Defining the critical-sized defect in a rat segmental mandibulectomy model.
OBJECTIVE
Advances in tissue engineering offer potential alternatives to current mandibular reconstructive techniques; however, before clinical translation of this technology, a relevant animal model must be used to validate possible interventions.


OBJECTIVE
To establish the critical-sized segmental mandibular defect that does not heal spontaneously in the rat mandible.


METHODS
Prospective study of mandibular defect healing in 29 Sprague-Dawley rats in an animal laboratory.


METHODS
The rats underwent creation of 1 of 4 segmental mandibular defects measuring 0, 1, 3, and 5 mm. All mandibular wounds were internally fixated with 1-mm microplates and screws and allowed to heal for 12 weeks, after which the animals were killed humanely.


METHODS
Analysis with micro-computed tomography of bony union and formation graded on semiquantitative scales.


RESULTS
Seven animals were included in each experimental group. No 5-mm segmental defects successfully developed bony union, whereas all 0- and 1-mm defects had continuous bony growth across the original defect on micro-computed tomography. Three of the 3-mm defects had bony continuity, and 3 had no healing of the bony wound. Bone union scores were significantly lower for the 5-mm defects compared with the 0-, 1-, and 3-mm defects (P < .01).


CONCLUSIONS
The rat segmental mandible model cannot heal a 5-mm segmental mandibular defect. Successful healing of 0-, 1-, and 3-mm defects confirms adequate stabilization of bony wounds with internal fixation with 1-mm microplates. The rat segmental mandibular critical-sized defect provides a clinically relevant testing ground for translatable mandibular tissue engineering efforts.
Department of Head and Neck Surgery, David Geffen School of Medicine, University of California, Los Angeles (UCLA).
Adam S
AS
DeConde
Department of Head and Neck Surgery, David Geffen School of Medicine, University of California, Los Angeles (UCLA).
Matthew K
MK
Lee
Department of Head and Neck Surgery, David Geffen School of Medicine, University of California, Los Angeles (UCLA).
Douglas
D
Sidell
Jonsson Comprehensive Cancer Center, David Geffen School of Medicine, UCLA3Division of Oral Radiology, School of Dentistry, UCLA4Division of Diagnostic and Surgical Sciences, School of Dentistry, UCLA.
Tara
T
Aghaloo
Jonsson Comprehensive Cancer Center, David Geffen School of Medicine, UCLA5Division of Advanced Prosthodontics, Biomaterials and Hospital Dentistry, School of Dentistry, UCLA.
Min
M
Lee
Jonsson Comprehensive Cancer Center, David Geffen School of Medicine, UCLA3Division of Oral Radiology, School of Dentistry, UCLA.
Sotirios
S
Tetradis
currently a postbaccalaureate student at School of Dentistry, UCLA.
Kyle
K
Low
Division of Diagnostic and Surgical Sciences, School of Dentistry, UCLA7Department of Medicine Statistics Core, David Geffen School of Medicine, UCLA.
David
D
Elashoff
Department of Medicine Statistics Core, David Geffen School of Medicine, UCLA.
Tristan
T
Grogan
Department of Radiology, David Geffen School of Medicine, UCLA.
Ali R
AR
Sepahdari
Department of Head and Neck Surgery, David Geffen School of Medicine, University of California, Los Angeles (UCLA)2Jonsson Comprehensive Cancer Center, David Geffen School of Medicine, UCLA.
Maie
M
St John
D000818:Animals; D004195:Disease Models, Animal; D016268:Internal Fixators; D008297:Male; D008338:Mandibular Injuries / Q000000981:diagnostic imaging / Q000601:surgery*; D063168:Mandibular Osteotomy; D051381:Rats; D017207:Rats, Sprague-Dawley; D014945:Wound Healing / Q000502:physiology; D055114:X-Ray Microtomography