A laboratory study of the accuracy of three electronic apex locators: influence of embedding media and radiographic assessment of the electronic apical limit.

AIM: To evaluate several factors that might interfere with the use of electronic root canal length measurement devices (ERCLMDs) in a laboratory setting, including two different embedding media (alginate and electroconductive gel), three different types of devices and the radiographic view on the assessment of the electronic readings. METHODOLOGY: Thirty single-rooted extracted human mandibular premolars were selected. After access and canal pre-flaring, a size 10 K-file was inserted in the canal up to the major apical foramen under magnification (×10), and this length was recorded as the actual length (AL) of the canal. Teeth were mounted on a specific endodontic training kit platform (ProTrain). Two different embedding media (electroconductive gel and alginate) and three different ERCLMDs: Apex ID (SybronEndo, Glendora, CA, USA), CanalPro Apex Locator (Coltene-Endo, Cuyahoga Falls, OH, USA) and the Root ZX II (J. Morita, Tokyo, Japan), were tested. Following the measurement at the 0.5 mark of each ERCLMD using alginate, two periapical radiographs (bucco-lingual and proximal views) were taken. The difference between the electronic readings and the AL, as well as the distance from the file tip to the apex of the roots on the radiographs, was calculated. Data were analysed statistically (two-way anova, Tukey's and chi-squared tests) at 5% significance level. RESULTS: The incidence of over-extended readings was significantly greater (P < 0.05) when using the ProTrain electroconductive gel, except for Root ZX II at the 0.5 mark. Root ZX, CanalPro and Apex ID had similar accuracy when the 0.0/APEX mark was used to locate the foramen. For the radiographic method, no difference was found between the devices or radiographic views. CONCLUSION: Compared with alginate, the conductive gel of the ProTrain kit negatively affected most of the electronic readings. The three evaluated ERCLMDs had similar accuracy in locating the apical foramen when using the mark 0.0/APEX and alginate as the embedding media. Although the ProTrain platform allows radiographs to be exposed in both bucco-lingual and proximal views, no difference was found between the views when evaluating the apical limit provided by the 0.5 mark in mandibular premolars embedded in alginate.

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.

Measurement of torque generated during intracanal instrumentation in vivo.

AIM: To compare two different clinical techniques when using endodontic rotary instruments by monitoring the torque in vivo. METHODOLOGY: Ten single-rooted maxillary anterior teeth were prepared by an endodontist using size 25, .06 taper TF rotary instruments (KerrEndo, Orange, CA, USA). All instruments were rotated at 500 rpm with maximum torque set at 2.5 N cm using an endodontic motor (Kavo, Biberach, Germany), which automatically recorded the torque values every 1/10 of a second. Instruments were used with two modi operandi: (i) Inward action: short-length intermittent progression with slight apical pressure aiming to reach the working length (also known as pecking motion), followed by (ii) Outward action: lateral brushing action selectively directed to address the canal circumference whilst removing instruments in the coronal direction. The mean, maximum and accumulated torque values were recorded and analysed statistically (t-test and Wilcoxon test) with a significance level set at 5%. None of the recorded values exceeded the selected torque limit. RESULTS: A significant difference between inward and outward actions was found regarding the evaluated parameters (P < 0.05). The outward action (brushing) was significantly safer (requiring less torque) compared to the inward action (pecking). CONCLUSIONS: Torque measurements during in vivo instrumentation provided useful information regarding the techniques evaluated. Although the torque limit was not reached by any of the two actions, the technique impacted significantly on the torque applied to the instrument.

Fatigue Resistance of New and Used Nickel-Titanium Rotary Instruments: a Comparative Study.

OBJECTIVES: Aim of the present study was twofold. First, to evaluate in vitro, the performance of two different NiTi rotary instruments in one molar case; then, to evaluate their resistance to cyclic fatigue, compared to new ones. MATERIAL AND METHODS: 25 ProTaper Next (PTN) nickel-titanium (NiTi) instruments (Maillefer-Dentsply, Baillagues, CH) for each of the following two sizes: X1 (17.04 ) and X2 (25.06) were randomly divided into two groups. The first group (n = 10) immediately under- went to a cyclic fatigue test. The second group (n = 15) was initially used to prepare 15 extracted molar teeth and then subjected to a cyclic fatigue test. Same was done for 25 Horizen (HZ) instruments (Kerr Endodontics, Orange, Ca) for each of the following two sizes: 20.04 and 25.06. Instruments were rotated in curved artificial canal until fracture occurred and times to fracture were recorded. All data were collected and statistically analyzed using a variance test (confidence interval CI = 95%). RESULTS: HZ reached working length more rapidly than PTN, and with less deformations. For the fatigue tests, all the new instruments were significantly more resistant than the used ones. The HZ instru- ments were significantly more resistant in all sizes than PTN, both when new and used instruments were tested. CONCLUSIONS: Since in previous studies ProTaper Next demonstra- ted a better resistance to cyclic fatigue than most of nickel-titanium instruments, Horizen's performance put them in a high rank amongst the most resistant nickel-titanium rotary instruments.

