Showing papers in "Critical Reviews in Oral Biology & Medicine in 1994"

Candida and Oral Candidosis: A Review

Abstract: Candida species are the most common fungal pathogens isolated from the oral cavity. Their oral existence both as a commensal and an opportunist pathogen has intrigued clinicians and scientists for many decades, and recent investigations have revealed many attributes of this fungus contributing to its pathogenicity. In addition, the advent of the human immunodeficiency virus infection and AIDS has resulted in a resurgence of oral Candida infections. Clinicians are witnessing not only classic forms of the diseases but also newer clinical variants such as erythematous candidosis, rarely described hithertofore. Therefore, this review is an attempt at detailing the current knowledge on Candida and oral candidoses together with the newer therapeutic regimes employed in treating these mycoses.

Saliva-Bacterium Interactions in Oral Microbial Ecology

Abstract: Saliva is thought to have a significant impact on the colonization of microorganisms in the oral cavity. Salivary components may participate in this process by one of four general mechanisms: binding to microorganisms to facilitate their clearance from the oral cavity, serving as receptors in oral pellicles for microbial adhesion to host surfaces, inhibiting microbial growth or mediating microbial killing, and serving as microbial nutritional substrates. This article reviews information pertinent to the molecular interaction of salivary components with bacteria (primarily the oral streptococci and Actinomyces) and explores the implications of these interactions for oral bacterial colonization and dental plaque formation. Knowledge of the molecular mechanisms controlling bacterial colonization of the oral cavity may suggest methods to prevent not only dental plaque formation but also serious medical infections that may follow microbial colonization of the oral cavity.

Sex Steroid Hormones and Cell Dynamics in the Periodontium

Abstract: The biological changes that occur in tissues of the periodontium during puberty, the menstrual cycle, pregnancy, menopause, and oral contraceptive use have heightened interest in the relationship between sex steroid hormones and periodontal health. These clinical observations coupled with tissue specificity of hormone localization, identification of hormone receptors, as well as the metabolism of hormones have strongly suggested that periodontal tissues are targets for androgens, estrogens, and progestins. The etiologies of periodontal endocrinopathies are diverse; nonetheless, periodontal pathologies may be a consequence of the actions and interactions of sex steroid hormones on specific cells found in the periodontium.

Internal organization in the human jaw muscles.

Abstract: The human jaw muscles are essential to mastication and play an important part in craniofacial growth. They contribute to dental and articular forces, deform the mandible, and, like other tissues, are subject to disorders, often manifested as pain. The literature describes how their contraction is controlled by the nervous system, and how their general structure and function contribute to craniofacial biology, but there has been little appraisal of their internal organization. Most of these muscles are not simple; they are multipennate, complexly layered, and divided by aponeuroses. This arrangement provides substantial means for differential contraction. In many ways, jaw muscle fibers are intrinsically dissimilar from those found in other skeletal muscles, because they are arranged in homogeneous clusters and generally reveal type I or type II histochemical profiles. Most are type I and are distributed preferentially in the anterior and deeper parts of the jaw closers. Additionally, most motor unit (MU) territories are smaller than those in the limbs. There is circumstantial evidence for intramuscular partitioning based in part on innervation by primary muscle nerve branches. During normal function. MU recruitment and the rate coding of MU firing in human jaw muscles follow the general principles established for the limbs, but even here they differ in important respects. Jaw muscle MUs do not have stable force recruitment thresholds and seem to rely more on rate coding than on sequential unit recruitment to grade the amplitude of muscle contraction. Unlike those in the limbs, their twitch tensions correlate weakly with MU fatiguability and contraction speed, probably because there are so few slow, fatigue-resistant MUs in the jaw muscles. Moreover, the type I fibers that are present in such large numbers do not contract as slowly as normally expected. To complicate matters, estimation of jaw MU twitch tensions is extremely difficult, because it is affected by the location used to measure the twitch, the background firing rate, muscle coactivation, and regional, intramuscular mechanics. Finally, there have been very few systematic studies of jaw MU reflex behavior. The most recent have concentrated on exteroceptive suppression and suggest that MU inhibition following intra- and perioral stimulation depends on the location of the MU, its background firing rate, the timing of the stimulus, and the task used to drive the unit. Task dependency is a common feature of human jaw MU behavior, reflecting interaction between peripheral sensory information from orofacial and muscle afferents and corticobulbar drive.(ABSTRACT TRUNCATED AT 400 WORDS)

Composition and Cariogenic Potential of Dental Plaque Fluid

Abstract: Our understanding of the chemical events that take place at the tooth-plaque interface has improved greatly through studies of the chemical composition and properties of dental plaque fluid. In the absence of fermentable carbohydrate, plaque fluid has been found to be supersaturated with respect to tooth mineral and other calcium phosphate phases, thus exhibiting the potential to support calculus formation and the remineralization of incipient carious lesions. Following the exposure to fermentable carbohydrate, the degree of saturation of plaque fluid decreases rapidly, primarily due to lactic acid production and the lowering of plaque fluid pH. The extent of these chemical changes has been shown to be associated with differences in caries history. Such studies have been facilitated by the recent development of microanalytical techniques. Unfortunately, little is known about the relationship between the observed chemical changes in plaque fluid and the microbial composition of plaque. Limited information is also available on the association of immune factors in plaque fluid with dental disease.

