Does plate adaptation affect stability? A biomechanical comparison of locking and nonlocking plates

Area of Science:

• Oral and Maxillofacial Surgery
• Biomechanical Engineering
• Materials Science

Background:

• Mandibular angle fractures are common and require stable fixation for optimal healing.
• Plate adaptation and locking screw technology are critical factors influencing the mechanical stability of fixation devices.

Purpose of the Study:

• To evaluate the influence of plate adaptation (offset) and locking versus nonlocking mechanisms on the mechanical performance of fixation systems for simulated mandibular angle fractures.

Main Methods:

• 130 polyurethane synthetic mandibles were used to test 2.0-mm monocortical superior border plates and 2.4-mm reconstruction plates.
• Plates were tested with varying degrees of adaptation (0.0, 1.0, and 2.0 mm offset) in both locking and nonlocking configurations.
• Mechanical testing (load/displacement) was performed under incisal edge and molar loading conditions to determine yield load, yield displacement, and stiffness.

Main Results:

• Locking systems (both 2.0-mm and 2.4-mm) showed no significant differences in mechanical properties across all adaptation degrees.
• Nonlocking 2.4-mm plates exhibited significant differences in mechanical properties between the 0.0-mm offset group and both 1.0-mm and 2.0-mm offset groups.
• Nonlocking 2.0-mm plates showed significant differences between the 2.0-mm offset group and both 0.0-mm and 1.0-mm offset groups.

Conclusions:

• The degree of plate adaptation significantly affects the mechanical behavior of nonlocking fixation systems for mandibular fractures.
• Locking fixation systems are less sensitive to the degree of plate adaptation, maintaining consistent mechanical performance.
• Observed failure patterns were consistently 'all-or-nothing'.