bluuebunny/crossref_metadata_2025 huggingface dataset:
An in vitro Model for Assessment of Fluoride Uptake from Glass-ionomer Cements by Dentin and its Effect on Acid Resistance
Authors: Tsanidis V. , Koulourides T.
Published: November 2010

This investigation presents an experimental model for studying interactions of glass-ionomer cements (GICs) with bovine dentin slabs. Fluoride incorporation was studied with five serial abrasion biopsies, each being approximately 10 μm thick. The time of interaction was a very important parameter, indicating continuous fluoride release from the GIC and diffusion into dentin over a 30-day period. Expressed in mass per volume (mg F/cm3), the fluoride incorporation reached 12.0 mg at the first and 2.5 mg at the fifth layer, several times greater than the baseline of 0.27 mg/cm3 in bovine dentin. A subsequent test of acid resistance in a lactic acid buffer (pH 4.0), followed by microradiography of lesions, showed a characteristic 40-μm-wide acid-resistant zone on surfaces exposed to the GICs. In contrast, the untreated control surfaces had lesions demineralized evenly from the surface to the intact tissue, without the higher-density zone at the surface of the lesion. The model seems promising for screening fluoride incorporation into dentin from fluoride-releasing dental materials.
Light and Transmission Electron Microscopy of the Intact Interfaces Between Non-submerged Titanium-coated Epoxy Resin Implants and Bone or Gingiva
Authors: Listgarten M.A. , Buser D. , Steinemann S.G. , Donath K. , Lang N.P. , Weber H.P.
Published: November 2010

This experiment was aimed at studying the intact tissue/implant interface of non-submerged dental implants with a titanium surface. Epoxy-resin replicas were fabricated from 3.05 x 8 mm cylindrical titanium implants with a plasma-sprayed apical portion and a smooth coronal collar. The replicas were coated with a 90-120-nm-thick layer of pure titanium and autoclaved. The coated replicas were inserted as non-submerged endosseous implants in the edentulous premolar region of dog mandibles and allowed to heal for three months. Jaw sections containing the implants were processed for light and electron microscopic study of the intact tissue/implant interface with and without prior demineralization. Gingival connective tissue fibers were closely adapted to the titanium layer, in an orientation more or less parallel to the implant surface. There was no evidence of any fiber insertions into the surface irregularities of the smooth or rough titanium surface. Undemineralized bone was intimately adapted to the titanium surface without any intervening space. In demineralized sections, the collagen fibers of the bone matrix tended to be somewhat thinner and occasionally less densely packed in the vicinity of the implant surface. However, they extended all the way to the titanium surface, without any intervening fibril-free layer.
Masticatory Muscle Activity in Different Jaw Relations During Submaximal Clenching Efforts
Authors: Visser A. , McCarroll R.S. , Naeije M.
Published: November 2010

The EMG activities of the masseter muscles and the anterior and posterior parts of the temporalis muscles were investigated in different vertical and sagittal jaw relations. Surface EMG recordings were made. Relative muscle activities were quantified by means of the Activity Index and the Asymmetry Index. Ten subjects with a healthy masticatory system were asked to clench at 10% and 50% of their maximum voluntary clenching level. Registrations were made during clenching in the intercuspal position, on a thin stabilization splint (SSP, 1-2 mm increase of vertical dimension at first molar), on a thick stabilization splint (3 mm thicker at the incisal edge relative to SSP), and on a protrusive re-positioning splint (3 mm protrusive to SSP). The masseter EMG amplitudes were the same for all the jaw positions investigated. However, at the 10% clenching level, the temporalis muscle activity decreased after the vertical dimension was raised and decreased further after the mandible was protrusively positioned (p < 0.01). An independent function for the posterior and the anterior parts of the temporalis muscle was not found in any of the intermaxillary jaw relations investigated. At the 50% clenching level, a decrease in anterior temporalis muscle activity was observed only with the protrusive position in relation to the other three positions. Also at this level, the index relating the activity of the anterior to that of the posterior part of the temporalis muscle was not different between jaw positions. Raising the vertical dimension and protrusive positioning of the mandible decreased the activity of the temporalis muscles. This may be a factor related to the therapeutic effect of the stabilization splint in the treatment of craniomandibular disorder patients.
Influence of Anticoagulation on Blood Loss Following Dental Extractions
Authors: Declerck D. , Vinckier F. , Vermylen J.
Published: November 2010

The coagulation activity level at which oral surgical procedures can be performed in anticoagulated patients without triggering bleeding complications and without enhancing the risk of developing thrombo-embolic events remains controversial. The objective of the present study was to evaluate blood loss following dental extractions at different levels of anticoagulation and to determine its effect on wound closure rates.

Blood loss was measured following the removal of four front teeth in warfarinized rabbits. Immediate blood loss was evaluated by determining the tooth socket bleeding times and by using a technique based on hemoglobin determinations. Long-term blood loss was assessed by comparison of labeled red-blood-cell disappearance curves.

