bluuebunny/crossref_metadata_2025 huggingface dataset:
Fracture Surface Analysis of Clinically Failed Fixed Partial Dentures
Authors: Taskonak B. , Mecholsky J.J. , Anusavice K.J.
Published: January 2009

Ceramic systems have limited long-term fracture resistance, especially when they are used in posterior areas or for fixed partial dentures. The objective of this study was to determine the site of crack initiation and the causes of fracture of clinically failed ceramic fixed partial dentures. Six Empress 2® lithia-disilicate (Li2O·2SiO2)-based veneered bridges and 7 experimental lithia-disilicate-based non-veneered ceramic bridges were retrieved and analyzed. Fractography and fracture mechanics methods were used to estimate the stresses at failure in 6 bridges (50%) whose fracture initiated from the occlusal surface of the connectors. Fracture of 1 non-veneered bridge (8%) initiated within the gingival surface of the connector. Three veneered bridges fractured within the veneer layers. Failure stresses of the all-core fixed partial dentures ranged from 107 to 161 MPa. Failure stresses of the veneered fixed partial dentures ranged from 19 to 68 MPa. We conclude that fracture initiation sites are controlled primarily by contact damage.
Evaluation of a Self-limiting Concept in Dentinal Caries Removal
Authors: Silva N.R.F.A. , Carvalho R.M. , Pegoraro L.F. , Tay F.R. , Thompson V.P.
Published: January 2009

The mechanical removal of dentinal caries traditionally involves the use of tactile sensation and/or caries-indicating dyes. This study tested the hypothesis that self-limiting polymer burs are as effective as conventional carbide burs in creating substrates for dentin bonding. Carious dentin from extracted human molars was removed with carbide or polymer burs, with dental explorer hardness as the end-point for caries removal. Dentin substrates were bonded with etch-and-rinse or self-etch adhesives and prepared for microtensile bond testing and transmission electron microscopy. For each bur type, there was no difference in bond strength between adhesives. However, the polymer bur surface exhibited significantly lower bond strengths than the carbide bur, and both were lower than flat, non-carious dentin controls. TEM revealed areas of incompletely removed, denatured caries-infected dentin in the polymer bur specimens. These first-generation polymer burs might best be utilized for deep caries removal where pulpal exposure is a concern.
Stress, Cortisol, and Periodontitis in a Population Aged 50 Years and Over
Authors: Hilgert J.B. , Hugo F.N. , Bandeira D.R. , Bozzetti M.C.
Published: January 2009

Periodontitis and its relationship with psycho-neuro-immunological variables, such as psychological stress and cortisol, have been little explored. The objective of this study was to evaluate the extent and severity of chronic periodontitis and its association with the levels of salivary cortisol and the scores obtained with a stress questionnaire in a population aged 50 years and over. We studied 235 individuals in a cross-sectional study. They answered the Lipp’s Inventory of Stress Symptoms for Adults, were instructed to collect three saliva samples for cortisol analysis, and were examined for evaluation for periodontitis. Based on logistic regression, cortisol levels were positively associated with the following outcomes: means of clinical attachment level (CAL) > = 4 mm [OR = 5.1, 95%CI (1.2, 20.7)]; 30% of sites with CAL > = 5 mm [OR = 6.9, 95%CI (1.7, 27.1)]; and 26% of sites with probing depth > = 4 mm [OR = 10.7, 95%CI (1.9, 54.1)] after adjustment for confounding variables. The results suggest that cortisol levels were positively associated with the extent and severity of periodontitis.
Phenotypic Variation in Dentinogenesis Imperfecta/Dentin Dysplasia Linked to 4q21
Authors: Beattie M.L. , Kim J.-W. , Gong S.-G. , Murdoch-Kinch C.A. , Simmer J.P. , Hu J.C.-C.
Published: January 2009

Dentinogenesis imperfecta (DGI) and dentin dysplasia (DD) are allelic disorders that primarily affect the formation of tooth dentin. Both conditions are autosomal-dominant and can be caused by mutations in the dentin sialophosphoprotein gene ( DSPP, 4q21.3). We recruited 23 members of a four-generation kindred, including ten persons with dentin defects, and tested the hypothesis that these defects are linked to DSPP. The primary dentition showed amber discoloration, pulp obliteration, and severe attrition. The secondary dentition showed either pulp obliteration with bulbous crowns and gray discoloration or thistle-tube pulp configurations, normal crowns, and mild gray discoloration. Haplotype analyses showed no recombination between three 4q21-q24 markers and the disease locus. Mutational analyses identified no coding or intron junction sequence variations associated with affection status in DMP1, MEPE, or the DSP portion of DSPP. The defects in the permanent dentition were typically mild and consistent with a diagnosis of DD-II, but some dental features associated with DGI-II were also present. We conclude that DD-II and DGI-II are milder and more severe forms, respectively, of the same disease.
Dental Plaque pH and Micro-organisms during Hyposalivation
Authors: Eliasson L. , Carlén A. , Almståhl A. , Wikström M. , Lingström P.
Published: January 2009

We have previously reported that minor gland and whole saliva flow rates and salivary proteins showed differences in individuals with primary Sjögren’s syndrome or head and neck radiation therapy, compared with controls ( Eliasson et al., 2005 ). We now hypothesize that pH and number of acidogenic micro-organisms in dental plaque as well as saliva buffering capacity also differ in these individuals. Plaque pH was measured by the microtouch method up to 60 min after a sucrose rinse. Plaque collected from the same sites was analyzed for counts of total and acidic micro-organisms. Compared with their controls, the irradiated group but not the Sjögren’s syndrome group displayed significantly lower plaque pH, increased numbers of lactobacilli and Candida species, as well as reduced buffering capacity. Stepwise regression tests suggested that the buccal minor-salivary-gland secretion rate in the test groups and counts of mutans streptococci in the controls were of significant importance for dental plaque pH.
Oral Health Beliefs in Adolescence and Oral Health in Young Adulthood
Authors: Broadbent J.M. , Thomson W.M. , Poulton R.
Published: January 2009

