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Digital technology used in the application of colour measurement and colour formulation of skin in maxillofacial prosthetics

Student thesis: Doctoral ThesisDoctor of Philosophy

Statement of problem: Colour degradation and deterioration of mechanical properties of maxillofacial prostheses requires their frequent renewal; and the traditional trial and error method of colour matching natural skin with silicone elastomer is unpredictable and requires a more scientific approach.
Materials and methods: For colour stability and mechanical properties testing, M511 silicone was coloured with Spectromatch Pro colourants and stored in darkness, exposed to accelerated ageing and outdoor weathering. Test groups included non-pigmented, individually pigmented samples and Caucasian skin tone coloured specimens. Investigations further involved the use of UV-light absorbers and silicone surface sealants to improve the colour stability of elastomer. For assessment of the Spectromatch Pro colour formulation software in comparison with the traditional colour matching method, the same elastomer and colourants were utilised. Colour measurements of skin and elastomer were recorded utilising a spectrophotometer and mean colour differences (̅∆̅̅E̅) were calculated based on the recorded L*a*b* values. All data was analysed using linear mixed models and Šídák’s multiple comparison of means test (α = 0.05).
Results: There was a significant effect of time and environment on colour and mechanical properties of elastomer (p = 0.001), apart from tear strength which was not significantly different. Greatest ̅∆̅̅E̅ were observed for specimens exposed to accelerated ageing. Caucasian skin coloured samples demonstrated ̅∆̅̅E̅ of 3.26; but application of a surface sealant with incorporated UV-light absorber improved its colour stability (1.56 ̅∆̅̅E̅). Use of the Spectromatch Pro colour formulation software resulted in better colour matching results than did the traditional method; with non-perceivable ̅∆̅̅E̅ of 0.79 for Afro/Afro-Caribbean subjects and perceivable but acceptable ̅∆̅̅E̅ of 1.46 for Caucasian skin tones.
Conclusions: M511 in conjunction with Spectromatch Pro colourants demonstrated good overall colour stability; and the Spectromatch Pro software achieved best colour matching results and makes these systems suitable for daily clinical use.
Original languageEnglish
Awarding Institution
Award date2018


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