A recent study said that enamel samples treated with orange juice for 20 minutes over 5 cycles (to simulate daily exposure over 5 days) had a 64% decrease in microhardness versus no statistically significant changes in samples treated with 6% hydrogen peroxide (a component of many whitening packages).
Source: Ren Y et al, Effects of Tooth Whitening and Orange Juice on Surface Properties of Dental Enamel, Journal of Dentistry, June 2009, Vol 37, No 6, pg 424-431
Hans Skariah, B.Sc., DMD
Promenade Court Dental Health Group in Mississauga
2233 Hurontario St., Mississauga, ON, Canada
(1/2 km north of the QEW in the Dome Building)