Dental Materials Lecture INLAY CASTING WAX Dental Materials Lecture BDS II Year Dr. Raghuwar D Singh Associate Professor Prosthodontic Department King George’s Medical University UP, Lucknow

First procedure in the casting of an inlay or crown is the preparation of a wax pattern. TECHNIQUES for WAX PATTERN Preparation:: * Direct Technique * Indirect Technique

TYPES OF INLAY CASTING WAX -- * According to ADA Specification No. 4 :: TYPE I = Medium Wax for Direct Technique TYPE II = Soft Wax for Indirect Technique

COMPOSITION Paraffin wax = 40 to 60 % Gum dammar Carnauba wax Coloring agent

PARAFFIN WAX : * Derived from high boiling fraction of petroleum. * Depending upon Molecular Wt. & Distribution can be obtained in a wide melting or softening range. * Paraffin used for Type I waxes have higher melting point than the Paraffin used for Type II waxes.

DISADVANTAGES – Flake when it is trimmed. Does not present Smooth, Glossy surface.

GUM DAMMAR or DAMMAR RESIN : Natural Resin. Added to improve the smoothness in molding. Resistant to Cracking & Flaking. Increases the Toughness of the wax. Enhances the Smoothness of the surface.

CARNAUBA WAX : Occurs as fine powder. Quite Hard in nature. High Melting point. Combined with paraffin to Decrease the flow at mouth temperature. Give more Glossiness to wax surface than dammar resin.

CANDELILLA WAX can also be added to replace the Carnauba wax. Its Melting point is lower. Not as hard as Carnauba wax. CERESIN may replace part of Paraffin to modify the toughness & carving characteristics of wax.

In modern Inlay Waxes, the Carnauba Wax is often replaced in part with certain Synthetic Waxes that are compatible with Paraffin wax. Two waxes of this Types are :: Complex Nitrogen derivatives of higher fatty acids. Esters of acids derived from Montan wax.

PROPERTIES OF INLAY WAX When softened wax should be uniform. Color should contrast with the die material. No Flakiness or similar surface roughness when wax is bent & molded after softening.

Should Vaporize completely during burnout Wax should not pull or chip during carving. Wax pattern should be completely rigid & dimensionally stable.

FLOW THERMAL PROPERTIES WAX DISTORTION MANIPULATION OF INLAY WAX OTHER DENTAL WAXES

FLOW – Requirements according to ADA Specification no. 4, At 450C -- Both Type I & II should have a flow b/w 70 to 90 %. At 370C -- Type I should not flow more than 1 %. At 300C -- Type II should not flow more than 1 %.

THERMAL PROPERTIES – THERMAL CONDUCTIVITY : Low. Takes time to heat the wax uniformly.

COEFFICIENT OF THERMAL EXPANSION : High. Thermal changes are higher than any other materials. Linear expansion of 0.6 % when heated from 25 to 370C is permitted for Type I waxes. This property is more significant in Direct Tech.

* Other Factors that influence the Coefficient of Thermal Expansion are – Temperature of the Die. Method used for applying pressure to the wax.

WAX DISTORTION – Most serous problem in Inlay wax. It is due to Release of Stresses in pattern due to,, * Contraction on cooling. * Occluded gas bubbles. * Change of shape of wax during moulding. * From Manipulation, Carving, Pooling & Removal.

CAUSES OF DISTORTION : If wax is not at uniform temp. when inserted in the cavity. If wax is not help under uniform pressure during cooling. If wax is added in an area of deficiency.

TO AVOID DISTORTION OF WAXES : Minimal carving & change in temperature. Minimal Storage of pattern. Use warm instrument for carving. Store it in a Fridge if necessary.

MANIPULATION OF INLAY WAX TECHNIQUES – DIRECT TECHNIQUE INDIRECT TECHNIQUE

DIRECT TECHNIQUE :: Softened the stick of wax over the flame. Inserted into the cavity & held under finger pressure. Allow to cool gradually at mouth temperature. Withdraw the wax pattern carefully.

INDIRECT TECHNIQUE :: Pattern is prepared over a lubricated die. If molten wax used, very little stresses occur.

