bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Human Jaw Movement on Cerebral Blood Flow
Authors: Hasegawa Y. , Ono T. , Hori K. , Nokubi T.
Published: January 2009

Temporal changes in cerebral blood flow induced by jaw movement have yet to be investigated. To assess the influence of pattern and intensity of muscle contraction during jaw movement on task-induced change in cerebral blood flow, we performed bilateral transcranial Doppler ultrasound examination during clenching, gum chewing, and tooth tapping in healthy volunteers. A random-effects model analysis revealed a significant increase in middle cerebral artery blood flow velocity during clenching (high muscle activity) and gum chewing (moderate muscle activity), compared with the preceding rest period; however, such an increase was not detected during tooth tapping (low muscle activity). Cerebral blood flow was greater on the working side during the intensive isometric contraction of the masseter muscle in clenching. These results suggest that task-induced change in cerebral blood flow during jaw movement is influenced by the change in peripheral circulation evoked by muscle contraction.
A Novel Missense Mutation (p.P52R) in Amelogenin Gene Causing X-linked Amelogenesis Imperfecta
Authors: Kida M. , Sakiyama Y. , Matsuda A. , Takabayashi S. , Ochi H. , Sekiguchi H. , Minamitake S. , Ariga T.
Published: January 2009

Amelogenesis imperfecta (AI) is a hereditary disease with abnormal dental enamel formation. Here we report a Japanese family with X-linked AI transmitted over at least four generations. Mutation analysis revealed a novel mutation (p.P52R) in exon 5 of the amelogenin gene. The mutation was detected as heterozygous in affected females and as hemizygous in their affected father. The affected sisters exhibited vertical ridges on the enamel surfaces, whereas the affected father had thin, smooth, yellowish enamel with distinct widening of inter-dental spaces. To study the pathological cause underlying the disease in this family, we synthesized the mutant amelogenin p.P52R protein and evaluated it in vitro. Furthermore, we studied differences in the chemical composition between normal and affected teeth by x-ray diffraction analysis and x-ray fluorescence analysis. We believe that these results will greatly aid our understanding of the pathogenesis of X-linked AI.
Effective Bone Engineering with Periosteum-derived Cells
Authors: Agata H. , Asahina I. , Yamazaki Y. , Uchida M. , Shinohara Y. , Honda M.J. , Kagami H. , Ueda M.
Published: January 2009

Bone augmentation via tissue engineering has generated significant interest. We hypothesized that periosteum-derived cells could be used in place of bone marrow stromal cells (which are widely used) in bone engineering, but the differences in osteogenic potential between these 2 cell types are unclear. Here, we compared the osteogenic potential of these cells, and investigated the optimal osteoinductive conditions for periosteum-derived cells. Both cell types were induced, via bFGF and BMP-2, to differentiate into osteoblasts. Periosteal cells proliferated faster than marrow stromal cells, and osteogenic markers indicated that bone marrow stromal cells were more osteogenic than periosteal cells. However, pre-treatment with bFGF made periosteal cells more sensitive to BMP-2 and more osteogenic. Transplants of periosteal cells treated with BMP-2 after pre-treatment with bFGF formed more new bone than did marrow stromal cells. Analysis of these data suggests that combined treatment with bFGF and BMP-2 can make periosteum a highly useful source of bone regeneration.
Delivery Mode and Efficacy of BMP-2 in Association with Implants
Authors: Liu Y. , Huse R.O. , de Groot K. , Buser D. , Hunziker E.B.
Published: January 2009

Bone healing may be improved in implant patients by the administration of osteogenic agents, such as bone morphogenetic protein 2 (BMP-2). But the efficacy of BMP-2 depends upon its mode of application. We hypothesized that BMP-2 is capable of a higher osteogenic efficacy when delivered physiologically, viz., when incorporated into a calcium-phosphate carrier that mimics mineralized bone matrix, than when administered via simple pharmacological modes, such as by adsorption onto a carrier surface. Using an ectopic rat model, we compared the osteoinductive efficacies of calcium-phosphate implant-coatings bearing either incorporated, adsorbed, or incorporated and adsorbed BMP-2. When adsorbed directly onto the naked implant surface, BMP-2 was not osteogenic. When adsorbed onto a calcium-phosphate coating, it was osteoinductive, but not highly efficacious. When BMP-2 was incorporated into calcium-phosphate coatings, it was a potent bone-inducer, whose efficacy was compromised, not potentiated, by the additional deposition of an adsorbed pool.
Tissue-engineered Oral Mucosa: a Review of the Scientific Literature
Authors: Moharamzadeh K. , Brook I.M. , Van Noort R. , Scutt A.M. , Thornhill M.H.
Published: January 2009

Tissue-engineered oral mucosal equivalents have been developed for clinical applications and also for in vitro studies of biocompatibility, mucosal irritation, disease, and other basic oral biology phenomena. This paper reviews different tissue-engineering strategies used for the production of human oral mucosal equivalents, their relative advantages and drawbacks, and their applications. Techniques used for skin tissue engineering that may possibly be used for in vitro reconstruction of human oral mucosa are also discussed.
Secular Trends in Socio-economic Disparities in Edentulism: USA, 1972–2001
Authors: Cunha-Cruz J. , Hujoel P.P. , Nadanovsky P.
Published: January 2009

