Changes in the fine structure of the dental pulp in human caries pulpitis. 2. Inflammatory infiltration

Stimulation of interleukin-6 production in human dental pulp cells by peptidoglycans from Lactobacillus casei

Interleukin-6 (IL-6), which is a multifunctional cytokine, has an important role in acute and chronic inflammation. The peptidoglycan (PG) was purified from Lactobacillus casei, which was a Gram-positive bacteria frequently isolated from deep carious lesions and suspected to be a pathogen of pulpitis. In this study, the effects of PG on the production of IL-6 in human dental pulp cells were examined. PG stimulated IL-6 production in a time- and dose-dependent manner. Reverse transcriptase-polymerase chain reaction experiments showed that the increase was dependent on the enhancement of IL-6 mRNA levels. These findings suggest that Gram-positive bacteria, such as L. casei, from carious lesions, might be involved in developing pulpitis through the stimulation of IL-6 production.

The association of carious dentin microflora with tissue changes in human pulpitis

Correlations were sought between the number and type of microorganisms recovered from sampled carious dentin and the cellular responses observed in dental pulpal tissues from a sample of 65 vital, carious teeth extracted from adult humans who had declined the option of tooth restoration. Standardized homogenates of carious dentin were plated using selective and nonselective media under anaerobic and microaerophilic conditions. Pulpal responses were characterized histopathologically on the basis of the nature of the cellular infiltrate and the extent of degenerative changes. A significant association between the number of Prevotella intermedia and Prevotella melaninogenica in carious dentin and extensive, principally mononuclear, inflammatory infiltration was evident despite a high degree of complexity and intersubject variability in the microbial flora. There was no apparent association between other microorganisms or total microbial load and the histopathological category.

Healing of pulp exposures: an ultrastructural study

The fine structure of tissue changes during the first 14 days following pulp exposure and capping with a hard setting Ca(OH)2 cement has been studied. The early changes included hemorrhage and moderate inflammation which were largely resolved during the first week. During the second week differentiation of cells occurred at the wound surface. These cells had the characteristic features of odontoblasts and formed a predentin-like collagen matrix. The capping material was closely adapted to cellular structures at the wound surface or to the predentin-like matrix at all observation periods. Dentin fragments displaced into the pulp tissue during cavity preparation, acted as sites for pulp stone formation.

Pulpal response to bacteria in the dog

Twenty-six teeth from 8-month-old beagle dogs were used to evaluate the pulpal response to bacteria in bacterially contaminated minimally exposed and unexposed pulp in the dog. The effects were evaluated by means of serial radiographs, consecutive vital dye injections, and histologic sections. Periapical lesions developed in all of the eight teeth which were bacterially infected and exposed. Out of ten teeth which were bacterially infected and had cavities without pulp exposure, only two teeth in the acute group demonstrated inflammatory changes and loss of odontoblastic function directly beneath the infected dentinal tubules. Within the limits of the experimental design, this study demonstrated the pulpal responses of the dog with respect to bacteria.

Arteriovenous shunts demonstrated in the apical circulation of rat incisor teeth by the use of radio-labeled microspheres

The distribution of systemically introduced 85Sr-labeled tracer microspheres to unexposed and previously exposed rat lower incisor tooth pulps was investigated. Fewer tracer microspheres entered the microcirculation of pulps that had been previously exposed as compared to control unexposed pulps. The presence of large numbers of dilated blood vessels in the apical tissues of teeth with exposed pulps was observed, and it is postulated that these vessels may be operating as arteriovenous anastomoses so that the pulpal microcirculation of teeth with inflamed pulps is bypassed by the tracer microspheres. The possible clinical significance of these findings is discussed.

Bacteria beneath composite restorations--a culturing and histobacteriological study

The occurrence, viability and identification of the microbial flora under composite fillings using an anaerobic technique were studied. Class V cavities were prepared on clinically healthy buccal surfaces of 7 contralateral pairs of premolars in children 11--15 years of age. After preparation, rubber dam was applied and one cavity in each pair of teeth was washed with water blasted dry with air and filled with Adaptic. The other cavity was washed with a cavity cleaner (Tubulicid) and a cavity liner (Tubulitec) was applicated prior to filling with Adaptic. The teeth were extracted after 4--6 weeks. Under anerobic conditions the tooth crown was split. From one half samples were taken from the pulpal wall under the filling and cultured on blood agar and in broth medium. The other half was examined with histobacteriological technique. No growth occurred in cultures from lined cavities but in 6 of the 7 unlined cavities. Full agreement was observed between the findings from the culturing and histobacteriological examinations concerning presence or absence of microorganisms at the pulpal wall in all 14 teeth. The flora was mixed. Gram-positive bacteria, mainly Streptococcus and Actinomyces, dominated over gram-negative bacteria including Veillonella, Fusobacterium, Campylobacter and Selenomonas. The composition of the flora was more similar to that observed in dental plaque than that found in carious dentin or in saliva in other studies.

Changes in the fine structure of the human dental pulp subsequent to carious exposure

Sections of human pulp tissue taken from the region of a carious exposure in four young patients each having a clinical history of spontaneous dental pain were examined with the electron microscope. All the tissues examined exhibited a generalized edema, and an infiltration with lymphocytes, plasma cells, polymorphonuclear leukocytes and macrophages. Varying degree of lysis of pulp and inflammatory cells were evident. The unmyelinated nerve axons of the pulp appeared to be least affected. Extracellular lysosomes were present in many of the necrotic areas. Edematous vacuoles were noted in two of the pulp specimens. In some of the sections these vacuoles appeared to be responsible for a physical distortion of adjacent unmyelinated nerve axons. It was postulated that such distortion may be a contributing factor to the pain of pulpitis. In another of the pulp specimens, micro-organisms were found intracellularly and extracellularly. Intracellularly they were present within the cytoplasm of polymorphonuclear leukocytes and macrophages and exhibited evidence of lysis. Only two morphological forms, a gram positive rod, and a gram positive coccus were identified.