bluuebunny/crossref_metadata_2025 huggingface dataset:
A Physicochemical Bench-scale Caries Model
Authors: Chow L.C. , Brown W.E.
Published: November 2010

A diffusion cell comprising two compartments separated by a commercial membrane of known ion permselectivity was used as an experimental model to study factors which may affect caries formation. One compartment (the "lesion") contained an excess of hydroxyapatite or fluorapatite crystals, and its solution was kept near saturation by stirring. An unsaturated acidic calcium phosphate solution flowed continuously through the other compartment (the "plaque-saliva"), thus providing the driving force for dissolution of the crystals as modified by the permeability of the membrane and/or the presence of fluoride. Calcium, phosphate, fluoride, and chloride concentrations, pH, and membrane potential were measured at steady state.

The permselective character of the membrane profoundly affected the solution in the "lesion": The initial Ca/P ratio of 1.6 was shifted, at steady state, to less than 1.1 ("neutral" membrane), to less than 0.48 (cation-permselective membrane), and to 3.3 (anion-permselective membrane). All the membranes caused Ca and PO4 concentrations in the "lesion" to increase (e.g., with the cation-permselective membrane, the Ca 22-fold and the PO4 75-fold). Substantial membrane potentials were encountered in all cases. The pH of the steady-state solution was always less than before diffusion was initiated; the average decrease was 1.1 units. In every case, the pH, and the Ca and PO4 concentrations of the F--containing solution were less than those in the F--free solution. The changes induced by the "neutral" membrane were unexpectedly large. In two cases, H3PO4 was diffusing against its chemical potential gradient at steady state. The results are relevant for understanding and for modeling of the caries process.
Preparation of Hydroxyapatite Crystals and Their Behavior as Seeds for Crystal Growth
Authors: Aoba T. , Moreno E.C.
Published: November 2010

Samples of crystalline hydroxyapatite [Ca5OH(PO4)3 HA] were prepared by precipitation from aqueous media under a variety of experimental conditions (temperature, concentration of reagents, rates of addition of the reagents, and seeding). The resultant products showed a wide range of particle sizes, i.e., specific surface areas, from 6.39 to 50.1 m2/g. In these preparations, relatively large crystals were obtained with low rates of addition of the reagents or by seeding the precipitating medium. Small differences in supersaturation of the reaction medium can markedly affect the particle sizes and crystalline habits of the resulting products, possibly by altering the processes of nucleation and subsequent crystal growth. When these crystalline materials were used as seeds to study the crystal growth of HA, it was confirmed that the precipitation rate of calcium apatite on seed crystals is highly dependent on the surface areas available for growth, rather than on the particle sizes and amounts of the seed crystals. Small differences in the kinetic runs were observed between the various seed crystals, which can be attributed to differences in the surface properties of these crystals. Additionally, transmission electron microscopy of the seed crystals revealed that some projections form, possibly on the basal planes of the crystals, during crystal growth. Since the growth rate of these projections was greater than the mean growth rate calculated on the basis of changes in solution composition and total surface area, it appears that the kinetics of the growth process is determined, to some extent, by the geometry of the seeds.
An Analysis of the Release and the Diffusion Through Dentin of Eugenol from Zinc Oxide-Eugenol Mixtures
Authors: Hume W.R.
Published: November 2010

Tritium-labeled eugenol was released from mixtures of zinc oxide eugenol (ZOE) into aqueous solution at rates which declined exponentially with time, and which were directly proportional to the liquid-powder ratio. The release pattern was consistent with a model of progressive hydrolysis of zinc eugenolate in a limited-thickness ZOE surface layer. Intervening dentin had a profound effect on this pattern of release. In human teeth in vitro containing ZOE as a base or temporary filling, peak eugenol release at the pulpal surface of dentin was of the order of a thousand-fold less than that at the salivary surface. In such teeth, eugenol reached concentrations in excess of 10-2 M in dentin just beneath ZOE, and 10-4 M or less adjacent to the pulp space. Both pulpal outflow and dentin concentrations of eugenol remained relatively constant for more than a week, unlike release into aqueous solution. While these data were derived from studies on human teeth in vitro, they give a strong indication of probable events in vivo, and appear to provide a basis for the explanation of the paradox of the therapeutic and toxic actions of ZOE.
Inhibitory Effect of Inositol Phosphates on Parathyroid Hormone-induced Bone Resorption in Organ Cultures
Authors: Gomes B.C. , Kaufman H.W. , Bloom J.R. , Navon J. , Wilkens T.J. , Rifkin R.A.
Published: November 2010

This study investigates the ability of phytic acid, its inositol phosphate derivatives (inositol penta-, tetra-, tri-, di-, and monophosphate), and inorganic phosphate to inhibit parathyroid hormone (PTH)-induced resorption of fetal rat long bones in organ culture. Pregnant rats injected with 45Ca on the 18th day of gestation were killed the next day and their fetuses removed. Half of each pair of dissected long bones was incubated in a chemically defined control medium, while the contralateral half was incubated in medium containing PTH or PTH plus the phosphate compound to be tested. 45Ca released into the medium was indicative of the amount of bone resorption. All phosphate compounds tested inhibited resorption. The inositol phosphates should be studied further to assess their suitability as therapeutic agents for treatment of metabolic bone diseases involving increased turnover.
In vivo and in vitro Wear of Potential Posterior Composites
Authors: Lutz F. , Phillips R.W. , Roulet J.F. , Setcos J.C.
Published: November 2010

