Dental Orofacial implants and Tissue Engineering

Question 1

what is a endosseous implant

Answer 1

sits in the bone

most common

Question 2

what is a subperiosteal implant

Answer 2

rare, but used in cases of atrophic bone/ site on top of the bone

Question 3

what is a transosteal implant

Answer 3

uncommon, higher failure rates. Transverses the entire mandible, not used on the maxilla
Disadvantage: complete facial butchery

Question 4

what is the alveolar process?

Answer 4

ridge on surface of mandible/maxilla wherein dwell teeth

Question 5

basal bone

Answer 5

bone underlying the alveolar process

Question 6

alveolar bone proper

Answer 6

-compact bone (cribriform plate, lamina dura)

Question 7

supporting alveolar bone

Answer 7

both compact and trabecular bone

• cortical plates: compact bone component
• central spongiosa: trabecular bone component

Question 8

what is critical for maintaining bone density?

Answer 8

loading

Question 9

loss of alveolar bone in edentulous patients results in having what type of bone?

Answer 9

basal bone

Question 10

what is osseointegration?

Answer 10

deposition of bone in close apposition to implant surface

• mediated by mesenchymal progenitor cells
• provides mechanical stability of implant and a tight seal

Question 11

what is the key first step to osseointegration?

Answer 11

hole fills with a clot, which is then converted to a highly cellular granulation tissue

Question 12

what does the granulation tissue become over time?

Answer 12

bone tisuse

Question 13

when a formation of fibrous soft tissue(collagen) around an implant occurs what is this called? and is it good or bad?

Answer 13

fibrous encapsulation

• bad news, results in poor stability of implant
• can result from peri-implantitis

Question 14

what are the mechanical forces acting on implants?

Answer 14

tensile, compressive, and shear forces

Question 15

what must bone experience to keep from resorbing?

Answer 15

strain

Question 16

why are ceramics a bad choice for implants?

Answer 16

tend to be stiff and do not transfer adequate strain to surrounding bone, resulting in stress shielding

Question 17

why is titanium a better choice for implants?

Answer 17

more elastic (lower elastic modulus) and transfers some strain to surrounding bone

Question 18

what must an implant material have to be successful?

Answer 18

structurally sound but also must have mechanical properties which are physiologically compatible

Question 19

if the elastic modulus is too high what happens to the bone?

Answer 19

there is less transfer of force to bone and thus lower bone loading

Question 20

when is bone strongest?

Answer 20

when it is compressed

Question 21

when is bone weak?

Answer 21

under tensile forces

Question 22

when is bone weakest?

Answer 22

when it is subject to shear forces

Question 23

why is a smooth implant a bad idea?

Answer 23

because the force on the bone will almost be completely shear

Question 24

why does threading an implant make it much better than a smooth one?

Answer 24

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

Question 25

does increasing the length of an implant make it better worse? What is a minimal advantage?

Answer 25

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

Question 26

does increasing the width make an implant better or worse?

Answer 26

once again you are increasing the surface area thus decreasing the stress as well as stress shielding due to the more stiff wide implant

Question 27

what are the properties of titanium that make it the most common material for dental implants?

Answer 27

elastic modulus
strength
non immunogenic
low corrosion (oxide layer)
biocompatible (non toxic)
-also it can be modified in a large number of ways

Question 28

what is the oxide layer of titanium?

Answer 28

the outer layer that has interacted with air and what biological systems interact with

Question 29

what is the purpose of coating the implant or roughening/etching?

Answer 29

enhancing osseointegration by:

• osteoblast differentiation/migration
• improving mechanical interlocking with bone tissue, providing better loading characterisitics

Question 30

Implant surface chemistry modification

Answer 30

• refers to increasing oxide layer

- titanium oxide layer favors protein absorption

Question 31

what does hydroxylation do?

Answer 31

increases hydrophilicity (wettability)

Question 32

what does anodization do?

Answer 32

increases oxide layer thickness

Question 33

ceramic and glass coatings are bioactive but they are only as strong as what?

Answer 33

the metal -ceramic interface

Question 34

what does coating with short peptide sequences to?

Answer 34

increase cell attachment

eg: integrin, RGD cell attachment sequences, collagen, fibrin

Question 35

coating with growth factors is associated with what?

Answer 35

wound healing

Question 36

what is the survival rate of endosseous implants?

Answer 36

7 year rate of around 95%

Question 37

for implants you must have careful patient selection, what are somethings to look for in patients?

Answer 37

good bone around site

not be compromised in terms of bone healing

Question 38

what are bioactive materials?

Answer 38

materials which are designed to drive repair/ regeneration through the use of bioactive factors

Question 39

what are the three components in tissue engineering?

Answer 39

relevant cell source
biomaterial or scaffold
bioactive component to drive cell responses

Question 40

what are 4 general classifications of relevant cell sources?

Answer 40

autograft
allograft
xenograft
alloplast

Question 41

what is an autograft?

Answer 41

implanted material derived from the same individual as the implant is to be delivered into

Question 42

what is an allograft?

Answer 42

implant material derived from another individual of the same species

Question 43

what is a xenograft?

Answer 43

implanted material derived from another species

Question 44

what is an alloplast?

Answer 44

implanted material that is not derived from a living source or is synthetic (very broad category)

Question 45

what are Dental Pulp Progenitor Cells?

Answer 45

population of mesenchymal progenitors resident in the dental pulp, derived from the neural crest

Question 46

what can dental pulp progenitor cells differentiate to regenerate?

Answer 46

vasculature
mineralized tissue
soft tissue
nerves
-represent a capacity of the tooth for self repair.

Question 47

cellular vs. acelluar approaches

Answer 47

additional material containing cells vs. application of materials to existing tissues

Question 48

how do you isolate dental pulp progenitor cells (DDPCs)?

Answer 48

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

Question 49

DDPCs express high levels of what?

Answer 49

alpha 5 beta 1

Question 50

what does alpha 5 beta 1 bind to?

Answer 50

fibronecting, thus you can use fibronectin adhesion for isolation of DDPCs.

Question 51

what are some challenges to overcome in oral tissue regeneration?

Answer 51

microbial infection, inflammation, regeneration

Question 52

what is biomimetic?

Answer 52

mimicry of tissues/processes/structures that are biological.

Question 53

T/F through tissue engineering, it may be possible to manipulate the innate capacity of oral tissue to encourage REPAIR or perhaps REGENERATION?

Answer 53

true, this leads to more options for practitioners and improved outcomes for patients.