STENCILDENT

                 GLASS IONOMER CEMENT : MOST FRQUENTLY ASKED VIVA QUESTIONS: 1)DEFINE GLASS IONOMER CEMENT? A cement that consists of basic glass and acid polymer which sets by an acid -base reaction between these components . 2)Who discovered glass ionomer cement? Wilson and Kent in 1972  3) Other name of glass ionomer cement ? ASPA -Alumino silicate polyacryate  4)Composition: Powder : Silica-35-40% Alumina-20-30% Calcium fluoride-15-20% Aluminum fluoride-1.5-2.5% Aluminium phosphate-9-8% Sodium fluoride-5% liquid: Polyacrylic acid-40-50% Itaconic acid, malic acid and tartaric acid -5% Water-45-50% 5)Classification: A)according to Wilson and Kent: Type 1- luting cement Type 2 -restorative  Type 2 a -Restorative aesthetics Type 2b- Restorative reinforced B)According to application: Type 1 -Luting Type 2 -Restorative  Type 2 a -Restorative aesthetics Type 2b- Restorative reinforced Type 3-Lining cement Type4- Fissure cemen...

  DENTAL WAXES  Low molecular weight ester of fatty acids derived from natural or synthetic components such as petroleum derivatives that soften to a plastic state at relatively low temperature  Wax has been a valuable commodity for over 2000 years  Carnauba wax:hardest,more durable  CLASSIFICATION OF WAXES: 1)ACCORDING TO ORIGIN: NATURAL : MINERAL :Paraffin,ceresin Carnauba,candelilla PLANT;Carnauba,candelilla INSECT:Beeswax ANIMAL:Spermaceti wax SYNTHETIC WAX Acra wax Aldo wax 2)ACCORDING TO USE AND APPLICATION: A)PATTERN WAXES  Inlay wax Casting wax Base plate wax B)PROCESSING WAX: Boxing wax utility wax Sticky wax C)IMPRESSION WAX Bite registration or corrective wax BOXING WAX Mode of supply : sheets  Uses:controls the thickness of the border ,preserves the extension UTILITY WAX: Composition:beeswax,petrolatum Mode of supply :sticks and sheets  Properties:soft at room temperature  Uses:to build up border of impression tray attaching a pon...

 DENTAL CASTING ALLOY - Dental material  Dental casting alloy was introduced in the year 1907 by taggart ,he described method of making gold inlay using lost wax technique. AIM OF THIS POST : Will learn few historical significance,classification  of dental casting alloy,ideal requirement ,mechanical properties,heat  treatment,soldering,brazing,welding and finally about the  difference between soldering and brazing . In 1932 : national institute of standard and technology classified dental material by vicker hardness number  VHN TYPE 1 - SOFT TYPE 2- MEDIUM TYPE 3- HARD TYPE 4- EXTRA HARD  CLASSIFICATION  1)BASED ON NOBLE METAL CONTENT: HIGH NOBLE: Noble content more than or equal to 60% noble- noble content more than or equal to 25% by weight . predominantly base-  less than 25% by weight of noble metal 2)BASED ON MECHANICAL PROPERTIES: TYPE 1  - LOW (INLAY) TYPE 2 - MEDIUM (INLAY,ONLAY) TYPE 3 -  HARD (ONLAY,FULL CRO...

 RHEOLOGY Rheology is the study of deformation and flow characteristic of matter. Importance of Rheology in dentistry : In dentistry we are subjected to manipulate material which flow or deform when subject to stress. Classification of fluid based on rheology: Newtonian Pseudoplastic Dilatant plastic 1) Newtonin : Newtonian fluid have a constant viscosity they,have ideal fluid shear stress proportional  to strain rate . For example- water and newly mixed zinc phosphate cement. 2) Pseudoplastic: Pseudoplastic fluid is a shear thinning  fluid Viscosity decreases ,shear rate increases until it reaches constant value. For example: polycarboxylate cement ,elastomeric impression material. 3) Dilatant: Dilatant fluid is a shear thickening fluid Viscosity increases ,shear rate increases For example:traditional resin composite  4) Plastic fluid: Plastic fluid until certain yield stress is applied ,attain constant viscosity. The application of yield stress to cause flow in mat...

  TARNISH AND CORROSION  TARNISH : S urface discoloration  on a metal /even slight loss of surface finish. CORROSION:  D eterioration of a metal by reacting with environment,water ,oxygen,chloride ion,sulfide contribute corrosion attack. CAUSES FOR TARNISH    : Pigment producing bacteria formation of hard ,soft deposit on surface of restoration (eg-calculus) formation of thin film oxide and sulphide. CLASSIFICATION OF CORROSION CHEMICAL/DRY :  In chemical type of corrosion metal reacts to form oxide,sulphide  in the absence of  electrolyte for an example : oxidation of alloy particle in amalgam. 2) Electrochemical /wet corrosion: In electrochemical type of corrosion there will be formation of free electron ,electrolyte that provide pathway for transport of electrons. types of  electrochemical corrosion : A) galvanic corrosion B) concentration cell corrosion and C) stress corrosion  A) Galvanic corrosion: ...

GYPSUM PRODUCTS   DENTAL MATERIALS Gypsum was found in mines around city of Paris so its called plaster of Paris. ADA SPECIFICATION NUMBER: 25 Gypsum is classified into 5 types : Type1: Dental plaster for impression Type2: Dental plaster ,class 1- mounting,class 2-for moulds Type3: Dental stone for model Type4: Dental stone -high strength and low expansion Type5: Dental stone - high strength and high expansion  1 MOLE=    6.02214076×10 23 . Gaughing water: Excess water mixed with plaster ,makes manipulation quite easier . mechanism of setting in gypsum is explained through 3 theories out of which dissolution precipitation theory is widely accepted.                                    Advantage: 1)record fine details with least pressure 2)dimensional changes very minimal  3) economical Disadvantage: 1)g...