Root surface microcracks induced by orthodontic force as a potential primary indicator of root resorption

Area of Science:

• Orthodontics
• Biomaterials Science
• Dental Research

Background:

• Root resorption is a common complication in orthodontic treatment, with unclear underlying mechanisms.
• Microcracks on tooth roots are linked to bone resorption and may contribute to root resorption during orthodontic therapy.

Purpose of the Study:

• To investigate microcrack formation on tooth roots induced by orthodontic forces.
• To analyze the relationship between orthodontic force magnitude, duration, and microcrack development.
• To explore strategies for mitigating microcracks and preventing root resorption.

Main Methods:

• Application of controlled orthodontic forces (0.5, 1, 2 N) for varying durations (1-14 days) in a rabbit model.
• Scanning electron microscopy (SEM) to examine root surfaces for microcracks.
• Digital force testing to assess root apex breaking strength.
• Finite element (FE) modeling to analyze stress distribution and crack propagation.

Main Results:

• Microcracks were observed on the compressed root apex surfaces, correlating positively with force magnitude and duration.
• Root apex breaking strength was measured.
• FE analysis confirmed that high-stress regions coincided with observed microcrack locations.
• Orthodontic force directly induces microcracks, potentially leading to root resorption.

Conclusions:

• Orthodontic forces can directly cause microcracks on tooth roots.
• Microcrack development is dependent on force magnitude and duration.
• Adjusting orthodontic force application may reduce microcracks and prevent root resorption.