Bite Point

"NOW Can I have me some chewin' room?"

From the movie that remains, to this day, my favorite comedy, 1965's The Great Race:

Larry Storch's character, Texas Jack, says to Tony Curtis' always-spotless-white The Great Leslie: "Now can ah have me some fahh-tin' room?" in a schtick that repeats several times; sorry, tahmes, each more hilarious than the last. Here's the clip:

http://www.youtube.com/watch?v=Q6Pl71RpFRs&feature=results_main&playnext=1&list=PL1372D1D48A184993

Well, it is hilarious to a guy like me, who appreciates the slower, kindlier humor of that bygone era to today's often highly mean-spirited stuff. So many things in our culture have improved, but I submit that film is not one of them.

And so that Texas Jack clip is what I think of when I see prior dental treatments that fail partly because there wasn't enough "fahh-tin' room", or enough space for the restorative materials that we so often place in and on teeth in order to keep them going after they've been harmed by decay, fractures or just overall wear.

There are many types of dental crowns. The workhorse of the 20th and early 21st Century is the porcelain fused to metal, or PFM. This type of crown has a layer of semi-precious or non-precious metal, cast or milled, covering the tooth. The functional shape and esthetic look is then completed by porcelain layered on top and around the sides. Nine out of ten dentists, and eleven out of ten dental educators, assert that the materials involved in a PFM need to be at least 2 mm thick on the biting surface of the tooth.

Another way of looking at this is, we need to remove enough old filling and tooth to provide 2 mm of clearance between the opposing teeth and the one we're working so hard to restore.

Here is a pair of images of an old crown that I removed and sectioned:

 

The striking thing to note is that the porcelain on top of the tooth, on the biting surface, is very thin. Yes, it wore a bit over the years that this crown was in service. But porcelain wears slower than opposing teeth, when it is properly placed onto the metal. This crown started out on an underprepared tooth. It wasn't given enough fahh-tin' room between the top of the crown prep and the opposing teeth. Thus, the porcelain was very thin. The deeper layers of porcelain are opaquers and coarse layers that are not as effecive as the final ones at holding up to the rigors of chewing day after day. Thus, they wear away quickly and what was at first a thin layer becomes an uber-thin layer that tends to fracture.

It is said that the rate of porcelain fracture in new crowns done in America at this point is about 5% over the first five years. This includes every kind of fracture, from big ones that render the crown unserviceable and in need of replacement down to minor fractures that can simply be polished away. Still, everything we can do in dentistry to minimize treatment failures is important, and ensuring adequate reduction of our crown preps is vital.

Patients- if you ever have a "PFM" crown done and the biting surface shows metal or looks very odd  compared to the beauty of the rest of your crown; say, opaque and flat-looking, rather like a lawn ornament (I'm thinking plastic pink flamingo here); then there was probably an issue with the clearance between the treated tooth and the ones that oppose it. This truly should be corrected before your new crown is cemented into place, only to face a high likelihood of breaking in a short time.

Returning to important matters, the scene in the above Youtube clip must certainly be the greatest bar fight ever put on film. Barstools fly. Bottles are smashed. When the staircases come down, it's just magnificent. And there's that quirky exchange between Lily Ole and The Great Leslie early in the clip:

Lily: "Honey, your smile is downright painful!"

Leslie: "Thank you. Are you a native of Boracho?"

Indignant Lily: "I ain't no native, I was born here!"

But the pie fight... oh yes, the pie fight. Definitely, at 2,357 pies, the grandest pie fight ever on film.

http://www.youtube.com/watch?v=-0BOOgW7rHE

You will not regret watching it!

"Y-o-u  w-o-u-l-d-n-t  d-a-r-e!"

Root Canal Therapy: Take Two! Guest Post by Neha Shah, D.M.D.

