Effect of root canal curvature on the failure incidence of ProFile rotary Ni-Ti endodontic instruments.

AIM: To investigate the effect of root canal curvature on the failure incidence and fracture mechanism of ProFile rotary Ni-Ti endodontic instruments. METHODOLOGY: Three hundred mesial root canals of mandibular molars were instrumented using the ProFile system in a crown-down technique up to size 25 0.06 taper. Root canals were classified according to the angle and radius of curvature to: straight (group A: 0 + 10°, radius 0 mm), moderately curved (group B: 30 ± 10°, radius 2 ± 1 mm) and severely curved (group C: 60 ± 10°, radius 2 ± 1 mm). After each use, instruments were cleaned ultrasonically and autoclaved. Instruments that prepared 20 root canals, fractured or were plastically deformed without fracture were retrieved and substituted. Kaplan-Meier estimator was used for survival analysis and post hoc test for determination of significant differences (a=0.05). All fractured instruments were subjected to fractographic analysis under SEM, and all used instruments were viewed under the metallographic microscope. RESULTS: Regardless of the size of instrument, fracture and overall failure were significantly more frequent (P<0.05) in group C. SEM examination of the fracture surfaces revealed mainly the characteristic pattern of ductile failure, whereas examination under the metallographic microscope revealed no sign of cracks. CONCLUSIONS: The abruptness of root canal curvature negatively affected the failure rate of ProFile rotary Ni-Ti instruments. The fractographic results confirmed that failure of Ni-Ti files was caused by a single overload during chemomechanical preparation.

An unusual case of root perforation caused by surgical trephination.

AIM: To present the diagnosis and management of an unusual case of root perforation caused by surgical trephination. SUMMARY: A root perforation caused by surgical trephination on a maxillary lateral incisor with diagnosis of symptomatic chronic periradicular periodontitis was managed with standard root canal preparation and filling with thermoplasticized gutta-percha. Recall radiographs up to 1 year revealed healing of the periapical lesion. *During surgical trephination, there is risk of damaging anatomical structures surrounding the tooth as well as the tooth itself. *Root perforation caused by trephination was successfully managed by standard canal preparation and filling with thermoplasticized gutta-percha.

Ex vivo study of the efficacy of H-files and rotary Ni-Ti instruments to remove gutta-percha and four types of sealer.

AIM: To compare the efficacy of ProFile rotary Nickel-Titanium (Ni-Ti) instruments and Hedstroem-files (H-files) combined with Gates-Glidden (GG) drills during removal of gutta-percha root fillings used in combination with one of the four representative sealers. METHODOLOGY: Forty-eight single-rooted human teeth, with fully formed apices and straight root canals were used. The root canals were accessed and instrumented using a stepback technique with H-files. They were randomly assigned to four groups and subsequently filled with a combination of lateral and vertical condensation of gutta-percha and one of the following sealers: Roth 811, AH26, Endion and Roekoseal. The root fillings were removed 1 year later, using either H-files in combination with GG drills or the ProFile Ni-Ti system. Teeth were then grooved longitudinally and split. The amount of gutta-percha and sealer remaining on the root canal walls was traced and scored visually with the aid of a stereomicroscope. The scores were analysed and statistically compared with the Kruskal-Wallis test between the ProFile and H-file groups, as well as among the four sealer subgroups. Two samples from each group were studied under the scanning electron microscope to enhance inspection of canal walls and remaining material. RESULTS: Sealer remnants were observed with both techniques mainly in the middle and apical third of the root canal. The ProFile system and the H-files were associated with similar amounts of remaining filling material (P > 0.05). In the cervical third of the root canal all sealer remnants were removed with both techniques. In the middle and apical third AH26 was associated with a statistically significant greater quantity of remnants on the root canal walls with both removal techniques (P < 0.05). Endion, Roth 811 and Roekoseal were associated with approximately the same amount of filling material in the middle third of the root canal (P > 0.05), whereas in the apical third Endion was associated with significantly more remnants of filling material than the other two sealers with either ProFile or H-files (P < 0.05). CONCLUSIONS: None of the methods used for the removal of root fillings was totally effective, especially in the apical third of the root canal.

Removal efficacy of various calcium hydroxide/chlorhexidine medicaments from the root canal.

AIM: To compare the efficiency of removing calcium hydroxide [Ca(OH)(2)]/chlorhexidine (CHX) (gel), Ca(OH)(2)/CHX (solution) and Ca(OH)(2)/saline pastes with the use of instrumentation and irrigation with sodium hypochlorite and ethylene diamine tetraacetic acid (EDTA) solutions. Moreover the role of the patency file in the cleanliness of the apical third of the root canal was evaluated. METHODOLOGY: Sixty-four human single-rooted teeth with straight canals were used. Root canal preparation was performed with a stepback technique using Hedström (H) files. Teeth were randomly assigned to three groups and subsequently filled with one of the pastes: Ca(OH)(2)/CHX (gel), Ca(OH)(2)/CHX (solution) and Ca(OH)(2)/saline paste. The medicaments were removed 10 days later using instrumentation and irrigation with 1% sodium hypochlorite and 17% EDTA, with or without obtaining patency of the apical foramen with a size 10 H-file. The crowns were removed at the cemento-enamel junction and the roots were grooved longitudinally and split into halves. Images of all halves were acquired with the use of a flatbed scanner. A scoring system of 1 to 4 was used to assess the amount of residue on the cervical, middle and apical third of the canal. Data were subjected to statistical analysis using Kruskal-Wallis and Mann-Whitney tests, with Bonferroni correction, at 95% confidence level (P < 0.05). RESULTS: Remnants of medicament were found in all experimental teeth regardless of the experimental material used and the use of the patency file. When examining the root canal as a whole, Ca(OH)(2)/CHX (gel) paste was associated with significantly larger amount of residue, whereas the Ca(OH)(2)/CHX (solution) paste was associated with less amount (P < 0.05) than the other two medicaments with or without the use of a patency file. CONCLUSIONS: None of the techniques used in this study removed the inter-appointment root canal medicaments effectively; the use of the patency file facilitated removal of more of the medicament in the apical third of those straight canals.

Healing of a radiolucent periradicular lesion with periradicular radiopacity.

Periradicular radiopacities that reveal the existence of sclerotic bone are less common than periradicular radiolucencies. Replacement of a radiolucent periradicular area by sclerotic bone after endodontic treatment is not very often reported and may be confused with condensing osteitis. An unusual case is presented of sclerotic bone formation after endodontic treatment of a first mandibular molar with initial diagnosis of apical periodontitis.