Cytotoxicity of agents proposed for decontamination of implant surfaces

Objectives: Various chemical agents have been proposed for decontamination of implant surfaces in periimplantitis. This study used cell culture to investigate the cytotoxicity of agents over various time periods. Agents tested were chlorhexidine mouthwash (CMW,Corsodyl, 0.2% GSK,UK), citric acid (CA), phosphoric acid (PA) and oxytetracycline (Ox). Methods: Confluent 1x10⁴ Human Osteosarcoma cells (HOS) were placed into each well of 4 96 well plates. Various concentrations of the agents above were made up to 100 µl with HOS cell media. Positive (10% alcohol) and negative (media alone) controls were prepared. Plates were incubated at 37°C with 5% CO2 for 2min, 5min, 10min or 1hr. Elutions were removed and 100µl of Thiazoly Blue Tetrazolium Bromide and Dulbecco's Modified Eagle's Medium without ascorbic acid added. Plates were incubated for 4hrs. The medium was removed and 100µl dimethylsulphoxide added. Absorbance at 570nm was read. Results: Exposure to 10% alcohol had a limited effect on cellular survival. In contrast, exposure to all concentrations of PA (5 to 35%) caused complete cytotoxicity. Repeated measures ANOVA indicated that for each time point, there were significant differences between dilutions for CMW (1 in 16 dilution to 1 in 128) and for CA (10M (saturated, 1%) to 2.75mM) for cytotoxicity (p<0.001). Exposure time caused significant changes in cell survival at each dilution of Ox (p<0.017), but there were not consistent effects of variation in agent dilution at each time period. For citric acid treatments, cytotoxicity was significantly different between exposures at 500mM and 50mM, and between 50 and 2.75mM, at all time periods (p<0.0001 and p<0.053 respectively). Conclusions: Cytotoxicity of agents proposed for the decontamination of implant surfaces in periimplantitis is variable. Assessed by this method, PA is highly cytotoxic, whereas Ox has limited cytotoxicity and the effects of CMW and CA are influenced by concentration and exposure time.