CT in addition to 3D images offer several advantages over conventional radiography: it eliminates anatomical noise and high contrast resolution, allows differentiation of tissues with less than 1% physical density difference to be distinguished in comparison to conventional radiography that requires 10%. When examining jaws, axial scans are usually acquired to avoid artifacts caused by posts, crowns, and metallic fillings .

CT can even supply additional information about the morphology of the root-canal system provided that it does not contain metallic root-canal posts . However, the geometric resolution of CT is insufficient to reveal the exact shape of the root-canals , and a very high radiation dose is required to achieve a high enough resolution to assess root-canal anatomy in detail .CT may also be useful for the diagnosis of poorly localized odontogenic pain. In some circumstances in which periapical radiographs reveal nothing untoward, CT may confirm the presence of a periapical lesion .

The assessment of the ‘third dimension’ with CT imaging allows the determination of the number of roots and root canals,as well as where root canals join or divide. This knowledge is useful when diagnosing and managing failed endodontic motor treatment. CT can also be used to localize foreign bodies in the jaws such as gutta-percha and root-canal sealer. CT in endodontics has however some disadvantages such as the high radiation dose and the high costs of the scans . Other disadvantages are scatter due to metallic objects, relatively low resolution in comparison to conventional radiographs.

Micro-computed tomography (micro-CT), another alternative CT technique, has been considered in endodontic imaging .The use of micro-CT remains a research tool limited to in vitro measurementsof small samples; due to the high radiation dose required, and cannot be employed for human imaging in vivo .

Ultrasound imaging is based on the reflection of sound waves (echoes), with a frequency outside the rangeof human hearing (1-20 kHz), at the interface of tissues which have different acoustic properties . The echoesare detected by a transducer which converts them into an electrical signal, and a real-time black, white and shades of grey echo picture is produced on a computer screen .

The technique is easy to perform and may show the presence, exact size, shape, content and vascular supply of endodontic lesions in the bone . Ultrasound has been found to be a reliable diagnostic technique in the differential diagnosis of periapical lesions (granulomas versus cysts) with the aid of the echo picture (hyperechoic and hypoechoic) and through the use of the colour laser Doppler effect to provide evidence of vascularity within the lesion .

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