altered-cast.pptx

altered cast

1. Altered-cast technique: Overview around research and articles Supervision : Dr. Runak Prepared: Ammar G. Salem

2. introduction It was originally described more than 80 years ago. It was developed to improve the residual ridge to dentition relationship of the prosthesis. This technique has the potential benefits of reducing the number of postoperative visits, preserving the residual ridges, improving stress distribution, decreasing food impaction and decreasing the torqueing of abutment teeth .

3. What is successful RPD ( Steffel ) Cross-stability of the framework. Maximal coverage of the edentulous residual ridge. Stress control .

4. According to Becker and Kaiser Rigid major connector. Multiple positive rest seats. Mesial rests. Parallel guide planes. I-bar clasp design. Altered-cast technique The single most important factor in minimizing abutment tooth movement is the fit of the base . (Tylor and colleagues, Tebrock and colleagues) The tissue surface of the distal extension RPD should cover the residual ridges at the most relaxed stat e when not in function.

5. Importance of altered-cast technique Holmes and Leupold showed that the altered cast impression technique demonstrated the least amount of movement of the base at the time of placement and the most favorable ridge-to-denture-base relationship.

6. Basic technique The custom resin tray covers the occlusal surfaces of teeth with a minimum of three definitive stops to ensure repeatable placement in the mouth each time. The edentulous ridge was covered with single sheet of wax. Using fluid wax korecta Wax I-IV applied to tissue surface of the tray, it was applied incrementally to achieve the final impression.

7. What were the objectives of Applegate The area covered should be maximized to minimize the work of any given surface. Traumatic impact on any area must be avoided so that the workload is spread as uniformly as possible to avoid impinging on areas with less displaceable mucosa. At rest , there must not be any areas of ischemic mucosa . All areas under load must receive stimulation. Simultaneous support must be given to the base and the supporting teeth. Movable border structures should be extended during the making of the impression to avoid impingement on any functional movement after completion of the base.

8. Technique The impression material should be very accurate and easily manipulated to record the remaining dentition. (in this case you can use elastomeric impression material, or hydrocolloid in a stock metal tray. The residual ridge has two forms: Functional : when tissue is under load . Anatomic : when tissue at rest . It is desirable to record the residual ridge in its functional state , thus the material used to register the ridge may not be suitable to record the teeth . For this reason the RPD framework is cast and fitted before the altered cast final impression is made. This ensure that the metal framework and the base will be related in the same relationship as that which exist between abutment tooth and the supporting mucosa when the base has an occlusal force applied.

9. Technique (continue) Once the framework is fit, an acrylic resin custom tray attached to the metal framework on the physical retainer. The tray then border-molded (using impression compound). Place some vent holes in the tray over the ridge crest and retromolar pad . Final impression is done with polysulfide rubber impression . The framework attached to a custom tray that is lined with a wash of impression, is placed in the patient’s mouth and seated completely without any pressure on the tray. The finger pressure is applied only to the parts of the framework that in contact with teeth. Pressure on the tray area can cause lifting off of the framework off the teeth.

10. Improper impression can result : Overstimulation of the underlying bone (due to too much work and poor stress distribution). Understimulation of the softer mucosa (due to too little or no work). Destructive leverage applied to abutment teeth.

11. Final impression

12. Laboratory procedure Two saw cuts are made perpendicular to each other . 1 st cut 0.5-1.0mm distal to the most distal remaining tooth and perpendicular to the edentulous ridge. This cut carried from outer edge of the cast to 6.0-7.0mm medial to the lingual vestibule. 2 nd cut made parallel and medial to the edentulous ridge, extending from the most posterior aspect of the cast to the most medial aspect of the 1 st cut. 1 st and 2 nd cuts intersect , the edentulous ridge will separate from the cast. In case of maxillary arch, provide the internal finish line of the framework processed against the altered cast.

