bluuebunny/crossref_metadata_2025 huggingface dataset:
Developmental Properties of the Hertwig’s Epithelial Root Sheath in Mice
Authors: Yamamoto H. , Cho S.-W. , Kim E.-J. , Kim J.-Y. , Fujiwara N. , Jung H.-S.
Published: January 2009

Hertwig’s epithelial root sheath (HERS) plays an important role in tooth root formation. In this study, we examined root formation of the first molar in mice, focusing on cell proliferation, cell death, cell migration, and the expression patterns of the signaling molecules, including glycoproteins and proteoglycans between PN8 and PN26. The number of HERS cells decreased during root formation, although HERS retained total length until PN15. The migration of HERS cells did not occur during root formation. Moreover, the immunopositive reaction of laminin beta-3 and syndecan-1 in HERS indicates that both cell adhesion and cell proliferation are essential for HERS development. Bmp-2, Bmp-4, and Msx-2 were expressed in HERS cells during root formation. We also developed an in vitro culture system for investigating the periodontium and suggest that this system provides an excellent vehicle for full exploration, and hence improved understanding, of the development and regeneration of the periodontium. Together, our results provide a comprehensive model describing the morphogenesis of early root development in vertebrates.
Masticatory Function with Implant-supported Overdentures
Authors: van Kampen F.M.C. , van der Bilt A. , Cune M.S. , Fontijn-Tekamp F.A. , Bosman F.
Published: January 2009

The type of attachment that is used in implant-supported mandibular overdentures may influence the retention and stability of the prosthesis and, thus, masticatory function. In this within-subject cross-over clinical trial, we examined the hypothesis that greater retention and stability of the overdenture improve the masticatory function. Eighteen edentulous subjects received 2 oral implants, a new overdenture, and, successively, 3 different suprastructure modalities: magnet, ball, and bar-clip. Masticatory performance, masticatory efficiency, and swallowing threshold were measured. The masticatory function significantly improved after implant treatment with each of the 3 attachments. We observed small differences in masticatory function among the 3 attachment types: slightly better masticatory performance with ball and bar-clip than with magnet attachments. The number of chewing cycles until swallowing hardly decreased after implant treatment. We conclude that significantly better masticatory performance, combined with a slightly smaller number of chewing cycles after implant treatment, results in smaller food particles being swallowed.
Modulation of Clinical Expression of Plaque-induced Gingivitis: Effect of Incisor Crown Form
Authors: Trombelli L. , Farina R. , Manfrini R. , Tatakis D.N.
Published: January 2009

Evidence indicates that incisor crown form correlates with clinical periodontal features. It was hypothesized that incisor crown form may explain subject differences in gingivitis expression. The present experimental gingivitis study aimed to assess the effect of incisor crown form on plaque accumulation and gingival inflammation, and on individual susceptibility to plaque-induced gingivitis. Eighty-five periodontally healthy subjects were evaluated. A negative correlation was found between incisor crown width/crown length ratio and bleeding score (p = 0.045). From the 85 subjects, two groups of subjects with either ‘long-narrow’ or ‘short-wide’ incisor form were identified. The ‘long-narrow’ group had a significantly higher bleeding score than the ‘short-wide’ group (p = 0.014). No significant differences were found in the incisor crown width/crown length ratio between previously identified ‘high responder’ and ‘low responder’ subjects ( Trombelli et al., 2004a ). In conclusion, incisor crown form appears to affect the bleeding response of inflamed gingival tissues, while it exerts no influence on explaining differences in individuals’ susceptibility to plaque-induced gingivitis.
Collagen Cross-linking and Ultimate Tensile Strength in Dentin
Authors: Miguez P.A. , Pereira P.N.R. , Atsawasuwan P. , Yamauchi M.
Published: January 2009

Several studies have indicated differences in bond strength of dental materials to crown and root dentin. To investigate the potential differences in matrix properties between these locations, we analyzed upper root and crown dentin in human third molars for ultimate tensile strength and collagen biochemistry. In both locations, tensile strength tested perpendicular to the direction of dentinal tubules (undemineralized crown = 140.4 ± 48.6/root = 95.9 ± 26.1; demineralized crown = 16.6 ± 6.3/root = 29.0 ± 12.4) was greater than that tested parallel to the tubular direction (undemineralized crown = 73.1 ± 21.2/root = 63.2 ± 22.6; demineralized crown = 9.0 ± 3.9/root = 16.2 ± 8.0). The demineralized specimens showed significantly greater tensile strength in root than in crown. Although the collagen content was comparable in both locations, two major collagen cross-links, dehydrodihydroxylysinonorleucine/its ketoamine and pyridinoline, were significantly higher in the root (by ~ 30 and ~ 55%, respectively) when compared with those in the crown. These results indicate that the profile of collagen cross-linking varies as a function of anatomical location in dentin and that the difference may partly explain the site-specific tensile strength.
Head Movements during Chewing: Relation to Size and Texture of Bolus
Authors: Häggman-Henrikson B. , Eriksson P.-O.
Published: January 2009

