bluuebunny/crossref_metadata_2025 huggingface dataset:
Coaggregation of Eikenella Corrodens with Oral Bacteria Mediated by Bacterial Lectin-Like Substance
Authors: Ebisu S. , Nakae H. , Okada H.
Published: January 2017

E ikenella corrodens 1073, which has been shown to induce a periodontal syndrome in experimental animals, was found to coaggregate with eight of 42 oral bacterial strains examined. The mechanism(s) of coaggregation between E. corrodens 1073 and Actinomyces viscosus ATCC 19246, A. viscosus T14AV, Streptococcus sanguis 34, and S. sanguis ST160R was studied. Coaggregation reactions were not inhibited by 1 mol/L NaCl, were pH-dependent, and required calcium ions. Heating (100°C, 10 min) and trypsin or pronase treatment of E. corrodens cells abolished their ability to coaggregate with untreated A. viscosus or S. sanguis cells. Identical treatment of A. viscosus or S. sanguis cells did not affect their reactions with untreated E. corrodens cells. The coaggregations were significantly inhibited by N-acetyl-D-galactosamine- and D-galactose-containing sugars. These results suggested that E. corrodens 1073 coaggregates with certain strains of A. viscosus and S. sanguis by specific cell-surface interactions between lectin-like substances on E. corrodens and sugar receptors on its partner.
Clinical Application of Tissue Reflectance Spectrophotometry to Periodontal Disease
Authors: Shizukuishi S. , Hanioka T. , Tsunemitsu A.
Published: January 2017

Rapid, accurate, and non-invasive measurements of hemodynamics and oxygen utilization in gingiva are clinically important in evaluation of the severity of the inflammatory response in periodontal disease. In the present study, tissue reflectance spectrophotometry was used to examine gingiva in vivo to estimate hemoglobin concentration (Hb index) and the oxygen saturation level of hemoglobin in gingiva (HbSO2 index). Reflectance spectrophotometry was also used to examine these parameters in experimental periodontitis in dogs, and in patients with periodontal disease.

Both in vitro and in vivo experiments confirmed that the Hb index was positively correlated with hemoglobin concentration in gingival tissue. The relationship between the HbSO2 index and PO2 in gingiva was a sigmoid curve resembling the hemoglobin-oxygen dissociation curve. In rapidly advancing periodontitis resulting from ligature placement in dogs, the Hb index was significantly enhanced, but the HbSO2 index was reduced. This reduction corresponded to increases in gingival inflammation during the experiments. Furthermore, in humans, the Hb index was significantly higher in inflamed gingiva than in clinically healthy gingiva. A lower HbSO2 index was also found in inflamed gingiva. These findings are consistent with congested blood vessels, impaired venous return, and localized hypoxia in inflamed gingival tissue.

Tissue reflectance spectrophotometry is clinically useful in estimating blood volume and oxygen saturation in diseased gingiva.
X-Ray Micro-Analysis of the Mineralization Patterns in Developing Enamel in Hamster Tooth Germs Exposed To Fluoride in Vitro During the Secretory Phase of Amelogenesis
Authors: Lyaruu D.M. , Blijlevenz N. , Hoeben-Schornagel K. , Bronckers A.L.J.J. , Woltgens J.H.M.
Published: January 2017

The developing enamel from three-day-old hamster first maxillary (M1) molar tooth germs exposed to fluoride (F-) in vitro was analyzed for its mineral content by means of the energy-dispersive x-ray micro-analysis technique. The aim of this study was to obtain semi-quantitative data on the F--induced hypermineralization patterns in the enamel and to confirm that the increase in electron density observed in micrographs of F-treated enamel (Lyaruu et al., 1986, 1987b) is indeed due to an increase in mineral content in the fluorotic enamel. The tooth germs were explanted during the early stages of secretory amelogenesis and initially cultured for 24 hr in the presence of 10 ppm F- in the culture medium. The germs were then cultured for another 24 hr without F-. In order to compare the ultrastructural results directly with the microprobe data, we used the same specimens for both investigations. The net calcium counts (measurement minus background counts) in the analyses were used as a measure of the mineral content in the enamel. The aprismatic pre-exposure enamel, deposited in vivo before the onset of culture, was the most hypermineralized region in the fluorotic enamel, i.e., it contained the highest amount of calcium measured. The degree of the F--induced hypermineralization gradually decreased (but was not abolished) in the more mature regions of the enamel. The unmineralized enamel matrix secreted during the initial F- treatment in vitro mineralized during the subsequent culture without F-. The calcium content in this enamel layer was in the same order of magnitude as that recorded for the newly deposited enamel in control tooth germs cultured without F-.

