bluuebunny/crossref_metadata_2025 huggingface dataset:
Dentin Erosion Simulation by Cantilever Beam Fatigue and pH Change
Authors: Staninec M. , Nalla R.K. , Hilton J.F. , Ritchie R.O. , Watanabe L.G. , Nonomura G. , Marshall G.W. , Marshall S.J.
Published: January 2009

Exposed root surfaces frequently exhibit non-carious notches representing material loss by abrasion, erosion, and/or abfraction. Although a contribution from mechanical stress is often mentioned, no definitive proof exists of a cause-effect relationship. To address this, we examined dimensional changes in dentin subjected to cyclic fatigue in two different pH environments. Human dentin cantilever-beams were fatigued under load control in pH = 6 (n = 13) or pH = 7 (n = 13) buffer, with a load ratio ( R = minimum load/maximum load) of 0.1 and frequency of 2 Hz, and stresses between 5.5 and 55 MPa. Material loss was measured at high- and low-stress locations before and after cycling. Of the 23 beams, 7 withstood 1,000,000 cycles; others cracked earlier. Mean material loss in high-stress areas was greater than in low-stress areas, and losses were greater at pH = 6 than at pH = 7, suggesting that mechanical stress and lower pH both accelerate erosion of dentin surfaces.
Are Cementoblasts a Subpopulation of Osteoblasts or a Unique Phenotype?
Authors: Bosshardt D.D.
Published: January 2009

Experimental studies have shown a great potential for periodontal regeneration. The limitations of periodontal regeneration largely depend on the regenerative potential at the root surface. Cellular intrinsic fiber cementum (CIFC), so-called bone-like tissue, may form instead of the desired acellular extrinsic fiber cementum (AEFC), and the interfacial tissue bonding may be weak. The periodontal ligament harbors progenitor cells that can differentiate into periodontal ligament fibroblasts, osteoblasts, and cementoblasts, but their precise location is unknown. It is also not known whether osteoblasts and cementoblasts arise from a common precursor cell line, or whether distinct precursor cell lines exist. Thus, there is limited knowledge about how cell diversity evolves in the space between the developing root and the alveolar bone. This review supports the hypothesis that AEFC is a unique tissue, while CIFC and bone share some similarities. Morphologically, functionally, and biochemically, however, CIFC is distinctly different from any bone type. There are several lines of evidence to propose that cementoblasts that produce both AEFC and CIFC are unique phenotypes that are unrelated to osteoblasts. Cementum attachment protein appears to be cementum-specific, and the expression of two proteoglycans, fibromodulin and lumican, appears to be stronger in CIFC than in bone. A theory is presented that may help explain how cell diversity evolves in the periodontal ligament. It proposes that Hertwig’s epithelial root sheath and cells derived from it play an essential role in the development and maintenance of the periodontium. The role of enamel matrix proteins in cementoblast and osteoblast differentiation and their potential use for tissue engineering are discussed.
Bio-adhesive Surfaces to Promote Osteoblast Differentiation and Bone Formation
Authors: García A.J. , Reyes C.D.
Published: January 2009

Binding of integrin adhesion receptors to extracellular matrix components, such as fibronectin and type I collagen, activates signaling pathways directing osteoblast survival, cell-cycle progression, gene expression, and matrix mineralization. Biomimetic strategies exploit these adhesive interactions to engineer bio-inspired surfaces that promote osteoblast adhesion and differentiation, bone formation, and osseointegration. These emerging initiatives focus on directing integrin binding through presentation of bio-adhesive motifs derived from extracellular matrices. These biomolecular approaches provide promising strategies for the development of biologically active implants and grafting substrates for enhanced bone repair.
Professionally Applied Fluoride Gel in Low-caries 10.5-year-olds
Authors: Truin G.J. , van ’t Hof M.A.
Published: January 2009

The question has been raised whether low-caries children regularly using fluoride toothpaste will benefit from the professional application of additional fluoride gel. To investigate the caries-reducing effect of semi-annually-applied neutral 1% sodium fluoride gel, we carried out a double-blind randomized controlled clinical trial (n = 594) in a child population, initially aged 9.5–11.5 years, with baseline caries experience of D3MFS = 0 (decayed, missing, and filled tooth surfaces of permanent teeth). The mean number of tooth surfaces saved from caries development by fluoride gel application after 4 years was 0.2 D3MFS (SE = 0.17). The preventive fraction (PF) showed a mean relative effect of professionally applied fluoride gel of 18%. The cariostatic effect of the fluoride gel on pits and fissures would have been influenced by the sealant strategy in the study. Professionally applied fluoride gel showed no statistically significant effect on mean D3MFS score in low-caries 9.5- to 11.5-year-olds.
Effect of CaF2 Content on Rate of Fluoride Release from Filled Resins
Authors: Anusavice K.J. , Zhang N.-Z. , Shen C.
Published: January 2009

Information on the time-dependent release of fluoride from filled resins containing fluoride particles as a function of particle content and solution pH is limited. This study characterized the fluoride ion release from filled resins containing CaF2 particles as a function of filler content and pH. Urethane dimethacrylate and triethylene glycol dimethacrylate resins were used to make filled-resin disks containing 9.09, 23.08, or 33.33 mass% CaF2 filler. Fluoride ion release for the 9.09 mass% concentration was independent of pH. Increasing the filler content from 9.09 to 33.33 mass% increased the fluoride release rate in pH 4.0 buffer solution, because of greater surface degradation. Fluoride ion release from disks stored in pH 6.0 buffer solutions occurred mainly by diffusion from disk surfaces, while fluoride release from disks in pH 4.0 buffers was controlled by diffusion from disk surfaces and degeneration of the resin matrix, which exposed more CaF2 particle surface area.
Human Beta-defensins: Differential Activity against Candidal Species and Regulation by Candida albicans
Authors: Feng Z. , Jiang B. , Chandra J. , Ghannoum M. , Nelson S. , Weinberg A.
Published: January 2009

