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Biomedical subjects

M K Wu

Publications and source records attributed to M K Wu.

45 records · Page 3Linked to original sources
PubMed1993

Fluid transport and bacterial penetration along root canal fillings.

Convective transport of water from the coronal to the apical end of obturated root canals was determined by the movement of an air bubble in a capillary glass tube connected to the apex of the experimental root section using a headspace pressure of 120 kPa (1.2 atm). Water transport through existing voids in the obturated canals could be measured reproducibly in this way. The root canals of 60 human maxillary canines were filled with gutta-percha and sealer by the cold lateral condensation technique. Thirty of these were first exposed to a small motile bacterium, Pseudomonas aeruginosa, growing in a reservoir at the coronal end of each root. After 50 days, two specimens allowed penetration of bacteria to a reservoir at the apical end. All the roots were then assessed quantitatively for convective transport of water. The results were divided into three defined categories: 39 obturated canals were in the 'bacteria tight' category, 14 canals in the 'slight leakage' and 7 canals in the 'gross leakage' category. The two specimens that showed bacterial penetration fell into the slight and gross leakage categories. The previous test for bacterial passage did not statistically influence the fluid transport pattern of these roots which was measured subsequently. These findings indicate that fluids transport through obturated root canals, most of which do not allow the passage of bacteria.

Biological Transport↗
PubMed1990

Bactericidal effects of human neutrophils and sera on selected endodontic pathogenic bacteria in an anaerobic environment.

Phagocytosis by normal human neutrophils and the bactericidal activity of normal human pooled serum were measured under anaerobic conditions on six endodontic pathogenic bacterial species from the genera Actinomyces, Bacteroides, Fusobacterium, Peptostreptococcus and Streptococcus. The results revealed that Actinomyces viscosus was not killed either by human neutrophils or by 20 per cent serum; Peptostreptococcus anaerobius was not killed by either 20 per cent or 95 per cent serum; and Bacteroides intermedius was susceptible to both 20 per cent and 95 per cent serum, but was not killed by neutrophils after exposure for 20 minutes. The other species showed intermediate susceptibility patterns. Such results suggest that oral pathogens vary with regard to the bactericidal effects of these two host defense mechanisms, and that this variation may at least in part explain the relative quantities of microbes recovered in certain oral infections.

Actinomyces↗
PubMed1990

Quantitative microleakage study on a new retrograde filling technique.

An in vitro endodontic leakage model was used to compare the sealing ability of conventional retrograde amalgam fillings with a new retrograde filling technique by measuring dye leakage quantitatively. The new technique consisted of retrograde preparation of the root canal using the Endocursor, an endodontic handpiece. The canal was then filled with sealer and injection-moulded gutta-percha, using either the Hygenic Ultrafil system or the Unitek Obtura method. In both cases the gutta-percha was vertically condensed and subsequently cold-burnished. The two experimental groups and the amalgam group each consisted of 20 extracted human canine teeth and lower premolars. The results were analysed statistically by ANOVA and a Student-Newman-Keuls multiple comparison test. After 1 week at 37 degrees C, very little leakage was observed in the amalgam and gutta-percha groups. After a second week, during which leakage was enhanced by gas pressure, leakage in the amalgam group was significantly greater than that in the gutta-percha groups (P less than 0.01). There were no significant differences between the two experimental gutta-percha groups. It is concluded that the new retrograde filling technique causes less leakage than the conventional amalgam retrograde filling technique in an in vitro model.

Analysis of Variance↗
PubMed1989

Antibody formation to dog pulp tissue altered by a paste containing paraformaldehyde.

Pulpotomy treatment was performed weekly on the teeth of four dogs for 5 weeks. Antibody formation to pulp tissue altered by paraformaldehyde paste within the pulp cavity was measured by enzyme linked immunosorbent assays (ELISA). The results indicated that the reaction between antigen and antibody did occur when pretreatment or post-treatment serum reacted with the antigen of either the pulp tissue incubated with saline or that incubated with paraformaldehyde paste. No evidence was found to prove that antibody formation was related to the pulpotomy treatment with paraformaldehyde paste.

Animals↗
PubMed1989

Capacity of anaerobic bacteria enclosed in a simulated root canal to induce inflammation.

In an effort to simulate the infected dental root canal, bacteria were enclosed in polyethylene tubes that were subcutaneously implanted into rats. Four different bacterial combinations, selected from nine oral species, were tested. The contents of 144 inoculated and implanted 'root canals' were analysed after 2 and 4 weeks of implantation. Bacteroides, Streptococcus, Actinomyces and Fusobacterium were inoculated in low numbers but dominated the mixed flora at the end of the experiment. The bacteria-filled tubes induced inflammation of the rat tissue at the implant opening ('foramen'). It is confirmed that mixed bacterial populations survive, show succession and develop within an enclosed environment. Such florae cause significant inflammation at the interface with the host tissues.

Animals↗
PubMed1986

Clinical and experimental observations on resinifying therapy.

The principles, indications, and techniques of resinifying therapy and the composition of a resinifying agent are described in this article. The permeability and bacteriostasis of the agent and the volume change of the agent after treatment were observed, and 14C-labeled phenoaldehyde showed that the agent not only filled the main canals and accessory canals but also infiltrated into dentinal tubules with a depth one fourth to one third the total length of the tubules. The antimicrobial activity of the agent after polymerization for 2 to 6 months was determined. Even 9 months after treatment, no change in volume of the agent was found in vivo, and sealing of canals was maintained. Seventy-eight teeth in 69 patients with pulpoperiapical diseases were subjected to resinifying therapy and followed up for 6 to 12 months; the success rate was 82.05%. The histologic study indicated that, of the specimens experimentally treated for 6 to 12 months, 85.7% showed mild or no inflammation while 53.6% showed complete healing or an obvious healing tendency. Furthermore, the mechanisms and advantages of this therapy are discussed.

Animals↗