13. Lab procedure (continue) The cut surface should have grooves to aid retention of newly poured stone. Completely seat the framework on the cast. Lute the framework to the cast via sticky wax. (an error at this stage will create prosthesis with faulty relationship between the edentulous ridges and the remaining dentition). Bead and box , then soak in a cool water bath to saturate the base of the remaining cast. Using model stone type III poured and wait to set in minimum 45 minutes. After the cast prepared remove the acrylic resin tray from the framework. The frame then fitted back to the cast.

14. Making an index tissue stops It is mandatory that the occlusal rests be completely seated during both clinical and laboratory procedures to avoid over- or under-displacement of the soft tissues. For patients with few anterior teeth remaining , a condition result in long distal-extension ridges in which the rotational stability of RPD is mainly tissue dependent. As can be seen tissue stops are touching the cast on crest ridge.

15. Procedure For stabilizing the framework in class I Kennedy, tissue stops are commonly used to contact the edentulous ridges of the cast. A 3 rd reference point (stone index) placed under the lingual bar must be used before altered-cast impression is made. Why? Because the tissue stops will be covered by the impression material and will be useless for re-orienting the framework to the altered-cast.

16. Procedure The idea of the stone index is to aid the occlusal rests in orientation of the framework to the master cast. Fabricate the framework for RPD and refine its fit intraorally. Place the framework on the master cast and fill the space under the bar with stone. While the framework is on the master cast, adapt acrylic resin over its latticework to make a custom impression tray.

17. Procedure 4. Make a corrected impression of the distal extension residual ridges at the established vertical dimension of occlusion and horizontal jaw relationship. 5. Alter the master cast by a removing the residual edentulous ridge nd reposition the completed impressio n on the sectioned master cast. The secure it with sticky wax around the clasp arms. 6. Box the cast and add dental stone to the impressions of the edentulous portions to make the altered-cast.

18. Procedure 7. Soak the poured altered-cast in warm slurry water to soften the impression material, clean the cast, and reposition the cleaned metal framework onto the lingual index of the altered cast.

19. Making framework try-in, altered cast impression and occlusal registration in one appointment (Introduction) This method use detachable custom-made prefabricated impression trays. It uses this impression as a stable recording base to make the jaw relation record .

20. Making framework try-in, altered cast impression and occlusal registration in one appointment (Procedure) Apply the separating medium on the master cast. Place the framework on the master cast. Block out all undercuts around the retentive grid on the edentulous portion of the framework with wax. Make individual impression trays over the distal extension bases with autopolymerizing tray resin.

21. Making framework try-in, altered cast impression and occlusal registration in one appointment (Procedure) 5. Remove the tray and trim the excess resin. 6. try-in the framework and adjust it to fit. 7. Place the framework on the master cast and attach the prefabricated trays with autopolymerizing resin. 8. adjust the borders and tissue surface of the bases in the mouth. Examine the thickness of the tray to be certain that it does not interfere with the occlusion. 9. Remove any interferences and prepare few grooves as an index on the occlusal surface of the tray to permit reseating the jaw registration material.

22. Making framework try-in, altered cast impression and occlusal registration in one appointment (Procedure) 10. Make the altered cast impression with alginate or silicon impression material and mold the material around the border as it sets. 11. Trim excess of impression especially in the occlusal surface of the denture base. 12. Make the jaw relation record with accurate registration material (silicon, polyether, or zinc oxide eugenol). 13. Remove the framework with the distal extension altered cast impression and the jaw relation record from the patient’s mouth. 14. Box the framework and the altered cast impression with alginate and pour the altered cast in dental stone.

23. Making framework try-in, altered cast impression and occlusal registration in one appointment (Procedure)

24. Making framework try-in, altered cast impression and occlusal registration in one appointment (Procedure) 15. mount the maxillary and mandibular casts in articulator with the jaw record. 16. After mounting the cast, remove the registration material, impression trays, and impression material from the framework. (using hot water or alcohol frame to soften the material). 17. set the teeth and process, finish and polish.

25. The undercuts are blocked out with wax in the retentive grid areas where impression trays will be attached. The surfaces need block-out beneath the retentive grid and around soldered wire clasps. Separating medium is applied to the cast, framework and block-out.

