Masking ability of additively manufactured definitive crown materials

Additively manufactured (3D-printed) definitive crown materials are continuously gaining popularity in prosthodontic rehabilitation as an alternative to subtractive manufacturing (milling). Current scientific literature on the optical properties and masking ability of these materials is scarcely available. This study aimed to measure colour change and translucency parameters of additively manufactured permanent crown materials to investigate their masking ability with varying printing parameters. 60 specimens were milled; 120 specimens were additively manufactured (3D printed) at 0° and 45° with DLP printer and SLA printer each. Specimens were post-processed according to the manufacturer’s instructions and cemented onto three different shades of substrates, simulating natural (ND3), discoloured (ND8), and severely discoloured (ND9) dentine. Values L, a, and b were measured with spectrophotometer Vita EasyShade V and used to calculate the colour difference (ΔE) and translucency parameter (ΔTP) using the CIELAB formula. Collected data was statistically analysed with two-way ANOVA and post-hoc analysis was performed. ΔE and ΔTP were significantly lower in 2mm milled and additively manufactured specimens. The lowest mean ΔE was observed in DLP 2mm 0° group against ND3 (0.76 ± 0.12) and the lowest mean observed in DLP 2mm 0° group against ND9 (1.06 ± 0.26). All 2mm specimens were considered acceptable matches, with mean values >PT and ≤AT in DE (1.2 > ΔE ≤ 2.7). and ΔTP (1.33 > ΔTP ≤ 4.43). All 1mm specimens were unacceptable matches (>AT × 3) for masking ND9. The masking ability of additively manufactured crown materials is influenced by different printing factors. Between 3D printer types, SLA-printed specimens showed better masking ability and higher translucency parameters compared to DLP-printed specimens. SLA-printed at 2 mm and 0° angle, demonstrated sufficient masking for ND3 and ND8 substrates, while milled materials were superior in masking the darkest substrate (ND9). Clinical Significance : This study highlights the importance of understanding additive manufacturing technologies, printing parameters and choice of permanent crown materials. This is the first study to provide scientific evidence for optical properties of additively manufactured crown materials and their masking ability.