Electromagnetic interference of endodontic equipments with cardiovascular implantable electronic device.

OBJECTIVES: Assess the electromagnetic interference (EMI) of endodontic equipment with cardiovascular implantable electronic devices (CIEDs) and related factors. METHODS: The laser device, electronic apex locators (EAL), optical microscope, endodontic rotary motors, gutta-percha heat carrier (GH), gutta-percha gun and ultrasonic device were tested next to CIEDs (Medtronic and Biotronik) with varied sensitivity settings and distances. CIEDs were immersed in a saline solution to simulate the electrical resistence of the human body. The endodontic equipment was tested in both horizontal and vertical positions in relation to the components of the CIED. The tests were performed on a dental chair in order to assess the cumulative effect of electromagnetic fields. RESULTS: It was found no EMI with the Biotronik pacemaker. EALs caused EMI with Medtronic PM at a 2 cm distance, with the NSK(®) EAL also affecting the Medtronic defibrillator. GH caused EMI at 2 cm and 5 cm from the Medtronic defibrillator. EMI occurred when devices were horizontally positioned to the CIED. In the majority of the cases, EMI occurred when the pacemaker was set to maximum sensitivity. There was cumulative effect of electromagnetic fields between GH and dental chair. CONCLUSIONS: EALs and GH caused EMI which ranged according to type and sensitivity setting of the CIEDs and the distance. However, no endodontic equipment caused permanent damage to the CIED. The use of GH caused a cumulative effect of electromagnetic fields. It suggests that during the treatment of patients with CIEDs, only the necessary equipments should be kept turned on. CLINICAL RELEVANCE: Patients with CIEDs may be subject to EMI from electronic equipment used in dental offices, as they remain turned on throughout the treatment. This is the first article assessing the cumulative effect of electromagnetic fields.

Influence of Heat Treatment of Nickel-Titanium Rotary Endodontic Instruments on Apical Preparation: A Micro-Computed Tomographic Study.

INTRODUCTION: The aim of this study was to make a 3-dimensional comparison of the canal transportation and changes in apical geometry using micro-computed tomographic imaging after canal preparation with K3 (SybronEndo, Orange, CA) and K3XF (SybronEndo) file systems. METHODS: Twenty-eight mandibular molars were randomly divided into 2 groups according to the rotary system used in instrumentation: K3 or K3XF. The specimens were scanned by micro-computed tomographic imaging before and after instrumentation. Images before and after instrumentation from each group were compared with regard to canal volume, surface area, and structure model index (SMI) (paired t test, P < .05). After instrumentation, the canals from each group were compared regarding the changes in volume, surface area, SMI, and canal transportation in the last 4 apical mm (t test, P < .05). RESULTS: Instrumentation with the 2 rotary systems significantly changed the canal volume, surface area, and SMI (P < .05). There were no significant differences between instrument types concerning these parameters (P > .05). There were no significant differences between the 2 groups with regard to canal transportation in the last 4 apical mm (P > .05). CONCLUSIONS: Both rotary systems showed adequate canal preparations with reduced values of canal transportation. Heat treatment did not influence changes in root canal geometry in the apical region.

An initial investigation of the electrochemical dissolution of fragments of nickel-titanium endodontic files.

INTRODUCTION: A recent study presented the concept of an electrochemical-induced dissolution technique of fractured instruments. The purpose of this study was to test the ability to dissolve embedded fragments of K3 nickel-titanium (NiTi) files. The surface of the fragment exposed to the electrolytic solution was the main parameter evaluated as an interfering factor on the dissolution process. METHODS: Three types of K3 NiTi 30.06 file fragments were produced, resulting in different exposed cross-section areas. Anodic current was recorded and used as a reference to evaluate the dissolution process of the fragments. Analysis of variance (P < .05) was used to compare the total electrical charge obtained from current versus time records among the fragments of the 3 groups. Radiographic analysis was carried out before and after the tests to observe the extension of dissolution achieved. RESULTS: The total electrical charge values generated during the tests evidence a statistical difference among the 3 groups of fragments (analysis of variance, P < .05). The larger is the diameter of the exposed surface cross section, the higher is the total value of electrical charge. The radiographic images obtained before and after the tests showed a significant reduction of the fragment length as a result of the polarization imposed. CONCLUSIONS: The results presented here showed that it is possible to obtain a significant dissolution of K3 NiTi endodontic instrument fragments. The diameter of the surface of fragment exposed to the medium affects the current levels used to promote the dissolution.

