Rationale for Occlusal Adjustments
Occlusal adjustment, through selective grinding of the tooth surfaces, is one modality of improving the overall contact pattern of the teeth. It can be used as an adjunct to orthodontic, restorative or prosthetic and endodontic (emergency) treatment. Occlusal adjustment may involve one or multiple, natural and or prosthetic teeth. Indications for Occlusal Adjustment:
- To eliminate isolated occlusal interferences, when a tooth becomes symptomatic after the placement of a new, hyperoccluding restoration or following orthodontic treatment (In rare cases, therapeutically-induced changes in occlusion can be associated with the onset of TMD-like symptoms. In these uncommon instances, adjustment of the occlusion may be warranted, as it will decrease the pain and mobility and it will improve function, but it should be undertaken with as little invasiveness as possible.)
- When it is determined that a periodontally involved tooth has increased mobility which is due to traumatic occlusion rather than solely to attachment loss
- In the management of symptomatic fractured teeth or of prosthetically restored teeth which fracture repeatedly
- Occasionally, prior to procedures which will result in major occlusal changes, such as prosthetic reconstructions
- Following orthodontic treatment to correct minor interferences that cannot be corrected solely by tooth movement
- As a form of limited supportive therapy, e.g. when a tooth in parafunction becomes hypermobile and hypersensitive, keeping in mind that selective grinding does not replace treatment aimed at decreasing parafunction (In these cases the occlusal contact should be reduced, but not eliminated altogether.)
- Following occlusal splint therapy, selective grinding is indicated, once occlusal appliance therapy has eliminated the TMD symptoms, and only if it is determined that the symptoms would disappear permanently, if the occlusal contacts and jaw position provided by the appliance were permanently reproduced in the patient’s occlusion.
- Following the placement of implant-supported crowns, in order to decrease the incidence of biomechanical complications, such as crown-screw loosening or denture tooth fracture.
With regards to the management of TMDs, routine, prophylactic removal of occlusal interferences is not indicated, as the severity of malocclusion does not correlate well with the severity of TMD symptoms, in part due to the great variance in individual patient tolerance levels, in part because malocclusions are often stable and cause no adverse TMD signs or symptoms. On the contrary, clinical research indicates that TMD signs and symptoms, especially if they have been present for a short duration (less than one year), are often self-limiting and require no treatment whatsoever.
Extensive restorative and prosthetic procedures, resulting in major occlusal changes, sometimes require prior selective grinding, so that a stable functional mandibular position is established, to which the new restorations, with optimal occlusal contacts, can be fabricated. In these cases, the end result of occlusal adjustment must be determined in advance by performing mock adjustments on mounted casts, as only minimal corrections are possible within the enamel layer of the teeth. If more extensive surface alterations are necessary, the patient must be prepared for the possibility that crown restorations might, eventually, be required.
Occlusal Adjustment Guidelines
With respect to the removal of vertical interferences, the rule of thirds can be used to determine if selective grinding should be attempted. Accordingly, if the occlusal interference represents a cusp tip occluding against the opposing cusp incline close to the opposing fossa, selective grinding is likely to eliminate the interference without exposing dentin. If, however, the cusp tip occludes against the opposing cusp incline closest to the opposing cusp tip, selective grinding would likely expose dentin, and restorative procedures would be, eventually, required.
With respect to the removal of horizontal, lateral or anterior-posterior interferences, it may be expected that slides of less than 2mm can be eliminated by selective grinding.
Occlusal Adjustment Goals
- Develop a stable intercuspal position in CO, so that all possible posterior teeth centric cusp tips contact opposing flat surfaces evenly and simultaneously with the occlusal forces directed along the long axis of teeth
- Develop a plane of occlusion with adequate inter-arch space for prostheses replacing missing teeth
- Provide laterotrusive contacts to disocclude the posterior teeth when the mandible moves laterally
- Provide anterior contacts to disocclude the posterior teeth, when the mandible is protruded
- In the upright head position, provide for heavier contacts of the posterior teeth than of the anterior teeth.
Contraindications to Occlusal Adjustment
- The absence of signs and symptoms of TMD
- The presence of acute orofacial pain and /or dysfunction unrelated to occlusion
- When the occlusal adjustment would require grinding beyond the enamel (e.g. slides greater than 2mm).
Occlusal Adjustment Procedure for natural teeth or combinations of natural and fixed or removable bridges
- The patient is reclined.
- The teeth are brought together the patient identifies the side of the first contact.
- The first contact is identified with double-sided articulating paper (Accufilm) and confirmed with a shim stock.
- The contacting inclines are reshaped (using fine diamond or carbide burs) as either a cusp tip, if the contact is near the cusp tip or as a flat surface, if the contact is near a fossa (as the inclines are adjusted into cusp tips and flat surfaces, the VDO approaches the ICP, intercuspal position).
- The teeth are adjusted so that the maximum number of teeth can occlude.
- Once established, the posterior contacts should not be altered.
- There should be only light contact between the anterior teeth.
- Anterior guidance is developed by providing canine or canine and incisor contacts, when the mandible moves anteriorly and laterally. The occluding surfaces in excursive movements are marked with articulating paper of one colour and the maximum intercuspation contacts are marked in a different colour. The posterior excursive contacts are then removed, creating the anterior guidance.
- If the canines are not in position to guide the mandible initially, the bicuspid or even molar buccal cusps can be used. The posterior non-working contacts are removed.
- The bicuspid and molar lingual cusps should not contact in lateral and anterior movements.
- Once the occlusal adjustment in the reclined position is completed, the occlusion is evaluated with the patient in the upright position. Here again, the contacts between the anterior teeth should be lighter than that between the posterior teeth.
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