The results showed that blood loss following dental extractions was significantly greater in animals anticoagulated at a therapeutic level than in non-anticoagulated control animals. Determination of blood loss at different levels of anticoagulation clearly demonstrated that complete correction of the coagulation activity was unnecessary. Partial correction (INR values of 1.6-1.8) allowed extractions to be performed without extensive blood loss. With this technique of partial correction, the period of interruption of the anticoagulation could be kept very short, and the risk of postoperative bleeding complications was minimal. Wound closure rates were negatively influenced in anticoagulated animals.
Fitting Genetic Models to Carabelli Trait Data in South Australian Twins
Authors: Townsend G.C. , Martin N.G.
Published: November 2010

This study aimed to clarify genetic and environmental contributions to Carabelli trait variation on permanent first molar teeth in a large sample of South Australian twins. Estimates of polychoric correlations were obtained between pairs of monozygous (MZ) and dizygous (DZ) twins for Carabelli data and various gene-environment models fitted by a weighted least-squares approach. The favored model included additive genetic effects together with both a general environmental component and an environmental effect specific to each side. An estimate of heritability around 90% indicated a very strong genetic contribution to observed variation. The pattern of correlations for MZ and DZ data suggested that further studies involving other types of relatives would be worthwhile for detection of possible non-additive genetic effects of dominance or epistasis.
Daily Dose Calculations from Measurements of Intra-oral Mercury Vapor
Authors: Olsson S. , Bergman M.
Published: November 2010

Measurements of intra-oral mercury vapor from amalgam fillings are discussed. It was shown that the only quantity which it is possible to measure is the mercury release rate, and that the concentrations of mercury vapor in the oral cavity published in most earlier studies are the mercury concentrations in the measuring cell of the measuring apparatus and not the concentrations in the oral cavity. The consequences for the daily dose equations of the facts that the mercury source is present inside the oral cavity and that the amount of mercury released during a certain time is limited are discussed. It was found that most daily dose equations used have a questionable mercury distribution on inspiration, expiration, and swallowing. Re-calculations of almost all the available daily dose data showed a mean daily dose value of about 1.3 μg Hg/day (range, 0.3-2.2 μg Hg/day). The mean swallowed amount of mercury from intra-oral mercury vapor was calculated as being in the order of 10 μg Hg/day (range, 2.4-17 μg Hg/day), resulting in an estimated absorption of about 1 μg Hg/day from the gastro-intestinal tract.
Synthesis and Evaluation of Novel Multifunctional Oligomers for Dentistry
Authors: Stansbury J.W.
Published: November 2010

A new type of multifunctional oligomer was synthesized, and its potential as a base monomer in dental composite formulations was evaluated. The oligomer of ethoxylated bis-phenol A diacrylate (OEBPA) was prepared in good yield by a formaldehyde insertion/ condensation reaction. Although double bonds along the oligomer backbone are arranged in pairs such that cyclopolymerization is possible, it is not presently known whether this process plays a significant role in the polymerization. Indirect evidence supporting efficient cyclopolymerization involves the reduced polymerization shrinkage observed for polymerized OEBPA relative to polymers of other monomers used as base resins. Photo-cured composites containing either OEBPA, BIS-GMA, or ethoxylated bis-phenol A dimethacrylate (EBPADM) as base resin and TEGDMA as diluent were compared. While the resulting diametral tensile and transverse strengths did not differ significantly, the values for the energy absorbed to failure indicated that the OEBPA- and EBPADM-based formulations yielded composites with somewhat greater toughness than that of the BIS-GMA material. This multifunctional oligomer offers mechanical strength and conversion values that are comparable with those of existing base resin monomers while providing an approximate 30% reduction in polymerization shrinkage.
Effect of a Two-solution Fluoride Mouthrinse on Remineralization of Enamel Lesions in vitro
Authors: Chow L.C. , Takagi S. , Shih S.
Published: November 2010

A previous study showed that a two-solution fluoride (F) rinse deposited significantly more loosely-bound F on the tooth surface than did a sodium fluoride (NaF) rinse with the same F concentration (12 mmol/L). In the present study, this experimental rinse was evaluated for its ability to cause remineralization of enamel lesions in an in vitro pH-cycling model. Caries-like lesions were formed in the enamel of extracted human molars by means of a pH 4 demineralizing solution. Fifty-one ~120-μm-thick sections containing lesions were randomly divided into (1) control, (2) NaF rinse, and (3) two-solution F rinse groups. With the cut surfaces protected, the control samples were immersed in a pH 7 remineralizing solution for 12 days, and twice daily the sections were also exposed to a pH 4 demineralizing solution for 30 min. Samples in the NaF group received an additional one-minute rinse with a NaF (12 mmol/L) solution twice daily. Samples in the two-solution rinse group received the rinse treatment with a 12 mmol/L F solution prepared by combination of a Na2SiF 6 and phosphate-containing solution with a calcium solution just before use. The mineral contents of the lesions were assessed by quantitative microradiography. The results showed that (1) no significant de- or remineralization was detected in the controls; (2) a 46% decrease in mineral loss (AZ) ofthe lesion was produced by the NaF rinses; and (3) a 94% decrease in AZ and a 20-μm-thick, mineral-dense surface-coating were produced by the two-solution F rinse treatment.
Changes in Oxygen Consumption in Dog Gingiva during Induction of Experimental Periodontitis
Authors: Hanioka T. , Amano A. , Inoshita E. , Tamagawa H. , Shizukuishi S.
Published: November 2010

