I definitely agree with Jordan. The first step is really to differentiate yourself from the competition. If you want to learn more about it, look around for stuff about USP's (unique selling proposition, or sometimes known as unique sales proposition).
One other thing to remember is that people don't buy your product, people are buying what your product does. The common example is that people aren't buying a drill, they are buying the hole that you make with the drill. In your case it would be that they are buying clean teeth, and you may be able to extend that to fresh breath and cavity protection ... especially if your toothbrush does something that other toothbrushes don't (again, differentiating yourself).
It helps to dig down into niches too. If you're marketing to everyone, you're not marketing to anyone. Do you have different types of toothbrushes? Do you have a toothbrush for little kids? How about a toothbrush for little boys that play soccer? Or how about a toothbrush for CEO's that are obsessed with golf? People are much more likely to buy something if they feel that it's been made just for them, rather than buying a generic commodity.
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