Oral epithelial cell-derived human beta-defensins-1, -2, and -3 participate in innate immune responses against Candida. We hypothesized that these peptides utilize several mechanisms for protection. Recombinant hBD-1 and -2 were produced with the use of an insect cell/baculovirus expression system, while rhBD-3 was expressed as a fusion protein in E. coli. RhBD-2 and -3 were more effective at killing the candidal species at low micromolar concentrations than was rhBD-1, except for C. glabrata. While this species was relatively resistant to rhBD fungicidal activity, its adherence to oral epithelial cells was strain-specifically inhibited by the rhBDs. C. albicans hyphae were important in regulating hBD2 and -3 mRNA expression in primary human oral epithelial cells. Confocal microscopy of rhBD-2-challenged C. albicans suggests disruption of the fungal membrane. Results support the hypothesis that hBDs control fungal colonization through hyphal induction, direct fungicidal activity, and inhibition of candidal adherence.
Penetration of Fluoride into Natural Plaque Biofilms
Authors: Watson P.S. , Pontefract H.A. , Devine D.A. , Shore R.C. , Nattress B.R. , Kirkham J. , Robinson C.
Published: January 2009

Caries occurs at inaccessible stagnation sites where plaque removal is difficult. Here, the penetration through plaque of protective components, such as fluoride, is likely to be crucial in caries inhibition. We hypothesized that topically applied fluoride would readily penetrate such plaque deposits. In this study, plaque biofilms generated in vivo on natural enamel surfaces were exposed to NaF (1000 ppm F−) for 30 or 120 sec (equivalent to toothbrushing) or for 30 min. Biofilms were then sectioned throughout their depth, and the fluoride content of each section was determined with the use of a fluoride electrode. Exposure to NaF for 30 or 120 sec increased plaque fluoride concentrations near the saliva interface, while concentrations near the enamel surface remained low. Fluoride penetration increased with duration of NaF exposure. Removal of exogenous fluoride resulted in fluoride loss and redistribution. Penetration of fluoride into plaque biofilms during brief topical exposure is restricted, which may limit anti-caries efficacy.
Tannerella forsythia-induced Alveolar Bone Loss in Mice Involves Leucine-rich-repeat BspA Protein
Authors: Sharma A. , Inagaki S. , Honma K. , Sfintescu C. , Baker P.J. , Evans R.T.
Published: January 2009

Tannerella forsythia (formerly Bacteroides forsythus) is one of the periodontal pathogens recently implicated in the development of periodontal disease. The cell-surface-associated, as well as the secreted, leucine-rich-repeat protein (BspA) of this bacterium have been suggested to play roles in bacterial adherence, and also in inflammation, by triggering release of pro-inflammatory cytokines from monocytes and chemokines from osteoblasts, leading to inflammation and bone resorption. In this study, we sought to determine the pathogenic potential of T. forsythia and the in vivo role of the BspA protein in pathogenesis in the mouse model of infection-induced alveolar bone loss. The results showed alveolar bone loss in mice infected with the T. forsythia wild-type strain, whereas the BspA mutant was impaired. In conclusion, evidence is presented in support of T. forsythia as an important organism involved in inducing alveolar bone loss, and the BspA protein is an important virulence factor of this bacterium.
Properties of BKCa Channels in Oral Keratinocytes
Authors: Shieh D.-B. , Yang S.-R. , Shi X.-Y. , Wu Y.-N. , Wu S.-N.
Published: January 2009

Keratinocytes are important for epithelial antimicrobial barrier function. The activity of ion channels can affect the proliferation of keratinocytes. Little is known about Ca2+-activated K+ currents in these cells. Ion currents in normal human oral keratinocytes were characterized with a patch-clamp technique. In whole-cell configuration, depolarizing pulses evoked K+ outward currents ( I K) in oral keratinocytes. Iberiotoxin (200 nM) and paxilline (1 μM) suppressed I K; however, neither apamin (200 nM) nor 5-hydroxydecanoate (30 μM) had any effects on it. Caffeic acid phenethyl ester, a compound of honeybee propolis, increased I K with an EC50 value of 12.8 ± 1.2 μM. In inside-out patches, a BKCa channel was observed in keratinocytes, but not in oral squamous carcinoma (OCE-M1) cells. Caffeic acid phenethyl ester or cinnamyl-3,4-dihydroxy-α-cyanocinnamate applied to the intracellular surface of a detached patch increased BKCa-channel activity. The results demonstrate that the properties of BKCa channels in normal human oral keratinocytes are similar to those described in other types of cells. Caffeic acid derivatives can also stimulate BKCa-channel activity directly.
Potassium Channel-blockers as Therapeutic Agents to Interfere with Bone Resorption of Periodontal Disease
Authors: Valverde P. , Kawai T. , Taubman M.A.
Published: January 2009

