The topic of dental adhesives has consistently complicated the world of dentistry for quite some time. Newer generations of both self-etch and total-etch systems, with the intent of simplifying the process, has actually added a little more confusion.
When compared to self-etch systems, total-etch systems have been said to be more technique-sensitive due to the separate step of etching enamel and dentin. With the self-etch systems being undoubtedly more user-friendly, the total-etch system poses some risks that all dentists need to be aware of.
Over-etching:Over-etching can demineralize too deep a zone. Most hybrid zones are about 10-20 microns in depth, over-etching can lead you to demineralize up to 80 microns in depth, which is too deep for hydrophilic resin to penetrate. This could leave you with a gap of demineralized dentin that will result in a very weak bond. However, a solution to this issue is rather simple: just limit your etching time to 15-20 seconds.
Over-drying: Drying correctly in total-etch systems means leaving a slightly damp surface to the dentin. This allows the collagen to remain standing up. If a tooth were to be desiccated during this process, you only leave dentinal tubules and virtually nothing for the resin to flow into, basically diminishing the entire hybrid zone. There has been a lot of research around the proper way to dry a tooth with self-etch systems. The best method of drying in terms of bond strength is to simply blot the area with cotton or tissue paper to achieve damp dentin.