Tooth Microcracks Comparison Of Continuous Rotating And Reciprocating Rotary Files During Root Canal Biomechanical Preparation: In-Vitro Study

European Journal of Prosthodontics and Restorative Dentistry (2025) 34, (2) 79–85

Continuous rotation; Dentinal defects; Dental materials; Dentinal microcracks; Endodontic instrumentation; Nickel-titanium instruments; Prosthodontic prognosis; Root canal preparation; Reciprocating motion Vertical root fracture.

Dennis Dennis1*,
*Department of Conservative Dentistry, Faculty
of Dentistry, Universitas Sumatera Utara,
Padang Bulan, Medan, Indonesia Jl. Alumni
No.2. Kampus USU. Medan 20155
email: dennis@usu.ac.id,
https://orcid.org/00000003 1718 4363
Trimurni Abidin2,
Department of Conservative Dentistry, Faculty
of Dentistry, Universitas Sumatera Utara,
Padang Bulan, Medan, Indonesia Jl. Alumni
No.2. Kampus USU. Medan 20155
email: tri.murni@usu.ac.id
https://orcid.org/00000003 4865 4874
Wandania Farahanny3,
Department of Conservative Dentistry, Faculty
of Dentistry, Universitas Sumatera Utara,
Padang Bulan, Medan, Indonesia Jl. Alumni
No.2. Kampus USU. Medan 2015 email:
wandania@usu.ac.id
https://orcid.org/00000001 5157 9866
Widi Prasetia4
Department of Conservative Dentistry, Faculty
of Dentistry, Universitas Sumatera Utara,
Padang Bulan, Medan, Indonesia Jl. Alumni
No.2. Kampus USU. Medan 20155
https://orcid.org/00090004 6026 4267
email: widi.prasetia@usu.ac.id
CHEUNG Shun Pan Gary5,
The University of Hong Kong- Shenzhen
Hospital (Department of Dental Surgery)
ORCID ID- 0000-0002-6892-431X
email spcheung@hku.hk

*Correspondence to:
Dennis Dennis
Department of Conservative Dentistry, Faculty
of Dentistry, Universitas Sumatera
Utara, Jl, Alumni No.2, Kampus USU, Medan
20155, Sumatera Utara, Indonesia
https://orcid.org/00000003 1718 4363
email dennis@usu.ac.id

Received: 09.12.2025
Revised: 05.02.2026
Accepted: 08.04.2026

Tooth
Microcracks
Comparison Of Continuous
Rotating And Reciprocating
Rotary Files During Root
Canal
Biomechanical
Preparation: In-Vitro Study
-------------------------------------------------------------------ABSTRACT
Newly developed nickel-titanium alloy (NiTi) instruments enable the
instrument to be used with remarkable flexibility in root canals, such that the
instrument can safely prepare curved root canals without the need to straighten
them. There are two kinds of motion systems used when NiTi rotary
instruments are applied: continuous rotating and reciprocating. In the process
of biomechanical preparation, high stress concentrations inside the apical
dentin create microcracks or craze lines when tools come into contact with the
dentin wall surface. The study aimed to observe the effect and differences
between continuously rotating and reciprocating rotary instruments on the
incidence of microcrack formation on the dentin surface of tooth root canals.
Thirty-two extracted mandibular and maxillary first premolar teeth were
collected and divided into two groups (n=16) as per the instrumentation
protocol: group I: Continuous rotating (Protaper Universal file) and group II:
Reciprocating (Wave One file). Each group was subsequently instrumented
with the standardized working length assigned file system. The samples were
collected to be tested following instrumentation and cut to identify the
microcracks under 18-24x magnification under the microscope. Pearson ChiSquare test was used to statistically analyze the data. There is no statistically
significant difference in the microcrack levels for both groups, which have p =
0.110 > 0.05. The rate of microcrack in the continuous rotating and
reciprocating groups was not significantly different. Most incidence of the
microcracks was experienced in the apical part (9mm) in both the continuous
rotating and reciprocating groups, as opposed to the coronal (3mm) and middle
(6mm) parts.

The goals of root canal treatment are to preserve the oral cavity tooth's appearance and functionality, to get rid of bacteria and their byproducts from the root canal system, manage pain, control sepsis and abnormalities in the pulp and surrounding periapical tissue, and use the surrounding tissue to heal the damaged tooth and return it to a healthy state. 1-2 The "endodontic triad" is a three-phase root canal treatment that includes biomechanical treatment (cleaning and shaping), sterilization (irrigation and disinfection), and root canal filling.1-3 Chemo mechanical root canal preparation, the process of eliminating bacteria from the root canal using mechanical instruments and antibacterial irrigation.1- 4 In the mid-1800s, the first endodontic file was made, which was a standard stainless steel K-File, the kind used mostly in dental clinics, that was manually operated.5 Subsequently, in 1963, W.F.Buehler, a metallurgist at the Naval Ordnance Laboratory in Silver Springs, Maryland, USA, discovered “nitinol”, an abbreviation for nickel (56%), titanium (44%), and Naval Ordnance • • • • • • • • • • • • • • • EJPRD ejprd.org - Published by Riset Publishing Services LLC.

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