1. Basic module- Quick Revision on the lab procedures of complete and partial removable and fixed prosthesis A. Complete and partial Co-Cr denture B. Crown and bridge C. Precision attachment Supervisor: AP Dr Norhayati Luddin Prepared by: Ho Yee Mun

2. Complete denture

3. Customised impression tray • Well-designed customised tray in conjunction with appropriate impression material is essential to achieve a good quality working impression • If majority of denture-bearing area is free from large undercuts close fitting trays • Large undercut areas which prohibit the use of close-fitting trays as removal without casting distortions would be difficult perforated spaced tray for use with alginate impression material (wax spacer to provide room for impression material) Modified tray with ‘window’ • Fibrous ridges: modified tray with ‘window’ over fibrous ridge Close fitting trays Spaced tray

4. Identify peripheral extension • Identify the deepest part of sulcus, then draw proposed peripheral relative to this • Spaced tray: draw extent of tray 1.5mm toward alveolar ridge from deepest part of sulcus (to allow room for impression material) Wood, D.J., 2012. Techniques in complete denture technology. John Wiley & Sons.

5. Model preparation • Closed-fittingtrays: any undercuts should be filled with modelling wax • Spaced trays: adapt appropriate thickness of modelling wax to model and trim short of the required peripheral depth required for impression material

6. Steps • Construct tray base (light curing material or autopolymerising resin) • Handle construction • Finishing the tray ensure tray is strong and rigid • Tray used with alginate: 2mm holes drilled in the base material after curing (holes should be 10mm apart and finish 3-4mm from periphery of tray) • Final smoothing by sandpaper mandrel and sandpaper strips • Secondly impression and working models

7. Occlusal registration Construction of registration rims • Fill undercut areas on model and coat exposed plaster with separating solution • Adapt light-curing blank closely to model, trim away the excess to reveal land area of mode (base should extend to fill entire sulcus) • Soften wax rim in warm water until pliable, then slightly melt underside with flame and immediately place and adapt tightly onto the base • Ensure labial surface is correctly aligned 10mm forward of incisal papillae on maxillary base and over centre of ridge on mandibular base • Use hot wax knife seal the edges of wax rims to base with modelling wax

8. • Draw a pencil mark on outside of the model to be level with lowest point of sulcus next to central frenum • Measure from this mark: • Maxillary rim: 22-23mm • Mandibular rim: 18-19mm • Occlusal rim inclination placed across hamular notches to form anteroposterior angle of maxillary block • Mandibular block: level the rim with two-third the way up the retromolar pad • Adjust the rim width to be ~5-6mm anteriorly and 8-9mm posteriorly

9. Split cast mounting technique • Allows model to be mounted onto the articulator and then removed and replaced back onto mounting plaster • Steep chamfered cuts made down the side of models using model • Chamfered sections and bottom of the model are coated in separating medium prior to mounting plaster applied • Once mounting plaster is set and trimmed, the model can be detached from the mounting plaster by sharply tapping the join line between model and plaster • To reattach the model to the mounting plaster, model can be accurately positioned into the mounting plaster and seal with sticky wax

10. Positioning denture teeth Anatomical landmarks and aids used to position denture teeth • Upper borders • Midline: reference plane to achieve anterior symmetry • Rugae: to locate canine • Tuberosity: defines maximum posterior border of occlusal table • Alveolar ridge: asses bucco-palatal position of teeth • Lower borders • Retromolar pad: distal border of lower denture; a point of two-thirds the way up the retromolar pads may be used to approximate occlusal plane • Alveolar ridge: asses bunco-palatal position of teeth • Buccal shelf: provide support for denture and angulation of occlusal surfaces of posterior teeth • External oblique and mylohyoid ridges: bony structures and muscle attachment sites that should not be included in denture-bearing area

11. Incisal papillae • Key landmark in denture design (does not change position as alveolar resorb) • Highlights the anatomical midline of alveolar • Labial surface of maxillary anterior teeth ~8mm anterior to centre of incisal papillae • Labial surfaces of canine ~10mm from edge of the first rug fold as average position

12. Alveolar ridge • Straight lines often used between retromolar pad and the 1st premolar to represent the centre of alveolar ridge • However, using centre of ridge may result in restricted tongue space if severe resorption and ridges that resorbed lingually • Best method: use pencil to mark centre of denture bearing area (in some case may be the crest of alveolar ridge) • This indicates the optimum position to be used as the bunco-lingual determinant of teeth in both upper and lower arches

