bluuebunny/crossref_metadata_2025_split huggingface dataset:
Computer Correction of Projective Distortions in Dental Radiographs
Authors: Webber R.L. , Ruttimann U.E. , Groenhuis R.A.J. 
Published: November 2010

Distortions in radiographic images caused by changes in shape and position of the film relative to the x-ray beam can result in registration artifacts which interfere with interpretation of subtracted images. A warping transformation is described which maps known points of reference in one image into homologous points in another. The corrected image pair can then be superimposed and subtracted with significantly-reduced differences in registration to facilitate the detection of localized changes of diagnostic interest.
Materials Science Cement Distribution and Bond Strength in Cemented Posts
Authors: Goldman M. , DeVitre R. , Tenca J. 
Published: November 2010

Rods of lucite were drilled to receive a #5 parapost to a depth of 4 mm and 7 mm. Posts were fitted and cemented either by coating the post with cement or by placing the cement in the prepared hole with a lentulo spiral in a low-speed hand-piece and then inserting the pre-coated post. Photographs were taken to determine the distribution of the cement. The lentulo spiral distributed the cement along the entire length of the preparation, but coating alone did not distribute the cement evenly. The tensile strength with these two methods of post cementation was also compared in four groups of extracted teeth. In Groups IA and IIA, the post preparation was rinsed with 2 ml of 5.25% NaOCl and dried with paper points and blasts of air. In Group IA, the post was coated with zinc phosphate cement and seated. In Group IIA, the cement was placed into the post space with a lentulo spiral in a slowly rotating hand-piece; the post was then coated and seated. In Groups IB and IIB, the post preparation was rinsed with 1 ml of 17% Na2 EDTA followed by 1 ml of 5.25% NaOCl to remove the smeared layer at the dentin-cement interface. The posts were then cemented as in IA and IIA. Under the conditions of this experiment, the following conclusions can be drawn: (1) Placing cement into the preparation with a lentulo spiral increased the tensile strength and the overall cement distribution. (2) Removing the smeared layer increased the tensile strength, whether the post was simply coated with cement or cemented into place using a lentulo spiral. (3) The greatest tensile strength occurred when the smeared layer was removed and the post was cemented into place using a lentulo spiral and coating combination.
Analysis of Covariance in Caries Clinical Trials using Groupings of Teeth
Authors: Worthington H.V. , Adkins B.L. 
Published: November 2010

An empirical investigation was carried out on data from four caries clinical trials of subjects who were initially 11 to 12 years old. The three baseline variables suggested by Adkins (1977), as possibly being related to caries increment, were each calculated on specific groupings of teeth, and these were then considered as predictor variables for the dependent variable, caries increment. A gain in efficiency of approximately 20% was obtained when an analysis of covariance was used with these predictor variables, over a straightforward analysis of variance. However, this was only slightly more efficient than using baseline DMFS as a covariable. This investigation did not support the results of initial work done by Adkins (1977).
Effects of a Fusobacterium nucleatum Extract on Immunoregulation in Mice
Authors: Yoshie H. , Mitsuma T. , Kozima K. , Hara K. 
Published: November 2010

The purpose of this study was to examine the effect of an extract of Fusobacterium nucleatum on humoral and cell-mediated immunity and phagocyte functions in mice. The extract was obtained from the heat-inactivated supernatant of sonicated F. nucleatum. Mouse splenocytes were cultured with sheep red blood cells (SRBC), and antibody formation was assayed by counting the plaque-forming cells (PFC). After C3H mouse skin was grafted onto the BALB/c mouse, cytotoxicity of BALB/c mouse splenocytes to L-cells was enumerated, T- and B-cell blastogenesis was determined by the uptake of 3H-thymidine. In vivo phagocyte functions were measured using carbon clearance test, bactericidal, and acid phosphatase activity assays. The number of SRBC-specific and non-specific PFC in splenocytes stimulated with the extract increased 2.5-8. 7-fold over that of unstimulated splenocytes. Cytotoxicity of splenocytes from the extract-injected mice decreased in a dose-dependent fashion at 12 days after grafting. T cell mitogenicity of the extract was observed. The carbon clearance rate was reduced, and bactericidal and acid phosphatase activities were elevated by the extract injection of the mice. In conclusion, F. nucleatum extract has an adjuvant effect on humoral immunity, and a suppressive effect on cell-mediated immunity and activated phagocyte functions.
Ultrastructural Study of Epithelial Cell Attachment to Implant Materials
Authors: Jansen J.A. , De Wijn J.R. , Wolters-Lutgerhorst J.M.L. , Van Mullem P.J. 
Published: November 2010

