Understanding Dentistry is Understanding Dentin

 

The original flaws

The tooth in simple terms is a hard enamel castle. The walls of this castle are incredibly strong and thick and impenetrable. Fluoride makes those walls stronger and acid resistant. The problem is the workers who were supposed to put in all the doors and windows in the castle never showed up. So the castle was unfinished and vulnerable to the hordes, the microbes that came later. Inside the enamel castle is a hostess twinkle, the dentin a variable 24-hour buffet.

 

When the bacteria come they go right around the enamel walls and through the open unfinished doors and windows, all the way to the dentin. Life doesn’t get any better for a bug (the bacteria that cause disease), food, water and a warm dark protected place for the next 80 years if they are lucky enough to find a dentist who will just watch and wait.

 

A lifetime of cascading dental issues and failures are all related to that initial contamination through these open doors and windows, or into the developmental pits and fissures.

 

We discuss carries (decay) as a process that take place in the presence of teeth, bacterial plaques and sugars. This destruction of enamel is the result of a long-term acid attack that decalcifies and leaches the calcium out from this structure. 

 

Take away anyone of these three factors and enamel decay stops. The problem with this concept as a guiding philosophy is that it may work with the rather homogeneous structure of enamel, but does not hold up with dentin. Dentin has a structure with at least seven different materials or structures. Dentin and pulp tissue can be destroyed with no decalcification or acid production. Two organisms that we know of produce acid that decalcifies enamel, 30 or 40 can cause damage in dentin, pulpal tissue or inside the body after an easy access.

 

Dentin and dentin contamination

The leakage into and around dentin and the seals to dentin represent a bacterial problem like the Chinese army at the border in a land war, the porosity of the Arizona border or the caves in Afghanistan. You can’t get at it and you can’t stop it.

 

Openings and leakage are the reasons dental deterioration is an ongoing problem and is generally not stable over any length time much less a lifetime. Bacteria use the tubular structure of dentin as their own restaurant, mass transit and housing system.

 

Forces of bending and repeated flexure attack the integrity in natural tooth structures and at the interfaces of all restorative materials and the tooth structure were they meet. The concentrations of these flexural compression and elongation forces on the root or dentin above the bone and below the enamel crown causes or accelerates the lost of attachment of the periodontal tissue and weakens the structure of the underling dentin. Gingival recessions, abfraction, erosion and root carries are all related the general properties of dentin and action of repetitive force over long time periods.

 

 

Volumetric Contamination

How much of the volume of the dentin is contaminated?

The greater the volume of contamination the greater the adverse load on the pulpal tissue. By removing as much of this contaminated dentin as is possible the volumetric load is decreased and stress on the pulpal tissue is reduced and recovery and long-term survival of that pulpal tissue increases. Not all of this contamination absolutely needs to be removed but the more the better.

 

Under high magnification and illumination you have the ability to stop just short of a pulpal exposure. The closer to removing all the contamination the better and the closer you get to the pulp the easer it gets. The contamination tends to get darker and easier to see the as the bacterial activity increases as the nutrient resources increase as you get closer to the pulp. There is a point as you almost touch the pulpal tissue where the bacterial activity almost stops as the ability of the pulpal tissues defenses penetrate into the dentinal tubules.

 

With the increased motor control that comes as a consequences of the increased visual feedback from higher levels of magnification you can inspect pulpal health at times and vascular blood flow by seeing it through very thin almost microns of dentin capping the pulp chamber itself.

 

Rules for Removing Contamination in Dentin

The use of fresh sharp large diameter carbide slow speed burs in a very concentric preferable electric hand piece aids in removal and evaluation of hardness through tactical feedback.

 

Under ideal conditions the hardness, the type of shavings coming off the bur and discolorations in the dentin can be evaluated to remove the maximum amount of contamination before the placement of the restoration. This leaves the dentin in the best condition to receive a bonded restoration with the maximum durability and predictability in the interface stability.

 

The ultimate indicator of durability of that stable interface with dentin is the lack of change over time at that interface in the condition of that of that bond and in lack of changes in the color of the dentin at and beyond that interface.

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Misconceptions:

Sensitivity is caused by the proximity of the drill or restoration, False.

The volume and activity of the remaining bacterial contamination left in the tooth, left in the contaminated dentinal tubules control sensitivity, long-term ill prognosis and pulpal death. Frank exposure with the drill or restorative bonding and bonding materials including the acid etch in direct contact with the pulp tissue do not affect immediate or long term sensitivity or pulpal prognosis.

 

Volume of tubules

The dentinal tubules in a single rooted tooth to an average molar represent between 5-35 miles of open tubes with fluid, nutrients and live pulpal tissue with free access to the pulp, the circulatory system and the whole body. After the surface area of the periodontal tissue tooth interface this dentin exposure represents the second largest source of bacterial access from the oral cavity to the body.

 

Chart of Dentinal Tubules Length

The length of the dentinal tubules from the DEJ to the pulpal tissue,

          approximately 2.5mm.

The surface area of the dentin at the DEJ for a molar tooth,

          approximately 1 sq.in. or 57.6 sq.mm.

Tubules in dentin per sq. mm,                              

          approximately 40,000.

 

40,000 x 2.5 x 57.6 = 57,600,000 mm,

 

or 57,600 meters,

or 57 Km,

or 35.7 miles of tubules.

 

100,000 mm/sq. mm,

or 100 meter per sq. mm of tubules, lots of volume for bacteria to live in.

 

 

Opinions:

The two biggest problems that I see in dentistry today are the lack of understanding of the concept of sealing the original holes in the teeth and the abandonment of the quality of seals in restorative dentistry. These pits and fissure flaws and the failure to remove the contamination and the decay left under existing restorations leads to on going disease and predictable recurrent and catastrophic failure.  Issue one is about prevention for a lifetime and the other is conceptual and about restorative theory.

 

The work-arounds for both of these dentin contamination issues are three fold. 

 

#1. Completely open and seal all pits and fissures in all teeth early and well.

 

#2. Do much more aggressive and successful dentinal tubular cleanout procedures in all contaminated teeth.

 

#3. Disassemble all leaking and marginally failed restorations with a different cleanout protocols to achieve a more sealable, predictable and durable interface.

 

Basis for opinions:

The use of high magnification

 

                        2.5 - 25 X power microscope

                        4.5 x surgical optics plus headlight

                        4.5 –120 X camera photography plus 30-inch high-resolution display

 

40 years of longitudinal research and records

40 years of following the same patients, many form dental school

Over 10,000 consecutive pits and fissures, opened up, photographed and sealed

Over 10,000 fillings, restorations removed, photographed and refilled

Over 5,000 endodonticly treated teeth, disassembled, photographed and re-treated