Rahman, Ahmed Mushfiqur
(2019)
Surface roughness and mechanical properties of maxillofacial prosthetic silicone elastomers subjected to outdoor weathering in Malaysian environment.
Masters thesis, Universiti Sains Malaysia.
Abstract
Silicone elastomers are widely used for fabricating maxillofacial prostheses to
rehabilitate craniofacial defect. However, the average service life of a silicone elastomer
can be influenced by local weather condition. In clinical practice, it is noticed that hot and
humid weathers further affects the lifespan of silicone material in terms of surface
degradation and tear, thereby frequent replacement of the prostheses is required. So, the
aim of this study was to evaluate the surface roughness, tensile strength, and percentage
elongation of different silicone elastomers subjected to outdoor weathering in the
Malaysian environment. An in-vitro experimental study was performed on 120 type-II
dumbbell-shaped specimens (non-weathered=15, weathered=15) made from three room
temperature vulcanized (A-2000, A-2006, and A-103) and one heat temperature
vulcanized (M-511) silicone (Factor II, Inc., AZ, USA) materials. For 6 months,
weathered specimens were subjected to outdoor weathering in customised exposure rack,
while the non-weathered specimens were kept in a dehumidifier at 25°C ± 1°C and 50 ±
5% relative humidity. Afterwards, surface roughness was measured using a profilometer
(Surfcom Flex, Tokyo, Japan); tensile strength and percentage elongation was determined
using Universal Testing Machine (Shimadzu, Japan). Independent t-test and one-way
ANOVA was performed to compare means of the tested properties between nonweathered
and weathered specimens within each silicone group, and weathered specimens
among the different silicone groups respectively. After subjected to outdoor weathering
at Universiti Sains Malaysia, Kelantan, Malaysia, only A-2000 silicone elastomer showed
a statistically significant difference in surface roughness between non-weathered and
weathered specimens (p=0.005). The silicone materials (A-2000, A-2006, and M-511)
showed a statistically significant difference in tensile strength and percentage elongation
values (p<0.05) after outdoor weathering compared to the non-weathered specimens. In
terms of tensile strength and percentage elongation, all the elastomers were adversely
affected by weathering, except for A-103 silicone which demonstrated the least changes.
A-2000, A-2006, and M-511 showed higher values of mechanical properties but showed
more changes after weathering. For Malaysian weather, A-103 can be suggested as a
suitable silicone based on the least changes to its mechanical properties after weathering.
However, the higher mechanical properties of A-2000, A-2006, and M-511 make them a
viable option as well despite their significant changes after weathering. So, the clinicians
need to decide whether to use A-2000, A-2006, and M-511 silicone for higher mechanical
properties, or A-103 for better resistance in the Malaysian environment based on their
cases.
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