Inflammatory lesions of periodontal disease contain all the cellular components, including abundant activated/memory T- and B-cells, necessary to control immunological interactive networks and to accelerate bone resorption by RANKL-dependent and -independent mechanisms. Blockade of RANKL function has been shown to ameliorate periodontal bone resorption and other osteopenic disorders without affecting inflammation. Development of therapies aimed at decreasing the expression of RANKL and pro-inflammatory cytokines by T-cells constitutes a promising strategy to ameliorate not only bone resorption, but also inflammation. Several reports have demonstrated that the potassium channels Kv1.3 and IKCa1, through the use of selective blockers, play important roles in T-cell-mediated events, including T-cell proliferation and the production of pro-inflammatory cytokines. More recently, a potassium channel-blocker for Kv1.3 has been shown to down-regulate bone resorption by decreasing the ratio of RANKL-to-OPG expression by memory-activated T-cells. In this article, we first summarize the mechanisms by which chronically activated/memory T-cells, in concert with B-cells and macrophages, trigger inflammatory bone resorption. Then, we describe the main structural and functional characteristics of potassium channels Kv1.3 and IKCa1 in some of the cells implicated in periodontal disease progression. Finally, this review elucidates some recent advances in the use of potassium channel-blockers of Kv1.3 and IKCa1 to ameliorate the clinical signs or side-effects of several immunological disorders and to decrease inflammatory bone resorption in periodontal disease. ABBREVIATIONS: AICD, activation-induced cell death; APC, antigen-presenting cells; B(K), large conductance; CRAC, calcium release-activated calcium channels; DC, dendritic cell; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; IFN-γ, interferon-γ; IP3, inositol (1,4,5)-triphosphate; (K)ir, inward rectifier; JNK, c-Jun N-terminal kinase; I(K), intermediate conductance; LPS, lipopolysaccharide; L, ligand; MCSF, macrophage colony-stimulating factor; MHC, major histocompatibility complex; NFAT, nuclear factor of activated T-cells; RANK, receptor activator of nuclear factor-κB; TCM, central memory T-cells; TEM, effector memory T-cells; TNF, tumor necrosis factor; TRAIL, TNF-related apoptosis-inducing ligand; OPG, osteoprotegerin; Omp29, 29-kDa outer membrane protein; PKC, protein kinase C; PLC, phospholipase C; RT-PCR, reverse-transcriptase polymerase chain-reaction; S(K), small conductance; TCR, T-cell receptor; and (K)v, voltage-gated.
Low HEMA Conjugation Induces High Autoantibody Titer in Mice
Authors: Sandberg E. , Bergenholtz G. , Kahu H. , Dahlgren U.I.
Published: January 2009

2-hydroxyethylmethacrylate (HEMA) is a known causal agent of hypersensitivity to resin composites. We have reported that immunization with HEMA conjugated to mouse serum albumin (MSA) induces an autoantibody response in mice. In this study, we investigated both the activity and the avidity of autoantibodies induced by immunization with various HEMA conjugations to MSA. Female Balb/c mice were given MSA carrying 3, 7, 15, or 22 HEMA molecules. Antigen-specific IgG and IgE antibodies were determined by ELISA, and average antibody avidity by thiocyanate dissociation. Immunization with MSA carrying the lowest number of HEMA molecules induced a significantly higher IgG and IgE anti-MSA autoantibody response, with significantly higher IgG antibody avidity, than did the more heavily conjugated preparations. The results suggest that the lower the degree of HEMA conjugation to self-protein, the higher the risk for autoantibody production to the carrier protein. These findings suggest a mechanism of potential relevance in humans.
Functional Activity of Superior Head of Human Lateral Pterygoid Muscle during Isometric Force
Authors: Ruangsri S. , Whittle T. , Wanigaratne K. , Murray G.M.
Published: January 2009

There is controversy as to the jaw tasks for which the superior head of the human lateral pterygoid muscle (SHLP) becomes active. The aim was to describe the functional activities of SHLP single motor units (SMUs) during horizontal isometric force tasks. In 11 subjects, 48 SMUs were recorded from computer-tomography-verified SHLP sites during generation of horizontal isometric force in the contralateral (CL), protrusive (P), and ipsilateral (IL) directions and intermediate directions (CL-P, IL-P). In eight subjects, SHLP SMUs were active in CL, CL-P, and P. Qualitatively, SHLP EMG activity increased with increased isometric force. Forty-two SMUs were active in directions other than IL; 6 exhibited activity at IL and other directions. The similarity of these data to previous human lateral pterygoid (IHLP) data supports the notion that SHLP and IHLP should be regarded as a single muscle, with activities shaded according to the biomechanical demands of the task.
Survey of Oral Microbial Diversity using PCR-based Denaturing Gradient Gel Electrophoresis
Authors: Li Y. , Ku C.Y.S. , Xu J. , Saxena D. , Caufield P.W.
Published: January 2009

Polymicrobial biofilms in the human oral cavity exhibit marked diversity. PCR-based denaturing gradient gel electrophoresis (PCR-DGGE) surveys microbial diversity by displaying PCR-generated 16S rDNA fragments that migrate at different distances, reflecting the differences in the base-pair ( i.e., % G+C) composition of the fragment. This study examined DGGE-generated diversity profiles of cultivable bacteria from individuals with different caries status. Initially, we developed a set of PCR-DGGE running conditions appropriate to oral bacteria. Next, we assessed migration standards from known oral bacterial reference strains. To test the methods, we profiled 20 bacterial saliva samples cultivated from young adults. The study produced a battery of species-specific 16S rDNA amplicons that could be used as a migration distance standard necessary for computer-assisted profile analysis. From the clinical samples, we found a significantly greater diversity of oral microbes in caries-free individuals compared with caries-active individuals ( P = 0.01). These findings suggest thtat a portion of oral microbiota of caries-active individuals may be absent, suppressed, or replaced.
Lipopolysaccharide Heterogeneity: Innate Host Responses to Bacterial Modification of Lipid A Structure
Authors: Dixon D.R. , Darveau R.P.
Published: January 2009