From these results, and in combination with the ultrastructural data obtained in previous studies, it is concluded that in vitro: (1) F- treatment during the secretory phase of amelogenesis induces hypermineralization of the pre-exposure enamel; (2) F- decontrols or abolishes enamel crystal growth in length and promotes crystal growth in thickness, thus producing enamel hypermineralization; and (3) enamel matrix secreted during F- exposure retains its capacity to support crystal growth when F- is removed from the culture environment.
Developmental Disturbances of the Rat Molar Induced By Two Diphosphonates
Authors: Fouda N. , Caracatsanis M. , Hammarstrom L.
Published: January 2017

Very few reports have been published about the effects of diphosphonates on the cells and tissues of developing teeth. The present study was designed to investigate possible morphological changes in ameloblasts and odontoblasts and relate these changes to defects in the enamel surface of erupted teeth. Young rats were injected subcutaneously with single or multiple doses of HEDP or Cl2MDP (10 mg P/kg b.w.). Light microscopic examination of developing maxillary first molars showed that single injections of HEDP or Cl2MDP induced subameloblastic cysts between the secretory ameloblasts and the developing enamel. The ameloblastic lining of the cysts contained numerous calcified deposits. A few days after injection, hypoplasias were seen in the enamel in areas previously occupied by cysts. In the erupted teeth, scanning electron microscopic examination revealed enamel hypoplasias which were mainly localized on the mesial sides of the cusps. In addition to the previously mentioned disturbances, multiple injections resulted in more extensive cysts, some of which contained non-mineralized enamel matrix. Inhibition of the mineralization of dentin and alveolar bone was also noticed.
Crystal Morphology and Decalcification Patterns Compared in Rat and Human Enamel and Synthetic Hydroxyapatite
Authors: Simmelink J.W. , Abrigo S.C.
Published: January 2017

The purpose of this investigation was to compare morphology and dissolution patterns by ultrastructural examination of rat and human enamel crystals as well as synthetic apatite crystals. Mature enamel crystals were of particular interest, since crystal maturation appears to be inhibited in amelogenesis imperfecta. Specimens were isolated from developing and mature rat incisor enamel. Rat enamel, mature human enamel, and synthetic apatite were thin-sectioned without decalcification and examined by transmission electron microscopy. Some sections were exposed to acid, and selected synthetic apatite sections were further treated for removal of embedding plastic, followed by vacuum-shadow-coating with carbon. Results showed that cross-sections of rat, human, and synthetic crystals had a distortion in the flattened hexagonal outline in regions where the growth of one crystal impinged on another. Crystal dissolution occurred preferentially along the c-axis, producing a central defect or hole in the crystals. Preliminary studies with weak acid on mature human enamel indicate that the relatively soluble crystal core is quickly dissolved, while the outer shell remains intact over a much longer period of time. In the mature rat and human enamel, this crystal hole formation had a consistent dimension of approximately 10-nm thickness. The crystal hole dimension was the same size as crystals that are formed during the early secretory phase in rat amelogenesis. Acid-treated synthetic apatite also showed dissolution of the crystal core along the c-axis, but dimensions of the hole were not consistent. Shadowed grids showed that the defective hole penetrated the entire section thickness. Mature human enamel showed a unique variation to acid at rod borders where larger, isohexagonal crystals were resistant to acid dissolution. It was concluded that (1) crystals of rat and human enamel show evidence of diphasic growth that may affect their dissolution properties, and (2) unique acid-resistant crystals in human enamel at rod borders may be a result of long oral exposure.
Developmental Defects of Enamel - Historical and Present-Day Perspectives of Their Pathogenesis
Authors: Suckling G.W.
Published: January 2017

Developmental defects of enamel are visible deviations from the normal translucent appearance of tooth enamel resulting from enamel organ dysfunction. In the past, information about the activities of the ameloblasts has determined the terminology used to describe the lesions. Advances in our understanding of the complicated secretory and maturation phases of amelogenesis have required a re-appraisal of the concepts of defect formation. The phase of ameloblast activity, the duration of the disturbance, and its severity leading to temporary or permanent inactivity of the cells determine the appearance of the three common types of lesions—hypoplasia, and diffuse and demarcated opacities.
Caries Prevention Fluoride
Authors: Clarkson B.H.
Published: January 2017

A clear understanding of the mechanism of action of fluoride and its pharmacokinetics would ensure appropriate clinical use of fluoride and fluoride-containing modalities. Convincing evidence exists that fluoride has a major effect on the demineralization and remineralization of dental hard tissues, and that it interferes with the acid production from "cariogenic" bacteria. However, it has also been shown to be physiologically harmful if fluoride concentrations and/or exposure periods are inappropriate. In order to establish appropriate clinical concentrations and exposure periods for fluoride administration, this review is concentrated on the theme that fluoride controls but does not prevent caries. The review is organized along classical lines, with a discussion of the role of systemic vs. topical fluoride. Discussion of the systemic effects of fluoride includes ingestion through water fluoridation, fluoride supplements, topical fluoride applications, and dentifrices. The benefits and problems associated with the systemic route of fluoride administration are discussed with special reference to caries control and fluoride's mechanism of action and its toxic effect. The same discussions are focused on the role of the topical effects of fluoride, with particular emphasis placed upon: low vs. high fluoride concentrations; calcium fluoride vs. fluorhydroxyapatite; and fluoride distribution, in both the mouth and in the teeth.
Side-Effects: Mercury Contribution to Body Burden From Dental Amalgam
Authors: Reinhardt J.W.
Published: January 2017

The purpose of this paper is to examine and report on studies that relate mercury levels in human tissues to the presence of dental amalgams, giving special attention to autopsy studies. Until recently, there have been few published studies examining the relationship between dental amalgams and tissue mercury levels. Improved and highly sensitive tissue analysis techniques have made it possible to measure elements in the concentration range of parts per billion.

