Operative dentistry aje qualtrough, jd satterthwaite la morrow, pa brunton

PULP PROTECTION
In discussing aspects of pulp protection, it is useful to consider
definitions of a sealer, liner and base
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Chapter 2
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• Sealer – a cavity sealer is a material which seals the dentinal tubules
and provides a protective coating for the freshly cut tooth structure
of the prepared cavity.
• Liner – a cavity liner is an aqueous or volatile organic suspension or
dispersion of zinc oxide or calcium hydroxide that can be applied
to a cavity surface in a relatively thin film. Glass-ionomer cement
and resin-modified glass-ionomer cements are also suitable for use
as lining materials.
• Base – a cavity base is a material, usually a type of cement, used to
base a prepared cavity before the insertion of a permanent restora-
tion, to protect the pulp and act as a dentine replacement.
Historical concepts
Microleakage is the term used for the passing of fluids, micro-
organisms or ions between the restoration and the adjacent prepara-
tion walls. Microleakage occurs around all restorations currently used 
in restorative dentistry, including those that are adhesively bonded 
to enamel and dentine. Such leakage provides a path for the ingress 
of bacteria and their products around restorations and has been 
implicated in a variety of clinical conditions, including marginal dis-
coloration, pulpal irritation and subsequent necrosis, postoperative
sensitivity, recurrent caries and eventual failure of restorations
15,16
.
The methods used to treat the preparation walls before restora-
tion placement have changed over the years. This is thought to be a
response to better understanding of the cause of pulpal damage,
Brannstrom’s hydrodynamic theory of pulpal pain
17,18
and the 
development of new dental materials.
Traditional dental teaching advocated the generous use of bases
and liners under restorations (especially amalgam) to limit post-
operative sensitivity and to act as a thermal insulator. It was originally
thought that the primary cause of pulpal inflammation was related to
the direct cytotoxic effect of the dental restorative material. However,
this has been shown to be a mild and transitory effect
18
.