The innate host response system is composed of various mechanisms designed to detect and facilitate host responses to microbial components, such as lipopolysaccharides (LPS). To enable this to occur, innate systems contain multiple pattern recognition receptors ( i.e., LBP, CD14, and TLRs), which identify certain features within bacterial LPS that are foreign to the host, as well as essential and uniquely specific for bacteria. Innate host identification of unique bacterial components or patterns, therefore, relies on the inability of bacteria to alter these essential or critical components dramatically. Historically, LPS have been viewed as essential outer-membrane molecules containing both a highly variable outer region (O-segment) as well as a relatively conserved inner region (lipid A). However, over the last decade, new evidence has emerged, revealing that increased natural diversity or heterogeneity within specific components of LPS, such as lipid A—resulting in minor to moderate changes in lipid A structure—can produce dramatic host responses. Therefore, examples of natural lipid A heterogeneity, and the mechanisms that control it, represent a novel approach in which bacteria modulate host responses and may thereby confer specific advantages to certain bacterial species under changing environmental host conditions.
Drug-induced Disorders of Teeth
Authors: Tredwin C.J. , Scully C. , Bagan-Sebastian J.-V.
Published: January 2009

It is essential that every health care professional who is involved with the prescription or recommendation of drugs be fully aware of any resultant disorders that may arise as a side-effect. A range of drugs can affect the teeth. In this review article, drugs that have the potential to induce changes in teeth have been classified as those leading to tooth discoloration (intrinsic and extrinsic), physical damage to tooth structure (enamel, dentin, and cementum), and alteration in tooth sensitivity.
Mouse Amelogenin Exons 8 and 9: Sequence Analysis and Protein Distribution
Authors: Papagerakis P. , Ibarra J.M. , Inozentseva N. , DenBesten P. , MacDougall M.
Published: January 2009

Amelogenin is the major protein of the developing enamel. Two additional exons, termed 8 and 9, have been characterized in the rat. Our aim was: to identify the mouse amelogenin exons 8/9 sequences; to investigate the potential presence of the alternative spliced isoforms of amelogenin exons 8/9; and to immunolocalize proteins containing sequences encoded by exons 8/9 during odontogenesis. RT-PCR analysis with exon 9 anti-sense primer generated 2 major amplicons with the use of a mouse tooth cDNA library and dental cell lines. DNA sequence analysis showed 93% identify with the rat exons 8/9 sequence. Alternative splicing of exon 3 was also found, but only in cDNAs lacking exons 8 and 9. Immunohistochemistry localized exons 8/9-encoded proteins in ameloblasts, young odontoblasts, and stratum intermedium cells. Analysis of our data supports the hypothesis that: (1) AMELX contains 2 additional exons; (2) ameloblasts and odontoblasts synthesize amelogenin 8/9; and (3) amelogenin splice variants may have unique functions during tooth formation.
Validation of the Child Perceptions Questionnaire (CPQ11-14)
Authors: Foster Page L.A. , Thomson W.M. , Jokovic A. , Locker D.
Published: January 2009

While the use of adult oral-health-related quality-of-life (OHRQoL) measures in supplementing clinical indicators has increased, that for children has lagged behind, because of the difficulties of developing and validating such measures for children. This study examined the construct validity of the Child Perceptions Questionnaire (CPQ11-14) in a random sample of 12- and 13-year-old New Zealanders. It was hypothesized that children with more severe malocclusions or greater caries experience would have higher overall (and subscale domain) CPQ11-14 scores. Children (N = 430) completed the CPQ11-14 and were examined for malocclusion (Dental Aesthetic Index) and dental caries. There was a distinct gradient in mean CPQ11-14 scores by malocclusion severity, but there were differences across the four subscales. Children in the worst 25% of the DMFS distribution had higher CPQ11-14 scores overall and for each of the 4 subscales. The construct validity of the CPQ11-14 appears to be acceptable.
Water Concentration in Self-etching Primers Affects their Aggressiveness and Bonding Efficacy to Dentin
Authors: Hiraishi N. , Nishiyama N. , Ikemura K. , Yau J.Y.Y. , King N.M. , Tagami J. , Pashley D.H. , Tay F.R.
Published: January 2009

Water is required to ionize acid resin monomers for demineralization of tooth substrates. We tested the null hypothesis that altering the water concentration in two-step self-etching primers has no effect on their aggressiveness and bonding efficacy to dentin. Five experimental self-etching primers were prepared with resin-water-ethanol volume ratios of 9-0-1, 8-1-1, 7-2-1, 5-4-1, and 3-6-1. They were applied to smear-layer-covered dentin, followed by a bonding resin and composite build-ups for microtensile bond testing and TEM examination of tracer penetration. Increasing water concentration from 0–60 vol% improved acidic monomer ionization that was manifested as increasing hybrid layer thickness. However, significantly higher bond strength was observed in the 7-2-1 group, with minimal nanoleakage in the corresponding hybrid layer. When self-etching primers are formulated, a balance must be achieved to provide sufficient water for adequate ionization of the acidic monomers, without lowering the resin concentration too much, to optimize their bonding efficacy to dentin.
Resin Composite Properties and Energy Density of Light Cure
Authors: Peutzfeldt A. , Asmussen E.
Published: January 2009

According to the ‘total energy concept’, properties of light-cured resin composites are determined only by energy density because of reciprocity between power density and exposure duration. The kinetics of polymerization is complex, and it was hypothesized that degree of cure, flexural strength, and flexural modulus were influenced not only by energy density, but also by power density per se. A conventional resin composite was cured at 3 energy densities (4, 8, and 16 J/cm2) by 6 combinations of power density (50, 100, 200, 400, 800, and 1000 mW/cm2) and exposure durations. Degree of cure, flexural strength, and flexural modulus increased with increasing energy density. For each energy density, degree of cure decreased with increasing power density. Flexural strength and modulus showed a maximum at intermediate power density. Within clinically relevant power densities, not only energy density but also power density per se had significant influence on resin composite properties.
Anode Glow Discharge Plasma Treatment of Titanium Plates Facilitates Adsorption of Extracellular Matrix Proteins to the Plates
Authors: Yamamoto H. , Shibata Y. , Miyazaki T.
Published: January 2009

