Dental Wax Materials 1 Definition thermoplastic molding material

Dental Wax Materials 1

Definition thermoplastic molding material. solid at room temperature. 2

Types of waxes - Baseplate wax: sheets, establish initial arch - - form in construction of CD. Bite wax: record the occlusal surfaces of teeth. Boxing wax: sheet wax used as a border of an impression to provide base of the cast to be made. Inlay wax: applied to dies to form direct or indirect patterns for the lost-wax tech. Sticky wax: adheres to dry clean surfaces. 3

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General Composition BASE Wax: that is almost always paraffin (not smooth, not glossy, flake when trimmed) (1) Hydrocarbon of paraffin or esters (2) High or low MW MODIFIER Waxes: contribute properties such as increased hardness, stickiness, or brittleness (1) Hydrocarbon or ester types; (2) High or low MW COLORANT: 1% Fillers: some waxes contain it to control expansion and shrinkage of the wax product. 6

Chemical composition Natural (mineral, vegetable, or animal origin and/or synthetic waxes (more homogeneous & pure) Natural waxes are complex combinations of organic compounds of high molecular weight: Hydrocarbons, e. g. saturated alkanes, & microcrystalline wax series, carnauba wax, candelilla wax. Esters, e. g. myricylpalmitate. Some waxes also contain free alcohol and acid. (Esters are formed from union of higher fatty acids with higher aliphatic alcohol with elimination of water) Alcohol+Fatty Acid Ester+Water 7

Natural waxes Synthetic waxes Additives Minerals: Paraffin Acrawax C Aerosol, OT Castorwax Flexowax C Epolene N-10 Albacer Aldo 33 Durawax 1032 Microcrystalline Barns Dahl Ozokerite Ceresin Montan Plants : Carnauba Ouricury Candelilla Japan wax Coca butter Insect: Beeswax Animal: Spermaceti Fats o. Stearic acid o. Glyceryltristearate o. Oils o. Turpentine o. Color Natural Resins o. Rosin o. Copal o. Dammar o. Sandarac o. Mastin, Shellac o. Kauri Synthetic Resins o. Elvax o. Polyethylene Polystyrene 8

Common Modifier Waxes Gum dammar: smoothness, resistant to flaking, toughness. (resin) Ceresin the hardness and water resistance of wax. Improves carving properties. Carnuba the hardness and water resistance, melting range, gives glossiness, flow at mouth temp. Beeswax the stickiness, improves flow properties at mouth temperature. (esters) Rosin the brittleness. (resin) Microcrystalline waxes stress release on cooling. 9

Properties 10

Melting range Occurs because of the Multiple wax mixtures The liquidus line (representing the temperature at which complete melting has occurred) The solidus line (below which the composition is entirely solid) the solid + liquid range in between is quite broad (almost 40°C). To allow manipulation To develop wax flow, the temperature only needs to be heated to a point within the solid+liquid range or up to the point of the liquidus line but not much higher. Excessive heating would cause decomposition. 11

Melting range TEMPERATURE (C) LIQUID 90 Melting Completion (Liquidus) 80 70 LIQUID + SOLID 60 50 40 Melting Onset (Solidus) 30 SOLID 20 25 Paraffin 50 COMPOSITION (%) 75 100 Carnuba 12

Density and Melting ranges Name: Origin: PARAFFIN Composition: Melting ( C) Density (20 C) Mineral Hydrocarbon mixture 50 -57 0. 90 CERESIN Mineral Complex hydrocarbons 61 -78 0. 91 -0. 92 BEESWAX Animal Ester mixture 62 -65 0. 95 -0. 96 CANDELILLA Plant C 21 hydrocarbons 68 -70 0. 95 -0. 99 CARNAUBA Plant Hydrocarbon, Ester, Fatty Acid 82 -86 0. 99 -0. 999 GUM DAMMAR Plant Aromatic resin ca 120 1. 040 -1. 120 ROSIN Plant Aromatic resin acid 100 -150 1. 08 13

Heating issues Methods: 1. Flame heated instruments 2. warmth of hand? ? 3. dry heat as wax pot 4. Water bath, but not for inlay wax? ? Flow : after the highest melting point is reached. Temperature 1/ viscosity Flow temperature must be > mouth temp if needed in solid state Over heating should be avoided? the base or modifier waxes can be decomposed. 14

