This document outlines the key steps in a laboratory procedure for dentures: 1) Beading the upper major connectors to prevent food impaction and provide retention. 2) Adding relief under connectors and saddles to free the gingival margin and protect sensitive areas. 3) Using parallel, tapered, or arbitrary block outs to protect the mold from distortions and provide retention for clasp patterns. 4) Duplicating the master cast using reversible hydrocolloid or silicone to preserve the original while forming the wax pattern.

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