bluuebunny/crossref_metadata_2025_split huggingface dataset:
Long-term F Release from Glass Ionomer Cements
Authors: Swartz M.L. , Phillips R.W. , Clark H.E. 
Published: November 2010

Fluoride release from three commercial glass ionomer filling cements and three glass ionomer luting cements was measured in the laboratory over a 12-month period. Fluoride release from these glass ionomer cements was compared with that released from a silicate, silicophosphate, and a fluoride-containing polycarboxylate cement. The fluoride released from the glass ionomer cements throughout the one-year period was similar, both in quantity and pattern, to that released by the silicate cement. The silicophosphate cement tended to release fluoride in somewhat lesser amounts, while the amount of fluoride released by the polycarboxylate was negligible after the first few days. Analysis of these data indicates that these glass ionomer cements probably possess anticariogenic properties similar to those of silicate cement.
A Conceptual Model for the Co-existence of Streptococcus Spp. and Actinomyces Spp. in Dental Plaque
Authors: Van der Hoeven J.S. , De Jong M.H. , Rogers A.H. , Camp P.J.M. 
Published: November 2010

One of the most important questions in ecology is how to explain the co-existence of the variety of physiologically related organisms in the same habitat. A model is presented for the co-existence of Streptococcus species and Actinomyces species in dental plaque. The hypothesis is that these organisms co-exist because they simultaneously utilize several carbon and energy substrates. The hypothesis follows from the observation that the growth yield of oral streptococci and actinomyces in saliva is limited by carbohydrate. Preliminary experiments were undertaken to test the hypothesis using mixed chemostat cultures and gnotobiotic rats. Competition between S. mutans K1R and A. viscosus Ut2 in mixed chemostat cultures on glucose and asparagine was hampered by the early appearance of high-glucose-affinity variants of A. viscosus. From the physiological characteristics of S. sanguis and S. milleri, it might be predicted that simultaneous utilization of carbohydrate and arginine would enable these organisms to co-exist with S. mutans in an ecosystem. To test this mechanism under natural conditions, germ-free rats were inoculated with a combination of S. mutans K1R and S. sanguis P4A7 or the combination S. mutans K1R and S. milleri B448. The rats were fed on three different diets: (1) 58% cornstarch ; (2) 48% cornstarch and 10% sucrose; and (3) 53% cornstarch and 5% arginine. The results of this experiment demonstrated that dietary arginine caused a significant decrease of the ratios K1R/P4A7 and K1R/B448 in dental plaque. Thus, arginine stimulated S. sanguis and S. milleri, whereas sucrose promoted S. mutans. It can be concluded that bacterial substrate is a major ecological factor for dental plaque. This factor can potentially be studied in mixed-chemostat cultures and in gnotobiotic rats.
Host Response in Experimental Periodontal Disease
Authors: Taubman M.A. , Yoshie H. , Ebersole J.L. , Smith D.J. , Olson C.L. 
Published: November 2010

Experiments were performed to determine the role of the immune response in rat periodontal disease. Germ-free rats were fed defined antigen-free liquid diets or a diet containing ovalbumin(OVA) as a prototype antigen. The OVA-fed rats demonstrated increased gingival lymphocytes (mainly T at early times), OVA-sensitized spleen cells, and increased periodontal bone loss. In further studies, rats pre-sensitized with OVA, and receiving OVA in the diet, showed elevated IgG antibody, sensitized spleen cells, and elevated periodontal bone loss scores. The concept that bone loss was due to mixed hypersensitivity reaction is consistent with the periodontal pathology. The effects of pre-immunization with A. actinomycetemcomitans (Aa ) on periodontal bone loss in Actinobacillus (Aa ) - infected rats was examined. Delayed hypersensitivity (DTH) was present in immunized rats throughout the experimental period. Sham-immunized rats showed DTH after 30 days of infection. In addition, immunized rats showed elevated bone loss scores. These experiments support the contention that a combination of hypersensitivity reactions (i.e., mixed hypersensitivity to Aa) could give rise to the periodontal pathology observed. Congenitally athymic rats (nude) were shown to have more periodontal bone loss than did normal littermates. However, bone loss in thymus-cell reconstituted nude rats was not different from that in control rats. Normal rats receiving Aa-sensitized T lymphocytes prior to infection with Aa demonstrated increased DTH and periodontal bone loss. These studies support the concept that T-cell functions and thymic regulation of immune responses can exert protective and/or destructive effects in periodontal disease. In order to modify disease, it will be necessary to enhance the protective aspects of the immune response and to minimize the detrimental aspects.
Clinical Science Cusp Reinforcement by the Acid-etch Technique
Authors: Morin D. , DeLong R. , Douglas W.H. 
Published: November 2010