Glow discharge plasma (GDP) supplied to an anode (GDP+) promotes calcium phosphate adsorption onto titanium better than that supplied to a cathode (GDP-). However, the adsorption of extracellular matrix (ECM) proteins is crucial for cell adhesion to titanium. Since GDP+ induced both inorganic adsorption and cell adhesion, we hypothesized that the inorganic adsorption in a culture medium might affect the adsorption of the ECM proteins. In this study, ECM proteins adsorbed on titanium with and without GDP were examined by x-ray photoelectron spectroscopy. After 1 hr of incubation, increasing sodium adsorption on GDP+ specimens induced adsorption of ECM proteins as shown by NH+ and COO− signals without calcium adsorption. In contrast, since no specific adsorption of sodium on GDP-specimens was detected, GDP-did not contribute to the adsorption of ECM proteins. Thus, promotion of sodium adsorption of GDP+ was effective, at least in the initial ECM protein adsorption on a titanium surface.
Epithelial-Mesenchymal Transformation during Craniofacial Development
Authors: Kang P. , Svoboda K.K.H.
Published: January 2009

Epithelial to mesenchymal phenotype transition is a common phenomenon during embryonic development, wound healing, and tumor metastasis. This transition involves cellular changes in cytoskeleton architecture and protein expression. Specifically, this highly regulated biological event plays several important roles during craniofacial development. This review focuses on the regulation of epithelial-mesenchymal transformation (EMT) during neural crest cell migration, and fusion of the secondary palate and the upper lip. Abbreviations used in this paper: BMP, bone morphogenic protein; CCFSE, 5 (and 6) carboxy 2,7′ dichlorofluorescein diacetate succinimidyl ester; CNC, cranial neural crest; DiI, 1,1-dioctadecyl-3,3,3′-tetramethylindocarbocyanine perchlorate; EMT, epithelial-mesenchymal transformation; FGF, fibroblast growth factor; ILK, integrin-linked kinase; LEF1, Lymphoid enhancer factor-1; MEE, medial edge epithelia; MFS, mean fusion score; MMP, matrix metalloproteinase; PDK, 3-phosphoinostide-dependent protein kinase; Pax, paired box-1 to -9; PI-3 kinase, phosphatidylinositol-3 kinase; Ptc, patched; PTEN, phosphatase and tensin homolog deleted on chromosome ten; Shh, Sonic hedgehog; Tbx, T-box family; TGF, transforming growth factor; TIMP, tissue inhibitor of metalloproteinase.
Fusobacterium nucleatum Apoptosis-inducing Outer Membrane Protein
Authors: Kaplan C.W. , Lux R. , Huynh T. , Jewett A. , Shi W. , Haake S. Kinder
Published: January 2009

The periodontal pathogen Fusobacterium nucleatum induces apoptosis in lymphocytes. We previously identified the autotransporter protein Fap2 in F. nucleatum strain PK1594 that induced apoptosis in lymphocytes when expressed in Escherichia coli. In this study, we identified protein homologs of Fap2 in the transformable F. nucleatum strain ATCC 23726, to determine their role in the induction of apoptosis in lymphocytes. We used a new gene-inactivation vector conferring thiamphenicol resistance (pHS31) to construct a mutant deficient in one of the homologs, aim1. Transcriptional analyses demonstrated disruption of aim1 expression, and phenotypic analyses revealed a 41% decrease in the ability of the mutant to induce apoptosis in Jurkat cells, as compared with the parental strain. These studies demonstrate, in the native host cell background, the contribution of aim1 to F. nucleatum induction of apoptosis and, to the best of our knowledge, represent the first report of a genetically defined and phenotypically characterized mutation in F. nucleatum.
Incompatibility of Oxalate Desensitizers with Acidic, Fluoride-containing Total-etch Adhesives
Authors: Yiu C.K.Y. , King N.M. , Suh B.I. , Sharp L.J. , Carvalho R.M. , Pashley D.H. , Tay F.R.
Published: January 2009

The use of oxalate desensitizers on acid-etched dentin prior to adhesive application can result in subsurface tubular occlusion by calcium oxalate crystals. However, the solubility of calcium oxalate increases in acidic solution. We hypothesized that total-etch adhesives can, depending upon their pH, interact with oxalate-desensitizer-treated dentin in an adverse manner. Acid-etched human dentin treated with 2 oxalate desensitizers (BisBlock and Super Seal) was bonded with 4 simplified total-etch adhesives: One-Step (OS), Single Bond (SB), OptiBond Solo Plus (OB), and Prime&Bond NT (PB). Composite-dentin beams were examined by SEM and TEM, both of which revealed numerous spherical globules on OB- and PB-bonded, desensitizer-treated dentin, but not in OS or SB samples. Bond strengths produced by OB and PB were significantly lower in oxalate-treated specimens than those produced by OS or SB. These surface globules may have interfered with hybridization of demineralized dentin with OB and PB resins and caused compromised bond strengths.
Effects of a High-cholesterol Diet on Cell Behavior in Rat Periodontitis
Authors: Tomofuji T. , Kusano H. , Azuma T. , Ekuni D. , Yamamoto T. , Watanabe T.
Published: January 2009

