3 Diagnostic Records

       Aodhan Docherty and Christopher C.K. Ho

3.1 Principles

      3.1.1 Diagnostic Imaging and Templates

      Prosthodontically driven treatment planning is the objective of implant therapy, and imaging is an essential component of diagnosis and treatment planning. The use of radiographic imaging and templates (guides/stents) allow correct three‐dimensional positioning of implants as well as avoiding any critical anatomical zones which may lead to neurovascular injury or damage to other structures.

      Diagnostic imaging provides information about:

      Radiographic imaging is used in pre‐surgical planning to determine the length and width of the proposed dental implant, and the position within the alveolus. Modern implant dentistry requires accuracy of implant positioning to attain natural aesthetics with correct emergence and proper contours of the final restorations. The use of imaging and surgical guides can facilitate proper 3D placement. Poor implant placement can lead to soft tissue deficiencies with loss of papilla, recession, or damage to other anatomical structures.

      Historically, clinicians were limited to using conventional two‐dimensional imaging for dental implant treatment planning. The main drawbacks of 2D imaging are the lack of cross‐sectional information and precise location of anatomical structures [1]. These 2D imaging techniques include the following:

      3.1.1.1 Three‐Dimensional Imaging

      Computed tomography (CT) has revolutionised treatment planning for dental implants. It provides a vast array of images in high resolution, such as panoramic, cross‐sectional, axial, and 3D. The major drawbacks are cost, accessibility, and higher radiation dosage. With radiation dosage in mind, the advent of cone beam computed tomography (CBCT) scanners in the late 1990s have been designed for the maxillofacial region. CBCT imaging reduces the radiation exposure to the patient and is also more accessible as many dental offices and radiology centres possess these machines. CBCT provides high‐resolution images allowing visualisation of anatomical structures and identification of local pathology, and provides multiplanar views of the tissue volume to be investigated. CBCT utilises a cone‐shaped X‐ray beam with both the source and detector rotating around the patient. It is currently the recommended comprehensive diagnostic method to obtain a comprehensive analysis for implant placement. The American Academy of Oral and Maxillofacial Radiology consider the CBCT as a standard of care examination for dental implant planning [2].

Radiographic imaging aims to follow the ALARA principle, which is to use a dose that is as low as reasonably achievable. Intra‐oral radiographs and orthopantomograms typically deliver dosage equivalent to days of background radiation, while the CBCT emits dosages of a week or more of additional background radiation. CT imaging is equivalent to several weeks of background radiation. The CBCT allows selection of smaller field of view (FOV) and by restricting it to the region of interest (ROI) there is a reduction in the effective dose of radiation (Table 3.1).

Table 3.1 Ionising radiation dosage chart: comparing background radiation to both dental, medical and the yearly Australian safety limit.

      Sources: Ludlow, J.B., Davies‐Ludlow, L.E., Brooks, S.L. et al. (2006). Dosimetry of 3 CBCT devices for oral and maxillofacial radiology. Dentomaxillofac. Rad. 35: 219–226; White, S.C. and Pharaoh, M.J. (2009). Oral Radiology: Principles and Interpretation. St. Louis, MO: Mosby Elsevier; Australian Radiation Protection and Nuclear Safety Agency (2016). Radiation Protection in Planned Exposure Situations. ARPANSAR.