LAB Medicine - file 03
Why are we born without Teeth? – Natal Teeth
As you know, our teeth bite off food, cutting it into pieces, and grinding it for digestion. As it's impossible to swallow a whole apple as it is, like a snake, our teeth play the most important role in taking food into our bodies.
But do you know anything else about your teeth?
Our teeth break down food into smaller pieces, allowing the tongue and oropharynx to shape it into a bolus for swallowing, facilitating digestion. In anatomy and biology, the function of chewing is called Mastication.
Our teeth also work besides biting and chewing:
● Speech production
Teeth are vital for articulating sounds for speech, particularly consonants, by shaping various airflows and acting as a barrier for the tongue.
● Facial support
Teeth provide a solid structure to form our faces, supporting the cheeks and lips to prevent premature facial sagging. Good-conditioned teeth look entirely healthy!
Are Teeth Bones?
Our teeth look like a bone, but actually are NOT part of the skeletal system. Teeth are classified as part of the digestive system!
● Bones are a living tissue that constantly break down and rebuild themselves. So, if accidentally broken, a bone can heal over time.
But teeth can NOT heal or regenerate themselves. So, if teeth have been chipped or decayed, they require dental treatment.
● Bones are made of collagen, which gives them a flexible framework.
But teeth are composed of enamel, which is the hardest substance in the human body, dentin, cementum, and pulp. So teeth lack flexibility and the ability to regenerate.
● Bones contain marrow, which produces blood cells.
But teeth do NOT contain marrow.
Why are we born without Teeth?
Despite teeth being very important for taking food into our bodies, Why are we born without teeth? If we were born with the whole set of teeth, it would be more convenient to eat food, wouldn't it?
Having said that, the most important true fact is that we humans are NOT actually born without teeth! We are simply born without erupted teeth.
Children typically have 20 deciduous teeth (or primary teeth). Adults generally have 32 permanent teeth, which include 4 third molars (or wisdom teeth).
Deciduous (primary) teeth consist of 8 incisors, 4 canine teeth, and 8 primary molars.
Permanent teeth include 8 incisors, 4 canine teeth, 8 premolars, and 12 permanent molars. Accordingly, adults generally get 8 more premolars and 4 more third molars (or wisdom teeth) as permanent molars than in childhood.
In addition, in terms of anatomy, our 4 canine teeth are designed to be pointy and sharp, referred to as fangs in animals. Ours are also very fangs.
Canine teeth are specifically adapted for tearing off food, and also act as weapons or tools for intimidation and mating. While our canine teeth are shorter than animal fangs, they serve the absolutely same functional purpose.
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| Deciduous teeth (left) and permanent teeth (right) (source: Spadental) |
As for infants, the buds for ALL 20 primary teeth (or deciduous teeth), and even the starting points for permanent teeth, are already tucked away inside the jawbones at birth.
In medical and dental terms, the state of being toothless is called ‘edentulous’. In the case of infants, it's specifically called ‘physiologically edentulous’ to distinguish them from adults who have unfortunately lost teeth due to age or accidental injury.
So, correctly speaking, infants are physiologically edentulous, and their teeth actually stay hidden for the first few months.
● The Mechanics of Breastfeeding
From an evolutionary perspective, the primary reason why our teeth are hidden is for the survival of the nursing relationship. Humans are mammals, and our infants rely entirely on milk for the first several months of life.
If infants were born with a full set of sharp incisors, as we can easily imagine, it would make breastfeeding extremely painful and still more dangerous for the mother.
By delaying tooth eruption, nature ensures a peaceful nursing period that allows the infant to get the nutrients needed for rapid brain growth without injuring the mother’s nipples.
● Jaw Growth and Spacing
An infant's jaw is initially tiny. If the teeth were to erupt at birth, there simply would NOT be enough room for the teeth to align properly.
Teeth are rigid and made of the hardest substance in the human body, enamel. Unlike skin or bone, teeth can NOT expand or grow once they have formed.
The jawbone needs several months of rapid growth to create enough foundations so that when the teeth finally emerge, they have the proper place to sit. It's impossible to rearrange later as the jawbone grows.
● The Soft Food Phase
In the view of evolution, teeth are expensive for the body to produce and maintain. Since infants lack the digestive enzymes and the motor skills of the digestive system to process solid food for the first six months, having teeth would be a metabolic waste of energy.
Until weaning, solid foods are still inappropriate for infants. Our body initially prioritizes building the brain, the immune system, and the skeleton first.
● Craniofacial Development
Our skull undergoes a massive amount of shifting and molding during birth to fit through the birth canal. If an infant had rigid, erupted teeth embedded in a still-hardening jawbone, it could be highly dangerous, leading to structural damage to the infant's mouth or the mother's birth canal during delivery.
Keeping the teeth submerged is reasonable to protect both the infant and the mother from unnecessary birth injuries.
Babies born with Teeth — Natal Teeth
Nevertheless, 1 in 2,000–3,000 newborns is born with teeth. This case is called Natal Teeth.
Natal teeth often appear in a pair of incisors on the lower gum. These natal teeth are usually premature deciduous (primary) teeth rather than extra teeth.
