The quadrilateral analysis: a differential diagnosis for surgical orthodontics.

The integration of the diagnostic and treatment skills of both the orthodontist and the maxillofacial surgeon has become a standard procedure in the treatment of severe dentofacial dysplasias. Orthognathic surgery, surgery without prior tooth movement, is being replaced by an interdisciplinary approach as the treatment of choice. When a proper tooth-to-denture-base relationship is obtained, an ideal maxillomandibular relationship can be achieved surgically. The quadrilateral analysis enables the practitioner to obtain an individualized skeletal, dental, and soft-tissue assessment of each patient requiring treatment. It determines the direction and extent of the skeletal dysplasia in millimeter measurements and allows the clinician to outline the appropriate surgical orthodontic procedures. The quadrilateral analysis indicates that in a balanced facial pattern a 1:1 ratio exists between the maxillary bony base length (Max.Lth.) and the mandibular bony base length (Mand.Lth.); also that the average of the anterior lower facial height (ALFH) and the posterior lower facial height (PLFH) equals these bony base lengths. Simply stated, the Max.Lth. = Mand.Lth. = (formula; see text) An accurate diagnosis locates the area and quantifies the magnitude of skeletal dysplasia. Then the correct placement of a dentition within the denture bases and the appropriate surgery in the area of dysplasia can produce an individualized, balanced facial pattern.