Recording Maxillo-mandibular Relationships For Complete Denture
In order to fabricate complete dentures outside of the patient’s mouth, certain relationships need to be transferred to an articulator, which will be used to set the teeth and arrange the denture occlusion. These relationships include:
Occlusal vertical dimension – amount of separation between the mandible and maxilla when the denture teeth will be in contact
Hinge Axis Location – locating the relationship of the maxilla to the transverse horizontal axis and an anterior reference point
Centric position – the horizontal relationship (anterior/posterior and medio-lateral) of the maxilla and mandible, where maximum intercuspation of the denture teeth will be created
Protrusive relationship – used to program the articulator to simulate the relationship of the maxilla and mandible in excursive movements so that the denture teeth can be set in a harmonious relationship
Record Bases (Baseplates) and Occlusion Rims
The maxillary and mandibular casts can be accurately related on an articulator using record bases and wax occlusion rims. The record bases simulate the finished denture base and the wax occlusion rims simulate the position of the teeth for the purposes of making these records. To make the recording of jaw relationships easier, the occlusion rims are made slightly bulkier than the denture teeth to provide additional stability during record making. After the maxillary and mandibular casts are related on the articulator, the bulk of the wax rim is replaced by denture teeth, so that the contours of the denture and position, size and other aspects of the dentures can be evaluated prior to processing. The maxillary record base should be retentive. A non-retentive record base usually results from failure to adapt the resin (particularly from the posterior border and palate) during polymerization. Alternatively, looseness may be caused by over- or under-extension, or by the use of too much blockout. In cases of minimal looseness, a denture adhesive may be used to keep the record base in place. If pronounced looseness exists, time will be saved by remaking the record base prior to jaw relation records. Make the rims slightly higher than required (23 mm average height from the flange of the record base to the rim), so you can reduce the height as necessary.