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Aim: To evaluate the correlation between the volume of dental hard tissues removed and the fracture resistance of mandibular molar teeth with ultraconservative (UltraAC) or traditional (TradAC) access cavity preparations. Methodology: Sixty recently extracted and intact mandibular first molars were scanned in a microcomputed tomographic (micro‐CT) device, anatomically matched and assigned at random to 2 groups (n = 30), according to the access cavity type: UltraAC or TradAC. After access preparation, mesial and distal canals were prepared using Reciproc instruments and a new scan was taken. The volumes of pulp chamber and dental hard tissues in each specimen were measured before and after the experimental procedures, and the percentage volume reduction of hard tissues calculated for the entire tooth and for the crown separately. Teeth were then root filled, restored and subjected to fracture resistance tests in an universal testing machine. The force required to fracture was recorded in Newtons (N). The adherence of the variables to a Gaussian curve was verified using a Shapiro–Wilk test. Skewed data were analysed with nonparametric Wilcoxon signed rank or Spearman correlation tests, whilst the normally distributed data were analysed with a dependent samples Student t‐test. Level of significance was set at 5%. Results: Pre‐operatively, no difference was observed between groups regarding the volume of pulp canal space or dental hard tissues (P > 0.05). After access preparation, volumes of the removed hard tissues from the entire tooth and from the crown were significantly greater in teeth prepared with TradAC than with UltraAC (P < 0.05). No significant difference was observed in the fracture resistance values between TradAC (902.9 ± 347.8 N) and UltraAC (948.7 ± 405.7 N) groups (P = 0.975). The Spearman test was unable to identify a correlation between fracture resistance and percentage volume of removed dental hard tissues in the entire root (P = 0.525, r = −0.084) or only in the crown (P = 0.152, r = −0.187). Conclusion: The volume of hard dental tissues removed, although greater in teeth with TradAC compared to UltraAC, did not correlate with the fracture resistance results, indicating that a minimally invasive access cavity did not increase the resistance of restored mandibular first molars to fracture. [ABSTRACT FROM AUTHOR]

Aim: To validate a new method for the evaluation of pulp tissue debridement in the root canals of extracted teeth using an impregnation protocol involving potassium triiodide, a radiocontrast solution known as Lugol's, combined with micro‐computed tomographic (micro‐CT) imaging. Methodology: The impact of NaOCl on the radiopacity of Lugol's solution was assessed using a two‐fold dilution series of Lugol in distilled water and 5.25% NaOCl, which were then pipetted into transparent dishes and radiographed. To verify the influence of Lugol on the proteolytic effect of NaOCl, a dissolution test was performed using fresh bovine meat. Ten slices did not undergo any tissue processing, whilst twenty slices were fixed in formaldehyde for 24 h. After that, 10 of them were immersed in Lugol for another 24 h. Then, all specimens were placed in NaOCl and the time required for a complete tissue dissolution was recorded. For the last experiments (histological validation and micro‐CT assessment), 8 extracted mandibular premolars with formerly vital pulps were immersed in buffered formalin, scanned in a micro‐CT device, accessed, immersed in Lugol for 7 days and scanned again. Then, the root canals of 5 teeth were prepared and scanned, and the volume of remaining pulp tissue identified and quantified, whilst 3 teeth were histologically processed. The same specimens were subjected to histological assessment, and the images of the histologic sections were registered with the corresponding micro‐CT images to verify whether the pulp tissue in the histological sections matched its counterpart in the Lugol‐impregnated tissues identified in the micro‐CT slices. Results: There was no discernible effect on radiopacity when NaOCl was mixed with Lugol's solution. Tissue processing did not affect the time required for the complete dissolution of fresh bovine meat. Histological evaluation revealed a correlation between micro‐CT and histological images confirming the identification of Lugol‐impregnated pulp tissue in micro‐CT images. Conclusions: The radiocontrast Lugol's solution was unaffected by NaOCl and did not interfere with its soft tissue dissolution capability. The impregnation protocol using Lugol's solution allowed the visualization of pulp tissue on the micro‐CT images and the identification of pulp remnants after chemical–mechanical canal procedures. [ABSTRACT FROM AUTHOR]

Aim: To evaluate the incidence of root dentinal microcracks after two extraction techniques through micro‐computed tomographic (micro‐CT) analysis. Methodology: Thirty pairs of premolars, extracted for orthodontic reasons, were assigned to two experimental groups, following a split‐mouth design (n = 30): traumatic technique group (TTG) – teeth extracted following a conventional protocol using forceps, and an atraumatic technique group (ATG) – teeth extracted following an atraumatic technique protocol in which the root was gently detached from the periodontal ligament using a periotome. All teeth were immediately immersed in distilled water and scanned in a micro‐CT device within 72 h following the extraction. The assessment of the images was completed on cross‐section images by two masked evaluators. The Mann–Whitney test was used to assess the significant differences between the groups regarding the number of cross‐sections displaying microcracks whilst the Fischer's exact test was used to assess differences in the frequency of specimens with defects (P < 0.05). Results: A total of 52 750 micro‐CT cross‐sectional images were evaluated. A total of 352 cross‐sections had at least one dentinal defect. Microcracks were observed in five teeth of the TTG group (n = 352 slices) and in two teeth of the ATG group (n = 103 slices). The statistical analysis used was unable to detect a significant difference between the groups in terms of the number of dentinal microcracks (P = 0.233) and in the frequency of teeth displaying microcracks (P = 0.424). Conclusion: A small number of sound teeth without endodontic treatment had dentinal microcracks regardless of the extraction technique applied. No difference was noticed between the traumatic and atraumatic techniques in the incidence of microcracks. [ABSTRACT FROM AUTHOR]

