Challenges in the transition to clinical training in dentistry: An ADEE special interest group initial report.

INTRODUCTION: Curricular integration in higher education has been widely supported in the educational literature. As a result, several health care and specifically dental curricula have evolved from compartmentalised disciplinary training to integrated modalities; however, in many courses, a pre-clinical-clinical watershed remains a barrier to integration in dental education. This article introduces a general description of the pre-clinical-clinical transition in dentistry according to the outcomes of the discussion held during the first working group session of the "Transition to Clinical Training" Special Interest Group during the 2016 annual meeting of the Association for Dental Education in Europe. MATERIALS AND METHODS: An online questionnaire was made available before the meeting to survey the curricular characteristics of the participants' schools. During the meeting, a working session related to the pre-clinical-clinical transition occurred. Conclusions from the discussion are summarised in this article. RESULTS: Fourteen dental schools from 12 countries participated in the online survey. The included programmes had an average duration of 5.3 years (SD = 0.48), with high school or the local equivalent as the required entrance level for dentistry. The hybrid curriculum was the leading curriculum design (n = 9) followed by competence-based curricula (n = 3), with patient treatment as the core of clinical training in every included programme. CONCLUSION: The pre-clinical-clinical transition in dentistry is a recognisable matter in dental education that requires assessment and research to ease the management of a stage with relevant influence on educational outcomes. This article presents an initial framework for further research and educational intervention.

Innovation in dental education: The "On-the-Fly" approach to simultaneous development, implementation and evidence collection.

INTRODUCTION: This study outlines an approach for education innovation and addresses the ambivalence between evidence-based and non-evidence-based conditions. The "on-the-fly" approach was described as involving implementation during the development of an innovation for dental education. MATERIALS AND METHODS: The process of designing and implementing cutting-edge technology of the MOOG Simodont Dental Trainer (DT) whilst systematically collecting evidence illustrates the "on-the-fly" approach. RESULTS: Using the "on-the-fly" approach for developing, implementing and collecting evidence simultaneously in an academic environment appears feasible in serving both the professionals, users and developers and system designers. During the implementation of the new technology, growing evidence stepwise strengthened its position; therefore, showing stakeholders that evidence was used to improve the technology seemed to support and increase acceptance of the new technology. CONCLUSIONS: When pioneering an innovative technology in a specialty field, the development stage often precedes evidence for its effectiveness. Consciously choosing the "on-the-fly" approach clarifies to stakeholders in advance about the lack of evidence in an innovation and the need of their support to collect such evidence for improvement and in order to facilitate implementation.

[Real patients in virtual reality: the link between phantom heads and clinical dentistry]. / Echte patiënten in de virtuele realiteit: de schakel tussen fantoom en kliniek.

Preclinical training in phantom heads has until now been considered the 'gold standard' for restorative dental education, but the transition from preclinic to the treatment of real patients has remained a challenge. With the introduction of the latest generation of virtual reality simulators, students and dental practitioners can make digital impressions of their patients in virtual reality models and practice procedures in virtual reality before clinically performing them. In this way, clinical decisions can be investigated and practiced prior to actual treatment, enhancing the safety of the treatment and the self-confidence to perform it. With the 3M™ True Definition Scanner and the Moog Simodont Dental Trainer, 3 masters students and a general dental practitioner practiced their procedures in virtual reality prior to performing them on real patients. They were very satisfied with this preparation and the result of the treatment.

Effect of students' determination of testing time on their test performance.

This article investigates whether giving students control over preparing for and the moment of taking a test affects their test results in comparison with when the school is in control of the amount of training followed by a predetermined test moment. The students participated in training for manual dexterity. After the training, the students performed a test. The results of the test were stored in a database. Students from the group with freedom to select the moment of the test performed much better than those in the other group who did not have the freedom to select the moment for the test, with significantly fewer students requiring three attempts to pass the test. The fact that students when given the responsibility to develop manual skills performed better than when guided by the policy of the school is hopeful in the sense that students can learn in an early stage of their study to take responsibility for learning.

Porosity and sealing ability of root fillings with gutta-percha and BioRoot RCS or AH Plus sealers. Evaluation by three ex vivo methods.

