Flexibility of Various Nickel-Titanium Rotary Endodontic Files

Introduction: Nickel-titanium rotary files were originally developed to allow for greater flexibility when instrumenting root canals. The increased flexibility of nickel-titanium instruments allowed operators to negotiate canal curvatures with greater ease. File design is continually changing. Manufacturers are trying to produce files that will work more efficiently and safely. Knowing the properties of files marketed is especially important in helping to choose an appropriate file system. Current ISO standards require force measurements at a static point along the file. The purpose of this study was to evaluate the flexibility of four different nickel-titanium files at three different points along the file. Materials and Methods: Flexibility of four different nickel-titanium rotary files (EndoSequence, ProFile, Vortex, and Vortex Blue) was measured. Each file was clamped at 3mm, 5mm, or 7mm (n = 10/length/file) and a universal testing machine was used to bend the files to a maximum deflection of 4.5mm. All data were statistically analyzed by two-way analysis of variance and post-hoc Tukey test (P = 0.05) to determine any significant differences. Results: Statistically significant (P \u3c 0.05) differences were present. In general, ProFile was the stiffest, displaying the greatest force and bending moment values. Vortex Blue was significantly more flexible, with lower force needed for deflection and bending moments. Conclusion: Vortex Blue files showed greater flexibility compared with the other nickel-titanium rotary files studied

Differential Scanning Calorimetric (DSC) Study of New and Sterilized Nickel-Titanium Rotary Endodontic Instruments

Introduction: Nickel-Titanium (NiTi) files have become popular in endodontic procedures compared to traditional stainless steel hand files owing to their increased flexibility which is especially advantageous in curved canals. Due to the associated costs, endodontic instruments are frequently re-used, which requires sterilization between uses. With the application of temperature NiTi has the ability to undergo phase transformations, altering the properties of the instruments. The purpose of this study was to investigate phase transformations of four brands of NiTi rotary endodontic instruments in the as-received condition and after multiple sterilization cycles under steam sterilization, using differential scanning calorimetry. Materials and Methods: Four brands of nickel-titanium endodontic rotary files size 35, .04 taper were evaluated in this study: ProFile (Dentsply Tulsa Dental Specialties, Tulsa, OK), ProFile Vortex (Dentsply), Vortex Blue (Dentsply), and HyFlex CM (Coltène/Whaledent, Cuyahoga Falls, OH). The transformation temperatures and phase transformations of these files were determined in the as-received condition and after 1, 3, and 5 cycles of steam sterilization by differential scanning calorimetry. Measurements were analyzed using a two-way ANOVA. Results: There were significant differences between file brands in austenite finish temperature (p \u3c 0.05) but the only statistical significant differences in thermal properties when comparing files before and after 1, 3, and 5 cycles of steam sterilization were found with onset heating (p \u3c 0.05). Conclusion: Repeated cycles of steam sterilization do not appear to influence the phase transformations of NiTi endodontic instruments

Insulin-like Growth Factor 1 and Transforming Growth Factor-β Stimulate Cystine/Glutamate Exchange Activity in Dental Pulp Cells

Introduction The growth factors insulin-like growth factor (IGF-1) and transforming growth factor-β (TGF-β) are protective to dental pulp cells in culture against the toxicity of the composite materials Durafill VS and Flow Line (Henry Schein Inc, New York, NY). Because the toxicity of these materials is mediated by oxidative stress, it seemed possible that the protective effects of IGF-1 and TGF-β were through the enhancement of an endogenous antioxidant mechanism. Methods We used cultured dental pulp cells to determine the mechanism of the protective effects of IGF-1 and TGF-β, focusing on the glutathione system and the role of cystine/glutamate exchange (system xc-). Results We found that the toxicity of Durafill VS and Flow Line was attenuated by the addition of glutathione monoethylester, suggesting a specific role for the cellular antioxidant glutathione. Supporting this hypothesis, we found that IGF-1 and TGF-β were protective against the toxicity of the glutathione synthesis inhibitor buthionine sulfoximine. Because levels of cellular cystine are the limiting factor in the production of glutathione, we tested the effects of IGF-1 and TGF-β on cystine uptake. Both growth factors stimulated system xc–mediated cystine uptake. Furthermore, they attenuated the glutathione depletion induced by Durafill VS and Flow Line. Conclusions The results suggest that IGF-1 and TGF-β are protective through the stimulation of system xc–mediated cystine uptake, leading to maintenance of cellular glutathione. This novel action of growth factors on dental pulp cells has implications not only for preventing toxicity of dental materials but also for the general function of these cells

