Cutting efficiency and corrosion resistance of heat-treated endodontic files after various disinfection protocols

The aim of this study is to evaluate the effect of various disinfection protocols on the cutting efficiency and chemical composition of ProTaper, Twisted File, Twisted File Adaptive, and Hedström files. Four experimental groups (n = 10) were presoaked in either enzymatic solution or 1% sodium hypochlorite for 30 min, followed by either 5 or 15 min of ultrasonic cleaning and then autoclaved. Resin-simulated canals with a single curvature of 38-40° were prepared by each instrument system. Cutting efficiency of each instrument was analyzed by subtracting the final weight from the initial weight of the resin blocks. Chemical compositions were studied by field emission scanning electron microscopy and X-ray energy-dispersive spectrometry. The cutting efficiency of Hedström, ProTaper, and Twisted File instruments decreased compared to their control groups (p < 0.05) whereas it did not change for Twisted File Adaptive. More corrosion was detected with longer ultrasonication time. No difference was observed regarding the pre-soaking media. Disinfection protocols exerted a significant overall effect on the performance of Hedström, ProTaper, and Twisted File instruments. Corrosion, microcracks, and crevices were evident on all tested instruments after disinfection protocols applied. All disinfection protocols, regardless of the pre-soaking media used or the ultrasonic cleaning time applied, have some effect on the cutting efficiency and the surface characteristics of the files.

Comparative Evaluation of Cutting Efficiency of Three File Systems-Kedo-SH Manual, Pedoflex Rotary, and Manual K File: An In Vitro Study

Aims

The purpose of this study was to comparatively evaluate the cutting efficiency of Pedoflex rotary, Kedo SH manual file, and manual K file systems used in root canal instrumentation while performing pulp therapy of deciduous teeth with a stereomicroscope.

Materials and Methods

Forty-five extracted primary human root canals were chosen, and following the removal of pulp tissue, the canals were dyed with Indian ink and left to dry for 2 h. The samples were randomly divided into three groups, Group A: Kedo SH manual file system (n = 15), Group B: Pedoflex rotary file system (n = 15), and Group C: Manual K files (n = 15). After root canal instrumentation, all the root canals were cleared to make them transparent. The teeth after clearing were observed under stereomicroscope and scored according to the amount of dye present in the root canals. The data were tabulated and statistically analyzed with SPSS version 16 using Chi-square, Kruskal-Wallis, and Dunn's test (post-hoc).

Results

With regards to cutting efficiency, there was a statistically noteworthy difference among groups A and C [P = 0.000] and groups B and C [P = 0.000]. Furthermore, groups A and B did not differ statistically significantly [P = 0.950].

Conclusions

Cutting efficacy of the Pedoflex rotary files was seen to be superior to that of Kedo SH and manual K files.

Clinical Significance

Rotary files in deciduous teeth have various benefits over manual files, resulting in a noticeable reduction in working time, which has aided in maintaining patient participation by reducing the risk for fatigue. We conclude that NiTi rotary devices result in a superior cutting efficiency and, as a result, greater clinical success.

Bone cutting efficiency and heat generation using a traditional fluted Burr and a novel fluteless resurfacing tool

BACKGROUND

Powered instrumentation is often used for bone preparation and/or removal in many orthopaedic procedures but does risk thermogenesis. This study compares biomechanical properties of a fluted burr and a novel fluteless resurfacing tool.

METHODS

Twenty cadaveric metatarsals were tested with four predetermined cutting forces to evaluate heat generation and cutting rate for the fluted burr and fluteless resurfacing tool over 40 s or until a depth of 4 mm was reached. Cutting rate was calculated from displacement transducer data. Heat generation was measured by thermocouples placed in the bone adjacent to the burring site. Assuming a body temperature of 37 °C, a 10 °C increase in heat was used as the threshold of inducing osteonecrosis.

FINDINGS

At 1.0 N and 1.7 N, the thermal osteonecrosis threshold was reached at comparable times between burrs, while the bone removed by the resurfacing tool was on average five times greater than fluted burr at 1.0 N and over twice as great at 1.7 N. Statistical analysis of these common cutting forces showed the resurfacing tool had significantly higher cutting rates (P < 0.01). As a result, the fluted burr produced higher temperatures for the same amount of bone removal (P < 0.01).

INTERPRETATION

In a cadaveric study, the fluteless resurfacing tool demonstrated higher bone cutting rates and lower heat generation for the same amount of bone removed than a traditional fluted burr.

