The acid etching technique is a filling technique in which the hard dental substance is etched with acids before the plastic filling material is inserted into the cavity. This etching process creates an enlarged surface. With the optical resolution of a strong microscope, the chalky-white discolouration of the tooth would display a typical etching pattern. These patterns are comparable with the surface of a honeycomb. After the etching process the teeth feel blunt.

We understand bonding as the technique of bonding plastic based filling material (composites, compomeres, and ormoceres) with the enamel and/or dentin surface. These materials adhere to the tooth (adhesion).
Possible application areas are fissure sealing or very small fillings in the molar's or upper incisor's pits.

Thin, viscous sealing plastic is used for fissure sealing and small cavities. This particular plastic permeates the microstructure created by the etching process and is hardened with a polymerisation lamp, thus lining the small cavity with a thin polymer layer. The plastic filling the defect is applied and also hardened with light. It chemically binds to the bonding material fixed in the microstructure, thus fully sealing and filling the defect.

In dentin bonding, the dentin is sealed simultaneously with the enamel through an adhesion advancing layer consisting of thin, viscous plastic.

Filling materials of the material classes composite, compomere and ormocere are attached to the tooth's surface through adhesion. This enables a plane bonding of filling material with the tooth and minimising of margins.

The images show how a composite filling is attached by adhesion. After removal of an old amalgam filling, the caries media diagnosed on an X-ray is exposed at the distal point of contact.

The carious hard substance is then removed and a mould is placed around and firmly pressed against the tooth with a small wooden wedge. During the etching process the enamel and dentin are coated with gel. The etching gel is removed with water spray.

Bonding material is applied after the cavity has been dried. This is then hardened with the light of a polymerisation lamp. The filling material is now inserted into the cavity and also hardened with light. Once any excess has been removed, the filling is moulded and polished.  

The amalgam filling was introduced in Europe around 1900. The former rules for cavity preparation of amalgam fillings still apply today.

1. Creation of the outline, resistance and retention form.
2. Removal of carious hard tooth structure.
3. Finishing the cavity edge.
4. Cleaning the cavity.

The old filling is removed after anaesthesia. The cavity is appropriately prepared for the positioning of a new filling: if required, the edges are smoothed with underfilling as thermal protection.

After the amalgam paste has been mixed, it is inserted into the cavity in small portions with an amalgam pistol and sealed with suitable plugging tools. When forming and inserting the new filling into the occlusion, the superficial amalgam layer is whittled away. The amalgam filling is polished no sooner than after 24 hours.