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LECTURE 7: MATERIALS USED IN THE MANAGEMENT OF EDENTULOUS PATIENTS DR. JOCHIN INTRODUCTIO...

LECTURE 7: MATERIALS USED IN THE MANAGEMENT OF EDENTULOUS PATIENTS DR. JOCHIN INTRODUCTION (2) The material should have adequate wettability of the oral The selection of materials for dental restorations is based on a tissues to allow for accurate adaptation and capturing of reconciliation of their biocompatibility, physical and biomechanical the oral structures and tissues properties and the acceptability of their esthetic qualities. (3) The material must have a pleasant taste and odor (4) In the mouth, the material should set into a rubbery or rigid Biocompatible condition of being compatible with a living tissue solid in a reasonable amount of time by not being toxic and injurious (5) Upon removal from the mouth, the set impression should show adequate elastic recovery with no permanent Adhesion physical attraction of unlike molecules, such as saliva and mucous membrane deformation (6) The material must have adequate strength to avoid tears Cohesion the physical attraction of like molecules for each or breakage upon removal from the mouth other, such as within the saliva layer (7) The impression should be dimensionally stable after setting and until pouring of the cast TL;DR (8) The impression can remain dimensionally stable to be → adhesion is the attraction between the molecules of two repoured after removal from the cast different substances (9) The material must be compatible with the cast material → cohesion is the attraction between the molecules or atoms of the (10) The material must be biocompatible, nontoxic, and without same substance irritant constituents (11) The material must be of a color and opacity that allows for ATMOSPHERIC PRESSURE proper evaluation of the impression by the dentist → may act to resist dislodging forces applied to dentures if the (12) The material could be readily disinfected without significant dentures have an effective seal around their borders loss of accuracy or loss of mechanical properties → also called a “suction” or “negative pressure” (13) The material must have an adequate shelf life for storage → in the absence of an effective seal, there would be no suction (14) The materials, associated processing time, and equipment → an effective seal is when the denture border should be shaped should be cost-effective so the channel between it and the sulcus tissue is as small as possible VISCOSITY o is why border moulding is done before taking a final → low viscosity means the material has low resistance to flowing impression; it shapes the impression border and allows the quickly (ex.: water, rubbing alcohol) muscle to function in harmony with the denture → high viscosity means it has high resistance to flowing (ex.: honey) TL;DR DIMENSIONALLY STABLE → the more harmonious the muscle function with the denture, the → measure of a material’s ability to retain its fit, form and more atmospheric pressure is produced which causes excellent functional properties retention for the denture TYPES OF IMPRESSION MATERIALS GRAVITY NON-ELASTIC IMPRESSION MATERIALS → may act as a retentive force for the mandibular denture but as IMPRESSION PLASTER a displacing force for the maxillary denture → used as a mucostatic impression because it does not compress and displace tissues during seating of the tray IMPRESSION MATERIALS → recommended as it is very brittle IMPORTANCE OF IMPRESSION MATERIALS → can undergo virtually no compressive or tensile strength without → fabrication of accurate preliminary and final casts necessitates fracturing impressions that are capable of capturing and replicating all anatomical, peripheral and denture supporting structures ZINC OXIDE EUGENOL IMPRESSION PASTE → this is a key factor in ensuring optimal retention, support and → negligible setting shrinkage of