The use of 3-dimensional (3D) cone-beam computed tomography (CBCT) imaging in the dental office has become a common imaging modality. The authors present an overview of multiple treatments that would benefit from the use of this technology. From preoperative, intraoperative, to postoperative patient management, 3D technology plays a vital role in the dental practice. With the incorporation of 3D CBCT, intraoral scanners, and 3D printing, a dental provider can accurately plan and execute the treatment with greater confidence. The contemporary dentist, however, has many options for incorporating the digital workflow based on the specific practice needs.
Key points
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The use of three-dimensional imaging in dental office.
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Implementation of digital workflow into dental practice.
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Methods of using computer-assisted design and manufacturing in the dental practice.
Introduction and background
The history and mechanism of image acquisition of cone-beam machines have been discussed in many publications. Small footprint and high clinical value return set 3-dimensional (3D) cone-beam computed tomography (CBCT) apart from other technologies in the clinical setting. The use of cone-beam technology brings an unprecedented diagnostic ability to the dental setting. CBCT is at the core of the digital workflow in the dental office, and the information obtained from these machines combined with digital intraoral scanners (IOSs) and 3D printers facilitates a precise and predictable treatment.
Clinically relevant technical data
CBCT is an invasive diagnostic modality. The terminology describing the radiation emitted during radiographic exposure and how it is measured has been recently modified. Effective radiation is the most important term in everyday clinical practice. It is a measure of the radiation that is determined based on the affected type of tissue. Because organs have variable sensitivity to radiation, a so-called tissue weighting factor exists as a multiplication factor. Gonads, for example, are twice as sensitive to radiation when compared with a structure located in the head and neck region. Therefore, for the amount of exposure, the effective radiation is higher for gonads than for dentoalveolar structures. The effective radiation is measured in milli-Sieverts. A single periapical radiograph has an effective dose of 0.005 mSv, and an average panoramic radiograph has an effective dose of 0.02 mSv. The effective radiation dose from a cone-beam scanner is highly variable with values as low as 0.02 mSv and as high as 1.2 mSv.
The other clinically essential details are the multiple projections within a given computed tomography (CT), their names, and their best uses. Just like bitewings are excellent in detecting interproximal caries, for example, some of the views within a CT are more suitable than others for a particular treatment. Fig. 1 summarizes these views and essential uses. The terminology is consistent with medical CT scans and provides an essential method of communication between practitioners.
Use of three-dimensional imaging in the dental office
General Dentistry
The use of 3D imaging in a dental office for the detection of caries remains quite limited. Two-dimensional intraoral radiographs still provide the most information for a given dose of radiation. 3D CBCT imaging, regardless of quality, results in significant artifacts (especially as the number of metal restorations nearby increases), and detection of caries, fractures, and decay is notoriously difficult with a high rate of false positives. Suspected fractures when detected on 3D CBCT are generally significant enough to be visualized on plain films, whereas the smaller fractures are challenging to spot on 3D CBCT. Although the cross-section may allow better visualization of vertical and oblique fractures, the use of 3D CBCT for the detection of fractures remains to be improved. Recently, software advances have improved artifact reduction and provide better caries detection and a decrease in false positives.
Endodontics
The use of cone-beam imaging is quite widespread in endodontics. In particular, the small field-of-view imaging has gained increasing popularity in practice. This type of imaging has a distinct advantage in dental anatomy representation, decreases radiographic artifacts, and is better able to evaluate healing after endodontic treatment. 3D imaging in endodontics also provides better reduction in the incidence of missed canals and avoidance of complications involving maxillofacial structures. It is also likely that the use of cone beam increases diagnoses of lesions suspected to be pathologic but is in fact superimposition of normal anatomy (maxillary sinus, nasopalatine duct, salivary gland depression). The most significant challenges in the use of CBCT in endodontics is the initial expense of ownership, lack of standardized protocol adopted by practitioners, and liability associated with the sheer volume of diagnostic information. The cost of ownership can be overcome by the availability of equipment financing options offered by many dental suppliers. The American Association of Endodontics has published excellent position papers on the appropriate use of CBCT in the initial diagnosis as well as endodontic treatment. However, in-office rigid radiographic treatment protocols are needed to provide treatment that is consistent with the ALARA principle (as low as reasonably achievable) and maximizes patient care. In what clinical situations and for what teeth requiring endodontic treatment will the cone beam be taken? Is cone beam to be used during the root canal treatment, such as verification of canals or only diagnosis? How would that happen logistically and still keep the field sterile? Is the cone beam to be used for posttreatment evaluation, and if so, what is the plan if adverse treatment is detected radiographically?
