Why are bases and liner used in a cavity preparation?

Bases

- To protect the pulp from chemical (acids), thermal (heat), and galvanic (metal) irritations

- To seal dentin tubules

- To minimize microleakage

- To provide strength to the restoration

- To compensate for the loss of tooth structure

Liners

- A liner is a thin layer of material that is applied to the floor of a cavity preparation before the placement of a final restoration.

- Liners are used to treat various clinical situations, including:

- Sealing dentin tubules and protecting the pulp: Liners can help to seal dentin tubules, which can prevent them from becoming irritated by the materials used in the final restoration. This can help to reduce the risk of postoperative sensitivity.

- Promoting adhesion between the final restoration and tooth: Liners can help to promote adhesion between the final restoration and the tooth, which can help to prevent leakage and ensure a long-lasting restoration.

- Insulating the pulp from temperature changes: Liners can help to insulate the pulp from temperature changes, which can help to prevent pulpal pain.

- Remineralizing the tooth: Some liners can help to remineralize the tooth, which can help to strengthen it and improve its resistance to decay.

- Antibiotic effects: Some liners have shown antibacterial effects, which can provide a protective shield against microbial invasions

_Liner and Base Materials_:

- Glass Ionomer Cement

- Zinc Phosphate Cement

- Zinc Oxide Eugenol and its Derivatives

- Calcium Hydroxide preparations