According to theory, health beliefs are related to health behaviors. We investigated whether individuals who hold favorable oral-health-related beliefs over time have better adult oral health than those who do not. Beliefs about the efficacy of water fluoridation, keeping the mouth clean, avoiding sweet foods, visiting the dentist, using dental floss, and using fluoridated toothpaste were assessed in a birth cohort at ages 15, 18, and 26 years. At each age, the majority of participants endorsed the importance of each practice. However, there was also evidence of instability across time. Individuals who held stable favorable dental beliefs from adolescence through adulthood had fewer teeth missing due to caries, less periodontal disease, better oral hygiene, better self-rated oral health, and more restorations. Dental beliefs can change between adolescence and young adulthood, and these changes are related to oral health. In particular, unfavorable dental health beliefs are related to poorer oral health.
Development of a Self-etch Adhesive for Resin-modified Glass Ionomers
Authors: Coutinho E. , Van Landuyt K. , De Munck J. , Poitevin A. , Yoshida Y. , Inoue S. , Peumans M. , Suzuki K. , Lambrechts P. , Van Meerbeek B.
Published: January 2009

The favorable self-adhesiveness of resin-modified glass ionomers (RMGIs) might be even further improved if the time-consuming and technically sensitive etch-and-rinse pre-treatment step with polyalkenoic acids could be avoided. We undertook this study to assess the effectiveness of an experimental self-etch adhesive for RMGIs that does not need to be rinsed off. Ultrastructural analysis and micro-tensile bond strength testing to enamel and dentin of a RMGI restorative material and a RMGI adhesive were performed after 4 different surface pre-treatments: no conditioning; 25% polyalkenoic acid; an experimental self-etch adhesive; and 37.5% phosphoric acid followed by the experimental self-etch adhesive. The use of an experimental self-etch adhesive increased the bond strength of RMGIs, especially after an additional conditioning step. Interfacial analysis showed the formation of a thin hydroxyapatite-containing hybrid layer. The self-etch technique enhances the user-friendliness of RMGIs and lowers their technique-sensitivity, while maintaining desirable characteristics of the conventional etch-and-rinse approach with polyalkenoic acids.
Effects of a Hydroxyapatite-based Biomaterial on Gene Expression in Osteoblast-like Cells
Authors: Sibilla P. , Sereni A. , Aguiari G. , Banzi M. , Manzati E. , Mischiati C. , Trombelli L. , del Senno L.
Published: January 2009

Biostite® is a hydroxyapatite-derived biomaterial that is used in periodontal and bone reconstructive procedures due to its osteoconductive properties. Since the molecular effects of this biomaterial on osteoblasts are still unknown, we decided to assess whether it may specifically modulate osteoblast functions in vitro. We found that a brief exposure to Biostite® significantly reduced the proliferation of MG-63 and SaOS-2 osteoblast-like cells to ~ 50% of the plateau value. Furthermore, gene array analysis of MG-63 cells showed that Biostite® caused a differential expression of 37 genes which are involved in cell proliferation and interaction, and related to osteoblast differentiation and tissue regeneration. Results were confirmed by RT-PCR, Western blot, and by an increase in alkaline phosphatase (ALP) specific activity. Biostite® also increased levels of polycystin-2, a mechano-sensitive Ca2+ channel, a promising new marker of bone cell differentiation. Biostite®, therefore, may directly affect osteoblasts by enhancing chondro/osteogenic gene expression and cytoskeleton-related signaling pathways, which may contribute to its clinical efficacy.
Impact of Endodontic Treatments on the Rigidity of the Root
Authors: Lang H. , Korkmaz Y. , Schneider K. , Raab W.H.-M.
Published: January 2009

The destabilizing effect of endodontic treatment upon teeth is still controversial. The purpose of this study was to investigate the effects of different steps of endodontic treatments upon the rigidity of teeth. Extracted untreated central maxillary anterior teeth were loaded (3.75 N), and deformations of the root were assessed by Speckle pattern interferometry. The following treatments (with subsequent determination of deformability) were conducted sequentially: access preparation, manual instrumentation (Kerr files ISO-40, ISO-60, ISO-80, ISO-110), and tapered and parallel-sided post preparation. It was found that the teeth were increasingly destabilized by any treatment. While the increased deformability was not significant with the manual enlargement (p > 0.05), we found a significant destabilization after access preparation and post preparation (p < 0.05). A corresponding difference was found after conversion of the post preparation from tapered to parallel-sided (p < 0.05). Both substance loss and modifications of the natural root canal geometry play an important role in tooth rigidity.
Streptococcus mutans: Fructose Transport, Xylitol Resistance, and Virulence
Authors: Tanzer J.M. , Thompson A. , Wen Z.T. , Burne R.A.
Published: January 2009

