bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on Dental Stains Induced by Antibacterial Agents and Rational Approaches for Bleaching Dental Stains
Authors: Nathoo S.A. , Gaffar A.
Published: January 2009

Extrinsic stain resides in the dental pellicle and can be caused by introduction of chromogenic materials or therapeutic agents into the oral cavity. In contrast, intrinsic tooth stain is found within the tooth structure and can be caused by a variety of agents, including hematological and developmental abnormalities and drugs such as tetracycline. The mechanisms of extrinsic stain formation differ with respect to the causative agent. For example, stain induced by chlorhexidine (CH) can be explained by an increased rate in the non-enzymatic browning reactions occurring at the pellicle surface, while food stains are retained on the surface via ion exchange mechanisms. Although most extrinsic dental stain can be removed by abrasive and/or surface-active materials, removal of certain types of surface stain, e.g., staining due to cationic antimicrobial agents, requires specific agents such as aminoguanidine to reduce the stain.

A broad-spectrum approach to reduce both intrinsic and extrinsic dental stains clinically requires oxygenating agents. To evaluate this approach and understand the mechanisms of stain removal, we developed a spectroscopic method for measuring stain in vivo. A series of clinical studies was performed to evaluate stain removal by the agents. The results showed that carbamide peroxide in combination with surfactants and anti-redeposition agents, e.g., sodium pyrophosphate, was more effective in bleaching dental stain compared with carbamide peroxide alone. A detailed examination of the tooth structure by microhardness measurements, x-ray photoelectron spectroscopy, and scanning electron microscopy showed that stain decolorization with this system did not have any adverse effects.
Investigation of Factors Influencing Stain Formation Utilizing an in Situ Model
Authors: Joiner A. , Jones N.M. , Raven S.J.
Published: January 2009

In order to understand the factors of extrinsic stain formation more fully, we have developed an in situ stain model. This consists of polished bovine enamel blocks attached to partial or full dentures worn by adult volunteers for 24 h per day. The dentures were cleaned twice daily with a commercial dentifrice and toothbrush, with care taken to avoid brushing the inserts. A Minolta CR321 Chroma Meter in the L*a*b* mode was used for taking reflectance measurements of the stain formed on the enamel inserts. From these values, changes in the color of the inserts were calculated and the level of stain determined. In general, the stain formed on the enamel inserts was yellow and increased in intensity and darkness with time. The enamel inserts with the largest stain increases were from smokers rather than non-smokers. No correlation was observed between amount of stain and quantity of tea and coffee consumed. When the effects of surface roughness on in situ stain formation were considered, the major variable in this study was found to be the location of the enamel insert in the denture rather than the surface roughness.
Differentiation of Dry Mouth Etiology
Authors: Fox P.C.
Published: January 2009

Dry mouth is a common complaint. While it is often considered to be synonymous with the diagnosis of salivary gland disease, this is not the case. There are many causes of the symptomatic complaint of oral dryness, both salivary and non-salivary. This paper will review the causes of "dry mouth" and the means of establishing the underlying diagnosis.
Is Sialography Effective in Diagnosing the Salivary Component of Sjögren's Syndrome?
Authors: Daniels T.E. , Benn D.K.
Published: January 2009

Parotid sialography has been used for many years as a means of assessing salivary glands in Sjogren's syndrome (SS), and it is occasionally used as a diagnostic criterion for the salivary component of SS. To assess its diagnostic effectiveness, we reviewed studies in which sialography was applied to patients with SS and control subjects for the purpose of estimating its diagnostic sensitivity and specificity or comparing it with other means of assessing salivary glands. Sialography appears to be diagnostically less sensitive but more specific than salivary flow rate measurement and more sensitive but less specific than labial salivary gland (LSG) biopsy. Such calculations are based on the diagnosis of SS established in each study, but the various studies used widely different criteria to establish that diagnosis. Therefore, these calculations are not based on a consistent standard, and comparison between the calculations may be misleading, which underscores the need to develop internationally accepted diagnostic criteria for SS. Studies conducted so far have not shown that parotid sialography is either a sensitive indicator of the salivary component of SS or more closely associated than LSG biopsy with keratoconjunctivitis sicca. the only other component of primary SS with which ultimately to assess diagnostic specificity.
Pathophysiology of Antinuclear Antibodies in Systemic Lupus Erythematosus and Related Diseases
Authors: Tan E.M.
Published: January 2009

Antinuclear antibodies in systemic lupus erythematosus (SLE) and related diseases have been used for characterizing nuclear antigens and for elucidating immune mechanisms that drive the autoimmune response. Each disease has its own characteristic profile of antinuclear antibodies, which has been useful for diagnostic purposes. In the biological context, concepts emerging from studies on nuclear antigens and antibodies show that the autoimmune response is antigen-driven, that autoantigens are components of subcellular particles involved in important biosynthetic functions, and that the epitopes recognized by autoantibodies are active sites or functional domain regions of these antigens. An intriguing hypothesis is that activated intracellular particles are the immunogens that drive the autoimmune response.
Autoimmune Mechanisms Involved in the Pathogenesis of Rheumatoid Arthritis
Authors: Williams R.C.
Published: January 2009

