Dentists prescribe various radiographic examinations every day to complement their clinical evaluations so as to reach the most accurate diagnoses. Patients rely on the dentist’s professional competency and judgment in interpreting these radiographic images. Extracting the required information is often complicated by the complexity of two-dimensional (2D) representation of three-dimensional (3D) anatomical structures unless the interpreter maintains in-depth familiarity or receives advanced training in oral and maxillofacial radiology.
The recent introduction of 3D cone beam computed tomography enables the dentist to visualize a more complete picture of structures and pathologies of the head and neck area in all dimensions. While this is a great advantage, it adds a level of complexity of dealing with 3D images and emphasizes the importance of the principles of radiographic interpretation to effectively diagnose pathologies and recognize the incidental findings that are present in the 3D scans. The purpose of this chapter is to demonstrate the systematic mental steps that a dentist should take when evaluating dental radiographs. The steps mentioned in this chapter are intended as suggestions for a thorough, step-by-step systematic approach to reviewing radiographs for logical differential diagnoses. However, providers must remain cognizant of the great variety of possible disease processes and consider consulting an oral and maxillofacial radiologist.
Introduction
Dentists prescribe multiple radiographic examinations in daily practice to complement clinical examinations and to help reach the most accurate diagnoses. While patients rely on dentists’ professional competency and judgment in interpreting those images, extracting the required information is often complicated by the complexity of two-dimensional (2D) representation of three-dimensional (3D) anatomical structures unless the interpreter maintains in-depth familiarity or receives advanced training in oral and maxillofacial radiology.
In addition to 2D images, the recent introduction of 3D cone beam computed tomography (CBCT) enables the dental provider to visualize a more complete picture of structures and pathologies of the head and neck area in all dimensions. While this is a great advantage, it adds a level of complexity of dealing with 3D images and emphasizes the importance of the principles of radiographic interpretation to effectively diagnose pathologies and recognize the incidental findings that are present in the 3D scans.
The purpose of this chapter is to demonstrate the systematic mental steps that an oral and maxillofacial radiologist takes when he/she examines a dental radiograph. Fortunately, radiographic appearances of most oral and maxillofacial pathologies have strong correlations with the lesion’s pathophysiology. Vigilance is nonetheless necessary because not all lesions follow typical clinical or radiographic behavior as described in literature.
The steps mentioned in this chapter are intended as suggestions for a thorough, step-by-step systematic approach to reviewing radiographs for logical differential diagnoses. However, providers must remain cognizant of the great variety of possible disease processes and consider consulting an oral and maxillofacial radiologist.
Normal Anatomy
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Knowledge of normal anatomical landmarks, their location/s, and their various presentations is important.
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This reduces the number of “false alarm” diagnoses that can cost the patient time and resources while reducing the dentist’s credibility as a competent practitioner.
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Some of the most common normal anatomy variations that are sometimes misdiagnosed as pathology are discussed in subsequent text.
Take a look at the panoramic image below (▶ Fig. 6.1):
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There is a well-defined corticated radiolucency located inferior to the lower border of the left mandibular canal.
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This is a typical location and appearance for the submandibular gland depression, which is a depression caused by the presence of the submandibular gland on the lingual aspect of the mandible.
▶ Fig. 6.2 shows a 3D volume rendering from CBCT data.
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In this case, radiographic evaluation and diagnosis help eliminate the need for surgical biopsy and/or further imaging studies.
Other normal anatomical landmarks, such as the incisive foramen, are sometimes present in the area of the midline between the maxillary central incisors and should not be mistaken for an abnormality unless the dimensions are larger than a certain size or if they are causing damage (resorption or displacement) to surrounding structures (such as teeth roots). ▶ Fig. 6.3 demonstrates a normal incisive canal while ▶ Fig. 6.4 demonstrates an incisive canal cyst.
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▶ Fig. 6.4 shows apical root lateral displacement secondary to the cystic lesion.
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This root displacement is absent in a normal incisive canal.
Symmetry
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For example, while evaluating a panoramic radiograph, start from the outer structures, such as the temporomandibular joints (TMJs), and compare both sides.
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If there is a severe discrepancy in size, shape, or cortication between the two sides, consider what other processes or pathologies may be occurring.
Consider the appearance of the TMJs in the panoramic radiograph shown in ▶ Fig. 6.5.
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Compare the condylar head, glenoid fossa, and articular eminences’ size, shape, and cortication on both sides (bilaterally).
In the panoramic radiograph below (▶ Fig. 6.6) compare the condylar heads.
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The condyle on the patient’s right shows a continuous cortication and minimal bony changes.
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The condylar head on the left side shows destruction of the cortex with a large round radiolucent area.
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This indicates that a different process other than normal wear and tear (other than osteoarthritic changes) should be considered.
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To better evaluate the TMJ in 3D, small volume CBCT scans of the right and left sides should be acquired and evaluated (▶ Fig. 6.7).
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Noting that this example demonstrates unilateral joint damage, the practitioner needs to consider other conditions that could affect the TMJ unilaterally.
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Systemic medical conditions such as rheumatoid arthritis—an autoimmune disease that could affect different joints in the body unilaterally—ought to be ruled out.
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Consider a referral to the patient’s primary medical doctor for assistance in working up medical conditions that pose risks for unilateral joint changes.
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This case demonstrates that systemic medical conditions may have effects on oral and maxillofacial structures and that dentists may be the first to recognize such conditions.
Mucous Retention (Antral) Pseudocyst
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Evaluate for symmetry when examining the right and left maxillary sinuses.
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Are the sinuses totally radiolucent or do they display shadows of radiopacity?
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Evaluate the floors of both maxillary sinuses for integrity and uniformity.
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If there is a soft tissue shadow (radiopacity) in either maxillary sinus, further examine and try to determine whether the pathology has grown into the sinus (elevated floor of the sinus) or if it has originated from the maxillary sinus and the floor is being pushed or interrupted.
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Consider the panoramic radiograph in ▶ Fig. 6.8.
