The first, known as primary dentition stage, occurs when only primary teeth are visible. Once the first permanent tooth erupts into the mouth, the teeth that are visible are in the mixed (or transitional) dentition stage.
In the early stages of dental growth, only primary teeth are present, marking the beginning of the primary dentition stage. As the first permanent tooth breaks through the gum, the visible teeth enter a transitional phase, known as the mixed dentition stage.