1 Recording Bases and Occlusion Rims

Record blocks are generally made of occlusion rims attached to well fit trial denture base. 2

3

Recording bases The recording base (trial denture b ase) It is used for recording maxillo mandibular jaw relationships and fo r setting the artificial teeth. 4

Requirements of an ideal recording base 1- Dimensionally stable, both on the cast an d in the mouth. 2- They must be rigid and strong. 3- They must be well adapted to the cast an d accurately fit the denture area. 4- They should retain their shape at mouth te mperature. 5

6 5- They should have smooth and round bord ers. 6- They should be non-irritant 7- They should be easy to manipulate. 8- Easily contoured and polished 9- They should be of proper thickness

Types of recording bases 7 I- Temporary recording ba ses II- Permanent recording ba ses

I- Temporary recording bases 1- Shellac baseplate 2- Cold curing acrylic resin 3- Vacuum formed vinyl or polystyr ene. 4- Baseplate wax. 5- Swaged tin baseplate. 8

II- Permanent recording bases It is the base of the finished denture. Th e materials used for permanent bases a re: 1- Heat-curing acrylic resin 2- Casted metal (gold, chromium-cobalt alloy and chromium nickel). 9

Temporary recording bases 1- Shellac baseplate It is a commonly used material for recording bases. 10

11 To increase strength and rigidity of shel lac base plates, reinforcing wires shoul d be embedded across the posterior pal atal seal area for the upper trial denture base and in the lingual flange of the low er one.

12

13

14 Advantages 1- Easily and quickly made. 2- Stronger than wax. 3- Laboratory time is saved. 4- Inexpensive.

15 Disadvantages 1- It is difficult to obtain good retention. 2- distortion may occur when left for a long ti me in the mouth. 3- It is a brittle material. 4- The bond between the shellac base and th e wax is less than that of acrylic base.

2- Cold-curing acrylic resin -Non -flasking method -Flasking method 16

17

18

19 Advantages 1- They are strong and have accurate fi t. 2- Do not soften or warp at mouth temp erature. 3- They are not easily distorted 4- Any type of occlusal rims can be mo unted to it.

20 Disadvantages 1- The retention may be reduced due to bloc king out of the undercuts on the cast. 2- They may take up space needed for settin g the teeth, necessitating some grinding of th e resin base in required areas.

3- Vacuum -formed vinyl or polysterene The vacuum method is very ea sy, fast and gives accurate resu lts. 21

4- Baseplate wax Advantages 1- Easily to construct. 2- Inexpensive. 22

8- Modiolus The point of meeting of buccinator and other facial muscles distal to the angle of the mouth. The modiolus is held in p osition by the arch-form of the maxillary teeth. 23

24 Disadvantages 1- It is softened and distorted at mouth tempe rature. 2- It does not withstand the pressure require d for recording jaw relationship. 3- It is very weak and not commonly used.

5- Swaged tin base plate Advantages 1- It does not warp at mouth tempe rature. 2- It gives a uniform thickness. 3- It has a suitable fitness. 25

26 Three tin layers of gauge (5) can be swaged one above the other on a metal die and trim med to the proper extend. The inside layers can be cemented together with wax or zinc oxide eugenol.

27

Permanent denture bases 1-Heat-curing acrylic resin 28

29 Advantages 1- The bases are rigid, accurate and stable. 2- It does not warp at mouth temperature. 3- The bond between the wax rim and the base is str ong. 4- Any type of occlusal rim can be used. 5- Retention and stability can be tested in the mouth before the finishing of the denture.

30 Disadvantages 1- Time consuming 2- Warpage always occurs when acrylic resin is reprocessed. However, this can be prevented by attaching the teeth to the base by cold-curing acrylic re sin. It is not advisable to finish the denture on these bases.

2- Cast alloys These recording bases are per manent and become part of t he finished denture. 31

32 Advantages 1- The bases are rigid, accurate an d dimensionally stable. 2- They add more weight to mandi bular denture and more thermal co nductivity to maxillary denture.

33 Disadvantages 1- They are more costly than other types of bases. 2- They require more time for fabrication.

34

Occlusion Rims They are horseshoe shaped occlud ing surfaces attached to the tempor ary or final denture base for the pur pose of recording jaw relations and arranging of teeth. 35

Types of occlusion rims: 1-Base plate wax rim 2-The composition (compound) rim 3-Plaster and pumice rim 36

Characteristics of occlusion rims: 1-The occlusion rims should be approximatel y the same size and shape as the natural tee th being replaced. 2- Wax rims are smooth and have a flat occlu sal surface. They are about as wide buccolin gually as denture teeth – wider in the posteri or, narrower in the anterior. 37

38 3-The occlusal rim must be centere d buccolingually over and parallel t o the residual ridge crest. 4- The occlusal rim is properly seal ed to the baseplate without any voi ds

39

The portion of the alveolar process & it's soft tissue covering that rema ins after extraction. It covers by a dense connective tis sue fibers so, it can be act as a 1ry stress bearing area. 40

41

The vault of the palate has diffe rent forms according to the patt ern of development of the maxil lary processes. The palatal arc h may be V-shaped, U-shaped or flat. 42