Dental waxes


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Dental waxes

  1. 1. Dental Waxes Waxes have versatile role to play in dentistry, few procedures in restorative dentistry can be completed without the use of wax in one of its many forms. Dental waxes may be composed of natural and synthetic resins and waxes, gums, fats, oils, fatty acids and pigments of various types. The chemical components of waxes impart characteristic physical properties to the wax. Following table details the components of Dental waxes. Components of Dental Waxes. Natural Waxes Synthetic Waxes Additives Mineral – Paraffin Acrawax Stearic acid Microcrystalline Aerosol ot Oils Barnsdahl Castor wax Turpentine Ozokerite Flexo wax c Natural resins Ceresin Epolene Rosin Plant – Carnauba N – 10 copal Candehlla Albacer Dammar Japan Wax Aldo 33 Shellac Coca butter Dura wax 1032 Colorants Insect – Bees wax Polyethylene Animal – Spermaceti Polystyrene Classification of Dental Waxes Historical classification of wax: Basically as 1. Natural waxes 2. Synthetic waxes According to origin classified as. A) Mineral B) Plant C) Insect D) Animal Classification of dental waxes: *Pattern *Processing *Impression Inlay Boxing Corrective Casting Utility Bite Sheet Sticky Ready Shapes Wax – up 1
  2. 2. Base plate Pattern Waxes – are used to form the general pre determined size and contour of an artificial dental restoration, which is to be contructed of a more durable material such as cast gold alloys, cobalt – chromium – nickel, acrylic resin etc. Processing waxes - used primarily as auxillary in constructing a variety of restoration and appliances either clinically or in lab. Impression waxes – used for bite registration and impression purposes, but due to property of distortion owing to high flow and ductility ,very limited role to play. Inlay Pattern Wax Gold inlays, crowns, bridges etc are formed by a casting process that uses the lost wax technique .Inlay wax provides the wax pattern used in this technique and thus accounts for one of the most widely used and important dental waxes. Composition – Principal waxes used are paraffin, microrystalline wax, ceresin, carnauba, candelilla and bees wax. One formulation is Paraffin – 60% Carnauba – 25% Ceresin - 10% Beeswax – 5% Role of components : A) Paraffin – Major constituent, can be derived of any desired melting point ,likely to flake on trimming and doesn’t present a smooth glossy surface, so modifying agents required. B) Carnauba Wax – Occurs as fine powder on leaves of urban tropical plants. Contributes in – decreasing flow at mouth temp, agreeable odour imparts glossiness Candelilla is an alternative to canauba wax. C) Gum dammar – is a natural resin, added to paraffin to improve smoothness in molding also enhances smoothness & luster. D) Ceresin – may be added to replace part of paraffin to modify toughness and carving characteristics. E) Beeswax improves handling characteristics. Alterations in properties occur due to change in percentage of major constituents. e.g. flow can be reduced by adding more carnauba wax or by selecting higher melting point paraffin wax and vice – versa. Mode of Supply – These are usually supplied in deep blue, green or purple rods or sticks. 2
  3. 3. Length – 7.5 cm Diameter – 0.64 cm Also may be supplied as small pellets or cones or in small metal ointment jars. Types: Revised ANSI/ADA specification No. 4 (ISO 1561) categories inlay pattern waxes basically of two types. Type I – (Soft inlay wax) Type II – (Hard inlay wax) Type I is utilized as an indirect technique wax. Type II is utilized for forming direct wax patterns in mouth where lower flow rate at 37o C tends to minimize distortion on removal. Desirable Properties: 1. Should be uniform when softened i.e. ingredients should blend with each other. 2. Colour should contrast with die natural or prepared tooth for proper finishing of margins. 3. There should be no surface roughness or chipping, flakiness when moulded after softening or carved. 4. Carvability should be there. 5. Elimination should be complete and burnout should not leave any residues on surface to cause deleterious effects to castings (ADA specification 4 – when vaporized at 500o C shall leave no solid residue in excess of 0.10% of original wt.) 6. Dimensional stability and toughness. 7. Should be easy to handle. FLOW: One of the desirable properties of Type I inlay wax is that it exhibits a marked plasticity or flow at temperatures slightly above that of mouth. Inlay waxes do not solidity with a space lattice as does a metal, the structure is more likely a combination of crystalline and amorphous materials. The flow of Type II wax is no more than 1% at body temperature and that of Type I is 9%. Low flow at this temperature tends to minimize distortion of well caved pattern to be withdrawn from the prepared cavity. Thermal Properties: Rate of expansion of Type I wax is greatest at just above 45o C. Knowing the amount of wax expansion or contraction , allows one to judge the compensation necessary to produce an accurate casting. The inlay wax has a high coefficient of thermal expansion average linear coeff. being 350 X 106 /o C. A decrease of 12o C – 13o C temp from mouth temperature to room temp ,of about 24o C causes a linear contraction 0.4% or about 0.04% Change per degree change in temp. 3
  4. 4. ‘Wax Distortion’ Probably the most serious problem one can experience when forming or removing patterns. Results from -Thermal changes and release of stresses arising from contraction, occluded air, carving and time and temp during storage. Inlay waxes tend to return to their original shape after manipulation depicting ‘elastic memory’. This can be depicted by opening of a horse – shoe shape molded inlay wax kept in water after manipulation. So to counteract the property of distortion, the pattern should be invested immediately on removal so as for best fitting of the casting. Manipulation of Inlay Wax Dry heat is generally preferred to use of water bath as latter can induce incorporation of water droplets that could splatter on flaming, smear the wax surface during polishing and distort the pattern during thermal changes. The stick should be twirled over flame till shiny for softening and care to be taken not to overheat the wax. The plastic wax is kneaded and pressure is applied by finger or biting to be adapted to the cavity. The pattern is then cooled gradually at mouth temperature and not by cold water. The pattern is then carved properly, and removed by use of pins or hooked by end of explores. MOD preparations are best removed by use of staples luted to the pattern. Avoid touching with finger ,after removal of pattern. Waxes oxidise on heating & on prolonged heating evaporate, darkening & gummy deposits can be precipitated, so care should be taken not to overheat. For indirect fabrication, the die is lubricated and melted wax is gradually filled in the prepared cavity or painted with brush on layers, overfilled carved properly and then removed. Base Plate Wax: It derives its name from its use on the baseplate tray to establish vertical dimension, plane of occlusion & Initial arch form in technique for complete denture fabrication. May also be used to form all or portion of tray too.  