AIM: To investigate the ability of BioRoot RCS, a tricalcium silicate-based root canal sealer and AH Plus to effectively fill the root canals of contralateral teeth using three evaluation methods, and to investigate also the correlation between the methods. METHODOLOGY: The prepared root canals of ten pairs of contralateral mandibular premolar teeth were filled with gutta-percha and sealer using lateral compaction. The percentage of voids within the root canal was assessed by micro-computed tomography, whilst sealing ability was investigated by fluid transport and leakage of fluorescent microspheres. The interaction of sealer with dentine, and sealer penetration were assessed by confocal microscopy. The void volume, fluid flow, microsphere leakage and sealer interaction with dentine for both materials were compared. Nonparametric (Mann-Whitney) tests were used to compare the % void and fluid transport of the two sealers. Spearman correlation was used to assess the pairwise relationships between the techniques. The level of significance was set to 0.05. RESULTS: BioRoot RCS exhibited significantly more percentage of voids than AH Plus. There was no difference in fluid flow and microsphere penetration. BioRoot RCS exhibited a different pattern of sealer penetration and interaction with the dentine walls compared to AH Plus. For both materials, the pairwise correlations between the three techniques were close to zero, indicating weak relationships. CONCLUSIONS: MicroCT analysis revealed a higher void volume for BioRoot RCS. The other techniques did not show a difference between the sealing ability of the sealers. The correlation between the three ex vivo methods of assessment was weak demonstrating their complementarity rather than their concordance.

Sealing efficacy of a single-cone root filling after post space preparation.

OBJECTIVES: The aim of the present study was to compare the sealing efficacy of root fillings made by a single-cone technique with three different sealers and a cold lateral compaction technique with an epoxy sealer. MATERIALS AND METHODS: Eighty extracted single-rooted human teeth were assigned to four experimental groups: group 1, single-cone and epoxy sealer; group 2, single-cone and calcium silicate-based sealer; group 3, single-cone and methacrylate resin-based sealer; and group 4, cold lateral compaction and epoxy sealer. Twenty extra teeth served as negative and positive controls. After preparation of a coronal post space, the sealing efficacy of the root fillings was assessed on a fluid transport setup. The results were analyzed using Kruskal-Wallis and Mann-Whitney U test. RESULTS: No fluid transport was detected for the negative controls whereas all the positive controls showed rapid fluid transport. No significant difference was detected between groups 1, 3, and 4 whereas group 2 demonstrated significantly more fluid transport than all the other experimental groups. CONCLUSIONS: Root fillings made by a single-cone technique with the epoxy or methacrylate-based sealers were as effective after post space preparation as those made by a cold lateral technique with the epoxy sealer in sealing the root canal. CLINICAL RELEVANCE: Specific root canal sealers in combination with single-cone technique represent a noteworthy alternative to the use of cold lateral compaction technique when a post space is required. The use of effective endodontic procedures with simplified technical implementation may positively affect endodontic outcome.

Student performance and appreciation using 3D vs. 2D vision in a virtual learning environment.

AIM: The aim of this study was to investigate the differences in the performance and appreciation of students working in a virtual learning environment with two (2D)- or three (3D)-dimensional vision. MATERIAL AND METHODS: One hundred and twenty-four randomly divided first-year dental students performed a manual dexterity exercise on the Simodont dental trainer with an automatic assessment. Group 1 practised in 2D vision and Group 2 in 3D. All of the students practised five times for 45 min and then took a test using the vision they had practised in. After test 1, all of the students switched the type of vision to control for the learning curve: Group 1 practised in 3D and took a test in 3D, whilst Group 2 practised in 2D and took the test in 2D. To pass, three of five exercises had to be successfully completed within a time limit. The students filled out a questionnaire after completing test 2. RESULTS: The results show that students working with 3D vision achieved significantly better results than students who worked in 2D. Ninety-five per cent of the students filled out the questionnaire, and over 90 per cent preferred 3D vision. CONCLUSION: The use of 3D vision in a virtual learning environment has a significant positive effect on the performance of the students as well as on their appreciation of the environment.

The correlation between fluid transport and push-out strength in root canals filled with a methacrylate-based filling material.

