Gilberto J. Debelian

Microbiota of periapical lesions refractory to endodontic therapy.

The periapical microbiota of 36 teeth with refractory apical periodontitis was investigated. None of the teeth had responded to conventional endodontic or long-term (> 6 months), calcium-hydroxide treatment. Eight patients had received antibiotics systemically. After anaerobic culture, a total of 148 microbial strains were detected among 67 microbial species. One of the 36 lesions was culture-negative. Approximately half (51.0%) of the bacterial strains were anaerobic. Gram-positive species constituted 79.5% of the flora. Facultative organisms, such as Staphylococcus, Enterococcus, Enterobacter, Pseudomonas, Stenotrophomonas, Sphingomonas, Bacillus, or Candida species were recovered from 27 of the lesions (75%). Sulfur granules were found in 9 lesions (25%). In these granules Actinomyces israelii, A. viscosus, A. naeslundii, and A. meyeri were identified. Other bacterial species, both gram-positive and gram-negative, were detected in the granules as well. Two sulfur granules did not contain Actinomyces. Scanning electron microscopy demonstrated rod- and spirochete-like cells in the granules, and transmission electron microscopy revealed organisms with copious amounts of extracellular material. Outer membrane vesicles were also seen. Some of the granules were calcified. This study demonstrated a wide variety of microorganisms, particularly gram-positive ones, in the periapical lesions of teeth with refractory apical periodontitis.

Effects of Electropolishing Surface Treatment on the Cyclic Fatigue Resistance of BioRace Nickel-Titanium Rotary Instruments

INTRODUCTION This study evaluated the influence of electropolishing surface treatment on the number of cycles to fracture of BioRace rotary nickel-titanium endodontic instruments. METHODS BioRace size BR5C instruments with or without electropolishing surface treatment were used in an artificial curved canal under rotational speed of 300 rpm until fracture. Fractured surfaces and the helical shafts of fractured instruments were analyzed by scanning electron microscopy (SEM). RESULTS Polished instruments displayed a significantly higher number of cycles to fracture when compared with nonpolished instruments (P < .001). Actually, the number of cycles to fracture of a polished BR5C instrument was 124% higher than that of a nonpolished instrument. SEM analysis showed that the fractured surface of both polished and nonpolished BR5C instruments had ductile morphologic characteristics. Evaluation of the separated fragments after cyclic fatigue testing showed the presence of microcracks near the fracture surface. Polished instruments exhibited fine cracks that assumed an irregular path (zigzag crack pattern), whereas nonpolished instruments showed cracks running along the machining grooves. CONCLUSIONS Electropolishing surface treatment of BioRace endodontic instruments significantly increased the cyclic fatigue resistance.

Profiling of root canal bacterial communities associated with chronic apical periodontitis from Brazilian and Norwegian subjects.

The aim of this study was to compare the bacterial community profiles of the root canal microbiota associated with chronic apical periodontitis from Brazilian and Norwegian patients using the denaturing gradient gel electrophoresis (DGGE) and the ribosomal intergenic spacer analysis (RISA) approaches. DNA extracted from root canal samples was subjected to polymerase chain reaction using primers appropriate for further DGGE or RISA analysis. The resulting banding patterns representative of the bacterial community structures in samples from the two locations were compared. DGGE and RISA fingerprints showed a great interindividual variability in the bacterial community profiles, irrespective of the geographic location of the patient. However, similarities among the bacterial community DGGE profiles revealed the existence of a geography-related pattern.

Glide Path Preparation in S-shaped Canals with Rotary Pathfinding Nickel-Titanium Instruments

INTRODUCTION This study compared the incidence of deviation along S-shaped (double-curved) canals after glide path preparation with 2 nickel-titanium (NiTi) rotary pathfinding instruments and hand K-files. METHODS S-shaped canals from 60 training blocks were filled with ink, and preinstrumentation images were obtained by using a stereomicroscope. Glide path preparation was performed by an endodontist who used hand stainless steel K-files (up to size 20), rotary NiTi PathFile instruments (up to size 19), or rotary NiTi Scout RaCe instruments (up to size 20). Postinstrumentation images were taken by using exactly the same conditions as for the preinstrumentation images, and both pictures were superimposed. Differences along the S-shaped canal for the mesial and distal aspects were measured to evaluate the occurrence of deviation. RESULTS Intragroup analysis showed that all instruments promoted some deviation in virtually all levels. Overall, regardless of the group, deviations were observed in the mesial wall at the canal terminus and at levels 4, 5, 6 and 7 mm and in the distal wall at levels 1, 2, and 3 mm. These levels corresponded to the inner walls of each curvature. Both rotary NiTi instruments performed significantly better than hand K-files at all levels (P < .05), except for PathFiles at the 0-mm level. ScoutRaCe instruments showed significantly better results than PathFiles at levels 0, 2, 3, 5, and 6 mm (P < .05). CONCLUSIONS Findings suggest that rotary NiTi instruments are suitable for adequate glide path preparation because they promoted less deviation from the original canal anatomy when compared with hand-operated instruments. Of the 2 rotary pathfinding instruments, Scout RaCe showed an overall significantly better performance.

A preliminary study of the percentage of sealer penetration in roots obturated with the Thermafil and RealSeal-1 obturation techniques in mesial root canals of mandibular molars.

OBJECTIVE The aim of this study was to evaluate the percentage of sealer penetration in root canals filled with the Thermafil or RealSeal-1 systems analyzed by confocal laser scanning microscopy (CLSM). STUDY DESIGN Twenty canals in 10 mesial roots of mandibular molars were cleaned and shaped using ProTaper and ProFile instruments to a size 35 and .04 taper at the apex and filled using RealSeal-1 or Thermafil systems in the mesial canal of each root. Horizontal sections were made at the 3 and 5 mm levels from the apex, and the percentage of sealer penetration in the root canal walls was analyzed using CLSM. RESULTS Thin layers of sealer (2-30 microm) and sealer tags into dentinal tubules were found in the root canal walls in a high percentage using both techniques at both evaluated levels, with no statistical differences between the techniques (Student t test: P > .05). CONCLUSION The percentage of sealer penetration in the root canal walls was similar using both thermoplastic carriers based systems.