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14 May 2024

Risk of damage to root dentin in endodontic treatments

Root canal instrumentation is performed using endodontic instruments, aided by irrigation systems, in aseptic working conditions. Canal instrumentation can be performed using manual or motorized (rotating) instruments.

Rotary preparation using NiTi instruments has become the traditional approach to mechanically widen the root canal space, overcoming most of the drawbacks of conventional preparation. However, an important concern has been raised, namely the creation of dentinal defects due to motorized instrumentation. This is a critical situation, considering the abundance of different designs, tapers, preparation protocols, number of files and kinematics of NiTi systems available.

During and after root canal instrumentation, the wall of the root canal can be damaged with the development of dentinal defects in the form of dentinal cracks or so-called "craze lines", which can lead to vertical fractures of the tooth roots, with the consequent need to extract the affected element. To try to stem this problem, several attempts have therefore been made to develop NiTi instruments with better performance by including changes in the design characteristics, mode of action and heat treatment of the NiTi alloy.

Materiasl and methods

In a study, published in the Journal of Contemporary Dental Practice, the authors analyzed seventy-five freshly extracted human maxillary first molars in patients aged between 20 and 30 years. After extraction, the soft tissues on the tooth surface were manually removed with periodontal curettes, and the teeth were stored in plastic containers with 0.1% thymol solution at room temperature. 

The criteria for tooth selection included the presence of a straight palatal root, without visible root caries, restorations, open apices, calculus, or anatomical irregularities.

To standardize the length of the palatal root for all specimens the root was sectioned at a length of 11 mm from the anatomical apex using a diamond disc.

Diagnostic radiographs were taken to confirm the existence of a single canal without curvature, the presence of a mature apex without signs of internal resorption, calcifications or previous endodontic therapies. For all teeth the canal width near the apex was compatible with a K-file 20 and the root surfaces were checked for visible cracks or fractures. The pulp tissue was then removed and consequently abundant irrigation was performed with 1% NaOCl and then irrigation with 5 ml of distilled water.

After processing and positioning the samples, they were randomly and equally divided into five groups. One group was left unprepared to serve as a control and the remaining four experimental groups were instrumented using the Reciproc Blue, ProTaper Gold, ProTaper Next, Reciproc systems. The root canal instrumentation sequences used in the study were performed according to the instructions of the manufacturer of the file system used in each group. All root canals were instrumented with MAF corresponding to apical size 40. All instruments were operated using the electric speed and torque controlled X-Smart Plus endodontic micromotor (Dentsply, Switzerland), equipped with a pre-programmed setting for the operation of the Reciproc, Reciproc Blue, ProTaper Gold and ProTaper Next instruments.


According to the data collected in the study, the Reciproc group presented the highest number of defective roots (9/15), followed by the ProTaper Next group (4/15), then by the ProTaper Gold group (3/15) while the highest number low number of defective roots was shown in the Reciproc Blue group (2/15). Fisher's exact test showed that there were statistically significant differences between groups (p ≤0.05). The Reciproc group showed a significant difference with the ProTaper Gold group (p ≤0.05) and a significant difference with the Reciproc Blue groups (p ≤0.01).


According to the proposed methodology, and based on the results of this in vitro study, the following conclusions can be drawn. All instrumentation systems used in this study caused dentinal defects. The Reciproc system resulted in an increased incidence of defective roots compared to ProTaper Gold and Reciproc Blue. At the apical, mid or coronal level there is no difference in the incidence of dentinal defects between all tests.

There was no difference in the incidence of dentinal defects between all levels (apical, mid or coronal) in each instrument tested.

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