Untouched canal areas and debris accumulation after root canal preparation with rotary and adaptive systems

Exploring morphometric transformations in temperature-sensitive NiTi instruments alongside real-time intracanal temperature dynamics

AIM

This study was twofold: (i) it aimed to investigate the morphometric changes of three temperature-sensitive nickel-titanium (NiTi) instruments at different temperatures, and (ii) to conduct an in vivo real-time analysis of intracanal temperature changes.

METHODS

Changes in the shape and length of XP-Endo Shaper, XP-Endo Finisher, and XP-Endo Finisher-R were evaluated in real time whilst heated in a temperature-controlled water bath from 22 to 45°C. Instruments were fixed to a laminated water-resistant 1 mm graph paper attached to a stone block. Instruments were imaged whilst subjected to increasing temperature using a digital camera attached to an operating microscope. From recorded videos, still frames were extracted at 10-s intervals and changes in the length and shape of each instrument were measured and changes were plotted against time. Moreover, the intracanal temperature of distal roots of lower molars was measured in vivo for patients attending the clinic for non-surgical root canal treatments. The temperature was measured using a K-type thermocouple probe inserted into the mid-root level after irrigating the canal with a solution set at room temperature (22°C) or heated to 45°C. The intraoral and intracanal temperatures were recorded using a video camera for 180 s at 5-s intervals to plot the change in the intraoral and intracanal temperature, after both irrigation solution temperatures, with time.

RESULTS

The shape transformation of XP-Endo Shaper began at 31.5 ± 2.0°C and reached its optimal transformation at 35.1 ± 1.0°C. For the Finisher and Finisher-R, shape transformations began at 29.2 ± 1.9 and 26.9 ± 2.2°C reaching the optimal transformation at 33.9 ± 1.4 and 32.7 ± 1.7°C, respectively. The average decreases in lengths of XP-Endo Shaper, Finisher, and Finisher-R after full transformation were 0.43 ± 0.23, 1.07 ± 0.22, and 1.15 ± 0.22 mm, respectively. The intracanal temperature reached 32.9 ± 0.8 and 33.2 ± 1.0°C after 3 min of application of irrigation solutions set at 22 or 45°C, respectively.

CONCLUSION

The tested instruments exhibited diverse changes in their shapes and lengths at varying temperatures. Despite the temperature of the irrigation solution, the intracanal temperature consistently remained lower than the intracanal temperature once equilibrium was reached. This highlights the importance of considering the temperature of irrigation solution during in vitro testing of endodontic instruments.

Comparative Evaluation of Three Access Cavity Preparation Techniques on Root Canal Instrumentation Using Micro-CT: An In Vitro Study

Background Access cavity preparation is a crucial step in nonsurgical root canal treatment. Recent advancements in access cavity designs focus on preserving maximum tooth structure while ensuring sufficient access to canal orifices for effective cleaning and shaping, resulting in minimally invasive procedures. However, there is limited information on the impact of three-dimensional (3D)-guided access cavity preparation in molars. A literature review found no prior studies comparing the effects of various access cavity preparation techniques on apical transportation, untouched surfaces, and debris formation within the canal. Objective The objective of this study is to compare and evaluate the effects of three different access cavity techniques on apical transportation, untouched surfaces, and debris formation within the root canal. Material and methods Thirty extracted permanent mandibular first molars were selected and randomly assigned to three groups for this study: Group I received 3D-printed static guided cavity preparation, Group II underwent conservative access cavity preparation, and Group III was subjected to traditional access cavity (TAC) preparation. The mesial canals in all samples were cleaned and shaped using TruNatomy files. Preoperative and postoperative micro-CT imaging was performed on each sample to assess the effects of the different access cavity preparation techniques on apical transportation, untouched surfaces, and debris formation within the root canal. Results The study found that Group I, which used 3D-printed static guided cavity preparation, exhibited significantly less apical transportation compared to Groups II and III, with mean differences of -0.1677 and -0.2079, respectively. Debris accumulation was similar across all groups, with mean values of 0.928 ± 0.824 for Group I, 0.751 ± 0.495 for Group II, and 0.938 ± 0.681 for Group III, indicating no significant impact of cavity preparation type on debris levels. For untouched canal surfaces, Group III (TAC preparation) had the fewest untouched surfaces, with mean differences of 3.0380 and 3.9020 compared to Groups II and I, respectively. Conclusions While TAC preparation reduces substantial tooth structure, it shows higher instrumentation efficacy and better cleaning of the root canal system. However, in complex cases where tooth structure preservation is crucial, guided access cavity preparation provides an effective balance between structural conservation and adequate canal access. This approach offers a tailored solution, optimizing treatment outcomes based on the specific clinical scenario.