Strain gauges were mounted on 12 maxillary pre-molars which were subjected to a sequence of restorative procedures for MOD preparations. An occlusal stress was applied using servohydraulics, and the cuspal flexure was assessed using a strain gauge. Two bonded and three non-bonded restorative procedures were tested for each tooth. The two bonded conditions showed significantly higher cuspal reinforcement when compared with the MOD preparation and the non-bonded restorative procedures. The non-bonded restorations showed some intragroup differences, with one non-bonded composite showing useful cuspal reinforcement. However, this was much less than that afforded by the bonded technique. The deformation of the cusp under occlusal force in restorations bonded by the acid-etch technique showed much less hysteresis when compared with non-bonded restorations.
Acceleration of Remineralization in vitro by Sodium Monofluorophosphate and Sodium Fluoride
Authors: Mellberg J.R. , Mallon D.E. 
Published: November 2010

Sixteen groups of artificial caries lesions were treated with from 75-900 ppm F from MFP, NaF, combinations of the two, or water for five min twice daily for ten days. Between treatments, the lesions were placed in a remineralizing solution at 37°C. Quantitative microradiography of the treated lesions vs. matched untreated lesions showed significant remineralization of the surface layer and lesion body of all groups, including the water-treated control group. Fluoride treatments improved remineralization. Increasing the concentration of NaF had only a small effect on remineralization, but MFP was more effective at higher concentrations. Evaluation of MFP/NaF mixtures showed that greatest remineralization was obtained from a 75/225 ppm F ratio of NaF/ MFP. This combination of F- and PO3F= was more effective than a fluoride concentration of 300 ppm F from either agent alone.
Extensibility Characteristics of Human Cheek-Visco-elastic Properties
Authors: Ho T.P. , Weinstein S. , Bowley W.W. 
Published: November 2010

Using a hydraulic bellows system mounted on a maxillary partial denture, continuous force-displacement data were taken in an edentulous area in the maxillary bicuspid-molar region on ten adults. Both loading and unloading force-displacement curves showed three segments. Two visco-elastic properties - hysteresis and relaxation - were consistently evident. The maximum difference in force-magnitude of the hysteresis loop was 1.02 g. A pre-conditioning phenomenon of the cheek tissue, evidenced by a reduction of the area of the hysteresis loop, was observed in a series of repeated runs. The significance of the study was that: (1) in some individuals, the cheek could be displaced, by expansion of the molars, up to 1 mm into a second stable position; and (2) the relaxation phenomenon suggests a limited adjustive capacity in cheek stiffness.
Influence of Silane Treatment and Filler Fraction on Thermal Expansion of Composite Resins
Authors: Soderholm K.-J.M. 
Published: November 2010

The coefficient of thermal expansion of experimental composite materials containing either silane-treated or untreated fillers in a triethylene glycol dimethacrylate (TEGDMA) matrix was investigated. The results show that an inverse linear relationship existed between volume fraction filler and coefficient of thermal expansion. No differences were seen between silane-treated and untreated composites, while it was found that repeated heating (aging) caused the thermal expansion to decrease for all material combinations. Reduction in the coefficient of thermal expansion with increased filler fraction of unbonded filler indicates that the polymerization shrinkage of the matrix induces hoop stresses around the fillers. By use of a simplified theoretical model (Appendix), these stresses could be estimated. These estimates revealed that the induced stresses were remarkably high, and that increased filler fraction increased the tensile stress level surrounding the filler particles. Since these tensile stresses could facilitate crazing and crack growth in the matrix, these estimates may explain why filled resins containing low fractions of microfilled particles seem to possess remarkably good clinical wear resistance when compared with composites containing higher filler concentrations, at least during the first years in service.
A Technique for Characterizing Casting Behavior of Dental Alloys
Authors: Hinman R.W. , Tesk J.A. , Whitlock R.P. , Parry E.E. , Durkowski J.S. 
Published: November 2010

