Rotary NiTi instrument fracture and its consequences

Journal of Endodontics, 2005

Numerous discarded ProFile GT, ProFile, and Pro-Taper nickel-titanium rotary instruments obtained from two graduate endodontic clinics were examined by scanning electron microscopy. These instruments had an unknown history of clinical use and had fractured or experienced considerable permanent torsional deformation without complete separation. The failure processes generally exhibited substantial ductile character, evidenced by a dimpled rupture fracture surface. Crack propagation at grain boundaries and cleavage surfaces indicative of transgranular fracture were observed for some specimens. It appeared that oxide particles from the manufacturing process served as nucleating sites for the microvoids, leading to dimpled rupture. A previously unreported fracture mode also was observed, in which crack propagation, approximately parallel to the local flute orientation, connected pitted regions on the surface. Combining present and previous scanning electron microscopy observations of clinically failed instruments, suggestions are offered for improving their fracture resistance.

South African Dental Journal, 2020

Instrument fracture is a serious complication during endodontic treatment of teeth, having an adverse effect on the outcome of the nickel titanium (NiTi) treatment, especially if the fracture prevents apical access to the infected root canal. Despite the advent of NiTi files, the risk of fracture during the endodontic preparation of root canals, especially in severely curved canals, remains a serious concern. The fracture of NiTi files during preparation may result in a compromised prognosis for the tooth. In the presence of periapical lesions, instrument fracture may reduce the chances of successful healing.

IOSR Journal of Dental and Medical Sciences, 2016

A successful root canal treatment depend upon so many factor but the most important factor which determine the efficacy of all subsequent procedures such as debridement ,medicament delivery, and obturation is mechanical preparation of root canal system .Traditionally stainless steel files were used, but with the introduction of nickel titanium (NiTi) alloys significantly broadened the instrument design. So many factors affect the separation of nickel titanium instrument and the rate of separation of nickel titanium is 30-60% and breakage rate 9.4%. The aim of this review article is to discuss the methods that prevent the separation of nickel titanium instrument and improve the success of root canal treatment to save teeth.

International Endodontic Journal, 2003

Aim To evaluate the e¡ect of rotational speed and the angle and radius of curvature of root canals on the fracture of two types of nickel-titanium rotary instruments: K3 1 and ProTaper 1. Methodology A total of 240 root canals of extracted human maxillary and mandibular molars were divided into two groups of 120, according to the angle of the canal curvature (group A: <308, group B: >308). Each group was then divided into two subgroups of 60 canals in order to perform instrumentation using K3 1 and ProTaper 1 rotary instruments at three di¡erent rotational speeds: 150, 250 and 350 r.p.m. (20 canals at each rotational speed). Each instrument was used a maximum of 20 times and at one rotational speed only. The angle and radius of canal curvature were measured in the only group in which fractures actually took place (group B). Results There were a total of 22 instrument fractures; all of these occurred in canals with curves >308. In a multivariate analysis, it was demonstrated that the ¢les used at a rotational speed of 350 r.p.m. were more likely to fracture than those used at 250 r.p.m. (OR: 1113.88; 95% CI: 2.36^526420.05) and than those used at 150 r.p.m. (OR: 13531.33; 95% CI: 5.37^34120254.00). A decrease in the angle of curvature of the canal also signi¢cantly reduced the likelihood of fracture (OR: 0.2083; 95% CI: 0.068^0.6502). These relationships remained signi¢cant after being adjusted for the potential interactions between the remaining variables. No signi¢cant di¡erences were found between the ¢les or the radii of the canals. Conclusions Instrument fracture was associated with rotational speed and the angle of curvature of the canal.

Journal of endodontics, 2005

Adoption of rotary nickel-titanium instruments has renewed concerns regarding instrument fracture and its consequences. The frequency of instrument fracture and its impact on treatment outcome were determined from an analysis of specialist endodontic practice records involving 8460 cases. A case-control study of treatment outcomes was conducted on a subset of 146 teeth with a retained instrument fragment (plus 146 matched controls), for which clinical and radiographic follow-up of at least 1 year was available. Masked radiographs were assessed by two calibrated examiners. Overall prevalence of retained fractured instruments was 3.3% of treated teeth. In the case-control study, overall healing rates were 91.8% for cases with a fractured instrument and 94.5% for matched controls (p &gt; 0.05, Fisher&#39;s exact test). Healing in both groups was lower in teeth with a preoperative periapical radiolucency (86.7% versus 92.9%, p &gt; 0.05). In the hands of skilled endodontists prognosis w...

