The color of natural teeth: A scoping review of In-Vivo studies

This review aimed to analyze and present information on the color of natural teeth and its distribution based on color measurement methods, types of studies, and research areas. Additionally, it identified knowledge gaps in dental color science and suggested areas for future research.

This review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) Checklist.

An electronic search was conducted in Medline/Pubmed, Scopus, and Web of Science - all databases using the keywords: human, tooth, color, color difference, spectrophotometer, colorimeter, spectroradiometer. The review included exclusively English-written research articles published after 1979, focusing on those in-vivo protocols that instrumentally evaluated the color of natural human teeth and provided CIEL*a*b*, CIEL*C*h° color coordinates, and/or shade guide designation.

The initial database search yielded 2501 results: Medline/Pubmed: n = 482; Scopus: n = 334; and Web of Science All databases: n = 1685. After selection, 53 research articles were included in the review.

Dental color is a complex phenomenon to objectively record, communicate, and reproduce. Although studies have reported color coordinates based on age, gender, ethnicity, and tooth type, there is no consensus within the scientific community. Most studies are cross-sectional, limiting the understanding of tooth color changes over time. Longitudinal studies involving diverse cultures with adequate sample sizes and consistent methodologies are necessary for objective color recording.

Studies assessing the color of in-vivo natural teeth show a high level of heterogeneity due to the diversity in the type of measurement devices used, experimental conditions, illuminant, number of teeth used, area of measurement, and color coordinates reported. Future research must consider more extensive and representative population samples, with standardized reporting of demographic characteristics (age, gender, ethnicity), and more detailed inclusion and exclusion criteria. It is crucial to prioritize the standardization of measurement conditions, using a non-contact instrument, calibration, and detailed reporting of color.