The purpose of this study was to examine changes in oxygen consumption in dog gingiva during induction of experimental periodontitis. The disease was induced in adult mongrel dogs during a 16-week period by placement of silk ligatures around selected teeth. The oxygen consumption rate of gingival tissue was determined in vivo by a non-invasive technique, tissue reflectance spectrophotometry. Changes in such clinical parameters as gingival index, plaque index, pocket depth, attachment level, and gingival crevicular fluid flow indicated acute inflammatory responses during the first three weeks after ligation, followed by the appearance of chronic inflammation during the remaining 13 weeks. The oxygen consumption rate increased during the first seven days after ligation and stayed near the maximum level for 2-7 weeks; this was followed by a gradual decrease during the final nine weeks. These results suggest that gingival oxygen consumption increases rapidly with the increase of acute inflammation responses and then decreases slightly with the gradual development of chronic inflammation. Positive correlations were observed between the oxygen consumption rate and other clinical indices. Thus, the tissue reflectance spectrophotometry is a new, useful method for objective, quantitative, and non-invasive assessment of gingival oxygen consumption.
Periapical Innervation of the Ferret Canine One Year After Pulpectomy
Authors: Holland G.R.
Published: November 2010

Previous studies have shown that, following removal of the dental pulp and its replacement with a filling material, the nerves in the periapical region proliferate within an area of chronic inflammation. This study examined these responses in the ferret in more detail, both quantitatively and in three dimensions, 12 months after pulpectomy which was followed by obturation with gutta percha and zinc oxide and eugenol sealer. The results were compared with the responses after three months. The basic patterns, in terms of both inflammation and neural proliferation, were similar at the two time periods. Both the sizes of the inflammatory lesions and the degree of neural proliferation were lower at 12 months than at three, although the differences were not significantly different in the small number of specimens examined. Bacterial stains failed to show bacteria either in the apical root canal delta or in the periapical area. It is possible that the persistent inflammation was due to the irritant nature of the obturating materials used but not due to the original tissue damage, since extraction sites, by comparison, healed very quickly. Apparently, following endodontic treatment, chronic periapical inflammation and concomitant neural proliferation can continue for long periods.
Immunohistochemical Evidence for the Occurrence of Endothelin in the Vascular Endothelium of Normal and Inflamed Human Dental Pulp
Authors: Casasco A. , Casasco M. , Ciuffreda M. , Springall D.R. , Calligaro A. , Bianchi S. , Polak J.M.
Published: November 2010

The occurrence and distribution ofthe regulatory peptide endothelin in normal and inflamed human dental pulp was studied by immunocytochemistry. Endothelial cells in both normal and inflamed pulp displayed endothelin-like immunoreactivity. Neither pulp cells nor dental nerves were immunoreactive. No significant change in the distribution of endothelin immunoreactivity could be detected in the samples of inflamed pulp tissue, the immunoreactive material being detectable only within the endothelium. However, the intensity of the immunostaining was less intense in the samples of inflamed pulp. It is reasonable to presume that endothelin, produced and released locally by endothelial cells, may participate via a paracrine mechanism in the regulation of blood pressure and flow in normal and pathological human dental tissues.
Strengthening of Feldspathic Porcelain by Ion Exchange and Tempering
Authors: Anusavice K.J. , Shen C. , Lee R.B.
Published: November 2010

This study investigated the effectiveness of tempering and ion-exchange treatments on crack growth and bi-axial flexural strength of seven feldspathic porcelains. The results showed that tempering treatment was more effective in strengthening porcelain than was the ion-exchange process as measured by the bi-axial flexural strength. However, the results of initial crack size induced by a microhardness tester showed that ion-exchange yielded a surface that was more resistant to crack initiation than was that yielded by the tempering treatment. EDX and microprobe analyses showed that there was evidence of exchange between Na+ within the porcelain surface and K+ from the ion-exchange agent applied on the surface.
Analysis of Tempering Stresses in Bilayered Porcelain Discs
Authors: Dehoff P.H. , Anusavice K.J.
Published: November 2010

Previous studies of opaque-porcelain/body-porcelain discs have shown that compressive stresses which develop in the porcelain surface by being tempered in air can inhibit the sizes of cracks induced within the surface. The objective of this study was to develop a theoretical model for analysis of transient and residual stresses in opaque-porcelain/body-porcelain discs which were produced under variable cooling conditions. The model incorporates the effects of stress and structural relaxation. Transient and residual stresses were calculated for bilayered porcelain discs 16 mm in diameter and 2 mm in thickness for three opaque-porcelain/ body-porcelain combinations. Transient temperature distributions in the discs for simulated convective cooling were calculated by finite-element analysis. Data from microhardness indentations reported by Anusavice et al. (1989) indicate that crack lengths measured for bilayered porcelain discs subjected to slow cooling conditions, for which the model predicted residual tensile stresses, were greater than those combinations for which residual compressive stresses were calculated. Calculated values of residual compressive stress for tempered specimens were considerably higher than those for specimens that were slowly cooled and those that were cooled by free convection. In general, residual stress levels calculated by use of the analytical model were in fairly good agreement with the trends observed for crack lengths and bi-axial flexural strengths reported by Anusavice and Hojjatie (1991). The results of the present study indicate that a visco-elastic model is a viable approach for determination of transient and residual stresses in opaque-porcelain/body-porcelain discs.
Dentinogenic Activity of Allogenic Plasma Fibronectin on Dog Dental Pulp
Authors: Tziafas D. , Alvanou A. , Kaidoglou K.
Published: November 2010

