Aim To examine the debridement of round and oval root canals prepared to two apical sizes with and without ultrasonically activated irrigation. Methodology Mandibular premolars with round (n = 48) and oval (n = 48) root canals were pair‐matched after microCT scanning and randomly divided into two experimental groups (n = 20): group 1, rotary NiTi to size 20, .04 taper; group 2, rotary NiTi to size 40, .04 taper. Specimens were subdivided into two subgroups (n = 10): subgroup A, syringe and needle (SNI); subgroup B, ultrasonically activated irrigation (UAI). Untreated canals (eight oval and eight round) served as controls. Specimens were processed for histological evaluation for measurement of the remaining pulp tissue and debris (RPT), and the perimeter percentage of root canal area untouched by the instruments (PRAU). Following assessment of normality, multiple‐way anova models were used to study the effects of preparation size, irrigation technique and canal cross‐sectional shape, and their interactions on the RPT and PRAU (α = 0.05). Results All experimental groups had significantly less RPT than the control (P < 0.05). Both the preparation size (20 vs. 40) and the irrigation technique (SNI vs. UAI) had a significant effect on RPT (P = 0.006 and P < 0.001, respectively). Groups irrigated with SNI always had significantly greater RPT than those irrigated with UAI, irrespective of the preparation size (P < 0.001). Canals prepared to size 20 had significantly greater RPT than those with size 40 in the SNI subgroup (P < 0.001), but there was no significant difference in the UAI subgroup (P = 0.481). Conclusions Root canals prepared to a larger size (40) were cleaner than those prepared to a smaller size (20), when irrigation was performed with a syringe and needle. When the irrigant was ultrasonically activated, smaller preparations resulted in canals that were as clean as larger preparations. This finding was common to both round and oval canals of freshly extracted premolars with vital pulp tissue.

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Aim To investigate the retreatability of two calcium silicate‐based materials (BioRoot RCS, Septodont, Saint–Maur‐des‐Fossés, France and GuttaFlow Bioseal, Colténe/Whaledent AG, Langenau, Germany) using rotary instrumentation combined with supplementary irrigant agitation techniques using extracted teeth in a laboratory setting. Methodology The root canals of extracted single‐rooted mandibular premolars were prepared to size 40, .04 taper and randomly divided into two experimental groups (n = 36) depending on the root filling material. Root canals were filled with gutta‐percha and GuttaFlow Bioseal (GB, group 1) or BioRoot RCS (BR, group 2), scanned using a micro‐CT scanner and stored in phosphate‐buffered saline for 4 months. Removal of root filling was performed with rotary instruments, and specimens were randomly allocated to one of the subgroups for supplementary irrigant agitation (n = 12): subgroup A, syringe irrigation (control); subgroup B, Tornado Brush (M.I.B, Suresnes, France) and subgroup C, ultrasonically activated irrigation. Specimens were re‐scanned with micro‐CT to calculate the volume of remnant root filling material. Data were analysed statistically by two‐way ANOVA and post hoc Tukey's tests (P = 0.05). Results Specimens filled with GuttaFlow Bioseal were associated with a significantly smaller volume of root filling remnants compared with BioRoot RCS (P < 0.05). There was no significant difference between the supplementary irrigant agitation subgroups in the removal of GB (P > 0.05). In group 2 (BioRoot RCS), subgroups B (Tornado Brush) and C (ultrasonically activated irrigation) were associated with a significantly smaller volume of root filling remnants compared with subgroup A (syringe irrigation) (P < 0.05). There was no significant difference between subgroups B and C (P > 0.05). Conclusions Significantly smaller volumes of root filling remnants of GuttaFlow Bioseal, than BioRoot RCS, were present after their removal with rotary instruments and irrigation. Supplementary irrigant agitation techniques were associated with smaller volumes of remnants during the removal of BioRoot RCS but not that of GuttaFlow Bioseal.

Background Root canal treatment (RCT) of molar teeth is very challenging to undergraduate dental students. Wellstructured self-assessment was shown to be the key for improving quality of dental education so that graduates could be properly prepared to act independently in dental practice. Aims To observe the effect of rubric self-assessment teaching during the preclinical stage on the performance of undergraduate students in treating patients' molars. Methods An improved rubric was introduced to the endodontic preclinical stage through which 128 students were trained on self-assessing their practical work over an entire year (Group A). While 149 students (Group B) were taught without self-assessment. The following year, during the clinical stage, both groups were asked to treat single rooted teeth only, after they finish at least ten teeth, students who feel confident enough were allowed to do simple molar PEER REVIEW Not commissioned. Externally peer reviewed.

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