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Biomedical subjects

G Sundqvist

Publications and source records attributed to G Sundqvist.

At least 37 records · Page 2Linked to original sources
PubMed1995

Effect of sonicated material from Fusobacterium nucleatum on the functional capacity of accessory cells derived from dental pulp.

Fusobacterium nucleatum-derived components were studied for their effect on the ability of accessory pulpal cells to induce T-lymphocyte proliferation. In initial experiments, spleen cells were used to establish concentration ranges at which testing of the effect of the bacterial components would be suitable. At low concentrations, bacterial substances induced a stimulatory effect on the proliferation rate of spleen cells, but not when purified T-lymphocytes were incubated in the presence of concanavalin A and pulpal accessory cells. At increasing concentrations, a dose-dependent reduction was observed. Pretreatment with the bacterial products for 4 h gave a stimulatory effect in the absence of concanavalin A for both spleen cells and T-lymphocytes. Removal of low-molecular weight components (<3.5 kDa) did not influence the inhibitory effect, whereas preheating the bacterial substances to 100 degrees C eliminated the observed inhibition. Findings show that heat-sensitive, high-molecular-weight components of F. nucleatum can evoke a concentration-dependent stimulatory or suppressive effect on the proliferation rate of T-lymphocytes in the presence of accessory cells derived from the dental pulp.

Analysis of Variance↗
PubMed1995

Tissue reaction to gutta-percha particles of various sizes when implanted subcutaneously in guinea pigs.

Tissue reaction to gutta-percha was studied using subcutaneously implanted Teflon cages in guinea pigs. Gutta-percha was tested in three forms: (i) as large particles prepared by dividing gutta-percha cones into pieces, (ii) as fine particles prepared by ball-milling of gutta-percha, and (iii) as particles produced by dissolving gutta-percha in rosin-chloroform. Gutta-percha evoked two distinct types of tissue response. The large pieces were well encapsulated and the surrounding tissue was free of inflammation. The fine particles evoked an intense, localized tissue response, characterized by the presence of macrophages and multinucleated giant cells. The rosin-chloroform treated gutta-percha induced a similar tissue reaction to that observed with the fine particles of gutta-percha. In addition, cell remnants were present in association with the material, which indicates an initial toxicity to rosin-chloroform treated gutta-percha. These results show that the size and surface character of gutta-percha can determine the type of tissue reaction to the material. The accumulation of macrophages around gutta-percha may be an important factor in the impairment of healing of periapical lesions when teeth are root filled with excess material.

Animals↗
PubMed1994

Taxonomy, ecology, and pathogenicity of the root canal flora.

The bacteria present in infected root canals include a restricted group of species compared with the total flora of the oral cavity. Conditions exist in the root canal that permit the growth of anaerobic bacteria capable of fermenting amino acids and peptides, whereas bacteria that mainly obtain energy by fermenting carbohydrates are restricted by lack of available nutrients. During the course of infection interrelationships develop between microbial species and population shifts are produced as a result of these interactions. Strong associations between certain species are present. These associations are most likely based on nutritional demands and nutritional relationships. The pathogenicity of the polymicrobial root canal flora is dependent on bacterial synergy.

Bacteria, Anaerobic↗
PubMed1993

Radicular cyst affecting a root-filled human tooth: a long-term post-treatment follow-up.

Apical periodontitis is caused primarily by microorganisms residing in the root canals of affected teeth. Nevertheless, there is convincing evidence implicating other independent factors that adversely affect the outcome of conventional root canal therapy. In this paper, morphological evidence is presented in support of the potential role of two endogenous factors that may interfere with post-endodontic healing of the periapex. The specimens consisted of a surgical biopsy of an asymptomatic periapical lesion which persisted for a follow-up period of 44 months. The biopsy was processed for correlated light and electron microscopy. The lesion was characterized by the presence of a large central lumen lined by a stratified squamous epithelium. The most striking feature of the lesion was the presence of vast numbers of cholesterol crystals which congregated in the connective tissue surrounding the cyst cavity. Extensive light and electron microscopic investigation of the apical part of the root canal and the lesion failed to reveal the presence of microorganisms. These findings strongly suggest that intrinsic factors like the accumulation of certain tissue break-down products such as cholesterol crystals, and the cystic condition of the lesion itself, can adversely affect the healing process of the periapex following root canal therapy. Consequently, such apical lesions can remain refractory to conventional endodontic therapy for long periods of time.

Adult↗
PubMed1992

Ecology of the root canal flora.