The response of ectomessnchymal cells of dog dental pulp to implantation of Millipore filters supplemented with bovine plasma fibronectin was evaluated after observation periods of one or four weeks. Two concentrations of plasma fibronectin were used (0.2 and 1 mg/mL). Experiments also included implants treated with control solutions (PBS or 1 mg/mL of dog albumin). Formation of a layer of elongated, polarized cells was demonstrated in direct contact with the implants treated with 1 mg/mL of plasma fibronectin solution, after one week post-operatively. Microfilamentous organization and orientation of rough endoplasmic reticulum was observed mainly in the supranuclear zone of the polarized cells. Implants treated with the same solution were consistently surrounded by a thick layer of dentinal matrix after four weeks of their exposure to pulp sites. Implants treated with control solutions or with the low concentration of fibronectin never showed any sign of cell polarization and matrix synthesis. These data provide evidence that the pulp cells can express their odontoblastic phenotype in response to a surface containing concentrated fibronectin (even allogenic), without the need of other molecules as exogenous inductive factors.
Expression of Fibronectin and Integrins in Cultured Periodontal Ligament Epithelial Cells
Authors: Uitto V.-J. , Larjava H. , Peltonen J. , Brunette D.M.
Published: November 2010

The process of attachment of epithelial cells obtained from the porcine periodontal ligament (cell rests of Malassez) to different extracellular matrix proteins and their expression of fibronectin and integrin receptors were studied by means of immunocytochemistry, in situ hybridization, and time-lapse cinemicrography techniques. The cell lines of periodontal ligament epithelial cells (PLE cells) attached to and spread rapidly on fibronectin, vitronectin, and type I collagen. One of the cell lines also attached to laminin, while the other cell line showed poor attachment to both laminin and Matrigel®, a basement membrane material. By use of the in situ hybridization technique, some PLE cells were found to express the fibronectin gene strongly. Immunocytochemical staining localized fibronectin in extracellular fibrils and intracellular granules. Fibronectin was also found in the tracks left behind by the cells migrating on the substratum. Arg-gly-asp-ser peptide inhibited the attachment of the PLE cells to fibronectin, laminin, type I collagen, and vitronectin by 47%, 43%, 83%, and 94%, respectively, suggesting that the cell-matrix interactions were partly mediated by receptors related to the integrin family. Antibodies against the β1-integrin subunit stained the cell bodies and the plasma membrane projections of spreading cells. After 24 h or longer in culture, β1-integrins were localized to the regions of cell-cell contact. Cinemicrography of the arg-gly-asp-ser-peptide-treated cells demonstrated that the spreading and migration of isolated cells were prevented by the peptide. The peptide did not appear to dissociate the cell-cell contacts or interfere with migration of spread-cell colonies. By immunoprecipitation with anti-β1 antibodies of the integrins from extracts of the radiolabeled cells, two bands characteristic of a- and B-subunits of β 1-integrins were resolved by SDS-gel electrophoresis. The results suggest that PLE cells synthesize and utilize fibronectin-containing material for their attachment, spreading, and migration. The cell-substratum and cell-cell contacts are at least partly mediated through integrin-type cell-surface receptors. During the different stages of cell growth and spreading, the integrins appeared to become reorganized, which facilitated cell-cell contact and allowed for migration of the cell colonies.
The Changing Patterns of Systemic Fluoride Intake
Authors: Burt B.A.
Published: November 2010

Fluorosis prevalence has increased in North America since the 1930's-1940's. It may also have increased since 1970, though the evidence for that is less clear. Continued monitoring will help determine whether increased fluorosis prevalence in children in the United States is a cohort effect from the 1970's. This review considers the evidence for an increase in fluoride ingestion from all sources since the 1970's. If an increase has occurred, the most likely sources are fluoride dietary supplements, inadvertent swallowing of fluoride toothpastes, and increased fluoride in food and beverages. For adults, there is no evidence from dietary surveys to show that fluoride intake has increased over the last generation. Dietary surveys for children aged six months to two years are similarly inconclusive, though the great variation in fluoride content of various infant foods might be obscuring real effects. The data on fluoride intake by children from food and beverages, infant foods included, are not strong enough to conclude that an increase in fluoride ingestion has occurred since the 1970's. However, the suggested upper limit of fluoride intake is substantially being reached in many children by ingestion of fluoride from food and drink (0.2-0.3 mg per day) and from fluoride toothpaste (0.2-0.3 mg per day). Two public health issues that arise from this review are: (a) the need for a downward revision in the schedule for fluoride supplementation, and (b) education on the potential for high fluoride concentration of soft drinks and processed fruit juices.
Biological Mechanisms of Fluorosis and Level and Timing of Systemic Exposure to Fluoride with Respect to Fluorosis
Authors: Denbesten P.K. , Thariani H.
Published: November 2010

