Effect of Incorporation of Nano-Oxides on Color Stability of Maxillofacial Silicone Elastomer Subjected to Outdoor Weathering R. N. Akash, MDS1 & Satyabodh S. Guttal, MDS2 1 2
Private Practice, Pune, India Department of Prosthodontics, SDM College of Dental Sciences & Hospital, Dharwad, Karnataka, India
Keywords Maxillofacial prostheses; maxillofacial silicone elastomer; color stability; nano-oxides; outdoor weathering. Correspondence Satyabodh S. Guttal, Department of Prosthodontics, SDM College of Dental Sciences & Hospital, Dhavalnagar Sattur, Dharwad, Karnataka 580 009, India. E-mail: [email protected]. The authors deny any conflicts of interest. Accepted May 25, 2014 doi: 10.1111/jopr.12252
Abstract Purpose: The aim of this study was to evaluate the effect of incorporation of two compositions of nano-oxides on color stability of intrinsically colored maxillofacial silicone elastomer subjected to outdoor weathering. Materials and Methods: Ninety Cosmesil M511 silicone elastomer specimens were fabricated. The control group was incorporated with intrinsic coloring agents (umber, brown, yellow), group A was incorporated with intrinsic coloring agents and nanosized titanium oxide (TiO2 ), and group B was incorporated with intrinsic coloring agents and nanosized zinc oxide (ZnO). For outdoor weathering, specimens were mounted on a treated plywood rack, and the assembly was weathered for 6 months. A GretagMacbeth Spectrolino spectrophotometer was used to determine the CIELAB (L*a*b*) parameter before and after weathering of each specimen, and the values were noted. The color change (࢞E) values were analyzed by one-way ANOVA, Tukey’s post hoc test, and paired t-test. Results: The color change (E*) for groups were control group > group A > group B. The control group (0.76 ± 0.32) and group A (0.47 ± 0.19) showed significant difference in the color change before and after weathering (p < 0.00001). Group B (0.03 ± 0.05) showed no significant difference in color change before and after weathering (p = 0.08). Conclusions: The present findings suggest that incorporation of nano-oxides improved the color stability of Cosmesil M511 silicone elastomer and also acted as an opacifier. ZnO-incorporated Cosmesil M511 specimens showed minimal or no color change and proved to be most color stable after being subjected to outdoor weathering.
Maxillofacial prosthodontics currently finds itself undergoing more transformation than at any other time in its existence. Maxillofacial prostheses will always be in need despite advances in plastic surgery. They are used to treat congenital, developmental, and acquired defects of the head and neck region and transform them into lifelike reproductions of the missing parts, thus giving patients a normal appearance, social acceptance, comfort, and improved function.1 Head and neck cancer is the 10th most common cancer in the world. In India, head and neck cancer prevalence is about 45% of the total cancers affecting the human body.2 Maxillofacial rehabilitation of patients with acquired or congenital deformities of the head and neck region is a challenge that needs a multidisciplinary approach. Maxillofacial prosthodontics aims to restore the patient’s appearance and protect the resection site, allowing improvement in quality of life. It is important that prostheses be fabricated with optimal esthetics
while maintaining an adequate appearance over its service lifetime.3 Modern materials for maxillofacial prostheses include vinyl plastisols, polymethylmethacrylates, polyurethanes, latex, and silicone elastomers. Properties like chemical inertness, strength, durability, and ease of manipulation make silicone elastomers the material of choice in maxillofacial prostheses.4 Silicone elastomers used for the fabrication of maxillofacial prostheses have individual physical and mechanical properties; however, clinical problems such as gradual deterioration of color in a service environment and degradation of physical, static, and dynamic mechanical properties are common for all.4 In the chemical industry, during the past 10 years, research has been devoted to the development of a new industrial process that incorporates nanoparticles into a polymeric matrix, providing a new class of polymeric materials that offers the strength of nano-oxides, with the flexibility of the organic polymer matrix.
