Cusped Occlusion

Adjusting cusped occlusion requires a little more expertise. The general philosophy is not to remove cusp structure that you will need in another excursion. If a cusp is high in centric, lateral and balancing then of course grind the cusp. This also includes the maxillary lingual cusp which is rarely touched because of its importance as a holding cusp. Draw a diagram for each problem. It will make the solution easier to understand.

A few examples will help you get started. *

Problem 1. The maxillary lingual cusp is high in centric, but correct in working and balancing.

Answer 1. Deepen the mandibular fossa. If you grind the maxillary lingual cusp it will no longer be correct in working or balancing.

Problem 2. The maxillary lingual cusp is high in centric and working but correct in balancing.

Answer 2. Deepen the mandibular fossa and grind the mandibular lingual cusp. Remember the law of BULL. The buccal of the upper and the lingual of the lower are not holding cusps. They can be ground without interfering with the vertical.

Problem 3. The maxillary buccal cusp is in a hyper relationship with the lower buccal cusp in working.

Answer 3. Grind the upper buccal cusp. If you grind the the lower buccal cusp you will take it out of centric contact.

Problem 4. The maxillary lingual cusp is hyper with the lower lingual cusp in working.

Answer 4. Grind the lower lingual cusp.

Problem 5. Both the buccal and lingual cusps are high in the working position.

Answer 5. By now the answer should be obvious. Grind the buccal of the upper and the lingual of the lower.

Problem 6. You can't go into working because on the balancing side the maxillary lingual cusp is hyper with the lower buccal cusp.

Answer 6. You would prefer not to grind either of the holding cusps, but you have to make a choice. Grind the lower buccal cusp. The maxillary lingual cusp has a more stabilizing influence because its force is over the crest of the ridge.

Problem 7. Anterior contact, no posterior contact

Answer 7. Grind the lingual of the upper anteriors and the facial of the lowers.

Problem 8. Posterior contact, no anterior contact

Answer 8. Here we are anticipating contact between the mesial inclines of the lower, hitting the distal inclines of the upper. As previously suggested if the upper lingual cusps are involved grind the mandibular tooth. In general grind the inclines of the non-holding cusps to achieve anterior protrusive contact.

* I have copied this material (with some adaptations) from the Dental Laboratory Technicians' Manual issued by the Department of the Air Force in March 1959 (pages 180-185). I served as a dentist in the USAF.

1981 Board Question

The mesiofacial cusp of the mandibular left first molar is in deflective occlusal contact in the centric occlusion but not in lateral excursions, which of the following might be selectively ground to effect a balanced occlusion?

1. The mesiofacial cusp of the mandibular right first molar
2. The marginal ridges of the maxillary first molar and the second premolar
3. The mesiofacial cusp of the maxillary left first molar
4. the distolingual cusp of the mandibular left first molar

Click for the Answer

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1999 by Julius Rosen, D.D.S.