Why are there so many types of cepholometric analysis? (there are more than 50!).

It's common knowledge that when the same case is examined using different methods, the results are very often contradictory, why is this?

To calculate the angle between the intersection of two lines, both of which pass through two points (eg.  the cranial mandible angle), only one method has been used: the equations of the two lines are calculated, followed by a system of equations, all of which are backed up by the validity of the results! However, orthodontics is not an accurate science, and we are therefore forced to research the same problem with many different methods,  often obtaining many different results in the process which are then analysed on the basis of often varying theoretical principles! If there is one "right" answer, what is it?

The comparative analyses method selects a collection of measures from a wide range of cephalometric analyses proposed by various different authors, each addressing the same problem and in the following order:

-Sagital relation between maxilla and mandible

-Skeletal vertical dimension

-Dento dental and dento basal relationship

-Aesthetic profile and dimensions

-Growth type

With this system and a fast processing computer, you can easily perform a great number of calculations, compare the relative results and thus reduce the possibility of error.

Just one new measure is introduced in the comparative analyses method: The class index.  This is represented by the ratio between the length of the maxilla  (Tmj Sna) and the mandible length (Tmj Pg), the values being obtained from the Harwold tables, and with this ratio it is possible to determine if an eventual discrepancy between the upper and lower maxilla originates in the over or under development of one base rather than the other, regardless of the respective objective values; we can therefore define them as “relative” hypo, hyper or normal mandibles / maxillas. 

All in all, the class index will always give an accurate indication as to whether the bone structure is too small, too big or in proportion compared with the antagonistic bone structure.

Cephalometric analysis has undergone a major advance in the past few decades.

Many advocates enthusiastically poured out an enormous quantity of cephalometric landmarks, some of which were particularly extravagant if not "improbable".

Operating in this sea of opinions means running the risk of perhaps even going off track!

There won't be room for any more landmark points in cephalometrics of the future, the real challenge will be to extrapolate the best possible meaning from the huge number of already existing points.