CONDENSATION POLYSILICONE IMPRESSION MATERIALS

CONDENSATION POLYSILICONE IMPRESSION MATERIALS. SUPARNA SAHA 190401082.

INTRODUCTION. Condensation polysilicone impression materials are those materials that condense to form an elastomer of high molecular weight with the formation of by-product..

WHAT ARE THE USES?. It is widely used in recording dentulous impressions in preparation of crowns and bridges, inlays, onlays and to some extent for partial dentures . It is also used to record edentulous impressions in preparation of complete denture.

DISPENSING FORM. They are supplied as:. Two paste system (Base paste + Reactor paste).

COMPOSITION. BASE PASTE. INGREDIENT FUNCTION Low molecular weight poly dimethyl siloxane with hydroxyl terminal groups It undergoes polymerization and cross linking to form rubber. Reinforcing fillers (35-75%) copper carbonate, colloidal silica As a paste former.

REACTOR PASTE. INGREDIENT FUNCTIONS Tetra ethyl ortho silicate Acts as a cross linking agent Tin or stannous octate Acts as a catalyst Reinforcing filler or thickening agents- colloidal silica To form a paste and to control the viscosity Color pigments To indicate a uniform mixing and to distinguish from the base paste.

CHEMISTRY AND SETTING REACTION. While mixing the two paste, a reaction begins immediately between the terminal hydroxyl groups of Polysilicone chains and Tetra Ethyl Orthosilicate. This reaction is catalyst by Tin Octate..

SETTING REACTION. Hydroxy terminal Poly dimethyl siloxane Tetra Ethyl Orthosilicate Silicone rubber + Ethyl alcohol.

Usually mean working time is measured at room temperature and mean setting time is measured at mouth temperature.

PROPERTIES.

ADVANTAGES: Pleasant odour and no staining. Adequate tear strength and flexibility. Can be electroplated. Better elastic property on removal. Reproduces all fine details. Adequate working time (2-3 mins) and setting time (6-10 mins)..

PROPERTIES. DISADVANTAGES: Poor dimensional stability. Potential for distortion. Slightly more expensive. Poor shelf life. Adequate accuracy if poured immediately. It is hydrophobic. Need for a tray adhesive before loading to the tray..

MODIFICATION. A major modification of the condensation silicone material is a change in the setting mechanism. This modification has brought about a new family of impression materials, the addition polysilicones..

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