bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of a Cholecystokinin Agonist on Masseter Muscle Activity in the Cat
Authors: Sitthisomwong P. , Weiner S. , Levin L. , Reisman S. , Siegel A.
Published: January 2009

The CCKB agonist, pentagastrin, has been shown to induce anxiety in human subjects. Similarly, in the cat model, pentagastrin facilitates the expression of hypothalamically activated emotional behavior. Because hypothalamically mediated emotional behavior is also accompanied by increased EMG activity in the jaw muscles, these experiments were designed to examine the combined effects of administration of pentagastrin with activation of hypothalamically mediated emotional behavior upon jaw muscle EMG activity. Electrodes were carefully lowered through previously placed guide tubes overlying the hypothalamus until a behavioral site was identified. Following the establishment of a stable threshold current for eliciting an emotional behavioral response, the skin overlying the ipsilateral masseter muscle was shaved and cleaned with alcohol, and surface electrodes were attached. The EMG was recorded, amplified, digitized, and stored in a microcomputer for analysis. Mean power frequencies (MPF) and latencies for behavior were calculated for baseline prior to infusion of all drugs. Following this, the effects of intravenous administration of pentagastrin and the CCKB antagonist LY288513 on the MPF were determined. The infusion of the CCKB agonist, pentagastrin (0.77, 1.92, and 3.84 μg/kg), decreased MPF in a time-related manner. The effects of pentagastrin 1.92 μg/kg were blocked by the CCKB antagonist, LY288513 (6.54 μg/kg). In addition, the infusion of LY288513 alone increased MPF. These results are surprising in that pentagastrin's anxiogenic properties would appear to make it likely to facilitate motor activity, not suppress it.
From Osseointegration to Osseoperception
Authors: Van Steenberghe Daniel
Published: January 2009

Periodontology has broadened its scope by the research and clinical use of osseointegrated implants. Since tactile and reflex functions have been associated with periodontal ligament neural receptors, osseoperception could be associated with endosseous and/or periosteal innervation.
Effects of Whisker-to-Silica Ratio on the Reinforcement of Dental Resin Composites with Silica-fused Whiskers
Authors: Xu H.H.K. , Quinn J.B. , Giuseppetti A.A. , Eichmiller F.C.
Published: January 2009

Resin composites need to be strengthened to improve their performance in large stress-bearing restorations. This study aimed to reinforce composites with whiskers and to investigate the effects of the whisker:silica ratio. It was hypothesized that changing the whisker-silica ratio would affect the whisker-matrix bonding and the filler's distribution, and hence alter the composite properties. Silica particles and whiskers were mixed at various whisker:silica mass ratios, thermally fused, and combined with a dental resin at filler mass fractions of 0-65%. Whisker :silica ratio and filler level had significant effects on composite properties. At 60% filler level, the silica composite (whisker:silica = 0:1) had a flexural strength (mean ± SD; n = 6) of 104 ± 21 MPa; that at a whisker:silica ratio of 1:0 was 74 ± 36 MPa. However, that of the silica-fused whisker composite (whisker:silica = 5:1) was 210 ± 14 MPa, compared with 109 ± 23 MPa and 114 ± 18 MPa of two prosthetic controls. Mixing silica with whiskers minimized whisker entanglement, improved filler distribution in the matrix, and facilitated whisker silanization and bonding to the matrix, thus resulting in substantially stronger composites.
Determination of Variation of Stimulated Salivary Flow Rates
Authors: Ghezzi E.M. , Lange L.A. , Ship J.A.
Published: January 2009

Salivary hypofunction is associated with oral and pharyngeal disorders and requires early diagnosis and intervention. Large variability in salivary flow rates within and between individuals has been reported, which has impaired the establishment of standard values. The objective of this study was to determine variations in stimulated parotid and submandibular flow rates over 6 hours and to define salivary hypofunction. Pooled mean, standard deviation, and coefficient of variation values for four collection time periods were obtained from 36 healthy males and females (18 young, ages 20-38; 18 older, ages 60-77). The results demonstrated 27-44% variation in salivary flow rates over time. Overall, there were no significant age or gender differences in variability between and within salivary flow rates at all collection time periods. The results suggest that a 45% range in salivary flow rates could be considered normal salivary variation, and values below 45% of normal levels could be used to define salivary hypofunction.
Effects of Head and Body Position on Two- and Three-dimensional Configurations of the Upper Airway
Authors: Ono T. , Otsuka R. , Kuroda T. , Honda E. , Sasaki T.
Published: January 2009

This study was carried out to test the hypothesis that changes in head/body position induce changes in upper-airway dimensions. Contiguous images were obtained by means of magnetic resonance imaging in normal awake subjects during nasal breathing. A statistical analysis was made on 5 consecutive slices, including the most constricted sites in both the retropalatal and retroglossal regions. Dimensional changes in the upper airway in association with changes in head/body position were evaluated. In the retropalatal region, there was a significant decrease in the lateral dimension in the lateral recumbent position compared with that in the supine position. The cross-sectional area in the retroglossal region was significantly increased in both the "supine with the head rotated" and "lateral recumbent" positions. This change was accompanied by significant volumetric changes in the retroglossal region. Thus, sleeping with the head rotated may be effective for improving upper-airway obstruction.
Dose-dependent Modulation of Octacalcium Phosphate Crystal Habit by Amelogenins
Authors: Wen H.B. , Moradian-Oldak J. , Fincham A.G.
Published: January 2009

