The Influence of an Isthmus on the Outcomes of Surgically Treated Molars: A Retrospective Study

Post-operative pain after single-visit root canal treatment using resin-based and bioceramic sealers in teeth with apical periodontitis: A randomised controlled-trial

The present study aimed to compare postoperative pain in teeth with symptomatic and asymptomatic apical periodontitis (AP) following a single-visit endodontic treatment using BioRoot™ RCS or AH Plus at 8 h, 24 h and 48 h postoperatively. Postgraduate students performed endodontic treatment on 101 teeth with AP, randomised into two obturation groups. A 100-mm Visual Analog Scale was used to document the intensity of pain at preoperative, 8-h, 24-h and 48-h intervals. The Kolmogorov-Smirnov test was used for normality, and the median and interquartile ranges were compared using the Mann-Whitney U test. Preoperative pain (1.90 ± 3.50) was more frequent in teeth with symptomatic AP (p < 0.05). However, no significant differences were observed in postoperative pain at the 8-h, 24-h and 48-h intervals. Pre and postoperative pain were directly associated (p < 0.05). Single-visit root canal treatment in teeth with AP using both sealers resulted in similar levels of postoperative pain.

Bacterial sealing ability of calcium silicate-based sealer for endodontic surgery: an in-vitro study

BACKGROUND

Apical surgery with standard retrograde maneuvers may be challenging in certain cases. Simplifying apical surgery to reduce operating time and streamline retrograde manipulation is an emerging need in clinical endodontics.

AIM OF THE STUDY

The aim of the study was to compare the bacterial sealing ability of a calcium silicate-based sealer with the single cone technique combined with root end resection only, and calcium silicate-based sealer as a retrograde filling versus MTA retrofilling, and to analyze bacterial viability using confocal laser scanning microscope (CLSM).

MATERIALS AND METHODS

In this in vitro experimental study, 50 extracted human maxillary incisor teeth were instrumented and randomly divided into five groups: three experimental groups, a positive control group, and a negative control group (n = 10/group). In the experimental groups, the roots were obturated using the single cone technique (SCT) and a calcium silicate-based sealer. In group 1, the roots were resected 3 mm from the apex with no further retrograde preparation or filling. In groups 2 and 3, the roots were resected, retroprepared, and retrofilled with either a calcium silicate-based sealer or MTA, respectively. Group 4 (positive control) was filled with a single gutta-percha cone without any sealer. In group 5 (negative control), the canals were left empty, and the roots were sealed with wax and nail varnish. A bacterial leakage model using Enterococcus faecalis was employed to assess the sealing ability over a 30-day period, checking for turbidity and analyzing colony forming units (CFUs) per milliliter. Five specimens from each group were examined using CLSM for bacterial viability. Data for the bacterial sealing ability were statistically analyzed using chi-squared and Kruskal-Wallis tests.

RESULTS

The three experimental groups did not show significant differences in terms of bacterial leakage, or bacterial counts (CFUs) (P > 0.05). However, significant differences were observed when comparing the experimental groups to the positive control group. Notably, the calcium silicate-based sealer, when used as a retrofilling, yielded the best sealing ability. CLSM imaging revealed viable bacterial penetration in all the positive control group specimens while for the experimental groups, dead bacteria was the prominent feature seen.

CONCLUSION

Within the limitations of this study, it could be concluded that the bacterial sealing ability of calcium silicate-based sealer with the single cone technique combined with root end resection only and calcium silicate-based sealer as a retrograde filling were comparable with MTA retrofilling during endodontic surgical procedures.

Accuracy and efficiency of dynamic navigated root-end resection in endodontic surgery: a pilot in vitro study

BACKGROUND

The operation accuracy and efficiency of dynamic navigated endodontic surgery were evaluated through in vitro experiments. This study provides a reference for future clinical application of dynamic navigation systems in endodontic surgery.

MATERIALS AND METHODS

3D-printed maxillary anterior teeth were used in the preparation of models for endodontic surgery. Endodontic surgery was performed with and without dynamic navigation by an operator who was proficient in dynamic navigation technology but had no experience in endodontic surgery. Optical scanning data were applied to evaluate the length and angle deviations of root-end resection. And the operation time was recorded. T tests were used to analyze the effect of dynamic navigation technology on the accuracy and duration of endodontic surgery.

RESULTS

With dynamic navigation, the root-end resection length deviation was 0.46 ± 0.06 mm, the angle deviation was 2.45 ± 0.96°, and the operation time was 187 ± 22.97 s. Without dynamic navigation, the root-end resection length deviation was 1.20 ± 0.92 mm, the angle deviation was 16.20 ± 9.59°, and the operation time was 247 ± 61.47 s. Less deviation was achieved and less operation time was spent with than without dynamic navigation (P < 0.01).

CONCLUSION

The application of a dynamic navigation system in endodontic surgery can improve the accuracy and efficiency significantly for operators without surgical experience and reduce the operation time.

Prevalence and anatomic associations of middle mesial canals and isthmi in mandibular first molars: A CBCT-based study in a Northern Chinese population

This study investigated the prevalence of the middle mesial canal (MMC) and isthmus in a northern Chinese subpopulation using cone-beam computed tomography (CBCT). CBCT images of 1060 mandibular first molars (MFMs) were analysed. Data analysis was performed using the chi-square test, t-test, and multiple logistic regression analysis (p < 0.05). The prevalence of MMC and isthmus was 15.2% and 40.6%, respectively. The average dentinal thickness in the danger zone was 1.61 ± 0.14 mm. Patients younger than 40 years were two times more likely to have MMC (odds ratio [OR] = 2.204). Additionally, for every 1 mm reduction in the MB-ML orifice distance, the likelihood of detection of MMC in MFM nearly doubled (OR = 1.738). Furthermore, MFMs with MB-ML isthmus were five times more likely to exhibit MMC than those without it (OR = 4.756). The findings revealed that the prevalence of MMC and isthmus in MFMs is high and suggested that anatomical and demographic variables can serve as valuable indicators for clinicians in anticipating their presence.