Rheumatoid arthritis (RA) was one of the first systemic disorders to be considered an autoimmune disease. Two major aspects of RA suggest a fundamental immune-mediated derangement in the disease: (1) presence of often massive lymphocytic infiltrates and activated CD4(+) T cells within the inflamed hypertrophied synovium, and (2) production of large amounts of rheumatoid factor (RF) by B-cells and plasma cells in the involved synovium itself. The actual tissue damage to joints and extra-articular structures affected by the disease comes from the rheumatoid inflammatory pannus or granulomatous collections of cells called rheumatoid nodules. RF production has long been studied as a prime example of apparent autoantibody production in association with the basic underlying disease process. RA patients who belong to subtype HLA DR4, Dw4 (DR B1 or 0401, Dw14 (0404/0408), or Dw15 (0405/0410) are most likely to be seropositive for RF and to have severe progressive disease. RFs are felt to represent an autoantibody associated with RA, since they show principal specificity for structures on the Cγ3 and C γ2 (Fc) domains of IgG. Recent work by our group has defined a number of solvent-exposed linear RF-reactive epitopes on Cγ3 and Cγ2 using a strategy of overlapping 7-mers of primary sequence. RFs also have been demonstrated to react with two different regions, SKDWSFY and LSQPKIVKWDR, on β2-microglobulin (β 2m). Many of the RF-reactive sites on Cγ2 and C γ3 as well as on β2m show common immunodominant valines, leucines, tryptophanes, arginines, lysines, and glutamines, thus comprising common reactive residues. In the future, this approach may provide more direct insight into the specificities of other autoantibodies.
Autoimmune Aspects of Pemphigus Vulgaris and Mucosal Pemphigoid
Authors: Sciubba J.J.
Published: January 2009

Oral mucosal lesions of ulcerative, desquamative, and bullous character are major problems for clinicians and patients alike. Underlying such processes is the autoimmune reaction manifesting as specific subsets of immunopathology. Responsible for the maintenance of mucosal integrity within the oral cavity are numerous adhesion proteins which operate at the cell-to-cell and cell-to-connective-tissue-matrix level. Two of the better-understood conditions characterized by altered or disordered levels of adherence are the pemphigus and the pemphigoid groups of lesions.

Autoantibodies in pemphigus vulgaris specifically attack normal proteins within the desmosomal structure. Cellular adhesion is affected by steric interference by antibodies directed against antigens residing within the intercellular space or the desmosome itself. Such alterations ultimately result in cell-to-cell separation, with production of the acantholytic element characteristic of pemphigus vulgaris.

Mucous membrane pemphigoid is characterized by a separation at the junction of the epithelium and connective tissue at the level of the basement membrane complex. Histologically, a split occurs in the sub-basilar region, with antibodies directed to the 230-kDa protein component of the hemidesmosome. Minor antigens residing within the basement membrane area include a 180-kDa element as well as other less commonly found proteins near the membrane complex. Manifestations of these illnesses are often severe. Management strategies of pemphigus vulgaris have changed over the recent past, with new modalities supplementing the traditional corticosteroid approach. Both conditions are usually lifelong, with the implications of management a major consideration.
The Association Between Immunodeficiency and the Development of Autoimmune Disease
Authors: Sleasman J.W.
Published: January 2009

There is a paradoxical relationship between immunodeficiency diseases and autoimmunity. While not all individuals with immunodeficiency develop autoimmunity, nor are all individuals with autoimmunity immunodeficient, defects within certain components of the immune system carry a high risk for the development of autoimmune disease. Inherited deficiencies of the complement system have a high incidence of systemic lupus erythematosus (SLE), glomerulonephritis, and vasculitis. Carrier mothers of children with chronic granulomatous disease, an X-linked defect of phagocytosis, often develop discoid lupus. Several antibody deficiencies are associated with autoimmune disease. Autoimmune cytopenias are commonly observed in individuals with selective IgA deficiency and common variable immune deficiency. Polyarticular arthritis can be seen in children with X-linked agammaglobulinemia. Combined cellular and antibody deficiencies, such as Wiskott-Aldrich syndrome, carry an increased risk for juvenile rheumatoid arthritis and autoimmune hemolytic anemia. Several hypothetical mechanisms have been proposed to explain the associations between autoimmunity and immunodeficiency. Immunologic defects may result in a failure to exclude microbial antigens, resulting in chronic immunologic activation and autoimmune symptoms. There may be shared genetic factors, such as common HLA alleles, which predispose an individual to both autoimmunity and immunodeficiency. Defects within one component of the immune system may alter the way a pathogen induces an immune response and lead to an inflammatory response directed at self-antigens. An understanding of the immunologic defects that contribute to the development of autoimmunity will provide an insight into the pathogenesis of the autoimmune process.
Opportunistic Oral Infections in the Immunosuppressed Patient: Oral Hairy Leukoplakia and Oral Candidiasis
Authors: Sciubba J.J.
Published: January 2009