In vitro studies on interactions between amelogenins and calcium phosphate crystals are critical for elucidating biomineralization mechanisms of tooth enamel. This work was aimed at investigating the effects of native porcine amelogenins on octacalcium phosphate (OCP) crystal growth in a gelatin gel. We prepared OCP mineral discs by circulating calcium and phosphate solutions on the opposite ends of the gels loaded with 0-2% amelogenin for one week. A dose-dependent modulation of OCP crystal habit by amelogenins was observed by scanning electron microscopy. While the incorporation of 0.125, 0.25, or 0.5% amelogenins showed no significant effect on the crystal morphology, in the presence of I and 2% amelogenins, the crystals were remarkably longer, having an average aspect ratio 3-5 times greater than that of those formed in the control gels. Transmission electron microscopy and atomic force microscopy suggested that amelogenin assemblies selectively blocked b-axial development, resulting in the c-axial elongation of OCP crystals.
N-terminal Sequence Analysis of Bovine Dentin Phosphophoryn after Conversion of Phosphoseryl to S-propylcysteinyl Residues
Authors: Huq N.L. , Cross K.J. , Talbo G.H. , Riley P.F. , Loganathan A. , Crossley M.A. , Perich J.W. , Reynolds E.C.
Published: January 2009

Bovine dentin phosphophoryn (BDP), a protein rich in aspartyl (Asp) and O-phosphoseryl (Ser[P]) residues, is synthesized by odontoblasts and is believed to be involved in matrix-mediated biomineralization of dentin. We have purified BDP, using selective precipitation and ion exchange chromatography, from an EDTA soluble dentin extract and converted the Ser( P) residues to S-propylcysteinyl residues that are stable to Edman degradation, facilitating the determination of the amino acid sequence of the N-terminal 38 residues. After the initial Asp-Ser(P)-Pro-Asn-Ser( P)-Ser( P)-Asp-Glu-Ser( P)-Asn-Gly-, the sequence contained the repeated motifs Asp-Ser( P) and Asp-Ser( P)-Ser( P). Purified BDP migrated as a single band on gradient SDS-PAGE with an apparent molecular weight of 156 kDa. This value was consistent with the molecular weight of the dephosphorylated protein of 105 kDa determined by means of MALDI mass spectrometry.
Improvement of Strength Parameters of a Leucite-reinforced Glass Ceramic by Dual-ion Exchange
Authors: Fischer H. , Marx R.
Published: January 2009

An innovative dual ion-exchange process can improve the limited strength and the scatter-in-strength of technical glasses. The objective of this study was to prove whether such a two-stage ion-exchange process can also improve the limited strength and the problematic scatter-in-strength of dental ceramic materials. The first exchange was done in KN03 on a leucite-reinforced glass-ceramic material, the second exchange in 70 mol% KN03, 30 mol% Na N03 at different treatment times and temperatures. The dual-exchange process approximately doubled the Weibull strength. Moreover, the Weibull modulus showed a four-fold increase, i.e., the coefficients of variation were reduced from 18.3 to 4.7%. We conclude that the dual-exchange process may help significantly to increase the clinical reliability of glass-ceramic dental restorations, because the strength and the scatter-in-strength will be substantially improved by this treatment.
Interferon-γ Down-regulates Gene Expression of Cathepsin K in Osteoclasts and Inhibits Osteoclast Formation
Authors: Kamolmatyakul S. , Chen W. , Li Y.-P.
Published: January 2009

The cytokine, IFN-γ, has been shown in vitro to inhibit bone resorption, but the mechanisms responsible for this inhibition have not been clearly defined. Cathepsin K is a major protease responsible for bone resorption. IFN-γ may inhibit bone resorption through down-regulation of osteoclast genes, including cathepsin K. To test the hypothesis, we investigated the effect of IFN-γ on cathepsin K expression in the MOCP-5 and wild-type mouse bone marrow co-culture systems by Northern blot as well as osteoclast formation at different stages of differentiation. The results show that IFN-γ down-regulates mRNA levels of cathepsin K in a time- and dose-dependent manner. Consequently, cathepsin K protein production is also reduced by IFN-γ. Moreover, our results indicate that IFN-γ inhibits osteoclast formation only early in osteoclast differentiation. IL-6 and TNFa did not significantly affect cathepsin K gene expression in osteoclasts. However, IL-la stimulated gene expression. In conclusion, our data suggest that the actions of IFN-γ on osteoclastic bone resorption may be mediated by its effects on both osteoclast formation at an early stage and osteoclast gene expression in mature osteoclasts.
Large-scale Early in vitro Response to Actinobacillus actinomycetemcomitans Suggests Superantigenic Activation of T-cells
Authors: Zadeh H.H. , Nalbant A. , Park K.
Published: January 2009

The mode of T-cell response to Actinobacillus actinomycetemcomitans is largely unknown. The present study sought to investigate the hypothesis that A. actinomycetemcomitans expresses superantigens, capable of antigen-non-specific T-cell activation. To that end, peripheral blood mononuclear cells were stimulated with A. actinomycetemcomitans, and T-cell expression of the early activation marker, CD69, was determined by flow cytometry. Results showed that A. actinomycetemcomitans activated a large number of T-cells with magnitude similar to that of staphylococcal enterotoxin superantigens. A. actinomycetemcomitans sonicate preferentially activated T-cells expressing Vβ5.1 and Vβ8, while the extracellular preparation activated Vβ5.1+, Vβ8+, and Vβ12 + T-cells. T-cell response to A. actinomycetemcomitans was observed in the presence of autologous, as well as heterologous, antigen-presenting cells, suggesting a MHC-non-restricted response. Thus, the in vitro response to A. actinomycetemcomitans is characterized by large-scale T-cell activation in a Vβ-specific and MHC-non-restricted manner, consistent with the involvement of superantigens.
Assessment of Acid Production by Various Human Oral Micro-organisms when Palatinose or Leucrose is Utilized
Authors: Peltroche-Llacsahuanga H. , Hauk C.J. , Kock R. , Lampert F. , Lütticken R. , Haase G.
Published: January 2009

