5 Key Points to Ensure Effective Dental Bonding with Total Etch System
1. Etch the enamel first for at least 15 seconds, followed by etching the dentin for a maximum of 15 seconds. This will ensure that the dematerialized areas created during etching will be filled through capillary action, subsequently forming resin tags.
Enamel should not be under-etched (less than 15 seconds) and dentin should not be over-etched (more than 15 seconds) either of which could result in a reduced bond strength because deeper demineralization of dentin makes it difficult to infiltrate it completely with the adhesive.
Also, the presence of some hydroxyapatite within the exposed collagen fibrils will provide some protection from hydrolysis.
Ensure that the dentin is slightly moist after rinsing-off the etchant and ‘drying’ the dentin.
This “moist bonding” helps prevent exposed collagen from collapsing and forming coagulate, which could prevent adhesive penetration into the dentin. Bonding is impaired, if the dentin is either too dry or too moist.
2. Dispense the etch-and-rinse primer or primer-adhesive combination immediately prior to placement, so as to avoid evaporation of the solvents contained therein. Use of delivery system that results in simultaneous dispensing is preferable.
3. Apply an amount of adhesive sufficient to thoroughly coat and penetrate the entire etched surface.
If using a two-step system, several layers of the primer-adhesive should be applied to ensure an adequately thick layer of adhesive solvent present in the primer-adhesive can otherwise result in a layer that is too thin.
Because etching dentin removes the smear layer, a larger surface area for adhesion is exposed, thus requiring more adhesive than is necessary for the etched enamel surface.
4. Thoroughly air-dry the adhesive to remove the ethanol, acetone, or hydrophilic solvent carrier, reducing the potential for interference with the polymerization process and to spread the adhesive evenly on prepared surface.
Solvent chase out the water from the dentinal tubules so that resins can penetrate deeper inside so after this work is over its presence dilute the bonding agent and weakens the bond.
Air drying removes the solvent and concentrates the resin in hybrid zone and strengthens it.
5. Ensure that the adhesive is thoroughly light-cured prior to composite restoration placement to avoid displacement of uncured adhesive during placement.
Flow able resins have low physical properties and exhibits high polymerization shrinkage. They are used in thin layers and should be cured for 10-15 seconds more because of increased presence of polymerizable resins.