The influence of cavity size, material composition, and curing mechanism on wear resistance of Class II MOD resin restorations was analyzed quantitatively. Wear resistance tends to increase both as cavity size decreases, and also from chemical- to light- to heat-cured. As to wear, among the composite resins tested, there was no acceptable resin-based amalgam substitute.
Materials Science Microprobe Analysis of Three High-copper Amalgams
Authors: Mahler D.B. , Adey J.D.
Published: November 2010

Three single-composition, high-copper amalgams were analyzed for the composition of their before- and after-reaction phases. The method used was electron probe microanalysis. The results may be summarized as follows:

(1) All alloys consist essentially of Ag3Sn (γ), Cu3Sn (∈), and, in some cases, Ag4Sn (β).

(2) When the original alloy contains higher amounts of Cu, more Cu is found in solution in the Ag3Sn (γ) and Ag4Sn (β) phases.

(3) The reaction phases in amalgams made from these alloys consist essentially of Ag22Sn Hg27(γ1) and Cu6Sn5 (η'), with no detectable Sn 8Hg (γ2).

alloys.

(4) When In is present, it is found principally in the Ag3Sn (γ) and Ag22Sn Hg 27(γ1) phases, and both the γ and γ1 phases are of different composition than that for the other

(5) When Pd is present, it is found principally in the Cu3Sn (e), Cu6Sn 5 (η'), and Ag22Sn Hg27(γ1) phases.
Tarnishing and Structures of Some Annealed Dental Low-gold Alloys
Authors: Herø H.
Published: November 2010

Tarnishing of low-gold alloys in a Tuccillo-Nielsen test with 2% Na2S is avoided when a single-phase structure is present as compared with multi-phase structures, unless the Ag content of the single-phased alloy is high. In all multi-phase structures, only the Ag-rich phase is attacked. The possibility of annealing alloys to a single-phase structure decreases with the reduction of Au content and with increasing amounts of Pd and Zn, which tend to follow the Cu-rich phase. In static polarization testing of single-phase materials in weak sulphide solutions, the Ag-rich alloys display considerably higher anodic current densities (5-10 μA/cm 2) than do the Cu-rich low-gold and high-gold alloys (1 μA/cm 2). No significant differences between the alloys were observed with respect to cathodic currents.
Wear Behavior of a Composite Restorative and Various Styli in Sliding Contact
Authors: Rice S.L. , Bailey W.F. , Roto M. , Wayne S.F.
Published: November 2010

Using a pin-on-disc sliding-wear test apparatus, the wear behavior of a typical composite restorative vs. styli fashioned from human enamel, sintered alumina, and magnesium fluoride was examined. The rates of restorative wear were found to be identical, within the experimental error of the measurements, for tests using either human enamel pins or styli fabricated from sintered alumina. Moreover, these two pin materials generated morphologically similar wear-tracks in the restorative disc. Thus, styli of sintered alumina produce restorative wear that is both qualitatively and quantitatively analogous to that observed in tests using human enamel pins.
Materials Science Acceleration of Corrosion of Dental Amalgam by Abrasion
Authors: Marek M.
Published: November 2010

Dental amalgam shows passive behavior, but the protective film can be destroyed by abrasion. In this study, specimens of both low- and high-copper amalgam were abraded, and the effect on the corrosion behavior was examined. The electrochemical measurements showed that the corrosion rate was substantially increased, and that re-passivation was relatively slow.
Tarnish and Corrosion of a Commercial Dental Ag-Pd-Cu-Au Casting Alloy
Authors: Niemi L. , Holland R.I.
Published: November 2010

The correlation between microstructure, tarnish, and corrosion behavior of a commercial dental Ag-Pd-Cu-Au casting alloy after various heat treatments was studied. The attacked structural components were identified by comparing SEM micrographs with light optical micrographs taken after exposure of the alloy to a 2% Na2S solution and after dynamic polarization in de-aerated artificial saliva. The characteristic dynamic polarization curves for the alloy after the heat treatments were established. The results were verified by analogous testing of two experimental alloys with compositions similar to those of the analyzed components in the commercial alloy annealed at 600°C for seven wk.

The matrix of the commercial alloy was decomposed, according to the heat treatments, into varying proportions of a tarnish- and corrosion-resistant Cu- and Pd-rich component (A) and a non-resistant Ag-rich component (B). The presence of A considerably increased the tarnish rate of B, due to galvanic coupling. Age-hardening of the alloy increased the proportion of the tarnish- and corrosion-prone component B.
Nerve Regeneration Through Collagen Tubes
Authors: Colin W. , Donoff R.B.
Published: November 2010

Severe nerve injuries may require microsurgical grafting to span a defect. Introduction of graft material into a highly vascular recipient bed is documented to aid in early regeneration of neuronal blood supply.

A silicone rod (SR)-induced fibrovascular sheath was employed to evaluate the regeneration of rat tibial nerve through 2-mmdiameter collagen tubes (CT) or contralateral nerve autografts (AUTO). At first operation, 5 mm of right tibial nerve was resected from 30 retired male breeder Sprague-Dawley rats. Resected nerve was replaced with either a 5 x 2 mm SR or the nerve ends were sutured to the intermuscular fascia.

