bluuebunny/crossref_metadata_2025 huggingface dataset:
Correlation of Dental Amalgam Crevice Corrosion with Clinical Ratings
Authors: Sutow E.J. , Jones D.W. , Hall G.C.
Published: November 2010

In vitro corrosion behavior of γ2-containing and γ2-free dental amalgams was examined under crevice conditions which simulated the amalgam-tooth interface. By means of potentiostatic testing, currentdensity/time behavior and integrated anodic current were measured for 16 hr. All of the amalgams demonstrated crevice corrosion susceptibility. Crevice corrosion propagation for γ2-free vs. γ2-containing amalgams was characterized by lower acceleration and maximum rates during the most dynamic period. Integrated anodic current results were correlated with marginal breakdown ratings reported in two clinical investigations. Strong and significant coefficients were found between integrated current and marginal breakdown ratings when γ2-containing and γ 2-free amalgams were correlated as a single group, but not when correlated separately.
Measurement in vivo of Masticatory Mucosal Thickness with 20 MHz B-Mode Ultrasonic Diagnostic Equipment
Authors: Uchida H. , Kobayashi K. , Nagao M.
Published: November 2010

Analysis of the movement of the denture foundation under function is very important for construction of a denture. For this analysis, the thickness of the masticatory mucosa gives the required quantitative information. The thickness measurements were taken from 21 oral sites in 100 edentulous patients, by means of 20 MHz B-mode ultrasonic equipment.

The average thickness of the masticatory mucosa ranged from 1. 92 mm to 2.38 mm at the upper edentulous ridge and from 1.45 mm to 1. 58 mm at the lower edentulous ridge. The center of the palate had the thinnest mucosa and the lateral area of the palate had the thickest among all the measuring points. Contrary to what is often believed, a decrease in mucosal thickness with age was not observed by one-way analysis of variance. Furthermore, as the degree of ridge reduction increased, a decrease in the mucosal thickness was found by one-way analysis of variance at only two of the 14 measuring sites on the ridges. At four of the 21 measuring sites, male patients had significantly thicker mucosa than did females, and the correlation coefficients of the thickness of mucosa between right and left sides in the palate were higher than those in residual ridges.
Increased pH-lowering Ability of Streptococcus mutans Cell Masses Associated with Extracellular Glucan-rich Matrix Material and the Mechanisms Involved
Authors: Van Houte J. , Russo J. , Prostak K.S.
Published: November 2010

Streptococcus mutans strain 1B-1600 was cultivated in Todd-Hewitt broth (THB) or THB supplemented with sucrose (S). Cell mass obtained from THB exhibited a high cell density and negligible glucan-rich extracellular matrix material (EMM), whereas cell mass from 2% S-supplemented THB exhibited widely-spaced cells separated by EMM. The pH-lowering potential of the different cell masses was studied in vivo with an intra-oral enamel demineralization test and rinsing with glucose solution, and in vitro with a model which permits vertical penetration of glucose through the cell mass and pH evaluation at different depths within the cell mass. In vivo, the pH profile of EMM-rich cell mass derived from 2% S-supplemented THB was characterized by a lower pH minimum and a slower return of the pH as compared with THB-derived cell mass. In vitro, an increase in cell mass EMM content was associated with a more rapid initiation and an increase in the rate of pH drop in the depth of the cell masses. Evaluation of the acidogenic potential of the cells in cell masses derived from THB and 2% S-supplemented THB with suspensions of dispersed cell mass and added glucose indicated no difference. The buffering capacity of cell mass derived from 2% S-supplemented THB within the pH range of 6.5-4.0 was greatly reduced as compared with that of THB-derived cell mass, due to the relatively low buffering capacity of EMM. The presence of EMM also appeared to enhance the porosity of the cell mass. Collectively, the data suggest that the presence of EMM increases the glucose supply, which leads to an increased rate of acid production by the cells and an enhanced pH-lowering ability of the cell mass. The possible implications of the findings with respect to the pH-lowering potential of human dental plaque are discussed.
Mechanical Properties of Poly(alkyl a-fluoroacrylate)s as Denture-base Materials
Authors: Kurata S. , Yamazaki N.
Published: November 2010

a-Fluoro-substituted acryl polymers, poly(methyl a-fluoroacrylate) (PMFA) and poly(2,2,2,-trifluoroethyl α-fluoroacrylate) (P3FFA) were investigated for extension to denture-base resins.

PMFA, in which fluorine attaches to the polymer chain, had excellent mechanical properties: For instance, compressive and bending strength and bending modulus were 50% higher than those of PMMA. P3FFA, in which fluorines are substituted at the end of the pendant alkyl ester, showed poor mechanical properties. Contrary to expectations, the amount of water sorption of PMFA was about twice that of PMMA, while that of P3FFA was almost zero. Copolymers of MFA and 3FFA were prepared in an attempt to optimize the mechanical properties and the water sorption. The copolymer with 40% of 3FFA showed higher compressive, diametral tensile, and bending strength; in particular, the bending modulus and water resistance were about 35% and 20% higher, respectively, than those of PMMA.