Streptococcus mutans, the primary etiological agent of human dental caries, possesses at least two fructose phosphotransferase systems (PTSs), encoded by fruI and fruCD. fruI is also responsible for xylitol transport. We hypothesized that fructose and xylitol transport systems do not affect virulence. Thus, colonization and cariogenicity of fruI− and fruCD− single and double mutants, their WT (UA159), and xylitol resistance (Xr) of S. mutans were studied in rats fed a high-sucrose diet. A sucrose phosphorylase ( gtfA−) mutant and a reference strain (NCTC-10449S) were additional controls. Recoveries of fruI mutant from the teeth were decreased, unlike those for the other strains. The fruCD mutation was associated with a slight loss of cariogenicity on enamel, whereas mutation of fruI was associated with a loss of cariogenicity in dentin. These results also suggest why xylitol inhibition of caries is paradoxically associated with spontaneous emergence of so-called Xr S. mutans in habitual human xylitol users.
Role of Secreted Frizzled-related Protein 1 (SFRP1) in Wound Healing
Authors: Li C.H. , Amar S.
Published: January 2009

Wound healing is a complex cascade of events, which diminishes the size of the wound and reestablishes tissue integrity. Secreted frizzled-related protein 1 (SFRP1) contributes to the inhibition of apoptosis in fibroblast populations. We investigated the role of SFRP1 in a mouse wound-healing model; 2.0-mm excisional wounds were created in the scalp and hard palate. Healing responses were measured by histomorphometric analysis, apoptosis assay, and immunohistochemistry. Dermal wounds did not harbor SFRP1, but healed faster than palatal wounds which expressed significant levels of SFRP1. Antibody experiments aimed at blocking SFRP1 in palatal wounds resulted in promotion of wound closure, enhancement of new tissue formation, decrease of inflammatory cell infiltrate, and increase of apoptotic fibroblasts. Analysis of the present data suggests that SFRP1 may be partly responsible for the poorer healing performance of the palatal wounds compared with dermal wounds. Blocking SFRP1 results in improvement of palatal healing outcomes.
Porphyromonas gingivalis-Epithelial Cell Interactions in Periodontitis
Authors: Andrian E. , Grenier D. , Rouabhia M.
Published: January 2009

Emerging data on the consequences of the interactions between invasive oral bacteria and host cells have provided new insights into the pathogenesis of periodontal disease. Indeed, modulation of the mucosal epithelial barrier by pathogenic bacteria appears to be a critical step in the initiation and progression of periodontal disease. Periodontopathogens such as Porphyromonas gingivalis have developed different strategies to perturb the structural and functional integrity of the gingival epithelium. P. gingivalis adheres to, invades, and replicates within human epithelial cells. Adhesion of P. gingivalis to host cells is multimodal and involves the interaction of bacterial cell-surface adhesins with receptors expressed on the surfaces of epithelial cells. Internalization of P. gingivalis within host cells is rapid and requires both bacterial contact-dependent components and host-induced signaling pathways. P. gingivalis also subverts host responses to bacterial challenges by inactivating immune cells and molecules and by activating host processes leading to tissue destruction. The adaptive ability of these pathogens that allows them to survive within host cells and degrade periodontal tissue constituents may contribute to the initiation and progression of periodontitis. In this paper, we review current knowledge on the molecular cross-talk between P. gingivalis and gingival epithelial cells in the development of periodontitis.
Osteopontin and Mucosal Protection
Authors: Sodek J. , Batista Da Silva A. Paes , Zohar R.
Published: January 2009

Protection of mucosal tissues of the oral cavity, intestines, respiratory tract, and urogenital tract from the constant challenge of pathogens is achieved by the combined barrier function of the lining epithelia and specialized immune cells. Recent studies have indicated that osteopontin (OPN) has a pivotal role in the development of immune responses and in the tissue destruction and the subsequent repair processes associated with inflammatory diseases. While expression of OPN is increased in immune cells—including neutrophils, macrophages, T- and B-lymphocytes—and in epithelial, endothelial, and fibroblastic cells of inflamed tissues, deciphering the specific functions of OPN has been difficult. In part, this is due to the broad range of biological activities of OPN that are mediated by multiple receptors which recognize several signaling motifs whose activities are influenced by post-translational modifications and proteolytic processing of OPN. Understanding the role of OPN in mucosal inflammation is further complicated by its contributions to the barrier function of the lining epithelia and the complexity of the specialized mucosal immune system. In an attempt to provide some insights into the involvement of OPN in mucosal diseases, this review summarizes current knowledge of the biological activities of OPN involved in the development of inflammatory responses and in wound healing, and indicates how these activities may affect the protection of mucosal tissues.
Bone Marrow Cells Can Give Rise to Ameloblast-like Cells
Authors: Hu B. , Unda F. , Bopp-Kuchler S. , Jimenez L. , Wang X.J. , Haïkel Y. , Wang S.L. , Lesot H.
Published: January 2009

Post-eruptive loss of ameloblasts requires identification of alternative sources for these cells to realize tooth-tissue-engineering strategies. Recent reports showed that bone-marrow-derived cells can give rise to different types of epithelial cells, suggesting their potential to serve as a source for ameloblasts. To investigate this potential, we mixed c-Kit+-enriched bone marrow cells with embryonic dental epithelial cells and cultured them in re-association with dental mesenchyme. Non-dividing, polarized, and secretory ameloblast-like cells were achieved without cell fusion. Before basement membrane reconstitution, some bone marrow cells migrated to the mesenchyme, where they exhibited morphological, molecular, and functional characteristics of odontoblasts. These results show, for the first time, that bone-marrow-derived cells can be reprogrammed to give rise to ameloblast-like cells, offering novel possibilities for tooth-tissue engineering and the study of the simultaneous differentiation of one bone marrow cell subpopulation into cells of two different embryonic lineages.
Sonic Hedgehog Signaling is Important in Tooth Root Development
Authors: Nakatomi M. , Morita I. , Eto K. , Ota M.S.
Published: January 2009

