Quantifying Changes in Tooth Luster Using Optical Coherence Tomography

OBJECTIVE: While tooth whitening has been substantiated in a number of studies, changes in luster have been more difficult to document.  The aim of this preliminary study was to measure the loss of tooth luster associated with tray whitening procedures using Optical Coherence Tomography (OCT).  Methods: Panelists (N=10) with intact anterior dentitions, applied a commercially available tray whiting gel 30 minutes daily for two weeks. Tooth brightness was assessed at baseline and at the conclusion of 2 weeks of whitening treatment using standard vita tooth shade guide (VTSG) comparisons.  Reflectivity of the labial enamel surface was measured at baseline and following the whitening procedure using a fiberoptic OCT system with a 1325nm light source having an axial resolution of 21µm.  OCT measurements were made at the enamel surface on a longitudinal axis at mid-facial and mid-incisal surface of the central incisors. Results:  Vital tooth whitening using H₂O₂ gels delivered in a custom fitted tray have proved to improve the aesthetics of teeth by significantly increasing brightness as measured by VTSG comparisons.  Friedman's test for repeated measures revealed brightness ranking increased from a mean of rank of 1.5 at baseline to 3.5 at two weeks (p<0.000). Subjects demonstrated up to a 26% reduction in surface enamel reflectivity as measured by OCT, following whitening procedures.  Analysis of variance revealed that changes in enamel luster at the mid-facial were significant (p<0.003), while changes at the incisal edge were more difficult to substantiate (p<0.18).  Conclusions: Based on these preliminary data, OCT technology shows promise for quantifying changes in enamel reflectivity that accompanies vital tooth whitening procedures.  It is established that concurrent with the increase in brightness using tray whitening procedures, there is a measurable decrease in enamel luster which over time, returns to baseline levels. (Grant Support: Colgate Palmolive Company)