Wax patterns in fpd/ dentistry course in india


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Wax patterns in fpd/ dentistry course in india

  1. 1. www.indiandentalacademy.com
  2. 2. INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  3. 3. contents  Introduction  Rationale  Material science  Pre requisites  Die lubricant  Waxing instruments  Wax pattern fabrication- occlusal morphology www.indiandentalacademy.com
  4. 4. www.indiandentalacademy.com
  5. 5.  Spruing  Wax patterns for all ceramic  Wax patterns for post and core  Recent advances  Conclusion  References www.indiandentalacademy.com
  6. 6. introduction  Following production of die  Next stage  Defines the shape and size of the resulting restoration  Eventually replaced by either a polymer or an alloy using the lost wax technique www.indiandentalacademy.com
  7. 7. rationale  Produce distributed contact pattern with small contacts  Occlusal forces distributed- minimize stress and wear  Allow for complete and rapid disclusion in excursive movements  Shearing action- more effective  Patients experience reduced efforts for chewing food www.indiandentalacademy.com
  8. 8. Materials science  type of pattern waxes- inlay waxes casting waxes base plate waxes Definition- specialized dental wax  can be applied to dies to form direct or indirect patterns  for the lost wax technique used for casting metals or hot pressing of ceramics www.indiandentalacademy.com
  9. 9. Dispensing:  rods or sticks-7.5 cm long and 3 mm wide  Pellets, cones, blocks of a variety of colors  Colors provide suitable contrast against die www.indiandentalacademy.com
  10. 10. Classification-  According to ANSI/ADA specification 4 :  Type I – medium wax used for direct wax pattern technique  Type II – soft wax used for indirect wax pattern technique www.indiandentalacademy.com
  11. 11.  Type I- Melts and flows at 45 degrees. Cools and hardens at 37 degrees allowing operator to carve and shape at mouth temperature  Type II- Hardens at 30 degrees more suitable for a laboratory www.indiandentalacademy.com
  12. 12. composition  Paraffin wax(m.p) 60%  Carnauba wax/candelilla wax (m.r, gloss) 20%  Ceresin wax(carving,toughness) 5%  Gum dammar(smoothness,toughness) 3%  Bees wax(flow) 5%  Synthetic resins(flow) 2% www.indiandentalacademy.com
  13. 13. Non volatile residues  Wax vaporize during burnout  ADA specification limits non vaporizable residue to a max of 0.1% at 500 C( 932F)  Excess residue can result in incomplete castings www.indiandentalacademy.com
  14. 14. Ideal requirements  No flakiness or roughening after softening  Should not chip out as it is carved  Rigid and dimensionally stable until eliminated  Should be uniformly soft on softening  Should completely vapourise at 500 C and leave no residue  Color contrasting to die material www.indiandentalacademy.com
  15. 15. Properties Flow property- ADA requirements  at 45 degrees- type I and II – flow 70-90%  at 37 degrees – type I should not flow more than 1%  at 30 degrees – type II should not flow more than 1% www.indiandentalacademy.com
  16. 16. Thermal conductivity-  Low  Sufficient time required to heat wax uniformly and cool them to body or room temperature www.indiandentalacademy.com
  17. 17. Coefficient of thermal expansion-  High COTE  Linear expansion of 0.7% with increase in temp of 20C  Significant in direct technique- contraction of pattern occurs when taken from mouth to room temp  Temperature of die and method of applying pressure to wax as it solidifies influences COTE www.indiandentalacademy.com
  18. 18. Distortion-  due to any method of manipulation that increases inhomogeneity of wax involving the intermolecular distance.  Occur due to relaxation of internal stresses if,  Wax not uniformly heated  Not subjected to uniform pressure during cooling  Added wax in area of deficiency induces stresses during cooling  During carving disturbance in molecular arrangement www.indiandentalacademy.com
  19. 19. The amount of residual stresses depend upon  Method of forming the pattern  Pattern handling  Time and temperature of storage of wax pattern www.indiandentalacademy.com
