bluuebunny/crossref_metadata_2025 huggingface dataset:
Enamel Matrix Derivative Promotes Human Periodontal Ligament Cell Differentiation and Osteoprotegerin Production in vitro
Authors: Lossdörfer S. , Sun M. , Götz W. , Dard M. , Jäger A.
Published: January 2009

Enamel matrix derivative (EMD) has been used successfully to aid periodontal repair. We sought to elucidate the mechanism of action of EMD and hypothesized that combined exposure to EMD and parathyroid hormone (PTH), which acts anabolicly when administered intermittently, would enhance periodontal ligament cell proliferation, differentiation, and local factor production. Confluent human periodontal ligament cells were exposed to EMD continuously or to PTH(1-34) intermittently, or a combination of both. Cell number, alkaline phosphatase activity, osteocalcin, and osteoprotegerin production were determined. Continuous challenge with EMD resulted in an increase of the differentiation parameters and osteoprotegerin production, while simultaneously inhibiting proliferation. Intermittent PTH(1-34) administration exerted opposite effects. Combined administration of EMD and PTH(1-34) weakened or even nullified the effects seen for the agents alone. These results suggest that EMD promotes periodontal ligament cell differentiation and osteoprotegerin production, potentially resulting in a microenvironment supporting periodontal repair, whereas combining EMD and PTH(1-34) failed to prove beneficial in this respect.
Social Gradients in Oral and General Health
Authors: Sabbah W. , Tsakos G. , Chandola T. , Sheiham A. , Watt R.G.
Published: January 2009

There are social gradients in general health and oral health. However, there have been few studies addressing whether similarities exist in the gradients in oral and general health in the same individuals. We set out to test, using data from NHANES III, whether there are social gradients in oral health, and whether they resemble the gradients in general health. Income, indicated by poverty-income ratio, and education gradients were examined in periodontal diseases, ischemic heart disease, and perceived oral/general health. Our analysis demonstrated consistent income and education gradients in all outcomes assessed. In the adjusted regression models, the probabilities of having poorer clinical and perceived health were attenuated, but remained significantly higher at each lower level of income and education for most outcomes. The results showed similar income and education gradients in oral and general health, implying commonalities of the social determinants of both oral and general health.
Association among Bad Breath, Body Mass Index, and Alcohol Intake
Authors: Rosenberg M. , Knaan T. , Cohen D.
Published: January 2009

Bad breath is a common condition, difficult to assess in the general population. In the present study, we tested the hypothesis that a self-administered questionnaire can help identify factors associated with greater risk of oral malodor. Persons (n = 88) undergoing routine medical check-ups completed a questionnaire including 38 questions on general and oral health, dietary habits, and their own oral malodor levels. Oral malodor assessments included odor judge scores, volatile sulfide levels ( via a Halimeter®, Interscan Corp.), and salivary β-galactosidase. Among the questionnaire results, 9 responses were significantly associated with odor judge scores (p < 0.05, unpaired t test), including questions on alcohol intake and body mass index (BMI). Predictions of odor judge scores based on these 9 questions (linear multiple regression analysis) yielded R = 0.601; when introduced together with Halimeter® and β-galactosidase scores, the correlation rose to R = 0.843. The results suggest that alcohol intake and BMI may be factors that help predict oral malodor.
Bonding BisGMA to Dentin—a Proof of Concept for Hydrophobic Dentin Bonding
Authors: Tay F.R. , Pashley D.H. , Kapur R.R. , Carrilho M.R.O. , Hur Y.B. , Garrett L.V. , Tay K.C.Y.
Published: January 2009

The use of TEGDMA as a diluent comonomer in the formulation of hydrophobic adhesives for ethanol wet-bonding is a concern, due to its leaching potential, higher water sorption, and bio-incompatibility. This study tested the hypothesis that hydrophobic bonding to acid-etched dentin may be accomplished with the use of ethanol-solvated BisGMA only. Phosphoric-acid-etched, oxalate-occluded, deep coronal dentin bonded under 20 cm water pressure with experimental BisGMA adhesives by ethanol wet-bonding exhibited tensile strengths that were not significantly different from that achieved with OptiBond FL bonded according to the manufacturer-recommended protocol, with similar acid-/base-resistant hybrid layers, resin tags, and nanoleakage distribution. Ethanol replacement of water-saturated dentin produced wider interfibrillar spaces, more extensive shrinkage of the collagen fibrils, and narrower hybrid layers. Experimental BisGMA adhesives provide the proof of concept that relatively hydrophobic resins may be coupled to acid-etched dentin by increasing its hydrophobic characteristics via ethanol replacement. They should be further optimized before clinical application.
Synthesizing Dental Radiographs for Human Identification
Authors: Tohnak S. , Mehnert A.J.H. , Mahoney M. , Crozier S.
Published: January 2009

The task of identifying human remains based on dental comparisons of post mortem (PM) and ante mortem (AM) radiographs is labor-intensive, subjective, and has several drawbacks, including: inherently poor image quality, difficulty matching the viewing angles in PM radiographs to those taken AM, and the fact that the state of the dental remains may entirely preclude the possibility of obtaining certain types of radiographs PM. The aim of the present study was to investigate the feasibility of using radiograph-like images reconstructed from PM x-ray computed tomography (CT) data to overcome the shortcomings of conventional radiographic comparison. Algorithms for computer synthesis of panoramic, periapical, and bitewing images are presented. The algorithms were evaluated with data from clinical examinations of two persons. The results demonstrate the efficacy of the CT-based approach and that, in comparison with conventional radiographs, the synthesized images exhibit minimal geometric distortion, reduced blurring, and reduced superimposition of oral structures.
Guiding Periodontal Pocket Recolonization: a Proof of Concept
Authors: Teughels W. , Newman M.G. , Coucke W. , Haffajee A.D. , Van Der Mei H.C. , Haake S. Kinder , Schepers E. , Cassiman J.-J. , Van Eldere J. , van Steenberghe D. , Quirynen M.
Published: January 2009

