Answer 1:
Replacements for decayed or lost teeth have been produced since antiquity. The most common material that was used for artificial teeth was ivory especially from elephants.
Human teeth were also used, pulled from the dead. These kind of false teeth soon rotted, turned brown and rancid. So the need for more stable material arose.
In the past artificial teeth made of metals like silver, gold were very common. If a damaged tooth is beyond repair, it must be extracted and replaced with an artificial tooth which is made of porcelain, metals like gold or plastic. False teeth made of acrylic are also being used.
The most commonly used materials for artificial teeth today are porcelain and acrylic. Acrylic teeth contain polymethyl methacrylate (PMMA) resin which forms its basic ingredient. PMMA resins are resilient plastics formed by joining multiple methyl methacrylate molecules. A cross linking agent is added which serves as a bridge that unites two polymer chains. In this manner it yields a net like structure that provides increased resistance to deformation. So these teeth have greater fracture toughness than porcelain teeth.
Furthermore resin teeth are easier to adjust. On the other hand ceramics or porcelain are characterised by their hardness, susceptibility to brittle fracture and chemical inertness.
Prosthetic teeth can also be made with a metal substrate to which porcelain is bonded for aesthetic enhancement. These teeth are called metal-ceramic restorations. A full porcelain (all-ceramic restoration), porcelain fused to gold, full gold and all metal crown restorations are also in practice.
The important goal of dentistry is to restore the colour and appearance of natural teeth. Two important attributes of dental ceramics are their potential for matching the appearance of natural teeth and their insulating property.
For this reason they are quite expensive when compared to acrylic teeth. Artificial teeth need a base to hold them in place. Many synthetic resins are used for this purpose.
Hardness, resistance to abrasion, natural look, ability to withstand stresses during chewing and thermo physical properties like thermal conductivity are the most important factors in considering materials for artificial teeth.
Answer 2:
Plastics which revolutionized modern living play a major role in replacing lost teeth. The particular form and morphology of plastic used in making artificial teeth is acrylic resin [poly (methyl methacrylate)]. The denture base (part of the denture that rests on soft tissues of the mouth) is also made of acrylic resin.
Also, in a complete denture (prosthesis replacing all missing natural teeth) artificial teeth made of metal, porcelain have been incorporated.
When replacing a few anterior teeth (partial denture) aesthetic material like resin, porcelain or porcelain fused to metal are used.
For posterior partial dentures, which need more strength metal fused with porcelain or porcelain fused to metal crowns is used selectively.
Source : The Hindu
