Influence of an interdental full pin on stability of an acrylic external fixator for rostral mandibular fractures in dogs

Objective-To determine total stiffness and gap stiffness of an external fix ation system in a canine mandibular fracture gap model incorporating a full interdental pin as the only point of rostral fixation in a bilateral type- I external fixator. Sample Population-10 canine mandibles. Procedure-Bilateral mandibular ostec tomies were performed between premolars 3 and 4. A type-I external fixator incorporating a full interdental pin was placed to stabilize a 0.5-cm fract ure gap. Four pin configurations (intact mandibular bodies with fixator; os tectomized mandibular bodies and complete fixator; ostectomized mandibular bodies with caudal pins of rostral fragment cut; ostectomized mandibular bo dies with ail pins of rostral fragment cut) were tested in dorsoventral ben ding 5 times on each mandible. The full interdental pin remained intact in ail configurations. Total stiffness and gap stiffness were determined for e ach configuration on a materials testing machine. Results-Total stiffness of intact mandibles was significantly greater than that of ostectomized mandibles, regardless of external fixator configuratio n. However, total stiffness and gap stiffness were not significantly differ ent among different external fixator configurations applied to ostectomized mandibles. Conclusion and Clinical Relevance-External fixator configurations with only the full interdental pin engaging the rostral fragment were as stiff as co nfigurations that had 2 or 4 additional pins in the rostral fragment for th e applied loads. External fixators for rostral mandibular fractures may be rigidly secured with rostral fragment implants applied extracortically, avo iding iatrogenic trauma to teeth and tooth roots.