For health care planning and policy, it is important to determine whether socio-economic disparities in edentulism, an ultimate marker of oral health, have improved over time. The aim of this study was to investigate the socio-economic disparities in edentulism between 1972 and 2001. Representative samples of the United States population, 25–74 years old, were obtained from NHANES I (1972), III (1991), and 1999–2002. Differences in the edentulism prevalence between high and low socio-economic positions (SEP) were compared. Differences in edentulism prevalence remained stable over approximately three decades (p = 0.480), being 10.6 percentage points in 1972, 12.1 percentage points in 1991, and 11.3 percentage points in 2001. Exploratory subgroup analyses suggested that disparities decreased for those individuals reporting a dental visit in the prior year and those reporting never having smoked. In conclusion, the absolute prevalence difference in edentulism between low and high socio-economic positions has remained unchanged over the last three decades.
Unilateral Posterior Crossbite is Not Associated with TMJ Clicking in Young Adolescents
Authors: Farella M. , Michelotti A. , Iodice G. , Milani S. , Martina R.
Published: January 2009

Unilateral posterior crossbite has been considered as a risk factor for temporomandibular joint clicking, with conflicting findings. The aim of this study was to investigate a possible association between unilateral posterior crossbite and temporomandibular disk displacement with reduction, by means of a survey carried out in young adolescents recruited from three schools. The sample included 1291 participants (708 males and 583 females) with a mean age of 12.3 yrs (range, 10.1–16.1 yrs), who underwent an orthodontic and functional examination performed by two independent examiners. Unilateral posterior crossbite was found in 157 participants (12.2%). Fifty-three participants (4.1%) were diagnosed as having disk displacement with reduction. Logistic regression analysis failed to reveal a significant association between unilateral posterior crossbite and disk displacement with reduction (odds ratio = 1.3; confidence limits = 0.6–2.9). Posterior unilateral crossbite does not appear to be a risk factor for temporomandibular joint clicking, at least in young adolescents.
Fracture of Porcelain-veneered Structures in Fatigue
Authors: Kim B. , Zhang Y. , Pines M. , Thompson V.P.
Published: January 2009

Porcelain-veneered crowns are widely used in modern dentistry, and their fracture remains problematic, especially in all-ceramic systems. We hypothesized that substructure properties have a significant effect on the longevity of porcelain-veneered crowns. Flat porcelain/metal or porcelain/ceramic structures were cemented to dentin-like composite, and a mouth-motion cyclic load of 200 N was delivered by means of a tungsten carbide spherical indenter ( r = 3.18 mm), emulating occlusal loading on crowns supported by dentin. Findings indicated that porcelain on a low-hardness gold-infiltrated alloy was vulnerable to both occlusal surface contact damage and porcelain lower surface radial fracture, while porcelain on a higher-hardness palladium-silver alloy fractured chiefly from occlusal surface damage. The advantage of a high-modulus metal substructure was less pronounced. Fracture in the porcelain/zirconia system was limited to surface damage in the veneer layer, similar to that in the porcelain/palladium-silver system. Bulk fracture, observed in veneered alumina layers, was not found for zirconia.
A Role for Proteoglycans in Mineralized Tissue-Titanium Adhesion
Authors: Nakamura H.K. , Butz F. , Saruwatari L. , Ogawa T.
Published: January 2009

Biomechanical properties of the bone-titanium interface have rarely been studied, due to the technical limitations involved; whether biological bonding mechanisms exist has not been determined. We hypothesized that a selected set of proteoglycan/glycosaminoglycan complexes plays a role in establishing the adhesion between bone and titanium, and utilized the rat bone-marrow-derived osteoblastic culture model to gain an insight into the hypothesis. Gene expression of selected proteoglycan core proteins was up-regulated in the osteoblasts cultured on titanium compared with those on polystyrene. Various sulfated glycosaminoglycans were immunochemically localized at mineralized tissue-titanium interfaces. The administration of various glycosaminoglycan-degrading enzymes into the cultures resulted in a 25–45% reduction of the tissue-titanium interfacial strength, measured by a nanoscratch test; while the hardness and elastic modulus of the mineralized tissue, evaluated by nano-indentation, were not altered. In conclusion, glycosaminoglycan degradation resulted in a decreased interfacial strength between cultured mineralized tissue and titanium, but did not alter the intrinsic strength of the mineralized tissue, suggesting a role for proteoglycan/glycosaminoglycan complexes in the establishment of tissue-titanium adhesion.
Processing of Ameloblastin by MMP-20
Authors: Iwata T. , Yamakoshi Y. , Hu J.C.-C. , Ishikawa I. , Bartlett J.D. , Krebsbach P.H. , Simmer J.P.
Published: January 2009

Ameloblastin (AMBN) cleavage products are the most abundant non-amelogenin proteins in the enamel matrix of developing teeth. AMBN N-terminal cleavage products accumulate in the sheath space between enamel rods, while AMBN C-terminal products localize within rods. We tested the hypothesis that MMP-20 is the protease that cleaves AMBN. Glycosylated recombinant porcine AMBN (rpAMBN) was expressed in human kidney 293F cells, and recombinant porcine enamelysin (rpMMP-20) was expressed in bacteria. The purified proteins were incubated together at an enzyme:substrate ratio of 1:100. N-terminal sequencing of AMBN digestion products determined that rpMMP-20 cleaved rpAMBN after Pro2, Gln130, Gln139, Arg170, and Ala222. This shows that MMP-20 generates the 23-kDa AMBN starting at Tyr223, as well as the 17-kDa (Val1-Arg170) and 15-kDa (Val1-Gln130) AMBN cleavage products that concentrate in the sheath space during the secretory stage. We conclude that MMP-20 processes ameloblastin in vitro and in vivo.
Phex Mutation Causes the Reduction of Npt2b mRNA in Teeth
Authors: Onishi T. , Okawa R. , Ogawa T. , Shintani S. , Ooshima T.
Published: January 2009

