Early root alterations after orthodontic force application studied by light and scanning electron microscopy

Area of Science:

• Dental Research
• Orthodontics
• Cell Biology

Background:

• Orthodontic treatment involves applying forces to move teeth.
• Root resorption is a common side effect of orthodontic tooth movement.
• Understanding the cellular processes of root resorption is crucial for minimizing damage.

Purpose of the Study:

• To characterize the sequential changes in root surface morphology during orthodontic tooth movement.
• To identify the cell types involved in different phases of orthodontically induced root resorption.
• To correlate specific resorption patterns with distinct cellular activities.

Main Methods:

• Utilized Wistar rats with mesially moved maxillary molars using a fixed appliance (50g force).
• Examined root surface alterations via scanning electron microscopy (SEM) and light microscopy at 1, 2, and 4 days post-force application.
• Analyzed nine animals per time point, with nine untreated controls.

Main Results:

• Identified three distinct resorption defect types: isolated small lacunae, wide shallow bays, and deep lacunae.
• Observed that isolated small lacunae were the earliest defects, associated with mononucleated macrophage-like cells.
• Noted deeper, dentine-invading lacunae appearing by day 4 within shallow bays, associated with multinucleated cells.

Conclusions:

• Orthodontically induced root resorption involves distinct cell types with varying resorptive potentials.
• Sequential phases of root resorption are characterized by specific morphological patterns and cellular interactions.
• Mononucleated and multinucleated cells play successive, interrelated roles in creating characteristic root surface defects.