Mechanical behavior and color change of facial prosthetic elastomers after outdoor weathering in a hot and humid climate

doi:10.1016/j.prosdent.2014.09.008

The Journal of Prosthetic Dentistry

Volume 113, Issue 2, February 2015, Pages 146-151

https://doi.org/10.1016/j.prosdent.2014.09.008 Get rights and content

Abstract

Statement of problem

A common reason for replacing a maxillofacial prosthesis is the deterioration of its properties.

Purpose

The purpose of this study was to compare the effect of weathering in a hot and humid climate on the tear strength, tensile strength, modulus of elasticity, elongation percentage, and color of 3 maxillofacial materials.

Material and methods

Three silicone materials were tested. Specimens were exposed to outdoor weathering for 6 months in a hot and humid environment. Tear and tensile strengths were measured with a universal testing machine before and after outdoor weathering. Color change was evaluated by recording L*, a*, and b* values at base line and after outdoor weathering with a spectrophotometer. The ΔE, ΔL*, Δa*, and Δb* of the specimens were calculated. Data were analyzed with 2-way ANOVA and the post hoc Scheffé test (α=.05).

Results

For all tested elastomers, outdoor weathering decreased the tear strength and modulus of elasticity values significantly (P<.001). Also, weathering reduced percentage elongation values significantly (P<.05). Tensile strength values were significantly reduced for TechSil S25 and MED-4210 specimens only (P<.05). The effect of weathering on the color of pigmented specimens was greater than the acceptable value (ΔE>3.0). The color change (ΔE) of pigmented specimens ranged from 4.31 to 6.68. A-2186 silicone elastomer experienced the greatest color changes (P<.05). Within nonpigmented specimens, none of the tested silicone elastomers showed significant color changes (P>.05).

Conclusions

Outdoor weathering in a hot and humid climate adversely affected the properties of silicone elastomers. The heat-polymerized TechSil S25 elastomer showed better mechanical durability and color stability compared with the room-temperature polymerized A-2186 and MED-4210 materials. TechSil S25 showed the greater values of tear and tensile strengths and elongation of specimens exposed to outdoor weathering conditions. It also showed the least amount of color change among the pigmented specimens exposed to outdoor weathering.

Section snippets

Material and Methods

Three silicone maxillofacial materials were used for this study: 1 high-temperature vulcanized (HTV) (TechSil S25) material and 2 room-temperature vulcanized (RTV) (A-2186, and MED-4210) materials. These materials are described in Table 1.

Hard wax patterns were invested in high strength dental stone (Castone; Dentsply Intl) to fabricate molds that were coated with sodium alginate (Hilier Dental). The silicone and catalyst were mixed manually at the ratio recommended by the manufacturers for 5

Results

The mechanical properties of the tested maxillofacial elastomers were adversely affected by outdoor weathering. For all tested silicone elastomers, outdoor weathering significantly decreased the values of tear strength and modulus of elasticity (P<.001). Also, weathering reduced the percentage elongation values significantly (P<.05). Tensile strength values were significantly reduced for TechSil S25 and MED-4210 materials only (P<.05). The means and standard deviations of tear strength, tensile

Discussion

The null hypothesis on the mechanical properties was rejected, except for the tensile strength of A-2186, which demonstrated no statistically significant difference. The null hypothesis on the color change was only partially rejected. For example, comparing the ΔE of pigmented TechSil S25 and pigmented A-2186, a statistically significantly difference was found. The heat-polymerized TechSil S25 elastomer showed better mechanical durability and color stability compared with the room-temperature

Conclusion

Within the limitations of this in vitro study, outdoor weathering in hot and humid climate adversely affected the mechanical properties of TechSil S25, A-2186, and MED-4210 silicone elastomers (P<.05). Weathering also caused unacceptable color changes in pigmented TechSil S25, A-2186, and MED-4210 silicone elastomers.