Dawson Classification RevisitedThe most commonly used occlusal classification in dentistry, the Angle’s classification,5 fails to observe the relationship of the teeth to the TMJs or consider the health, position, or condition of the TMJ. By contrast, in the Dawson classification,6 the health and stability of the joint is a primary concern, as well as the relationship of the joints to the maximal intercuspation. A joint that is changing position or deteriorating will directly impact the arch-to-arch relationship and ultimately radically affect occlusion.
Dawson I: Maximum intercuspation isin harmony with the CR.
This is one of the primary goals for the completion of occlusal therapy for a healthy TMJ. The teeth occlude in maximum intercuspation when the condyles are in CR (which is the maxillo-mandibular relationship when the properly aligned, condyle-disc assemblies are in the most superior position against the eminentiae, irrespective of tooth position or vertical dimension).7
Dawson Ia: Maximum intercuspationis in harmony with ACP.
This is one of the primary goals for the completion of occlusal therapy for a disordered TMJ. The teeth occlude in maximum intercuspation when the condyles are in ACP (the manageably stable relationship of the mandible to the maxilla that is achieved when deformed TMJs have adapted to a degree that they can comfortably accept firm loading when completely seated at the most superior position against the eminentiae).8 Technological advances using conventional computed tomography images or cone-beam computed tomography (CBCT) are indispensible aids in determining when a disordered TMJ is stable.