13. Gingival contouring and polished surfaces Palate Sulcus Smooth and extend to junction of hard and soft palate Fill the sulcus with denture base: provide optimum seal around denture, aiding retention Shape of anterior palate have significant effect on speech Buccal and lingual flange extension Gingival contour Sculpting wax around teeth can affect aesthetic hygiene Width of buccal and lingual flanges on both upper and lower dentures: fit fully into sulci of working models Flange should not encroach onto buccal or lingual frenum

14. Processing denture • Flasks must be in good condition (must close fully and accurately without resistance) • Coronal surfaces of teeth must be free from wax to ensure good adherence to acrylic resin is achieved within mould and to avoid tooth movement during processing • The wax needs to be removed (hot, non- recirculating water) • When dry, but while still hot, all exposed surface of plaster and stone mould should be painted with separating medium

15. Packing • Acrylic should be placed into mould just before dough reaches “snap dough” stage (to ensure it will be forced into surface details while under pressure) • “Snap dough” stage: little hard and may not full press into all detail within mould, also prevent flasks being closed together properly • Flasks closed under slow, constant pressure (80psi) to allow material to flow into fine detail and the excess out of the mould • After processing, copper headed hammer used to open flasks • Avoid excessive force and prevent shock wave forces passing through the flask, plaster/stone block and denture denture cracking

16. Finishing denture • Processed denture should be removed from the moulds, but not removed from models • Models can be re-secured back into mounting bases using super glue or sticky wax (for check record) • Grind premature occlusal contacts until increased dimension is reduced and incisal guidance pin touches table • Then, remove denture from models • Trim denture (preserve any detail that has been sculpted into outer surfaces, then polish using pumice) • Polishing paste used with goat hair brush (to ensure fine surface detail is not lost) • Check fitting surface of denture under magnification of any processing ‘blips’ or other projections before send to clinic • Store dentures in water for 24 hours prior to fitting (to ensure the relatively porous denture base is saturated in clean water rather than 1st cup of coffee the patient drinks)

17. Removable partial Co-Cr denture

18. Retripoding master cast • Place 3 easily identifiable marks on same horizontal plane • During survey and design process, clinician determine a specific path of insertion and removal for partial denture • Technician must ensure all framework fabrication steps are based upon this path of insertion and removal • Height of contour of teeth and soft tissue marked by carbon marker on surveyor Phoenix, R.D., Stewart's Clinical Removable Partial Prosthodontics ebook.

19. Design transfer • Technician should transfer the design from diagnostic cast to master cast • Areas of special consideration, such as undercut depths for retentive clasp arms, gauges of wrought wire clasps, cast clasps’ pattern sizes should be transferred to the master cast with extreme care and clearly marked

20. Blockout and relief • Place wax or other materials into undesirable undercuts on the master cast • Blockout wax can be shaped to provide a slight ledge just apical to clasp terminus guide the wax of plastic pattern and ensure clasp tip is accurately positioned in the desired undercut • Since only the terminal third of retentive clasp arms should be placed into undercut, the body and shoulder areas commonly required blockout • Certain areas where RPD do not need intimate contact framework are shaped to stand away from underlying tissues (by adding one or more wax spacers used in conjunction with denture base)

21. • Retentive latticework must be raised above the edentulous areas to allow resin to completely surround the longitudinal and transverse struts • 1mm of space should be created between struts and the surface of master cast allow resin to encompass the latticework • Finish line should be placed 1.5mm from neighbouring abutments ensure porous resin not contact with marginal gingiva • Relief for small or inoperable tori using thin, uniform wax covering

22. Sprue guide placement • Some RPD is sprued with an overjet sprue former and reservoir • This require the placement of a small tapered cylinder on master cast (cylinder made from wax, plastic, or metal and must be placed in the exact position that the main sprue will occupy on the refractory cast)

23. Duplication • Duplication materials and techniques are alloy specific • Impression making: blocked out master cast placed on the base of duplicating flask assemble the flask pour reversible hydrocolloid and let to cool remove the master cast • Refractory materials (investments) measured and mixed according to manufacturer’s instructions

24. Waxing the framework • Design transferred from master cast to refractory cast • Prefabricated plastic patterns (esp clasp arms) can be used • Once the plastic patterns are in place on refractory cast, these patterns must be joined using wax (similar to blue inlay wax - because it sets hard and polish easily) • Parts of denture framework must be waxed freehand to prevent excessive bulk and to create desired contours for a satisfactory custom-made RPD framework