Coordinated mandibular and head-neck movements during jaw opening-closing activities suggest a close functional linkage between the jaw and the neck regions. The present study investigated whether size and texture of bolus can influence head-neck behavior during chewing. Using an optoelectronic 3-D recording technique, we analyzed concomitant mandibular and head-neck movements in 12 healthy adults chewing small (3 g) and large (9 g) boluses of chewing gum and Optosil®. The main finding was a head extension during chewing, the amount of which was related mainly to bolus size. Furthermore, each chewing cycle was accompanied not only by mandibular movements, but also by head extension-flexion movements. Larger head movement amplitudes were correlated with larger size and, to some extent, also with harder texture of the bolus. The results suggest that head-neck behavior during chewing is modulated in response to changes in jaw sensory-motor input.
Chondroitin Sulfate in Palatal Wound Healing
Authors: Zou X.H. , Foong W.C. , Cao T. , Bay B.H. , Ouyang H.W. , Yip G.W.
Published: January 2009

Chondroitin sulfate is up-regulated in granulation tissue during wound healing. To investigate the role of chondroitin sulfate in the wound-healing process after surgical repair of cleft palate, we isolated and cultured rabbit palatal fibroblasts. Treatment with chondroitin-6-sulfate resulted in a dose-dependent increase in cell adhesion and cell proliferation, whereas the reverse effects were seen after chondroitinase degradation of chondroitin sulfate. The biological actions of chondroitin sulfate appeared to be dependent on the presence and position of sulfate groups. Inhibition of glycosaminoglycan sulfation by chlorate treatment led to reduced cell adhesion and cell proliferation and a slower rate of wound closure in vitro. Furthermore, exposure to chondroitin-4-sulfate resulted in a dose-dependent reduction in cell adhesion. Together, these results show that chondroitin sulfate is involved in palatal wound healing.
Parallels between Tooth Development and Repair: Conserved Molecular Mechanisms following Carious and Dental Injury
Authors: Mitsiadis T.A. , Rahiotis C.
Published: January 2009

The reparative mechanisms that operate following carious and traumatic dental injury are critical for pulp survival and involve a series of highly conserved processes. It appears that these processes share genetic programs—linked to cytoskeletal organization, cell movement, and differentiation—that occur throughout embryogenesis. Reactionary dentin is secreted by surviving odontoblasts in response to moderate stimuli, leading to an increase in metabolic activity. In severe injury, necrotic odontoblasts are replaced by other pulp cells, which are able to differentiate into odontoblast-like cells and produce a reparative dentin. This complex process requires the collaborative efforts of cells of different lineage. The behavior of each of the contributing cell types during the phases of proliferation, migration, and matrix synthesis as well as details of how growth factors control wound cell activities are beginning to emerge. In this review, we discuss what is known about the molecular mechanisms involved in dental repair.
Wear and Mechanical Properties of Nano-silica-fused Whisker Composites
Authors: Xu H.H. K. , Quinn J.B. , Giuseppetti A.A.
Published: January 2009

Resin composites must be improved if they are to overcome the high failure rates in large stress-bearing posterior restorations. This study aimed to improve wear resistance via nano-silica-fused whiskers. It was hypothesized that nano-silica-fused whiskers would significantly improve composite mechanical properties and wear resistance. Nano-silicas were fused onto whiskers and incorporated into a resin at mass fractions of 0%-74%. Fracture toughness (mean ± SD; n = 6) was 2.92 ± 0.14 MPa•m½ for whisker composite with 74% fillers, higher than 1.13 ± 0.19 MPa•m½ for a prosthetic control, and 0.95 ± 0.11 MPa•m½ for an inlay/onlay control (Tukey’s at 0.95). A whisker composite with 74% fillers had a wear depth of 77.7 ± 6.9 μm, less than 118.0 ± 23.8 μm of an inlay/onlay control, and 172.5 ± 15.4 μm of a prosthetic control (p < 0.05). Linear correlations were established between wear and hardness, modulus, strength, and toughness, with R = 0.95–0.97. Novel nano-silica-fused whisker composites possessed high toughness and wear resistance with smooth worn surfaces, and may be useful in large stress-bearing restorations.
Epitope Mapping of Porphyromonas gingivalis Heat-shock Protein and Human Heat-shock Protein in Human Atherosclerosis
Authors: Choi J.-I. , Chung S.-W. , Kang H.-S. , Rhim B.Y. , Park Y.-M. , Kim U.-S. , Kim S.-J.
Published: January 2009

To identify T- and/or cross-reactive B-cell epitopes of P. gingivalis and human heat-shock protein (HSP)60 in atherosclerosis patients, we synthesized 104 overlapping synthetic peptides spanning whole molecules of P. gingivalis HSP60 and human HSP60, respectively. T-cell epitopes of P. gingivalis HSP were identified with the use of previously established P. gingivalis HSP-reactive T-cell lines. B-cell epitopes of P. gingivalis HSP60 and human HSP60 were identified by the use of patients’ sera. Anti- P. gingivalis, anti- P. gingivalis HSP60, or anti-human HSP60 IgG antibody titers were higher in the atherosclerosis patients compared with the healthy subjects. Five immunodominant peptides of P. gingivalis HSP60, identified as T-cell epitopes, were also found to be B-cell epitopes. Moreover, 6 cross-reactive B-cell epitopes of human HSP60 were identified. It was concluded that P. gingivalis HSP60 might be involved in the immunoregulatory process of atherosclerosis, with common T- and/or B-cell epitope specificities and with cross-reactivity with human HSP60.
The Challenges of Validating Diagnostic Methods Relative to a Conventional Two-year Caries Clinical Trial
Authors: Biesbrock A.R. , Chesters R.K. , Ellwood R.P. , Smith S.R.
Published: January 2009