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.

Diamond-coated ultrasonic tip decreases debris and uninstrumented surface after preparation of curved canals with isthmus

The aim of this study was to evaluate root canal preparation with nickel titanium rotary instruments and complementary preparation with ultrasonic tip in curved canals of mandibular molars with isthmus. Twenty-eight mesial roots of mandibular molars with curvature between 20° and 40° and presence of isthmus throughout the entire extension of the root canals were prepared using ProDesign Logic CM (PDL) up to size 40.05, or HyFlex EDM (HFEDM) up to size 40.04. Complementary preparation was performed in the isthmus region using the ultrasonic insert E18D (Helse, Istmo Diamantada). The root canals were scanned using micro-CT (SkyScan 1176) at 9 µm voxel size before and after each preparation step. Transportation, percentage of increase in volume, debris and uninstrumented surface (UNS) were evaluated. Mann Whitney, Wilcoxon, paired and non-paired t-tests were used for statistical analysis (α = 0.05). The canals prepared with PDL and HFEDM obtained similar results for all the variables assessed before using E18D (p > 0.05). E18D significantly decreased the percentage of debris and UNS values in both Groups (p < 0.05). The complementary preparations with E18D caused a smaller quantity of debris in the isthmus of the canals previously prepared with PDL in comparison with HFEDM (p < 0.05). PDL and HFEDM provided similar root canal preparation. PDL promoted a smaller quantity of Debris in the isthmus than HFEDM after using E18D. E18D significantly improved cleaning, and reduced Debris and UNS.

Efficacy of different irrigant activation devices in removing dentin debris from an artificial isthmus connecting curved canals

The aim of this study was to evaluate the debridement efficacy of sonic irrigation (EDDY; VDW, Munich, Germany and EndoActivator; Dentsply-Sirona, Ballaigues, Switzerland) and ultrasonically activated irrigation (Irrısafe; Satelec Acteon, Merignac, France) in a simulated canal isthmus connecting curved canals. Transparent resin blocks were produced containing two curved canals connected with an isthmus. The isthmus was then filled with dentin debris. Three irrigant activation cycles were performed and the amount of remaining debris was compared analysing pictures taken after each activation cycle. Data were statistically analysed using one-way ANOVA and post hoc Tukey tests at a significance level of p < 0.05. EDDY showed greater efficiency in removing dentin debris from the simulated isthmus than the other techniques tested. An increase in the activation time enhanced the efficiency of both EDDY and ultrasonically activated irrigation in debris removal.

Unveiling Hidden Canals: Middle Mesial Canal Prevalence in Mandibular First Molars Using Cone-Beam Computed Tomography Analysis in Central India

Background The most frequent reason involving failure of root canal treatment in molar teeth is the inability to locate additional canals. While much research has been conducted on the morphology of mandibular molars, little is known about isthmuses and middle mesial (MM) canals in the Indian population. The primary aim of the present research was to determine the prevalence of MM canals and isthmuses of mandibular first molars in the Central India population using cone-beam computed tomography (CBCT) images. Methodology CBCT of 140 mandibular first molar teeth was analyzed from the institutional database images in the coronal, sagittal, and axial planes. Data concerning the number of root canals, the presence of middle mesial canals, and the presence of isthmus were noted. Information collected was transferred into an Excel sheet and analyzed using the Statistical Package for Social Sciences (IBM Corp., Armonk, NY, USA). Results Eight images (5.71%) revealed the presence of middle mesial canals with no statistically significant occurrence. The incidence of isthmi in the mandibular first molar was 84.3%, and the presence of isthmi in the coronal third was about 38.6%. This showed a considerable presence. Conclusion There is incidence of the middle mesial canal, which emphasizes the need to locate extra canals in patients undergoing root canal endodontic treatment. The implementation of CBCT will help identify the extra canal before the treatment. This will help ultimately in providing better patient care.

Effect of Passive Ultrasonic Irrigation, Er,Cr:YSGG Laser, and Photon-Induced Photoacoustic Streaming against Enterococcus faecalis Biofilms in the Apical Third of Root Canals

PURPOSE

This study aimed to compare the antibacterial effectiveness of passive ultrasonic irrigation (PUI), Er,Cr:YSGG laser (WTL), and photon-induced photoacoustic streaming (PIPS) using an Er:YAG laser against Enterococcus faecalis biofilms in the apical third of root canals.

METHODS

Root canals of 70 single-rooted human teeth were instrumented and infected with E. faecalis for 3 weeks to form biofilms. The samples were randomly divided into five groups as follows: (i) PUI + 3% NaOCl (n = 16); (ii) Er,Cr:YSGG laser (n = 16); (iii) PIPS + 3% NaOCl (n = 16); (iv) positive control group (n = 10); and (v) negative control group (n = 10). The bacterial content in the root canal was sampled using (a) the paper-point sampling method before (S1) and after (S2) treatment and (b) pulverising the apical 5 mm of the root. The number of bacteria recovered from each group was counted as colony-forming units (CFUs). The amount of reduction between the groups was compared with the Kruskal-Wallis test and post-test Dunn's multiple comparisons tests. The significance level was set at 5% (p < 0.05).

RESULTS

The samples from the paper-point sampling method showed that the amount of bacteria before (S1) and after treatment (S2) was significantly different between PIPS and WTL, as well as between the PUI and WTL groups. In contrast, no significant difference was found between the PIPS and PUI groups. From the pulverised samples, the results indicated no significant difference among all experimental groups in the amount of bacterial reduction in the apical 5 mm of the root.