Several opportunistic infections associated with immunosuppression are noted to occur secondary to an altered relationship between host and organism. In relation to diminished host immunologic defenses, associated commensal organisms may evolve to a pathogen state. Candidiasis. a common oral marker disease reflective of immunosuppression, results from dysfunction of complex cellular interactions keyed by depressed T-cell activity or function. Certain viral infections may also serve as probable markers of immunosuppression. One such infection is typified by the development of oral hairy leukoplakia, a condition highly correlated to HIV infection in most, but not all, patients. Detection of Epstein-Barr virus particles and subsequent molecular analytic verification of such and the absence of other potential viral candidates, such as papilloma and human immunodeficiency viruses, have led to a general acceptance of this virus as the cause of this condition.
Animal Models for Autoimmune Disease-Associated Xerostomia and Xerophthalmia
Authors: Humphreys-Beher M.G.
Published: January 2009

Numerous models of exocrine tissue pathology related to autoimmune initiation of disease have been described, primarily by either immunohistology or histopathology. These model systems include inbred mouse strains that develop systemic lupus erythematosus, rheumatoid arthritis, graft vs. host disease, and diabetes. Commonly observed features of these mice include organized lymphocytic foci, composed of CD4+ and CD8+ T-cells, in both the salivary and the lacrimal glands. However, only the diabetic mouse model (NOD) undergoes a corresponding loss in exocrine gland function related to the presence of lymphocytic infiltrates. As we define the underlying pathophysiology of Sjögren's syndrome, the future of animal models for this disease will involve genetic exploration of candidate genes for development of autoimmune exocrinopathy.
Cellular Interactions in the LPR and GLD Models of Systemic Autoimmunity
Authors: Sobel E.S.
Published: January 2009

The lpr and gld murine models have been important contributors to our understanding of systemic autoimmune diseases. Mice homozygous for either of these autosomal recessive genes develop a phenotypically identical disease characterized by the accumulation of CD4-CD8- T-cells and the production of a wide spectrum of autoantibodies. The lpr (lymphoproliferation) mutation encodes a defective Fas apoptosis receptor gene. More recently, gld (generalized lymphadenopathy) has been shown to be a point mutation in the Fas ligand gene. Despite the molecular characterization of these mutations, the exact mechanism by which tolerance is lost is still unknown, although in vivo cell transfer studies have provided clues. Chimera studies, in which normal and lpr bone marrow were co-infused into lpr mice, demonstrated not only that the normal Fas receptor is functionally expressed in both T- and B-cells, but that the Fas mutation is required in both for full expression of the lpr phenotype. Conversely, in analogous experiments with gld mice, co-infusion of normal and gld bone marrow largely prevented the development of autoantibodies. Sporadic autoantibody titers were seen in some mice, but were derived from both donors. The effects on T-cells were subtly different: The CD4-CD8- T-cells were also greatly reduced in number, but all were of gld origin. These data indicate that the gld defect is extrinsic to B-cells but only partially extrinsic to T-cells, and suggest that Fas ligand in T-cells may have an autocrine and paracrine function.
Immunohistochemical Localization of Signal Transduction Pathways During Amelogenesis: an Initial Exploration
Authors: Bawden J.W. , Moran R.A. , Deaton T.G. , Saour C.M.
Published: January 2009

This study was undertaken to map signal transduction pathway (STP) components uniquely associated with the four major receptor groups and their related STPs in association with the events involved in amelogenesis in the rat. Whole-head, freeze-dried sagittal sections were obtained at the level of the maxillary first molars and picked up on transparent adhesive tape. The sections were not decalcified or fixed, providing optimum conditions for immunohistochemical (IHC) localization. Antibodies to pathway components Gsa, Giα, Gqα, Sos-1, Grb-2, p125Fak, Jak2, and Vav were localized. The respective patterns of localization indicate that the G a-linked, the receptor tyrosine kinase-initiated, and the integrin receptor-initiated pathways are involved in the proliferating pre-ameloblast cells. In the differentiating and differentiated ameloblasts, the Gsa-linked cAMP pathway is involved, apparently reading a factor(s) released by the dentin matrix. The G a-linked, the receptor tyrosine kinase-initiated, the integrin receptor-initiated, and the cytokine receptor-initiated pathways are also up-regulated in the proximal ends of the ameloblasts. These observations indicate that all four of the major receptor groups are involved in amelogenesis and that the role of classes of ligands not previously implicated in enamel formation must now be considered. It seems that the cells of the enamel organ respond to the appearance and disappearance of autocrine and paracrine growth factors, but they also up-regulate specific STPs to enable them to respond to circulating hormones and growth factors whose concentrations in the extracellular fluids remain relatively constant.
Primary Structure of the Porcine 89-kDa Enamelin
Authors: Fukae M. , Tanabe T. , Murakami C. , Dohi N. , Uchida T. , Shimizu M.
Published: January 2009