This paper is directed to the question, “What are the appropriate validation criteria for the use of a new clinical trial methodology as a replacement for a conventional two- to three-year caries study?” It is important to recognize that the objective of a two- to three-year randomized, controlled caries trial is to test a precisely framed hypothesis, regarding an experimental product's efficacy relative to a control product. The external validity of conventional two- to three-year caries clinical studies in determining the efficacy and safety of anti-caries products is well-accepted. However, caries clinical trials are not without limitations and have increasingly been viewed as inefficient with respect to measuring the disease process in a holistic manner. The endpoint of a caries lesion with loss of enamel integrity (cavitation) focuses on one end of the caries progression continuum at the expense of early caries initiation and progression. Several early caries detection methods have been developed that correlate with mineral loss of the tooth surface. These diagnostics differ from conventional visual-tactile and radiographic methods in that they are capable of detecting early non-cavitated lesions, and this can generate continuous data. As diagnostic methods become accepted, they will lead to study designs that diverge from the conventional two- to three-year caries studies. Modification of the existing two- to three-year conventional caries design for assessment of product effectiveness, whether by the introduction of a new diagnostic method or by modification of the overall clinical design, must result in a clinical design that is able to differentiate known treatments on the basis of caries prevention efficacy. Given that the fluoride dose response has been characterized in the literature, this should form the basis of any validation package for new methodologies. In conclusion, a minimum expectation for acceptance as a replacement to conventional testing should be that the method or design can differentiate products of known efficacy from one another and that the efficacy relationship observed in a two- to three-year conventional study can be observed with the new method or design.
DIAGNOdent: An Optical Method for Caries Detection
Authors: Lussi A. , Hibst R. , Paulus R.
Published: January 2009

The onset of caries is characterized by demineralization of dental hard tissues. Optimal fluoridation with respective oral hygiene habits and diet may stop the progression of a lesion and even allow for its remineralization. The aim of modern dentistry must be a preventive approach rather than invasive repair of the disease. This is possible only with early detection and respective preventive measures. Some of today's diagnostic tools are not sensitive enough to detect this early onset of destruction. Tools based on fluorescence could have the possibility to overcome this problem. This overview will focus on today's knowledge of one possible tool, the DIAGNOdent.
Optical Methods—Quantitative Light Fluorescence
Authors: Stookey G.K.
Published: January 2009

Considerable research during the past two decades has focused upon the development of new technologies for the detection of dental caries. Of these technologies, the method that has been most extensively studied is based upon the indirectly assessed changes in the fluorescence of enamel associated with the loss of mineral. The purpose of this presentation was to review the available information regarding the use of this technology, commonly known as quantitative light fluorescence, for caries detection, particularly early caries detection, and the potential for the routine use of this technology in clinical caries trials. This technology is unique in its ability to measure small changes in the mineral content of enamel lesions quantitatively. The results of recent small-scale clinical trials have indicated that the impact of caries-preventive measures can be determined within a six-month period. With current hardware and software refinements and the results of long-term clinical validation studies that are in progress, it may be that this technology will be the future method of choice for caries clinical trials.
Statistical Issues for Combining Multiple Caries Diagnostics for Demonstrating Caries Efficacy
Authors: Katz B.P. , Huntington E.
Published: January 2009

Caries efficacy in clinical trials has been based primarily on visual examinations supplemented by Fiber Optic Transillumination (FOTI) and radiography, with the assessments combined at the surface level to classify each surface as to its caries status. Newer caries diagnostics techniques measure the caries process in a quantitative manner and so thus yield continuous rather than ordinal results. The objective of this study was to examine various methods for the analysis of multiple outcomes in clinical trials and to compare their usefulness for the analysis of caries trials. Four global tests (rank sum, ordinary least squares, general least squares, and generalized estimating equations) and two caries indices (based on average and maximum values of the methods) were evaluated with the use of one-year follow-up data from 1063 children in a recent caries trial. A new hybrid method was also developed and evaluated. All of the methods performed well when the diagnostic measures showed product differences in caries in the same direction. Ease of use, interpretability, and distributional assumptions must be considered before a consensus method for analysis of multiple diagnostic measures in caries trials can be determined.
The Junctional Epithelium: from Health to Disease
Authors: Bosshardt D.D. , Lang N.P.
Published: January 2009

The junctional epithelium is located at a strategically important interface between the gingival sulcus, populated with bacteria, and the periodontal soft and mineralized connective tissues that need protection from becoming exposed to bacteria and their products. Its unique structural and functional adaptation enables the junctional epithelium to control the constant microbiological challenge. The antimicrobial defense mechanisms of the junctional epithelium, however, do not preclude the development of gingival and periodontal lesions. The conversion of the junctional to pocket epithelium, which is regarded as a hallmark in disease initiation, has been the focus of intense research in recent years. Research has shown that the junctional epithelial cells may play a much more active role in the innate defense mechanisms than previously assumed. They synthesize a variety of molecules directly involved in the combat against bacteria and their products. In addition, they express molecules that mediate the migration of polymorphonuclear leukocytes toward the bottom of the gingival sulcus. Periodontopathogens—such as Actinobacillus actinomycetemcomitans or, in particular, Porphyromonas gingivalis—have developed sophisticated methods to perturb the structural and functional integrity of the junctional epithelium. Research has focused on the direct effects of gingipains, cysteine proteinases produced by Porphyromonas gingivalis, on junctional epithelial cells. These virulence factors may specifically degrade components of the cell-to-cell contacts. This review will focus on the unique structural organization of the junctional epithelium, on the nature and functions of the various molecules expressed by its cells, and on how gingipains may attenuate the junctional epithelium’s structural and functional integrity.
Increase in Cariogenic Bacteria after Initial Periodontal Therapy
Authors: De Soete M. , Dekeyser C. , Pauwels M. , Teughels W. , van Steenberghe D. , Quirynen M.
Published: January 2009