C 2014 by the American College of Prosthodontists Journal of Prosthodontics 24 (2015) 569–575
569
Effect of Nano-Oxides on Color Stability
Akash and Guttal
The enhanced properties discovered by adding nanoparticles into a polymeric matrix may be attributed to the higher surface energy and chemical reactivity of the particles, allowing them to interact with the silicone elastomer matrix and form a three-dimensional network within the silicone polyethylene chain. The nanosized material particles result in the optimization of individual material particle characteristics and control of biological, mechanical, electrical, magnetic, and optical characteristics as well. Nanosized rutile TiO2 and ZnO are known to have a high ultraviolet (UV) absorbing and scattering effect that results in protection from UV light. Nanosized SiO2 , TiO2 , and ZnO are characterized by their small size, large specific area, active function, and strong interfacial interaction with the organic polymer. Therefore, they can improve the physical properties and optical properties of the organic polymer, as well as provide resistance to environmental stress-caused aging. Little has been reported in the literature on how the addition of these particles to a maxillofacial elastomer could affect its properties.5 Han et al evaluated the effect of nanosized oxides of various compositions in different concentration on the mechanical properties of a commercially available silicone elastomer. They determined that incorporation of Ti, Zn, or Ce nano-oxides at a concentration of 2.0% improved the overall mechanical properties of silicone A-2186 maxillofacial elastomer.5 The purpose of this study was to evaluate the intrinsic coloration and assess the effect of incorporation of nano-oxides of two compositions on the color stability of medical grade silicone elastomer and to evaluate the color spectrophotometrically before and after outdoor weathering.
Materials and methods Ninety clear cast acrylic disk-shaped patterns were prepared by machine cutting a cast acrylic sheet of 2 mm thickness to the required dimensions (2 mm thick × 20 mm diameter) and were used to fabricate the specimen mold. These dimensions accommodated the aperture of the spectrophotometer effectively.6 Acrylic resin patterns were invested using the conventional compression molding method. The resultant mold was cleaned thoroughly with soap and warm water and was used to fabricate silicone specimens. Six flasks with five molds each were fabricated so that 30 specimens for each group could be fabricated at once to maintain consistency. A total of 90 silicone specimens were fabricated and separated into control group, group A, and group B with 30 specimens each. Control group specimens were intrinsically colored, group A specimens were intrinsically colored and incorporated with TiO2 , and group B specimens were intrinsically colored and incorporated with ZnO. Materials used are as presented in Table 1. For fabrication of control group specimens, a 10:1 ratio of Part A to Part B of Cosmesil maxillofacial rubber M511 was weighed on a digital weighing machine and mixed using a silicone mixing spatula on a large glass slab until a homogenous mixture was obtained (i.e., 100 g of Part A to 10 g of Part B along with 4 drops of antislump agent M514 and 1 g each of intrinsic coloring agents umber, brown, and yellow). For fabrication of group A specimens, a 10:1 ratio of Part A to Part B of Cosmesil maxillofacial rubber M511 was used (i.e., 100 g of Part A to 10 g of Part B). Part A of maxillofacial rubber 570
was incorporated with 2% concentration by weight (i.e., 2 g of TiO2 , rutile nanopowder,
Private Practice, Pune, India Department of Prosthodontics, SDM College of Dental Sciences & Hospital, Dharwad, Karnataka, India
Keywords Maxillofacial prostheses; maxillofacial silicone elastomer; color stability; nano-oxides; outdoor weathering. Correspondence Satyabodh S. Guttal, Department of Prosthodontics, SDM College of Dental Sciences & Hospital, Dhavalnagar Sattur, Dharwad, Karnataka 580 009, India. E-mail: [email protected]. The authors deny any conflicts of interest. Accepted May 25, 2014 doi: 10.1111/jopr.12252
Abstract Purpose: The aim of this study was to evaluate the effect of incorporation of two compositions of nano-oxides on color stability of intrinsically colored maxillofacial silicone elastomer subjected to outdoor weathering. Materials and Methods: Ninety Cosmesil M511 silicone elastomer specimens were fabricated. The control group was incorporated with intrinsic coloring agents (umber, brown, yellow), group A was incorporated with intrinsic coloring agents and nanosized titanium oxide (TiO2 ), and group B was incorporated with intrinsic coloring agents and nanosized zinc oxide (ZnO). For outdoor weathering, specimens were mounted on a treated plywood rack, and the assembly was weathered for 6 months. A GretagMacbeth Spectrolino spectrophotometer was used to determine the CIELAB (L*a*b*) parameter before and after weathering of each specimen, and the values were noted. The color change (࢞E) values were analyzed by one-way ANOVA, Tukey’s post hoc test, and paired t-test. Results: The color change (E*) for groups were control group > group A > group B. The control group (0.76 ± 0.32) and group A (0.47 ± 0.19) showed significant difference in the color change before and after weathering (p < 0.00001). Group B (0.03 ± 0.05) showed no significant difference in color change before and after weathering (p = 0.08). Conclusions: The present findings suggest that incorporation of nano-oxides improved the color stability of Cosmesil M511 silicone elastomer and also acted as an opacifier. ZnO-incorporated Cosmesil M511 specimens showed minimal or no color change and proved to be most color stable after being subjected to outdoor weathering.
