Effect of Different Bleaching Gels Thickeners on Cytotoxicity to Human Gingival Fibroblasts and Enamel Physical Properties: an in Situ Study.

Objective: This study evaluated in vitro, the effects of carbamide peroxide 10% (CP) associated with Carbopol® (CP-ct) and Aristoflex® (CP-at) thickeners on human gingival fibroblasts (HGF) cytotoxicity and assessed in situ their effects on dental enamel.

Material and methods: The cytotoxicity was analyzed using MTT - Vybrant® proliferation test. For in situ stage, 144 bovine enamel/dentin blocks were randomized into seven groups (n=12). Samples were stained, fixed in intraoral palatal devices and bleached for 4 h, during 14 days, with: Carbopol thickener (ct), Aristoflex thickener (at), CP-ct, CP-at, CP without thickener (CP-wot), Commercial CP (CP-com). The samples had their microhardness (SMH), roughness (Ra) and color analyzed using a microdurometer, a rugosimeter and a spectrophotometer, respectively. The analyses were performed at baseline and 24-h after completion of tooth bleaching.

Results: Different thickeners were similar regarding their cytotoxicity. The experimental gels with Carbopol exhibited lower SMH values, while the groups treated with CP exhibited higher Ra values. For the color change results, the groups treated with CP had values above the acceptability and perceptibility limits.

Conclusion: CP-at was able to promote an effective bleaching with less alterations of the tooth surface compared to the CP-ct. Hence, Aristoflex stands as a promising thickener in conjunction with CP in order to preserve the physical properties of dental enamel after home bleaching.