Minimal cavity design

I read your editorial entitled ‘The genesis of minimal cavity design’¹ with great interest. I concur with your views that Richard Elderton's work, taking a fresh look at cavity design, was ‘20 years ahead of its time’ and the need to investigate the merits of new concepts by means of high-quality clinical trials, prior to promoting the concepts as best practice.

Notwithstanding your ‘reservations with regard to whether the narrow isthmus and occlusal design (as and when occlusal preparation rather than fissure sealing may be indicated) would actually work with amalgam’, a study published in 1992 revealed a much more significant problem – the difficulty of adapting and condensing amalgam in the rounded (raindrop-shaped), limited occlusal access proximal portions of cavities of the type advocated by Elderton, even when condensation instrumentation of modified (rounded) design was used.² The outcome of this work, albeit a small study, precluded an ethical approval application to conduct a randomized controlled trial to compare the use and performance of amalgam and composite in the restoration of Class II cavities of conservative design, ie the sort of study you indicate remains to be conducted.

As concluded by Duncalf and Wilson:² ‘The trend toward more conservative cavity preparation is to be encouraged, because the loss of sound tooth tissue is reduced, and the restored tooth is better able to withstand the forces of occlusion. However, if restorations (of amalgam) in conservative preparations are defective and prone to early failure in clinical service, the benefits of a conservative approach to cavity preparation could be negated.’ I therefore maintain evidence-based guidance confirming that composite may be found to perform well in occlusal proximal cavities of conservative design³ – that amalgam has very little, if any, part to play in state-of-the-art minimum intervention dentistry, even when it comes to the repair of defective restorations of amalgam – a procedure best done using composite.⁴ So, I would suggest that those of your readers ‘still wedded to amalgam’ have a dilemma: continue to prepare relatively big cavities of conventional design to enable the amalgam to be well-adapted and condensed and thereby unnecessarily sacrifice sound tooth tissue and compromise the strength of the restored tooth, or join the ever-increasing number of colleagues who use composite in adopting and applying the principles of minimum interventive dentistry – composite, especially when inserted into a conservative cavity directly from a compule, tending to completely restore the proximal section of the preparation and have good marginal adaptation.⁵

Finally, I concur with your concluding remarks on the genesis of minimal cavity design: ‘…better still, embrace prevention, then we might not have to cut the cavity at all!’ – remembering that once a ‘restorative patient’ (possibly as young as six years of age), always a ‘restorative patient’. As and when colleagues are rewarded and valued for saving rather than filling teeth, we will hopefully see the day when prevention is embraced to the extent that it may realize its full potential.