Studies have shown an association between periodontitis and serum cholesterol levels. We hypothesized that high dietary cholesterol could influence periodontitis as a result of proliferation of the junctional epithelium. Rats were divided into 4 groups. Two groups were fed a regular diet, and 2 groups were fed a high-cholesterol diet. One of each dietary group was treated with periodontitis-inducing agents (lipopolysaccharide and proteases), while the other was treated with pyrogen-free water. Feeding rats with a high-cholesterol diet induced an increase in blood total cholesterol and a decrease in high-density lipoprotein cholesterol. Proliferation of the junctional epithelium with increasing bone resorption was promoted by the consumption of a high-cholesterol diet. High dietary cholesterol further increased the cell-proliferative activity of the junctional epithelium induced by lipopolysaccharide and proteases. These results suggest that high dietary cholesterol can initiate and augment periodontitis in the rat periodontitis model.
Fiber-type Composition of the Human Jaw Muscles—(Part 2) Role of Hybrid Fibers and Factors Responsible for Inter-individual Variation
Authors: Korfage J.A.M , Koolstra J.H. , Langenbach G.E.J. , van Eijden T.M.G.J.
Published: January 2009

This is the second of two articles about fiber-type composition of the human jaw muscles. It reviews the functional relationship of hybrid fibers and the adaptive properties of jaw-muscle fibers. In addition, to explain inter-individual variation in fiber-type composition, we discuss these adaptive properties in relation to environmental stimuli or perturbations. The fiber-type composition of the human jaw muscles is very different from that of limb and trunk muscles. Apart from the presence of the usual type I, IIA, and IIX myosin heavy-chains (MyHC), human jaw-muscle fibers contain MyHCs that are typical for developing or cardiac muscle. In addition, much more frequently than in limb and trunk muscles, jaw-muscle fibers are hybrid, i.e., they contain more than one type of MyHC isoform. Since these fibers have contractile properties that differ from those of pure fibers, this relatively large quantity of hybrid fibers provides a mechanism that produces a very fine gradation of force and movement. The presence of hybrid fibers might also reflect the adaptive capacity of jaw-muscle fibers. The capacity for adaptation also explains the observed large inter-individual variability in fiber-type composition. Besides local influences, like the amount of muscle activation and/or stretch, more general influences, like aging and gender, also play a role in the composition of fiber types.
Cost-effectiveness of Mandibular Two-implant Overdentures and Conventional Dentures in the Edentulous Elderly
Authors: Heydecke G. , Penrod J.R. , Takanashi Y. , Lund J.P. , Feine J.S. , Thomason J.M.
Published: January 2009

Implementation of new therapies is usually governed by financial considerations, so efficacy studies should also include cost comparisons. The cost and effectiveness of mandibular conventional dentures (CD, n = 30) and two-implant overdentures (IOD, n = 30) were compared in elderly subjects. Effectiveness (Oral Health Impact Profile, OHIP-20) and cost were measured up to one year post-treatment. Data for subsequent years were estimated by the Delphi method. Using an average life expectancy of 17.9 years, the equalized annual costs (in Canadian dollars) were $399 for CD and $625 for IOD (p < 0.001), and the equalized annual values for the outcome (OHIP-20) were 47.0 for CD and 31.3 for IOD treatment (p < 0.05). These values translate into a yearly additional cost for IOD treatment of $14.41 per OHIP-20 point. These results are key to the implementation of programs to provide this form of therapy for edentulous adults.
Mode of Delivery and Other Maternal Factors Influence the Acquisition of Streptococcus mutans in Infants
Authors: Li Y. , Caufield P.W. , Dasanayake A.P. , Wiener H.W. , Vermund S.H.
Published: January 2009

S. mutans plays a key role in dental caries. The extent to which perinatal events influence the acquisition of S. mutans is unclear. We hypothesized that several maternal factors, including the mode of delivery, influence the initial acquisition of S. mutans in infants. A prospective cohort study was conducted in 156 mother-infant pairs. The study found that maternal gestational age (p = 0.04), S. mutans level (p = 0.02), caries score (p = 0.02), sexually transmitted disease (STD) infection experience (p = 0.01), and family income (p = 0.03) had significant effects on the acquisition of S. mutans. Among infants who became infected, those delivered by Caesarean section acquired S. mutans 11.7 mos earlier than did vaginally delivered infants (p = 0.038). C-section infants harbored a single genotype of S. mutans that was identical to that of their mothers (100% fidelity). Analysis of the data demonstrated the possible perinatal influences on infants’ acquisition of a member of the cariogenic microbiota, and its potential effect on caries outcome.
Impact of Curing Protocol on Conversion and Shrinkage Stress
Authors: Lu H. , Stansbury J.W. , Bowman C.N.
Published: January 2009

Since considerable shrinkage stress develops during the curing of dental composites, various soft-start photocuring protocols, aiming to lower stress but not compromise conversion, have been proposed. We hypothesized that utilizing soft-start photocuring will result in not only reduced stress, but also decreased conversion. We evaluated the impact of 3 protocols (soft-start, pulse, and standard) on the stress development and polymerization extent of an experimental composite. A novel set-up capable of simultaneous shrinkage stress, conversion, and temperature measurements on the same specimen was utilized. Analysis of the data shows that stress rises dramatically as a function of conversion in the vitrified state, and the utilization of soft-start or pulse curing results in specimens with reduced final conversion and shrinkage stress, compared with specimens cured according to the standard full-intensity protocol. Finally, this study demonstrates that the predominant reason for the reduced shrinkage stress attained with soft-start or pulse curing is a modest decrease in final conversion.
Dendritic-NK Cell Interactions in P. gingivalis-specific Responses
Authors: Kikuchi T. , Willis D.L. , Liu M. , Purkall D.B. , Sukumar S. , Barbour S.E. , Schenkein H.A. , Tew J.G.
Published: January 2009