This study examined the hypothesis of an intra-oral shift, during initial periodontal therapy, from a periopathogenic to a cariogenic flora. Seventy-one patients with periodontitis were randomly allocated to one of the following treatment strategies: (1) scaling and root planing, quadrant by quadrant, at two-week intervals (NC); (2) full-mouth scaling and root planing within 24 hrs (FRP); or (3) full-mouth disinfection within 24 hrs, including antiseptics [chlorhexidine (CHX) or amine fluoride/stannous fluoride (F) for 2 mos, or CHX for 2 mos followed by F for 6 mos (CHX+F)]. At baseline and after 2, 4, and 8 mos, bacterial samples were taken from supra- and subgingival plaque, saliva, and tongue. The detection frequencies and relative proportions of Streptococcus mutans increased in the NC and FRP groups, but decreased in the F group. In the CHX group, these species disappeared temporarily, but they disappeared for the entire 8 mos in the CHX+F group. These observations were similar for all sample locations. The periopathogens decreased in all groups. This finding confirms the abovementioned hypothesis and indicates a need for caries prophylactic regimens.
Salivary Proteins Interact with Dietary Constituents to Modulate Tooth Staining
Authors: Proctor G.B. , Pramanik R. , Carpenter G.H. , Rees G.D.
Published: January 2009

Dietary components rich in polyphenols—for example, tea and red wine—are thought to cause tooth staining. In the present study, hydroxyapatite was used as a model of enamel for study of the influence of salivary proteins on the binding of different polyphenols to hydroxyapatite in vitro. Neither salivary protein pellicles nor salivary proteins in solution significantly altered the binding of the small polyphenol epigallocatechin to hydroxyapatite. However, hydroxyapatite binding of anthocyanin, a small grape-skin-derived polyphenol, or the larger polyphenols of black tea was increased by the presence of salivary proteins, either as a pellicle or in solution. Proline-rich proteins were enriched from parotid saliva and found to increase binding of anthocyanin and black tea polyphenols to hydroxyapatite, while enriched histatins did not increase binding. It is concluded that some salivary proteins, including proline-rich protein, can mediate increased staining of enamel by red-wine- and black-tea-derived polyphenols.
Inhibition of Root Caries Progression by an Antibacterial Adhesive
Authors: Kuramoto A. , Imazato S. , Walls A.W.G. , Ebisu S.
Published: January 2009

A dentin primer containing the antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB) has been shown to penetrate and kill the bacteria in artificially demineralized dentin. We hypothesized that an experimental adhesive system, which incorporates the MDPB-containing primer, would be effective in inhibiting the progression of root caries in vitro. Artificial caries lesions were prepared by either an acid-gel or a Streptococcus mutans culture technique on the roots of extracted human teeth. The progression of these lesions after the application of the experimental or proprietary adhesive system was examined. Further demineralization was completely prevented by the experimental adhesive system, while lesions managed with the proprietary materials showed limited ability to inhibit further demineralization. We conclude that the experimental adhesive system can inhibit the progression of root-surface caries in vitro, through a combination of its antimicrobial activity and sealing of the demineralized dentin.
Design and Validation of Anti-inflammatory Peptides from Human Parotid Secretory Protein
Authors: Geetha C. , Venkatesh S.G. , Bingle L. , Bingle C.D. , Gorr S.-U.
Published: January 2009

Parotid secretory protein (PSP) and palate-lung-nasal epithelium clone (PLUNC) are novel secretory proteins that are expressed in the oral cavity and upper airways. Both proteins are related to bactericidal/permeability increasing protein (BPI). Cationic peptides derived from BPI exhibit anti-inflammatory activity. To test if PSP (C20orf70 gene product) also contains anti-inflammatory peptides, we designed 3 cationic peptides based on the predicted structure of PSP and known active regions of BPI. Each peptide inhibited the lipopolysaccharide (LPS)-stimulated secretion of TNFα from RAW 264.7 macrophage cells. At 200 μg/mL, the peptide GK-7 exhibited inhibition similar to that achieved with 10 μg/mL of polymyxin B. PSP peptides directly inhibited the binding of LPS to LPS-binding protein. The cationic peptide Substance P had no inhibitory effect in these assays, confirming the specificity of the PSP peptides. These findings suggest that PSP peptides can serve as templates for the design of novel anti-inflammatory peptides.
Oral and Dental Aspects of Chronic Renal Failure
Authors: Proctor R. , Kumar N. , Stein A. , Moles D. , Porter S.
Published: January 2009

The present article reviews, in detail, the current knowledge of the oral and dental aspects of chronic renal failure (CRF). Worldwide, increasing numbers of persons have CRF; thus, oral health care staffs are increasingly likely to provide care for patients with such disease. Chronic renal failure can give rise to a wide spectrum of oral manifestations, affecting the hard or soft tissues of the mouth. The majority of affected individuals have disease that does not complicate oral health care; nevertheless, the dental management of such individuals does require that the clinician understand the multiple systems that can be affected. The clinician should also consider the adverse side-effects of drug therapy and appropriate prescribing, in view of compromised renal clearance.
Expression of Protein Kinases C βI, βII, and VEGF during the Differentiation of Enamel Epithelium in Tooth Development
Authors: Aida M. , Irié T. , Aida T. , Tachikawa T.
Published: January 2009