25. Spruing framework • Location and geometry of sprue former is based on the recommendations of the alloy manufacturer • Sprue should be large enough, molten metal in them will not solidify until after metal in the casting proper has frozen • Sprue should lead into the mold cavity directly and permit a configuration that will induce a minimal amount of turbulence in the stream of molten metal • Sprues should leave the crucible from a common point and be attached to the wax pattern at its bulkiest sections • Any area that is separated from the bulk of the framework by a long span of latticework or meshwork require a secondary sprue former

26. Investing refractory cast • Some system require a 2 part investment process, 1st part being a 3-4mm ‘paint’ on layer • As soon as the 1st layer reaches its initial set 2nd part of investment begins • Appropriate amount of refractory material is measure, mixed and placed into investment ring • Place the cast in proper relation to the bottom of the ring, allow adequate thickness of investment for the escape of gas during casting without sacrificing mold strength • Position of sprue former is marked on the outside of the mold to ensure proper orientation of casting machine

27. Wax elimination or burnout • For the mold to heat uniformly, it should be moist at the start of the burnout cycle • Steam will carry the heat into investment during the early stages of burnout • If investment is not burned out on the same day that it is poured, it should be soaked in water for few minutes before it is placed in furnace • Mold should be placed in the oven with sprue hole down • Temperature of oven should be increased slowly to a temperature recommended by manufacturer • It is important that the peak temperature recommended by manufacturer not be exceeded during burnout period

28. Casting • Method of casting varies widely with alloy and equipment used • All methods use force to quickly inject the molten metal into mold cavity Rosenstiel, S.F., Land, M.F. and Walter, R. eds., 2022. Contemporary fixed prosthodontics-e-book. Elsevier Health Sciences.

29. Removing the casting from investment • Co-Cr alloys usually allowed to cool in the mold and divested

30. Finishing and polishing • Done with special high-speed equipment • Just before they are polished (high-shine), Co-Cr castings are electropolished (controlled depleting process)

31. Attaching wrought-wire retainer arms by soldering • Wrought-wire retainers may be attached to a RPD framework after it has been cast and finished • Soldering procedure may be accomplished by electric soldering or by a direct-heat method with an oxygen-gas flame

32. • Technician should then seat the metal framework on duplicate master cast (identify areas that prevent proper seating) • Preliminary adjustments to the occlusion of RPD framework should be accomplished in the lab • Clinician should provide opposing cast and suitable interocclusal records to increase adjustment accuracy

33. Making record bases • Autopolymerising acrylic resin material (with sprinkling technique), visible light-cured denture base material (similar technique for making custom impression tray) • Blockout and lubrication of cast, relief of undercut areas, coated with separating medium • Bases for jaw relation records must have maximum contact with supporting tissues • Cast is wet with monomer from a doppler bottle • After surface has been wetted with monomer, polymer is sprinkled onto wet surface until all monomer has been absorbed • Cast then placed in a covered glass dish or covered with inverted bowl (permit final polymerisation)

34. Occlusal rims • Accuracy of the base supporting MMR must be ensured before the function of occlusal rims is considered • Hard baseplate wax rim • Occlusal rims for static jaw relationship should be so shaped that they represent the lost teeth and their supporting structure (avoid to broad and extended beyond prosthetic teeth that will be located)

35. Waxing and investing, processing RPD

36. Crown and bridge

37. Pouring stone dies • Dies: positive reproduction of prepared tooth and consists of suitable hard substance of sufficient accuracy • Type IV or V stone • Pick up small amount of stone with suitable brush or instrument, place in most critical area (occlusal aspect of narrow preparations), then add small quantities of stone incrementally, and allow it to set

38. Pindex system • Base ground flat in a plane that must be perpendicular to intended position of pindex pins • After cast is dried, location of pins is marked, and holes are drilled with special drill press • Pins are cemented in place with cyanoacrylate resin, special sleeves are positioned over cemented pins, and cast is positioned in the second pour that is made in mould • Saw cut prepared tooth • When die trimming is completed, dies are repositioned in definitive cast • Definitive cast is then mounted on articulator

40. Waxing • Very accurate wax pattern is essential in fabricating fixed prosthesis • From this pattern, the finished cast restoration is duplicated using lost-wax process • Die is modified as necessary and lubricated • An initial coping is waxed, forming the internal surface • Proximal surfaces are developed, with correctly located contact areas • Axial surfaces are waxed (avoid overcontouring near gingival margin) • Occlusal surfaces developed with wax addition technique • Margins are reflowed, and wax pattern is finished