Four weeks later, animals were repaired by replacing the SR with either a CT or a contralateral AUTO from the left tibial nerve. Three months later, EMG testing was performed, and histologic sections were prepared.

The EMG latency and the size of the compound action potential for sheathed or non-sheathed CT or AUTO were statistically superior to controls at the 95% confidence level. All other intergroup comparisons of latency and action potential size were statistically insignificant. The proportion of nerve fibers traversing the surgical sites was not influenced by the method of repair or by the presence or absence of sheathing. Tubulized repairs most closely resembled unoperated nerves, and autografted repairs had a large diameter, but much fibrosis, whereas controls displayed immaturity and disorganization.

Our observations suggest that there was no difference between repairs performed with or without a vascular pseudosheath. However, CT supported regeneration better than did AUTO repair.
Basic Biological Sciences Augmentation of Rat Mandibular Ridge with Demineralized Bone Implants
Authors: Kaban L.B. , Glowacki J.
Published: November 2010

Demineralized bone implants were placed as onlays in submucosal pockets on the edentulous segment of the rat mandible, between the incisor and posterior teeth. These implants, predictably, induced osteogenesis. The mass of induced bone and implant was united to the ridge by two weeks, and there was little or no resorption over a six-month follow-up period. This study suggests that demineralized bone implants may be useful for mandibular ridge augmentation.
Basic Biological Sciences Effect of Substance P on Exocrine Secretion by Rat Submandibular Gland Cells
Authors: Fleming N. , Bilan P.T. , Graham K.W.
Published: November 2010

The effects of the undecapeptide, substance P(SP), on the secretion of mucin and proteolytic enzymes from dispersed cells of the rat submandibular gland were studied. The peptide, at a concentration of 1 x 10-7 M, stimulated the release of 31.9 ± 3.0% (mean ± SEM) of intracellular mucin over 40 min, compared with 12.5 ± 1.5% in untreated controls (p<0.01). This effect was duplicated by the homologous peptides, physalaemin, and eledoisin-related peptide. Substance P action was not affected by pre-incubation of cells with phentolamine or propranolol and was therefore independent of adrenergic stimulation. Furthermore, SP did not enhance the intracellular concentrations of cyclic AMP or cyclic GMP, confirming that cyclic nucleotides were not involved in its stimulus-secretion coupling mechanism.

The isoproterenol-stimulated secretion of mucin from dispersed cells was reduced to 75.7% of the normal response (p<0.01) after a brief exposure to SP. This inhibitory effect was probably mediated by intracellular events rather than by direct effects on cell surface receptors. However, mucin release after treatment with SP followed by norepinephrine (NE) was 161% of that caused by NE alone (p<0.01) and may reflect an additive response to the independent stimulation of SP and NE receptors. Substance P and related peptides had no effect on arginine esterase secretion in the experimental model, although a response was elicited by α- and β-adrenergic agonists. It is, therefore, proposed that serous cells of the granular convoluted tubule in the rat submandibular gland lack substance P receptors.
The Ureolytic Microflora of Immature Dental Plaque Before and After Rinsing with a Urea-based Mineralizing Solution
Authors: Gallagher I.H.C. , Pearce E.I.F. , Hancock E.M.
Published: November 2010

Ureolytic bacteria were detected in the plaque flora of six subjects, and included members of the genera Actinomyces, Bifidobacterium, Staphylococcus, and Streptococcus. Proportions of these organisms did not change after subjects mouthrinsed thrice daily for four days with a plaque-mineralizing solution which contained urea and monofluorophosphate. The effectiveness of this rinse depends on the rapid metabolism of urea to alkali by plaque organisms, causing fluoridated apatite to precipitate in the matrix. Analysis of our data suggests that a numerically minor component of the flora, with a high turnover rate, is responsible for most of the ureolysis and the subsequent mineral precipitation.
A Comparison of the Tensile Bond Strengths of Composite Resins to Longitudinal and Transverse Sections of Enamel Prisms in Human Teeth
Authors: Munechika T. , Suzuki K. , Nishiyama M. , Ohashi M. , Horie K.
Published: November 2010

The tensile bond strengths of composite resins to transverse and longitudinal sections of enamel prisms etched with phosphoric acid were examined. The tensile bond strengths were 18-19 MPa to the transverse and 10-11 MPa to the longitudinal sections and thus were influenced by the nature of the enamel crystal planes. These facts suggest that composite resin restorations will have a longer life span if the enamel walls are given marginal forms to produce transverse rather than longitudinal sections of enamel prisms.
Incisional Biopsy and Seeding in Hamster Cheek Pouch Carcinoma
Authors: Safour I.M. , Wood N.K. , Tsiklakis K. , Doemling D.B. , Joseph G.
Published: November 2010

Surgical blades were contaminated by doing incisional biopsies on DMBA-induced cheek pouch carcinomas in hamsters. Contaminated blades were then used to: (1) make cytologic smears; (2) make incisions in the mucosal surface of the lower lip; (3) make incisions in the ventral surface of the tongue; (4) make incisions in the untreated left cheek pouch; and (5) make incisions in the pre-shaved back. One group of animals was killed three hr post-surgery. The second group was killed seven wk post-surgery. Tissues were excised and processed for microscopic study. Malignant cells were found in many of the incision sites of animals from the first group. In the animals of the second group, several tumors growing from the transplanted tumor cells were observed in the incision sites of the lower lips and the tongue. None was observed in the incision sites of the left cheek pouch or the back. Cervical lymph node metastases were found in approximately 50% of the animals of the second group.
Anti-bacterial Determinants of Stannous Fluoride
Authors: Camosci D.A. , Tinanoff N.
Published: November 2010

