Influence of solvent and a supplementary step with a finishing instrument on filling material removal from canals connected by an isthmus.

AIM: To evaluate the effectiveness of a solvent (eucalyptol) in improving filling material removal from canals connected by isthmuses, and the additional cleaning effect of a finishing instrument. METHODOLOGY: The mesial canals from 32 mandibular molars (Vertucci's type II morphology) were instrumented and filled with the single-cone technique using Reciproc R25 gutta-percha points (VDW, Munich, Germany) combined with Sealer 26 (Dentsply, Petrópolis, RJ, Brazil). Each root was then subjected to retreatment using the Mtwo instrument system (VDW), with or without a solvent (n = 16 per group). The volume of filling material in the canals was assessed by micro-computed tomographic (micro-CT) scans taken before and after retreatment. Canals with remnants of filling material received a supplementary procedure with the XP-endo Finisher R instrument (FKG Dentaire, La Chaux-de-Fonds, Switzerland), with or without eucalyptol, and another micro-CT scan was taken. All retreatment procedures were performed inside a cabinet under a controlled temperature (37 °C). Filling material removal was evaluated in the 5-mm apical canal system for the canal+isthmus space or the isthmus alone. Statistical analyses were performed to compare the removal of filling material with and without eucalyptol, and after a supplementary approach with XP-endo Finisher R. The level of significance was set at 5% for all statistical tests (P < 0.05). RESULTS: The amount of filling material removed from the canal+isthmus with Mtwo instruments was 83.2% when no solvent was used and 83.8% using the solvent (P > 0.05). When the isthmus area was evaluated separately, most specimens were associated with a reduction in the filling material, with no significant difference between the groups with or without using a solvent (P > 0.05). The supplementary step with XP-endo Finisher R significantly improved removal of filling material from both canal and isthmus area (P < 0.05), regardless of the use of a solvent (P > 0.05). CONCLUSION: The use of eucalyptol did not improve filling material removal from Vertucci's type II molar mesial canals and isthmuses. XP-endo Finisher R significantly enhanced removal of filling material from the canals and isthmuses.

Effects of preparation with the Self-Adjusting File, TRUShape and XP-endo Shaper systems, and a supplementary step with XP-endo Finisher R on filling material removal during retreatment of mandibular molar canals.

AIM: To compare the effects of three instrumentation systems, and a supplementary approach with a finishing instrument, on filling material removal during retreatment of mandibular molar canals. METHODS: Sixty mesial canals from mandibular molars (Vertucci's type IV anatomy) were instrumented, filled and subjected to retreatment. After initial removal of the root canal filling material using the D-RaCe system, the canals were randomly distributed into three groups (n = 20) according to the instrument system used for preparation: the Self-Adjusting File (SAF), TRUShape or XP-endo Shaper. The filling material volume in the apical 5 mm of the canals was assessed by means of micro-computed tomography (micro-CT) before and after retreatment. All specimens with residual filling material were subjected to a supplementary approach with the XP-endo Finisher R instrument and another micro-CT scan was taken. Data on the volumes of filling material and incidence of total removal were compared between groups by the general linear model for paired data and the Fisher's exact test. The effects of the refinement step were evaluated by the Wilcoxon Signed Ranks test. RESULTS: The amount of removed material was 92.4%, 96.9% and 96.9% for the SAF, TRUShape and XP-endo Shaper, respectively. There were no significant differences between them (P > 0.05). Canals were completely cleaned of filling material in 70% of the specimens for XP-endo Shaper, 55% for SAF and 30% for TRUShape; the difference between XP-endo Shaper and TRUShape was significant (P = 0.03). The supplementary step with the XP-endo Finisher R instrument was associated with additional filling material removal of 38% (P < 0.001). Six more canals were rendered free of filling material after using this finishing instrument. CONCLUSIONS: The tested systems were equally effective in removing the mass of filling material from the apical 5 mm of molar canals. The supplementary step with the XP-endo Finisher R instrument enhanced filling material removal.

Effects of increased apical enlargement on the amount of unprepared areas and coronal dentine removal: a micro-computed tomography study.

AIM: To evaluate the effects of progressive apical enlargement on the amount of unprepared root canal surface area and remaining dentine thickness. METHODOLOGY: The root canals of 30 extracted mandibular incisors with Vertucci's type I configuration were instrumented with rotary HyFlex CM instruments (Coltene-Whaledent, Altstätten, Switzerland) up to 4 instruments larger than the first one that bound at the working length (WL). Teeth were scanned in a micro-computed tomography (micro-CT) device before canal preparation and after instrumentation with the 2nd, 3rd and 4th larger instruments. The amount of unprepared surface area in the full canal or in the apical 4 mm as well as the remaining dentine thickness at 10 mm from the WL were calculated and compared. The general linear model for repeated measures adjusted by Bonferroni's post hoc test was used for statistic analysis. RESULTS: There was a significant reduction in the amount of unprepared areas after each increase in preparation size (P < 0.01). This was observed for both the full canal length and the 4-mm apical segment. The amount of remaining dentine was also significantly reduced after each file size (P < 0.01). However, dentine thickness always remained greater than 1 mm, even after using the largest instrument. CONCLUSION: Apical preparations up to 4 instruments larger than the first one to bind at the WL caused a significant progressive reduction in the unprepared canal area.

What happens to unprepared root canal walls: a correlative analysis using micro-computed tomography and histology/scanning electron microscopy.

