The first part of the lecture will present a mechanical study performed with feline mandibles.
The study compared the mechanical properties of two different types of intraoral splints and two different configurations of absorbable implants used to repair a simulated mandibular fracture between the third and fourth premolar tooth. Thirty mandibles were randomly assigned to 5 groups (intact mandibles, intraoral splint with a Stout configuration, intraoral splint with a modified Risdon configuration, absorbable mesh and 6 pins, absorbable 4-hole plate and 4 pins). Bending stiffness, angular displacement, bending moment were calculated from a ramp-to failure test and the deflection angle during cyclic loading test was obtained for each group. There was not significant difference between the intraoral splints and the absorbable implants. Intact mandibles were stronger and stiffer. Interfragmentary motion (deflection angle) was present in all constructs, but the difference was not statistically significant (ANOVA test, p>0.05). In the immediate postoperative period, the 4 constructs have similar properties. During the second part, we will present a case series of mandibular fractures in small breed dogs, which used absorbable implants to stabilize the fracture. In some cases, only resorbable plates were used, while in others, plates and osteoconductive graft material were utilized. During the postoperative period, a muzzle was used for the first four weeks, along with a soft diet and restricted activity. The mandibles healed without complications during the follow-up available at the time of submission of this abstract.

Mandibular fractures occur secondary to head trauma. Vehicular accidents and animal altercations are common but in many cases the type of trauma is unknown. Stabilization of mandibular fractures is advised in order to obtain bone healing and quick ability to eat and drink with no pain. Many different techniques have been described depending on surgeon’s preference, location and type of fracture. Non- invasive and minimally invasive (muzzling, suture labial though buttons, maxillomandibular fixation…) have the advantage of minimizing manipulation of the jaws but do not cause immediate fixation, which affects healing and impair jaw function. Intraoral splinting is a minimally invasive technique that uses teeth as anchor points to align teeth and, in theory, stabilize the alveolar bone in position facilitating secondary bone healing. Invasive techniques (titanium miniplates, wire and combined techniques), increase stability of the fragments and has been proved to achieve primary bone healing and quick return to function. All techniques have advantages and disadvantages and in many cases selection of one or the other depends on the surgeon’s ability and availability of the techniques, location of the fracture and size of the fragments, further injuries (most patients will have more than one jaw fracture) and costs, among others. Recently, another form of internal fixation has been introduced in small animals. Absorbable implants are known to be less rigid and strong than titanium miniplates, but have been used successfully in humans for stabilization of jaw fractures. While these specific implants (Resorb X and Sonic Pins, KLS Martin) are indicated for stabilization of fractures that do not support load such as midface (upper jaw, zygomatic arch …), one of the authors (YD) has been used them clinically in small animals. Experimental and clinical studies have shown the efficacy of intraoral splints in dogs and plating in dog and cats. 

This lecture will be divided in two parts.

During the first part, we will present a study (funded by the Veterinary Dental Foundation, Research Award 2022) performed with feline mandibles comparing the mechanical properties of four different constructs used to repair mandibular fractures between the third and fourth premolar tooth. Thirty mandibles were assigned to 5 groups (intact mandibles, intraoral splint with a modified Risdon configuration, intraoral splint with Stout configuration, absorbable mesh with pins and absorbable plate with pins.) After the procedure, the mandibles were tested mechanically (cyclic loading testing and ramp-to failure). Bending stiffness, angular displacement, bending moment at failure and deflection angle during the cycling loading tests were compared among the five groups. Intact mandibles were stronger and stiffer than intraoral splints and absorbable implants.
There was not significant difference between the four tested constructs. Interfragmentary motion (deflection angle) was not significantly different between any of the groups, but the modified Risdon configuration showed greater (although not significant) interfragmentary motion. Results and significance of this study will be discussed during the lecture.

During the second part, we will present a case series of mandibular fractures in small breed dogs and cats that used absorbable implants to stabilize the fracture. Initial interfragmentary motion was palpable but it decreased during the following weeks. Synthetic bone graft was used in some cases. Callus was palpable at recheck (1-3 months). During the postoperative period, a muzzle was used for the first 4 weeks, with soft diet and restriction in activity. The mandibles healed without no complication during the follow up available at the time of submission of this abstract.