One promising way of reducing caries is by using sucrose substitutes in food, e.g., palatinose or leucrose. Previous experiments addressing cariogenic potential of sucrose substitutes have focused mainly on Streptococcus mutans. However, given the many other micro-organisms in the oral cavity, this study compared the acid production of 100 bacterial strains representing 44 different species, by batch fermentation in a test tube containing, as a sole carbohydrate source, glucose, sucrose, palatinose, or leucrose. Selected strains were further analyzed in a fermenter. Additionally, 30 yeast strains were tested by an auxanographic sugar assimilation test. Only Lactobacillus spp., Stomatococcus mucilaginosus, Leuconostoc mesenteroides, and Weissella para-mesenteroides, and some of the yeasts studied-i.e., Candida albicans, C. tropicalis, C. parapsilosis, and Saccharomyces cerevisiae-utilized leucrose and/or palatinose well. Strikingly, Stomatococcus mucilaginosus produced water-insoluble polysaccharides by fermentation of leucrose and palatinose. In the fermenter, the respective sucrose substitutes were not only cleaved but also utilized. Thus, extracellular cleavage by autochthonous micro-organisms may produce cariogenic cleavage products (glucose, fructose) that can be used by other well-characterized cariogenic bacteria found in the oral flora. Therefore, the anticariogenic potential of sucrose substitutes in food might be limited.
CONCISE REVIEW Biological: Interleukin 1 Signal Transduction— Current Concepts and Relevance to Periodontitis
Authors: Boch J.A. , Wara-aswapati N. , Auron P.E.
Published: January 2009

This review examines a well-characterized factor, interleukin 1 (IL-1), that has recently received considerable attention. A level of understanding is emerging that goes beyond simple recognition that IL-1 plays a role in disease, and begins to explain the molecular mechanisms of function. This review summarizes some current information on the importance of IL-1 in periodontitis as well as the signal transduction of IL-1, from binding to its cell-surface receptors, to the activation of cytoplasmic mediators and transcription factors responsible for the induction of target genes. The effect of IL-1 signal transduction is ultimately the activation and repression of specific transcription factors that regulate genes responsible for cellular activities. As additional steps of signal transduction become better-characterized, these insights may facilitate the development of improved therapeutic approaches for controlling inflammation and connective tissue destruction in a variety of diseases.
Anisotropy of Tensile Strength of Root Dentin
Authors: Lertchirakarn V. , Palamara J.E.A. , Messer H.H.
Published: January 2009

An effect of dentinal tubule orientation on mechanical properties of dentin has been difficult to demonstrate. We have tested the hypothesis that ultimate tensile strength (UTS) of dentin is affected by tubule (and hence collagen fibril) orientation. The UTS of human root dentin was investigated by direct tensile and diametral testing of specimens of known orientation prepared from extracted teeth. Dumbbell-shaped samples were machined for direct tensile testing (load parallel or perpendicular to tubule direction) and cylinders for diametral testing (load at 0°, 45°, 67.5°, and 90°). Fractured surfaces were examined by SEM. UTS was lowest when the tensile force was parallel to tubule orientation, and greatest at 90° to tubule orientation (fracture parallel to tubule direction). SEM views of fractured surfaces suggested that microstructure contributes to fracture patterns. At least for properties involving disruption of the collagen matrix, root dentin shows a definite anisotropy.
Immunohistochemical Evidence for ATP Receptors in Human Dental Pulp
Authors: Alavi A.M. , Dubyak G.R. , Burnstock G.
Published: January 2009

Evidence is accumulating which supports a role for ATP in the initiation of pain by acting on P2X receptors, in particular P2X3, expressed on nociceptive afferent nerve terminals. To investigate whether this receptor plays a role in dental pain, we studied the presence and distribution of P2X3 receptors in human dental pulp, and their co-localization with other neural markers. Pulps were removed from extracted third molars and immunohistochemically stained with an antibody against P2X3 receptors. P2X3 immunoreactive (-ir) nerve fibers were detected in the main body of the pulp, in the sub-odontoblastic plexus of Raschkow, and within the odontoblastic area. Co-localization of the P2X3-ir neurons with neurofilament protein (NF) showed that the majority of the fibers were positive for both NF and P2X3. Double labeling with isolectin B4 (IB4) showed that all P2X3-ir neurons also bind IB4. We conclude that P2X3 receptors are present on both myelinated and unmyelinated nerve fibers in human dental pulp and may play a role in dental pain mechanisms.
Concise Review Biomaterials & Bioengineering: Fusing of Dental Ceramics to Titanium
Authors: Könönen M. , Kivilahti J.
Published: January 2009

Titanium is known as a useful biometal because of its good biocompatibility and mechanical performance. However, titanium is chemically an exceptional metal, reacting strongly with gaseous elements like oxygen, hydrogen, and nitrogen and also dissolving them extensively. This high reactivity causes problems, for example, when dental ceramics are fused to titanium. Commercial ceramic-titanium systems are increasingly used in prosthetic dentistry, but little is known about the microstructure and composition of the system. Better understanding of chemical reactions between ceramics and titanium is necessary if mechanically more compatible ceramic-titanium bonds are to be developed. This review deals with titanium as a metal, titanium's affinity for non-metallic elements (especially oxygen), and reactions with other elements. Different aspects are discussed relative to the fusing of dental ceramics to titanium.
Properties of Opaque Resin Composite Containing Coated and Silanized Titanium Dioxide
Authors: Yoshida K. , Taira Y. , Atsuta M.
Published: January 2009