Hertwig’s epithelial root sheath (HERS) is important for tooth root formation, but the molecular basis for the signaling of root development remains uncertain. We hypothesized that Sonic hedgehog (Shh) signaling is involved in the HERS function, because it mediates epithelial-mesenchymal interactions during embryonic odontogenesis. We examined the gene expression patterns of Shh signaling in murine developing molar roots. Shh and Patched2 transcripts were identified in the HERS, whereas Patched1, Smoothened, and Gli1 were expressed in the proliferative dental mesenchyme in addition to the HERS. To confirm whether Shh signaling physiologically functions in vivo, we analyzed mesenchymal dysplasia ( mes) mice carrying an abnormal C-terminus of the PATCHED1 protein. In the mutant, cell proliferation was repressed around the HERS at 1 wk. Moreover, the molar eruption was disturbed, and all roots were shorter than those in control littermates at 4 wks. These results indicate that Shh signaling is important in tooth root development. Abbreviations used: BrdU, 5-bromo-2′-deoxyuridine; HERS, Hertwig’s epithelial root sheath; NFI-C/CTF, nuclear factor Ic/CAAT box transcription factor; PCNA, proliferating cell nuclear antigen; Ptc, patched; Shh, sonic hedgehog; Smo, smoothened.
Activation of iCaspase-9 in Neovessels Inhibits Oral Tumor Progression
Authors: Pinsky M.S. , Song W. , Dong Z. , Warner K. , Zeitlin B. , Karl E. , Hall D.E. , Nör J.E.
Published: January 2009

Tumors of the oral cavity are highly vascularized malignancies. Disruption of neovascular networks was shown to limit the access of nutrients and oxygen to tumor cells and inhibit tumor progression. Here, we evaluated the effect of the activation of an artificial death switch (iCaspase-9) expressed in neovascular endothelial cells on the progression of oral tumors. We used biodegradable scaffolds to co-implant human dermal microvascular endothelial cells stably expressing iCaspase-9 (HDMEC-iCasp9) with oral cancer cells expressing luciferase (OSCC3-luc or UM-SCC-17B-luc) in immunodeficient mice. Alternatively, untransduced HDMEC were co-implanted with oral cancer cells, and a transcriptionaly targeted adenovirus (Ad-VEGFR2-iCasp-9) was injected locally to deliver iCaspase-9 to neovascular endothelial cells. In vivo bioluminescence demonstrated that tumor progression was inhibited, and immunohistochemistry showed that microvessel density was decreased, when iCaspase-9 was activated in tumor-associated microvessels. We conclude that activation of iCaspase-9 in neovascular endothelial cells is sufficient to inhibit the progression of xenografted oral tumors.
Regulation of PLAP-1 Expression in Periodontal Ligament Cells
Authors: Yamada S. , Ozawa Y. , Tomoeda M. , Matoba R. , Matsubara K. , Murakami S.
Published: January 2009

Periodontal-ligament-associated protein-1 ( PLAP-1) is preferentially expressed in the periodontal ligament (PDL) and encodes a novel small leucine-rich repeat proteoglycan protein. PLAP-1 expression was induced during the course of cytodifferentiation of PDL cells into mineralized-tissue-forming cells in vitro, suggesting the possible involvement of PLAP-1 in the mineralization process of PDL cells. In this study, we hypothesized that PLAP-1 expression is regulated by mineralization-related cytokines in PDL cells. PLAP-1 expression was clearly down-regulated when the cytodifferentiation of PDL cells was reversibly inhibited by fibroblast growth factor-2 (FGF-2). In contrast, bone morphogenetic protein-2 (BMP-2) enhanced PLAP-1 expression. Up-regulation of PLAP-1 expression by BMP-2 was confirmed at the protein level when PDL cells were immunostained with anti-PLAP-1 polyclonal antibody. These results revealed the cytokine-mediated regulatory mechanisms of PLAP-1 expression and suggested that PLAP-1 expression may be associated with the process of cytodifferentiation of PDL cells.
Accumulation of Non-steroidal Anti-inflammatory Drugs by Gingival Fibroblasts
Authors: Zavarella M.M. , Gbemi O. , Walters J.D.
Published: January 2009

Non-steroidal anti-inflammatory drugs (NSAIDs) are used to manage pain and inflammatory disorders. We hypothesized that gingival fibroblasts actively accumulate NSAIDs and enhance their levels in gingival connective tissue. Using fluorescence to monitor NSAID transport, we demonstrated that cultured gingival fibroblasts transport naproxen in a saturable, temperature-dependent manner with a Km of 127 μg/mL and a Vmax of 1.42 ng/min/μg protein. At steady state, the intracellular/extracellular concentration ratio was 1.9 for naproxen and 7.2 for ibuprofen. Naproxen transport was most efficient at neutral pH and was significantly enhanced upon cell treatment with TNF-α. In humans, systemically administered naproxen attained steady-state levels of 61.9 μg/mL in blood and 9.4 μg/g in healthy gingival connective tissue, while ibuprofen attained levels of 2.3 μg/mL and 1.5 μg/g, respectively. Thus, gingival fibroblasts possess transporters for NSAIDs that are up-regulated by an inflammatory mediator, but there is no evidence that they contribute to elevated NSAID levels in healthy gingiva.
Cyclical Tensile Force on Periodontal Ligament Cells Inhibits Osteoclastogenesis through OPG Induction
Authors: Kanzaki H. , Chiba M. , Sato A. , Miyagawa A. , Arai K. , Nukatsuka S. , Mitani H.
Published: January 2009

