1. Occlusal Relations for R P D
Dr. Monia M.N.Kandil

2. Occlusal Relations for R P D
In complete dentures:
Balanced occlusion is desirable on complete dentures because occlusal stresses may cause instability of the denture or trauma to the supporting structures.
In partial denture:
occlusal stresses are transmitted directly to the abutment teeth and other supporting structures, the resultant stresses may be more damaging than those transient stresses formed in complete denture. Therefore, it is important in PD to establish functional and harmonious occlusion.

3. In PD the remaining natural teeth influence the form of the denture teeth and must conform to an already established occlusal pattern, but in case of an opposing C.D. it can be made to harmonize with the partial denture.
In cases when only anterior teeth remain on both arches the recordings of jaw relations and the arrangement of teeth may be preceded in the same manner as with C.D.

4. Requirements of satisfactory occlusion:
To establish satisfactory occlusion the following factors are required:
1- Analysis of the existing occlusion.
2- Correction of existing occlusal disharmony.
3- Recording the centric relation.
4- Recording the eccentric (functional) relations.
5- Correction of occlusal discrepancies created in the denture.

5. General considerations in desirable occlusion of PD
a- Avoid placing the artificial teeth over the retromolar pad area to avoid shunting of the denture anteriorly.
b- Positioning the mandibular buccal cusps on the buccal turn point of the crest, to direct the occlusal stresses towards the buccal shelf, “primary stress bearing area”.
c- Positioning of the maxillary buccal cusps slightly buccal to the maxillary ridge, which is an unfavorable condition, but it is counteracted by direct retainers on the other side or by contact in the balancing or working sides (balance occl.).
d- Using of narrow artificial teeth buccolingually or using of smaller size canines and premolars instead of premolars and molars, to decrease the forces transmitted to the underlying structures.

6. Common occlusal disharmonies:
Problem I
Mesial inclination of the posterior molar severely
Solution:
1- Recontouring, through flat reduction distally
of the drifted tooth.
2- Restoring the tooth by crowns.
3- Orthodontic repositioning.
4- Extraction if it is severely damaged.

7. Loss of interarch distance
Problem II
Loss of interarch distance
Solution:
Approximately 2mm of enamel can be removed, but if the extrusion is greater than 1-2 mm, placement of an extracoronal metallic restoration is indicated.
In severe cases posterior segment osteotomy may be effective in correction of this problem.
Anterior maxillary osteotomy may also be effective for patients with severe protrusion of the anterior teeth or deep vertical overlap.

8. Problem III: Irregular or mal posed occlusal Plane
Solution:
1- Enameloplasty if the extrusion is in one cusp (1-2 mm).
2- Extracoronal metallic restoration.
3- Posterior or anterior segmental osteotomy.
4- Extraction of the malposed tooth or teeth.

9. Problem IV: Traumatic vertical overlap of anterior teeth
Solution:
Early recognition of the problem and treatment with orthodontic or combined orthodontic or orthognathic surgical procedures are the treatment of choice.

10. III - Recording the centric relation
According to
1-The number and distribution of existing teeth.
2-The decision whether the teeth will be arranged in centric occlusion or centric relation.

11. Methods of establishing occlusal relationship
1 - If there is sufficient number of teeth; either by:
a- Direct apposition of the casts, or,
b- Interocclusal record with posterior teeth remaining:
i. using Jone’s bite framework, or
ii. interocclusal wax record.
2- If there is no sufficient number of teeth:
Occlusal relation using occlusal rims on recorded bases.
Jaw relation records made entirely on occlusion rims.
Functional generating path method (dynamic occlusion).

12. a- Direct apposition of casts
1 - If there is sufficient number of teeth; either by:
a- Direct apposition of casts
If there are at least 3-4 positive contacts between the posterior natural teeth at each arch, then the upper and lower casts can be opposed by hands against each other, sticky wax and wire loops are needed to fix the casts together.
Advantage:
Avoid errors from patients.
Disadvantage:
The occlusion is controlled
By the exsisting vertical dimension

13. b- Interocclusal records with posterior remaining teeth
This technique is used if there are remaining posterior teeth but not sufficient to be opposed by hand e.g. class III Kennedy PD.
i- Jone’s bite framework.

14. b- Interocclusal records with posterior remaining teeth
ii. interocclusal wax record
Adjustable framework is used to relate mandibular cast to the previously mounted maxillary cast.
This technique done by using uniformly softened reinforced wax wafer corrected by zinc oxide paste or quick setting stone over the wax .

15. b- Interocclusal records with posterior remaining teeth
This technique is used if there are remaining posterior teeth but not sufficient to be opposed by hand e.g. class III Kennedy PD.
ii. interocclusal wax record.

16. a. RPD Jaw Relation Records Using Record Base Attached to the Framework.
Indications:
1 - In case of distal extension areas.
2- Long teeth bounded saddles.
3- No contact between opposing natural teeth.

17. b- Jaw relation records made entirely on occlusion rims
Used when there is no contact between the remaining natural teeth.
Maxillary complete denture opposed by mandibular PD.
Maxillary class I partial denture opposed by lower anterior natural teeth.
When the remaining natural teeth are few and do not occlude.
Jaw relation records in this
case is the some as for CD cases.

18. b- Jaw relation records made entirely on occlusion rims

19. Determination of the occlusal plane depends on:
Do not forget
Determination of the occlusal plane depends on:
1- Aesthetic base.
2- Functional base (chewing and speech).
3- Physical and mechanical bases (leverage action and parallelism).

20. c- Functional generating path method (Dynamic occlusion)
This technique produces an occlusion that is in functional harmony with the facial skeleton, the musculature, the TMJ and the remaining natural teeth.
advantage:
It eliminates the need for adjustment of an articulator and the need to make a face bow transfer because.
All the information desired are recorded in the pathway

21. Disadvantage:
1- If the two arches are partially edentulous, the occlusion in one of the arches must be complete before a generated patient can be developed.
2- If a partial denture is opposed by a complete denture, the partial denture must be constructed first in the conventional method and then the CD is constructed according to the functionally generated path.

22. Technique:
1- Construct an accurate, stable and finished acrylic denture base attached to the metallic framework.

23. 2- Fix the wax occlusion rim to the denture base
2- Fix the wax occlusion rim to the denture base. This wax should be hard enough to support biting stress and should be tough enough to resist fracture (Peek's purple hard inlay wax).

24. 3- The occlusion rim wax must have enough height and width to record all extremes of mandibular movement.
N.B: There must be positive occlusal contacts with the opposing dentition in order to avoid loss of vertical dimension.

25. 4- The patient should wear the occlusion rim constantly for a period of 24 hours or more including night time, except for removal during meals.

26. 5- The patient is instructed to chew and glide to curve the wax by the opposing teeth (To perform all voluntary excursive and involuntary movements).
6- If during this period the wax occlusion rim has not been reduced to the natural occlusal contact. The patient is instructed to use it for another 24 hours, till the registration is completed and accepted.
7- The accepted occlusion rim should show a continuous intact glossy surface indicating a functional contact with opposing teeth in all extremes of movements.

27. 8- Boxing the occlusal rim with wax filled with hard stone to form the occluding template.

28. 9- The whole assembly is then mounted onto a hinge articulator.
10- Open the articulator and remove the wax and arrange the teeth to the opposing natural or artificial teeth and the occlusion is established.

29. To avoid the failure of this technique:
11- Teeth are arranged and modified to occlude with the template and not according to rules of setting up of teeth.
To avoid the failure of this technique:
The denture base should be well supported