A Preliminary Study On Color Simulation Of Complicated Silicone Maxillofacial Prosthesis Using By Digital Camera And Transfer Printing

Maxillofacial prosthetic is the specialty of prosthodontics, which restore the orofacial defects with maxillofacial material to rehabilitate the patients'appearance and function. Color simulation is one of the most important factors in the maxillofacial restoration. During the color matching of the maxillofacial restoration, the dentists who select and evaluate the color of skin and restoration depend on perceptional method. The perceptional method relies on color perception by human eyes, which is effected by many factors: surrounding light condition, size of objective, background and eye fatigue. The purpose of this study is to increase the color accuracy of prothetic silicone elastomer with complex surface by using digital camera and the transfer printing technique. The paper includes three parts.Part 1 the color collection of human faceThe collected true color of human face is the first step in the color simulation of maxillofacial prothesis. The study is based on the application of digital color collection system which is established with a single lens reflect camera by recommended CIE standard light source, geometric condition of irradiation and fixed collection distance. The impact of the light stability and the background are also be considered in this study. The results are as follows:1. When the experimental light source irradiated in the blue background, it stabilized from 6 min to 70 min and ?E<0.58NBS. In the red background, it stabilized from 21min to 70min and ?E<0.85NBS. As observed, the ?E changed irregularly from 21 min to 70 min during the color measurement.2. It was obvious that the background had an important influence on the color measurement. The smallest chromatic aberration was 2.93NBS when using the skin color as the background. In addition, the silicone elastomer of different thicknesses in the same background could present different colors. So when we decided to measure the color of silicone maxillofacial prothesis, measuring it under the background of the defect area may be the best way.3. The L*a*b*chromaticity parameter of 122 subjects'right buccal skin color: L* 49~66,a* 7~18,b* 5~22. The distribution of L* and a*, L* and b*, a* and b* was all in certain areaes, which was coincide with the color's clustering of human skins.Part 2 the preliminary study on regional collection of the facial skin color by using 3DSS and digital camera techniqueThe face of human being is a complicated surface which can not be expanded to a flat surface. When we decide to measure the facial skin color with recommended geometric condition by using the digital single-lens reflex camera, it is inevitable to be impacted by the light irradiation angle and the facial anatomical structures. This study collects facial data from 3DSS and divides the data into several regions according to the curvature. The purpose of the division is decreasing the influnce of the uneven light. The results are as follows:1. The regions of the shadow, high light and normal areas existed on the face when we measured the facial skin color in only one time and angle with the standard light sources and geometric conditions. The P values of the Student-Newman-Keuls test was lower than 0.05, so the CIELAB values between these areas were different. In a word, it is easy to collect the wrong color data if we measure the facial skin color only in one facet or angle.2. The P values of the Student-Newman-Keuls test was higher than 0.05 of L* among the seven divided curved surfaces except the sixth region. So the lightness of the six regions was not different. The maximal ?E among the regions was 1.21NBS, and the average was only 0.61NBS. In addition, the ?E of the original and divided seventh region was 3.66NBS. The conclusion is that the color data which is collected from the divided curved surfaces could decrease the influence of the uneven illumination.Part 3 the preliminary study on maxillofacial prosthesis simulation by heat transfer printing techniqueThe true color of silicone elastomer prosthesis is simulated by internal and external color matching. It always requires the painting ability of the dentists and a long clinical time. The color of complex silicone elastomer surfaces can be transferred by heat transfer printing technique. And the physicochemical properties of the silicone elastomer won't be changed after the heating process. This experiment reseaches on the methods of transferring the obtained external facial skin color data on the complex surfaces of silicone elastomer which is corresponding to a certain part of human face. The results are as follows:1. The external facial skin color data was obtained from the photoshop mixed-layer calculation and the pigments'subtractive coloring mixing principle. 2. The color of a flat silicone elastomer could be transferred by heat transfer printing technique. The color of complex surface of silicone elastomer prosthesis could also be transferred by the application of heat transfer printing technique and the rapid prototyping technique.