Protein kinase C (PKC) is an important molecule involved in various cell function, and mediates induced secretion of vascular endothelial growth factor (VEGF). It is hypothesized that PKC and VEGF may be associated with tooth development. Using the laser microdissection method and real-time reverse-transcription-polymerase chain-reaction (RT-PCR), we investigated the expression of PKC βI and βII, VEGF, and amelogenin (used as a marker of differentiation to ameloblasts) in the inner and outer enamel epithelia, stellate reticulum, and dental papilla in each stage of the dental germ. We found that the expression levels of PKC βI and βII were increased in the inner enamel epithelium during the early bell stage. In addition, the increased expression levels of PKC βI and βII were accompanied by increased VEGF expression. These results indicate that PKC βI, βII, and VEGF are closely associated with the differentiation of the inner enamel epithelium to ameloblasts.
Thiazolidinedione (Pioglitazone) Blocks P. gingivalis- and F. nucleatum, but not E. coli, Lipopolysaccharide (LPS)-induced Interleukin-6 (IL-6) Production in Adipocytes
Authors: Yamaguchi M. , Nishimura F. , Naruishi H. , Soga Y. , Kokeguchi S. , Takashiba S.
Published: January 2009

An elevated level of C-reactive protein (CRP) predicts the future development of coronary heart disease. Periodontitis appears to up-regulate CRP. CRP is produced by hepatocytes in response to interleukin-6 (IL-6). A major source of IL-6 in obese subjects is adipocytes. We hypothesized that lipopolysaccharide (LPS) from periodontal pathogens stimulated adipocytes to produce IL-6, and that the production was suppressed by the drugs targeted against insulin resistance, thiazolidinedione (pioglitazone), since this agent potentially showed an anti-inflammatory effect. Mouse 3T3-L1 adipocytes were stimulated with E. coli, P. gingivalis, and F. nucleatum LPS. The IL-6 concentration in culture supernatants was measured. All LPS stimulated adipocytes to produce IL-6. Although pioglitazone changed adipocyte appearance from large to small, and completely suppressed P. gingivalis and F. nucleatum LPS-induced IL-6 production, E. coli LPS-induced IL-6 production was not efficiently blocked. Thus, pioglitazone completely blocked periodontal-bacteria-derived LPS-induced IL-6 production in adipocytes, a major inducer of CRP.
Modulation of Gingival Fibroblast Minocycline Accumulation by Biological Mediators
Authors: Walters J.D. , Nakkula R.J. , Maney P.
Published: January 2009

Gingival fibroblasts actively accumulate tetracyclines, thereby enhancing their redistribution from blood to gingiva. Since growth factors and pro-inflammatory cytokines regulate many fibroblast activities, they could potentially enhance fibroblast minocycline accumulation. To test this hypothesis, we treated gingival fibroblast monolayers for 1 or 6 hours with platelet-derived growth factor-BB (PDGF), fibroblast growth factor-2 (FGF), transforming growth factor-β1 (TGF), or tumor necrosis factor-α (TNF). Minocycline uptake was assayed at 37° by a fluorescence method. All 4 factors significantly enhanced minocycline uptake (P ≤ 0.008, ANOVA), primarily by increasing the affinity of transport. Treatment for 6 hours with 10 ng/mL FGF, PDGF, TGF, or TNF enhanced fibroblast minocycline uptake by 19% to 25%. Phorbol myristate acetate enhanced fibroblast minocycline uptake by 28%, suggesting that protein kinase C plays a role in up-regulating transport. These effects on transport provide a mechanism by which systemic tetracyclines could be preferentially distributed to gingival wound or inflammatory sites.
Initial Subgingival Colonization of ‘Pristine’ Pockets
Authors: Quirynen M. , Vogels R. , Pauwels M. , Haffajee A.D. , Socransky S.S. , Uzel N.G. , van Steenberghe D.
Published: January 2009

The treatment of periodontitis/peri-implantitis involves the reduction/eradication of periopathogens. After therapy, beneficial and pathogenic species recolonize the subgingival area. The dynamics of recolonization and especially the role of the supragingival environment in this process are still not well-understood. This prospective, split-mouth study followed the early colonization of ‘pristine’ pockets created during implant surgery (16 partially edentulous patients), to record the time needed before a complex subgingival flora could be established with the supragingival area as the single source. Four subgingival plaque samples were taken from shallow and medium pockets around implants (test), and neighboring teeth (undisturbed microbiota as reference) 1, 2, and 4 wks after abutment connection. Checkerboard DNA-DNA hybridization and culture data revealed a complex microbiota (including several pathogenic species) in the pristine pockets within a wk, with a minimal increase in counts up to 4 wks. Analysis of these data demonstrated that, even with the supragingival environment as the single source for colonizing bacteria, a complex subgingival microbiota can develop within 1 wk.
Viscoelasticity of Dental Tissue Conditioners during the Sol-gel Transition
Authors: Murata H. , Chimori H. , Hamada T. , McCabe J.F.
Published: January 2009