Enamel fluorosis can occur following either an acute or chronic exposure to fluoride during tooth formation. Fluorosed enamel is characterized by a retention of amelogenins in the early-maturation stage, and by the formation of a more porous enamel with a subsurface hypomineralization. The mechanisms by which fluoride affects enamel development include specific effects on both the ameloblasts and on the developing enamel matrix. Maturation-stage ameloblast modulation is more rapid in fluorosed enamel as compared with control enamel, and proteolytic activity in fluorosed early-maturation enamel is reduced as compared with controls. Secretory enamel appears to be more susceptible to the effects of fluoride following acute fluoride exposure, such as may occur with the use of fluoride supplements. However, both human and animal studies show that the transition/early-maturation stage of enamel formation is most susceptible to the effects of chronic fluoride ingestion at above-optimal levels of fluoride in drinking water.
The Level and Timing of Systemic Exposure to Fluoride with Respect to Caries Resistance
Authors: Hargreaves J.A.
Published: November 2010

Material related to water fluoridation and fluoride availability has been examined for changing patterns of fluoride intake by humans over recent years. The difficulty of separating systemic and topical fluoride action from water and foods from that found in fluoride agents used in preventive treatment programs is discussed.

Recommendations are made that water fluoridation is a wellproven program and should be continued, but that fluoride supplementation programs under the control of the individual should be carefully evaluated and, if used, should be restricted to periods after the secretory stage of enamel formation is normally finished for anterior teeth, with supplements commenced during the pre-eruption maturation period and continuing until permanent tooth eruption is complete. Although supplements can also give a topical source to the teeth, depending on the way the supplement is consumed and the duration of time it is available in the mouth, other methods of topical fluoride provision are endorsed, and these should continue through life. It is suggested, in respect of epidemiology studies, that data collected before the availability of fluoride dentifrices in 1971 should be re-examined.
Current Regulations and Recommendations Concerning Water Fluoridation, Fluoride Supplements, and Topical Fluoride Agents
Authors: Newbrun E.
Published: November 2010

In recent years, an increase in the prevalence of dental fluorosis, mostly of the very mild to mild category, has been seen in the United States. This paper therefore discusses the safety of dental fluoride products, primarily with respect to the risk of dental fluorosis due to chronic ingestion of these products by pre-school children. No change is indicated in the optimal fluoride level (0.7 to 1.2 ppm) for water fluoridation. A reduction in the dosage of fluoride supplements is recommended for children aged from three to six years (14.5 to 22 kg body weight) residing in communities with less than 0.7 ppm F. Physicians, pharmacists, and dentists need to be better educated in correctly prescribing fluoride supplements; such prescriptions should be based on the fluoride concentration of the domestic water supply and the child's weight/height/age. No change is recommended in the concentration of fluoride used in dentifrices and mouthrinses. The US Food and Drug Administration should require more explicit labeling of fluoride products with regard to avoidance of ingestion, use of small amounts, and need for supervised use by pre-school children. The efficacy of water fluoridation, fluoride supplements, and topical fluoride agents has been amply documented elsewhere.
A Comparison of Jaw Muscle Cross-sections of Long-face and Normal Adults
Authors: Van Spronsen P.H. , Weijs W.A. , Valk J. , Prahl-Andersen B. , Van Ginkel F.C.
Published: November 2010

Long-face subjects have smaller maximum molar bite forces than do normal individuals. This has been attributed both to differences in moment arms and size of the jaw muscles.

In this study, a comparison was made between the mid-belly cross-sectional areas of the jaw muscles of 13 long-face and 35 normal adults by means of serial MRI scans. The subjects were selected on the basis of anterior lower face height as a percentage of anterior total face height. These and other cephalometric variables were measured from lateral radiographs.

In the long-face group, the cross-sectional areas of the masseter, medial pterygoid, and anterior temporal muscles were, respectively, 30%, 22%, and 15% smaller than in the control group. By a discriminant analysis and a multivariate analysis of variance, these differences were found to be significant (p < 0.001).