Cytokines and T Cell Switching

Abstract: In recent years, the phenotypic characterization of T cell subsets has given way to a functional dichotomy based essentially on their cytokine profiles. In this context, the CD4+ helper T cell subset has been shown to consist of two types, termed Th1 and Th2. In general, Th1 cells produce interleukin (IL)-2 and interferon (IFN)-gamma, while Th2 cells characteristically produce IL-4, IL-5, and IL-6. The major function of the Th1 subset is to mediate delayed-type hypersensitivity reactions and their secondary function is suppression of B cell activity. In contrast, the major function of the Th2 subset is to provide B cell help, while their secondary function is cell-mediated immune suppression. A similar dichotomy has also been described for CD8+ T cells. The role that these functional T cell subsets and their cytokines play in terms of their protective and nonprotective outcomes in a variety of infectious and oral diseases is reviewed.

The role of proteoglycans in hard and soft tissue repair.

Abstract: Healing of soft and hard tissues results from a progression of events initiated by injury and directed toward reestablishing normal structure and function. The ubiquity of proteoglycans in mammalian tissues virtually guarantees their involvement in tissue restitution. The dramatic advances in cellular and molecular biology in recent years have added significantly to understanding the specific roles played by proteoglycans in wound repair processes.

HIV-related tumors of the oral cavity.

Abstract: In HIV-infected patients with AIDS the most frequent malignancies are Kaposi's sarcoma and non-Hodgkin's lymphoma. In these patients, the natural history of these tumors is quite different from those of HIV-negative subjects. These tumors may present atypical clinical aspects, may be very aggressive, and the coexistence of immunosuppression and opportunistic infections may render their treatment more difficult. The aim of this article is to provide updated information on the epidemiology, pathogenesis, natural history, and management of tumors that develop in the oral cavity of patients with AIDS.

Cell adhesion molecules in inflammation and immunity: relevance to periodontal diseases.

Abstract: Inflammatory and immune responses involve close contact between different populations of cells. These adhesive interactions mediate migration of cells to sites of inflammation and the effector functions of cells within the lesions. Recently, there has been significant progress in understanding the molecular basis of these intercellular contacts. Blocking interactions between cell adhesion molecules and their ligands has successfully suppressed inflammatory reactions in a variety of animal models in vivo. The role of the host response in periodontal disease is receiving renewed attention, but little is known of the function of cell adhesion molecules in these diseases. In this review we summarize the structure, distribution, and function of cell adhesion molecules involved in inflammatory/immune responses. The current knowledge of the distribution of cell adhesion molecules is described and the potential for modulation of cell adhesion molecule function is discussed.

Developmental aspects of fluid and electrolyte secretion in salivary glands.

Abstract: The salivary glands of rodents undergo considerable cytodifferentiation after birth and are useful models for the study of functional development, including the mechanisms of fluid and electrolyte secretion. In the rat submandibular gland, secretion of salivary fluid cannot be elicited until approximately 2 weeks of age. The currently accepted model of salivary fluid secretion indicates that this process depends on the activation, on stimulation of cholinergic receptors, of several ion transport systems, resulting in a net transport of osmotically active ions (primarily Cl- and Na+) across the acinar epithelium. This creates the necessary osmotic gradient for the transacinar movement of water. The process is associated with a signal transduction pathway involving the formation of phosphoinositide products (primarily inositol triphosphate or IP3) and the mobilization of Ca2+. The latter regulates monovalent ion conductances (K+, Cl-), which are critical for the secretory process. Immature submandibular glands and cells of early postnatal rats have a lower density of cholinergic receptors and release less K+ and Cl- than mature cells and gradually develop other ion transport systems (such as a Na, K, 2Cl cotransport system) involved in the secretory process. Surprisingly, they form more IP3 and show a larger increase in cytosolic Ca2+ when stimulated with maximal or supramaximal concentrations of agonist. Therefore, they show some interesting dissociations in the signal transduction mechanism that suggest differences in the coupling between receptors and membrane phosphoinositides, between IP3 and IP3-dependent Ca2+ stores, and between the Ca2+ signal and the monovalent ion transport systems which are critical for secretion.

Analysis of Longitudinal Data in Craniofacial Research: Some Strategies

Abstract: Although it is generally acknowledged that longitudinal data provide the most information on growth and development and other time-dependent phenomena, such data are often analyzed by conventional (cross-sectional) statistical methods. This widespread practice ignores the distinctive characteristics (e.g., covariance structure) of longitudinal data and may yield misleading results. The purpose of this article is to present some strategies and make available computer programs for the appropriate analysis of longitudinal data. User-friendly PC programs for the estimation of average growth curves, computation of tracking indices, prediction of future values, diagnosis, classification, clustering, estimation of missing values, and testing hypotheses concerning individual and group differences are presented. Benefits of these methods over the usual techniques are illustrated with the example of maxillary growth in the rhesus monkey.

Signal transduction mechanisms in mesenchymal cells.

Abstract: Mesenchymal cells are continually stimulated by a wide spectrum of biological mediators. These mediators bind to receptors on the cell surface and initiate a cascade of signaling events. The initial signal transduction pathways known to be stimulated in mesenchymal cells include phospholipase C, phospholipase D, phospholipase A2, adenylate cyclase, receptor tyrosine kinases, and receptor serine/threonine kinases. These pathways are reviewed and specific applications for therapeutic intervention in wound healing and regenerative therapy in the periodontium are discussed.