CONCLUSIONS

PUI and PIPS showed a significantly greater reduction in bacterial content within the main root canal compared with the WTL. There was no difference among all experimental groups in the apical third of the root.

Factors that influence the outcomes of surgical endodontic treatment

Surgical endodontic treatment encompasses a broad spectrum of procedures, amongst which root-end cavity preparation and filling, retrograde root canal treatment and through-and-through endodontic surgery, may be classified under the umbrella term 'Root-end surgery'. This narrative review considers the available data on periapical healing, soft tissue healing, tooth survival and oral health-related quality of life (OHRQoL), following root-end surgery and the factors that affect its outcomes. The pooled periapical healed rate for the studies published up to 2021 was 69% (95% CI: 65%, 73%) but increased to 76% (95% CI: 66%, 86%) when only data from the 2020's studies were analysed. The prognostic factors consistently reported for periapical healing have included: pre-operative periapical lesion with complete loss of buccal plate, quality of root-end preparation, remaining thickness of apical root dentine and restorative status. Soft tissue healing of the reflected flap was found to have a positive association with periapical healing. The survival rates following root-end surgery range from 48% to 93%, with failure of periapical healing associated with root and crown fracture, being the predominant reasons for tooth extraction. The factors influencing impact of root-end surgery on patients' quality of life could not be adequately evaluated due to design flaws in the available studies. In conclusion, if root canal treatment failure due to leakage through cracks, fractures or restoration margin are excluded, the remaining cases may represent localized residual infection and inflammation at the periapex that should be amenable to predictable management with the aid of modern root-end surgery.

Isthmus morphology influences debridement efficacy of activated irrigation: A laboratory study involving biofilm mimicking hydrogel removal and high-speed imaging

AIM

Little is known about the influence of isthmus morphology on the debridement efficacy of activated irrigation. The aim of this study was to investigate the influence of isthmus morphology on the debridement efficacy of laser-activated irrigation (LAI), EDDY and needle irrigation (NI), and to explain the methods of isthmus cleaning by LAI and EDDY.

METHODOLOGY

Four root canal models (apical diameter: 0.30 mm, taper: 0.06, curvature: 23°, length: 20 mm) were produced by CAD-CAM with different isthmus morphologies: long-wide (4 mm; 0.4 mm), long-narrow (4 mm; 0.15 mm), short-wide (2 mm; 0.4 mm) and short-narrow (2 mm; 0.15 mm). The isthmuses were filled with a hydrogel containing dentine debris. The canals were filled with irrigant and models were assigned to the following irrigation protocols (n = 240): needle irrigation (NI) with a 30G needle, Eddy, and LAI (2940 nm Er:YAG-laser, 15 Hz, 40 mJ, SWEEPS, tip at the canal entrance). Standardized images of the isthmuses were taken before and after irrigation, and the amount of removed hydrogel was determined using image analysis software and compared across groups using Kruskal-Wallis test followed by Dunn's multiple comparison. Visualization of the isthmus during activation was achieved using a high-speed camera. The pattern and speed of the flow in the isthmus as well as transient and stable cavitation were analysed using imaging software.

RESULTS

Laser-activated irrigation, EDDY and NI removed more hydrogel in short-wide isthmuses than in narrow isthmuses (p < .001). LAI and EDDY removed more hydrogel than NI in every isthmus configuration (p < .001). EDDY showed eddies and stable cavitation, and LAI showed transient cavitation at each pulse, and pulsed horizontal flow with the highest particle speed in closed short isthmuses.

CONCLUSIONS

Isthmus morphology influences debridement in all irrigation groups. Short-wide isthmuses were the easiest to clean while narrow isthmuses were the most challenging to clean. Width seems to be a more critical anatomical parameter than length. LAI and EDDY resulted in the greatest biofilm removal and performed better than NI. EDDY produced eddies and stable cavitation in the isthmus, and LAI showed transient cavitation and pulsed horizontal flow.

Clinical outcome of bioceramic sealer iRoot SP extrusion in root canal treatment: a retrospective analysis

Background

During the obturation procedure, sealer extrusion occurs in some cases. iRoot SP is a kind of bioceramic sealer with superior physicochemical and biological properties. This article reports the outcome of iRoot SP extrusion in root canal treatment and the potential factors associated with the outcome.

Methods

Ninety-nine patients and one hundred and eighty-five teeth treated between 2014 and 2020 were included in this retrospective study. All of the cases were filled with a single-cone technique and the iRoot SP sealer. The minimum follow-up visit period was 1 year. The outcome was evaluated by clinical examination and radiographic examination at recall and was classified as healed, healing (success), or not healed (failure).

Results

The overall success rate of all teeth was 96.8%. The success rate of adequately filled teeth was 97.3%, while that of iRoot SP extrusion was 95.8%; the difference was not statistically significant. Factors such as gender, age, tooth position, follow-up visit period, size of periapical lesion, treatment type and extruding sealer amount had no influence on the outcome of iRoot SP extruded teeth.

Conclusions

The results suggested that iRoot SP extrusion has no adverse effect on the outcome of root canal treatment, which may contribute to the endodontic treatment.

Evaluation of the band-shaped isthmuses in the mesiobuccal root canal system using micro-computed tomography

OBJECTIVES

This micro-computed tomography (micro-CT) study analyzed band-shaped isthmuses having their floor at the apical third of the mesiobuccal roots of maxillary molars in terms of 2D and 3D morphological parameters.

MATERIALS AND METHODS

A total of 199 maxillary first molars were scanned with micro-CT. Twenty-seven specimens, confirmed to have a band-shaped isthmus, were further examined in terms of the isthmus length, volume, structure model index (SMI), and surface area. The distance of apical foramina of mesial canals from the isthmus floor and major-minor diameters, roundness, perimeter, and area of the isthmus roof and floor were compared. Statistical analyses were performed with descriptive statistics and t-test with a 5% significance threshold.