Titanium dioxide (TiO 2) is mainly used as a pigment in opaque resin composites for application to the surface of a metal framework. The hypothesis in this paper is that particles of silica/alumina (SiO2/Al2O3)-coated Ti02 treated with a silane coupling agent could bond effectively with resin monomers of opaque resin composites. Untreated TiO2 was used as the control filler. Compressive and flexural strength specimens were prepared by the heat-curing method, because these bulk specimens could not be made by the typical photo-curing method. The treated composite had significantly higher compressive and flexural strengths than the untreated composite after 6 months' immersion in water. Scanning electron microscopy of the fractured composite surfaces showed an interface failure between TiO2 and resin for the untreated composite and cohesive failure within the resin for the treated composite after 6 months' immersion. The light-activated opaque resin composite containing treated TiO2 exhibited significantly higher bond strength to a noble dental alloy after 5000 thermal cycles than that containing untreated TiO2. Thus, silanized SiO2/Al 2O3-coated TiO2 appears to be clinically useful as a filler of opaque resin composites.
Metabolic Effects of Dental Resin Components in vitro Detected by NMR Spectroscopy
Authors: Engelmann J. , Leyhausen G. , Leibfritz D. , Geurtsen W.
Published: January 2009

Earlier studies have shown that the comonomer triethyleneglycol-dimethacrylate (TEGDMA) and the photostabilizer 2-hydroxy-4-methoxybenzophenone (HMBP) are cytotoxic and inhibit cell growth. It was the aim of this study to elucidate the underlying metabolic effects of TEGDMA and HMBP on immortal contact-inhibited Swiss albino mouse embryo cells (3T3 fibroblasts) by nuclear magnetic resonance (NMR) spectroscopy. Cell extracts and culture media were analyzed by NMR spectroscopy for metabolic changes after incubation for 24 hours with ED20-concentrations of TEGDMA and HMBP. TEGDMA could be detected in all fractions (cytosol, lipid fractions, and culture media) of 3T3 cells, while HMBP was found only in the lipid fraction accumulated at a maximum rate (51 nmol/mg DNA) compared with TEGDMA (27 nmol/mg DNA). TEGDMA increased the concentration of phosphomonoesters to 180 ± 36% and decreased the phosphodiesters to 65 ± 5% of controls (control = 100%). Thus, the turnover of phospholipids was enhanced, whereas content and composition of phospholipids of membranes did not alter markedly. Additionally, TEGDMA changed the metabolic state of cells, indicated by slight decreases of nucleoside triphosphates and an increase in the ratio of nucleoside diphosphates to nucleoside triphosphates, while HMBP had no effect. The most remarkable effect of TEGDMA was a nearly complete decline of the intracellular glutathione levels. Analysis of our data shows that NMR spectroscopy of cell-material interactions may reveal metabolic effects of organic test substances which are not detectable by standard in vitro assays. The comonomer TEGDMA affected the metabolism of the cells on different levels, while HMBP accumulated in the lipid fraction and induced significantly fewer effects on cell metabolism.
Mitogenic Effects of Neurotrophins on a Periodontal Ligament Cell Line
Authors: Tsuboi Y. , Nakanishi T. , Takano-Yamamoto T. , Miyamoto M. , Yamashiro T. , Takigawa M.
Published: January 2009

Nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3) are three representative neurotrophins responsible for the differentiation and survival of neurons, and their high-affinity receptors are tropomyosin-receptor-kinase (TRK)A, TRKB, and TRKC, respectively. In this study, we investigated the expression of neurotrophins in a mouse periodontal ligament cell line (MPL), by reverse transcription-polymerase chain-reaction (RT-PCR) and enzyme-linked immunoabsorbent assay (ELISA). We also studied the expression of TRK receptors on MPL by immunostaining and the effects of neurotrophins on the proliferation of MPL, with a hypothesis of autocrine mechanism of neurotrophins. Each neurotrophin and TRK receptor was expressed, and neurotrophins enhanced the proliferation of MPL. These findings suggest that the MPL has functional neurotrophin receptors involved in an autocrine function of neurotrophins. The expression level of neurotrophins and TRKs showed the reverse pattern, and we propose an auto-regulatory mechanism of ligands and receptors in accordance with the level of synthesized neurotrophins.
Dual Regulation of Osteoclast Differentiation by Periodontal Ligament Cells through RANKL Stimulation and OPG Inhibition
Authors: Kanzaki H. , Chiba M. , Shimizu Y. , Mitani H.
Published: January 2009

Periodontal ligament (PDL) cells play an important role in maintaining the homeostasis of periodontal tissues. However, it is not known how PDL cells contribute to osteoclastogenesis. In this study, we examined the consequences of cell-to-cell interactions between peripheral blood mononuclear cells (PBMCs) and PDL cells during osteoclastogenesis. PBMCs were co-cultured directly or indirectly with PDL cells for two to four weeks. PBMCs that were directly co-cultured with PDL cells formed significantly more resorption pits on dentin slices than did PBMCs that were cultured alone. However, soluble factor(s) produced from PDL cells inhibited the formation of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells. Furthermore, PDL cells expressed both receptor activator nuclear factor kappa B ligand (RANKL) and osteoprotegerin (OPG) mRNA. In conclusion, PDL cells support osteoclastogenesis through cell-to-cell contact. PDL cells might regulate osteoclastogenesis by opposing mechanisms-stimulation of resorptive activity by RANKL and inhibition by OPG-thus affecting processes such as periodontitis and orthodontic tooth movement.
Gene Transfer and Expression of Platelet-derived Growth Factors Modulate Periodontal Cellular Activity
Authors: Zhu Z. , Lee C.S. , Tejeda K.M. , Giannobile W.V.
Published: January 2009

