CD Lec 2 A - Impressions & Materials 2023.pdf

8/16/2023 Impressions & Impression Materials For Complete & Partial Dentures Impressions & Impression Materials For Complete & Partial Dentures Ronni A Schnell, DMD, MAGD, FICD, FACD RS522 ~ 8/16/23 8/16/2023 Sequence of Patient & Lab Visits α Preliminary Impressions Custom trays α Final Impr...

8/16/2023 Impressions & Impression Materials For Complete & Partial Dentures Impressions & Impression Materials For Complete & Partial Dentures Ronni A Schnell, DMD, MAGD, FICD, FACD RS522 ~ 8/16/23 8/16/2023 Sequence of Patient & Lab Visits α Preliminary Impressions Custom trays α Final Impressions Record bases & Occlusion rims α Intermaxillary Records Set‐up α Trial Denture Processing & Lab Remount α Insertion Clinical Remount = 8/16/2023 Sequence of Patient & Lab Visits α Preliminary Impressions Custom trays α Final Impressions Record bases & Occlusion rims α Intermaxillary Records Set‐up α Trial Denture Processing & Lab Remount α Insertion Clinical Remount = 8/16/2023 You’ll never get a second chance to make a great first impression… -Will Rogers …….unless you are a dental student -Dr. Paige 8/16/2023 Goal of an Impression Depends on 8/16/2023 Type of an Impression Depends on 8/16/2023 Purpose of an Impression Depends on 8/16/2023 Purpose of an Impression Type of Prosthesis 8/16/2023 Purpose of an Impression Type of Prosthesis 8/16/2023 Purpose of an Impression Type of Prosthesis 8/16/2023 Purpose of an Impression 1°Cast Support Surface Area 2° Cast Retention 8/16/2023 Retention is a function of: 1. 2. 3. 4. 5. Patient adaptation Polished surface contour Atmospheric pressure (PPS/suction) Adhesion Cohesion 8/16/2023 Physical Properties of Denture Retention • Adhesion—attraction of different molecules to each other. – Increase by increasing surface area. – Insuring that you have captured as much of the supporting structures as possible (1˚ impr) • Cohesion---attraction of the identical molecules to each other. – Increase by increasing contact (closeness) – Using a very low viscosity (m.static) impression material so the tissues are not displaced during 2˚ impr • Atmospheric Pressure--the pressure exerted on the denture by the air around it vs the lack of air inside the denture. – Suction developed by the PPS – posterior palatal seal 8/16/2023 Surface Area the longer the piece of adhesive… …the greater the surface area …the greater the adhesion 8/16/2023 Adhesion- Enough for Complete Denture impressions? clear acrylic base “patient” cast 8/16/2023 acrylic base on plastic cast 8/16/2023 base falls when held vertically 8/16/2023 water placed on cast (adhesion) 8/16/2023 water placed inside base (adhesion) 8/16/2023 base + water contacts cast + water (cohesion) 8/16/2023 base does not fall 8/16/2023 2 clear acrylic tiles 8/16/2023 2 tiles held vertically above bench top 8/16/2023 tiles separate 8/16/2023 water drops added to each tile (simulating saliva) 8/16/2023 Tiles held vertically, but do not separate Cohesion 8/16/2023 * Clinical Significance Saliva-Mucosa attraction is an example of ADHESION Saliva-Denture attraction is an example of ADHESION Saliva-Saliva attraction is an example of COHESION 8/16/2023 Atmospheric Pressure Pressure differential between the inside and the outside of the denture. The amount of suction present as formed by the Posterior Palatal Seal (post dam) and the peripheral borders Mucodynamic capture of the folds by the final impression Posterior border – Posterior Palatal Seal 8/16/2023 * Clinical Significance Atmospheric pressure Border seal : the contact of the denture border with the underlying or adjacent tissues to prevent the passage of air or other substances 8/16/2023 Atmospheric pressure Border seal : the contact of the denture border with the underlying or adjacent tissues to prevent the passage of air or other substances 8/16/2023 Atmospheric pressure Border seal : the contact of the denture border