Aim: To investigate the shaping and cleaning performance of the Clearsonic ultrasonic tip as a supplementary tool during the preparation of long oval‐shaped root canals through micro‐computed tomographic (micro‐CT) imaging technology. The Reciproc M‐Wire R40 instrument was used as a reference instrumentation technique for comparison. Methodology: Twenty mandibular incisors with single, straight and long oval‐shaped canals were selected and pair‐matched by micro‐CT scanning. The root canals were prepared with Reciproc R25 and R40 instruments, scanned again in a micro‐CT device and randomly allocated into one of the two experimental groups (n = 10), according to the supplementary debridement protocol used: Clearsonic or Reciproc R40 used in a brushing motion against buccal and lingual walls. Noninstrumented canal areas, accumulation of hard‐tissue debris (AHTD) and volume of removed dentine were assessed using micro‐CT imaging following the supplementary debridement protocols. Data were analysed statistically in two phases using a t‐test with a significance level of 5%. Results: In phase‐1, there was a significant similarity between the samples regarding the evaluated micro‐CT baseline parameters (P > 0.05), validating the anatomical similarity between the tooth pairs. In phase‐2, there was a significant difference between the groups for canal volume, surface area, noninstrumented root canal walls and the amount of removed dentine for both absolute and percentage values (P < 0.05), but not for AHTD (P = 0.759). Conclusions: The Clearsonic tip outperformed the Reciproc R40 instrument as a supplementary debridement protocol as it was associated with significantly greater reduction of noninstrumented root canals walls and consequently a larger amount of removed dentine. Both groups performed similarly regarding the AHTD. [ABSTRACT FROM AUTHOR]

Aim: To evaluate the influence of ultraconservative endodontic cavities (UEC) on canal shaping and filling ability, cleaning of the pulp chamber, time required to perform root canal treatment and fracture resistance of 2‐rooted maxillary premolars in comparison with traditional endodontic access cavities (TEC) in extracted teeth placed in a phantom head to simulate clinical conditions. Methodology: Twenty extracted intact 2‐rooted maxillary premolars were scanned in a micro‐computed tomographic device, matched based on similar anatomical features of the canals and assigned to UEC or TEC groups (n = 10). Then, teeth were mounted on a mannequin head and their pulp chamber accessed. After canal preparation, filling and cavity restoration, the time required to perform root canal treatment was recorded and the specimens were loaded to fracture in a universal testing machine. The maximum load at fracture was recorded. The sample was scanned after root canal instrumentation, filling and restoration procedures. Untouched canal areas, accumulation of hard‐tissue debris (AHTD), voids in root fillings and cleaning of the pulp chamber were analysed. Data were analysed statistically using Shapiro–Wilk and Student's t‐tests with a significance level of 5%. Results: The percentage of untouched canal area did not differ significantly between UEC and TEC groups (P > 0.05). However, UECs were associated with a greater percentage of AHTD after canal preparation (P < 0.05). No differences were observed in terms of voids in root fillings between the groups (P > 0.05). Nonetheless, UEC had a greater percentage of root filling remnants in the pulp chamber after cleaning procedures (P < 0.05). The time required to perform root canal treatment was significantly longer in the UEC group (P < 0.05). There was no difference regarding the mean load at fracture between the groups (P > 0.05). Unrestorable fractures were observed in all specimens of both groups. Conclusions: There was no true benefit associated with ultraconservative endodontic cavities. UEC resulted in more AHTD remaining inside the root canals. UEC did not influence the quality of root fillings; however, UEC made the cleaning procedure of the pulp chamber more difficult, thus increasing the total time required to perform root canal treatment. Moreover, UEC were not associated with an increase in fracture resistance of root filled 2‐rooted maxillary premolars. [ABSTRACT FROM AUTHOR]

Aim: To assess the shaping ability of the new XP‐endo Shaper instrument after different working times. Methodology: Ten mesial roots of mandibular molars were scanned in a micro‐computed tomographic device and prepared using the XP‐endo Shaper instrument up to the working length (WL) according to the manufacturer's recommendation. Then, each specimen was subjected to an extra 15, 30 and 45 s of active instrumentation at the WL. Postoperative scans were performed after canal preparation at each time‐point. Then, the registered pre‐ and postoperative datasets were examined to evaluate the percentages of volume and surface area of the instrumented canal, surface area of noninstrumented canal areas and the volume of removed dentine. Repeated measures general linear model was used to compare the differences in either the increase or the reduction of the parameters amongst the time‐points. Alpha‐error was set at 5%. Results: Extending the period of XP‐endo Shaper active instrumentation at WL significantly influenced several parameters such as volume (P < 0.001) and surface area (P < 0.001) of the instrumented canal, surface area of noninstrumented canal areas (P < 0.001), and volume of removed dentine (P < 0.001). Conclusions: Extending the activation time of XP‐endo Shaper instruments at WL resulted in a more comprehensive root canal preparation, increasing the volume and surface area of root canal preparation and the volume of removed dentine. [ABSTRACT FROM AUTHOR]

