Article
No-one would want to literally eat their hat so this expression is only used when someone is very sure about something. One of the earliest appearances of this phrase was in Charles Dickens' ‘The Pickwick Papers’ in 1837: ‘If I knew as little of life as that, I'd eat my hat and swallow the buckle whole’.
Bloomsbury International School for English, London
Readers will be aware that this is an expression describing a hypothetical act of penance that one promises to take when wrong! For me, that involved a past campaign against the so-called ‘veneerologists’, a group of dentists who cut teeth mercilessly purely for reasons of aesthetics. Although I remain totally opposed to the destruction of tooth substance in the absence of disease, I am now aware that the placement of a minimal-preparation veneer does not have such a deleterious effect on the life of a tooth as preparing a tooth for placement of a crown, for the reasons described below. It is especially relevant to one of the articles included in this issue, that being the one by Albino and colleagues from Brazil (page 22) describing the use of ceramic veneers on discoloured incisor teeth.
Readers will be aware that the porcelain laminate veneer started life over 30 years ago as a 0.5–0.7 mm thick layer of porcelain that was bonded to the tooth using the bond between the etched (with phosphoric acid) enamel surface and the etched (with hydrofluoric acid) veneer fitting surface. It was indicated as a more minimally invasive alternative to crowns for the aesthetic improvement of discoloured teeth. In theory, the preparation remained intra-enamel, given that it has been shown that the technique is significantly less successful if the preparation strays into dentine.1 However, some dentists mercilessly cut heavy porcelain veneer preparations, indeed, these being so heavy that they resembled full crown preparations. In this regard, crowns on anterior teeth are a treatment that I have recently advised strongly against, especially when one examines the longevity of the prepared tooth.2
Why am I eating my hat? Because, the results from a study,3 one of a series analysing a 13-million restoration dataset that consisted of the treatment carried out for General Dental Services' adult patients in England and Wales followed for 16 years,4 surprised me. The size of the dataset has allowed the analysis of how long restorations lasted, but also how long the restored tooth survived, which is arguably more important. There were 57,955 porcelain veneers included in the analysis. When longevity of the restorations was investigated after 15 years, 48% of crowns had not required a re-intervention, compared with 41% of porcelain veneers. However, when the longevity of the restored tooth was assessed, again at 15 years, the tooth restored with a porcelain veneer performs optimally, with 93% of the teeth restored with veneers surviving, compared with only 75% of the teeth restored with crowns. Looked at in the opposite way, only 7% of teeth restored with a veneer are lost at 15 years, compared with 25% of teeth that have received a crown, and 16% of teeth with a direct restoration. This applies to all age groups. The lesson is clear for all clinicians, namely, that maintaining the structurally stiff enamel layer of an incisor tooth rather than removing it (as is part of a crown preparation) helps protect the restored tooth from the need for an earlier-than-necessary extraction. This could be seen to be a strong advertisement for a minimal intervention restoration, such as a veneer, but, on the other hand, is 41% survival (i.e. a 59% failure rate) of the porcelain veneer restoration at 15 years a good result for a restoration type that is generally elective? The answer is no!
There are many things that would be very difficult to eat, so it is not known why a hat was chosen. However, some people think that it is because the king and his companions used to wear large and elaborate hats that would have been especially difficult to eat! To summarize, porcelain laminate veneers may have suboptimal survival per se, but they do not challenge the longevity of the restored tooth as crowns do. Nevertheless, despite me eating my hat, we should always think long and hard before we remove any tooth substance for reasons other than disease, and avoid entering a tooth into a restorative spiral from which it cannot get off.