Methods: A total of sixty A3 shade ceramic discs, 8mm diameter and 2mm thick, (15 discs /group) were constructed using porcelain (Omega 900, Vita, Zahnfabrik, Bad Säckingen, Germany). Three proprietary brands of composite used for intra-oral repairs to ceramic restorations (Arabisc Top Voco,Germany; Tetric, Ivoclar Vivadent, Liechtenstein; Filtek Z250, 3M ESPE, U.S.A) were used to produce discs of the same dimensions. CIELAB colour values were measured for each disc three times and averaged, against a black background using spectrophotometer (Easyshade, Vita, Zahnfabrik, Bad Säckingen, Germany) for D65 illumination and 2degree observer curve. The absolute value (E*) and colour difference (ΔE) between porcelain and porcelain- repairing resin composite were calculated using the following equations: E* = [(L*)2 + (a*)2 + (b*)2]1/2, ΔEab = [(L*a- L*b)2 + (a*a- a*b)2 + (b*a-b*b)2]1/2. Data were entered into SPSS (SPSS Inc, Chicago, USA) and analysis of variance was computed.
Results: there were statistically significant differences in colour between porcelain and resin composites and also between the three composite resins (p<0.0001). The ΔE values between ceramic and Arabisc, Tetric, Filtek resin composite were 8.9, 3.7, 9.9 respectively.
Conclusion: There were clinically perceptible colour differences [ΔE ≥3.7] between the porcelain and porcelain-repairing resin composites and between the three composite brands.