The findings of this study hint that differences in the sizes of the jaw muscles of long-face and normal subjects might explain, in part, the observed differences in maximum molar bite force.
Chlorhexidine Effects on Membrane Lipid Domains of Human Buccal Epithelial Cells
Authors: Audus K.L. , Tavakoli-Saberi M.R. , Zheng H. , Boyce E.N.
Published: November 2010

The effect of chlorhexidine gluconate on the adherence of Candida albicans to human buccal epithelial cells (BEC) and drug-induced alterations in BEC membrane-lipid packing order were examined. Treatment of BEC with attached yeasts with 0.1 and 0.2% chlorhexidine resulted in significant yeast detachment after 90 and 60 min, respectively. Following pre-treatment of BEC with > 0.1% chlorhexidine, yeast adherence was inhibited by > 80%. In parallel experiments, the fluorescence anisotropy of BEC labeled with fluorescent membrane probes-diphenylhexatriene (DPH) and trimethylammonium DPH-was assessed following exposure to chlorhexidine. The fluorescence anisotropy decreased with increasing concentrations of chlorhexidine, which indicated that the drug decreased epithelial-cell membrane-lipid packing order. Chlorhexidine concentrations that altered epithelial-cell membrane-lipid packing order, particularly in superficial regions, were similar to those drug concentrations required for detachment of adherent yeasts. Similar results were obtained with a second antifungal, nystatin A. While the effects of chlorhexidine on the buccal-cell membrane-lipid packing order were not reversed by multiple washings, the opposite situation occurred with nystatin A. The results suggest that chlorhexidine-induced alterations ofBEC membrane-lipid order may be involved in the antifungal actions of the drug.
Changes in the Microvasculature after Mechanical Pressure on the Hamster Cheek Pouch
Authors: Da J. , Inage S. , Kurihara S. , Miura F.
Published: November 2010

The reaction of the microvasculature in the periodontal ligament to mechanical pressure is considered a very important phenomenon with respect to the biological background to orthodontic tooth movement. For clarification of the microvascular reaction to mechanical pressure, an experimental model that incorporated a hamster cheek pouch was established. This in vivo model solves some of the problems of other experimental models of the microvasculature of the periodontal ligament. Blood plasma permeation in this model was examined by means of a blue dye (pontamine sky blue), and histological observation was performed by light and transmission electron microscopy.

Increased vascular permeability was observed within 30 min after removal of the mechanical stimulation. The threshold weight resulting in dye leakage was between 1 and 5 g applied for 60 min. From the histological observations, some large gaps between the endothelial cells in venules were found, while most basement membranes remained undisturbed. These observations suggest that the plasma leakage was due to mild traumatic injury to the endothelial cells. Both leukocytes and platelets were observed in the gaps between the endothelial cells in the venule. These types of microvascular reactions to mechanical pressure could initiate tissue changes in the periodontal ligament during orthodontic tooth movement.
A New Method for Promoting Adhesion between Precious Metal Alloys and Dental Adhesives
Authors: Ohno H. , Araki Y. , Endo K.
Published: November 2010

A new, simple method of modifying the adherend metal surface by a liquid Ga-Sn alloy (Adlloy) was applied to dental precious and base-metal alloys for adhesion with 4-META adhesive resin. Adhesions of 4-META resin to three other surface states-as-polished, oxidized at high temperature, and electroplated tin-were also performed for comparison with the adhesion on Adlloy-modified surfaces. Bond strength measurements were made, and the durability against water at the adhering interface was evaluated.

The Adlloy-modified gold alloys (Type IV and 14 K) and silverbasedalloys (Ag-Pd and Ag-Cu) showed not only high bond strengths but also excellent water durability at the adhesion interface. Surface modification by Adlloy, however, did not affect adhesion to Ag-In-Zn and base-metal (SUS, Co-Cr, and Ni-Cr) alloys. Adhesion to the tin-electroplated specimens was comparable with that to the Adlloy-modified specimens.
Effects of External Bleaching on Indentation and Abrasion Characteristics of Human Enamel in vitro
Authors: Seghi R.R. , Denry I.
Published: November 2010

The application of home-bleaching procedures as a means of lightening multiple teeth has become increasingly popular. Very few studies, however, have determined the effect of this treatment upon dental hard tissues. This in vitro study evaluated the effects of a 10% carbamide peroxide gel on the apparent fracture toughness, hardness, and abrasion characteristics of human enamel.

The apparent fracture toughness of enamel was reduced by about 30% after bleaching for a period of 12 hours with no significant change in surface hardness. Enamel treated with the bleaching gels also exhibited a small but significant decrease in abrasion resistance. This behavior was most likely due to an alteration of the organic matrix of enamel under the chemical action of hydrogen peroxide. Further investigation of the clinical significance of this process is needed.
The Effect of Orthodontic Retention on the Mechanical Properties of the Periodontal Ligament in the Rat Maxillary First Molar
Authors: Hong R.K. , Yamane A. , Kuwahara Y. , Chiba M.
Published: November 2010

The load-deformation curves obtained by extraction of the rat maxillary first molar from its socket in the dissected jaw were analyzed so that the effect of orthodontic retention on the mechanical properties of the periodontal ligament could be examined. An elastic band was inserted between the rat maxillary first and second molars for four days, and then the interdental space was filled with resin for four or eight days. The average interdental spaces between the teeth ranged from 315 to 398 μm during the experimental period. The maximum shear load, elastic stiffness, and failure energy in shear decreased markedly following application of an orthodontic force, but they increased gradually and reached control levels on the 8th day after the retention. Maximum shear deformation at maximum load was not significantly different between the experimental and control teeth during the experimental period. It is suggested that, following orthodontic tooth movement, occlusal function was restored after a relatively short retention period, as was the impaired mechanical strength of the periodontal ligament.
Clinical Criteria for the Diagnosis of Salivary Gland Hypofunction
Authors: Navazesh M. , Christensen C. , Brightman V.
Published: November 2010