Hyp mice (murine homologue of human X-linked hypophosphatemia) have a disorder in phosphate homeostasis, and display hypomineralization in bones and teeth. We investigated whether a mutation of Phex (phosphate regulating gene homologies to endopeptidase on the X chromosome) has an effect on the expression level of type II sodium-dependent phosphate co-transporter (Npt2) in the developing teeth of the Hyp mouse. Quantitative RT-PCR analyses revealed that the amount of Npt2b mRNA, an isoform of Npt2, in Hyp mouse tooth germs was significantly lower than that in wild-type mice, in both in vivo and in vitro experiments. In addition, tooth germs from wild-type mice cultured in medium supplemented with antisense oligo-deoxynucleotide for Phex also showed a reduction of Npt2b mRNA expression. These findings suggest that the loss of Phex function is related to the defect of Npt2b expression in teeth, and Npt2b reduction is an intrinsic defect of Hyp murine teeth.
Human Cytomegalovirus Enhances A. actinomycetemcomitans Adherence to Cells
Authors: Teughels W. , Sliepen I. , Quirynen M. , Haake S. Kinder , Van Eldere J. , Fives-Taylor P. , Van Ranst M.
Published: January 2009

Adherence of Actinobacillus actinomycetemcomitans to epithelial cells is an important step in periodontal disease pathogenesis. Recent publications describe the subgingival presence of a wide array of viruses [ e.g., human cytomegalo-virus (hCMV)]. Since viruses can increase cellular susceptibility for bacterial adherence, we investigated whether hCMV renders epithelial cells more prone to adherence by Actinobacillus actinomycetemcomitans. Cultivated HeLa and primary epithelial cells were shown to be semi-permissive for hCMV infection, which resulted in increased bacterial adherence. This increase correlated with viral concentrations, was evident in all Actinobacillus actinomycetemcomitans strains examined, and increased during the first 24 hrs, followed by a slight decrease. Immediate early antigen expression was not correlated with the increased adherence of Actinobacillus actinomycetemcomitans. The results confirmed our hypothesis that the adherence of Actinobacillus actinomycetemcomitans is influenced by hCMV in vitro.
P2X4 is Up-regulated in Gingival Fibroblasts after Periodontal Surgery
Authors: Binderman I. , Bahar H. , Jacob-Hirsch J. , Zeligson S. , Amariglio N. , Rechavi G. , Shoham S. , Yaffe A.
Published: January 2009

Several studies have shown that surgical detachment of marginal gingiva close to the cervical cementum of molar teeth in a rat mandible is a distinct stimulus for alveolar bone resorption. Recently, we found that P2X4, an ATP-receptor, is significantly up-regulated in marginal gingival cells soon after surgery. We hypothesized that local release of ATP signaling through P2X4 elicits activation of osteoclasts on the alveolar bone surface. In this study, we identified intense immunoreactivity of gingival fibroblasts to P2X4-specific antibodies and a 6.4-fold increase in expression by real-time RT-PCR. Moreover, a single local application, at the time of surgery, of Apyrase (which degrades ATP) or Coomassie Brilliant Blue (an antagonist of purinoreceptors) significantly reduced alveolar bone loss. We propose that ATP flowing from cells after surgery can directly activate P2X4 receptors in the sensor cells of marginal gingiva through Ca2+ signaling, or by direct activation of osteoclasts on the bone surface.
Candida glabrata, an Emerging Oral Opportunistic Pathogen
Authors: Li L. , Redding S. , Dongari-Bagtzoglou A.
Published: January 2009

Following the widespread use of immunosuppressive therapy and broad-spectrum antimycotic prophylaxis, C. glabrata has emerged as an important opportunistic pathogen in the oral mucosa. In the past, studies on the virulence factors and host-pathogen interactions of this organism were scarce, but continued to rise in recent years. Denture-wearing, immunosuppression, antibiotic therapy, and aging are risk factors for oral colonization or infection with C. glabrata. Compared with C. albicans, C. glabrata exhibits lower oral keratinocyte-adherence capacity, but higher denture-surface-adherence ability. The role of extracellular hydrolase production in the virulence of this organism does not appear to be as important as it is in C. albicans pathogenesis. Although traditionally thought of as a non-transforming yeast organism, both phenotypic switching and pseudohyphal formation have recently been identified in C. glabrata, but their role in pathogenesis is not known. With the exception of granulocyte monocyte colony-stimulating factor, C. glabrata triggers a lower proinflammatory cytokine response in oral epithelial cells than does C. albicans, in a strain-dependent manner. C. glabrata is less susceptible to killing by human beta-defensins than is C. albicans and exhibits various degrees of resistance to the antifungal activity of salivary histatins and mucins. In addition, C. glabrata possesses both innate and acquired resistance against antifungal drugs, due to its ability to modify ergosterol biosynthesis, mitochondrial function, or antifungal efflux. This resistance allows for its relative overgrowth over other susceptible species and may contribute to the recent emergence of C. glabrata infections in chronically immunocompromised populations. Further investigations on the virulence and host-pathogen interactions of C. glabrata are needed to better define the pathogenesis of oral C. glabrata infection in susceptible hosts.
Oral Mucosal Immunity and HIV/SIV Infection
Authors: Lü F.X. , Jacobson R.S.
Published: January 2009

