Special impression partial -MF 2.pptx

MOSTAFA FAYAD 1 Special impression Techniques for RPD Dr. Mostafa Fayad Professor of Removable Prosthodontics [email protected] 0534642247 MOSTAFA FAYAD 3 IMPRESSION It Is a negative reproduction of dental structures from which a positive cast can be made. Secondary impression It is a...

MOSTAFA FAYAD 1 Special impression Techniques for RPD Dr. Mostafa Fayad Professor of Removable Prosthodontics [email protected] 0534642247 MOSTAFA FAYAD 3 IMPRESSION It Is a negative reproduction of dental structures from which a positive cast can be made. Secondary impression It is an impression made in a special tray and is used for making the master cast, on which the denture is constructed. MOSTAFA FAYAD 4 Types of Removable Partial Dentures Functional Design Classification 1. Tooth Borne Partial Dentures 2. Extension Base Partial Dentures MOSTAFA FAYAD 5 Factors influencing the support of a distal extension base: a) b) c) d) e) f) g) Quality of soft tissue covering edentulous ridge Contour and quality of the residual ridge. Extent of residual ridge coverage by the denture base. Accuracy of the fit of the denture base. Design of the partial denture framework. Total occlusal load applied. Type and accuracy of the impression. MOSTAFA FAYAD 6 Different Displacement Between PDL & Mucosa Periodontal ligament (0.25mm) MOSTAFA FAYAD Mucosa (2.0mm) 7 TYPES OF IMPRESSION IMPRESSION MAKING PROCEDURES GENERALLY FALL IN TO TWO GENERAL GROUPS:ONE INVOLVES USE OF SINGLE MIX OF IMPRESSION MATERIAL TO MAKE IMPRESSION AND USE OF ONE PIECE CAST TO FABRICATE PROSTHESISSECOND GROUP INVOLVES USE OF TWO SECTION IMPRESSION AND USE OF EITHER A ONE OR TWO SECTION CAST TO FABRICATE PROSTHESIS- Dual Impression MOSTAFA FAYAD 8 Anatomic impression: It is an impression made with the least possible displacement of the tissues covering the residual ridge. Physiologic or functional impression (Dual impression): It is an impression that is made by placing occlusal load or finger load on the edentulous area as the impression is being made. MOSTAFA FAYAD 9 Impression 1Anatomic ridge form: Techniques  for tooth suppoted R.P.D. (Kenedy‘s class III, short span class IV)  so the edentulous ridges don´t contribute to the support of the R.P.D.  Single, pressure-free imp. records the teeth and soft tissues in their anatomic form . MOSTAFA FAYAD 10 A-Anatomic Impressions A tooth supported RPD Anatomic from. MOSTAFA FAYAD 11 Pressure - free impression, Single impression, Anatomic impression: It is an impression made with the least possible displacement of the tissues covering the residual ridge. This technique records the tissues in its anatomic form. It is used for removable partial dentures that are completely tooth-supported. MOSTAFA FAYAD 12 Anatomic impression This technique requires custom made tray fabricated over one layer wax spacer over edentulous areas and two layers over remaining teeth. Holes may also be added and minimal pressure with easy flowing material is applied. MOSTAFA FAYAD 13 Wax spacer Perforated tray Border molding Final impression MOSTAFA FAYAD 14 Impression 2-Physiologic or functional Techniques ridge form: ◦ ◦ for tooth- tissue supported R.P.D. (Kenedy‘s class I,II,long span class IV) When the occlusal forces fall on toothtissue supported R.P.D., the ridge contribute to support as well as teeth This imp. recordteeth in their anatomic form and the ridge in its functional form under pressure. MOSTAFA FAYAD 15 Secondary Impression Secondary Impression Pressure-free impression (Anatomic) dual impression MOSTAFA FAYAD 16 B- Dual impression A tooth tissue supported RPD MOSTAFA FAYAD 17 The purpose of this is to obtain the maximum support possible from the edentulous area of the extension partial denture. MOSTAFA FAYAD 18 Physiologic or functional impression (Dual impression): It is an impression that is made by placing occlusal load or finger load on the edentulous area as the impression is being made. It captures the physiologic form of the ridge and used for tooth-tissue supported cases. MOSTAFA FAYAD 19 Indications of Functional Impressions Mandibular distal extension ridge and Long- span anterior edentulous ridge MOSTAFA FAYAD 20 Dual impression The objectives of any functional impression technique are: ◦Equalize as much as possible the support derived from the edentulous area, and that received from the abutment teeth. ◦Provide maximum support for the removable partial denture base, thereby distribute the load over as large an area as possible. ◦ maintenance of occlusal contact between both natural and artificial dentition ◦Direct the force to the primary stress bearing areas. ◦Minimize movement of the base which would create leverage on the abutment. MOSTAFA FAYAD 21 Dual impression It could be classified according to prosthetic step at which