Etching or acid etching is another essential procedure in dentistry that involves etching the surface of the enamel to provide a better retention of certain materials.
The process of placing a filling is not as simple as it looks. It is made of several essential steps that provide the quality of a restoration. When it comes to etching, it is actually a procedure that involves using a special acid on the surface of the enamel. The main use of etching is to remove the smear layer of substances, to increase the mechanical retention, to improve the power of sealants and to open micropores in the enamel. It was first introduced in 1955, and the acid used was phosphoric. At that time the only system available was the total-etch technique, where every single step of the etching, priming, and bonding was done separately. This is still present in a lot of dental offices until this day. The new materials brought another trend called self-etch, where etching, priming, and bonding are all done in a single step. Self-etching is becoming more common, mostly because of the shorter procedure. It saves time and it’s less complicated.
There are several types of acids that are used in dentistry. All of them are weak acids that are only meant to make micropores on the surfaces of enamel. By creating these micro spaces, there is a better chance for the filling to adhere to the tooth. Back in the past when materials didn’t have as good characteristics as today, dentists couldn’t imagine working without etching. But thanks to the improved characteristics, some materials make the work much easier and faster.
The enamel is the most highly mineralized tissue in the body. It’s made of over 98% minerals, which gives the opportunity for dental bonding. By applying an acid, it creates small pores on the surface by melting a part of its ingredients. This cannot be seen with a naked eye, it is only visible under a microscope. After the etching, the enamel has a significantly whiter color. The concentration of the acids varies depending on the type. The most commonly used one is the phosphoric acid in a range between 30% to 40%. When the dentists apply it, the acid affects the mineral content and creates a roughness on the surface, visible only via microscope. That way, the retention and adhesion with the dental materials are much stronger. The resin sealant gets into those small pores and there is a significantly larger contact surface compared to before. The acid also removes the smear layer. In the beginning dentists, we supposed to etch for around 60 seconds. Today with the advanced characteristics, that process is shortened to around 15 seconds. The self-etching agent is placed on a dry surface and the dentist waits for around 15 seconds. There are several types. Some have to be stimulated by light, while others don’t. There are systems that come in only one bottle and the ones that come in two bottles and are mixed together.