Colourfast pigments in silicone hand and maxillofacial prostheses

An investigation of the effects of topical sunscreen protection products under natural weather conditions on intrinsic color stability in maxillofacial silicones

Aim

The relatively short lifespan of maxillofacial prostheses (ranging from 3-24 months) is mostly a result of colour instability of silicone elastomers caused by ultraviolet (UV) radiation, requiring frequent remakes. An improvement in colour preservation could result in fewer remakes, thus saving time and money for both clinician and patient. In the quest for a suitable colour protection method, sunscreen protection products were considered; the most recent study on this subject was carried out in 1994, albeit using a low protection factor. The aim of this research was to determine if there is value in using topical sun protection products on extraoral silicone prostheses to prevent colour degradation.

Settings and Design

This was an in vitro quantitative study.

Materials and Methods

Three commercially available sunscreen products were studied, Riemann P20, Boots Soltan, and Garnier Ambre Solaire all with a sun protection factor of 50. A total of 144 silicone elastomer samples were produced using a Caucasian (light) shade 1.2 (n = 72) and dark skin shade 3.2 (n = 72) from the Technovent Ltd. Reality Shade range. Each shade group (n = 72) was divided into three groups to be subjected to outdoor weathering (n = 24), indoor (n = 24), and dark storage (n = 24). Within each environmental group, samples were divided into groups of six samples (n = 6) to receive the three sunscreens plus a control group with no sunscreen. The CIEL* a* b* formula was used to obtain the color measurements.

Statistical Analysis Used

One way ANOVA test and Tukey's HSD test for multiple comparisons was used to analyse the data.

Results

The ΔE values had changed for all samples throughout the aging process.

Conclusion

Soltan showed promising results in protecting the dark-shaded samples in the outdoor environment only.

Color-matching techniques for creating esthetic hand and finger prostheses

BACKGROUND

Color matching is a critically important part of, and by far, also the most challenging aspect of producing esthetic silicone prosthesis. There is a knowledge gap in the literature and a lack of opportunities for training in the expertise, particularly regarding color-matching techniques.

OBJECTIVE

This article details a color-matching technique that is able to achieve life-like coloration in esthetic prosthesis.

TECHNIQUE

Each prosthesis is molded in an outer and inner layers of silicone tinted to different shades and opacities incorporating an intermediate touch-up layer to reproduce the detailed coloration of the hand (because of the presence of veins, finger joint/dermal pigmentations, a vascularized nail bed, and pinkish palm). This method of color-matching prosthesis combining intrinsic and extrinsic techniques simulates the layered anatomy and optical properties of the human skin to effectively replicate its esthetic and life-like coloration. Technical tips for achieving an accurate color match to the patient's skin, including pigment formulation adjustments for a tanned vs. a fair skin, and for painting the touch-up details are discussed. Methods for modifying the color tones of completed prosthesis and for minimizing metameric color differences when the prosthesis is viewed under different light sources are also presented.

DISCUSSION

The technique is instrumental in achieving good outcomes for life-likeness and esthetic coloration in the prostheses fitted at our center. Studies previously published that investigated patients' evaluation of important esthetic characteristics of their prosthesis after a period of adjustment to fitting have shown a generally high level of patient satisfaction.

Prosthetic rehabilitation of auricular defect: a clinical report

BACKGROUND

The absence of external ear may be due to congenital, traumatic, or surgical causes. Many case reports only describe impression techniques to record details of the defect side and the natural ear. The purpose of this case report is to explain in detail simple clinical and laboratory procedures involved in fabrication of ear prosthesis.

CASE DESCRIPTION AND METHODS

The use of three-part mold helps in the application of pigmented silicone in specific areas. The use of direct adhesive fixation provides the best esthetic result and if properly used the most satisfactory form of treatment.

FINDINGS AND OUTCOMES

The patient was satisfied with the life-like appearance of the prosthesis. The use of direct adhesive fixation gave the patient a sense of security and improved his confidence.

CONCLUSION

The technique described is economical, and additional steps of implant placement are avoided. The esthetics of the prosthesis made by hand carved clay pattern provides good details.

CLINICAL RELEVANCE

The technique describes the method of direct adhesive fixation of the prosthesis giving it a life-like appearance. The confidence of the patient is also restored.

