CD+Midterm+Exam+Review+ENK+DMA-part-4.pdf

Differences to note Primary crown is wider m-d than its cervcico-incisal dimension Primary teeth lack mammelons and have a very straight incisal edge The curvature of the CementoEnamel Junction (CEJ) is less distinct COLLEGE OF DENTAL MEDICINE COLLEGE OF DENTAL MEDICINE COLLEGE OF DENTAL MEDIC...

Differences to note Primary crown is wider m-d than its cervcico-incisal dimension Primary teeth lack mammelons and have a very straight incisal edge The curvature of the CementoEnamel Junction (CEJ) is less distinct COLLEGE OF DENTAL MEDICINE COLLEGE OF DENTAL MEDICINE COLLEGE OF DENTAL MEDICINE Comparison of Main Features of Tooth Types Central Incisors COLLEGE OF DENTAL MEDICINE COLLEGE OF DENTAL MEDICINE Impression Materials Yacoub Al Sakka, DDS COLLEGE OF DENTAL MEDICINE Purpose and Requirement (1) Sufficiently fluid to adapt to the oral tissues. (2) Viscous enough to be contained in a tray. (3) Able to transform (set) into a rubbery or rigid solid in the mouth in a reasonable time. (4) Resistant to distortion or tearing. (5) Dimensionally stable long enough (6) Biocompatible. (7) Cost-effective. Various materials are available for making a precision negative mold of soft and hard tissues. Main purpose is to duplicate the anatomical form of the oral tissue COLLEGE OF DENTAL MEDICINE Working and Setting Time • Working Time. • Setting Time. • Variables Dentsply Official website The working time begins at the start of mixing and ends just before the elastic properties develop. The setting time is the time elapsed from the beginning of mixing until the material has enough strength to be removed from the mouth without distortion. COLLEGE OF DENTAL MEDICINE Ratio, Mixing and Setting Time • Changes in W/P ratio will alter consistency, strength and quality. • Under/over mixing will affect strength of the set impression. • Setting rxn is chemical reaction. Changes with temperature differences The proportioning of the powder and water before mixing is critical to obtaining consistent results. Changes in the water-to-powder (W/P) ratio will alter the consistency and setting times of the mixed material and also the strength and quality of the impression. COLLEGE OF DENTAL MEDICINE Dental Biomaterials: Gypsum COLLEGEOF DENTAL MEDICINE COLLEGE OF DENTAL MEDICINE Gypsum(CaSO4•2H2O) • Calcium sulfate dihydrate • Naturally occuring mineral mined around the world • Supplied as fine hemihydrate (CaSO4 •½H2O) powders • Used in construction, soil conditioning, food additives, pharmaceuticals, medical devices • Dental applications • Study models for oral and maxillofacial structures • Auxiliary materials for dental laboratories for production of dental prostheses. COLLEGE OF DENTAL MEDICINE Model vs. Cast COLLEGE OF DENTAL MEDICINE Glossaryof Prosthodontic Terms (Journal of Prosthetic Dentistry) • model \mŏd ́ l \ n (1575): a facsimile used for display purposes; a miniature representation of something; an example for imitation or emulation • cast \kast\ n (14c): a life-size likeness of some desired form; it is formed from a material poured into a matrix or impression or from a CAM printed replica; comp, DENTAL CAST, DIAGNOSTIC CAST,FINALCAST,PRELIMINARYCAST,REFRACTORYCAST,REMOUNT CAST COLLEGEOFDENTALMEDICINE COLLEGE OF DENTAL MEDICINE Model Cast Arepresentationof the patient’s mouth/dentition that is not necessarilywithout inaccuracies used for planning and patient education An accurate representationof a patient’s mouth/dentition used for fabrication of a dental prothesis Typically made from plaster but can be stone Typically made from stone and not plaster COLLEGE OF DENTAL MEDICINE Properties of an ideal gypsum product for a dental purpose: • • • • • • Dimensional accuracy: the dimensional changes which occur during and after the setting of these model materials should be minimal in order to produce an accurate model or die. Fluid at the time it is poured into the impression so that fine detail can be recorded. Minimize the presence of surface voids on the set model by encouraging surface wetting. Strong to resist accidental fracture. Hard enough to resist abrasion during manufacturing of a dental prosthesis. Compatible with all the other materials with which it comes into contact. COLLEGE OF DENTAL MEDICINE