prosthesis

1. Record base
Definition Temporary base used for recording jaw relations and setting of artificial teeth
Criteria or
requirements
for
Record base
1. Well&easily adapted
2. Stable in cast and mouth (not distort or wrap) (dimensionally stable material)
3. Rigid
4. Exhibit a color not interfere with arrangement of teeth
5. Even thickness of 1mm over crest of ridge and 2mm over flangs and palate
6. Smooth surfaces , rounded borders
7. Extend to full depth of sulcus
8. No handle
Types of record bases
T
E
M
P
O
R
A
R
Y
Shellac Adv inexpensive , easily and quickly adapted
Disadv brittle , distort and wrap  need reinforcement : 12-14 guage wire in lingual flang
(mandible)
Adapted by heating , overheating should be avoided  molten shellac penetrate pores of cast 
fracture of cast surface in removing the shellac base from the cast
Overheating detected by  budding or smoking or blacking of the shellac
Self cure Most widely used as it permits the production of base plate wax
Fabrication techniques :
1. Non flasking  (non compression dough stage) (autopolymerizing)
2. Flasking  (compression dough stage) adaptation in flask - record base done in duplicated cast
accurate , stable but more time, high cost
3. Sprinkle-on method  monomer and excess polymer are applied alternately
accurate , rigid , stable , low polymerization shrinkage but more time so used in small areas
N.b  cast and base can be placed in pressure cooker or mold in hot water for 20 minutes under less
than 24 pounds of pressure  to hasten polymerization and eliminate excess monomer
Visible light
cure (VLC)
Fill in undercuts with pink bite rim wax , Coat the impression area with a thin layer of petroleum jelly
Remove plastic sheets from pink VLC material and adapted it to cast
Accurate , rigid , stable , need less time
Baseplate
wax
Used in Emergency Cases only
Adv Inexpensive , easily formed , esthetic
Disadv  not rigid , easily distorted  need reinforcement (PPS in maxilla) (lingual flang in mandible)
Swaged tin Three tin pieces of guage 5 are swaged one above the other on a matel die made from the master cast
P
E
R
M
E
N
T
Heat cure Adaptation occur in flask , record base done in duplicated cast (refractory cast)
Adv  accurate , rigid , stable , low polymerization shrinkage
Disadv  more time , complicated technique , final cast destruction , teeth deattachment may occur
Cast alloys Gold – Nichel Chromium – Cobalt Chromium
Investing and molding technique
Adv  accurate , rigid , stable , heavy , thermal conductivity
Disadv  more time , high cost
Occlusion rims
Definition Occluding surfaces constructed on record bases to record jaw relation and arrange teeth
Objectives Determine  midline of arch – length&width of teeth – vertical dimension – occlusal plane – lip support
Requirements
Of occlusion
rims
Easy managed material – well attached to record base –
centralized over crest of the ridge – same shape of the ridge – the sides formed 90 with occlusal surface
– maxillary occ rim make 1-2 mm horizontal overjet with mandibular occ rim –
labial surface of max occ rim is about 10 mm anterior to incisive papillae –
posterior borders ended at ant borders of maxillary tuberosity and retromolar pad
Dimensions Upper : ant (5 w X 22 h) post (8-10 w X 18 h) lower : ant (3-5 w X 15-18 h) post (8-10 w X 2/3 RMP h)
Types of
occlusion
rims
Wax Most used  quick , simple but easily distorted , softened at mouth temp
Plaster and
pumice
When dynamic relation between mandible&maxilla is to be recorded as this technique allow
patient to form their own occlusal plane  used in chew impression technique
Modeling
compound
Used in neutral zone impression technique
Not softened at mouth temp , not distorted but more time to cut and trim than wax
Difference between record base and special tray
Criteria for
material used
for record base
PPS area (maxilla)
Stabilization of RBs  to support during record jaw relation instable RB  cases of short borders , thin and thick portions (uneven)
materials use  Zinc oxide impression material (most used) – light bodied rubber base – soft denture liner – denture adhesive
RECORD BLOCK
PROSTHEASY