Platelet-derived growth factor (PDGF) is a potent stimulator of wound healing. PDGF gene therapy may promote greater periodontal regeneration than local protein application, due to sustained growth factor delivery to the target tissue. This investigation tested the ability of recombinant adenoviruses (rAds) encoding PDGF-A or PDGF-1308 (a PDGF-A dominant-negative mutant that disrupts endogenous PDGF bioactivity) to affect cells derived from the periodontium. Osteoblasts, periodontal ligament fibroblasts, and gingival fibroblasts were transduced with rAds, and gene expression, DNA synthesis, and cell proliferation were evaluated. The results revealed strong message for the PDGF-A gene for 7 days following gene delivery. Ad2/PDGF-A enhanced the mitogenic and proliferative response in all cell types, while Ad2/PDGF-1308 potently inhibited mitogenesis and proliferation. In conclusion, Ad2/PDGF can effectively transduce cells derived from the periodontium and promote biological activity equivalent to PDGF-AA. These studies support the potential use of gene therapy for sustained PDGF release in periodontal tissues.
Condylar Motion in Patients with Reduced Anterior Disc Displacement
Authors: Miyawaki S. , Tanimoto Y. , Inoue M. , Sugawara Y. , Fujiki T. , Takano-Yamamoto T.
Published: January 2009

The influence of reduced anterior disc displacement on condylar motion has not been fully examined in young adults. Reduced anterior disc displacement was hypothesized to inhibit condylar motion. Using a six-degrees-of-freedom jaw-tracking system, we recorded bilateral condylar motion during maximum open-close jaw movement and gum-chewing on both sides in ten young adults with unilateral reduced anterior disc displacement and in ten control subjects without temporomandibular disorders. The bilateral condylar motion during both maximum open-close jaw movement and chewing on the disc-displacement side was inhibited in the test group. The condylar motion on the disc-displacement side during chewing on the non-disc-displacement side was also inhibited in the test group. These results suggest that the limitation of condylar motion on the disc-displacement side may influence condylar motion on the non-disc-displacement side during maximum open-close jaw movement, and mastication on the disc-displacement side in young adults.
Characteristics of Incisor-Premolar Hypodontia in Families
Authors: Arte S. , Nieminen P. , Apajalahti S. , Haavikko K. , Thesleff I. , Pirinen S.
Published: January 2009

Nonsyndromic tooth agenesis is a genetically and phenotypically heterogenous condition. It is generally assumed that different phenotypic forms are caused by different mutated genes. We analyzed inheritance and phenotype of hypodontia and dental anomalies in 214 family members in three generations of 11 probands collected for genetic linkage study on incisor-premolar hypodontia (IPH). Our analysis confirms the autosomal-dominant transmission with reduced penetrance of IPH. The prevalence of hypodontia and/or peg-shaped teeth was over 40% in first-and second-degree relatives and 18% in first cousins of the probands. Four of nine noted obligate carriers of hypodontia gene had dental anomalies, including small upper lateral incisors, ectopic canines, taurodontism, and rotated premolars. These anomalies were also observed at higher than normal frequency in relatives affected with hypodontia. We conclude that incisor-premolar hypodontia is a genetic condition with autosomal-dominant transmission and that it is associated with several other dental abnormalities.
Oral Health Status and Oral Health Behaviors in Chinese Children
Authors: Wong M.C.M. , Lo E.C.M. , Schwarz E. , Zhang H.G.
Published: January 2009

The objectives of the study were to describe the oral health status and treatment needs of the 5- to 6-year-old and 12-year-old children in Southern China; to describe the patterns of oral health behaviors, knowledge, and attitudes among the 12-year-olds; and to assess the effects of socio-behavioral factors on the 12-year-old children's dental caries experiences. The study sample was comprised of 1587 5- to 6-year-old and 1576 12-year-old urban and rual schoolchildren living in Guangdong Province. Three calibrated dentists clinically examined the children, and trained interviewers interviewed the 12-year-olds. Caries prevalence of the 5- to 6-year-old children was high (urban 78% vs. rural 86%); the mean dmft of the urban and rural children was 4.8 and 7.0, respectively. The caries prevalence and mean DMFT score of the 12-year-olds were 41% and 0.9 (urban) and 42% and 0.9 (rural). Only 2% of the 12-year-olds exhibited no calculus or gingival bleeding, while more than 70% had calculus. In conclusion, there is an urgent need for establishing caries-preventive activities for preschool children. The prevalence of caries among the 12-year-olds was not high, but their periodontal condition was unsatisfactory. Knowledge about gum bleeding and the use of fluoride was low. More oral health education activities should be organized, especially for the rural children.
Concise Review Clinical: Equivalence Testing with Dental Clinical Trials
Authors: Burns D.R. , Elswick R.K.
Published: January 2009

