Measuring restoration longevity: it's easier now!

I was recently researching the topic of restoration longevity in the UK. Why, you might ask! Because, in my view, being able to measure restoration longevity/survival is central to providing patients with realistic expectations (thereby avoiding medico-legal complications) and ultimately for maintaining faith in our profession.

The literature took me back to a publication in 1969, which I identified as the first UK paper published on this important subject, with there being little prior to that. Readers will have realized that, prior to the arrival of computer technology to aid the compilation of data, this was a time-consuming and laborious task, therefore, it was not frequently undertaken. In that regard, one could consider that the analysis of data from patients' dental records was a labour of love by enthusiasts in the field. One such enthusiast, in 1969, was Douglas Allan, an academic in the Sutherland Dental School, which is what they then called the dental school in Newcastle upon Tyne. For his ‘statistical survey’, he used ‘unselected patients who attended for conservation’, and included 887 restorations.¹ All filled teeth were critically examined by one examiner (the author), and the length of service of the restoration charted in years. At that time there were no clear guidelines as to what actually could be defined as failure of a filling, hence he defined the ‘rules’ for his project which are likely to surprise readers, namely, that a filling was charted as failed if it required extension, or if the tooth was extracted for orthodontic or prosthetic reasons. He used two categories for failure: (1) failures due to poor restorative technique (classified as true failures); and (2) failures not due to poor restorative technique (false failures). The most prevalent failure was ‘lack of extension’ (in the way decreed by GV Black (25%) and ‘faulty marginal integrity’(41%)). Allan's statistical analysis indicated no difference between class I and II amalgams and the equivalent gold inlays – possibly also a surprise to readers. His analysis provided no survival data, but he added that ‘it is the way that a material is employed is more related to its duration than the actual material used’, something that is still true today.