Critical reviews in oral biology and medicine : an official publication of the American Association of Oral Biologists最新文献

Smokeless tobacco has been associated with oral cancer for many decades. The purpose of this article is to review research relevant to this association, including epidemiologic studies, studies of putative carcinogens such as tobacco-specific nitrosamines (TSNAs) and other contaminants, and possible cancer inhibitors. Epidemiologic studies addressing this issue primarily consist of case-control studies. They show that the use of chewing tobacco and moist snuff is associated with very low risks for cancers of the oral cavity and related structures (relative risks [RR] from 0.6 to 1.7). The use of dry snuff is associated with higher RRs, ranging from 4 to 13, while the RRs from smokeless tobacco, unspecified as to type, are intermediate (RR = 1.5 to 2.8). With regard to TSNAs, historical levels in American moist snuff products were higher than those in their Swedish counterparts, but levels in contemporary products are uniformly low. TSNA levels in chewing tobacco have always been low, but levels in dry snuff have been higher, including some very high levels in current products. In general, smokeless tobacco users are not exposed to significant levels of cadmium, lead, benzo(a)pyrene, polonium-210, and formaldehyde, when compared with concentrations of these compounds in foods. Finally, low oral cancer risk from smokeless tobacco use may be influenced by the presence of cancer inhibitors, mainly anti-oxidants, in smokeless tobacco products.

Patients with a severely resorbed edentulous mandible often suffer from problems with the lower denture. These problems include: insufficient retention of the lower denture, intolerance to loading by the mucosa, pain, difficulties with eating and speech, loss of soft-tissue support, and altered facial appearance. These problems are a challenge for the prosthodontist and surgeon. Dental implants have been shown to provide a reliable basis for fixed and removable prostheses. This has resulted in a drastic change in the treatment concepts for management of the severely resorbed edentulous mandible. Reconstructive, pre-prosthetic surgery has changed from surgery aimed to provide a sufficient osseous and mucosal support for a conventional denture into surgery aimed to provide a sufficient bone volume enabling implants to be placed at the most optimal positions from a prosthetic point of view. The aim of this paper is to review critically the literature on procedures related to the severely resorbed edentulous mandible and dental implant treatment. The study includes the transmandibular implant, (short) endosseous implants, and reconstructive procedures such as distraction osteogenesis, augmentation of the mandibular ridge with autogenous bone, and bone substitutes followed by the placement of implants. The number of patients participating in a study, the follow-up period, the design of the study, the degree of mandibular resorption, and the survival rate of the dental implants all are considered evaluation parameters. Although numerous studies have described the outcome results of dental implants in the edentulous mandible, there have been few prospective studies designed as randomized clinical trials that compare different treatment modalities to restore the severely resorbed mandible. Therefore, it is not yet possible to select an evidence-based treatment modality. Future research has to be focused on long-term, detailed follow-up clinical trials before scientifically based decisions in treating these patients can be made. This will contribute to a higher level of care in this field.

A wide spectrum of drugs can sometimes give rise to numerous adverse orofacial manifestations, particularly dry mouth, taste disturbances, oral mucosal ulceration, and/or gingival swelling. There are few relevant randomized double-blind controlled studies in this field, and therefore this paper reviews the data from case reports, small series, and non-peer-reviewed reports of adverse drug reactions affecting the orofacial region (available from a MEDLINE search to April, 2003). The more common and significant adverse orofacial consequences of drug therapy are discussed.

Motile bacteria often use sophisticated chemotaxis signaling systems to direct their movements. In general, bacterial chemotactic signal transduction pathways have three basic elements: (1) signal reception by bacterial chemoreceptors located on the membrane; (2) signal transduction to relay the signals from membrane receptors to the motor; and (3) signal adaptation to desensitize the initial signal input. The chemotaxis proteins involved in these signal transduction pathways have been identified and extensively studied, especially in the enterobacteria Escherichia coli and Salmonella enterica serovar typhimurium. Chemotaxis-guided bacterial movements enable bacteria to adapt better to their natural habitats via moving toward favorable conditions and away from hostile surroundings. A variety of oral microbes exhibits motility and chemotaxis, behaviors that may play important roles in bacterial survival and pathogenesis in the oral cavity.

