bluuebunny/crossref_metadata_2025 huggingface dataset:
A Clinical Evaluation of Implants in Irradiated Oral Cancer Patients
Authors: Visch L.L. , van Waas M.A.J. , Schmitz P.I.M. , Levendag P.C.
Published: January 2009

In this prospective study, we determined the effects of the time interval between irradiation and implant therapy, implant location, bone-resection surgery, and irradiation dose on implant survival. We analyzed the survival of 446 implants inserted after radiotherapy over a period of up to 14 years in 130 consecutive patients treated for oral cancer. The 10-year overall Kaplan-Meier implant survival percentage is 78%. The difference in survival percentages of implants inserted < 1 year and ≥ 1 year after irradiation (76% and 81%, respectively) is not significant. We concluded that implant survival is significantly influenced by the location (maxilla or mandible, 59% and 85%, respectively; p = 0.001), by the incidence of bone-resection surgery in the jaw where the implant was installed (p = 0.04), and by the irradiation dose at the implant site (< 50 Gray or ≥ 50 Gray, p = 0.05).
Salivary Biochemistry in Buffalo: The Legacy of Michael J. Levine
Authors: Scannapieco Frank A.
Published: January 2009

The author pays tribute to the contributions of Michael J. Levine to the field of salivary biochemistry.
Destruction of Parotid Glands Affects Nitrate and Nitrite Metabolism
Authors: Xia D.S. , Deng D.J. , Wang S.L.
Published: January 2009

The role of salivary glands in nitrate and nitrite metabolism is poorly understood. The aim of the present study was to investigate the effect of parotid gland ablation on dynamic metabolism of nitrate and nitrite in miniature pigs. The parotid glands of 5 healthy miniature pigs were bilaterally ablated by methyl violet. Concentrations of nitrate and nitrite of whole saliva, serum, and urine samples were analyzed by high-performance liquid chromatography. Results showed that bilateral ablation of the parotid glands led to a significant decrease of nitrate secretion from blood to saliva (P < 0.05) and thus low nitrite levels. Dysfunction of the parotid glands temporarily increased the systemic level of nitrate in miniature pigs after nitrate loading. This study suggests that the parotid glands play an important role in the balance of nitrate and nitrite levels in both whole saliva and the body.
Sex Differences in Masticatory Muscle Pain after Chewing
Authors: Karibe H. , Goddard G. , Gear R.W.
Published: January 2009

Neither the etiology of muscle-related temporomandibular disorders (TMD) nor the reason for the disproportionate number of women suffering from these disorders is well-established. We tested the hypothesis that physiologically relevant exercise ( i.e., chewing bubble gum for 6 min) increases masticatory muscle pain in patients, but not in asymptomatic control subjects, and that female patients experience a significantly greater increase than males. Chewing increased pain in both female and male patients and, unexpectedly, also in female control subjects. One hour after chewing, the pain remained above pre-test levels for female patients but not for the other groups. Thus, sex differences in chewing-induced pain were found in control subjects but not as hypothesized in patients. Because chewing-induced masticatory muscle pain was significantly greater in female control subjects than in males, and persisted longer in female patients than in males, these results suggest greater susceptibility in women.
Construct and Predictive Validity of Clinical Caries Diagnostic Criteria Assessing Lesion Activity
Authors: Nyvad B. , Machiulskiene V. , Baelum V.
Published: January 2009

Even though there is no “gold standard” for determining caries lesion activity, it is nonetheless possible to evaluate the validity of such diagnostic measures. The aim of this study was to estimate the construct and predictive validity of caries lesion activity assessments by means of their ability to reflect known effects of fluoride on caries. A three-year trial of the effect of daily supervised brushing with fluoride toothpaste was carried out among 273 12-year-old children. All children were examined clinically according to diagnostic criteria for activity assessment. The relative risk (fluoride vs. control) for caries lesion transitions among diagnostic categories was calculated. Fluoride inhibited progression of caries at all stages of lesion formation while at the same time enhancing lesion regression. The effects were most pronounced for active non-cavitated lesions. It is concluded that the clinical diagnostic criteria have construct and predictive validity for the assessment of caries lesion activity.
Association of Edentulism and Diet and Nutrition in US Adults
Authors: Nowjack-Raymer R.E. , Sheiham A.
Published: January 2009

Dental status and its relationship to diet and nutritional status have been little explored. In this study of a representative sample of the US civilian, non-institutionalized population (NHANES III), we predicted that the intake of nutritious foods, dietary fiber, and levels of biochemical analytes would be lower, even after adjusting for potential social and behavioral factors, among those who were edentulous and wore complete dentures than for those who had all their natural teeth. Multivariate analyses indicated that intake of carrots and tossed salads among denture-wearers was, respectively, 2.1 and 1.5 times less than for the fully dentate (p < 0.0001), and dietary fiber intake was 1.2 times less (p < 0.05). Serum levels of beta carotene (9.8 μg/dL), folate (4.7 ng/dL), and vitamin C (0.87 mg/dL) were also lower among denture-wearers (p < 0.05). Intakes of some nutrient-rich foods and beta carotene, folate, and vitamin C serum levels were significantly lower in denture-wearers.
Effect of Smear Layer on Root Demineralization Adjacent to Resin-modified Glass Ionomer
Authors: AL-Helal A.S. , Armstrong S.R. , Xie X.J. , Wefel J.S.
Published: January 2009