The root canal represents a special environment in which selective pressures result in the establishment of a restricted group of the oral flora. Population shifts occur over time with obligate anaerobes ultimately dominating the bacterial mix. Bacterial interrelationships and the nutritional supply are key factors in determining the outcome of the infection. Endodontic treatment, apart from directly eliminating bacteria, can completely disrupt the delicate ecology and deprive persisting bacteria of their nutritional source.

Bacteria, Anaerobic↗
PubMed1992

Pathogenicity of Actinomyces israelii and Arachnia propionica: experimental infection in guinea pigs and phagocytosis and intracellular killing by human polymorphonuclear leukocytes in vitro.

Strains of Actinomyces israelii and Arachnia propionica, isolated from clinical cases of failed endodontic therapy, were examined for: (i) their ability to survive and establish themselves in the soft connective tissue that grew into subcutaneously implanted tissue cages in guinea pigs; (ii) cell-surface hydrophobicity; and (iii) phagocytosis and killing by human polymorphonuclear leukocytes (PMNs) under aerobic and anaerobic conditions. Bacteria were inoculated into the tissue cages in guinea pigs and the cage contents were retrieved after 1, 7, 14 and 21 d for culturing and light and electron microscopy. Both bacterial species showed substantial decline in the number of bacteria by day 7 after the inoculation. Thereafter, the A. israelii strain recovered and, by day 21, had started to increase in number. Light and electron microscopy revealed the formation of typical actinomycotic colonies. A. propionica, on the other hand, continued to decline in number during the entire period of experimental infection and did not form colonies. Both strains were hydrophobic, readily phagocytosed and were efficiently killed by human PMNs under aerobic and anaerobic conditions in vitro. These results suggest that the pathogenicity of A. israelii is due to its ability to establish characteristic cohesive colonies consisting of branching filamentous organisms that are enmeshed in an extracellular matrix. It seems that the organisms existing in such colonies can collectively evade destruction and elimination by host phagocytic cells, whereas in vitro suspensions of the bacteria are easily phagocytosed and efficiently killed by PMNs. With respect to A. propionica, further investigations are necessary to understand its pathogenicity.

Actinomyces↗
PubMed1992

Associations between microbial species in dental root canal infections.

The existence of commensal or antagonistic relationships between microorganisms in the root canals of teeth with apical periodontitis was investigated. Samples were taken from 65 infected human root canals and were analysed according to species, frequency of occurrence and proportion of the total isolated flora. The most frequent species were Fusobacterium nucleatum, Prevotella intermedia, Peptostreptococcus micros, Peptostreptococcus anaerobius, Eubacterium alactolyticum, Eubacterium lentum and Wolinella recta. An odds ratio system was used to calculate positive or negative associations between the isolated bacteria. Strong positive associations were found between F. nucleatum and P. micros, Porphyromonas endodontalis, Selenomonas sputigena and W. recta. There was also a positive association between P. intermedia and P. micros, P. anaerobius and the eubacteria. In general, species of streptococci, Propionibacterium propionica, Capnocytophaga ochracea and Veillonella parvula showed no or negative associations with the other bacteria. The results are consistent with the concept of a special and selective environment occurring in the root canal that is due, in part, to the cooperative as well as antagonistic nature of the relationships between bacteria in the root canal.

Actinomyces↗
PubMed1991

The antimicrobial effect of calcium hydroxide as a short-term intracanal dressing.

The antibacterial effect of calcium hydroxide as a short-term intracanal dressing was clinically evaluated by applying the medicament for 10 minutes or 7 days in root canals of teeth with periapical lesions. The results showed that the 7-day dressing efficiently eliminated bacteria which survived biomechanical instrumentation of the canal, while the 10-minute application was ineffective.

Bacteria, Anaerobic↗
PubMed1991

Phagocytosis and virulence of different strains of Porphyromonas gingivalis.

In this study 17 strains of Porphyromonas gingivalis, both reference and clinical isolates, were investigated for their in vitro interaction with human polymorphonuclear leukocytes, hydrophobicity, density, and virulence in a mouse model. The results of the phagocytosis, hydrophobicity, and density experiments showed that P. gingivalis strains could be divided into two distinct groups. One group of strains were readily attached and phagocytosed when exposed to the leukocytes. These bacteria were hydrophobic and had a higher buoyant density than the other group, which were poorly phagocytosed, had a low buoyant density, and were hydrophilic. This latter group also exhibited an extracellular meshwork resembling a glycocalyx when examined by electron microscopy. There were also significant differences between strains in the mouse pathogenicity model. Two strains caused an invasive, spreading infection compared with the other 15 strains which produced small, localized abscesses. There was no clear correlation between the results of the phagocytosis assay and the virulence of the bacteria when injected subcutaneously in mice. Resistance to phagocytosis may be important for survival of these bacteria, but it does not in itself imply the ability to cause damage to the host.