Improvement of the mechanical properties and increase of the water sorption of PMFA may be due to intermolecular forces induced by polarizability of the fluorine and carboxy group along the polymer chain. Decrease of the water sorption by fluorine substituted on the alkylester group as in P3FFA may be due to higher hydrophobicity and steric ejj"ect of the fluoroalkyl substitute.
Relationships Between the Size, Position, and Angulation of Human Jaw Muscles and Unilateral First Molar Bite Force
Authors: Sasaki K. , Hannam A.G. , Wood W.W.
Published: November 2010

Human subjects commonly show large variations in bite force produced at the first molar teeth. To evaluate the role of muscle cross-sectional sizes and lever arms in bite-force production, we correlated these variables in 11 healthy adults. Axial and coronal images obtained by magnetic resonance were combined with conventional lateral cephalograms and dental cast data to reconstruct the craniomandibular morphology in each subject. The cross-sectional sizes of the right masseter and medial pterygoid muscles, their lever arms, and the bite-point lever arms were measured directly from these reconstructions. Physiological recordings of bite force were made in the region of the right first molar by means of a customized transducer aligned perpendicular to the functional occlusal plane. The average bite force for the sample as a whole was 189 ± 78 N. The coefficients of variance were greater for bite forces, and for the cross-sectional sizes of the two muscles, than for their respective lever arms. Highly significant Pearson Product Moment correlation coefficients (p<0.005) were found between masseter and medial pterygoid cross-sectional size, and between the cross-sectional size of each muscle and bite force. No significant correlations (p>0.1) were found between muscle or bite-point lever arms and bite force. Despite the fact that craniofacial spatial morphology may differ among subjects, jaw muscle size alone seems to explain most of the variation in bite force reported by ourselves and others.
Initial Characterization of Cells Derived from Human Periodontia
Authors: Piche J.E. , Carnes D.L. , Graves D.T.
Published: November 2010

The studies presented in this report describe an initial characterization of cell types derived from explants of human periodontia. Cell cultures were established from human periodontal ligament (PL4, PL7), gingival tissue (GF2), and alveolar bone (BP1) by means of explant techniques and monolayer culture. Cells were studied at passage numbers 2-4 and were characterized on the basis of morphological, biochemical, and proliferative parameters. Subconfluent cells did not have distinct morphologies useful in distinguishing them from one another. At confluence, PL4 and BP1 cells formed multilayered cultures of randomly oriented cells, while PL7 and GF2 cells grew in a monolayer of parallel cells. Biochemically, PL4 and BP1 cells exhibited characteristics consistent with an osteoblast-like phenotype. These included a significant increase in PTH-stimulated cyclic AMP and high basal levels of alkaline phosphatase activity, which were decreased on exposure to PTH and increased after stimulation by 1, 25 dihydroxyvitamin D3. In contrast, PL7 and GF2 cells exhibited basal alkaline phosphatase levels that were low, and cyclic AMP levels were not modulated by PTH stimulation. Cell populations PL7 and GF2 did not proliferate in culture medium supplemented with 3% platelet-poor plasma. After the addition of platelet-derived growth factor (PDGF) to this medium, the proliferation of these cell populations was equal to that in media supplemented with 10% fetal bovine serum. In contrast, PL4 and BP1 cells did proliferate in culture medium supplemented with 3% platelet-poor plasma. The addition of PDGF to the medium resulted in only a moderate increase in the proliferation of cell populations PL4 and BP1. These results establish that both osteoblast-like and fibroblast-like cells can be cultured from adult human periodontal ligament and suggest methods for studying the cells in vitro.
The Contribution of Dental Amalgam to Mercury in Blood
Authors: Snapp K.R. , Boyer D.B. , Peterson L.C. , Svare C.W.
Published: November 2010

We determined the exposure to mercury from dental amalgam by comparison of blood levels of mercury before and after removal of all amalgams from ten subjects. Baseline concentrations of mercury in whole blood were measured weekly for four to 18 weeks (median = 6.6 weeks) prior to removal. All amalgams were removed in a single appointment. The subjects had an average of 14 surfaces of amalgam, seven of which were occlusal surfaces. Weekly blood sampling was continued for five to 18 weeks (median=7.6 weeks) after the amalgams were removed. The mean baseline concentration of total mercury in whole blood of the ten subjects was 2.18 (SD = 0.90) ng Hgl mL before the amalgams were removed. The baseline mercury levels were related to the number of amalgam surfaces. The linear correlation coefficient was 0.724 with number of occlusal surfaces, and 0.433 with total number of surfaces. After removal of the amalgams, nine of the ten subjects exhibited a statistically significant decrease in blood mercury at the 95% level of confidence. The mean decrease in mercury was 1.13 (SD = 0.60) ng Hg/mL. The half-time for elimination of mercury from blood after amalgam removal was 30.2 (SD = 5.8) days. Removal of the amalgams provided an additional exposure of 1. 46 (SD = 1.17) ng HglmL that was rapidly cleared from the blood with a half-time of 2.9 days. The daily intake of mercury from amalgam in the subjects was estimated to be at least 1.3 μg.
The Influence of Surface Free-energy on Planimetric Plaque Growth in Man
Authors: Quirynen M. , Marechal M. , Busscher H.J. , Weerkamp A.H. , Arends J. , Darius P.L. , van Steenberghe D.
Published: November 2010

The purpose of this study was to examine the change in plaque area over nine days in vivo on four materials with different surface free-energies (s.f.e.). Twelve healthy dental students participated in a crossover, split-mouth, double-blind study. Supragingival plaque formation was recorded over a nine-day period, on four different materials: fluorethylenepropylene (Teflon) (FEP), parafilm (PAR), cellulose acetate (CA), and enamel (E) with s.fe. of 20, 26, 57, and 88 erg/cm2, respectively. Strips made from the first three materials were stuck to the buccal surface of an upper incisor. The remaining incisor was carefully polished and served as an enamel surface. The increase in plaque was evaluated after three, six, and nine days. A planimetrical analysis was used so that the plaque area could be expressed as a percentage of the total buccal tooth surface. This procedure was repeated on each subject, so that at the end, each pair of central or lateral incisors received the four tested materials.

