This study evaluated the resistance of the enamel to an artificial caries challenge after removing orthodontic bands cemented with a glass ionomer cement (GIC). Ten extracted caries-free molars were cleaned with a slurry of pumice and randomly divided into 2 groups of 5 teeth each: Group 1: Cementation with GIC (Fuji) and Group 2: Cementation with a zinc phosphate cement (Mizzy). Both cements were handled according to manufacturer's instructions. Before cementing the bands, an area of S x S mm was masked with adhesive tape on the lingual surfaces of all teeth. The orthodontic bands were cemented over this adhesive tape. After band cementation, the occlusal and gingival margins of the band were delineated with a bur on the tooth surface. The teeth were thermocycled (200 cycles, 5-55 degrees C, 30-second dwell time) and stored in distilled water for 24 hours. Then, the bands and adhesive tape were removed and the teeth again stored in distilled water for a week, changing the water daily. The teeth were then varnished with the exception of a 5 x 5 mm window (including previously exposed and covered areas) on the buccal and lingual surfaces. All teeth were then placed in an acidified gel (pH 4.5) for 5 weeks to produce artificial caries. At least three sections from the exposed and covered areas were made from the buccal and lingual challenged areas. Sections were ground to approximately 100 microns. Polarized microscopy and image analysis were used to analyze the results.(ABSTRACT TRUNCATED AT 250 WORDS)