The cariostatic effect of resin-modified glass ionomer (RMGI) on secondary root caries is well-documented. However, this beneficial effect may be dependent upon the mode of cavity surface treatment. To investigate this relationship, we studied 4 cavity surface treatments prior to the placement of RMGI: no treatment (None), polyacrylic acid (PAA), phosphoric acid (H3PO4), and Scotchbond Multi-Purpose adhesive (SMP) as a control. Specimens were aged for two weeks in synthetic saliva, thermocycled, and subjected to an artificial caries challenge (pH 4.4). Polarized light microscopy (PLM) and microradiography (MRG) showed significantly less demineralization with the H3PO4 cavity surface treatment as revealed by ANOVA and Tukey’s multiple comparisons (p ≤ 0.05). Dentin fluoride profiles determined by electron probe microanalysis (EPMA) supported PLM and MRG findings. It may be concluded that removal of the smear layer with phosphoric acid provides significantly enhanced resistance to secondary root caries formation adjacent to RMGI restorations.
Oral Clefts and Syndromic Forms of Tooth Agenesis as Models for Genetics of Isolated Tooth Agenesis
Authors: Vieira A.R.
Published: January 2009

Genetic defects responsible for tooth agenesis are only now beginning to be uncovered. MSX1 and PAX9 have been associated with tooth agenesis in mice and humans, but interestingly for humans, these genes are associated with specific missing teeth. Mouse models also show that specific genes contribute to the development of specific types of teeth. A precise description of the phenotype specifying which teeth are missing has become fundamental. Mendelian segregation can be identified in families with tooth agenesis, but heterogenous or multiple genes may be responsible for the development of specific types of teeth agenesis in humans. Data from animal models are still very complex, and the human embryology is still poorly understood. Oral clefts and syndromic forms of tooth agenesis may be the best models for isolated tooth agenesis. In the future, a precise description of the missing teeth in syndromes involving tooth agenesis may be useful.
Retention in Plaque and Remineralization of Enamel Lesions by Various Forms of Calcium in a Mouthrinse or Sugar-free Chewing Gum
Authors: Reynolds E.C. , Cai F. , Shen P. , Walker G.D.
Published: January 2009

Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) nanocomplexes incorporated into sugar-free chewing gum have been shown to remineralize enamel subsurface lesions in situ. The aim of this study was to compare the ability of CPP-ACP, with that of other forms of calcium, to be retained in supragingival plaque and remineralize enamel subsurface lesions in situ when delivered in a mouthrinse or sugar-free gum in randomized, double-blind trials. In the mouthrinse study, only the CPP-ACP-containing mouthrinse significantly increased plaque calcium and inorganic phosphate levels, and the CPP were immunolocalized to the surfaces of bacterial cells as well as the intercellular matrix. In the chewing gum studies, the gum containing the CPP-ACP, although not containing the most calcium per piece of gum, produced the highest level of enamel remineralization independent of gum-chewing frequency and duration. The CPP could be detected in plaque extracts 3 hrs after subjects chewed the CPP-ACP-containing gum. The results showed that CPP-ACP were superior to other forms of calcium in remineralizing enamel subsurface lesions.
Lifetime Prediction of All-ceramic Bridges by Computational Methods
Authors: Fischer H , Weber M , Marx R
Published: January 2009

There has been limited use of ceramic materials for all-ceramic posterior bridges. Major reasons are the low strength, the strength scatter, and the time-dependent strength decrease of ceramics due to slow crack growth. The objective of this study was to predict the long-term failure probability and loading capability of all-ceramic bridges (Empress 1, Empress 2, In-Ceram Alumina, and ZrO2) by computational techniques. The lifetimes of different bridge model designs were predicted by means of the NASA post-processor CARES. Bridges made of zirconia showed a very high mechanical long-term reliability. Empress I and InCeram Alumina seem to be insufficient as posterior bridge materials based on this prediction. The lifetime of the all-ceramic bridges can be significantly increased by improving the design in the connector area. We conclude that computational techniques can help to judge a ceramic material and a specific ceramic bridge design with respect to mechanical reliability before clinical use.
Effects of Fluoride and Aluminum from Ionomeric Materials on S. mutans Biofilm
Authors: Hayacibara M.F. , Rosa O.P.S. , Koo H. , Torres S.A. , Costa B. , Cury J.A.
Published: January 2009

Ionomeric materials release different proportions of fluoride and aluminum. Their simultaneous effect on the acidogenicity and composition of S. mutans biofilm is unknown. Six cylindrical specimens of each material (Ketac-fil, Vitremer, Fuji-Ortho LC, F-2000, and Z-100) were incubated with S. mutans GS-5 in culture media containing 5% sucrose (w/v). The media were changed daily for seven days, during which the pH and concentrations of fluoride and aluminum were determined. Furthermore, the concentrations of these ions and insoluble polysaccharide were determined in the biofilm formed at the end of the experimental period. The results showed that all the materials tested released fluoride. However, Vitremer released the highest amount of aluminum and was the most effective in reducing the acidogenicity of S. mutans biofilms. It also significantly affected both biofilm formation and composition. Thus, this study suggests that aluminum released by ionomeric materials may enhance the biological effects of fluoride.
Correlations of the Expression of Fibroblast Growth Factor-2, Vascular Endothelial Growth Factor, and their Receptors with Angiogenesis in Synovial Tissues from Patients with Internal Derangement of the Temporomandibular Joint
Authors: Sato J. , Segami N. , Yoshitake Y. , Nishikawa K.
Published: January 2009

