Dental and Orofacial Implants and Tissue Bioengineering Flashcards
1
Q
what are endosseous implants?
A
- the most common type of dental implant
- sits in the bone
2
Q
what are subperiosteal implants?
A
- used in cases of atrophic bone
- sits on top of bone
3
Q
what are transosteal implants?
A
- uncommon; higher failure rates
- traverses the entire mandible
- not used on the maxilla
- disadvantage: complete facial butchery
4
Q
what is the alveolar process?
A
- ridge on the surface of mandible/maxilla where the teeth reside
5
Q
what is basal bone?
A
bone underlying the alveolar process
6
Q
alveolar bone proper vs supporting alveolar bone
A
- alveolar bone proper
- compact bone
- cribriform plate, lamina dura
- compact bone
- supporting alveolar bone
- both compact and trabecular bone
- cortical plates: compact bone component
- central spongiosa: trabecular bone component
- both compact and trabecular bone
7
Q
describe alveolar bone structure relative to implant placement
A
- loading via mastication is critical for maintaining bone density
- loss of alveolar bone in edentulous patients
- no loading = no alveolar ridge, only basal bone
- patient selection/site preparation is critical for high success rate of dental implants
8
Q
what is osseointegration?
A
- deposition of bone in close apposition to implant surface
- process is mediated by mesenchymal progenitor cells
- provides mechanical stability of implant and a tight seal
- some debate as to how this occurs
- osseointegration vs biointegration
9
Q
describe the process of osseointegration
A
- wound healing: space management
- extraction of tooth leaves a hole
- hole fills with a clot, which is then converted to a highly cellular granulation tissue
- epithelial invasion vs. bone regeneration
- osteoblast differentiation and bone deposition (osseointegration)
10
Q
describe distance osteogenesis and contact osteogenesis
A
11
Q
what is fibrous encapsulation?
A
- formation of fibrous soft tissue (collagen) around implant
- not good for mechanical anchoring
12
Q
what can fibrous encapsulation result from?
A
- peri-implantitis brought on by problems/delays in osseointegration
- microbial infiltration or poor stability after placement
- untimely space management = problems in wound healing
13
Q
describe the mechanical forces acting on implants
A
- tensile, compressive, and shear forces
- up to 1250 N reported
- material properties and integration of implants are ciritical due to the forces involved
14
Q
T or F:
bone will resporb if it does not experience strain
A
true
15
Q
what happens to bone if the elastic modulus is too high?
A
- lower transfer of force to bone
- leads to lower bone loading
16
Q
describe the use of ceramics in implants
A
they tend to be stiff and do not transfer adequate strain to surrounding bone, resulting in stress shielding
17
Q
describe titanium in dental implants
A
somewhat more elastic than ceramics and transfers some strain to surrounding bone
18
Q
an implant material must be ___ but also have mechanical properties which are ___
A
- structurally sound
- physiologically compatible
19
Q
bone is strongest when ___, weaker under ___ forces, and weakest when subjected to ___
A
- compressed
- tensile
- shear
20
Q
the ___ interface is critical when considering mechanical loading of implants
A
bone-implant
21
Q
what happens to bone in apposition to smooth implants?
A
- it is subjected to almost total shear when the implant is loaded
- less surface area for attachment
22
Q
why is added texture important for the success of implants?
A
- added texture (ex. threads) 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 attachment
23
Q
describe how alterations in length of implants can implicate implant loading
A
- increasing length
- increase surface area of attachment = descreased stress on bone
- minimal advantage, as most force transfer happens at the upper part of an osteointegrated implant
24
Q
describe how alterations in width can have implications for implant loading
A
- increasing width
- increased surface area for attachment = decreased stress on bone
- implant stiffness increases, leading to stress shielding of bone
25
what is the most common material used for dental implants?