A technique for characterizing casting behavior of dental alloys has been developed and tested. The method employs easily reproducible specimen patterns and uses equipment and procedures generally available in dental prosthetic laboratories. A castability value is arrived at by counting complete segments of a cast alloy grid. Test results indicate that the castability evaluation procedure described can be a valuable aid in the laboratory for both selecting and using dental materials for producing cast restorations. The test method would also appear useful for the evaluation of products and techniques during research and development. An absolute minimum for the castability value determined relative to clinical and laboratory efficacy has yet to be established.
Contribution of Stereochemical Interactions in the Adhesion of Streptococcus sanguis C5 to Experimental Pellicles
Authors: Gibbons R.J. , Etherden I. , Moreno E.C. 
Published: November 2010

Parameters for the adsorption of Streptococcus sanguis C5 to experimental salivary pellicles were determined to assess the relative contributions of stereochemical and less specific hydrophobic-electrostatic interactions in this process. S. sanguis C5 cells possess hydrophobic surfaces and also an adhesin which exhibits stereochemical binding to sialic acid-containing salivary receptors. The adsorption of S. sanguis C5 to untreated pellicles was significantly better described by a two-site adsorption model than by a one-site model (p<0.001). One class of binding sites had an affinity for the organism that was more than 400 times that of the second class of binding sites. However, adsorption of the organism was better described by a one-site model to asialo pellicles prepared by neuraminidase treatment which destroyed the receptors for the organism's adhesin. The affinity of the organism to sites in asialo pellicles was low, and approximated that to the low-affinity sites in untreated pellicles. These observations suggest that, in the absence of stereochemical interactions involving the organism's adhesin and specific salivary receptors, S. sanguis C5 cells only exhibit low-affinity binding to experimental pellicles. This was substantiated by studies which showed that adsorption of the organism to albumin-coated hydroxyapatite and to polystyrene beads was also better described by a one-site model, and it occurred with only low affinity.
Pharmacokinetics of Chronic Fluoride Ingestion in Growing Pigs
Authors: Richards A. , Kragstrup J. , Nielsen-Kudsk F. 
Published: November 2010

The present study was undertaken to estimate bio-availability and biological half-life of fluoride and accumulation of fluoride in bone in the domestic pig. Eight animals receiving 2 mg F-/kg b.w. per day from age 8 to 14 months were compared with eight controls. Plasma fluoride concentrations just prior to the daily oral dose were measured at regular intervals. After 112 days post-dose, plasma fluoride levels were measured over a 48-hour period following the daily oral dose or a single intravenous dose. Mean bio-availability factor for the oral dose was 0.3 (range 0.2-0.4), and mean biological half-life was 59 days (range 49- 72). Bone fluoride content calculated from the pharmacokinetic parameters derived from plasma data was similar to the content of fluoride measured in the bone at slaughter. The study showed that accumulation of fluoride in bone influences plasma fluoride levels during chronic administration of fluoride to growing pigs. The long biological half-life found showed that it was not possible to achieve steady-state plasma levels within the six-month experimental period used. This means that, for dose-response studies of dental fluorosis in this animal, it is not possible to achieve steady-state plasma concentrations as a basis for correlations to the degrees of pathological change observed in the teeth.
A New Method for Matching Tooth Colors with Color Standards
Authors: Van Der Burgt T.P. , Ten Bosch J.J. , Borsboom P.C.F. , Plasschaert A.J.M. 
Published: November 2010

