Bite Point

Tooth Sealants: Sealing Is Not Just For Driveways

Asphalt is a very durable substance. However it is still under constant assault from sun, rain, temperature changes, salt in winter, physical stresses...

Wear and tear!

 

Our teeth are also subjected to extraordinary stresses. Chewing itself puts high repetitive mechanical stresses on teeth. There are drastic temperature changes as we bounce between the heat of the corn on the cob and the burger, to the cold of the salad, or the iced tea. There are sugars and salts and hard popcorn kernels and gritting when we hit a baseball. (Next time you go to the batting cages, take note of how hard you grit your teeth together as bat connects to ball. It's astonishing!) Some of us even grind our teeth every night. Or during the day, when your boss wants those TPS reports yesterday and you got a letter from the IRS calling for an audit and your son sends you a cryptic text that seems to indicate that the water heater is leaking but he's going to the skate park now...

 

It all adds up, and yet the biggest threat to the health of our teeth is sugar. Our Caries Clock explains it all quite well:

http://www.smilephiladelphian.com/clock/Caries.php

 

High frequency sugar intake is the overwhelming causative factor of cavities. They can occur anywhere on teeth but there are some main areas where they are most common.

 

Interproximal or between-teeth cavities can really damage a tooth; here is a large, obvious one:

Yet perhaps the most common place for cavities is in the grooves on the tops of our back teeth. My own tooth, no cavity in those grooves on the biting surface:

Those deep grooves are the other main place that cavities occur. Many years ago, in the 1920's and 30's, when the roles of sugar intake and oral hygiene in cavity formation were not so well known, it was estimated that over 95% of back teeth present in the American population either had cavities or fillings in their grooves.

 

There are many preventive strategies aimed at reducing the chance of tooth decay. The greatest is to limit the frequency of refined sugars in one's diet, a la our Caries Clock. Another is cleaning the bacterial plaque from our teeth each day, and seeing a dentist and hygienist on a regular schedule for professional cleaning of the surfaces of each tooth. We can also employ fluoride to strengthen the enamel against cavities.

 

Another way of protecting those grooves from decay is the dental sealant. This is a composite resin filling-like material. The difference between a sealant and a restoration is that there is no drilling, and thus no need for anesthesia, when a sealant is placed. They are essentially painted on to the tooth and stay there because of the power of dental adhesion. We can make our dental materials stick very well indeed these days:

http://rickwilsondmd.typepad.com/rick_wilson_dmds_blog/2010/11/enamel-bonding-dentin-bonding.html

 

Here are views of sealants in place on two six-year molars, an upper and a lower one, while orthodontic bands are in place:

 

The grooves are blocked out, sealed, and it makes it very difficult to get a cavity in the top surface of the teeth. Not impossible, any system can be overloaded, in this case with too much constant sugar use. But it's nearly impossible to get a cavity in the grooves of a tooth with a sealant in place.

 

Between-tooth cavities? For now, there is not a predictable way to prevent decay. Flossing and moderation in diet are the best strategy. But on the biting surfaces of back teeth? Sealants rock.

 

Dental Porcelains, With and Without Metal Substructures

Porcelain forms the basis of the very first instance of what we now term "industrial espionage" in human history, according to some sources.  Apparently, long ago porcelain manufacture was understood only by a very few Chinese artisans, and they were not inclined to give up the secret.  Europeans wanted to make porcelain themselves, though, and were very keen to figure out how.  All their attempts failed.  And then in the early 1700's a Jesuit priest, Francois Xavier d'Entrecolles, a member of the Jesuit China missions, made direct observations of the kilns of Jingdezhen and learned some of the technical knowledge of his converts.  He was able to transfer this knowledge back to Europe.  Not, of course, via the Internet, but through letters (gasp! how pre-Victorian!) and publishing in Jesuit annual reports. 

A succinct online source is: http://en.wikipedia.org/wiki/Francois_Xavier_d'Entrecolles

In dentistry, porcelains came to be highly valued as restorative materials for a number of reasons including their ability to be precisely colored, their translucency, their hardness, and the fact that they didn't stain as much in use as natural materials like ivory.  Or wood.  Or human teeth extracted from cadavers.  Yes, really.

Many artificial dental crowns today are porcelain-fused-to-metal.  This design has served us well for a long time as it combines very good esthetics and high strength.  Their strength is somewhat odd considering the vastly different properties of metal alloys and porcelains, not to mention the nature of the bond between them, but they are quite strong and fracture-resistant.

Porcelain-fused-to-metal crowns have one critical esthetic limitation, however- they can never allow a portion of the light that hits their surface to pass all the way through them.  Natural teeth reflect some light, they refract (or bend) some light within them, and yet some light also passes entirely through them.  You can easily demonstrate this by taking a small LED light like a book-reading light and shining it from behind your front teeth while standing in front of a mirror.  A lot of light will come through!