The fact that mercury can be absorbed and reach toxic levels in human tissues makes any and all exposure to that element of scientific interest. Dental amalgams have long been believed to be of little significance as contributors to the overall body burden of mercury, because the elemental form of mercury is rapidly consumed in the setting reaction of the restoration. Studies showing measurable elemental mercury vapor release from dental amalgams have raised renewed concern about amalgam safety.

Mercury vapor absorption occurs through the lungs, with about 80% of the inhaled vapor being absorbed by the lungs and rapidly entering the bloodstream. Following distribution by blood circulation, mercury can enter and remain in certain tissues for longer periods of time, since the half-life of excretion is prolonged. Two of the primary target organs of concern are the central nervous system and kidneys.
Documented Clinical Side-Effects to Dental Amalgam
Authors: Ziff M.F.
Published: January 2017

Since all dental restorative materials are foreign substances, their potential for producing adverse health effects is determined by their relative toxicity and bioavailability, as well as by host susceptibility. Adverse health effects to dental restoratives may be local in the oral cavity or systemic, depending on the ability of released components to enter the body and, if so, on their rate of absorption.

The medical scientific community is now in general agreement that patients with dental amalgam fillings are chronically exposed to mercury, that the average daily absorption of mercury from dental amalgam is from 3 to 17 micrograms per day, and that the amalgam mercury absorption averages 1.25-6.5 times the average mercury absorption from dietary sources (World Health Organization, 1991). The health significance of this chronic mercury exposure is now being investigated by several medical research groups.
Dental Amalgam and Mercury Vapor Release
Authors: Osborne J.W.
Published: January 2017

Dental diseases are among the most common ailments, and dentists in the United States spend over 50% of their time in dental practice rebuilding carious, malformed, and traumatically injured teeth. It is logical, therefore, that the majority of the dental school curriculum is devoted to the diagnosis, prevention, and treatment of teeth with anomalies. Dentists have several choices of materials they can use to accomplish the task of rebuilding teeth. Besides amalgam, they have ceramic materials, resin composites, base-metal and noble casting alloys, and glass-ionomer cements to use to restore the posterior dentition. Each of these restorative materials has advantages and disadvantages, and the clinical judgment as to when a particular material should be used is given a high priority in dental education.

Amalgam is the most widely used of these restorative materials, with 92% of dentists listing it as the material of choice in the posterior of the mouth (Clinical Research Associates, 1990). Dentists have been placing amalgams for over 150 years in the US. They placed 150 million last year, which represents over 75 tons of amalgam alloy. The reasons that dentists use this restorative material so frequently are its durability, ease of manipulation, and low cost. Numerous clinical studies have been conducted on the serviceability of amalgam. Most of these have been on the old, low-copper alloys, and results indicate that they last from 8 to 15 years (Bailit et al,, 1979; Osborne et al., 1980; Qvist et al., 1986). In the past 20 years, vast improvements have been made in amalgams with the development of the high-copper systems. Clinical studies initiated in the 1970's are reporting that the well-placed high-copper amalgam will last over 30 years (Laswell et al., 1989; Letzel et al., 1989; Osborne and Norman, 1990; Osborne et al., 1991). The ease with which amalgam is manipulated has no equal. Placement of amalgam takes only 20-50% of the time it takes to restore a tooth with other materials. For the amalgam, this cost in placement time and the cost to purchase the material are considerably less. The one factor that amalgam does not have in its favor is esthetics. The other-restorative materials, frankly, look better.
Problems and Benefits Associated With Restorative Materials: Side-Effects and Long-Term Cost
Authors: Mjör Ivar A.
Published: January 2017

The paper reviews data on biological side-effects of dental materials on patients and also on personnel who routinely handle the materials. The incidence of adverse effects is low-in one study indicated to be 1:700 for all types of treatments. For individual types of materials, it will be significantly lower, and for restorative materials, probably in the 1 : 10,000 to 1:20,000 range. Allergic reactions are the most common type of adverse effect of dental materials. Lichenoid reactions on the oral mucous membrane adjacent to amalgam restorations are the most frequently encountered side-effects for a specific group of restorative materials.

