Finishing of Cast Restoration 2023 PDF

FINISHING THE CAST RESTORATION Presented by Dr. Mohammed Hosny Professor of Fixed Prosthodontics Collage of Dentistry Taibah University 2/11/2023 M.Hosny 2 Lab Steps 2/11/2023 M.Hosny 3 Recovery of the casting  For precious alloys:  The ring is quenched when the red glow of the button...

FINISHING THE CAST RESTORATION Presented by Dr. Mohammed Hosny Professor of Fixed Prosthodontics Collage of Dentistry Taibah University 2/11/2023 M.Hosny 2 Lab Steps 2/11/2023 M.Hosny 3 Recovery of the casting  For precious alloys:  The ring is quenched when the red glow of the button disappears. This helps disintegrate the investment.  Pickling in warm 50% HCl solution to remove black oxide layer  For base metal alloy:  Ring cooled to room temp, the broken manually.  NOT pickled--------contaminated, BUT Sandblasting with Al2O3 particles under pressure 2/11/2023 M.Hosny 4 Recovery of the casting 2/11/2023 M.Hosny 5 2/11/2023 M.Hosny 6 Casting Finishing ZONE 1: INTERNAL MARGIN ZONE 2: INTERNAL SURFACE ZONE 3: THE SPRUE ZONE 4: PROXIMAL CONTACTS ZONE 5: OCCLUSAL SURFACE ZONE 6: AXIAL WALLS ZONE 7: EXTERNAL MARGINS 2/11/2023 M.Hosny 7 Zone 1:- Internal margin Objective: To minimize any dissolution of the luting agent, a 1-mm-wide band of metal must be obtained by carefully reflowing the wax pattern . Procedure:  If a defect occurs in the marginal area… the restoration must be remake  Even small nodule can prevent a casting from seating completely …… careful examination under ample magnification helps identify interferences small nodules  If far enough away from the margin itself, can be removed under a binocular microscope  Use of small rotary instruments (e.g., No.1/2 round bur) 2/11/2023 M.Hosny 8 2/11/2023 M.Hosny 9 Zone 2:- Internal surface Objective.  No contact should exist between the die and the internal surface of the casting.  A uniform space of 25 to 35 um is necessary for the luting agent to spread evenly.  Any contact(s) must be identified and relieved by careful selective grinding of the internal surface. 2/11/2023 M.Hosny 10 Zone 2:- Internal surface Procedure.  Examined the internal surface by a binocular microscope for nodules before the restoration is seated on the die.  Under normal circumstances, a casting internal surface does not require finishing.  When a nodule is removed from the internal aspect of a casting It's recommended in one step rather than through sequential relief.  Great care should be exercised when seating a casting on its die.  Any significant force will abrade so that the casting will seat on the die but will not seat fully on the prepared tooth. 2/11/2023 M.Hosny 11 Marking Agents  Used to facilitate identification of the seating interference between the casting and the die.  Water-soluble dies (e.g., Liqua- Mark)  Solvent-based dies (e.g., Accufilm IV)  Powdered sprays (e.g., Occlude).  A suspension of rouge in chloroform or an elastomeric detection paste (e.g., Fit Checker).  These agents should be applied as a thin film to the internal surface of the casting.  Regardless of the method used, the internal surface of the casting should always be thoroughly cleaned before the luting procedure. 2/11/2023 M.Hosny 12 2/11/2023 M.Hosny 13 Occlude Step 2: Seat the crown Step 1: Apply a thin layer of Occlude Step 3: Locate and remove the high spots 2/11/2023 M.Hosny 14 Zone 3:- The sprue Objective: To reestablish proper coronal morphology and function, the sprue must be sectioned, and the casting must be recontoured in the area of its attachment. Procedure: A carborundum separating disk is used to cut through the sprue. Cutting performed circumferentially, maintaining a small area in the center of the sprue. The last connection is broken by twisting and separating it from the casting. Any excess in the area of the sprue attachment is removed with the disk, and the area is refined with stones and sandpaper disks. 2/11/2023 M.Hosny 15 Zone 3:- The sprue 2/11/2023 M.Hosny 16 Zone 4:- Proximal contact Objective: The proximal contact areas are adjusted in the laboratory so that they will be correct (or slightly too tight) when the casting is evaluated in the mouth. Procedure:  Slightly excessive contact may be corrected easily during clinical evaluation. The proximal contacts on the stone cast can be minimally relieved by careful scraping with a scalpel.  The proximal contacts should be left slightly too tight in the dental laboratory.  