Perceptibility and acceptability thresholds for colour differences in dentistry

Introduction
Data on acceptability (AT) and perceptibility thresholds (PT) for colour differences vary in dental literature. There is consensus that the determination of ΔE* is appropriate to define AT and PT, however there is no consensus regarding the values that should be used. The aim of this clinical review was to provide a systematic approach to the topic of colour science of high clinical relevance to dental research.

Materials and methods
MEDLINE/PubMed, WoS and EBSCO databases were searched up to January 7, 2013; the outcome was restricted to English, and to clinical studies were spectrophotometers were used for measurement.

Results
Forty-eight studies were eligible and met the inclusion criteria. Of the 48 studies there appeared to be a trend in their source references: 44% referred to the same study for the PT (ΔE* = 1); and 35% referred to the same article for the AT (ΔE* = 3.7).

Conclusions
More than half the studies defined PT as ΔE* = 1, and one third of the studies referred to ΔE* = 3.7 as the threshold at which 50% of observers accepted the colour difference. Most clinical studies refer to the same few in vitro literature that have attempted to determine PT and AT from decades ago.