To compare the effects of metal-free materials to metal-ceramic or other conventional all-metal materials for prosthodontic treatments aimed to restore severely damaged teeth or to replace missing teeth.
Fixed prosthodontic treatment is a routine dental procedure in which one or more missing or severely damaged teeth are replaced by artificial substitutes. The material used to make the prosthesis may be made of a metal framework with a veneering of an aesthetic material (ceramic) or entirely in metal or it can be made with different non-metal structures (metal-free materials). There is still uncertainty regarding metal-free long-term performance compared to metal-based crowns and bridges.
This review of existing studies was carried out by Cochrane Oral Health authors and the evidence is current up to 3 May 2017. We searched scientific databases for randomised controlled trials (studies where people are randomly put into one of two or more treatment groups) comparing different types of materials for prosthodontic treatment in people who were followed up for at least one year.
Of the nine included trials three were conducted in Germany, one in Sweden, one in Spain, one in Switzerland and the USA, one in Denmark, one in Italy, and one in Switzerland. All the included trials were single-centre conducted at university dental clinics and had a parallel-group study design. All the included trials received support from industry.
The review included nine studies with 448 participants in which a total of 224 crowns and 132 bridges on natural teeth, and a total of 74 crowns and 25 bridges on implants were used. Each trial was addressing a different type of intervention. The studies had durations up to 10 years but included very small numbers of participants and were assessed as at unclear or high risk of bias. Based on these studies, there is currently insufficient reliable evidence to support which of these materials are more effective.
Quality of the evidence
Two trials were at unclear risk of bias and seven were at high risk of bias. The overall quality of evidence was very low, therefore caution should be exercised when generalising the results of the included trials. Future research should aim to provide more reliable information which can help clinicians to decide on appropriate materials for fixed prosthodontic treatment whilst taking into consideration the individual circumstances and preferences of their patients.