The primary structure of the 89-kDa enamelin found in porcine secretory enamel at an early stage of development was investigated. The fragments of the enamelin cDNA were amplified by polymerase chain-reaction from the first-strand enamelin cDNA, and were sequenced. The results indicated that the 89-kDa enamelin consisted of 627 amino acid residues and had a molecular mass of 70,448. A hydrophobic domain is located in the region of the 21 st-62nd amino acid residues of the molecule. Acidic domains are located in two regions of the molecule-one in the region of the 135th-238th amino acid residues and the other in the C-terminal region. A basic domain is located in the region of the 239th-360th amino acid residues. The results also indicated that the low-molecular-weight enamelins were fragments derived from a prototype enamelin.
Comparative HPLC, SDS-PAGE, and Immunoblot Analyses of Dental Enamel Proteins
Authors: Ryu O.H. , Hu C.-C. , Simmer J.P.
Published: January 2009

The primary structures of amelogenins expressed from different genes vary because of DNA sequence divergence and variations in alternative RNA splicing. The pattern of splicing is unique for each amelogenin gene yet investigated, even when two copies of the gene are expressed in the same cell. Despite the high conservation of amelogenin sequences, diversity in the pattern of RNA splicing leads to significant differences in the number and character of amelogenin isoforms in the developing enamel matrix. Since conservation of molecular structure is an indicator of functional significance, we compared enamel protein preparations from rat, porcine, rabbit, and opossum developing tooth organs. Enamel extracts were fractionated by reversed-phase high-performance liquid chromatography (HPLC) and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Western blot analyses were performed with polyclonal antibodies raised against recombinant murine amelogenin and the polypeptide encoded by murine exon 4.

The opossum enamel extract produced the simplest chromatogram, suggesting that fewer proteins are secreted into the developing enamel matrix. The predominant opossum amelogenin has an apparent molecular mass of 28 kDa and reacts strongly with the recombinant amelogenin antibody but is not recognized by the murine exon 4 antibody. Opossum amelogenin mRNA was amplified with murine amelogenin primers specific for the amino- and carboxyl-terminal coding regions. The mobility of the amplification products on 4% agarose gels indicates that the leucine-rich amelogenin polypeptide (LRAP) is expressed in the opossum and that the major amelogenin is larger than its homologue in the mouse. We conclude that the alternative splicing of amelogenins pre-dates the metatherian and eutherian divergence over 100 million years ago.
Developmental Changes in the PH of Enamel Fluid and Its Effects On Matrix-Resident Proteinases
Authors: Smith C.E. , Issid M. , Margolis H.C. , Moreno E.C.
Published: January 2009

The objectives of this study were to measure pH in developing enamel at progressively older (more mature) stages of amelogenesis in vivo, and then to formulate synthetic enamel fluid mixtures that approximated these pH values for in vitro studies. The ultimate goal was to characterize the molecular weights of proteinases visualized by enzymograms incubated in synthetic enamel fluid using gelatin and casein as substrates. For most experiments. the proteinases were extracted en masse from small freeze-dried enamel strips directly into a non-reducing sample preparation buffer. In some experiments, we pre-treated the enamel strips with acetic acid to determine if this common method for demineralization and protein extraction caused any changes in the activity levels of the enamel proteinases. In other experiments, we first soaked enamel strips in synthetic enamel fluid to determine solubility of the proteinases within an aqueous phase. The results indicated that the pH of developing enamel remained fairly constant near pH 7.23 across the secretory stage, but it was generally more acidic (6.93) and fluctuated in focal areas between mildly acidic (6.2-6.8) and near-neutral (7.2) conditions across the maturation stage. The pH then slowly rose to near 7.35 when the enamel was almost mature (hard). The acidic conditions were generally inhibitory to most enamel proteinases, but there were some caseinase activities in mid-maturation-stage enamel near 23-30 kDa which appeared to be activated by weakly acidic conditions (pH 6.28). Pre-treatment of enamel samples with 0.5 M acetic acid markedly altered the overall profile of enamel proteinases, causing activation of some latent proteinase activities and permanent inhibition of other activities. Most proteinases in whole homogenates were insoluble in synthetic enamel fluid. This suggests that they may be tightly bound, directly or indirectly, to matrix proteins or mineral components in situ.
Possible Actions of Metalloproteinases Found in Porcine Enamel in an Early Secretory Stage
Authors: Tanabe T. , Fukae M. , Shimizu M.
Published: January 2009

In an outermost layer of porcine secretory enamel, metalloproteinases were detected by enzymography with gelatin used as a substrate. When the sample extracted from the outermost layer of the secretory enamel was incubated with calcium ions at 37°C prior to electrophoresis, an increase of the 34-kDa proteinase activity and a decrease of the 76- and/or 78-kDa proteinase activities were observed. The results suggest that the metalloproteinases mediate the conversion from 76- and/or 78-kDa proteinases to the 34-kDa proteinase or the activation of a latent type of the 34-kDa proteinase, and that their activities are regulated by free Ca ions.
Crystal Growth in Dental Enamel: the Role of Amelogenins and Albumin
Authors: Robinson C. , Brookes S.J. , Kirkham J. , Bonass W.A. , Shore R.C.
Published: January 2009