RESULTS

The band-shaped isthmus frequency was 13.5% and its length reached up to 5.5 mm. The distances of the apical foramina of mesiobuccal canals (MB1 and MB2) from the isthmus floor were similar (p > .05). Isthmus roof and floor showed significant differences in terms of their major diameter and area (p < .05), whereas their minor diameter, roundness, and perimeter values were similar (p > .05).

CONCLUSION

The band-shaped isthmuses are not rare and can reach through the half of the root length with oval cross-sections in the floor and roof anatomy. The distance between the isthmus floor and apical foramina did not differ between MB1 and MB2.

CLINICAL RELEVANCE

The band-shaped isthmus morphology contributes to the complexity of the apical anatomy of maxillary first molar teeth with various lengths and diameters.

A retrospective cohort study on outcome and interactions among prognostic factors of endodontic microsurgery

BACKGROUND/PURPOSE

Endodontic microsurgery (EMS) is a reliable treatment for teeth with non-healing apical periodontitis. This study evaluated the outcome of EMS with mineral trioxide aggregate as the retrograde filling material and identified potential prognostic factors associated with the EMS outcome.

METHODS

Consecutive clinical and radiographic records of EMS performed in a teaching hospital from 2013 to 2017 were reviewed. Cases of root fracture, cemental tear, re-surgery, and incomplete records were excluded. After selection, 268 EMS-treated teeth with the follow-up period more than one year were included. Surgical outcome as success or failure was evaluated according to Molven's criteria. For analysis of potential prognostic factors, multivariate logistic regression was performed followed by bivariate chi-square tests. Stratified analysis was performed to understand the interactions between two prognostic factors.

RESULTS

The overall EMS success rate was 89.9% in this study. Tooth type (anteriors vs. molars, odds ratio (OR) = 6.83, P = 0.001, anteriors vs. premolars, OR = 4.27, P = 0.010) and endodontic-periodontal (endo-perio) communicating defects (with vs. without, OR = 4.92, P = 0.005) both had a significant influence on the EMS outcome. The negative impact of endo-perio communicating defects was closely associated with tooth type. Premolars with endo-perio communicating defects had significantly higher rates of failure.

CONCLUSION

The EMS outcome is significantly affected by the tooth type and endo-perio communicating defect. The presence of endo-perio communicating defects has a greater negative influence on the success rate for premolars than for anteriors and molars.

Outcome of Periapical Surgery in Molars: A Retrospective Analysis of 424 Teeth

INTRODUCTION

The objective of this retrospective study was to assess the outcome of periapical surgery in a large number of molars in order to identify possible variables that might affect the outcome.

METHODS

The healing outcome of patients undergoing periapical surgery of molars from October 1999 to October 2019 was retrospectively evaluated. Outcome was dichotomized into "healed" and "nonhealed" using well-established clinical and radiographic healing criteria. The potential influence of patient-, tooth-, and treatment-related parameters on the healing outcome was analyzed.

RESULTS

A total of 424 molars in the same number of patients (45.5% male and 54.5% female) were evaluated. Three hundred seventy-two molars were classified as healed (87.7%). Three significant outcome predictors were identified: 1-year follow-up versus >1-5 years, >5-10 years, and >10 years (95.3% vs 82.2%, 76.3%, and 76.5% healed, respectively; P < .0001); root end filling material with bioceramic root repair material versus mineral trioxide aggregate (96.9% vs. 86.3% healed, respectively; P = .001); and preoperative evaluation based on cone-beam computed tomographic imaging versus 2-dimensional radiography (90.2% vs 81.4% healed, respectively; P = .02). Sex, age, tooth location, type of restoration, attachment level, presence of a post, quality of the root canal filling, technique of root end preparation, administration of antibiotics, and type of surgery had no significant impact on the healing outcome.

CONCLUSIONS

The healed rate for the concave (Retroplast) and cavity (mineral trioxide aggregate, SuperEBA [Staident International, Staines, UK], and bioceramic root repair material) root end preparation technique over all follow-up periods was 84% and 88.5%, respectively. The follow-up period, root end filling material, and preoperative evaluation based on cone-beam computed tomographic imaging had a significant influence on the healing outcome.

Presence of voids after three obturation techniques in band-shaped isthmuses: a micro-computed tomography study

Background

The objective of the present micro-computed tomography (micro-CT) study was to assess the presence of voids in band-shaped isthmuses obturated using three different filling techniques.

Methods

Twenty-four artificial molar teeth with a band-shaped isthmus were allocated to three groups (n = 8) for obturation, according to the filling technique: single-cone (SC), continuous wave of condensation (CWC) or lateral condensation (LC). Obturation was performed with gutta-percha (GP) cones and iRoot SP (Innovative Bioceramix, Vancouver, Canada). Post-filling micro-CT scanning was performed. The percentage of filling materials and void volumes were calculated in the isthmus areas and data were analyzed using one-way ANOVA and Tukey tests.

Results

The mean percentage of void volumes and corresponding filling percentages in the isthmus areas after obturation in the SC groups was 22.98 % ± 1.19 %, 77.02 % ± 1.19 %; in the CWC groups 10.46 % ± 2.28 %, 89.54 % ± 2.28 %; and in the LC groups was 13.14 % ± 1.85 %, 86.86 % ± 1.85 %, respectively.

Conclusions

In band-shaped isthmus area, the obturation quality of CWC was superior to SC and LC techniques.

