STENCILDENT

  STRENGTHENING CERAMIC   Ceramic brittle matter and have low tensile strength - this makes it chip of at certain clinical condition. Therefore necessary to strengthen ceramic to increase longevity.  TECHNIQUE : 1)MINIMISING THE EFFECT OF STRESS CONCENTRATION: A)DESIGN OF PROSTHESIS: Select stronger and tougher ceramic  Grinding of surface of ceramic restoration should be minimised Avoid sharp line angle in tooth preparation  2)DEVELOPMENT OF RESIDUAL COMPRESSIVE STRESS: In post metal ceramic restoration : Metal should have more thermal coefficient of expansion than ceramic  Induce compressive stress this can withstand fracture  In all -ceramic : core ceramic have more thermal coefficient of expansion  3)MINIMISING NUMBER OF FIRING CYCLES: Repeated firing will result in : weaker and fragile ceramic If we reduce the number the number of firing we can strengthen ceramic  4)THERMAL TEMPERING : Ceramic is heated to a higher temperature ,once it reaches high temperature its quenched rapidly

 ELASTOMERIC IMPRESSION MATERIAL  PART 2 ADDITION SILICONE: AVAILABLE AS : 1)LIGHT 2)MEDIUM 3)HEAVY 4)PUTTY VISCOSITIES: PASTE: 2 equal size collapsible tube Cartridge:use with gun Putty jar Base paste : 1)Poly methyl hydrogen siloxane 2)Other siloxane pre-polymer 3)Hybrid silicone 4)Filler CATALYST PASTE : 1)Polydimethylsiloxane 2)Platinum salt activator 3)Palladium 4)Retarder  5)Filler  SETTING REACTION: Addition reaction No by product  Cross linkage between vinyl terminated silicone with silane terminated silicon  2nd reaction: Moisture +residual hydride Hydrogen gas is formed  Addition noble metal (platinum or palladium )to component that act as hydrogen absorber HYDROPHILIC SILICONE : Addition of surfactant  Advantage : Decreases air bubble in gypsum , Better wetting of soft tissue Disadvantage: Difficult to electroplate  Character: No by product  More dimensional stable Addition of surfactant turn to hydrophilic  ADVANTAGE: Clean,pleasant easily seen margin elasticity pour repeat

  ELASTOMERIC IMPRESSION MATERIALS  - PART 1  ELASTOMERIC :Rubber -like polymers that shows as elastic behaviour at the time of load application  These polymer molecules have weak interaction in between (Van der wall forces) They have tied together in 3D network  4 ELASTOMERIC IMPRESSION MATERIALS: 1)POLYSULFIDE 2)CONDENSATION -POLYMERIZATION SILICONE 3)ADDITION-POLYMERISATION SILICONE 4)POLYETHER   1)POLYSULPHIDE: 1st material introduced also known as mercaptan/thiokal Collapsible tubes : Base: White colour Catalyst: Brown,grey  VISCOSITIES: Heavy Medium Putty BASE : Low molecular weight polysulphide Filler (Titanium dioxide) plasticizer(Dibutyl phthalate) Accelerator(0.5% Sulphuric acid ) CATALYST: Lead oxide Filler (Titanium dioxide) Plasticizer(Dibutyl phthalate) Retarder(Oleic acid and Stearic acid) Condensation polymerisation: Mercaptan+lead dioxide  = polysulphide +water CHARACTER: Water by product +polymerisation shrinkage =dimensional changes Water could cause air bubble in st

  DENTAL IMPLANT  A dental implant is a material /device in and or on oral tissue to support an oral prosthesis PARTS OF AN IMPLANT  : ABUTMENT- Support crown,provide retention IMPLANT BODY-Placed in bone HEALING SCREW-Prevent growth of tissue at edge of implant HEALING CAP-Maintenance of tissue  CHARACTERISTICS OF IMPLANT : 1)Sterile 2)Highly biocompatible 3)Should have primary stability 4)Should have adequate loading at time of healing 5)It should have surface configuration 6)It should consist of 2 parts :  a)Favour bioadhesion b)Non-adhesion  CLASSIFICATION: A)MATERIAL USED : 1)METAL AND ALLOY :Titanium and its alloy ,stainless steel 2)CERAMIC:Made of carbon with stainless steel 3)POLYMER AND COMPOSITE:Polymethylmethacrylate,polytetrafluorethylene B)BIOLOGICAL RESPONSE: 1)BIOTOLERANT : Gold Cobalt-chromium Not easily rejected when implanted in living tissue 2)BIOINERT: Titanium Allow close opposition of bone 3)BIOACTIVE: Bioglass Material that allow formation of bone onto their surf

 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:

HELLO DOCTOR VANAKKAM, Warm welcome to stencildent family  Contents: v  Introduction to casting procedure v  Sprue v  Specification of sprue v  Methods to prevent v  Function of sprue v  HAND WRITTEN NOTES Introduction : v Casting procedure steps: 1) Tooth preparation 2) Impression 3) Die preparation 4) Wax pattern 5) Sprue former 6) Casting ring liner 7) Investing 8) Wax elimination and burnout 9) Casting 10)Quenching 11)Sandblasting 12)Finishing and polishing   SPRUE ·        It’s a channel created in the investment through which molten alloy enter the mould space which is created due to burnout of wax pattern. ·        Sprue former are material used to form sprue ·        They are made up of wax, metal,resin. SPECIFICATION OF SPRUE: 1)    SPRUE DIAMETER: Ø Same a size as thickest area of wax pattern Ø If large cause distortion Ø Small : suck back porosity 2)    Sprue position : Ø At greatest bulk in pattern