Selective Grinding Technique for Final Balancing of the Occlusion in Complete Dentures

INTRODUCTION

A denture relies on a different type of retention system than is found in natural teeth. In order to stabilize the disadvantaged denture; a special lingual contact occlusion has been developed with a bilaterally balanced denture occlusion. The objective of balancing a denture occlusion is to create simultaneous bilateral contacts from the centric relation position to all eccentric occlusal positions that are free of interferences.
These multiple contacts should be smooth, uni¬form, and in harmony with the temporomandibular joints and neuromuscular activity. Once achieved, first by the proper positioning of the teeth during the set up and then refined by selec¬tive grinding, a lingual contact balanced occlu¬sion also provides lever stability for the denture bases

Requirments for Balancing the Occlusion

There are four specific conditions that must be met by the mandibular posterior teeth in order to achieve a balanced occlusion:

1. Mandibular posterior teeth must be set so that the occlusal surfaces are horizontal
2. The plane of occlusion must have a proper orientation
3. A compensating curve must be set
4. The teeth must be modified so that there are no interlocking transverse ridges

The maxillary teeth must be

1. Modified to eliminate buccal cusp contact,
2. Set so that the upper lingual cusps have a positive but static centric occlusal contact,and
3. Have no buccal cusp contacts in lateral excursions

SELECTIVE GRINDING FOR CENTRIC CONTACTS

Once the initial balance is achieved during the set up of the maxillary posteriors, the complete occlusion must be refined by selective grinding. First remove the incisal guide pin so that only the teeth are holding the proper occluding ver¬tical dimension. A length of thin articulating paper is placed on the posterior teeth, and the articulator is gently tapped several times in cen¬tric occlusion. There should be marks on each of the areas.
If marks show on lower cusp inclines, gently grind the inclines to eliminate deflective contacts. If there are any upper lingual cusps out of contact, the non occluding maxillary teeth are repositioned by mov¬ing the lingual cusps down into contact. It is also possible to selectively grind the teeth into a stable centric occlusion. Only the lower central fossae or marginal ridges should be ground, not the upper lingual cusps. If any significant grind¬ing is done on the lower teeth, the occlusal vertical dimension will be reduced and anterior interference will occur. The method of attaining a stable centric occlusion in which all the upper lingual cusps are in the lower common central fossa depends on the assessment of the problem.
If the non occluding upper lingual cusps are nearly in contact, modest grinding can be done, as it will not significantly close the occlusal ver¬tical dimension. If any upper buccal cusps or inclines are in contact, they should be ground out of contact. Only the upper lingual cusp, that is the pestle of the mortar-and-pestle-type lingual contact occlusion, should articulate with the lower posteriors. The final result after several tapping’s and spot grindings should be stable contacts with all upper lingual cusps in the common lower central fossae. The occlusion is now ready to be refined for working and balancing contacts.

SELECTIVE GRINDING FOR WORKING AND BALANCING CONTACTS

When the mandible moves to the left this becomes the working side. The upper left lin¬gual Cusps should contact the lower left lingual cusps. The right side is then the balancing side, and the upper lingual cusps should contact the lower buccal cusps. Only one lateral excursion (either the left or right) should be checked at a time. After the working and balancing contacts for left lateral excursion have been equilibrated, then check the right lateral excursion.
Place a strip of thin articulating paper between the posterior teeth bilaterally. While keeping gentle pressure on the maxillary mem¬ber of the articulator, move it to the right (this is equivalent to moving the mandible to the left). This duplicates a left lateral excursion. Ideally, in this occlusal scheme there should be five working cusp contacts, five balancing cusp con¬tacts, and no upper buccal cusp contacts. When functioning as balancing contacts, upper lingual cusps ride lower buccal (lingual-facing inclines) cusp inclines diagonally. When acting as work¬ing cusps, upper lingual cusps pass between modified triangular ridges of the lower lingual cusps that run either to the marginal ridge or to the groove between the cusps of the lower mo¬lars.
There usually is some prematurity on the working or balancing side that prevents total working or balancing cusp contact. Grind the marked premature balancing contacts, heavily marked working side contacts, or both, on the lower teeth. By selectively spot grinding the premature inclines and cusps, a smooth harmonious multiple contacts of the desired contacts will occur. Do not grind the upper palatal cusp.
There may also be upper buccal cusp contact on the working side. This is usually the result of inadequate buccal cusp rise made during the setup. The upper posterior teeth may be reset to increase clearance if the contact is severe or may be ground if the contact is slight. Do not grind the lower buccal cusp.. There should be no up¬per buccal cusp contact in any excursion.
As the premature inclines and high cusps are selectively ground until there is simultaneous contact of working and balancing cusps, the cusp rise is gradually reduced. This may create ante-rior interference on the working side, which must be eliminated. Usually, there is sufficient com-pensating horizontal overlap for any vertical overlap to allow for a simple solution by grinding. The lingual of the upper incisal edges and the labial of the lower of anterior ground to eliminate any interference that develops while selectively grinding to balance occlusion.
Grinding on the anterior always be conservative so that the esthetic value of the anterior is not disturbed. When it is apparent that selective grinding to balance occlusion will cause anterior interference the upper posterior teeth should be reset to open the occlusal vertical dimension enough to clear the the anterior teeth after balancing for eccentric excursions. The finished result should be a smooth gliding left lateral excursion with ten simultaneous working and balancing contacts (five working and five balancing contacts). Now equilibrate the right side with opposite lateral excursion in the same manner.

SELECTIVE GRINDING FOR PROTRUSIVE BALANCE

The upper right and left second molar cusps should ride up the distal inclines of the lower right and left second molars with enough rise to clear the anteriors. There should be no interfer¬ence between the buccal cusps of the upper teeth and any of the lower buccal cusps. The movement itself must be smooth .If anterior interference occurs, either move or grind the lower offending anterior tooth slightly or increase the distal incline on the lower second molar by increasing the compensating curve.

CONCLUSION

In order to achieve a lingual contact balance occlusion to provide lever stability for the denture it is mandatory to correct small discrepancies in the intial setting as well as error due to small tooth movement during the final waxing by judicious selective grinding

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