RADIOGRAPHY AND PERIODONTAL
DIAGNOSIS
radiographs
are often used to supplement diagnostic information gathered through examination
of the soft tissues. The most commonly used radiographs in general dental
practice are bitewings and periapicals;however, an increasing number of
practices are also taking OPG's in their own surgeries |
1. Bitewing radiographs
Bitewing radiographs are
taken to show the proximal surfaces of the teeth and the crest of the alveolar
bone of both the maxilla and the mandible on the same film. While they
are used primarily to detect interproximal decay, they can also provide
some information on the patient's periodontal status. The height of the
interproximal alveolar· bone margin relative to the cemento-enamel
junction can be observed. Also, deposits of subgingival calculus may be
detected. However, the value of bitewing radiographs in the diagnosis of
periodontal diseases is limited by the fact that only the coronal sections
of the roots of the teeth are observed, and they are limited to the molar-premolar
regions.
In younger individuals,
careful observation of the alveolar bone height around first permanent
molars may help detect those individuals at risk of early-onset forms of
periodontitis (juvenile periodontitis and rapidly progressive periodontitis).
However, radiographs should be used only as a supplement to a careful clinical
examination using a periodontal probe around such sites, as up to 30 per
cent of bone may be lost before it is evident radiographically.
2. Periapical radiographs
Periapical radiographs are
frequently used not only to aid the differential diagnoses of patients'
presenting symptoms, but also to screen for otherwise undetected pathological
processes of the teeth and surrounding alveolar bone.
In the diagnosis of periodontal
diseases, periapical radiographs can provide useful information that cannot
be obtained through examination of the soft tissues alone. Such information
includes:
a) Teeth
-
Clinical crown-root ratio:
In essence, this term refers to the ratio between the length of the root
that is surrounded by bone and the remainder of the tooth.
-
Shape and size of the crown
and root: A tooth with a small crown and a long root has a better prognosis
than one with a large cr-own and a short root. A tapered root has less
surface area for periodontal attachment than a blunt root.
-
Position of the roots in
multirooted teeth: In rnultirooted teeth, roots close together present
a poorer prognosis than those which are widely separated.
-
Position of a tooth in relation
to adjacent teeth: Open contact points or close proximity of adjacent
teeth can be seen in radiographs, and may highlight areas where periodontal
problems are occurring.
-
Presence of callculus: Both subgingival and supragingival calculus deposits can be seen on periapical
radiographs.
-
Presence of root resorption:
internal or external root resorption can be detected.
-
The contours and margins
of restorations: The relationship between interproximal overhangs and/or
poorly contoured restorations, and loss of periodontal bone can be screened
by radiographic examination.
-
Fractures of the root: A tooth with a horizontal or vertical root fracture can present with periodontal
symptoms.
-
Foreign bodies and root tips:
these may produce or aggravate periodontal lesions and can best be
detected in radiographs.
-
Pulpal anatomy and pathology: the shape of the pulpal chamber and root canals can be seen, as well as
pulpal pathology.
b) Bone
The pattern of bone loss
around individual teeth can be determined only through examination of radiographs.
Periapical radiographs, using the lon~- cone paralleling technique, provide
the most accurate representation of the height of the bone in relation
to the CEJ, and to the actual length of the tooth. In the examination of
bone features in periapical radiographs as part of periodontal diagnosis,
special attention is paid to:
Pattern of bone loss:
is the bone loss horizontal or vertical?
Extent of bone loss:
is the bone loss generalised over the dentition or localised to certain
teeth?
Severity of bone loss:
this can be expressed in percentage terms, taking normal bone height to
be just below the CEJ, and accounting for the length of the root.
Furcation involvement:
is there evidence of radiolucencv in furcation areas?
Lamina durn: The significance
of the lamina dura is unclear. Whereas its presence indicates good supporting
bone, its absence does not always signify pathology.
Periodontal lignment space:
A widening of the periodontal ligament space may indicate that the tooth
is subject to occlusal forces or is mobile. It may also be an early sign
of pulpal inflammation, therefore a careful clinical examination is necessary
to make a diagnosis.
3. Panoramic radiographs:
Panoramic radiographs provide
a general view of the oral structures, and are useful for screening bone
loss patterns in general. They are not suitable for accurate assessment
of the degree of bone loss associated with individual teeth, as there is
severe distortion and the outline of the bone rnargin is often unclear
due to superimposition of intervening structures.
Technical problems with
radiographs
Rinn device - posterior area
Variations in x-ray technique
that produce distortion, coupled with the projection of a three-dimensional
object onto a two-dimensional plane, limits the diagnostic value of the
radiograph. The bone level, the pattern of bone destruction, the radiodensity
and trabecular pattern of the interdental bone, all are modified by altering
the exposure and development time, the type of film and the x-ray angulation.
These features must be considered when trying to compare pre- and post-treatment
radiographs. The long cone paralleling technique is recommended for all
periapical radiographs taken for periodontal diagnostic reasons, as it
produces the most realistic image of the alveolar bone.
Rinn device - anterior area
The bisection of the angle
technique increases the angle of projection and makes the bone margin appear
closer to the crown; the level of the facial bone is distorted more than
the lingual. Shifting the cone mesially or distally without disturbing
the horizontal plane pr-qjects the x-rays obliquely and changes the image
of the interdental bone, and may distort the extent of furcation involvement.
For these reasons, it is strongly recommended that you use beam aligning
holders for taking long-cone parallel technique radiographs. (for example
the RINN aligning devices, available through Dentsply). This technique
also allows for more standardised comparisons of radiographs over time
even if taken by different operators.
Recording of radiographic findings
It is important to note the findings of your radiographic examination
in the patient's treatment record, and to mount and store the radiographs
for fUture reference. Notations in the treatment record should indicate:
-
the date the radiographs were
taken
-
the type of radiographs taken
-
the reason for taking the radiographs
-
diagnostic information gained
from examination of radiographs
-
further diagnostic tests that
may need to follow up any pertinent radiographic findings.
This material has been
compiled with the assistance of Dr Louise Brown, Lecturer in Periodontics
at the University of Melbourne.
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