Osseointegration

Question 1

Define osseointegration:

Answer 1

A process whereby clinical asymptomatic rigid fixation of alloplastic materials is achieved and maintained in bone during functional loading

Question 2

How long does a treatment plan usually suggest an implant is left unloaded for?

Answer 2

3-6 months

Question 3

What is primary stability?

Answer 3

What is achieved immediately by mechanical fixation (i.e. screwed into a surgically created hole?

Question 4

Why is primary stability paramount for clinical success?

Answer 4

If its moving it won’t heal properly and therefore will be unable to resist forces on tooth in all directions

Question 5

Which 4 factors influence the degree of primary stability achieved?

Answer 5

• Bone quality and quantity
• Implant design
• Patient factors
• Surgical technique

Question 6

What are the two main factors for failure of an implant?

Answer 6

Mobility and pain

Question 7

What is secondary stability?

Answer 7

Osseointegration

Question 8

What does the presence of fibrous tissue between the implant and bone mean for the future of the implant?

Answer 8

It will fail -> mobility

Question 9

What happens in osseointegration?

Answer 9

Direct contact between implant and bone (histologically osteoblasts and mineralised matrix contact the implant surface)

Question 10

Describe the healing process of implants:

Answer 10

Highly dynamic, continuous process = maintenance of peri-implant bone and depends on both bone modelling and remodelling

Question 11

What happens when load is applied to an implant?

Answer 11

Amount of contact between bone and implant increases (needs forces to maintain)

Question 12

What is the abutment important for?

Answer 12

Soft tissue attachment (blocks pathway for infection = peri-implantitis -> bone resorption)

Question 13

What are the 3 phases of endosseous wound healing (within the bone)?

Answer 13

• Osteoconduction
• De novo bone formation
• Bone remodelling

Question 14

What is distance osteogenesis?

Answer 14

Bone formation on the old bone (distant from the implant)

Question 15

What is contact osteogenesis?

Answer 15

Bone formation on the implant

Question 16

How is contact osteogenesis encouraged?

Answer 16

Surface of implant treated -> aimed to attract by osteoconduction of cells = more favourable for secondary stability

Question 17

What is the process of osteogenesis?

Answer 17

Activated platelets release a number of growth factors = mitogenic for fibroblasts and osteoblasts, chemotactic for fibroblasts, neutrophils and osteogenic cells

Question 18

What is mitogenic?

Answer 18

Encourages cells to divide

Question 19

What is chemotactic?

Answer 19

Attracts cells

Question 20

Why is implant surface important?

Answer 20

Potentially modulates level of platelet induction and/or maintains anchorage of fibrin scaffold along which cells must migrate

Question 21

What % implant surface is integrated to be deemed successful?

Answer 21

60-70% of implant

Question 22

What % of bone implant contact (BIC) did albresktsson find in his study of implants in the maxilla and the mandible?

Answer 22

Maxilla = >50%, mandible = >75%

n.b. clinical relevance of this is unknown

Question 23

What % of bone implant contact (BIC) did albresktsson find in his study of implants between loaded and unloaded implants?

Answer 23

10% less in unloaded

Question 24

What is visible when looking at an osteointegrated implant under an electron microscope?

Answer 24

A 20-500nm thick layer of dense amorphous substance between bone and implant (organic bone matrix origin, probably proteoglycans an possible osteopontin and bone sialoprotein) = partly calcified

Question 25

How do we assess implants clinically?

Answer 25

Radiographs (poor resolution) and resonance frequency analysis (measure resistance to vibration of the abutment in the surrounding bone) = can convert to number which can be compared against other implants

Question 26

How do we no longer assess implants clinically?

Answer 26

Gripping with forceps and wiggle

Question 27

What is failure of implants correlated with?

Answer 27

Interposition of fibrous tissue between implant and bone

Question 28

What classifies as failure of an implant?

Answer 28

Mobility, pain, gingival inflammation, bone erosion, fracture

Question 29

What are the 3 different categories of compromising factors for implants?

Answer 29

- poor surgical technique - Poor design - patient related factors

Question 30

What is a poor surgical technique?

Answer 30

Infection, overheating of bone, over-instrumentation

Question 31

What is a poor design?

Answer 31

Implant surface factors, shape of implant, overloading due to poor prosthetic design, loading too early

Question 32

What are patient related factors?

Answer 32

Limited available bone, poor oral hygiene, bruxism, age, smoking, radiotherapy, medications

Question 33

Why can implants not be placed in a growing child?

Answer 33

Implant becomes ankylosed to bone = stops jaw being able to grow normally = 'sinking implant'

Question 34

What 4 factors do we promote to improve the osseointegration process?

Answer 34

- Faster and stronger bone formation - Better stability - More rapid loading - Improved clinical performance in areas of poor quantity/quality of bone

Question 35

Which 3 ways do we achieve better osseointegration?

Answer 35

- use surface topography to enhance osteoconduction - use surface coating to provide biological means to manipulate the type of cells that grow on the implant surface - use of implant as a vehicle for delivery of a bioactive coating that may achieve osseoinduction along its surface

Question 36

What have studies for using surface topography to enhance osteoconduction shown?

Answer 36

Osteoblasts might attach better, spread and proliferate on smooth surfaces but differentiate faster, produce higher levels of growth factors and mineralise faster on rougher surfaces

Question 37

What have studies for using surface coating to provide biological means to manipulate the type of cells that grow on the implant surface shown?

Answer 37

Superior initial rates of osseointegration have been achieved, experimentally long term failure is caused by delamination of coating and particle release from implant surface = need longer term studies to be sure, also no increase in BIC or osteoblast differentiation shown yet, and non-specific absorption of plasma proteins may occur with unfavourable interactions with inflammatory molecules

Question 38

What have studies using implants as a vehicle for delivery of a bioactive coating that may achieve osseoinduction along its surface?

Answer 38

-BMPs and PDGF enhance osteogenesis