Laser-fluorescence assessment of sodium hypochlorite quenching reversal agents on human dentine

Laser-fluorescence diagnostic technology for real-time clinical assessment of residual bacteria could help assist in determining the endpoints for root canal debridement. Sodium hypochlorite (NaOCl) can however quench fluorescence and lead to false low reading. This study aims to evaluate various antioxidant for their ability to recover quenched fluorescence in dentine treated with NaOCl.

Human dentine fluorescence was measured using 655 nm laser at baseline and again after a 2 min application of 4% NaOCl. The putative recovery agents were then applied, and the fluorescence measured after 5, 10, 20, 30 and 60 min. Recovery from quenching was also assessed using laser confocal scanning microscopy (CLSM) with a bound tetracycline fluorophore using 488 nm excitation.

A 5 min application of vitamin E oil or buffered 2% lignocaine solution (1:80,000 adrenaline) was effective in regaining quenched fluorescence within the following 5 mins. Distilled water, sodium thiosulfate, unbuffered 2% lignocaine with 1:80000 adrenaline and phosphate buffered saline were less effective, and of equal performance. Ascorbic acid and butylated hydroxyanisole were not effective and had deleterious effects on the levels of dentine fluorescence. CLSM provided confirmation of recovery from quenched fluorescence using vitamin E oil.

Based on these findings, reversal agents should be employed when assessing the fluorescence of dentine that has been exposed to NaOCl or other quenching agents.