A Short Introduction of Dental Bonding Systems

Author Jefferson R. Pereira

Simplified draft by Staff Researcher.

Buonocore, in the 1950s did experiments to show the different types of adhesion techniques on our teeth. Through his experiments, we came to know about three major techniques; Enamel, Dentin and Adhesives. Some of these are highly used in the modern era and lay a foundation to the modern dentistry.

Enamel is the layer that is on the crown of the teeth and majorly provides its shape. A technique known as Enamel Acid Etching was developed, where the retention power of enamel was increased by exposing it to acids. This provided better adhesion. At first, it was tried with Phosphoric acid, but later experimented with Maleic acid solution and Nitric acid. However, Phosphoric acid is still the most popularly used acid. Owing to its inorganic nature and stability, enamel retention on teeth occurs for a longer period of time. It is also cost effective and hence used extensively.

Dentin lies beneath the enamel. It is a hard, dense, heterogeneous tissue and has more water content than enamel. Dentin is composed of numerous long thin channels called the dentinal tubes. These tubes are filled with tissue fluids and are usually funnel shaped with varying levels of water content. Thus, the permeability factor in the dentin varies. In Dentin Acid Etching, the two layers of permeability, namely intratubular layer and the intertubular layer are affected.

The intratubular layer is responsible for tooth sensitivity and humidity and the intertubular layer helps in regeneration of the dentin layer through various chemical processes within the tooth. In Dentin Acid Etching, the intertubular layer is exposed and the water content in it, determines, how well the acid etching is done. If the area is too dehydrated, then it can hinder the bonding procedure. For this particular reason, Dentin Acid Etching is not so popular nowadays. It is difficult to control and is extremely unpredictable.

Next, we come to the Adhesive System. An adhesive is basically a fluid that solidifies two substrate layer of the tooth. It thus, bonds the tooth and defines its structure.  The most important factor is an adhesive, is its strength and durability. The fluids first, wet the surface of the tooth to be bonded through hydrophilic and hydrophobic resin molecules and solvents. These penetrate the layers in the tooth and cause the required bonding. It is said, that since Adhesives only cause marginal sealing; hydrophobic monomers should be used, as far as possible and any type of solvents must be avoided. However, if solvents are used anyway, it is always better to use water/ethanol solution as they promote better resin dilution.

Conventional Adhesive Systems is another popular method characterized by a 3-step procedure for maximum bonding. First, it completely removes the smear layer of the tooth, then they promote the opening of the dental tubes and thirdly, they help in formation of the hybrid layer. In order to form the hybrid layer, Self Etching Adhesive Systems are sometimes used. In this method, the fluid infiltration and the bonding occur at the same time. This system acts like a primer base to the tooth before acid etching actually occurs.

The Dental Associations credit Adhesive Systems to be the most effective in tooth bonding. Although there is a debate that poor adhesion and moisture content can destroy the hybrid layer over time, it is still considered to be more promising in the long run. However, treatment varies with different patients and proper assessment of the medical situation must be done before any sort of procedure.