The periodontal ligament (PDL) maintains homeostasis of periodontal tissue under mechanical tensile-loading caused by mastication. Occlusal load inhibits atrophic alveolar bone resorption. Previously, we discovered that continuous compressive force on PDL cells induced osteoclastogenesis-supporting activity, with up-regulation of RANKL. We hypothesized that, unlike compression, cyclical tensile force up-regulates OPG expression in PDL cells via TGF-beta up-regulation, and does not induce osteoclastogenesis-supporting activity. PDL cells were mechanically stimulated by cyclical tensile force in vitro. The conditioned media of PDL cells that had been subjected to cyclical tensile force inhibited osteoclastogenesis. Cyclical tensile force up-regulated not only RANKL mRNA expression, but also OPG mRNA expression in PDL cells. Tensile force up-regulated TGF-beta expression in PDL cells as well. Administration of neutralizing antibodies to TGF-beta inhibited OPG up-regulation under cyclical tensile-force stimulation in a dose-dependent manner. Additionally, the osteoclastogenesis-inhibitory effect of the conditioned media of PDL cells under cyclical tensile force was partially rescued by the administration of TGF-beta neutralizing antibodies. In conclusion, tensile force inhibited the osteoclastogenesis-supporting activity of PDL cells by inducing the up-regulation of OPG via TGF-beta stimulation.
Nutrition Counseling Increases Fruit and Vegetable Intake in the Edentulous
Authors: Bradbury J. , Thomason J.M. , Jepson N.J.A. , Walls A.W.G. , Allen P.F. , Moynihan P.J.
Published: January 2009

Edentulous denture-wearers eat fewer fruits and vegetables than do comparable dentate individuals. Improved chewing ability with new dentures has resulted in little dietary improvement, suggesting that dietary intervention is necessary. The objective of this randomized controlled trial was to have a positive impact upon dietary behavior of patients receiving replacement complete dentures through a tailored dietary intervention. Readiness to change diet (Stage of Change), intake of fruits, vegetables, and nutrients, and chewing ability were assessed pre-and 6 weeks post-intervention. The intervention group (n = 30) received two dietary counseling sessions; the control group (n = 28) received current standard care. Perceived chewing ability significantly increased in both groups. There was significantly more movement from pre-action into action Stages of Change in the intervention group, who had a greater increase in fruit/vegetable consumption (+209 g/d) than did the control group (+26 g/d) (P = 0.001). Tailored dietary intervention contemporaneous with replacement dentures can positively change dietary behavior.
Extracellular Phosphate Alters Cementoblast Gene Expression
Authors: Rutherford R.B. , Foster B.L. , Bammler T. , Beyer R.P. , Sato S. , Somerman M.J.
Published: January 2009

Genetic data from humans and mice reveal that the formation of cementum is sensitive to intra- and extracellular phosphate/pyrophosphate distribution. The intracellular molecular pathways whereby altered levels of extracellular phosphate concentration may affect cementum formation have not been elucidated. To initiate inquiry, we have studied the temporal effects of extracellular phosphate on global patterns of gene expression in a line of immortalized mouse cementoblasts. Total RNA from cultured cementoblasts treated with 5 mM inorganic phosphate over a designated time period, from 1–48 hrs, was analyzed for global patterns of gene expression by means of DNA microarrays representing the complete mouse genome. Analyses of significant hybridization signals indicated that 5 mM extracellular phosphate alters the expression of genes comprising several gene ontology (GO) groups, including transcription factor activity and Wnt signaling.
Diabetes Enhances Periodontal Bone Loss through Enhanced Resorption and Diminished Bone Formation
Authors: Liu R. , Bal H.S. , Desta T. , Krothapalli N. , Alyassi M. , Luan Q. , Graves D.T.
Published: January 2009

Using a ligature-induced model in type-2 Zucker diabetic fatty (ZDF) rat and normoglycemic littermates, we investigated whether diabetes primarily affects periodontitis by enhancing bone loss or by limiting osseous repair. Diabetes increased the intensity and duration of the inflammatory infiltrate (P < 0.05). The formation of osteoclasts and percent eroded bone after 7 days of ligature placement was similar, while four days after removal of ligatures, the type 2 diabetic group had significantly higher osteoclast numbers and activity (P < 0.05). The amount of new bone formation following resorption was 2.4- to 2.9-fold higher in normoglycemic vs. diabetic rats (P < 0.05). Diabetes also increased apoptosis and decreased the number of bone-lining cells, osteoblasts, and periodontal ligament fibroblasts (P < 0.05). Thus, diabetes caused a more persistent inflammatory response, greater loss of attachment and more alveolar bone resorption, and impaired new bone formation. The latter may be affected by increased apoptosis of bone-lining and PDL cells.
Simvastatin Decreases IL-6 and IL-8 Production in Epithelial Cells
Authors: Sakoda K. , Yamamoto M. , Negishi Y. , Liao J.K. , Node K. , Izumi Y.
Published: January 2009

