Occlusal Scheme in Complete Dentures — A Key Decision at Wax-up

Why does the occlusal scheme matter for functionality?

The occlusal scheme dictates how denture teeth interact during mastication. A poor scheme results in denture instability during chewing (lateral forces displace the base).

Curing a denture with a poor scheme means the patient will complain, "I can't chew, my denture moves."

Balanced Occlusal Scheme

Tooth Geometry

In a balanced scheme, teeth are designed (crown geometry) such that:

1. In a resting position, they masticate evenly (upper + lower tooth).
2. During mastication (lateral movements), forces are distributed evenly across both sides of the denture base.

Advantages

1. Denture Stability — Masticatory forces work evenly, preventing lateral denture movement.
2. Patient Comfort — Less discomfort during chewing.
3. Longevity — The denture doesn't "work" laterally, reducing wear of the denture base material.
4. Standard — The balanced scheme is the standard taught in universities.

When to Choose

• Patient has strong masticatory force (naturally muscular).
• Patient exhibits bruxism (grinds teeth at night).
• Patient desires maximum stability.
• Patient has minimal residual ridge (little bone) — necessitating reliance on a good occlusal scheme.

Lingually Inclined Occlusal Scheme

Tooth Geometry

In a lingually inclined scheme, teeth are designed with a lingual inclination (towards the tongue). This provides:

1. Faster "disengagement" of the fossa during chewing.
2. Reduced lateral forces (teeth are more "vertical," less "sweeping" laterally).

Advantages

1. Simpler Design — Less design time in CAD.
2. Faster Printing — Simpler geometry, quicker layer slicing.
3. Esthetics — Teeth appear more natural (lingual inclination is the natural position of anterior teeth).
4. Less load on implant (if overdenture) — More vertical forces.

When to Choose

• Patient has weak masticatory force (elderly, lack of muscle).
• Patient does not exhibit bruxism.
• Patient desires a more natural appearance.
• Patient has a substantial residual ridge (plenty of bone) — can afford a less stable scheme.

Comparison of Schemes

Errors in Occlusal Scheme Design

1. Incorrect scheme for the clinical scenario — The clinician thinks, "the patient is elderly, so lingually inclined," but the patient has bruxism → wrong choice.
2. Lack of communication with the lab — The clinician doesn't specify the desired scheme, and the lab decides on its own (which might be unsuitable).
3. Excessively inclined teeth — Even in a lingually inclined scheme, the inclination can be too great → the denture will move.
4. Discrepancy between wax-up and final cure — It looks good at try-in (wax-up is accurate), but changes after curing (rare, but happens).