26. method to register the mucosa and its supporting form Functional reline; after the denture base has been proc essed onto the framework, it has disadvantage of greater degree of occlusal adjustment after the processing of acrylic resin. Altered-cast method; carried out before the denture bases are processed.

27. Other method to separate the edentulous portion from the rest of the cast Separating the cast without use of the plaster saw. Advantages: Edentulous portion can be separated easily . No need to saw the cast or make dovetails for retention. Edentulous portion can be separated even if cast is wet . Disadvantage: The cast cannot be used with hydrocolloid impression because it require quick pouring of the impression. The impression cannot be boxed because it will distort as a result of pressure.

28. Other method to separate the edentulous portion from the rest of the cast (Procedure) Make a bar with baseplate wax with shape of a 5mm equilateral triangle in cross section. It should be made in advance to save time. Cut several pieces of the wax bar 15mm long and set them aside. Box the elastomeric final impression. Separate the edentulous ridges distal to the last tooth in the impression by contouring a piece of baseplate wax to fit the anatomic contour of the impression, and seal it to the base to make three separate compartments of the impression. If separating wax is not close enough to the distal surface of the last tooth of the impression, the edentulous portion of the cast left distal to the last tooth can be trimmed after the edentulous pieces of the cast are removed.

29. Other method to separate the edentulous portion from the rest of the cast (continue) 5. wax the 15mm long pieces of triangular wax bars to the separating baseplate wax. Make the apex of the triangle sealed securely to the separating baseplate wax toward the tongue side and anterior to the edentulous ridge. 6. fill the three compartments with dental stone above the level of separating wax to make a master cast. 7. after setting of stone, remove the boxing wax and impression and trim the base of the cast until a stone base at least 3 to 5 mm thick remains below the separating wax. (to prevent premature separation). 8. after making framework, and fitted to the cast and patient’s mouth, place the framework on the cast and adapt a shellac baseplate or form an acrylic resin baseplate over the edentulous retention portion of the ridges and proceed to make the impression. After displacement impression is made, separate the edentulous portion of the original cast and discard it, to permit placing the framework with the new impression on the original cast.

30. Other method to separate the edentulous portion from the rest of the cast (continue) 9. soak the cast in slurry water for 3-5 minutes and trim the base of the cast up to the line to expose the separating wax. 10. put the master cast in boiling water for 5 minutes. The clear slurry water should be saturated with stone in order not to dissolve the cast. 11. after melting the wax, the edentulous portions will be separated from the rest of the cast and dovetails will appear. 12. flush to remove all wax, seat the framework with the new impression and pour the new portions of the cast. (if too much of the old edentulous ridge is left, the framework with the new impression may not seat well. (use sharp knife to trim the ridge back to the distal side of the last tooth).

31. Other method to separate the edentulous portion from the rest of the cast

32. In 2004, (Richard et al.) compared between altered case and one-piece cast with regard to base support, abutment health, and patient comfort over time. He reported that the altered cast impression procedure does not offer significant advantages over the one-piece cast, provided the standards used in his are met, including a completely extended impression , use of magnification to adjust and ensure complete framework seatin g, and coverage of the retromolar pad and buccal shelf by the base . He reported that those studies which are in favor of ACIP did not involve more than 7 subjects and 2 studies and the evaluation of base support done in a manner not used in clinical practice. It was hypothesized that there would be no difference between the ACIP and OPC relative to these variables: border extension, frequency/amount of base adjustment needed, base movement, base adaptation, need for reline, changes in direct abutment mobility, gingival index, sulcus depth, quality of posterior occlusion, health of tissues beneath the RPDs, patient satisfaction, time worn, and soreness reported by the patient. All were accepted in the result except for border extension and adaptation of the base to the ridge crest . Under extension was noted in 22% of the OPC and in none of the ACIP. Causing of under-extension could be: difficulty to recognize anatomical landmarks, underextended impressions, under-waxed or over-finished bases, aggressive base adjustment, lack of space, or patient demand.

