Contact stress between the gear teeth in mesh determines the ability of the gear to transmit the power safely. In improving the contact strength of gear teeth, profile shift is found to be the best option beyond the use of high strength materials and surface treatment techniques. This paper discusses an alternate yet simple method of improving contact strength by the way of altering the tooth-sum. Altering the tooth-sum working between a specified center distances for a given module changes the operating pressure angle and hence necessitates profile shift. Using this profile shift gears can be designed to advantage. Few cases are considered for the purpose of discussion for clear understanding of the presentation. Large volume of monographs are developed which the practicing engineers can use.