Synovitis in internal derangement of the temporomandibular joint (TMJ) is accompanied by the growth of new blood vessels. Fibroblast growth factor-2 (FGF-2) and vascular endothelial growth factor (VEGF) are well-characterized angiogenic factors. The objective of this study was to elucidate the correlation between the expression of FGF-2, VEGF, and their receptors—FGF receptor-1 (FGFR-1) and VEGF receptor-1 (Flt-1)—with microvessel density in synovial tissues of the TMJ. Using an immunohistochemical technique, we examined 47 joints (45 patients) with internal derangement. Individual microvessel density was evaluated by means of the CD34 antibody, a specific endothelial marker. The correlation between the percentage of immuno-positive cells and microvessel density was evaluated. In multiple logistic regression analysis, the correlation between the percentage of Flt-1-positive cells and microvessel density was significant [p = 0.005, odds ratio = 1.071, 95% confidence interval = 1.021-1.124]. These results suggest that the expression of the VEGF/Flt-1 system is involved in angiogenesis in inflamed synovial tissue in the TMJ.
Patterns of Fluoro-Gold Entry into Rat Molar Enamel, Dentin, and Pulp
Authors: Byers M.R. , Yoon Lin K.J.
Published: January 2009

Permeabilities of enamel and dentin are not fully understood despite their importance for caries, restorative materials, and pulp-dentin-enamel interactions. We have found that Fluoro-Gold is useful for examining tooth permeability, and we designed studies to test the effects of aging, injury, neural function, and dentinal repair on its influx into vital rat teeth. We used fluorescence microscopy and immunocytochemistry to show that Fluoro-Gold rapidly penetrates enamel, the dentin-enamel junction, and outer dentinal acellular tubules, and then concentrates in odontoblasts, where it remains for weeks. As predicted, influx was greatest in immature teeth, and formation of reparative dentin impeded it. We expected that denervation would disrupt influx, because of neural regulation of dentinal fluid movement, but it did not. Damage to odontoblasts under injured dentin caused increased influx and efflux of Fluoro-Gold. Analysis of our data suggests that permeabilities of enamel and dentin to Fluoro-Gold are age-related, inter-dependent, and regulated by odontoblasts.
The Use of Small Titanium Screws for Orthodontic Anchorage
Authors: Deguchi T. , Takano-Yamamoto T. , Kanomi R. , Hartsfield J.K. , Roberts W.E. , Garetto L.P.
Published: January 2009

The use of conventional dental implants for orthodontic anchorage is limited by their large size. The purpose of this study was to quantify the histomorphometric properties of the bone-implant interface to analyze the use of small titanium screws as an orthodontic anchorage and to establish an adequate healing period. Overall, successful rigid osseous fixation was achieved by 97% of the 96 implants placed in 8 dogs and 100% of the elastomeric chain-loaded implants. All of the loaded implants remained integrated. Mandibular implants had significantly higher bone-implant contact than maxillary implants. Within each arch, the significant histomorphometric indices noted for the “three-week unloaded” healing group were: increased labeling incidence, higher woven-to-lamellar-bone ratio, and increased osseous contact. Analysis of these data indicates that small titanium screws were able to function as rigid osseous anchorage against orthodontic load for 3 months with a minimal (under 3 weeks) healing period.
Different Mechanisms of Syndecan-1 Activation through a Fibroblast-growth-factor-inducible Response Element (FiRE) in Mucosal and Cutaneous Wounds
Authors: Rautava J. , Soukka T. , Heikinheimo K. , Miettinen P.J. , Happonen R.-P. , Jaakkola P.
Published: January 2009

Syndecan-1 expression is enhanced in cutaneous and mucosal wounds. We have previously demonstrated that wounding-induced syndecan-1 expression in the skin occurs transcriptionally, through a fibroblast-growth-factor-inducible element (FiRE). Here, we show that FiRE is also activated in mucosal wounds. However, both the expression patterns and the activation mechanisms of FiRE are different from those in the skin. In the mucosa in vivo, the activation starts and ends earlier than in cutaneous wounds. FiRE is first detected at around 12 hours in keratinocytes, and the activation declines by the third day after wounding occurs. The activation is seen on the migrating sheet of epithelial mucosa, as in the case of cutaneous wounding. In contrast to the situation in vivo, organ-cultured mucosal wounds exhibit no FiRE activity, while organ-cultured cutaneous wounds show robust activity. Activation in mucosal wounds is enhanced, however, by the application of epidermal growth factor. This suggests that exogenous growth factor activity is required for activation of syndecan-1 in mucosal wounds but not in cutaneous wounds.
Altered pH Regulation During Enamel Development in the Cystic Fibrosis Mouse Incisor
Authors: Sui W. , Boyd C. , Wright J.T.
Published: January 2009

Regulation of pH is necessary to the production of an environment conducive to enamel growth and mineralization. We hypothesize that abnormal extracellular pH in the enamel matrix of mice with the cystic fibrosis gene knocked out (CF mice) results in altered enamel mineralization. The enamel matrix pH during amelogenesis was studied in 10 normal and 10 CF mice. Freshly dissected incisors were immersed in pH indicator or glyoxal bis (2-hydro-xyanil) (GBHA). The normal mouse enamel matrix pH was generally higher and modulated differently than did the CF mouse enamel. GBHA staining showed that normal mice had 2 well-demarcated bands in the maturation zone that correlated to the neutral pH zones, while CF mice showed no staining. These results indicate that CFTR plays a role in pH regulation during enamel development and that a reduced pH results in a lack of calcium influx during enamel maturation and hypomineralization of the CF incisor enamel.
Intrinsic Regulation of CGRP Release by Dental Pulp Sympathetic Fibers
Authors: Hargreaves K.M. , Bowles W.R. , Jackson D.L.
Published: January 2009

