Topic 1+2 tissue interactions

Question 1

What is a biomaterial

Answer 1

A biological or synthetic material that is implanted in a living organism

Question 2

What 2 examples of main goals are there when implanting a biomaterial?

Answer 2

The distance should be as small as possible between the tissue and the implant. The tissue should grow as fast as possible to the implant.

Question 3

Roughly describe the healing process of an titanium implant in bone

Answer 3

1 week - just lots of liquid and space
Then the gap starts getting smaller and smaller, collagen fibers start forming and filling out the space.
The oxide layer becomes thicker as ions go out due to corrosion and reaction with the tissue.

Question 4

What is an very important aspect regarding a biomaterial?

Answer 4

The implant surface plays a key role in the wound healing and tissue regeneration. The optimal biomaterial is specific to the specific location of the implant as they vary. Sometimes different parts of the implant because it interacts with different tissues.

Question 5

Why is it so important that the cells attach tightly to the tissue of a dental implant?

Answer 5

To prevent bacteria and food from entering the gap in between.

Question 6

The top tissue in the mouth - what is it called and what does it consist of?

Answer 6

The Gingival epithelium - like the skin but in the mouth.

The epithelium consists of epithelial cells that are tightly packed to form tight junctions (physical barrier).

Question 7

How does the titanium interact with the Gingival epithelium?

Answer 7

Titanium can create a tight junction with the epithelial cells just like they can do with each other.

Question 8

What is the Gingival connective tissue?

Answer 8

Cells are not so densely packed as in the epithelia. Contain blood vessels, fibroblasts that creates a collagen fiber network.

Question 9

Describe compact bone

Answer 9

A very dense tissue that is mineralized. Contain osteocytes that have a lot of protruding arms, they also produce collagen fibers.

Question 10

Describe cancellous bone

Answer 10

More porous (spongy) than compact bone and have different cells - fibroblasts, osteoblats (premature osteocyte) etc. The cells are surrounded by lots of fluid.

Question 11

What components on which length scale? Dental implant vs. tissue

Answer 11

(mm) Geometrical design - organized tissue
(µm) surface roughness - cells
(100nm) Dislocation - proteins
(10nm) metal oxide thickness - peptides
(nm) point defects in metal oxide - cell membrane

Question 12

How is passivation used in dental implants?

Answer 12

You grow the titanium oxide surface thicker than needed in order to make the material more passive e.g. less corrosive/overall affected by the surroundings.

Question 13

What is the water bilayer that is created after implantation?

Answer 13

The water will form organized or disorganized layers between the bioliquid and the material. Ions can be hydrated by this layer when it interacts with the water molecules.

Question 14

Briefly explain the time progression of events at the implant surface

Answer 14

the surface atoms are contaminated by other molecules - cleaning - passivation - proteins arrive (form the absorbed protein layer) - cells arrive and sense the protein coating

Question 15

What happens in the water bilayer after a while

Answer 15

proteins arrive and gets hydrated (water shell). more and more proteins arrive and then cells (the first most often a blood cell).

Question 16

What is one main role of the first arriving proteins to the material surface?

Answer 16

Transmembrane/receptor proteins on cells can bind to them so they get attached to the material surface. Very important since the cell itself cannot otherwise bind to the material. This can also induce signaling that influence the cells behaviour.

Question 17

How can the surface polarity affect water absorption?

Answer 17

If the surface is too hydrophilic it can bind very strongly to water and create dislocations, if it is hydrophobic water tend to form a disorganized structure. This is important since it will affect how well the proteins attach to the surface.

Question 18

How can the surface polarity affect protein adhesion and cell attachment?

Answer 18

It will affect how the protein will bind to the surface - if it will unfold or be in its native form, or even denature. This in turn will affect how well the cell receptors can bind to the surface interacting proteins! It can have a negative effect (conformational change result in no binding) or positive (the active site gets exposed when the protein unfolds on surface).

Question 19

How does the implant topography affect cell and protein adhesion?

Answer 19

Highly affected by the length scale of the roughness, weather the cell/protein can form around the roughness or if it cannot - will result in no bind.

Question 20

Why is the conformation important when the protein bind to the surface?

Answer 20

It will affect the surface coverage and the binding strength depending on surface contact.

Question 21

Explain competitive protein absorption

Answer 21

Protein adsorption from mixed solutions is determined by kinetics and affinity.
Kinetics: proteins will move in the concentration gradient and the size/diffusion constant will affect the speed.
Affinity: protein size, charge and conformational stability will affect how strong the protein will bind to the surface and for how long. Generally, larger proteins have higher affinity than smaller ones.

Question 22

Why is it important to know which proteins arrive first to the surface?

Answer 22

The first arriving proteins will affect the charge and conformation of the surface - will affect the next coming proteins. It might block the next coming or it will jump off to give room.

Question 23

What is the Vroman effect?

Answer 23

Describes the protein exchange at biomaterial surfaces. Smaller protein in higher conc. will arrive first to the surface, and are then replaced by larger proteins with higher affinity to the surface. (The graph with proteins vs. time)

Question 24

What important reactions are affected by protein type and conformation?

Answer 24

Absorbed proteins can induce blood coagulation and if they are highly unfolded they can be recognized as “foreign” and stimulate inflammatory cells and the immune system. To reduce this effect, pre-absorbed proteins on the surface can be used to help the interaction with the right type of cells.

Question 25

What is biocompatibility?

Answer 25

Biocompatibility is the ability of a material to perform with an appropriate host response in a
specific application.

Question 26

What is the new definition of a biomaterial?

Answer 26

A biomaterial is a nonviable material used in a
medical device, intended to interact with
biological systems.

Question 27

Which tissue types are an implant in contact with?

Answer 27

Bone and gingval tissue.