Mandibular Prognathism (MP) or skeletal Class III malocclusion with a prognathic mandible is one of the most severe maxillofacial deformities. Facial growth modification can be an effective method of resolving skeletal Class III jaw discrepancies in growing children with dentofacial orthopedic appliances including the chin cup, face mask. Orthognathic surgery in conjunction with orthodontic treatment is required for the correction of adult MP.
The two most commonly applied surgical procedures to correct MP are sagittal split ramus osteotomy (SSRO) and intraoral vertical ramus osteotomy. Both procedures are suitable for patients in whom a desirable occlusal relationship can be obtained with a setback of the mandible, and each has its own advantages and disadvantages.
In bilateral SSRO, the intentional ostectomy of the posterior part of the distal segment can offer long-term positioned stability. This may be attributable to reduction of tension in the pterygomasseteric sling that applies force in the posterior mandible. While various environmental factors have been found to contribute to the development of MP, heredity plays a substantial role. The relative contributions of genetic and environmental components in the etiology of MP are unclear.
In this case, the arrangement of teeth is normal when the upper and lower teeth are Occluded.If the chin looks like a jutting chin due to the growth of the mentum forwards or downwards,this is not a genuine mandibular prognathism and it can be fixed easily by plastic surgery on the mentum.
In this case, not only the mandible is protruded forward but also the whole maxillary bone is protruded. Because the whole teeth is protruded, the molars don’t fit together and the lower front teeth is protruded unusually compared to the normal condition of teeth so the upper and lower teeth are not occluded well.In case of normal teeth, the upper teeth are protruded 1-2mm from the lower teeth, but in this case, the lower teeth are protruded from the upper teeth.