Inlay Casting Waxes & Wax Pattern Fabrication

Blue Inlay Casting Wax

Blue inlay wax: Blue inlay wax is a type of pattern wax that is used for making patterns for inlays, crowns, and bridges which is later replaced by metal or alloy.

Ideal Requirements of Blue Inlay Wax:

• When soften, the wax should be uniform, there should be no graininess or hard spots in the plastic material.
• The color should contrast with die.
• There should be no flakiness, or roughening of the surface when the wax is molded after softening.
• The wax should not pull or chip during carving.
• During burnout (500°C), it should vaporize completely without residue.
• The wax pattern should be rigid and dimensionally stable till it is eliminated.
• It is sufficiently plastic slightly above the mouth temperature and get rigid when cooled to mouth temperature.
• Wax should have good flow when heated and it set rigidly when cooled.

Composition of Blue Inlay Wax:

Classification of Blue Inlay Wax:

According to ISO 15854:2005

• Class 1: Soft extraoral or laboratory use
• Class 2: Hard intraoral use.

According to ADA specification no. 4 there are two types of inlay waxes, i.e.

• Type I — Medium wax: Used in the fabrication of direct patterns
• Type II — Soft wax: For indirect technique for inlays and crowns.

Supplied as of Blue Inlay Wax: Blue, green, or purple sticks are also available as small pellets and cones.

Properties of Blue Inlay Wax:

1. Physical properties

Type I inlay casting wax is meant for use in the mouth, whereas. Type II wax is used in the laboratory. Both would have slightly different properties.

Flow: Flow is a change in shape under an applying force.

• Flow is highly dependent upon time and temperature.
• Flow is denoted as a percentage of actual height but as time approaches the melting range of flow increases.
• For pattern wax, the flow is generally not desirable at room temperature. Since it results in permanent distortion of the wax pattern.
• According to ADA specification no.
  • 4. At 45°C – Class 1 and Class 2 should have a flow between 70 to 90%
  • At 37°C    –  Class 2 should not flow more than 1%.
  • At 30°C    – Class 1 should not flow more than 1%.
• Class 1 inlay wax: This type melts and flows when heated to 45°C. Temperature is tolerated by the patient. Good flow at this temperature ensures good reproduction of the inlay cavity. Wax cools down and hardens at 37°C (mouth temperature), allowing the operator to carve and shape it in the mouth.
• Class 2 inlay wax: It hardens at 30°C (room temperature). This wax is more suitable for the laboratory. Flow characteristics are not suitable for use in the mouth.
• Homogeneity: Components of the wax should be evenly distributed since it should have the same property throughout the solid.
• Contact Angle: At wax is melted, it should wet the surface of the material to which it is added and should spread easily on, it, i.e. it should have a low contact angle.
• Ductility: Inlay wax consists of moderate ductility. This allows the wax to be more plastic so that it will deform rather than get fractured. This property also allows the wax to be carved or burnished.
• Residual Stress: This property is responsible for the distortion of wax pattern. Residual stress is minimized by working the wax at a high temperature or by preheating die. For minimizing the residual
  stress molding of wax is done slightly above the melting point or above transitional temperature.

2. Thermal property:

• The thermal conductivity of waxes is low. It takes time to heat the wax uniformly and to cool it to room temperature.
• The coefficient of thermal expansion of inlay wax is high. Its value is 350 × 10^-6 °C.
• Its thermal changes are higher than any other dental materials.
• The addition of modifir wax, i.e. bees wax and carnauba wax decreases the coefficient of thermal expansion of inlay wax.
• This decreases the susceptibility of wax to distortion on cooling.
• This property is a more significant indirect technique because contraction of the pattern can occur when it is taken from mouth to room temperature.

3. Chemical property: When inlay wax is pyrolyzed, oxidation completely transforms in water vapor and carbon dioxide, so there is no residue left.

Manipulation of Blue Inlay Wax:

• Direct Technique:
  • Hold the stick of wax over the visible flame and rotate it rapidly until it becomes plastic taking care not to volatile the wax.
  • The wax is inserted into the cavity and it is held under finger pressure ask the patient to bite the wax, while it solidifies. The wax should be allowed to cool gradually to mouth temperature.
• Indirect Technique:
  • Dipping method: In full crowns die can be dipped repeatedly in hot liquid wax. Wax should be allowed to cool, carve, and is removed from the dye.
  • Softening in warm water: Technique is not recommended.
  • Addition: Wax is melted and is added in layers by a spatula or brush.

Polishing of Blue Inlay Wax: Polishing is done by rubbing with silk cloth.

Uses or Application of Inlay Casting Wax or Inlay Wax

• Blue Inlay Wax is used in the fabrication of direct patterns
• Blue Inlay Wax is used in indirect techniques for inlays, crowns, and FPDs.