Flow In solids its analogous to creep In liquids its analogous to viscosity Waxes are usually non-flowable at room temperature Temperature 1/ viscosity It is critical for inlay wax to have flow less than 1% 15

Thermal conductivity It is low Wax should be softened evenly by rotation above the flame until it evenly softens or flows Tempered in a water bath alternately with the flame heating to allow the core to soften before dripping If a soft core of a bulk of wax is to be made, roll the wax when it is in softened status – (unable to hold shape by itself) 16

Lost wax technique Used with cast metal techniques Wax patterns need to be burned to the point where no excess residue may interfere with metal casting Heat melt and/or decompose wax by the process of oxidation which completely transform it into water vapor and carbon dioxide so that no residue is left. 17

Tackiness or stickiness Created by the bees wax addition in the mixture Increased if material is warmed by hand Solid waxes become tacky to other material if heated Adhesives may be applied on casts before wax application Wax dipping in bees wax increase stickiness of refractory casts Old wax adheres to new one if surface is dry 18

Dimensional stability Wax should be dimensionally stable once it has solidified (less than 1%). Invest the pattern immediately after removal from the die. Deformations: Plastic deformation Under force is by ductility. Ductility allows it to be carved or burnished Residual stress recovery Elastic Recovery 19

Residual stress reduction Heat material evenly Follow manufacturer instructions Invest within 30 min of carving Whenever wax additions are cooled. The exterior surface tends to cool first. The molten interior slowly solidifies and contracts. This encourages distortion or flow. Add in small increments, layering Store at low temperatures 20

Coefficient of thermal expansion Very high ceramics (1 -15 ppm/°C) metals (10 -30 ppm/°C) waxes (30 -600 ppm/°C) inlay wax (250 -300 ppm/°C) ( wax pattern made in the mouth will shrink appreciably) Residual thermal stresses may change ÑDo not heat above melting point during work dimensions Paraffin > beeswax >carnuba 21

Thermal Expansion 250 ppm/ C 1. 2 n sw a x 1. 0 0. 8 Bee Paraffi EXPANSION (%) KERR HARD WAX 0. 6 0. 4 a ub n r Ca 0. 2 0 0 25 30 35 40 45 TEMPERATURE (C) 50 22

Surface tension Wax is hydrophobic To increase its wetting a surfactant could be sprayed over wax to increase flow of investment material 23

Coloring is not standardized Dark colors provide good color contrast for processing wax Opaque and Tooth-colored waxes provide good material for esthetic case presentations and patient education 24

Applications 25

CLASSIFICATION OF DENTAL WAXES 26

Pattern Waxes 27

Pattern waxes Uses metal castings of Inlays Attachments Crowns Pontics Partial dentures Denture base material 28

Inlay wax Forms sticks pallets, tins -Blue or green Consistencies Removable Die with Waxed Inlay -Hard, medium, soft, regular Application -indirect and direct technique 29

INLAY WAX Composition Paraffin + Carnuba + Ceresin +Beeswax + Colorants Properties - low thermal dimensional change - flow temp higher than mouth - must have clean excess residue 30

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Casting waxes Application ØUsed for metal framework Øcomplete and partial dentures Forms Sheets and preformed shapes Properties Ølow thermal dimensional change Ømust have clean excess residue 32

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Base Plate wax Form sheets Types I, II & III Application -wax registration of ridge form -Carved into tissue forms and Support teeth -Bite registration Properties -melting range higher than mouth temperature -Customised to climate 35

Processing wax 36

Impression wax Uses For edentulous impressions Corrects undercuts Closes bubbles Properties flow at mouth temperature E. g. Bite wax, mizzy 37

Wax Bite Registration Uses To articulate models correctly Forms horse shoe shape May be supported by metal foil for stability 38

Boxing wax Forms 1 inch sheets Uses used to form base of the cast pouring May be used to modify borders of trays Properties Tacky at room temp Transfer to impression 39

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Utility wax Forms Ropes manipulated at room temp Applications Add to the tray - customize for pt mouth - Comfort from sharp edges - Control imp material in mouth -Cover ortho bands and wires - to register the bite -Block out undercuts 41

Sticky wax Forms Pencil shape orange or yellow Properties hard and brittle – can reorient if broken Adhere temporarily the metal, gypsum, resin – for fabrication or repair 42

Thank you 43