Material selection in crown and bridge work



Durability and aesthetic and practical features



With the development of the range of all-ceramic restoration materials for crown and bridge work seems endless. Each material has its strengths and weaknesses and thus its own display area. Paul Cook gave a brief presentation on the sustainability and the aesthetic and practical properties of the materials that are available today for dental restorations .

Once the first crown could be made of a metal alloy consisting mainly of gold only. This manufacturing process has changed very little today. What has changed is the man for whom the crowns are intended. His demand for aesthetic restorations and developments in adhesive dentistry have led the gold restoration which has fallen from grace. This while the clinical experience shows that gold restorations cause few problems . With a survival rate of 95 percent after 25 years, gold seems to sustainability than lonely at the stand . The antagonist has little to fear . Gold For by its soft material properties does no harm to opposing enamel and is simultaneously self- abrasion . Gold has the disadvantage that it is not adhesive to cement and thus has little to hold the adhesion of cement . This means that a preparation should provide sufficient retention , leading to more tissue removal. The ability of gold thin to work can reduce tissue contrast decrease again.



Gold Porcelain



Due to the limited aesthetic of gold was soon working on decorating the unnatural gold restorations to tooth-colored , strong crown . Initially this was done by letting , then bring . Because a shield of a prosthetic tooth in a window in the buccal surface of the crown open Later it became possible to predict to bake with veneering , or feldspar the gold. As we got more control over this opbakproces were fully hash crowns and bridges , and there was a big step put into improving the aesthetics . Feldspar is a material that can withstand little strength , and therefore should be fired , with adequate support of the structure .

At a minimum , uniform thickness Thanks to years of experience with this technique can be manufactured . Hash with metal durable restorations Although zirconium has supplanted the gold porcelain restorations in the background there for bridges in the ( pre) molar area is still a good indication of gold porcelain , especially with a large span . Namely the survival of zirconium bridges surpasses not those of gold porcelain.


Despite this improvement , annoyance persisted over the opaque metal understructure , a few natural appearance. In addition, the price of gold increased over the course of the years . Therefore, there have been many attempts to make . Durable, all-ceramic restorations These efforts had mixed success , and the indication was limited to single crowns in the front.
The big breakthrough came with the advent of all-ceramic CAD / CAM techniques . Because there could be milled and sintered , accurately , it was possible to process in dental restorations . Industrial , hard oxide ceramics As a result, the dark metal could be replaced by a sub-structure of the white aluminum oxide and zirconium dioxide later .



Alumina



In 1998, aluminum was introduced on the Dutch market , the most famous variant Procera Alumina Nobel Biocare . At that time it was the strongest available ceramic substructure . The literature indicates that this material has sufficient strength to form . Sustainable , reliable long-term restoration After the arrival of the stronger zirconia alumina remained popular because it is thinner to work , and then translucenter zirconium. This creates a much more natural light transport through the crown and there with this material an attractive final result achievable. In the course of time , it became possible to zirconium thinning working . For several years it has also in different colors and even different translucencies available . This development means that alumina is used less frequently . As restorative



zircon



The ' white steel ' zirconium dioxide is by far the strongest ceramic materials in dentistry where we possess. Because it is very opaque and there- not so pretty , it must still be buckets. Feldspar This is also the Achilles heel of the right material. For although the literature shows good clinical survival outcomes of both zirconium crowns and bridges , there appear to be more problems to occur than with gold porcelain. The main problem is fracture of the veneering porcelain to zirconia , the so-called chipping . This problem was in the early part caused by habituation of all parties who had to work . Using this new material By misuse of feldspar and oven temperatures by dental technicians and by angular preparations and use of outdated cement by dentists , fracture rates were much higher than in the old familiar gold porcelain. The moderate form of the zirconium substructure in the start-time , leading to insufficient evenly supported veneering porcelain and thus to more chipping . The expectation is that with the current knowledge of the material , the durability of zirconia restorations of gold porcelain restorations able to match .


Referance By:- 

http://blog.excent.eu/materiaalkeuze-in-kroon-en-brugwerk/