New Technique for Mandibular Symphyseal Distraction by a Double-Level Anchorage and Fixation System: Advantages and Results

Introduction: A surgical technique to widen the mandible is the mandibular midline distraction: the most common indications for mandibular midline distraction are severe mandibular anterior crowding, severe mandibular transverse deficiency, uni- or bilateral crossbite, impacted anterior teeth with inadequate space, and tipped teeth. Commonly used distraction devices can be divided into 2 systems: bone-borne distraction system appliance, dental-borne distraction systems. Each system has peculiar advantages, disadvantages, and different indications. To combine advantages of both systems we developed a new technique adopting an immediate basal bone widening with fixation after osteotomy and a dental borne rigid lingual system for distraction.

Aim: The aim of this work is to show a new technique for symphysis mandibular distraction based on a double-level anchorage and fixation system on clinical patients showing final results and advantages.

Methods: Two patients affected by dento-alveolar and basal bone maxillary and mandibular transversal collapse even in association with other skeletal malocclusion were selected. Patients were clinically and radiographically studied and analyzed at different times before and after surgery. Dental and basal bone measurements were performed clinically and radiographically.

Results: The results were optimal with perfect dental arches alignment followed by closing of the open bites with multiple-segmented surgery in a second surgical time. No misalignment of the 2 mandibular halves was noticed during the distraction procedure.

Discussion: Dental-bone discrepancies correction is mandatory before orthodontic treatment alignment. Transversal jaw expansion can be achieved safely and stably by distraction of both maxillae for the combination of osteogenesis and histogenesis with augmentation of both bone and soft tissue. Bone-borne distraction will result in more stable results; dental-borne devices will result in more simple and aesthetically rewarding procedures. Hybrid techniques usually show mixed results depending on the characteristics of the device. For this reason we developed a combination of both the aforementioned systems which is not a hybrid system but the combination of an immediate expansion of the symphysis and fixation by 1 miniplate with only 2 screws acting like hinges during distraction, combined with a lingual distraction system at the alveolar bone level.

Conclusions: Bone-borne distraction systems result in more efficient basal bone mandibular widening with increased stability for dental results. For dental-borne appliance the advantages consist in no second surgery need for their removal, no transmucosal hardware emergence and better aesthetic, especially when lingual devices were used. Our technique combines advantages of both procedures.