Attachment of gingival tissues to the protruding post of an endosseous dental implant is of great importance for the prognosis of its clinical success. Little is known about the requirements an implant material must meet to secure a durable permucosal seal. The objective of this study, therefore, was to gain insight into the morphology of epithelial cell-implant interfaces for a number of well-known or potential implant materials. Guinea pig epithelial cells were cultured on gold, titanium, carbon, hydroxylapatite, carbonate apatite, and modified polystyrene substrates. The metallic and carbon substrates were obtained by vapor-phase deposition of thin films on polystyrene carriers. This technique allowed for the preparation of ultra-thin sections for transmission electron microscopy containing substrate as well as the cells adhering to it. The cultures on apatite were decalcified prior to sectioning. The results revealed that as attachment structures, focal contacts, extracellular matrix contacts, and hemidesmosome-like contacts could be distinguished. Hemidesmosome-like contacts were only observed on apatite and polystyrene and not on the metallic or carbon surfaces. The results of this study suggest the existence of some, as yet unknown, property of the substrate that determines the nature and the structure of the contact site with epithelial cells.
Appearance of Dentin γ-Carboxyglutamic Acid-containing Proteins in Developing Rat Molars in vitro
Authors: Finkelman R.D. , Butler W.T. 
Published: November 2010

An in vitro model of mineralization was devised in order to study the developmental appearance of dentin γ-carboxyglutamic acid-containing proteins (DGPs) in relation to the onset of mineralization. Maxillary third molars from 11-day-old rats were cultured with or without fetal calf serum (FCS) as modified from Navia et al. (1984).- Molars were incubated without radiolabel, or with either 45CaCl2 (5 μCi/ml) for 24 hr at various stages of a ten-day culture period or [3H]-leucine (10 μCi/ml) for 24 hr at the eighth day of culture. Molars were lyophilized and extracted with 10% formic acid overnight at 4°C. DGPs in extracts were detected by immunologic and chromatographic techniques; DGPs in molar sections were detected by immunolocalization using indirect immunofluorescence. Molar development was evaluated histologically using the Von Kossa staining technique. Molars cultured with FCS showed histologic evidence for mineralized dentin and enamel and a significant increase in 45Ca uptake after the sixth day in vitro. Eleven-day-old molars in vivo and molars cultured without FCS showed no evidence of the presence of mineralized tissues. [3H]-Leucine-labeled DGPs were isolated and identified by affinity and reversed-phase high-performance liquid chromatography and by gel electrophoresis from both mineralized and unmineralized molars. DGP antigens were localized immunohistochemically using rabbit anti-rat antibodies raised against a highly purified DGP preparation. In the unmineralized molar, antigenicity was seen in odontoblasts but not in predentin matrix, pre-odontoblasts, or in any other cell type. Antigens in the mineralized molar were localized to odontoblasts and dentin. Analysis of these data indicates that rat molars cultured with FCS show de novo mineralization in vitro and suggests that rat molar odontoblasts synthesize DGPs concurrently with the elaboration of predentin matrix but independently of mineral deposition.
Effects of Dietary Carbohydrates on the Numbers of Streptococcus mutans and Actinomyces viscosus in Dental Plaque of Mono-infected Gnotobiotic Rats
Authors: De Jong M.H. , Van den Kieboom C.W.A. , Lukassen J.A.M. , Van der Hoeven J.S. 
Published: November 2010

