Answer and Explanation:
Dolphins are homodont. This means that all their teeth are all equal. They do not differentiate between each other as the human´s teeth or other mammal´s teeth.
Dolphins have different feeding strategies according to the species. They might be suction feeders, or they might catch their prey using the jow and mandible occlusion strenth.
Dolphins that catch their prey by using their jow and mandible do not chew, so they use teeth mostly to catch their prey and manipulate them before swallowing them. This is why they do not need differentiated teeth. Because they just use them to catch and manipulate.
Those dolphin species that are suction feeders do not need teeth to catch their prey because they just suck them. Most of these species only have a few teeth, mostly in their jows. These teeth are used for fighting with other individuals. Inter- and intra-specific fights among animals of the same gender and age are very common. It is believed that as these species do not need teeth for catching their prey, they evolved loosing most of them but those needed during confrontations. This is the case of Grampus griseus, Risso´s Dolphin, that only have 5 to 7 teeth in their jows.