Human Immunodeficiency Virus (HIV) transmission through genital and rectal mucosa has led to intensive study of mucosal immune responses to HIV and to the development of a vaccine administered locally. However, HIV transmission through the oral mucosa is a rare event. The oral mucosa represents a physical barrier and contains immunological elements to prevent the invasion of pathogenic organisms. This particular defense differs between micro-compartments represented by the salivary glands, oral mucosa, and palatine tonsils. Secretory immunity of the salivary glands, unique features of cellular structure in the oral mucosa and palatine tonsils, the high rate of oral blood flow, and innate factors in saliva may all contribute to the resistance to HIV/Simian Immunodeficiency Virus (SIV) oral mucosal infection. In the early stage of HIV infection, humoral and cellular immunity and innate immune functions in oral mucosa are maintained. However, these particular immune responses may all be impaired as a result of chronic HIV infection. A better understanding of oral mucosal immune mechanisms should lead to improved prevention of viral and bacterial infections, particularly in immunocompromised persons with Acquired Immune Deficiency Syndrome (AIDS), and to the development of a novel strategy for a mucosal AIDS vaccine, as well as vaccines to combat other oral diseases, such as dental caries and periodontal diseases.
Indentation Modulus of the Alveolar Process in Dogs
Authors: Huja S.S. , Fernandez S.A. , Hill K.J. , Gulati P.
Published: January 2009

One mechanism of bone adaptation is alteration in tissue level material properties. We hypothesized that alteration in the indentation modulus of the alveolar process is an adaptive response to the localized mechanical environment. Forty-eight specimens representing anterior and posterior regions of the maxilla and mandible were obtained from 6 mature male beagle dogs. The indentation properties of the alveolar bone proper and more distant osteonal cortical bone were estimated. The bone types were further divided into 3 regions (coronal, middle, and apical), with 27 indents being made in each region of tooth-supporting bone. There was a significant difference (p < 0.001) in the indentation moduli of the jaws (maxilla/mandible), location (anterior/posterior), and bone type (alveolar bone proper vs. cortical bone). However, statistical interactions exist which preclude the simple interpretation of results. The distribution of relative stiffness provides a better understanding of bone adaptations in the alveolar process.
Submandibular Glands Contribute to Increases in Plasma BDNF Levels
Authors: Tsukinoki K. , Saruta J. , Muto N. , Sasaguri K. , Sato S. , Tan-Ishii N. , Watanabe Y.
Published: January 2009

Brain-derived neurotrophic factor (BDNF) promotes survival and differentiation of neural cells in the central and peripheral nervous systems. BDNF has been detected in plasma, but its source has not yet been established. Expression of BDNF mRNA has been identified in the submandibular glands when male rats are exposed to acute immobilization stress. In the present study, we investigated whether plasma BDNF is influenced by the submandibular glands in this model. Acute immobilization stress for 60 min significantly increased the level of plasma BDNF. However, plasma BDNF elevation was markedly suppressed in bilaterally sialoadenectomized rats. There were no significant differences between stressed (60 min) and non-stressed rats with respect to the BDNF mRNA expression in the hippocampus, heart, lung, liver, pancreas, or spleen, as determined by real-time polymerase chain-reaction. These findings suggest that the submandibular glands may be the primary source of plasma BDNF in conditions of acute immobilization stress.
Localization of Palatal Area in Human Somatosensory Cortex
Authors: Bessho H. , Shibukawa Y. , Shintani M. , Yajima Y. , Suzuki T. , Shibahara T.
Published: January 2009

To determine the ’hard palate representing’ area in the primary somatosensory cortex, we recorded somatosensory-evoked magnetic fields from the cortex in ten healthy volunteers, using magnetoencephalography. Following electrical stimulation of 3 sites on the hard palate (the first and third transverse palatine ridges, and the greater palatine foramen), magnetic responses showed peak latencies of 15, 65, and 125 ms. Equivalent current dipoles for early magnetic responses were found along the posterior wall of the inferior part of the central sulcus. These dipoles were localized anterior-inferiorly, compared with locations for the hand area in the cortex. However, there were no significant differences in three-dimensional locations among the 3 selected regions for hard palate stimulation. These results demonstrated the precise location of palatal representation in the primary somatosensory cortex, the actual area being small.
Relationship of Metabolic Syndrome to Periodontal Disease in Japanese Women: The Hisayama Study
Authors: Shimazaki Y. , Saito T. , Yonemoto K. , Kiyohara Y. , Iida M. , Yamashita Y.
Published: January 2009

Recent studies have suggested that several systemic conditions—such as obesity, hypertension, hyperlipidemia, and diabetes—are related to periodontitis. The objective of this study was to examine the relationship between periodontitis and 5 components of metabolic syndrome—abdominal obesity, triglyceride level, high-density lipoprotein cholesterol level, blood pressure, and fasting blood sugar level—in 584 Japanese women. In multivariate analyses, persons exhibiting more components of metabolic syndrome had significantly higher odds ratios for a greater pocket depth and clinical attachment loss than did those with no components; the odds ratios for a greater pocket depth and clinical attachment loss of the persons exhibiting 4 or 5 components were 6.6 (95% confidence interval = 2.6–16.4) and 4.2 (95% confidence interval = 1.2–14.8), respectively. These results indicate that metabolic syndrome increases risk of periodontitis, and suggest that people exhibiting several components of metabolic syndrome should be encouraged to undergo a periodontal examination.
An Eight-year Follow-up to a Randomized Clinical Trial of Aftercare and Cost-analysis with Three Types of Mandibular Implant-retained Overdentures
Authors: Stoker G.T. , Wismeijer D. , van Waas M.A.J.
Published: January 2009