Patients with localized aggressive periodontitis have type-1 cytokines in gingival crevicular fluid and high titers of IFN-γ-dependent IgG2 reactive with P. gingivalis in gingival crevicular fluid and serum. Localized aggressive periodontitis monocytes spontaneously differentiate into dendritic cells that can stimulate IFN-γ production by NK cells. These relationships prompted the hypothesis that P. gingivalis-dendritic cell-NK cell interactions might promote type-1 cytokine responses. Although P. gingivalis is not a potent inducer of Th1 responses, it stimulated strong IL-12 responses by monocyte-derived dendritic cells in the presence of IFN-γ, and IFN-γ was produced by NK cells within 24 hrs in the presence of dendritic cells. Anti- P. gingivalis IgG2 responses were enhanced by dendritic cells, and removal of NK cells reduced IFN-γ- and P. gingivalis-specific IgG2. Thus, P. gingivalis-dendritic cell-NK cell interactions apparently resulted in reciprocal stimulation and increased type-1 cytokine production by both dendritic cells and NK cells, and increased P. gingivalis-specific IgG2.
Tubular Occlusion Prevents Water-treeing and Through-and-Through Fluid Movement in a Single-bottle, One-step Self-etch Adhesive Model
Authors: Tay F.R. , Pashley D.H. , Hiraishi N. , Imazato S. , Rueggeberg F.A. , Salz U. , Zimmermann J. , King N.M.
Published: January 2009

Water entrapment occurs at resin-dentin interfaces of one-step self-etch adhesives. We hypothesized that by preventing water fluxes from dentin, any water entrapment would be attributed to incomplete removal of adhesive solvents. We tested this hypothesis by bonding to transparent carious dentin containing occluded dentinal tubules. An experimental single-bottle, one-step self-etch adhesive was applied to flat surfaces of caries-affected dentin surrounded by sound dentin, with or without pulpal pressure. Resin-dentin interfaces were examined with TEM after silver-impregnation. Although caries-affected dentin was highly porous, adhesive layers were devoid of silver deposits when tubules were occluded. Conversely, variable extents of water-treeing and water-droplets were identified from adhesive layers in bonded sound dentin. Water-treeing and water-droplet formation, being manifestations of evaporative and convective water fluxes, can be eliminated during bonding to occluded transparent carious dentin. However, the highly porous nature of this clinically relevant substrate after bonding may lead to potentially undesirable consequences.
Recovery of Stem Cells from Cryopreserved Periodontal Ligament
Authors: Seo B.-M. , Miura M. , Sonoyama W. , Coppe C. , Stanyon R. , Shi S.
Published: January 2009

Human post-natal stem cells possess a great potential to be utilized in stem-cell-mediated clinical therapies and tissue engineering. It is not known whether cryopreserved human tissues contain functional post-natal stem cells. In this study, we utilized human periodontal ligament to test the hypothesis that cryopreserved human periodontal ligament contains retrievable post-natal stem cells. These cryopreserved periodontal ligament stem cells maintained normal periodontal ligament stem cell characteristics, including expression of the mesenchymal stem cell surface molecule STRO-1, single-colony-strain generation, multipotential differentiation, cementum/periodontal-ligament-like tissue regeneration, and a normal diploid karyotype. Collectively, this study provides valuable evidence demonstrating a practical approach to the preservation of solid-frozen human tissues for subsequent post-natal stem cell isolation and tissue regeneration. The present study demonstrates that human post-natal stem cells can be recovered from cryopreserved human periodontal ligament, thereby providing a practical clinical approach for the utilization of frozen tissues for stem cell isolation.
Magnesium Deficiency is Associated with Periodontal Disease
Authors: Meisel P. , Schwahn C. , Luedemann J. , John U. , Kroemer H.K. , Kocher T.
Published: January 2009

In the multifactorial pathogenesis of periodontitis, there are still unknown factors influencing the outcome of the disease. An association between magnesium and periodontitis has been suggested by preliminary studies. However, relevant clinical data are lacking. We investigated the association between magnesium status and periodontal health in a population-based analysis. We conducted a cross-sectional epidemiological investigation involving 4290 subjects aged 20–80 yrs. We recorded periodontal risk factors and determined concentrations of serum magnesium and calcium, relating them to periodontal parameters. In a matched-pair study, 60 subjects using oral magnesium-containing drugs and 120 without were compared. In subjects aged 40 yrs and older, increased serum Mg/Ca was significantly associated with reduced probing depth (p < 0.001), less attachment loss (p = 0.006), and a higher number of remaining teeth (p = 0.005). Subjects taking Mg drugs showed less attachment loss (p < 0.01) and more remaining teeth than did their matched counterparts. These results suggest that nutritional magnesium supplementation may improve periodontal health.
Bioavailability of Fluoride in Drinking Water: a Human Experimental Study
Authors: Maguire A. , Zohouri F.V. , Mathers J.C. , Steen I.N. , Hindmarch P.N. , Moynihan P.J.
Published: January 2009

