Hardness Tests Humans 4 hardness 4 human 4 surface property 4 Dental Enamel 3 In Vitro Techniques 3 Microscopy, Electron, Scanning 3 Surface Properties 3 enamel 3 in vitro study 3 scanning electron microscopy 3 Hardness 2 Spectrometry, X-Ray Emission 2 comparative study 2 demineralization 2 drug effect 2 procedures 2 spectroscopy 2 Acetic Acid 1 Adolescent 1 Air Abrasion, Dental 1 Article 1 Bicuspid 1 Bifluorid 12 1 Bioglass 1 Bone and Bones 1 Calcium Fluoride 1 Cariostatic Agents 1 Carnoy solution 1