Acid Etching: How Does It Work
Just as you might sand the varnish off a smooth wooden table before you paint it a new color, the etching process makes a tooth surface rougher so it can better hold onto a prosthetic. Microscopically, etching dissolves some of the minerals contained in the enamel and dentin. This controlled erosion creates rough features called "tags and tunnels" that are better able to absorb bonding resin and can chemically and physically lock it into place on the enamel and dentin surface.
The acid itself is usually a 35 percent phosphoric acid gel that is colored to make it visible on a tooth. The gel is left on the tooth's surface for about 15 to 30 seconds, and the erosion it creates gives the smooth enamel surface a frosty appearance.
The bonding material is then "cured" with a special light of a certain wavelength, and the filling material is placed on top of the bond in layers and cured in place until the filling or restoration is built up to its final shape.
Depending on the procedure and the size of the restoration, there are three basic etching techniques:
- Total etch. The acid etch material is placed on all of the surfaces of the enamel and dentin layers. This technique is best used when a large amount of bonding material is expected to be placed, and retention may be an issue. If the preparation of the tooth is anticipated not to be deep or near the nerve (dental pulp) portion, a total etch is the most efficient technique.
- Selective etch. This is similar to the total etch technique, but the etching material is applied only to the enamel surface. If your dentist thinks that the acid gel might cause sensitivity in deep areas of the tooth, they might use this technique to minimize post-operative sensitivity.
- Self etch. The acid etch material and bond material are actually combined and layered onto the tooth in a single step. This technique is very effective for a tooth that is expected to easily retain the new restoration. Dental Economics notes that the material your crown or veneer is made of, such as zirconia or porcelain, may also influence which etch technique your dentist uses.
Each technique has its benefits and drawbacks, but the most common complication of any etching technique is post-operative sensitivity. Sensitive teeth can be noticeable for a few days or weeks, depending on how deep the preparation is. According to Dental Economics, carefully protecting the gums and coating the preparation with a desensitizing fluid after acid etching and before the bonding layer can help prevent patient discomfort.
Maintaining good oral care can help you avoid the need for restorations in the first place. If you need a veneer or a crown to maintain your healthy smile, talk to your dentist about your restoration options.
This article is intended to promote understanding of and knowledge about general oral health topics. It is not intended to be a substitute for professional advice, diagnosis or treatment. Always seek the advice of your dentist or other qualified healthcare provider with any questions you may have regarding a medical condition or treatment.