There is considerable difficulty in the making of initial clinical decisions as to whether a given patient has salivary gland hypofunction, and hence requires additional salivary gland evaluation. This study identified a set of four clinical measures that, together, successfully predicted the presence or absence of salivary gland hypofunction. The four measures were: dryness of lips, dryness of buccal mucosa, absence of saliva produced by gland palpation, and total DMFT; they were derived from discriminant analysis of data collected from 71 individuals with normal and low salivary flow rates. These measures are proposed as criteria for clinical decision-making, as well as for classification of patients in studies of salivary gland dysfunction syndromes. This study also identified unstimulated whole salivary flow rates of 0.12-0.16 mL/ min as the critical range separating individuals with salivary gland hypofunction from those with normal gland function.
Fluoride Intake from Beverage Consumption in a Sample of North Carolina Children
Authors: Pang D.T.Y. , Phillips C.L. , Bawden J.W.
Published: November 2010

Since the 1940's, the prevalence of dental fluorosis has increased in the US, concomitant with a reduction in dental decay. These changes have been attributed in part to the widespread use of systemic and topical fluorides. Various sources of increased systemic fluoride exposure have been investigated. However, little is known regarding fluoride intake from beverages in a sample of children of ages susceptible to dental fluorosis. The purpose of this study was to estimate the amount of fluoride ingested from beverages by a sample of North Carolina (NC) children of ages 2-10 years. Data on beverage consumption were collected by means of a diary format. A questionnaire was included so that demographic information and self-assessment on the accuracy of the diaries could be obtained. Beverages reported in the diaries were purchased, and their fluoride content was assayed. Daily total fluid intake ranged from 970 to 1240 mL, and daily beverage consumption ranged from 585 to 756 mL. The estimated mean daily fluoride intakes from beverages for children 2-3, 4-6, and 7-10 years of age were 0.36, 0.54, and 0.60 mg, respectively.
Effect of Contact Area Size on Enamel and Composite Wear
Authors: Krejci I. , Lutz F. , Zedler C.
Published: November 2010

The effect of contact area dimensions on the wear of composite specimens and their opposing enamel cusps was evaluated in vitro. Thirty-six standardized cylindrical composite specimens were placed into metal cavities (8 mm x 2 mm) and divided randomly into five groups. The composite used was a fine-particle hybrid and was stressed as follows: storage in 75% aqueous ethanol solution for 24 h, toothbrush/toothpaste-abrasion for 30 min, followed by 300 thermal cycles in water ranging from 5° to 55°C and simultaneous 120,000 occlusal chewing loads at a frequency of 1.7 Hz at 53 N maximum force. In group 1 (n = 12), the occlusal chewing loads were applied by palatal cusps of extracted human maxillary molars with natural morphology. In groups 2 to 5 (n = 6), the cusp tips had standardized contact area dimensions of 0.26, 0.38, 1.18, and 4.10 mm2, respectively. Wear of composite specimens and antagonistic enamel cusps (means ± SD) was assessed in μm by means of a 3-D scanner. Additionally, the contact surfaces of the restorations and of the antagonistic enamel cusps were evaluated by SEM. Increases in enamel contact areas after being loaded were measured by means of a digitizer and expressed in percent of the initial size before stress exposure. The wear of the composite specimens varied from 69.8 ± 19.9 to 9.5 ± 3.6 μm, and that of antagonistic enamel cusps from 31.3 ± 3.4 to 8.8 ± 1.5 μm. The increase in contact area varied between 27.8 and 0.1%. Composite and antagonistic enamel wore significantly (p < 0.001, ANOVA, Scheffe) less with increased contact area dimensions. The most severe disintegration of the composite was found in specimens occluding with the smallest enamel contact area. The extent of wear and the wear mechanisms were related to the chewing pressure, which in turn was governed by the contact area dimension.
Arachidonic Acid Regulates the Phosphoinositide Signal Transduction Pathway in Submandibular Acinar Cells
Authors: Chung H.C. , Fleming N.
Published: November 2010

Modulation of the phosphoinositide signal transduction pathway by arachidonic acid (AA) in collagenase-dispersed rat submandibular acinar cells was investigated. The muscarinic agonist, carbachol, stimulated PIP2hydrolysis and the generation of IP3to five-fold the control levels. This response was inhibited by 75% on pre-treatment of cells with AA. The AA inhibitory effect was not duplicated by a range of prostaglandins and leukotrienes and was not reversed by blockers of the cyclo-oxygenase and lipoxygenase synthetic pathways, indicating that AA action was not mediated by eicosanoid metabolites. Additional experiments confirmed that the enzyme, protein kinase C, was also not a mediator of the AA effect. Arachidonic acid did not affect the uptake of radioactive inositol into acinar cells, but it did inhibit the incorporation of inositol into inositol phospholipids of the phosphoinositide cycle. In studies on inositol phospholipid turnover, AA alone reduced the level of PIP2but not of PIP or PI. Under conditions of PI cycle stimulation with carbachol, AA significantly lowered PIP and PIP but not PI. These findings suggest that arachidonic acid may regulate the phosphoinositide response by inhibiting the synthetic phase of the cycle at a locus distal to PI generation.
Axon Populations in Cat Lingual and Chorda Tympani Nerves
Authors: Holland G.R. , Robinson P.P.
Published: November 2010