An Update on Endodontic Microsurgery of Mandibular Molars: A Focused Review

Endodontic microsurgery is a highly predictable treatment option in most cases when conventional endodontic treatment is not feasible. Nevertheless, mandibular molars are still considered by clinicians to be the most difficult type of teeth, with the lowest success rate. In recent years, endodontic microsurgery has been attempted more frequently with the emergence of modern cutting-edge technologies such as dental operating microscopes, various microsurgical instruments, and biocompatible materials, and the success rate is increasing. This review describes the current state of the art in endodontic microsurgical techniques and concepts for mandibular molars. Notably, this review highlights contemporary equipment, technology, and materials.

The effect of different confluence confirmation strategies on the obturation of Vertucci type II canal: micro-CT analysis

Objectives

The present study aims to compare the obturation quality of 2 confluence confirmation techniques in artificial maxillary first premolars showing Vertucci type II root canal configuration.

Materials and Methods

Thirty artificial maxillary premolars having Vertucci type II root canal configuration were made. They were divided into 3 groups according to the confluence confirmation technique as follows. Gutta-percha indentation (GPI) group (confluence confirmation using a gutta-percha cone and a K file); electronic apex locator (EAL) group (confluence confirmation using K files and EAL); and no confluence detection (NCD) group. In the GPI group and the EAL group, shaping and obturation were performed with the modified working length (WL). In the NCD group, shaping was performed without WL adjustment and obturation was carried out with an adjusted master cone. Micro-computed tomography was used before preparation and after obturation to calculate the percentage of gutta-percha occupied volume (%GPv) and the volume increase in the apical 4 mm. Data were analyzed using 1-way analysis of variance and post hoc Tukey's test.

Results

Statistically significant difference was not found in terms of the %GPv from the apex to apical 4 mm. However, the NCD group showed a statistically significant volume increase compared with the EAL group (p < 0.05).

Conclusions

In terms of gutta-percha occupied volume, no significant difference was observed among the 3 groups. Confluence confirmation using an EAL in teeth with Vertucci type II configuration showed less volume increase during canal shaping compared with no confluence confirmation.

The Buffalo study: Outcome and associated predictors in endodontic microsurgery- a cohort study

AIM

To (i) evaluate and compare the outcome of endodontic microsurgery (EMS) using periapical radiographs (PAs) and cone-beam computed tomography (CBCT) scans; (ii) identify prognostic factors affecting the outcome; and (iii) correlate the effect of guided tissue regeneration (GTR) on the pattern of apical bone remodelling.

METHODOLOGY

Eighty-two patients (101 teeth) who received EMS were included and followed-up using clinical and radiographic examinations (PAs and CBCT scans). Two calibrated endodontists evaluated the radiographic healing (favourable or unfavourable) by assessing PAs and CBCT. The success (favourable radiographic outcome with no clinical symptoms) and survival rates (tooth retention without clinical symptoms) were calculated, and the cause of failure (diseased or fractured) was identified. Pre-treatment (age, sex, tooth type, position, sequence of treatment, quality of root canal before surgery, presence/absence of through-and-through lesion, presence/absence apico-marginal defect) and treatment (presence/absence of errors during surgery, type of error (major or minor), retro-preparation depth, presence/absence of an isthmus, retro-filling material used, presence/absence bone graft material and/or resorbable membrane) factors were recorded. Data were analysed statistically to determine the inter-observer, intra-observer and inter-radiographic agreements. Univariate, bivariate and logistic regression analysis were used to determine prognostic factors affecting the outcome and the effect of GTR on the pattern of apical bone remodelling. The significance level was set at 5%.

RESULTS

Sixty-eight patients (83 teeth) presented for outcome evaluation (recall rate: 84%). The survival rate was 93%. The success rate was 88% using PA and 86% using CBCT when vertical root fracture (VRF) cases were included and 94% using PAs, and 91% using CBCT when VRF cases were excluded. The intra- and inter-observer agreements were substantial using CBCT, slight to a fair agreement using PA (P < 0.001), and slight to moderate for inter-radiographic agreement. The occurence of a major procedural error during surgery was the only negative predictor for the outcome of EMS (P = 0.013). GTR did not affect the success rate or the type of healing when assessed using PA but it affected the type of healing on CBCT scans (complete vs incomplete healing) and the pattern of cortical plate remodelling (P < 0.001).

CONCLUSION

The success and survival rate of endodontic microsurgery was very high, and the occurrence of a major procedural error during surgery was the only factor affecting the outcome. GTR did not improve the outcome, but did affect the quality of apical bone remodelling following EMS.

CFD analysis on the effect of combining positive and negative pressure during the irrigation of artificial isthmuses

Fluid dynamics generated by irrigation needles have not been deeply analyzed in root canal irregularities such as apical ramifications or isthmus where the cleaning capacity of irrigants might be compromised and hence the treatment outcome. The goal of this study was to compare the key irrigation parameters (flow pattern, irrigant velocity, apical pressure, and shear stress) between two irrigation needles and the additional effect of aspiration cannulas through computational fluid dynamics. A 3D-model consisting of two canals linked by an isthmus was modeled. The abovementioned needles irrigated the primary canal, whereas an aspiration cannula was located inside the secondary canal. Both the geometry definition and spatial discretization were carried out with ANSYS 16.2, through which six different simulations were performed: lateral exit (LE) needle, frontal exit (FE) needle, LE and cannula in crown (LEC), FE and cannula in crown (FEC), LE and cannula in middle third (LEM), FE and cannula in middle third (FEM). FE and FEM showed that the irrigation flow only passes through the isthmus in the most apical section (maximum irrigant velocity / shear stress = 8.44 m/s / 1628.44 Pa and 8.63 m/s / 1185.69 Pa, respectively). However, the remaining simulations showed the irrigation flow passing through the isthmus twice, through the most apical section first and through the upper part of the isthmus later (maximum irrigant velocity / shear stress = 8.48 m/s / 1298.24 Pa (LE), 8.61 m/s / 1261.36 Pa (LEM), 8.61 m/s / 1355.24 Pa (LEC), 8.59 m/s / 1256.87 Pa (FEC)). Furthermore, the highest velocity values were detected when aspiration cannulas were added.

