520 likes | 722 Vues
Graduate Presentations. Apr 19 Mike Sherman Apr 21 Danica Nelson Aleksander Skardal Curtis Lee Apr 24 Seth Hills Ben Christensen Jungkym Kim. Medical Adhesives and Sealants. Adhesion. Definition:
E N D
Graduate Presentations Apr 19 • Mike Sherman Apr 21 • Danica Nelson • Aleksander Skardal • Curtis Lee Apr 24 • Seth Hills • Ben Christensen • Jungkym Kim
Adhesion Definition: The state at which two surfaces are held together by interfacial forces, which may consist of all known chemical attractive forces, as well as mechanical interlocking action or both.
Adhesive • A substance capable of holding materials together by surface attachment (performance). • A general term that includes cement, glue, mucilage and paste.
Sealant • A material applied to a joint in paste or liquid form that hardens or cures in place, forming a barrier against gas or liquid entry.
Adhesives and Sealants-Biomaterials? • Join components of medical devices-Mechanical fastening; • Prevent corrosion; • Fill space – smooth contours-joining prosthesis to bone; • Wound sealing & closure
Adhesive Materials can be classified in a number of ways: • Natural or synthetic polymer base; • Thermoplastic or thermosets; • Physical form (one or multiple component, films, etc) • Functional type (structural, hot melt, pressure sensitive; • Chemical families (epoxy, silicone, etc.)
General Considerations in the Application of Adhesive Bonding • When applied adhesives have to 'wet' the surface; • They need to be mobile and flow into all the tiny surface features of the substrate; • If the adhesive does not wet the substrate well, poor adhesion is likely to be the result; • Once good wetting takes place, an adhesive needs to become solid and not flow at all. This is called setting or curing (polymerization); and, • Positional indication (imaging).
Adhesive Joint Breaking strength is determined by: • Mechanical properties of the materials of the joint; • The extent of the interfacial contact (number, extent, type and distribution of voids); • Presence of internal stresses; • The joint geometry; and, • The details of mechanical loading.
Adhesives are Polymers • Thermoplastics • Thermosets • Available as solids, liquids and pastes and most can be supported by films of various thickness.
Adhesives • Acrylics • Epoxies • Polyurethanes • Silicones
Bonding Mechanisms • Mechanical Interlocking; • Formation of covalent bonds across the interface; • Electrostatic attraction-dominant • Forces are not significant beyond 0.5 nm-therefore contact is necessary
Surface Treatment • No treatment (low cost poor reproducibility); • Solvent wiping; • Vapor degreasing; • Mechanical abrasion; • Plasma treatment; • Etching; • Chemical deposition-primers, organosilanes
Modes of Failure A uniform stress pattern in an adhesive joint is seldom produced by the application of external force. • Structural failure • Adhesive failure • Cohesive failure
Urethanes • Urethane polymerization-diisocyanate and a diol or diamine • Condensation polymerization; • Two part system- mix, spread and cure; • Flexible joint and sealing agent.
Poly (methyl methacrylate) PMMA R-Group Bone Cement
Selection of the starting monomers • C4-C12-alkyl acrylates supply the initial adhesion owing to the low glass transition temperature (Tg).
Cure Profile of Condensation versus Addition Polymerization Addition polymer Condensation polymer Degree of Cure -----> Time
Methyl 2- cyanopropanoate R-Group Methyl -cyanoacrylate monomer polymerizes in the presence of trace amounts of almost any electron-donor compound (the initiator) by anionic vinyl polymerization, examples include water, alcohols, amines, carboxylate ions, and electron rich olefins.
Medical grade products currently available contain either butyl, isobutyl or octyl esters. They are bacteriostatic and painless to apply, break down harmlessly in tissue by hydrolysis and are essentially inert once dry. • Butyl products are rigid when dry, but provide a strong bond; octyl products are more flexible when dry, but produce a weaker bond. • Histoacryl Blue (n-butyl cyanoacrylate) has been used extensively for a variety of surgical applications including middle ear surgery, bone and cartilage grafts, repair of cerebrospinal fluid leaks, and skin closure -- adhesives appear are basically safe. • DMSO (dimethyl sulfoxide) or acetone serve as removers.
The Market • The global medical and surgical sealant market is $542 million and growing rapidly (19% annually), driven particularly in the U.S. • Adhesives and sealants are a critical component of medical devices. • As medical devices become smaller and more complex, greater demands are being made on the materials and components used in them. • Medical devices are being exported from the U.S. to foreign countries at an increasing rate.
Considerations • speed of application; • This is an area where UV-curable adhesives have made the strongest technological advances of any of the newer technologies currently on the market.
Light Cure Systems • Designed for high speed cure on demand medical product assembly; • Solvent free; and, • Wide range of viscosities designed for automated dispensing
Light Cure Adhesives • consist essentially of low or medium molecular weight resins (called oligomers), monofunctional or multifunctional monomers, photoinitiators and/or photosensitisers; • wavelengths of 250-365nm. • typically 5-15 seconds at 80-100 mW/cm2 is sufficient for curing adhesive • visible light curing materials (e.g. resins used in dental restoration or for bonding and sealing photo-optic devices) can be cured with blue light (wavelength = 470nm).