Influence of pigments and pigmenting methods on color stability of different silicone maxillofacial elastomers after 1-year dark storage

PURPOSE

The purpose of this study was to measure spectrophotometrically the color changes of pigmented maxillofacial silicone elastomers with different pigments and pigmenting methods after storing 1 year in the dark environment.

METHODS

Three maxillofacial silicones, Cosmesil M511 (CosM511), Cosmesil M522 (CosM522), and Multisil-Epithetic (Mult-Epit), were selected for this study. A total of 240 specimens were fabricated; 80 of each of the 3 elastomers (n = 5) (18 mm in diameter and 2 mm in thickness) were prepared in 6 colorant categories (5 colorant and 1 with no colorant). Specimens were stored in a black box representing a condition of total darkness and placed in a dark environment at ambient room temperature (22°C ± 10°C) and humidity (50% ± 10%) for 1 year. A color spectrophotometer was used to measure the ΔE* values of the test specimens to determine the color changes.

RESULTS

The lowest color changes were observed in CosM511 in white color (ΔE* = 1.31) and in Mult-Epit in white color (ΔE* = 1.82) in extrinsic coloration group. The highest color changes were observed in yellow color in CosM511 (ΔE*= 21.61) and CosM522 (ΔE*= 23.78) in silicone pigmented intrinsic coloration method. In coloration methods, intrinsic silicone pigmented groups in all colors except brown in Mult-Epit had the highest ΔE* values.

CONCLUSIONS

Significant color changes were observed in both pigmented and unpigmented specimens, which were stored in dark environment and not exposed to sunlight.

The effect of accelerated ageing on performance properties of addition type silicone biomaterials

The UV-protection provided to addition type silicone elastomers by various colorants, such as conventional dry earth pigments, as well as the so called "functional or reactive" pigments, was investigated. Moreover, the effect of a UV light absorber and a silica filler was also explored. Under the experimental parameters of this work, the exposure of silicone to UV radiation resulted in some changes of the IR absorbance, thermal decomposition after 400 degrees C, T(g) and tensile properties, whereas the storage modulus of samples was not affected. The obtained spectroscopic data, as well as the results of TGA and storage modulus, were interpreted by assuming that chain scission takes place during aging, whereas the improvement of tensile strength allows the hypothesis of a post-curing process, initiated by UV radiation. Therefore, the increase of T(g) could partly be due to the above reason and, furthermore, to the contribution of a rearrangement of chain fragments within the free volume of the elastomeric material. Regarding the evaluation of various coloring agents used in this work, the obtained results show that dry pigments are more sensitive to accelerated ageing conditions in comparison with functional liquid pigments. Moreover, the hydrophobic character of silicone matrix is enhanced, with the addition of this type pigments because of the vinyl functional silanes groups present in their chemical structure. Finally, it should be noted that the incorporation of silica nanofiller did not seem to prevent the silicone elastomer from degradation upon UV irradiation, but showed a significant reinforcing effect.

Assessment of colour differences in silicone hand and digit prostheses: perceptible and acceptable thresholds for fair and dark skin shades

This study addresses the dilemma of initial clinical and social acceptance of a newly fabricated silicone prosthesis in relation to its colour match to the natural skin. This was achieved by derivation of specific colour difference thresholds defining perceptible and acceptable levels of colour sensitivity. Two separate sets of 10 fair and dark shade digit prosthesis samples were each fabricated with a stepped increase in colour difference (deltaE) against the baseline hand prosthesis. Ninety individuals with normal colour vision scores were selected as colour assessors. The colour difference of each prosthesis in the two series was evaluated visually against the baseline by the assessors, using defined scores. The thresholds for perceptible and acceptable colour difference determined in this study were deltaE= 0.8 and deltaE= 1.8 for the fair series and deltaE = 1.3 and deltaE = 2.6 for the dark series, respectively. The acceptable threshold values differed from the perceptible threshold values by deltaE= 1.0 for the fair-shade samples and deltaE= 1.3 for the dark-shade samples. This study demonstrated that subjective visual assessment is positively correlated with deltaE values computed from colorimetric measurements for both fair and dark-shade silicone samples (p<0.001). This results shows that human subjects with normal colour vision are capable of accurately assessing colour differences. These observations emphasize the importance of subjective feedback on colour by the patient, provided the latter has perfect colour-tested vision. The study also showed that human subjects were less sensitive to perceived colour differences in darker-shade than fairer-shade samples (p < 0.001). This finding seems relevant in a clinical setting involving a multi-ethnic patient population.