A blog that tries to assist clinical decision-making by using evidence and other resources - by Dominic Hurst
Hi Dr Hurst,I watched this and saw a lot of the dentists recommending placement of a crown on a posterior root treated tooth and it came across that they recommend this as standard. I tried searching for evidence for this vs. other restorative techniques but didn't really find much...Is this decision usually based on the remaining tooth structure or is there a general opinion that it's worth doing a crown on a root treated molar even if it would be possible to restore with something like a large amalgam? And is this based on 'expert opinion' from clinical experience or am I missing something in my literature search?!(I guess after the way this programme came across I should also consider that it could be due the pricing vs. costs of crowns on NHS!)
Great that you went away and asked that question! About a year ago I did a critically-appraised topic on whether crowns were better than restorations for root-filled posterior teeth. At that time there was just one randomised-controlled trial comparing crowns versus composites on root-filled premolars. It was an underpowered study (about 55-60 participants in each arm of the trial) and was over just 3 years. There was no difference in failure between the two groups. see: http://www.ncbi.nlm.nih.gov/pubmed/12426500I believe there is a Cochrane review on this being conducted at the moment but we may have to wait a little while before we see it...I quickly re-ran my search and didn't find any more studies. We are therefore required to work down the 'hierarchy of evidence' to case-series and then expert opinion. Interestingly much of the argument for crowns to be placed comes from retrospective studies, which don't even show on most hierarchies of evidence due to their high risk of bias. But this is probably the best evidence we have and some studies of this type suggest crowns on root-filled molars are better.My concern is that dentists may be more likely to place crowns on teeth they already think have a better prognosis. So if you then look back at your clinical records and conclude that the teeth that were crowned lasted longer on average they may have done so regardless of whether a crown was placed or not.Regarding your comment about the pricing, I have no doubt that this will play a part in the recommendation to place a crown. They're expensive things, which makes it more important from a patient's point of view (and the NHS if it's paying for them) to know how effective they are. Unfortunately we can't make that assessment yet.I hope that long ramble helps...
Oh - by the way - feel free to send me your search strategy if you wish, since you mentioned you wondered if you were missing something in your literature search. I'll be happy to add some constructive comments.Cheers - and thanks for posting.