Neurotransmission from sympathetic and peptidergic afferent fibers participates in the regulation of pulpal blood flow (PBF) via opposing effects. In this study, we directly tested the hypothesis that activation of pulpal sympathetic terminals inhibits exocytosis of immunoreactive calcitonin gene-related peptide (iCGRP) from peptidergic afferents innervating bovine dental pulp. The results demonstrate that norepinephrine inhibits capsaicin-evoked iCGRP release. The application of α-adrenergic antagonists (phentolamine or phenoxybenzamine) increased spontaneous release of iCGRP. Moreover, administration of agents that evoke the release of sympathetic neurotransmitters (guanethidine or reserpine) inhibited capsaicin-evoked iCGRP release. Collectively, these results indicate that sympathetic neurotransmission inhibits exocytosis from pulpal peptidergic afferent fibers. Analysis of these data supports the hypothesis that peripheral sympathetic vasomotor control may operate by a direct mechanism (vasoconstriction) as well as by an indirect mechanism ( e.g., inhibition of exocytosis from afferent fibers). Since capsaicin-sensitive neurons are nociceptors, it is possible that certain sympathetic neurotransmission may modulate pain.
Interaction of Dendrimers (Artificial Proteins) with Biological Hydroxyapatite Crystals
Authors: Chen H. , Banaszak Holl M. , Orr B.G. , Majoros I. , Clarkson B.H.
Published: January 2009

This investigation sets out to mimic protein-crystal interaction during biomineralization with the use of artificial proteins (dendrimers). It is hypothesized that these interactions depend on the surface charge of hydroxyapatite crystals. This was investigated with the use of dendrimers with capped surfaces of different charges to probe the surface. We used AFM images of crystal-bound dendrimers to determine the distribution of the surface charge, and its magnitude was correlated to the binding capacity of the dendrimers to the surface. The binding capacity of the dendrimers in ascending order at pH 7.4 was: acetamide-capped, -NHC(O)CH3, neutral charge; carboxylic-acid-capped, -COOH, negative charge; and amine-capped, -NH2, positive charge. AFM images of the crystals showed dendrimers spaced equally along the crystal. The results suggest that the crystal surface has alternating bands of positive and negative charge or a differential charge array, i.e., alternating bands of either more or less positive or negative charge.
Dentin-induced in vivo Inflammatory Response and in vitro Activation of Murine Macrophages
Authors: Lara V.S. , Figueiredo F. , da Silva T.A. , Cunha F.Q.
Published: January 2009

The activation of inflammatory cells and consequent release of mediators play an important role in the resorption of mineralized tissues. In the present study, we examined the ability of dentin extracts to induce inflammatory cell recruitment and activation. We showed here that dentin extracts triggered an intense cell migration and progressive cell maturation, in a time- and dose-dependent manner. Expression of interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), nitric oxide (NO), and hydrogen peroxide (H2O2) was also up-regulated by dentin extracts. These results show that inflammatory events can be elicited in response to dentin, which may suggest a possible involvement of dentin molecules in the inflammatory events, coupled with their release at the root resorption sites.
Segregation Analysis of Mandibular Prognathism in Libya
Authors: El-Gheriani A.A. , Maher B.S. , El-Gheriani A.S. , Sciote J.J. , Abu-shahba F.A. , Al-Azemi R. , Marazita M.L.
Published: January 2009

The etiology of mandibular prognathism has been attributed to various genetic inheritance patterns and some environmental factors. The variation in inheritance patterns can be partly due to the use of different statistical approaches in the respective studies. The objective of this study was to investigate the role of genetic influences in the etiology of this trait. We performed segregation analysis on 37 families of patients currently being treated for mandibular prognathism. Mandibular prognathism was treated as a qualitative trait, with cephalometric radiographs, dental models, and photographs used to verify diagnosis. Segregation analysis of a prognathic mandible in the entire dataset supported a transmissible Mendelian major effect, with a dominant mode of inheritance determined to be the most parsimonious.
Biomechanics of the Human Temporomandibular Joint during Chewing
Authors: Naeije M. , Hofman N.
Published: January 2009

Experimental data on the loading of the human temporomandibular joint during chewing are scarce. Coincidence of the opening and closing chewing strokes of the condyles probably indicates compression in the joint during chewing. Using this indication, we studied the loading of the joint during chewing and chopping of a latex-packed food bolus on the left or right side of the mouth. Mandibular movements of ten healthy subjects were recorded. Distances traveled by the condylar kinematic centers were normalized with respect to the distances traveled during maximum opening. We judged coincidence of the opening and closing condylar movement traces without knowing their origin. When subjects chewed, the ipsilateral condyles traveled shorter distances than did the contralateral condyles. During chewing and chopping, all contralateral condyles showed a coincident movement pattern, while a significantly smaller number of ipsilateral condyles did. These results suggest that the ipsilateral joints were less heavily loaded during chewing and chopping than were the contralateral joints.
Genetic Expression Profiling of Six Odontogenic Tumors
Authors: Carinci F. , Francioso F. , Piattelli A. , Rubini C. , Fioroni M. , Evangelisti R. , Arcelli D. , Tosi L. , Pezzetti F. , Carinci P. , Volinia S.
Published: January 2009

