Humans are not born with a full set of adult teeth. Tooth development is a complex, gradual process beginning before birth and continuing through childhood and adolescence. This process ensures appropriate teeth for changing developmental needs.
Teeth Before Birth and Early Childhood
The foundation for both primary and permanent teeth is established within the jawbones before birth. Primary, or baby, teeth begin forming as early as six to eight weeks into prenatal development. By birth, the crowns of all 20 primary teeth are nearly fully formed beneath the gums.
The eruption of primary teeth typically starts around six months of age, with lower central incisors often appearing first. Most children have a complete set of 20 primary teeth by two and a half to three years. These teeth are essential for chewing and digesting food, facilitating clear speech, and maintaining space for permanent teeth.
The Journey to Permanent Teeth
Permanent, or adult, teeth begin developing around the 20th week of prenatal development, while primary teeth are still present. They form beneath the primary teeth, growing and preparing for eruption. Around age six, primary tooth roots resorb, causing them to fall out.
This transition, known as mixed dentition, involves both primary and permanent teeth, typically from age six to twelve years. The first permanent molars often emerge behind the primary teeth, usually between six and seven, without replacing any baby teeth. Other permanent teeth then replace primary teeth as they are lost.
Most individuals have 28 permanent teeth by age 12 to 14, excluding the third molars, commonly known as wisdom teeth. These typically erupt later, between ages 17 and 21. A full set of adult dentition, including wisdom teeth, consists of 32 teeth.
The Purpose of Two Sets of Teeth
Humans develop two sets of teeth due to significant jaw growth and changing dietary needs from infancy to adulthood. A newborn’s jaw is smaller and cannot accommodate larger, stronger adult teeth. Primary teeth are smaller, suited for a child’s mouth and initial soft diet.
Unlike bones, teeth do not grow in size once formed. As a child’s jaw expands, it creates space for larger teeth. This permanent set is designed to withstand the forces of chewing a varied adult diet and to function for a lifetime.