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IntrOductIOnBonding is the most sensitive procedure during orthodontic treatment. The presence of moisture in the oral cavity is the most common cause for bond failure. Contamination causes plugging of the porosities which are produced by acid etching and this reduces the surface energy. As the resin penetration is impaired it leads to poor mechanical interlocking [1]. The detrimental effect of moisture on orthodontic bonding could be due to induction of the plasticizing effect in the polymer network caused by water absorption. The latter creates hydrated zones at the polar monomer sites and the oxidation of pendant C=C bonds attached to the network, which liberate by-products such as formaldehyde so producing a plasticizing effect [2]. Bonding of brackets requires a completely dry field of operation and involves a series of technique sensitive steps, as contamination during this period leads to bond failure. The aim of this study was, therefore, to evaluate the role of mineral content (hardness) of the water used for washing the etchant on the bond strength of the brackets. The null hypothesis tested was that there are no significant differences in bond strength when different levels of hardness of water are used for washing the etched surface. MAterIAls And MethOdsThe present study was conducted in 2014 in the Department of Orthodontics, School of Dental Sciences, Krishna institute of medical sciences deemed university, karad. Seventy five human extracted premolars were collected which were extracted for orthodontic reasons. As per the selection criteria, the teeth had to be intact and free from restorations, caries, or previous surface treatment by acid. The teeth were divided in three groups of 25 each and mounted in an acrylic mould [Table/ Fig-1] with cold cure acrylic. Non fluoridated prophylactic paste and rubber cups were used to clean the surfaces of all the teeth for 20 seconds to simulate recent cleaning [3]. The surface of each tooth was etched using 37% phosphoric acid (Transbond XT, 3M UNITEK). The etchant in group I was cleaned using distilled water (soft, 14.7ppm), group II with corporation water (moderately hard, 93.2ppm) and Group III with very hard water (216ppm) respectively. The hardness of water was measured with TDS machine (HM Digital, Inc). The samples of water were divided based on the hardness as classified by the U.S. Department of Interior and the Water Quality Association [Table/ Fig-2]. Later, orthodontic brackets (RothP/1 st and 2 nd premolar S/DSlot 0.18"; monalisa, JJ orthodontics, kerala, India) were bonded to the flattest surface of each tooth. The bond strength was measured in an Instron universal testing machine [Table /Fig-3]. The machine cross head speed was set at 1.0 mm/min, the recording speed was maintained at 20 mm/min, and the scale was set at 50 kg [4]. The force needed to disrupt the orthodontic bracket bond was verified for each sample [ ABstrActBackground: Bonding is a very important step in the ortho dontic treatment planning. Effective bonding enhances the tr...