the impression is done: Impression at the secondary impression stage. Impression after constructing metal framework. Impression at insertion step. MOSTAFA FAYAD 22 Impression for distal extension R.P.D. At the imp. stage: Mclean´s and Hindel´s methods = dual imp. Technique = pseudo-functional imp. or Impressions with custom trays. At the framework stage: Altered cast method either by functional imp.method (fluid wax) or by selected pressure imp.method At the finished denture stage: Functional relining method using fluid wax or zinc oxide euginol or rubber base relining method. MOSTAFA FAYAD 23 Dual impression Selected pressure Functional impression (physiologic) technique: impression Relate the residual ridge to techniques: the remaining natural teeth Relate the residual ridge to as if a functional the remaining natural teeth masticatory load is applied as if a functional to the denture base and masticatory load is applied direct the force to the to the denture base so positions in the ridge that equalize the support most capable of FAYAD MOSTAFA between the abutment 24 DUAL IMPRESSION MOSTAFA FAYAD 25 Imp. for Dis. Ex. 1At the imp. stage: R.P.D. ◦ ◦ ◦ McLean‘s technique (closed mouth) The technique consists of making an impression of the edentulous ridge in border-moulded denture base tray which is provided with occlusion rims. Impression paste is used to record ridge areas under biting stresses After setting of ZnO eugenol it is removed, tested, reinserted; overall alginate impression is made with the ZnO imp.seated in the mouth. MOSTAFA FAYAD 26 Mclean impression This impression require custom tray over edentulous areas. Physiologic impression is done under occlusal forces. An overall alginate impression is done under finger pressure. The main weakness of this type of impression is the occlusal pressure could not be transferred to the final impression. MOSTAFA FAYAD 27 Custom impression tray with a modeling plastic occlusion rim A functional impression of the distal extension ridge MOSTAFA FAYAD 28 MOSTAFA FAYAD 29 DISADVANTAGES: 1. The 2nd impression is made under finger pressure , that could not record exactly the functional displacement of the tissues that the biting force produced. 2. The mouth is closed , so visibility is not good. MOSTAFA FAYAD 30 Imp. for Dis. Ex. 1- At the imp. stage: R.P.D. Hindle‘s technique (opened mouth) ◦ The same idea of McLean‘s technique but instead of the occlusion rims, use finger pressure through 2 circular openings in the posterior region of the hydrocolloid imp. Tray. MOSTAFA FAYAD 31 MOSTAFA FAYAD 32 Hindle impression This impression also requires custom tray over edentulous areas. After physiologic impression done under finger pressure, stock tray with two large holes is prepared. An overall alginate impression is done with pressure applied by fingers through the two holes. MOSTAFA FAYAD 33 MOSTAFA FAYAD 34 The main drawback of this technique is: The use of the tray with holes in this technique eliminates the possibility of error arising from incorrectly placed modeling plastic stops (in the previous technique). However, it did not eliminate the variable of the dentist's individual interpretation of what constitutes functional loading. MOSTAFA FAYAD 35 Disadvantages ◦If the clasp action is sufficient to maintain the denture base in its intended position, This may result in compromised blood flow with adverse soft tissue reaction and bone resorption. ◦If clasp action is not sufficient to maintain that functional relationship of the denture base to the soft tissue, this will result in floating denture with premature contact and patient dissatisfaction. MOSTAFA FAYAD 36 Physiologic impression The main disadvantages of these impressions If clasps is rigid The tissues have no chance to rest and so impingement on the blood supply If clasps is flexible tissue rebound will expected with initial occlusal contact on artificial teeth MOSTAFA FAYAD 37 One stage selected pressure impression technique MOSTAFA FAYAD 38 One stage selected pressure impression technique It is a single impression made after the mouth preparation & made before framework construction 1) Special tray is constructed on study cast as follow • 2 layers of base plate wax relief is adapted on the teeth and residual ridges . • Aluminum foil is burnished over the wax . • Cutting boxes through the foil and making occlusal stops which are placed over the remaining teeth to ensure proper seating of the tray • Construct a special tray short 2 mm of the border . • Remove wax and foil MOSTAFA fromFAYAD the cast and wet the surface 39 2) Softened compound is applied on the tissue surface on the tray corresponding to the ridge , (first seat the compound on the cast to shape the compound before placement intra-oral) . 3) Reheat compound and place it in the mouth . 