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BDS 2: Oral Ecosystems > OE L41 Implantology: Osseointegration > Flashcards

OE L41 Implantology: Osseointegration Flashcards

1
Q

What are the main metals used for dental implants?

A
  • Titanium (pure or alloy)
  • Zirconium (pure)
  • Stainless steel (alloy)
  • Cobalt-chronium (alloy)
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2
Q

Describe heamostasis and coagulation following implant insertion.

A
  • Blood vessel injury increases blood release
  • Blood coagulates and fibrin clot forms due to aggregating platelets
  • Clot is rich in fibronectin, hyaluronan, vitronectin, thrombospondin
  • Clot stems blood flow, and acts as reservoir for cytokines and pro-inflammatory GFs which regulate the healing process
  • Clot acts as provisional matrix for inflammatory cell migration/activation

(Some elements of osteointegration are beginning to occur: proteins present in blood and other fluids e.g. saliva, begin to absorb onto the implant surface to aid the attachment of other cell types later on)

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3
Q

Which cells are present during the inflammatory phase after implant insertion?

A
  • Neutrophils, monocytes and type 1 macrophages
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4
Q

What is the role of inflammatory cells?

A
  • Produce proinflammatory cytokines (IL-1, TNF-α) to recruit more inflammatory cells
  • Produce MMPs and lysozyme to attack bacteria
  • Produce ROS
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5
Q

How long does the inflammatory phase last for?

A
  • 5-10 days
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6
Q

Describe the granulation tissue phase of wound healing.

A
  • M1 macrophages decrease in number
  • M2 macrophages increase in number
  • M2 macrophages phagocytose remaining debris in the tissue
  • Fibrin clot is degraded through fibrinolysis and granulation tissue rich in hyaluronan left behind
  • Granulation tissue acts as provisional matrix for MSC differeniation into osteoblasts
  • Angiogenesis also occurs: there is endothelial cell migration, proliferation and differentiation to form vascular loops and a capillary network
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7
Q

Describe osteoinduction.

A
  • MSCs migrate and proliferate

- Mediated by TGF-β, BMPs, PDGF, VEGF

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8
Q

Describe osteoconduction.

A
  • Once MSCs are present in sufficient number, they differentiate into osteoprogenitor cells and then into mature osteoblasts
  • Induced by BMPs, TGF-β, VEGF
  • Inhibited by PDGF and bFGF
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9
Q

Which transcription factor must ostoeprogenitor cells express to become osteoblasts?

A

RUNX2

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10
Q

What are some osteoblast phenotypic markers?

A
  • Alkaline phosphatase
  • Type I collagen
  • Osteocalcin
  • Osteonectin
  • Osteopontin
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11
Q

Describe the tissue remodelling phase of implant healing.

A
  • Mature osteoblasts are induced by BMPs and TGF-β to secrete osteoid
  • Osteoid is rich in proteoglycans, e.g. hyaluronan, versican, fibronectin which inhibit mineralisaiton
  • Matrix is remodelled to contain type I collagen and bone glycoproteins (removal of hyaluronan, versican etc), this allows matrix maturation and mineralisation to take place
  • Facilitators of mineralisation = osteonectin, osteopontin, osteocalcin, CS-decorin, CS-biglycan
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12
Q

What type of bone is formed initially?

A
  • Woven bone (weak, porous, low mineral density)

- Gradually replaced by lamellar bone

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13
Q

What is osteoadaptation?

A

The recruitment of osteoclasts to work in conjunction with osteoblasts to remodel bone around the implant.

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14
Q

Describe the action of osteoclasts.

A
  • Cause mineral dissolution and ECM degradation
  • Have a ruffled border, form a sealing zone, release HCl into resoprtion pits to cause HAP dissolution
  • Secrete cysteine proteinases which degrade the ECM (e.g. cathespin K and MMPs)
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15
Q

Which cells are osteoclasts derived from?

A

Haemopoietic stem cells in bone marrow.

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16
Q

What are distance and contact osseointergration?

A

Distance osseointegration = bone formation from adjacent alveolar bone

Contact osseointegration = bone formation from implant surface

Bone from both aspects eventually meets and closes the gap formed during surgery.

17
Q

Does bone come into direct contact with the implant surface?

A

No.

There is a cement line.

18
Q

What is the cement line?

A
  • A nanometre thick layer of unmineralised matrix directly adjacent to implant
  • Rich in CS-decorin, CS-biglycan and hyaluronan
  • No collagen, therefore mineralisation is inhibited
19
Q

How does cement line thickness differ between implant materials?

A
  • Titanium = most narrow CL
  • Zirconium = second thickest CL
  • Stainless steel = thickest CL
20
Q

Why may a narrow CL be preferable?

A

Hypothesised that thinner CL allows more mineralised tissue to be closer to the implant surface and increase stability and mechanical properties.

21
Q

Describe the main features of titanium as an implant material.

A
  • Biocompatible, low corrosion/toxicity, good mechanical properties
  • Thin CL: hypothesised that this is due to ROS reacting with titanium oxide surafce causing titanium peroxy gel formation
  • Titanium peroxy gel degrades the proteoglycan layer at the implant surface thus decreasing CL size so mineralised tissue is closer to implant
22
Q

Implant failure causes can be divided into 2 groups, what are these?

A
  • Primary factors: reasons associated with insertion

- Secondary factors: reasons associated with implant loading

23
Q

What is the main reason for implant failure?

A
  • Poor surgical technique
24
Q

Name some secondary factors which cause implant failure.

A
  • Poor oral hygiene leading to periimplantitis
  • Impaired healing by host factors (e.g. smoking, type2 diabetes)
  • Poor bone quality and premature loading (e.g. osteoporosis)
25
Q

What is the Branemark classification of bone ?

A

Classifies the quality of bone which implants are inserted into.

26
Q

Describe type I bone.

A

Homogenous cortical bone

27
Q

Describe type II bone.

A

Thick cortical bone with marrow cavity

28
Q

Describe type III bone.

A

Thin cortical bone with dense trabecular bone of good strength

29
Q

Describe type IV bone.

A

Very thin cortical bone with low density trabecular bone or poor strength.

30
Q

Which bone type is associated with implant failure?

A

Type IV.

Maxilla is predominantly III and IV contributing to lower implant success rates

31
Q

What 2 types of methods are being used to manipulate titanium implant surfaces?

A
  • Physical methods

- Chemical methods

32
Q

Describe physical methods used to modify implant surfaces.

A
  • Grit blasting
  • Plasma treatment (spraying/sputtering/ion implantation)
  • Laser treatment
33
Q

Describe chemical methods used to modify implant surfaces.

A
  • Acid etching
  • Alkali/heat treatment
  • Anodic oxidation
  • Hydrothermal treatment
  • Hydrogen peroxide pre-treatment
34
Q

How does pre-treatment with hydrogen peroxide improve osseointegration?

A
  • Increases surface roughness
  • Promotes MSC attachment and proliferation
  • Risk: could it also increase bacterial adherence to implant surface?

BDS 2: Oral Ecosystems (42 decks)

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