Clinical trials whose purpose are to show equivalence of two or more treatments have traditionally utilized methods for demonstrating superiority, and, if no statistical differences are found, the treatments are assumed to be equivalent. Methods for directly demonstrating equivalence have been developed by the pharmaceutical industry to establish the bioequivalence between drug formulations. This approach should have significant future implications for dental research. It is presently well-characterized in the statistical literature, but is virtually unknown within the dental literature and has had limited documented application with dental clinical trials. The purpose of this paper is to consider equivalence testing with dental clinical trials. Equivalence and superiority testing are contrasted, and comparisons between parallel and crossover designs with equivalence testing are discussed. To exemplify equivalency trial methodology for dental research application, several examples are proposed, including, in detail, an implant overdenture clinical trial to test the equivalence of treatment outcome between a two- and a four-implant overdenture treatment. Sample size calculations for otherwise-identical crossover and parallel equivalence studies are demonstrated. Results show that for a power of 0.90, a sample size of 24 is required for the crossover trial and over 150 subjects for the parallel design. For this dental research application, the equivalence/crossover design methodology is shown to be an efficient and appropriate approach.
Vanilloid Receptor Expression and Capsaicin Excitation of Rat Dental Primary Afferent Neurons
Authors: Chaudhary P. , Martenson M.E. , Baumann T.K.
Published: January 2009

Little is known about the molecular mechanisms that cause excitation of neurons which innervate the teeth. We investigated whether rat dental sensory neurons express the vanilloid (capsaicin) receptor (VR1). Dental sensory neurons were identified by retrograde transport of the fluorescent dye DiIC18 placed in maxillary molars. Patch-clamp recordings in culture showed that 65% of DiIC18-labeled rat trigeminal ganglion neurons are excited by capsaicin. Responders covered the entire range of cell sizes examined (soma diameter, 24 to 48 μm). All non-responders had a soma diameter > 33 μm. Capsazepine (1 μM) reduced the capsaicin-evoked membrane current (6/6) and depolarization (7/7 responders). RT-PCR amplified a 375-bp product from DiIC18-labeled neurons which was identical to that expected for VR1. Thus, many rat dental primary afferent neurons are excited by capsaicin, and the response appears to be mediated by VR1. These results suggest that pharmacological blockers of VR1 may provide significant relief of dental pain.
High-resolution Electron Microscopy of the Crystallites of Fossil Enamels Obtained from Various Geological Ages
Authors: Kakei M. , Nakahara H. , Kumegawa M. , Mishima H. , Kozawa Y.
Published: January 2009

To elucidate the stability of the central dark line (CDL) in biologically induced hydroxyapatite crystals, we examined the diagenetic changes on the microstructures of the crystallites during the course of fossilization. Using transmission electron microscopy, we investigated the enamel crystallites of fossil animals of various geological ages ranging from Pleistocene to Cretaceous. Electron micrographs indicated that the microstructures and lattice images of each crystallite in fossil enamels were well-preserved regardless of the thickness of the enamel layer, and the presence of CDLs in fossil enamel crystals was also confirmed. The results indicated that the microstructure of hydroxyapatite crystals containing lattice images of CDLs appear stable during long geological periods. In addition, we conclude that the existence of lattice images in apatite with CDLs may be an indicator for the assessment of the evolution of dental enamel from fossil remains.
Evidence of a Critical Leucite Particle Size for Microcracking in Dental Porcelains
Authors: Mackert J.R. , Twiggs S.W. , Russell C.M. , Williams A.L.
Published: January 2009

The leucite particles in dental porcelains are often partially encircled by microcracks that are the result of the thermal expansion mismatch between leucite and the surrounding glass matrix. Although the magnitude of the stress at the particle-matrix interface is independent of the particle size (Selsing, 1961), Davidge and Green (1968) showed experimentally that there is a critical particle size below which microcracking is absent. The critical particle size is explained by a Griffith-type energy balance criterion: Below the critical size, the stress magnitude may be sufficient to cause cracking, but there is insufficient strain energy for the creation of the new surfaces of the microcrack. The purpose of the present study was to determine whether the mean leucite particle size of a dental porcelain influences the degree of microcracking in the porcelain. Microcrack density, leucite particle surface area per unit volume, and leucite mean volume-surface diameter, D3,2, were determined by quantitative stereology on 10 specimens each of 6 dental porcelains and Component No. 1 of the Weinstein et al. patent (US Patent 3,052,982, 1962). The fraction of leucite particles with microcracks around them, fmc, was estimated for each porcelain from the microcrack density and the leucite surface area. Using the equations of Selsing (1961) and Davidge and Green (1968), we calculated the critical particle diameter, Dc, for leucite to be 4 μm. The porcelains were partitioned according to whether their mean leucite particle diameters, D 3,2, fell above or below Dc, and their values of fmc were analyzed by a permutation test with random re-sampling. The porcelains with mean leucite particle diameters below D c had a significantly lower fraction of cracked particles compared with the porcelains with mean leucite particle diameters above D c (p < 0.05). This study provides evidence that microcracking in dental porcelain can be minimized by a reduction of the mean leucite particle diameter to less than 4 μm.
The Induction of Micronuclei in vitro by Unpolymerized Resin Monomers
Authors: Schweikl H. , Schmalz G. , Spruss T.
Published: January 2009

Components of resin materials may damage DNA, leading to genetic alterations in mammalian cells. Here, monomers were analyzed for the induction of chromosomal aberrations indicated by micronuclei induced in V79 cells. A dose-related increase in the numbers of micronuclei was observed with triethyleneglycol dimethacrylate (TEGDMA), 2-hydroxyethyl methacrylate (HEMA), and glycidyl methacrylate (GMA). These effects were reduced, however, by a metabolically active microsomal fraction from rat liver. The very low activity of Bis-GMA and UDMA and the elevated numbers of micronuclei caused by high concentrations of methyl methacrylate and bisphenol A were associated with cytotoxicity. Our findings provide evidence for the induction of micronuclei by TEGDMA, HEMA, and GMA under physiological conditions, indicating clastogenic activity of these chemicals in vitro. Since it has been shown that TEGDMA also caused gene mutations and DNA sequence deletions in mammalian cells, the activity of this substance should be analyzed in vivo.
Relationship between Upper Body Obesity and Periodontitis
Authors: Saito T. , Shimazaki Y. , Koga T. , Tsuzuki M. , Ohshima A.
Published: January 2009

