Unilateral TMJ hypoplasia: an incidental finding in a cone beam computed tomography (CBCT) study

Troy E. McCartney

McCartney, Troy E.
Faculty / Advisor: Dayo, Adeyinka
University of Pennsylvania School of Dental Medicine, Department of Oral Medicine


To demonstrate the usefulness of cone beam computed tomography (CBCT) as a diagnostic and treatment planning tool in management of Orthodontic patients with Temporomandibular disorders (TMD).


Case report: We present a 26-year-old female patient with history of cleft lip and palate that reports for orthodontic treatment. She was initially worked up with panoramic and lateral cephalometric radiographs and, the temporomandibular joint (TMJ) and mandible were both diagnosed as “within normal limits.” There was no clinical symptoms of bruxing, clenching, pain, disc dislocation, deviation, or locking. However, after acquisition and analysis of a CBCT scan, there was clear indication of left condylar and mandibular hypoplasia. Our report highlights the impact of 3-dimensional nature of the CBCT in the diagnosis of Temporomandibular disorders (TMD).


Temporomandibular joint (TMJ) disorder has been a highly dynamic and evolving study throughout the ages of dentistry. With significant development of imaging modalities, diagnosis of this disorder has advanced past subjective clinical findings to spatial localization and evaluation of the osseous components of the TMJ utilizing 3D imaging techniques such as CBCT and evaluation of the disc and surrounding soft tissue by magnetic resonance imaging. These new advances in technology have positively imparted orthodontics with the ability to utilize CBCT for a variety of diagnosis and treatment planning purposes. We present a case of a patient seeking orthodontic treatment for re-alignment of her teeth to obtain functional occlusion and an aesthetically pleasing dentition/ smile. Evaluation of the panoramic and lateral cephalometric radiograph yielded a “within normal limits” report for analysis of the TMJs. However, the evaluation of the CBCT data and reconstructed panoramic image with the ability to make distinct measurements without geometric distortion, the final diagnosis was left mandibular and condylar hypoplasia. Gross skeletal discrepancies play a significant role in the treatment planning of the orthodontic patient, especially when the TMJs are involved. The initially missed diagnosis emphasizes the importance of providers obtaining the skill for appropriate interpretation of CBCT scans.


CBCT acquisition and interpretation is a critical skill in comprehensive diagnosis of complex cases. The case demonstrates the effectiveness of 3D imaging and the ability to interpret the scans. The case also shows how TMJ hypoplasia plays a consequential role in an orthodontic treatment plan. Clinical Significance: CBCT interpretation is becoming an essential skill for providers of all fields. The ability to interpret, understand and diagnose, all play a comprehensive role in delivering the best possible care for the patient.