Effects of Vinyl Acetate Content and Extrusion Temperatures on Ethylene Vinyl Acetate (EVA) Tetracycline HCL Fibers Used for Periodontal Applications
Authors: Shady Sally F. , McCarthy Stephen 
Published: February 2017

Periodontal disease is a prevalent disease that effects all types of ages. Mild cases of periodontal disease include infection and gingivitis. Severe cases of periodontal disease include loss of teeth, and the increased likelihood of systemic diseases such as: cancer, osteoporosis and pneumonia. Current treatments of periodontal disease include systemic approaches such as oral tablets of antibiotics or localized treatments such as the periodontal chip. Oral antibiotics require high dosages to effectively treat the infection therefore causing unwanted side effects. Other treatments include surgery, scaling and rooting. These methods have disadvantages as they are more invasive and require long term maintenance.

The aim of this study was to develop a periodontal fiber containing Tetracycline HCl and ethylene vinyl acetate (EVA) that can be implanted in the periodontal pocket and demonstrate a drug release for up to 10 days. To develop this drug-embedded fiber, ethylene vinyl acetate and tetracycline HCL were combined and subsequently formed into a fiber. First, both materials were melted and mixed for several minutes in a Brabender mixer. The resulting material was then pelletized and the fiber was synthesized using the hot melt extrusion process. To produce the most optimal fiber, various vinyl acetate contents were mixed and extruded at high and low processing temperatures. The fiber uniformity, tensile strength, and drug release was tested on three groups: 40% vinyl acetate with low processing temperatures, 40% vinyl acetate with high processing temperatures and 7% vinyl acetate with low processing temperatures. To test the uniformity of the fiber, an inline IR reader was used to monitor the outer diameter of the fiber. Since a 0.5mm would be easily implanted into the periodontal pocket, this was the desired fiber dimension. The Instron was used to analyze the tensile strength of each group to ensure that the fiber was durable enough to withstand the harsh environment of the oral cavity. For the drug release testing the fibers were placed into H2O and incubated to 37°C. Samples from the release media were taken at various time intervals for a total of 10 days. The samples were tested on the UV spectrophotometer for peak absorbances at 360nm.

The IR reader testing showed that the Elvax 40W (40% vinyl acetate content) material was easier to extrude than the Innospec (7% vinyl acetate content). The tensile strength tests of the fibers were approximately 0.025 ± 0.05 MPa. In-vitro drug release studies indicated that the low processing temperatures fibers released approximately three times the amount of tetracycline HCl than the high processing temperature group. This indicated that the fibers with low processing temperatures had the most favorable drug release profiles for bacterial inhibition. The overall feasibility for the periodontal fiber application was demonstrated in the 40% vinyl acetate group at lower processing temperatures and has shown the potential for multiple antimicrobial applications.