Anatomical analysis of mandibular posterior teeth for endodontic microsurgery: a cone-beam computed tomographic evaluation

OBJECTIVE

The purpose of this study was to analyze the anatomical structures relevant for endodontic microsurgery in the mandibular posterior teeth using a cone-beam computed tomography (CBCT).

MATERIAL AND METHODS

A total of 963 mandibular posterior teeth were analyzed in CBCT scans from 133 patients. The buccolingual and mesiodistal dimensions of the root and the buccal bone thickness overlying the root were measured at the site of root resection (apical 3 mm). At this location, the relationship between the buccal cortical bone and root was classified into three types (separated, contact, and exposed), and the distance from the root apex to the mandibular canal was measured.

RESULTS

The thickest buccolingual dimension of the roots was found in the mesial roots of first molars, at 5.59 ± 0.97 mm. The buccal bone thickness overlying the root became thicker in posterior tooth locations. In the first premolar and first molar mesial root, contact was the most common type of relationship between the buccal cortical bone and root. As the position of the teeth became more posterior, the distance from the apex to the mandibular canal became shorter.

CONCLUSIONS

As the position of the teeth became more posterior, the buccal bone thickness increased and the distance to the mandibular canal became closer; therefore, particular attention is required for posterior teeth. The first premolar and the first molar mesial root are often in contact with the buccal cortical bone, which may allow infections to spread to the buccal structure more easily and negatively affect for post-surgical healing.

CLINICAL RELEVANCE

When planning and performing endodontic microsurgery, understanding the anatomical structure of the surgical site will help minimize tissue damage and reduce complications.

The application of "bone window technique" using piezoelectric saws and a CAD/CAM-guided surgical stent in endodontic microsurgery on a mandibular molar case

Apical surgery for a mandibular molar is still challenging for many reasons. This report describes the applications of computer-guided cortical ‘bone-window technique’ using piezoelectric saws that prevented any nerve damage in performing endodontic microsurgery of a mandibular molar. A 49-year-old woman presented with gumboil on tooth #36 (previously endodontically treated tooth) and was diagnosed with chronic apical abscess. Periapical lesions were confirmed using cone-beam computed tomography (CBCT). Endodontic microsurgery for the mesial and distal roots of tooth #36 was planned. Following the transfer of data of the CBCT images and the scanned cast to an implant surgical planning program, data from both devices were merged. A surgical stent was designed, on the superimposed three-dimensional model, to guide the preparation of a cortical window on the buccal side of tooth #36. Endodontic microsurgery was performed with a printed surgical template. Minimal osteotomy was required and preservation of the buccal cortical plate rendered this endodontic surgery less traumatic. No postoperative complications such as mental nerve damage were reported. Window technique guided by a computer-aided design/computer-aided manufacture based surgical template can be considerably useful in endodontic microsurgery in complicated cases.

Cone-beam computed tomography investigation of middle mesial canals and isthmuses in mandibular first molars in a Chinese population

Background

While there is ample research into the anatomy of mandibular molars, little is known regarding isthmuses and middle mesial (MM) canals in Chinese populations. The goal of this study was to determine the prevalence of MM canals and isthmuses in the mesial root of mandibular first molars using Cone-beam Computed Tomography.

Methods

Cone-beam Computed Tomography images of 357 mature mandibular first molars were retrospectively analyzed. Presence of isthmuses and MM canals, and the length of isthmuses in the mesial root were recorded. Meanwhile, we also recorded possible correlated factors such as demographics, side of mandible, presence of separated distal-lingual roots.

Results

Of these 357 teeth, 209 showed evidence of either complete or partial communication in the mesial root. Of these, 11(3.1%) exhibited true MM canals while 198(55.5%) exhibited isthmuses. Sex or side of mandible was not correlated with the prevalence of isthmuses (P > 0.05). However, there was a significant association between the presence of a distal-lingual root and the prevalence of such communication (P < 0.001). The average length of isthmuses was 4.3 ± 3.1 mm.

Conclusions

We detected high rate of isthmuses and low rate of MM canals in mesial roots of mandibular first molars, which is important as such areas should be identified and cleaned during root canal treatment.

Topographic Analysis of the Isthmus in Mesiobuccal and Mesial Roots of First Molars in a South Korean Population

The purpose of this study was to evaluate the incidence and microscopic anatomy of the isthmus to provide more precise anatomical information about the mesiobuccal (MB) roots of the maxillary first molars and the mesial (M) roots of the mandibular first molars. Twenty-eight maxillary and 31 mandibular first molars were embedded, sectioned, stained, and observed at 30× magnification to evaluate the incidence and microscopic anatomy of the isthmus. The incidence of an isthmus 3 mm from the apex was 89.3% and 100% in the MB roots of the maxillary first molars and in the M roots of the mandibular first molars, respectively. The mean dentin thickness between the isthmus and the distal root surface was <1 mm at a distance of 3 mm from the apex in both types of roots. In this study, whenever two main canals were located in the MB roots of the maxillary first molars and in the M roots of the mandibular first molars, the likelihood of the presence of an isthmus increased. Therefore, clinicians should be aware of the thinnest dimensions in the distal surface of the MB roots of the maxillary first molars and the M roots of the mandibular first molars during nonsurgical and surgical root canal treatment.

Volume of Voids in Retrograde Filling: Comparison between Calcium Silicate Cement Alone and Combined with a Calcium Silicate-based Sealer

INTRODUCTION

The aim of this study was to compare the volume of voids between retrograde filling using calcium silicate cement alone and retrograde filling using a combination of calcium silicate cement with a calcium silicate-based sealer.