Patterns for orthodontic appliances and prosthesis other than complete dentures.  To check various articulating relation in mouth & transfer them to articulators. Composition: 70-80% paraffin based waxes or ceresin , 12% beeswax , 2.5% carnauba, 3% natural or synthetic resins, 2.5% Microcrystalline or synthetic Waxes Types: Type 1: Soft wax used for building contours and veneers Type 2: Hard wax used for patterns to be tried in mouth in Temperate weather. Type 3: Extra hard wax for patterns to be tried in mouth in tropical weather. 4
  5. 5. Requirement of Base plate wax:  Should be easily trimmed with sharp instrument at 23o c.  Should yield a smooth surface after gentle flaming.  Should not leave any residue on plastic or porcelain teeth & colouring agents should not separate or impregnate the mould.  Softened sheets should cohere readily without becoming flaky or adhering to fingers.  No irritation to oral tissues.  No adhesion to other sheets of wax or storing paper on storage. Bite Registration Wax: Use - Used to accurately articulate certain moulds of opposing quadrants Composition: Beeswax or hydrocarbon waxes such as paraffin or ceresin. Certain bite waxes contain aluminium or copper particles. Flow of 2.5% to 22% at 370 c has been suggested indicating these waxes are susceptible to distortion on removal from mouth. Special considerations to be given not to use them in undercut areas thus. Boxing Wax Use: Used for forming a plaster or stone cast from an inpression of the edentulous arch into which freshly mixed plastic or stone is poured and vibrated. The names carding wax & boxing wax have been used interchangeably but boxing wax is more acceptable. MODE of supply: Supplied as green or black strips or sticks. Boxing Procedure: First a long, narrow stick or strip of wax is adapted around the impression below its peripheral height, followed by a wide strip of wax, producing form around entire impression. Ideal requirements: Acc to federal specification no. U-W-138  It should be readily adaptable to impression. at room temp, as increase in temp might distort viscoelastic impression materials.  Should be slightly tacky & have sufficient strength & roughness for convenient manipulation.  Pliable at 210 c , retains shape at 350 c  Smooth, glossy surface on flaming.  Seals easily to plaster with hot spatula DIRECT WAX TECHNIQUE – As name suggests is the technique of wax pattern fabricated directly in mouth. Indications: 5
  6. 6.  Tooth accessible in the oral cavity to work on.  Cavity preparations with minimal proximal extensions  Good deal of supporting tooth structure to stabilize pattern during carving  Cavity preparations where walls are flat, internal line angles are sharp & gingival level is definite Method: The inlay stick is heated on flame until shiny throughout & completely softened. It should be kept moving. The wax can then be flattened by using vaseline applied finger so as to expose more area for thorough softening. This softened wax is pushed into the prepared cavity and finger pressure is maintained. The wax is allowed to cool gradually, excess wax is then removed and carving of the pattern is done with help of plastic instruments. The pattern is lifted by use of narrow strip of copper ribbon bent is U or V shape, heated and inserted as a staple on marginal ridge area, can be fabricated with or without matrix band application. Advantages: Direct preparation on tooth and not on a replica that may be altered. less lab work required, time saving procedure. Disadvantages: Technique sensitive & great skill required ,fabrication in indirect vision difficult, gingival discrepancies difficult to judge before withdrawal ,chairside time is increased ,if casting fails patient has to be recalled. Indirect wax technique: This type of fabrication done in lab on a replicated die. Indications: When access to tooth is hampered,  Chairside time has to be reduced.  Extensive preparations  More pressure is required. Method: After fabrication of die, a lubricant is applied to facilitate withdrawl of pattern, e.g. castor oil, cocoa butter, machine oil etc (Some author suggest disuse of lubricants as they can change dimensions). For larger castings die spacer may be used. The blue inlay wax is softened, molded and pushed into the cavity as in direct technique. The pattern is allowed to cool, properly carved, and removed in same manner as with the direct technique. Occlusal adjustments can also be done precisely. Sprue former should be added till the pattern is in tooth only as less distortion occurs. Advantages: More precise patterns.  Less chairside time  Adjustments can be done  Repeated castings can be done from single die. Disadvantages: Though less chairside time more lab work is requested, The replica may be of altered dimensions. 6
  7. 7. Sticky wax Uses: Used to assemble metallic or resin pieces on a fixed temporary position Used primarily on dental stones & plasters for sealing purposes etc. Composition: Rosin, yellow beeswax, Gum dammar, colouring agents Requirements: Acc to Federal specification NO U-W-00149 a (DSA-DM)  It should have a dark or vivid colour to be readily distinguished from light gypsum materials  To be sticky when melted  Adheres closely  No more than 0.2 % residue or burnout  No more shrinkage than 0.5 % from 43o C to 280 C  Max flow at 300 C – 5 %  Min flow at 430 C – 90 %  Should be firm, free from tackiness & brittle at room temp.  Should fracture rather than flow if deformed during repair procedures. 7