Cost analyses were based on reports of longevity of different restorations and the cost of restorations at the time of placement. Amalgam restorative therapy was more cost-effective than composite restorations and gold castings.
Dental Ceramics: the State of the Science
Authors: Fairhurst C.W.
Published: January 2017

This review covers the properties of dental ceramics. Castable systems, bioactive glass, PMF systems, CAD/CAM, and ceramic brackets in orthodontics are briefly discussed. Many of the advances made between 1960 and 1975 were directed toward the understanding, controlling, and developing of new ceramic processes. New and deeper understanding of the structure of non-crystalline solids, structural imperfections, sintering physics, and other physical phenomena related to the melting and solidification processes has brought ceramics from the near-total art form process of the mid-century to the status of a highly sophisticated science it enjoyed in the 1980's.
Dental Tissue Effects of Fluoride
Authors: Fejerskov O. , Larsen M.J. , Richards A. , Baelum V.
Published: January 2017

It is now well-established that a linear relationship exists between fluoride dose and enamel fluorosis in human populations. With increasing severity, the subsurface enamel all along the tooth becomes increasingly porous (hypomineralized), and the lesion extends toward the inner enamel. In dentin, hypomineralization results in an enhancement of the incremental lines. After eruption, the more severe forms are subject to extensive mechanical breakdown of the surface. The continuum of fluoride-induced changes can best be classified by the TF index, which reflects, on an ordinal scale, the histopathological features and increases in enamel fluoride concentrations. Human and animal studies have shown that it is possible to develop dental fluorosis by exposure during enamel maturation alone. It is less apparent whether an effect of fluoride on the stage of enamel matrix secretion, alone, is able to produce changes in enamel similar to those described as dental fluorosis in man. The clinical concept of post-eruptive maturation of erupting sound human enamel, resulting in fluoride uptake, most likely reflects subclinical caries. Incorporation of fluoride into enamel is principally possible only as a result of concomitant enamel dissolution (caries lesion development). At higher fluoride concentrations, calcium-fluoride-like material may form, although the formation, identification, and dissolution of this compound are far from resolved.

It is concluded that dental fluorosis is a sensitive way of recording past fluoride exposure because, so far, no other agent or condition in man is known to create changes within the dentition similar to those induced by fluoride. Since the predominant cariostatic effect of fluoride is not due to its uptake by the enamel during tooth development, it is possible to obtain extensive caries reductions without a concomitant risk of dental fluorosis.
Epidemiologic Indices for Measuring the Clinical Manifestations of Dental Fluorosis: Overview and Critique
Authors: Rozier R.G.
Published: January 2017

Several indices have been used to describe the clinical appearance of dental fluorosis. The purpose of this paper is to describe and compare the three principal ones in use today: those developed by Dean (1934, 1942), Thylstrup and Fejerskov (1978), and Horowitz et al. (1984). A recent index (Fluorosis Risk Index) developed by Pendrys (1990) is also included in this review. The continued use of Dean's classification system and derived index (CFI) for more than a half century is testimony to its simplicity and utility. The index has been criticized because the unit of analysis is the person, because criteria are unclear for some categories, or that they lack sensitivity, particularly for severe fluorosis, and because of the way in which data are summarized and reported. The Thylstrup and Fejerskov Index is appealing to clinicians and epidemiologists alike in that it corresponds closely to histological changes that occur in dental fluorosis and to enamel fluoride concentrations, thereby having biological validity. The TSIF described by Horowitz et al. makes a useful contribution because it provides clearer diagnostic criteria and provides for an analysis based on esthetic concerns. The Fluorosis Risk Index appears to be particularly useful for analytical epidemiologic studies, because it is designed to permit a more accurate identification of associations between age-specific exposures to fluoride and the development of dental fluorosis. All three indices in common use today provide useful indices for the study of dental fluorosis. The utility of the Fluorosis Risk Index will be determined as it receives wider use. The selection of one of these indices for use in an epidemiologic study depends in large measure on the purpose of the study. Research needs to continue on the validity of these indices, particularly for mild fluorosis, and on the public's perception of the cosmetic appearance of teeth with different severity levels of fluorosis.
Current Techniques for Measuring Dental Fluorosis: Issues in Data Analysis
Authors: Kingman A.
Published: January 2017

The currently popular scoring systems used to diagnosis fluorosis use different measurement units, evaluate variable numbers of sites per person, and involve non-comparable groupings of clinical symptoms. Although none of these factors is related to the level of fluoride exposure in the examined population, their combined effect produces fluorosis prevalence values for a population which vary considerably among and within these scoring systems. Intrinsic factors for a scoring system include the inclusion of a questionable category, the minimal level of fluorotic involvement, and the number of affected sites within a subject required for case definition. Thus, a case definition of fluorosis for each scoring system, although not mandatory, would certainly be desirable so that dental epidemiologists and clinical investigators can interpret fluorosis scores relative to risk assessment. On the other hand, ratios of fluorosis prevalence magnitudes, as evidenced by odds ratios, can be more stable between scoring systems when groups with different fluoride exposure levels are compared.

