The aim of the present study was to evaluate the association of hand preference of dentists and the position of dental chairs in treatment of dental calculus. The dentists were last-class students from the School of Dentistry (Erzurum, Turkey). They were directed to dental chairs designed for right- and left-handers (right- sided and left-sided chairs) to remove calculus from the lower anterior teeth in volunteer patients having similar amounts of calculus, which was measured by Calculus index (CI). The right-handed dentists were more successful in right-sided (traditional) chairs than left-sided chairs; the left-handed dentists were more successful on left-sided chairs than right- sided chairs. The highest posttreatment CI (lowest success) was due to the right- handed dentists on the left-sided chairs. The lowest posttreatment CI (highest success) belonged to the left-handers working on the left-sided chairs. The left-handed dentists were better than right-handed dentists in the treatment of the mesial and distal surfaces of teeth, whereas the right-handers were successful only in the treatment of the distal parts of teeth. These results were explained by a better coordination between right and left hands and with higher skill in both hands in left-handers than right-handers.