While it would often be harmless, natal teeth might be removed if in a case loose on the still hardening jawbone to prevent a risk of choking or swallowing.
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| Natal teeth (source: Pandit Clinic) |
As you can see above, the appearance of natal teeth is usually small, a little yellowish or brownish, with weak or absent roots.
The common location of natal teeth is said to appear most often as a pair of lower front incisors.
The potential complications of natal teeth include breastfeeding difficulties by biting, damage to the baby’s tongue, so-called Riga-Fede disease (RFD), and potential risks of inhaling or swallowing a fallen loose tooth.
Why do the Natal Teeth happen?
Natal teeth are rare, occurring in roughly 1 baby in 2,000–3,000 births.
While the exact cause is said to be unknown, natal teeth could be primarily linked to the superficial position of the tooth germ, heredity, endocrine disturbances, etc.
Natal teeth are said to be rarely associated with genetic syndromes, like Sotos syndrome, Hallermann-Streiff syndrome (HSS), or Ellis-van Creveld syndrome (EVC).
If a baby is born with teeth, I strongly recommend that, first of all, they should be examined and evaluated by a pediatrician or pediatric dentist to determine the best course of action properly.
Supernumerary Teeth (ST)
On the other hand, at most 1 in 30–40 people have more extra teeth.
Supernumerary teeth(ST), also called hyperdontia, refer to the condition of having extra teeth beyond the normal set of 20 deciduous teeth for children or 28–32 permanent teeth for adults.
Supernumerary teeth are said to affect around 0.1%–3.8% of people, varying by study. Caused by hyperactivity of the dental lamina, supernumerary teeth could often cause overcrowding, impaction, or damage to adjacent teeth.
Furthermore, supernumerary teeth can be more commonly seen in permanent teeth than deciduous (primary) teeth, and are twice as likely to affect males compared to females.
In general, supernumerary teeth can be 2 types:
● Supplemental type — The extra teeth resemble normal teeth.
● Rudimentary type — The extra teeth are undeveloped, small, peg-shaped, or conical.
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| Supernumerary teeth via X-ray (source: The Open Dentistry Journal) |
Supernumerary teeth are commonly seen in the maxilla (the upper jawbone), especially between the two top front teeth. This case is specifically called Mesiodens.
Mesiodens is a supernumerary tooth present in the midline between the two central incisors. The possible prevalence of mesiodens varies between 0.09% and 2.05% of people by study.
The cases of mesiodens could result in some oral problems, such as malocclusion, food impaction, and cyst formation.
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| Mesiodens via X-ray |
In cases of supernumerary teeth, extra teeth could block normal teeth and delay the eruption from coming out. Besides, extra teeth could cause crowding with adjacent normal teeth to turn away, or misalignment, overlapping each other.
Or, cysts could occasionally form around impacted, unerupted extra teeth. Although supernumerary teeth themselves could often be asymptomatic, as we saw, they could cause crowding, misalignment, pain, discomfort, or cyst formation.
Why does the Supernumerary Teeth (ST) happen?
Supernumerary teeth, or hyperdontia, are said to be caused by hyperactivity of the dental lamina, in which excessive, independent tooth buds form during development.
While the exact cause is NOT fully understood yet, the main possible factors could include hereditary genetics, developmental syndromes, such as Gardner syndrome and cleidocranial dysplasia (CCD), besides environmental factors, such as cleft lip or cleft palate.
You may be surprised that the prevalence of supernumerary teeth, 1 in 30–40 people, is quite frequent. But actually, in most cases of supernumerary teeth, the extra teeth could be impacted, that is, buried within the jawbone.
Accordingly, in most cases, the extra teeth couldn't be seen and might be discovered via dental X-ray inspection for the first time. In cases, supernumerary teeth could be typically treated by surgical removal or orthodontics to remove the interferences around extra teeth.
Fortunately, teeth grow very slowly, and supernumerary teeth could be often asymptomatic.
Having said that, if you have noticed discomfort or symptoms, I strongly recommend asking a dentist for medical consultations and diagnosis via dental X-ray inspection.
With early detection, the prognosis of supernumerary teeth is said to be excellent. Early surgical removal of extra teeth could allow normal teeth to erupt normally as they should, and the professional treatments, including orthodontics, could correct crowding and misalignment.
Further reading (sponsored by Amazon):
● Peter S. Ungar (2014). Teeth: A Very Short Introduction. 194 pages. Oxford University Press.
(sponsored by Amazon)
Teeth are amazing - the product of half a billion years of evolution…
In “Teeth: A Very Short Introduction,” Peter S. Ungar, a leading scientist, presents the story of teeth! In “Teeth: A Very Short Introduction,” Ungar outlines the key concepts, including insights into the origin of teeth and their evolution. Considering why teeth are important, “Teeth: A Very Short Introduction” describes how they are made, and how they work, including their fundamental importance in the fossil record.
Table of Contents
List of illustrations
1: Teeth matter
2: Types and parts of teeth
3: What teeth do: food and feeding
4: Teeth before the mammals
5: The evolution of teeth in mammals
6: Mammalian teeth today
7: Human teeth and their history
8: Endless forms
Further reading
Index
