Interstitial fluid pressure in normal and inflamed pulp.
Tissue pressure is the hydrostatic pressure in the interstitial fluid which surrounds the pulpal cells. This pressure outside the vessels is normally considerably lower than the blood pressure inside the vessels. The dental pulp has a relatively low interstitial compliance due to its enclosure between rigid dentin walls. Accordingly, even a modest increase in pulpal fluid volume will raise the tissue pressure, which may compress blood vessels, leading to ischemia and necrosis. Inflammation may lead to an increase in both interstitial fluid volume and blood volume in the low-compliant pulp and thereby increase the tissue pressure. However, the increased tissue pressure may, in turn, initiate increased lymph flow and absorption of fluid into capillaries in nearby non-inflamed tissue. Both of these latter factors will transport fluid out of the affected area and subsequently out of the tooth and consequently lower the tissue pressure. Increased tissue pressure, whether caused by increased blood volume or increased capillary filtration, will promote outward flow of fluid through exposed dentin tubules and thereby help to protect the pulp against entry of harmful substances. It seems physiologically beneficial, therefore, for the pulp to have a high tissue pressure, which promptly increases when blood flow increases due to its low compliance. (+info)
Evidence for bacterial causation of adverse pulpal responses in resin-based dental restorations.
The widespread use of resin and resin-monomers for bonding of dental restorations to dentin has occurred because of a fundamental shift in the view that injury to the pulp is induced by restorative procedures. While, for many years, the toxic effects of restorative materials were thought to be of crucial importance in the development of adverse pulpal responses, the key role of bacterial leakage at the restoration-tooth interface is now well-recognized. Consequently, if optimal conditions for the preservation of pulpal health are to be ensured, dental restorations should provide an impervious seal against the surrounding tooth structure. However, polymerization shrinkage and contraction stresses induced during setting, as well as a variety of technical difficulties encountered during the clinical operation, often produce less than perfect results. Therefore, modern restorative procedures involving resin and resin-bonded restoratives must still rely on the ability of the pulp to cope with the injurious elements to which it may be exposed during and after the procedure. This review examines factors that may govern the pulp's response to restorative procedures that involve adhesive technologies. An assessment is made of the risks involved as far as the continued vital function of the pulp is concerned. It is concluded that an intact, although thin, wall of primary dentin often enables the pulp to overcome both toxic material effects and the influences of bacterial leakage. In contrast, the pulp may not do equally well following capping of open exposures with resin composites. A dearth of controlled clinical studies in this area of dentistry calls for confirmation that pulpal health prevails over the long term following the use of total-etch and resin-bonding techniques. (+info)
Taxonomic characterization of Mogibacterium diversum sp. nov. and Mogibacterium neglectum sp. nov., isolated from human oral cavities.
Novel isolates, strains HM-7, HM-6, HH-31, P9a-hT and UJB13-d, which were isolated from tongue plaque and necrotic dental pulp, were studied taxonomically and phylogenetically. These organisms were anaerobic, non-spore-forming, gram-positive, rod-shaped bacteria that were inert in most of the conventional biochemical tests and phenotypically resemble Mogibacterium species or asaccharolytic Eubacterium species. The G+C contents of the DNAs from the novel isolates ranged from 41 to 42 mol %. DNA-DNA hybridization studies demonstrated that these strains might be assigned to the genus Mogibacterium but not to the previously described species. It was also apparent that strain HM-7 belonged to the same species as strains HM-6 and HH-31, and that strains P9a-hT and UJB13-d belonged to a second species. The levels of DNA-DNA relatedness to asaccharolytic Eubacterium species, including Eubacterium brachy, Eubacterium nodatum, Eubacterium saphenum and the more recently proposed Eubacterium minutum and Eubacterium exiguum (reclassified as Slackia exigua), are less than 2%. The results of 16S rDNA sequence comparisons revealed that these organisms represent novel lineages distinct from all previously described species of gram-positive, rod-shaped bacteria. On the basis of phenotypic characteristics, DNA-DNA hybridization data and phylogenetic analysis with 16S rRNA gene sequence data, new species are proposed, namely Mogibacterium diversum (for strains HM-7, HM-6 and HH-31) and Mogibacterium neglectum (for strains P9a-hT and UJB13-d). HM-7T (= ATCC 700923T = JCM 11205T) is the type strain of the former and P9a-hT (= ATCC 700924T = JCM 11204T) is the type strain for the latter. (+info)
PCR-based identification of bacteria associated with endodontic infections.