AIM: To investigate the correlation between fluid transport and dislocation resistance in canals filled with a methacrylate-based filling material. METHODOLOGY: The root canals in sixty-five single-rooted human teeth were prepared to size 40, 0.06 taper. Sixty roots were filled with a single-cone technique using RealSeal SE sealer and divided into 3 groups, whilst five roots served as fluid transport positive control. Group 1 (n = 20): correlation group. Specimens were consecutively tested with fluid transport for 90 min and thereafter with the push-out test at coronal and apical root levels. Group 2 (n = 20): push-out control. Specimens were only subjected to the push-out test at coronal and apical root levels. Group 3 (n = 20): fluid transport negative control. Specimens were totally covered with nail varnish. The correlation between fluid transport and dislocation resistance was assessed by Kendall's tau-b coefficient. The Mann-Whitney U-test was used to compare dislocation resistance between groups 1 and 2 and fluid transport between groups 1 and 3. Significance level was set at P < 0.05. RESULTS: Kendall's tau-b correlation coefficients between fluid transport and dislocation resistance were weak, being coronally 0.139 (P = 0.444) and apically -0.080 (P = 0.658). No significant difference in dislocation resistance could be detected between groups 1 and 2 at both root levels (P = 0.052 and P = 0.336, respectively). CONCLUSION: No significant correlation could be identified between fluid transport and dislocation resistance, meaning that the corono-apical sealing ability of a methacrylate-based root canal filling is independent of its adhesive properties as indicated by its dislocation resistance.

Cytotoxicity, interaction with dentine and efficacy on multispecies biofilms of a modified salt solution intended for endodontic disinfection in a new in vitro biofilm model.

AIM: To investigate the cytotoxicity of a modified salt solution (MSS) and evaluate the antimicrobial properties of MSS on in vitro biofilm models. METHODOLOGY: In a metabolic assay, fibroblasts derived from periodontal ligaments (PDL) of human extracted teeth were cultured and challenged with MSS or controls. Then, in active attachment biofilm models, the efficacy of MSS in the presence of dentine powder and in eliminating mature biofilms was investigated. In the dentine assay, a biofilm of Enterococcus faecalis was employed. For the final assay, microorganisms were retrieved from infected root canals and cultured to produce biofilms. After the treatments with MSS or the controls, the biofilms were collected, serially diluted and plated. The colony-forming units were counted. One-way anova was used to analyse the differences between the groups. A P < 0.05 was considered significant. RESULTS: The PDL fibroblasts remained metabolically active after challenges with MSS. Dentine powder did not alter the efficacy of MSS (P > 0.05). In endodontic biofilms, the culturable bacteria were equally reduced by MSS, 2% chlorhexidine (CHX) or 2% sodium hypochlorite (NaOCl) (P > 0.05). CONCLUSIONS: Modified salt solution is noncytotoxic in vitro and has good antimicrobial properties equal to CHX and NaOCl. Although the results are promising, ex vivo and in vivo studies are needed before its use as an interappointment root canal dressing can be considered.

Evaluation of the appreciation of virtual teeth with and without pathology.

AIM: Virtual teeth with and without tooth pathology have been developed for use in a virtual learning environment in dental education. The objective of this study was to evaluate the appearance of these virtual teeth for use in dental education and to compare them with contemporary educational models, such as plastic teeth (Frasaco GmbH) and extracted human teeth. MATERIAL AND METHODS: Six sets of photographs representing six different teeth were shown to dentists, teachers (dentists) and dental students (bachelor's and master's degree students). Each set consisted of 15 pictures showing five views of the extracted human tooth, the similar virtual tooth and the plastic tooth. The five views represented the mesial, distal, occlusal, buccal and lingual surfaces. The virtual tooth was the same as the extracted tooth (scanned with a cone beam CT, coloured and edited in ColorMapEditor(®) ), and the plastic tooth presented the best possible match to the extracted tooth. The participants were asked to rate the appearance of the virtual teeth (overall and in terms of caries, restoration and colours), whether the virtual or plastic teeth resembled the extracted teeth better and from which teeth they expected to learn the most (extracted, virtual or plastic). RESULTS: Each group of participants found that the virtual teeth resembled the extracted teeth more than they resembled the plastic teeth; 71% of the participants expected to learn more from the virtual teeth than from the plastic teeth. CONCLUSION: The results show that the appearance of the virtual teeth was considered more realistic than the appearance of the plastic teeth. The expectation was that the learning opportunities of the virtual teeth are better than of the plastic teeth.

Influence of refreshment/activation cycles and temperature rise on the reaction rate of sodium hypochlorite with bovine dentine during ultrasonic activated irrigation.

