STENCILDENT

  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 pontic of a bridge STICKY WAX Composition:yello

 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 CROWN) TYPE 4 - EXTRA HARD (CROWN,BRIDGE) 3) BASED ON PRINCIPLE ELEMENT:

 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 material is known as b

  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:   When two dissimilar metal lie on direct contact with each other ,saliva acts

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)gag reflex 2)cannot be used in undercut regions  Thanks for reading kindly comment down ur suggestion below