Formation of tissue conditioners is a process of polymer chain entanglements. This study evaluated the influence of composition and structure on dynamic viscoelasticity of concentrated polymer solutions based on poly(ethyl methacrylate) (PEMA) used as tissue conditioners through the sol-gel transition. The hypothesis was that the ethanol content is the most influential factor in determining gelation speed. Rheological parameters were determined with the use of a controlled-stress rheometer. Analysis of variance by orthogonal array L16(45) indicated that the strong polar bonding of ethanol (contribution ratio ρ = 53.8%; confirming the hypothesis) and molecular weight of polymer powders (ρ = 26.7%) had a greater influence on the gelation times of PEMA-based systems than did the molar volume of plasticizers (ρ = 9.0%) and concentration of polymers ( i.e., powder/liquid ratio) (ρ = 4.5%). The results suggest that the gelation of tissue conditioners based on PEMA can be controlled over a wide range by varying the polymer molecular weight, and especially ethanol content.
Impaired Cytotoxicity in Papillon-Lefèvre Syndrome
Authors: Lundgren T. , Parhar R.S. , Renvert S. , Tatakis D.N.
Published: January 2009

Papillon-Lefèvre syndrome (PLS), palmoplantar hyperkeratosis with periodontitis, has been genetically characterized. However, suspected associated immune dysfunctions remain elusive. The purpose of this study was to evaluate peripheral blood lymphocyte levels and natural killer (NK) cell cytotoxicity in PLS. Twenty patients and 20 healthy controls were examined. Peripheral blood lymphocytes were analyzed by flow cytometry for surface markers. NK cell cytotoxicity against K562 cells was determined by means of a 51Cr release assay. White blood cell differential and proportions of B-, T-, T-helper, T-suppressor, and NK cells revealed only sporadic borderline variations from control values. In contrast, NK cell cytotoxicity was consistently and severely depressed (32–53% of control values) in all patients. To the best of our knowledge, this newly described impairment of NK cell cytotoxic function is the first consistent immune dysfunction reported in PLS. This suggests that the impaired NK cell cytotoxicity might contribute to the pathogenesis of PLS-associated periodontitis.
Platelet-rich Plasmas: Growth Factor Content and Roles in Wound Healing
Authors: Fréchette J.-P. , Martineau I. , Gagnon G.
Published: January 2009

Platelet-rich plasmas (PRPs) are used in a variety of clinical applications, based on the premise that higher growth factor content should promote better healing. In this study, we have determined the effects of calcium and thrombin on the release of EGF, TGF-α, IGF-1, Ang-2 and IL-1β from PRPs, and assessed the mitogenic potential of PRP supernatants on osteoblast and endothelial cell division. ELISA assays indicate that (i) mean growth factor concentrations vary from traces (TGF-α) to 5.5 ng/mL (IGF-1), (ii) there are significant variations in growth factor concentrations between individuals, and (iii) calcium and thrombin regulate growth factor release, synthesis, and/or degradation in stereotyped patterns that are specific to each growth factor. PRP supernatants promote strong osteoblast and endothelial cell divisions, supporting the concept that PRPs may be beneficial in wound healing. Abbreviations: PRPs, platelet-rich plasmas; GFs, growth factors; EGF, epidermal growth factor; TGF-α, transforming growth factor-alpha; IGF-1, insulin-like growth factor-1; Ang-2, angiopoietin-2; IL-1β, interleukin-1 beta; HUVECs, human umbilical vein endothelial cells; hFOB 1.19, human fetal osteoblasts; and FBS, fetal bovine serum.
Parotid Secretory Granules: Crossroads of Secretory Pathways and Protein Storage
Authors: Gorr S.-U. , Venkatesh S.G. , Darling D.S.
Published: January 2009

Saliva plays an important role in digestion, host defense, and lubrication. The parotid gland contributes a variety of secretory proteins—including amylase, proline-rich proteins, and parotid secretory protein (PSP)—to these functions. The regulated secretion of salivary proteins ensures the availability of the correct mix of salivary proteins when needed. In addition, the major salivary glands are targets for gene therapy protocols aimed at targeting therapeutic proteins either to the oral cavity or to circulation. To be successful, such protocols must be based on a solid understanding of protein trafficking in salivary gland cells. In this paper, model systems available to study the secretion of salivary proteins are reviewed. Parotid secretory proteins are stored in large dense-core secretory granules that undergo stimulated secretion in response to extracellular stimulation. Secretory proteins that are not stored in large secretory granules are secreted by either the minor regulated secretory pathway, constitutive secretory pathways (apical or basolateral), or the constitutive-like secretory pathway. It is proposed that the maturing secretory granules act as a distribution center for secretory proteins in salivary acinar cells. Protein distribution or sorting is thought to involve their selective retention during secretory granule maturation. Unlike regulated secretory proteins in other cell types, salivary proteins do not exhibit calcium-induced aggregation. Instead, sulfated proteoglycans play a role in the storage of secretory proteins in parotid acinar cells. This work suggests that unique sorting and retention mechanisms are responsible for the distribution of secretory proteins to different secretory pathways from the maturing secretory granules in parotid acinar cells.
Enamel Matrix Derivative Gel Stimulates Signal Transduction of BMP and TGF-β
Authors: Suzuki S. , Nagano T. , Yamakoshi Y. , Gomi K. , Arai T. , Fukae M. , Katagiri T. , Oida S.
Published: January 2009