A new method for quantitative intra-oral tooth color determination is presented. Basically, the tooth color is assessed by visual comparison with opaque color standards, which are logically arranged according to three visual color dimensions. The standards were analyzed spectrophotometrically, and the C.I.E. color coordinates were computed. Illumination and observation were standardized during the matching procedure. Two distinct situations, method 1 and method 2, were investigated. The situation in method 1 is to be considered as large window illumination and small window collection of the reflected light. For method 2, the same small window was used for both illumination and observation. Using both methods, the color of a tooth could be quantified into three separate color dimensions. Using method 1, the consistency among 25 examiners was high in determining the color of ten teeth; using method 2, the inter-examiner agreement was low. For the same tooth, different color standards were selected with method 1 or method 2. The standard selected with method 2 often appeared to be in disagreement within clinical expectations. The differences in results between method 1 and method 2 are explained by the optical properties of the translucent dental enamel (e.g., volume reflection). Method 1 allows for reproducible quantification of clinical tooth discoloration according to C.I.E. color specifications and can possibly be applied in prosthetic dentistry.
Depth of Penetration of in vitro Root Surface Lesions
Authors: Phankosol P. , Ettinger R.L. , Hicks M.J. , Wefel J.S. 
Published: November 2010

An acidified gel system was used to produce artificial caries lesions in root surfaces and in enamel. The teeth were exposed to the gel system for two weeks and four weeks, after which the lesions were examined by polarized light microscopy and photographed by standardized techniques. The depths of penetration of the lesions were measured from these standardized photomicrographs. The lesions in root surfaces were deeper than those in enamel for all teeth. After two but not four weeks of exposure in the gel system, the lesions in the root surfaces of anterior teeth were deeper than those in pre-molars.
A Survey of the Reasons for Dental Extractions in France
Authors: Cahen P.M. , Frank R.M. , Turlot J.C. 
Published: November 2010

3516 French dentists, selected at random, were asked to record every tooth they extracted during January, 1984. They were also asked to give the reason for extraction in each case. These were assigned to eight groups: caries, periodontal diseases, eruption problems, prosthetics, trauma, orthodontics, occlusal problems, and other reasons. Data were received from 910 dentists (25.3%) relating to a total of 14,621 extractions. Overall, caries was the most frequent cause for extraction (49%), followed by periodontal diseases (32.4%) and orthodontics (8.4%). In the age group under 50, dental caries was the main reason for extraction. However, in the age group over 50, periodontal diseases became the principal reason for extraction. Orthodontic extractions were most prominent in the 6-12 and 13-20 age groups, with respective frequencies of 72.6% and 24.8% of all extractions. Eruption problems contributed most frequently in the 13-20 and 21-30 age groups, their respective percentages being 8.7% and 12.3%. Extractions resulting from trauma were most frequently noted in the under-6 age group (frequency of 8.8%). As far as the type of tooth was concerned, first and second molars taken together made up 29.6% of extractions These were followed by pre-molars, anterior teeth, and third molars at levels of 25.8%, 29.9%, and 14.7%, respectively. The teeth most frequently extracted because of caries were the molars (40.9%); because of periodontal disease, the anteriors (49.1%); and, for prosthetic reasons, again the anteriors (57.5%). Extractions from the various regions of France showed important variations. Percentage frequencies for caries and periodontal extractions were inversely linked.
Materials Science Structure, Corrosion, and Tarnishing of Ag-Pd-Cu Alloys
Authors: Niemi L. , Herø H. 
Published: November 2010

