FEATURE DENTISTRY
INTRODUCTION The variations in root canal morphology, especially in multi-rooted teeth, are a constant challenge for diagnosis and successful endodontic therapy. Complete knowledge of the root canal anatomy is mandatory because the nontreatment of one canal can lead to endodontic failure. Conventional intra-oral periapical
radiographs are an important diagnostic tool in endodontics for assessing the canal configuration. Nevertheless, it is not completely reliable owing to its inherent limitations. Recently newer diagnostic methods such as computed tomography have been valuable in overcoming the disadvantages of conventional radiography by producing a three dimensional image and have emerged as a powerful tool for the evaluation of root canal morphology. The term Dental CT does not
represent a particular modality but rather a specific investigation protocol. The main features of this protocol include the acquisition of axial scans of the jaw with the highest possible resolution together with curved and orthoradial multiplanar reconstructions. Dentists commonly diagnose and work in the submillimeter scale; hence, a highly detailed image quality is required and challenges CT to its technical limits. This article aims at bringing forward
the valuable contributions of dental CT to the field of endodontics.
HISTORY Tomography had been one of the pillars of radiologic diagnostics until the 1970s when the availability of minicomputers and of transverse axial scanning method, this last due to the work of Godfrey Hounsfield and Allan McLeod Cormack, gradually supplanted it as the modality of C.T. The first commercially viable CT scanner was invented by Sir Godfrey Hounsfield in Hayes UK, at EMI Central Research Laboratories using x-rays. Hounsefield conceived his idea in 1967 and it was publicly announced in 1972. Allan McLeod Cormack of Tufts University in Massachusetts independently invented a similar process, and both Hounsfield and Cormack shared the 1979 Nobel Prize in Medicine. The technique of
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‘dental CT’ also called as ‘dentascan’ was developed by Schwartz et al in 1987 when these investigators first used curved multiplanar reconstructions of the jaw.
TECHNIQUE Existing diagnostic methods such as the computerised transverse axial scanning (CT) greatly facilitates access
When compared to medical CT, CBCT has increased accuracy, higher resolution, reduced scan time, a reduction in radiation dose, and reduced cost for the patient
to the internal morphology of the soft tissue and skeletal structures. Recently, a newer CT technique, SCT or volume acquisition CT has been developed that has its inherent advantage. By employing simultaneous patient translation through the x-ray source with continuous rotation of the source-detector assembly, SCT acquires raw projection data with a spiral- sampling locus in a relatively short
period. Without any additional scanning time, these data can be viewed as conventional transaxial images, such as multiplanar reconstructions, or as three dimensional reconstructions. With SCT, it is possible to reconstruct overlapping structures at arbitrary intervals and thus the ability to resolve small objects is increased.
ENDODONTIC APPLICATIONS Specific endodontic applications of spiral CT have been identified as the technology becomes more prevalent. Potential endodontic applications include diagnosis of endodontic pathosis and canal morphology, assessment of pathosis of non- endodontic origin, evaluation of root fractures and trauma, analysis of external and internal root resorption and invasive cervical resorption, presurgical planning, treatment of aberrant and extra root canals, developmental anomalies like dens invaginatus, C-shaped canals, volumetric analysis and more. Tachibana and Matsumoto studied
the applicability of CT to endodontics. They concluded that this method allowed the observation of the morphology of the root canals, the roots and the appearance of the tooth in every direction. Moreover the
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