The Study Of Effects On Fracture Resistance Of Artglass Crowns

Identified by the manufacturer (Heraeus/Kulzer) as a new polymer glass, Artglass has been on market since 1995. It combines the advantages of porcelain and conventional composite resin. Because its hardness is approximate to that of enamel, so it doesn't cause the excessive abrasion of opposite tooth structure, and the patients feel more comfortable. The making of Artglass restorations is similar to that of traditional composite resin.Artglass can be used in inlays > crowns and bridges. The product instructions of the company recommend that it should be best combined with metal substructure. And it is a contraindication that Artglass is used in occlusal surface without metal frame when thickness of the restoration is less than 1.0 nun The long term clinical survey revealed that the Artglass veneers often debonded from the metal substracture, thus resulted in unesthetical surfaces of restorations . But when used in crowns without metal, the rate of failure is lower. This study was designed to test whether Artglass could be used in full crowns or not from the aspect of fracture resistance. Many factors can affect fracture resistance ,for example wall taper of abutment , shape of shoulder , cement , thickness of crowns etc. The purposes of this study include the evaluation of the effect of different cementation techniques on the fracture resistance of metal-free Artglass crowns; and the evaluation of the effect of thickness of crown on the fracture resistance.The study is composed of three parts: the first part is about the effect of different cementation technique on the fracture resistance of metal-free Artglass crowns. Methods: The extracted human maxillary premolars receivedstandardized tooth preparation. Artglass crowns were cemented with zinc phosphate cement (ZnP), glass ionomer cement(GIC),or a resinous cement in combination with a dentinal bonding agent. Artificial crowns were vertically loaded until compression to failure. Significant differences of fracture loads between experimental groups were assessed by paired t-test. The second part is about the effect of different thickness on fracture resistance of crowns cemented onto teeth . The last part is about the effect of thickness (0.5 nraix i Q mm) of crowns cemented onto metal dies on fracture resistance of crowns. Stainless steel dies were used to replace the extracted teeth. The conclusions are as follows:1. Three common cements are all suitable compared to the maximum occlusal force.2. Adhesive cementation gets the greater stability for premolar metal-free Artglass crown.3. There is no significant difference among the groups of the crowns with different thickness cemented onto the extracted teeth.4. The dose of preparation of abutment can be adjusted according to the clinical situation.5. With the increasing thickness,the fracture resistance of crowns cemented onto metal dies increased.6. When the thickness of crowns is in the same, the fracture resistance of crowns cemented onto teeth is higher than that of crowns cemented onto metal dies.