The growth of bacteria on stainless steel wires was used as a model to investigate which properties of SnF2 produced anti-bacterial effects against S. mutans. Wire-adherent bacteria were exposed for one min, twice a day, to various fluoride or control compounds having similar ions, pH, valence, or atomic weights. After two days, the thickness of adherent bacteria was scored visually, and the decrease in pH of the growth medium was determined. Bacteria from each wire were then dried, weighed, and analyzed for metal content. Electron microscopy and electron microprobe were used to identify the location of heavy metal deposits in the bacteria.

Only SnF2 dramatically altered S. mutans growth and metabolism, and this anti-bacterial effect was associated with a large uptake of tin into the bacterial cells. The fluoride salts of sodium, lead, zinc, and copper had little influence on S. mutans growth in this test system. The pH of the various fluoride salts or controls generally had no effect on the activity of the test compounds, except for the noted inactivation of SnF2 at elevated pH's. Since SnF4 did not alter the growth or metabolism of S. mutans, a unique property of SnF2 - possibly the reactivity in an aqueous environment - may be responsible for its anti-bacterial properties.
Clinical Science Whole-saliva Secretion Rates in Old and Young Healthy Subjects
Authors: Ben-Aryeh H. , Miron D. , Szargel R. , Gutman D.
Published: November 2010

Resting and stimulated whole-saliva secretion rates were compared in old and young healthy volunteers. The stimulated secretion rate was similar in both age groups, while the resting flow rate was significantly lower in the old females and males as compared with rates in the young.
Sustained Release Device Containing Metronidazole for Periodontal Use
Authors: Golomb G. , Friedman M. , Soskolne A. , Stabholz A. , Sela M.N.
Published: November 2010

The purpose of this study was to develop a sustained release device containing metronidazole for insertion within periodontal pockets and to examine the release kinetics in vitro and in vivo. Cast films of ethyl cellulose with or without polyethylene glycol, containing metronidazole, were prepared and exhibited sustained release. Release rate of metronidazole from the film was measured by means of a UV spectrophotometer, and kinetics of release in vitro was found to conform to Higuchi's diffusional model. The microbiological results proved that embedding metronidazole in ethyl cellulose film does not inhibit the biological activity. The release kinetics in vivo correlated with in vitro results, exhibiting a sustained release of metronidazole over a period of three days from 30% metronidazole with polyethylene glycol or 40% metronidazole in ethyl cellulose chloroform cast.

This study demonstrates that, by embedding metronidazole in ethyl cellulose, it is possible to obtain sustained release of the drug within the periodontal pocket for three days.
A Model System to Demonstrate the Role of Cavitational Activity in Ultrasonic Scaling
Authors: Walmsley A.D. , Laird W.R.E. , Williams A.R.
Published: November 2010

A model system consisting of vacuum-deposited aluminum on glass was developed to demonstrate the effectiveness of cavitational activity (occurring within the cooling water supply of a dental ultrasonic scaler) in the removal of particulate material from solid surfaces. The amount of solid material removed from the model system by this cavitational activity was quantified by a spectrophotometric technique. It was shown that cavitational activity occurring within the cooling water is an important contributory factor in the cleaning efficacy of the ultrasonic scaler operated under conditions similar to those employed clinically.
Materials Science
Authors: Pilliar R.M. , Smith D.C. , Maric B.
Published: November 2010

The wear behavior of 12 commercial restorative composites (conventional and microfilled) and an unfilled restorative material was evaluated using an in vitro wear test referred to as an oscillatory wear test. The effect of varying test conditions was evaluated in a series of preliminary experiments in order to define test conditions for material evaluation. The materials were tested after being aged in water at 37°C for periods of from seven days to one year. The results indicated consistently lower wear rates for the microfilled materials as compared with those of the conventional composites. Aging did not result in significant differences in wear rates measured by this method. Scanning electron micrography of worn surfaces suggested a possible effect of filler particle shape and bonding to the matrix to explain this difference. Although the relevance of the results to clinical behavior is not yet known, the study indicated the importance of material variables on wear.
Comparative in vitro Sliding-wear Study of Conventional, Microfilled, and Light-cured Composite Restoratives
Authors: Rice S.L. , Bailey W.F. , Wayne S.F. , Burns J.A.
Published: November 2010

The sliding-wear behavior of a number of commercially available microfilled and light-cured composite restoratives has been investigated and compared with the wear characteristics of conventional composites. The surface profiles of the composite restoratives, both pre- and post-test, have also been examined in order to study material attrition processes. The results indicate that: (1) microfilled composites are significantly more resistant to sliding wear than are restoratives containing conventionally-sized filler particles; (2) light-cured, microfilled composites exhibit a lower rate of sliding wear than do self-curing, microfilled restoratives; and (3) the wear process leads to an increase in surface roughness for all materials tested, but microfilled materials display lower surface roughness values, both before and after sliding-wear tests, than do restoratives containing conventional-sized filler particles.
Basic Biological Sciences Unstimulated and Stimulated Parotid Salivary Flow Rate in Individuals of Different Ages
Authors: Heft M.W. , Baum B.J.
Published: November 2010