Oxygen Self-Supplied Nanoplatform for Enhanced Photodynamic Therapy against Enterococcus Faecalis within Root Canals

The successful treatment of persistent and recurrent endodontic infections hinges upon the eradication of residual microorganisms within the root canal system, which urgently needs novel drugs to deliver potent yet gentle antimicrobial effects. Antibacterial photodynamic therapy (aPDT) is a promising tool for root canal infection management. Nevertheless, the hypoxic microenvironment within the root canal system significantly limits the efficacy of this treatment. Herein, a nanohybrid drug, Ce6/CaO2/ZIF-8@polyethylenimine (PEI), is developed using a bottom-up strategy to self-supply oxygen for enhanced aPDT. PEI provides a positively charged surface, which enables precise targeting of bacteria. CaO2 reacts with H2O to generate O2, which alleviates the hypoxia in the root canal and serves as a substrate for Ce6 under 660 nm laser irradiation, leading to the successful eradication of planktonic Enterococcus faecalis (E. faecalis) and biofilm in vitro and, moreover, the effective elimination of mature E. faecalis biofilm in situ within the root canal system. This smart design offers a viable alternative for mitigating hypoxia within the root canal system to overcome the restricted efficacy of photosensitizers, providing an exciting prospect for the clinical management of persistent endodontic infection.

Bacteria debridement efficacy of two sonic root canal irrigant activation systems

OBJECTIVE

To evaluate the bacteria debridement efficacy of two generations of sonic root canal irrigant activation systems: EndoActivator (Dentsply Sirona), the first generation, and SmartLite Pro EndoActivator, the second generation.

METHODS

Instrumented, autoclaved, single-rooted human premolars were inoculated with Enterococcus faecalis (ATCC-29212) for 21 days. The bacteria biofilm-containing teeth were randomly divided into 5 groups (N=8): Group 1: Syringe-side-vented needle (S-N) delivery of saline for 1 min; Group 2: S-N delivery of 2% NaOCl for 1 min; Group 3: S-N delivery of 2% NaOCl for 5 min; Group 4: EndoActivator activation of 2% NaOCl for 1 min; Group 5: SmartLite Pro EndoActivator activation of 2% NaOCl for 1 min. The teeth were evaluated for bacterial reduction using CFU counts, and the percentages of dead bacteria within the dentinal tubules using confocal laser scanning microscopy.

RESULTS

Activation of NaOCl with EndoActivator or SmartLite Pro EndoActivator significantly reduced the overall intracanal bacterial load, compared with S-N irrigant delivery (P<0.05), with no significant difference between the two agitation devices (P>0.05). Nevertheless, S-N delivery of 2% NaOCl for 5 min produced better bacteria debridement than either sonic agitation system. Different degrees of bacteria kill were identified in the coronal-middle portions and apical portion of the canal space.

CONCLUSION

Delivery time of NaOCl affects the efficacy of bacteria disinfection. Activation for 1 min with the EndoActivator or SmartLite Pro EndoActivator demonstrated comparable canal wall biofilm and intracanal bacteria reduction efficacy when 2% NaOCl was used as irrigant for disinfecting E. faecalis in single-rooted teeth.

CLINICAL SIGNIFICANCE

Although the sonic root canal irrigant activation devices investigated do not completely eliminate live bacteria biofilms from the canal space, they help reduce bacteria load during irrigant activation.

Shaping outcomes of Reciproc Blue and Rotate in roots canals with band-shaped isthmuses: micro-CT study

OBJECTIVE

This study assessed the outcome of shaping the mesial roots of mandibular first molars containing band-shaped isthmuses with an isthmus floor located at the apical third with Reciproc Blue and Rotate instruments in terms of canal transportation, canal aberrations and unprepared apical canals.

