Development of a 3D printable maxillofacial silicone: Part II. Optimization of moderator and thixotropic agent.

STATEMENT OF PROBLEM

Conventionally, maxillofacial prostheses are fabricated by hand carving the missing anatomic defect in wax and creating a mold into which pigmented silicone elastomer is placed. Digital technologies such as computer numerical control milling and 3-dimensional (3D) printing have been used to prepare molds, directly or indirectly, into which a biocompatible pigmented silicone elastomer can be placed.

PURPOSE

The purpose of this in vitro study was to develop a silicone elastomer that could be 3D printed directly without a mold to create facial or body prostheses by varying its composition.

MATERIAL AND METHODS

The room temperature vulcanizing silicone composition was divided into 2 components which were mixed 1:1 to initiate polymerization in the printer before printing began. Different types of moderators and thixotropic agents were used, and the base composition was varied to obtain 11 formulations. The specimens were printed and polymerized from these formulations and tested for tear and tensile strength and hardness. Ten readings of the specimens were recorded for tear and tensile strength and 6 for hardness. Results were analyzed using ANOVA (α=.05). Visual assessment of uncured printed specimens was undertaken for 5 formulations to assess any differences in their ability to hold their shape after printing.

RESULTS

The tear and tensile strength of the 11 formulations with varying moderators, thixotropic agents, and base compositions were statistically similar to each other (P>.05). Five of 11 formulations were chosen for the visual assessment as they had sufficient thixotropic agent to avoid slumping while printing. The specimens showed varied slumping behavior until they polymerized. The filler content was increased in the selected formulation, and the tear and tensile strength of the formulation was increased to 6.138 kNm and 3.836 MPa; these increases were comparable to those of commercial silicones currently used for the fabrication of facial prostheses.

CONCLUSIONS

The optimum combination of mechanical properties implies the use of one of the formulations as a suitable material for the 3D printing of facial prostheses.