There is a strong correlation between extent and specific measures of fluorosis severity for Dean's Index (DI) and the Tooth Surface Index of Fluorosis (TSIF) scoring system, as well as within each scoring system separately. Parallel patterns in fluorosis severity were found among groups with different fluoride exposures for the DI and TSIF scoring systems. The effects of fluoride exposure on severity levels of fluorosis may be better understood by using relative measures rather than by using differences in severity levels.
Determination of Fluorine in Biological Materials: A Review
Authors: Venkateswarlu P.
Published: January 2017

This review on determination of fluorine in biological materials briefly covers (a) a discussion of various forms of fluorine in body fluids and tissues [and also in foods]; (b) methods of their determination, including pretreatment of samples, separation and concentration of F and its final measurement; (c) an evaluation of the analytical methods used and interpretation of results; and (d) some recommendations for future research in fluorine analytical methods applicable to biological materials.
Endangered species: science writers in the Canadian daily press
Authors: Saari Mary-Anne , Gibson Candace , Osler Andrew
Published: January 2017

The last comprehensive study of Canadian science journalists and science reporting was done over 20 years ago (Dubas and Martel 1973). A more recent content analysis of seven major Canadian dailies found most science stories are “hard” news in style and originate from wire sources (Einsiedel 1992).

This 1994 survey of 105 of Canada's daily English-language newspapers and their commitment to science journalism revealed a general weakening and dilution of reporter allocation. Over 50 percent of Canadian dailies did not allocate a science reporter. Only 18 full-time science reporters were identified. A follow-up of 45 journalists covering science at least half-time revealed most covered science policy. The vast majority had no science training. Time problems and competing demands hindered professional development.

Confirming suggestions of previous literature, this study also indicates the Canadian daily newspaper structure is not supportive of the style of reportage required for quality science writing, nor of the development of such writers.
Science and the environment: assessing cultural capacity for ecological modernization
Authors: Cohen Maurie J.
Published: January 2017

Ecological modernization is emerging as a new paradigm for the environmental improvement of advanced nations. Rather than emphasize the use of remedial technologies as has been customary since the 1970s, this approach reframes the relationship between economics and the environment to overcome the zero-sum antagonism of the earlier era. This transformation faces numerous obstacles, and ultimate success will depend on a wide range of predisposing national characteristics, including institutional design and economic organization. The current analysis focuses specifically on an often overlooked third factor, cultural endowment, examining the extent to which it will likely condition the capability of individual nations to meet these challenges. Particularly important cultural attributes for ecological modernization are a strong public commitment to science and a robust environmental consciousness. Using data from several cross-national sources, including the Euro-Barometer, the World Values Survey, and the International Social Survey Programme, this analysis assesses the cultural capacities of a sample of fifteen advanced nations. The Netherlands and the Scandinavian countries, because of widespread lay respect for science and extensive public endorsement of environmental protection, appear to have enhanced cultural potential to pursue ecological modernization.
Designing Video Classrooms
Authors: Price Michael A.
Published: January 2017

Adult educators often overlook the physical environment in which video instruction takes place. But quality video classrooms and teleconference facilities are important, not only because a properly designed viewing room will enhance program objectives and increase acceptance of this type of instruction, but also because as a group, adult learners may be resistant to nontraditional instructional methods and may have hearing or sight difficulties.
Mechanistic Aspects of the Interactions Between Fluoride and Dental Enamel
Authors: ten Cate J.M. , Featherstone J.D.B.
Published: January 2017

For many years after the discovery of its caries preventive effect, fluoride was thought to be primarily active by lowering the solubility of the apatitic mineral phase of the dental hard tissues. Recent findings have shed new light on the mechanisms by which fluoride inhibits or delays dental caries. Fluoride present in the oral fluids alters the rate of the naturally occurring dissolution and reprecipitation processes at the tooth-oral fluid interface. Demineralization of enamel is inhibited by concentrations of fluoride in the sub-ppm range. Likewise, remineralization of incipient caries lesions (the earliest stage of enamel caries) is accelerated by trace amounts of fluoride. As these two processes comprise dental caries the physiological balance between hard tissue breakdown and repair is favorably shifted by fluoride. The driving force for both phenomena is thermodynamic, that is, fluorapatite or a fluoridated hydroxyapatite may form when fluoride is supplied at low concentrations. This article critically reviews the current information about tooth-fluoride interactions, both from laboratory and clinical studies.
Tetracyclines Inhibit Connective Tissue Breakdown: New Therapeutic Implications for an Old Family of Drugs
Authors: Golub Lorne M. , Ramamurthy N.S. , McNamara Thomas F. , Greenwald Robert A. , Rifkin Barry R.
Published: January 2017

Tetracyclines have long been considered useful adjuncts in peridontal therapy based on their antimicrobial efficacy against putative periodontopathogens. However, recently these drugs were found to inhibit mammalian collagenases and several other matrix metalloproteinases (MMPs) by a mechanism independent of their antimicrobial activity. Evidence is presented that this property may be therapeutically useful in retarding pathologic connective tissue breakdown, including bone resorption. The experiments leading to this discovery are described and possible mechanisms are addressed, including the specificity of tetracyclines' anti-collagenase activity, the role of the drugs' metal ion (Zn2+, Ca2+)- binding capacity, and the site on the tetracycline molecule responsible for this nonantimicrobial property. Of extreme interest, the tetracycline molecule has been chemically modified in multiple ways, generating a new family of compounds called CMTs (chemically modified tetracyclines) that lack antimicrobial but still retain anti-collagenase activity. The first of these CMTs, 4-de-dimethylaminotetracycline, was found not to produce a major side-effect of antimicrobial tetracycline therapy- its administration to experimental animals did not result in the emergence of tetracycline-resistant microorganisms in the oral flora and gut. Numerous examples of the clinical potential of this non-antimicrobial property of tetracyclines in the treatment of periodontal and several medical diseases (e.g., sterile corneal ulcers, rheumatoid arthritis, skin bullous lessions, tumor-induced angiogenesis and metastasis) are discussed.
Extracellular Matrix Molecules and their Receptors: An Overview with Special Emphasis on Periodontal Tissues
Authors: Uitto Veli-Jukka , Larjava Hannu
Published: January 2017

