The colour stability of 3D-printed, non-invasive restorations after 24 months in vivo – esthetically pleasing or not?

The aim of the present prospective study was to evaluate the colour stability of 3D-printed non-invasive restorations after 24 months in vivo. The study included 29 patients, who received 3D-printed restorations made of a computer-aided design (CAD) / computer aided-manufacturing (CAM) hybrid material ( n = 354). Restoration colour of 190 restorations was measured using a spectrophotometer. By applying the CIELAB system, *L (lightness), a* (red-green) and b* (blue-yellow) values were recorded. An evaluation of the colour differences (ΔE) after 6, 12 and 24 months was conducted. Analysis of colour differences of 3D-printed restorations showed continuous discolouration of the restorations. After one year 34 % and after two years 18 % of the restorations were rated alpha or bravo, indicating no or hardly visible colour change. After two years, 54 % of the evaluated restorations yielded a colour difference with ΔE > 6.8 (delta). More than 82 % of the evaluated restorations showed values between ΔE 3.8 – 6.8 (charlie) and ΔE ˃ 6.8 (delta) after two years. 3D-printed non-invasive restorations showed an overall reduced colour stability after 24 months in vivo. The present study provides first clinical data regarding 3D-printed restorations. These restorations are recommended for a wearing time of about 6 months.