Primary teeth are identified by letter; in contrast to adult teeth, which are identified by number. In the primary dentition, there are 20 teeth:
Primary teeth (also called baby teeth or deciduous teeth) begin to erupt at age 6 months and this process is complete by 24 and 36 months. There is considerable variation of eruption patterns and the sequence of eruption is more important than the absolute dates.
There is rarely need to be concerned about lack of eruption unless there is evidence of a syndrome or developmental issues; or if no teeth have erupted by 18 months of age, then a dental consult would be reasonable.