Mandibular implant overdentures increase satisfaction and the quality of life of edentulous individuals. Long-term aftercare and costs may depend on the type of overdentures. One hundred and ten individuals received one of 3 types of implant-retained overdentures, randomly assigned, and were evaluated with respect to aftercare and costs. The follow-up time was 8 years, with only seven drop-outs. No significant differences (Kruskal-Wallis test) were observed for direct costs of aftercare (p = 0.94). The initial costs constituted 75% of the total costs and were significantly higher in the group with a bar on 4 implants, compared with the group with a bar on 2 implants and the group with ball attachments on 2 implants (p = 0.018). The last group needed a significantly higher number of prosthodontist-patient aftercare contacts, mostly for re-adjustment of the retentive system. It can be concluded that an overdenture with a bar on 2 implants might be the most efficient in the long term.
Age- and Flow-dependency of Salivary Viscoelasticity
Authors: Zussman E. , Yarin A.L. , Nagler R.M.
Published: January 2009

Measuring salivary viscoelasticity (by relaxation times) is of paramount importance, since salivary rheology behavior has been associated with the development of oral disease conditions (such as dental caries) in animal and human model studies. In addition, novel and improved methods to evaluate salivary distribution and lubrication are of clinical interest. We used a novel method for measuring the viscoelasticity of saliva secreted from the different glands, at rest or under stimulation and at different ages, all conditions where different viscoelastic properties might be clinically important. Submandibular/sublingual salivary viscoelasticity was significantly higher than that of parotid saliva, especially under stimulation. In addition, an age-related reduction in flow rate (by 62%) was demonstrated, accompanied by an increase in both relaxation time (by 54%) and protein (by 48%). Increased salivary viscoelasticity results in compromised salivary rheology and lubrication properties, which may render the oral cavities of the elderly and other xerostomic persons more vulnerable.
Is SPARC an Evolutionarily Conserved Collagen Chaperone?
Authors: Martinek N. , Shahab J. , Sodek J. , Ringuette M.
Published: January 2009

The construction of collagen fiber scaffolds, which provide the structural integrity of the extracellular matrix of connective tissues and basement membranes, is initiated by a complex mechanism of protein-folding, whereby pro-collagen α-chains are assembled into triple-helical procollagen molecules. This unique assembly of the procollagen molecules is guided by several endoplasmic reticulum resident molecular chaperones, including HSP47, which dissociates from procollagen molecules prior to their transport from the endoplasmic reticulum into the cis-Golgi network. SPARC, an evolutionarily conserved collagen-binding glycoprotein, which is frequently co-expressed with collagen in rapidly remodeling tissues, binds to the triple-helical region of procollagen molecules. Analysis of data from genome projects indicates that specific amino acids and sequences in SPARC that are critical for collagen binding are evolutionarily conserved in organisms ranging from nematodes to mammals. Studies of invertebrates, which do not encode HSP47, indicate that SPARC expression is required for the deposition of collagen IV in basal lamina during embryonic development. In mammals, defects in collagen deposition have been observed in normal and wound-healing tissues in the absence of SPARC expression. Based on these and other observations, we propose that intracellular SPARC acts as a collagen molecular chaperone in the endoplasmic reticulum, and that in higher organisms, SPARC acts in concert with HSP47 to ensure that only correctly folded procollagen molecules exit the endoplasmic reticulum. In contrast to HSP47, SPARC is transported from the endoplasmic reticulum through the Golgi network and into secretory vesicles for exocytosis at the plasma membrane. Hence, SPARC may also play a role in regulating post-endoplasmic reticulum events that promote collagen fibrillogenesis.
Chemokines in Oral Inflammatory Diseases: Apical Periodontitis and Periodontal Disease
Authors: Silva T.A. , Garlet G.P. , Fukada S.Y. , Silva J.S. , Cunha F.Q.
Published: January 2009

The inflammatory oral diseases are characterized by the persistent migration of polymorphonuclear leukocytes, monocytes, lymphocytes, plasma and mast cells, and osteoblasts and osteoclasts. In the last decade, there has been a great interest in the mediators responsible for the selective recruitment and activation of these cell types at inflammatory sites. Of these mediators, the chemokines have received particular attention in recent years. Chemokine messages are decoded by specific receptors that initiate signal transduction events, leading to a multitude of cellular responses, including chemotaxis and activation of inflammatory and bone cells. However, little is known about their role in the pathogenesis of inflammatory oral diseases. The purpose of this review is to summarize the findings regarding the role of chemokines in periapical and periodontal tissue inflammation, and the integration, into experimental models, of the information about the role of chemokines in human diseases.
Validation of Amelogenesis Imperfecta Inferred from Amelogenin Evolution
Authors: Delgado S. , Ishiyama M. , Sire J.-Y.
Published: January 2009

We used the evolutionary analysis of amelogenin (AMEL) in 80 amniotes (52 mammalian and 28 reptilian sequences) to aid in the genetic diagnosis of X-linked amelogenesis imperfecta (AIH1). Out of 191 residues, 77 were found to be unchanged in mammals, and only 34 in amniotes. The latter are considered crucial residues for enamel formation, while the 43 residues conserved only in mammals could indicate that they play new, important roles for enamel formation in this lineage. The 5 substitutions leading to AIH1 were validated when the mammalian dataset was used, and 4 of them with the amniote dataset. These 2 sequence datasets will facilitate the validation of any human AMEL mutation suspected of involvement in AIH1. This evolutionary analysis also revealed numerous residues that appeared to be important for correct AMEL function, but their role remains to be elucidated.
Transgenic Mice that Express Normal and Mutated Amelogenins
Authors: Gibson C.W. , Yuan Z.A. , Li Y. , Daly B. , Suggs C. , Aragon M.A. , Alawi F. , Kulkarni A.B. , Wright J.T.
Published: January 2009

