Elastomeric Impression Materials DA 122 Dental Materials

Elastomeric Impression Materials Polysulfide Polyether Polyvinylsiloxane (known as addition silicone) All are supplied as 2-paste systems (tubes): Base + catalyst Automix: Extruder guns (catalyst + base) with cartridge and mixing tips Base and Catalyst are mixed to homogeneous consistency Base = paste in tube, cartridge, or putty Catalyst = paste in tube, cartridge, or liquid in bottle with dropper (AKA “accelerator”) Self-curing (chemical action)

Mixing elastomeric impression material Objective when mixing elastomeric impression materials is: To obtain a homogenous mix To obtain a uniform cure of the mix Wear non-latex gloves

Tubes Base and catalyst tubes Narrow stiff impression spatula Large mix pad (6X6) Syringe for light-body material Adhesive-prepared tray for heavy-body

Cartridges Light-body cartridge with applicator tip or syringe Heavy-body cartridge Extruder gun; one for each cartridge; hand-held or mechanical

Automatic Mixing Mechanical device for mixing cartridges Ex. MixStar Pentamix

Putty-Polyvinyl Siloxane Addition Silicone Base = jar or bucket Catalyst = jar or liquid Large mix pad (6X6) Narrow, stiff spatula Non-latex gloves Impression tray Prepared with adhesive

Curing Stages Self-cure = polymerization Initial set: includes mix and work time until material stiffens and you cannot manipulate it Final set: in mouth; material goes from elasticity phase into rubber phase Final cure: takes place from 1 – 24 hours after final set; slight dimensional changes can occur

Viscosities Light-bodied = syringe type “wash” Thin body, can flow in and around tooth structure Used in syringe or extruder gun and placed directly on tooth or structures in mouth Regular or heavy-bodied = tray type Thicker Used to fill tray to make chairside custom tray which will hold light-bodied material against teeth for better detail

Polysulfide Impression Material Common Uses Characteristics: Final impressions for dentures and partial dentures RATIO: Equal amounts Mix to homogeneous consistency Known as “rubber base” or mercaptan Unpleasant odor (sulphur) Long setting time Stains clothing (mercaptan) Shrinkage after setting (disadvantage-lacks dimensional stability) Greater strength and tear resistance than colloids Flexible

Polysulfide Armamentarium Clean-up Stiff, narrow impression spatula Paper mixing pad Catalyst and base 2x2 gauze squares Adhesive-painted custom impression tray Syringe to apply light-bodied material Orange solvent 2x2 gauze squares Wait until set to peel set material off spatula Remove used sheet of mixing pad Recap impression materials MIX Surface: paper mixing pad MIX instrument: Stiff, narrow spatula

Polysulfide Times Appearance Mix = 60 seconds Work = 3-6 minutes Set = 10 – 20 minutes in mouth Shiny light blue or chocolate brown Homogenous end product COMMON BRAND NAMES: Permlastic Coe-flex Kerr

Polysulfide Impression material

Polyether Impression Material Common Uses Special Properties Final impression for crowns, bridges, indirect inlays or onlays RATIO: Base : Catalyst Equal amounts Accuracy Stability Stiff enough to be used without putty on tray Shorter working time

Polyether Impression Material Armamentarium Clean-up Impression tray prepared with adhesive Narrow, stiff spatula 6x6 paper mix pad Base and catalyst Syringe for application Wait until material sets and then peel it off of spatula or other non-porous surfaces Wipe item clean with rubbing alcohol MIX surface: paper pad MIX instrument: Narrow, stiff spatula **automatic mix units available **

Polyether Impression Material Times: Appearance Mix = 30 – 45 seconds Work = 2 – 3 minutes Set = 6 – 7 minutes in mouth Shiny color Common Brand Names: Impregum Polyjel NF (we use)

Polyether Impression material

Polyvinylsiloxane Impression Material (also known as addition silicone) Common Uses Special Properties Final Impressions: crowns, bridges, indirect inlays or onlays, implant crowns Bite registrations RATIO: equal amounts of base and catalyst Available in range of viscosities (“bodies”) or forms: Light, medium, heavy body Highly accurate Easy to spatulate Odor-free Tends to bubble on setting Latex gloves may inhibit set; use vinyl or nitrile gloves

Polyvinylsiloxane Impression Material Armamentarium Clean-up Extruder gun with Cartridge Tips Adhesive-prepared impression tray (custom or stock) Also available in automatic mix machine Immediately on porous surfaces; can stain Wait to set to peel off non-porous surfaces Mix surface/instrument: Not necessary because extruder gun is used

Extruder gun dispenser Extruder gun dispenser for impression materials: Impression material moves plunger forward to force the: Base and accelerator from the individual chambers Then the pastes move into mixing tip They blend and exit tip as a uniform paste

Polyvinylsiloxane Disadvantage of polyvinylsiloxane (also known as silicone) Expensive Short shelf life

Polyvinylsiloxane Impression Material Times: Appearance: Mix = 30 seconds Work = 2 minutes Set = 5 minutes in mouth Brightly colored, shiny, rubbery when set Common Brand Names: Take 1 Express President

Techniques for Polyvinylsiloxane Wash Technique Heavy body + light body Heavy body = putty in tray Light body=put in syringe