The results indicated that the adherence of micro-organisms on pellicle-coated substrata was influenced by the material's s.f.e.; there was an association between the s.f.e. of the substrata and the supragingival plaque extension in vivo. High surface free-energy substrata in the oral cavity attracted more micro-organisms than did low energetic materials. Additionally, the bacterial adhesion seemed very weak on surfaces with a low s.f.e.
A Bond Strength Study of Luted Castable Ceramic Restorations
Authors: McInnes-Ledoux P.M. , Ledoux W.R. , Weinberg R.
Published: November 2010

Accurate intra coronal castings can be produced using a castable ceramic-DICOR®-for which there is a need to identify a suitable luting cement. The aim of this investigation was to evaluate the bond strength of three glass-ionomer luting cements and one resin cement to treated and untreated DICOR®, enamel, and dentin surfaces. Forty "cerammed" DICOR® specimens were assigned to four groups: (1-3) grit-blasting and bonding to each of the three glass-ionomer cements; and (4) acid-etching, silane coating, and bonding to the resin cement. Seventy enamel specimens were assigned to seven groups: (1-3) no etching and bonding to each of the glass-ionomer cements; (4-7) acid-etching and bonding to the glass-ionomer cements and the resin cement. Seventy dentin specimens were assigned to seven groups: (1-4) bonding to each of the three glass-ionomer cements and the resin cement; (5-7) polyacrylic acid preconditioning and bonding to each of the three glass-ionomer cements. The mean resin cement bond strengths (MN/m 2) to DICOR® (9.4) and to etched enamel (10.7) were significantly greater (p<0.01) than those of the glass-ionomer cements (DI-COR®, 0.8-1.2 ; enamel, 0.4-0.9). Preconditioning of enamel and dentin significantly increased (p<0.05) the bond strengths to the glass-ionomer cements. The mean bond strength of the resin cement to untreated dentin (4.3) was significantly higher (p<0.05) than the glass-ionomer bond strengths to untreated dentin (1. 0-1.7) and to preconditioned dentin (2.1-3.3). The high bond strengths achieved with the resin cement are encouraging. Selected surface treatment of DICOR®, enamel, and dentin prior to luting should be clinically useful.
The Modified Model Cavity Method for Assessing Antibacterial Properties of Dental Restorative Materials
Authors: Meryon S.D. , Johnson S.G.
Published: November 2010

A new in vitro method for assessing the antibacterial properties of dental restorative materials is described with ratios of test material/ culture medium volume aiming to simulate conditions around a restoration in vivo. Antibacterial activity is determined by the reduction in optical density of the test culture relative to controls. The method was used for assessment of the antibacterial activity of five dental materials of different composition against five oral bacteria. Release of zinc and fluoride from these materials was also measured and correlated with antibacterial activity. There was a general trend toward greater antibacterial activity with increased zinc release, while fluoride release had a significant effect on only one organism. While all the materials, when freshly mixed, were strongly toxic to three out of the five bacteria studied, much of this activity was lost after the materials had set.
Changes in Plasma Epinephrine Concentration after Dental Infiltration Anesthesia with Different Doses of Epinephrine
Authors: Knoll-Kohler E. , Frie A. , Becker J. , Ohlendorf D.
Published: November 2010

To define the cardiovascular risk as a result of epinephrine in local anesthetic solutions used in dental anesthesia, we measured the plasma epinephrine levels, the mean arterial brachial pressure (MAP), and heart rate for 15 min, after infiltration anesthesia in the area buccal to the upper permanent left lateral incisor and canine. For this purpose, 12 dental student volunteers received 2.0 mL 2% lidocaine with and without 20 or 80 μg epinephrine, in a double-blind cross-over trial.

- Plain lidocaine solution caused no significant changes in the parameters under study when compared with the baseline values.

- Lidocaine with 20 μg epinephrine caused a sustained doubling of the plasma epinephrine concentration two min after injection, and at the same time, a slight but significant (p<0.05) decrease in MAP. Two min and 45 s after injection, the heart rate increased by four beats/min when compared with the baseline rate.

- Lidocaine with 80 μg epinephrine caused a doubling of the basal plasma epinephrine value as early as one min and 25 s after injection, and a ten-fold increase above the basal value at the end of the observation period (15 min). The heart rate increased significantly (p<0.01) by five beats/min above the baseline value starting two min after injection, and rose to a maximum of 13 beats/min until the end of the observation period. The time-point of the decrease in MAP was earlier, but the amount of the decrease equaled that measured after submucosal injection of 20 μg epinephrine with 40 mg lidocaine.
Maxillary Arch Dimensions after Palatal Surgery at Different Ages on Beagle Dogs
Authors: Wijdeveld M.G.M.M. , Grupping E.M. , Kuijpers-Jagtman A.M. , Maltha J.C.
Published: November 2010

Changes of maxillary arch dimensions were studied longitudinally until maturity, after palatal surgery was performed on 37 beagle dogs at different ages. The dogs were divided into three experimental groups, a sham group, and a control group. At the age of 6, 16, or 25 weeks in the experimental groups, we created a soft-tissue cleft in the medial region of the palate, made relaxation incisions, and elevated and closed the mucoperiosteum in the midline, thus leaving two areas of denuded bone adjacent to the dentition. We made dental casts regularly until the age of 37 weeks, and studied maxillary arch dimensions.