AIM: To evaluate the effect of multiple refreshment/activation cycles and temperature on the reaction rate of sodium hypochlorite (NaOCl) with bovine dentine during ultrasonic activated irrigation (UAI) under laboratory conditions. METHODOLOGY: The root canal walls of 24 standardized root canals in bovine incisors were exposed to a standardized volume of NaOCl at different temperatures (24 °C and 38 °C) and exposure times (20, 60 and 180 s). The irrigant was refreshed and ultrasonically activated four times for 20 s followed by a 40 s rest interval, with no refreshment and no activation as the controls. The reaction rate was determined by measuring the amount of active chlorine in the NaOCl solution before and after being exposed to dentine during the specific experimental conditions. Calorimetry was used to measure the electrical-to-sonochemical conversion efficiency during ultrasonic activation. RESULTS: Refreshment, activation and exposure time all increased the reaction rate of NaOCl (P < 0.05). During activation, the temperature of the irrigant increased up to 10 °C. Such temperature rise was insufficient to enhance the reaction rate of NaOCl (P > 0.125). CONCLUSIONS: The reaction rate of NaOCl with dentine is enhanced by refreshment, ultrasonic activation and exposure time. Temperature rise of irrigant during ultrasonic activation was not sufficient to alter the reaction rate.

Detection and measurement of artificial periapical lesions by cone-beam computed tomography.

AIM: To test the ability of periapical radiography (PA) and cone-beam computed tomography (CBCT) to determine the presence/absence of periapical lesions and examine the reliability of volumetric measurements of periapical lesions on CBCT scans. METHODOLOGY: After tooth extractions in human mandibles, bone defects were cut at the base of extraction sockets to mimic periapical bone lesions. The teeth were then returned into the extraction sockets. Sixty-three roots of anterior teeth, premolars and molars with artificial periapical lesions and 37 roots without lesions were examined with PA and CBCT. Presence/absence of periapical lesion was noted. The CBCT-based volume of each lesion (Vct) was measured using Amira software 5.4 (Visage Imaging GmbH, Berlin, Germany). A replica of each lesion was created using silicone impression material, and the volume of the replica was measured using a water displacement method, representing the physical volume of the lesion (Vp). Regression analysis was used to test the correlation between the Vp and Vct values. RESULTS: The positive and negative predictive values and accuracy for CBCT in diagnosing periapical lesions were all 1, compared with 1, 0.64 and 0.79 for PA diagnosis. Twenty-one (33%) lesions were undetected by PA. The Vp (21.5 ± 11.0 mm(3) ) and Vct (21.4 ± 11.5 mm(3) ) values of 63 lesions were highly correlated (R(2) = 96.9%, P < 0.001). CONCLUSION: Cone-beam computed tomography is more accurate than PA in diagnosing periapical lesions associated with mandibular teeth. The volumes of artificial mandibular periapical lesions were accurately measured with CBCT data.

Improving the accuracy of a fluid transport method.

AIM: To compare the sealing ability of the same root fillings when measured by a conventional fluid transport method that uses water or by a modified fluid transport method that uses a wetting fluid as tracer. METHODOLOGY: The amount of fluid transport along the same root fillings (AH26, cold lateral compaction of gutta-percha) was measured in a cross-over design in fluid transport set-ups using either water or a wetting fluid as tracer. RESULTS: A Wilcoxon signed-rank test revealed a significant difference in the amount of fluid transport measured along the same root fillings by the two fluid transport methods (P = 0.013). The fluid transport method using wetting fluid detected a significantly higher percentage of root fillings with fluid transport (P = 0.021). CONCLUSIONS: Fluid transport using a wetting fluid as a tracer was more sensitive in the assessment of sealing ability of root fillings than the conventional fluid transport method using water.

Bisphosphonates and their clinical implications in endodontic therapy.

This review gives an overview of the factors that may play a role in the development of osteonecrosis of the jaw in patients treated with bisphosphonates (BPs) and undergoing nonsurgical endodontic treatment as well as some recommendations for its prevention. BPs are a widely prescribed group of drugs for diverse bone diseases. The occasional but devastating adverse effect of these drugs has been described as bisphosphonate-related osteonecrosis of the jaw (BRONJ). As this condition is debilitating and difficult to treat, all efforts should be made to prevent its occurence in patients at risk. The main triggering event is considered to be dental extraction. Even though nonsurgical endodontic treatment appears to be a relatively safe procedure, care remains essential. After an overview of this class of drugs, the clinical presentation, epidemiology and pathogenesis of BRONJ, as well as the possible risk factors associated with its development after nonsurgical endodontic treatment will be described. Finally, several strategies will be proposed for the prevention of BRONJ during nonsurgical endodontic treatment.

