Final answer:
The maxillary and mandibular first primary molars typically have four cusps. These first molars appear during early childhood and are crucial for proper chewing and maintaining space within the jaw for the development of permanent teeth later on.
Step-by-step explanation:
The facial surface of the maxillary and mandibular first primary molars generally have four cusps. These teeth appear in childhood typically between 12-16 months of age and are part of the deciduous dentition, also known as baby teeth. When considering the arrangement of the teeth, it is important to note that the morphology of primary molars is somewhat different from their permanent counterparts, which can include up to five cusps. Primary molars are important for maintaining space for their permanent successors and are necessary for proper chewing and digestion in young children.
While premolars and molars in permanent dentition serve as crucial tools in mastication with varying numbers of cusps, the first primary molars do not usually possess five cusps or more as could sometimes be seen in permanent molars. Their structure is simpler to accommodate the developing oral cavity of a child. The final answer for the number of cusps on the facial surface of maxillary and mandibular first primary molars is four cusps.