limited to crevicular PMNs, because of difficulties in obtaining viable SPMNs free of epithelial cells. A method to obtain SPMNs is presented. Donors performed rapid sequential rinsings by placing in their mouths 15 mL of Hanks' balanced salt solution [free of calcium or magnesium ions (HBSS-CMF)], which contained 0.1% gelatin, then swishing the solution for 30 s, and expectorating into a polypropylene receptacle containing 400 mL 4°C HBSS-CMF. This sequence was repeated for 20 min. The collected solution was stirred for 10 min, the cells were washed, and the re-suspended pellet was passed sequentially through a 20-μm and a 10-μm nylon mesh. The cells consisted of 97.7 ± 1.7% SPMNs, only 2.3% epithelial cells, and were almost free of oral debris. The SPMNs were studied for CDllb expression, H2O2 production, and F-actin polymerization. SPMNs had significantly higher resting values for CDIIb, H2O 2 production, and F-actin polymerization compared with blood neutrophils (BPMNs). SPMNs responded to stimulation by chemotactic peptide or phorbol ester in a dose-dependent fashion, with levels of CDllb, H2O 2, and F-actin comparable with BPMNs at optimal stimulant concentrations. The elevated resting levels of CD11b, H2O2, and F-actin for SPMNs were probably caused by exposure to gingival and oral bacteria. The ability of in vitro-stimulated SPMNs to increase their levels of CDllb, H2O2, and F-actin to levels comparable with BPMNs indicates that these cells can function after leaving the gingival crevices. The method described is relatively simple and provides a high number (4-30 × 10 6) of purified and functional SPMNs.
Fluoride Incorporation into and Retention in Remineralized Enamel
Authors: Jima Y. , Koulourides T. 
Published: November 2010

This study assessed the incorporation of fluoride into remineralized enamel and the stability of the incorporated fluoride under various test conditions. Lesions were produced on bovine enamel slabs by a two-day immersion in 0.01 mollL lactic acid buffer containing 3.0 mmol/L Ca, 1.8 mmol/L P, and 1% CMC adjusted to pH 4. 0 at 37°C. The remineralizing solution contained the same amount of Ca, P, and CMC, plus 150 mmol/L NaCl and 3 ppm F, and was adjusted to pH 7.0 at 37°C. All slabs were exposed to this unstirred solution, which was changed every two days during the ten-day remineralizing period. The remineralized slabs were divided into four groups. Group A (the control group) received no further treatment. The other three groups were exposed for 24 h to either the intra-oral environment (Group B), a 1. 0 mol/L KOH solution (Group C), or a 0.01 mol/L lactic acid buffer (Group D). Fluoride incorporation assessed by abrasion biopsy in 10-μm layers showed about 10,000 ppm F maximum in Group A. Similar levels of fluoride concentration from the surface to approximately 30μm thick were found in Groups A, B, and C. No appreciable fluoride was released from remineralized slabs from Groups B or C, and only a small fraction from Group D. Statistical analyses of the fluoride values showed no significant differences between the various test conditions in any of the layers sampled. No difference was evident in the CalP ratio between the ten-day remineralized enamel (Group A) and the treatment groups. The lack of appreciable fluoride loss from enamel with any of the above three conditions indicated a stable fixation of fluoride in the remineralized enamel lesions.
The Effect of Chronic Atropine Treatment on Salivary Composition and Caries in Rats
Authors: Watson G.E. , Pearson S.K. , Falany J.L. , Culp D.J. , Tabak L.A. , Bowen W.H. 
Published: November 2010

Many instances of salivary dysfunction in humans can be traced to the use of medications that have hyposalivary side-effects. In this study, atropine, a cholinergic antagonist, was administered chronically to rats by use of osmotic mini-pumps. Steady-state blood levels, similar to levels obtained in human multiple oral dosing, were thus maintained. Atropine delivered in this manner for 24 days was found to decrease protein concentration of parotid saliva (p<0.05) elicited by pilocarpine, and to increase smooth-surface caries scores (p<0.05) in rats fed a cariogenic diet. Parotid saliva collected via ductal cannulation from rats subjected to chronic atropine administration (and stimulated to secrete by pilocarpine) exhibited increased levels of two basic proline-rich proteins (Peak A and SP-3), as evaluated by SDS-PAGE, compared with those observed in saliva from controls. Cannulation of sublingual glands in animals receiving high doses of atropine produced no measurable secretion upon pilocarpine stimulation. Carbachol stimulation of dispersed cell aggregates of sublingual glands from sham-operated and high-dose atropine groups indicated that the glands responded similarly once the antagonist was washed from the system, implying that the lack of secretion in vivo was caused by antagonism of the cholinergic receptor by atropine. Our observations suggest that this model system can be exploited for determination of the effects of chronic administration of hyposalivary drugs on salivary composition and caries rates.
The Measurement of Toothbrush Wear
Authors: Rawls H.R. , Mkwayi-Tulloch N.J. , Casella R. , Cosgrove R. 
Published: November 2010

Toothbrushes wear out and progressively lose their ability to clean as the bristles abrade and become curled and matted. To study the factors that influence this process, we developed a quantitative measure of bristle splaying (wear index) and a method for judging and ranking the overall state of brush deterioration (wear rating) and used these to determine the effects of the individual user, brush design, time in use, and bristle material. Wear index is the average increase in brush-head dimensions normalized for maximum bristle length, and is dimensionless. Wear rating is a subjective means of classifying the increasing severity of deterioration on a scale of 0 to 3. The wear characteristics of a variety of commercial and experimental brushes with different design features were determined. Test variables were time in use, brush design (e.g., geometry and size of the brush head), and bristle composition. Time of use, the individual user, and bristle composition were found to have the strongest influences on splaying, and brush design was found to have the least influence. The wear index offers a quantitative means of comparing brushes of different dimensions at various stages of splaying. The wear rating, although qualitative, is a quick means of ranking brushes in various stages of deterioration. The two methods correlate (R2 = 0.87), and both are sensitive to several factors that affect brush durability. Therefore, these methods appear to be suitable not only for research, but also for quality control, the setting of standards, and for substantiation of advertising claims.
Effects of Varnishes Containing Chlorhexidine on the Human Dental Plaque Flora
Authors: Schaeken M.J.M. , Van der Hoeven J.S. , Hendriks J.C.M. 
Published: November 2010

This study describes the effects of varnishes containing 0%, 10%, 20%, or 40% chlorhexidine diacetate on the microflora of human fissure dental plaque. Sandarac, a natural resin, was used as the varnish base. Ten subjects, each with at least four sound fissures harboring high levels of Streptococcus mutans, participated in the study. The fissures in each of the individuals were randomly assigned to four experimental groups, in each of which one of the varnishes was tested. The varnish treatment consisted of a single application of a small amount of varnish onto the fissures. Apart from the selected fissures, the rest of the dentition was left untreated. All chlorhexidine-containing varnishes selectively suppressed S. mutans in fissure plaque, and had no effect on total viable counts or on the numbers of Actinomyces viscosus/naeslundii and Streptococcus sanguis beyond one week. The extent of the suppression depended upon the concentration of chlorhexidine in the varnish, 40% chlorhexidine varnish giving the greatest suppression of S. mutans. At 22 weeks, after a single treatment with varnish containing 40% chlorhexidine, mean S. mutans counts were more than ten times lower than in the control or 10%chlorhexidine varnish group. At that time, S. mutans was still undetectable in five out of ten experimental fissures in this group. The results suggested that sandarac varnishes containing high concentrations of chlorhexidine can be used successfully for long-term suppression of S. mutans in dental fissures.