Blog post by Sabine von Sinner, SSOP Teacher
For fully removable prostheses, the stability and proper function of dentures depend on a bilaterally balanced occlusion, i.e. simultaneous and harmonious contacts on both sides during protrusive and lateral mandibular movements. To understand the factors that influence this balance, Rudolph Hanau described a basic concept known as Hanau's Quint. This concept combines the five factors that determine occlusal balance and that need to be harmonized in the arrangement of the denture teeth.
The first factor is the condylar guidance, which represents the inclination of the condylar path within the temporomandibular joint. It is an anatomical feature that is specific to each patient and cannot be changed by the practitioner.
The second factor is the incisal guidance, which is determined by the vertical overlap and the horizontal overbite of the anterior teeth. In contrast to condylar guidance, it is adjustable and should be kept as low as possible in full dentures in order to reduce destabilizing forces.
The third factor is the occlusal plane, which refers to the alignment of the occlusal surfaces in relation to anatomical and esthetic reference points.
The fourth factor is the cusp inclination, which depends on the type of denture teeth selected (anatomical, semi-anatomical or non-anatomical).
The fifth factor is the balance curve, a combined anterior-posterior and mediolateral curvature that is fixed in the posterior tooth arrangement to maintain tooth contact during mandibular movements. The relationship between these factors is expressed by Hanau's Quint formula: occlusal balance is proportional to the product of condylar guidance and incisal guidance divided by the product of occlusal plane, cusp inclination and compensation curve.
This relationship means that these factors are interdependent: As one factor increases, the others must be adjusted to maintain occlusal balance. In clinical practice, condylar guidance is determined by the patient's anatomy, so the clinician mainly controls the modifiable factors by reducing the incisal guidance, selecting an appropriate tooth morphology, properly aligning the occlusal plane and establishing an appropriate compensation curve. Thus, Hanau's Quint serves as an important clinical guideline for achieving a functional, stable and comfortable occlusion in fully removable dentures.