with the underlying or adjacent tissues to prevent the passage of air or other substances 8/16/2023 Atmospheric pressure Border seal : the contact of the denture border with the underlying or adjacent tissues to prevent the passage of air or other substances 8/16/2023 Mucodynamic vs. Mucostatic 8/16/2023 Great Complete Denture Impressions are… • Muco-dynamic at the borders to create suction • Muco-static everywhere else to limit resorption and increase cohesion • Cover as much surface area as possible to reduce movement and limit resorption & increase adhesion 8/16/2023 Muco-dynamic selective displacing certain musculature and tissues of the oral cavity during an impression to force out air, changing the atmospheric pressure and create suction 8/16/2023 Muco-static an impression taken without displacing any tissue the mucosal tissues of the jaws as they are in a state of rest … 8/16/2023 Types of impression Selective pressure 8/16/2023 • Is there ANY single impression material that can accomplish all these goals? – No! • How do we make GREAT edentulous or partially edentulous impressions? – Selective Impressioning - Two-step impression technique • Preliminary (1°) and Final (2°) – Mucodynamic border molding and – Mucostatic final wash impression 8/16/2023 General Impression Materials Rigid • • • Impression compound ZOE paste Plaster of Paris Elastomeric • • • • • NOT good for undercuts Hydrocolloids Polysulfide (rubber-base) Silicones (PVS) Polyether • Good for Undercuts 8/16/2023 General Impression Materials Irreversible Reversible • • Impression compound Reversible hydrocolloid • • • • • Irreversible hydrocolloid- (alginate) Polysulfide - (rubber-base) Silicones – (Polyvinyl Siloxane-PVS) Polyether – (Impregum) Impression plaster 8/16/2023 Impression Materials for Edentulous Arches 2° - Final Impressions 1° - Preliminary Impressions • • Impression compound Alginate • • • • Polysulfide - (rubber-base) Silicones – (Polyvinyl Siloxane-PVS) Polyether – (Impregum) Impression plaster 8/16/2023 Compound impressions… • • • • • • • Mucodynamic More stable than alginate Better extension into vestibule/folds Can be removed before set (gagger) Can bead & box Inelastic Cost-low 8/16/2023 Armamentaruim • Thermoplastic Compound: • Cakes and sticks: • • • • • Fusing temp… Black> Red> Green> Grey 8/16/2023 Alginate Impressions… 8/16/2023 Alginate impressions… • Mucodynamic for soft tissue (heavy body) • Heavy body best for edentulous • Best for undercuts • Cannot bead and box, may deform under weight of stone if unsupported. Pour up within 8 min, decast after 20 min. • Syneresis if left in the air • Undergo imbibition if too wet • Cost- low 8/16/2023 Syneresis vs Imbibition 8/16/2023 Two equal mixes of alginate Dry Wet Imbibition A material that will absorb mater molecules from its surroundings Syneresis The process in which a gel contracts on standing and extrudes liquid 8/16/2023 * Clinical Significance Imbibition when wrapping with a paper towel to maintain moisture… Wring it out! Towel is DAMP, NOT WET Syneresis Poor dimensional stability Pour within 8 minutes 8/16/2023 Alginate preliminary impression trays Must use edentulous trays if patient is edentulous Dentate stock trays will hold excessive alginate 8/16/2023 “Best” tray fit Periphery wax may be added to extend the tray for over the RMP or the Hamular notches since alginate is not as heavy as compound 8/16/2023 Alginate preliminary impression 8/16/2023 Final Impressions are: Muco-Selective BOTH Mucostatic and Mucodynamic Requiring two different types of impression materials 8/16/2023 Dynamic Impression Materials for “Border Moulding” To record extensions into vestibules (folds) and compressible tissues posterior palatal seal): 1. Compound – Red stick corrected by green stick, correct by grey stick compound 1. Rigid, thermoplastic (reversible), poor detail, muco-compressive, 2. Polyvinyl Siloxanes – Heavy body PVS – Green 1. Rigid, poor detail, muco-compressive 1. 