A preliminary assessment of a new dedicated endodontic software for use with CBCT images to evaluate the canal complexity of mandibular molars.

AIM: To investigate in vivo the complexity of canals within mesial roots of mandibular molars using 3D Endo™ software linked to CBCT images. METHODOLOGY: The CBCT images of 100 mandibular first molars were analysed using the 3D Endo™ software. The number of canals in the mesial roots, the presence of apical confluences, the canal lengths and the canal configurations using Vertucci's classification were evaluated in buccolingual (BL) and mesiodistal (MD) views. The software allowed the visualization of canal trajectories in three dimensions using a coloured outline, which was used to develop a new objective scoring system to provide an overall assessment of canal complexity. Data were analysed statistically using anova and t-tests with the significance set at P < 0.05. RESULTS: Vertucci type IV canals were found in 44% of the cases, whilst 54% were type II. The mean distance from the apical foramen to the orifice was 13.15 mm (±1.21) and that between a confluence and the foramen, 2.81 mm (±1.13). The number of curvatures and the canal complexity scores in the MD view were significantly higher than in the BL view (P < 0.05). The scores were not directly correlated to the canal (MB versus ML), to the canal length or to the presence of confluences. CONCLUSIONS: 3D Endo software features the automatic detection and measurement of several anatomical canal parameters, and is a promising tool for the study of canal complexity in vivo. The unpredictable anatomy of the mesial roots of mandibular molars highlights the value of a three-dimensional preoperative evaluation of each case. The proposed scoring system aims to provide the clinician with an overall assessment of canal complexity.

The Influence of a New Clinical Motion for Endodontic Instruments on the Incidence of Postoperative Pain.

OBJECTIVES: Previous studies showed that motor motions play an important role in determining apical extrusion of debris. Therefore a new clinical motion (MIMERACI) has been proposed. The basic idea is to progress slowly (1mm advancement), and after each 1mm, to remove the instrument from the canal, clean flutes and irrigate. The aim of the study was to prove whether the clinical use of MIMERACI technique would influence or not postoperative pain. MATERIALS AND METHODS: 100 teeth requesting endodontic treatment were selected for the study and divided into two similar groups based on anatomy, pre-operative symptoms and vitality, presence or absence of periapical lesion. All teeth were shaped, cleaned and obturated by the same operator, using the same NiTi instruments. The only difference between the two groups was the instrumentation technique: tradional (group A) vs MIMERACI (group B). Assessment of postoperative pain was performed 3 days after treatment. Presence, absence and degree of pain were recorded with a visual analogue scale (VAS), validated in previous studies. Collected data statistically analyzed using one-way ANOVA post hoc Tukey test. RESULTS: For VAS pain scores MIMERACI technique showed significantly better results than group A (p=0,031). Overall, both incidence and intensity of symptoms were significantly lower. Flare ups occurred in 3 patients, but none treated with the MIMERACI Technique. CONCLUSIONS: Since extruded debris can elicit more postoperative pain, results obtained by using MIMERACI technique are probably due to many factors: better mechanical removal and less production of debris and more efficient irrigation during instrumentation.

An in vivo evaluation of the auto apical reverse function of the Root ZX II.

AIM: To evaluate in vivo the accuracy of the Root ZX II (J. Morita) apex locator in controlling the apical extent of rotary instrumentation when using the Auto Apical Reverse (AAR) set at the levels 0.5, 1.0 and 1.5. METHODOLOGY: Thirty single-rooted premolar teeth scheduled for extraction were divided into three groups (n = 10), according to the AAR setting 0.5, 1.0 and 1.5. The root canals were prepared using ProTaper (Dentsply Maillefer). After rotary instrumentation, the last file used (F3) was manually introduced into the extent of the root canal preparation and fixed before tooth extraction. The apical third of the root was dissected until exposure of the file. The distance from the file tip to the major apical foramen was obtained. RESULTS: Measurements within the range -1.0 to 0.0 mm were obtained in 30% of the teeth with AAR 0.5, 50% with AAR 1.0 and in 0% with AAR 1.5. The proportions test revealed a significant difference between the AAR settings 1.0 and 1.5 (P = 0.0188). Overinstrumentation occurred in 70% of the teeth with AAR 0.5 and in 40% with AAR 1.0. The measurements short of the acceptable range occurred in 10% of the teeth with setting AAR 1.0 and in 100% of the cases with AAR 1.5. A significant difference was found when comparing the percentage of teeth in which the file tip was short and beyond the established range between groups, except when comparing AAR 0.5 and AAR 1.0. CONCLUSION: The AAR function of the Root ZX II was not an accurate method for controlling the apical extent of rotary instrumentation in vivo. The setting 0.5 presented overinstrumentation in most of the canals, the setting 1.5 was short in all cases, and the setting 1.0 provided an adequate working length in only 50% of the teeth.