Occlusal schemes in prosthodontics: guidance is chosen from what remains, not from theory

The debate on occlusal schemes is among the most ideological in dentistry, with schools defending opposing positions for decades. The clinical evidence is less clear-cut than the positions suggest.

The three main schemes have different indications. Canine guidance has only the canines contacting in lateral movement, disoccluding all other teeth; group function distributes contact across several teeth on the working side; balanced occlusion maintains contacts on the non-working side as well.

Balanced occlusion has one precise and limited indication: the complete denture. There, balanced contacts stabilise the base during movement, whereas in natural dentition they would be a source of overload.

Between canine guidance and group function, the choice depends on the available canine. A canine with intact periodontal support and a sound crown can assume guidance; one with attachment loss or a compromised crown cannot withstand the concentrated load.

Group function is therefore indicated where the canine is weak, absent, or where rebuilding its guidance would require excessive crown lengthening.

The principle common to all schemes in natural dentition is posterior disocclusion in eccentric movements. Posterior sectors must contact in maximum intercuspation and separate in lateral and protrusive movement.

The reason is biomechanical: a posterior contact during an eccentric movement creates a third-class lever with the condyle as fulcrum, and the resulting forces far exceed those of contact in centric.

The non-working side interference is the one with the greatest documented consequences: cusp fractures, debonding, loosening of implant screws. It must be actively sought, because the patient does not perceive it.

Articulating paper should be used in two colours and in sequence: centric contacts in one colour first, then eccentric movements in the other. A single colour produces an illegible pattern on which adjustment becomes guesswork.

Paper thickness matters: 200-micrometre papers mark contacts that do not in fact exist. For refinement, thicknesses of 8 to 12 micrometres are used, marking only real contacts.

On a limited rehabilitation, the most prudent choice is almost always to copy the existing occlusion. If the patient has functioned for years with group function, imposing canine guidance means changing an established neuromuscular pattern without necessity.

Rebuilding from nothing is different: there, canine guidance is preferable where the canines allow, because it reduces load on posterior sectors and simplifies management of the restorations.

In summary: copy the existing occlusion when it works, choose canine guidance when rebuilding and the canine holds, use group function when it does not. And always look for non-working side interferences, because those are the ones the patient never reports.