The bilaterally symmetric body plan of vertebrates features several consistent asymmetries in the placement, structure, and function of organs such as the heart, intestine, and brain. Deviations from the normal pattern result in situs inversus, isomerisms, or heterotaxia (independent randomization), which have significant clinical implications. The invariance of the left-right (LR) asymmetry of normal morphology, neuronal function, and phenotype of several syndromes raises fascinating and fundamental questions in cell, developmental, evolutionary, and neurobiology. While a pathway of asymmetrically expressed signaling factors has been well-characterized in several model systems, very early steps in the establishment of LR asymmetry remain poorly understood. In particular, the origin of consistently oriented asymmetry is unknown. Recently, a candidate for the origins of asymmetry has been suggested: bulk transport of extracellular morphogens by rotating primary cilia during gastrulation. This model is appealing because it 'bootstraps' morphological asymmetry of the embryo from the intrinsic structural (molecular) chirality of motile cilia. However, conceptual and practical problems remain with this hypothesis. Indeed, the genetic data are also consistent with a different mechanism: cytoplasmic transport roles of motor proteins. This review outlines the progress and remaining questions in the field of left-right asymmetry, and focuses on an alternative model for 'Step 1' of asymmetry. More specifically, based on wide-ranging data on ion fluxes and motor protein function in several species, it is suggested that laterality is driven by pH/voltage gradients across the midline, which are established by chiral movement of motor proteins with respect to the cytoskeleton.

Human papillomavirus (HPV) infection with high-risk types 16 and 18 has widely been reported as one of the prominent mechanisms behind the development of cervical squamous cell carcinoma. Links between HPV and oral cavity cancer have been suggested as well, based on epidemiologic and molecular means, though the association is less well-established. It is likely that HPV plays a role in oral cavity carcinogenesis, though only in a small subset of cases. The difficulty in providing true causal evidence of HPV's role in oral cancer lies in our lack of understanding of the significance of mechanisms by which HPV leads to oral carcinogenesis, as well as limitations in the molecular analysis of HPV. Further studies are necessary for the contribution of HPV in oral cavity malignancy to be better demonstrated.

The etiology and pathogenic mechanisms underlying Sjögren's syndrome (SS) remain unclear. Recent studies have emphasized that the specific autoantibodies that occur in a high proportion of patients with SS may provide important insights into the circumstances that initiate and propagate tissue damage in this disease. Although autoantigens targeted in systemic autoimmune diseases share little in common in terms of structure, subcellular distribution, or function in normal cells, these molecules are unified by becoming clustered and concentrated in the surface blebs of apoptotic cells. Furthermore, their structure is altered during some types of cell death to generate structures not previously generated during development and homeostasis. This review highlights the susceptibility of SS autoantigens to undergoing such structural changes during activation of immune effector pathways, and synthesizes a model of SS incorporating these concepts. An understanding of the mechanisms responsible for activating the specific immune response in SS, and the role of specific immune effector pathways in propagating both the autoimmune response and tissue damage, is of potential therapeutic importance. Abbreviations used in this paper are: CTL, cytotoxic T-lymphocytes; ER, endoplasmic reticulum; GluR3, subunit III of the glutamate receptor; GrB, granzyme B; M3R, type III muscarinic receptor; NK cells, natural killer cells; PARP, poly(ADP-ribose)polymerase; SS, Sjögren's syndrome; SLE, systemic lupus erythematosus; and UV, ultraviolet.

