The polymerization of resin based products is inhibited by oxygen. We deal with this uncured ” Air or Oxygen Inhibited” resin layer everyday. It is the smeary outer coating on a bisacryl provisional that gunks up and ruins burs. This same smear layer remains inside the provisional matrix, and can result in reduced accuracy if they are reused. It is also the layer that can bond your bisacryl provisional to freshly prepared teeth if you have placed a composite the same appointment or followed the protocol of immediate dentin sealing. Lastly, if you follow a protocol of making your provisionals directly prior to the final impression, it is this layer that interferes with the set of some VPS impression materials.
Managing this air inhibited layer in the process of curing resin comes from using an oxygen barrier to prevent it’s formation. In other clinical situations, instead of preventing the formation of the air inhibited layer, we need to remove it. One simple chemical is the solution to this clinical dilemma, rubbing alcohol. When we fabricate provisional restorations we keep a small dappen dish or cup of rubbing alcohol available. Once the bisacryl is cured, prior to beginning the process of trimming and shaping it, we drop it into the rubbing alcohol. Let it sit for 30 seconds or so, and then we remove and wipe it with a 2 x 2 that is wet with rubbing alcohol as well. This technique will extend the life of your acrylic burs, and diamond disks, and make cleaning them easier at the end of a procedure. For the inside of a provisional matrix, dip a cotton tip applicator into rubbing alcohol and wipe down the inside surfaces.
In the situation where the smear layer is left behind on the teeth following a bonding procedure or the fabrication of a direct provisional, alcohol is still the answer. For this application I add rubbing alcohol to flour of pumice, and using a prophy cup clean all of the tooth surfaces to remove the uncured resin layer. I have in the past tried wiping the teeth off with a 2 x 2 or cotton tipped applicator wet with alcohol, but this is imprecise and difficult to cover all of the tooth surfaces adequately and can leave resin behind.
LeeAnn,
What are your thoughts on “sealing” a prep after a prep. They are doing this in Europe, haven’t seen much here in the US. I assume it is like applying Optibond prior to cementing the temporary. To seal the dentin tubules. “Wound healing” I have heard. Makes sense,l but is it practical? Have you experience with this, has it worked, is it clinically significant? Have they had problems with lockon of temps after the sealing of dentin tubules?
This should give you a couple days of digging around. Thanks, David
Hi David,
It’s interesting that you mentioned “sealing” a prep. I have been doing it for years. I seal all my crown preps as well as cavity preps. My experience have been very positive. I have very little reports of post-op sensitivities or problems with adhesion. I use rubber dam for most of my preprations. I usually alcohol wipe the prep then very lightly air dry it and apply one layer of bonding matterial that you use. I seal the tooth immediately after prep is done( before etching if I must do). I say try it.
Mary
David,
Probably the person you teaches this in the US is Pascal Magne. Immediate dentin sealing is accomplished when the prep is finished, you utilize your dentin adhesive, any generation will work for this. Being careful not to get the dentin adhesive on the enamel margins and cure it. You can cure it under glycerin to prevent an air inhibited layer. Or once cured you pumice the teeth with four of pumice and alcohol to remove it. You have to seal prior to final impressions as it does add film thickness to the prep. Pascal uses acrylic for his temps, so bonding is not a problem, if you use bisacryl again the important step is to remove the air inhibited layer as soon as the tooth is sealed. The concept is to seal all of the dentin tubules preventing bacterial infiltration during the temporization which is a contributing factor to post op endo and sensitivity. I do this from time to time when a tooth is sensitive during the prep or the decay is deep, but I do not do this in my practice routinely.
Hi lee, I want to be clear on sealing the prep do you etch the tooth first?
Sue, It depends on the type of dentin adhesive you use. If you are using a self etch, simply apply the one or two steps and cure. If you are using a total etch, etch, prime, bond and cure. If you are doing this to seal dentin, stay off the margins, clean off the air inhibited layer, then take final impressions and make provisionals.
Lee do you need to use say a separating agent like mucolube or liquid strip also after immediate dentin sealing before using bisacyrl?? Thank you !!
Sharon,
Yes, you need to do something to keep bisacryl from sticking, see the post on Immediate dentin sealing. https://leeannbrady.com/restorative-dentistry/restorative-techniques/immediate-dentin-sealing
Dr LeeAnn,
When placing the last layer of composite and in order to prevent/reduce the air inhibited layer could I place some glycerin gel before curing that last layer? or cure it and then rub it with alcohol? is that right?
Thanks, Natalia
Natalia,
You are absolutely correct. Cure under glycerin or an oxygen barrier, or remove with rubbing alcohol.
Lee
Dear Lee,
I guess even when we use any plastic barrier before curing will not completely prevent oxygen from forming OIH. That some oxygen will be trapped between the barrier and composite during the placement of the barrier.
if that is right, has any paper or study discussed this point before?