The creation of virtual teeth with and without tooth pathology for a virtual learning environment in dental education.

PURPOSE: To describe the development and opportunities for implementation of virtual teeth with and without pathology for use in a virtual learning environment in dental education. MATERIAL AND METHODS: The creation of virtual teeth begins by scanning a tooth with a cone beam CT. The resulting scan consists of multiple two-dimensional grey-scale images. The specially designed software program ColorMapEditor connects these two-dimensional images to create a three-dimensional tooth. With this software, any aspect of the tooth can be modified, including its colour, volume, shape and density, resulting in the creation of virtual teeth of any type. RESULTS: This article provides examples of realistic virtual teeth with and without pathology that can be used for dental education. ColorMapEditor offers infinite possibilities to adjust and add options for the optimisation of virtual teeth. DISCUSSION: Virtual teeth have unlimited availability for dental students, allowing them to practise as often as required. Virtual teeth can be made and adjusted to any shape with any type of pathology. Further developments in software and hardware technology are necessary to refine the ability to colour and shape the interior of the pulp chamber and surface of the tooth to enable not only treatment but also diagnostics and thus create a greater degree of realism. CONCLUSION: The creation and use of virtual teeth in dental education appears to be feasible but is still in development; it offers many opportunities for the creation of teeth with various pathologies, although an evaluation of its use in dental education is still required.

The ability of cone-beam computed tomography to detect simulated buccal and lingual recesses in root canals.

AIM: To compare the ability of cone-beam computed tomography (CBCT) and digital periapical radiographs (PR) to detect simulated tissue-occupied recesses in root canals. METHODOLOGY: A standard canal was created in 30 extracted mandibular premolar roots. Each root was longitudinally split into buccal and lingual halves. In 20 teeth, a standard groove, 4mm in length, 0.5mm deep and 0.3mm wide, was prepared on each root half and filled with radiolucent plasticine (a modelling clay), simulating tissue-occupied buccal and lingual recesses. In the other 10 teeth, no grooves were cut. Each root was reassembled and filled with laterally compacted gutta-percha and sealer. PR and CBCT were used to detect the plasticine-filled grooves. The images were pooled and blindly evaluated by three calibrated examiners (A, B and C). A chi-square test was used to analyse the data. RESULTS: Examiner A, B, C detected grooves on CBCT scans in 20, 20 and 23 teeth, respectively, of which 19, 18 and 19 were true positives. The accuracy of CBCT in diagnosing plasticine-filled grooves was 82-92% for three examiners, significantly higher than the accuracy of PR (30-33%; P<0.001). CONCLUSIONS: Cone-beam computed tomography accurately detected simulated tissue-occupied buccal and lingual recesses.

Ecology of the microbiome of the infected root canal system: a comparison between apical and coronal root segments.

AIM: To evaluate the microbial ecology of the coronal and apical segments of infected root canal systems using a complete sampling technique and next-generation sequencing. METHODOLOGY: The roots of 23 extracted teeth with apical periodontitis were sectioned in half, horizontally, and cryo-pulverized. Bacterial communities were profiled using tagged 454 pyrosequencing of the 16S rDNA hypervariable V5-V6 region. RESULTS: The sequences were classified into 606 taxa (species or higher taxon), representing 24 bacterial phyla or candidate divisions and one archaeal phylum. Proteobacteria were more abundant in the apical samples (P < 0.05), whilst Actinobacteria were in significantly higher proportions in the coronal samples. The apical samples harboured statistically significantly more taxa than the coronal samples (P = 0.01) and showed a higher microbial diversity. Several taxa belonging to fastidious obligate anaerobes were significantly more abundant in the apical segments of the roots compared with their coronal counterparts. CONCLUSIONS: Endodontic infections are more complex than reported previously. The apical part of the root canal system drives the selection of a more diverse and more anaerobic community than the coronal part. The presence of a distinct ecological niche in the apical region explains the difficulty of eradication of the infection and emphasizes the need for new treatment approaches to be developed.