The complexity of the periodontal microbiota resembles that of the gastro-intestinal tract, where infectious diseases are treatable via probiotics. In the oropharyngeal region, probiotic or replacement therapies have shown some benefit in the prevention of dental caries, otitis media, and pharyngitis, but their effectiveness in the treatment of periodontitis is unknown. Therefore, this study addressed the hypothesis that the application of selected beneficial bacteria, as an adjunct to scaling and root planing, would inhibit the periodontopathogen recolonization of periodontal pockets. Analysis of the data showed, in a beagle dog model, that when beneficial bacteria were applied in periodontal pockets adjunctively after root planing, subgingival recolonization of periodontopathogens was delayed and reduced, as was the degree of inflammation, at a clinically significant level. The study confirmed the hypothesis and provides a proof of concept for a guided pocket recolonization (GPR) approach in the treatment of periodontitis.
Oral Health Impact of Periodontal Diseases in Adolescents
Authors: López R. , Baelum V.
Published: January 2009

The need for treatment of destructive periodontal diseases is based on observations made by oral health professionals, who, prompted by clinical findings, recommend treatment. We hypothesized that clinical signs of periodontal destruction have an impact on the oral-health-related quality of life of adolescents. We conducted a cross-sectional study among 9203 Chilean high school students sampled by a multistage random cluster procedure. We recorded clinical attachment levels and the presence of necrotizing ulcerative gingivitis. The students answered the Spanish version of the Oral Health Impact Profile and provided information on several socio-economic indicators. The results of multivariable logistic regression analyses (adjusted for age, gender, and tooth loss) showed that both attachment loss [OR = 2.0] and necrotizing ulcerative gingivitis [OR = 1.6] were significantly associated with higher impact on the Oral Health Related Quality of Life of adolescents. Individuals in lower socioeconomic positions systematically reported a higher impact on their oral-health-related quality of life.
Influence of Psychological Factors on Risk of Temporomandibular Disorders
Authors: Slade G.D. , Diatchenko L. , Bhalang K. , Sigurdsson A. , Fillingim R.B. , Belfer I. , Max M.B. , Goldman D. , Maixner W.
Published: January 2009

Psychological characteristics potentially may be a cause or consequence of temporomandibular disorder (TMD). We hypothesized that psychological characteristics associated with pain sensitivity would influence risk of first-onset TMD, but the effect could be attributed to variation in the gene encoding catechol- O-methyltransferase (COMT). We undertook a prospective cohort study of healthy female volunteers aged 18–34 yrs. At baseline, participants were genotyped, they completed psychological questionnaires, and underwent quantitative sensory testing to determine pain sensitivity. We followed 171 participants for up to three years, and 8.8% of them were diagnosed with first-onset TMD. Depression, perceived stress, and mood were associated with pain sensitivity and were predictive of 2- to 3-fold increases in risk of TMD (P < 0.05). However, the magnitude of increased TMD risk due to psychological factors remained unchanged after adjustment for the COMT haplotype. Psychological factors linked to pain sensitivity influenced TMD risk independently of the effects of the COMT haplotype on TMD risk.
Caries-related Bacteria and Cytokines Induce CXCL10 in Dental Pulp
Authors: Adachi T. , Nakanishi T. , Yumoto H. , Hirao K. , Takahashi K. , Mukai K. , Nakae H. , Matsuo T.
Published: January 2009

Marked infiltration of inflammatory cells, such as activated T-cells, is observed in the progression of pulpitis; however, little is known about the mechanism of their recruitment into pulpal lesions. It has been recently demonstrated that CXC chemokine ligand 10 (CXCL10) chemoattracts CXC chemokine receptor 3 (CXCR3)-positive activated T-cells. We therefore examined whether CXCL10 is involved in the pathogenesis of pulpitis. CXCL10 mRNA expression levels in clinically inflamed dental pulp were higher than those in healthy dental pulp. Immunostaining results revealed that CXCL10 was detected in macrophages, endothelial cells, and fibroblasts in inflamed dental pulp, and that CXCR3 expression was observed mainly on T-cells. Moreover, cultured dental pulp fibroblasts produced CXCL10 after stimulation with live caries-related bacteria, peptidoglycans, and pro-inflammatory cytokines. In contrast, heat-killed bacteria did not induce CXCL10 secretion. These findings suggest that CXCL10-CXCR3 may play an important role in the pulpal immune response to caries-related bacterial invasion. Abbreviations: CXCL10, CXC chemokine ligand 10; CXCR3, CXC chemokine receptor 3; IFN, interferon; FBS, fetal bovine serum; LTA, lipoteichoic acid; PGN, peptidoglycan; IL, interleukin; TNF, tumor necrosis factor; PBS, phosphate-buffered saline; ELISA, enzyme-linked immunosorbent assay; CCL, C-C chemokine ligand; TLR, Toll-like receptor; NOD, nucleotide oligomerization domain; HDPF, human dental pulp fibroblasts.
Effects of Fluoride on the Interactions between Amelogenin and Apatite Crystals
Authors: Tanimoto K. , Le T. , Zhu L. , Chen J. , Featherstone J.D.B. , Li W. , DenBesten P.
Published: January 2009

