Lost Wax Technique and Investment Casting Quiz

Investment Expansion in Casting Process

• The purpose of investment expansion is to compensate for the shrinkage of the alloy during solidification.

Factors Influencing Setting Expansion of Gypsum

• The setting expansion of gypsum is influenced by the type of gypsum and the time allowed for its setting.

Casting Alloys for Crowns and Fixed Dental Prostheses

• Nickel-chromium alloy is suitable for crowns and fixed dental prostheses.

Recommended Material for Sprue

• The recommended material for the sprue is wax or plastic.

Purpose of Crucible Former

• The crucible former is used to hold the casting alloy in the correct shape.

Function of Liner in Casting Ring

• The liner is used to facilitate the removal of the investment material from the casting ring.

Investing Process

• The first step in the investing process is to coat the wax pattern with a refractory material.

Purpose of Wax Elimination

• Wax elimination is done to create a cavity for the casting alloy.

Temperature for Wax Elimination

• The recommended temperature for placing the ring in the furnace during wax elimination is 538°C.

Purpose of Quenching

• Quenching the ring into cold water after wax elimination is done to prevent distortion and cracking of the investment material.

Function of Sprue

• The sprue is used to direct the flow of molten alloy into the casting ring.

Primary Consideration for Selecting a Casting Alloy

• The primary consideration for selecting a casting alloy is its biocompatibility.

Lost Wax Technique

• The first step in the Lost Wax Technique is to create a wax pattern.
• The purpose of the sprue in the Lost Wax Technique is to direct the flow of molten alloy into the casting ring.

Shrinkage Percentage for Nickel-Chromium Alloys

• The shrinkage percentage for nickel-chromium alloys used for dental restorations is 2.1-2.3%.

Mold Size in Lost Wax Technique

• The mold must be larger than the original wax pattern to accommodate the shrinkage of the alloy.

Investment Material for Metal Ceramic Alloys

• Phosphate-bonded investment material is stable above 650°C and suitable for metal ceramic alloys.

Binder for Phosphate Bonded Investment Material

• The binder for Phosphate bonded investment material is phosphoric acid.

Silica Bonded Investment Material

• Silica bonded investment material is not suitable for casting metal ceramic alloys due to the high heat requirement.
• The common outcome of using Silica bonded investment material is a rough surface finish.
• The main limitation of Silica bonded investment material is its thermal instability.

Requirements for Investment Material

• The three important requirements for investment material are thermal stability, strength, and refractoriness.

Purpose of Investment Material

• The purpose of the investment material in the Lost Wax Technique is to hold the shape of the casting and provide a smooth surface finish.

Primary Purpose of Sprue

• The primary purpose of the sprue in the Lost Wax Technique is to direct the flow of molten alloy into the casting ring.