Internal Fit
The accuracy of adaptation between the internal surface of an indirect restoration and the prepared tooth surface, typically assessed by measuring the cement space.
Full Definition
Internal fit refers to the closeness of the interface between the intaglio (inner) surface of an indirect restoration—such as a crown, inlay, or bridge—and the prepared tooth or die. It is commonly quantified by measuring the cement gap (in micrometres) at specified reference points using microscopy, micro-CT, or the replica technique. Adequate internal fit is critical because excessive cement space compromises retention and increases luting agent exposure to oral fluids. Editors should distinguish 'internal fit' from 'marginal fit' (adaptation at the preparation margin) and 'occlusal fit', noting that some authors conflate these terms. The ISO/TS 15599 standard provides guidance on fit assessment terminology.
Usage
Usage note: Distinguish from 'marginal fit' (edge adaptation) and 'total fit' (combination of both). Authors sometimes use 'fit' generically; editors should query which aspect is being measured and ensure consistent terminology throughout.
In Context
- "The mean internal fit of the milled zirconia copings was 78 µm, within the clinically acceptable threshold of 120 µm." — Results section, CAD/CAM crown accuracy study
- "The editor noted that the author alternated between 'internal fit' and 'internal gap'; the latter was standardised throughout the manuscript." — Copy-editing log, dental technology journal