Both unstimulated and stimulated parotid saliva samples were collected from 85 healthy, unmedicated individuals between the ages of 23 and 81 years. There were no significant differences in flow rate related to age with either unstimulated or stimulated secretion.
Effect of Chlorhexidine-Fluoride Applications Without and With Sr and Zn on Caries, Plaque, and Gingiva in Rats
Authors: Luoma H. , Seppa L. , Koskinen M. , Syrjanen S.
Published: November 2010

Molar teeth of four groups of Osborne-Mendel rats, kept on a cariogenic dict, were treated once per day for 48 days with either distilled water (solution C), a solution containing 0.05% chlorhexidine gluconate and 0.04% NaF, pH 5.8 (solution CXF), CXF plus 1000 ppm Sr (solution CXFS), or CXFS plus 1000 ppm Zn (solution CXFSZ). Caries of the hemi-sectioned lower molars was scored according to grades of severity, and the extent of the buccal plaque was estimated. Inflammatory cell infiltration, vascularity, and thickness of the oral mucosa were estimated from stained sections of the buccal oral mucosa to detect possible adverse effects of the treatments.

Fissure caries lesions with involvement of the dentin were reduced by 57% (p < 0.01) with the CXF treatment and by 68% (p < 0.001) with the CXFS treatment. The CXFSZ treatment reduced the fissure caries least (44%, p < 0.05), but it appreciably reduced the extent of plaque. The mucosal changes were greatest in the group receiving the CXFSZ treatment, but they were generally small and at a non-pathological level. Supplementation of the CXF solution with Sr thus appeared beneficial for caries reduction.
Selection of Streptococcus mutans and Lactobacilli in an Intra-oral Human Caries Model
Authors: Arneberg P. , Ogaard B. , Aa. Scheie A. , Rölla G.
Published: November 2010

Microbiologic changes during caries development underneath a plaque-retaining band were investigated by the use of selective media for streptococci, Streptococcus mutans, and lactobacilli. The final four-week plaque samples on 16 experimental teeth in six young subjects were assessed. Seven experimental teeth in three other subjects were sampled at baseline and after one, two, and four weeks.

All 23 experimental teeth developed a white spot lesion. In the final four-week plaque samples on the lesions, S. mutans accounted for 8% and lactobacilli 0.1% of the total CFU, both being significantly higher than in plaque from unbanded control surfaces. All experimental teeth sampled during lesion formation showed consistently elevated plaque levels of S. mutans and lactobacilli in comparison with baseline and control values at weeks one, two, and four. The results demonstrated a cariogenic environment in the human mouth associated with rapid selection of aciduric bacterial species such as S. mutans and lactobacilli.
Fluoride-treated Roots and Viability and Attachment of Human Gingival Fibroblasts
Authors: Al-Joburi W.A. , Denys F.R. , Cogen R.B.
Published: November 2010

Topical fluoride treatment is used to help prevent root caries. It may also be useful in periodontal therapy because of its antimicrobial property. In addition, for therapeutic new attachment to occur, the fibroblasts approximating the treated root surface should remain viable, and should also be able to attach and grow onto the treated root surface. These conditions, at least, are required for fluoride not to interfere with new attachment. This study was designed to determine whether treatment of roots with fluoride adversely affects human gingival fibroblasts in culture; and what effect fluoride treatment has on attachment and growth of cells to the root surface.

Cells originally obtained from human gingiva were allowed to grow to confluency in multi-well tissue culture petri dishes, and were then incubated for 24 hr in the presence of root sections as follows: (1) no treatment; (2) root-planed only; (3) 2% NaF only; (4) root-planed + 2% NaF; (5) root-planed + citric acid, pH 1 + 2% NaF. In addition, cells were plated onto roots similarly treated and were subsequently allowed to incubate for 72 hr.

Viability of cells was determined by exclusion of vital dye and 51Cr retention. Attachment and growth of cells were determined by histology and scanning electron microscopy. Results indicated that, after 24 hours' exposure, there was little or no difference in cell viability between different treatment groups and control cultures. Also, all roots which had been planed accommodated cell attachment, regardless of additional treatment rendered. We conclude that treatment of roots with NaF or citric acid, or both, did not adversely affect the viability of cells, and also that attachment of cells to the roots could occur as long as they were previously planed.
Alpha Level Distortions with Repeated Testing of Follow-up Dental Data
Authors: Cohen M.E.
Published: November 2010

The statistical consequences of repeated significance testing of follow-up dental data were evaluated by computerized Monte Carlo simulation. Substantial distortions in nominal alpha level were noted, particularly when the scores for individual subjects were not highly correlated between statistical observations. Suggested methods of controlling this distortion include the pre-specification of a terminal statistical analysis that would be given best evidence status and the partitioning of alpha error among all analyses by Bonferroni's inequality.
Clinical Science The Influence of Modification of Cavity Design on Distribution of Stresses in a Restored Molar
Authors: De Vree J.H.P. , Peters M.C.R.B. , Plasschaert A.J.M.
Published: November 2010