The structure of Ag-Pd-Cu-Au-Zn alloys can be expected to have an influence on their corrosion and tarnish resistance. Four experimental Ag-based alloys (I-IV) with varying PdlAg ratios were studied by scanning electron microscopy (SEM), microprobe analyses, and x-ray diffraction analyses. Both as-cast and in the annealed state, they contain a Pd-Cu-Zn-enriched compound A and a Ag-rich matrix (compound B) with a fcc structure, α2. X-ray diffraction data indicated that compound A consisted of two fcc phases (α1 and α 2) in addition to a bcc PdCuxZnx-1 phase. The phases of compound A were too small to be distinguishable by SEM. Alloys I-IV could not be solid-solution-annealed to a single phase. Static anodic polarization testing was carried out in an artificial saliva containing Na2S (pS=5). It was found that an alloy made as a duplicate of the Pd-Cu-Zn-rich compound A for a given potential had current density clearly lower than that of the Ag-rich alloys. Furthermore, cathodic reduction of oxygen took place at a considerably higher rate on this Pd-Cu-Zn-rich duplicate alloy than on the Ag-based alloys. It is suggested that micro-galvanic cells are created between the Pd-Cu-Zn-rich compounds A and the Ag-rich matrix in alloys I-IV. Immersion tests in aqueous Na2S solutions (pS=1.6) showed tarnishing to take place only on the Ag-rich matrix. However, increasing the Pd content of an Ag-rich single-phase alloy increased its tarnish resistance.
Clinical Science
Authors: Lagerlöf F. , Dawes C. 
Published: November 2010

A theoretical study of oral sugar clearance (Caries Res 17:321-334, 1983) suggested that the unstimulated salivary flow rate (UNSTFR) and the volume of saliva present in the mouth before swallowing (VMAX) can greatly affect the rate of sugar clearance. The object of this study was to determine whether variations in UNSTFR, by water infusion into the mouth, and in VMAX, which can be altered by varying the swallowing frequency, would influence sugar clearance and whether changes in VMAX would affect the extent of the pH fall produced by S. mitior in vivo after sucrose consumption. In three experiments on each of ten adult subjects, UNSTFR was measured initially (mean value = 0.55 mllmin), and a swallowing schedule was calculated so that the volumes swallowed were either 0.3 ml or 1.0 ml. After a 10-second rinse with 20 ml of a 10% sucrose solution, the subjects maintained a swallowing frequency such that the volumes swallowed were either 0.3 ml or 1.0 ml at normal UNSTFR or were 0.3 ml when UNSTFR was increased by infusing water at 0.5 mllmin. In all subjects, clearance of sugar was faster at the higher swallowing frequency and at the higher flow rate, as predicted by the theoretical model. Small acrylic splints were made to fit over the lower incisors of ten subjects and to hold in the floor of the mouth an antimony microelectrode covered by a 0.5-mm layer of S. mitior, which was held in place by a dialysis membrane. On two occasions, and in random order, the subjects rinsed with a 25% sucrose solution for 10 sec. Then, with the bacteria-covered electrode in the floor of the mouth, pH changes were followed for 30 min while the subjects swallowed either once each 15 sec or once each 120 sec. In all subjects, the pH fall from an initial mean value of 6.6 was less at all time points at the high swallowing frequency (min. mean pH = 6.05) than at the low (min. mean pH = 5.56). The results confirm the predictions of the theoretical model that, with larger values of UNSTFR and smaller values of VMAX, less time is required for sugar clearance. In addition, they show that, with larger values of VMAX, a greater pH fall is produced by oral bacteria. Thus, VMAX may be an important determinant of caries susceptibility.
Analysis of Alloy-Porcelain Compatibility Using a Multi-component Material Strip Equation
Authors: Dehoff P.H. , Anusavice K.J. 
Published: November 2010

An analytical model has been developed to calculate residual stresses and curvature changes due to thermal contraction differences in metal-porcelain strips consisting of any number (n) of component materials. This model was also used to analyze transient and residual stresses due to solidification of a semicircular arch casting. Results obtained from this model were in close agreement with those obtained from finite element calculations for the cases studied. Some experimental evidence exists to suggest that thermal contraction coefficients of certain body porcelains progressively increase with the number of firing cycles. Therefore, a parametric study was conducted to determine the effects of variations in the thermal contraction coefficient of each porcelain layer on residual stresses and gap changes produced in porcelainized semicircular arch specimens. Based on the analytical model developed in this study, we found that calculated residual stresses near interfacial areas of adjacent layers of porcelain are most sensitive to variations in thermal contraction coefficients of the material layers.