Defining the critical-sized defect in a rat segmental mandibulectomy model.

Area of Science:

• Biomaterials Science
• Regenerative Medicine
• Surgical Innovation

Background:

• Current mandibular reconstruction methods have limitations.
• Tissue engineering offers promising alternatives for mandibular repair.
• A validated animal model is essential for preclinical assessment of tissue engineering interventions.

Purpose of the Study:

• To determine the critical-sized segmental mandibular defect in rats that prevents spontaneous healing.
• To establish a reliable animal model for evaluating mandibular tissue engineering strategies.

Main Methods:

• A prospective study involving 29 Sprague-Dawley rats.
• Creation of segmental mandibular defects of 0, 1, 3, and 5 mm.
• Internal fixation of all defects using microplates and screws.
• Assessment of bony union and formation via micro-computed tomography after 12 weeks.

Main Results:

• No 5-mm defects achieved bony union.
• All 0-mm and 1-mm defects showed complete bony growth.
• 3-mm defects exhibited partial healing in 50% of cases.
• Significantly lower bone union scores were observed in 5-mm defects compared to smaller defects (P < .01).

Conclusions:

• A 5-mm segmental mandibular defect in rats represents a critical-sized defect that does not heal spontaneously.
• The internal fixation method with microplates effectively stabilized smaller defects (0-3 mm), allowing for healing.
• The established rat critical-sized mandibular defect model is suitable for preclinical testing of mandibular tissue engineering and regenerative therapies.