  20. 20. Methods to minimise wax distortion:  Select the proper type of waxes as specified by ADA  Soften wax uniformly  Use warm instruments for carving  Place molten wax increments quickly to bond with earlier increment  After overfilled pattern hardens , carefully do carving without pulling from margins  Remove pattern carefully- apply die lubricant  Invest pattern without delay or store in cold water for short time delay www.indiandentalacademy.com
  21. 21. Manipulation- www.indiandentalacademy.com
  22. 22. Indirect technique-  Dipping method  Softening in warm water- soluble contents leach out- change properties water gets into wax - splattering on the flame  Adding in layers www.indiandentalacademy.com
  23. 23. To be noted-  Waxes oxidise on heating  Prolonged heating causes it to evaporate  Darkening and precipitation of gummy deposits  Use of lowest temperature needed for melting www.indiandentalacademy.com
  24. 24. Types of inlay waxes-  Occlusal waxes  Milling waxes  Cervical waxes  Underlining waxes  Crown waxes  Waxes for all ceramics  Block out waxes  Stick on waxes  Occlusal powder www.indiandentalacademy.com
  25. 25. OCCLUSAL WAXES  Ideal for efficient and aesthetic modelling of chewing surfaces.  The advantage of light pastel colours, is that they provide a strongly contrasting optical view of waxed-up chewing surface contours, thus supporting the implementation of occlusal concepts.  A high degree of hardness is necessary when modelling occlusal area with a stable centre  more tolerance for jaw movement  Setting temperature approx. 59° C. www.indiandentalacademy.com
  26. 26. MILLING WAX  optimised composition for processing with milling tools.  Wax-up surfaces are made very smooth, with sharp contours.  Because of its ideal hardness, millings cannot stick to the wax-up and do not smear in the recommended speed range of 2000 - 5000 rpm.  Setting temperature approx. 62° C. www.indiandentalacademy.com
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  28. 28. CERVICAL WAX  cervical edges in aubergine  for details on cervical edges of crowns, precision parts and inlays.  The wax can be modelled reliably and extremely thinly as far as the preparation limits.  shrinkage after the application of individual layers is only very slight.  has a very low limit of elasticity; deformations have only plastic effects.  Setting temperature approx. 62° C. www.indiandentalacademy.com
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  30. 30. UNDERLINING WAX  As first layer of waxing-ups for inlays, cowns, secondary parts and sculpturing within the cervical area.  high density enables the carving of sharp crown edges  stable in form and exact fitting  opaque for a better contrast to the die www.indiandentalacademy.com
  31. 31. CROWN WAX  hard and medium-hard waxes in the colours blue and dark blue,  The scraping properties are ideal  Deciding whether to use the hard or the medium-hard product mainly depends on climate conditions (room temperature) and the desired stability when removing the wax-up or for investment.  Setting temperature Crown wax hard approx. 61° C, Crown wax medium hard approx. 60° C.  Contraction of the wax can be reduced by applying smaller quantities at a time. www.indiandentalacademy.com
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  33. 33. Wax for full ceramic systems (e.g. Empress)  They are filtered several times and are free from any opaque particles, which could possibly react with the embedding material or casted objects. www.indiandentalacademy.com
  34. 34. Block-Out Wax  not suitable for casting technique does not burn without residue.  block-out undercuts or to smooth rough surfaces on dies.  It is extremely hard and adapts easily to the contour of the die.  The higher melting point avoids bonding to the other dipping waxes, underlining wax or cervical waxes.  Easy to remove from the die at the end in order to hand over the unspoilt die to the dentist www.indiandentalacademy.com