Surgery performed before or during the transition of teeth did not change maxillary arch dimensions in the deciduous dentition, but after the transition, the increase in arch width in the pre-molar region was reduced. Surgery performed after completion of the permanent dentition did not change maxillary arch dimensions. Delay of palatal surgery until the transition of teeth was completed favored normal development of the maxillary dental arch.
Iron Concentration in Teeth of Tetra-odontiform Fishes and its Phylogenetic Significance
Authors: Suga S. , Wada K. , Taki Y. , Ogawa M.
Published: November 2010

It is known that iron is deposited in the enameloid of some teleost fishes, although its biological significance has not been clarified. In the present investigation, a quantitative analysis of iron in the enameloid of fishes of a primitive suborder, the Balistoidei, and an advanced suborder, the Tetra-odontoidei, of the Tetra-odontiformes of marine teleosts was performed by means of the electron microprobe. The results indicated that the enameloid of Balistoidei contained from 0.4-13.5% iron at its surface layer, whereas that of Tetra-odontoidei was very low in iron, which could not be discriminated from the background value of the emission intensity. The enameloid of three perciform species belonging to the Acanthuridae-from which the Tetra-odontiformes are considered to have been derived-also contained high iron (2. 7 - 3.9%) throughout its entire layer. The iron concentration in the enameloid seemed to be related to the phylogeny of fishes rather than to their environmental water and feeding habits, and it is believed that the mechanisms of iron concentration into the developing enameloid have been lost during evolution from the Achanthuridae to the Tetra-odontoidei. Since a similar phenomenon has been previously observed with respect to the fluoride concentration in the enameloid of the same fishes (Suga et al., 1981a), it is speculated that the concentrations of iron and fluoride, which have originally no chemical correlation, have some special biological significance, although the timing and distribution pattern of their deposition are completely different.
A Microbiological Study of Early Caries of Approximal Surfaces in Schoolchildren
Authors: Marsh P.D. , Featherstone A. , McKee A.S. , Hallsworth A.S. , Robinson C. , Weatherell J.A. , Newman H.N. , Pitter A.F.V.
Published: November 2010

A cross-sectional epidemiological study has been undertaken to relate the bacterial composition of approximal dental plaque with the earliest stages of caries development in schoolchildren. Small samples of plaque were removed from multiple sites around the contact areas of 42 premolars extracted for orthodontic reasons from 29 schoolchildren (mean age = 13.5 yr). Caries diagnosis was based on polarized light microscopy and contact microradiography of thin sections cut through the sample sites. Fifty-seven percent of sites (37l60) showed histological evidence of demineralization. Both the isolation frequency and the mean percentage viable count of mutans streptococci and Actinomyces viscosus were higher at sites with early caries, although mutans streptococci could not be detected at 37% of sites with early caries. At these latter sites, the proportions of Veillonella were markedly reduced. Lactobacilli were rarely isolated and were never recovered from caries-free surfaces. Analysis of the data shows that the relationship between plaque bacteria and enamel is neither merely passive nor indifferent, and that particular stages of lesion formation may be associated with different combinations of bacteria.
Oral Gram-negative Bacilli in Bone Marrow Transplant Patients Given Chlorhexidine Rinses
Authors: Brown A.T. , Sims R.E. , Raybould T.P. , Lillich T.T. , Henslee P.J. , Ferretti G.A.
Published: November 2010

Fifteen bone marrow transplant (BMT) patients who received three 0.12% chlorhexidine digluconate (CHX) mouthrinses daily for eight weeks were monitored weekly for the occurrence of oral opportunistic Gram-negative bacilli (GNB). Tongue and buccal mucosa were sampled with use of Culturette swabs that were streaked on plates containing selective MacConkey agar. After incubation, colony-forming units were scored and putative GNB classified with use of the API 20E rapid identification system and supplemental biochemical tests. After identification, the susceptibilities of all GNB to CHX were determined by means of a disk diffusion sensitivity assay. Sixty-seven percent (10) of the BMT subjects had at least one GNB-positive tongue culture, and 53% (8) had GNB in samples taken from the buccal mucosa. Of 218 samples taken, 26% and 24% from the tongue and buccal mucosa, respectively, were GNB-positive. The predominant clinical GNB isolates were Enterobacter cloacae (46%) and Klebsiella pneumoniac (30%). Their respective CHX minimum inhibitory concentrations (MICs) were similar to those of ATCC reference strains. Although the CHX MIC values of the clinical GNB isolates were high (≤37.5 to ≤300 μg/mL), they were not dependent upon length of exposure to the agent. Therefore, changes in sensitivity or resistance to CHX did not appear to occur. The results suggest that the mouths of BMT patients - and perhaps of other immunosuppressed individuals - should be routinely monitored for GNB, as are other clinically important sites, such as the throat and the urinary and gastro-intestinal tracts.
Rheological Properties of Elastomers during Setting
Authors: McCabe J.F. , Carrick T.E.
Published: November 2010