Upper body obesity, related to visceral fat accumulation, is known to increase the risk of various adult diseases, especially type 2 diabetes and cardiovascular disease. This study was conducted to clarify the relationship between upper body obesity and periodontitis. We studied 643 apparently healthy, dentulous Japanese adults who attended programs at Fukuoka Health Promotion Center. Waist-hip ratio, body-mass index (BMI), and body fat were significant risk indicators for periodontitis after adjustment for known risk factors (p < 0.002). Subjects were divided into four BMI (or body fat) categories. In only the subjects with high waist-hip ratio, higher categories of BMI (or body fat) significantly increased the adjusted risk of periodontitis, compared with subjects with low waist-hip ratios and the lowest category of BMI (or body fat). The reported relationship between cardiovascular disease and periodontitis should be reconsidered, since abdominal adiposity or visceral fat can be related to both diseases.
Gelatinase A (MMP-2) in Developing Tooth Tissues and Amelogenin Hydrolysis
Authors: Caron C. , Xue J. , Sun X. , Simmer J.P. , Bartlett J.D.
Published: January 2009

Matrix metalloproteinases (MMPs) are thought to play important roles during enamel and dentin biomineralization. Previously, membrane type-1 matrix metalloproteinase (MT1-MMP) was localized to the plasma membranes of ameloblasts and odontoblasts of the developing tooth. The best-characterized function of MT1-MMP is to initiate the activation of gelatinase A (MMP-2). Thus, we hypothesized that gelatinase A may also be expressed by developing tooth tissues. A full-length porcine gelatinase A mRNA was isolated by RT-PCR homology cloning of an enamel-organ-specific cDNA library. Northern blot and in situ hybridization analyses demonstrated gelatinase A expression in developing tooth tissues. Immunohistochemical analysis localized gelatinase A close to the plasma membrane of these tissues. Furthermore, recombinant gelatinase A was demonstrated to cleave recombinant amelogenin into several fragments of differing molecular masses. Thus, gelatinase A is expressed by developing tooth tissues along with its activator MT1-MMP and may, therefore, play an important role during tooth development.
IL-1 Genotype and Adult Periodontitis among Young New Zealanders
Authors: Thomson W.M. , Edwards S.J. , Dobson-Le D.P. , Tompkins G.R. , Poulton R. , Knight D.A. , Braithwaite A.W.
Published: January 2009

Several recent studies have investigated the association between interleukin-1 genotype and periodontitis in clinical samples, where generalizability is an issue. The aim of this study was to investigate the association between adult periodontitis and IL-1 genotype in a population-based sample of 26-year-olds. Based on probing depth (PD) measurements, participants were divided into three disease groups: "Severe" (1+ teeth with 5+mm PD; N = 25), "Moderate" (2+ teeth with 4+mm PD; N = 36), and "Controls" (the remainder ; N = 800). The "periodontitis-associated genotype" (PAG; Kornman et al., 1997) was present in 20.0% of the "Severe" group and in 34.8% of "Controls", whereas the IL-1A+4845 [1, 1]/IL-1B+3953 [2,2] genotype was present in 12.0% and 0.9%, respectively. After controlling for sex, smoking status, and plaque levels, we found that those with IL-1B+3953 [1,1]/IL-1A+4845 [2,2] had 12.3 times the odds of being in the "Severe" group. Analysis of these data suggests that the IL-1A+4845 [1,1]/IL-1B+3953 [2,2] genotype is associated with periodontal disease in this young population. Future periodontal data collections as this cohort ages are required to confirm the predictive value of that genotype.
Effects of Gallium and Mercury Ions on Transport Systems
Authors: Moschen I. , Schweizer K. , Wagner C.A. , Geis-Gerstorfer J. , Lang F.
Published: January 2009

Mercury was previously shown to exert toxic effects by influencing ion channels and transporters in the kidney and brain. Gallium alloys were suggested as less toxic restorative materials. To compare the toxicity of gallium ions with those of mercury ions, we applied gallium nitrate Ga(NO3)3(0.1-100 μM and mercuric chloride (HgCl2) (0.001-10 μM) to Xenopus oocytes expressing mammalian ion channels and transport proteins. Mercury (10 μM) inhibited the K+-channels ROMK and HERG, the phosphate transporter NaPi-3, the amino acid transporter rBAT, the cation transporter OCT-2, and the osmolyte transporter BGT. It activated the IKschannel but did not affect the Na+-channel ENaC, the anion channel NaPi-1, and the glucose transporter SGLT-1. Gallium was without significant effect on the channels and on SGLT1, NaPi-3, and rBAT, but inhibited BGT and OCT-2. In conclusion, both Hg2+and Ga3+may exert toxic effects on transport systems, which may partially explain their cytotoxic effects.
Preparation of and Tissue Response to DNA-Lipid Films
Authors: Fukushima T. , Inoue Y. , Hayakawa T. , Taniguchi K. , Miyazaki K. , Okahata Y.
Published: January 2009