  35. 35. STICK-ON-WAX  To place casting channels, sprues and pontics  perfect sticking, easy correction of position  stays smooth and sticky  burns without residue www.indiandentalacademy.com
  36. 36. OCCLUSION POWDER / SPRAY  consists of 100% wax  easy to apply with a brush  indicates frictions or undesired contact spots when using the articulator  serves as a separating powder when applying hot wax  burns without residue - washing not necessary www.indiandentalacademy.com
  37. 37. Pre requisites  Correction of defects and blocking of undercuts  Provision of adequate luting agent space- 20 to 40 um  Marking the margins with cyano acrylate www.indiandentalacademy.com
  38. 38. Die lubricant  isolates wax against plaster, metal and wax.  Oil based www.indiandentalacademy.com
  39. 39. Waxing instruments  Designed by Peter K Thomas  For wax additive waxing technque  No 1 and no 2 – wax addition instruments  No 3 – burnisher for refining occlusal anatomy  No 4 and no 5 – wax carvers www.indiandentalacademy.com
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  42. 42. Electric waxers www.indiandentalacademy.com
  43. 43. Wax pattern fabrication  Coping fabrication- wax heated resin sheets vacuum adapted polystyrene pressure formed polypropylene By no. 7 wax spatula Dipping the die in molten wax Proximal contacts on adjacent teeth lightly scraped www.indiandentalacademy.com
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  45. 45. Axial contours  Refine axial contours  Proximal surfaces are flat and slightly concave occlusogingivally  Proximal contact area is in occlusal 1/3rd except between 1st and 2nd maxillary molar – middle 1/3rd  Overcontouring apical to contacts cause gingival inflammation www.indiandentalacademy.com
  46. 46.  Proximal contacts are located slightly facial- lingual embrassures are slightly larger  Height of contour of posteriors on facial surfaces at cervical 1/3rd  On lingual surfaces of mandibular , occurs in middle 1/3rd www.indiandentalacademy.com
  47. 47. Emergence profile-  By Stein and Kuwata  Part of axial contour that extends from the base of the gingival sulcus past the free margin of the gingiva  Extends to the height of contour ,producing a straight profile in the gingival 3rd of the axial surfaces  Facilitates the access for oral hygiene procedures www.indiandentalacademy.com
  48. 48. on proximal surface on facial and lingual contours www.indiandentalacademy.com
  49. 49. Occlusal morphology  Occlusal scheme classified by location of occlusal contact made by the functional cusp on the opposing tooth in centric relation. 1) Additive technique 2) Subtractive technique www.indiandentalacademy.com
  50. 50. Additive technique Cusp – marginal ridge Cusp – fossa Functionally generated path technique www.indiandentalacademy.com
  51. 51. Cusp fossa arrangement Cusp marginal arrangement www.indiandentalacademy.com
  52. 52. Cusp marginal ridge arrangement  By E V Payne  First wax added technique  Widely used method of teaching functional waxing by H L Lundeen  Location of occlusal contact- marginal ridges and occlusal fossae  Relation with opposing teeth- tooth to two teeth  Natural type of occlusion www.indiandentalacademy.com
  53. 53.  Used for single restorations  Food impaction and the displacement of teeth if wedging action of functional cusps  Most cast restorations done in daily practice www.indiandentalacademy.com
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  58. 58. Cusp fossa arrangement  By P K Thomas  Location of occlusal contact on opposing teeth- occlusal fossae only  Relation with opposing tooth- tooth to tooth www.indiandentalacademy.com
  59. 59.  Occlusal forces are directed parallel with long axis of tooth  Food impaction prevented  Improved stability from tripod contacts for each functional cusp  Rarely found on natural teeth  Used when restoring several contacting teeth and the teeth opposing them  In full mouth reconstruction www.indiandentalacademy.com
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  61. 61. www.indiandentalacademy.com