A controlled stress rheometer has been used to monitor the changes in rheological properties occurring in five elastomeric impression materials during setting. The rheometer differs from conventional rotary viscometers in that the torque is the controlled variable, and the resulting deformation is measured. The use of such an instrument in oscillatory mode enables a range of rheological parameters-including viscosity, rigidity, and elasticity-to be monitored during setting. The polyvinylsiloxane impression materials develop elasticity at a rate that would not be apparent from measurements of viscosity or rigidity alone. This highlights the potential danger of basing the evaluation of clinically important properties, such as working time, on simple measurements of viscosity or rigidity.
Effect of Visco-elastic Behavior on Stress Development in a Metal-Ceramic System
Authors: Dehoff P.H. , Anusavice K.J.
Published: November 2010

We developed an analytical model to calculate transient stress and gap displacement during cooling of a porcelainized semicircular arch with a gapped diametral segment. Constant cooling rates were assumed after the specimens were slowly cooled (with power terminated to the furnace) from the porcelain firing temperature. The analytical model incorporates linear visco-elasticity and structural relaxation effects.

We calculated transient and residual gap displacements and stresses for a semicircular arch specimen (composed of an experimental opaque porcelain and a Ni-Cr-Be alloy) for six thickness ratios at a cooling rate of 3°C/min. Residual gap displacements were measured for metal-porcelain arch specimens of six thickness ratios. Compared with measured values, calculations based on the visco-elastic theory overestimated gap closure for porcelain/metal thickness ratios below 1.5, and underestimated gap closure at thickness ratios above 1.5.
A Three-dimensional Evaluation of the Effects of Functional Occlusal Forces on the Morphology of Dental and Periodontal Tissues of the Rat Incisor
Authors: Steigman S. , Michaeli Y. , Yitzhaki M. , Weinreb M.
Published: November 2010

We examined the effect of function on tooth and periodontal ligament (PDL) morphology in 40 lower incisors of adult female rats. Ten teeth were exposed to occlusal hyperfunction for three months, ten to hypofunction for three weeks, ten to hypofunction for three months, while ten teeth in normal occlusion served as control. Transverse ground sections were cut at various levels perpendicular to the tooth long axis, and their distances from the apex were calculated. The outlines of the tissues were traced and fed into a computer. We plotted the measurements according to their location and fitted them by second-order polynomials. We calculated tissue volume for the proximal 18 mm of bone-embedded tooth.

Hyperfunction affected tooth shape, in that it became more rounded. The volumes of the dental tissues remained unchanged, while width and volume of the cementum-bordering PDL increased. Hypofunction did not alter tooth shape, but influenced its size: After three weeks, tooth circumference decreased, and after three months, it expanded. Dentin width was reduced, with concomitant increase of pulp size. The amount of enamel diminished initially, but after three months returned to normal values. The PDL bordering enamel expanded proportionally to the duration of hypofunction. The changes in socket size reflected the total dimensional variations in the tooth and its PDL. The results demonstrate that the shape and size of growing teeth and their periodontium are influenced by functional occlusal forces.
Depth and Area of Dental Erosions, and Dental Caries, in Bulimic Women
Authors: Jones R.R.H. , Cleaton-Jones P.
Published: November 2010

Dental caries and the severity (depth) and area of erosions of tooth substance were studied in 11 bulimic subjects and 22 matched controls. Erosions were seen in 69% of the bulimics' teeth and in only 7% of the controls' (p< 0.001). Depth of penetration was greater in the bulimics, extending even into the pulp, and the area of erosion was also larger. Scores for dental caries were higher in bulimics (mean DMFS 27.9, median 36) than in controls (mean DMFS 19.1, median 13.5), although the difference was not statistically significant. This study suggests that when erosions are present on the lingual surfaces of maxillary anterior teeth, as well as on the buccal surfaces of maxillary canines, premolars, and maxillary incisors, a diagnosis of bulimia is likely. Patients with these signs should be referred for medical help.
Adsorbed Salivary Acidic Proline-rich Proteins Contribute to the Adhesion of Streptococcus mutans JBP to Apatitic Surfaces
Authors: Gibbons R.J. , Hay D.I.
Published: November 2010

Experimental pellicles formed on hydroxyapatite (HA) beads from parotid or submandibular saliva promoted the adhesion of Streptococcus mutans JBP cells to a greater extent than did pellicles prepared from buffer; human plasma, or serum. The nature of the salivary components responsible was studied by the preparation of pellicles from fractions of parotid saliva obtained by chromatography on Trisacryl GF 2000 columns. Two groups of fractions promoted attachment of the organism. Components migrating in the high-molecular-weight mucin fraction were most effective, but a later-eluting fraction also possessed adhesion-promoting activity. Subfractionation of the latter material indicated that the adhesion-promoting activity was associated with the acidic proline-rich proteins (PRPs). Pellicles prepared from 10-20-μg/mL solutions of pure PRP-1 were effective in promoting attachment of S. mutans JBP cells. PRP-3 was less effective, while human salivary statherin, fibrinogen, fibronectin, type 1 collagen, and the amino-terminal tryptic peptide derived from PRP-1 were ineffective. The quantities of 150-residue and 106-residue PRPs and of statherin, which became incorporated into experimental pellicles prepared from saliva, were estimated with use of radiolabeled protein tracers. The data obtained suggest that these proteins compete for similar binding sites on HA, and that their ratios in saliva would therefore influence the quantity of the larger PRPs that become incorporated into the pellicle. Such competition may contribute to the variability observed in the adhesion-promoting activities of different saliva samples.
Substitutes for N-Phenylglycine in Adhesive Bonding to Dentin
Authors: Johnston A.D. , Asmussen E. , Bowen R.L.
Published: November 2010

