Effect of Heat Treatment on Mechanical Properties of Nickel-Titanium Instruments.

INTRODUCTION: The aim of this study was to evaluate the torsional resistance, cyclic fatigue resistance, and bending stiffness of nickel-titanium (NiTi) file systems with different heat treatments and cross-sectional designs. METHODS: WaveOne Primary treated with memory-triple (MT) heat treatment (WOMT) was compared with WaveOne Primary (WO) and WaveOne Gold Primary (WOG). Torsional resistance test was performed using a customized device, and the distortion angle, ultimate strength, and toughness were evaluated. For cyclic fatigue resistance test, the instruments were reciprocated with continuous 4 mm up-and-down movement until fracture in a customized device, and the time to fracture was compared. Fracture surfaces of each group were examined under the scanning electron microscope. Bending stiffness was measured using a custom-made device. The results were analyzed using one-way analysis of variance and the Tukey's post hoc comparison at a significance level of 95%. RESULTS: WOMT showed higher ultimate strength and toughness than the other systems (P < .05). WOMT also showed highest cyclic fatigue resistance among the tested groups (P < .05). WO had the highest bending stiffness than others, whereas WOMT had a larger residual angle than others (P < .05). CONCLUSIONS: This new MT heat treatment technique makes NiTi file more flexible and improves its mechanical properties. In addition, the effect of heat treatment on flexibility was found to be more significant than that of the cross-sectional area.

The pararadicular radiolucency with vital pulp: Clinicopathologic features of 21 cemental tears.

OBJECTIVE: The investigation was conducted to better characterize the clinical, radiographic, and histopathologic features of cemental tears from a review of 21 cases. STUDY DESIGN: This was a retrospective review of consecutive cases collected from patient records of the investigators. RESULTS: Twenty-one cases were identified during an 8-year period. Maxillary incisors were most often affected (47.6%). All lesions presented with pain. They occurred as radiolucencies along the root of a vital or endodontically treated tooth and were classified as D-shaped (38.1%), thin-vertical-line (23.8%), thick-vertical-line (14.3%), J-shaped (19.0%), or periapical radiolucencies (4.8%). All lesions showed focal destruction of the lamina dura, with 66.7% exhibiting extension into the medullary bone. Histopathologic diagnoses included intramedullary fibrous scar (28.6%) and chronic fibrosing osteomyelitis (71.4%), all associated with embedded cemental fragments. Five associated teeth were also examined: All showed tears beneath the remaining cementum. Four cases were successfully treated with curettage without tooth extraction; endodontic therapy was performed, probably mistakenly, in 8 cases. CONCLUSIONS: Cemental tears produced symptomatic, localized chronic inflammation characterized usually by a vertical radiolucency adjacent to a root. These lesions may not be as rare as previously thought and extraction may not be the best treatment.

Classification and Clinical Management of Retrograde Peri-implantitis Associated with Apical Periodontitis: A Proposed Classification System and Case Report.

Biological complications involving dental implants include peri-implant diseases such as peri-implant mucositis and peri-implantitis. The latter presents with progressive bone loss from the alveolar crest in a coronal apical direction. However, a separate disease entity termed retrograde peri-implantitis (RPI), which presents with progressive bone loss at the periapex of the implant, also exists and may be of particular interest to endodontists because it typically presents with periapical pathology of both the implant and adjacent tooth or at a site that previously housed an endodontically treated tooth. The reported prevalence of retrograde peri-implantitis is 0.26%, which is much lower than the prevalence of marginal peri-implantitis; however, its incidence increases to 7.8% when teeth adjacent to the implant exhibit an endodontic infection. It is positively correlated with a shorter distance between the implant and the adjacent tooth and a shorter time elapsed from the endodontically treated adjacent tooth to implant placement. This case report describes a patient diagnosed with an RPI lesion (RPI) associated with an adjacent endodontically treated tooth with a persistent periapical radiolucent lesion. The diagnosis, possible etiology, and management of the RPI lesion is thoroughly reported including follow-up visits showing complete resolution after subsequent periodontal and endodontic therapy. Endodontic evaluation of teeth adjacent to the implant site should be performed for primary prevention of RPI. Proper classification of RPI will aid in determining the course of treatment; class 1 and 2 cases require endodontic therapy of the involved teeth for healing to occur.

