Biocompatibility 2 Flashcards
What reactions can occur when material is placed in the mouth?
- allergic reaction to materials
- material degradation
- material interaction with tissues
- and with bacteria
Why can allergic reactions occur to material?
- the body’s way of responding to an ‘invader’
- immune system triggered when antigen sensed
- begins immediately after exposure usually
- anaphylaxis - most severe hypersensitivity reaction
Clincial appearance of allergic reactions
- redness/whiteness of mucosa
- swelling of lips, tongue, cheek
- ulcers/blisters
Frequency of allergic reactions
- 1:000 to 1:10000
- rare
- more common when using deoderants or antiperspirants
How are allergies recorded?
- often not noticed by patients
- recorded in routine dental exams
- questioned about existing allergiesn at first exam and updated with new ones every time
Who has increased potential for reaction?
- children have increased sensitivity to food additives
- dental practitioners more at risk repeated handling of unset products
3 groups that can cause reactions
- metals
- polymers
- cements
Types of metal we can have a reaction to
- metal and/or ionic metal hydroxides/oxides
- corrosion products
- wear products
Kinds of polymers that cause reactions
- residual monomers
- leachable compounds
Cements that cause reactions
- eugenol
- acids
- leachable compounds
- residual monomers
Common problems in patients with material caused hypersensitivity
- stomatitis (chromium, cobalt, mercury, monomers, formaldehyde, eugenol)
- lichenoid reactions (amalgam, composite resins)
- plasma cell gingivitis
- angioedema
- erythema multiforme
Issues for the dentist with material caused hypersensitivity
- contact dermititis
- when surface contacts allergen like nickel or monomers
- like monomers of bonding agent
- mainly distal parts of fingers and palmer aspects of fingertips
List reasons why materials degrade
- oral environment
- corrosion
- wear
How does the oral env degrade material?
- chemical degradation in aqueous env, hydrolysis and saliva esterases breaking down resins
- pH range
- temp
- solvents
- bacteria
How does corrosion degrade material?
- metals and alloys
- dietary acids increase it
How does wear degrade materials?
- contact and relative motion
- roughness effect
- loss of material
- wear debris - increase wear, biological response of inflammation and osteolysis/bone resorption)
Consequences of degradation
- loss of materials (less mechanical proporties and reduction in mass)
- degradation products increase wear and cause immunological response locally and systemically
Bulk properties of material
- chemical composition
- structure
- purity
- presence of leachables
Bulk properties cause …
irritation
Surface proporties of material
- roughness
- geometry
- hydrophilicity
- surface change
Surface properties cause what?
adhesion (protein and cellular)
Mechanical properties of material
- loading
- wear
- creep
- deformation
- stress corrosion cracking
Mechanical properties cause what?
particulate release
Interaction of material depends on …
application
Materials of dental implants
- titanium and its alloys
- coatings with ceramics
- all-ceramic implants available (zirconia)
Osseointegration
Biointegration
of dental implants
- direct bone contact with implant surface. Gap less than 10nm
- no gap
Materials in fracture fixation plates
- titanium and its alloys commonly
- resorbable polymers (polylactic acid, polyglycolic acid, copolymers)
Negatives to titanium as a fracture plate
- post-op complications
- stress shielding
- screw fixation
Features of resorbable polymers
- lower stiffness than titanium
- resorb over time
- acidic byproducts
Immediate biological reactions that happen within seconds and minutes
- water and ion interaction
- protein adsorption
- cellular deposition and spreading
- activation of body’s cellular and immune response
Biological interactions that happen intermediately (hours/days)
- inflammation
- infection
Biological interactions that occur long term (months/years)
- remodelling of surrounding tissues
- calcification
- tumour or cancer formation
Local response to implanted material
- infection
- toxicity
- modification of normal healing
- tumorigenesis
Systemic effects to implanted material
- embolization
- hypersensitivity
- elevation of implant elements in blood
Patient characteristics can influence how tissues react. Which ones?
- age and health (immunology and metabolism)
- tissue damage - the procedure
- contamination (exposure to operating env, patient’s response to infection)
Bacteria adhere to … and form …
- surfaces and form nucleated colonies
- form biofilms and all surfaces
- inflammation forms at interface of bacteria and tissues e.g gingivitis
Material dependent factors that help attachment ofbacteria
- chemical composition of material
- hydrophobic or philic
- material surface - morphology e.g roughness
Which is more resistant to bacterial adhesion? Hydrophobic or philic materials
hydrophobic
Bacteria dependent factors favouring attachment of bacteria
- hydrophobicity of bacteria
- surface charge of bacteria
Excluding material dependent and bacteria dependent factors, what other factors can affect bacterial adhesion?
fluid dynamics
Are there any links between oral and systemic health?
- yes between the oral biofilm and periodontal disease and systemic
- systemic dissemination of oral bacteria and their metabolites is linked to pathophysiology of atherosclerosis