  62. 62. Functionally generated path technique  First described by Meyer  Adapted in complete occlusal rehabilitation by Mann and Pankey  Use in restoration of a single tooth in the presence of optimal occlusion  Correct anterior guidance must be present  Absence of posterior interferences www.indiandentalacademy.com
  63. 63.  Recording simple yet precise manner the pathways travelled by the cusps in the border movements of the mandible  Wax adapted over occlusal surfaces of prepared tooth  Patient occludes in intercuspal position  Moves mandible through all excursions www.indiandentalacademy.com
  64. 64.  Tips of opposing cusps act as recording styli  Carve in 3D a record of border movements in all mandibular positions  Stone is brushed and poured onto the wax record in the mouth - a functional core www.indiandentalacademy.com
  65. 65.  The cast with prepared tooth on lower member of twin stage occluder  The anatomic cast on upper left member  The functional core on upper right member  Verticulator - alternative www.indiandentalacademy.com
  66. 66. subtractive technique  Mount the master die on twin stage occluder  Develop axial contours  Acc to occlusal scheme, block out areas of functional core that should not be in contact with inlay wax  Lubricate these areas on functional core  Warm each occlusal surface of master die with chip blower  Close lubricated functional core over warmed occlusal wax and observe  Remove extruded wax and repeat for each wax pattern separately www.indiandentalacademy.com
  67. 67. Wax Cut back  3 distinct types of cut backs are commonly employed for anterior teeth  Ceramic veneer over metal - 1 mm cut back www.indiandentalacademy.com
  68. 68. Waxing connectors  Join the separate components of the fixed dental prosthesis  Mechanical- large for optimal strength  Biological- not impinging on gingiva  1mm from crest of interproximal soft tissue  Cervically- smooth arch like configuration  Placed lingually for anterior prosthesis www.indiandentalacademy.com
  69. 69.  Check the occlusion with 0.0005 inch shim stock.  Cusps on wax patterns and stone teeth must all hold shim stock www.indiandentalacademy.com
  70. 70. Margin fixing www.indiandentalacademy.com
  71. 71.  Re adapt wax to finish lines  Remodelling of pattern margins improve adaptaion to die. ( Rafael et al JPD feb 1985:53:2;168-173 )  Burnish the marginal wax with beaver tail burnisher  Krug and Markley overwaxed margins by 0.25 mm with soft red wax that could be refined post casting (JPD sept 1986:56:3;279-283) www.indiandentalacademy.com
  72. 72.  smoothen and polish with cotton tip applicator soaked in die lubricant  rubbing with silk cloth in apical strokes www.indiandentalacademy.com
  73. 73. RETENTION PEARLS FOR VENEERED CROWNS  Used for acrylic-veneering crowns and in the sprue technique; when space is limited, they are used in place of loop retentions. www.indiandentalacademy.com
  74. 74. spruing www.indiandentalacademy.com
  75. 75. Hollow or solid wax , plastic or metal medium-hard wax from 2.5 to 5 mm in 0.5 mm increments www.indiandentalacademy.com
  76. 76. PLASTIC STICKS AND HOLLOW PLASTIC STICKS  casting reservoir in the sprue technique for casting.  stabilise the wax-up when casting with precious metal alloys, easy to shape over a flame and burn without residue.  Hollow sticks with larger diameters are used for non- precious metal castings, but also for precious metal castings when a greater loss of volume is expected on account of the dimensions involved.  Before planned investment under pressure, the ends of the hollow sticks must be sealed very deeply with wax. www.indiandentalacademy.com
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  78. 78. Rules of spruing  Use short thick sprue- prevents shrink spot porosity localised shrinkage porosity suck back porosity {10 gauge/2.5 mm- runner, 12 gauge/2 mm-pattern}  Attach sprue to bulkiest part of pattern  Never feed a bulky section through a thin section www.indiandentalacademy.com