Odontogenic tumors are rare neoplasms arising from the odontogenic apparatus. We aimed to identify molecular characteristics associated with odontogenic tumorigenesis and malignancy. To this end, we investigated the expression level of human genes by using, for the first time in odontogenic tumors, the technique of expression profiling. Gene expression alterations common to all six odontogenic tumors were identified by the use of cDNA microarrays containing 19,000 human cDNAs. Statistical analysis on a subset of 4974 cDNAs present in the biopsies identified 506 distinct genes associated with the tumors (p-value < 0.01). Gene ontology analysis of the cellular processes which were differentially regulated in odontogenic tumors was accomplished by the use of a subset of 1409 annotated genes. Finally, 43 cDNAs differentiated the three malignant odontogenic tumors (ameloblastic carcinoma, clear cell odontogenic tumor, granular cell odontogenic tumor) from the three benign ameloblastoma biopsies (p < 0.01). The identified genes might help us better classify borderline odontogenic tumors.
An Involvement of Trigeminal Mesencephalic Neurons in Regulation of Occlusal Vertical Dimension in the Guinea Pig
Authors: Zhang W. , Kobayashi M. , Moritani M. , Masuda Y. , Dong J. , Yagi T. , Maeda T. , Morimoto T.
Published: January 2009

Although the occlusal vertical dimension (OVD) is strictly controlled, the neuronal mechanism of its regulation is still unclear. We hypothesize that neurons in the trigeminal mesencephalic nucleus (MesV) play an important role in the regulation of the OVD, because the MesV receives the projection from jaw-closing muscle spindles and periodontal mechanoreceptors. We measured the temporal OVD change in the guinea pig to study the effects of MesV lesions on the OVD. OVD-raised animals without MesV lesions showed a rapid OVD decrease to the same level as that in naïve controls, followed by an OVD increase after the OVD-raising appliance was removed. In contrast, OVD-raised animals with MesV lesions showed only a slight decrease in the OVD for 15 days after removal of the appliance, and then the OVD increased. The time-course of OVD development in normal-bite animals with MesV lesions was similar to that of naïve controls. These results suggest that MesV neurons are involved in OVD regulation.
Regional Alterations in Fiber Type Distribution, Capillary Density, and Blood Flow after Lower Jaw Sagittal Advancement in Pig Masticatory Muscles
Authors: Gedrange T. , Walter B. , Tetzlaff I. , Kasper M. , Schubert H. , Harzer W. , Bauer R.
Published: January 2009

Muscular remodeling is known to be a prerequisite for permanent correction of mandibular-maxillary malocclusion. The objective of this study was to clarify if an increase in type I fiber number is accompanied by an increased capillary density and improved muscular blood flow. Juvenile pigs received build-ups on the molars, which induced a protrusion of 7.6 + 1.5 mm. After 4 weeks of treatment, chronic lower jaw protrusion induced a marked muscle blood flow increase in the anterior and medial regions of the superficial part of the masseter and in the medial pterygoid muscle ( P < 0.05). Furthermore, an increase in capillary density and in the amount of type I fibers was found in all regions of masticatory muscles with an increased muscle blood flow ( P < 0.05). Finally, the capillary-to-fiber ratio increased ( P < 0.05). Muscle blood flow and capillary density showed a strong linear correlation (r = 0.89, P < 0.01). These changes suggest a complex muscle adaptation for long-term, fatigue-resistant activity during the early corrective period of mandibular-maxillary malocclusion treatment.
Artifacts from Dental Casting Alloys in Magnetic Resonance Imaging
Authors: Shafiei F. , Honda E. , Takahashi H. , Sasaki T.
Published: January 2009

The potential advantage of magnetic resonance imaging (MRI) has been limited by artifacts due to the presence of metallic materials. For quantitative evaluation of the magnitude of artifacts from dental casting alloys and implant materials in MR imaging, 11 dental casting or implant materials were imaged by means of 1.5 T MRI apparatus with three different sequences. Mean and standard deviation of water signal intensity (SI) around the sample in the region of interest (1200 mm2) were determined, and the coefficient of variation was compared for evaluation of the homogeneity of the SI. A variety of artifacts with different magnitudes was observed. Only one of the samples, composed mainly of Pd, In, and Sb, showed no artifacts in all imaging sequences. We concluded that selection of specific dental casting alloys according to their elemental compositions could minimize the metal artifacts in MRI; however, titanium alloys currently pose a problem with respect to causing MRI artifacts.
PTHrP Regulates Chondrocyte Maturation in Condylar Cartilage
Authors: Rabie A.B.M. , Tang G.H. , Xiong H. , Hägg U.
Published: January 2009

PTHrP is a key factor regulating the pace of endochondral ossification during skeletal development. Mandibular advancement solicits a cascade of molecular responses in condylar cartilage. However, the pace of cellular maturation and its effects on condylar growth are still unknown. The purpose of this study was to evaluate the pattern of expression of PTHrP and correlate it to cellular dynamics of chondrocytes in condylar cartilage during natural growth and mandibular advancement. We fitted 35-day-old Sprague-Dawley rats with functional appliances. Experimental animals with matched controls were labeled with bromodeoxyuridine 3 days before their death, so that mesenchymal cell differentiation could be traced. Mandibular advancement increased the number of differentiated chondroblasts and subsequently increased the cartilage volume. Higher levels of PTHrP expression in experimental animals coincided with the slowing of chondrocyte hypertrophy. Thus, mandibular advancement promoted mesenchymal cell differentiation and triggered PTHrP expression, which retarded their further maturation to allow for more growth.
Human Dental Pulp Vasculogenesis Evaluated by CD34 Antigen Expression and Morphological Arrangement
Authors: Trubiani O. , Tripodi D. , Delle Fratte T. , Caputi S. , Di Primio R.
Published: January 2009