METHODS OF INDIRECT TECHNIQUE – Dipping Method – * In full crowns. * Die is dipped in hot liquid wax. Softening In Warm Water – Not recommended. Adding in Layer – Using spatula or brush.

OTHER DENTAL WAXES

RPD WAXES PRECESSING WAXES * Boxing & Beading Waxes. * Utility Wax. * Sticky Wax. IMPRESSION WAXES * Corrective impression Wax * Bite Registration Wax

RPD WAXES To make patterns of metallic framework of RPD. USES – To make patterns of metallic framework of RPD. Pattern for RPD is made on a special cast known as the Refractory Cast.

SUPPLIED AS -- * Sheets .40 and .32 mm thickness. * Readymade shapes, Round, Half round Grid or Meshform Clasp shapes Other forms. * Bulk.

PROPERTIES – Highly Ductile, as they must adapt easily and stick onto the refractory cast. Must Vaporize during burnout.

BASEPLATE WAX or MODELING WAX Supplied as, Sheets of pink or red colour.

USES – To make Occlusion rim. To form the desired contour of denture after teeth are set. To make patterns for Orthodontic appliances.

CLASSIFICATION – Type I = Soft ; for building Veneers. Type II = Medium Type III = Hard

COMPOSITION – Paraffin wax or Ceresin = 80 % Beeswax = 12 % Carnauba wax = 2.5 % Natural or Synthetic resin = 3 % Microcrystalline = 2.5 %

PROCESSING WAX ** Used mainly as accessory aids.

Examples are , Boxing Wax & Beading Wax. Utility Wax. Sticky Wax.

BOXING & BEADING WAX USES -- To build up vertical walls around the impression. SUPPLIED AS – Boxing wax as sheets. Beading wax as strips.

UTILITY WAX Supplied as – Sticks and Sheets. Uses – To adjust the contour of perforated tray. Composition – Petrolatum & other waxes. ** It is adhesive and can stick to the tray.

STICKY WAX USES -- To join metal parts before soldering. To join fragments of broken dentures before repair.

COMPOSITION -- Mainly Yellow Beeswax, Rosin & Natural resins such as Gum dammer. PROPERTIES – Sticky when melted & Adheres closely to surface. Firm and Brittle at room temperature.

IMPRESSION WAXES Used to record non – undercut edentulous portions of the mouth. Examples are , ** CORRECTIVE IMPRESSION WAX ** BITE REGISTRATION WAX

CORRECTIVE IMPRESSION WAX USES -- To make functional impression of RPD. To record Posterior Palatal Seal. Functional Impression for Obturatures.

COMPOSITION -- Paraffin wax Ceresin wax Beeswax May contain metal particles. PROPERTIES – FLOW at 37 0 C is 100 %. Should be poured immediately.

BITE REGISTRATION WAX USES -- To record the relationship between the upper and lower teeth. SUPPLIED AS -- U shaped rods. COMPOSITION -- Beeswax, Paraffin, Ceresin.

MCQs 1. The role of gum dammar in Inlay casting wax is: a) To improve cracking resistance b) To provide strength to wax c) To impact smoothness to pattern d) All of the above

2. Carnauba was is preffered to candelila wax as: It is harder and has less flow It has low melting temperature It provides luster to the pattern All of the above

3. Inlay wax should have following requisites: Its colour should be in contrast with tooth or die material It should have capability to be carved according to tooth anatomy and there should be no flaking. When heated, it should be completely eliminated from the mould. All of the above.

4. Which of the following waxes is used for making of casting pattern: Boxing wax Inlay wax Modeling wax Utility wax

5. The minimum flow of inlay wax at 450C should be: 60% 6% 70% 100%

6. Which of the following correctly describe type I inlay casting wax: Soft wax used for direct technique Medium wax used for indirect technique Soft wax used for indirect technique Medium was used for direct technique

7. The maximum ingredient of inlay casting wax: Paraffin wax Ceresin Carnauba wax Gum dammar

8. Which of the following is added inlay casting was to improve the smoothness: Ceresin Candellila wax Gum dammar Synthetic wax

9. Percentage of Carnauba wax in inlay casting wax is: 40% 60% 25% 10%

10. Inlay casting wax is supplied as: Sheets only Mesh form only Both of the above None of the above