MATERIALS AND METHODS

Pair-matched mesial roots of mandibular first molars according to their isthmus location (distance from apical foramina) and size were constructed based on quantitative measurements (length, major and minor diameter at isthmus roof and floor) on preoperative micro-CT scanning (n = 10). The pair-matched specimens were prepared either using Reciproc Blue R25 (25.08v) or Rotate (15.04, 20.05, 25.06) instruments and then subjected to a second micro-CT scanning. Micro-CT scans were analysed to evaluate the canal transportation at the apical foramen and isthmus floor levels and the frequency of procedural errors (separated instruments, artificial canal preparation, cross shaping and unprepared apical canals). Canal transportation values were compared using Mann-Whitney U, and the distribution of procedural errors was compared with chi-square tests with a 5% significance threshold.

RESULTS

Greater transportation values were detected in the apical foramen level compared to the isthmus floor in both groups. No significant difference was detected between Rotate and Reciproc Blue groups in terms of absolute transportation values and the incidence of procedural errors (p > .05).

CONCLUSION

Preparation of mesial root canals containing a band-shaped isthmus at the apical portion with Reciproc Blue and Rotate instruments caused transportation of the original canal position at the isthmus floor and the apical foramen levels and resulted in procedural errors.

CLINICAL RELEVANCE

This ex vivo micro-CT study using controlled pair-matched specimens showed that presence of a band-shaped isthmus complicates canal preparation procedure irrespective of the preparation systems.

Knowledge, Attitude, and Practice towards Chelating Agents in Endodontic Treatment among Dental Practitioners

The use of chelating agents (CAs) in the endodontic irrigation protocol is required to dissolve the inorganic components of the smear layer. We aimed to assess the knowledge, attitude, and practice of dental professionals regarding the use of CAs during root canal treatment. A cross-sectional anonymous online survey was conducted among specialized endodontists and general dentists who routinely perform endodontic treatment and work in government-funded or private clinics in Moscow. The 8 min survey consisted of four parts: basic demographic data, knowledge (five items), attitude (four items), and practice (five items). We collected 376 completed questionnaires; a majority of the respondents were general dentists (87.5%) and worked in private clinics (77.4%). Most respondents (83.5%) showed a fair knowledge of the CAs used in endodontics, while 16.5% showed a poor knowledge of the topic. Small yet significant differences were found between endodontists and general practitioners and between dentists employed by private and government-funded clinics. A majority of dental practitioners (83%) demonstrated a positive attitude towards the use of CAs in endodontic treatment, and there were no differences among the study subgroups. Almost a third of the respondents always used chelating solutions during endodontic treatment, while 17% of the respondents did not use them at all. There were significant differences in this parameter between dentists working in private and government-funded clinics. Practice significantly correlated with attitude towards chelating agents and with knowledge of the topic. In conclusion, dental practitioners demonstrated a fair knowledge of CAs. Despite a positive attitude, 71% of the respondents did not use CAs for all endodontic patients.

Effect of preparation size on the removal of accumulated hard-tissue debris from the mesial root canal system of mandibular molars using SWEEPS technology

OBJECTIVES

This study assessed the influence of preparation size on the efficacy of shock wave-enhanced emission photoacoustic streaming (SWEEPS) and conventional irrigation (CI) on removal of accumulated hard tissue debris (AHTD) from isthmus-containing mandibular molars using micro-computed tomographic analysis.

MATERIALS AND METHODS

Sixty extracted mandibular molars with two mesial canals connected by an isthmus were selected. Canals were shaped with Mtwo instruments (VDW, Munich, Germany) up to sizes 25/.06, 40/.04 or 40/.06 (n = 20), and specimens were distributed into 2 final irrigation groups (n = 10): SWEEPS and CI. Roots were scanned at a resolution of 10.5 µm before and after preparation and final irrigation. Data sets were co-registered, and the percentage reduction of AHTD calculated for each specimen was statistically compared using analysis of variance with a of 5% significance level.

RESULTS

The preparation size did not significantly influence the percentage reduction of AHTD (p < 0.05), whereas the final irrigation technique had a significant effect on debris removal (p < 0.05). A significant reduction of AHTD was achieved after final irrigation in all groups (p < 0.05); however, SWEEPS was associated with a significantly greater percentage reduction of debris than CI (p < 0.05). None of the specimens presented a completely clean isthmus.

CONCLUSIONS

Removal of AHTD was not significantly affected by the preparation size. SWEEPS was associated with significantly less debris than CI.

CLINICAL RELEVANCE

SWEEPS performed significantly better than CI regarding the removal of AHTD from isthmus-containing mandibular molars irrespective of the preparation size.

