Impression Trays PDF

IMPRESSION TRAYS D R. S A R A K A MAL lecturer, department of prosthodontics. AASTMT D R. M A I S A LAH E L - D IN A H M E D Lecturer, Department Of Prosthodontics. AASTMT D R. Y A R A K AMMOUN Lecturer, Department Of Prosthodontics. AASTMT 1 ...

IMPRESSION TRAYS D R. S A R A K A MAL lecturer, department of prosthodontics. AASTMT D R. M A I S A LAH E L - D IN A H M E D Lecturer, Department Of Prosthodontics. AASTMT D R. Y A R A K AMMOUN Lecturer, Department Of Prosthodontics. AASTMT 1  OUTLINE Introduction & terminology. Objectives of impression. Parts of impression trays. Types of impression trays. 2  Introduction & terminology.  Impression: It is an imprint or negative reproduction of an object from which a positive likeness or cast can be made. 3  Introduction & terminology.  Impression: In dental prosthetics, an impression is a negative registration of the entire denture bearing area. *An impression is made in order to reproduce a positive form of the oral tissue (cast). 4  INTRODUCTION & TERMINOLOGY.  Cast: It is a positive reproduction of the form of the tissues of the upper or lower arch over which denture bases or other dental restorations may be fabricated. 5  INTRODUCTION & TERMINOLOGY.  Impression tray: It is a device used to carry, confine and support impression material in correct position while it is hardening (during the impression procedure) Thus … Functions are : Support impression material in contact with oral tissues. Support impression material when removed from the mouth so it can be poured. 6  Introduction & terminology. Complete Denture Construction Steps: Clinical steps Laboratory steps 1.Examination of the patient. 2-Primary Impression (preliminary) a. Pouring the impression and preparation of the study cast b. Construction of custom tray 3- Final impression (secondary) a. Pouring master cast b. Construction of record blocks. 4- Recording jaw relation Mounting the cast on the articulator Selection of teeth Arrangement of artificial teeth Wax contouring.. 5- Trying in the denture. Flasking 6- Denture insertion. 7. Post insertion care. 7  Introduction & terminology.  Preliminary Impression: It is an impression in a stock tray for making a study cast on which a custom tray is constructed.  Introduction & terminology.  Study (diagnostic) cast: A cast formed from a primary impression for use in diagnosis or the construction of custom tray.   Preliminary Impression:  Study (diagnostic) cast: It is an impression in a stock tray for A cast formed from a primary impression for use in diagnosis or making a study cast on which a the construction of custom tray. custom tray is constructed.  Introduction & terminology.  Final Impression  Master cast (definitive): It is an impression made in custom tray and it is used for the purpose A cast formed from a final impression and of making the master cast on used for fabrication of the prosthesis. which the denture is constructed.  OBJECTIVES OF IMPRESSION 1. Preservation of remaining tissues. 2. Support. 3. Retention. 4. Stability. 5. Esthetics. 12  OBJECTIVES OF IMPRESSION 1. Preservation of remaining tissues : Pressure in the impression technique is reflected as pressure in the denture base and results in soft tissue damage and bone resorption. 13  OBJECTIVES OF IMPRESSION 2. Support: It is the quality of prosthesis to resist the forces which dislodge the denture in a tissue- ward direction. Maximum coverage provides the greater the support and distributes applied forces over as wide an area as possible. 14  OBJECTIVES OF IMPRESSION 3. Retention: It is the resistance to the forces which tries to dislodge the denture in a direction opposite to the path of insertion (away from the tissues). 15  OBJECTIVES OF IMPRESSION 4. Stability: It is the resistance to horizontal or rotational movements which try to dislodge the denture. 16  OBJECTIVES OF IMPRESSION 5. Esthetics : Border thickness should be varied with the needs of each patient in accordance with the extent of residual ridge loss. The vestibular space should be filled, but not overfilled, to restore facial contour. 17  PARTS OF IMPRESSION TRAYS 1- Handle (NOT interfere with lip) 2- Body consists of : a)floor b)flanges 18  TYPES OF IMPRESSION TRAYS a)According to arch related: 1-Upper tray ….. Palatal part… Vault 2-Lower tray … lingual flange 19 b)According to impression type: 1- Stock impression trays (pre-fabricated): used for making preliminary impressions. 2- Custom impression trays (special): prepared for a particular patient, improve the primary impression, So a superior results are possible. used for making secondary impressions. 20  1- Stock impression trays (pre-fabricated): a) Factors affecting tray selection. b) Requirements of stock trays. c) Stock tray modification.  1- Stock impression trays (pre-fabricated): a)Factors affecting tray selection: 1. Presence or absence of natural teeth. 2. The nature of impression material. 3. Size of arches. 4. Material of tray fabrication. 1. Presence or absence of natural teeth: Dentulous Trays: Edentulous Trays: Square or flat floor & long flanges. Round/ oval floors & short flanges.  2. The nature of impression material: 1. Perforated trays for alginate material “mechanical adherent”. 2. Non-perforated trays” for compound impression material (sticky). Alginate Impression Compound Impression Material 26 3. Size of arches: Small (size 1), Medium (size 2) , Large (size 3) 4. Material of tray fabrication: 1. Metallic trays (Aluminum, Stainless steel). 2. Non metallic tray: plastic trays (may be disposable or sterilizable). b)Requirements of stock trays: 1-The tray should be rigid and strong, but not too thick. 2-It should retain its shape throughout the impression procedure and pouring of the impression. 3-It should be at least 3-4 mm clearance between the ridge and stock trays. 4-The handle of the tray should be angulated so that it aids in manipulation of the tray without distorting natural lip contour. b)Requirements of stock trays: 5-Border extension of the tray should be 2 mm short of the vestibular depth with no interference with muscle or frenal attachments. 6-The entire borders of the tray should be smooth and rounded to avoid injury. 