Anaerobiosis↗
PubMed1990

Factors affecting the long-term results of endodontic treatment.

The influence of various factors that may affect the outcome of root canal therapy was evaluated in 356 patients 8 to 10 yr after the treatment. The results of treatment were directly dependent on the preoperative status of the pulp and periapical tissues. The rate of success for cases with vital or nonvital pulps but having no periapical radiolucency exceeded 96%, whereas only 86% of the cases with pulp necrosis and periapical radiolucency showed apical healing. The possibility of instrumenting the root canal to its full length and the level of root filling significantly affected the outcome of treatment. Of all of the periapical lesions present on previously root-filled teeth, only 62% healed after retreatment. The predictability from clinical and radiographic signs of the treatment-outcome in individual cases with preoperative periapical lesions cases was found to be low. Thus, factors which were not measured or identified may be critical to the outcome of endodontic treatment.

Dental Pulp Diseases↗
PubMed1990

Intraradicular bacteria and fungi in root-filled, asymptomatic human teeth with therapy-resistant periapical lesions: a long-term light and electron microscopic follow-up study.

Light and electron microscopy were used to analyze nine therapy-resistant and asymptomatic human periapical lesions, which were removed as block biopsies during surgical treatment of the affected teeth. The cases that required surgery represented about 10% of all of the cases which received endodontic treatment and root fillings during the period 1977 to 1984. These cases revealed periapical lesions when they were examined 4 to 10 yr after treatment. The biopsies were processed for correlated light and electron microscopy. Six of the nine biopsies revealed the presence of microorganisms in the apical root canal. Four contained one or more species of bacteria and two revealed yeasts. Of the four cases in which bacteria were found, only in one biopsy could they be found by light microscope. In the other three specimens, the bacterial presence could be confirmed only after repeated electron microscopic examination of the apical root canal by serial step-cutting technique. Among the three cases in which no microorganisms could be encountered, one showed histopathological features of a foreign body giant cell granuloma. These findings suggest that in the majority of root-filled human teeth with therapy-resistant periapical lesions, microorganisms may persist and may play a significant role in endodontic treatment failures. In certain instances such lesions may also be sustained by foreign body giant cell type of tissue responses at the periapex of root-filled teeth.

Adult↗
PubMed1990

Therapy-resistant foreign body giant cell granuloma at the periapex of a root-filled human tooth.

Although the primary etiological factor of periapical lesions is microbial, there are other independent factors that can adversely affect the outcome of endodontic treatment. In this communication, we present morphological evidence in support of the role of a foreign body reaction of periapical tissue to root-filling materials. The specimen consisted of a surgical biopsy of an asymptomatic periapical lesion which persisted after a decade of postendodontic follow-up. The biopsy was processed for correlated light and electron microscopy and was analyzed by various microtechniques. The unique feature of the lesion was the presence of vast numbers of large multinucleated cells and their cytoplasmic inclusion bodies. Morphologically, these multinucleated cells resembled foreign body giant cells. They contained characteristic birefringent cytoplasmic inclusions which on electron-probe X-ray microanalysis consistently revealed the presence of magnesium and silicon. The magnesium and silicon are presumably the remnants of a root-filling excess which protruded into the periapex and had been resorbed during the follow-up period. These observations strongly suggest that in the absence of microbial factors, root-filling materials which contain irritating substances can evoke a foreign body reaction at the periapex, leading to the development of asymptomatic periapical lesions that may remain refractory to endodontic therapy for long periods of time.

Biopsy↗
PubMed1989

Prevalence of black-pigmented bacteroides species in root canal infections.

The prevalence of black-pigmented Bacteroides species in the root canals of 72 teeth with apical periodontitis was evaluated. Twenty-two of the canals contained one or more species of black-pigmented Bacteroides. Bacteroides intermedius (14 strains) and Bacteroides endodontalis (5 strains) were most common. Of the species Bacteroides gingivalis, Bacteroides loeschei, and Bacteroides denticola, 2, 3, and 1 strains, respectively, were isolated. The median number of bacterial cells recovered from the root canals containing black-pigmented Bacteroides was 2.8 x 10(5) and from the other canals 3.0 x 10(3). The mean number of strains was 7.9 and 3.3, respectively. Sixteen of the 22 root canals containing black-pigmented Bacteroides species were associated with acute apical abscesses and purulent drainage through the root canal. The other six teeth with black-pigmented Bacteroides were asymptomatic. One additional abscess was present among the 72 cases. This root canal contained Actinomyces israelii and Actinomyces naeslundii.

Actinomyces↗