Zirconiumdioxide in fixed prosthodontics

Project description

The purpose of the present research program is to give a further and deeper understanding on the use of zirconium dioxide as reconstructive material; its clinical performance and possible technical and biological complications when used for crowns, fixed dental prostheses (FDPs) and resin-bonded fixed dental prostheses (RBFDPs). The studies should also contribute to facilitate treatment choices based on scientific evidence.

Background

Patients suffering from tooth loss show several functional impairments such as masticatory-, phonetic-or aesthetic shortcomings or a combination of the mentioned. To compensate for the losses, they can be offered reconstructions made of different materials with different design and extension, retained in different ways. Traditionally crowns and FDPs based on metal alloys covered with porcelain veneers have been used. Metalceramic can provide treatment outcomes with high survival rates and good predictability. With the desire for metal-free replacements, all-ceramic materials have been introduced and developed. Modern ceramics are strong, stiff, inert, and biocompatible and enable the production of reconstructions with comparably high aesthetics. The term dental ceramics includes silicate-based ceramics and oxide ceramics. In the group silicate-based dental ceramics, we find traditional porcelain and glass-ceramics, and among the oxide ceramics alumina and zirconia. Zirconium dioxide (ZD) is an oxide ceramic with very good properties such as high strength, toughness and inertness.

Today, we use zirconia-based ceramics routinely in dentistry to produce both crowns and FDPs. It is currently considered a well-documented material. Initially, however, ZD was only used as core materials, which involved a framework/core veneered with a porcelain. Studies done on those materials show very high survival rate but with a varying incidence of surface porcelain fractured, so-called chip-off fractures. The zirconia material therefore got improved and the translucency increased. By this we could make crowns and FDPs without surface porcelain so-called monolithic ZD.

By using the monolithic form, it is possible to gain a strong material with excellent biological properties, but without the risk of chip-off fractures. Laboratory and clinical trials have shown very promising results regarding those monolithic ZD materials . Since the esthetic properties of zirconia is inversely proportional to the mechanical ones, it is sometimes impossible to gain both good esthetics and sufficient mechanical properties by only changing the translucency of the ZD. In such cases it is still needed to add porcelain to an otherwise strong core material, in order to improve the esthetics.

Recent years that have been done by combining monolithic ZD with so called cut-back technique, where the buccal surface of a crown or an FDP is reduced and replaced with a porcelain veneer. Studies made on those new appliances of zirconia, monolithic and partially veneered ZD are however scarce. Especially clinical studies on both monolithic and semi-monolithic ZD used for resin-bonded fixed dental prostheses are lacking.

Including studies

1. A randomized clinical trial aiming at systematically evaluate the clinical outcome of crowns in the posterior dentition made of monolithic zirconium dioxide, and to compare with crowns made of lithium disilicate.
2. A randomized clinical trial aiming at systematically evaluate the clinical outcome of monolithic and partially veneered translucent zirconium dioxide FDPs in the posterior dentition over time.
3. The purpose of this in vitro study is to evaluate different stripling techniques on the fracture strength within monolithic high translucent zirconium dioxide under simulated loads and thermocycling.
4. The aim of this prospective clinical randomized split-mouth trial is to systematically evaluate and compare translucent zirconium dioxide-based RBFDPs as replacements for missing laterals in the upper jaw and to evaluate them regarding clinical performance, technical and biological complications.