Influence of sterilization procedures on the physical and mechanical properties of rotating endodontic instruments: a systematic review and network meta-analysis

The fracture of endodontic instruments inside the canal represents a problem that is not always easy to solve. The reutilization of endodontic instruments after sterilization procedures raises the question of how these processes affect their physical and mechanical properties. Alterations can involve the surface of the instruments, as well as their cutting effectiveness, shape and resistance to torsional and cyclic fatigue. The methodology adopted for this systematic review followed the PRISMA guidelines for systematic reviews. The following search terms were used in PubMed and Scopus: "endodontic sterilization", "endodontic autoclave", "cyclic fatigue", "torsional", "cutting efficiency", "sterilization", "surface characteristics" and "corrosion". After the screening phase, the application of exclusion criteria and the removal of duplicates, 51 studies were identified and divided into four outcomes: cyclic fatigue; deformation and torsional fatigue; corrosion or surface alterations; and cutting efficiency. Our study of the scientific literature highlights disagreements between studies on these effects. After autoclaving, instruments exhibit a reduction in the cutting efficiency, but NiTi alloy instruments have an improved resistance to cyclic and torsional fatigue.

Operative Torque Analysis to Evaluate Cutting Efficiency of Two Nickel-Titanium Rotary Instruments for Glide Path: An In Vitro Comparison

AIM AND OBJECTIVE

The aim and objective of this study was to evaluate and compare the cutting efficacy of two different nickel titanium rotary instruments by a novel methodology: the operative torque (torque and time needed to progress toward the apex).

MATERIALS AND METHODS

Ten fresh extracted upper first premolars with two canals were instrumented with a KaVo (Biberach, Germany) and a KaVo 1:1 handpiece at 300 rpm with maximum torque set at 2 N. One canal was instrumented with ProGlider NiTi rotary instruments (Dentsply Sirona Endodontics, Ballaigues, Switzerland), with tip size of 16.02, and the other one with EgdeGlidePath rotary instrument (EdgeEndo, Albuquerque, New Mexico). Mean instrumentation time, mean torque values, and maximum torque values were evaluated for each instrument. The significance level was set at p <0.05.

RESULTS

EdgeGlidePath instruments reached the working length in significantly less time with a significantly smaller amount of torque when compared to ProGlider (p >0.05). No instruments exhibited flute deformation or underwent intracanal failure.

CONCLUSIONS

Operative torque is related to the capability to cut dentin and progress toward the apex: the smaller the torque values, the higher the cutting ability (and safety). Operative torque is also dependent on debris removal and irrigation techniques. Nevertheless, both operative torque and instrumentation time are clinically relevant parameters for evaluating instruments' performance (i.e., cutting ability).

CLINICAL SIGNIFICANCE

Operative torque during endodontic instrumentation helps understanding the overall performance in terms of both cutting efficiency and safety.

Enhancement of NiTi superelastic endodontic instruments by TiO2 coating

Rotary nickel-titanium (NiTi) endodontic instruments were coated with a nanometric flexible TiO2 layer through dip-coating sol-gel. Control groups and coated samples of superelastic NiTi instruments model RaCe 25/0.06 (0.25mm tip-diameter, 6% conicity) were comparatively investigated with respect to the cutting efficiency, fatigue life, and corrosion resistance. Results showed an improvement in cutting efficiency for the coated samples and a high resistance to corrosion in NaClO. The coated instruments showed a better performance in fatigue life after corrosion.

Mechanical behavior of deep cryogenically treated martensitic shape memory nickel-titanium rotary endodontic instruments

OBJECTIVES

The aim of this study was to investigate the role of deep cryogenic treatment (DCT) on the cyclic fatigue resistance and cutting efficiency of martensitic shape memory (SM) nickel-titanium (NiTi) rotary endodontic instruments.

MATERIALS AND METHODS

Seventy-five HyFlex(®) CM instruments were randomly divided into three groups of 25 each and subjected to different DCT (-185° C) conditions based on soaking time: DCT 24 group: 24 h, DCT 6 group: 6 h, and control group. Each group was randomly subdivided for evaluation of cyclic fatigue resistance in custom-made artificial canals (n = 15) and cutting efficiency in plexiglass simulators (n = 10). The cyclic fatigue resistance was measured by calculating the number of cycles to failure (NCF) and cutting efficiency was measured using the loss of weight method.

RESULTS

Increase in NCF of instruments in DCT 24 group was highly significant (P < 0.01; Tukey's honest significant difference). There was no difference in weight loss of plexiglass simulators in all the groups (P > 0.05; one-way analysis of variance). In conclusion, deep dry cryogenic treatment with 24 h soaking time significantly increases the cyclic fatigue resistance without affecting the cutting efficiency of SM NiTi endodontic instruments.