AIM: To microscopically examine the cleanliness of root canal walls that remained unprepared as revealed by micro-CT. METHODOLOGY: The root canals of 10 freshly extracted mandibular premolars with necrotic pulps and apical periodontitis along with the mesiobuccal canals of 11 mandibular molars with vital pulps were prepared using Reciproc instruments R40 and R25, respectively, and 2.5% sodium hypochlorite irrigation. Specimens were scanned in micro-CT before and after preparation, and the unprepared areas were identified. The outer root surface corresponding to the untouched areas was marked on each root third to guide further analysis using histological (for teeth with vital pulps) and scanning electron microscopic (SEM; for necrotic teeth) examination. In the teeth with vital pulps, the root canal area occupied by tissue remnants was calculated. In SEM analysis of teeth with necrotic pulps, scores were attributed for the amount of debris on the untouched areas. RESULTS: The proportion of unprepared areas in the mesiobuccal molar canals was 18.1% and 9.6% over the full canal length and apical canal, respectively. In premolars, corresponding figures were 34.6% and 17.6%, respectively. Histological analysis of canals with vital pulps revealed tissue remnants over the untouched walls almost exclusively in the apical canal. SEM analysis of the canals with necrotic pulps revealed debris along the untouched walls in all root canal thirds. CONCLUSION: The areas that remain untouched by Reciproc instruments used with 2.5% NaOCl irrigation as revealed by micro-CT analysis were usually covered with debris, in the form of pulp tissue remnants, bacteria and dentine chips, especially in the apical root canal.

Micro-CT evaluation of the efficacy of hard-tissue removal from the root canal and isthmus area by positive and negative pressure irrigation systems.

AIM: To evaluate the removal of accumulated hard-tissue debris (AHTD) from the root canal system of mandibular molars by positive and negative pressure irrigation systems, using micro-CT imaging analysis. METHODOLOGY: Mandibular molars with a single canal in the distal root and 2 canals connected by an isthmus in the mesial root were matched based on similar morphological dimensions using micro-CT evaluation and assigned to 2 experimental groups (n = 20 mesial and 10 distal canals), according to the irrigation protocol: apical positive (conventional irrigation) or negative (EndoVac system) pressure. Changes in root canal volume and surface area as well as percentage of uninstrumented canal wall surface and accumulated hard-tissue debris (AHTD) after canal preparation were compared statistically using the independent sample t-test and Mann-Whitney U-test, with the significance level set at 5%. RESULTS: Volume, surface area and percentage of static voxels in either mesial or distal root canal systems were not significantly different between groups before or after root canal preparation (P > 0.05). After preparation, AHTD was not observed in the distal canal of both groups. However, in the mesial root canal system, the conventional irrigation group was associated with a significantly higher median percentage of AHTD (11.48%; IQR: 5.9-22.6; range: 1.86-41.98) than the EndoVac group (3.40%; IQR: 1.5-7.3; range: 0.82-12.84) (P < 0.05). CONCLUSIONS: Neither irrigation protocol succeeded in rendering the mesial canal system free of AHTD; however, apical negative pressure irrigation resulted in lower levels of AHTD than conventional irrigation.

Shaping ability of single-file reciprocating and heat-treated multifile rotary systems: a micro-CT study.

AIM: To investigate changes in three-dimensional geometry, in various cross-sectional morphological parameters and in the centring ability of root canals prepared with different preparation systems using microcomputed tomographic imaging technology. METHODOLOGY: Sixty-four mesial canals of mandibular molars were matched based on similar morphological dimensions using micro-CT evaluation and assigned to four experimental groups (n = 16), according to the canal preparation technique: Reciproc, WaveOne, Twisted File and HyFlex CM systems. Changes in several 2D (area, perimeter, form factor, roundness, minor and major diameter) and 3D [volume, surface area, structure model index (SMI)] morphological parameters, as well as canal transportation, were compared with preoperative values using Kruskal-Wallis and anovapost hoc Tukey's tests with the significance level set at 5%. RESULTS: Preparation significantly increased all tested parameters in the experimental groups. No significant differences were observed between groups regarding changes in volume, surface area, SMI, form factor and roundness of the root canal after preparation (P > 0.05). In the apical third, the Reciproc group had significantly greater changes in canal area, perimeter, major and minor diameters than the other groups (P < 0.05). Overall, the Twisted File and HyFlex CM systems were associated with significantly less transportation than the reciprocating instruments, Reciproc and WaveOne (P < 0.05). CONCLUSIONS: Shaping procedures led to the enlargement of the root canal space with no evidence of significant preparation errors. Changes in 3D parameters were not different between groups whilst, in the apical third, Reciproc was associated with significantly greater changes in several 2D parameters compared to the other groups. Twisted File and HyFlex CM systems were able to maintain the original canal anatomy with less canal transportation than Reciproc and WaveOne; however, these differences are unlikely to be of clinical significance.

Pre-eruptive intracoronal resorption in a third upper molar: clinical, tomographic and histological analysis.

Radiolucent or hypodense lesions in the crown of unerupted teeth may be due to pre-eruptive intracoronal resorption. Clinicians must be aware of this risk so that they can diagnose and appropriately treat this condition. The purpose of this study is to present a well-documented clinical case of pre-eruptive intracoronal resorption in an impacted third upper left molar of a 63 year old female patient. This was an unexpected finding, which occurred after cone-beam computed tomography was used to investigate the first upper left molar, which had an acute periradicular abscess. A multidisciplinary team followed up the case to describe clinical, radiographic and histological findings. The available treatment options were discussed, and the tooth extraction was the option chosen. Previous case studies describing such resorption in third upper molars have not been reported. This case shows that all permanent teeth in a pre-eruptive stage must be analysed radiographically to detect early pre-eruptive intracoronal resorption.