DNA-containing films have the potential to form complexes with antibiotics or cytokines by intercalation or groove-binding. This principle can be highly relevant for regenerative wound-healing around oral implants and in periodontology. In this study, we prepared DNA-lipid films and examined tissue responses to them as an indicator of their biological properties. The lipids were synthesized from the reaction of L-alanine, n-alkyl alcohol, and p-toluenesulfonic acid. We prepared the self-standing, water-insoluble DNA-lipid films by casting the DNA-lipid complex from chloroform/ethanol solution. The DNA-lipid complexes, which had 1:1 ratios of phosphate anions to cationic lipid, were found to have a double-helical B-form structure. The DNA-lipid films were almost dissolved 3 days after subcutaneous implantation in the backs of rats. There were no inflammatory reactions or inhibition of new tissue formation. We concluded that DNA-lipid films can be prepared by simple methods, and that they do not cause an unfavorable tissue response.
Effects of Dental Resins on TNF-α-induced ICAM-1 Expression in Endothelial Cells
Authors: Kostoryz E.L. , Tong P.Y. , Strautman A.F. , Glaros A.G. , Eick J.D. , Yourtee D.M.
Published: January 2009

Many reports have demonstrated inflammation after the placement of dental restorations. To explain this side-effect, we studied a biomarker in the inflammatory response. The intercellular adhesion molecule-1 (ICAM-1) is a key mediator for recruitment of leukocytes to the site of inflammation. Therefore, we investigated whether methacrylates (a BISGMA-based dental resin, BISGMA, and MAA) and Cyracure™ UVR 6105, an epoxy monomer, could alter ICAM-1 expression in unstimulated and TNF-a-stimulated endothelial cells. Six-well plates with monolayers of human umbilical vein cells, ECV 304 (ATCC CRL 1998), were exposed to TNF-a (1 ng/mL) in the presence and absence of subtoxic and TC50 doses of chemicals for 24 hrs at 37°C/5% CO2. Several doses of TNF-a (0.5-2 ng/mL) were co-incubated with 100 μL of undiluted aqueous dental resin extracts. Cells were harvested and stained with mAB FITC-conjugated anti-human ICAM-1 (CD54). ICAM-1 expression was measured by flow cytometry. Cells expressed basal levels of ICAM-1, which was up-regulated by TNF-a but was not changed by all samples studied. Except for UVR 6105, the methacrylates significantly decreased ICAM-1 expression in TNF-α-stimulated cells. These findings suggest that methacrylates may decrease the recruitment of leukocytes to sites of inflammation.
Laser-Matrix-Fluoride Effects on Enamel Demineralization
Authors: Hsu C.-Y.S. , Jordan T.H. , Dederich D.N. , Wefel J.S.
Published: January 2009

Laser and fluoride have been shown to inhibit enamel demineralization. However, the role of organic matrix and their interactions remains unclear. This study investigated the interaction among CO2 laser irradiation, fluoride, and the organic matrix on the demineralization of human enamel. Twenty-four molars were selected and cut into halves. One half of each tooth was depleted of its lipid and protein. The other half served as a matched control. Each tooth half had two window areas, treated with a 2.0% NaF gel. All left windows then received a laser treatment. Next, the tooth halves were subjected to a four-day pH-cycling procedure that created caries-like lesions. Tooth sections were cut from the windows, and microradiographs were used for quantification of the demineralization. The combined fluoride-laser treatment led to 98.3% and 95.1% reductions in mineral loss for enamel with and without organic matrix, respectively, when compared with sound enamel.
The Glass-ionomer Phase in Resin-based Restorative Materials
Authors: Tay F.R. , Pashley E.L. , Huang C. , Hashimoto M. , Sano H. , Smales R.J. , Pashley D.H.
Published: January 2009

Glass-ionomer (GI) fillers are added to restorative materials, but it is unclear if they truly react with these materials. This TEM study evaluated the existence of the GI phase in a conventional GIC (ChemFlex), a resin-modified GIC (Fuji II LC), a giomer (Reactmer Paste), a compomer (Dyract AP), and a composite (Spectrum TPH), before and after water uptake. Wafers were stored at 100% RH for 24 hrs, or in water for 7 or 84 days. ChemFlex glass particles were surrounded by 300-nm-thick silica gel layers. In Fuji II LC, we found thinner hydrogel layers (100 nm) that became thicker upon water storage. No appreciable change occurred in Reactmer Paste. Only a very thin hydrogel layer occurred in Dyract AP, and none was seen in SpectrumTPH after water storage for 84 days. We conclude that the variable extent of the GI phase is determined by differences in the resin composition of the restoratives.
Effects of Heat Treatments on Mechanical Strength of laser-welded Equi-atomic AuCu-6at%Ga Alloy
Authors: Watanabe I. , Liu J. , Atsuta M.
Published: January 2009

There is little information available on the mechanical strengthening of laser-welded gold alloys to achieve reliable dental prostheses. This study examined the hypothesis that heat treatments increase the mechanical strength of a laser-welded equi-atomic AuCu-6at%Ga alloy with age "hardenability" at intra-oral temperature. Cut cast gold alloy plates were laser-welded. The specimens were given one of three heat treatments: (1) solution treatment, (2) high-temperature aging after solution treatment, and (3) simulated intra-oral aging after solution treatment. As-cast and uncut specimens were also prepared. Tensile testing was conducted, and the breaking stress and yield strength were recorded. The yield strength values of all the heat-treated specimens nearly reached the values of the corresponding heat-treated control specimens. The results of this study indicated that, for high mechanical strength to be achieved, the laser-welded alloy tested should be aged at a high temperature or be intraorally aged after being laser-welded.