Using bond strength measurements, we investigated a number of related compounds in order to elucidate the role of the surface-active ingredient, N-phenylglycine (NPG), in experimental two-step and three-step bonding protocols resulting in adhesive bonding to dentin. All active compounds identified for the two-step or the three-step protocol were N-aryl-α-amino acids, and the results delineate some of the key features of the NPG molecule for bonding. For the three-step protocol, there was a requirement for a secondary or tertiary aromatic amino group, a carboxylic acid group, and a single (secondary or tertiary) methylene unit between those two functional groups of the amino acid. For the two-step protocol, additional substitutions at the para position of the phenyl ring on the amine improved the bond strength. In both protocols, para-methyl- and para-chloro-substituted NPG analogues ranked higher than NPG. A "catalytic" effect of the aromatic tertiary amino group on the polymerization of the adhering resin in both procedures could not be ruled out.
Role of Parotid Amylase in Starch Digestion in the Gastro-intestinal Tracts of Diabetic Rats
Authors: Kurahashi M. , Inomata K.
Published: November 2010

In order for the role of parotid amylase in starch digestion in the gastro-intestinal tracts of diabetic rats to be clarified, this study investigated the effect of parotid-duct ligation on both amylase secretion from the parotid glands and pancreas into the gastro-intestinal tract and on starch digestion in the gastro-intestinal contents during feeding. In both diabetic rats and control rats, parotid-duct ligation reduced amylase activity in both the parotid glands during fasting and in the gastric contents after feeding. The amylase activity in the intestinal contents after feeding was reduced by parotid-duct ligation in the diabetic rats. Starch digestion in the gastro-intestinal tract after feeding was reduced by parotid-duct ligation in the diabetic rats. The results suggest that most of the amylase activity in the gastric contents and a large part of the amylase activity in the intestinal contents are derived from the parotid glands, and that parotid amylase plays an important role in starch digestion in the gastro-intestinal tracts of diabetic rats.
Transglutaminase Expression in Rat Parotid Gland after Isoproterenol Stimulation
Authors: Cocuzzi E. , Kim H.C. , Beninati S. , Hand A.R. , Chung S.I.
Published: November 2010

Transglutaminases (E.C. 2.3.2.13) are calcium-dependent enzymes that catalyze the covalent cross-linking of proteins, and occur in multiple molecular forms in a variety of tissues. Distribution of each form of transglutaminase varies with different tissues. Studies were undertaken to characterize the form of transglutaminase expressed in rat parotid gland, and to examine a possible physiological role for the enzyme. It was found that chronic treatment of rats with the β-adrenergic agonist isoproterenol (IPR) resulted in the induction of parotid transglutaminase activity. The properties of this transglutaminase appeared to be distinct from those of the well-characterized guinea pig liver cytosol transglutaminase (TGase C). The findings that protein polymerization (observed on SDS-PAGE) and incorporation of radioactive putrescine, a polyamine, into protein occur in the presence of exogenous transglutaminase and calcium indicated that certain rat parotid salivary proteins are or could be substrates for this enzyme. Analysis of proteolytic digests of rat parotid salivary proteins on an amino acid analyzer and by high-performance liquid chromatography also indicated that these salivary proteins contain γ-glutamyl derivatives of primary amines (e.g., polyamines or lysine), post-translational products of transglutaminase catalysis. The possible physiological function of this enzyme in the oral cavity might be stabilization of proteinaceous structures during normal oral homeostasis and/or wound-healing.
Estimation of the Velocity of the Salivary Film at Some Different Locations in the Mouth
Authors: Dawes C. , Watanabe S. , Biglow-Lecomte P. , Dibdin G.H.
Published: November 2010

Previously, we studied the clearance rates of KCI from agarose gels positioned at different locations in the mouth, and showed that the rates were much slower than when clearance was into a well-stirred solution. We designed the present in vitro study to test the effect on KCI clearance of the velocity of a 0.1-mm-thick film of water flowing over an agarose gel of the same diameter and composition as those used in vivo. The thickness of the salivary film overlying dental plaque has been estimated to be about 0.1 mm, and we assumed that when clearance rates in vitro matched those found in vivo, velocities of the fluid film (in vitro) and the salivary film (in vivo) must be equal. On this basis, it was calculated in the present experiments that when salivary flow was unstimulated, the velocity of the salivary film at the level of the teeth varied between about 0.8 mm/min (upper-anterior buccal region) and 8.0 mm/min (lower-anterior lingual region). When salivary flow was stimulated, this was estimated to increase the velocity of the salivary film from 2 to 40 times, depending on the location in the mouth. It is postulated that the slow movement of the salivary film when flow is unstimulated allows for accumulation of diffusants from dental plaque, which reduces the concentration gradient for diffusion from plaque and prolongs the clearance time of such metabolic products as acid.
An Analysis of Factors Influencing Diffusion from Dental Plaque into a Moving Film of Saliva and the Implications for Caries
Authors: Dawes C.
Published: November 2010

Recent studies have indicated that saliva in the mouth is present as a film only about 0.1 mm thick, and that this film moves at different rates (about 0.8 to 7.6 mm/min) in different regions of the oral cavity. The clearance rates of KCI, as a model diffusant, from agarose gels at different sites in the mouth have also been found to vary markedly, and it has been proposed that these variations are related to differences in the velocity of the salivary film.

