DEN203 Prosthetic Dentistry II Lecture Notes PDF

DEN203 Prosthetic Dentistry II Lecturer: Dr. Rana Turunç Oğuzman & Dr. Demet Ayvalıoğlu E-posta: [email protected] Impression Trays Altınbaş Üniversitesi Rana Turunç Oğuzman [email protected] DEN203 Protetik Diş Tedavisi 2 Definition A dental impression is a negative im...

DEN203 Prosthetic Dentistry II Lecturer: Dr. Rana Turunç Oğuzman & Dr. Demet Ayvalıoğlu E-posta: [email protected] Impression Trays Altınbaş Üniversitesi Rana Turunç Oğuzman [email protected] DEN203 Protetik Diş Tedavisi 2 Definition A dental impression is a negative imprint of hard (teeth) and soft tissues in the mouth from which a positive reproduction (cast or model) can be formed. Impression tray is a device used to carry, confine & control the impression material in the patient's mouth. While taking an impression, the tray facilitates insertion & removal of impression material from the patient's mouth. Requirements Of Impression Trays 1. The tray should be rigid and strong but not too thick. 2. It should simulate the finished denture in size and shape. 3. The border extension of the tray should be 2mm short of the vestibular depth with no interference with muscle or frenal attachment. 4. The entire border of the tray should be smooth and rounded. 5. The tray should retain its shape throughout the impression procedure and while pouring stone on the impression. 6. The handle of the tray should be angulated to exclude the lips Classification Types of Impression Trays Impression trays can be of various types: • 1. According to the material used to fabricate the trays: a. Metallic trays (stainless steel, Aluminum) b. Non-metallic trays (plastic trays, acrylic resin trays) Types of Impression Trays 2. According to the method of fabrication of trays: • A. Stock trays: - Full arch trays - Sectional trays - Quadrant trays • B. Custom trays or Special trays Types of Impression Trays 3. According to the teeth present /absent in mouth: a.Edentulous trays b.Dentulous trays How can I identify between Dentulous and Edentulous trays? Dentulous Trays – Square CrossSection For patients with teeth! Edentulous Trays – Rounded Cross-Section For patients without teeth! Types of Impression Trays 4. According to the method of interlocking of material: a.Perforated trays b.Non-perforated trays c.Rim-lock trays i. Water-cooled ii. Non water-cooled What is the difference between Stock trays and Custom trays? • STOCK TRAYSStock trays are ready-made and comes in specific sizes, so the stock tray which fits the patient’s mouth best should be selected. They are re-useable after sterilization. Sterilization can be achieved by autoclaving, dry heat or chemical vapors • CUSTOM TRAYS Custom trays are fabricated on the particular patient’s cast thereby making it unique to the patient. This is why custom trays always fit better than stock trays. They are useful only for the particular patient. Then they are discarded. Stock Trays Definition Stock Trays Impression tray that serve to carry the impression material to the mouth & support it in the correct position while it is polymerizing. This type of tray can be used for several patients & used for making primary impression. They are made of different materials such as Al, Tin, Brass or Plastic, in variety of sizes to fit different mouths. Factors affecting selection of stock tray: 1- The type of impression material used in the primary impression procedure. e.g. For polyether impression material (thixotropic) we use non-perforated tray, because of its viscosity, otherwise it would all flow form the tray. but if we use alginate impression material we should use perforated stock tray, not to make so much pressure on the tissues an to let the excess material flow from the holes. 2- Size of the arch. 3- Form of the arch. (round , square , taper ). Factors affecting selection of stock tray: 4- The stock tray must cover all the anatomical landmarks needed in complete denture & this is a crucial point. 5- Stock tray should give a sufficient space to impression material in all directions. Impression material should be in homogenous thickness all around the tray. Metal Trays Properties • • • • • Provide maximum support for impression materials Rigid Durable and long lasting Can be perforated or solid Can be used with all elastomeric materials Plastic Trays Properties • Disposable • Eliminate cross-contamination • Can be modified • Have rigid, thick walls to provide lateral support for the impression material to prevent distortion when pouring the model What type of stock tray should I use? Stock Trays should be selected to the best fit according to the size of the jaw. This selection is based on • The type of mouth you want to make an impression of• Dentulous Mouth – use Dentulous Trays. • Edentulous – use Edentulous Trays. • Partially Edentulous – use Combination Trays. • Type of impression material you want to use. • Elastic Impression Materials – generally use Perforated trays. • Inelastic materials – generally use Non-Perforated trays. Custom Trays Definition ▪ An individualized impression tray made from a cast recovered from primary impression. ▪ It is used in making a final impression. Primary Impression Preliminary Cast Special Tray Final impression Advantages of special trays: 1. More accurate impression. 2. Special tray provides even thickness of impression material. This minimize tissue displacement & dimensional changes of impression material. 3. To work with special tray is more easier & quicker than modifying stock tray to provide accurate impression. 4. Special tray is more accurately adapted to the oral vestibules, this helps in better retention of denture. 