Typical Applications • Bonding latex balloon onto PVC lumen in catheters. • Bonding high pressure latex balloons onto urethane lumens in high pressure catheters, catheters for angioplasty, thermodilution, or foley catheters. • Bond needle to tubing in winged infusion sets • Hypodermic needle.
Flexible Adhesive Applications • Bonding/sealing tracheal tubes made of silicone rubber. • Bonding/sealing extruded silicone parts, colostomy, ileostomy, urostomy bags and appliances. • Sealing of inflators.
Pressure-Sensitive Adhesives • Arcylics on PET • Labels-many medical devices require a label that can be printed after the adhesive has been applied and/or can be written on after application to the device. • Adhesive tapes for attaching equipment drapes in sterile environment applications. • Lidding-effective protective barrier against contamination for storage or shipping; • EKG electrode bonding;
Benefits of Adhesives • Joins dissimilar materials • Even stress distribution • Fills large gaps • Seals and bonds • Easily automated • Aesthetically acceptable
Limitations of Adhesives • Requires cure • Requires fixture time • Can be messy • Requires chemicals in plant
Chemistry Benefits Limitations Typical Applications Cyanoacrylate Substrate versatilityRapid cureAdhesion topolyolefins withprimers Thermoplastic resinwhen curedPoor peel strength,rigidRefrigerationrequired Catheter componentsTube-set bondingPolyolefin bonding Light-CurableAcrylic Substrate versatilityGood resistancepropertiesCure on demand Capital expenditurefor light-cureequipment Needle assemblyAnesthesia masksHeat exchangersOxygenatorsTube-set bonding Epoxy Substrate versatilitySuperior thermaland chemicalresistanceLow shrinkageHigh gap filling Poor peel strength,rigidExothermic reactionTwo-part systemsrequire mixing Needle assemblyDeep section potting Polyurethane Substrate versatilityHigh peelGood resistanceproperties Moisture sensitivityPrimers required forsome substratesTwo-part systemsrequire mixing Deep section pottingBonding of tips ontovarious components
ADHESIVE DENTISTRY Indications • Replace carious and fractured tooth structure. • Fill erosion or abrasion defects. • Correct unaesthetic shapes, positions, dimensions, or shades. • Cement crowns.
Indications-continued • Bond orthodontic brackets. • Treat hypersensitivity. • Repair fractured porcelain, amalgam, and resin restorations. • Core build up foundations.
2. Apply sealant Sealants 1. Etch enamel 3. Light cure 37% phosphoric acid for 30 seconds Courtesy of 3M Dental Products
Enamel surface etched with 35% and 10% phosphoric acid gels for 15 and 60 seconds. Areas with preferential removal of prism core material and the prism peripheries relatively intact (SEM X2000).
Enamel surface etched with 10% maleic acid gel for 15 seconds. The apatite crystals were partially removed from the prism core, but the type I etching pattern may be observed (SEM X2000)
Enamel surface etched with 10% maleic acid gel for 60 seconds. The topographical view of the prism core structure is similar to the etching patterns produced by 35% and 10% phosphoric acid gels (SEM X2000).
Glass-ionomers • Most commonly referred to as glass ionomer cements (GIC's). • These are materials which consist of an aqueous polyacrylate and a fluoroaluminosilicate glass. • These set by an acid-base reaction in the presence of water. • These cements appear to adhere to tooth structure by formation of ionic bonds as a result of chelation of the carboxyl groups in the acid with the calcium and/or phosphate ions in the apatite of enamel and dentin.
COMPOSITION POWDER = CALCIUM FLUOROALUMINOSILICATE GLASS • Silicon 13.3% Phosphorus 2.5% • Aluminum 13.3% Fluoride 22.7% • Calcium 17.3% Oxygen 28.0% • Sodium 1.6% • LIQUID = POLYACRYLIC ACID OR • COPOLYMER OF ACRYLIC ACID • WATER
Most Common Dental Resin bisphenol A glycol dimethacrylate triethylene glycol dimethacrylate
Fractured incisors http://www.seattle-dentist.com/chipped-teeth.htm
LINKMAX 50 Yellow & 50 Pink Micro-Tips Self-Etching Primer EP-B Packaging Self-Etching Primer EP-A Mixing Pad LINKMAX A3 Cartridge Ceramic Primer LINKMAX Clear Cartridge Dispensing Dish Metal Primer II Package Micro-Tip Handle Mixing Spatula
Paste Pak Dispenser • Produces Ideal Consistency Every Time. • Dispenses The Exact Mixing Ratio No Matter How Little Or How Much Material Dispensed. • Metering Slide Enables The User To Control The Volume Of Material Dispensed To Reduce Waste. More Less
Dual Cure: Light Cure & Self Cure • Temporary Light-Cured Linkmax Removes Easily With Hand Instrument One Minute After Seating. • No Radical Clean-Up Procedure Should Be Required. • Light-Cure Each Surface Of Restoration 20 Seconds. • When Used Under Metal Or When Cement is Difficult To Expose To Light, Linkmax Self-Cures In 6 Minutes From Placement Of Prosthesis.
BONDING PORCELAIN • Etchant Etchant • • Ceramic Primer Ceramic Primer • LINKMAX LINKMAX Self-Etching Primer Self-Etching Primer Porcelain Inlay Ceramic Primer Etchant LINKMAX Ceramic Primer LINKMAX Self-Etching Primer Self-Etching Primer Porcelain Veneer Etchant