Abstract: Aim: To compare the shaping ability of four root canal instrumentation systems in oval‐shaped canals using micro‐computed tomographic analysis. Methodology: Forty anatomically matched mandibular incisors were scanned and assigned to four groups (n = 10), according to the canal preparation protocol: BioRace, Reciproc, Self‐Adjusting File (SAF) and TRUShape systems. After canal instrumentation, the specimens were rescanned, and the registered pre‐ and postoperative datasets were examined to evaluate the percentages of accumulated hard‐tissue debris, untouched canal walls and dentine removed. Kruskal–Wallis and Mann–Whitney U‐tests with Bonferroni correction were used to compare the variables in the groups (α = 5%). Results: The preparation techniques did not affect the percentage of accumulated hard‐tissue debris (P = 0.126). The percentage of untouched canal areas was significantly higher for BioRace (32.38%)compared to Reciproc (18.95%) and SAF (16.08%) systems (P < 0.05). Reciproc removed significantly more dentine (4.18%) than BioRace (2.21%) and SAF (2.56%) (P < 0.05). The TRUShape system had intermediate results for both untouched canal walls (19.20%) and dentine removed (3.77%), with no significant difference compared to BioRace, Reciproc and SAF systems. Conclusions: The preparation techniques resulted in the same level of accumulated hard‐tissue debris. Compared to the other tested systems, BioRace was associated with more untouched canal walls and Reciproc produced the greatest amount of removed dentine. Although it touched more of the root canal walls, the SAF system removed less dentine, whereas TRUShape had intermediate results for these same parameters. None of the systems tested were able to provide optimal shaping ability in oval‐shaped canals. [ABSTRACT FROM AUTHOR]

Aim To evaluate the amount of apically extruded debris produced by ProTaper Universal ( PTU), ProTaper Next ( PTN), WaveOne ( WO) and Reciproc (R) systems after large apical preparations. Methodology Sixty mandibular premolars with a single canal were selected and randomly assigned into 4 groups ( n = 15) according to the system used for root canal preparation: PTU, PTN, WO and R groups. Canal preparations were performed up to size 40 in each group. Distilled water was used as an irrigant, and the apically extruded debris from each tooth was collected in pre-weighted glass vials and dried. The average weight of debris was assessed using a microbalance, and the data were analysed statistically using one-way analysis of variance and the post hoc Tukey multiple comparison test (α = 0.05). Results The PTU system was associated with significantly more debris than the other systems ( P < 0.05). No significant differences were found between PTN, WO and R systems ( P > 0.05). Conclusions All systems were associated with apical debris extrusion when canals were prepared to a large apical size. The PTU system was associated with more debris extrusion. [ABSTRACT FROM AUTHOR]

Aim: To evaluate the influence of different preparation tapers on the reduction in planktonic bacteria and biofilms of Enterococcus faecalis and Candida albicans in the apical third (4 mm) of the mesial roots of mandibular molars, correlating decontamination with canal shape., Methodology: After microtomography analysis for morphological standardization of the canals, 48 mandibular molar roots, each containing two canals (96 canals), were contaminated with E. faecalis and C. albicans and divided into four groups (n = 11) for canal instrumentation using ProDesign Logic 2 files with different tapers G (.03): # 25.03; G (.04): # 25.04; G (.05): # 25.05; and G (.06): # 25.06 and irrigation with 2.5% sodium hypochlorite. Four roots were examined under a scanning electron microscope (SEM) to qualitatively assess biofilm formation. Eight roots were used as the negative control group (samples were not contaminated). Bacteriological samples were taken exclusively from the apical third of the roots before and after chemical-mechanical preparation and bacterial counts were determined (CFU/mL). The final micro-CT scan was used to quantify the volume variation and unprepared canal area in the apical third. Statistical analysis was performed using the Kruskal-Wallis, Student-Newman-Keuls and Wilcoxon tests for analysis of microbiological data. anova and the Tukey or Games-Howell test were used for analysis of micro-CT data and Spearman's test for correlations (α = 5%)., Results: All groups showed a significant reduction in bacteria (p < .05), with no statistically significant difference between groups. There was no significant difference in per cent volume increase between groups. The unprepared area (Δ%) was affected by the file used (p = .026) and was significantly lower for G (.06) compared to G (.03). There was no statistically significant correlation among bacterial reduction, volume and unprepared area (p > .05)., Conclusion: The different preparation tapers influenced root canal shaping in the apical third but did not improve decontamination in this region., (© 2024 British Endodontic Society. Published by John Wiley & Sons Ltd.)