2. Tissue stops Border moulding 8/16/2023 Mucostatic Impression Materials To record excellent tissue detail of the “intaglio” w/o compressing tissue. – ZOE (Zinc Oxide-Eugenol) - Best, but rarely used today due to technique and poor pt. tolerance – Polysulfide rubber –Excellent surface details Light Body Rubber Base – Polyvinyl Siloxanes –Excellent surface details – used most often for edentulous applications Light Body PVS - Aquasil LV (light viscosity) or XLV (extra light viscosity) – Polyether – Very good surface details • Poor sheer-thinning (rheological properties) • Used in Fixed pros applications where tissue closeness is not critical • E.g. - Impregum and Permadyne 8/16/2023 Zinc Oxide-Eugenol (ZOE) Impressions… • • • • • are the most mucostatic but are very sensitive to moisture* and are inelastic / rigid (like a cement) Irreversible but relinable Pt. sensitivity issues (Eugenol = Oil of Cloves) *contraindicated if patient has excess saliva or if xerostomic 8/16/2023 Poly Sulfide Rubber Impressions “Rubber Base” … Available: Light, Med, Heavy-body • • • • • • • • • • • are mucostatic if light bodied are less sensitive to moisture than ZOE and are elastomeric poor elastic memory hydrophobic good tear strength long setting time excellent details needs support excellent sheer thinning Stability (0.13% to 0.39% in 24 hrs) – Must be poured with in the hour 8/16/2023 Poly Vinyl Siloxane Impressions “(Extra) Light Viscosity” (Aquasil LV or XLV) XLV • • • • • • Are very mucostatic if light bodied (LV and XLV) Are less sensitive to moisture than Rubber Base Are elastic Better elastic recovery and less deformation than other elastomeric materials BUT… MUCH higher tear energy than rubber base Contraindicated with significant undercuts and large embrasures – For Complete Dentures – need custom tray: wax spacer & tissue stops necessary – For Partial Dentures – can take final impression with stock tray or custom tray with double blockout and tissue/tooth stops LV Monophas e LV XLV 8/16/2023 Adequate tray spacing is a must LV Show-throughs are common Due to the Rheological property… Thixotropic It does not thin well. Poly-ethers are worse ZOE and PSR - best Tissue stops are required for a PVS impression 8/16/2023 Evaluation of Impressions 1. 2. 3. 4. 5. 6. 7. 8. Stability (trim and re-insert) – check for rocking Border thickness & height (symmetry) Tissue detail Tray penetration Folds or creases Surface texture Voids Retention Upper-Y Lower-Y/N 8/16/2023 Border Width √ Look for expected anatomy X √ √ 8/16/2023 Border Height and Symmetry Look for expected anatomy √ X X √ 8/16/2023 Tray Penetration Must have sufficient space for impression material: • Wax spacer • Tissue stops • Compatible tray adhesive 8/16/2023 Voids, Creases, Folds & Surface Detail Do not add impression material to a limited area. Reline/”WASH” the entire impression with XLV 8/16/2023 Clinical Hints for Impressions • Prior removal of old dentures and adhesive to rest tissues if dentures are contributing to problems • Tray selection 1/4” larger or custom for thickness of impression material • Head position Upright for safety / tissues vertical • Dentist position Upper behind pt. / Lower in front of pt. • Muscle movements (“border molding”) • Saliva control – suction & astringent mouthwash • Syringe teeth for Partial Denture impressions 8/16/2023 Upper is done from behind for patient safety Lower is done from in front for patient comfort 8/16/2023 Retract far side with fingers Retract near side with tray Handle points to near side 8/16/2023 Rotate tray until centered over teeth Handle points forward 8/16/2023 Center tray to frenum Then seat tray To measure an empty tray, insure it reaches into the hamular notches in the posterior and then bring it forward over the labial frenum. 