As we all know the resins we use in our practices all have one thing in common: They all have an outermost layer that when exposed to air does not set, which is known as the air-inhibited layer. While some materials have a thin air-inhibited layer others have a thick layer. Whether thick or thin this layer can cause a real issue if itâs not managed properly when cementing or bonding our indirect restorations.
This potential issue starts with the fact that no matter how good our margins, there are small gaps between the margin of our restorations and the finish line of our preparations. If our materials contain any resinâincluding resin reinforced glass ionomer cementsâand the excess cement is removed right to margin prior to being cured or set, then there will be an air-inhibited layer present that will washout quickly. To prevent this there are two easy steps that can be taken.
The first would be to leave a small bead or material at the margin until the material is fully set. Once set you can then trim away the remaining small excess (including the air-inhibited layer) which will leave nothing but fully cured cement which will not be prone to premature washout.
One potential issue with this method is excess resin cement, no matter how small the amount it can be tedious and time consuming to remove. Given this my recommendation is to reserve this method for cement where excess is easy to remove such as resin reinforced glass ionomer cements, or in cases where the margins are easy to access with rotary instruments.
The second method is to clean the excess cement back to the margin prior to it completely setting and then place a gel such as water-soluble glycerin gel over the margin. This will block the air from the cement, which will then prevent the air-inhibited layer from forming and nothing to clean up afterwards. While you can get gels, such as Oxyguard from Kuraray for this purpose from your dental supplier, you can also find generic options at your local pharmacy.