Change in Working Length at Different Stages of Instrumentation as a Function of Canal Curvature

The aim of this study was to determine the change in working length (∆WL) before and after coronal flaring and after complete rotary instrumentation as a function of canal curvature. One mesiobuccal or mesiolingual canal from each of 43 extracted molars had coronal standardization and access performed. Once the access was completed, canal preparation was accomplished using Gates Glidden drills for coronal flaring and EndoSequence files for rotary instrumentation. WLs were obtained at 3 time points: pre-instrumentation (unflared), mid-instrumentation (flared) and post-instrumentation (concluded). Measurements were made via direct visualization (DV) and the CanalPro apex locator (EM) in triplicate by a single operator with blinding within the time points. Root curvature was measured using Schneider’s technique. The change in working length was assessed using repeated-measures ANCOVA. The direct visualization measurements were statistically larger than the electronic measurements (paired t-test difference = 0.20 mm, SE = 0.037, P \u3c .0001), although a difference this large may not be clinically important. Overall, a greater change in working length was observed in straight canals than in curved canals, and this trend was more pronounced when measured electronically than via direct visualization, especially in the unflared-concluded time points compared with unflared-flared time points. A greater change in working length was also observed in longer canals than in shorter canals.https://scholarscompass.vcu.edu/gradposters/1032/thumbnail.jp

Postoperative Pain After The Use Of A Dexamethasone Rinse As An Irrigant Prior To Obturation

Purpose: The purpose of this randomized, double-blind pilot study was to determine the effect of dexamethasone on post-operative pain when used as an intracanal rinse prior to obturation. Materials and Methods: Nine adult volunteers consented to enroll. They presented to the Marquette University School of Dentistry Endodontic Department with a diagnosis of irreversible pulpitis. Patients recorded their baseline pain levels on the numering rating scale (NRS). Patients were randomly assigned to either experimental or control group. Patients in the experimental group received 4 mg/mL dexamethasone solution as a final rinse prior to obturation were as patients in the control group received saline as a final rinse. Patients recorded their pain levels at 3, 6, 12, 24, and 48 hours post-operatively. Means and standard deviations were calculated. Treatment effects were analyzed using repeated measures ANOVA. Statistical significance was set at p\u3c.05. Results: Eight patients returned the participation forms. Pain reduction after endodontic treatment was statistically significant (p=0.039). There was no significant difference in post-operative pain between the control and experimental groups (p-0.789). Conclusion: The patient sample size was not large enough to state any conclusions with confidence. However, endodontic treatment remains an effective means of reducing post-operative pain

Treatment Rate Of Second Mesio-Buccal Canals In Maxillary Molars In A Musod Endodontic Resident Patient Population

Purpose: The primary reason for non-surgical root canal treatment (NSRCT) failure in an upper molar is inadequate cleaning, shaping and filling of the second mesio-buccal root canal (MB2). Failure to locate and treat a present MB2 will lead to a worsened long-term prognosis. This retrospective study investigated the treatment rate of MB2s in a sample of patients who were treated in Marquette University School of Dentistry\u27s (MUSOD) advanced dental education program in Endodontics. Materials and Methods: The study protocol was approved by Marquette\u27s IRB. Data were gathered from records of 447 patients who received endodontic treatment between 2008 and 2012 and include; presence of an MB2 (dependent variable), tooth number, patient age (years), and gender (independent variables). Personal identifiers subject to HIPAA regulations were not collected. Presence of an MB2 was determined from clinical notes and verified radiographically. Frequencies of present or absent MB2s were tabulated as a function of various independent variables and statistically analyzed using chi-square tests. Results: Overall, 50.3% of all patients presented with an MB2. Male and female patients had MB2s in 60.6% and 43.8%, respectively. MB2s were found in 53.1% (172 out of 324) and 43.1% (53 out of 123) of maxillary first and second molars, respectively. The mean age of the sample was 42.4 years. Below the mean age, MB2 canals were found in 56.0%, while above the mean age, they were present in 43.2%. There was no statistically significant difference in side distribution (left side of maxillary arch compared to right side). Respective frequencies were 49.3% and 51.4%. Conclusion: MB2 treatment rates may serve as a guide for practicing endodontists because they were achieved with the most current treatment techniques, advanced visualization, adequate time, and clinical expertise