The Obstructive Sleep Apnea-Hypopnea Syndrome (OSAHS) is a common sleep-related breathing disorder characterized by repetitive obstructions of the upper airway during sleep. Modification of pharyngeal patency by Oral Appliance (OA) therapy has been suggested as an alternative to various treatment modalities for OSAHS. To determine the evidence base with respect to the efficacy and co-morbidity of OA therapy in OSAHS, we conducted a systematic review of the available literature. Primary outcome measures were the reduction in number of upper-airway obstructions and co-morbidity related to the craniomandibular or craniofacial complex, respectively. Eligible studies regarding efficacy were independently assessed by two assessors using a quality assessment scale. Effect sizes of methodologically sound studies were calculated. In identical interventions, effect sizes were pooled with the use of a random-effects model. Given the scarcity of controlled studies related to co-morbidity, appraisal was confined to a description of eligible studies. Sixteen controlled trials related to efficacy were identified. With respect to the primary outcome measure, OA therapy was clearly more effective than control therapy (pooled effect size, -0.96; 95% confidence interval [CI], -1.49 to -0.42) and possibly more effective than uvulopalatopharyngoplasty. Although patients generally preferred OA therapy, improvement of respiratory variables, such as the number of upper-airway obstructions, was usually better in Continuous Positive Airway Pressure (CPAP) therapy (pooled effect size, 0.83; 95% CI, 0.59 to 1.06). Moreover, specific aspects related to OA design may influence patient-perceived efficacy and preference. Twelve patient-series and one controlled trial related to co-morbidity were identified. Analysis of the data suggests that OA therapy may have adverse effects on the craniomandibular and craniofacial complex. Although CPAP is apparently more effective and adverse effects of OA treatment have been described, it can be concluded that OA therapy is a viable treatment for, especially, mild to moderate OSAHS. Controlled studies addressing the specific indication and co-morbidity of OA therapy are warranted.

Polymerization contraction stress of dental composites is often associated with marginal and interfacial failures of bonded restorations. The magnitude of stress depends on composite composition (filler content and matrix composition) and its ability to flow before gelation, which is related to the cavity configuration and curing characteristics of the composite. This article reviews variations among studies regarding contraction-stress-testing methods and contraction stress values of current composites, and discusses the validity of contraction stress studies in relation to results from microleakage tests. The effects of lower curing rates and alternative curing routines on contraction stress values are also discussed, as well as the use of low-elastic-modulus liners. Moreover, studies with experimental dimethacrylate-based composites and recent developments in low-shrinkage monomers are described.

The extracellular matrix (ECM) of bone and dentin contains several non-collagenous proteins. One category of non-collagenous protein is termed the SIBLING (Small Integrin-Binding LIgand, N-linked Glycoprotein) family, that includes osteopontin (OPN), bone sialoprotein (BSP), dentin matrix protein 1 (DMP1), dentin sialophosphoprotein (DSPP), and matrix extracellular phosphoglycoprotein (MEPE). These polyanionic SIBLING proteins are believed to play key biological roles in the mineralization of bone and dentin. Although the specific mechanisms involved in controlling bone and dentin formation are still unknown, it is clear that some functions of the SIBLING family members are dependent on the nature and extent of post-translational modifications (PTMs), such as phosphorylation, glycosylation, and proteolytic processing, since these PTMs would have significant effects on their structure. OPN and BSP are present in the ECM of bone and dentin as full-length forms, whereas amino acid sequencing indicates that DMP1 and DSPP exist as proteolytically processed fragments that result from scission of X-Asp bonds. We hypothesized that the processing of DMP1 and DSPP is catalyzed by the PHEX enzyme, since this protein, an endopeptidase that is predominantly expressed in bone and tooth, has a strong preference for cleavage at the NH2-terminus of aspartyl residue. We envision that the proteolytic processing of DMP1 and DSPP may be an activation process that plays a significant, crucial role in osteogenesis and dentinogenesis, and that a failure in this processing would cause defective mineralization in bone and dentin, as observed in X-linked hypophosphatemic rickets.