Dietary sucrose and glucose are known to promote the accumulation of, respectively, Streptococcus mutans and Actinomyces viscosus in complex dental plaque microflora. In this study, we have investigated the effects of these carbohydrates on the numbers of S. mutans and A. viscosus colonizing the teeth of mono-infected gnotobiotic rats. Sucrose at a dietary concentration of between 0.25 and 0.5 percent (corresponding with 7-15 mM in the drinking water) caused an increase in the numbers of S. mutans. This result strongly suggested that the increase was due to extracellular polysaccharide (EPS) synthesis by glucosyltransferase, whose Km value (1.0-7.0 mM) is in the same concentration range. The numbers of A. viscosus increased three-fold when 10% glucose was added to the basal diet. It seems plausible that this was due to extracellular heteropolysaccharide produced by A. viscosus in the presence of excess glucose. Although in most microbial ecosystems provision of additional substrates leads to an increase in biomass, glucose had only a small effect on the numbers of S. mutans. Mechanical dislodging forces could be limiting the accumulation of dental plaque. EPS synthesis from dietary carbohydrates seems to enable the population to withstand mechanical dislodging at least partially by providing a matrix wherein cells are entrapped or to which the cells are firmly attached.
The Relationship between Serum IgG Levels to Subgingival Gram-negative Bacteria and Degree of Periodontal Destruction
Authors: Naito Y. , Okuda K. , Takazoe I. , Watanabe H. , Ishikawa I. 
Published: November 2010

The relationship between the serum IgG antibody titer against seven species of Gram-negative periodontopathic bacteria and clinical parameters (including plaque index, gingival index, periodontal pocket depth, and alveolar bone loss) was studied in 38 subjects. IgG antibody titer against the sonicated antigens was determined by micro-ELISA. A statistically significant correlation was found between the serum antibody titer against B. gingivalis and the degree of clinical parameters, especially pocket depth. The serum IgG levels against the seven micro-organisms in 16 periodontal patients before and after clinical treatment were also determined. Responses to B. gingivalis decreased (p<0.001), whereas responses to E. corrodens (p<0.01) increased slightly. No marked differences were noted between pre- and post-treatment sera in titers against B. intermedius, B. loescheii, F. nucleatum, A. actinomycetemcomitans, and C. ochracea.
Measurement of the Permeability of Dental Enamel and its Variation with Depth using an Electrochemical Method
Authors: Hoppenbrouwers P.M.M. , Scholberg H.P.F. , Borggreven J.M.P.M. 
Published: November 2010

To investigate the permeability of the dental enamel of erupted and unerupted human pre-molars and its variation with depth, we determined the resistivity of successive 100-μm-thick layers. The electrical resistance of halved tooth crowns at zero Hertz, which according to Scholberg et al. (1982, 1984) is inversely related to the permeability, was measured before and after removal of successive enamel layers from the outer surface toward the dentino-enamel junction (D.E.J.). The resistivity of the successive enamel layers increased from the D.E.J. toward the outer surface in approximately the same way in erupted as well as in unerupted pre-molars, except within the outermost layer of 100 to 200 μm thickness. The resistivity of this layer in erupted pre-molars was considerably higher than that in unerupted pre-molars, which may be due to post-eruptive mineralization.
Host Factors in Juvenile Periodontitis
Authors: Cogen R.B. , Roseman J.M. , Al-Joburi W. , Louv W.C. , Acton R.T. , Barger B.O. , Go R.C.P. , Rasmussen R.A. 
Published: November 2010

