Cephalometric analysis
[1] It is frequently used by dentists, orthodontists, and oral and maxillofacial surgeons as a treatment planning tool.
To carry out cephalometry, the X-ray source is placed a steady five feet away from the mid sagittal plane, with film situated just 15 cm from there.
With an object-to-film interval of 15 cm and a source-to-object span of 5 feet, magnification of anatomical landmarks will be reduced in all three dimensions.When attempting to analyze a patient's anatomy through lateral and frontal cephalograms, the challenge arises due to these images being two-dimensional projections of three-dimensional structures.
Magnification and distortion as an outcome of traditional radiography further complicates the process by blurring important details.
True vertical is an external reference line, commonly provided by the image of a free-hanging metal chain on the cephalostat registering on the film or digital cassette during exposure.
The true vertical line offers the advantage of no variation (since it is generated by gravity) and is used with radiographs obtained in natural head position.
[13] PA ceph can be evaluated by following analyses that have been developed through the years: A cephalometric tracing is an overlay drawing produced from a cephalometric radiograph by digital means and a computer program or by copying specific outlines from it with a lead pencil onto acetate paper, using an illuminated view-box.
Tracings are used to facilitate cephalometric analysis, as well as in superimpositions, to evaluate treatment and growth changes.
Historically, tracings of the cephalometric radiographs are done on an 0.003 inch thick matte acetate paper by using a #3 pencil.
The process is started by marking three registration crosses on the radiograph which are then transferred to the acetate paper.
[14] By using a comparative set of angles and distances, measurements can be related to one another and to normative values to determine variations in a patient's facial structure.
The ANB angle can be affected by multitude of environmental factors such as: Therefore, it measured the AP positions of the jaw to each other.
[21] In this analysis, he tried describing the lower incisor position in relation to the basal bone and the face.
[24] The analysis interprets how the craniofacial growth may affect the pre and post treatment dentition.
The analysis is based on 5 points: Nasion (Na), Sella (S), Menton (Me), Go (Gonion) and Articulare (Ar).
These points are used to study the anterior/posterior facial height relationships and predict the growth pattern in the lower half of the face.
Therefore, a tendency to open bite will occur and a downward, backward growth of mandible will be observed.
Using the O as the centre, Sassouni created the following arcs This analysis was developed by Egil Peter Harvold in 1974.
[29] Medium = -4mm to 0mm Large = -2mm to +2mm This analysis was developed by Charles J. Burstone when it was presented in 1978 in an issue of AJODO.
Computerized cephalometrics offers the advantages of instant analysis; readily available race-, sex- and age-related norms for comparison; as well as ease of soft tissue change and surgical predictions.
Computerized cephalometrics has also helped in eliminating any surgeon inadequacies as well as making the process less time-consuming.
According to American Board of Orthodontics, this method is based on series of study performed by Arne Bjork,[33][34] Birte Melsen[35] and Donald Enlow.
