Do all human teeth fall out?

No, not all human teeth fall out. Humans have two sets of teeth: primary teeth, or "baby teeth," and permanent teeth. Primary teeth start to come in when a baby is about 6 months old and are mostly in place by age 3. Permanent teeth begin to erupt around age 6 and gradually replace the primary teeth. There are 20 primary teeth and 32 permanent teeth. The last permanent teeth come in around age 12 to 18. Once the permanent teeth erupt, they should last a lifetime with proper care.