Fluorosed enamel is more porous and less mineralized, possibly related to altered amelogenin-modulated crystal growth. The purpose of this study was to examine the role of fluoride in interactions between amelogenin and apatite crystals. Recombinant human amelogenin (rh174) was bound to carbonated hydroxyapatite containing various amounts of fluoride, and analyzed by protein assay, SDS PAGE, and AFM. Interactions between rh174 and fluoride were assayed by isothermal titration calorimetry (ITC). The initial binding rate of rh174, as well as total amount of rh174 bound to fluoride-containing carbonated hydroxyapatite, was greater than that in the control carbonated hydroxyapatite. Fluoride in solution at physiologic (5.3 micromolar, or 0.1 ppm) concentrations showed no significant effect on binding, but higher fluoride levels significantly decreased protein binding. ITC showed no interactions between fluoride and rh174. These results suggest that fluoride incorporation into the crystal lattice alters the crystal surface to enhance amelogenin binding, with no direct interactions between fluoride and amelogenin.
Phenotypic Analysis of Dlx5 Overexpression in Post-natal Bone
Authors: Zhang J. , Zhu J. , Valverde P. , Li L. , Pageau S. , Tu Q. , Nishimura R. , Yoneda T. , Yang P. , Zheng W. , Ma W. , Chen J.
Published: January 2009

Dlx5 plays an important role in the embryonic development of mineralized tissues. We hypothesized that Dlx5 also functions in regulating post-natal bone formation in mice. To prove this hypothesis, we infected 5-day-old bone sialoprotein (BSP)/avian retroviral receptor gene (TVA) transgenic mice with replication-competent retroviral vectors expressing wild-type Dlx5 (RCAS- Dlx5WT) and mutated Dlx5 at arginine (R) 31 of its homeodomain (RCAS- Dlx5RH). Immunohistochemistry indicated that RCAS- Dlx5WT increased BSP and osteopontin (OPN) expression, whereas it decreased that of osteocalcin (OC). RCAS- Dlx5RH mediated opposite effects. Semi-quantitative RT-PCR confirmed these results. Ex vivo overexpression of RCAS- Dlx5WT in BSP/TVA calvarial cells promoted, whereas that of RCAS- Dlx5RH inhibited, mineralized nodule formation as compared with that in control cells. Our results suggest that Dlx5 promotes expression of early markers of osteogenic differentiation and increases mineralization post-natally.
Premature Stop Codon in MMP20 Causing Amelogenesis Imperfecta
Authors: Papagerakis P. , Lin H.-K. , Lee K.Y. , Hu Y. , Simmer J.P. , Bartlett J.D. , Hu J.C.-C.
Published: January 2009

Proteolytic enzymes are necessary for the mineralization of dental enamel during development, and mutations in the kallikrein 4 ( KLK4) and enamelysin ( MMP20) genes cause autosomal-recessive amelogenesis imperfecta (ARAI). So far, only one KLK4 and two MMP20 mutations have been reported. We have identified an ARAI-causing point mutation (c.102G>A, g.102G>A, and p.W34X) in exon 1 of MMP20 in a proband with autosomal-recessive hypoplastic-hypomaturation amelogenesis imperfecta. The G to A transition changes the tryptophan (W) codon (TGG) at amino acid position 34 into a translation termination (X) codon (TGA). No disease-causing sequence variations were detected in KLK4. The affected enamel is thin, with mild spacing in the anterior dentition. The enamel layer is hypomineralized, does not contrast with dentin on radiographs, and tends to chip away from the underlying dentin. An intrinsic yellowish pigmentation is evident, even during eruption. The phenotype supports current ideas concerning the function of enamelysin.
The Relationship between Periodontitis and Preterm Low Birthweight
Authors: Vettore M.V. , Leal M. doC. , Leão A.T. , da Silva A.M. Monteiro , Lamarca G.A. , Sheiham A.
Published: January 2009

There is no consensus about the influence of periodontal disease on preterm low birthweight. The objective was to investigate the relationship between periodontal disease and preterm low birthweight. A case-control study with 542 post partum women aged over 30 yrs was conducted. Three groups of cases were compared with non-preterm and non-low-birthweight control individuals (n = 393): low birthweight (n = 96), preterm (n = 110), and preterm and low birthweight (n = 63). Periodontal clinical parameters and covariates were recorded. Periodontal disease levels were higher in control individuals than in cases. The extent of periodontal disease did not increase risk of preterm low birthweight according to 15 measures of periodontal disease. Mean periodontal pocket depth and frequency of periodontal sites with clinical attachment level ≥ 3 mm in preterm low birthweight cases were lower than in control individuals. Periodontal disease was not more severe in women with preterm low birthweight babies.
Scaffold and Growth Factor Selection in Temporomandibular Joint Disc Engineering
Authors: Allen K.D. , Athanasiou K.A.
Published: January 2009

Temporomandibular joint disc tissue-engineering studies commonly fail to produce significant matrix before construct contraction. We hypothesized that poly-L-lactic acid (PLLA) non-woven meshes would limit contraction, allow for comprehensive mechanical evaluation, and maintain viability relative to polyglycolic acid (PGA) non-woven mesh controls. Additionally, we proposed that growth factor stimulation, while limiting contraction, would increase construct properties relative to previous reports. After 4 wks, cell proliferation and matrix deposition were similar between the two meshes, but PGA constructs had contracted significantly. Furthermore, only PLLA constructs could be tested in tension and compression. Additional PLLA constructs were formed, then treated with insulin-like growth factor-1 (10 ng/mL), transforming growth factor-beta 1 (5 ng/mL), or transforming growth factor-beta 3 (5 ng/mL). Transforming growth factor-beta 1 yielded the most cells, collagen, and glycosaminoglycans at 6 wks; these constructs also demonstrated improved mechanics. Analysis of these data demonstrated significant temporomandibular joint disc-engineering potential for PLLA and transforming growth factor-beta 1.
Wnt/β-catenin Inhibits Dental Pulp Stem Cell Differentiation
Authors: Scheller E.L. , Chang J. , Wang C.Y.
Published: January 2009