The lingual and chorda tympani nerves from five cats were examined so that normal axonal populations could be determined. After perfusion fixation, the chorda tympani and lingual nerves were removed and processed, and sections were taken from individual and combined nerves for both light and electron microscopy. The chorda tympani remained as a distinct group of smaller axons for at least 4 mm distal to its junction with the lingual nerve. The mean number ± S.D. of myelinated axons in the chorda tympani central to the junction was 1322 (± 268) and in the lingual nerve central to the junction, 3227 (± 510). The counts were not significantly different distal to the junction, and there were no side-to-side differences. Mean myelinated axon circumferences were significantly smaller in the chorda tympani (12.86 ± 0.87) than in the lingual nerve (22.79 ± 1.99; p < 0.01). The mean size of axons in the chorda tympani was slightly but consistently larger on the left (13.1 ± 0.73) than on the right side (12.61 ± 1.01; p < 0.05). Distal to the junction, the average proportion of non-myelinated axons was 44% in both chorda tympani and lingual nerves.
Influence of Aldehydes on Selected Mechanical Properties of Resin Composites
Authors: Peutzfeldt A. , Asmussen E.
Published: November 2010

The present study investigated whether propanol, a monofunctional aldehyde, was able to improve the mechanical properties of dental polymers. The underlying hypothesis was that a cross-linking reaction is possible between various functional groups of different polymers. Propanol was added to monomer mixtures, which were then made light-curing and loaded with filler. The monomer mixtures were varied with respect to monomer composition and content of aldehyde. Four mechanical properties of the experimental resin composites were determined. Addition of propanol gave rise to significant improvements in mechanical properties, which may be indicative of a cross-linking ability of monofunctional aldehydes. With the exception of modulus of elasticity, the mechanical properties of resin composites based on UEDMA/HEMA were superior to those of BISGMA/TEGDMA-based materials, even though the improvements in flexural strength and modulus of resilience were most pronounced for the BISGMA/TEGDMA-based resin composites.
Morphological Aspects of the Resin-Dentin Interdiffusion Zone with Different Dentin Adhesive Systems
Authors: Van Meerbeek B. , Inokoshi S. , Braem M. , Lambrechts P. , Vanherle G.
Published: November 2010

Cross-sections of resin-dentin interfaces were etched with an argon-ion beam to make their substructure detectable by scanning electron microscopy. The dentin adhesive systems were categorized morphologically into three groups, and an attempt was made to clarify their adhesive mechanism.

The first group of products removed the smear layer. The argon-ion bombardment clearly disclosed a hybrid or resin-impregnated dentin layer. It is hypothesized that conditioning with acidic or chelating agents demineralized the dentin surface-layer to a certain depth, leaving behind a collagen-rich mesh-work. Hydrophilic monomers are then believed to alter this collagen-fiber arrangement in a way that facilitates penetration of the adhesive resin, resulting in a mechanical, intermingled link between collagen and the adhesive resin.

The second group preserved the smear layer. In this case, the dentinal tubules were obliterated with globular particles at their orifices and remained patent underneath these smear plugs. This type of adhesive system aims at the incorporation of the smear layer into the hydrophilic monomers, which have an affinity for the organic and/or inorganic components of the underlying dentin.

Finally, a third, small group only partly dissolved the smear layer, creating a thin resin-impregnated dentin layer and a resin-impregnated smear plug.

This study clearly showed that the application of recent adhesive systems induced structural changes in the dentin surface morphology, creating a retentive interface, called the interdiffusion zone, between the deep, untouched dentin layers and the composite filling material. This resin-dentin interdiffusion zone offers bonding sites for copolymerization with the resin composite and, concurrently, might have protective potential for the pulp tissues.
Inhibition of Plaque Formation and Gingivitis in Beagle Dogs by Topical Use of a Degradable Controlled-release System Containing Chlorhexidine
Authors: Kozlovsky A. , Sintov A. , Zubery Y. , Tal H.
Published: November 2010

The in vivo efficacy of a newly-developed dental application of a film-forming, chlorhexidine-containing system was examined in beagle dogs. A self-disintegrating film-forming solution was applied three times weekly to the dentitions of 7 out of 13 dogs, which were fed a soft-food diet. Plaque accumulation (Plaque Index) and gingival inflammation (Gingival Index) were recorded at one, two, four, six, and eight weeks. The local delivery of low-dose chlorhexidine to dogs significantly inhibited gingivitis and plaque formation. It is concluded that the dental application of a film-forming system may be a preferable method of periodontal disease prophylaxis, and may enhance supragingival plaque control in areas of isolated periodontal problems associated with obvious local predisposing factors.