Cephalometric radiographs are used in orthodontic diagnosis to evaluate the pre-treatment dental and facial relationship of a patient, to evaluate changes during treatment and to assess tooth movement and facial growth at the end of treatment. On the cephalometric film, teeth can be related to one another, to the jaw in which they reside, and to cranial structures. The maxilla and mandible can be related to one another and other structures into the cranium and the soft tissue profile can be evaluated. Cephalometric analysis is one among various diagnostic aids.
An orthodontic diagnosis is not possible only on the basis of cephalometry. Cephalometric analysis is an important aid in orthodontic diagnosis only if its findings are correctly and wisely interpreted with the help of other diagnostic aids.
In the cephalometric assessment, certain carefully defined points are located on the radiographs, and linear and angular measurements are made from these points. The expressions of these measurements in various ways produce analysis of skeletal size and form.
Types of Cephalogram
There are following two types of cephalograms
- Lateral cephalogram: Lateral cephalogram provides a lateral view of the skull (Fig. 1.1). It is taken with the head in a standardized reproducible position at a specified distance from the source of the X-ray. Lateral cephalogram commonly is used for cephalometric analysis.
- Frontal cephalogram: This provides an antero-posterior view of the skull (Fig. 1.2).
Uses of Cephalometric Analysis
- Cephalometric analysis is routinely used for diagnostic purpose to assess whether malocclusion dental or skeletal in origin.
- It enables clinician to know accurately the extent to which patient deviates from described norms.
- It is used to monitor the changes occurring due to growth or treatment or their combination. In other words, precise evaluation of patient's response to treatment is made possible.
- Yet another use of cephalometrics is to predict changes that should occur in future for patient after orthodontic treatment. An architectural plan / blueprint of orthodontic treatment.
The cephalometric radiographs are taken using an apparatus that consists of an X-ray source and a head holding device called cephalostat. The cephalostat consists of two ear rods that prevent the movement of the head in the horizontal plane. Vertical stabilization of the head is brought about by an orbital pointer that contacts the lower border of the left orbit. The upper part of the face is supported by the forehead clamp positioned above the region of the nasal bridge. The distance between the X-ray source and the mid-sagittal plane of the patient is fixed at 5 feet (152.4 cm). Thus the equipment helps in standardizing the radiographs by use of constant head position and source film distance so that serial radiographs can be compared.
There are many systems of cephalometric analysis, which utilize various points and outline on the lateral cephalogram radiograph.
Cephalometric X-ray Tracing Techniques
Masking tape is used to attach the cephalometric X-ray to the acrylic acetate tracing paper sheet. Tracing is made on the frosted surface of acetate tracing sheet.
The tracing is begun by marking the hard and soft tissue points needed for the analysis on the tracing sheet. Soft tissue profile is traced and then the sella turcica going forward to the planum sphenoidale along the floor of the anterior cranial fossa of the shadows of the greater wings of sphenoid bone are traced. The anterior surface of the frontal and nasal bones are then traced followed by tracing the outline of the maxilla and from the anterior nasal spine along the floor of the nasal cavity back to posterior nasal spine from posterior nasal spine.
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