We take it for granted that when our tooth aches
We can get it fixed even if it's scary
or costs a lot of money
But did you know there was a time that fillings
would just fall out of your mouth
days after seeing your dentist?
But thanks to better engineering
fillings became inexpensive and reliable
by creating structures so they could stay in place
and not break when you bite on them
These older silver fillings are still used today
and have successfully repaired billions of teeth
But now
people want white fillings
but you can’t just stick them in
Otherwise they’ll start leaking
It took researchers 25 years of failed attempts
before figuring it out and dentists are still
struggling today to do this well
I promise you
the science is fascinating
I’m Andrew and let’s uncover the
hidden engineering behind great dentistry
This video is sponsored by Masterworks
more on them later
90% of people have had a cavity
and you're likely one of them
These are caused by acid-releasing bacteria
that demineralize your teeth
eventually creating a small hole that
becomes larger and more painful
Before modern dentistry
there were only rudimentary techniques and tools
to try to fix cavities
and any repairs would often fail quickly
This changed when the genius GV Black
made three improvements in 1895
that forever improved dentistry
At that time gold fillings were often used
and pounded in layer by layer
which was slow and expensive
GV Black’s solution was to
invent a long-lasting filling
made of mercury and other metals
called an amalgam
that starts as a paste when mixed together
and can easily be placed and sculpted
into the final shape
Minutes later these would turn rock-hard
These were far faster and cheaper than gold
which made dentistry available to more people
The problem is amalgam will fall out of place
if not held in as it's just a lump of metal
GV Black solved that by creating a system of
structures called retention and resistance forms
Retentive structures wedge the amalgam in place
as its jigsaw puzzle shape keeps the filling
from being sucked out of a tooth
These basic shapes are still used today and
overtime more complex additions were created
such as locks, slots, and coves which help in
holding larger restorations
These weren’t possible in GV Black's time
as many dentists only had hand tools
like axes, hoes, and chisels
which created large boxy preparations
but overtime it shrank
as faster and more precise tools were created
like powered handpieces
Dentists also started using different drills bits
such as the pear-shaped bur
as its curves makes the preparation step far easier
as it automatically carves the retentive angles needed
and rounds the corners
to prevent it from cracking as easily
It's the same reason airplane windows are always round
as square windows caused a number of accidents
when cracks kept forming at the corners
GV also created resistance structures like flat floors
to evenly distribute forces when biting down
If it's rounded it can rotate push up against a cusp
and shear it off over time
When cutting these structures
Dentists have to be aware of the tooth's anatomy
They will often drill past the hard enamel surface
and go down to the softer dentin
but they need to avoid touching the pulp
which is filled with nerves and blood
and with its raised horns
can make figuring out when to stop a challenge
If it’s successfully done
the tooth is ready to accept the amalgam filling
This now comes inside a capsule
and shaken by a machine
which is like a paint mixer to combine it
and then applied to tooth and shaped with different tools
most importantly the margins
where the tooth and amalgam meet
are completely sealed
to prevent bacteria from getting in
If amalgam is applied between teeth
a shaping tool called a matrix band
is tightened around the tooth with a wedge placed to create a good
seal against the curves
This helps your dentist create the right shape
which is critical to prevent food from being stuck
and causing a cavity
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Getting back to Amalgam
they’re widely used today
as it’s its durable, reliable
and easy to put in
which is great for less controlled conditions
like public health clinics
Unfortunately there are many drawbacks
including the health concerns of mercury
While studies show amalgam’s impact
is likely below being toxic
zero use would be best
As well removed amalgam fillings
are a major source of mercury pollution in water
but this should get better as many countries
require separators that spin out the mercury
and have signed the Minamata convention
which removes mercury from general use
Finally, amalgam doesn’t restore the tooth’s strength
which can cause long-term instability
that can fracture a tooth
To learn why
we need to look at modern white fillings
and see how they fixed that issue
While there are several white fillings types
the rest of this video will focus on resin composites
which are the most common
most durable, and beautiful filling
That’s important
as these are often used on visible biting areas
It's made of a hard filler material like quartz
suspended in a gel-like resin
This starts as a paste
that’s squirted onto your tooth
sculpted with tools
and a strong light then cures it rock hard.
Unlike amalgam
these resin composite fillings require
a special adhesive layer applied beforehand
to hold the composite to the tooth
This is a challenging, multi-step process
and the star of the show
even though few people know about it
Small mistakes here can greatly reduce
the adhesive’s bonding strength
causing it to detach which can let in bacteria
and cause a second cavity
The problem is not all dentists do this well
In one study they brought in 30
and made them use different adhesives
and they calculated the bond strengths using a special machine
They found a huge variation from terrible
to those with double the strength
versus the average
even with dentists familiar with a product
That means your dentist’s skill
can add or remove years off the life of your filling
on something you likely
didn’t know existed before now.
