Color stability and colorant effect on maxillofacial elastomers. Part II: weathering effect on physical properties.
BACKGROUND
The clinical life of a maxillofacial prosthesis averages about 6 months, before it needs to be refabricated. Degradation of the color and physical properties of the prosthesis are the principle reasons for replacement.


OBJECTIVE
This second part of a 3-part in vitro investigation evaluated the change in physical properties of popular colorant-elastomer combinations as a result of weather exposure.


METHODS
Fifteen dumbbell-shaped and 15 trouser-shaped specimens were fabricated for each of the 3 elastomers (Silastic medical adhesive type A, Silastic 4-4210, and Silicone A-2186) and 6 colorant combinations (dry earth pigments, rayon fiber flocking, artist's oil paints, kaolin, liquid cosmetics, and no-colorants) for a total of 540 specimens. The 15 dumbbell-shaped and trouser-shaped specimens of each elastomer colorant combination were separated into 5 of each shape among 3 test condition groups (control, time passage, and natural weathering). Control specimens were evaluated within 1 month of fabrication. The time passage group was sealed in glass containers and kept in the dark for 6 months before testing. The natural-weathering groups were placed on the roof of the dental school for 6 months and exposed to sunlight and weathering. Evaluations of hardness and tear strength were made on trouser-shaped specimens, and evaluations of the ultimate tensile strength and percentage elongation on dumbbell-shaped specimens. Physical property data for each elastomer-colorant combination were subjected to a 1-way analysis of variance to examine effects among the test conditions. When significant differences were observed, the Student-Newman-Keuls multiple range test was performed to identify differences in elastomer-colorant combinations among each test condition at a significance level of .05.


RESULTS
Exposure to weathering and time changes of the physical properties of many colorant-elastomer combinations indicated that properties of a clinical prosthesis can change with time.


CONCLUSIONS
The addition of colorants to the silicones altered the effects of weathering. In addition, the silicones were not as stable as previously assumed.
Haug
S P
SP
Indiana University School of Dentistry, Indianapolis, Ind. 46202, USA. sphaug@iusd.iupui.edu
Moore
B K
BK
Andres
C J
CJ
D000704:Analysis of Variance; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004396:Coloring Agents / Q000737:chemistry*; D004355:Drug Stability; D006245:Hardness Tests / Q000379:methods; D006801:Humans; D008422:Materials Testing / Q000379:methods / Q000706:statistics & numerical data; D008447:Maxillofacial Prosthesis / Q000706:statistics & numerical data; D017797:Prosthesis Coloring / Q000706:statistics & numerical data; D011474:Prosthesis Design / Q000379:methods / Q000706:statistics & numerical data; D012826:Silicone Elastomers / Q000737:chemistry*; D013718:Tensile Strength; D013997:Time Factors; D014887:Weather
D004396:Coloring Agents; D012826:Silicone Elastomers