An application framework of 3D assessment image registration accuracy and untouched surface area in canal instrumentation laboratory research with micro-computed tomography

OBJECTIVES

The purpose of this study was to develop a customized framework for evaluating the registration accuracy of four registration techniques and measuring the untouched surface area of canal instrumentation by visually inspecting and calculating the overlapping area of the surfaces.

METHODS

Twenty-one mandibular incisors were scanned by micro-computed tomography before and after instrumentation. Elastix registration, surface registration, manual registration, and DataViewer registration techniques were used to align the pre- and post-operative datasets. The customized MeVisLab framework was created to investigate the registration accuracy by visual inspection and calculating overlapping areas. The canal surfaces were imported into the same framework to measure the untouched surface area and the consistence test was validated. The correlation between registration accuracy and untouched surface area was analyzed.

RESULTS

There is a statistically significant difference between manual registration and automatic registration (P < 0.05). There is no statistical difference between the two untouched surface measure methods (P > 0.05). The partial correlation coefficients for the untouched surface area and registration accuracy were 0.45 (P < 0.05).

CONCLUSIONS

This application framework based on free customizable software, allows a new method to measure registration accuracy and untouched surface area in an efficient and sensitive way. The application of a precise registration method would improve the quality of micro-CT canal instrumentation studies.

CLINICAL RELEVANCE

This study developed a customized framework based on free software for evaluating the registration accuracy of different registration techniques and measuring the untouched surface area of canal instrumentation could help researchers to improve the quality of micro-CT studies of canal instrumentation.

Antibacterial efficacy of antibiotic pastes versus calcium hydroxide intracanal dressing: A systematic review and meta-analysis of ex vivo studies

Background

Conflicting findings on the potency of antibiotic pastes versus calcium hydroxide (CH) have been evident in the literature.

Aims

To compare the antibacterial efficacy of single antibiotic paste (SAP), double antibiotic paste (DAP), triple antibiotic paste (TAP), and modified TAP (mTAP) with CH on bacterial biofilms.

Methods

PubMed, Scopus, and Embase were comprehensively searched until August 23, 2021. The study protocol was registered in the PROSPERO. Ex vivo studies performed on Enterococcus faecalis or polymicrobial biofilms incubated on human/bovine dentin were selected. The quality of the studies was assessed using a customized quality assessment tool. Standardized mean difference (SMD) with a 95% confidence interval (CI) was calculated for the meta-analysis. Meta-regression models were used to identify the sources of heterogeneity and to compare the efficacy of pastes.

Results

The qualitative and quantitative synthesis included 40 and 23 papers, respectively, out of 1421 search results. TAP (SMD = -3.82; CI, -5.44 to -2.21; P < 0.001) and SAPs (SMD = -2.38; CI, -2.81 to - 1.94; P < 0.001) had significantly higher antibacterial efficacy compared to the CH on E. faecalis biofilm. However, no significant difference was found between the efficacy of DAP (SMD = -2.74; CI, -5.56-0.07; P = 0.06) or mTAP (SMD = -0.28; CI, -0.82-0.26; P = 0.31) and CH. Meta-regression model on E. faecalis showed that SAPs have similar efficacy compared to TAP and significantly better efficacy than DAP. On dual-species (SMD = 0.15; CI, -1.00-1.29; P = 0.80) or multi-species (SMD = 0.23; CI, -0.08-0.55; P = 0.15) biofilms, DAP and CH had similar efficacy.

Conclusions

Ex vivo evidence showed that antibiotic pastes were either superior or equal to CH. The studied SAPs had considerably higher or similar antibacterial effectiveness compared to DAP, CH, and TAP. Hence, combined antibiotic therapy was not necessarily required for root canal disinfection ex vivo.

