The presence of clinically detectable areas of decalcification (observable as whitened areas) following the removal of orthodontic appliances is well recognized. The aim of the present study was to determine quantitatively the amount of demineralization and the ability of commercially available products to inhibit or reverse orthodontically related demineralization. Twenty orthodontic patients scheduled to have premolars extracted were randomly divided into four groups--one control and three test groups. The extracted premolars (numbering 58) were bracketed using an acid-etch composite system; each patient was given precise oral hygiene instructions and supplied with a sodium fluoride (1,100 ppm fluoride) dentifrice and an orthodontic toothbrush. The control group brushed only with the supplied dentifrice. In addition to brushing with the dentifrice, those in test group I rinsed once each night with a sodium fluoride (0.05%) mouthrinse; group II received a weekly topical APF treatment (1.2% fluoride); and Group III received a weekly topical APF treatment and rinsed once each night with the sodium fluoride mouthrinse. All premolars were extracted after 1 calendar month. Mineral profiles were determined on cross-sectioned teeth 50 to 75 micron occlusal and cervical to the brackets, directly underneath the brackets, and 500 micron away from the brackets. The control teeth (dentifrice only) demonstrated up to 15% demineralization to a depth of 50 micron. All of the test teeth produced rehardening and/or inhibition of demineralization (P less than 0.01). Those in test group III showed a particularly hard outer layer. The study demonstrated that measurable demineralization occurred around orthodontic appliances after only 1 month and this demineralization can be completely inhibited and/or reversed by the use of commercially available fluoride products.