5. Special tray is less bulky than stock tray which is more comfortable for the patient. Materials used for construction of special tray: Metallic Non-Metallic Thermoplastic Material Resin Cast or Swaged Metal (Time Consuming) (Not popularly used) 1. Shellac base plate 2. Impression compound 1. Cold cure acrylic resin 2. Hot cure acrylic resin 3. Light cure acrylic resin Cold cure acrylic custom tray materials have some disadvantages: • Polymerization shrinkage • A time interval must be allowed between the fabrication and the use of these custom trays • The hazardous effects caused by the monomer (methyl methacrylate) include dermatologic reactions While Light cure acrylic resin is: • less hazardous, • reduces preparation time, • easy to use and • has good handling properties. Types of Custom Tray • Close-fit Tray • Tray with spacer and stop (Openings in the wax where acrylic will flow in to form stops) SPACER (WAX) What is the difference between a close-fit tray and a spaced tray? • CLOSE –FIT TRAY : adapted directly on to the cast without any wax spacer. Usually used with impression materials that have a light viscosity to obtain a wash impression, e.g. light bodied elastomers, ZOE impression paste. • TRAY WITH SPACER AND STOPS : these trays use a wax spacer to provide space for the impression material. This is because impression materials used here need extra space as they have higher viscosity e.g. Alginate, medium and heavy bodied elastomers. Fabrication of Custom Tray Criteria for Special tray construction : 1- The impression tray must not impinge upon movable structures such as muscles. 2- The borders must be under extended (2mm) from the vestibular sulcus . 3- The posterior limits of the upper impression tray should be slightly over- extended to ensure inclusion of the posterior detail for development of the post-dam area. Criteria for Special tray construction : 4- The tray should be rigid & of sufficient thickness, so that it will not fracture during its use. 5- The tray must have a handle for manipulation & the handle must not interfere with functional movement of the oral structures. 6- The tray must be smooth on its exposed surfaces, and should not have any sharp corner or edges which would hurt the patient. Equipment and Materials needed Vaseline Bunsen burner Straight handpiece Wax spatula, wax knife, Pink base plate wax, Pencil Procedural Steps for custom tray with spacer and stop A. Preparation of the primary cast : 1. Undercuts should be find out with the help of a dental surveyor and should be blocked out . A. Preparation of the primary cast : 2. Outline of the border of the tray should be marked with pencil which is 2-3 mm short of the reflection. 3.The relief areas should also be marked in the cast. 4. The border of the tray marked on the cast may be grooved deeper using a carver. B. Adapting the relief wax: Relief wax should be adapted over the relief areas marked on the cast. Relief areas are: In Maxilla In mandible Incisive papilla Canine eminence Mid palatine raphe Crest of the residual ridge Fovea palatinae Sharp spiny ridges Torus palatinus Bony prominences Undercut ridge Mental foramen Genial tubercles Torus mandibularis Mylohyoid ridge Materials for giving relief: a. Baseplate wax b. Non-asbestos casting liner. C. Adapting the spacer: A spacer should be adapted throughout the extent of special tray( coincide with the second line), except posterior palatal seal area in maxilla and buccal shelf area in mandible. • Function of spacer/ stops: a. The spacer allows the tray to be properly positioned in the mouth during border molding procedure. b. To allow the impression to have an even thickness of impression material. c. Prevent distortion of the material at final stage. • Materials used in spacer: a. Baseplate wax b. Non asbestos casting liner D. The use of stops: The spacer should be cut out in 2-4 places so that the special tray touches the ridge in these areas . Location: Usually 4 stoppers are placed, Size and shape : Stopper can be 2mm square or 2 by 4 mm rectangle (2 mm mesiodistally, palatally over the crest of the ridge and buccally half way into the sulcus) E. Application of separating medium Apply separating media on the cast so that acrylic resin does not stick to the cast. Applying separating media F. Acrylization: F. Acrylization: When monomer and polymer are mixed in the proper proportions, a workable mass is produced. Upon standing, the resultant mass passes through five distinct stages. (1)Sandy (2)stringy (3)dough, (4)rubbery, or elastic, and (5)stiff Manipulation and Stages G. Fabrication of handle: Criteria of handle : 1. The handle should be parallel to the long axis of the teeth that are to be replaced. 2. The handle should not arise horizontally directly from the tray because it may interfere with lip movements. and 3. It should be 3-4 mm thick , 8 mm long , 8 mm high. G. Fabrication of handle: 4. The vertical distance from the sulcus to the handle is 2 cm 5. The handle upstand must be made long enough for the handle to exit through the oral commissure. G. Fabrication of handle: 6. For mandibular tray two posterior handle should be given as finger rests. Functions of handle 1. Supports the lip while making impression. 2. Tray handles are particularly helpful when loading, placing and orientating custom trays in the mouth. Functions of finger rest 1. Stabilize tray in mouth 2. Equal distribution of pressure 3. Reduces pressure applied to tissues The next phase is preparing the tray for border molding procedure: Close-fit Tray Procedures • Follow all the steps mentioned previously except we skip spacer and stop making. Sterilizing trays • Trays should be cleaned properly and disinfected before use on patients • Disposable trays are recommended to prevent cross-contamination Videos Fabrication of impression tray 1. With light cure acrylic without stoppers but the handle is ideal https://youtu.be/t8ZVGSrSuUY 2. With light cure acrylic with stoppers but the handle is different https://edpuzzle.com/media/5f4d0ebe3c80703f2cae55db 3. With self cure acrylic with stoppers, the handle is different (Turkish) https://youtu.be/dAgvUXS-ZBU