Knowledge of extracellular matrix molecules and their cell receptors has increased exponentially during the last 2 decades. It is now known that the structure and function of each tissue is based on specific combinations of matrix molecules. The major constituents of the extracellular matrix are collagens, proteoglycans, and adhesive glycoproteins. The rapid development of biochemical, molecular biological, and immunological research has revealed a lot of interesting details pertaining to these molecules. Several new collagen types have been discovered. In addition to being responsible for the strength and form of tissues, each collagen type has specific sequences providing them with special features such as flexibility and the ability to interact with other matrix molecules and cells. Proteoglycans are another large group of matrix molecules with a variety of functions. Proteoglycans play an important role in tissue resilience and filtering. Some proteoglycans have a capacity to specifically bind other matrix molecules and growth factors, while others act as matrix receptors on the cell surface. An important part of regulation of the cell behavior is played by adhesive glycoproteins belonging to the fibronectin and laminin families. Several isoforms of fibronectin and laminin that result from alternative RNA splicing serve specific functions such as controlling the attachment, migration, and synthetic activity of cells. A major group of cell receptors for cell-matrix and cell-cell interactions is termed integrins. The integrins are cell surface proteins composed of two polypeptides whose structure dictates the specificity of each receptor. The cytoplasmic domain of the integrins interacts with cytoskeletal elements within the cell, and thereby relays the information from the extracellular space into the protein synthesis machinery. The expression of the integrins is controlled by the extracellular matrix and growth factors, most notably TGFβ. During periodontal diseases several aspects of the cell-matrix interactions may be disturbed. Therefore, an understanding of the special features of the extracellular matrix and their receptors in periodontal tissues is a prerequisite for developing new approaches to the prevention and treatment of periodontal diseases.
Osteoclast Differentiation
Authors: Roodman G. David
Published: January 2017

The osteoclast is the primary bone resorbing cell. It is a highly specialized multinucleated cell whose primary function is to help in the control of calcium homeostasis. The osteoclast has been very difficult to study because of its relative inaccessability, low numbers, and fragility when isolated from bone. Recently, techniques have been developed to study the cell biology of the osteoclast that have expanded our ability to understand the biological and functional properties of osteoclasts. In this article, studies on the origin of the osteoclast are reviewed and the differentiation markers that are used to detect cells in the osteoclast lineage are discussed. Factors that affect osteoclast differentiation are presented and model systems currently in use for studying osteoclast differentiation are evaluated for their relative strengths and weaknesses. In addition, osteoclast differentiation during tooth eruption and root resorption and the effects of bone matrix elements on osteoclast differentation are reviewed.
The Therapy of Oral Lichen Planus
Authors: Eisen Drore
Published: January 2017

Oral lichen planus is a chronic mucocutaneous disease that is relatively common. Although many patients are asymptomatic and require no therapy, those who exhibit atrophic and erosive lesions are often a challenge to treat. All therapies are palliative, and none is effective universally. Currently employed treatment modalities include corticosteroids administered topically, intralesionally, or systemically. Alternative therapies include topical and systemic retinoids, griseofulvin, Cyclosporine, and surgery. Other medical treatments and experimental modalities, including mouth PUVA, have been reported to be effective. Controversy concerning the efficacy of all these treatments suggests that oral lichen planus is a heterogeneous disorder. Eliminating lichenoid drug eruptions, candidiasis, trauma, contact mucositis, and emotional stress may play a role in the management of these patients. This article is a review of the many treatments and measures that have been employed in the management of patients with oral lichen planus.
Virulence Factors of Mutans Streptococci: Role of Molecular Genetics
Authors: Kuramitsu Howard K.
Published: January 2017

Biochemical approaches were utilized initially to identify the virulence factors of the mutans streptococci (primarily Streptococcus mutans and S. sobrinu). Traditional mutant analysis of these organisms further suggested the important role of several of these factors in cariogenicity. However, because these mutations were not clearly defined, the utilization of cloned genes was necessary to verify their significance. The introduction of molecular genetic approaches for characterizing these factors has led not only to a clearer understanding of the role of these virulence factors in cariogenicity but has also suggested some novel approaches for reducing further the incidence of dental caries.
Matrix Metalloproteinases: A Review
Authors: Birkedal-Hansen H. , Moore W.G.I. , Bodden M.K. , Windsor L.J. , Birkedal-Hansen B. , DeCarlo A. , Engler J.A.
Published: January 2017

