A Correction of Hypoplastic Mandible Using Mandibular Shape Porous High Density Polyethylene (PHDPE)

ABSTRACT

The mandible with the lower maxilla comprises the lower third of the face. A correction of the mandible in facial asymmetry would be helpful in improving aesthetic appearance. In general, surgical techniques for improving the contour of lower jaw deformities include correcting the deficient mandible by osteotomies, distraction osteogenesis and the augmentation of the mandible with alloplastic or autogenous materials. In a patient with satisfactory occlusal relationships and mild hypoplasia, alloplastic material for augmentation of the mandible on the affected side is more practical than autogenous augmentation. The porous high density polyethylene (PHDPE) implant is a widely available alloplast which is an attractive alternative to other alloplasts and autogenous tissues. Thirteen patients (8 men, 5 women), ages ranging from 17 to 47 years old, have types IA (n = 6) and IB (n = 5) hemifacial microsomia(Munro and Lauritzen, 1985), Klippel-Feil syndrome (n = 1), Romberg's disease (n = 1) were corrected with prefabricated porous high density polyethylene over a 4 year period (1996- 1999). The average follow-up period was 12 months, however the range has been between 6 and 36 months. Preoperative planning was done based on an aesthetic assessment of thickness of the soft tissue, the use of life size photographs, cephalometric and panorex x-rays and three dimensional computed tomography. The surgical technique consists of an intraoral approach incision, the an implant was placed subperiostealy, appropriately sculptured and fixed to posterior and inferior border of the mandible at the gonial angle. In four patients the implant had to be removed due to complications which included three cases of infection and one case of extrusion by iatrogenic trauma. One of the above four patients' implant was replaced with a smaller one, approximately 3 months after its removal. With the others nine patients there was no infection or permanent morbidity. Postoperative appearance was considered very satisfactory, the mandible was well outlined, and the facial proportions were improved. Porous high density polyethylene implant is recommended for hypoplastic mandible augmentation when proper indication are strictly observed and surgical steps are accurately followed.