Question

For the following materials: a) Titanium alloy; b) Cobalt alloy; c) Stainless steel; d) amalgam; e) NiTiNOL; f) Aluminum oxide; g) Pyrolytic carbon; h) hydroxyapatite; i) UHMWPE; j) PP; k) PMMA; l) PET; m) PTFE; n) Silicone; o) PU. Which of these materials would you choose for the following applications? Why?

(1) Tooth filling

(2) Bone cement

(3) Bone graft substitute

(4) Vascular graft

(5) Contact lenses

(6) Finger joint replacement

Answer 1

Tooth filling -

Teeth can be filled with gold; porcelain; silver amalgam (which consists of mercury mixed with silver, tin, zinc, and copper); or tooth-colored, plastic, andmaterials called composite resinfillings. There is also a material that contains glass particles and is known as glass ionomer.

Advantages of silver fillings:

1. Durability -- silver fillings last at least 10 to 15 years and usually outlasts composite (tooth-colored) fillings.
2. Strength -- can withstand chewing forces
3. Expense -- may be less expensive than composite fillings

2- bone cement

Bone cements consist of a powder (i.e., pre-polymerized PMMA and or PMMA or MMA co-polymer beads and or amorphous powder, radio-opacifer, initiator) and a liquid (MMA monomer, stabilizer, inhibitor). ... The individual components of the bone cement are also known in the area of dental fillermaterials.

The two components are mixed and a free radical polymerization occurs of the monomer when the initiator is mixed with the accelerator. The bone cement viscositychanges over time from a runny liquid into a dough like state that can be safely applied and then finally hardens into solid hardened material.^[4] The set time can be tailored to help the physician safely apply the bone cement into the bone bed to either anchor metal or plastic prosthetic device to bone or used alone in the spine to treat osteoporotic compression fractures.

3- .Bone substitutes can be broadly categorized into bone grafts (autograft, allograft, xenograft), ceramics (hydroxyapatite, TCP, calcium sulphate) and growth factors (DBM, PRP, BMP'S) [10]. The ideal bone substitute should be biocompatible and not evoke any adverse inflammatory response

4- vascular bypass (or vascular graft) is a surgical procedure performed to redirect blood flow from one area to another by reconnecting blood vessels. Often, this is done to bypass around a diseased artery, from an area of normal blood flow to another relatively normal area. It is commonly performed due to inadequate blood flow (ischemia) caused by atherosclerosis, as a part of organ transplantation, or for vascular access in hemodialysis. In general, someone's own vein (autograft) is the preferred graft material (or conduit) for a vascular bypass, but other types of grafts such as polytetrafluoroethylene (Teflon), polyethylene terephthalate (Dacron), or a different person's vein (allograft) are also commonly used. Arteries can also serve as vascular grafts. A surgeon sews the graft to the source and target vessels by hand using surgical suture, creating a surgical anastomosis.

5- Most extended wear contact lenses are made out of silicone hydrogel - a material that combinesthe water-absorbing plastic of soft lenses with silicone. Adding silicone to the hydrogel plasticcreates a lens that stays moist and allows more oxygen to transmit through the contact lens into the eye. Any contact lens wearer who keeps their contacts in during the day and at night, or leaves lenses in for days at a time needs a contact that allows their eyes to breathe. The addition of silicone to the lens offers this functionality for optimal contact lens health.

6- Some patients receive more than onefinger-joint replacement—and, in some cases, during a single operation. ... The most commonly used material for artificial finger joints is silicone.