Dentine In Our Teeth: Its Fishy Roots
“New research shows that dentine, the inner layer of teeth that transmits sensory information to nerves inside the pulp, first evolved as sensory tissue in the armoured exoskeletons of ancient fish.”
– Matt Wood, University of Chicago
Ancient Fish Sensing Via Dentine In Their Exoskeleton
All life emanated from the sea and thus our link to fish should not come as a big surprise. The dentine assisted the ancient fish in sensing the water conditions around them. The consequences for us is the toothache that some of us can get from eating too cold foods. Dentine’s journey over some half a billion years echoes in the sensory tissue inside our teeth today. Can’t eat ice cream! Blame it on those Ordovician ancient fish.
Our Teeth Brought To You By Fish
“When you think about an early animal like this, swimming around with armour on it, it needs to sense the world. This was a pretty intense predatory environment and being able to sense the properties of the water around them would have been very important,” said Neil Shubin, PhD, Robert R. Bensley Distinguished Service Professor of Organismal Biology and Anatomy at UChicago and senior author of the new study. “So, here we see that invertebrates with armor like horseshoe crabs need to sense the world too, and it just so happens they hit on the same solution.”
– Science Daily
Dentine helped ancient aquamarine creatures survive in their environment. Hundreds of millions of years later, it is helping dentists make plenty of money by promoting the fixing of toothaches. If our teeth weren’t full of sensitive dentine we would not feel the painful need to seek relief at the dental clinic. Life is a strange and funny thing when you pull back and see it from such a panoramic perspective.
The Weird Nature Of Our Teeth
Teeth are funny things in that they are such a mix of hard and soft stuff. The enamel is super hard whilst the dentine is so sensitive and soft. It is akin to putting alive sensory nerves inside drill bits in industrial machines. Our teeth grind and rip food stuffs to aid in the eating process. Meanwhile, they contain this vulnerable substance, which hurts us when cracks and holes in the enamel reveals it. Hard and soft.
The scientists at the University of Chicago were not looking for the origins of teeth – they were looking for the oldest vertebrates on record. The fishy roots of dentine were revealed via the examination of tiny specimens from fossilised records.
“She then took them to Argonne National Laboratory for an all-night scanning session using the Advanced Photon Source, which captured extremely high-resolution CT images of the fossils. “It was a night at the particle accelerator; that was fun,” Haridy said.”
– Yara Haridy, Sam C. P. Norris, Matteo Fabbri, Karma Nanglu, Neelima Sharma, James F. Miller, Mark Rivers, Patrick La Riviere, Phillip Vargas, Javier Ortega-Hernández, Neil H. Shubin. The origin of vertebrate teeth and evolution of sensory exoskeletons. Nature, 2025; DOI
They recognised the chemical signature of dentine in one of the samples Anatolepis. Yara Haridy, PhD researcher at the University of Chicago, reported that teeth can be sensory even when they are not in the mouth. The armour of the fish and arthropods tested showed that. The team scanned modern crabs, snails, beetles, sharks, skates and loads of fossils. Sharks and skates have tooth-like structures called denticles upon their rough skins. The denticles are connected to nerves like our teeth.
“We think that the earliest vertebrates, these big, armoured fish, had very similar structures, at least morphologically. They look the same in ancient and modern arthropods, because they’re all making this mineralised layer that caps their soft tissue and helps them sense the environment,” she said.”
– Yara Haridy, Sam C. P. Norris, Matteo Fabbri, Karma Nanglu, Neelima Sharma, James F. Miller, Mark Rivers, Patrick La Riviere, Phillip Vargas, Javier Ortega-Hernández, Neil H. Shubin. The origin of vertebrate teeth and evolution of sensory exoskeletons
Defensive & Sensitive Capabilities
Dentine puts sensory capabilities into hard surfaces, thus allowing armour to be both defensive and sensitive. This is a pretty handy dual capability to possess, you would have to admit. Kind of like the tough guy with a heart of gold stereotype. Or the strong woman with a big heart cliché. Life demands both qualities or characteristics at different times. So, perhaps, our teeth are not that weird after all or maybe weird and wonderful at the same time. I do know dentists thank their lucky stars for all that dentine every single day of our well remunerated careers. Teeth – cant live with them or without them! The fishy roots of dentine in our teeth has a special story to tell us.
The dentine is formed from the odontoblasts that are present in the outermost layer of the dental pulp. The odontoblasts first form predentin which then matures into dentin. Unlike the enamel, dentin is regenerative and is replaced if it becomes worn out or decayed.
Structure of the Dentin
The dentine is covered by the enamel at the crown of the tooth, the portion that is visible in the mouth. At the root, the dentin is covered by the cementum. The mineral hydroxyapatite makes up around 70% of the dentine, while 20% is organic matter and 10% water. It is yellow and looks much like the tooth enamel. However, since enamel is nearly transparent, it is the dentine that is thought to give colour to the tooth.”
– Medical News
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