When interpreting 3D imaging, the clinician is exposed to considerable diagnostic liability. To successfully interpret cone-beam radiographs, the dentist needs a thorough understanding of head-neck anatomy and a solid background in 3D radiology. Although many dental schools have acquired cone-beam machines, the incorporation of this advanced imaging modality into the curriculum is slow and is taught without integration with patient care. This liability can be further minimized by obtaining a radiology interpretation of the cone beam and by reducing the field of view to include only the area of importance.
Oral Surgery
The use of 3D CBCT for dental and oral maxillofacial surgery is quite common. Most common indications are visualization of root structures of teeth and their proximity to anatomical structures (such as maxillary sinuses and the inferior alveolar canal). When considering dental surgery and the use of 3D CBCT, there are certain assumptions that are made by general dentists, surgeons, and patients that have not been validated by clinical research. First and foremost, obtaining the 3D CBCT itself does not affect the overall risk of complications associated with the inferior alveolar nerve. Second, even with the use of cone-beam technology, there is almost no change in technique for the extraction of wisdom teeth. , In most instances, the same surgical principles are used whether the mandibular canal is on the buccal or the lingual. Some practitioners find CBCT useful in deciding between coronectomy and extraction. 3D CBCT remains a technologically advanced tool and should not be used solely to determine the management of third molars. The treatment is determined based on a multitude of factors, such as the presence of disease, pain, and pericoronitis. In the most severe impaction cases whereby the patient would not accept the small risk of a neurosensory deficit, there is no need to obtain a cone beam, and the 2-dimensional panoramic radiographic image is sufficient because the treatment approach is not changed.
The Use of Three-Dimensional Imaging in a Dental Office to Detect Pathologic Condition
CBCT can also aid in the management of oral and maxillofacial pathologic condition. CBCT has poor soft tissue differentiation, and its use in the management of malignancies remains limited. Dentoalveolar pathologic condition, however, is an excellent indication for 3D CBCT. Fig. 2 shows a section of the cone beam for a patient with odontogenic keratocyst immediately after decompression.
Arguably the first method of formulating the pathologic differential diagnosis should be a 2-dimensional film, and if it does not allow enough visualization, then a 3D CBCT should be obtained. The cone beam provides better localization and better quality of the image so that the differential diagnosis can be more realistic. Fig. 3 demonstrated a panoramic image of the pathologic lesion found on orthodontic examination and failure of adult teeth eruption. The same patient after 3D CBCT ( Figs. 4 and 5 ) was obtained; note both of the premolars and the location of the actual lesion are now visible. This type of image significantly improves the ease of surgical access.
Use of three-dimensional cone-beam computed tomography for dental implants
The mainstream use of cone-beam imaging remains for dental implants. There are specific advantages that 3D imaging provides when considering placing dental implants. For this section, the authors separate implant treatment into planning, the actual procedure for dental implants, and the detection of potential complications associated with dental implants.
The planning for dental implants is significantly more predictable with the use of cone beam. The use of CBCT provides a more efficient workflow in dental practice. For example, a patient who needs dental implants obtains a 3D CBCT in the dental office. The dentist uses a variety of available software to review the 3D radiograph, plans the dental implant placement while virtually determining the size, length, and width of the dental implant, then assures that this actual implant is available in stock and schedules the appointment for the surgery. This workflow eliminates the need for having a significant number of different implant sizes in stock, reduces the overall expense, and provides a better and more efficient workflow.
The cone-beam imaging provides predictable planning for dental implant surgery. Because no magnification is present, the exact width and length of the implant can be determined. The implant can be planned virtually on a variety of available software, and many possible complications can be predicted ahead of time. Many of the modern computer programs also provide a method to place a virtual crown, further improving the position of the implant. Because implant surgery is a restoratively driven procedure, the virtual crown presents an opportunity to visualize the simulated final result and interact with implant components to anticipate the need for custom components and restorative complications ( Fig. 6 ).
