Synthesis of novel chlorhexidine spheres with controlled release from a UDMA-HEMA resin using ultrasound.

Objective: Establish the release kinetics of new chlorhexidine particles incorporated in a dental resin, and with the application of ultrasound.

Methods: Spherical chlorhexidine particles (SCP) were synthesized (5wt%), freeze dried and incorporated into UDMA-HEMA resins. Chlorhexidine diacetate (CDP) (5wt%) was similarly incorporated in separate resins. Resin discs were immersed in deionized water, and a release profile established (650h). Ultrasound was used to trigger chlorhexidine (CHX) release from the resin discs at specific durations (10-30s) and time intervals (1-425h). Chlorhexidine content was determined by UV-vis absorption. The chlorhexidine particles/polymer composites were characterized using TGA, SEM, and confocal microscopy.

Results: SCP exhibited structures with high chlorhexidine content (90-95%), and a Mean (SD) diameter of 17.2 (2.5)μm which was significantly (p<0.001) smaller than the CDP crystals at 53.6 (33.7)μm. The SCP discs had a lower (7.7%) CHX release compared to the CDP group (16.2%). Ultrasonication of the resin discs with increasing durations (10-30s) resulted in higher drug release rates. CDP release rates (CHX) over 650h were: 23.5% (10s), 42.6% (20s), 51.2% (30s), and for SCP (CHX) were; 9.8% (10s), 12.3% (20s), and 14.0% (30s). SEM/confocal microscopy revealed CDP discs exhibited dissolution associated with the particle surface and SCP from the interior.

Significance: Chlorhexidine spheres incorporated in a dental resin demonstrated a responsive and lower CHX release. Ultrasound enhanced CHX release and is useful in clinical situations where the drug is required on demand to treat severe or persistent infections.