Amelogenin proteins are secreted by ameloblasts within the enamel organ during tooth development. To better understand the function of the 180-amino-acid amelogenin (M180), and to test the hypothesis that a single proline-to-threonine (P70T) change would lead to an enamel defect similar to amelogenesis imperfecta (AI) in humans, we generated transgenic mice with expression of M180, or M180 with the proline-to-threonine (P70T) mutation, under control of the Amelx gene regulatory regions. M180 teeth had a relatively normal phenotype; however, P70T mineral was abnormally porous, with aprismatic regions similar to those in enamel of male amelogenesis imperfecta patients with an identical mutation. When Amelx null females were mated with P70T transgenic males, offspring developed structures similar to calcifying epithelial odontogenic tumors in humans. The phenotype argues for dominant-negative activity for the P70T amelogenin, and for the robust nature of the process of amelogenesis.
Isolation of Human Oral Keratinocyte Progenitor/Stem Cells
Authors: Izumi K. , Tobita T. , Feinberg S.E.
Published: January 2009

Progenitor/stem cell populations of epithelium are known to reside in the small-sized cell population. Our objective was to physically isolate and characterize an oral keratinocyte-enriched population of small-sized progenitor/stem cells. Primary human oral mucosal keratinocytes cultured in a chemically defined serum-free culture system, devoid of animal-derived feeder cells, were sorted by relative cell size and characterized by immunolabeling for β1 integrin, nuclear transcription factor, peroxisome proliferator-activated receptor-gamma, and cell-cycle analysis. Sorted cells were distinguished as progenitor/stem cells by functional assays and their ability to regenerate an oral mucosal graft. Small-sized cells demonstrated the lowest expression of peroxisome proliferator-activated receptor-gamma, the highest colony-forming efficiency, a longer long-term proliferative potential, an enriched quiescent cell population, and the ability to regenerate an oral mucosal graft, implying that the small-sized cultured oral keratinocytes contained an enriched population of progenitor/stem cells.
MMPs, IL-1, and TNF are Regulated by IL-17 in Periodontitis
Authors: Beklen A. , Ainola M. , Hukkanen M. , Gürgan C. , Sorsa T. , Konttinen Y.T.
Published: January 2009

Periodontitis is characterized by periodontal tissue destruction. Since interleukin-17 (IL-17) has been reported to up-regulate IL-1β and tumor necrosis factor-alpha (TNF-α), it was hypothesized that it is increased in periodontitis and up-regulates these cytokines and tissue-destructive matrix metalloproteinases (MMP) in local migrant and resident cells. Immunocytochemistry disclosed elevated IL-1β, TNF-α, and IL-17 levels in periodontitis. These cytokines induced proMMP-1 and especially MMP-3 in gingival fibroblasts, whereas MMP-8 and MMP-9 were not induced. IL-17 was less potent as a direct MMP inducer than IL-1β and TNF-α, but it induced IL-1β and TNF-α production from macrophages, and IL-6 and IL-8 from gingival fibroblasts. In accordance with these findings, immunocytochemistry disclosed that MMP-1 and MMP-3 were increased in periodontitis. Gingival fibroblasts may play an important role in tissue destruction in periodontitis via cytokine-inducible MMP-1 and MMP-3 production, in which IL-17 plays a role as a key regulatory cytokine.
Role of NF-κB in TNF-α-induced COX-2 Expression in Synovial Fibroblasts from Human TMJ
Authors: Ke J. , Long X. , Liu Y. , Zhang Y.F. , Li J. , Fang W. , Meng Q.G.
Published: January 2009

In the temporomandibular joint (TMJ) synovium, cyclo-oxygenase-2 (COX-2) expression has been believed to be directly related to joint pain and synovitis. Here we investigated the role of Nuclear Factor κB (NF-κB) in the regulation of COX-2 expression in synovial fibroblasts from human TMJ induced by tumor necrosis factor-α (TNF-α). By reverse-transcriptase/polymerase chain-reaction (RT-PCR) and Western blotting analysis, TNF-α induced a dose- and time-dependent increase in COX-2 expression. Electrophoretic mobility shift assay (EMSA) revealed that transient NF-κB activation in the COX-2 promoter was triggered by TNF-α. In parallel with transient NF-κB activation, the rapid translocation of NF-κB, particularly the p65 subunit, from the cytoplasm into the nucleus was demonstrated. Pre-treatment with pyrolidine dithiocarbamate (PDTC), one of the NF-κB inhibitors, prevented binding to the COX-2 promoter and expression of COX-2 protein in response to TNF-α. These findings indicate that activation of NF-κB is responsible for TNF-α-induced COX-2 expression in synovial fibroblasts from the TMJ.
Effects of Calcium Phosphate Nanoparticles on Ca-PO4 Composite
Authors: Xu H.H.K. , Weir M.D. , Sun L. , Takagi S. , Chow L.C.
Published: January 2009

