Adhesives Flashcards
1
Q
Adhesive
A
- general term
- in specific contexts can be replaced by designations like cement, glue, paste, fixative, and bonding agent
2
Q
Bonding/groutin
A
- creating durable interfacial bond between the material and the host tissue while space-filling (bone cement)
3
Q
Sealing
A
- prevention of ingress of moisture, air, biological fluids, bacteria, and other species through the bonded zone
4
Q
Abhesion
A
- prevention of adhesion (non-fouling surfaces)
5
Q
Adherend
A
- surface to which an adhesive adheres
6
Q
Basics of Adhesives
A
- generally presented as fluid agents that have a means of converting into a solid form
- utility is based on context (hard or soft tissue, timescale, and strength/durability needed)
- primarily used in wound closure and surgical adhesives
7
Q
Logic of Adhesion
A
- effective intimate contact area between surfaces becomes too minimal for adhesion due to IMFs
8
Q
Requirements
A
- wet both adherend surfaces (may require etchant or primer on surface, or roughening, to increase porosity, etc.)
- create a fluid-solid interface resistant to tensile load through nanoscale primary (covalent, ionic, and metallic) or secondary bonds (hydrogen, VdW), micro-mechanical bonds or interlocking (can be disrupted by air voids, weak boundaries, etc)
- solidifies so the interface becomes resistant to shear forces
9
Q
Means of solidification
A
- phase transformation
- solvent evaporation
- polymerization of monomers or oligomers (widely used but susceptible to polymerization shrinkage phenomena!)
- acid/base reactions
10
Q
Bone/Tooth Cements
A
- PMMA/MMA cement is used to fix acetabular and femoral components in a THA
- solidifies through benzyol peroxide initiator, free radical reaction, or using an amine activator (exothermic reaction, so avoid too high temperatures otherwise bubbles occur… 5-13 min to set)
11
Q
Bonding of PMMA, Polymerization Shrinkage
A
- bonding occurs through microscale interlocking, polymer penetrated interstices of cancellous bone (adapts to surface of stem)
- shrinkage can create unwanted porosity at interface between metal implant and bone cement (this is a weak link, and can lead to micro-cracks)
- heating the implant surface will induce pore formation AWAY from prothesis surface
12
Q
Alternative Bone/Tooth Cement list
A
- inorganic calcium phosphate systems
- zinc phosphate
- poly (carboxylic acid) cements
- zinc polyacrylate cements
- glass-ionomer cements (GIC)
13
Q
Inorganic calcium phosphate systems
A
- e.g. hydroxyapatite and tricalcium phosphate
- bond through intermolecular adhesion to calcified tissue, micro-mechanical interlocking
14
Q
Zinc phosphate
A
- traditional cement formed of zinc oxide powder and phosphoric acid solution
- effective in vivo for 10-20 years (dental)
- bonding is micro-mechanical interlocking through surface roughness
- opaque upon hardening
15
Q
Glass-ionomer cements (GIC)
A
- based on poly (acrylic acids), use aluminosilicate glass powder instead of zinc
- crosslinking through calcium and aluminum ions and silica gel formations
- forms translucent, rigid cement with similar adhesive properties to zinc
