1. LABORATORY PROCEDURE
1- Beading of upper major connectors
Fading 5 mm - 6 mm from gingival margin
Prevent food impaction and provide physical retention
2- Relief
Under denture base of distal extension base or long span bounded saddle
Under all lower major connectors
Free gingival margin
Any bony projection , sensitive area
Not used with under cut
3- Block out
Parallel block out For undercuts included in design as in proximal surface and
lingual surface
Done by
Straight wax trammer
Tapered wax trammer used in free end saddle
providing more movement
Need survior
Arbitrary block out For undercuts out the design
To protect the mold from distortion when lifting the master
cast from the duplicating material
Shaped block out Ledges on which clasp patterns (retentive & reciprocal arms)
are to be replaced
4- Duplication
By reversible hydrocolloid (Agar) or silicone
In duplicating flask
To preserve the original cast , eliminate danger of fracture or abrading the
original master cast , forming the wax pattern
5- Spruing
Single spruing used for ticonium casting
Multiple spruing top spruing – inverted spruing
6- Packing of acryl done in master cast
N.b :-
Internal finish line contact between metal and acryl from fitting surface (metal to tissue)
External finish line contact between metal and acryl from polishing surface(metal to acryl)
PROSTHEASY
