Biomechanical testing of different osteosynthesis systems for segmental resection of the mandible.
OBJECTIVE
This investigation assessed the mechanical behavior of 3 different locking and nonlocking reconstruction systems-Unilock 2.4, Reconstruction 2.4, and Reconstruction 2.7-with regard to plate and screw fracture.


METHODS
Five different plate/screw configurations (Unilock 2.4-locking screws, Unilock 2.4 -conventional screws, Reconstruction 2.4-conventional screws, Reconstruction 2.7-conventional screws, and Unilock 2.4-locking screws with a 1-mm gap; Synthes, Umkirch, Germany) were tested on synthetic mandibles. All mandibles were resected on the left side between the canine and third molar, reconstructed, and loaded cyclically between 30 and 300 N up to 250,000 cycles or until screw or plate failure occurred.


RESULTS
No screw fractures were observed. All plates fractured close to the distal fragment. The Unilock plates fixed with locking screws withstood significantly more cycles until failure than the Reconstruction plates 2.4 fixed with conventional MF-Cortex screws. No significant differences were found in the other groups. Only 2 of the 34 plates tested, both of the Reconstruction 2.7 system, reached the runout limit.


CONCLUSIONS
Unilock plates fixed with locking screws have a higher long-term stability than the Reconstruction 2.4 system. A 1-mm gap between the plate and mandible does not lead to early screw failure in the Unilock 2.4 system with locking screws. The Reconstruction 2.7 system seems superior if well contoured, because 2 of those plates reached the runout limit; however, this system is not as easy to handle as the 2.4 systems, and good contouring is difficult to achieve. Therefore, we consider the Unilock 2.4 system with locking screws the best choice.
Schupp
Wiebke
W
Senior Resident, Department of Oral and Maxillofacial Surgery, University Hospital of Freiburg, Freiburg, Germany. wiebke.schupp@uniklinik-freiburg.de
Arzdorf
Michael
M
Linke
Berend
B
Gutwald
Ralf
R
D001696:Biomechanical Phenomena; D001732:Bite Force; D001860:Bone Plates; D001863:Bone Screws; D003799:Dental Stress Analysis; D019544:Equipment Failure Analysis; D005593:Fracture Fixation, Internal / Q000295:instrumentation*; D006801:Humans; D019248:Jaw Fixation Techniques / Q000295:instrumentation*; D008334:Mandible / Q000601:surgery; D008336:Mandibular Diseases / Q000601:surgery; D008341:Mandibular Prosthesis / Q000706:statistics & numerical data*; D008422:Materials Testing; D011474:Prosthesis Design; D019651:Plastic Surgery Procedures / Q000295:instrumentation