Anatomical Evaluation of Root and Root Canal Morphology of Permanent Mandibular Dentition among the Saudi Arabian Population: A Systematic Review

This study aimed to conduct a compendious review of root canal morphology of “permanent mandibular teeth in different regions of Saudi Arabia” to obtain a large sample representing the total population. A detailed search through the databases Web of Science, Scopus, and PubMed was conducted following the PRISMA guidelines. The data were analyzed based on the following inclusion criteria: original full-length original articles that reported the variables of interest “(number of roots, number of canals, Vertucci's classification system and C-shaped canals or mid-mesial canals)” of the mandibular teeth and conducted on Saudi subjects. The retrieved data were presented as frequencies and percentages. The results revealed that 56.6% of mandibular central incisors had one canal and Vertucci type I (56.6%), while 57.4% of the mandibular lateral incisors had one canal, with Vertucci types I and III most frequent. In mandibular canines, 91.8% had one canal and 8.2% had two canals. Most of the mandibular first premolars had one root (86.6%), while almost all mandibular second premolars (91.5%) had one canal, and 96.9% had Vertucci type I configuration. Among the mandibular first molars, three and four canals were prevalent in 58.7% and 40.6%, respectively. The majority of mesial roots had Vertucci type IV (60.6%), and most of distal roots had Vertucci type I (72.2%). Most of the mandibular second molars had three canals (87.3%) and showed Vertucci type IV (39.4%) canals for mesial roots and Vertucci type I (95.6%) for distal roots. The C-shaped canals were seen in 8% of first premolars and 9.8% of second molars. The middle mesial canal was found in 4.2% and 0.4% of first and second molars, respectively. This review could represent “the population of Saudi Arabia as the included samples were combined from different regions of the country.” Some variations were noticed within the same group of teeth from different regions. However, the overall results of combined samples were comparable to the other international studies.

Cytotoxicity and Efficacy in Debris and Smear Layer Removal of HOCl-Based Irrigating Solution: An In Vitro Study

In the present study we evaluated the cytotoxicity of super-oxidized water on human gingival fibroblasts and its efficacy in debris and smear layer removal from root canal walls. Cultured gingival fibroblasts were exposed to super-oxidized water (Sterilox), which was diluted in Iscove’s modified Dulbecco’s medium (IMDM) at 30%, 40%, 50%, 60% and 70% concentrations. The control group was maintained in IMDM. The cell viability was evaluated by means of an MTT assay after incubation periods of 1 h, 2 h, 24 h and 48 h. Pathological cellular changes were also observed under fluorescence and phase contrast microscopes. The efficacy in debris and smear layer removal was evaluated in comparison to the conventional application of sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (EDTA). Forty maxillary premolars were randomly divided into two equal groups (n = 20) and shaped with ProTaper NEXT rotary instruments using Sterilox or NaOCl/EDTA for irrigation. Afterwards, roots were split longitudinally and examined under a scanning electron microscope. The results revealed that super-oxidized water and sterile distilled water have acceptable biological properties for endodontic applications at concentrations up to 50% (p > 0.05). Moreover, super-oxidized water is equally effective in debris and smear layer removal as compared to NaOCl/EDTA (p > 0.05).

Anatomical Evaluation of Root and Root Canal Configuration of Permanent Maxillary Dentition in the Population of the Kingdom of Saudi Arabia

AIM

This study is aimed at combining the sample sizes of all studies on permanent maxillary teeth conducted in different regions of the Kingdom of Saudi Arabia (KSA) to obtain a large sample size that represents the population of the KSA. The outcome of these combined studies is compared with international studies in terms of the number of roots, number of canals, and canal configurations on the basis of Vertucci's classification. Methodology. The studies were systematically reviewed using the Preferred Reporting Items for Systematic Review and Meta-analysis chart. Studies were included in the analysis if they were conducted in the KSA, involved permanent human maxillary teeth, and had a sample of more than 10 teeth (power). By contrast, studies were excluded if they involved deciduous teeth in the sample size, investigated nonhuman teeth, were not conducted in the KSA, and were case reports, case series, review studies, and anomalies. Relevant literature was searched from PubMed, Scopus, Web of Science, Embase, Cochrane, and Direct Science by two calibrated teams, starting in August 2020, without time limits or language restrictions.

RESULTS

The database searches and cross-referencing identified a total of 19 relevant studies. All maxillary canines (N = 1,018) had one root, whereas 98.4% had one canal and 98.3% had Vertucci type I. Moreover, 63.2% of the maxillary first premolars had two roots, and 91.4% had two canals. The most common Vertucci root canal configuration was type IV (64.6%). The maxillary second premolars mostly had one root (84.4%) and one canal (50.4%). The most common canal configuration was Vertucci type I (47.1%). The majority of maxillary first molars had three roots (98.9%), 48.7% of which had three canals, and 46.4% had four canals. The most prevalent feature of the canal morphology of mesiobuccal roots was Vertucci type II (35.3%). The investigated maxillary second molars had three roots, 88.0% of which had three canals.