Amelogenin-mineral interactions were investigated using an in vitro binding approach. Rat incisor enamel matrix proteins (mainly amelogenins) were dissolved in synthetic enamel fluid and allowed to equilibrate with deproteinised developing enamel crystals. The results showed that amlogenin proteins of 21, 23, 24, 26 and 27-kDa (corresponding to nascent and partially degraded amelogenins) were associated with the crystals whilst the lower Mr amelogenins (<21KDa) remained free in the synthetic enamel fluid. These data suggest the nascent and partially degraded amelogenins may interact with developing enamel crystals and could influence their growth. Albumin-mineral interactions were investigated by extracting developing rat incisor enamel with synthetic enamel fluid. Insoluble material (including the enamel crystals) was then further extracted with 0.1 M phosphate buffer (pH 7.4) to desorb any mineral bound proteins. Western blotting using anti-albumin antibodies showed that almost all of the albumin from the secretory stage enamel and a significant proportion of the albumin present in early transition stage was extractable in the synthetic enamel fluid. However. synthetic enamel fluid did not extract albumin from late transition or maturation stage tissue, which could only be removed following further extraction with phosphate buffer. Albumin degradation was apparent during the transition and maturation stages, where it is degraded and ultimately removed. This binding pattern may be related to amelogenin degradation and removal during the transition stage,. permitting albumin access to the previously obscured crystal surfaces. That the secretory stage matrix appears to "protect" secretory stage crystals from albumin may be an important consideration in the aetiology of enamel hypoplasias (i.e. incomplete crystal growth) and when using dissociative extraction procedures for the identification of mineral bound proteins.
High Expression of Human Amelogenin in E. Coli
Authors: Deutsch D. , Chityat E. , Hekmati M. , Palmon A. , Farkash Y. , Dafni L.
Published: January 2009

A human cDNA, encoding for the 175-aminoacid human amelogenin, was prepared by RT PCR from tooth bud mRNA and sub-cloned into pGEX-KG expression plasmid for over-expression in E. coli. The expressed protein was characterized by SDS-PAGE, Western blotting, and N-terminal amino acid sequencing.
Gene Expression and Localization of Amelogenin in the Rat Incisor
Authors: Inage T. , Shimokawa H. , Wakao K. , Sasaki S.
Published: January 2009

Gene expression and localization of amelogenin were studied in the developing rat incisor by the methods of in situ hybridization and immunohistochemistry. ISH revealed the first expression of amelogenin mRNA in the inner enamel epithelium of the cervical loop. The signals were clearly observed in pre-ameloblasts in the region bordering on predentin formation and became more intense toward the cells on the initial enamel matrix secretion. The maximal signals were found in the cytoplasm of secretory ameloblasts. From the terminal secretion zone, the signals then became gradually weaker toward the incisal edge but were still evident in the cytoplasm of shortening, transitional ameloblasts and those at the early maturation stage. No signals were found in the cells of the stratum intermedium and stellate reticulum throughout amelogenesis. Immunohistochemistry by means of an antibody against amelogenin C-telopeptide consisting of 12 amino acids revealed immunoreaction in the secretory ameloblasts reacting to the ISH. When a polyclonal antibody against amelogenin was used, immunoreaction was found in the distal ends of ruffle-ended ameloblasts (RA) in the maturation zone. Those results indicated that amelogenin is synthesized by ameloblastic cells from the inner enamel epithelium to the early maturation stage and is then resorbed by the RA.
Disturbed Enamel Mineralization in a Rat Incisor Model
Authors: Sato K. , Hattori M. , Aoba T.
Published: January 2009

Possession of full-thickness hard enamel appears to be one of the indispensable life-saving characteristics of rats. Previous studies by Suga and his colleagues and by others demonstrated that various types of malformation are evoked in continuously erupting rat incisors. In the current report, we directed our effort to oversee various types of enamel malformation caused experimentally in rat incisors. We surveyed the specimens collected by Suga and his colleagues, as well as specimens we obtained. From the results, it is conceivable that perturbation of the programmed sequential events during enamel development is a major factor in the establishment of enamel malformation. Animal studies with either 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) or a multidentate phosphonic acid (EDTPO) confirmed that dentin mineralization provides a certain inductive effect on the secretion of enamel matrix and subsequent enamel crystallization. Our recent studies using anti-microtubular agents led to the conclusion that the acceleration of mineralization in outer enamel is a type of enamel malformation, most likely due to disruption of the cellular regulation of calcium transport under severe toxic regimens. In future work, experimental approaches combining measurements of kinetic factors with static observation of enamel lesions are required before we can gain a comprehensive understanding of the pathogenesis of disturbed enamel mineralization. The kinetic factors to be considered include the rates of tissue apposition and tooth eruption which determine the total volume of tooth substance formed, and the rate of mineral accretion. Furthermore, information as to the composition, crystallinity, solubility, and mechanical properties of enamel defects is needed before we can assess the susceptibility of teeth having those lesions to caries and other physico-chemical attacks in the oral environment.
Anion Translocation Through the Enamel Organ
Authors: Prostak K.S. , Skobe Z.
Published: January 2009

The objective of this study was to determine whether cells of the secretory- and maturation-stage enamel organ of rats contain anion translocation mechanisms similar to those found in other ion-regulating epithelia. Sodium bromide (Br) was used to localize the distribution of anions in the enamel organ. Furosemide, an inhibitor of the Na-K-2C1 co-transporter and other anion transporters, was administered with NaBr or sodium fluoride (F) to investigate if halogens other than Cl can use these transport mechanisms. We obtained the data by using freeze-fracture and freeze-drying methodology in conjunction with scanning and transmission electron microscopy (SEM, TEM) and energy-dispersive x-ray spectroscopy (EDS).

