1. 24
The Use of Radiographs in the Detection of Dental Caries

2. Objectives Define the key words.
Explain why caries appear radiolucent on radiographs.
Define the role radiographs play in detecting caries.
Identify the ideal type of projection, technique and exposure factors that enhance a radiograph’s ability to image caries.

3. Objectives
List and describe the four categories of the caries depth grading system.
List the four locations of dental caries and identify their radiographic appearance.
Define and identify the radiographic appearance of recurrent dental caries.
List three conditions that resemble dental caries radiographically and discuss how to distinguish these from caries.

4. Key Words Advanced caries Arrested caries Buccal caries Caries
Cemental (root) caries
Cementoenamel junction (CEJ)

5. Key Words Cervical burnout Dentinoenamel junction (DEJ)
Incipient (enamel) caries
Interproximal
Interproximal caries
Lingual caries

6. Key Words Mach band effect Moderate caries Nonmetalic restoration
Occlusal caries
Proximal caries
Rampant caries
Recurrent (secondary) caries
Severe caries

7. Introduction
The detection of caries (tooth decay) is probably the most common reason for exposing dental radiographs.
The dental hygienist and dental assistant who is skilled in identifying normal radiographic anatomy, should be able to differentiate between the appearance of normal tooth structures and dental caries on a radiograph.

8. PROCEDURE 24-1 Radiographic interpretation for caries

9. Dental Caries
Description
Detection

10. Figure Proximal surface caries found just apical to the contact area between two adjacent teeth.

11. TABLE 24-1 Radiographic Appearance of Caries

12. Figure 24-2 Vertical angulation
Figure Vertical angulation. (1) Excessive vertical angulation prevents viewing this proximal surface carious lesion. (2) Proper vertical angulation shows the proximal surface caries. Note the difference in alveolar bone crest heights between the two radiographs indicating a change in the vertical angulation.

13. Figure 24-3 Horizontal angulation
Figure Horizontal angulation. (1) Incorrect horizontal angulation causes overlapping between adjacent teeth, which prevents viewing for interproximal caries. (2) Improved horizontal angulation, but caries difficult to view. (3) Correct horizontal angulation clearly images caries.

14. Figure 24-4 Periapical radiograph records proximal surface caries.

15. Figure 24-5 Drawing showing ratio of caries to enamel
Figure Drawing showing ratio of caries to enamel. X-ray A passing through a small ratio of caries to enamel, resulting in the caries being difficult to view. X-ray B passing through a large ratio of caries to enamel, results in the caries being easier to view.

16. Figure Diagram of classification of dental caries recommended by Haugejorden and Slack. (1) C-1 caries. Less than halfway through the enamel (incipient caries). (2) C-2 caries. Penetrate over halfway through the enamel (moderate caries). (3) C-3 caries. At or through the dentinoenamel junction (DEJ), but less than halfway through the dentin toward the pulp (advanced caries). (4) C-4 caries. Penetrate over halfway through the dentin toward the pulp (severe caries).

17. Figure Drawing indicating the area to examine for interproximal caries. View the area where two adjacent teeth contact, and apical down to where the gingival margin would most likely be (boxed area). Avoid mistaking caries in the region apical to the gingival margin, where the optical illusion cervical burnout is most likely to be appear.

18. Classification of the Radiographic Appearance of Caries
There are four locations on the tooth where caries occur:
Proximal (mesial and distal)
Occlusal
Buccal/lingual
Cemental (root surface)

19. Figure 24-8 Drawing of occlusal caries, early stage
Figure Drawing of occlusal caries, early stage. Early occlusal caries (C-1 and C-2) extend along the dentinoenamel junction (DEJ) and may not be seen on the radiograph, even though the lesion may be detected clinically.

20. Figure 24-9 Drawing of advanced occlusal caries
Figure Drawing of advanced occlusal caries. Advanced (up to halfway toward the pulp) or severe occlusal caries (more than halfway toward the pulp) will most likely be imaged radiographically.

21. Figure 24-10 Radiograph of occlusal caries
Figure Radiograph of occlusal caries. (1) Severe occlusal caries appearing as a large radiolucent lesion in the first molar.

22. Figure 24-11 Drawing of buccal or lingual caries
Figure Drawing of buccal or lingual caries. Advanced buccal or lingual caries have well-defined borders.

23. Figure Radiograph of buccal or lingual caries on this mandibular second premolar appears as a round radiolucency (superimposed over the pulp chamber).

