Effects of pigments on dynamic mechanical properties of a maxillofacial prosthetic elastomer

Pigmentation and coloration play a key role in fabricating a maxillofacial prosthesis. The addition of pigments and dyes to the maxillofacial material may alter the dynamic mechanical behaviors of the prosthesis, possibly influencing the success of the prosthesis.

The purpose of this study was to investigate the effects of the type and concentration of intrinsic pigments on the dynamic mechanical properties of a commercially available maxillofacial silicone elastomer over a small range of low frequencies.

Ten pigmented mixtures (6 specimens per mixture) were made by using a base silicone elastomer mixed with each intrinsic silicone pigment (Black, Red, Tan, or Yellow) or all the pigments (MixAll) in a designated high or low concentration. The base elastomer without pigment (Unpigment) was prepared as a control. Dynamic mechanical analysis was performed over 5 low frequencies (0.5, 1.0, 1.5, 2.0, and 2.5 Hz) at room temperature. The storage modulus (E'), loss modulus (E″), and loss tangent (tanδ) in compression were determined. Mixed models for repeated measures were used for the comparisons of E', E″, and tanδ among mixtures (α=.05).

The means of E', E″, and tanδ of all the pigmented specimens were lower than those of Unpigment. MixAll with high concentration had the lowest values in E' and E″. The means of E' and E″ of Red and Yellow in high concentration were lower than those in low concentration, whereas the means of E' and E″ of Black and Tan in low concentration were significantly lower than those in high concentration; the means of tanδ for all the mixtures in high concentration were significantly lower than those in low concentration. The means of E', E″, and tanδ of all the specimens tested increased as frequency increased from 0.5 to 2.5 Hz (P<.05).

Within the limitations of this study, it was concluded that the addition of intrinsic silicone pigments into a base maxillofacial elastomer significantly influenced dynamic mechanical properties of the maxillofacial silicone elastomer tested over the low frequencies from 0.5 to 2.5 Hz at room temperature. This effect, which was a quick elastic return to its original shape after deformation during pigmentation or coloration, seems desirable to a certain extent in clinical application. The type and concentration of pigment may influence the elastic and viscous portion of the properties of the maxillofacial elastomeric materials tested. Low frequencies (0.5 to 2.5 Hz) affect the dynamic viscoelastic properties of the materials.