The secretory- and maturation-stage enamel organ prevented Br from entering the enamel matrix. Br was localized in the Tomes' processes, but not in the enamel matrix, strongly suggesting that the distal intercellular junctions of ameloblasts are "tight". Furosemide disrupted anion transport to allow not only Cl but also Br to enter the forming enamel matrix.

Periodic administration of high F doses promoted the formation of bands of disrupted enamel, reflecting the periodicity of F administration. The same concentration of F administered with furosemide increased the severity of disrupted enamel, resulting in "blisters" and pits in the maturing enamel. The enamel "blisters" contained pools of small, disorganized enamel crystallites. The group receiving furosemide only displayed normal enamel structure but had increased C1 in the enamel matrix. This study provides evidence that anion transporters, possibly the Na-K-2CI co-transporter, function to regulate anion translocation, including F, to the enamel matrix in secretory- and maturation-stage enamel organ. These mechanisms may explain why the ionic composition on the cellular side of the anion barrier is different from that of the enamel matrix.
Properties of Heterogeneous Apatites Containing Magnesium, Fluoride, and Carbonate
Authors: Okazaki M. , Legeros R.Z.
Published: January 2009

Biological apatites present in the mineral phases of normal and pathological calcifications contain magnesium, Mg, and carbonate, CO3. As a consequence of fluctuations in the composition of the micro-environment, these apatites may sometimes form by heterogeneous precipitation. The purpose of this study was to investigate the properties of (Mg, CO3)-apatites formed heterogeneously in the presence of fluoride, F. Two types of fluoridated (Mg, CO3)-apatites formed from solutions with low and high levels of Mg were prepared at 80°C, pH 7.4. We prepared FMgCO3-MgCO 3AP (Type 1) by adding the F-containing solution to those containing calcium, Mg, and phosphate ions during the first half of the precipitation period. We prepared MgCO3-FMgCO3Ap (Type 2) by adding the F-containing solution during the final half of the period. The apatites were analyzed by x-ray diffraction (XRD), infrared absorption spectroscopy, and scanning electron microscopy (SEM).

SEM and XRD analyses showed evidence of mixed crystals in the heterogeneous apatites. The presence of Mg inhibits, while F promotes, apatite crystal growth. In addition, Mg incorporation increased with increasing fluoride concentration. The extent of dissolution in acid buffer of both types of heterogeneous apatites increased with Mg: Type 1 > Type 2.

These results suggest that the crystal and dissolution properties of heterogeneous fluoridated (Mg, C03)-apatites are greatly affected by the mode of F incorporation and Mg concentrations in the environment.
Effects of Accelerated Eruption On the Enamel of the Rat Lower Incisor
Authors: Risnes S. , Møinichen C.B. , Septier D. , Goldberg M.
Published: January 2009

The effect of accelerated eruption of the rat lower incisor on enamel was studied in a series of segments obtained when the incisor was cut repeatedly out of occlusion over a five-week period. The segments were ground, cleaned, acid-etched, observed with SEM, and analyzed with EDX. Pigmentation was lost within 11 days. Pigmented superficial enamel was more acid-resistant than the rest of the enamel, but this quality decreased with decreasing iron content. Hypomineralized enamel first appeared in a restricted area at the mesio-labial angle of the tooth in the 6th-7th segment obtained after 11-14 days. Later, hypomineralization became more generalized. All enamel zones were retained throughout the experiment. The geometry of the prism pattern was affected. The angle between prism rows and the enamel-dentin junction increased from 44° to 48°, while the angle of decussation increased from 60° to 70°. The angle between the enamel surface and prisms in the outer enamel was more difficult to assess, but tended to increase from about 25° to 29°. However, the prisms retained their incisal direction. The connection between enamel and dentin was partly disrupted from about the 9th segment onward. The depth of the mesial concavity of the enamel-dentin junction decreased from about the 10th segment onward. Accelerated eruption affects all stages of enamel formation and is a suitable and predictable model for studying regulatory mechanisms in amelogenesis.
Enamel Mineral Composition of Normal and Cystic Fibrosis Transgenic Mice
Authors: Wright J.T. , Hall K.I. , Grubb B.R.
Published: January 2009

