Wednesday, 25 January 2012

Zinc-oxide-eugenol and composite

For a little while I have been keeping a secret. I had read that eugenol was a pretty effective antibacterial agent and it had been suggested by a specialist endodontist that we place it in the coronal portion of the root canal as an antibacterial plug.

So I place IRM as a plug. What do I then do when I want to place a composite? Well, I place a composite.

That's the secret and I'm ashamed. But why? Because when I was an undergraduate student I seemed to remember being told Zinc oxide eugenol stopped composite from.....what? Setting? Bonding? I couldn't remember but I figured all that eugenol was far enough away from where I was bonding so what did it matter.

But there was always a niggling doubt.

Anyway, it all came out when a student on clinic needed to place a restoration in a tooth that had had IRM placed as a temporary, and which plugged the root canal. I suggested she leave the IRM plug and suddenly I heard this voice saying "that's wrong - very wrong" and I hastily said to the student that it was likely the materials lecturers would lynch me if she ever told them.

But then I thought, what is the science that underpins this doubt I have about using zinc-oxide eugenol? And what about leaving it as a sedative base in those deeply-cavitated pulpitic teeth?

I did a search in pubmed:
(composite OR bonding*agent*) AND (eugenol OR IRM OR kalzinol OR ZnO) AND (strength OR hard*)

There were 116 hits. There were conflicting results on the whether zinc oxide eugenol (rather than just eugenol) significantly affected the bond strength of resins to enamel and dentine. It certainly wasn't as clear cut as I had thought.

I was only able to find one paper that looked at how the composite itself (rather than the bonding agent) was affected. In this paper, whilst composite hardness was affected by the presence of IRM, it was only to a depth of 100 microns - 0.1mm. (He LH, Purton DG, Swain MV: A suitable base material for composite resin restorations: Zinc oxide eugenol. J Dent 2010;38:290-295.) The authors suggested this wouldn't have an affect on bonding elsewhere.

This is in no way a good systematic appraisal of the literature and I hope to soon get round to doing one but  for the moment I'm feeling like I might have a defence should anyone from the materials team coming looking for me... ;-)

Thursday, 19 January 2012

DEBTs in the EBD journal

You may be aware of papers in the EBD journal called DEBTs - or Dental Evidence-based Topics.

The idea is that you as a clinician or student will have a clinical question. You might wonder if you should be putting adhesive under fissure sealants or not, how best to treat caries in deciduous teeth or how long a posterior resin-bonded bridge is likely to last.

In order to arrive at a (hopefully) more informed position you then search for research evidence that could help using the PICO structure to guide you as discussed elsewhere in this blog.

It's important to think about what research would best inform your decision - it may not always be randomised controlled trials.

Having found what evidence there is, you then need to critically-appraise it and summarise whether the evidence you have found is valid internally and externally, and how it informs you in trying to answer your clinical question.

If well conducted the journal will publish these DEBTs because they bring the latest level of clinical evidence to the notice of other clinicians, who may well be wondering about the same clinical problem.

Any students who would like to have a go and get a publication to their name, feel free to drop me a note.