CONCLUSION

This systematic review represents the Saudi population since samples were combined from different studies from different regions of the country. Variations in findings were observed in the same group of teeth from different regions and the same region, while the overall combined samples results fell within the range of other international studies.

Combination of a new ultrasonic tip with rotary systems for the preparation of flattened root canals

Objectives

This study evaluated 2 nickel-titanium rotary systems and a complementary protocol with an ultrasonic tip and a small-diameter instrument in flattened root canals.

Materials and Methods

Thirty-two human maxillary second premolars with flattened canals (buccolingual diameter ≥4 times larger than the mesiodistal diameter) at 9 mm from the radiographic apex were selected. The root canals were prepared by ProDesign Logic (PDL) 30/0.01 and 30/0.05 or Hyflex EDM (HEDM) 10/0.05 and 25/0.08 (n = 16), followed by application of the Flatsonic ultrasonic tip in the cervical and middle thirds and a PDL 25/0.03 file in the apical third (FPDL). The teeth were scanned using micro-computed tomography before and after the procedures. The percentage of volume increase, debris, and uninstrumented surface area were analyzed using the Kruskal-Wallis, Dunn, Wilcoxon, analysis of variance/Tukey, and paired and unpaired t-tests (α = 0.05).

Results

No significant difference was found in the volume increase and uninstrumented surface area between PDL and HEDM (p > 0.05). PDL had a higher percentage of debris than HEDM in the middle and apical thirds (p < 0.05). The FPDL protocol resulted in less debris and uninstrumented surface area for PDL and HEDM (p < 0.05). This protocol, with HEDM, reduced debris in the middle and apical thirds and uninstrumented surface area in the apical third (p < 0.05).

Conclusions

High percentages of debris and uninstrumented surface area were observed after preparation of flattened root canals. The HEDM, Flatsonic tip, and 25/0.03 instrument protocol enhanced cleaning in flattened root canals.

The Influence of Root Canal Preparation with ProTaper Next, WaveOne Gold, and Twisted Files on Dentine Crack Formation

(1) Background: Root canal preparation constitutes an important factor for success in endodontics. However, various complications may occur during this stage. The aim of this study was to compare the incidence of cracks within radicular dentin after instrumentation with ProTaper Next (PTN), WaveOne Gold (WOG), and Twisted Files (TF), which utilize different kinematics. (2) Methods: Eighty single-rooted teeth were classified into four groups (n = 20). Three groups were instrumented using PTN (X1, X2), WOG (Primary), and TF (SM1–3). The non-instrumented group constituted the control group. Post-preparation, the roots were sectioned 3, 6, and 9 mm from the apex using a low-speed saw (Southbay Technology Inc., San Clemente, CA, USA). The specimens were viewed through a microscope at x25 magnification (Leica M320, Wetzlar, Germany), and their surface was assessed tactilely to determine the presence of the crack. (3) Results: Partial cracks within radicular dentine were observed in all study groups (PTN: n = 4/20%, WOG: n = 3/15%, TF: n = 4/20%); no cracks were observed in the control group. No significant differences were observed among experimental groups. OR values for the incidence of cracks were: OR = 11.182 for PTN, OR = 8.2 for WOG, and OR = 8.2 for TF. (4) Conclusions: Instrumentation with PTN, WOG, and TF may result in dentinal cracks formation.

The Effect of Ultrasonic Agitation on the Porosity Distribution in Apically Perforated Root Canals Filled with Different Bioceramic Materials and Techniques: A Micro-CT Assessment

The present study evaluated the effect of ultrasonic agitation on the porosity distribution of BioRoot RCS/single gutta-percha cone (BR/SC) and MTA Flow (MF) root canals fillings used as apical plugs in moderately curved and apically perforated roots. Eighty mesial root canals of mandibular first molars were enlarged up to ProTaper NEXT X5 rotary instrument 2 mm beyond the apical foramen, simulating apical perforations. Specimens were randomly divided into four experimental groups (20 canals per group) according to the material and technique used for root canal obturation: BR/SC, BR/SC with ultrasonic agitation (BR/SC-UA), MF and MF with ultrasonic agitation (MF-UA). The ultrasonic tip was passively inserted into the root canal after the injection of flowable cement and activated for 10 s. The specimens were scanned before and after obturation with a high-resolution micro-computed tomography scanner, and the porosity of the apical plugs was assessed. The differences between groups were analyzed using the Kruskal-Wallis and Mann-Whitney tests, with the significance level set at 5%. None of the obturation materials and techniques used in this study was able to provide a pore-free root canal filling in the apical 5 mm. Considerably higher percentages of open and closed pores were observed in the MF and MF-UA groups, with the highest porosity being in the MF-UA group (p < 0.05). No significant differences were observed between the BR/SC and BR/SC-UA groups, where the quantity of open and closed pores remained similar (p > 0.05).