The ability of ameloblasts and the enamel organ to control the influx of ions into the developing enamel is of considerable interest. The development of transgenic mice lacking a cAMP-regulated chloride channel, the cystic fibrosis transmembrane conductance regulator (CFTR), provides a model that may prove valuable for the study of ion regulation in developing teeth. The purpose of this investigation was to characterize the mineral content of normal and CF mice. Five homozygous and five heterozygous adult mice having the CFTR knockout transgene were evaluated. The mice were killed with CO2 and their mandibular incisors removed, embedded in methacrylate, and sectioned, and enamel particles from the incisal region were then dissected for analysis. Each particle was analyzed for its calcium, phosphorus, and magnesium content. The normal mice had a mean mineral content of 80.5%, in contrast to the CF mice, that had markedly hypomineralized enamel (mean = 51.5%). The calcium/ phosphorus ratios were similar for both groups of mice and were compatible with the enamel consisting primarily of hydroxyapatite mineral. The enamel magnesium content was significantly elevated in the CF mice (mean = 3560 ppm) compared with the normal mice (mean = 2280 ppm). Normal mouse enamel was highly mineralized, while the CF mouse enamel mineral content was significantly reduced and had an elevated level of magnesium. The altered mineral content of CF mouse enamel indicates that CFTR could play an important role in ion regulation and consequently mineralization of mouse enamel.
Dendritic Cells: A Novel Cellular Component of the Rat Incisor Enamel Organ Appearing in the Late Stages of Enamel Maturation
Authors: Takano Y. , Kawahara I. , Hoshino M. , Takeuchi K. , Maeda T. , Ohshima H. , Hanaizumi Y. , Kawano Y.
Published: January 2009

Immunocompetent cells in the enamel organ of rat incisors were examined immunohistochemically using OX6, ED1, and ED2 monoclonal antibodies known to recognize the Class II MHC molecules, a monocyte-macrophage lineage, and residential macrophages, respectively. The OX6 immunopositive cells (MHC cells) were located exclusively in the enamel maturation zone. MHC cells increased in number in the incisal direction and occasionally extended cytoplasmic processes deep into the ameloblast layer. Migration of MHC cells in the ameloblast layer were also encountered. MHC cells lacked phagolysosomes and could be distinguished from typical macrophages. ED2 immunopositive cells were not seen in the enamel organ. ED1 positive cells displayed identical localization to MHC cells except that some appeared in the transitional zone. MHC cells could not be seen in the enamel organ of rat molar tooth germs. Our data confirmed the presence of a large population of "dendritic" immunocompetent cells in the enamel organ of rat incisors and characterized the ultrastructural features of these cells. Biological significance of the immunocompetent cells in the enamel organ during amelogenesis needs to be clarified.
Growth Dynamics in a Natural Biofilm and Its Impact on Oral Disease Management
Authors: Liljemark W.F. , Bloomquist C.G. , Reilly B.E. , Bernards C.J. , Townsend D.W. , Pennock A.T. , Lemoine J.L.
Published: January 2009

Measurements of the microbial growth dynamics in natural biofilm communities are almost non-existent. In a recent study, the biofilm formation on teeth was examined. A previously unknown active period of bacterial division occurred at a certain density of plaque bacteria on tooth enamel. The density-dependent cell-division phase of plaque formation contributed 90% of the biomass in the first 24 hrs of plaque formation. This suggested that growth was induced by the bacteria. In vitro assays were developed for rapid evaluation of the growth of surface-linked bacteria by the measurement of cellular components associated with growth on a per cell per time basis. Cell-free supernatants (termed START) of media in contact with bacteria were assayed for their effects on DNA synthesis and other cellular components associated with growth. START was found to increase the incorporation of [3H- methyl ]-thymidine on a per cell per time basis, when compared with media not in contact with bacteria. Additional in vivo studies and in situ-based models of complex biofilms are needed if all of the mechanisms involved in the rapid accumulation of biofilm bacteria on teeth and other surfaces are to be understood.
Physiological Approaches to the Control of Oral Biofilms
Authors: Marsh Philip D. , Bradshaw David J.
Published: January 2009

Evidence that physiological strategies may be potential routes for oral biofilm control has come from (i) observations of the variations in the intra-oral distribution of members of the resident oral microflora, (ii) changes in plaque composition in health and disease, and (iii) data from laboratory model systems. Key physiological factors that were identified as significant in modulating the microflora included the local pH, redox potential (Eh), and nutrient availability. Increases in mutans streptococci and lactobacilli occur at sites with caries; growth of these species is selectively enhanced at low pH. In contrast, periodontal diseases are associated with plaque accumulation, followed by an inflammatory host response. The increases in Gram-negative, proteolytic, and obligately anaerobic bacteria reflect a low redox potential and a change in nutrient status due to the increased flow of gingival crevicular fluid (GCF). Consequently, physiological strategies for oral biofilm control should focus on reducing the frequency of low pH in plaque by (i) inhibiting acid production, (ii) using sugar substitutes, and (iii) promoting alkali generation from arginine or urea supplements. Similarly, strategies to make the pocket environment less favorable to periodontopathogens include (i) anti-inflammatory agents to reduce the flow of (and hence nutrient supply by) GCF, (ii) bacterial protease inhibitors, and (iii) redox agents to raise the Ehh locally. Most laboratory and clinical findings support the concept of physiological control. However, some data suggest that the ordered structure and metabolically interactive organization of mature dental plaque could generate a community with a high level of homeostasis that is relatively resistant to deliberate external manipulation.
Physico-Chemical Interactions in Initial Microbial Adhesion and Relevance for Biofilm Formation
Authors: Busscher H.J. , Van Der Mei H.C.
Published: January 2009

