1. Common disease of teeth and supporting structure

2. The bitewing projection is the most useful radiologic examination for detecting caries.

3. 1-DENTAL CARIES
Radiograph cannot reveal whether the lesion is active or arrested.
So a second radiograph taken at a later time can reveal whether the disease is active.

4. The shape of the early radiolucent lesion.
but other appearances are common, such as a “ notch, ” a dot, a band, or a thin line

5. Distinguish between cervical burnout and proximal caries:
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6. the actual depth of penetration of a carious lesion is often deeper than seen radiographically, Because lesions confined to enamel may not be evident radiographically until approximately 30% to 40% demineralization has occurred.

7. False interpretations
On occasion a carious lesion may be incorrectly detected when the tooth surface is actually unaffected (a false-positive outcome). Various morphologic phenomena, such as pits and fissures, cervical burnout, and Mach band effect, and dental anomalies, such as hypoplastic pits and concavities produced by wear, can mimic the appearance of a carious lesion .

8. What is Mach band effect
Mach bands is an optical illusion named after the physicist Ernst Mach in It exaggerates the contrast between edges of the slightly differing shades of gray, as soon as they contact one another, by triggering edge-detection in the human visual system.

9. This visual phenomenon is important to keep in mind when evaluating dental radiographs for evidence of decay, in which grayscale images of teeth and bone are analyzed for abnormal variances of intensity. Afalse-positive radiological diagnosis of dental caries can easily arise if the practitioner does not take into account the likelihood of this illusion.

10. Mach bands manifest adjacent to metal restorations or appliances and the boundary between enamel and dentin. Mach bands may also result in the misdiagnosis of horizontal root fractures because of the differing radiographic intensities of tooth and bone.Mach effect can also lead to an erroneous diagnosis of pneumothorax by creating a dark line at the lung periphery (whereas a true pneumothorax will have a white pleural line)

12. Lesions with and without clinical cavitation
the presence of cavitation cannot be accurately determined radiographically
Approximately half of lesions that are just into dentin have surface cavitation.

13. Occlusal surfaces
Occlusal lesions commonly start in the sides of a fissure wall rather than at the base and then tend to penetrate nearly perpendicularly toward the DEJ.
The classic radiographic appearance of lesions extending into the dentin is a broad-based, radiolucent zone, often beneath a fissure, with little or no apparent changes in the enamel.

14. Buccal and lingual surfaces
It may be difficult to differentiate between buccal and lingual carious lesions on a radiograph.

15. Root surfaces
Root surface caries should be detected clinically, and most often radiographs are not needed for diagnosis.

16. PERIODONTAL DISEASES
Radiographs play an integral role in the assessment of periodontal disease. They provide unique information about the status of the periodontium and a permanent record of the condition of the bone throughout the course of the disease.

17. It is important to emphasize that the clinical and radiographic examinations are complementary. The clinical examination should include periodontal probing, a gingival index, mobility charting, and an evaluation of the amount of attached gingiva.
Interproximal (bitewing) images more accurately record the distance between the cementoenamel junction (CEJ) and the crest of the interradicular alveolar bone .

18. Note: Panoramic radiographs are not recommended for evaluation of periodontal disease because the distortion and poor image detail of panoramic views tend to lead the clinician to underestimate minor marginal bone destruction and overestimate major destruction.

19. For radiography of the alveolar bone, a beam energy of 80 kVp should be used. Films that are slightly light are more useful for examining cortical margins of bone. A properly collimated beam reduces scattered radiation and improves image definition.

20. Horizontal Bone Loss
Mild bone loss may be defined as approximately a 1- to 2-mm loss of the supporting bone, and moderate loss is anything greater than 2 mm up to loss of half the supporting bone height. Severe loss is anything beyond this point.

22. Vertical Bone Defects
The term vertical (or angular) osseous defect describes a bony lesion that is localized to a single tooth, although an individual may have multiple vertical osseous defects. These defects develop when bone loss progresses down the root of the tooth, resulting in deepening of the clinical periodontal pocket.

24. Often vertical defects are difficult or impossible to recognize on a radiograph because one or both of the cortical bony plates remain superimposed over the defect
gutta-percha

25. Local irritating factors
calculus
Defective restorations with overhanging
poorly contoured margins can also lead to the accumulation of plaque

26. INTERNAL RESORPTION
Internal resorption occurs within the pulp chamber or canal and involves resorption of the surrounding dentin.
Radiographs can reveal symptomless early lesions of internal resorption. The lesions are localized, radiolucent, and round, oval, or elongated within the root or crown and continuous with the image of the pulp chamber or root canal.

28. EXTERNAL RESORPTION odontoclasts resorb the outer surface of the tooth
This most commonly involves the root surface but may also involve the crown of an unerupted tooth.
In many cases the etiology is unknown, but in others causes can be attributed to localized inflammatory lesions, reimplanted teeth, tumors and cysts, excessive mechanical and occlusal forces, and impacted teeth.