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Comparison between hydrocolloids
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Comparison between hydrocolloids

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Applied Dental Material

Applied Dental Material
Second Year

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Comparison between hydrocolloids Comparison between hydrocolloids Presentation Transcript

  • Elastomers comparison Origin. Supplied form. Shelf life. Setting reaction. Thickness of the impression Hydrocolloid Agar Alginate Gel Natural polymer. Powder Good. Limited. It is sensitive to moisture& temperature. Chemical gelation reaction. Physical gelation reaction. Thick section [4-6mm] to avoid tearing Flow. Nature. High flow Since the dispersion medium is water, they are hydrophilic. Dimensional accuracy during setting. Slight contraction due to agglomeration of the dispersed phase. Adhesion to the tray. Non-adhesive to the tray. .·.They need mechanical retention [perforation]. Highly The most flexible flexible. among the elastic impression materials. Flexibility. Tear resist. Polysulphide Low tear resistance. Good. Elastomers Condensation Addition Silicone Silicone Synthetic polymer. 2pastes in different viscosities Light, regular, heavy, putty. Limited due to Good. oxidation of the catalyst. Condensation Condensation polymerization. polymerization. Addition polymeriztion Polyether Good. Ring opening polymerization. Thin section [2-3mm] to reduce the polymerization & thermal shrinkage. Thick section to avoid tearing due to their limited flexibility in hydrophylized addition silicone & polyether. High flow according to consistency Hydrophobic. Extremely Hydrophilic due to hydrophobic. presence of ethylene oxide .˙. Surfactant is unit. added. Polymerization shrinkage due to decreased interatomic between monomer units. Highest Lowest polymerization polymerization shrinkage. shrinkage. Non-adhesive to the tray. .·. An adhesive is applied to the tray. The most flexible among the elastomers Flexible. But the hydrophylized addition silicone & polyether are of limited flexibility High tear resistance
  • Elastic recovery. Disinfection 98.8% 97.3% .·.The lowest Since they are hydrophilic, they can be disinfected by spraying. Dimensional stability during storage. Since the dispersion medium is water, they suffer from synersis & imbibition. .˙. Immediate pouring is required after the gradual recovery. Compatibilit y to model & die Since they are hydrocolloids, materials. they retard the setting of gypsum model. They should contain an accelerator for the setting of gypsum to obtain a model with adequate hard surface after separation. Since they are hydrophilic, they can not be electroplated. 97.9% 99.5% 99.8% 98.5% .·. The highest Since they are hydrophobic, they can be disinfected by immersion. Since hydrophylized addition silicone & polyether are hydrophilic, they can be disinfected by spraying. They suffer from polymerization shrinkage [continuous for 24 hours] & thermal shrinkage from oral to room temperature. .˙.Immediate pouring is required Lowest values Since it is hydrophilic in after the gradual recovery. .˙.The most nature, it suffers from dimensional stable imbibition. in elastic .˙. Better to pour it impression immediately after gradual material. recovery. Compatible. .˙. No need for separating medium. Since they are hydrophobic, There are 2 Since it is hydrophilic, it is porous models are frequently problems: easily wetted by the obtained. * Extreme gypsum. Care should be given during hydrophobic pouring. .˙. Surfactants are added. *Hydrogen gas evolution. .˙. Wait 1 hour before pouring. Or Gas absorber is added. Since they are hydrophobic, they can be electroplated Since hydrophylized addition silicone & polyether are hydrophilic, they can not be electroplated.