Matrix metalloproteinases (MMPs) are a family of nine or more highly homologous Zn++endopeptidases that collectively cleave most if not all of the constituents of the extracellular matrix. The present review discusses in detail the primary structures and the overlapping yet distinct substrate specificities of MMPs as well as the mode of activation of the unique MMP precursors. The regulation of MMP activity at the transcriptional level and at the extracellular level (precursor activation, inhibition of activated, mature enzymes) is also discussed. A final segment of the review details the current knowledge of the involvement of MMP in specific developmental or pathological conditions, including human periodontal diseases.
Development of Artificial Salivas
Authors: Levine Michael J.
Published: January 2017

Salivary research is at a critical crossroads regarding the clinical application of basic knowledge. Studies by numerous salivary researchers over the last 5 years using advanced technologies (e.g., protein chemistry, molecular biology, and biophysics) have demonstrated that the structural requirements for salivary function are quite complex. Nevertheless, several patterns or principles have evolved. First, the majority if not all salivary molecules are multifunctional. Second, the conformation of a molecule is an important factor in biological activity. Third, many molecules have overlapping functions (e.g., mucins and amylase interact with viridans streptococci; statherin and proline-rich proteins are involved in mineralization). Thus, saliva has "built-in" compensatory or redundant properties. Nevertheless, it must be determined which molecule is more potent or effective with respect to a particular function. Fourth, salivary molecules may be "amphifunctional". In other words, the different functions of a single molecule may be protective or potentially harmful depending on the intraoral site of action. Examples of amphifunctional molecules are amylase and statherin. Fifth, functional relationships may exist between different salivary components. The principles mentioned above can provide experimental strategies for the design and synthesis of a first generation of salivary substitutes that can be topically applied to oral surfaces. These molecules should be used to combat microbial mediated diseases and occlusal disharmony in subjects with normal salivary flow as well as those with xerostomia. In general, these substitutes should be long-lasting, biocompatible, biodegradable, and provide specific protective qualities that can be targeted to selected intraoral sites. Subsequent research endeavors will focus on the design and subsequent engineering of a second generation of artificial salivas comprised of molecules with enhanced as well as multiple functions. Examples of these strategies are provided.
Low-Molecular-Mass Human Salivary Mucin, MG2: Structure and Binding of Pseudomonas aeruginosa
Authors: Reddy Molakala S. , Levine Michael J. , Paranchych William
Published: January 2017

Low-molcular-mass human salivary mucin, MG2, was isolated from human submandibular-sublingual saliva (HSMSL) employing citraconylation, gel filtration, and ion-exchange chromatography. Following proteolysis with trypsin, two glycopeptides were purified. The higher molecular weight glycopeptide was highly glycosylated with O-linked units. The lower molecular weight glycopeptide was less glycosylated and contained most of the N-linked units. Interaction between components of HSMSL and pili of Pseudomonas aeruginosa was examined by an overlay binding assay. Pili were found to bind to MG2. Preliminary studies indicated that the binding may involve a protein to protein interaction.
The High-Molecular-Weight Human Mucin Is the Primary Salivary Carrier of ABH, Lea, and Leb Blood Group Antigens
Authors: Prakobphol Akraporn , Leffler Hakon , Fisher Susan J.
Published: January 2017

Because many bacteria interact with the carbohydrate portions of receptor molecules, factors controlling glycosylation probably influence the ability of salivary components to mediate bacterial adherence/clearance. Important sources of diversity in glycosylation are the ABO, secretor, and Lewis genes, which code for glycosyltransferases that add specific sugar sequences to the termini of carbohydrate chains of glycolipids and glycoproteins. We identified, by Western blotting, salivary glycoproteins carrying the ABH and Le a or Leb antigens. Samples of whole, unstimulated saliva were obtained from 19 subjects whose blood group was determined by agglutination of red blood cells with specific antisera. After centrifugation, the samples were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and blotted onto nitrocellulose. Glycoproteins carrying blood group antigens were identified by staining the blot with monoclonal antisera specific for the A, B, H, Lea, or Leb antigens. The most intensely staining component from all the samples migrated at the same position as the high-molecular-weight mucin. Saliva samples from the nonsecretors contained only the Lea antigen. Samples from the secretors contained one or more of the ABH antigens and, variably, the Leb antigen. In all cases, the salivary blood group antigens corresponded to those found on the red blood cells of the same subject. The functional consequences of the expression of blood group antigens on the high-molecular-weight mucin are not known, but their presence could modulate the adherence of certain oral microorganisms that interact preferentially with this molecule.
Emergence of Immune Competence in Saliva
Authors: Smith Daniel J. , Taubman Martin A.
Published: January 2017