Many cardiovascular studies have suggested that 3-hydroxy-3-methylglutaryl co-enzyme A reductase inhibitors (statins) have anti-inflammatory effects independent of cholesterol lowering. As a chronic inflammatory disease, periodontitis shares some mechanisms with atherosclerosis. Since oral epithelial cells participate importantly in periodontal inflammation, we measured simvastatin effects on interleukin-6 and interleukin-8 production by cultured human epithelial cell line (KB cells) in response to interleukin-1α. Simvastatin decreased production, an effect reversed by adding mevalonate or geranylgeranyl pyrophosphate, but not farnesyl pyrophosphate. Simvastatin was found to reduce NF-κB and AP-1 promoter activity in KB cells. Dominant-negative Rac1 severely inhibited interleukin-1α-induced NF-κB and AP-1 promoter activity. Our results may indicate an anti-inflammatory effect of simvastatin on human oral epithelial cells, apparently involving Rac1 GTPase inhibition.
Inhibition of Apoptosis in Early Tooth Development Alters Tooth Shape and Size
Authors: Kim J.-Y. , Cha Y.-G. , Cho S.-W. , Kim E.-J. , Lee M.-J. , Lee J.-M. , Cai J. , Ohshima H. , Jung H.-S.
Published: January 2009

Apoptosis plays important roles in various stages of organogenesis. In this study, we hypothesized that apoptosis would play an important role in tooth morphogenesis. We examined the role of apoptosis in early tooth development by using a caspase inhibitor, z-VAD-fmk, concomitant with in vitro organ culture and tooth germ transplantation into the kidney capsule. Inhibition of apoptosis at the early cap stage did not disrupt the cell proliferation level when compared with controls. However, the macroscopic morphology of mice molar teeth exhibited dramatic alterations after the inhibition of apoptosis. Crown height was reduced, and mesiodistal diameter was increased in a concentration-dependent manner with z-VAD-fmk treatment. Overall, apoptosis in the enamel knot would be necessary for the proper formation of molar teeth, including appropriate shape and size.
MSX1 and Orofacial Clefting with and without Tooth Agenesis
Authors: Modesto A. , Moreno L.M. , Krahn K. , King S. , Lidral A.C.
Published: January 2009

MSX1 has been considered a strong candidate for orofacial clefting, based on mouse expression studies and knockout models, as well as association and linkage studies in humans. MSX1 mutations are also causal for hereditary tooth agenesis. We tested the hypothesis that individuals with orofacial clefting with or without tooth agenesis have MSX1 coding mutations by screening 33 individuals with cleft lip with or without cleft palate (CL/P) and 19 individuals with both orofacial clefting and tooth agenesis. Although no MSX1 coding mutations were identified, the known 101C>G variant occurred more often in subjects with both CL/P and tooth agenesis (p = 0.0008), while the *6C-T variant was found more often in CL/P subjects (p = 0.001). Coding mutations in MSX1 are not the cause of orofacial clefting with or without tooth agenesis in this study population. However, the significant association of MSX1 with both phenotypes implies that MSX1 regulatory elements may be mutated.
A Two-year Randomized Clinical Trial of Chlorhexidine Varnish on Dental Caries in Chinese Preschool Children
Authors: Du M.Q. , Tai B.J. , Jiang H. , Lo E.C.M. , Fan M.W. , Bian Z.
Published: January 2009

The objective of this study was to assess the effect of six-monthly professional applications of chlorhexidine varnish on the prevention of dental caries in primary molars in Chinese preschool children. In a double-blinded, randomized, placebo-controlled clinical trial, 334 children aged 4–5 years were randomly divided into two groups. Children in the test group received six-monthly applications of a 40% chlorhexidine varnish, and the control children received a placebo varnish. Caries status of the children was assessed by two calibrated examiners at baseline and after 24 months, according to criteria recommended by the World Health Organization. The two-year mean caries increments in the test and the control group children were 1.0 and 1.6 decayed, missing, or filled molar surfaces (dmfs-molar), respectively, a 37.3% reduction ( t test, p = 0.036). No side-effects were found. It was concluded that six-monthly applications of chlorhexidine varnish were effective in reducing the incidence of dental caries in primary molars.
Harder and Stiffer Bone Osseointegrated to Roughened Titanium
Authors: Butz F. , Aita H. , Wang C.J. , Ogawa T.
Published: January 2009

Mechanisms underlying the beneficial anchorage of roughened titanium implants have not been identified. We hypothesized that the implant surface roughness alters intrinsic biomechanical properties of bone integrated to titanium. Nano-indentation performed on two- and four-week post-implantation bone specimens of rats revealed that bone integrated to acid-etched titanium was approximately 3 times harder than that integrated to the machined titanium, both at the osseointegration interface and at the inner area of the peri-implant bone. The hardness of the acid-etched surface-associated bone was equivalent to that of untreated cortical bone at week 4, while the bone hardness around the machined surface was equivalent to that of the untreated trabecular bone. The elastic modulus of the integrated bone was 1.5 to 2.5 times greater around the acid-etched surface than around the machined surface. Analysis of the data suggests that the implant surface roughness affects the biomechanical quality of osseo-integrated bone, and that the bone integrated to the acid-etched surface is harder and stiffer than the bone integrated to the machined surface.
Genes Differentially Expressed in Titanium Implant Healing
Authors: Ogawa T. , Nishimura I.
Published: January 2009

Bone generation occurs around titanium implants; however, its underlying mechanisms are unknown. We hypothesized that molecular determinants distinct from those undertaking normal bone healing regulate osseointegration. Using differential display-polymerase chain-reaction in the male rat model, we isolated 3 genes that are differentially expressed in bone healing with implants, but not in osteotomy healing. A homology search indicated that these 3 genes are apolipoprotein E, prolyl 4-hydroxylase α-subunit, and an unknown transcript. Differential expression of these genes was remarkable during early healing stages up to week 2, and accelerated with rough acid-etched surfaces compared with machined surfaces. The differential expression was confirmed in the female rats, with enhanced expression for the acid-etched surfaces. The osseointegration-unfavorable condition created by gonadal estrogen deficiency reduced the level of differential expression. This study provides evidence that selected gene transcripts are induced by titanium implants under regulatory control strongly associated with the nature of osseointegration.
Inflammation-induced Bone Remodeling in Periodontal Disease and the Influence of Post-menopausal Osteoporosis
Authors: Lerner U.H.
Published: January 2009