41. Wax patterns for metal-ceramic restorations • Restorations are waxed to anatomic contour • The patterns are troughed to obtain correct porcelain thickness in the completed restoration • Cut-back is completed • Ceramic veneer should extend far enough inter proximally, particularly in cervical half of restoration, to avoid metal display • Depth cuts (troughing) can be used to standardise the amount of wax to be removed from veneering area • Make depth cuts around the periphery of the cut-back area that are perpendicular to the surface of wax pattern • Margins are finalised before investing

42. Investing and casting • Lost-wax casting technique: convert wax pattern to cast metal • Surrounding wax pattern with mold made of heat-resistant investment material, eliminate the wax by heating, and then introducing molten metal into the mold through a channel called sprue

43. • A sprue of 2 or 2.5mm in diameter is attached to the bulkiest nonfunctional cusp (larger size for molar and metal- ceramic patterns, smaller size for premolar and partial coverage) • The pattern is removed from the die and attached to a crucible former • The pattern is painted with surface tension reducer (surface must be wet completely), then coated with vacuum- mixed investment • Place the lined casting ring over the pattern, pour the investment down the side of the ring, and allowed it to set for minimum of 1 hour

44. • Bring to furnace for wax elimination • Prepare casting machine, and preheat the crucible • Alloy is melted, the ring is transferred, and the casting is made • The casting is recovered from investment • Defects are identified and corrected if possible

45. Metal-ceramic restoration • Consist of metal substructure supporting a ceramic veneer that is mechanically or chemically bonded to it • Chemical component of the bond is achieved through firing • Porcelain powders of varying composition and colour are applied and fired to produce desired appearance • First ceramic layer (the opaque), masks the dark metal oxide and is the primary source of colour for completed restoration • The opaque is covered with slightly translucent body porcelain, which is then veneered with a more translucent enamel overlay that contains only a few pigments • Shiny, lifelike appearance of completed metal-ceramic restorations results form a surface glaze formed during additional firing after restoration has been shaped

46. Metal preparation • Avoid sharp angles or pits on veneering surface of metal- ceramic restoration (contribute to internal stress in final porcelain) • Metal framework must be sufficiently thick to prevent distortion during firing (min. 0.3mm for noble metal alloy; 0.2mm for base metal alloy) • After framework has been cast, all investments removed ultrasonically with airborne particle abrasion or with steam • Oxide layer has been formed on metal surface during casting must be partially removed with either acid or air abrasion • Metal finishing: in one direction with light pressure (using ceramic-bound stones or carbide burs; because organic binders in conventional rotary instruments can cause contamination) • After surface has been smoothed, it should be abraded with aluminium oxide

47. Porcelain manufacture • Dental porcelain is usually received from manufacture in powder form (mixed with water or water-based glycerin-containing liquid) to form paste of workable consistency • Several condensation technique (vibration and blotting): to remove as much excess water as possible minimise steam generation during drying phase of firing • When the mass is heated, individual porcelain particles conglomerate by sintering

48. Opaque porcelain • Opaque porcelain is applied as the first ceramic coat • Dispense powder on glass slab, add modelling liquid and mix with spatula • Moisten substructure with liquid, pick up small bead of opaque and apply to the coping • Use light vibration to spread the material thinly and evenly • Apply second bead on top of the first, and spread it in a similar manner • After entire veneering surface has been covered, remove excess and prepare for firing • Coping is transferred to a sagger tray and placed near the open muffle of porcelain furnace (allow moisture to evaporate) • After first firing, remove the work from muffle and set it aside to cool to room temperature

49. Body and incisal porcelain • Mix powders with recommended liquid or distilled water • Wet the previously fired opaque layer with liquid, and place a bead of neck powder on cervical portion of veneering surface • Then build the veneer to anatomic contour with body porcelain (use adjacent and opposing tooth as guide) • To compensate for firing shrinkage that results when particles fuse, slightly overbuild the porcelain • Apply incisal powder in same manner and overbuild the restoration • Moisten the proximal contact areas before remove the completed buildup (reduce risk of fracture of buildup) • Place the restoration on sagger tray close to open muffle at drying temperature • After drying process, proceed with firing • When firing is completed, the work should cool to room temperature before further handling

50. Restorations after firing of the first body bake Development of incisal mamelons with opacious dentine Porcelain is added in areas of deficient contour Cervical and body powders are added to the contour After firing, proximal contours are adjusted, and the restorations are seated on the cast Alternatively, incisal index can be used to establish incisal edge position Restorations are contoured by grinding. Careful attention is paid to the shape and position of the line angles and incisal edges. When completed, the restorations are ready for clinical evaluation and final contouring intraorally Restorations are slightly overbuilt