A computer model has been developed for prediction of clearance half-times for substances diffusing from plaque of variable dimensions into a film of fluid 0.1 mm thick, moving at different velocities. The results show that over the range of velocities calculated to occur in the mouth, the clearance half-times are directly related to the length of plaque over which the fluid passes, and inversely related to the salivary film velocity. The predictions of the model are in good agreement with experimental results from a physical model. Tests were made of the predicted effect of salivary film velocity on the shape of the pH curve initiated by exposure of plaque to a saturated sucrose solution, followed by normal salivary clearance. With a low salivary film velocity, the fall in pH was greater and more prolonged. These results are relevant to the site-specificity of caries, since they imply that, given two plaque samples of identical area, depth, and microbial composition, the sample located in a region of the mouth where the salivary film velocity is lower will show a more extensive and prolonged pH fall after exposure to fermentable carbohydrate.
Scanning Electron Microscopic Characterization of Sensitive vs. Insensitive Human Radicular Dentin
Authors: Yoshiyama M. , Masada J. , Uchida A. , Ishida H.
Published: November 2010

Our aim was to investigate the structural changes of dentinal tubules in specimens obtained from both hypersensitive and naturally desensitized areas in wedge-shaped defects on the same exposed cervical dentin surface of a hypersensitive tooth. A new biopsy technique that makes use of a hollow, cylindrical diamond bur was designed so that specimens from exposed root dentin of vital teeth could be obtained. Twenty-two dentin biopsy pairs were divided into two groups; one was prepared for scanning electron microscopy (SEM) and the other for microradiography (MR). Small hypersensitive areas were identified by a scratch test on exposed human dentin in vivo. SEM observation of the dentin biopsies showed that the orifices of many dentinal tubules in hypersensitive areas were open and that membranous structures appeared on the walls of dentinal tubules. In naturally desensitized areas on the same dentin surface, most of the dentinal tubules were obturated with rhombohedral crystals of all sizes; membranous structures were not observed in these tubules. These results showed that hypersensitivity occurred on the exposed dentin when most of the tubular orifices were open.
Differences in the Rate of Molar Wear between Monkeys Raised on Different Diets
Authors: Teaford M.F. , Oyen O.J.
Published: November 2010

The purpose of this study was to make detailed comparisons of rates and patterns of tooth wear in 15 growing vervet monkeys raised on hard vs. soft diets. Dental impressions were taken every six to eight weeks over a four-year period. Cusp heights and areas of dentin exposure on the buccal cusps of the left mandibular first molar were measured from high-resolution epoxy casts, by use of a Reflex Measuring Microscope. Areas of dentin exposure were regressed against time (by use of least-squares regression) so that the course of tooth wear in animals from both diet groups could be charted. By use of a two-sample t test and the Mann-Whitney test, slopes of the regressions and changes in cusp height were compared between diet groups. In both comparisons, animals raised on the hard diet showed more rapid tooth wear than did animals raised on the soft diet. Analyses of other parameters indicate that this was probably because of differences in dietary consistency between the two groups.
Dental Casting of Titanium and Ni-Ti Alloys by a New Casting Machine
Authors: Hamanaka H. , Doi H. , Yoneyama T. , Okuno O.
Published: November 2010

The purpose of this study was to develop a new casting machine for titanium and Ni-Ti alloys. Properties of cast pure titanium and Ni-Ti alloys were studied by means of the tensile and casting tests. As gas in the mold was removed by the mold being heated under a high vacuum, the reaction between the molten metal and the mold decreased. The new control system and the two types of crucibles developed proved very useful for prevention of internal macro-defects in castings and for improvement of castability. Mechanical properties and castability of pure titanium were improved. Ni- Ti alloys could be cast without loss of their shape-memory effect or super-elasticity characteristics. The new casting machine is thought to be promising for the casting of titanium and Ni-Ti alloys. Furthermore, we can cast these alloys using conventional techniques and investments.
The Microflora Associated with the Development of Initial Enamel Decalcification below Orthodontic Bands in vivo in Children Living in a Fluoridated-water Area
Authors: Boyar R.M. , Thylstrup A. , Holmen L. , Bowden G.H.
Published: November 2010

