The Punisher is an ex-marine, who goes out every night and battles the criminal

Question

The Punisher is an ex-marine, who goes out every night and battles the criminal

population of New York. He's described in the comics as a force of nature, but he is

always human. Or is he? Cuts heal, bones knit, and even the most egregious injury

can be survived. The Punisher is shown getting his teeth knocked out again and

again and again. Sometimes, by the end of a fight, he has only one or two left in his

mouth. Yet in the next book he's got a mouth full of teeth again! Clearly, this guy has

a power he's not admitting to.

1. Let’s work through a design for a ceramic tissue-engineered scaffold that would

allow this same dental tissue regeneration as The Punisher.

a) What type of bioceramic will your scaffold use? Bioinert, porous and inert,

bioactive, bioresorbable, or some combination? Why?

b) Tissue ingrowth is desired in the implant. Describe why porosity is critical.

c) What methods of fabrication would be appropriate?

d) The primary structural component of teeth is dentin, which is primarily

composed of hydroxyapatite (HA). How does this native HA differ from

synthetic HA that you might have chosen to use for your scaffold?

e) Name two challenges of using a biodegradable material in the tissue

engineering construct. Name two advantages to using a biodegradable

material.

f) The Punisher looks like a guy that clenches his teeth a bit too much, exposing

his teeth and the tissue engineering scaffold to a constant load over periods

of time. In this context, describe why a ceramic would be a more favorable

biomaterial in this application than a metal implant.

g) Explain how molecular or atomic structure gives rise to the difference in

ductility between ceramics and metals.

h) In the real world (where mistakes can be made), what determines the

strength of ceramics and glasses? Hint: is any real material perfectly

crystalline?

2. Bone is strongest in compression, weak in shear, and intermediate in tension.

Bone is a composite of collagen and hydroxyapatite (and cellular material).

(a) Collagen has a low E, good tensile strength, but poor compressive

strength. What class of materials (polymers, metals, ceramics) does collagen belong

to and (based on the chemical structure) why does it have these associated

mechanical properties?

(b) Hydroxyapatite (HA) is an ionic mineral that is stiff and brittle but has

good compressive strength. What class of materials (polymers, metals, ceramics)

does HA belong to and why (based on the chemical structure) does it have these

associated mechanical properties?

Explanation / Answer

1)a) The type of bioceramic that can be used as a scaffold for regeneration of teeth includes a combination of bioactive and porous materials. The substance has to be bioactive as it needs to get interacted with extracellular matrix. It has also need to be porous to allow tissue ingrowth.

b) Porosity is essential for blood supply, transport of substances and tissue ingrowth.

c) Both microfabrication and nanofabrication techniques will be appropriate for tissue remodelling.

d) Native hydroxyapatite differs from synthetic hydroxyapatite in the following aspects,

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