Dissolution of nickel-titanium endodontic files via an electrochemical process: a new concept for future retrieval of fractured files in root canals.

INTRODUCTION: The retrieval of fractured instruments from root canals has been largely reported in the literature. However, a less complex retrieval method that causes minimum damage to the dental structures is needed. The aim of this article is to introduce a new concept of retrieval of fractured instruments from root canals based on an electrochemical process. METHODS: Current register tests were used to evaluate the dissolution process of 25.04 nickel-titanium (NiTi) K3 rotary files. A constant anodic potential was applied to the NiTi files, whereas the Potentiostat registered the anodic current. After the tests, all files were observed by using an optical microscope. RESULTS: The current attained initial values of approximately 55 mA that declined during the entire test. A good reproducibility of results was observed. The optical microscopy analysis evidenced a progressive consumption of the files with increasing polarization time. CONCLUSIONS: The results presented here show that the concept of fractured file retrieval by an electrochemical process is feasible. This concept resulted in a consistent basis for the development of a method to remove fractured instruments from root canals.

Postoperative pain and associated factors in adolescent patients undergoing two-visit root canal therapy.

This prospective study investigated the frequency and intensity of postoperative pain and identified associated factors in adolescents undergoing two-visit root canal therapy. Sixty-four patients aged 11 to 18 years old presenting with molars with pulp necrosis were assigned consecutively to two visits (plus an interappointment dressing using calcium-hydroxide paste). Pain intensity was recorded on a visual analogue scale (VAS) of 0-5. Data were analysed using multivariate logistic regression. The frequency of postoperative pain was 32.8% (21/64), with intensities of VAS 1 and VAS 2 in 81%, VAS 3 in 14.3% and VAS 4 in 4.7% of the 21 cases in which it was experienced. Spontaneous preoperative pain (odds ratio (OR) = 6.60; 95% confidence interval (CI) = 1.61-26.97; P = 0.009) and absence of apical perodontitis (OR = 5.65; 95% CI = 1.34-23.87; P = 0.01) were associated with postoperative pain. The frequency of postoperative pain was high, but the intensity, in general, was low, including flare-ups. The presence of spontaneous preoperative pain and absence of apical periodontitis increase the probability of suffering from postoperative pain.

Influence of electrochemical polishing on the mechanical properties of K3 nickel-titanium rotary instruments.

Instrument fracture is a serious concern in endodontic treatment. Several studies have evaluated the influence of various factors on the fracture of nickel-titanium endodontic rotary instruments. The present study analyzes the influence of electrochemical polishing on flexural fatigue and torsional properties of K3 nickel-titanium endodontic rotary instruments. New files and polished files were tested for flexural fatigue and for resistance to fracture by twisting. The t test was used to compare the groups for number of cycles, angle of rotation, and maximum torque necessary to fracture. No statistical difference existed between these groups. Scanning electron microscopy analysis showed no significant differences caused by electrochemical polishing between these groups. These results suggest that electrochemical polishing has no influence on resistance to fracture of K3 rotary instruments.

Fractographic analysis of K3 nickel-titanium rotary instruments submitted to different modes of mechanical loading.

The aim of the present study was to analyze the fracture surface of nickel-titanium K3 rotary files submitted to different modes of mechanical loading. Torsional and flexural fatigue tests were realized separately in 2 groups of files. Additional 2 groups of files were tested in mixed loading modes, torsional test after incomplete flexural fatigue test and flexural fatigue test after incomplete torsional test. Scanning electronic microscopy observation was used to make a fractographic analysis of the files under test. The files fractured during torsional resistance tests showed fractographies with a central area containing dimples, which are oval-shaped depressions in the microstructure in places of high local plastic deformation. The peripheral area of these files' fractographies presented a flattened aspect without dimples. The fractographies of the files fractured by flexural fatigue presented one area with radial striations and another area containing dimples. The fractographic patterns observed when mixed loading modes were imposed correspond to the pattern defined by the second stage test. The patterns established for the fractured files provide consistent bases to explain the fracture process in clinical conditions by fractographic analysis.