Humans develop two sets of teeth: 20 primary (deciduous) teeth and 32 permanent teeth. The transition from smaller primary teeth to larger permanent teeth often causes confusion about which teeth are temporary. Many people are uncertain about the molars, the large grinding teeth at the back of the mouth, and whether the first ones to appear are baby teeth that will eventually fall out.
The Permanent Status of First Molars
The teeth known as the first molars, commonly called the “6-year molars,” are permanent teeth that are never replaced. There are four of these teeth—two on the top arch and two on the bottom arch—and they are the earliest permanent teeth to appear. Unlike permanent front teeth, these molars do not replace any existing primary teeth. They emerge in a new space created by the lengthening of the jawbone, erupting at the very back of the mouth, behind the last primary molars. The lack of a preceding loose tooth often leads people to mistakenly believe these are temporary teeth.
The Eruption Timeline and Why the Confusion Exists
These permanent molars typically break through the gums between the ages of five and seven, earning them the nickname “6-year molars.” This eruption occurs while the child still has a full set of primary teeth in the front of their mouth. The first baby teeth to fall out are usually the lower central incisors, which often happens after the first permanent molars have already appeared in the back.
The timing creates misunderstanding because parents expect the loss of a baby tooth to signal the arrival of a permanent tooth. When a large molar appears without any tooth being shed first, parents often assume it is temporary. This new tooth adds to the total count, increasing the number of teeth from 20 to 24. This phase, where a child has a mixture of primary and permanent teeth, is known as the mixed dentition period.
The Role of First Molars in Oral Development
The first permanent molars hold a special position in the alignment and function of the jaw structure. They are often described as the foundation of the bite. These large teeth are the first to interlock the upper and lower jaws into their correct relationship, known as occlusion.
The surfaces of these molars are designed with broad cusps and deep grooves to withstand heavy forces and effectively grind food during chewing. They help establish the vertical dimension of the face and guide the positions of all the other permanent teeth that follow. Maintaining the integrity of these four teeth is important for the long-term health and stability of the dental arch. If a first molar is lost prematurely, it can cause the teeth in front of it to drift backward, leading to spacing and alignment issues.
Protecting These Foundation Teeth
Because first permanent molars erupt early and must last a lifetime, they are vulnerable to decay. Their chewing surfaces contain deep depressions, known as pits and fissures, which are often narrower than a single toothbrush bristle. This complex anatomy makes it difficult to clean away food particles and acid-producing bacteria effectively, even with diligent brushing.
One of the most effective preventive measures available is the application of dental sealants. A sealant is a thin, liquid resin material painted directly onto the chewing surface of the molar. It flows into the deep grooves and hardens to create a smooth, protective layer that seals out bacteria and food debris. Sealants can reduce the risk of decay in the molars by as much as 80% and are recommended shortly after the teeth fully erupt.
Parents should also ensure that the proper brushing technique is used for these newly emerged back teeth. Since they are located far back in the mouth, they are often missed during routine brushing. The child should use a soft-bristled toothbrush and a pea-sized amount of fluoride toothpaste, taking care to scrub the tops of these molars with a back-and-forth motion. It is advised to supervise brushing until at least age seven or eight to ensure these permanent teeth receive the attention they need.