4) Apply compound to the borders for border molding . 5) Relief tissue surface of the compound except 1ry stress bearing area . 6) Rubber base impression with finger pressure . 7) Master cast , and framework construction . MOSTAFA FAYAD 40 Selective pressure impression This type of impression is done using adequately spaced special tray. Low fusing compound is added in the edentulous areas then seated in the patient mouth then border molded. Scrapping of the areas that require relief as an edentulous ridge is done. Elastic impression material wash (like rubber base) is done. MOSTAFA FAYAD 41 One Stage Selected Pressure Impression Technique Adapt two layers of base plate wax to provide enough space for alginate bulk The wax spacer is short of the vestibule Wax Spacer for the alginate custom tray: MOSTAFA FAYAD 42 One Stage Selected Pressure Impression Technique A P P LY S PA C E R F O R I M P R E SS I O N M AT E R I A L . E L A S T O M E R I C M AT E R I A L : 2 - 4 M M A L G I N AT E : M I N I M U M 3 M M MOSTAFA FAYAD 44 Imp. for Dis. Ex. R.P.D. 2. At the framework stage: MOSTAFA FAYAD 45 Altered cast method : Steps: 1- after the RPD frame work is constucted on anatomic imp.cast.it should be evaluated for any metal projections and sharp edges. 2-check the RPD metal frame work in the patient’s mouth MOSTAFA FAYAD 46 Altered cast method 3-the impression tray is made using chemically activated resin, a the frame work with the attached impression tray is placed in the patient’s mouth and correct peripheral extension 4-border molding the impression tray using low fusing modeling plastic < green or grey sticks > MOSTAFA FAYAD 47 Altered cast method 5-the final impression is made by using zinc-oxide euginol paste with the mouth opened and tripod pressure is applied on occlusal rests and indirect retainer 6-after the impression material is set, the tray is removed and checked for any discrepancies MOSTAFA FAYAD 48 Altered cast method 7. The metal framework with the attached imp. is positioned on the master cast with all occlusal rests properly seated in their prepared recesses. 8. The entire assembly is boxed and poured in a different colored stone. MOSTAFA FAYAD 49 Altered cast technique This technique could be named according to cast formation as a split cast technique or may be named according to impression material used as fluid wax technique. Special tray made from acrylic resin attached to the metal framework which is fabricated on anatomic cast. The frequently used fluid waxes are Iowa wax and Korrecta wax No 4. MOSTAFA FAYAD 50 Altered cast technique The tray is selectively relieved for the lower arch. In addition holes are drilled opposite to the residual ridge and retromolar pad to allow escape of excess impression material as the impression is being made. Wax is painted in the fitting surface then inserted in the patient mouth for about 5 minutes with the dentist three fingers placed on the two principal occlusal rest and indirect retainer. MOSTAFA FAYAD 51 MOSTAFA FAYAD 52 Vent holes are placed in the plastic tray near the finish line for escape of excess impression material MOSTAFA FAYAD 53 MOSTAFA FAYAD 54 The sectional impression on the sectioned cast. MOSTAFA FAYAD 55 Retention grooves are placed in the cast. The impression is beaded and boxed and ready to be poured in vacuum-mixed stone. MOSTAFA FAYAD 56 A new base poured into the sectional impression MOSTAFA FAYAD 57 Imp. for Dis. Ex. R.P.D. 3- At the finished denture stage: Functional relining method: MOSTAFA FAYAD 58 Functional reline method This procedure is accomplished before the insertion of the partial denture. The partial denture is constructed on a master cast made from a single. A space is provided on the tissue surface of the denture base to allow room for the impression material. Low fusing compound is added, border molded then checked for any pressure. MOSTAFA FAYAD 59 Functional reline method Compound is shortened and releived by scrapping except buccal shelf area. Free flowing zinc oxide is used to make the wash impression with operator fingers resting on principles rests and the indirect retainer. As in all reline procedures, occlusal discrepancies must be corrected after the denture base has been processed. MOSTAFA FAYAD 60 MOSTAFA FAYAD 61 Disadvantages: a) Failure to maintain the correct relationship between the framework and the abutment teeth. b) Failure to maintain correct occlusion. MOSTAFA FAYAD 62 The functional impression techniques can be performed with different impression materials Zinc oxide and eugenol paste or Fluid wax. After border molding with green stick compound MOSTAFA FAYAD 63 Fluid wax are waxes that are firm at room temperature and have the ability to flow in mouth tempratures (lowa wax no. 1 and Korrecta wax no 4) MOSTAFA FAYAD 64 Thank You MOSTAFA FAYAD 65