In this study, two different cavity designs were compared from a mechanical point of view: (a) an axisymmetric model of a conventional class 1 cavity preparation and restoration; and (b) an axisymmetric model of a modified cavity design. The modified design was characterized by a cavo-surface angle (c.s.a.) of approximately 90° and a stepped cavity wall. Using a mathematical model, stresses were calculated by finite element analysis to compare the force distribution. It is concluded that the clinical superiority of the modified cavity design, with respect to the marginal breakdown of the amalgam restoration, can be supported by stress calculations.
Build-up and Repair of Light-cured Composites: Bond Strength
Authors: Boyer D.B. , Chan K.C. , Reinhardt J.W.
Published: November 2010

Interfacial bond strengths of light-activated composites were measured as a function of age using a transverse strength test. Bond strength between layers decreased with the age of the initial layer and reflected the setting curves of the composites. The highly-filled composites exhibited the greatest bond strengths. Uncut surfaces provided a better substrate for bonding than did ground surfaces. Use of a bonding agent on both uncut and ground surfaces improved bond strengths. Mean repair strengths of light-activated composites were similar to those of selfcuring composites. Composites with ground surfaces aged for one wk had mean repair strengths 27% of the cohesive strength without bonding agent and 48% with bonding agent.
Hydrolytic Degradation of Dental Composites
Authors: Söderholm K.-J. , Zigan M. , Ragan M. , Fischlschweiger W. , Bergman M.
Published: November 2010

The leakage of filler elements from four composites after storage in water was investigated by use of atomic absorption spectrophotometry. The results confirmed previous findings that leaching of silicon from different composites is strongly dependent on filler composition. Consideration of the total filler surface of each composite material indicated that quartz as well as pyrolytic silica-containing composites leached less silicon than did composites containing fillers of strontium and/or barium glasses. A correlation between leakage and crack formation in the matrix appeared to exist for all composites except for the microfilled resin. These cracks were explained as a result of osmotic pressure built up at the matrix-filler interface due to hydrolytic degradation of the filler.

Of the investigated materials, the microfilled resin was found to be the most stable material in a wet environment with respect to crack formation. This finding was explained by filler composition, filler form, and the specific structure of the microfilled resin.
Basic Biological Sciences Effect of Eugenol on Respiration and Division in Human Pulp, Mouse Fibroblasts, and Liver Cells in vitro
Authors: Hume W.R.
Published: November 2010

Eugenol depressed cell respiration in homogenates of human dental pulp and in mouse fibroblast monolayers. The depression was concentration-dependent, with a threshold at about 10 -4M and a maximum at 10-3M in both preparations. Onset of the depression appeared to be rapid. The effects of variation in both duration and concentration of eugenol exposure on subsequent uptake of 3H-thymidine were examined in mouse fibroblast monolayers and human pulp explants. Fibroblasts survived short-term (up to 12 hr) exposure to 10-3M eugenol or less, but died after exposure to 10-3M for one day or more. The cells survived exposure to 10-4M for ten days, the longest period examined Human pulp maintained in tissue culture medium showed similar eugenol susceptibility. Analysis of these data, when coupled with those of previous studies on eugenol release from ZOE and diffusion through dentin, gives strong support for the concepts that: (1) the blandness of ZOE when applied to intact dentin is due to eugenol reaching the pulp in sub-toxic concentrations, and (2) the irritant effect of ZOE when applied directly to soft tissue is due to the development of concentrations of eugenol in tissue adjacent to ZOE sufficient to inhibit respiration and thus kill cells.
Salivary Clearance of Sugar and its Effects on pH Changes by Streptococcus mitior in an Artificial Mouth
Authors: Lagerlöf F. , Dawes R. , Dawes C.
Published: November 2010

We recently developed a computer model of oral sugar clearance (Dawes, 1983), and an artificial mouth has now been constructed which will allow variation in the salivary parameters identified in the model and the study of their effects on bacterial acid production. Using a thin layer of S. mitior, strain 572, over a miniature Sb electrode to measure bacterial pH changes during sugar clearance from the "mouth", we found that three consecutive sets of "Stephan curves" could be obtained with the same bacteria during one day. In each of several experimental series, one salivary parameter was varied, while other parameters were held constant. The maximum pH decrease and the surface area of the registered Stephan curve (Δ pH.min) were used as measures of acid production.

The results indicate that the volume of "saliva" in the mouth before and after swallowing, the unstimulated salivary flow rate, and the buffer capacity had significant influences on the extent of the pH changes. Other factors, such as the maximum flow rate, the delay between start of stimulation and maximum flow, the volume of saliva in the mouth at time zero, and the taste threshold for sugar, were of lesser importance, confirming some predictions from the computer model.
Screening of Sugars Inhibitory against Sucrose-dependent Synthesis and Adherence of Insoluble Glucan and Acid Production by Streptococcus mutans
Authors: Imai S. , Takeuchi K. , Shibata K. , Yoshikawa S. , Kitahata S. , Okada S. , Araya S. , Nisizawa T.
Published: November 2010

Various sucrose derivatives and a sucrose analogue were enzymatically synthesized on the assumption that structural similarities of the sugars to sucrose would endow them with an ability to inhibit the cariogenicity of sucrose. The effect of these sugars on sucrose-dependent synthesis and adherence of insoluble glucan and on acid fermentation of sucrose by Streptococcus mutans was examined in vitro. Although none of them inhibited the acid fermentation, several sugars not only inhibited the synthesis and adherence of insoluble glucan, but were themselves only slightly fermented as well.
Three-dimensional Measurements of the Occlusal Surfaces of Upper Molars in a Dutch Population
Authors: Kanazawa E. , Sekikawa M. , Ozaki T.
Published: November 2010