* titanium
* CP Ti or TI-6Al-4V alloy
26
describe the properties of titanium that make it a good material for dental implants
* elastic modulus
* strength
* immune-inert (not immunogenic)
* low corrosion (passivation - continual presence of a passive oxide layer)
* biocompatible (non-toxic)
27
describe the ways in which titanium can be modified
* alterations in oxide layer - oxide layer is mainly what biological systems interact with
* coatings - biomemtic or ceramic
* roughening/etching - grit blasting or acid etching
28
describe the two ways in which surface modification enhances osseointegration
1. osteoblast differentiation/migration
2. improving the mechanical interlocking with bone tissue, providing better loading characteristics
\*"optimal" surface is still unclear
29
describe implant surface chemistry modification
* refers to increasing oxide layer
* TiO2 forms the stable oxide layer
* oxide layer is generally biologically favorable (protein absorption)
* modifications, such as hydroxylation, increase hydrophilicity (wettability)
* anodization used to increase oxide layer thickness
30
describe ceramic and glass coatings
* applied to implants to increase cell attachment and help with wound healing
* hydroxyapatite/tricalcium phosphate/bioglass
* bioactive, although only as strong as the metal-ceramic interface
31
describe implant coating components that increase cell attachment
* short peptide sequences
* integrin
* RGD cell attachment sequences
* collagen
* fibrin
32
describe implant coating components associated with wound healing
* growth factors
* TGFbeta1
* FGF-2
* VEGF
* PDGF
33
describe the survival rate of endosseous implants
* 7 year survival rate of around 95%
* careful patient selection plays a large role in the success rates
34
describe patient selection for implants
* patient selection is critical due to requirements for rapid osseointegration
* must have good bone around the site to anchor implant during loading
* many edentulous patients have atrophied bone - not good candidates
* must not be compromised in terms of bone healing
* diabetes, immune-compromised patients can pose problems
35
what is tissue engineering?
a discipline which seeks to encourage the restoration of function and structure to a pre-injury state
36
what are bioactive materials?
materials which are designed to drive repair/regeneration through the use of bioactive factors
37
describe 3 key components in tissue engineering
1. relevant cell source
2. biomaterial or scaffold
3. bioactive component to drive cell responses
38
what are 4 general classifications of relevant cell sources?
1. autograft
2. allograft
3. xenograft
4. alloplast
39
describe autograft
implanted material derived from the same individual as the implant is to be delivered to
40
describe allograft
implanted material derived from another individual of the same species
41
describe xenograft
implanted material derived from another species
42
describe alloplast
implanted material is not derived from a living source or is "synthetic"
43
dental pulp progenitor cells are a population of ___ progenitors resident in the dental pulp, derived from the \_\_\_
* mesenchymal
* neural crest
44
dental pulp progenitor cells can theoretically differentiate to regenrate what 4 biological components?
* vasculature
* mineralized tissue
* soft tissues
* possibly nerves
45
dental pulp progenitor cells represent a capacity of the tooth for \_\_\_
self repair
46
describe cellular vs. acellular approaches to tissue engineering
* addition of material containing cells vs. application of materials to existing tissues
* tissues need cells to regenerate, but many tissues have cells containing the necessary cells (ex. capacity to self repair)
* advantages and disadvantages:
* soft tissues - peridontal ligament, dental pulp, oral mucosa, skin
* hard tissues - bone, dentin, cementum?
47
describe the practical difficulties of the isolation of dental pulp progenitor cells (DPPCs)
* relatively low cell numbers
* possibly around 1% of cells
* lack of single specific marker to ID cells
48
what is the gold standard for isolation of DPPCs?
1. population doublings over long periods in culture
2. multi-potency: ability to differentiate in various lineages
1. adipose, endothelial, chondro-, osteo-
49
DPPCs are adherent cells. What does that mean?
* they attach to tissue culture plastic
* they typically express high levels of alpha5beta1 integrin receptor, which binds fibronectin
* fibronectin adhesion isolation
50
what are 3 main challenges to overcome in oral tissue regeneration?
* microbial infection
* inflammation
* regeneration
51
through \_\_\_, it may be possible to manipulate the innate capacity of oral tissue to encourage ___ and/or \_\_\_
* tissue regeneration
* repair and/or regeneration
52
describe the benefits of new bioactive materials
* more options for practitioners
* improved outcomes for patients
53
what does it mean if a material is "biomimetic"?
mimicry of tissues/processes/structures that are biological