Thirty-four caries-free teeth destined for orthodontic extraction were banded to provide a protected area for the accumulation of plaque. The teeth were extracted at one, two, four, eight, and 14 days after being banded, and samples of the flora below the band were analyzed for the presence of Streptococcus sanguis, Streptococcus 'mitior', 'mutans streptococci', Actinomyces viscosus, Actinomyces naeslundii, Actinomyces odontolyticus, Lactobacillus species, and Veillonella. After plaque sampling, the teeth were sent to the Royal Dental College (Copenhagen) for histological analysis. The results showed that S. mutans could colonize the area below the band after one day, but that colonization was only 100% at 14 days. Lactobacillus was only isolated from 2/8 samples at four days and from 4/8 samples at 14 days. S. sanguis and 'S. mitior' were regularly isolated at all banding times, and Veillonella was isolated from all samples. A. viscosus was the most commonly isolated Actinomyces. The numbers of Streptococcus and Veillonella were significantly higher at day 1 than at day 14 (p < 0.05). S. mutans and A. viscosus were isolated more frequently at day 14 than at day 1 (p < 0.01). Histological examination revealed that dissolution of the enamel below a band could occur after two days, but that even after 14 days dissolution could be questionable. Dissolution was detected in areas where S. mutans was not isolated (8/34), but S. mutans was also present in samples showing dissolution (12/34). There was no relationship between dissolution and the numbers of S. mutans; however, the isolation frequency of S. mutans was associated with dissolution (p < 0.05). The results also suggested that there were subject-associated factors that influenced the composition of the bacterial community, as evidenced by Lactobacillus being isolated from all samples from one subject after 14 days, while the other subject was negative for Lactobacillus.
Performance Assessment of Colorimetric Devices on Dental Porcelains
Authors: Seghi R.R. , Johnston W.M. , O'Brien W.J.
Published: November 2010

The selection of an appropriate material that duplicates the appearance of natural tooth structure is very important in restorative dentistry. Photometric and colorimetric analysis techniques offer great potential as a tool for aiding in the duplication process. The degree to which these techniques will be useful depends on the accuracy and precision with which they can be applied to translucent as well as opaque surfaces. The purpose of this investigation was to evaluate the performance of three currently-available photometric devices.

The performance capabilities of the instruments were tested on various shades of opaque and translucent dental porcelain surfaces. The performance tests were designed for evaluation of the accuracy and precision of the instrument relative to a well-studied reference instrument. CIELAB color difference metrics were used for the performance analysis.

The results revealed that each of the photometric instruments evaluated was capable of producing color measurements with precision. However, the degree of accuracy with which the color measurements were made varied depending on the instrument used and the type of material surface being measured. A photo-electric tristimulus colorimeter showed the best overall performance on the porcelain surfaces, supporting its use as a valuable tool for evaluating color in dentistry.
Visual and Instrumental Colorimetric Assessments of Small Color Differences on Translucent Dental Porcelain
Authors: Seghi R.R. , Hewlett E.R. , Kim J.
Published: November 2010

The CIELAB colorimetric system was used for the study of the relationship between measured color difference values and human observer responses. This study verified that a specific, visually meaningful and precise relationship exists between the magnitude and direction of the measurements and the average dental-observer responses. The results support the use of this system in dentistry as a means of evaluating color by differences. The further development of such systems for clinical use would be warranted and could serve as a valuable tool for material selection and restoration design, particularly in the area of aesthetic restorative dentistry.
Cohort Effects in the Prevalence of Caries in Child Populations in Tanzania
Authors: Frencken J.E. , Van't Hof M.A. , Truin G.-J. , Lembariti B.S. , König K.G.
Published: November 2010

In 1984, a four-year mixed-longitudinal study of oral health was begun in Morogoro Town and Morogoro District, Tanzania. Its main goal was to detect a possible upward trend in prevalence of caries in child cohorts in this developing country. The sample consisted of 722 seven-to nine-year-olds in 1984, 833 seven- to 11-year-olds in 1986, and 989 seven- to 13-year-olds in 1988. Mixed-longitudinal studies provide the opportunity for application of the Age-Period-Cohort analysis. On the basis of external information, either age and/or cohort and/or period effects can thus be isolated. Apart from significant age and period effects, a cohort effect was found, indicating that the prevalence of caries has decreased in these child populations between 1984 and 1988.
Continuous Stressing of Mouse Interparietal Suture Fibroblasts in vitro
Authors: Yen E.H.K. , Pollit D.J. , Whyte W.A. , Suga D.M.
Published: November 2010

The morphological and biochemical response of sutural fibroblasts in vitro to continuous force was examined. Cells from mouse interparietal sutures were grown and subcultured on glass slides. Titanium disks coated with collagen were allowed to attach to the cellular multilayers. Four of the glass slides were then placed at an angle of 75° for a period of three days so that continuous stress would be created, while four others were left flat. Also, four glass slides were left flat with no disk. Following the incubation period, the dishes were labeled with 14C-glycine for 15 h. The cells and medium were then collected for collagen extraction followed by SDS-polyacrylamide gel electrophoresis. Dried gels impregnated with fluor were exposed to x-ray films that were then scanned densitometrically for collagen types I and III. It was found that the proportion of newly-synthesized type III collagen increased significantly with the application of continuous stress. A second set of experimental and control glass slides was fixed in glutaraldehyde and post-fixed in osmium tetroxide. Following critical-point drying and coating, the glass slides were examined under a scanning electron microscope. The scanning images showed the formation of a ligament-like structure between the disk and the glass slide. Moreover, mitotic activity, as evidenced by spheroidal cells, was stimulated in the areas previously adjacent to the disc, which had since moved away. This system offers a standardized continuous force system that can stress cells in a ligament-like structure and thus provides an in vitro model analogous to clinical orthodontic and orthopedic stress.