PCR primers that target the bacterial 16S rRNA genes (or the tuf gene for the genus Enterococcus) were used to identify 10 putative bacterial pathogens in root canals with necrotic pulp. In addition, the associations of these microorganisms with symptoms and a history of diabetes mellitus were investigated. Microbial samples from the root canals of 24 teeth with necrotic pulp were included in the study. PCR with universal bacterial primers identified bacterial DNA in 22 specimens; the remaining 2 specimens were from intact teeth that had been traumatized 6 months prior to treatment. PCR with specific primers showed that preoperative symptoms were significantly associated with the presence of Streptococcus spp. (P < 0.001 by chi-square analysis). There was also a nonsignificant trend for symptoms to be associated with Fusobacterium nucleatum and Porphyromonas gingivalis (odds ratio, >2) and for diabetes mellitus to be associated with P. gingivalis and Porphyromonas endodontalis (odds ratio, >2). Cloning and sequencing of the universal PCR product in one specimen revealed the presence of an organism related to the genus Olsenella, which has not previously been described in endodontic infections. (+info)
Yeasts in apical periodontitis.
Microbiological reports of apical periodontitis have revealed that yeasts can be isolated from approximately 5-20% of infected root canals. They occur either in pure cultures or together with bacteria. Almost all isolated yeasts belong to the genus Candida, and the predominant species is C. albicans. Pheno- and genotypic profiles of C. albicans isolates show heterogeneity comparable with those of isolates from other oral sites. C. albicans expresses several virulence factors that are capable of infecting the dentin-pulp complex, including dentinal tubules. This causes, consequentially, an inflammatory response around the root apex, which suggests a pathogenic role for this organism in apical periodontitis. Yeasts are particularly associated with persistent root canal infections that do not respond favorably to conservative root canal therapy. This may be due to the resistance of all oral Candida species against a commonly used topical medicament, calcium hydroxide. However, other antimicrobial agents may offer alternative therapeutic approaches and improve the treatment of these persistent cases of apical periodontitis. (+info)
Prevalence of microorganisms in root canals of human deciduous teeth with necrotic pulp and chronic periapical lesions.
The objective of this study was to evaluate bacterial prevalence in 31 root canals of human deciduous teeth with necrotic pulp and periapical lesions using bacterial culture. After crown access, the material was collected using absorbent paper points for microbiological evaluation and determination of colony forming units (CFU). Anaerobic microorganisms were found in 96.7% of the samples, black-pigmented bacilli in 35.5%, aerobic microorganisms in 93.5%, streptococci in 96.7%, and S. mutans in 48.4%. We concluded that in human deciduous teeth root canals with necrotic pulp and periapical lesions the infection is polymicrobial, with a large number of microorganisms and a predominance of streptococci and anaerobic microorganisms. (+info)
Pathogenesis of apical periodontitis and the causes of endodontic failures.
Apical periodontitis is a sequel to endodontic infection and manifests itself as the host defense response to microbial challenge emanating from the root canal system. It is viewed as a dynamic encounter between microbial factors and host defenses at the interface between infected radicular pulp and periodontal ligament that results in local inflammation, resorption of hard tissues, destruction of other periapical tissues, and eventual formation of various histopathological categories of apical periodontitis, commonly referred to as periapical lesions. The treatment of apical periodontitis, as a disease of root canal infection, consists of eradicating microbes or substantially reducing the microbial load from the root canal and preventing re-infection by orthograde root filling. The treatment has a remarkably high degree of success. Nevertheless, endodontic treatment can fail. Most failures occur when treatment procedures, mostly of a technical nature, have not reached a satisfactory standard for the control and elimination of infection. Even when the highest standards and the most careful procedures are followed, failures still occur. This is because there are root canal regions that cannot be cleaned and obturated with existing equipments, materials, and techniques, and thus, infection can persist. In very rare cases, there are also factors located within the inflamed periapical tissue that can interfere with post-treatment healing of the lesion. The data on the biological causes of endodontic failures are recent and scattered in various journals. This communication is meant to provide a comprehensive overview of the etio-pathogenesis of apical periodontitis and the causes of failed endodontic treatments that can be visualized in radiographs as asymptomatic post-treatment periapical radiolucencies. (+info)
Fiber optic fluorescence microprobe for endodontic diagnosis.
Successful endodontic therapy requires total debridement as well as complete obturation of the root canal to the cemento-dentinal junction. The goal of this study was to investigate the feasibility of using quantitative fluorescence spectroscopy for the detection and localization of pathological dentin, pulpal remnants, and microorganisms within the root canal. Specific aims were to identify: 1) characteristic excitation/emission spectra for healthy dentin, decayed dentin, enamel, and pulp; 2) the potential of specific spectral data for differentiating between these tissues; and 3) the potential of spectral data for detecting the presence and identifying four common endodontic pathogens. Fluorescence spectra were determined in the tissues of permanent human teeth, extirpated healthy and necrotic pulps, and four endodontic pathogens. Excitation/emission spectra were collected at 366 nm, 405 nm, and 440 nm excitation. Marked differences in spectral signatures between the different tissues under investigation were observed. We postulate that the differences in fluorescence spectra of decayed vs. healthy dentin are due to the loss of mineralized tissue components and increased organic presence and water in these tissues. Pulpal tissue showed distinctly different fluorescence spectra from healthy and decayed dentin, providing a basis for differentiating between tissue categories. Each bacterial species demonstrated distinct spectral emission patterns. (+info)