Dentinal Tubule Penetration of a Calcium Silicate-based Root Canal Sealer with Different Obturation Methods.

INTRODUCTION: The purpose of this study was to investigate the depths of penetration of a calcium silicate-based sealer in dentinal tubules by using 3 different obturation methods. METHODS: One hundred extracted human permanent anterior teeth were endodontically prepared and divided equally into 3 experimental groups and 1 control group as follows: CPoint single cone (CPSC), gutta-percha single cone (GPSC), gutta-percha vertical condensation (GPVC), all with a calcium silicate-based sealer and calcium indicator Fluo-3, and CPoint single cone with a calcium indicator Fluo-3 (CPF3) without sealer as the control. The roots of the teeth in each group were axially cross-sectioned, and the surfaces were examined under confocal laser scanning microscopy at ×10 and ×20 magnifications. The sealer penetration depths were measured at their maximum depths and at 4 circumferential depths (12, 3, 6, and 9 o'clock) by using fluorescence. RESULTS: Statistical analyses by using one-way analysis of variance and repeated measures analysis with linear mixed models showed no statistically significant difference among the mean maximum depth measurements (CPSC, 283.83 µm; GPSC, 318.66 µm; and GPVC, 313.03 µm; P = .7553) and among the average depths across all points (CPSC, 111.24 µm; GPSC, 135.38 µm; and GPVC, 126.62 µm; P = .5304) for the 3 experimental groups. CONCLUSIONS: The pressure derived from hygroscopic expansion of CPoint or warm vertical condensation did not enhance penetration depths of the calcium silicate-based sealer. Sealer penetration into the dentinal tubules occurred independent of the obturation technique.

Evaluation of a calcium silicate-based cement as a root reinforcement material for endodontically treated maxillary anterior teeth.

STATEMENT OF PROBLEM: Fractures of endodontically treated teeth have been attributed to weakened tooth structure caused by root canal enlargement and post preparation. PURPOSE: The purpose of this in vitro study was to evaluate the fracture resistance of roots filled with either gutta percha, composite resin (LuxaCore Dual), or calcium silicate-based cement (Biodentine). MATERIAL AND METHODS: One hundred twenty freshly extracted, human, permanent maxillary anterior teeth were sorted by type and assigned to 1 of 4 groups (n=30). The teeth in group NT were not endodontically treated and served as the control. The teeth in groups GP, LC, and, BD were accessed and instrumented to size 40/06. In group GP, the root canals were completely filled with gutta percha. In groups LC and BD, only the apical 5-mm portion of the root canals was filled with gutta percha, and the remaining portion of the root canals was filled with (LuxaCore Dual) in group LC and with (Biodentine) in group BD. Fracture resistance (kN) was assessed at the middle portion of each root, using a 3-point bending test with a universal testing machine exerting a compressive load on a loading pin at a crosshead speed of 0.5 mm/min until fracture occurred. One-way ANOVA was used to compare the mean root fracture resistance among the 4 groups (α=.05). RESULTS: The mean ± SD fracture loads were 2.13 ±0.53 kN for group NT, 1.97 ±0.60 kN for group GP, 2.18 ±0.71 kN for group LC, and 2.22 ±0.54 kN for group BD. No statistically significant differences were found among the 4 groups (P>.05). CONCLUSIONS: The roots of endodontically treated maxillary anterior permanent incisors filled with gutta percha, Biodentine, or LuxaCore Dual had resistance to fracture similar to that of teeth that were not endodontically treated.

Analysis of radiopacity, pH and cytotoxicity of a new bioceramic material.