A community of learners in the evidence-based dental clinic.

UNLABELLED: An increasing emphasis has been placed on the need for an evidence-based approach in dentistry. This calls for effort in dental education to develop and implement tools for the application of evidence in clinical decision-making (evidence-based decision-making, EBDM). AIM: To evaluate whether the implementation of a community of learners (COL) within a clinical EBDM course enables students, clinical teachers and scientists to discuss the application of evidence in clinical decision-making and whether it stimulates a scientific approach in students. MATERIAL AND METHODS: A clinical course in EBDM was created. Students presented and discussed patient cases in a COL of student-peers, clinical teachers and scientists. From the discussion, clinical questions arose and were translated into PICO format (Problem, Intervention, Comparison and Outcome). Students searched for evidence in the literature. Four weeks later, they presented and discussed the evidence found. Before and after the implementation of the course, students, clinical teachers and scientists completed a questionnaire anonymously on the procedure adopted, its content, the learning outcomes and their appreciation of this course. Assessment of the competence EBDM was performed at the end of the course. Grading scores of students in the COL were compared with scores of a student group that did not participate in the COL and were not advised by scientists. RESULTS: Evaluation showed that scientists, clinical teachers and students gradually became more positive on the adopted procedure, content, learning outcomes and the appreciation of this course (ANOVA Bonferoni P<0.05). The student's evaluation showed the development of a more scientific approach. Assessment scores of EBDM were sufficient and promising. CONCLUSION: A stimulating arena was created: a COL, in which the evidence used in clinical decision-making, was discussed. The COL involved dental students, clinical teachers and scientists. In this setting, an EBDM course appeared to result in a more scientific approach from dental students. The COL provided a good working concept for EBDM in dental education.

[The Simodont in dental education]. / De Simodont in het onderwijs.

The Simodont is a virtual learning environment for students of dentistry which is intended to expand and optimize the preparation ofstudents for the treatment ofpatients so that the transition in education from pre-clinic to clinic is reduced. The Simodont makes it possible to offer students more realistic clinical problems. In that way, students can practice much more extensively than they can in the pre-clinic on phantom heads. The Simodont also provides a safe learning environment in which unlimited mistakes can be made without unfortunate consequencesfor the student and patient. The simulator is coordinated with reading material on a computer, which makes it possible to integrate techniques and theory in dental education. Virtual teeth, with and without pathology, have been created for application in the Simodont, to allow unlimited possibilities for practice. The future possibilities for the Simodont offer many opportunities for students in dental education, for supplementary and post-graduate education andfor the re-integration of dentists in their profession.

Identification of root filling interfaces by microscopy and tomography methods.

AIM: To assess differences in observed cross-sectional areas of root canals and filling materials, as imaged by three microscopy and two tomography methods. METHODOLOGY: Six roots filled with laterally compacted Gutta-percha and AH26 were scanned with phase-contrast enhanced microtomography in a synchrotron facility. Reconstructed virtual slices were compared with sections of both wet and acrylic-embedded roots, evaluated also by light and electron microscopy (EM) and laboratory-based microtomography (µCT). The different contrasts of Gutta-percha, voids, sealer and root dentine were identified and correlated. Inner canal border, outer Gutta-percha rim and the external margin of a void were manually delineated, and the enclosed areas were repeatedly measured by three observers. Interobserver and interimaging method differences were tested by 2-way anova with Bonferroni adjustments (P < 0.05). Percentages of Gutta-percha-filled canal areas (PGP) were determined. RESULTS: Phase-contrast enhanced microtomography revealed internal interfaces and detailed 3D volumes of accentuated voids as well as micrometre-sized particles and gaps within the treated roots. Overestimates in the cross-sectional areas were obtained by light microscopy, whereas underestimates were obtained by µCT and EM. Differences exceeded 40%; however, PGP values by all methods were within 5% for the same slice. Differences between observers were sometimes significant, but they were not method related (<3%). CONCLUSIONS: Phase-contrast enhanced microtomography is a powerful non-destructive ex vivo investigation method for studying the interfaces within root canals and filling materials at a micrometre resolution. The method does not require damage-prone sectioning/polishing during sample preparation procedures. Caution should be used when quantifying the extent of Gutta-percha in root fillings by measurements using µCT, light and EM.