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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.

There must be a change in our approach to orthodontic diagnosis, especially in those cases involving skeletal dysplasias. The orthodontic practice of today requires a more in-depth diagnostic approach before a realistic treatment plan can be developed. An understanding of the problem that exists is emerging as the essential ingredient before appliance therapy can begin. Diagnosis should dictate the direction of treatment for both the orthodontist and the surgeon. A cephalometric analysis should be able not only to detect but to locate the area of the skeletal dysplasia. Surgery, if at all possible, should be performed where the problem exists. In many cases, it becomes rather confusing to determine whether or not surgical orthodontic treatment is indicated, because most of the cephalometric measurements that are used do not reveal whether a skeletal problem exists, its location, or its magnitude. We believe that current cephalometric analyses do not completely recognize the extent of the dysplasia or where it is located within the jaws. Because of this, surgery is performed by repositioning bones to mask the defect rather than to restore a normal balance between the bones of the face. The only recourse the surgeon has is to achieve an acceptable facial profile by relying on cephalometric norms or to make the necessary correction on what appears visually to be an acceptable profile. The quadrilateral analysis offers an individualized cephalometric diagnosis on patients with or without skeletal dysplasias. We believe that it is a reliable and accurate method of assessing whether orthodontic treatment, surgical treatment, or a combination of both is required to achieve a satisfactory result.