Dental Orofacial implants and Tissue Engineering Flashcards
what is a endosseous implant
sits in the bone
most common
what is a subperiosteal implant
rare, but used in cases of atrophic bone/ site on top of the bone
what is a transosteal implant
uncommon, higher failure rates. Transverses the entire mandible, not used on the maxilla
Disadvantage: complete facial butchery
what is the alveolar process?
ridge on surface of mandible/maxilla wherein dwell teeth
basal bone
bone underlying the alveolar process
alveolar bone proper
-compact bone (cribriform plate, lamina dura)
supporting alveolar bone
both compact and trabecular bone
- cortical plates: compact bone component
- central spongiosa: trabecular bone component
what is critical for maintaining bone density?
loading
loss of alveolar bone in edentulous patients results in having what type of bone?
basal bone
what is osseointegration?
deposition of bone in close apposition to implant surface
- mediated by mesenchymal progenitor cells
- provides mechanical stability of implant and a tight seal
what is the key first step to osseointegration?
hole fills with a clot, which is then converted to a highly cellular granulation tissue
what does the granulation tissue become over time?
bone tisuse
when a formation of fibrous soft tissue(collagen) around an implant occurs what is this called? and is it good or bad?
fibrous encapsulation
- bad news, results in poor stability of implant
- can result from peri-implantitis
what are the mechanical forces acting on implants?
tensile, compressive, and shear forces
what must bone experience to keep from resorbing?
strain
why are ceramics a bad choice for implants?
tend to be stiff and do not transfer adequate strain to surrounding bone, resulting in stress shielding
why is titanium a better choice for implants?
more elastic (lower elastic modulus) and transfers some strain to surrounding bone
what must an implant material have to be successful?
structurally sound but also must have mechanical properties which are physiologically compatible
if the elastic modulus is too high what happens to the bone?
there is less transfer of force to bone and thus lower bone loading
when is bone strongest?
when it is compressed
when is bone weak?
under tensile forces
when is bone weakest?
when it is subject to shear forces
why is a smooth implant a bad idea?
because the force on the bone will almost be completely shear
why does threading an implant make it much better than a smooth one?
it engages bone in compression where it is strongest
-interlocking also provides much better transfer of load to bone(less resorption) and increased surface area for attachement
does increasing the length of an implant make it better worse? What is a minimal advantage?
worse because the increased surface area leads to less load on the bone
-most force happens at the coronal portion of the implant. Anatomy and heating
does increasing the width make an implant better or worse?
once again you are increasing the surface area thus decreasing the stress as well as stress shielding due to the more stiff wide implant
what are the properties of titanium that make it the most common material for dental implants?
elastic modulus strength non immunogenic low corrosion (oxide layer) biocompatible (non toxic) -also it can be modified in a large number of ways
what is the oxide layer of titanium?
the outer layer that has interacted with air and what biological systems interact with
what is the purpose of coating the implant or roughening/etching?
enhancing osseointegration by:
- osteoblast differentiation/migration
- improving mechanical interlocking with bone tissue, providing better loading characterisitics
Implant surface chemistry modification
- refers to increasing oxide layer
- titanium oxide layer favors protein absorption
what does hydroxylation do?
increases hydrophilicity (wettability)
what does anodization do?
increases oxide layer thickness
ceramic and glass coatings are bioactive but they are only as strong as what?
the metal -ceramic interface
what does coating with short peptide sequences to?
increase cell attachment
eg: integrin, RGD cell attachment sequences, collagen, fibrin
coating with growth factors is associated with what?
wound healing
what is the survival rate of endosseous implants?
7 year rate of around 95%
for implants you must have careful patient selection, what are somethings to look for in patients?
good bone around site
not be compromised in terms of bone healing
what are bioactive materials?
materials which are designed to drive repair/ regeneration through the use of bioactive factors
what are the three components in tissue engineering?
relevant cell source
biomaterial or scaffold
bioactive component to drive cell responses
what are 4 general classifications of relevant cell sources?
autograft
allograft
xenograft
alloplast
what is an autograft?
implanted material derived from the same individual as the implant is to be delivered into
what is an allograft?
implant material derived from another individual of the same species
what is a xenograft?
implanted material derived from another species
what is an alloplast?
implanted material that is not derived from a living source or is synthetic (very broad category)
what are Dental Pulp Progenitor Cells?
population of mesenchymal progenitors resident in the dental pulp, derived from the neural crest
what can dental pulp progenitor cells differentiate to regenerate?
vasculature mineralized tissue soft tissue nerves -represent a capacity of the tooth for self repair.
cellular vs. acelluar approaches
additional material containing cells vs. application of materials to existing tissues
how do you isolate dental pulp progenitor cells (DDPCs)?
low cell numbers (1% of cells)
lack of single specific marker to ID cells.
DDPCs are adherent cells and will stick to tissue culture plastic
DDPCs express high levels of what?
alpha 5 beta 1
what does alpha 5 beta 1 bind to?
fibronecting, thus you can use fibronectin adhesion for isolation of DDPCs.
what are some challenges to overcome in oral tissue regeneration?
microbial infection, inflammation, regeneration
what is biomimetic?
mimicry of tissues/processes/structures that are biological.
T/F through tissue engineering, it may be possible to manipulate the innate capacity of oral tissue to encourage REPAIR or perhaps REGENERATION?
true, this leads to more options for practitioners and improved outcomes for patients.