During physiological conditions, the skeleton is remodeled in so-called bone multi-cellular units. Such units have been estimated to exist at 1–2 x 106 sites in the adult skeleton. The number and activities of these units are regulated by a variety of hormones and cytokines. In post-menopausal osteoporosis, lack of estrogen leads to increased numbers of bone multi-cellular units and to uncoupling of bone formation and bone resorption, resulting in too little bone laid down by osteoblasts compared with the amount of bone resorbed by osteoclasts. Inflammatory processes in the vicinity of the skeleton, e.g., marginal and apical periodontitis, will affect the remodeling of the nearby bone tissue in such a way that, in most patients, the amount of bone resorbed exceeds that being formed, resulting in net bone loss (inflammation-induced osteolysis). In some patients, however, inflammation-induced bone formation exceeds resorption, and a sclerotic lesion will develop. The cellular and molecular pathogenetic mechanisms in inflammation-induced osteolysis and sclerosis are discussed in the present review. The cytokines believed to be involved in inflammation-induced remodeling are very similar to those suggested to play crucial roles in post-menopausal osteoporosis. In patients with periodontal disease and concomitant post-menopausal osteoporosis, the possibility exists that the lack of estrogen influences the activities of bone cells and immune cells in such a way that the progression of alveolar bone loss will be enhanced. In the present paper, the evidence for and against this hypothesis is presented.
Taste Loss and Recovery Following Radiation Therapy
Authors: Sandow P.L. , Hejrat-Yazdi M. , Heft M.W.
Published: January 2009

Previous investigators have reported deficits in taste acuity in patients following radiation therapy for oropharyngeal cancer. In the present longitudinal study, 13 patients (mean age = 51.6 yrs) received conventional or hyperfractionated radiotherapy (63–76.8 Gy) for primary tumors of the oropharynx. One or both parotid glands and at least two-thirds of the tongue were included in the radiation field. Smell recognition and taste detection thresholds were determined at baseline, 1 month, 6 months, and 1 year post-radiation. Differences for smell recognition and the 4 taste qualities were assessed (independently) at the 4 time intervals, with a one-way ANOVA. Smell recognition was unaffected by radiation. There were significant elevations in thresholds for sweet (p < 0.005), salty (p < 0.005), bitter (p < 0.005), and sour (p< 0.001) during radiation therapy that were restored to baseline levels at 6 months and 1 year after radiation. This study demonstrated that radiation-induced taste deficits can be recovered by 6 months.
Increase in RANKL: OPG Ratio in Synovia of Patients with Temporomandibular Joint Disorder
Authors: Wakita T. , Mogi M. , Kurita K. , Kuzushima M. , Togari A.
Published: January 2009

Although a recent study suggested the involvement of RANKL and osteoprotegerin (OPG) in the pathogenesis of bone-destructive disease, no study has focused on the RANKL:OPG ratio in the synovial fluid of patients with temporomandibular joint (TMJ) disorder. This communication reports on the concentrations of RANKL and OPG in synovial fluid from TMJ patients and healthy control individuals. In contrast to an unchanged concentration of RANKL, a strong decrease in the concentration of OPG was detected in the synovial fluid from patients with TMJ internal derangement. Treatment with the synovial fluid of osteoarthritis (OA) patients resulted in the high production of osteoclast-like cells from blood mononuclear cells in vitro, as well as in pit formation in dentin slices. The addition of anti-RANKL IgG or OPG attenuated OA-synovial fluid-induced osteoclast formation, suggesting that the increase in the RANKL:OPG ratio in the microenvironment of the joint has the potential to induce osteoclastogenesis in TMJ osteoarthritis.
Transplanted Endothelial Cells Enhance Orthotopic Bone Regeneration
Authors: Kaigler D. , Krebsbach P.H. , Wang Z. , West E.R. , Horger K. , Mooney D.J.
Published: January 2009

The aim of this study was to determine if endothelial cells could enhance bone marrow stromal-cell-mediated bone regeneration in an osseous defect. Using poly-lactide-co-glycolide scaffolds as cell carriers, we transplanted bone marrow stromal cells alone or with endothelial cells into 8.5-mm calvarial defects created in nude rats. Histological analyses of blood vessel and bone formation were performed, and microcomputed tomography (μCT) was used to assess mineralized bone matrix. Though the magnitude of the angiogenic response between groups was the same, μCT analysis revealed earlier mineralization of bone in the co-transplantation condition. Ultimately, there was a significant increase (40%) in bone formation in the co-transplantation group (33 ± 2%), compared with the transplantation of bone marrow stromal cells alone (23 ± 3%). Analysis of these data demonstrates that, in an orthotopic site, transplanted endothelial cells can influence the bone-regenerative capacity of bone marrow stromal cells.
Mandibular Biomechanics and Development of the Human Chin
Authors: Ichim I. , Swain M. , Kieser J.A.
Published: January 2009