It has been shown that Emdogain® Gel (Emd-Gel) containing enamel matrix proteins promotes biomineralization, such as osteogenesis and cementogenesis, during the regeneration of periodontal tissues. However, the growth factors involved in these activities of Emd-Gel remain unclear. In this study, Emd-Gel was fractionated into 22 sub-fractions by size exclusion chromatography. The osteoinductive factors, TGF-β and BMP, were examined by a specific luciferase reporter gene assay. In the unfractionated Emd-Gel, TGF-β-like activity was detected, while BMP activity was not. In contrast, in the fractionated Emd-Gel samples, TGF-β-like activity was detected from fractions 8 to 13, and BMP-like activity was detected from fractions 4 to 6. Also, it was confirmed that the BMP-like activity in Emd-Gel was inhibited by authentic TGF-β1 and TGF-β-like activity. These results indicate that Emd-Gel contains both TGF-β- and BMP-like growth factors that contribute to the induction of biomineralization during periodontal regeneration.
Molecular and Biomechanical Characterization of Mineralized Tissue by Dental Pulp Cells on Titanium
Authors: Nakamura H. , Saruwatari L. , Aita H. , Takeuchi K. , Ogawa T.
Published: January 2009

The application of implant therapy is still limited, because of various risk factors and the long healing time required for bone-titanium integration. This study explores the potential for osseointegration engineering with dental pulp cells (DPCs) by testing a hypothesis that DPCs generate mineralized tissue on titanium. DPCs extracted from rat incisors positive for CD44, alkaline phosphatase activity, and mineralizing capability were cultured on polystyrene and on machined and dual-acid-etched (DAE) titanium. Tissue cultured on titanium with a Ca/P ratio of 1.4 exhibited plate-like morphology, while that on the polystyrene exhibited fibrous and punctate structures. Tissues cultured on titanium were harder than those on polystyrene, 1.5 times on the machined and 3 times on the DAE. Collagen I, osteopontin, and osteocalcin genes were up-regulated on titanium, especially the DAE surface. In conclusion, DPCs showing some characteristics of the previously identified dental pulp stem cells can generate mineralized tissue on titanium via the osteoblastic phenotype, which can be enhanced by titanium surface roughness.
Dental Epithelial Histomorphogenesis in vitro
Authors: Hu B. , Nadiri A. , Bopp-Küchler S. , Perrin-Schmitt F. , Lesot H.
Published: January 2009

Recent developments in tooth-tissue engineering require that we understand the regulatory processes to be preserved to achieve histomorphogenesis and cell differentiation, especially for enamel tissue engineering. Using mouse first lower molars, our objectives were: (1) to determine whether the cap-stage dental mesenchyme can control dental epithelial histogenesis, (2) to test the role of the primary enamel knot (PEK) in specifying the potentialities of the dental mesenchyme, and (3) to evaluate the importance of positional information in epithelial cells. After tissue dissociation, the dental epithelium was further dissociated into individual cells, re-associated with dental mesenchyme, and cultured. Epithelial cells showed a high plasticity: Despite a complete loss of positional information, they rapidly underwent typical dental epithelial histogenesis. This was stimulated by the mesenchyme. Experiments performed at E13 demonstrated that the initial potentialities of the mesenchyme are not specified by the PEK. Positional information of dental epithelial cells does not require the memorization of their history.
Cyclosporin A Affects Signaling Events Differentially in Human Gingival Fibroblasts
Authors: Bostrom A. , Bharath H. , Saulewicz A. , Narayanan A.S.
Published: January 2009

Gingival overgrowth is a common side-effect of the administration of cyclosporin A (CSA), phenytoin, and calcium blockers. To identify the signaling mechanisms possibly involved in the overgrowth, we examined how CSA affects the activities of MAP kinases and transcription factors in human gingival fibroblasts (HGF). The HGF were treated with CSA and TNF-α or PDGF. DNA-binding activity of NFAT, NFκB, and AP-1 transcription factors was determined by gel shift assay, and JNK, p38, and ERK1 and ERK2 activation was assessed by Western blot analysis of immunoprecipitates. The CSA inhibited NFAT, NFκB, and p38 and JNK activities; however, ERK1 and ERK2 were not affected significantly. AP-1 activity increased ~ 4.5-fold. Our results indicate that CSA affects signaling molecules in HGF differently from other cell types, and that a CSA-induced increase in AP-1 activity may affect the expression of fibrogenic molecules in gingiva and promote gingival overgrowth.
Organized Tooth-specific Cellular Differentiation Stimulated by BMP4
Authors: Ohazama A. , Tucker A. , Sharpe P.T.
Published: January 2009

Mammalian teeth develop on the oral surface of the first pharyngeal arch by a series of reciprocal interactions between epithelial and mesenchymal cells. The embryonic first pharyngeal arch oral epithelium is able to induce tooth formation when combined with mesenchymal cells from the second pharyngeal arch, a region devoid of tooth development. Second pharyngeal arch mesenchyme is thus competent to form teeth if provided with the correct signals. First-arch oral epithelium expresses several signaling molecules that could be potential inducers of tooth development, including BMP4. The addition of BMP4 to intact second-arch explants resulted in the development of organized structures containing layers of cells that express marker genes of tooth-specific cells, odontoblasts and ameloblasts. Thus, although overt tooth development did not occur, BMP4 has the ability to stimulate organized differentiation of epithelial- and mesenchymal-derived dental-specific cells from non-dental primordia.
NO-cGMP Signaling Molecules in Cells of the Rat Molar Dentin-Pulp Complex
Authors: Korkmaz Y. , Baumann M.A. , Steinritz D. , Schröder H. , Behrends S. , Addicks K. , Schneider K. , Raab W.H.-M. , Bloch W.
Published: January 2009

