Adhesion is defined as the bonding of two different materials with each other by the attraction of atoms or molecules. Adhesion is defined by American society for testing and materials as “the state in which two surfaces are held together by interfacial forces which may consist of valence forces or interlocking forces or both“. Adhesive strength is a measure of the load bearing capacity of an adhesive joint. Adhesion in dentistry is between dental materials and tooth substrate depends upon attainment of a proper bonding, most preferably chemically between restorative material and tooth structure.
Adhesion is measured in bond strength between the adhesive and substrate. Adhesion is important in Dentistry as it is useful in Restorations, Crown fixations which are chemical, mechanical and micromechanical retention. Retention of orthodontic brackets to the Enamel surface, mechanical and micromechanical adhesion of fixed partial dentures or bridges. There are 2 types of Adhesion for teeth – Enamel Adhesion and Dental Bonding.
The various restorative materials used in Dentistry adhere to the tooth structure differently. It is important to know which material to use in which situation depending on the bonding surface
Glass Ionomer Cement:
- Adheres to Enamel and Dentin, Composite resin, Metals
- Type of Adhesion – Ionic (chemical) – Enamel, Micromechanical – Composite Resin and Mechanical interlocking (no chemical adhesion) – Metals
Composite Resin:
- Adheres to Enamel and Dentin, Glass ionomer cement, Metals
- Type of Adhesion – Enamel and Dentin (Micromechanical), Glass Ionomer Cement (Micromechanical), Metals (Micromechanical (HF acid and sand blasting) and mechanical
Ceramic:
- Adheres to Metals and Composite Resin
- Type of Adhesion – Metals (Chemical (metal oxides) and micromechanical, Composite resin (Micromechanical)
Amalgam:
- Adheres to Enamel and Dentin
- Type of Adhesion: Enamel (Mechanical undercuts), Dentin (Resiliency of dentin)
Zinc Phosphate cement:
- Adheres to Tooth structure and Metals
- Type of Adhesion: Tooth structure (Mechanical), Metals (Mechanical)
Zinc Polycarboxylate Cement:
- Adheres to Enamel, Dentin and Metals
- Type of Adhesion: Enamel (Ionic or Chemical) and Metals (Mechanical)
Gaining proper adhesion is important as it determines the Success or Failure of the treatment, so knowing which material adheres to which substrate is very important and helps in successful treatment. Failure of Adhesion can be caused due to contamination between the adhesive and the surface, interfacial degradation and expired adhesive.
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