1. Occlusal Relationships For Removable Partial Dentures
Dr.Shanai M.

2. Occlusal harmony between a removable partial denture and the remaining natural teeth is a major factor in the preservation of the health of their surrounding structures.
Balanced occlusion is desirable with complete dentures because unbalanced occlusal stresses may cause instability of the dentures and trauma to the supporting structures. These stresses can reach a point that causes movement of the denture bases. In removable partial dentures, however, because of the attachment of the removable partial denture to the abutment teeth, occlusal stresses can be transmitted directly to the abutment teeth and other supporting structures, resulting in continued stresses that may be more damaging than those transient stresses found in complete dentures.
The occlusion on a removable partial denture is established with remaining natural teeth by either
1- Intraoral adjustment of the removable partial denture against the natural dentition
2- Extraoral adjustment that is easier for both dentist and patient, is more accurate, and accomplished in a better manner

3. Establishment of a satisfactory occlusion for the removable partial denture patient should include the following:
(1) analysis of the existing occlusion;
(2) correction of existing occlusal disharmony;
(3) recording of centric relation or an adjusted centric occlusion;
(4) harmonizing of eccentric jaw movements for a functional eccentric occlusion; and
(5) correction of occlusal discrepancies created by the fit of the framework and during processing of the removable partial denture.

4. Desirable Occlusal Contact Relationships for Removable Partial Dentures
The following occlusal arrangements are recommended to develop a harmonious occlusal relationship among removable partial dentures and to enhance stability of the removable partial dentures:
Simultaneous bilateral contacts of opposing posterior teeth must occur in centric occlusion.
Occlusion for tooth-supported removable partial dentures may be arranged similarly to the occlusion seen in a harmonious natural dentition, because stability of such removable partial dentures results from the effects of direct retainers at both ends of the denture base.
Bilateral balanced occlusion in eccentric positions is necessary when a maxillary complete denture opposes a mandibular removable partial denture.

5. Working side contacts should be obtained for the mandibular distal extension denture.
Simultaneous working and balancing contacts should be formulated for the maxillary bilateral distal extension removable partial denture. This is necessary due to the unfavorable position the maxillary artificial teeth in relation to the residual ridge

6. Only working contacts need to be formulated for the maxillary or mandibular unilateral distal extension removable partial denture. Balancing side contacts would not enhance the stability of the denture because it is entirely tooth supported by the framework on the balancing side.
In the Kennedy Class IV removable partial denture , contact of opposing anterior teeth in the planned intercuspal position is desired to prevent eruption of the opposing natural incisors, unless they are otherwise prevented from extrusion by means of a lingual plate or by splinting. Contact of the opposing anterior teeth in eccentric positions can be developed to enhance incisive function but should be arranged to permit balanced occlusion.
Artificial posterior teeth should not be arranged farther distally than the beginning of a sharp upward incline of the mandibular residual ridge or over the retromolar pad. To do so would have the effect of pushing the denture anteriorly
Working contact

7. Methods for Establishing Occlusal Relationships
There are four main methods of establishing interocclusal relations for removable partial dentures to fit a partially edentulous situation:
Direct Apposition Of Casts
The first method is used when sufficient opposing teeth remain in contact to make the existing jaw relationship obvious. This can be achieved when only few teeth are to be replaced on short denture bases. With this method, opposing casts may be occluded by hand and later mounted in an articulator.
Interocclusal Records With Bounded Edentulous Spans
A second method is used for bounded edentulous spans but the relation of opposing natural teeth dose not permit the occluding of casts by hand.
Interocclusal wax record alone can be used but is the least accurate because of the
dimensional instability of wax after cooling. Also,
excess wax that contacts the mucosa may distort soft tissue and prevent accurate seating of the wax records onto the stone casts.
distortion of wax during or after removal from the mouth may also interfere with accurate seating

8. Therefore the procedure for making interocclusal wax records alone is as follows:
The patient is exercised the correct closure first
A uniformly softened sheet of wax is placed between the teeth, and the patient is guided to close in centric relation
The wax then is removed and immediately cooled in room-temperature water and replaced a second time to correct the distortion that results from cooling and then again cooled after removal.
All excess wax and especially that in contact with the mucosal surfaces should be removed with a sharp knife
An interocclusal wax record can be further corrected with a metallic oxide paste, which is used as final recording medium. This material is applied to both sides of the metal reinforced wax record and the patient occludes in centric relation.

9. Some of the advantages of using a metallic oxide past over wax as a recording medium for occlusal records include
Ease of displacement on closer.
Accuracy of occlusal surface reproduction.
Dimensional stability.
The possibility of some modification in occlusal relationships after closer, if its made before the material sets
Reduced distortion during mounting procedure.

10. 3.Occlusal relations with distal extension areas using occlusion rims on record bases
Occlusion rims on record bases are used when 1) one or more distal extension areas are present, 2) when a tooth-supported edentulous space is large.
Occlusion rims on a denture base are substituted for missing teeth are used and the procedure for recording centric relation is as follows:
The wax occlusal rims should be reduced in height until out of occlusal contact at the correct vertical dimension of occlusion.
A single stop is then added to maintain the occlusal rims in their correct position until the registering material sets to a hard stat.

11. Any registration material may be placed on the occlusal rims and the teeth are allowed to occlude in centric relation. With any of these materials, opposing teeth must be lubricated to facilitate easy separation. Whatever the recording medium, 1) it must permit normal closure into centric relation without resistance and 2) must be accurate for mounting of casts in an articulator. examples of registration materials quick-setting impression plaster, metallic oxide past, and auto-polymerizing resin

12. 4. Jaw Relation Records Made Entirely On Occlusion Rim
The fourth method is used when no occlusal contact occurs between the remaining natural teeth, such as 1) a maxillary complete denture opposes a mandibular removable partial denture and 2) in rare situations in which the few remaining teeth so not occlude. In any of these situations, jaw relation records are made entirely on occlusion rims.
The choice of method for determining the vertical dimension of occlusion and recording jaw relations is the same as that for complete dentures.