By the formation of cyclic guanosine 3′,5′-monophosphate (cGMP), nitric oxide (NO)-sensitive enzyme-soluble guanylate cyclase (sGC) plays a receptor role for NO within the NO-cGMP signaling cascade, which is involved in vasodilatation and neurotransmission. The hypothesis that NO-cGMP signaling molecules modulate cells of the dentin-pulp complex was investigated in rat molars by histochemical, immunohistochemical, immuno-ultrastructural, and organ bath techniques. NO synthase (NOS) I-III, the sGC α2-subunit/β1-subunit, and cGMP were detected in odontoblasts and blood vessels. NOS I, sGC α2, and cGMP were identified in nerve fibers. Treatment of rat molars with the NO donor NONOate (10−5 M) increased cGMP staining intensities in blood vessels and odontoblasts, while NO synthase inhibitor L-NAME (10−4 M) attenuated intensity of the reaction products for cGMP, suggesting an effect of endogenous NO on sGC. These correlations of patterns and alterations of cGMP staining intensities after treatment with the NO donor or NO inhibitor might represent an NO-sGC-cGMP signaling-dependent modulation of odontoblasts, blood vessels, and nerve fibers in the dentin-pulp complex.
Effect of Occlusal Interference on Habitual Activity of Human Masseter
Authors: Michelotti A. , Farella M. , Gallo L.M. , Veltri A. , Palla S. , Martina R.
Published: January 2009

It has been suggested that occlusal interference may increase habitual activity in the jaw muscles and may lead to temporomandibular disorders (TMD). We tested these hypotheses by means of a double-blind randomized crossover experiment carried out on 11 young healthy females. Strips of gold foil were glued either on a selected occlusal contact area (active interference) or on the vestibular surface of the same tooth (dummy interference) and left for 8 days each. Electromyographic masseter activity was recorded in the natural environment by portable recorders under interference-free, dummy-interference, and active-interference conditions. The active occlusal interference caused a significant reduction in the number of activity periods per hour and in their mean amplitude. The EMG activity did not change significantly during the dummy-interference condition. None of the subjects developed signs and/or symptoms of TMD throughout the whole study, and most of them adapted fairly well to the occlusal disturbance.
Monomer Conversion of Pre-heated Composite
Authors: Daronch M. , Rueggeberg F.A. , De Goes M.F.
Published: January 2009

The potential for maximizing conversion of room-temperature, photoactivated resin composite in the oral environment is limited. Pre-heating composite prior to light-curing is hypothesized to increase monomer conversion and reduce the duration of light exposure. Composite temperature was controlled at between 3°C and 60°C prior to exposure with a conventional quartz-tungsten-halogen curing unit: 5, 10, 20, or 40 sec. Monomer conversion was calculated from infrared spectra at 0 mm (top) and 2-mm-deep surfaces 5 min after light initiation. A strong, positive correlation existed between temperature and monomer conversion: top r2 = 0.999, 2 mm r2 = 0.998. Conversion ranged from 31.6% (3°C) to 67.3% (60°C). The duration of light exposure, reduced by 50 to 75% with pre-heated composite, yielded the same or significantly higher conversion (p = 0.001) than with control (22°C, 20 sec). Both hypotheses were accepted: Pre-heating composite prior to photoactivation provides greater conversion requiring reduced light exposure than with room-temperature composite.
New Coronal Caries in Older Adults: Implications for Prevention
Authors: Griffin S.O. , Griffin P.M. , Swann J.L. , Zlobin N.
Published: January 2009

To characterize the extent and severity of coronal caries among older US adults and document their need for prevention interventions, we systematically reviewed studies on coronal caries incidence, increment, and attack rate. We abstracted six studies and calculated summary measures using a random-effects model (95% confidence interval [95%CI]). We tested for heterogeneity and identified associated factors by examining the correlation between outcome measures and baseline population risk and study characteristics. We re-calculated summary measures after adjusting outcomes that netted out examiner reversals. Incidence and increment varied significantly by study. Adjusting studies for netting out examiner reversals reduced heterogeneity significantly. Annual attack rate among adjusted North American studies was 1.4 surfaces per 100 surfaces (95%CI = 1.0–1.9), or approximately 1 new carious surface per person per year. These rates are equal to or higher than those in children and indicate a need for caries-prevention services.
EDTA Treatment Improves Resin-Dentin Bonds’ Resistance to Degradation
Authors: Osorio R. , Erhardt M.C.G. , Pimenta L.A.F. , Osorio E. , Toledano M.
Published: January 2009

The existence of unprotected collagen fibrils within the hybrid layer compromises the longevity of restorations. This phenomenon may be avoided if solutions other than strong acids are used for dentin demineralization. The hypothesis to be tested is that bond durability may be improved by EDTA demineralization. Dentin surfaces (human and bovine) were bonded: (1) after phosphoric-acid-etching, and after EDTA demineralization with (2) a total-etch adhesive and (3) a self-etching adhesive. After the teeth were sectioned into beams, half of the specimens were immersed in NaOCl, while the other half was immersed in water. Beams were tested to failure in tension. ANOVA and multiple-comparisons tests were used (P < 0.05). No differences in bond strength were found among the 3 bonding procedures, although bonds made to human molars were 43-61% higher than those to bovine incisors. After NaOCl immersion, only specimens subjected to EDTA demineralization maintained the initial bond strength. We conclude that the collagen network is better-preserved after EDTA demineralization.