There are some sources that are now telling us that dandelions are really beneficial for your lawn because the do root deeply and bring up nutrients that grasses need but cannot reach because they are too deep in the soil, beyond where the grasses roots are. Contrary to what those that sell the poisons tell you eliminating dandelions, or other "weeds", is not going to happen and we are polluting our world trying to eliminate them.
Meadows, upon which our lawns are based, are not the monocultures we have made out lawns that are now susceptible to insect pests and plant diseases that are kept under control in those meadows.
Expend much less time, energy, and money and just keep you dandelions cut, especially the flowers, and don't get overly paranoid about them.