  79. 79.  Attach sprue at 45 degree angulation- prevents turbulence  Do not plunge hot sprue deeply into pattern  Reservoir- prevents localised shrinkage porosity  Chill set- 18 gauge sprue on opposite side www.indiandentalacademy.com
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  81. 81.  Never use a bottleneck sprue- flare the point of attachment  Firmly secure the sprue to the pattern so it doesn’t dislodge during investment www.indiandentalacademy.com
  82. 82.  Sprue length- most distal part of pattern is ¼ inch or 6-7 mm from open end of casting ring  Allows adequate diffusion of mould gasses through investment  Back pressure porosity www.indiandentalacademy.com
  83. 83.  Wash wax patterns with a liquid detergent solution to remove excess lubricant  Alternatively sprayed with debubblizer www.indiandentalacademy.com
  84. 84.  Wetting agent for reducing tension on wax-ups and silicone duplicating moulds.  It is a reliable preparation agent for investment and eliminates the water-repellent effects of the wax-up or silicone mould, thus ensuring smooth casting surfaces.  the investment material adapts precisely to the waxwork  sprayed on thinly and evenly.  Always blow-dry before investment. Wet areas may cause rough casting www.indiandentalacademy.com
  85. 85. Wax patterns for all ceramic  All contours – min 1 mm thickness – adequate strength  Smooth and completely formed internal surface  Waxed margins should have no over extensions  Chipping of glass ceramic may result during try in or fitting www.indiandentalacademy.com
  86. 86.  8 to 10 gauge sprue attached to incisal surface of anteriors  Two 10 gauge for posteriors attached to facial and lingual cusp tips  For adequate ingress of ceramic material www.indiandentalacademy.com
  87. 87. Wax patterns for post and core  Roughen a loose fitting plastic post and make sure it extends into entire depth of canal in the die  Use impression as guide  Apply thin coat of sticky wax to post ,lubricate the stone cast  Add soft inlay wax in increments- start from apical  Post should be correctly oriented  Wax core added and shaped www.indiandentalacademy.com
  88. 88. Recent advances light cure blocking out material  suitable to be used with all SPACERS  does not build up any dispersion layers  aimed at precise application due to its fluid and paste consistency  Curing time: 4-5 min.  Package: in light protected bottles of 10 ml www.indiandentalacademy.com
  89. 89. light spacer  light curing liquid spacer  homogeneous curing  creates a very hard and durable surface  resistant against scratching and evaporating  extremely smooth surface - no problem when lifting the coping  excellent adhesion on plaster base  unlimited application time - cures only when put in the light curing box  Curing time: approx. 2 - 5 min www.indiandentalacademy.com
  90. 90.  CAD/CAM wax pattern fabrication www.indiandentalacademy.com
  91. 91. conclusion  Crown /FDP should resemble natural dentition in form and function  Composite form and nomenclature of natural teeth,  Determinants of occlusion and their effect on the occlusal surface of teeth  Able to interpret harmonious relationship with adjacent teeth and soft tissues. www.indiandentalacademy.com
  92. 92. references  Contemporary fixed prosthodontics- Rosenstiel , Land and Fujimoto. 4th edition. Pg 555-588  Fundamentals of fixed prosthodontics- shillingburg,et al. 3rd edition. Pg 335-364  Dental laboratory procedured- fixed partial dentures- Rhoads , Rudd, Morrow. 2nd edition.pg 170-212  Tylmans theory and practice of fixed prosthodontics- Malone et al. 8th edition  Craig’s restorative materials. Pg 339-356  Anusavice’s dental materials. 11th edition. Pg 286-291  Applied dental materials- Mc cabe et al. pg 36-40 www.indiandentalacademy.com
  93. 93.  Guide to occlusal waxing- Shillingburg, wilson, Morrison. 2nd edition.  Full mouth waxing technique- Charles E stuart  Wax up for functional occlusion- Lang , Gipp et al  Occlusion- Ash, Ramfjord. 4th edition  JPD feb 1985:53:2;168-173  JPD sept 1986:56:3;279-283  JPD may 1997:77:5;553-555  JPD mar2002:87:3;341-342 www.indiandentalacademy.com
  94. 94. www.indiandentalacademy.com