The development of the chin, a feature unique to humans, suggests a close functional linkage between jaw biomechanics and symphyseal architecture. The present study tests the hypothesis that the presence of a chin changes strain patterns in the loaded mandible. Using an anatomically correct 3-D model of a dentate mandible derived from a CT scan image, we analyzed strain patterns during incisal and molar biting. We then constructed a second mandible, without a chin, by ‘defeaturing’ the first model. Strain patterns of the second model were then compared and contrasted to the first. Our main finding was that chinned and non-chinned mandibles follow closely concordant patterns of strain distribution. The results suggest that the development of the human chin is unrelated to the demands placed on the mandible during function.
Omega-3 Fatty Acid Effect on Alveolar Bone Loss in Rats
Authors: Kesavalu L. , Vasudevan B. , Raghu B. , Browning E. , Dawson D. , Novak J. M. , Correll M.C. , Steffen M.J. , Bhattacharya A. , Fernandes G. , Ebersole J.L.
Published: January 2009

Gingival inflammation and alveolar bone resorption are hallmarks of adult periodontitis, elicited in response to oral micro-organisms such as Porphyromonas gingivalis. We hypothesized that omega (ω)-3 fatty acids (FA) dietary supplementation would modulate inflammatory reactions leading to periodontal disease in infected rats. Rats were fed fish oil (ω-3 FA) or corn oil (n-6 FA) diets for 22 weeks and were infected with P. gingivalis. Rats on the ω-3 FA diet exhibited elevated serum levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), documenting diet-induced changes. PCR analyses demonstrated that rats were orally colonized by P. gingivalis; increased IgG antibody levels substantiated this infection. P. gingivalis-infected rats treated with ω-3 FA had significantly less alveolar bone resorption. These results demonstrated the effectiveness of an ω-3 FA-supplemented diet in modulating alveolar bone resorption following P. gingivalis infection, and supported that ω-3 FA may be a useful adjunct in the treatment of periodontal disease. Abbreviations: PUFA, polyunsaturated fatty acid; EPA, eicosapentanoic acid; DHA, docosahexanoic acid; and PCR, polymerase chain-reaction.
Condylar Mineralization Following Mandibular Distraction in Rats
Authors: Liu Z.J. , King G.J. , Herring S.W.
Published: January 2009

The impact of mandibular distraction on condyles is poorly understood. To examine how condylar mineralization is affected, we performed distraction in 128 one-month-old rapidly and 126 three-month-old slowly growing rats. The rate of distraction was 0.0 mm (sham), 0.2 mm (slow), 0.4 mm (moderate), or 0.6 mm (rapid). From 7 to 9 rats from each rate (n = 29–32) were killed at 4 time periods (D6, D10, D24, and D38) following osteotomy. Calcein and alizarin were injected 6 and 3 days, respectively, prior to death. Methacrylate-embedded sagittal condylar sections were examined under epifluorescence, and mineral apposition rates were measured. Results indicated that: (1) rapidly growing rats showed higher mineral apposition rates (p < 0.01–0.001) than did slowly growing rats; (2) mineral apposition rates were lower in distracted sides at all times in rapidly growing rats (p < 0.05–0.01), while this side-dependency was seen only at D24 in slowly growing rats (p < 0.05); and (3) distraction rates had little effect on mineral apposition rates. Thus, mandibular distraction decreases condylar mineral apposition rates, but only in rapidly growing rats, which is related to surgery and its functional consequences, not to the distraction rate.
Preventive Intervention Possibilities in Radiotherapy- and Chemotherapy-induced Oral Mucositis: Results of Meta-analyses
Authors: Stokman M.A. , Spijkervet F.K.L. , Boezen H.M. , Schouten J.P. , Roodenburg J.L.N. , de Vries E.G.E.
Published: January 2009

The aim of these meta-analyses was to evaluate the effectiveness of interventions for the prevention of oral mucositis in cancer patients treated with head and neck radiotherapy and/or chemotherapy, with a focus on randomized clinical trials. A literature search was performed for reports of randomized controlled clinical studies, published between 1966 and 2004, the aim of which was the prevention of mucositis in cancer patients undergoing head and neck radiation, chemotherapy, or chemoradiation. The control group consisted of a placebo, no intervention, or another intervention group. Mucositis was scored by either the WHO, the National Cancer Institute-Common Toxicity Criteria (NCI-CTC) score, or the absence or presence of ulcerations, or the presence or absence of grades 3 and 4 mucositis. The meta-analyses included 45 studies fulfilling the inclusion criteria, in which 8 different interventions were evaluated: i.e., local application of chlorhexidine; iseganan; PTA (polymyxin E, tobramycine, and amphotericin B); granulocyte macrophage-colony-stimulating factor/granulocyte colony-stimulating factor (GM-CSF/G-CSF); oral cooling; sucralfate and glutamine; and systemic administration of amifostine and GM-CSF/G-CSF. Four interventions showed a significant preventive effect on the development or severity of oral mucositis: PTA with an odds ratio (OR) = 0.61 (95% confidence interval [CI], 0.39–0.96); GM-CSF, OR = 0.53 (CI: 0.33–0.87); oral cooling, OR = 0.3 (CI: 0.16–0.56); and amifostine, OR = 0.37 (CI: 0.15–0.89). To date, no single intervention completely prevents oral mucositis, so combined preventive therapy strategies seem to be required to ensure more successful outcomes.
Cervantes: Father of Don Quixote and Son of a Dentist
Authors: del Valle Antonio , Romero Martín
Published: January 2009

In the works of Cervantes, one can observe a detailed knowledge of dental matters. Although some of his biographers think that this is the result of the very broad cultural knowledge of this distinguished Spanish writer, the authors of this paper think differently. Having studied and analyzed many documents referring to the Cervantes family, especially those which dealt with the strong influence the teachings of Cervantes’ father had on his son, we have reached the conclusion that his father must have been a 16th Century dentist.