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Restorative Dentistry

Does placing a resin coating on a setting GIC impair fluoride release?

(Content under development)

The following question was submitted by a practising dentist: Is there any solid evidence that the coating recommended for Resin Based Glass Ionomer Restorations impedes the release or uptake of Fluoride?

JCDA Editorial Consultant Dr. Alan Kilistoff of the University of Alberta provided this initial response for consideration:

The immediate answer is yes, but in context it is probably not clinically significant.  An article from Mazzaoui et al, demonstrates that fluoride release is about 75-90% less available after coating with a resin adhesive, but that fluoride is still available.

The main purpose of the coating is to maintain the aqueous environment within the restoration at optimum to facilitate the completion of the acid/base reaction.  Without a resin coating, the restoration will either imbibe more water than is necessary or it will desiccate.  Either of these situations will interfere with the proper setting of the material.  The resin will wear off fairly quickly but is usually present long enough for the reaction to go to completion.

The reason this may not be clinically significant is that the time that the restoration is releasing a significant amount of fluoride is measured in days, whereas the life expectancy of the restoration is considerably longer, as confirmed by a recent study.  GIC does seem to be “rechargeable” with topical fluoride treatment, but it will then release fluoride for only a few days after treatment.  This temporary fluoride may be beneficial, but may not be the reason for the presumed cariostatic effect seen with GIC’s, as described in a recent article in the Australian Dental Journal.

The resin coating does seem to fill in any porosity or voids on the surface of the GIC restoration and may provide a smoother surface and increased fracture strength.  Evidence seems to support increasing fracture strength, but does not support improvements in wear.  The benefits of using a resin coating seem to outweigh the consequences of the reduction in fluoride release.

Follow-up: Readers are invited to comment on this initial response and provide further insights by posting in the comment box which you will find by clicking on “Leave a reply“ below. Comments come directly to me for approval prior to posting. You are welcome to remain anonymous. We will never post your email address in any response. John


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