Povidone-Iodine Decreases Poly(methylmethacrylate) Polymerization (PMMA)

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Authors: Bingham J, McLaren A, Clarke H, McLemore R.
Banner Good Samaritan Medical Center, Phoenix, AZ and Mayo Clinic, Phoenix, AZ

Title: Povidone-Iodine Decreases Poly(methylmethacrylate) Polymerization (PMMA)

Background: Dilute Povidone-iodine ( PVP-1) solution is being used to irrigate following implantation of orthopaedic prostheses. The active agent, triiodide, is a strong oxidizing agent that could inhibit polymerization of PMMA.

Hypothesis/Purpose: Does PVP-1 inhibit free radical polymerization of PMMA?

Methods: 200 standardized PMMA test cylinders (6mm diameter x 12 mm length,) were studied, 50 from each of four groups 1) control - no additive, 2) 4 mL of: 10% PVP-1, 3) 4mL DI H20, and 4) 4 mL 4% chlorhexidine. PMMA was hand mixed without vacuum, and formed into test cylinders using a Teflon mold at room temperature. Set times (start of mixing to hard non-dentable surface) were measured for each group. Specimens were allowed to cure for 48 hours. Ten cylinders (n=10) were loaded to failure in a Test Resources AT830 at 24mm per minute (ASTM F451-08). The yield point was identified in accordance with F451-08. Data was analyzed with ANOVA and t-test.

Results: The set times for the control, DI, and chlorhexidine groups were 13.75, 8.75, and 10.25 minutes. The betadine group did not set. Over time the monomer evaporated leaving a hard cylinder. Load to failure for the PVP-1 was less than the other three groups (P < 0.001, t-test). Load to failure for DI and chlorhexidine were less than the control group (p < 0.001), but not different from each other. Compressive strength for control, betadine, DI, and chlorhexidine was 114.4 MPa, 24.1 MPa, 90.9 MPa, and 89.9 MPa respectively (Fig.1).

Discussion: The PVP-1 group never became warm, and stayed pliable until the next day. DI and chlorhexidine caused lower compressive strength but not below 70 MPa specified for arthroplasty fixation (ISO 5833). PVP-1 failed at 1/3 of the specified strength. Mixing antiseptics with bone cement during polymerization is an extreme test for use of antiseptic irrigation during arthroplasty surgery where the cement has usually progressed to at least the dough phase before exposure to irrigation. These data draw attention to a possible interaction between polymerizing bone cement and betadine. It may be prudent to have the bone cement fully polymerized before exposure to betadine in clinical practice.

Conclusion: PVP-1 slows polymerization of PMMA.

Povidone-Iodine Decreases Poly(methylmethacrylate) Polymerization (PMMA)