Commentary

Systematic reviews developed according to the methodological rigour of the Cochrane Collaboration format leave little room for criticism of the procedural steps leading up to the authors' conclusions. Nevertheless, the authors choose to include only RCT, which severely limited the scope of possible trials. Only one such trial was included, which does not allow any general statements to the made about clinical performance. The authors described the lack of studies as disappointing and recommend that more well-designed trials should be carried out. The question is whether this is realistic, given the indications and contraindications for using ceramics intraorally.

Restoring posterior teeth with ceramic inlays is relatively limited, in spite of ceramics being among the oldest restorative materials we have. This relates to restoration, following caries destruction, to salvage remaining tooth tissue and not to, improving the smile (posteriorly). The positive side of ceramic restoration is that ceramics are highly biocompatible and can be made to match tooth colour perfectly. Unfortunately, they are also brittle. The consequence of this is that extensive tooth preparation is required, contrasting with modern restorative thinking where minimal-intervention dentistry is favoured. Moreover, the techniques for producing and for placing well-fitting intracoronal ceramic inlays are time-consuming and highly technique-sensitive. The novelty of modern ceramics is the wider spectrum of production possibilities, that is, there is traditional sintering, cast- and/or pressed- as well as infiltrated-ceramics. Innovative concepts for machining prefabricated ceramic blocks are constantly being developed and some new, interesting, high-strength ceramics have emerged. These have the potential to reduce the need for removal of tooth substance to reach a necessary minimum thickness of the inlay.

There is a disturbing trend emerging in dentistry reflected by a recent paper stating, “Our patients have a higher dental IQ than those of the past, more disposable income, and are demanding conservative, aesthetically pleasing, non-metallic restorations.” I am not so sure if this would be the case if the dentist were to describe the option, “Yes, we can restore the tooth with something that looks very nice, but I will have to remove more sound tooth structure than would otherwise be necessary, it will probably last a fraction of the time of the alternatives and it is rather expensive because it is technically complicated to create.”

Ethically, one cannot carry out clinical trials unless there is equipoise about a working hypothesis. Based on our current knowledge about material properties and the data from a limited number of mostly short-term cohort studies, is there any reason to assume that a ceramic inlay will perform better than another restorative material with respect to longevity? I think not. It is also very probable that publication bias exists regarding the clinical performance of ceramics. Moreover, it should always be the informed patient who should decide on the choice of treatment. Given that patients are provided with adequate and correct information, although perhaps not described as pointedly as above, is it likely that they will consent to being randomised into a group where an alternative non-ceramic, or even a metallic, restorative material is to be used? Again, I think not. Because of this I do not believe there will be numerous RCT published on the topic in the future, the exception perhaps being comparisons between conventional and, hopefully, new higher-strength ceramics.

Practice point

  • Little evidence is available that supports any difference in clinical performance of ceramic inlays and other posterior restorations.