An In Vitro Evaluation Study of the Geometric Changes of Root Canal Preparation and the Quality of Endodontic Treatment

Introduction

The geometry of root canals differs in different parts, especially in the apical region, and it is affected by different preparation techniques. The aim of this study was to evaluate the geometric changes of root canal preparation by general dentists regardless of the endodontic instrumentation systems and to study the quality of endodontic treatment by evaluating the untouched areas after mechanical preparation and the smear layer removal.

Materials and Methods

100 extracted maxillary canines were collected for the in vitro study from 10 dentists, and the dentists were asked to treat the teeth endodontically. The teeth then were separated and examined under an optical microscope to evaluate the root canal final diameter and the untouched areas. Then, the teeth were examined under a scanned electronic microscope to evaluate the smear layer in coronal, middle, and third parts of the canal. Statistical significance was set as P < 0.05.

Results

The mean diameter of the root canal after instrumentation in the coronal and middle thirds was 2.50 ± 1.12 and 1.75 ± 1.24 mm, respectively, and the untouched area percentage observed in the apical thirds was 71%. For smear layer removal, it was better in the coronal and middle thirds than in the apical (P < 0.05).

Conclusion

The changes in the diameter of the root canal, the percentage of untouched areas after mechanical preparation, and the percentage of smear layer were observed in a higher percent in the apical third than in the coronal and middle thirds, and this raises the question of changing the technique of processing the root canal, especially in the apical third.

Influence of activation mode and preheating on intracanal irrigant temperature

This ex vivo study assessed the effectiveness of two activation modes to increase the intracanal temperature of 5.25% NaOCl solution and the time for a preheated-irrigant to return to its initial temperature. Ten single-rooted extracted human teeth were used. Thermocouples were adapted to the root surface and the temperature was registered following two activation modes: ultrasound (US) and thermal. Furthermore, a preheated-solution (45°C/60°C) was flushed into root canal to test the time needed to return to its initial temperature. Data were analysed using two-way ANOVA and Tukey's post-hoc tests (P = 0.05). Statistical analysis showed differences between the activation modes. US and thermal activation increased from 37 to 40.4°C and to 62.8°C respectively in 60 s. Time for preheated-irrigant to return to its initial temperature was longer for 60°C. Preheating irrigant at 60°C and using thermal activation to keep it warm may represent a further step of the irrigation protocol.

Micro-CT comparison of XP-endo Finisher and passive ultrasonic irrigation as final irrigation protocols on the removal of accumulated hard-tissue debris from oval shaped-canals

OBJECTIVE

To compare the effectiveness of the XP-endo Finisher instrument and passive ultrasonic irrigation (PUI) as final irrigation protocols on the removal of accumulated hard-tissue debris (AHTD) from oval-shaped canals using micro-computed tomographic (micro-CT) analysis.

METHODS

Twenty mandibular incisors were anatomically pair-matched based on similar morphological dimensions (length, volume, aspect ratio, and configuration) through micro-CT analysis, prepared with Reciproc R25 instrument, scanned again, and assigned to one of the two experimental groups (n = 10), according to the final irrigation protocol: XP-endo Finisher and PUI. After the final irrigation protocols, the specimens were rescanned and the registered datasets were examined to quantify the amount of AHTD. Data were statistically analyzed using Student's t test with a significance level of 5%.

RESULTS

The final irrigation protocols were highly similar in terms of volumetric percentage reduction of AHTD (P = 1.000).

CONCLUSIONS

XP-endo Finisher and PUI showed the same effectiveness on the removal of AHTD. None of the tested final irrigation protocols completely removed the AHTD from oval-shaped root canals.

CLINICAL RELEVANCE

AHTD may be considered clinically relevant because it could harbor bacterial contents away from the disinfection procedures. Both final irrigation protocols were effective on the removal of AHTD.