Nickel-titanium instruments in endodontics: a concise review of the state of the art

Novel Approaches to Detect and Treat Biofilms within the Root Canals of Teeth: A Review

Biofilms located within the root canals of teeth are a unique and pressing concern in dentistry and in medical microbiology. These multispecies biofilms, which include fungi as well as bacteria, form in a protected site with low shear stress and low oxygen tension. Systemic antibiotics are of limited value because of the lack of blood flow of the site, and issues with innate and acquired resistance. Physical disruption using hand or rotary powered instruments does not reach all locations in the root canal system where biofilms are present. Alternative strategies including agitated irrigation fluids, continuous chelation, materials with highly alkaline pH, and antimicrobial nanoparticles are being explored to meet the challenge. Detection and quantification of biofilms using fluorescence-based optical methods could provide an indication of successful biofilm removal and an endpoint for physical and chemical treatments.

Current Trends in Use and Reuse of Nickel-Titanium Engine-driven Instruments: A Survey of Endodontists in the United States

INTRODUCTION

Information is scarce regarding current usage practices of nickel-titanium (NiTi) engine-driven instruments in clinical practice. Therefore, the specific purpose of this survey was to assess trends among endodontists regarding the use and reuse of NiTi instruments.

METHODS

A 16-question survey was sent by e-mail to about 4000 active members of the American Association of Endodontists. Data were collected over a 6-month period and compared using chi-square tests.

RESULTS

A total of 957 surveys were collected (response rate = 23%). Of the respondents, 40.2% worked in solo practices; among them, there were significantly fewer recent graduates (<10 years) compared with those who graduated more than 10 years ago. Furthermore, 41.7% were in a group practice, 4.3% in corporate practice, 10.7% in university settings, and 3% in the military. Overall, 98.3% of respondents reported using NiTi instruments. Respondents who graduated less than 25 years ago use NiTi instruments significantly more (99%) than those who graduated more than 25 years ago (92.6%). Although 22.9% of respondents buy presterilized instruments, 41.6% sterilize them before use, and 35.5% do not sterilize new instruments before use; dental officers in the military reported that they use sterile new instruments in 100% of cases. NiTi instruments were reused by 74% of respondents. The 2 largest segments of the specialist endodontic instrument market belonged to Dentsply (York, PA; 56.9%) and EdgeEndo (Albuquerque, NM; 28.8%).

CONCLUSIONS

There are significant differences in the use of NiTi instruments among types of practice and years since graduation. There were noticeable changes compared with findings reported about 10 years ago.

Laboratory Rational of Changes in the Crystal Lattice of Nickel-Titanium Endodontic Rotary Files in Autoclaving

Objectives

The aim of this study was to investigate the changes of the crystal lattice of NiTi instruments after repeated autoclave sterilization cycles based on the results to conclude about the influence of multiple sterilization on the characteristics of ProTaper clinical use.

Methods

21 samples of ProTaper Universal rotary files were divided into 3 groups of 7 samples. After 1, 4, and 7 cycles of sterilization, the samples were observed using еnergy-dispersive X-ray spectroscopy (EDX), X-ray powder diffraction (XRD), and scanning electron microscopy (SEM).

Results

EDS analysis confirmed that all samples were composed mainly of nickel and titanium, also Fe (presumably steel), Cr, Co, and Zn were found. The percentage of nickel and titanium was affected by repeated sterilization cycles. The mass fraction of Fe, Co, Zn, and Cr decreased after 1, 4, and 7 sterilization cycles. According to the results of the second study, it was found that, with increasing autoclaving cycles, the percentage of Fe decreased. There were changes in the three obtained diffractograms, which indicated an increase in the number of the martensitic phase and a decrease in austenitic. The cutting efficiency of the ProTaper is also reduced during repeated sterilization cycles, which can be caused by the austenitic and martensitic phase displacement.

Conclusion

Manufacturing features and repeated sterilization cycles increase the internal deformation in the structure of NiTi alloy, which increases the risk of fracture.

Evaluation of Flexibility, Microstructure and Elemental Analysis of Some Contemporary Nickel-Titanium Rotary Instruments

BACKGROUND:

Contemporary nickel-titanium (NiTi) rotary endodontic instruments had a revolutionary impact on the success of root canal treatment.

AIM:

To evaluate the flexibility, microstructure and elemental analysis of four different recent NiTi rotary instruments, namely; Wave One Gold, TF adaptive, HyFlex EDM and Gr_Reciproc Blue compared to conventional Protaper Universal (F2).

MATERIAL AND METHODS:

The NiTi rotary files were subjected to cantilever bending test to evaluate their flexibility. The microstructural characteristics and elemental analysis were examined via scanning electron microscopy (SEM) and energy dispersive X-ray spectrometer (EDX).

RESULTS:

The TF adaptive, HyFlex EDM and Wave One Gold endodontic files showed significantly lower cantilever bending values (i.e., higher flexibility) than Protaper F2 and Gr_Reciproc Blue (p < 0.05). The SEM micrographs showed that the bulk of all examined files showed multiple striations due to the cutting process, on the other hand, their external surfaces were different: The Protaper Universal F2 showed multiple voids, while the TF Adaptive surface exhibited more uniform structure. The Hyflex EDM had a crater-like surface, whereas Wave one Gold showed machining grooves with minimum defects, while Reciproc Blue displayed machining grooves with random scratch lines. There was a significant difference in bulk and surface elemental analysis of the various examined files, yet composed mainly of the same elements.

CONCLUSION:

Chemical composition, heat treatment, manufacturing process and geometrical design of the NiTi rotary instrument have a great influence on their flexibility and microstructure.

Microcomputed Tomography Studies of the Effectiveness of XP-endo Shaper in Root Canal Preparation: A Review of the Literature

The aim of this study was to undertake a literature review on the use of XP-endo Shaper (FKG Dentaire SA, La Chaux-de-Fonds, Switzerland) for root canal preparation evaluated using microcomputed tomography (micro-CT) technology, with emphasis on the analysis of untouched canal walls. We searched the PubMed, Science Direct, SciELO, and MEDLINE databases for articles published from 2017 to 2019 using the following keywords: micro-CT, untouched walls, XP shaper, and XP endo. Articles without an abstract were excluded. Five papers were selected. Few studies on this topic are available. The studies published so far show that the XP-endo® Shaper system performs well in terms of canal preparation but leaves untouched walls.