Fabrication of a successful maxillofacial prosthesis with appearance match to the patient’s skin is often a significant challenge. An accurate method for collecting appearance information and the application of advanced colorant formulation theories would make possible a pleasing appearance match of a maxillofacial prosthesis to the patient’s skin.
Dental and maxillofacial applications of a non-contact spectral reflectance system with its potential to provide more reliable measurements recently initiated. A study on accuracy and precision of this measuring system is conducted by comparing with four commonly used contact color measuring instruments, which provides more evidence for its further application on color matching of maxillofacial prosthesis.
A newly-developed laser light diffusing method, which correlates laser light diffusing area (LLDA) to translucency parameter (TP), is investigated on maxillofacial elastomeric specimens by comparing a previously proposed method, color difference due to edge loss (CDEL). The translucency of human skin and translucent maxillofacial materials can be described quantitatively with this non-destructive, non-contact method, which might be further applied on application of reproduction of facial morphology and appearance.
Pigments and dyes play a key role in pigmentation and coloration of maxillofacial prosthetic elastomers. Addition of pigments and dyes into the base material might produce complicated reactions or interactions which in turn may cause various effects on optical properties, biocompatibility and thermal properties of the material.
Optical properties of a base maxillofacial prosthetic material are significantly affected when pigmentation by pigments and dyes. Kubelka-Munk (K-M) theory has been widely used on pigmentation and coloration of maxillofacial materials. Accuracy of the K-M theory with three different interfacial reflection corrections (IRC) on maxillofacial elastomers is evaluated, and the IRC value for translucent materials provides the least error for pigmented maxillofacial prosthetic elastomers. Furthermore, rather than the first order linear regression model traditionally used in concentration additivity, a newly proposed second order regression model in concentration additivity is evaluated and recognized as a regression model with the least error in colorant formulation based on the K-M theory for pigmented maxillofacial materials.
Biocompatibility of maxillofacial prosthetic elastomer is potentially affected after pigmentation and coloration. Cytotoxicity testing is used to initially investigate effects of pigments on biocompatibility of the material. Indirect test with olorimetric assay of MTS (an MTT analog), and direct test with digital imaging are performed. Maxillofacial prosthetic materials show a minor cytotoxicity, but no practically significant effects are found on cytotoxicity of pigmented maxillofacial elastomers.
Differential scanning calorimetric analysis is used to investigate effects of pigments on thermal properties of pigmented maxillofacial elastomers. A strong endothermic peak associated with melting and recrystalization is investigated and found to be at approximately -43°C, with an enthalpy change of approximately 11 J/g, which is consistent with results found in previous studies. No practically significant effects of pigments are found on pigmented maxillofacial elastomers, suggesting no significant effects on mechanical properties of the materials as well.