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

PRINCIPLES OF PREPARATION FOR INDIRECT RESTORATIONS
The general principles that apply when preparing and restoring any
tooth have been covered in detail in the section on direct restorations.
These principles are those guiding ideals that determine the rationale
for operative intervention and the final form of the preparation pro-
duced and shape of restoration. In general, principles that apply to all
restorations have either a mechanical or a biological basis and include
steps to achieve:
• Elimination of diseased tissue
• Preservation of tooth structure
• Restoration of form
• Occlusal stability
• Pulpal health
• Periodontal health
• Durability of tooth and restoration
• Acceptable aesthetics
A few of these principles, either directly or by extrapolation, 
have particular importance when applied to preparation of teeth for
provision of indirect restorations
10
. These are:
Principles of indirect restoration


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Chapter 5
• Preservation of tooth structure
• Retention and resistance form
• Marginal integrity
• Strength and structural durability
• Occlusal stability
The following arguments apply equally to extra-coronal and intra-
coronal restorations, though for simplicity, the explanations refer
mostly to extra-coronal restorations.
Preservation of tooth structure
The need to preserve tooth structure wherever possible is axiomatic.
With regard to the reduction and loss of tooth structure required to
place an indirect restoration, it is important to note that although
destructive, the provision of an extra-coronal restoration may actually
result in preservation of tooth substance in the long term – for 
example, posterior root-filled teeth have a much higher fracture rate
compared with similar teeth that have been crowned. In other cases 
in which indirect restorations are planned for an improvement 
in aesthetics only, for example aesthetic veneers, then the ‘cost’ to 
the tooth must be weighed carefully against the perceived benefit. 
In determining the amount of removal of tooth structure for provi-
sion of an indirect restoration, there are three main considerations: 
the requirement for protection from fracture and wear, the pattern of
tooth substance removal and the type of restoration to be provided.