Anatomic Two-dimensional and Three-dimensional Models for Cyclic Fatigue Testing of Endodontic Instruments

Area of Science:

• Endodontics
• Dental Materials Science
• Biomechanical Engineering

Background:

• Cyclic fatigue testing (CFT) is crucial for evaluating endodontic instrument durability.
• Accurate simulation of root canal anatomy is essential for reliable fatigue testing.
• Existing 2D models may not fully represent the complex 3D internal anatomy of root canals.

Purpose of the Study:

• To develop and evaluate novel devices for cyclic fatigue testing (CFT) of endodontic instruments.
• To compare the fatigue behavior of endodontic instruments in 2D and 3D replicas of mandibular molar root canals.
• To assess the influence of different anatomical representations on instrument lifespan and failure modes.

Main Methods:

• New CFT devices were developed for testing in 2D (bucco-lingual and mesio-distal views) and 3D replicas of a mandibular molar's mesial root canal.
• Root canal trajectories were obtained from CT scans, virtually enlarged, and used to create 2D and 3D models.
• Vortex Blue 25/0.06 instruments were subjected to fatigue testing (n=12), recording the number of cycles to failure (NCF) and fragment length.

Main Results:

• Significant differences in mean NCF were observed across all tested canal models (P<0.05).
• Endodontic instruments exhibited longer lifespans in 2D-bucco-lingual models, followed by 2D-mesio-distal and 3D models.
• Significant differences in mean fragment length were also found among the tested 2D and 3D models (P<0.05).

Conclusions:

• 2D and 3D representations of the same canal trajectory yield significant differences in stress accumulation and failure location.
• The study highlights the impact of anatomical model dimensionality on cyclic fatigue outcomes for endodontic instruments.
• Further research is needed to elucidate the effects of complex 3D curvatures on endodontic instrument fatigue behavior.