Superb endodontist (and awesome human being) Neha Shah DMD writes our latest guest post and explains a pervasive mystery in dental treatment:

*****

Many people are surprised when they hear that they need a root canal on a tooth that has already been previously root canal treated. Wasn't the entire purpose of doing the root canal to not to ever feel pain again in the tooth? Commonly I hear from patients, “All the nerves are out, so how come this tooth is hurting?” The most common misconception from patients is that when a tooth has had root canal treatment, it is as if the procedure has created a force around it so strong that not even kryptonite can penetrate it. However, this is far from reality.

When a tooth has been treated for a root canal, it is in essence "rendered dead." A tooth that has had root canal therapy is essentially devoid of the living pulp tissue at the core of the tooth and therefore not able to respond to temperature stimulation. So the tooth is not able to tell you if something is hot or cold. However, it is still able to perform other functions of a mature, vital tooth because it still has the basic structures of a natural tooth namely enamel, dentin and cementum. This is what renders it susceptible to all of the threats that a vital healthy tooth is susceptible to. In fact, some may argue that a root canal treated tooth is slightly more vulnerable than a healthy, vital tooth. This means a tooth that has been treated for a root canal is susceptible to decay (cavity), fracture, and infection just like any other tooth in the mouth. So it is imperative that a root canal treated tooth is properly cared for and protected.

One of the biggest threats to our teeth is BACTERIA. Our teeth are constantly bathed in saliva that contains bacteria. These bacteria which are naturally present in our mouth are opportunists and when the environment is ripe will attack the basic structures of the tooth. So at every opportunity, at every level from performing the root canal, to sealing the root canal, to sealing the tooth, this basic goal of keeping the bacteria out is rigorously practiced by the dental health provider and encouraged to the patient.

So what is causing that previously root canal treated tooth to hurt? Infection and Inflammation. For every infection there is associated symptomatic (painful) or asymptomatic (no pain) inflammation. The primary reason why root canal needs to be redone is for what we term "coronal leakage" ("coronal" meaning "crown"). What this essentially means is that bacteria have penetrated through and into a previously disinfected root canal system. Other less common factors that lead to retreatment is a previously untreated canal, undetected root fracture, or persistent infections within the root canal system due to complex anatomy or extraradicular infections. Regardless, the common thread that runs through these causes of failures is again bacteria, "bugs," or microorganisms.

In a nutshell, the cause is bacteria and the treatment is disinfection. Disinfection is precisely the primary goal of retreatment therapy. During retreatment any existing restorations or posts leading to the root canal system have to be disassembled. The root filling material has to be removed and the entire root canal system has to be disinfected. Once the disinfection process has been completed, which usually is completed in two or more visits, new root filling material is then placed and once again an opportunity has been set to seal the tooth properly and restore it to full function. In essence, retreatment is like giving the tooth a second life.

In some ways you can use the analogy of the life lines from “Who Wants to be a Millionaire?” #1 life line for a tooth is root canal therapy. #2 life line is your endodontist when (s)he performs retreatment procedure due to reinfection of the initial root canal therapy. Your last life line is your endodontist when (s)he performs an apicoectomy on a tooth that has already had root canal therapy more than once. Your million dollar is when you save yourself of the aggravation of extracting the tooth and finding a way to replace it with a prosthesis.

To illustrate, here is a case that has failed for many of the reasons mentioned above:

*Coronal leakage
*Missed canal
*Separated files
*Persistent infection due to anatomy
*Inadequate initial debridement

 

 

Once the etiologies (causes) were identified, all of them needed to be addressed to set the stage for success.

For the above case, the tooth’s prior root canal had to be disassembled through a permanent crown. Goals of the retreatment for this case were to remove the post, remove separated files from the canals, locate additional canals, remove existing root filling and fully debride and disinfect the root canal system, and then medicate to create an environment for healing. The last two x-rays show the finished treatment.

You may realize from the similarities on the X-ray that the tooth behind the one that was treated is in a similar predicament. It too will require retreatment for long term success.

Root canal therapy is a highly predictable, highly successful procedure when the tooth is treated and restored properly. Like any medical/dental procedure, the responsibility of performing the procedure properly lies in the hands of the health care provider but the care and maintenance after the procedure is shared by the patient and the provider. Remember, if at first you don’t succeed, try, try again.