The occlusal surfaces of the first upper molars of a Dutch population were measured three-dimensionally by moire contourography. Cusps and ridges were higher than those of a Japanese population, but distances between cuspal tips were smaller. Differences in occlusal form may influence jaw movements in the two populations.
Crown Area as an Indicator of Changing Crown Size in Human Pre-natal Teeth
Authors: Prasad N. , Burdi A.R.
Published: November 2010

This study deals with correlations of tooth size in human primary teeth. Traditionally, mesiodistal or buccolingual measurements have been used to express crown size. However, in this study, crown area was used as a reference parameter.

Graphic reconstructions of 38 histologically prepared human fetuses with Crown-Rump Length (CRL) between 54 and 280 mm were used to obtain linear and area measurements. Based on clinical records and physical examinations, these fetuses were considered typical-for-age, or "normal". Correlation matrices indicated high levels of concordance among all developing deciduous tooth crowns and arch measurements. It was concluded that crown area is a statistically better trait to use in comparison of teeth rather than the traditional mesiodistal measurement.
Clinical Science Humoral Immune Responses to Adenoviruses, Herpes Virus Type 1, and Candida albicans in Sera of Dental Patients with Oral Neoplastic and Periodontal Diseases
Authors: Winters W.D. , Guest G.F. , McAnear J.T.
Published: November 2010

Levels of immunoglobulin class-specific antibodies as determined by solid phase radioimmunoassays to herpes simplex virus type 1 (HSV-1), human adenovirus types 5, 21, and 31 and to Candida albicans in sera from untreated healthy dental patients were not significantly different from levels of these antibodies in sera from untreated dental patients with benign oral tumors, oral carcinoma, or periodontal disease. These results show that higher levels of immunoglobulin class-specific antibodies to HSV-1, the three adenoviruses, or Candida albicans are not a consistent finding in sera from patients with oral cancer when comparisons are made with healthy patients and patients with other oral diseases.
Chemical Analyses of Membranes Isolated from Streptococcus mutans BHT
Authors: Crowley P.J. , Hurst S.F. , Bleiweis A.S.
Published: November 2010

Cell membranes of Streptococcus mutans BHT (serotype b) were prepared following glass-bead disruption or mutanolysin digestion of whole cells. Major constituents of purified BHT membranes included: protein (60-65%), fatty acids (10%), glucose (3%), and phosphorus (0.5%). The principal amino acids measured were glutamate, aspartate, lysine, alanine, and leucine. The principal fatty acids measured were octadecenoic, palmitoleic, palmitic, and eicosenoic acids; smaller amounts of eicosanoic acid were also detected. Chemical analyses of membranes from cellsgrown to four different growth phases revealed no major shifts in composition during batch growth under our experimental conditions. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of these four membrane preparations confirmed the apparent compositional stability of cell membranes during growth.
Fracture Properties of Human Enamel and Dentin in an Aqueous Environment
Authors: Rasmussen S.T. , Patchin R.E.
Published: November 2010

SEM fractography and work-of-fracture techniques were used to investigate the fracture properties of human enamel and dentin as a function of the temperature of an aqueous environment. Both enamel and dentin were found to be anisotropic with respect to mechanical failure but were found to have little variation in fracture properties with respect to temperatures from 0° to 70°C. Fractographs of a naturally fractured tooth were consistent with experimental findings. The results of this research indicate that natural fracturing of teeth probably cannot be explained on the basis of a reduced work of fracture resulting from chewing hot or cold foods. It was also shown that if dentin surfaces can be kept below 100°C during cavity preparation, the restored tooth will not be weakened by an irreversible reduction of its work of fracture.
Clinical Science Determination of Rpm, Time, and Load Used in Oral Prophylaxis Polishing in vivo
Authors: Christensen R.P. , Bangerter V.W.
Published: November 2010

Clinically relevant values for revolutions per minute (rpm), time, and load should be used when one evaluates effects of abrasive slurries on teeth. However, in the past, these variables have not been measured in vivo to determine clinical means. This study describes an instrument and computer software which monitored rpm, time, and load used by 29 clinicians during routine oral prophylaxes performed on 76 patients. Grand means and standard deviations determined for the three variables were: rpm, x = 2571 (s = 739); time per tooth surface, x = 4.5 sec (s = 2.9) ; and load, x = 145 g (s = 66). Mean rpm, time, and load used on facial and lingual surfaces of the 32 teeth were also determined. Statistical tests showed that rpm was not altered significantly by tooth location, surface, or type and amount of deposit, but time was affected significantly by tooth location, surface, and amount of calculus; load was affected by tooth location, surface, and amount and intensity of stain.
Clinical Evaluation Methods for Posterior Composite Restorations
Authors: Goldberg A.J. , Rydinge E. , Santucci E.A. , Racz W.B.
Published: November 2010

Two methods of evaluating the in vivo wear of posterior composite restorations are described and compared with the USPHS direct clinical evaluation system. The three methods were consistent among themselves and over the two years of the study. In order of increasing sensitivity, the methods were: USPHS, total ranking of models, and categorizing of models according to a set of standards. The last procedure identified statistically significant differences (p < 0.05) between the composite formulations as early as the nine-month recall. All formulations experienced increasing wear with time, but at a decreasing rate.
The Competition between the Composite-Dentin Bond Strength and the Polymerization Contraction Stress
Authors: Davidson C.L. , De Gee A.J. , Feilzer A.
Published: November 2010

The influence of contraction stresses, developed during the polymerization of composites, on adhesion to dentin treated with a dentin adhesive was studied for a chemically- and a light-activated microfilled composite, in both linear and 3-D models.