Dental pulp stem cells (DPSCs) are a unique precursor population isolated from postnatal human dental pulp and have the ability to regenerate a reparative dentin-like complex. Canonical Wnt signaling plays a critical role in tooth development and stem cell self-renewal through β-catenin. In this study, the regulation of odontoblast-like differentiation of DPSCs by canonical Wnt signaling was examined. DPSCs were stably transduced with canonical Wnt-1 or the active form of β-catenin, with retrovirus-mediated infection. Northern blot analysis found that Wnt-1 strongly induced the expression of matricellular protein osteopontin, and modestly enhanced the expression of type I collagen in DPSCs. Unexpectedly, Wnt-1 inhibited alkaline phosphatase (ALP) activity and the formation of mineralized nodules in DPSCs. Moreover, over-expression of β-catenin was also sufficient to suppress the differentiation and mineralization of DPSCs. In conclusion, our results suggest that canonical Wnt signaling negatively regulates the odontoblast-like differentiation of DPSCs. Abbreviations used: DPSC, dental pulp stem cell; ALP, alkaline phosphatase; BSP, bone sialoprotein; MSC, mesenchymal stem cell; β-GP, β-glycerophosphate; APC, adenomatous polyposis coli; GSK-3β, glycogen synthase kinase-3β; LRP, LDL receptor-related protein; Tcf, T-cell factor; LEF, lymphoid enhancer factor; FCS, fetal calf serum; AA, L-ascorbic acid 2-phosphate; α-MEM, α-modified Eagle’s medium; PBS, phosphate-buffered saline; HA, hemagglutinin; ON, osteonectin; OPN, osteopontin.
Inhibition of Experimental Periodontitis by a Topical Boron-based Antimicrobial
Authors: Luan Q. , Desta T. , Chehab L. , Sanders V.J. , Plattner J. , Graves D.T.
Published: January 2009

AN0128 is a boron-containing compound with antibacterial and anti-inflammatory properties. To test its potential effectiveness in treating periodontal disease, we induced experimental periodontitis in the rat by placing ligatures and assessed the impact of AN0128 and positive and negative controls by micro-CT and histologic measurements. The formation of an inflammatory infiltrate was measured in hematoxylin-and-eosin-stained sections. Daily application of AN0128 (1%) compared with controls reduced bone loss by 38 to 44% (P < 0.05), while vehicle alone had no effect (P > 0.05). The reduction in bone loss with AN0128 was similar to that achieved with a NSAID, ketorolac, and Total toothpaste containing triclosan. AN0128 also reduced the level of gingival inflammation 42% compared with the ligature only (P < 0.05), whereas vehicle alone had no effect (P > 0.05). The results indicate that AN0128 significantly reduces the formation of an inflammatory infiltrate and reduces bone loss, measured histologically and by micro-CT.
An Uncommon Cleft Subtype of Unilateral Cleft Lip and Palate
Authors: Yamanishi T. , Kobayashi C. , Tsujimoto I. , Koizumi H. , Miya S. , Yokota Y. , Okamoto R. , Iida S. , Aikawa T. , Kohara H. , Nishio J. , Kogo M.
Published: January 2009

The finding that the vomer plays a crucial role in maxillary growth suggests that the bilateral cleft configuration of unilateral cleft lip and palate (UCLP), in which the vomer is detached from the non-cleft-side secondary hard palate, negatively influences palatal development, and this hypothesis was tested. Sixty persons with complete UCLP, including those with the vomer detached from (n = 30, b-UCLP) and attached to (n = 30, u-UCLP) the secondary hard palate, were analyzed morphologically, with the use of cast models taken at 10 days, 3 mos, and 12 mos of age. The anterio-posterior palatal length at 12 mos of age in those with b-UCLP was significantly shorter than that in those with u-UCLP, by 8.7% (p < 0.05). In addition, palatal width development in the first year in those with b-UCLP was also significantly retarded. These results suggest that the uncommon bilateral cleft subtype in UCLP should be included in the cleft classification.
Periodontal-Masseteric Reflexes Decrease with Tooth Pre-load
Authors: Sowman P.F. , Türker K.S.
Published: January 2009

The responses of incisal periodontal mechanoreceptors to increasing mechanical stimulation are known to follow a hyperbolic-saturating course. The implications of these properties for the reflexive control of bite-force have not been examined directly. In line with the abovementioned receptor characteristics, we hypothesized that the periodontal-masseteric reflex will reduce as a function of increasing incisal pre-load. In 10 participants, a central incisor was repeatedly tapped (0.4 N). We measured the modulation by pre-load (0.2–2.0 N) of the reflex frequency-response at and between 3 and 20 Hz. The entrainment of the reflex increased with frequency up to 20 Hz and diminished with increasing pre-load. Importantly, the hyperbolic relationship shown here between the periodontal-masseteric reflex and tooth pre-load agreed with the load/response relationships predicted by single-receptor and tooth movement studies. This study demonstrated that periodontal mechano-receptors are able to contribute to the ongoing control of only small bite-forces.
Diversity of Veillonella spp. from Sound and Carious Sites in Children
Authors: Arif N. , Sheehy E.C. , Do T. , Beighton D.
Published: January 2009