Nano-particles of dicalcium phosphate anhydrous (DCPA) were synthesized for the first time. The objectives of this study were to incorporate DCPA nano-particles into resin for Ca-PO4 release to combat dental caries, and to investigate the filler level effects. Nano-DCPA and nano-silica-fused silicon nitride whiskers at a 1:1 ratio were used at filler mass fractions of 0–75%. The flexural strengths in MPa (mean ± SD; n = 6) of DCPA-whisker composites ranged from (106 ± 39) at 0% fillers to (114 ± 23) at 75% fillers, similar to (112 ± 22) of a non-releasing composite (TPH) (p > 0.1). The composite with 75% fillers in a NaCl solution (133 mmol/L, pH = 7.4, 37°C) yielded a Ca concentration of (0.65 ± 0.02) mmol/L and PO4 of (2.29 ± 0.07) mmol/L. Relationships were established between ion-release and DCPA volume fraction VDCPA: Ca = 4.46 VDCPA1.6, and = 66.9 VDCPA2.6. Nano-DCPA-whisker PO4 composites had high strength and released high levels of Ca-PO4 requisite for remineralization. These new nano-composites could provide the needed combination of stress-bearing and caries-inhibiting capabilities.
Obesity, Inflammation, and Periodontal Disease
Authors: Pischon N. , Heng N. , Bernimoulin J.-P. , Kleber B.-M. , Willich S.N. , Pischon T.
Published: January 2009

The prevalence of obesity has increased substantially over the past decades in most industrialized countries. Obesity is a systemic disease that predisposes to a variety of co-morbidities and complications that affect overall health. Cross-sectional studies suggest that obesity is also associated with oral diseases, particularly periodontal disease, and prospective studies suggest that periodontitis may be related to cardiovascular disease. The possible causal relationship between obesity and periodontitis and potential underlying biological mechanisms remain to be established; however, the adipose tissue actively secretes a variety of cytokines and hormones that are involved in inflammatory processes, pointing toward similar pathways involved in the pathophysiology of obesity, periodontitis, and related inflammatory diseases. We provide an overview of the definition and assessment of obesity and of related chronic diseases and complications that may be important in the periodontist’s office. Studies that have examined the association between obesity and periodontitis are reviewed, and adipose-tissue-derived hormones and cytokines that are involved in inflammatory processes and their relationship to periodontitis are discussed. Our aim is to raise the periodontist’s awareness when treating obese individuals.
Gene Polymorphisms and the Prevalence of Key Periodontal Pathogens
Authors: Nibali L. , Ready D.R. , Parkar M. , Brett P.M. , Wilson M. , Tonetti M.S. , Griffiths G.S.
Published: January 2009

Growing evidence suggests that individual genetic susceptibility may influence the host’s response to infections. The aim of this project was to study whether gene polymorphisms of inflammatory markers are associated with the presence of viable periodontopathogenic bacteria. We extracted genomic DNA from 45 young adults diagnosed with generalized aggressive periodontitis to study Fc receptors, formyl peptide receptor, Interleukin-6, tumor necrosis factor-α, and vitamin D receptor polymorphisms. The presence and viable numbers of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, and Tannerella forsythensis were determined by culture, and their identities confirmed by PCR. Multiple logistic regressions revealed that both Fcγ receptor and IL-6 -174 polymorphisms were associated with increased odds of detecting A. actinomycetemcomitans, P. gingivalis, and T. forsythensis after adjustment for age, ethnicity, smoking, and periodontitis extent. These findings support the hypothesis that complex interactions between the microbiota and host genome may be at the basis of susceptibility to aggressive periodontitis.
Self-assembling Peptide Scaffolds Promote Enamel Remineralization
Authors: Kirkham J. , Firth A. , Vernals D. , Boden N. , Robinson C. , Shore R.C. , Brookes S.J. , Aggeli A.
Published: January 2009

Rationally designed β-sheet-forming peptides that spontaneously form three-dimensional fibrillar scaffolds in response to specific environmental triggers may potentially be used in skeletal tissue engineering, including the treatment/prevention of dental caries, via bioactive surface groups. We hypothesized that infiltration of caries lesions with monomeric low-viscosity peptide solutions would be followed by in situ polymerization triggered by conditions of pH and ionic strength, providing a biomimetic scaffold capable of hydroxyapatite nucleation, promoting repair. Our aim was to determine the effect of an anionic peptide applied to caries-like lesions in human dental enamel under simulated intra-oral conditions of pH cycling. Peptide treatment significantly increased net mineral gain by the lesions, due to both increased remineralization and inhibition of demineralization over a five-day period. The assembled peptide was also capable of inducing hydroxyapatite nucleation de novo. The results suggest that self-assembling peptides may be useful in the modulation of mineral behavior during in situ dental tissue engineering.
Zymographic Analysis and Characterization of MMP-2 and -9 Forms in Human Sound Dentin
Authors: Mazzoni A. , Mannello F. , Tay F.R. , Tonti G.A.M. , Papa S. , Mazzotti G. , Di Lenarda R. , Pashley D.H. , Breschi L.
Published: January 2009

The role and function of dentin matrix metalloproteinases (MMPs) are not well-understood, but they may play a key role in dentinal caries and the degradation of resin-bonded dentin matrices. To test the null hypothesis that MMP-9 is not found in dentin matrix, we used gelatin zymography to extract and isolate all molecular forms of gelatinolytic MMPs in demineralized mature sound dentin powder obtained from extracted human molars, characterizing and identifying the enzymes by Western blotting. Gelatinolytic MMPs were detected in extracts of demineralized dentin matrix and identified as MMP-2 and MMP-9. Acidic extracts (pH 2.3) yielded 3–8 times more MMP activity than did EDTA (pH 7.4). Their activation may contribute to dentin matrix degradation, which occurs during caries progression and following resin bonding. Inhibition of MMP-2 and -9 proteolytic activity may slow caries progression and increase the durability of resin-dentin bonds.
Mouse Molar Dentin Size/Shape is Dependent on Growth Hormone Status
Authors: Smid J.R. , Rowland J.E. , Young W.G. , Coschigano K.T. , Kopchick J.J. , Waters M.J.
Published: January 2009

