Today’s Dental Imaging: Providing Clinicians Improved Control Over Treatment

The first digital radiography system introduced in dentistry was RadioVisioGraphy by the company Trophy in France in 1987.¹ Since then, advances in both intraoral (periapical, bitewing, occlusal) and extraoral (panoramic, lateral cephalometric, Water’s view) 2-dimensional (2-D) radiography systems have resulted in greatly decreased radiation exposure, along with easier image manipulation and storage. All of these methodologies produce a 2-D image of a 3-dimensional (3-D) object. As a result, overlying structures are superimposed over one another. These images are adequate for the diagnosis of most dental diseases; however, in cases of difficult diagnoses or the planning of many surgical procedures, such as implant placement or third-molar extraction close to the mandibular nerve, advanced 3-D imaging techniques that provide more thorough and detailed information are desirable.¹

First used in medicine in 1973, computed tomography (CT) scanners were made available for dentistry in 1987.¹ Wide acceptance followed the introduction of the cone-beam CT (CBCT) system in Europe in 1996 and in the US market in 2001 by QR s.r.l. (NewTom 9000, www.newtom.it).¹ CBCT has been used for diagnosis in all fields of dentistry. Oral and maxillofacial surgery, endodontics, orthodontics, and implantology have all benefited from CBCT scans, which can be invaluable for the diagnosis of a variety of dental maladies.²

Most recently, the ability to merge computer-aided design (CAD) files from intraoral, laboratory desktop, and facial scanners with the digital imaging and communications in medicine (DICOM) files generated by a cone-beam scanner has expanded the utility of CBCT data beyond the realm of diagnosis. CBCT scans are now also used for planning treatment and for the CT-guided execution of planned treatment.

CBCT data merged with 3-D data from other sources such as stereolithography (.stl) files from scanned models can be used with appropriate planning software to plan complex orthognathic procedures. This approach enables a greater degree of accuracy in predicting changes in soft-tissue profile.

Placement of temporary anchorage devices can be made much more precise using CBCT data. Root proximity, sinus proximity, and the location of the inferior alveolar canal can be accurately measured.

CBCT data, along with CAD data, can be used to design a patient’s smile and occlusion. From the resulting plan, custom orthodontic appliances that will be used to execute the plan can be fabricated for direct bonding to the teeth.³

Presurgical, immediate postsurgical, and long-term postsurgical CBCT data can be overlaid to evaluate treatment progress and stability.⁴

Limited-volume (covering an area less than a complete jaw) CBCT has been used extensively in endodontics. It has been shown to be useful in the diagnosis of periapical lesions and vertical root fractures, and is also beneficial in determining the origin of a lesion as either of endodontic or non-endodontic causes. CBCT is an aid in determining root shape, number of roots and canals, and the location of separated instruments. It not only can be used to diagnose internal and external resorption, but it can determine its extent. As a presurgical diagnostic tool, CBCT is critical to evaluating a tooth’s proximity to vital structures as well as the size, extent, and anatomy of a lesion.⁵

The ready availability of cone-beam scanners in dental offices has had a major impact on the practice of implantology. Many options exist for the use of CBCT data in planning and executing both implant surgery and implant prosthodontics.

The most basic usage of the DICOM data generated by CBCT is to use a simple DICOM viewer to evaluate potential implant sites. Such computer programs are usually supplied with the CBCT scanner. In addition, a number of public domain programs are available for download. More advanced software includes implant libraries that allow for the virtual placement of implants in the plan.

The most advanced planning software lets the clinician plan the implant placement and have a surgical guide fabricated that, when used with the appropriate surgical kit, will allow the implant sites to be prepared and the implants placed, often using a flapless approach. These surgical guides can either be tooth-, soft-tissue-, or bone-supported.⁶

Having the ability to merge a CAD file of the existing dentition from either an intraoral or desktop scanner allows restorative procedures to be precisely planned. A guide solution such as SIMPLANT® (DENTSPLY Implants, www.dentsplyimplants.com) even includes the fabrication of an abutment and provisional restoration, using these merged scans for placement at the time of surgery.

Another benefit of these digital imaging methods is that they serve as an entry point into the digital workflow, ranging from planning to surgery to restoration fabrication. Presently, the “missing link” in the workflow is the integration of this data with the patient’s smile line and facial structures; a try-in still needs to be performed to verify esthetics. Work is currently being done to allow the import of DICOM data from a CBCT into CAD software that combines extraoral facial scans with implant surgical planning and restoration design and milling (Face Hunter, Zirkonzahn, www.zirkonzahn.com; priti®face, pritidenta® GmbH, www.pritidenta.com; ProFace™, Planmeca USA, www.planmeca.com).

Magnetic resonance imaging (MRI) has become the preferred method for visualizing soft tissues; it does not use ionizing radiation.¹ Because it uses a magnet to create an image, MRI may not be safe in patients with pacemakers, defibrillators, some artificial heart valves, or other ferrous foreign bodies. MRI scans are very useful for detection of internal derangements of the temporomandibular joint (TMJ), joint effusions, erosions, and associated bone marrow edemas. MRI is also used to identify soft-tissue neoplasms involving the tongue, cheek, salivary glands, neck, and lymph nodes. Because of the high cost of MRI, its use is limited to instances where it is specifically needed for a correct diagnosis.

Ultrasound is another noninvasive imaging modality that does not use ionizing radiation. Ultrasound can be a useful tool for patients for whom MRI is contraindicated. However, ultrasound examination is usually reserved for the more superficial structures in the head and neck, as the facial skeleton tends to shield the deeper tissues.

Digital imaging is a rapidly changing field. Technologies that were previously “stand-alone” tools are now being integrated with other imaging modalities to provide surgeons, restorative dentists, and dental laboratory technicians with much greater control and precision at each stage of a patient’s treatment. As these technologies become increasingly incorporated into mainstream dentistry, more and more clinicians will begin to realize the benefits of an integrated digital workflow.

Harold S. Baumgarten, DMD
Clinical Professor
University of Pennsylvania School of Dental Medicine
Philadelphia, Pennsylvania
Private Practice
Philadelphia, Pennsylvania