# Comparative Evaluation of Resistance of Teeth to Vertical Fracture After Root Canal Preparation With Different Instrumentation Techniques: An In Vitro Study

## TL;DR

This study compares how different dental tools affect the strength of teeth after root canal treatment, finding that hand tools preserve more tooth structure.

## Contribution

The study provides empirical evidence on how various instrumentation techniques influence vertical fracture resistance in endodontically treated teeth.

## Key findings

- The control group (untreated teeth) showed the highest resistance to vertical fractures.
- WaveOne Gold instrumentation resulted in the lowest fracture resistance among tested methods.
- Hand K-file instrumentation preserved more dentinal structure compared to other techniques.

## Abstract

Introduction: Nickel-titanium (Ni-Ti) instrumentation systems have been extensively studied for their clinical performance; however, limited evidence exists regarding their effect on the resistance of endodontically treated teeth to vertical root fractures (VRFs). This investigation aimed to assess and compare the VRF resistance of teeth prepared using various root canal instrumentation methods.

Methods: An a priori power analysis was performed to determine the required sample size. Seventy extracted human mandibular premolars were decoronated and assigned to one control and four experimental groups: Hand instrumentation using hand K-files (Dentsply Maillefer, Ballaigues, Switzerland), rotary instrumentation using ProTaper NEXT (Dentsply Sirona, Ballaigues, Switzerland), reciprocation WaveOne Gold (Dentsply Sirona, Ballaigues, Switzerland), and a hybrid technique, a combination of ProTaper Universal (Dentsply Sirona, Ballaigues, Switzerland) with hand K-file (Dentsply Maillefer, Ballaigues, Switzerland). Root canals were shaped and filled following each system's protocol, except in the control group. All specimens were mounted in acrylic resin and subjected to vertical fracture testing using a universal loading machine (Shanta Engineering, Maharashtra, India).

Results: The control group exhibited the greatest resistance to VRFs (271 ± 65.7 N). Among the instrumented groups, the hand K-file group demonstrated the highest resistance (221.33 ± 58.8 N), whereas the WaveOne Gold group showed the lowest resistance (189.33 ± 47.9 N). A statistically significant difference was observed between the control and experimental groups (p = 0.004).

Conclusion: Instrumentation using hand K-files preserved more dentinal structure, resulting in greater fracture resistance. Conversely, WaveOne Gold preparation was associated with reduced VRF resistance compared to the other techniques.