Growth hormone (GH) status affects dental development, but how GH influences tooth size/shape is unclear. Since GH affects dental epithelial proliferation, we hypothesized that GH influences the tooth crown and root dimensions. Dentin matrix dimensions were measured in longitudinal sections of decalcified first mandibular molars from 3 genetically modified mice: giant (GH-Excess) mice and dwarf (GH-Antagonist and GH-Receptor-Knockout) mice. GH status was found to influence crown width, root length, and dentin thickness. Analysis of these data suggests that GH influences both tooth crown and root development prior to dentinogenesis as well as during appositional growth of dentin. This is concordant with the expression of paracrine GH and GH receptors during tooth bud morphogenesis, and of GH receptors in the enamel organ, dental papilla, and Hertwig’s epithelial root sheath during dentinogenesis. Based on prior studies, these GH morphogenetic actions may be mediated by the induction of both bone morphogenetic protein and insulin-like growth factor-1 expression.
Resin Elasticity and the Strengthening of All-ceramic Restorations
Authors: Addison O. , Marquis P.M. , Fleming G.J.P.
Published: January 2009

Resin luting of all-ceramic restorations results in increased performance; however, the strengthening mechanism and the role of the mechanical properties of the resin are not fully understood. The hypothesis tested is that ceramic strength enhancement is dependent on the elastic modulus of the resin. Three-point flexural moduli of a flowable, luting, and hybrid composite resin were characterized. Two hundred forty porcelain discs were air-abraded. One group acted as a control, and 3 additional groups were coated with 120 ± 20 μm of each resin prior to bi-axial flexure testing. All resins significantly increased in mean strength, and the associated strength increase was related to the elastic modulus of the resin (R2 = 0.9885), so the hypothesis was accepted. The combination of Poisson constraint and the creation of a resin-inter-penetrating layer sensitive to the elastic modulus of the resin may provide an explanation of the strengthening mechanism.
Effects of EDTA on the Hydration Mechanism of Mineral Trioxide Aggregate
Authors: Lee Y.-L. , Lin F.-H. , Wang W.-H. , Ritchie H.H. , Lan W.-H. , Lin C.-P.
Published: January 2009

Ethylenediaminetetraacetic acid (EDTA) is commonly used during the preparation of obstructed root canals that face a high risk of root perforation. Such perforations may be repaired with mineral trioxide aggregate (MTA). Due to EDTA’s ability to chelate calcium ions, we hypothesized that EDTA may disrupt the hydration of MTA. Using scanning electron microscopy and energy-dispersive x-ray spectroscopy, we found that MTA specimens stored in an EDTA solution had no crystalline structure and a Ca/Si molar ratio considerably lower than those obtained for specimens stored in distilled water and normal saline. Poor cell adhesion in EDTA-treated MTA was also noted. X-ray diffraction indicated that the peak corresponding to portlandite, which is normally present in hydrated MTA, was not shown in the EDTA group. The microhardness of EDTA-treated specimens was also significantly reduced ( p < 0.0001). These findings suggest that EDTA interferes with the hydration of MTA, resulting in decreased hardness and poor biocompatibility.
NGF Up-regulates TRPA1: Implications for Orofacial Pain
Authors: Diogenes A. , Akopian A.N. , Hargreaves K.M.
Published: January 2009

The transient receptor potential ankyrin repeat 1 (TRPA1) channel is believed to be involved in many forms of acute and chronic hyperalgesia. Nerve Growth Factor (NGF) regulates chronic inflammatory hyperalgesia by controlling gene expression in sensory neurons, including genes involved in inflammatory hyperalgesia in the dental pulp. We hypothesized that NGF increases functional activities of the TRPA1 channel in trigeminal ganglion neurons. Here, we show that NGF induced a concentration- and time-dependent up-regulation of TRPA1 mRNA in trigeminal ganglia neurons, as detected by real-time RT-PCR and in situ hybridization. In addition, NGF evoked a time-dependent increase of mustard oil (MO)-evoked TRPA1 activation in trigeminal ganglia neurons. Collectively, these findings demonstrate that NGF participates in the functional up-regulation of TRPA1 in trigeminal ganglia neurons. These enhanced activities of TRPA1 could play an important role in the development of hyperalgesia following nerve injury and inflammation in the orofacial region.
Nuclear Factor κB p65 Phosphorylation in Orthodontic Tooth Movement
Authors: Zuo J. , Archer L.A. , Cooper A. , Johnson K.L. , Holliday L.S. , Dolce C.
Published: January 2009

Osteoclasts play a vital role in orthodontic tooth movement. Transactivation of nuclear factor κB (NFκB) by phosphorylation of the p65 component of NFκB at amino acid 536 (p65*536) plays a role in osteoclast differentiation stimulated by receptor activator of nuclear factor κB-ligand (RANK-L). We hypothesized that this transactivation pathway might be involved in the responses of alveolar bone cells during orthodontic tooth movement. We detected sharp increases in the levels of p65*536 3 and 12 hrs after the application of orthodontic stimuli in rats. In cell culture, osteoclast-like cells displayed no changes in p65*536 in response to RANK-L, but levels rapidly increased after the cells were mechanically scraped. We conclude that p65*536 is produced rapidly in response to orthodontic stimuli and mechanical insults, and may be important in bone remodeling associated with orthodontic tooth movement.