Natural occlusions come in all arrangements. Although straight teeth, good interdigitation and maximum intercuspation gives the maximum stability and functional efficiency, sometimes crroked teeth also may seem to be stable and functional. So why would anybody make the teeth straight to improve stability and function?
So when is orthodontic intervention necessary to change or improve the teeth arrangements?
For me that decision is made when the patient meets one of two criteria:
- The signs and symptoms present in the occlusion have exceeded the patients adaptive capacity and hence are likely to show or already are showing signs and symptoms of degradation.
- If the dentistry required will need the change in the occlusal relationship to attain seated joint position and maximum intercuspal position.
When one or both of these criteria is met, the orthodontist must now fulfill a set of requirements for designing a stable occlusion.
Requirement 1:
The condyle and disk are appropriately positioned in the glenoid fossa in centric relation
Requirement 2:
Posterior teeth touch simultaneously in centric relation.
Requirement 3:
Occlusal forces are directed down the long axis of the teeth.
Requirement 4:
Front teeth have light contact in the maximum intercuspal position. This relates to providing freedom for the movement of the condyle in translation as well as rotation in early opening and late closing.
Requirement 5:
Absence of jaw deviation during function.
Requirement 6:
Canines are the guiding teeth when ever possible.
Requirement 7:
Anterior guidance moves as far forward as quickly as possible, eventually transferring the contact to the incisors at end-to-end.
Requirement 8:
If group function is appropriate premolars are preferred over molars.
Requirement 9:
No balancing side interferences.
Requirement 10:
Straight protrusive moves on both centrals smoothly and evenly. Movements of the mandible side-to-side during protrusion create a disharmony as the muscles
