Artificial Aging of Chlorinated Polyethylene and Maxillofacial Silicone Elastomer

Facial pathologies and congenital deformities require surgical intervention creating a need of prosthesis to minimize disfigurement as an effort to improve quality of life after surgery. Color pigments are added in maxillofacial biomaterial to achieve desired esthetics. Prosthesis undergoes color change during clinical functions affecting esthetics, requiring patients to get color adjustment at 3-12 mo. Silicone Rubber (SR) is conventionally used maxillofacial material while Chlorinated Polyethylene (CPE) is reported as an emerging biomaterial with proven biocompatibility.

Objective: To characterize color change in SR and CPE by exposing them to artificial aging factors like Ultra-violet (UV) light and humid conditions.

Methods: Four materials were evaluated: pigmented and unpigmented SR and CPE. The materials were processed in molds placed in dental flasks to obtain 9󬝮 mm samples under 10 lbs pressure for 10 minutes using a electric pressure pot. Three samples from each category were exposed to UV radiation by Color Stability Apparatus for 100 and 200 h time duration. Four samples of each category were immersed in PBS solution at 37癈 in a Humidity apparatus for 30 days. CIE L*a*b* values were measured by Minolta Chromameter and color difference (ΔE*) were compared. Further analysis of UV exposed samples was performed by FT-IR.

Results: Addition of pink pigments in SR and CPE decreased the ΔE* values for both materials. SR became lightly translucent while CPE became more opaque with increased duration of UV exposure. PBS induced significant opacity in CPE than SR. FT-IR analysis revealed new absorbance peaks at 1717cm^-1 and 1643cm^-1 in CPE after UV exposure, corresponding to C=C and C=O stretching.

Conclusion: UV may cause oxidation/breakdown of CPE, with appearance of C=C and C=O spectral peaks. The aging factors induced more pronounced effects in CPE than SR.