Methods: Sixteen extracted bovine teeth were used in the staining experiment. The roots of the teeth were sectioned off and access cavities were created via the lingual surface and root canals of these teeth. The cleaned and pumiced labial surfaces of the teeth were coated with acid resistant clear nail varnish and left to air dry for 24 hours. The teeth were attached to lengths of cotton and suspended in pots containing 30 ml of tea solution. The teeth were left in the tea solution and gently stirred for six days with the solution changed daily. Stain development was monitored daily with QLF™ (Inspektor Research systems BV, NL) and Spectrophotometer (Easy shade®, Vita Zahnfabrik H.Rauter GmbH & Co.KG, Germany). The readings were taken at baseline and once daily. Mean DE and DF values with standard errors were obtained. The stain values (DF from QLF and DE from the spectrophotometer) for the progression of stain intensity observed by the two methods were tested for correlation using Pearson's correlation coefficient.
Results: QLF showed a high correlation with spectrophotometry for detecting and monitoring intrinsic tooth stain progression The Pearson coefficient r was -0.987 (R2=97.4%) with correlation significant at 0.01 level. There was a reverse correlation between DE and DF as staining progressed.
Conclusion: The ability of both methods to monitor the progression of intrinsic staining development longitudinally was demonstrated. It is envisaged that QLF will be applicable and useful for monitoring stain in vivo