Detailed data on the distribution of Veillonella in caries-free and caries-active subjects are scarce. We hypothesized that the diversity of the genus would be lower in caries lesions than in plaque from caries-free individuals. The proportions of Veillonella were not significantly different in the two groups. All isolates (n = 1308) were genotyped by REP-PCR, and different genotypes (n = 170) were identified by 16S rRNA, dnaK, and rpoB sequencing. V. parvula, V. dispar, and V. atypica were in both groups, V. denticariosi only in caries lesions, and V. rogosae only from the caries-free individuals (p < 0.009). Lesions were more likely to harbor a single predominant species (p = 0.0018). The mean number of genotypes in the lesions was less than in the fissure (p < 0.001) or buccal (p = 0.011) sites. The Veillonella from caries-free sites were more diverse than those from caries lesions, and may be related to the acidic environment of caries lesions.
Micromechanical Property Recovery of Human Carious Dentin Achieved with Colloidal Nano-β-tricalcium Phosphate
Authors: Shibata Y. , He L.H. , Kataoka Y. , Miyazaki T. , Swain M.V.
Published: January 2009

Reconstitution of carious dentin has been recognized as difficult, because it progresses by loss of collagen polymerization and by demineralization under acidic conditions. Recently, colloidal alkaline nano-calcium phosphate, prepared by electrical discharge in a buffered physiological saline solution, has been shown to be effective in the formulation of a bone-like biocomposite by simply being mixed with acidic collagen solution. It was hypothesized that colloidal calcium phosphate was suitable for the reconstitution of carious dentin. Natural caries lesions in dentin from permanent teeth were exposed to colloidal hydroxyapatite and β-tricalcium phosphate for 10 days. The micromechanical properties of these tissues were evaluated by nano-indentation. The elastic modulus of human carious dentin improved after samples were immersed in colloidal β-tricalcium phosphate. The mineral density of carious dentin exposed to β-tricalcium phosphate increased more than that immersed in hydroxyapatite. However, since it was not directly proportional to micromechanical recovery, mineral density alone was not a sufficient indicator of mechanical behavior.
Veneer vs. Core Failure in Adhesively Bonded All-ceramic Crown Layers
Authors: Lee J.J.-W. , Kwon J.-Y. , Bhowmick S. , Lloyd I.K. , Rekow E.D. , Lawn B.R.
Published: January 2009

Joining a brittle veneer to a strong ceramic core with an adhesive offers potential benefits over current fabrication methods for all-ceramic crowns. We tested the hypothesis that such joining can withstand subsurface radial cracking in the veneer, from enhanced flexure in occlusal loading, as well as in the core. Critical conditions to initiate fractures were investigated in model crown-like layer structures consisting of glass veneers epoxy-joined onto alumina or zirconia cores, all bonded to a dentin-like polymer base. The results showed a competition between critical loads for radial crack initiation in the veneers and cores. Core radial cracking was relatively independent of adhesive thickness. Zirconia cores were much less susceptible to fracture than alumina, attributable to a relatively high strength and low modulus. Veneer cracking did depend on adhesive thickness. However, no significant differences in critical loads for veneer cracking were observed for specimens containing alumina or zirconia cores.
Mesenchyme is Responsible for Tooth Suppression in the Mouse Lower Diastema
Authors: Yuan G.H. , Zhang L. , Zhang Y.D. , Fan M.W. , Bian Z. , Chen Z.
Published: January 2009

Between the incisor and molars in each dental quadrant, mice have a toothless gap (diastema) that may contain vestigial tooth primordia. It is still not clear whether suppression of odontogenesis in the mouse lower diastema can be attributed to epithelium, mesenchyme, or both. Therefore, using recombination experiments with mouse tissues from E11.5 and E13.5 stages, we investigated whether the epithelium or mesenchyme is responsible for the suppression of odontogenesis. Five groups of recombinants were established and cultured under mouse kidney capsules. The results demonstrated that at E11.5, the lower diastemal epithelium and mesenchyme possessed odontogenic potential and competence, respectively; at E13.5, both the lower diastemal epithelium and mesenchyme had odontogenic competence, while the lower diastemal mesenchyme did not possess odontogenic potential. On the basis of comparison of the odontogenic capabilities between the lower diastemal and molar tooth primordia, we conclude that mesenchyme is responsible for tooth regression in the mouse lower diastema.
Luteolin Induces Apoptosis in Oral Squamous Cancer Cells
Authors: Yang S.-F. , Yang W.-E. , Chang H.-R. , Chu S.-C. , Hsieh Y.-S.
Published: January 2009

Oral squamous cell carcinoma is the most common malignancy of the oral cavity, and treatment approaches are inadequate. Luteolin, a natural flavonoid compound, has been shown to have anti-tumorigenic properties on various types of tumors. Therefore, we hypothesized that luteolin has anti-tumorigenic properties for oral squamous cell carcinoma, and may provide effective chemotherapy. Results revealed that luteolin reduced the viability of SCC-4 cells and induced apoptosis by decreasing the expression of cyclin-dependent kinase (CDKs), cyclins, and phosphor- retinoblastoma (p-Rb) anti-apoptotic protein, but increased the expression of pro-apoptotic proteins and activated caspase 9 and 3, with a concomitant increase in the levels of cleaved poly-ADP-ribose polymerase (PARP). Combination treatment of luteolin with paclitaxel enhanced the cytotoxic effect of paclitaxel in SCC-4 cells, and continuous administration of luteolin suppressed the growth of xenograft tumors in nude mice. These results suggest that luteolin could be an effective chemotherapeutic agent for the treatment of oral squamous cell carcinoma.
Oral Health and Mortality Risk from Pneumonia in the Elderly
Authors: Awano S. , Ansai T. , Takata Y. , Soh I. , Akifusa S. , Hamasaki T. , Yoshida A. , Sonoki K. , Fujisawa K. , Takehara T.
Published: January 2009

