Below: The tracing of a patient’s lateral head X-ray: The outline of the soft-tissue facial profile is not required by the “mathematical” model of the skull. I have drawn it in to assist the viewer to orient themselves. In addition, in the original dissertation study the “calotte” (the very top part of the cranium had to be interpolated since it was absent in all lateral head X-rays.
“The ruler without numbers“
Composite Standard (Norm): Males Age12-years-old (standards were also created for males age 10 and 12, and females age 10,12 and 14
How to use the ruler:
Place the patient’s tracing over the composite-Standard by placing the “X” on the “X” of the standard and make the planes of the tracing and the standard parallel to each other. (Alternative positioning methods are used to detect and evaluate a variety of dimensional and positional deviations from the norm.)
Positioning strategies for overlaying the patient’s skull tracing on the Composite Standard:
Standard Position : (Tracing centered on the “X”) In comparison to the normal male age 12: Fritz’s mid-face is not overgrown. His lower jaw is rotated “down and back” compared to the average 12-year-old. Were his lower jaw in a more normal position is facial height would be at the high limit of normal. The length of his “cranial base” is much shorter than then the normal sample. (“X” to the nose) His upper front teeth lean forward but not drastically. His back molars are positioned very similarly to the normal sample of 12-yer-old males. His lower teeth lean forward moderately. His back molars are positioned more back than the normal sample and that is because his jaw is rotated down and back. Treatment: a device to reposition has jaw forward (encourage his jaw to accept a new more forward position. Plan: use of a fixed “orthopedic” device. The recommended device among others is a “Forcus” lower jaw anterior repositioning appliance. Treatment time 12-18 months to take advantage of the fact of jaw growth during the adolescent pubertal growth spurt.
Center tracing on bridge of nose: If you take the nose point to be normally positioned you would be forced to conclude that the mid-face is excessively forward in relation to the normal sample and that the mandible is in its normal position. Othodontists believe that the variation (excessively larger or small) is rarely seen in the “anterior cranial base”
Tracing centered on Point “Gonion (where the vertical part of the back off the lower jaw meets the horizontal part) “to measures “Length” : the length of the lower border of the lower jaw. The length of Fritz’s lower jaw is “spot-on”.
Tracing centered on the back margin of the lower jaw to measure “Angle” of the of Mandible which orthodontists describe as “obtuse” or “acute” Lower jaws that are obtuse are frequently associated with deep overbites which is Fritz’s condition. Lower jaws showing and acute angle are often associated with “open bites” Clinically when you look at Fritz you would conclude that he has a pushed back lower jaw in relation to a normal looking mid-facial skeleton.
Conclusion: Fritz presents with a Class II division 1 malocclusion. It is a result of the lower jaw having grown down and back in comparison to normal 12-year-old males/ males. The mid-face is not overgrown in comparison to the normal sample of 12-year-old males. The treatment is to promote growth of the lower jaw.