This study was undertaken to determine whether defects in leukocyte function or in genes at the MHC play a role in the etiology of either localized (LJP) or generalized (GJP) juvenile periodontitis. Thirteen LJP and five GJP patients (ranging in age from 13 to 22 years) and their matched controls were compared with respect to selected leukocyte functions and HLA phenotypic frequencies. The results of these studies indicated that there were significant decreases in the phagocytic and chemotactic abilities of polymorphonuclear leukocytes (PMN) in both LJP and GJP. All JP patients displayed intrinsic cell defects in chemotaxis compared with controls; in addition, some patients displayed multiple defects, including those which were serum-associated. Also, there appeared to be a significant association between JP and HLA-DR2 and HLA-A33 phenotypes. Fifty percent of the JP patients were HLA-DR2-positive, whereas only six percent of the matched controls were positive. Thirty-six percent of JP patients were HLA-A33-positive, whereas none of the controls was positive. The association seen with DR2 may be due to sampling, since there were no significant differences between the JP cases and a larger unmatched control sample which was not evaluated for periodontal disease. We conclude from these data that increased susceptibility of some patients to a very aggressive and destructive form of periodontal disease (JP) is based on defects in PMN responsiveness. Further investigations are necessary to determine whether these defects are under genetic control.
Influence of Plasticizer on Soft Polymer Gelation
Authors: Jones D.W. , Sutow E.J. , Graham B.S. , Milne E.L. , Johnston D.E. 
Published: November 2010

An evaluation has been made of the soft polymer gel systems of the type used as prosthodontic short-term denture-lining materials. The purpose of the study was to determine the effect upon gel strength and gelation time produced by variations in the composition of the plasticizer liquids. Poly(ethylmethacrylate) co-polymers were mixed with combinations of ethyl alcohol and the esters dibutyl phthalate (DBP), butylphthalyl butylglycolate (BPBG), and benzyl salicylate (BS). The relative rate of gelation of plasticizer polymer compositions was obtained by means of a reciprocating rheometer. The gelation rate was found to increase rapidly with an increase in the ethyl alcohol content. Significantly shorter gelation times were also found with liquids containing the lower-molecular-weight esters. A linear relationship was found between the ethyl alcohol content and the log of the gelation time. The higher-molecular-weight esters produced the strongest gel. A linear relationship was found between the gelation (log) times and the seven-day puncture strength. The ratio of polymer to plasticizer liquid was found to have a very significant influence upon the puncture strength and gelation time. Molecular weight or molecular volume of the ester plasticizers was found to have a greater influence on gel formation than the cohesive energy parameter. The strong polar bonding of ethyl alcohol was found to have a significant influence on both the rate of gel formation and the subsequent gel strength. The data indicate that controlled variations in the characteristics of plasticity and gel strength of dental soft polymer systems can be made to suit different clinical prosthodontic requirements.
Thermal Behavior of the Gypsum Binder in Dental Casting Investments
Authors: Mori T. 
Published: November 2010

This study examined the thermal behavior of cast gypsum specimens, with and without additives, by means of simultaneous differential thermal analysis-thermogravimetry (DTA-TG) and dilatometry. Specimens were prepared from wet-calcined hemihydrates (Hydrocal and Den-site). The additives studied were boric acid (H3BO 3) and sodium chloride (NaCl), and these were added to the hemihydrate powders in concentrations of 2 wt% (in the case of H3BO3) and 0.5 wt% (in the case of NaCl). A large shrinkage was observed in the range of 300 to 500°C, and this was greatly reduced when either H3BO3 or NaCl was present. The dehydration of gypsum (calcium sulfate dihydrate) was not completed until the initial stage of this large shrinkage was reached, but the phase transition of calcium sulfate anhydrite (III-CaSO4 to II-CaSO4) was the major cause for the large shrinkage. This phase transition occurred over a much wider temperature range than that suggested by the DTA-TG results. Dehydration conditions similar to those employed in wet calcination of gypsum appeared to be produced under atmospheric pressure when NaCl was present.
Periodontal Mechanoreceptors and Parotid Secretion in Animals and Man
Authors: Anderson D.J. , Hector M.P. 
Published: November 2010

Parotid flow was determined in rabbits during feeding. The animals produced more saliva when chewing hard laboratory pellets than with carrots, confirming the findings of Gjörstrup (1980a). We showed that one gland always produced more secretion than the other, and that the dominant gland alternated from side to side with changes in the chewing side. Strain-gauge recordings revealed a remarkable similarity in pattern between mandibular strain and ipsilateral parotid flow. Together, these data suggest that chewing movements and chewing force are involved in the control of parotid secretion. In man, flow rates of parotid saliva collected with a Lashley cup and cannula were recorded. During intermittent clenching on a bite block, we found: (1) a positive correlation between rectified integrated masseter EMG and parotid flow; and (2) that anesthesia of various intra-oral nerves could reduce the flow almost to zero. Crushing a particle of breakfast cereal between two teeth resulted in a reproducible parotid flow which was reduced by infiltration anesthesia around one of these teeth. These data point to the involvement of periodontal mechanoreceptors in the control of parotid secretion in rabbits and man.
The Effect of Rate of Increase of Electrical Current on the Sensation Thresholds of Teeth
Authors: Abdel Wahab M.H. , Kennedy J.G. 
Published: November 2010

