INDIAN DENTAL ACADEMYINDIAN DENTAL ACADEMY Leader in continuing dental educationLeader in continuing dental education www.indiandentalacademy.comwww.indiandentalacademy.com www.indiandentalacademy.comwww.indiandentalacademy.com
INTRODUCTIONINTRODUCTION IMPRESSIONIMPRESSION IMPRESSION TRAYSIMPRESSION TRAYS TRAYS USED IN RPD IMPRESSIONTRAYS USED IN RPD IMPRESSION PROCEDUREPROCEDURE FACTORS INFLUENCING THE CHOICE OFFACTORS INFLUENCING THE CHOICE OF IMPRESSION MATERIALIMPRESSION MATERIAL IMPRESSION MATERIALS USED-OVERVIEWIMPRESSION MATERIALS USED-OVERVIEW www.indiandentalacademy.comwww.indiandentalacademy.com
RPD IMPRESSION Vs COMPLETE DENTURE IMPRESSION PRIMARY IMPRESSION OBJECTIVES PROCEDURE PATIENT MANAGEMENT CONTROL OF SALIVA PRECAUTIONS TO BE TAKEN FOR GAGGERS EXAMINATION OF IMPRESSION REASONS FOR REJECTING AN IMPRESSION www.indiandentalacademy.comwww.indiandentalacademy.com
FINAL IMPRESSION METHODS McLEANS TECHNIQUE HINDELS TECHNIQUE SELECTIVE PRESSURE TECHNIQUE FUNCTIONAL RELINING TECHNIQUE FLUID WAX TECHNIQUE ALTERED CAST TECHNIQUE MODIFICATION REVIEW OF LITERATURE CONCLUSION REFERENCES www.indiandentalacademy.comwww.indiandentalacademy.com
INTRODUCTIONINTRODUCTION Sensitive to technique and material procedures.Sensitive to technique and material procedures. Not a passive activity.Not a passive activity. Impression material accomplishes the taskImpression material accomplishes the task operator is merely an observer.operator is merely an observer. www.indiandentalacademy.comwww.indiandentalacademy.com
Combined effort event accomplished by:Combined effort event accomplished by: OperatorOperator basic fundamental knowledge of all aspects ofbasic fundamental knowledge of all aspects of the impression proceduresthe impression procedures Intra oral condition of the patient.Intra oral condition of the patient. The position of the patient.The position of the patient. The size and position of the tray.The size and position of the tray. The selection of the material and technique.The selection of the material and technique. Patients actions and facial muscle activity.Patients actions and facial muscle activity. www.indiandentalacademy.comwww.indiandentalacademy.com
Impression A negative likeness or copy in reverse of the surface of an object ; imprint of teeth and adjacent structures for use in dentistry. GPT 8 Partial denture impression A negative likeness of a part or all of a partially edentulous arch - GPT 8 www.indiandentalacademy.comwww.indiandentalacademy.com
An impression of partially edentulous arch must record accurately the anatomic form of teeth and surrounding tissues. Unless the cast upon which the prosthesis is to be constructed is an exact replica of mouth, the prosthesis cant be expected to fit. Properly made and accurate cast can be obtained only from an accurate impression. www.indiandentalacademy.comwww.indiandentalacademy.com
Impression trays A receptacle in to which suitable impression material is placed to make negative likeness OR A device that is used to carry, confine and control impression material while making an impression. www.indiandentalacademy.comwww.indiandentalacademy.com
Impression trays can be classified broadly in to stock trays and custom trays Stock trays for partially edentulous patients may be perforated to retain the impression material or they may be constructed with a rimlock for this purpose. Another type of stock tray designed for the reversible type of hydrocolloid is water cooled trays. It contains tubes through which water can be circulated for purpose of cooling the tray.www.indiandentalacademy.comwww.indiandentalacademy.com
Modified stock tray (individual tray) Robert R Renners technique The stock tray can be modified with modeling composition and with wax to create an accurately fitting tray. This technique can be employed in class I and class II cases. Technique: Softened modeling compound is placed in the stock impression tray in such a way that it may capture the edentulous areas of mouth and include one or two teeth adjacent to the space.www.indiandentalacademy.comwww.indiandentalacademy.com
The tray is positioned in the mouth and compound is allowed to cool but it not permitted to harden completely, so that it is prevented from becoming hard when in contact with the adjacent teeth. When it is hardened sufficiently to contour it is removed from the mouth and thoroughly chilled. www.indiandentalacademy.comwww.indiandentalacademy.com
The compound is trimmed so that it does not contact the adjacent teeth and surface of compound in the edentulous areas is scraped to a depth of 2 - 4 mm to provide space for a uniform layer of impression material. In maxillary impression the compound should cover the edentulous ridges and the palate and should accurately fit to post dam area. www.indiandentalacademy.comwww.indiandentalacademy.com
Modification of the tray to make it adhesive If Impression material to be used is either alginate or agar, we can heat surface of compound with a flame. An alternate method Is to paint the surface of compound with a solvent such an chloroform to make it tacky and then to embed cotton fibers in it, the impression material will become enmeshed in cotton fiber. And if rubber base material is to be employed rubber adhesive is painted on the compound www.indiandentalacademy.comwww.indiandentalacademy.com
Advantages over custom tray: 1. Impression can be accomplished in one appointment. 2. Can be used inpatient with tendency to gag. Advantages over conventional use of stock stray: Especially useful for mouth that is either exceptionally large or small or the one with anomalous contour which cannot be accurately fitted with conventional stock tray. www.indiandentalacademy.comwww.indiandentalacademy.com
Disadvantages: STOCK TRAY a. The peripheral borders cannot be accurately recorded. b. Considerably more bulkier than a custom tray. www.indiandentalacademy.comwww.indiandentalacademy.com
Custom impression trays: a. Peripheral borders can be precisely recorded in the impression b. Thickness of impression material can be controlled. This is important consideration when using rubber base type material, which should not exceed thickness of 2-4 mm because a section thicker than this is subject to distortion. www.indiandentalacademy.comwww.indiandentalacademy.com
C. Well fitted tray will better support the impression in the palate, then avoiding even present danger of material slumping in vital areas. Custom trays are sometimes needed for mouths that are abnormally or of unusual configuration. www.indiandentalacademy.comwww.indiandentalacademy.com
Factors that influence the selection of impression materials are: Convenience of use Time of manipulation and set Cost Need for special trays Operator training and preference www.indiandentalacademy.comwww.indiandentalacademy.com
Reversible Hydrocolloid (Agar) Indications crown and bridge high accuracy Example Slate Hydrocolloid (Van R) www.indiandentalacademy.com
Composition Agar complex polysaccharide seaweed gelling agent Borax strength Potassium sulfate improves gypsum surface Water (85%) agar hydrocolloid (hot) agar hydrocolloid (cold) (sol) (gel) cool to 43 C heat to 100 C OBrien Dental Materials & their Selection 1997 www.indiandentalacademy.com