Saliva contains essentially no IgA at birth. However, secretory immune responses to oral and non-oral microbial antigens emerge early in life. We have investigated the characteristics of these responses in salivas of infants less than 1 month through 4 years of age, using cross-sectional and longitudinal approaches. Antibody specificities (IgA, IgAl, and IgA2) were measured in ELISA and Western blot analysis to antigens of Streptococcus mitis and S. salivarius that colonize during the neonatal period. Antibodies reactive with S. sanguis and mutans streptococci, which colonize later in the infant's life, were also determined. Concurrent investigation of the oral flora of each infant was performed and related to the observed antibody specificities. The secretory nature of the immunoglobulins in these salivas was analyzed immunologically and chromatographically. The primary molecular form of salivary IgA was dimeric in all salivas tested. Both IgA subclasses were found, although a subset of infant salivas initially contained >90% IgAl. IgM (>1 μg/ml) was detected in 58% of 3- to 17-week-old infants. By 2 months of age, salivas from most infants contained IgA antibody reactive with at least two S. mitis components. Many salivas also contained antibody reactive with S. salivarius components. By the end of the first year, most salivas contained IgAl and IgA2 antibody to S. mitis antigens. Maturation of secretory responses in the second and third year was evidenced by the appearance of increased concentrations and additional specificities of salivary IgA antibodies to S. mitis antigens. Antibody to S. mitis, S. salivarius, and S. sanguis extracellular components was detected only after infection with the respective species. However, salivary IgA antibody to mutans streptococci occasionally was detected before colonization was demonstrated.
An Epidemiologic Perspective of Saliva Flow Rates as Indicators of Susceptibility to Oral Disease
Authors: Billings Ronald J.
Published: January 2017

Catastrophic hyposalivation significantly increases susceptibility to dental caries in dentate individuals and may cause the expression or exacerbation of other oral diseases/disorders as well. The effect of subcatastrophic hyposalivation on susceptibility to caries or other diseases/disorders is less well understood. The aim of this study (part of a larger study on the prevalence of hyposalivation) was to determine the prevalence and to measure the association of oral pathologic conditions with unstimulated and stimulated whole saliva flow rates.

Only 6.3% of all study participants had significantly diminished unstimulated (<0.05 ml/min) and stimulated (<0.50 ml/ min) saliva flow rates. A total of 15 individuals were encountered with oral pathologic lesions and none of these lesions were associated with hyposalivation. Although the prevalence of coronal caries, root surface caries, abrasion, and erosion tended to increase as salivary flow decreased, when the effect of age was considered no significant differences were present. These data suggest that low saliva flow rates alone, at least from an epidemiologic perspective, do not have a clinically relevant effect on susceptibility to oral diseases/disorders.
Involvement of α2-Adrenoreceptors and G Proteins in the Modulation of Platelet Secretion in Response to Streptococcus sanguis
Authors: Herzberg Mark C. , Krishnan Lissy K. , MacFarlane Gordon D.
Published: January 2017

In the presence of plasma, human platelets secrete the contents of their dense granules and then aggregate in response to certain strains of Streptococcus sanguis. After 2 to 5 min of incubation with streptococci, platelets from fast-responding donors will begin to aggregate. Slow responders aggregate after a longer delay. Platelets may secrete after a short (fast responder) or long (slow responder) delay because of differences in the basal levels or responses to potentiating catecholamines. To test this hypothesis in vitro, endogenous basal catecholamine levels in platelets and plasma from fast and slow responders were analyzed by HPLC with electrochemical detection. The total basal concentration of epinephrine in platelets plus plasma was fourfold higher in fast responders, with the platelet compartment showing the greatest difference. The basal affinity of α2-adrenoreceptors in platelets from both groups was similar when estimated using a specific antagonist, [3H]-yohimbine. Platelets from all donors showed decreased α 2-adrenoreceptor affinity in the presence of low (2 n M), but not higher (10 n M), concentrations of added epinephrine. Platelets in the two groups were then compared for secretion of ATP. More ATP was secreted after a shorter delay from fast responding platelets, which was mimicked in slow responders by adding physiologically attainable levels (40 n M) of epinephrine. Addition of the α2-antagonist, phentolamine (10 μ M), to the platelets of slow and fast responders completely inhibited or reduced secretion by one third, respectively. Therefore, α 2-adrenoreceptors modulate the secretory response of platelets to cells of S. sanguis. Modulation of secretion may involve coupling of the α2-adrenoreceptor and S. sanguis receptor via G proteins because secretion in response to S. sanguis was inhibitable by pertussis or cholera toxins, or GTPyS.
Rat Submandibular and Parotid Protein Phosphorylation and Exocytosis: Effect of Site-Selective cAMP Analogs
Authors: Quissell David O. , Barzen Katherine A. , Deisher Lynn M.
Published: January 2017

A series of cAMP analogs that have different specificities for the two different binding sites on the regulatory subunit of type I and type n cAMP-dependent protein kinase (PKA) were used to determine whether selective activation of type I or type II PKA could link either or both isozyme forms of PKA with exocytosis and specific protein phosphorylation in salivary gland cells. Using dispersed rat submandibular or parotid cells, selective activation of either type I or type II resulted in a synergistic response for both rat submandibular mucin and parotid amylase secretion and the phosphorylation of a 26-kDa integral membrane phosphoprotein. These data suggest that the activation of either isozyme of PKA can elicit cellular exocytosis and specific protein phosphorylation in both of these cell types.