Although poor oral health influences the occurrence of pulmonary infection in elderly people, it is unclear how the degree of oral health is linked to mortality from pulmonary infection. Therefore, we evaluated the relationship between oral health and four-year mortality from pneumonia in an elderly Japanese population. The study population consisted of 697 (277 males, 420 females) of the 1282 individuals who were 80 years old in 1997. Data on oral and systemic health were obtained by means of questionnaires, physical examinations, and laboratory blood tests. One hundred eight of the study persons died between 1998 and 2002. Of these, 22 deaths were due to pneumonia. The adjusted mortality due to pneumonia was 3.9 times higher in persons with 10 or more teeth with a probing depth exceeding 4 mm (periodontal pocket) than in those without periodontal pockets. Therefore, the increase in teeth with periodontal pockets in the elderly may be associated with increased mortality from pneumonia.
Fluoride and Casein Phosphopeptide-Amorphous Calcium Phosphate
Authors: Reynolds E.C. , Cai F. , Cochrane N.J. , Shen P. , Walker G.D. , Morgan M.V. , Reynolds C.
Published: January 2009

Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) slows the progression of caries and remineralizes enamel subsurface lesions. The aim of this study was to determine the ability of CPP-ACP to increase the incorporation of fluoride into plaque and to promote enamel remineralization in situ. Randomized, double-blind, cross-over studies involved mouthrinses and dentifrices containing CPP-ACP and fluoride. The mouthrinses were used for 60 sec, three times/day for 5 days, and supragingival plaque was collected and analyzed for F. The dentifrices were rinsed as a water slurry for 60 sec four times/day for 14 days in an in situ model. The addition of 2% CPP-ACP to the 450-ppm-F mouthrinse significantly increased the incorporation of fluoride into plaque. The dentifrice containing 2% CPP-ACP produced a level of remineralization similar to that achieved with a dentifrice containing 2800 ppm F. The dentifrice containing 2% CPP-ACP plus 1100 ppm F was superior to all other formulations.
Genome-wide Scan Finds Suggestive Caries Loci
Authors: Vieira A.R. , Marazita M.L. , Goldstein-McHenry T.
Published: January 2009

Here we report the first genome-wide scan performed for caries. Evidence from twin studies suggests a genetic component to caries. We aimed to identify genetic factors contributing to caries in a population similarly influenced by confounding factors, such as diet, oral hygiene habits, fluoride exposure, and access to dental care. Forty-six families with similar cultural and behavioral habits, and living in the Philippines, were studied, and genome-wide genotype data and DMFT (Decayed, Missing due to caries, Filled Teeth) scores were evaluated. Suggestive loci logarithmic odds (LOD) scores above 2.0 or non-parametric p-values below 0.0009) were found for low caries susceptibility (5q13.3, 14q11.2, and Xq27.1) and high caries susceptibility (13q31.1 and 14q24.3). Genes that may be related to saliva flow and diet preferences are proposed as possible candidates. A protective locus for caries in the X chromosome may explain the gender differences seen in caries frequency.
Proteome of Human Minor Salivary Gland Secretion
Authors: Siqueira W.L. , Salih E. , Wan D.L. , Helmerhorst E.J. , Oppenheim F.G.
Published: January 2009

Recent research efforts in oral biology have resulted in elucidation of the proteomes of major human salivary secretions and whole saliva. One might hypothesize that the proteome of minor gland secretions may show significantly different characteristics when compared with the proteomes of parotid or submandibular/sublingual secretions. To test this hypothesis, we conducted the first exploration into the proteome of minor salivary gland secretion. Minor gland secretion was obtained from healthy volunteers, and its components were subjected to liquid-chromatography-electrospray-ionization-tandem-mass-spectrometry. This led to the identification of 56 proteins, 12 of which had never been identified in any salivary secretion. The unique characteristics of the minor salivary gland secretion proteome are related to the types as well as the numbers of components present. The differences between salivary proteomes may be important with respect to specific oral functions.
Mechanisms of Tooth Eruption and Orthodontic Tooth Movement
Authors: Wise G.E. , King G.J.
Published: January 2009

Teeth move through alveolar bone, whether through the normal process of tooth eruption or by strains generated by orthodontic appliances. Both eruption and orthodontics accomplish this feat through similar fundamental biological processes, osteoclastogenesis and osteogenesis, but there are differences that make their mechanisms unique. A better appreciation of the molecular and cellular events that regulate osteoclastogenesis and osteogenesis in eruption and orthodontics is not only central to our understanding of how these processes occur, but also is needed for ultimate development of the means to control them. Possible future studies in these areas are also discussed, with particular emphasis on translation of fundamental knowledge to improve dental treatments.
Can Caries Fissures be Sealed as Adequately as Sound Fissures?
Authors: Hevinga M.A. , Opdam N.J.M. , Frencken J.E. , Bronkhorst E.M. , Truin G.J.
Published: January 2009

