logging in or signing up gypsum+silica+bonded+investment+material dr.shahza Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT lite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 642 Category: Education License: All Rights Reserved Like it (0) Dislike it (0) Added: July 26, 2011 This Presentation is Public Favorites: 0 Presentation Description No description available. Comments Posting comment... By: ebtsam1980 (3 week(s) ago) I want to download this presentation please Saving..... Post Reply Close Saving..... Edit Comment Close Premium member Presentation Transcript “DENTAL INVESTMENT MATERIAL” : “DENTAL INVESTMENT MATERIAL”INTRODUCTION: INTRODUCTION Following the production of a wax pattern the next stage involves the INVESTMENT of the pattern to form a mold. Preparation of mold - It is done by pouring the mixed investment material around the waxDEFINITIONS:: DEFINITIONS: Dental casting Investment: Material consisting principally of an allotrope of silica and a bonding substance may be gypsum, phosphates and silica. Refractory investment : An investment that can withstand high temperature using a casting. Allotropic phase : Phases of similar composition but different crystallographic structures, with different properties.CLASSIFICATION OF DENTAL INVESTMENT :: CLASSIFICATION OF DENTAL INVESTMENT :SILICA: A REFRACTORY MATERIAL : SILICA: A REFRACTORY MATERIAL Silicon dioxide (SiO2) Two allotropic forms are used: 1.Quartz 2.Cristobalite Quartz undergoes inversion at 575c from low to high form Cristobalite undergoes inversion at 210c from low to high form They act as fillers and function as refractories at high temperature, show expansion and also counter shrinkage of gypsum.GYPSUM BONDED MATERIAL:: COMPOSITION: 1. Calcium sulfate ( - hemihydrate) act as binder 2. Silica - 60-25% - quartz/ cristobalite act as refractory material/ filler 3.MODIFIERS: a) Carbon/ copper powder; provide non-oxidizing atmosphere in mold. b) Balancing agents - Boric acid and NaCl – regulate : - Setting time - Setting expansion - Shrinkage above 3000c GYPSUM BONDED MATERIAL:Setting reaction of gypsum bonded investments :: Setting reaction of gypsum bonded investments : CaSo4 ½ H2O + 1½ H2O CaSo4 . 2H2o + 3900 Cal/g mol. The heat causes expansion of the mold. The micro-structure of set material shows, rod-like particles of gypsum intermeshed with large irregular particles of silica refractory.Properties of gypsum bonded investment: Properties of gypsum bonded investment Strength: Compressive strength depending on amount of gypsum binder present and increase W:P ratio Contraction: After thermal expansion if the investment is allowed to coal. The process of heating and cooling cause internal cracks ExpansionSETTING EXPANSIONS:: SETTING EXPANSIONS: THERE ARE THREE TYPES OF EXPANSIONS: Normal setting expansion : at room temperature Thermal expansion : 1.6% for cristobalite 1.4% for quartz Hygroscopic expansion : water immersion expansion:6 times than normal expansion Water added technique: much controlledTYPES OF GYPSUM: TYPES OF GYPSUM Type I - For Inlay and crown – use mainly thermal expansion Type II - For Inlay and crown – use mainly hygroscopic expansion Type III - For RPD frameworkApplications of gypsum bonded investment. : Applications of gypsum bonded investment. Investing of wax for crown and bridge. gypsum bonded material used for casting investments for dental gold alloys used for alloys that fuses below 1200cDISADVANTAGE: DISADVANTAGE not suitable for casting metal ceramic alloys as it unstable at higher temperature contraction above 320c Water loss which cause fracture. At higher temperature it react with silica and form SO 3 which weaken the investment CaSO 4 + SiO 2 CaSiO 3 + SO 3 carbon react with gypsum and form CaS an CO and CaS will further liberate SO 2Silica bonded investment: Silica bonded investment COMPOSITION: A. Binder : silica acid gel B. Refractory silica (cristobalite) C. Additive magnesium oxide – Silica gel: Mixture of ethyl silicate and HCl(dil) & spirit(ind) will give silicic acid and C2H5OH Si(OC2H5)4 + 4 H2O Si (OH)4 + 4C2H5OH (Ethyl alcohol)MANUPILATION: MANUPILATION Powder + hydrolyzed ethyl silicate liquid allow heavier particles to settle mixed quickly and vibrated into a mold. Small grains fill in the space b/w larger grains to form a strong investment the accelerator (NH4cl) hardens the settled parPROPERTIES:: PROPERTIES: - Compressive strength: 1.5 mPa/min - Setting contraction :0.4% small shrinkage occurs at the early stage due to loss of water - Thermal expansion :1.5-1.8% (This investment can withstand higher temperature 1,1170c ) No Porosity .(space/ vents must be left in investment to permit escape of air from the mold. )ADVANTAGES:: ADVANTAGES: 2. Low setting expansion (contraction) reduces refractory partial denture models that may be articulated against stone model. 3. used at high temperature. 4. They form smooth castings. Investment is more refractory 5. easy removal of castings and cleaning of oxides from the castings.DISADVANTAGES: DISADVANTAGES 1. Limited shelf life of liquid. .Complicated and time consuming . Very expensive. . Give off flammable components during setting.(C 2 H 5 OH) Geline shrinkage at room temperature Because of the low strength and the large thermal expansion, crack formation in the investment can easily occur during somewhat too fast heatingUSES:: USES: Co-Cr alloy RPD Ni-Co alloy RPD 1. They are mainly used for casting Co-Cr R. P. D. framework. 2. Accurate casting of nickel –based alloysSlide 19: MADE BY: Gr.L:SHAHZA HASSAN Co.wrkrz: zummer, saima marium sundus nazrah shafaq amina sumaiya reem You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.