But let's switch gears so I can tell you why
white fillings not only look better
but can save your teeth from cracking in half
That starts with greatly reducing
how much tooth is removed for the same cavity
as you can rely on the adhesive to hold it together
instead of retention and resistance structures
That's important as your tooth
is like this teacup holding up a Tesla
It relies on its shape to create incredible strength
The more a tooth is cut
the more unstable it gets when you bite down
as one study showed
Dr Graeme Milicich demonstrated this with a flimsy bucket
that even when cut he can still stand on it
However, take away the middle parts
like some larger cavities
and the bucket will collapse
Turns out there’s a critical structure
in the middle of your tooth
that helps hold its shape
and if cut dramatically weakens a tooth’s strength
Using composite and a strong adhesive bond
restores this connection
But that’s not the case for amalgam
as it’s an unattached block of metal
so the remaining tooth
flexes way more than normal during biting
and eventually causes a crack
and parts to fall out
Composite fillings not only prevent this
but also reduce how much tooth needs to be removed
and this philosophy is called conservative
or minimally invasive dentistry
You might think every dentist
would embrace this idea but that's not true
One reason is their education
depending on their school or mentors they may
not get taught the most conservative approaches
Here's an example
one study gave 33 American and Canadian dental schools
a picture survey of how they taught students
to remove a cavity between teeth
with composite fillings
A few use the least invasive option
Most chose a slightly larger prep
While 9% chose an old-school retention form
which removes a ton of tooth material
As well some dentists may not trust dental adhesives
as they’ve heard it doesn’t last long
or had problems themselves
You see dental glues have three components
Acid
Primer
and glue
and each require precise timing
to form a strong bond
On older products acid etch is a separate step
and it works by dissolving tooth material to
increase the surface area for the glue to hold onto
Think of this like creating handholds
on a rock surface
and if you leave the acid on too long or short
it ruins the bond by destroying the surface
or not creating enough roughness
When the acid is washed off and dried,
a little water has to be left
as this floats tiny fibers inside your dentin
that link with the glue to form a strong bond
But if there’s too much water or too little
the glue can’t get in
There are many other places it can go wrong
and it’s all microscopic so you can’t see your mistakes
Newer products combine steps
and make this easier
but it’s still challenging to master
This difficulty can split dentists' opinions
on treating teeth between old school traditional
conservative
and everything in between
which can cause battles like the ones over crowns
which are metal or ceramic caps
that are placed over a tooth
that’s too damaged for a filling
Some dentists think this is a really outdated design
as it carves a retentive post to hold a crown
like a baseball cap that sits on your head
The conservative method is called an overlay
which uses a flat base
that saves far more tooth
but requires trust in adhesives to keep it in place
One group pushing this idea are biomimetic dentists
They’re big on Instagram
and it feels like I discovered a secret answer
to what is great dentistry.
Biomimetic means mimicking biology or life
and it's an engineering concept that says we can
look at nature to create better designs
Biomimetic dentists choose techniques like overlays
because it better mimics the way stresses are distributed in a natural tooth
versus crowns
I also love that they can poke some fun at “traditional dentistry”
But more so
they care a lot about pushing dentistry forward
and helping dentists make long lasting
and beautiful repairs
For example
this x-ray of a badly damaged tooth
has been repaired using biomimetic principles and materials
like ribbond
which is a layer of kevlar fibers
that strengthen the tooth
and stop future cracks from progressing
It's somewhat similar to an isolation membrane
for tiled floors called Ditra
which dissipates stress and cracks
instead of traveling through
and breaking your floor
Biomimetic dentists say a tooth’s natural engineering is amazing
and they want to protect that by doing two things
The first is doing more to keep your tooth alive
aka protect the pulp
when you have a deep cavity
That’s important as a living tooth pumps water
into your dentinal tubules
and just like this bottle of water
gives your tooth strength from being crushed
When drained
your tooth is far more susceptible to cracking
which is what happens when you have a root canal
This is a common procedure that drills in
and removes all pulp when a dentist thinks
a tooth is too infected for it to be saved.
But sometimes you need a root canal
and they claim they can
save more damaged teeth from being pulled out
due to better techniques and training
This also delays going down the cycle of tooth death
as repairs fail and you need bigger fixes
which ends with the tooth being pulled out
and replaced with an implant
Those are huge claims so over the last three months
I’ve dug into the research
Much of it is important but very technical
and outside what this video can cover
But I felt so moved
that I switched my dentist of over a decade
to one with biomimetic credentials
By the way
none of this is medical advice
and not something you should just do
in fact there are some downsides to Biomimetic Dentistry
as it’s not a guarantee that a dentist is good
as their skills, judgment or attitude can suck
and it can be more time consuming and expensive upfront
but hopefully repairs should last longer
My goal with this video is to show
what I thought was cool in the dental community
and give you another data point to understand
and access high-quality dentistry
If you do want to learn more
I'm going to leave links below
on the best resources I've used to make this video
Also, there's no conflict of interests
Big Tooth didn't pay me to say any of this.
Masterworks was the sponsor
check them out if you want to support this channel
Leave me a comment below
if you’ve learned something new today
and thanks for watching