Dr. Beistle proposed the cephalometric “bottom line” which enumerates skeletal and dental landmarks for the analysis. The skeletal A-P shows the maxillomandibular relationships namely Class I, II, II, IIT and IIIT. The “T” notation indicates a tendency towards Class II or III. The patient’s vertical skeletal development is key to stability after the orthodontic treatment. It is determined as the Anterior Skeletal Vertical (ASV) which is an age sensitive measurement of the skeletal anterior facial height. The Upper Incisors, a horizontal length, indicates the position of the upper incisor tip in relation to the anterior arc. The Lower Incisor shows the angle of the long axis of the lower incisor to the mandibular plane. The vertical (clockwise) or horizontal (counterclockwise) growth occurs in a curve or is called arcial. The functional appliance selection relies on the estimation of growth direction. This angular relationship is determined by dividing the Gonial angle into two parts. The upper angle indicates the slant of the ramus while the lower angle shows the slant of the mandible. A larger upper angle indicates a forward (counterclockwise) growth while a larger lower angle predicts a downward and backward (clockwise) growth. The latter portion of the “bottom line” includes the maxillary position, upper first molar position, mandibular position, mandibular length, upper lip angle and the upper inclination to the optic plane. The optic plane, stable skeletal landmark and the true horizontal reference of the analysis, relates with the palatal plane to observe the cant of the palatal plane. The presence of malocclusion may be described by anterior convergence of the two planes. It shows the lack of normal downward and forward growth of the anterior maxilla or the pre-maxilla is tipped superiorly. This is usually caused by an anterior tongue thrust, thumb sucking habit or mouth breathing due to an upper airway obstruction. On the other hand, a posterior convergence of the planes may be due to the lack of posterior dental and skeletal growth of patients with posterior deep bites. This is seen usually in patients with hyperactive masseter muscles, TMJ pain and headache. Most of the anterior or posterior convergence shows a 2-3 degrees angle. This shows that the modified Sassouni Analysis is very beneficial to the treatment of functional orthodontic and TMD patients.
The Modified Sassouni analysis has been shown to be of great benefit to
determine vertical proportion and growth potential of the patient. It has the ability to show incisor position relative to opening and closing trajectory used in neuromuscular and airway studies and where to functionally position the mandible.