gypsum+silica+bonded+investment+material dr.shahza Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT lite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 642 Category: Education License: All Rights Reserved Like it (0) Dislike it (0) Added: July 26, 2011 This Presentation is Public Favorites: 0 Presentation Description No description available. Comments Posting comment... By: ebtsam1980 (3 week(s) ago) I want to download this presentation please Saving..... Post Reply Close Saving..... Edit Comment Close Premium member Presentation Transcript “DENTAL INVESTMENT MATERIAL” : “DENTAL INVESTMENT MATERIAL”INTRODUCTION: INTRODUCTION Following the production of a wax pattern the next stage involves the INVESTMENT of the pattern to form a mold. Preparation of mold - It is done by pouring the mixed investment material around the waxDEFINITIONS:: DEFINITIONS: Dental casting Investment: Material consisting principally of an allotrope of silica and a bonding substance may be gypsum, phosphates and silica. Refractory investment : An investment that can withstand high temperature using a casting. Allotropic phase : Phases of similar composition but different crystallographic structures, with different properties.CLASSIFICATION OF DENTAL INVESTMENT :: CLASSIFICATION OF DENTAL INVESTMENT :SILICA: A REFRACTORY MATERIAL : SILICA: A REFRACTORY MATERIAL Silicon dioxide (SiO2) Two allotropic forms are used: 1.Quartz 2.Cristobalite Quartz undergoes inversion at 575c from low to high form Cristobalite undergoes inversion at 210c from low to high form They act as fillers and function as refractories at high temperature, show expansion and also counter shrinkage of gypsum.GYPSUM BONDED MATERIAL:: COMPOSITION: 1. Calcium sulfate ( - hemihydrate) act as binder 2. Silica - 60-25% - quartz/ cristobalite act as refractory material/ filler 3.MODIFIERS: a) Carbon/ copper powder; provide non-oxidizing atmosphere in mold. b) Balancing agents - Boric acid and NaCl – regulate : - Setting time - Setting expansion - Shrinkage above 3000c GYPSUM BONDED MATERIAL:Setting reaction of gypsum bonded investments :: Setting reaction of gypsum bonded investments : CaSo4 ½ H2O + 1½ H2O CaSo4 . 2H2o + 3900 Cal/g mol. The heat causes expansion of the mold. The micro-structure of set material shows, rod-like particles of gypsum intermeshed with large irregular particles of silica refractory.Properties of gypsum bonded investment: Properties of gypsum bonded investment Strength: Compressive strength depending on amount of gypsum binder present and increase W:P ratio Contraction: After thermal expansion if the investment is allowed to coal. The process of heating and cooling cause internal cracks ExpansionSETTING EXPANSIONS:: SETTING EXPANSIONS: THERE ARE THREE TYPES OF EXPANSIONS: Normal setting expansion : at room temperature Thermal expansion : 1.6% for cristobalite 1.4% for quartz Hygroscopic expansion : water immersion expansion:6 times than normal expansion Water added technique: much controlledTYPES OF GYPSUM: TYPES OF GYPSUM Type I - For Inlay and crown – use mainly thermal expansion Type II - For Inlay and crown – use mainly hygroscopic expansion Type III - For RPD frameworkApplications of gypsum bonded investment. : Applications of gypsum bonded investment. Investing of wax for crown and bridge. gypsum bonded material used for casting investments for dental gold alloys used for alloys that fuses below 1200cDISADVANTAGE: DISADVANTAGE not suitable for casting metal ceramic alloys as it unstable at higher temperature contraction above 320c Water loss which cause fracture. At higher temperature it react with silica and form SO 3 which weaken the investment CaSO 4 + SiO 2 CaSiO 3 + SO 3 carbon react with gypsum and form CaS an CO and CaS will further liberate SO 2Silica bonded investment: Silica bonded investment COMPOSITION: A. Binder : silica acid gel B. Refractory silica (cristobalite) C. Additive magnesium oxide – Silica gel: Mixture of ethyl silicate and HCl(dil) & spirit(ind) will give silicic acid and C2H5OH Si(OC2H5)4 + 4 H2O Si (OH)4 + 4C2H5OH (Ethyl alcohol)MANUPILATION: MANUPILATION Powder + hydrolyzed ethyl silicate liquid allow heavier particles to settle mixed quickly and vibrated into a mold. Small grains fill in the space b/w larger grains to form a strong investment the accelerator (NH4cl) hardens the settled parPROPERTIES:: PROPERTIES: - Compressive strength: 1.5 mPa/min - Setting contraction :0.4% small shrinkage occurs at the early stage due to loss of water - Thermal expansion :1.5-1.8% (This investment can withstand higher temperature 1,1170c ) No Porosity .(space/ vents must be left in investment to permit escape of air from the mold. )ADVANTAGES:: ADVANTAGES: 2. Low setting expansion (contraction) reduces refractory partial denture models that may be articulated against stone model. 3. used at high temperature. 4. They form smooth castings. Investment is more refractory 5. easy removal of castings and cleaning of oxides from the castings.DISADVANTAGES: DISADVANTAGES 1. Limited shelf life of liquid. .Complicated and time consuming . Very expensive. . Give off flammable components during setting.(C 2 H 5 OH) Geline shrinkage at room temperature Because of the low strength and the large thermal expansion, crack formation in the investment can easily occur during somewhat too fast heatingUSES:: USES: Co-Cr alloy RPD Ni-Co alloy RPD 1. They are mainly used for casting Co-Cr R. P. D. framework. 2. Accurate casting of nickel –based alloysSlide 19: MADE BY: Gr.L:SHAHZA HASSAN Co.wrkrz: zummer, saima marium sundus nazrah shafaq amina sumaiya reem