33. Although Maxfield et al. reported that ACIP decreases the load on the direct abutments, it does not appear that such difference has any detrimental effect. But the increase in inflammation around the direct retainer underscores the importance of periodic reinforcement of oral hygiene instructions (Bregman et al) To substitute ACIP, three conditions should be met; a framework that exhibit complete seating under x2.5 magnification , the impression records all applicable landmark s, and the base extension is neither under-extended nor over-finished. Otherwise, the practitioner should either use the ACIP, a custom impression tray, or evaluate base movement during framework evaluation with an attached occlusion rim (if movement is noted ACIP should be performed).

34. Framework fit and altered cast impression Problems that may arise because the impression material being placed between framework and mucosa, which lift away the framework from the mucosa; subsequently, during flasking, the framework will depress again, producing inaccuracies in the prosthesis. Pressing down on the framework while making the impression, may give inacceptable results, because it is difficult to judge how much pressure to exert; in addition, the act of pressing down may itself cause slight displacement. An alternative approach is to take the altered cast impression first, and then to obtain jaw relation record in silicon; however, major two disadvantages come ahead; first, it is difficult to ensure that the framework will remain in the correct position. Second, the impression material used for obtaining the jaw relation record may be displaced slightly, leading to inaccuracies in the final structure. Another approach is to use the framework as record base; however, this procedure is also sometimes inaccurate.

35. Framework fit and altered cast impression Check the fit of framework for its passive fit and absence of occlusal interferences. Make a tray base by light-cured acrylic resin, modeling compound or thermoplastic baseplate material.

36. procedure Build ¼ inch diameter column of light-cured resin on the resin-retention part of the framework in the position corresponding to the hole in the acrylic resin tray. Extend the column up to the opposing occlusion in the correct jaw relation. This tripod of anterior teeth and two columns distally ensures the framework seating in the same way each time. Remove the framework and seat it on the master cast and mount it on an articulator with an opposing cast. A stone index prepared below the lingual major connector, facilitating and improving positioning when the framework is reseated on the altered master cast. Enlarge the holes, if necessary, in the bases so that they fit correctly over the resin columns. Seat the bases over the framework and heat them and adapt them to the framework, making certain that they are firmly attached to it.

37. Procedue

38. Procedure 3. place framework with the base in the mouth and relieve over-extensions and pressure spots, then apply low heat softened compound to the borders and border mold it. 4. remove the framework-tray complex, apply impression wax into the tray, then reinsert the whole structure and maintain it in the mouth while the wax adapts to the edentulous ridge. Ask the patient to make molding movements. 5. remove the edentulous ridge from the cast by two cuts, longitudinal and at right angle to the longitudinal axis of the ridge, 1mm distal to the abutment.

39. Procedure

40. Procedure 6. score the cut surfaces with a knife or bur to ensure good attachment of the new stone to the old. 7. position the framework-impression assembly on the cast, making sure the framework seating correctly on the teeth and in the index for the bar. If there is any chance of change in positions during the boxing procedure, wax it securely in place with sticky wax. 8. bead and box the cast with wax. And seal it very well. 9. pour a mix of stone and allow it to set. 10. remove block-out and boxing from the cast but do not separate framework-impression assembly from the cast. 11. mount mandibular cast in articulator after reassuring the correct position of resin against maxillary cast. 12. remove framework-impression assembly.

41. procedure

42. Discussion The index overcome the problem of too much or less pressure exerted during impression, ensuring correct position during impression taking. The index act as jaw relation record. This photochemical index is more reliable than elastomeric material which does not remain joined to the impression. A minor disadvantage, if the patient has an antagonist edentulous area. To avoid such problem instruct the patient not to clench tightly, but simply bring the maxillary and mandibular arches together Advantages; molding can be made with mouth closed, require little time, can be performed in clinic without new jaw relation trays, obviates the stage of functional and harmonious occlusion, and stable and rigid jaw relation index.