Sealing caries fissures is considered an appropriate treatment option for arresting the caries process. However, little information is available regarding the sealing of occlusal cavitated dentin lesions. The hypothesis tested in this in vitro study was that no difference in microleakage and sealant penetration depth exists between cavitated and sound sealed fissures when a resin is used. Eighty molars, each with an occlusal cavitated dentin lesion, were treated according to 5 experimental protocols and compared with a control group of sealed sound molars. In the experimental groups, fissure sealants were placed with and without an adhesive, and in various ways. All teeth were sectioned, and microleakage and sealant penetration into the fissure were evaluated. Sealed caries fissures showed significantly more microleakage and insufficient sealant penetration depth than sound fissures. Neither the use of an adhesive nor its intermediate curing influenced the microleakage score and the penetration ability of sealants.
Mechanical Stress Induces Osteopontin via ATP/P2Y1 in Periodontal Cells
Authors: Wongkhantee S. , Yongchaitrakul T. , Pavasant P.
Published: January 2009

Our previous study showed that mechanical stress induced the expression of osteopontin (OPN) in human periodontal ligament (HPDL) cells through the Rho kinase pathway. The increase of OPN expression via Rho kinase has been demonstrated to be triggered by nucleotide. Therefore, we hypothesized that nucleotides, particularly adenosine triphosphate (ATP), participated in the stress-induced OPN expression in HPDL cells. In the present study, the roles of ATP and P2Y1 purinoceptor were examined. Reverse-transcription polymerase chain-reaction and Western blot analysis revealed that the stress-induced ATP exerted its stimulatory effect on OPN expression. The inductive effect was attenuated by apyrase and completely inhibited by the Rho kinase inhibitor, as well as by the P2Y1 antagonist. We here propose that stress induces release of ATP, which in turn mediates Rho kinase activation through the P2Y1 receptor, resulting in the up-regulation of OPN. Stress-induced ATP could play a significant role in alveolar bone resorption.
N-acetyl Cysteine Protects Pulp Cells from Resin Toxins in vivo
Authors: Paranjpe A. , Sung E.C. , Cacalano N.A. , Hume W.R. , Jewett A.
Published: January 2009

Potential risks of the use of resin-based restorative materials include direct damage to the pulp cells and the induction of hypersensitivity reactions in patients. In this study, we tested the hypothesis that N-acetyl cysteine (NAC) inhibits resin toxicity and restores the function of pulp cells. Analysis of our data demonstrates toxicity of composite resins on pulp cells in both an in vivo rat and an ex vivo human model system. Moreover, cells that survive after the placement of composites are weaker, and they are induced to undergo cell death when exposed to 2-hydroxyethyl methacrylate (HEMA). The toxic effect of composites on pulp cells is neutralized by NAC. Therefore, NAC protects the cells from damage induced by clinically relevant levels of restorative materials, in both rat and human model systems. The addition of N-acetyl cysteine prior to or concomitant with the application of restorative materials may be beneficial for the health and safety of dental patients.
Enhanced Enamel Remineralization under Acidic Conditions in vitro
Authors: Yamazaki H. , Margolis H.C.
Published: January 2009

We conducted this study to test the hypothesis that acidic solutions undersaturated with respect to enamel and supersaturated with respect to fluorapatite can enhance enamel remineralization by reducing preferential remineralization of the outer lesion and promoting mineral ion penetration. We used quantitative microradiography to assess mineral changes in artificial surface-softened and subsurface lesions in human enamel in vitro, induced by such an acidic solution and by a neutral remineralizing solution. For surface-softened lesions, the extent of remineralization was similar for both solutions, although preferential remineralization of the outer lesion was observed with the neutral solution. For subsurface lesions, preferential remineralization of the outer lesion was not observed with either solution. However, the extent of subsurface lesion remineralization by the acidic solution was significantly greater than that observed with the neutral solution. Results obtained are noted to reflect inherent differences in lesion type and the properties of the solutions studied.
Antigen-presenting Cells in Human Radicular Granulomas
Authors: Kaneko T. , Okiji T. , Kaneko R. , Nör J.E. , Suda H.
Published: January 2009

Substantial numbers of dendritic cells have been detected in radicular granulomas. To test the hypothesis that local antigen presentation from dendritic cells to T-cells is involved critically in immunological responses within radicular granulomas, we compared characteristics of dendritic cells and macrophages by morphological and biological analyses. Under light microscopy, HLA-DR+ and CD68+ cells showed diverse profiles, including dendritic-shaped cells. Transmission electron microscopy revealed that HLA-DR+ dendritic cells, with long cytoplasmic processes and lacking distinct phagosomes, were concentrated in the lymphocyte-rich area. HLA-DR alpha-chain, CD83, and CD86 mRNAs from HLA-DR+ dendritic cells, and CD28 mRNA from CD28+ T-cells were up-regulated in lymphocyte-rich area. Scanning electron microscopy demonstrated that the density of gold particles on dendritic cells was higher than that on HLA-DR+ macrophages. These results suggest that dendritic cells in radicular granulomas are associated with local defense reactions as stronger antigen-presenting cells, as compared with macrophages.
Changing Clinicians’ Behavior: a Randomized Controlled Trial of Fees and Education
Authors: Clarkson J.E. , Turner S. , Grimshaw J.M. , Ramsay C.R. , Johnston M. , Scott A. , Bonetti D. , Tilley C.J. , Maclennan G. , Ibbetson R. , MacPherson L.M.D. , Pitts N.B.
Published: January 2009

