Human teeth with periapical pathosis after overinstrumentation and overfilling of the root canals: a scanning electron microscopic study.

AIM: The aim of this study was to determine whether overinstrumentation followed by immediate overfilling could be a potential risk in the treatment of infected root canals. METHODOLOGY: Thirty-five human teeth with infected root canals were overinstrumented and overfilled approximately 45 min after their extraction. The experimental teeth were enlarged up to size 40 and the overinstrumentation and overfilling were checked with the aid of a magnifying glass. The specimens were fixed in glutaraldehyde plus sodium cacodylate solution and prepared for scanning electron microscope examination. RESULTS: Bacteria were detected on the flute of the files and mostly at the root apices around the main foramen, remaining firmly attached to resorptive lacunae despite the fact that the apices had undergone great changes, including fracture or zipping. A control group consisting of 10 human teeth root canals containing vital pulps were also overinstrumented and overfilled. No bacteria were detected on the flutes of the files, at the apices or on the extruded master cone overfilling these samples. CONCLUSIONS: The high percentage of bacteria adhering to the resorptive lacunae or in the flutes of files used in overinstrumented human teeth with infected root canals carry a potential risk for postoperative pain, clinical discomfort and flare-ups. The hazards observed in these circumstances do not support the one-visit treatment of teeth having acute or chronic periapical abscesses.

Apical foraminal openings in human teeth. Number and location.

One hundred forty extracted permanent human teeth were prepared for examination with a scanning electron microscope to determine the number of foramina, their distances from the apices, and their locations. In most of the specimens, the root canals deviated to one side and ended short of the apices. Some specimens showed interradicular openings; others had configurations on the top of the apices that were similar to the crest on a helmet.

Diffusion of medicaments within root canal dentin. A scanning electron microscopic study.

Root canals of 21 maxillary human teeth were enlarged with reamers and flushed alternatively with sodium hypochlorite and hydrogen peroxide. After its mechanical preparation, root canals were dressed with camphorated paramonochloropherol and/or formocresol delivered by paper points. All three medicaments crystallize both on dentin walls and inside dentinal tubules. The clinical implications of these findings are discussed.

The risk of intentional dissolution of the smear layer after mechanical preparation of root canals.

The root canals of 27 caries-free human cuspids were divided into 3 groups of 9 teeth each. Group I was mechanically prepared with reamers and files. Alternate irrigation with 5.25% NaOCl and 3% hydrogen peroxide was used between each instrument. The group II root canals were prepared with the use of alternate irrigation with the same concentrations of NaOCl and hydrogen peroxide and finally flushed with 17% EDTA and NaOCl solution. Group III was prepared mechanically with the use of sterile distilled water as an irrigant followed by a final flush with 17% EDTA solution. The root canals of all specimens were obturated with gutta-percha points and Tubliseal by means of the lateral condensation technique. After the root canals were obturated, samples of each of the three groups were immersed in separate flasks containing Streptococcus mutans, Staphylococcus epidermidis, and Corynebacterium hofmannii. All the microorganisms tested invaded the coronal dentin--where the access cavity had been sealed with Fynal--and/or the main foramen.

Scanning electron microscope study on the action of endodontic irrigants on bacteria invading the dentinal tubules.

Three groups of 10 maxillary anterior teeth each, which had been exposed to oral media, were flushed with 9 ml of tap water, physiologic saline solution, and alternating irrigation with NaOCl and hydrogen peroxide respectively. Residual caries, necrotic tissue remnants, intertubular cavitation, and dentinal tubule invasion by bacteria were searched for by means of the scanning electron microscope. Cuboidal sodium chloride crystals were very frequently found deposited in the main root canal, in lateral canals, and inside the dentinal tubules. This study discusses the important role NaOCl may play as a solvent of dental plaque and necrotic tissue remnants in the clinical endodontic treatment of infected teeth that had been exposed to oral media.

Immune responses induced by root canal cements containing synthetic polymers.

Immunoglobulins G, A, M, and C3 were quantitated by the single radial immunodiffusion technique. The antibody response to AH26, Diaket A, and Tubliseal were also determined by the hemagglutination method using tannized erythrocytes. No increments of Ig and C3 were found by those methods and conditions under which the experiments were conducted.

Virulencia en el cobayo de cepas de Mycobacterium tuberculosis aisladas de pacientes no tratados en nueve paises americanos. / Virulence in the guinea-pig of Mycobacterium tuberculosis strains isolated from untreated patients in 9 American countries

Algunas experiencias efectuadas en el sur de la India indicarian que cepas de Mycobacterium tuberculosis de baja virulencia podrian estar produciendo efectos inmunologicos que modificarian la accion protectora de la vacuna BCG. En el estudio que aqui se presenta se trata de determinar la prevalencia de ese tipo de cepas de baja virulencia en nueve paises de las Americas. Los resultados indican que la prevalencia de esas cepas es relativamente baja en dichos paises