METHODS

Twenty single-rooted, extracted human teeth were instrumented with nickel-titanium files and obturated with gutta-percha. We resected the roots at a point 3 mm from the apex, prepared the root ends, and filled the root-end cavities with Endocem Zr (Maruchi, Wonju, Korea) or Endoseal MTA (Maruchi) plus Endocem Zr. Then, we scanned the prepared samples using micro-computed tomographic imaging and performed 3-dimensional reconstruction. The percentage volume of the gap between the canal wall and root-end filling was calculated along with the percentage volume of voids in the filling materials. All data were analyzed using the Mann-Whitney U test. Selected specimens were further observed using scanning electron microscopy.

RESULTS

There were no significant differences in the percentage volumes of the gaps and internal voids between the 2 groups. Both calcium silicate and the calcium silicate-based sealer exhibited good adaptation to the cavity wall.

CONCLUSIONS

The findings of our micro-computed tomographic and scanning electron microscopic analyses suggested that the volume of voids in retrograde filling using a combination of calcium silicate cement and calcium silicate-based sealer was comparable with that in retrograde filling using calcium silicate cement only. Calcium silicate-based sealers could be used in retrograde filling for clinical convenience without harmful effects on the quality of filling.

Effects of fast- and slow-setting calcium silicate-based root-end filling materials on the outcome of endodontic microsurgery: a retrospective study up to 6 years

OBJECTIVES

The purpose of this retrospective study was to evaluate and compare the effects of fast- and slow-setting calcium silicate-based materials (CSMs) used for root-end filling on the outcome of endodontic microsurgery.

MATERIALS AND METHODS

We searched a clinical database for patients who had received endodontic microsurgery between 2001 and 2016. Included cases were divided into two groups according to the type of CSM used for root-end filling: slow-setting CSM (SCSM) and fast-setting CSM (FCSM). The cases in two groups were subjected to 1:1 nearest neighbor propensity score matching for the following variables: age, sex, tooth type, quality of canal filling, lesion type, and postoperative restoration. For each matched case, the outcome was determined as success or failure according to clinical and radiographic evaluations performed at least 1 year after surgery. Multivariate logistic regression analysis was performed to identify prognostic factors and estimate their effects.

RESULTS

In total, 304 cases of endodontic microsurgery (179 SCSM and 125 FCSM) were identified, and 1:1 propensity score matching finally included 122 cases from each group. After matching, all covariates were associated with an absolute standardized difference of < 0.1. The overall success rates were 85.2% and 93.4% for the SCSM and FCSM groups, respectively (p = 0.062). Age, tooth type, lesion type, and CSM type were significantly associated with the outcome of endodontic microsurgery (p < 0.05).

CONCLUSIONS

Within the limitations, the outcome of endodontic microsurgery using FCSMs was comparable with that of SCSMs. The findings suggest that the type of CSM used for root-end filling, particularly in terms of the initial setting time, could affect the outcome of endodontic microsurgery.

CLINICAL RELEVANCE

FCSMs could be considered for use as root-end filling materials in endodontic microsurgery, particularly in complicated clinical situations which require rapid initial setting of the materials.

Stress Analyses of Retrograde Cavity Preparation Designs for Surgical Endodontics in the Mesial Root of the Mandibular Molar: A Finite Element Analysis-Part I

INTRODUCTION

The aim of this study was to investigate the influence of various apical preparation designs for surgical endodontics on stress concentrations in the mesial root of the mandibular molar under different experimental conditions using finite element analysis.

METHODS

We designed 2 apical preparation groups according to whether an isthmus was present or not. Each group contained 4 subgroups according to the size of the apical preparation. We constrained the displacement of all nodes at the base of the supporting bone and applied a force of 150 N to the vertical axis. We analyzed stress generation and concentrations numerically for the groups and subgroups.

RESULTS

In the subgroups, the von Mises and maximum principal stresses reduced gradually according to the enlargement of the prepared cavity. However, when the preparation extended excessively in the isthmus preparation groups, the situation reversed (ie, both von Mises and maximum principal stresses increased).

CONCLUSIONS

Within the limitations of this study, the apical preparation design influenced the distribution of stress concentration. Unlike the overall pattern in which stress decreased as the amount of apical preparation increased, stress increased when the amount of residual dentin was extremely thin.

Isthmus Incidence in Human Permanent Mandibular First Molars of a South Indian Population: A Cone-Beam Computerized Tomographic Study

Aim:

This study aimed to analyze incidence of isthmus in human permanent mandibular first molar teeth using cone-beam computed tomographic imaging techniques in a South Indian population.

Materials and Methods:

Three hundred permanent mandibular first molar teeth were collected, cleaned, and stored in normal saline. They were divided into groups (GPs) I and II based on number of roots, and were further subdivided (right and left [RL] subgroups A and B for GP I; and RL subgroups C and D for GP-II). Samples were processed and isthmus incidence was evaluated by cone-beam tomography, compared, and statistically analyzed.

Results:

Overall in mandibular first molars, the isthmus incidence in mesial root was 97.2%, distal root was 39%, and distolingual root was 0%. There was no statistically significant difference between the right and left mandibular first molar teeth with regard to incidence of isthmus (P > 0.05). There was an incidence of type I (38.67%), type II (56.33%), type III (3%), and type IV (2%) isthmuses in mesial root and type I (12.33%), type II (16%), and type III (10.67%) in distal root.

Conclusion:

Incidence of isthmus was very high in the mesial root of the mandibular first molar and should be factored during nonsurgical and surgical endodontic treatment procedures to achieve successful treatment outcomes.

[Cone-beam computed tomography for determination of mesial root canal curvatures of human mandibular first molars]

OBJECTIVE

To investigate mesial root canal curvatures of human mandibular first molars using cone-beam computed tomography (CBCT).