8/16/2023 When seating a tray filled with impression material, first seat it anteriorly to insure it captures the anterior undercut, then over the palate and finally into the hamular notches posteriorly. During removal Retract upper lip with fingers Pull tray downward 8/16/2023 Retract far side with fingers Retract near side with tray Rotate tray so handle faces near side 8/16/2023 Blot lips with patient napkin – Check intraorally for any remaining material that could be aspirated or swallowed 8/16/2023 Retract near side with fingers Retract far side with tray Tray handle faces far side 8/16/2023 Retract near side with fingers Rotate tray until handle faces forward 8/16/2023 Center tray over teeth Then seat tray 8/16/2023 During removal Retract lower lip with fingers Pull tray upward 8/16/2023 Retract near side with fingers Retract far side with tray Tray handle faces far side 8/16/2023 Blot lips with patient napkin Check intraorally for any remaining material 8/16/2023 Comparison of Denture Impression Materials 8/16/2023 Modeling Plastic Irreversible Hydrocolloid Zinc-Oxide & Eugenol Polysulfide Rubber Polyvinyl Siloxane General Type Thermoplastic Hydrocolloid Modified Cement Rubber Elastomer Addition reaction silicone elastomer Common Names Compound Alginate ZOE Rubber Base PVS, Aquasil Examples Kerr Impression Compound Alginate Jeltrate Optpw Luralite Permlastic Coe-Flex Heavy-Green Monophase-purple LV-Teal XLV-Yellow Cost $ $$ $$$ $$$$ $$$$$ Dispensing Form Cake / Stick Powder / Water Base / Accelerator (tubes) Base / Accelerator (tubes) Base / Accelerator (cartridges) Composition TP:Gum,Wax Fil: Chalk Soluble Alginate React: CaSO4 Sof:Stearin Glycerin Retard: NaPO4 Base (color) ZnO Acc (clear): Eugenol Base (white): Rubber Acc:Sulfur React: PbO2 Base-polymethyl hydrogen silooxane copolymer, Accvinyl-terminated polydimethyl siloxane. Method Warm water bath Cool to set Bowl 3 min set Pad 3 min set +H20 instant set Pad 5-10 min set +H20 3 min set Cartridges with auto mix nozzles Reg and fast set Flow F G EX Light Body VG-EX Heavy body F LV & XLV VG-Ex Monophase - F, Heavy - P Accuracy F G EX Light Body VG-EX Heavy body F LV & XLV Ex Monophase Ex 8/16/2023 Modeling Plastic Irreversible Hydrocolloid Zinc-Oxide & Eugenol Polysulfide Rubber Polyvinyl Siloxane Patient Tolerance EX G F F + Smell - Taste F - Smell + taste Tray Stock Stock w retention or Adhesive Custom Custom w Adhesive Custom w spacer & adhesive * (see handout) or Massad Tray Need min thickness to be cohesive to itself Muco-static (S) Muco-Dynamic (D) D S – Teeth D – Tissue S S – Light body D – Med/Heavy body Indications 1º, 2º, other 1º 1º 2º 2º 2º Bites and FB Elasticity -- + -- ++ + undercuts w/ Thermal Reaction -- -- -- -- -- Thermal Contraction + ++ -- -- -- Dimensional Stability F P* EX VG-Ex MUST be poured with in 1 hour May be poured up to 24 hours LV & XLV Monophase S D caution Syneresis/Imbibition EX 8/16/2023 Other Modeling Plastic Irreversible Melting Range (lo-hi) Gray Green Red Black  Tempslows set  Shake can to “fluff” “Snap” out Pour STAT Sep STAT (alginate retards surface set of gypsum. May tx w K2SO4) FL reacts w CaSo4 to harden cast Correctible Can be removed from mouth BEFORE set… bec has greater cohesion to itself than it does to mucosa Hydrocolloid Zinc-Oxide & Eugenol Modifiers (Resins and Plasticizers)  Irritation  Speed  Smooth  Crystal Accel: ZnAc CaCl Thin Vaseline Polysulfide Rubber Smell Slow set Continues to cure Polyvinyl Siloxane PVS is CONTRAINDICATED in dentitions with: • Large gingival embrasures • Cemented fixed bridges with high pontics • Mobile teeth Tray Spacer Required: • Single layer wax block out with tissue stops for CD • Double layer wax block out with tissue and tooth stops for PD PVS ADHESIVE required Nitrile gloves only******** 8/16/2023 Impression Objectives: 1º vs 2º 1º • • • • • Patient diagnosis Tissue outline Preliminary cast Tray fabrication Adhesion (surface area) 2º • • • • • Denture diagnosis Tissue detail Final cast Denture fabrication Cohesion (closeness/detail)