OBJECTIVE: RetroMTA® is a new hydraulic bioceramic indicated for pulp capping, perforations or root resorption repair, apexification and apical surgery. The aim of this study was to compare the radiopacity, pH variation and cytotoxicity of this material to ProRoot® MTA. MATERIAL AND METHODS: Mixed cements were exposed to a digital x-ray along with an aluminum stepwedge for the radiopacity assay. pH values were verified after incubation period of 3, 24, 48, 72 and 168 hours. The cytotoxicity of each cement was tested on human periodontal ligament fibroblasts using a multiparametric assay. Data analysis was performed using ANOVA and Tukey'spost hoc in GraphPad Prism. RESULTS: ProRoot® MTA had higher radiopacity than RetroMTA®(p<0.001). No significant differences were observed for the pH of the materials throughout experimental periods (p>0.05) although pH levels of both materials reduced over time. Both ProRoot® MTA and RetroMTA® allowed for significantly higher cell viability when compared with the positive control (p<0.001). No statistical difference was observed between ProRoot® MTA and RetroMTA® cytotoxicity level in all test parameters, except for the ProRoot® MTA 48-hour extract media in the NR assay (p<0.05). CONCLUSION: The current study provides new data about the physicochemical and biological properties of Retro® MTA concerning radiopacity, pH and cytotoxic effects on human periodontal ligaments cells. Based on our findings, RetroMTA® meets the radiopacity requirements standardized by ANSI/ADA number 572, and similar pH values and biocompatibility to ProRoot® MTA. Further studies should be performed to evaluate additional properties of this new material.

Analysis of radiopacity, pH and cytotoxicity of a new bioceramic material

AbstractObjective RetroMTA® is a new hydraulic bioceramic indicated for pulp capping, perforations or root resorption repair, apexification and apical surgery. The aim of this study was to compare the radiopacity, pH variation and cytotoxicity of this material to ProRoot® MTA.Material and Methods Mixed cements were exposed to a digital x-ray along with an aluminum stepwedge for the radiopacity assay. pH values were verified after incubation period of 3, 24, 48, 72 and 168 hours. The cytotoxicity of each cement was tested on human periodontal ligament fibroblasts using a multiparametric assay. Data analysis was performed using ANOVA and Tukey’spost hoc in GraphPad Prism.Results ProRoot® MTA had higher radiopacity than RetroMTA®(p<0.001). No significant differences were observed for the pH of the materials throughout experimental periods (p>0.05) although pH levels of both materials reduced over time. Both ProRoot® MTA and RetroMTA® allowed for significantly higher cell viability when compared with the positive control (p<0.001). No statistical difference was observed between ProRoot® MTA and RetroMTA® cytotoxicity level in all test parameters, except for the ProRoot® MTA 48-hour extract media in the NR assay (p<0.05).Conclusion The current study provides new data about the physicochemical and biological properties of Retro® MTA concerning radiopacity, pH and cytotoxic effects on human periodontal ligaments cells. Based on our findings, RetroMTA® meets the radiopacity requirements standardized by ANSI/ADA number 572, and similar pH values and biocompatibility to ProRoot® MTA. Further studies should be performed to evaluate additional properties of this new material.

Evaluating the effects of different dental devices on implantable cardioverter defibrillators.

INTRODUCTION: The implantable cardioverter defibrillator (ICD) is an electronic device that emits electrical signals to the heart via lead wires and electrodes. It is used for cardiac rhythm monitoring and treatment. Because electronic dental devices have been shown to produce electromagnetic fields, we hypothesize that they may interfere with ICD function. METHODS: Nine dental devices (heat carrier, electronic apex locator, electric pulp tester, unipolar electrosurgery unit, electric motor, curing light, and 3 gutta-percha guns) were tested in this study for their ability to interfere with the function of 4 ICDs (2 single-chambered and 2 dual-chambered ICDs). ICD activity was monitored for 30 seconds using an ICD programmer (Medtronic 2090; Minneapolis, MN) and evaluated through an electrogram test strip printout. RESULTS: Electromagnetic interference was detected with the electric motor, curing light, electric pulp tester, and electrosurgery unit although no electromagnetic disturbances were detected with these devices. No electromagnetic interferences were observed for the gutta-percha guns, heat carrier, and apex locator. However, the electrosurgery unit affected the dual-chambered ICD (Consulta CRT-D, Medtronic) and delivered therapies for fibrillation when no ventricular fibrillation was present. CONCLUSIONS: Our results suggest that the electrosurgery unit produces electromagnetic disturbances with unwanted therapy delivery shock and potentially clinically significant outcomes.