This paper summarizes initial microbial adhesion events in dental plaque formation, including the physico-chemistry of the interaction between micro-organisms and solid substrata, detachment phenomena under the fluctuating shear of the oral cavity, co-adhesion between pairs of microbial strains, and biosurfactant release. A hypothesis is forwarded on how these initial events might influence the final microbial composition and structure of the plaque, although it is simultaneously emphasized that the necessary techniques for verification of the hypothesis have only recently become available, and supporting evidence is still to be collected.
Germ Theory Vs. Community Theory in Understanding and Controlling the Proliferation of Biofilms
Authors: Caldwell Douglas E. , Atuku Elijah , Wilkie Darryl C. , Wivcharuk Kyle P. , Karthikeyan Subramanian , Korber Darren R. , Schmid Dirk F. , Wolfaardt Gideon M.
Published: January 2009

Germ theory and pure culture methods have provided invaluable information concerning the role of bacteria in diseases resulting from a single organism which bypasses a host's defenses. However, they do not provide sufficient information concerning the synergisms which allow the members of biofilm communities to proliferate more effectively as communities rather than as individuals. The mechanisms of these synergies are potential targets for antimicrobial agents as well as potential mechanisms of resistance to antimicrobial agents. Understanding community-level phenomena in oral biology requires the culture, identification, and classification of functional plaque communities as well as new methods of identifying and quantifying communal relationships. Cultured biofilm communities also provide ideal models of bacterial self-organization in which information related to adaptive strategies arises not only through the recombination of genes within genomes, but also through the recombination of organisms within communities.
Consequences of Biofilm and Sessile Growth in the Large Intestine
Authors: Macfarlane S. , McBain A.J. , Macfarlane G.T.
Published: January 2009

The human colonic ecosystem is an extremely complex environment comprised of several hundred different strains of bacteria. Studies were undertaken to determine whether these organisms formed metabolic or genotypically distinct assemblages in the gut microbiota in relation to polysaccharide fermentation. Measurements of depolymerizing enzymes (4 polysac-charidases, 6 glycosidases) showed that specific amylase and pectinase activities were comparable in bacteria desorbed from the surfaces of food particles and in non-particulate organisms. However, xylanase, β-xylosidase, arabinogalac-tanase, a-arabinofuranosidase, and β-galacturonidase activities were always significantly greater in particulate bacteria. Short-term in vitro fermentations with both groups of bacteria showed marked differences in relative rates of starch, arabinogalactan, and mucin metabolism, while rates of fermentation product formation with pectin and xylan were broadly comparable. Significant differences were observed with respect to formation of individual fermentation products, especially when mucin or pectin were substrates, where particulate bacteria produced proportionally higher amounts of acetate. Bacteriological studies showed that communities of polymer-degrading bacteria and other groups of intestinal anaerobes growing on particulate matter were essentially similar to those occurring elsewhere in the gut lumen, at genus and species levels. In vitro colonization experiments demonstrated that a variety of polysaccharide-fermenting bifidobacteria and bacteroides-together with other cross-feeding organisms such as peptostreptococci, fusobacteria, and coliforms-rapidly attached to particulate intestinal materials.
Host-Pathogen Interactions in Bacterial Endocarditis: Streptococcal Virulence in the Host
Authors: Herzberg Mark C. , Meyer Maurice W. , Kiliç Ali , Lin Tao
Published: January 2009

To identify streptococcal genes that are expressed during experimental endocarditis, we developed a promoter-less dual reporter gene-fusion (amy, cat) plasmid, pAK36. Chromosomal DNA from S. gordonii V288 was digested with Sau3Al. The resulting fragments were ligated into pAK36. Following transformation into S. gordonii, the library of random gene fusion clones was inoculated into a rabbit to induce experimental endocarditis. Chloramphenicol treatment effected positive selection. Upon euthanization of the rabbits, the valvular vegetations were excised in a sterile field. Surviving clones were isolated and screened in vitro for chloramphenicol sensitivity and negative amylase activity. From the 48 randomly picked, double-negative clones. DNA was isolated and analyzed by Southern hybridization with labeled pAK36 probe. Different insertion patterns were identified, suggesting that no fewer than 13 S. gordonii genes were induced. Therefore, S. gordonii genes are induced during experimental endocarditis, which may contribute to virulence.
ICS-II USA Research Design and Methodology
Authors: Rana H. , Andersen R.M. , Nakazono T.T. , Davidson P.L.
Published: January 2009

The purpose of the WHO-sponsored International Collaborative Study of Oral Health Outcomes (ICS-II) was to provide policy-makers and researchers with detailed, reliable, and valid data on the oral health situation in their countries or regions, together with comparative data from other dental care delivery systems. ICS-II used a cross-sectional design with no explicit control groups or experimental interventions. A standardized methodology was developed and tested for collecting and analyzing epidemiological, sociocultural, economic, and delivery system data. Respondent information was obtained by household interviews, and clinical examinations were conducted by calibrated oral epidemiologists. Discussed are the sampling design characteristics for the USA research locations, response rates, sample size for interview and oral examination data, weighting procedures, and statistical methods. SUDAAN was used to adjust variance calculations, since complex sampling designs were used.