7- It should accept the desired modification.  c)Stock tray modification: 1-Bending: (Aluminium) The tray flanges may be bent inward or outward with pliers to accommodate enough thickness of impression material. 2-Cutting : (Aluminium) The tray flanges can be trimmed with scissors to correct overextension (long). 31 3-Addition of moldable material :Border tracing: Soft utility wax or green compound may be used to : a) Under-extension flange (short). b) In high palatal vault in order to support the material against the palate. c) To the posterior border of the upper tray to provide a better seal preventing the excess from flowing back into the throat. 32  Custom (special) Trays a) Advantages. b) Requirements. c) Steps of construction. d) Materials used for construction. 33  Custom (special) Trays An individualized tray made on study cast recovered from primary impression. It is used in making a final impression. Final impression will be incorporated as fitting surface of the denture. Any mistakes during impression making will be reproduced in the final denture and directly affecting the outcome of the denture 34  a)Advantages: 1. Economical (less impression material required in special tray). 2. Less bulky than stock tray & more comfortable for the patient. 3. Provides even thickness of impression material. This minimizes tissue displacement and dimensional changes of impression material and produce impression with correct extension. 4. More accurately adapted to the oral vestibules, this helps in better retention of denture. 5. More accurate impression. 35 b) Requirements: 1- Well adapted to the primary cast. 2- Rigid & dimensionally stable on the cast & patient mouth. 3- It should not bind to the cast & easily removed from it. 4- It should not react with impression material. 5- It should simulate the finished denture in size and shape.  b) Requirements: 5- 2mm short of the sulcus for border molding. 6- At least 2 mm thick in the palatal area and lingual flange for adequate rigidity. 7-Contrasting color to make its margins appear prominent when placed in the patient’s mouth. 8- Must cover all the anatomical landmarks needed in complete denture. Zinc Oxide Eugenol Impression  c)steps of construction: Identify the deepest part of the sulcus, then draw the proposed periphery outline… vestibular depth. Tray outline should 2 mm short of the vestibular depth in all areas of the maxillary and mandibular arches except on the lingual sulcus of the mandibular arch, where the custom tray is extended to the full depth of the sulcus. This is the area most often under-extended in a primary impression 39  The maxillary posterior border is determined by a line extending between the hamular notches, passing just posterior to the fovea palatine. The entire retromolar pad should fall within the outline of the mandibular tray. The outline of the wax spacer should be 2 mm short and parallel to the tray outline 40  Adapt the appropriate thickness of base-plate wax to the model and trim short of the required extension of the tray. The spacer thickness according to planned impression Material: a)ZnO eugenol (rigid in thin section).. 0.5-1mm (closely fitting tray… No tissue stops). b)Alginate / elastomeric ( if tissue undercuts) … 3mm 41  Tissue Stops: ( tripod or quadrilateral stops): -Strategically placed ,two on the canine eminences on either side and two on the posterior of the ridge. (1st molar) -Spacers should be cut out in 3-4 places so that the special tray touches the ridge in these areas. 42 a) To place custom tray to the mouth in a repeatable position during border molding procedures. b) In addition, this will ensure even & uniform thickness of impression material. Spacer should also be coated with a separating medium (petrolatum) to avoid the special tray from binding to the cast. 43 d)Materials used for construction of special trays (most common) 1. Auto polymerizing (chemical cured) acrylic resin. 2. Visible light cure resin (VLC). 3. Vacuum-form vinyl polysiloxane sheets. + Old denture of the patient may be used as a custom tray. 44 1. Auto polymerizing ( chemical cure) acrylic resin: There are two techniques for chemical cure acrylic resin: A. Finger adapted dough method. B. Sprinkle-on acrylic method. 45 A. Finger Adapted Dough Method: The powder and liquid supplied should be mixed in the ratio of 3:1 by volume in GLASS container. If this ratio is not maintained will result in excessive shrinkage, porosities and granularity may occur. The mixture undergoes polymerization in stages: (sandy stage, stringy stage, dough stage, rubbery stage, solid stage ). 46  In the dough stage the material is kneaded in the hand, to achieve a homogenous mix and shaped into a 2 mm thickness. ` Then adapted over the cast from the center to the periphery to prevent the formation of wrinkles. ……. Light finger pressure. Cut the excess material before setting the material ( rubbery stage). Excess dough material is used to fabricate the handle. ( biconcave , 8x8 mm & at 45 angle). 47 B. Sprinkle-on acrylic method: Monomer and polymer are applied in alternate layers till relative thickness is achieved…. minimal waste of material. 48  The tray and the borders are reduced 2 mm short of the depth of the vestibules and the frenuli attachments….. using acrylic trimming bur to produce a rounded profile. This assures that there is sufficient room for the border-molding, 2. Visible light cure resin (VLC): VLC resins are supplied in lightproof packages. After the package is opened, the material is molded to the desired shape and then made rigid by exposure to high-intensity visible light in a light-curing unit. 50  It has superior mechanical properties (rigid & better dimensional stability) , reduces preparation time and is easy to use… long working time Used in patients allergic to chemical cure resins, because no residual monomer. BUT expensive, requires special light-curing unit for processing and is difficult to trim when cured. 51 52  Is there is no further need for impression trays? DIGITAL IMPRESSION: Taking an optical impression by a digital capture unit (3D intra-oral scanner) as the dentist will capture series images & converting it to 3D model on the computer screen. 54