This document describes the radiographic diagnosis of dental caries. It discusses how caries is caused by acid-producing bacteria and can be diagnosed clinically and through radiographs. Bitewing and periapical films are used to identify caries at different angles. Caries appears at different stages from incipient to severe on radiographs. Factors like tooth thickness and x-ray angle affect detectability. Recurrent, root, and radiation-induced caries are also addressed.

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Caries Diagnosis
The following slides describe the radiographic
diagnosis of caries.
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2. Caries
Caries is the breakdown of tooth structure
caused by acid-producing bacteria in the mouth.
These bacteria are found in the white or pale
yellow plaque that builds up on the teeth if they
are not cleaned properly on a regular basis. The
bacteria break down carbohydrates (sugars) to
form the acid that demineralizes tooth structure,
leading to caries.
The diagnosis of caries is made through a
combination of the clinical examination and
radiographs.
Unless fairly large, interproximal caries in the
posterior region usually requires radiographs to
make a diagnosis.

3. Radiographs
The bitewing film is primarily used for caries
identification, but the periapical film is also helpful.
The difference in angulation between the two films
gives two different perspectives and can be especially
helpful in diagnosing recurrent caries around existing
restorations.
There is a lot of discussion on which film speed (D or
F) should be used. Many dentists use D-speed film
because they feel it provides sharper images as a
result of the smaller grain size. Most educators, on the
other hand, recommend the F-speed film (Insight)
because of the significant reduction in x-ray exposure
to the patient (approximately 60% less than when using
D-speed film).

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Proximal caries susceptible zone
caries
Approximately 40-50 % demineralization is required
for radiographic detection of a lesion. As seen in the
occlusal view, above right, the thickness of the tooth
buccolingually masks the carious lesion when it is
small.
The actual depth of penetration of a carious lesion
is actually deeper than it appears on the radiograph.

5. Factors affecting appearance of caries
on radiographs:
Buccolingual thickness of tooth. The thicker the
tooth, the more difficult it is to see the extent of
the caries.
Limitations of two-dimensional film. The extent of
carious involvement can not be seen in a
buccolingual (cheek to tongue) direction.

6. Factors affecting appearance of caries
on radiographs (continued):
X-ray beam angle (horizontal or vertical). This is
especially important when trying to identify
recurrent caries, since changes in angulation may
cause the superimposition of the existing
restoration with the carious lesion. Overlap due to
improper horizontal angulation makes it very
difficult to diagnose early interproximal caries.
Exposure factors. Caries detection is improved
with a lower kVp setting, which provides a higher
contrast. If the overall density of the film is too
light or too dark, the diagnostic potential of the
film is limited.

7. Transillumination 0
In the anterior region,
interproximal caries can
often be diagnosed using
transillumination, which
involves directing a bright
light through the contact
areas. Combining
transillumination with
radiographs enhances the
diagnostic information transilluminator
obtained.

8. Caries Classification
I M A
A
I = Incipient (Stage I)
M = Moderate (Stage II)
A = Advanced (Stage III) S
S = Severe (Stage IV)

9. Interproximal Caries
(Incipient)
I
Up to half the thickness of enamel
Usually not restored unless patient
has high level of caries activity (high
risk). Treat with fluoride.

10. The arrow points to incipient lesions on the
mesial of # 19 and the distal of # 20.

11. Incipient
Moderate
Advanced

12. Interproximal Caries
(Moderate)
M
More than halfway through the
enamel (up to DEJ)

13. The bottom arrow points to a moderate lesion
on the distal of # 20. The upper arrow points to
one of several incipient lesions on the molar
and premolars.

15. Moderate lesion seen on previous film

16. Class III moderate lesion seen in the
anterior region

17. Interproximal Caries
(Advanced)
A
A

18. Advanced lesion identified by arrows.

19. Advanced lesions seen on previous film

20. Advanced lesion

21. Advanced lesion

22. Interproximal Caries
(Severe)
S
More than halfway
through the dentin

23. Severe lesion

24. Severe lesion

25. Occlusal Caries
Must have penetrated into dentin
Diagnosed from clinical exam
May be seen as thin radiolucent line or
cup-shaped zone underlying occlusal
enamel, but difficult to see on
radiographs unless lesion is large.
Some feel that a sharp explorer used too
forcefully may contribute to spread
of caries by opening up pit or fissure

26. Occlusal caries

27. Occlusal caries

28. Buccal/Lingual
Caries
Should be identified from clinical
exam. Sometimes seen as well-
defined circular area in middle of
tooth, although it is not very
radiolucent. Depth can not be
determined radiographically.

29. Lingual caries (Can’t tell whether it’s buccal
or lingual from one radiograph

30. Buccal caries with severe interproximal
caries on # 12

31. Root Caries
Saucer-like cratering on the roots of the
teeth, involving the cementum. Usually
found on older individuals with
prominent recession and/or
periodontitis. May have xerostomia due
to medications. May be confused with
cervical burnout (discussed on later
slide).

32. Root caries

33. Root caries

34. Cervical Burnout
Cervical burnout is an apparent radiolucency
found just below the CE junction on the root
due to anatomical variation (concave root
formation posteriorly) or a gap between the
enamel and bone covering the root
(anteriorly). Mimica root caries. Posteriorly,
this radiolucency usually disappears when
another film of the region is examined. Caries
does not occur on the root of the tooth unless
there is loss of alveolar bone and gingival
tissue due to recession or periodontitis.

35. Posterior cervical burnout. The invagination
of the proximal root surfaces allow more x-
rays to pass through this area, resulting in a
more radiolucent appearance on the
radiograph. X-rays directed at a different
angle usually pass through more tooth
structure and the radiolucency disappears.

36. Radiolucency seen at left (arrow)
disappears on periapical film of
same tooth. This is cervical burnout.

37. Anterior cervical burnout. The space between
the enamel and the bone overlying the tooth
will appear more radiolucent than either the
enamel or the bone-tooth combination.
bone level

38. Cervical burnout in the
anterior region due to
gap between enamel
(red arrows) and
alveolar bone over root
(blue arrows).

39. Recurrent Caries
Found around the margins of existing
restorations. May be due to unusual
susceptibility to caries, poor oral
hygiene, failure to remove all of the
caries during cavity preparation, a
defective restoration or a combination
of the above.

40. Recurrent caries

41. Recurrent caries

42. Recurrent caries

43. Rampant Caries
Extensive and rapidly progressing
caries usually found in children
and teens with poor diet and
inadequate oral hygiene

45. Radiation Caries
Found in head/neck radiation
therapy patients with xerostomia
Fluoride used for control

47. Before radiation

48. 1 year after radiation

49. Mach Band
Optical illusion giving appearance of increased
radiolucency at the junction of differing tissue
densities, such as enamel and dentin. If you block
off the enamel with a fingernail, the radiolucency
will disappear if due to the mach band effect. If the
radiolucency persists, it may be caries.

50. 0
This concludes the section on Caries.
Additional self-study modules are available
at: http://dent.osu.edu/radiology/resources.htm
If you have any questions, you may e-mail
me at: jaynes.1@osu.edu.
Robert M. Jaynes, DDS, MS
Director, Radiology Group
College of Dentistry
Ohio State University