European Oral Research, 2019

Evaluation of deformation and fracture rates for nickel-titanium rotary instruments according to the frequency of clinical use Purpose To evaluate the deformation and fracture rates for ProTaper Universal (PTU) nickeltitanium rotary instruments according to the frequency of clinical use. Materials and Methods A total of 619 PTU instruments (S1, S2, F1, F2, and F3) that have been used in the clinic by a single endodontist were collected over a period of 4 years. These instruments were grouped on the basis of one to three (Group A), four to six (Group B) and seven to nine (Group C) clinical uses (one canal = one use). All instruments were evaluated by a blinded investigator under a stereomicroscope at 15×-45× magnification for the presence of deformation and fracture. Results The overall rates of deformation and fracture were 10% and 1.2%, respectively. The deformation and fracture rates for the S2, F1, and F2 instruments showed no significant differences among groups. However, fracture rate for S1 instruments in Group A was significantly higher than for those in Group B (p=0.025) and Group C (p=0.004). In Group C, the S1 instruments showed a significantly higher deformation rate compared with the S2 (p=0.04), F1 (p=0.008) and F2 (p=0.049) instruments; there were no other significant differences within groups. Conclusion Under the conditions of the current study, frequency of use seemed to influence the deformation rates of PTU rotary instruments. Except S1, these instruments could be used without any fracture or deformation in up to 9 clinical cases by an experienced endodontist.

British Dental Journal, 2006

Adoption of rotary nickel-titanium instruments has renewed concerns regarding instrument fracture and its consequences. The frequency of instrument fracture and its impact on treatment outcome were determined from an analysis of specialist endodontic practice records involving 8460 cases. A case-control study of treatment outcomes was conducted on a subset of 146 teeth with a retained instrument fragment (plus 146 matched controls), for which clinical and radiographic follow-up of at least 1 year was available. Masked radiographs were assessed by two calibrated examiners. Overall prevalence of retained fractured instruments was 3.3% of treated teeth. In the case-control study, overall healing rates were 91.8% for cases with a fractured instrument and 94.5% for matched controls (p Ͼ 0.05, Fisher's exact test). Healing in both groups was lower in teeth with a preoperative periapical radiolucency (86.7% versus 92.9%, p Ͼ 0.05). In the hands of skilled endodontists prognosis was not significantly affected by the presence of a retained fractured instrument.

Journal of endodontics, 2001

The purpose of this work was to investigate the process history on fracture life of nickel-titanium endodontics files. The results are based on microstructural investigations of nickel-titanium engine-driven rotary instruments based on X-ray diffraction, scanning electron microscopy, and microhardness tests. Endodontic files are very work-hardened, and there is a high density of defects in the alloy that can disturb the phase transformation. The microhardness Vickers confirmed these observations (dislocations and precipitates). The X-rays show that experimental spectrum lines are extended, typical of a distorted lattice. The surface state of the endodontic files (scanning electron microscopy) is an important factor in failure and fracture initiation.

Le Journal de Physique IV, 2001

Endodontic treatments consist to eliminate the vascular nervous system of the tooth. The objectives of this treatment are adequate cleaning and shaping the root canals of the tooth. The endodontic treatment is essential to the success of prosthetics therapy and the lifetime of the tooth. The difficulties of endodontic treatments lie in the abruptness of canal curvature. Ni-Ti endodontic instruments were introduced to facilitate instrumentation of curved canals. They are superelastic and flex far more than stainless-steel instruments. Despite the increased flexibility we can observe unexpected fractures of these Ni-Ti files. The purpose of this work is to understand the process history on fracture life. Our results are based on microstructural and mechanical investigations of Ni-Ti engine-driven rotary files: X-ray diffraction, SEM, DSC, microhardness and bending tests. Thus, and as we expected, endodontic files are very work-hardened: there is a high density of defects in the alloy, which will impede the phase transformation. DSC : the phase transformation A/R-Phase is predominant, the martensitic transformation is difficult to observe. The microvickers hardness confirms these observations (dislocations and precipitates). The X-rays show that the experimental peaks are broad, which is typical of a distorted lattice. Morover, machining resulted in the work hardening of files. Some thermal treatments are involved in promoting some changes in the mechanical properties and transformation characteristics. Annealing around 400°C shows good results : the recovery allows a compromise between an adequate density of defects to see the R-Phase germination and a low density to limit the brittleness of these instruments. The surface state of the endodontic files is an important factor for failures and fractures initiation. In these applications, it is very critical to predict the service life based on the theoretical modeling.

Endodontic Practice, 2008

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