Quality Resource Guide l Intraoral Bitewing Radiographic Technique 8th Edition 2 www.metdental.com rectangular collimator into the positioning ring, the radiographic beam is automatically aligned at 90 degrees to the receptor. The one limitation to using the beam alignment device is the potential to sacrifice horizontal alignment resulting in interproximal overlap. To address this limitation, place the holder intraorally and then rotate the biteblock and aiming ring horizontally (mesial or distal) to open the interproximal contact. Characteristics of Diagnostic Bitewing Projections The radiographic projection best suited for the interpretation of dental caries and periodontal disease in the posterior area of the mouth is the bitewing radiograph. This is primarily due to the vertical angulation used in exposing the projection. In contrast, in a periapical projection the vertical angulation can distort the caries lesion or superimpose other structures to mask or hide a lesion or distort bone topography. Figure 1 depicts the projection geometry principles for bitewing and periapical radiographs. With the angulation of a bitewing projection, approximately 40% of a proximal surface is imaged compared to only 15% in a periapical projection. Introduction Bitewing radiographs are the most common intraoral radiographic tool used for diagnosis in dentistry. It is estimated that bitewings account for nearly 60% of all dental radiographic surveys taken. When combined with thorough clinical examinations, bitewings are a valuable diagnostic tool. They are excellent aids for the identification of certain types of pathology, defective restorations, dental caries, and periodontal disease. However, like most radiographic procedures, posterior bitewings are technique sensitive. To prevent or reduce the frequency of technique- related problems, this module will describe the characteristics of good diagnostic bitewings, present three common technique errors, and describe methods for solving technique errors. Bitewing Devices There are primarily two common devices used to expose bitewing projections, bitewing tabs and XCP® bitewing holders. The technique and strengths/weaknesses are discussed. Bitewing Tabs The bitewing tab is attached to the active side of the receptor cover and the circular collimator aligned to completely irradiate the receptor. The collimator is preset at a positive 10 degrees angulation. This angulation allows for maximum display of the proximal contact area of the tooth. The disadvantages of this technique are the inability to use rectangular collimation and the freehand alignment of the beam to the receptor. Beam-Alignment Device (XCP ® ) Use of a beam-alignment receptor holder (i.e., XCP®) allows for the use of a rectangular collimator, which decreases the radiation dose to the patient. The receptor is placed in the holder with the active side facing the collimator. Once the receptor is placed intraorally, as described in this module, the rectangular collimator is aligned to the positioning ring. By anchoring the Because radiographs can detect proximal caries lesions and alveolar bone not easily seen in a clinical examination, it is essential that the radiograph clearly display interproximal surfaces of the teeth and the crestal ridge of the adjacent alveolar bone. For a caries lesion to be detected radiographically, the mineral content of the tissue must change or demineralize 30-50%. As a result, a lesion will often tend to be larger clinically than that displayed by the radiographic image. Thus, an image with adjacent interproximal surfaces not overlapped will enhance the ability to detect lesions early, which in turn impacts management considerations. Problem-Solving Techniques Receptor Placement Packet placement is one of the most critical elements in exposing a diagnostic radiograph. It is also one of the most common sources of error. Because of the contour of the dental arch, it is often difficult to place the packet and angle the beam to create an open proximal contact between those teeth. There are two easy steps that ensure proper placement of the receptor. First, for a premolar bitewing, place the receptor as far forward in the mouth as possible. Second, angle/rotate the receptor so it is positioned behind the mandibular lateral on the opposite side of the mouth. Remember, for improved patient comfort and ease in positioning the packet, place the packet towards the tongue or midline of the floor of the mouth by pushing towards the tongue. This also allows for proper positioning behind the mandibular lateral on the opposite side. This technique is also effective when tori are present. Beam Orientation Proper orientation of the central beam is essential to obtaining diagnostic projections. Horizontal misalignment of the x-ray beam through the interproximal spaces can cause overlap of the proximal areas. When this occurs, the SLOB rule The beam positioning for the bitewing (BW) allows more of the contact area to be imaged compared to the periapical (PA). Figure 1