METHODS

CBCT was performed for scanning the mandibular first molars of 1600 Chinese subjects, among whom the subjects identified to have middle mesial canals were divided into 5 age groups, namely group A (18-29 years), group B (30-39 years), group C (40-49 years), group D (50-59 years), and group E (60-80 years) for further analysis. All the CBCT images were reconstructed using Planmeca Romexis CBCT image reconstruction system, and the curvature of the mesial root was measured using the Schneider method.

RESULTS

A total of 2856 CBCT images were obtained from the 1600 subjects, among whom 168 (5.88%) were found to have middle mesial canals in the mandibular first molars. The prevalence of middle mesial canals was 37.50% in group A, 17.80% in group B, 14.88% in group C, 19.64% in group D, and 10.12% in group E. The moderate of the curvature in the mesiodistal direction was significantly higher in group A than in the other groups (P < 0.05); the curvature in mesiodistal direction differed significantly among the 5 groups (P < 0.05), and was the greatest in group A followed by group C and group D, and was the smallest in group E. The curvature in the buccolingual direction was similar among the 5 groups. The incidence of mesiodistal and buccolingual curvature of the middle mesial canals was significantly higher in the middle 1/3 of the root canal than in the upper 1/3 and apical 1/3 of the root canal.

CONCLUSIONS

The incidence of middle mesial canals in the mesial root of the mandibular first molars decreases with age. The middle mesial canal system of the mandibular first molar is complex and variable, and most of the first molars have obvious curvature in the mesiodistal and buccolingual directions. CBCT can provide reference for clinical treatment to reduce the treatment failure rate.

Outcome of Endodontic Surgery: A Meta-analysis of the Literature-Part 3: Comparison of Endodontic Microsurgical Techniques with 2 Different Root-end Filling Materials

INTRODUCTION

The aim of the present study was to investigate the influence of root-end preparation and filling material on endodontic surgery outcome. A systematic review and meta-analysis was conducted to determine the outcome of resin-based endodontic surgery (RES, the use of high-magnification preparation of a shallow and concave root-end cavity and bonded resin-based root-end filling material) versus endodontic microsurgery (EMS, the use of high-magnification ultrasonic root-end preparation and root-end filling with SuperEBA [Keystone Industries, Gibbstown, NJ], IRM [Dentsply Sirona, York, PA], mineral trioxide aggregate [MTA], or other calcium silicate cements).

METHODS

An exhaustive literature search was conducted to identify prognostic studies on the outcome of root-end surgery. Human studies conducted from 1966 to the end of December 2016 in 5 different languages (ie, English, French, German, Italian, and Spanish) were searched in 4 electronic databases (ie, Medline, Embase, PubMed, and Cochrane Library). Relevant review articles on the subject were scrutinized for cross-references. In addition, 5 dental and medical journals (Journal of Endodontics; International Endodontic Journal; Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontics; Journal of Oral and Maxillofacial Surgery; and International Journal of Oral and Maxillofacial Surgery) were hand checked dating back to 1975. All abstracts were screened by 3 independent reviewers (H.B., M.K., and F.S.). Strict inclusion-exclusion criteria were defined to identify relevant articles. Raw data were extracted from the full-text review of these selected articles independently by each of the 3 reviewers. In case of disagreement, an agreement was reached by discussion, and qualifying articles were assigned to group RES. For EMS, the same search strategy was performed for the time frame October 2009 to December 2016, whereas up to October 2009 the data were obtained from a previous systematic review with identical criteria and search strategy. Weighted pooled success rates and a relative risk assessment between RES and EMS were calculated. To make a comparison between groups, a random effects model was used.

RESULTS

Sixty-eight articles were eligible for full-text review. Of these, per strict inclusion exclusion criteria, 14 studies qualified, 3 for RES (n = 862) and 11 for EMS (n = 915). Weighted pooled success rates for RES were 82.20% (95% confidence interval [CI], 0.7965-0.8476) and 94.42% for EMS (95% CI, 0.9295-0.9590). This difference was statistically significant (P < .0005).

CONCLUSIONS

The probability for success for EMS proved to be significantly greater than the probability for success for RES, providing best available evidence on the influence of cavity preparation with ultrasonic tips and/or SuperEBA (Keystone Industries, Gibbstown, NJ), IRM (Dentsply Sirona, York, PA), MTA, or silicate cements as root-end filling material instead of a shallow cavity preparation and placement of a resin-based material. Additional large-scale randomized clinical trials are needed to assess other predictors of outcome.

Endoscopic Evaluation of Cut Root Faces and Histologic Analysis of Removed Apices Following Root Resection: A Clinical Study

Objective:

To evaluate the resection plane after root-end resection during apical surgery using endoscopy.

Methods:

Following apicectomy of 69 roots, the cut root faces were inspected with a rigid endoscope for the presence of unfilled areas of the root canal space, gaps between the obturated root canal and dentinal wall, isthmi, ‘opaque’ dentine and cracks. Endoscopic pictures were captured and assessed using a 12-sectorn transparent grid for determination of location of the studied elements. Furthermore, the removed apices were examined histologically (n=47). The surfaces of the removed apices opposite the cut root faces were histologically analysed for the same outcome measures.

Results:

Endoscopy revealed the following findings: opaque dentine in 84.1%, unfilled parts of the root canal system in 59.4%, gaps between the existing root canal filling and dentinal walls in 49.3%, and cracks in 10.1% of cases. With regard to isthmi, histology of the removed apices demonstrated an isthmus in two-thirds of those seen with endoscopy at the root end. Ramifications were histologically observed only in 6 root apices.

Conclusion:

The studied elements may cause failure of the root canal treatment, and conventional root canal retreatment or apical surgery may be indicated. The clinical significance of opaque dentine with regard to tooth prognosis after apical surgery remains unclear and warrants further research.