Do position and soft tissue affect distraction vector? An in vitro investigation.

Area of Science:

• Biomechanical Engineering
• Craniofacial Surgery
• Orthodontics

Background:

• Distraction osteogenesis is a surgical technique used to lengthen bone.
• Understanding factors influencing the distraction vector is crucial for predictable outcomes.
• The effects of soft tissue and device position on distraction vector require in vitro evaluation.

Purpose of the Study:

• To evaluate the in vitro effects of simulated soft tissues and distractor position on the distraction vector during mandibular distraction.

Main Methods:

• A polyurethane skull and mandible replica was used with an internal distraction device.
• Distractor position (inferior, mid, superior body) and simulated soft tissues (suprahyoid muscles, mastication muscles, periosteum, mucosa) were varied.
• A laser and grid system measured deflection (vertical, horizontal, absolute distance) after 8.0 mm of distraction.

Main Results:

• Distractor position alone showed minimal effect on vector, except for vertical deflection between inferior and superior groups without soft tissues.
• Simulated soft tissues significantly altered the distraction vector across all measures and positions.
• Deflection patterns differed: without soft tissues, lateral and superior; with soft tissues, lateral and inferior, with less x-axis deflection closer to the inferior border.

Conclusions:

• Simulated soft tissues significantly influence the distraction vector.
• Distractor position alone has a minimal effect on the distraction vector.
• The interplay between distractor position and simulated soft tissues critically affects the distraction vector during mandibular distraction.