43. Stereolithographic resin pattern Using CAD/CAM/RP technologies, a one-piece stereolithographic resin structure is used for making framework evaluation, altered-cast impression, and maxillomandibular relationship record in a single appointment. Procedure: Scanning the cast, then design the framework with CAD software. Make altered cast impression trays based on the original framework design. Transfer the finished design to rapid prototyping machine. Make a stereolithographic resin pattern of the framework and cast it. Print the one-piece stereolithographic resin structure of the altered cast impression trays and record rims. Make altered cast impression with compound border molding and polyvinyl siloxane material. Obtain maxillomandibular relationship with occlusal registration material. Mount the cast in the articulator, remove the 1-piece stereolithographic resin structure from the altered cast and place the cast framework.

44. Using altered-cast technique in prosthetic rehab of a patient after a maxillectomy After primary impression capturing the crowns was made with irreversible hydrocolloid impression material. This captures all the intraoral structures of non-resected side and part of the resection defect with sufficient extension for the production of a cast framework for the maxillary obturator. Poured with dental stone, a maxillary obturator cast framework produced from Co-Cr-Mo alloy. The cast framework was modified in such a way that retentive mesh and dowels were added over the resection defect to ensure retention for secondary alter cast impression material and for acrylic resin bulb of the obturator. An altered cast impression was made with condensation high and low viscosity silicone materials placed on and inserted intraorally with the obturator framework serving as the tray.

45. Procedure (continue) The stone cast was altered and the portion of the cast corresponding to the resection defect was trimmed until it was possible for the obturator cast framework to be place on it with altered cast impression, then it was poured in dental stone. The predicted shape of maxillary sinus was formed by using polyvinyl siloxane to produce a concave shape of the obturator toward sinus cavity. The hollow bulb obturator was made by pouring autopolymerizing acrylic resin in the newly formed resection defect on the altered cast, covering retentive elements of the case framework.

46. References: Santana- penin U., Gil Lozano J. 1998, ‘an accurate method for occlusal registration and altered-cast impression for removable partial dentures during the same visit as the framework try-in’, the journal of prosthetic dentistry , vol. 80, no. 5, pp. 615-618. Ansari 1994, ‘a new procedure for separating the edentulous distal extension portion from the master cast when an altered cast is made’, the journal of prosthetic dentistry, vol. 72, no. 6, pp. 666-669. Daniel B. 1999, ‘ the altered cast technique revisited’, JADA, Vol. 130, October, pp. 1476-1481. Frank Richard P., Brudvik James S., Noonan Carolyn Jean 2004, ‘clinical outcome of the altered cast impression procedure compared with use of a one-piece cast’, the journal of prosthetic dentistry, Vol. 91, no. 5, pp. 468-476. Lay Lih-Shou , Lai Wing-Hong, Wu Chen- Tsye 1996, ‘making the framework try-in, altered-cast impression, and occlusal registration in one appointment’, the journal of prosthetic dentistry, Vol. 75, no. 4, pp. 446-448. Lee Ju- Hyoung , Lee Cheong- Hee 2015, ‘a stereolithographic resin pattern for evaluating the framework, altered cast partial removable dental prosthesis impression, and maxillomandibular relationship record in a single appointment’, the journal of prosthetic dentistry, Vol. 114, no. 5, pp. 625-626. Lund Peter S., Aquilino Steven A. 1991, ‘prefabricated custom impression trays for the altered cast technique’, the journal of prosthetic dentistry, Vol. 66, pp. 782-783. Shifman Arie 1991, ‘index to reposition the metal framework accurately on the altered cast’, the journal of prosthetic dentistry, Vol. 68, pp. 979-981. Vojvodic Denis, Kranjcic Josip 2013, ‘a two-step (altered cast) impression technique in the prosthetic rehabilitation of a patient after a maxillectomy: a clinical report’, the journal of prosthetic dentistry, Vol. 110, no. 3, pp. 228-231.

47. Thank you for attention Created 23/11/2019