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Synonyms : Spare denture, back-up denture.

TECHNIQUES :

There are mainly three techniques.

(1)Modified denture flask method-(Brewer and Morrow 1975)-

• Remove a rectangular section from the upper pat of the flask for the wax sprue.
• Add utility or orthodontic tray wax in thin areas in the external surface of the denture.
• 75mm long with a diameter of 15mm wax is rolled to make the sprue which is attached the lingual surface of the mandibular heel region.
• Apply adhesive on the interior surface of the flask to aid in the retention of alginate.
• Mix alginate and place in the lower part of the flask and the remaining alginate is painted on the interior of the denture.
• Place the denture in to the alginate in the flask with the sprue projecting out through the triangular opening and supporting the denture.
• After alginate has set, the other half of the flask is filled with another mix of alginate and the flask is closed.
• After alginate has set separate the flasks and remove the denture.
• Dry the tooth indentations using tissue paper and mix tooth coloured acrylic and add in to the indentations till the cervical region.
• Now assemble the flask together and mix pour type acrylic resin and pour it through one sprue hole till the other sprue hole fills.
• Gently rock the flask to avoid air entrapment. Sprue should be upward facing and the flask is immersed in warm water at 20psi for 30minutes

(2)Pour resin flask method (Boos and Carpenter 1974)-

• Attach the denture in the base of the flask using modeling clay.
• Place the counter and pour a mixture of alginate.
• Allow it to set.
• Open the flask and remove the clay.
• Mix alginate and pour it.
• Once the second pour of alginate is set open the flask and remove the denture.
• Mix tooth coloured self cure resin and pour it in the teeth indentation and later pink colour pour type resin the denture base area.

(3)The cup flask method(Wanger 1970) or zipper technique by singer (1975)-

• In this method a 12 ounce ceramic cup is used to duplicate the denture using hydrocolloids. Singer modified it by adding a dental floss to section the alginate.
• A  16 inch floss is dipped in melted orthodontic tray wax and this is placed 2-3mm below the border of maxillary denture and across the posterior region.
• In case of mandibular denture the 2 floss are used one on buccal side and another on lingual side and extend it to the sprue wax which is attached to the heel of the cast.
• Suspend the denture using two wooden rods.
• A modeling clay wedge is placed on the inner surface of the cup and the alginate is mixed with three times the water recommended by the manufacturer.
• Fill the cup with alginate and sink the denture in to it.
• Wooden rod and the clay wedge is removed and a stream of air is blown through the space of the clay wedge to remove the mold from the cup.
• Now the floss is pulled across the posterior border and flanges to section the mold in to two halves.
• Tooth coloured self cure resin is placed in the tooth indentations and the halves are assembled back in the cup.
• Through the sprue holes the pour type resin is mixed and poured.