24. Figure Drawing of cemental (root) caries illustrates involvement of only the roots of teeth. Gingival recession and bone loss precede the demineraliztion process to expose the root surfaces.

25. Figure 24-14 Radiograph of cemental (root) caries
Figure Radiograph of cemental (root) caries. The large radiolucency on the distal surface of the distal root of the first mandibular molar is cemental caries. Note the bone loss exposing the root surface.

26. Figure 24-15 Radiograph of recurrent caries
Figure Radiograph of recurrent caries. (1) Radiolucent caries under the metallic restoration.

27. Figure 24-16 Radiographs of rampant caries
Figure Radiographs of rampant caries. Multiple teeth affected by severe cemental caries.

28. Figure Radiograph of nonmetalic restorations and carious lesions in anterior teeth. (1) Radiolucent nonmetallic restorations on the mesial surface of the lateral incisor and distal surface of the central incisor. Note that under both restorations is a base of radiopaque material. (2) The radiolucencies on the mesial surfaces of both central incisors are carious lesions.

29. Conditions Resembling Caries
Nonmetallic restorations
Cervical burnout
Mach band effect

30. Figure 24-18 Drawing of cervical burnout
Figure Drawing of cervical burnout. (1) Thin cervical root surface between dense crown and alveolar bone crest allows more x-rays to pass and reach the image receptor. This cervical area of the teeth will most likely be imaged at an increased radiolucency.

31. Figure 24-19 Radiograph demonstrating cervical burnout
Figure Radiograph demonstrating cervical burnout. Note the radiolucent optical illusion of cervical burnout on the mesials and distals between the enamel and restorations and the alveolar crest of bone.

32. Figure 24-20 Caries and optical illusions that mimic decay
Figure Caries and optical illusions that mimic decay. (1) Severe occlusal caries. (2) Radiolucent lines creating a mach band effect caused by overlapped enamel. (3) Incipient distal surface caries. (4) Cervical burnout.

33. Review: Chapter Summary
The detection of caries is probably the most common reason for taking dental radiographs.
Caries appear radiolucent because the demineralization of the tooth allows more x-rays to pass through to reach the image receptor.

34. Recall: Study Questions
General
Chapter Review

35. Reflect: Case Study
You are interpreting a full mouth series of radiographs on a patient who had dental hygiene services at your facility this morning. The completed patient’s dental examination chart is available, but the patient has been dismissed. As you examine the radiographs, you notice the following:

36. Reflect: Case Study
Incipient proximal caries on the distal of the maxillary right first molar.
Describe the radiographic appearance of this lesion.
Indicate why you classified this lesion as incipient.

37. Reflect: Case Study
Moderate proximal caries on the mesial of the maxillary left first premolar.
Describe the radiographic appearance of this lesion.
Indicate why you classified this lesion as moderate.

38. Reflect: Case Study
Advanced proximal caries on the mesial of the mandibular left second premolar.
Describe the radiographic appearance of this lesion.
Indicate why you classified this lesion as advanced.

39. Reflect: Case Study
Severe proximal caries on the distal of the mandibular right first molar.
Describe the radiographic appearance of this lesion.
Indicate why you classified this lesion as severe.

40. Reflect: Case Study
Advanced occlusal caries on the maxillary right second molar.
Describe the radiographic appearance of this lesion.
Indicate why you classified this lesion as advanced.

41. Reflect: Case Study
Cemental caries on the mesial of the mandibular right first premolar.
Describe the radiographic appearance of this lesion.
Indicate why you classified this lesion as cemental.

42. Reflect: Case Study
The patient’s chart indicates incipient occlusal caries detected clinically on the maxillary left first and second molars. However, these do not seem to be evident radiographically.
Explain why these caries are not observed on the radiographs.

43. Reflect: Case Study
The patient’s chart indicates incipient buccal caries detected clinically on the mandibular left first molar. However, this lesion does not seem to be evident radiographically.
Explain why the buccal caries is not observed on the radiographs.

44. Reflect: Case Study
The radiographs reveal two radiolucencies resembling cemental (root) caries around the cervical of the mandibular right first and second premolars. However, the patient’s chart does not indicate that cemental caries were detected clinically.
Explain the possible cause of these radiolucencies.

45. Reflect: Case Study
The periapical radiograph of the maxillary left molar region is overlapped between the maxillary first and second molars.
Explain why detecting caries in this area will be compromised.
What optical illusion will most likely present in this area?
Describe the appearance of this optical illusion.

46. Relate: Laboratory Application
Proceed to Chapter 24, Laboratory Application, to complete this activity.