Vasculogenesis describes the process by which endothelial precursor cells form new blood vessels. To characterize the topography and the cellular processes underlying vascularization of human dental pulp, we examiend the expression of the human hematopoietic progenitor cell antigen CD34. Dental pulps, obtained from deciduous and permanent teeth, were morphologically examined at light- and electron-microscope levels and by expression of CD34. The findings indicate that vasculogenesis of dental pulp is a complicated process starting from single CD34+ cells. These subsequently coalesce to form solid vascular cords inside the developing connective tissue, which later hollows. Pericytes were embedded within the fully formed microvessels’ basement membrane. The presence of CD34+ endothelial cells in permanent teeth reveals that the process of vasculogenesis persists into adult life, where it contributes to continuous adjustment of vessel and network structures in response to functional needs and dental tissue homeostasis.
Prions and the Oral Cavity
Authors: Smith A.J. , Bagg J. , Ironside J.W. , Will R.G. , Scully C.
Published: January 2009

Prion diseases have recently emerged as a significant challenge to health-care workers, including those involved in dentistry. Abnormal prion proteins are resistant to complete inactivation by conventional sterilization techniques. In the last decade, a new form of prion disease emerged in the UK, termed "variant CJD", thought to be acquired by consumption of bovine spongiform encephalopathy-contaminated food products. At present, CJD is an invariably fatal disease with no immediate prospect of treatment or vaccination. Of concern with the variant form of CJD, unlike the more classic forms of the disease, is the appearance of significant levels of infectivity outside the central nervous system. This raises concerns for the potential transmission of prion proteins via surgical procedures from individuals in the asymptomatic stage of the disease. This article reviews the existing knowledge base on the nature of prions, their distribution in oral tissues, and the implications for dental treatment.
Activation of Vanilloid Receptor 1 (VR1) by Eugenol
Authors: Yang B.H. , Piao Z.G. , Kim Y.-B. , Lee C.-H. , Lee J.K. , Park K. , Kim J.S. , Oh S.B.
Published: January 2009

The structural similarity of eugenol with capsaicin suggests that these two agents may share molecular mechanisms to produce their effects. We investigated the effects of eugenol in comparison with those of capsaicin using whole-cell patch clamp and Fura-2-based calcium-imaging techniques in a heterologous expression system and with sensory neurons. In vanilloid receptor 1 (VR1)-expressing human embryonic kidney (HEK) 293 cells and trigeminal ganglion (TG) neurons, eugenol activated inward currents, whereas capsazepine, a competitive VR antagonist, and ruthenium red (RR), a functional VR antagonist, completely blocked eugenol-induced inward currents. Moreover, eugenol caused elevation of [Ca2+]i, and this was completely abolished by both capsazepine and ruthenium red in VR1-expressing HEK 293 cells and TG neurons. Our results provide strong evidence that eugenol produces its effects, at least in part, via VR1 expressed by the sensory nerve endings in the teeth.
Influence of Post-deposition Heating Time and the Presence of Water Vapor on Sputter-coated Calcium Phosphate Crystallinity
Authors: Yang Y. , Kim K.-H. , Agrawal C.M. , Ong J.L.
Published: January 2009

Extensive research suggested that calcium phosphate (CaP) coatings on titanium implants are essential for early bone response. However, the characterization of CaP crystallinity and the means to control coating crystallinity are not well-established. In this study, the effect of a 400°C heat treatment for 1, 2, or 4 hours, and in the presence or absence of water vapor, on CaP crystallinity was investigated. Scanning electron microscopy indicated dense as-sputtered coatings. Increase in coating crystallinity was observed to be consistent with the increasing number of PO4 peaks observed as a result of different heat treatments. In addition, x-ray diffraction analyses indicated amorphous as-sputtered coatings, whereas crystalline CaP coatings in the range of 0-85% were observed after different post-deposition heat treatments. It was concluded that the presence of water vapor and post-deposition heat treatment time significantly affect the crystallinity of CaP coatings, which may ultimately affect bone healing.
Detectable Dioxins in Human Saliva and Their Effects on Gingival Epithelial Cells
Authors: Ogawa T. , Asai Y. , Yamashita M. , Takasuga T.
Published: January 2009

Dioxin, a powerful hormone-disrupting chemical, exhibits serious health effects when it reaches body fat. Here we analyzed coplanar polychlorinated biphenyls (PCBs) and polychlorinated-dibenzo- p-dioxins (PCDDs) in human saliva as compared with blood specimens, and examined their effects on human gingival epithelial cells (HGEC). High levels of tri- and tetrachlorinated PCBs were found in saliva, whereas we detected predominantly hexa- and heptachlorinated PCBs in blood. Among PCDDs, the saliva and blood specimens contained mainly 1,2,3,4,6,7,8,9-octachlorodibenzo- p-dioxin (OCDD). Among the toxic dioxins proposed by the World Health Organization (WHO) in 1998, 2,3′,4,4′,5-pentachlorobiphenyl (PCB 118) and OCDD, which were mainly found in saliva, significantly induced IL-8 production in HGEC. Furthermore, these two dioxins markedly augmented IL-8 production stimulated with fimbriae from Porphyromonas gingivalis, which is well-known as a pathogenic factor in periodontal diseases. These results suggest that dioxins in saliva may be a risk factor for periodontal diseases.
Blood Flow and Interstitial Fluid Pressure in the Rat Submandibular Gland during Changes in Perfusion
Authors: Berggreen E. , Wiig H. , Heyeraas K.J.
Published: January 2009