Outcomes of Primary Endodontic Therapy Provided by Endodontic Specialists Compared to Other Providers

Introduction: The objective of this study was to compare the outcomes of initial non-surgical root canal therapy (NSRCT) for different tooth types provided by both endodontists and other providers. Methods: Using an insurance company database, 487,476 initial NSRCT procedures were followed from the time of treatment to the presence of an untoward event indicated by Current Dental Terminology (CDT) codes for retreatment, apical surgery, or extraction. Population demographics were computed for provider type and tooth location. Kaplan-Meier survival estimates were calculated for 1, 5, and 10 years. Hazard ratios for provider type and tooth location were calculated using the Cox proportional hazards model. Analyses were performed using SAS 9.4 (Cary, NC). Results: The survival of all teeth collectively was 98% at 1 year, 92% at 5 years, and 86% at 10 years. Significant differences in survival based on provider type were noted for molars at 5 years, and for all tooth types at 10 years. The greatest difference discovered was a 5% higher survival rate at 10 years for molars treated by endodontists. This was further evidenced by a hazard ratio of 1.394 when comparing other provider’s success to endodontists within this ten-year molar group. Conclusions: These findings show that survival rates of endodontically teeth is high at ten years post treatment regardless of provider type. Molars treated by endodontists after 10 years have significantly higher survival rates than molars treated by non-endodontists

Effect of Additives on Mineral Trioxide Aggregate Setting Reaction Product Formation

Introduction Mineral trioxide aggregate (MTA) sets via hydration of calcium silicates to yield calcium silicate hydrates and calcium hydroxide (Ca[OH]2). However, a drawback of MTA is its long setting time. Therefore, many additives have been suggested to reduce the setting time. The effect those additives have on setting reaction product formation has been ignored. The objective was to examine the effect additives have on MTA\u27s setting time and setting reaction using differential scanning calorimetry (DSC). Methods MTA powder was prepared with distilled water (control), phosphate buffered saline, 5% calcium chloride (CaCl2), 3% sodium hypochlorite (NaOCl), or lidocaine in a 3:1 mixture and placed in crucibles for DSC evaluation. The setting exothermic reactions were evaluated at 37°C for 8 hours to determine the setting time. Separate samples were stored and evaluated using dynamic DSC scans (37°C→640°C at10°C/min) at 1 day, 1 week, 1 month, and 3 months (n = 9/group/time). Dynamic DSC quantifies the reaction product formed from the amount of heat required to decompose it. Thermographic peaks were integrated to determine enthalpy, which was analyzed with analysis of variance/Tukey test (α = 0.05). Results Isothermal DSC identified 2 main exothermal peaks occurring at 44 ± 12 and 343 ± 57 minutes for the control. Only the CaCl2 additive was an accelerant, which was observed by a greater exothermic peak at 101 ± 11 minutes, indicating a decreased setting time. The dynamic DSC scans produced an endothermic peak around 450°C–550°C attributed to Ca(OH)2 decomposition. The use of a few additives (NaOCl and lidocaine) resulted in significantly less Ca(OH)2 product formation. Conclusions DSC was used to discriminate calcium hydroxide formation in MTA mixed with various additives and showed NaOCl and lidocaine are detrimental to MTA reaction product formation, whereas CaCl2 accelerated the reaction

Quality of Root Canal Obturation Performed by Senior Undergraduate Dental Students

The aim of the present study was to assess the quality of canal obturation performed by undergraduate denal students at Saveetha Dental College and Hospitals, Chennai. Records of 200 endodontically treated teeth from patients who were visited by undergraduate students between month of November 2014 to May 2015. Periapical radiographs of all treated teeth were assessed in terms of canal obturation quality (adequate density and length). Forty-five percent of teeth fulfilled the criteria of an acceptable root canal obturation. Adequate length and density of root filling was found in 89% and 34% of teeth, respectively. There was a significant difference between maxillary and mandibular teeth regarding the length of root canal obturation. A significant difference was observed between molars and other tooth types. The frequency of root canals with an acceptable filling was significantly greater in the anterior teeth compared to premolars or molars. The technical quality of root canal treatment performed by undergraduate dental students was found to be less than ideal