The properties of Endocal 10 and its potential impact on the structural integrity of the root.

The purpose of this research was to determine if the use of Endocal 10 (previously called Biocalex 6.9) is associated with root fracture and to assess its sealability. Thirty-six freshly extracted, single canal human mandibular incisors were instrumented and randomly divided into two equal groups (n = 15). Canals in group A were obturated with vertically compacted gutta-percha and Sealapex, and those in group B were filled with Endocal 10 placed with a #25 Lentulo spiral per manufacturer's instructions. Two blinded investigators evaluated the teeth for fractures using transillumination and an operating microscope at 12 x magnification. Three of the fifteen samples filled with Endocal 10 had vertically fractured in half, whereas none of the teeth filled with gutta-percha had any evident fracture lines. The remaining teeth were tested for leakage via a fluid filtration model at 1 wk and 30 days postobturation. No leakage was found among any of the samples whether filled with gutta-percha or with Endocal 10 at either time interval. Statistical analyses were completed using Fisher's exact test (p = 0.023), which showed that there was a significant increase in chance of fracture when using Endocal 10 versus gutta-percha. The results indicate that, although Endocal 10 is able to seal the tooth as well as gutta-percha and sealer, there is a significant potential risk of root fracture.

An in vitro evaluation of the sealing ability of a new root-canal-obturation system.

In this study the sealing ability of a new urethane methacrylate resin-based sealer, EndoRez, was evaluated using a fluid-filtration model. Sixty-four single-rooted lower bicuspids were decoronated, instrumented, and divided into 3 groups of 20 each with 4 teeth used as controls. In group A, the roots were obturated with EndoRez and a single cone of gutta-percha, group B with AH Plus and a single cone of gutta-percha, and group C was obturated using gutta-percha with warm vertical compaction and AH Plus sealer. All specimens were allowed to set for 7 days in 100% humidity at 37 degrees C. The groups were compared for differences in the amount of leakage (mm/h) using a Chi-square test. The leakage of group A was significantly higher at p = 0.01 than the other two groups. There was no significant difference in leakage between groups B and C.

The crystallization of sodium hypochlorite on gutta-percha cones after the rapid-sterilization technique: an SEM study.

The purpose of this study was to identify the presence, crystallization, and subsequent removal of sodium hypochlorite crystals on gutta-percha cones after rapid sterilization. Seventy-two, fresh, standardized, gutta-percha cones were randomly selected. Each cone was observed under the scanning electron microscope and the elemental analysis machine before and after rapid sterilization using 5.25% and 2.5% sodium hypochlorite. Gutta-percha cones were rinsed after sterilization with 96% ethyl alcohol, 70% isopropyl alcohol, and distilled water independently to determine which of these agents removed the sodium-chloride crystals. There were no crystals present on the gutta-percha cones directly from the box. All gutta-percha cones had sodium-chloride crystals present after the rapid-sterilization technique using 5.25% and 2.5% sodium hypochlorite. However, the sodium-chloride crystals were removed by 96% ethyl alcohol, 70% isopropyl alcohol, and distilled water.

Effect of electronic apex locators on cardiac pacemaker function.

The purpose of this study was to assess the effects of five electronic apex locators on pacemaker function in vitro. A Biotronik Actros DR+ pacemaker was evaluated at maximum sensitivity on a flat bench top. The pacemaker lead, electronic apex locator, and oscilloscope were connected across a 150-ohm resistor. Pace monitoring was carried out with a Biotronik EPR 1000 programmer and a Tektronix TDS 220 2-channel digital real-time oscilloscope. Four of five electronic apex locators tested did not cause inhibition or interfere with normal pacemaker function. It seems that electronic apex locators can be used safely in patients with pacemakers.