Maxillofacial prosthodontics currently finds itself undergoing more transformation than at any other time in its existence. Maxillofacial prostheses will always be in need despite advances in plastic surgery. They are used to treat congenital, developmental, and acquired defects of the head and neck region and transform them into lifelike reproductions of the missing parts, thus giving patients a normal appearance, social acceptance, comfort, and improved function.1 Head and neck cancer is the 10th most common cancer in the world. In India, head and neck cancer prevalence is about 45% of the total cancers affecting the human body.2 Maxillofacial rehabilitation of patients with acquired or congenital deformities of the head and neck region is a challenge that needs a multidisciplinary approach. Maxillofacial prosthodontics aims to restore the patient’s appearance and protect the resection site, allowing improvement in quality of life. It is important that prostheses be fabricated with optimal esthetics
while maintaining an adequate appearance over its service lifetime.3 Modern materials for maxillofacial prostheses include vinyl plastisols, polymethylmethacrylates, polyurethanes, latex, and silicone elastomers. Properties like chemical inertness, strength, durability, and ease of manipulation make silicone elastomers the material of choice in maxillofacial prostheses.4 Silicone elastomers used for the fabrication of maxillofacial prostheses have individual physical and mechanical properties; however, clinical problems such as gradual deterioration of color in a service environment and degradation of physical, static, and dynamic mechanical properties are common for all.4 In the chemical industry, during the past 10 years, research has been devoted to the development of a new industrial process that incorporates nanoparticles into a polymeric matrix, providing a new class of polymeric materials that offers the strength of nano-oxides, with the flexibility of the organic polymer matrix.
C 2014 by the American College of Prosthodontists Journal of Prosthodontics 24 (2015) 569–575
569
Effect of Nano-Oxides on Color Stability
Akash and Guttal
The enhanced properties discovered by adding nanoparticles into a polymeric matrix may be attributed to the higher surface energy and chemical reactivity of the particles, allowing them to interact with the silicone elastomer matrix and form a three-dimensional network within the silicone polyethylene chain. The nanosized material particles result in the optimization of individual material particle characteristics and control of biological, mechanical, electrical, magnetic, and optical characteristics as well. Nanosized rutile TiO2 and ZnO are known to have a high ultraviolet (UV) absorbing and scattering effect that results in protection from UV light. Nanosized SiO2 , TiO2 , and ZnO are characterized by their small size, large specific area, active function, and strong interfacial interaction with the organic polymer. Therefore, they can improve the physical properties and optical properties of the organic polymer, as well as provide resistance to environmental stress-caused aging. Little has been reported in the literature on how the addition of these particles to a maxillofacial elastomer could affect its properties.5 Han et al evaluated the effect of nanosized oxides of various compositions in different concentration on the mechanical properties of a commercially available silicone elastomer. They determined that incorporation of Ti, Zn, or Ce nano-oxides at a concentration of 2.0% improved the overall mechanical properties of silicone A-2186 maxillofacial elastomer.5 The purpose of this study was to evaluate the intrinsic coloration and assess the effect of incorporation of nano-oxides of two compositions on the color stability of medical grade silicone elastomer and to evaluate the color spectrophotometrically before and after outdoor weathering.
Materials and methods Ninety clear cast acrylic disk-shaped patterns were prepared by machine cutting a cast acrylic sheet of 2 mm thickness to the required dimensions (2 mm thick × 20 mm diameter) and were used to fabricate the specimen mold. These dimensions accommodated the aperture of the spectrophotometer effectively.6 Acrylic resin patterns were invested using the conventional compression molding method. The resultant mold was cleaned thoroughly with soap and warm water and was used to fabricate silicone specimens. Six flasks with five molds each were fabricated so that 30 specimens for each group could be fabricated at once to maintain consistency. A total of 90 silicone specimens were fabricated and separated into control group, group A, and group B with 30 specimens each. Control group specimens were intrinsically colored, group A specimens were intrinsically colored and incorporated with TiO2 , and group B specimens were intrinsically colored and incorporated with ZnO. Materials used are as presented in Table 1. For fabrication of control group specimens, a 10:1 ratio of Part A to Part B of Cosmesil maxillofacial rubber M511 was weighed on a digital weighing machine and mixed using a silicone mixing spatula on a large glass slab until a homogenous mixture was obtained (i.e., 100 g of Part A to 10 g of Part B along with 4 drops of antislump agent M514 and 1 g each of intrinsic coloring agents umber, brown, and yellow). For fabrication of group A specimens, a 10:1 ratio of Part A to Part B of Cosmesil maxillofacial rubber M511 was used (i.e., 100 g of Part A to 10 g of Part B). Part A of maxillofacial rubber 570
was incorporated with 2% concentration by weight (i.e., 2 g of TiO2 , rutile nanopowder,