It has been suggested that systemic fluoride absorption from drinking water may be influenced by the type of fluoride compound in the water and by water hardness. Using a human double-blind cross-over trial, we conducted this study to measure cmax, Tmax, and Area Under the Curve (AUC) for plasma F concentration against time, following the ingestion of naturally fluoridated hard and soft waters, artificially fluoridated hard and soft waters, and a reference water. Mean AUC over 0 to 8 hours was 1330, 1440, 1679, 1566, and 1328 ng F•min•mL−1 for naturally fluoridated soft, naturally fluoridated hard, artificially fluoridated soft, artificially fluoridated hard, and reference waters, respectively, with no statistically significant differences among waters for AUC, cmax, or Tmax. Any differences in fluoride bioavailability between drinking waters in which fluoride is present naturally or added artificially, or the waters are hard or soft, were small compared with large within- and between-subject variations in F absorption. Abbreviations used: F, fluoride; AUC, Area under the Curve for plasma F concentration against time; AUC(0-3), Area under the Curve for plasma F concentration against time for 0 to 3 hours following water ingestion; AUC(0-8), Area under the Curve for plasma F concentration against time for 0 to 8 hours following water ingestion; cmax, maximum plasma F concentration corrected for baseline plasma F and dose ( i.e., F concentration of individual waters); Tmax, time of cmax.
Induction of MMP-3 by Hyaluronan Oligosaccharides in Temporomandibular Joint Chondrocytes
Authors: Ohno S. , Ohno-Nakahara M. , Knudson C.B. , Knudson W.
Published: January 2009

Low-molecular-weight hyaluronan (LMW-HA) is often increased in osteoarthritic joints; however, its biological function in cartilage has not been clarified. We hypothesize that LMW-HA causes the catabolic activation of chondrocytes through its interaction with CD44. Cartilage explants and chondrocytes, derived from bovine temporomandibular joints (TMJ), were examined for matrix loss and the expression of matrix metalloproteinase-3 (MMP-3) following treatment with hyaluronan oligosaccharides (HAoligos). Hyaluronan and CD44 were uniformly distributed throughout the fibrous and cartilaginous zones of the TMJ condyle. Treatment of cartilage explants with HAoligos resulted in cartilage matrix loss with increased secreted caseinolytic activity. HAoligos treatment of TMJ chondrocytes resulted in enhanced MMP-3 expression, whereas wash-out of the HAoligos in the middle of the experimental period reduced this induction. These results suggest that HAoligos activate chondrocytes, resulting in a substantial enhancement of proteinase expression, and the removal of HAoligos by wash-out reverses this catabolic activation.
Apigenin and tt-Farnesol with Fluoride Effects on S. mutans Biofilms and Dental Caries
Authors: Koo H. , Schobel B. , Scott-Anne K. , Watson G. , Bowen W.H. , Cury J.A. , Rosalen P.L. , Park Y.K.
Published: January 2009

Apigenin (Api) and tt-farnesol (Far) are two naturally occurring agents that affect the development of cariogenic biofilms. Fluoride (F) interferes physicochemically with caries development and also exhibits antibacterial activity. We examined whether the association of Api and Far enhance the anti-caries properties of F by acting cooperatively on the expression of virulence of Streptococcus mutans. The biological effects of each of the agents were greatly enhanced when used in combination with F. In general, biofilms treated with Api and/or Far in combination with F displayed less biomass and fewer insoluble glucans and iodophilic polysaccharides than did those treated with the test agents alone ( P < 0.05). The combination of the test agents with F was highly effective in preventing caries development in rats, especially Api+Far+F, and results were comparable with those observed with chlorhexidine + F (positive control). Results from these studies showed that apigenin and tt-farnesol may enhance the cariostatic effectiveness of fluoride.
X-ray Microanalysis of Elements in the Masticatory Muscle after Paresis of the Right Masseter
Authors: Gedrange T. , Mai R. , Richter G. , Wolf P. , Lupp A. , Harzer W.
Published: January 2009

Muscle activity and function appear to be related to ionic concentrations in the muscle. We investigated whether muscle paresis induced by injection of Botulinum toxin A (Botox) in 16-week-old pigs over a 56-day period is associated with ionic changes in the affected muscles. Tissue samples were taken from the masseter, temporalis, medial pterygoid, and geniohyoid muscles by a standardized method and used for energy-dispersive x-ray microanalysis in an environmental scanning electron microscope. The largest increase in Na+ was measured in the right and left sides of the masseter muscle in treated animals. Additionally, a significant elevation of Na+ was measured in the anterior part of the temporalis muscle and in the pterygoid muscle (P < 0.05). In temporalis and pterygoid muscles, an increase in sulfur in both sides of treated pigs’ heads was observed. Botox® has an indirect impact on ion concentrations, resulting in changes in muscle functional capacity and adaptive compensation of paretic muscle function by other muscles.
Phenotype of ENAM Mutations is Dosage-dependent
Authors: Ozdemir D. , Hart P.S. , Firatli E. , Aren G. , Ryu O.H. , Hart T.C.
Published: January 2009

Five mutations in the ENAM gene have been found to cause hypoplastic amelogenesis imperfecta (AI), with phenotypes ranging from localized enamel pitting in carriers to severe hypoplastic AI. To determine the generality of ENAM mutations in hypoplastic AI, we sequenced the ENAM gene in ten Turkish families segregating autosomal hypoplastic AI. In two families, ENAM mutations were found. A novel nonsense mutation (g.12663C>A; p.S246X) was identified in one family segregating local hypoplastic AI as a dominant trait. Affected individuals in a second family segregating autosomal-recessive AI were compound heterozygotes for a novel insertion mutation (g.12946_12947insAGTCAGTACCAGTACTGTGTC) and a previously described insertion (g.13185_13186insAG) mutation. Heterozygous carriers of either insertion had a localized enamel-pitting phenotype. These findings substantiate that enamel phenotypes of ENAM mutations may be dose-dependent, with generalized hypoplastic AI segregating as a recessive trait and localized enamel pitting segregating as a dominant trait.