A Novel Antimicrobial Orthodontic Band Cement

Objective: To develop a novel antimicrobial orthodontic band cement with in situ generated silver nanoparticles (AgNP).  

Method: 18 groups (including 2 controls) of AgNP-loaded Opal Band Cement (OBC; Ultradent Products, Inc.) were formulated with different concentrations of additional benzoyl peroxide (BPO; 0.5, 1, 1.5 or 2 wt%) and 2,2-(p-Tolylimino)diethanol (P-TIDE; 0.5 or 1 wt%), and silver benzoate (AgBz; 0.5 or 1 wt%) to generate AgNP in situ.  Controls include OBC and the same cement formulated in house (UTOBC).  Cements were light-cured and tested with Rockwell_15T hardness and near-infrared FTIR (NIR) to determine degree of cure, and three-point bending to determine mechanical properties.  In vitro Ag⁺ ion release was measured for 4 months.  

Result: OBC had significantly (p<0.5) higher hardness, modulus, and ultimate transverse strength (UTS) than all groups due to better filler loading and dispersion.  UTOBC and all 0.5 wt% AgBz experimental groups had significantly higher hardness, modulus, and UTS than all 1 wt% AgBz groups except the group with additional 1.5 wt% BPO/0.5 wt% P-TIDE.  Previous studies have shown that addition of AgBz reduces mechanical properties.  Here, additional BPO and P-TIDE increased moduli and UTS to comparable levels as those of UTOBC.  Interestingly, OBC had significantly lower NIR degree of conversion (DoC) than all groups.  All experimental groups had comparable DoC to UTOBC.  Ag⁺ ion release was observed for all AgNP-loaded groups for up to 4 months and release rates were comparable to that of previous studies.  Thus, these cements are expected to be significantly antibacterial.  

Conclusion: AgNP-loaded OBC (adhesive orthodontic band cement) with comparable mechanical properties as UTOBC have been fabricated.  Additional BPO and P-TIDE increased mechanical properties of AgNP-loaded cements to comparable levels as UTOBC.  All experimental groups released significant amounts of Ag⁺ ions in vitro over 4 months.  We are currently conducting in vitro antibacterial tests.