The submandibular gland is a cell-rich encapsulated organ with high transport of fluid through the interstitial space during salivation. We hypothesized that the gland is a low-compliant tissue, i.e., that a modest increase in fluid volume will produce a rise in interstitial fluid pressure (IFP) counteracting fluid filtration into the interstitium. To test this hypothesis, we measured IFP with micropipettes and glandular blood flow (GBF) with a laser-Doppler flowmeter during changes in perfusion. Clamping of the carotid artery or the jugular vein, or electrical stimulation of the sympathetic or parasympathetic nerve to the gland, induced changes in perfusion. Baseline IFP averaged 3.5 ± 0.5 mm Hg. Clamping of the artery reduced IFP and GBF (−56.5 ± 8.4% and −53.1 ± 6.4%, respectively), whereas clamping of the vein decreased GBF (−21.6 ± 14.3%) and increased IFP (141.2 ± 27.4%). Sympathetic nerve stimulation reduced both parameters (−86.9 ± 16.5% and −74.4 ± 7.0%, respectively). In contrast, stimulation of the parasympathetic nerve elicited an increase in GBF (133.2 ± 5.9%) and in IFP (173.3 ± 41.4%). Thus, changes in vascular volume led to concomitant changes in IFP consistent with low tissue compliance, a phenomenon of importance for fluid volume regulation.
Regulating Bone Formation via Controlled Scaffold Degradation
Authors: Alsberg E. , Kong H.J. , Hirano Y. , Smith M.K. , Albeiruti A. , Mooney D.J.
Published: January 2009

It is widely assumed that coupling the degradation rate of polymers used as cell transplantation carriers to the growth rate of the developing tissue will improve its quantity or quality. To test this hypothesis, we developed alginate hydrogels with a range of degradation rates by gamma-irradiating high-molecular-weight alginate to yield polymers of various molecular weights and structures. Decreasing the size of the polymer chains increased the degradation rate in vivo, as measured by implant retrieval rates, masses, and elastic moduli. Rapidly and slowly degrading alginates, covalently modified with RGD-containing peptides to control cell behavior, were then used to investigate the effect of biodegradation rate on bone tissue development in vivo. The more rapidly degrading gels led to dramatic increases in the extent and quality of bone formation. These results indicate that biomaterial degradability is a critical design criterion for achieving optimal tissue regeneration with cell transplantation.
Incorporation of Casein Phosphopeptide-Amorphous Calcium Phosphate into a Glass-ionomer Cement
Authors: Mazzaoui S.A. , Burrow M.F. , Tyas M.J. , Dashper S.G. , Eakins D. , Reynolds E.C.
Published: January 2009

Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) nanocomplexes have been shown to prevent demineralization and promote remineralization of enamel subsurface lesions in animal and in situ caries models. The aim of this study was to determine the effect of incorporating CPP-ACP into a self-cured glass-ionomer cement (GIC). Incorporation of 1.56% w/w CPP-ACP into the GIC significantly increased microtensile bond strength (33%) and compressive strength (23%) and significantly enhanced the release of calcium, phosphate, and fluoride ions at neutral and acidic pH. MALDI mass spectrometry also showed casein phosphopeptides from the CPP-ACP nanocomplexes to be released. The release of CPP-ACP and fluoride from the CPP-ACP-containing GIC was associated with enhanced protection of the adjacent dentin during acid challenge in vitro.
The Role of Auditory Cues in Modulating the Perception of Electric Toothbrushes
Authors: Zampini M. , Guest S. , Spence C.
Published: January 2009

Recent research shows that what people hear can influence what they feel. We investigated whether the perception of an electric toothbrush might also be affected by the sound that it makes. Participants were required to make stereotypical brushing movements with a standard electric toothbrush while they rated either the pleasantness or the roughness of the vibrotactile stimulation they felt on their teeth. The results demonstrate that the perception of the sensations experienced during toothbrush use were systematically altered by variations in the auditory feedback elicited by the brushing action. Participants reported that the toothbrush felt more pleasant and less rough when either the overall sound level was reduced, or when just the high-frequency sounds were attenuated. These results highlight the significant role that auditory cues can play in modulating the perception and evaluation of everyday products in use, and provide a paradigm for future study in this area.
Four Reasons to Consider a Novel Class of Innate Immune Molecules in the Oral Epithelium
Authors: LeClair E.E.
Published: January 2009

An expanding number of innate immune molecules occupy the “epithelial frontier”. This review introduces a recently recognized class of mammalian proteins with similarity to PLUNC (palate, lung and nasal epithelium clone), which is itself related to the host defense protein BPI (bactericidal/permeability-increasing protein). Four emerging lines of evidence unite the PLUNC-like proteins: conserved genetic structure, epithelial expression, three-dimensional protein similarity, and a physiological response to injury or inflammation. By analogy to known proteins of the innate immune system, an emerging hypothesis for this family is that they act as sensors of Gram-negative bacteria in the oral cavity, among other areas.
Central Muscarinic Receptors Signal Pilocarpine-induced Salivation
Authors: Takakura A.C.T. , Moreira T. S. , Laitano S.C. , De Luca L.A. , Renzi A. , Menani J. V.
Published: January 2009

