Complete Denture Impression PDF

Impressions for C.D By DR/ Ahmed Khair-Allah  Complete denture impressions An impression is a negative record or imprint of the tissues of the oral cavity Cast Reproduce a positive form and shape of the same oral tissues (Cast). Duri...

Impressions for C.D By DR/ Ahmed Khair-Allah  Complete denture impressions An impression is a negative record or imprint of the tissues of the oral cavity Cast Reproduce a positive form and shape of the same oral tissues (Cast). During the process of complete denture construction two impressions are made: A- Primary imp (Preliminary). B- Secondary imp (Final)  Types of Complete denture Impressions Types of Primary Secondary impression Impression made for Impression made for the certain patient for the same patient for second first time and doesn't time and records all fine register fine details of details of the oral the oral structures. structures. Trays used Stock tray. Special tray. Made by manufacturers Made specially for one patient and discarded later Cast Study cast. Master cast. produced after pouring Used for Custom tray Denture construction. fabrication.  Objectives of impression making P – preservation of remaining natural structures R – retention E – esthetics S – stability S – support  I)Preservation of remaining natural structures Muller De Van (1952): preservation of that which remains is of utmost importance and not the meticulous replacement of that which has been lost I)Preservation of remaining natural structures -Pressure in the impression technique is reflected as pressure from the denture base to soft tissue and bone. -In appropriate pressure could lead damage to tissue and to bone resorption  I)Preservation of remaining natural structures Requirements of an acceptable impression: 1- Impression should record details in appropriate form to prevent injury to the tissues 2- Relief to non-stress bearing areas, thus preventing damage 3- Avoid overextensions 2-Retention  2-Retention Seal 3-Esthetics  3-Esthetics Depends on -Thickness of flanges & borders -Differs from patient to patient According to amount of ridge resorption  4-Stability Denture stability is important to the preservation of the denture supporting structures (soft tissues and bone).  5-support Maximum coverage provides distribution of the load over wide area so that load per unit area will be reduced  Basic rules for making Impression Operator’s position  Basic rules for making Impression Patient’s position I- Primary Impression Impression trays Design Sizing of Impression trays Width of Impression trays Anteroposterior extension of Impression trays Length of Impression trays Anteroposterior extension of Impression trays Modifications of Impression trays 1- Bending : Modifications of Impression trays 2- cut and trim the flange 3-Addition: in case of Shortness in the flanges  Alginate impression material Alginate impression material Alginate impression material Compound impression material  Types of Complete denture Impressions Types of Primary Secondary impression Impression made for Impression made for the certain patient for the same patient for second first time and doesn't time and records all fine register fine details of details of the oral the oral structures. structures. Trays used Stock tray. Special tray. Made by manufacturers Made specially for one patient and discarded later Cast Study cast. Master cast. produced after pouring Used for Custom tray Denture construction. fabrication. Border Molding Most Commonly used border molding materials are:- -Modelling compound sticks. -Autopolymerising acrylic resin -Metallic paste -Elastomeric materials -Impression waxes.  Techniques of border molding: - Hand manipulated - Functional movements A- Hand manipulated:- Border moulding is done and impression is made with the hands of the dentist. B- Functional movements:- The functional movements are done by the patient like sucking, grinning, licking, swallowing Checking MAXILLARY AND MANDIBULAR SPECIAL TRAYS. Tray outline marked 2-3 mm short of denture outline. Adjustment of tray border if needed Techniques of Final Impression Making Condition of oral mucosa during recording impression Static Undisplaced (resting form ) Muco-static Non-Pressure Dynamic Displaced (Functional) Muco-Displacive Muco-compressive Combination Muco-static Muco-Displacive Selective pressure  I- Muco- static Muco = Mucosa Minimal pressure impression technique Static = condition of oral mucosa Anatomic form during impression making Open Mouth Def:- -Impression is made with the soft tissues are in anatomical form (without pressure) Dr/Ahmed samir  Advantages 1- There is less distortion to the mucosa. 2-It is the technique of choice for flabby and thin wiry ridges. Disadvantages 1- The mucosal topography is not static over a 24- hours period. 2-It neglects the principle of distributing masticatory forces over the largest possible basal seat area. Requirements: Impression material Fluid impression material Tray : flow readily and impose no 1-Perforations pressure on the mucosa 2- Spacer with stoppers II- Muco- compressive Muco = Mucosa Definitive pressure impression technique Compressive = condition of oral Functional form mucosa during Closed mouth impression making Def:- -Impression is made under biting force  Advantages 1- The patient can exert his own masticatory force on the impression material. 2- It permits adequate trimming of the lingual borders of the lower impression. Disadvantages 1- Dentures constructed from such an impression do not fit well at rest, as the compressed tissues tend to rebound. 2-It interferes with blood supply and this may accelerate ridge resorption. Requirements: Impression material Tray: 1- Not easy to flow. 1-closely fitting 2- Longer setting time 2- with an occlusion rims (to allow functional movements)  III-Selective pressure Impression Technique Aim: Impression technique in which pressure is applied to some areas to gain support + at the same time other areas are captured with minimal pressure