The effect of the rate of increase of electrical current during stimulation of human teeth was examined on clinically sound upper anterior teeth. The teeth were stimulated with a current of 10 msec duration at a frequency of 50 Hz. Eight different rates of current increase were used, viz.: 1, 2, 3, 4, 5, 6, 7, and 8 μa/sec. The results showed that there was a linear relationship between the sensation threshold and the rate of current increase, and that the threshold increased significantly as the rate of current rise increased. Slowly increasing current gave more accurate and reproducible results than did rapidly increasing current, and a rate of 2 μa/sec was found to be appropriate for clinical pulp-testing.
Dental Papilla Cells Synthesize But Do Not Deposit Fibronectin in Culture
Authors: Thesleff I. , Partanen A.-M. , Kuusela P. , Lehtonen E. 
Published: November 2010

The dental papilla cells play a major regulatory role during tooth morphogenesis, and they are the only mesenchymal cells capable of differentiating into odontoblasts secreting dentin. In this paper, we have extended our studies on the behavior of cultured dental papilla cells which have been disaggregated from 17-day mouse embryo teeth. Quite unexpectedly, we observed that these cells, which in vivo are embedded in a fibronectin-rich extracellular matrix, lose all surface-associated fibronectin when cultured as monolayers. Fibronectin was, however, detected intracellularly, and metabolic labeling and immunopreciopitation studies indicated that the dental papilla cells continued to synthesize fibronectin in culture. Furthermore, when purified plasma fibronectin was added at 50 μl/mL to the culture medium, it became incorporated as fibrillar matrix on the surfaces of dental papilla cells. This indicates that the cells are not deficient in cell-surface receptors or other surface-associated molecules which bind fibronectin. When pieces of dental palpillae were cultured as explants, an abundant matrix containing fibronectin was deposited on their surfaces. This matrix was gradually lost as the cells migrated from the explants. Furthermore, when the cells were disaggregated and cultured at high cell density, the cells in the central area of the pellet were covered by fibronectin containing fibrillar structures which were lost as the cells spread out. This indicates that the maintenance of close contacts between the dental papilla cells is required for the assembly of fibronectin into the extracellular matrix. Three other lineages of mesenchymal cells from the jaws of 11-, 13-, and 17-day-old embryos all developed a fibronectin-containing fibrillar network typical of fibroblastic cells in culture. When the ultrastructure of dental papilla cells was compared with that of gingival mesenchymal cells of 17-day-old embryos, both showed electron-dense material in the cisternae of rough endoplasmic reticulum. On the other hand, only minor amounts of extracellular material could occasionnally be found associated with the dental cells, whereas the gingival cells regularly showed abundant deposits of fibrillar extracellular material.
The Effects of Cheese Snacks on Caries in Desalivated Rats
Authors: Krobicka A. , Bowen W.H. , Pearson S. , Young D.A. 
Published: November 2010

Rats that had had their submandibular/sublingual glands removed surgically, and their parotid ducts tied, developed fewer and less severe caries lesions on coronal and root surfaces when fed cheese snacks in addition to a cariogenic diet than when fed additional cariogenic snacks or no additional snacks. The effects of cheese snacks were particularly dramatic on root-surface caries. These observations may be relevant for elderly humans who are most likely to develop root surface caries. Populations of Streptococcus mutans did not differ among the groups. Actinomyces viscosus was not detected at the end of the experiment in any of the groups. The results of this study demonstrate that cheese exerts a protective effect against coronal and root-surface caries in rats with a severely limited salivary function.