The fissure-sealing of newly erupted molars is an effective caries prevention treatment, but remains underutilized. Two plausible reasons are the financial disincentive produced by the dental remuneration system, and dentists’ lack of awareness of evidence-based practice. The primary hypothesis was that implementation strategies based on remuneration or training in evidence-based healthcare would produce a higher proportion of children receiving sealed second permanent molars than standard care. The four study arms were: fee per sealant treatment, education in evidence-based practice, fee plus education, and control. A cost-effectiveness analysis was conducted. Analysis was based on 133 dentists and 2833 children. After adjustment for baseline differences, the primary outcome was 9.8% higher when a fee was offered. The education intervention had no statistically significant effect. ‘Fee only’ was the most cost-effective intervention. The study contributes to the incentives in health care provision debate, and led to the introduction of a direct fee for this treatment.
Extracorporeal Shock Wave Therapy Induces Alveolar Bone Regeneration
Authors: Sathishkumar S. , Meka A. , Dawson D. , House N. , Schaden W. , Novak M.J. , Ebersole J. L. , Kesavalu L.
Published: January 2009

Periodontal inflammation with alveolar bone resorption is a hallmark of periodontitis. We hypothesized that extracorporeal shock wave therapy (ESWT) could promote the regeneration of alveolar bone following Porphyromonas gingivalis-induced periodontitis in rats. Rats were infected with P. gingivalis for 10 wks, which caused alveolar bone resorption. The rats were then treated with a single episode of 100, 300, or 1000 impulses of shock wave on both cheeks at energy levels 0.1 mJ/mm2. Alveolar bone levels were determined at 0, 3, 6, and 12 wks following ESWT and compared with those in untreated controls. Infected rats treated with 300 and 1000 impulses demonstrated significantly improved alveolar bone levels at 3 wks compared with untreated controls, and the improved levels remained for at least 6 wks in most rats. The results demonstrated effective regeneration of alveolar bone by ESWT and suggested that ESWT should be evaluated as an adjunct in the regeneration of periodontal tissues following periodontal disease. Abbreviations: ESWT, extracorporeal shock wave therapy; PCR, polymerase chain-reaction.
Periodontal Breakdown in the Dmp1 Null Mouse Model of Hypophosphatemic Rickets
Authors: Ye L. , Zhang S. , Ke H. , Bonewald L. F. , Feng JQ.
Published: January 2009

Dentin Matrix Protein 1 (DMP1) is highly expressed in alveolar bone and cementum, which are important components of the periodontium. Therefore, we hypothesized that Dmp1 is critical for the integrity of the periodontium, and that deletion may lead to increased susceptibility to disease. An early-onset periodontal defect was observed in the Dmp1 null mouse, a mouse model of hypophosphatemic rickets. The alveolar bone is porous, with increased proteoglycan expression. The cementum is also defective, as characterized by irregular, punctate fluorochrome labeling and elevated proteoglycan. The osteocyte and cementocyte lacuno-canalicular system of both alveolar bone and cementum is abnormal, with irregular lacunar walls and fewer canaliculi. As a consequence, there is significant interproximal alveolar bone loss, combined with detachment between the periodontal ligament (PDL) and cementum. We propose that defective alveolar bone and cementum may account for the periodontal breakdown and increased susceptibility to bacterial infection in Dmp1 null mice.
Compositional Determinants of Mechanical Properties of Enamel
Authors: Baldassarri M. , Margolis H.C. , Beniash E.
Published: January 2009

Dental enamel is comprised primarily of carbonated apatite, with less than 1% w/w organic matter and 4–5% w/w water. To determine the influence of each component on the microhardness and fracture toughness of rat incisor enamel, we mechanically tested specimens in which water and organic matrix were selectively removed. Tests were performed in mid-sagittal and transverse orientations to assess the effect of the structural organization on enamel micromechanical properties. While removal of organic matrix resulted in up to a 23% increase in microhardness, and as much as a 46% decrease in fracture toughness, water had a significantly lesser effect on these properties. Moreover, removal of organic matrix dramatically weakened the dentinoenamel junction (DEJ). Analysis of our data also showed that the structural organization of enamel affects its micromechanical properties. We anticipate that these findings will help guide the development of bio-inspired nanostructured materials for mineralized tissue repair and regeneration.
Differentiation of Stem Cells in the Dental Follicle
Authors: Yao S. , Pan F. , Prpic V. , Wise G.E.
Published: January 2009

The dental follicle (DF) differentiates into the periodontal ligament. In addition, it may be the precursor of other cells of the periodontium, including osteoblasts and cementoblasts. We hypothesized that stem cells may be present in the DF and be capable of differentiating into cells of the periodontium. Stem cells were identified in the DF of the rat first mandibular molar by Hoechst staining, alkaline phosphatase staining, and expression of side-population stem cell markers. These cells were shown to be able to differentiate into osteoblasts/cementoblasts, adipocytes, and neurons. Treating the DF cell population with doxorubicin, followed by incubation in an adipogenesis medium, suggested that the adipocytes originated from stem cells. Thus, a possibly puripotent stem cell population is present in the rat DF.
Degradation, Fatigue, and Failure of Resin Dental Composite Materials
Authors: Drummond J.L.
Published: January 2009

The intent of this article is to review the numerous factors that affect the mechanical properties of particle- or fiber-filler-containing indirect dental resin composite materials. The focus will be on the effects of degradation due to aging in different media, mainly water and water and ethanol, cyclic loading, and mixed-mode loading on flexure strength and fracture toughness. Several selected papers will be examined in detail with respect to mixed and cyclic loading, and 3D tomography with multi-axial compression specimens. The main cause of failure, for most dental resin composites, is the breakdown of the resin matrix and/or the interface between the filler and the resin matrix. In clinical studies, it appears that failure in the first 5 years is a restoration issue (technique or material selection); after that time period, failure most often results from secondary decay.