Pulp Protection
A base or cavity base is a layer of cement placed beneath a permanent restoration to encourage recovery of the injured pulp and to protect it against numerous types of insults to which it may be subjected.
Types of insults depend on particular restorative material. It can be thermal or chemical or galvanic. The base serves as a replacement or substitute for protective dentin which is destroyed by dental caries or cavity preparation.
Classification of Bases and Liners
- Low-strength base
- Zinc oxide eugenol (ZOE) and calcium hydroxide
- Used under temporary or interim restorations
- Calcium hydroxide is used as sub-base
- High-strength bases
- GIC, reinforced ZOE, zinc phosphate, Zinc polycarboxylate
- Used under direct and indirect metallic restorations.
Indications of Bases and Liners
- For protecting the pulp against thermal injury, galvanic shock, and chemical irritation.
- To withstand forces of condensation of restorative material and act as a shock absorber.
- To substitute dentin in deep cavities
- To serve as an intermediate bonding material between the tooth and composite restoration
- To prevent ingress of bacteria and their noxious products in dentinal tubules via microleakage.
Clinical Considerations of Bases and Liners
- The base should be 0.5 to 0.75 mm in thickness. If the base is very thick, it can compromise the bulk of restoration and increase the potential for fracture of restoration.
- Sound tooth structure should never be removed to provide space for placing the base.
- The base should always be applied on the internal wall of the cavity in preparation for preventing its dissolution by saliva.
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