Although cholinergic agonists such as pilocarpine injected peripherally can act directly on salivary glands to induce salivation, it is possible that their action in the brain may contribute to salivation. To investigate if the action in the brain is important to salivation, we injected pilocarpine intraperitoneally after blockade of central cholinergic receptors with atropine methyl bromide (atropine-mb). In male Holtzman rats with stainless steel cannulas implanted into the lateral ventricle and anesthetized with ketamine, atropine-mb (8 and 16 nmol) intracerebroventricularly reduced the salivation induced by pilocarpine (4 μmol/kg) intraperitoneally (133 + 42 and 108 + 22 mg/7 min, respectively, vs. saline, 463 + 26 mg/7 min), but did not modify peripheral cardiovascular responses to intravenous acetylcholine. Similar doses of atropine-mb intraperitoneally also reduced pilocarpine-induced salivation. Therefore, systemically injected pilocarpine also enters the brain and acts on central muscarinic receptors, activating autonomic efferent fibers to induce salivation.
Relationship of Periodontal Disease and Edentulism to Stroke/TIA
Authors: Elter J.R. , Offenbacher S. , Toole J.F. , Beck J.D.
Published: January 2009

Periodontitis has been shown to increase the systemic inflammatory response, which has been implicated in atherosclerosis and cerebrovascular events. We hypothesized an association between periodontitis or edentulism and Stroke/TIA in the ARIC Study. Data on 9415 dentate and 1491 edentulous adults included demographics, cardiovascular outcomes, lifestyle, laboratory measures, and, for 6436 of the dentate, a dental examination. The dependent variable was Stroke/TIA, and the exposure was extent (%) of attachment level 3+ millimeters (AL). Quartiles of AL and edentulism were compared for Stroke/TIA using odds ratios (OR) and 95% confidence intervals (CI), and confounders were controlled by logistic regression. Stroke/TIA was prevalent in 13.5% of periodontal examinees, 15.6% of dentate non-examinees, and 22.5% of edentulous persons. The highest quartile of AL (OR 1.3, CI 1.02-1.7) and edentulism (OR 1.4, CI 1.5-2.0) were associated with Stroke/TIA.
Novel Identification of a Four-base-pair Deletion Mutation in PITX2 in a Rieger Syndrome Family
Authors: Wang Y. , Zhao H. , Zhang X. , Feng H.
Published: January 2009

Rieger syndrome is one of the most serious causes of tooth agenesis. Mutations in the PITX2, FOXC1, and PAX6 genes have been associated with Rieger syndrome. We have studied a three-generation Chinese family affected with Rieger syndrome and showing prominent dental abnormalities. Mutational screening and sequence analysis of the PITX2 gene revealed a previously unidentified four-base-pair deletion of nucleotides 717-720 in exon 5 in all affected members. The mutation causes a frame shift after Thr44, the 7th amino acid of the homeo-domain, and introduces a premature stop codon in the gene sequence. This deletion is the first unquestionable loss-of-function mutation, deleting all the functionally important parts of the protein. Our novel discovery indicates that the oligodontia and other phenotypes of Rieger syndrome observed in this family are due to this PITX2 mutation, and these data further support the critical role of PIXT2 in tooth morphogenesis.
The in vivo Levels of Matrix Metalloproteinase-1 and -8 in Gingival Crevicular Fluid during Initial Orthodontic Tooth Movement
Authors: Apajalahti S. , Sorsa T. , Railavo S. , Ingman T.
Published: January 2009

Orthodontic force induces biochemical responses in the periodontal ligament (PDL), but the matrix metalloproteinase (MMP)-dependent molecular mechanisms in orthodontically induced periodontal remodeling have remained unclear. Previous studies indicate that mechanical stress induces MMP-1 production in human PDL cells in vitro. We tested the hypothesis whether the in vivo levels, molecular forms, and degree of activation of MMP-1 and MMP-8 in gingival crevicular fluid (GCF) reflect an early stage of orthodontic tooth movement. Molecular forms of MMP-1 and MMP-8 were analyzed by Western blot, and MMP-8 levels by quantitative immunofluoro-metric assay (IFMA). The results showed that GCF MMP-8 levels for orthodontically treated teeth were significantly higher at 4-8 hrs after force application than before activation, and when compared with the control teeth (p < 0.05). Analysis of our data indicates that the cells within the periodontium are up-regulated to produce MMP-8, and the increased expression and activation of GCF MMP-8 reflect enhanced periodontal remodeling induced by orthodontic force.
Mesenchymal Stem Cells Acquire Characteristics of Cells in the Periodontal Ligament in vitro
Authors: Kramer P.R. , Nares S. , Kramer S.F. , Grogan D. , Kaiser M.
Published: January 2009

Mesenchymal stem cells differentiate into multiple types of cells derived from mesenchyme. Periodontal ligament cells are primarily derived from mesenchyme; thus, we expected mesenchymal stem cells to differentiate into periodontal ligament. Using a combination of immunohistochemistry and in situ hybridization on co-cultures of mesenchymal stem cells and periodontal ligament, we observed a significant increase in mesenchymal stem cells’ expression of osteocalcin and osteopontin and a significant decrease in expression of bone sialoprotein, characteristics of periodontal ligament in vivo. Increased osteopontin and osteocalcin and decreased bone sialoprotein expression was detected within 7 days and maintained through 21 days of co-culture. We conclude that contact or factors from periodontal ligament induced mesenchymal stem cells to obtain periodontal-ligament-like characteristics. Importantly, analysis of the data suggests the feasibility of utilizing mesenchymal stem cells in clinical applications for repairing and/or regenerating periodontal tissue.