The evolution of Sassouini Analysis

The success of orthodontic treatment lies in careful diagnosis and treatment planning. The cephalogram provides descriptive information of the patient’s skeletal and dental malocclusion. The radiographic data are analyzed to predict growth patterns and determine case classifications in order to arrive at a well studied and effective treatment plan for each patient.

The Sassouni analysis was developed in 1955 by Dr. Viken Sassouni of the University of Pittsburgh. He measured 100 Caucasian children aged 7-15 years (51 females/49 males) of mainly Mediterranean origin. It was the first method to highlight vertical and horizontal relationships as well as the interaction between vertical and horizontal proportions. His analysis focused on skeletal proportions rather than absolute statistical values. They preferred the concept of proportionality over the concept of arithmetic normality. Simply by drawing lines and angles, a visual assessment of the proportionality may be clearly seen. Sassouni showed that the horizontal anatomic planes – anterior cranial base plane, Frankfort plane, palatal plane, occlusal plane and mandibular plane – converge posteriorly at a single point O in well-proportioned faces. The angle of each plane shows the vertical proportionality of the face. The analysis, which is also popularized as Archial analysis, uses the anterior and posterior arcs to study vertical facial proportions and to analyze the divergence of the horizontal planes. All growth direction is archial and does not occur on a straight line.

In 1984, The Sassouni+ Analysis, a complete craniomandibular analysis, was first introduced by Dr. Richard Beistle of Buchanan, Michigan. The authors used the visual format of Sassouni analysis to determine facial and skeletal growth patterns. It is useful in evaluating patients from a functional and neuromuscular perspective including TMJ and airway function. It combined the parameters of Sassouni Archial analysis and the Plus portion consists of landmarks from Ricketts, Downs, Steiner, Tweed, Bjork, and Jacobson analysis. Though it is a comprehensive analysis, it is time consuming to use. There were nineteen landmarks used except for porion and orbitale. Such points were the following: sella, clinoidale, sella superior, sella inferior, clinoidale, roof of orbit, floor of the orbit, cribriform point, supraorbitale, temporale, nasion, articulare, posterior nasal spine, anterior nasal spine, A-point, constructed gonion, B-point, pogonion, gonion and menton. Then the planes are constructed: the supraorbital plane, parallel plane, palatal plane, occlusal plane, mandibular plane, infraorbital plane, and optic plane. A Center O point is located by the intersection of the four major planes: the mandibular, palatal, occlusal and parallel planes. Using the landmarks and the origin of the compass set at Center O, the archial analysis is done involving five arcs: the Anterior arc (to Nasion), ANS Arc (to ANS), “A” Arc (to A Point), Midfacial Arc (to Temporale), and Posterior Arc (to Sella posterior wall). The eight important factors must be considered essential prior to orthodontic treatment were: (1) skeletal A-P relationship, (2) skeletal vertical relationship, (3) direction of growth, (4) an assessment of the lower face height, both numerically and proportionally, (5) the angulation/position of the upper and lower incisors, and the position of the upper first permanent molar, (6) an assessment of the soft tissue profile, (7) the size and position of the maxilla relative to the cranium, and (8) the size and position of the mandible relative to the cranium.

In the 1987 Simplified Sassouni+ Analysis, Dr. Beistle simplified the analysis to only three short linear and three angular measurements The PLUS part enables us to predict a growth pattern which is either counterclockwise or clockwise occurring as a curve. As a guide, the analysis provided eleven questions named as the cephalometric “bottomline”, which, when answered, provides a comprehensive data on the cephalometric state of the patient. The questions include the following, what is (1) the skeletal AP relationship? (2) the skeletal vertical relationship? (3) the position/angulation of the upper incisor? (4) the position/angulation of the lower incisor? (5) the direction of growth? (6) the length of the maxilla? (7) the location of the maxilla relative to the cranium? (8) the position of the upper 1st permanent molar? (9) the length of the mandible? (10) the position of the mandible relative to the cranium? (11) the upper lip angle? Dr. Beistle intended to provide a simpler updated analysis that is useful to diagnosis and treatment planning in dentofacial orthopedics.
In 2006, Dr. Jay Gerber and Dr. Thomas Magill, further improved the analysis as the Modified Sassouni Cephalometric Analysis with the additional parameters such as the dentoalveolar compensation (DAC), effective length of premaxilla (ELP) and upper incisor angulation to optic plane. Similar to the previous analyses, it emphasized the importance of the growth direction indicator or the treatment response indicator, which is the split gonial angle. This is constructed by drawing a line from nasion to constructed gonion forming a division of the upper (slant of Ramus) and lower (slant of the body of the mandible) compartments of the mandibular gonial angle. The upper compartment indicates horizontal or counterclockwise growth while the lower compartment indicates vertical or clockwise growth. The two parts are measured based on excess or deficiency to determine growth direction and subsequent selection of the appropriate functional appliance. The percentage of growth pattern is determined by dividing the upper angle by the lower angle. The analysis provided a chart of values for growth prediction which could be neutral growth, clockwise tendency, clockwise growth, extremely clockwise growth, counterclockwise tendency, counterclockwise growth or extremely counterclockwise growth. The direction of growth determines how the mandible will respond to functional orthopedic therapy. The Modified Sassouni Analysis is very helpful in functional orthodontics and temporomandibular disease treatment. Similar to the previous analysis, it is useful in determining vertical proportion and growth potential of the patient. It can show incisor position in relation to opening and closing trajectory. It can also determine where to position the mandible for functional advancement.