For such multiple castings, clinical evaluation is done sequentially and on an individual basis. 2/11/2023 M.Hosny 17 Zone 4:- Proximal contact  Adjustments are made for each casting independently.  When adjusting proximal contacts, placing a thin Mylar articulating film between adjacent castings or between the casting and the adjacent tooth is helpful. 2/11/2023 M.Hosny 18 Mesial & Distal Contacts  Fit die and crown  If tight contact take articulating paper, then mark and remove some metal.  Remove heavy contact mesial first, with sandpaper-disk or rubber wheel.  Try in again, repeat if needed. 2/11/2023 M.Hosny 19 Connectors.  Unless they are properly contoured and highly polished, periodontal health will invariably be affected, even in the presence of the most meticulous oral hygiene.  Rotary instruments such as rubber wheels, which allow access to the cervical aspect of the connector for finishing while not injury the margin, are essential in these situations.  In cases of root proximity between adjacent teeth, this can be quite problematic. After preliminary finishing with rubber wheels, a piece of twine can be used to impart the final polish to the cervical aspect of the connector. 2/11/2023 M.Hosny 20 Zone 5:- Occlusal surface Objective:  Occlusal contacts are reestablished in static and dynamic relationships to the opposing arch.  Occlusal morphology must ensure positional stability and satisfy all functional requirements. Procedure:  The occlusal contacts are checked with thin Mylar articulating film.  If an occlusal contact is heavy in wax, it will spring back slightly when the articulator is opened and produce an occlusal prematurity in the casting.  If "pinpoint“ contacts are established carefully during the waxing phase, significant occlusal adjustment should not be necessary. 2/11/2023 M.Hosny 21 Zone 5:- Occlusal surface  Occlusal adjustments can be performed with flame shaped finishing burs or diamonds .  The correct technique for occlusal adjustment is to redevelop the anatomy of entire ridge or cusp rather than grinding only the point of interference.  The grooves and any nodules can be defined with a finishing bur or a small rounded bur.  Before starting any adjustment, the practitioner should use a thickness gauge on the metal. If only minimum clearance was established at the tooth preparation stage. 2/11/2023 M.Hosny 22 2/11/2023 M.Hosny 23 Zone 6:- Axial walls The objective: Axial wall should be smoothly contoured and highly polished, enabling the patient to carry out optimum plaque control. Procedure: Surface defects are removed by grinding with abrasive particles bound into a grinding stone or rubber wheel, and a paper disk. The axial surfaces of the restoration are polished. Jeweler's rouge will rapidly produce a high polish on a well- prepared surface of a dense casting. 2/11/2023 M.Hosny 24 Zone 7:- External margins The objective: All cast restoration finishing is a highly polished metal surface without ledges or steps. The parts of the margin that cannot be finished on the tooth are finished on the die. Procedure: Finishing should be performed by gently brushing a fine grit stone over the surface to remove casting roughness followed by a soft rubber wheel or point and finally by rouge on a brush. The margin should be supported with a finger during final polishing. 2/11/2023 M.Hosny 25 Finishing and polishing summary 1. The internal margin is inspected to confirm that the casting accurately reproduces the prepared tooth and is intimately adapted to the prepared surfaces adjacent to the margin. 2. The internal surface is inspected under magnification and adjusted as necessary with small stones and tungsten carbide burs. 3. The casting should seat completely without force and without noticeable rocking or instability. 4. The sprue is removed, and the area of its attachment is reshaped. 5. The proximal contact areas are identified. 6. On the cast, proximal contacts can be left slightly tight before the clinical evaluation appointment. 2/11/2023 M.Hosny 26 Finishing and polishing summary 7. The occlusal surfaces are evaluated and adjusted. No centric or excursive interferences should remain . 8. The axial surfaces are finished and polished . 9. The polished restoration is cleaned. A steam cleaner or ultrasonic cleaner (with the appropriate solutions) can be used cleaned castings are seated on the definitive cast. 2/11/2023 M.Hosny 27 Any Questions References Contemporary of Fixed Prosthodontics. 5th edition. P. 736 2/11/2023 M.Hosny 28 2/11/2023 M.Hosny 29