The linear model consisted of an arrangement set up in a tensilometer in which the composites could be applied to a flat dentin surface fixed to the stationary cross-head at one end, and mechanically clamped to the cross-head connected to the load cell at the other end. The increase of the bond strength was measured at different time intervals from the start of mixing and was compared with the developing contraction stress. Throughout the complete polymerization process, the adhesion survived the contraction stress, which is explained by flow relaxation, which can occur sufficiently in this configuration.

In the three-dimensional model, the composites are attached to more than two dentin walls. In this situation, flow is severely limited, and contraction stress values can exceed the bond strength, leading to separation. This was demonstrated in Class V cavities. The shape of the cavity is considered to be of great importance in conservation of the composite-dentin bond.
Changes in Collagen Types During the Healing of Rabbit Tooth Extraction Wounds
Authors: Kurita K. , Hashimoto Y. , Takei T. , Kawai T. , Hayakawa T.
Published: November 2010

Three α chains of type V collagen - α1(V), α2(V), and α3(V)- were initially demonstrated together with the expected collagen types I and III in the pepsin-soluble fraction of both normal mandibular bone and tooth extraction wound tissues of rabbits, as analyzed by sodium dodecyl sulfate-gel electrophoresis. The total collagen content of each extraction wound, as determined by the hydroxyproline assay, was observed to increase continuously from day 5 through day 17 and then leveled off or decreased. The ratio of type V to type I collagen was significantly higher in the initial stage of wound healing and decreased sharply down to the level of mandibular bone by day 5. The ratio of type III to type I collagen in the pepsin-soluble fraction increased and reached a maximum on day 5, whereas it was maximal on day 7 in the cyanogen bromide-soluble fraction, and thereafter decreased gradually in both fractions. The ratio for the pepsin-soluble fraction was, however, significantly higher than that for the cyanogen bromide-soluble fraction in the early stage of wound healing.
Evaluation of 2-Phosphono-butane 1,2,4 Tricarboxylate as a Crystal Growth Inhibitor in vitro and in vivo
Authors: Gaffar A. , Moreno E.C.
Published: November 2010

The inhibitory activity of 2-phosphono-butane 1,2,4 tricarboxylic acid (PBTA) in the formation of hydroxyapatite (HA) was studied in vitro and in vivo. PBTA, at 4 ppm, inhibited the spontaneous formation of HA in vitro from a supersaturated solution. PBTA, at 2 ppm, completely inhibited the crystal growth of HA; at lower concentrations, a direct relationship was found between the reduction of the initial precipitation rates and PBTA concentrations in the solution.

The effects of PBTA on human dental enamel in vitro were also evaluated at pH 5.0 and 7.5. Equimolar levels of EDTA served as the controls. In comparison with EDTA, the dissolution of enamel induced by PBTA was negligible. One percent solution of PBTA was evaluated in a rat calculus assay. In comparison with a placebo solution, it significantly (p = 0.05) reduced calculus formation when applied topically. It was also tested against calculus formation in beagle dogs. A topical application once a day of a 1% solution at pH 7.0 reduced calculus formation by 84% for 16 weeks. Analysis of these data suggests that the agent effectively reduces calculus formation in vivo.
Structural Changes in the Oxidation Zones of Gold Alloys for Porcelain Bonding Containing Small Amounts of Fe and Sn
Authors: Ohno H. , Kanzawa Y.
Published: November 2010

The oxidized surfaces of cross-sections of gold alloys containing a total of 1.5 mass % Fe and Sn, oxidized at 1000 °C for one hr, have been studied by various techniques, including secondary electron micro-analysis, X-ray micro-analysis, X-ray diffraction, and thermogravimetry.

Over the composition range (0.30 - 1.50 mass % Fe), an external oxidation zone containing only Fe oxides was formed. The quantity of Fe203 was greater than that of Sn02 for 0.45 - 1.50 mass % Fe. With an Fe content below 0.45 mass %, the amount of Sn02 was greater than that of Fe2O3 . Traces of Fe304 were formed in high Sn content alloys.

Internal oxidation particles composed of Fe203 and Sn02 precipitated deep in the alloy matrix (0.90 - 1.50 mass % Fe), and these changed to an internal oxidation band composed mainly of Sn02 for 0.3 mass % Fe.
Caries Prevalence in Turner's Syndrome (45,X Females)
Authors: Takala I. , Alvesalo L. , Palin-Palokas T. , Paunio K. , Suoranta K.
Published: November 2010

Dental caries prevalence in permanent teeth (DFS) was studied in 50 patients with Turner's syndrome (45,X females) and 41 normal first-degree female relatives. Caries prevalence was lower in 45,X women than in controls, and this difference was more pronounced in the incisor region than in pre-molar and molar teeth.