MATERIALS AND METHODS

Seventy-five HyFlex(®) CM instruments were randomly divided into three groups of 25 each and subjected to different DCT (-185° C) conditions based on soaking time: DCT 24 group: 24 h, DCT 6 group: 6 h, and control group. Each group was randomly subdivided for evaluation of cyclic fatigue resistance in custom-made artificial canals (n = 15) and cutting efficiency in plexiglass simulators (n = 10). The cyclic fatigue resistance was measured by calculating the number of cycles to failure (NCF) and cutting efficiency was measured using the loss of weight method.

RESULTS

Increase in NCF of instruments in DCT 24 group was highly significant (P < 0.01; Tukey's honest significant difference). There was no difference in weight loss of plexiglass simulators in all the groups (P > 0.05; one-way analysis of variance). In conclusion, deep dry cryogenic treatment with 24 h soaking time significantly increases the cyclic fatigue resistance without affecting the cutting efficiency of SM NiTi endodontic instruments.

Cutting efficiency of apical preparation using ultrasonic tips with microprojections: confocal laser scanning microscopy study

Objectives

The purpose of this study was to compare the cutting efficiency of a newly developed microprojection tip and a diamond-coated tip under two different engine powers.

Materials and Methods

The apical 3-mm of each root was resected, and root-end preparation was performed with upward and downward pressure using one of the ultrasonic tips, KIS-1D (Obtura Spartan) or JT-5B (B&L Biotech Ltd.). The ultrasonic engine was set to power-1 or -4. Forty teeth were randomly divided into four groups: K1 (KIS-1D / Power-1), J1 (JT-5B / Power-1), K4 (KIS-1D / Power-4), and J4 (JT-5B / Power-4). The total time required for root-end preparation was recorded. All teeth were resected and the apical parts were evaluated for the number and length of cracks using a confocal scanning micrscope. The size of the root-end cavity and the width of the remaining dentin were recorded. The data were statistically analyzed using two-way analysis of variance and a Mann-Whitney test.

Results

There was no significant difference in the time required between the instrument groups, but the power-4 groups showed reduced preparation time for both instrument groups (p < 0.05). The K4 and J4 groups with a power-4 showed a significantly higher crack formation and a longer crack irrespective of the instruments. There was no significant difference in the remaining dentin thickness or any of the parameters after preparation.

Conclusions

Ultrasonic tips with microprojections would be an option to substitute for the conventional ultrasonic tips with a diamond coating with the same clinical efficiency.

Twisted vs Protaper Files in Contemporary Pediatric Endodontics

Objective: To compare the cutting efficiency of twisted files with protaper files in primary teeth.

Study design: It is an experimental, in vitro study comparing two groups.

Results: The obtained results from the experiment were statistically analyzed with Mann-Whitney U-test. Twisted files showed better cutting efficiency when compared to protaper files.

Conclusion: Since twisted files show a better cutting efficiency, they can be efficiently incorporated into the contemporary pediatric endodontic armamentarium.

How to cite this article: Prabhakar AR, Yavagal C, Vallu RK. Twisted vs Protaper Files in Contemporary Pediatric Endodontics. Int J Clin Pediatr Dent 2014;7(2):93-96.

An Epidemiological Study on the Selection, Usage and Disposal of Dental Burs among the Dental Practioner's

AIM

The purpose of this cross sectional study was to understand and evaluate local practioner's knowledge on dental bur selection, its usage, sterilization procedures undertaken and the method of disposal of dental burs in restorative procedures.

MATERIALS AND METHODS

A Questionnaire proforma was prepared with each question having 4 answers. A total of 20 questions were framed and were sub-divided in to 3 categories namely selection, usage sterilization and disposal. These Questionnaire were sent to all the local practioner's by mail and to ensure a high response rate as they were followed up by telephone calls. The results were analyzed statistically and were represented in the form of percentage.

RESULTS

A total 131 out of 150 practioner's answered the questions, a response rate of 87%. Most of the practioner's preferred diamonds (75%) over tungsten carbide (15%) burs. most of the dentists used burs till they were worn out (85%) and many of the dentists agreed that the cutting efficiency of bur decreased with usage (33%). Clinicians usually sterilized burs either once daily (35%) or for every patient (35%). Almost every practioner discarded their worn out burs into dustbin (100%).

CONCLUSION

From the survey we came to know the operators attitude towards one group of burs in terms of cutting efficiency. In terms of cutting efficiency diamond burs predominated the choice irrespective of the grit size. Burs were used repeatedly till they were worn out and minimal coolant was used during tooth preparation and believed that it didn't have any effect on the cutting efficiency.