 Let's look at what this means in a practical way:

 

The tooth on the far left of the photo has a silver amalgam restoration in it that does lead to some significant graying.  There is also a composite resin restoration on the outer side which has been in service long enough to have a bit of edge wear, yet it is still a serviceable bonding.

The second tooth from the left is restored with an older porcelain-fused-to-metal crown.  It is from a technological era ("eras" change very rapidly with tech these days, so probably late 80's or so) where porcelain colors could be matched well, but properties like translucency and opacity were not as sophisticated as they are now.  Thus, the crown looks opaque in the middle third and gumline third.  Further, no incident light rays can penetrate through the crown, so it always looks different than the surrounding teeth.

The next tooth over, the second from the right, is a brand new all-porcelain crown.  Note how the surface texture, color, and translucency all precisely match the adjacent tooth on the far right, which is a totally unrestored natural tooth.  Close-up photos like this are also the ultimate test of dental esthetics; this tooth will be indistinguishable from its natural neighbors at any reasonable conversational distance. 

Note also the gum tissue at the margins of the various materials.  From the left, they are: composite resin, porcelain-to-metal crown, all porcelain crown, and natural tooth.  There is a zone of inflammation around only the tooth with the metallic substructure.  While this chronic gum inflammation does not always occur around porcelain-fused-to-metal crowns, and is a complex issue with several contributing causes, it is not entirely avoidable.  For the most part, well-contoured porcelain and composite resin materials without any metal components are highly biocompatible and do not commonly demonstrate this kind of chronic inflammatory issue.

Where indicated, all-ceramic crowns are among dentistry's finest artificial means to restore teeth that have been damaged by decay, trauma or other factors.

Joel D Canfield's 11:59

My friend Joel D Canfield took a little seed of an idea that I bandied about awhile back and has written an engaging and remarkable book, 11:59.

 

The hard copy edition is priced at $11.59, which is just brilliant and cool.  The Kindle edition is a tad less, as is usually the case with eBooks.

Here's the Amazon.com link:

http://www.amazon.com/TIme-Now-11-59-ebook/dp/B005DB88R8/ref=sr_1_1?ie=UTF8&qid=1311178335&sr=8-1

And here is the product description from Amazon:

"To someone who looks backwards it’s easy to see 11:59 as a moment of doom; the end of something. They look back at what they didn’t get done; what went wrong.
You’re looking forward. At 11:59 a new day is about to begin, a blank slate to take your pen.
I’m not foolish or ignorant enough to pretend there’s nothing wrong in business. I’m not suggesting that you forget yesterday like it didn’t happen. Just don’t pretend that yesterday determines what happens after 11:59 today.
I realise business is broken. The thinking that caused the problems we have in business today is not going to solve them. We need to think fundamentally differently.
The purpose of this book is not just to point out that things are broken but to inspire you to think differently; to stop accepting the way business has always been done. It’s time to start creating new concepts, ideas, and ways of connecting."

 

Oh.  And Joel honored me greatly by asking me to write the Foreward.  Thanks, Joel- I never got to do that before.  It was a fine experience, writing the Foreward to your excellent book.  I could see myself getting very Foreward-addicted.  Which, in a manner of speaking, is what 11:59 is all about.  Moving For(e)ward.

The Bottle Project

On a recent trip to California- my first, and on which I met the redoutable writer Tom Bentley in person- I was astonished when my wife said, "Hey Rick, look at this bottle!"

It wasn't plastic!

It was made from plant material, not petroleum.  This will change the whole game.  Plastics in our garbage stream are especially problematic since they never really go away, they just degrade into smaller and smaller pieces.

For more, have a look at my previous post:
http://rickwilsondmd.typepad.com/rick_wilson_dmds_blog/2011/05/plastic-versus-plant-based-beverage-bottles.html

After admiring this simple consumer product for a few weeks- come on, you would too- I decided to start The Bottle Project.  I've placed two bottles into my garden, a conventional plastic one and this new plant-based bottle.  I'm going to take a picture once a week until one biodegrades completely.  Exposed to whatever elements Pennsylvania throws at them, we shall see in a most Visceral way what happens to each material, and at what rate.  Half of each bottle is in the dirt, exposed to soil microorganisms.  Half is exposed to sunlight.

Don't worry, I won't post each and every picture here.  But from time to time I will update you all on this important change in our consumer culture.

May the best bottle win!

 

*Updated photo, from 7/22/2012:

Not much degrading yet, ya know? But let's give it time. I've taken 1 pic a week since I started, so the record is thorough.