Literature

The field of dentistry has been fortunate to experience a vast amount of dramatic changes.  Modern procedures that are able to be performed are wonderful.  It used to be that changing an unattractive smile was a major undertaking, often taking years to accomplish.  Today, these changes can be accomplished in days.  No longer do we have to live with an unattractive smile because the process required was too much to endure, and the results were often obvious unnatural replacements.  Today, to paraphrase an old hair color commercial, "only your dentist knows for sure".  The smile is the gateway to our personality and is usually the key to a good first impression. 

One of the he most revolutionizing developments in dentistry is the ability to bond to existing tooth structure.  This allows restorations to be placed without the dentist having to grind down most of the tooth to have the restoration stay in place.  Today, aesthetic restorations can be created with minimal preparation.  Although dentistry has been able to bond to the enamel (the outer portion of the tooth) for years, it wasn’t until relatively recently that predictable and confident bonding of the inner layer of tooth, the dentin, was perfected.

The other revolutionizing changes in dentistry have been in the area of materials. Porcelains, ceramics, and resins have been developed that can eliminate the need for any metals in the mouth.  The improved physical properties of these materials mean that aesthetic restorations can be placed that not only are superior to conventional restorations, but look like natural tooth structure.  They are, however, much more technique sensitive and proper protocol must be followed in order to insure success.

Porcelain Veneers (The “Smile Lift”)
 

Porcelain veneers are thin shells of porcelain bonded to the existing teeth.  Like false fingernails, although much more durable and lasting, they cover the front of the teeth and are able to whiten the teeth, fill gaps, change shape, eliminate crooked teeth, lengthen short teeth, and dramatically improve unattractive smiles. This very conservative treatment ( since little tooth reduction is usually necessary) is very aesthetic as no metal is used; therefore, the translucent  appearance of teeth is maintained.  The dark gumline appearance seen with so many of the conventional crowns is also eliminated because the natural light is allowed to enter the tooth and reflect down the root surface as there is no metal to block this from occurring.

This procedure involves a minimum of two appointments, the first being the preparation and impression appointment. Depending on the correction necessary, a thin amount of the surface of the teeth is removed so that when the porcelain is placed, the tooth will not be any thicker than the original teeth.  For the proper “smile lift”, 8 to 10 teeth are often included.  A common mistake is to only include the front 4 or 6 teeth, leaving the smile incomplete and therefore, phony looking.  The color and shapes of the teeth are determined and instructions are sent to the laboratory for proper construction.

The second appointment involves the seating or bonding of the veneers to the existing teeth.  This is the critical appointment as a thorough understanding of the principles of bonding must be applied.  The teeth are cleaned and undergo a series of steps to prepare the surface to be bonded.   The veneers are permanently attached to the tooth surface using a composite resin material, which becomes incorporated into the tooth structure as well as the porcelain. Using different colors of resins, the color of the veneers may be subtly altered for maximum aesthetics.  Using a high intensity light or laser curing light, the resin is cured, or hardened, and the veneers become bonded to the teeth. 

All Porcelain Crowns

When too much tooth structure is damaged for a porcelain veneer, it becomes necessary to crown the tooth.  In the past, this would be done with a porcelain fused to gold crown that would often look opaque and unnatural, as well as having the problem of a dark line at the gumline.  The crowns were opaque or chalky white because stark white material would have to be painted on the metal to block out the dark layer as the layer of porcelain placed over it is translucent.  Utilizing the same principles as the porcelain veneer, the all porcelain crown can be attached to the tooth structure, creating the strength necessary to eliminate the need for a metal substructure.  Just like a ceramic kitchen tile, it is fragile by itself, but when “bonded” to the concrete floor, you can put all your weight on it without it breaking.  Bonding the porcelain or ceramic to the tooth accomplishes the same thing.

Another advantage of the all porcelain/ceramic crown is that since the margins are invisible as no metal is used, they can be placed above the gumline.  With the metal substructure crowns, they had to be placed below the gums to hide the margins.   This invaded the integrity of the gums and would often cause inflammation.  The health of the tissue is enhanced by keeping the margins above the gumline where they can easily be cleaned and prevented from causing inflammation of the tissue.  Having a tooth crowned can now be a natural, cleansable result that rivals what mother nature creates.

Tooth Colored Fillings

For the back teeth, the common way of filling cavities was with the silver-mercury filling.  With the controversy surrounding the mercury in these fillings, alternatives have surfaced that now surpass these fillings, not only in looks, but in function. 

The controversial debate lies in the question of whether the mercury absorbed in the body by its release from the fillings is enough to cause any health problems.  Because of mercury’s toxicity, the World Health Organization opposes using the silver-mercury fillings.  The American Dental Association supports it. Silver-mercury fillings are being banned in Sweden and Japan. Likewise, scrutiny is occurring in Germany as their equivalent to the Surgeon General is advising the material not to be used on any women of child bearing age because of the ability for the mercury to be absorbed by the fetus.  Many follow-up studies are currently being performed worldwide with interesting results.  This debate may never reach an answer, but with the superior new materials available, the controversy becomes a moot point.

For small restorations, a composite resin material can be utilized in a direct technique.  This means the filling can be done in one appointment.  For larger restorations, the indirect method is best as the physical properties are enhanced with heat and pressure.  This, however, requires two appointments.  

The advantage of either solution is that they are bonded in place.  The tooth with a silver-mercury filling is 30% as strong as a healthy tooth, but the bonded filling restores the tooth to over 95% of the original strength of a healthy tooth.  Kinder, less aggressive preparation designs exist for the tooth receiving the resin fillings.  Finally, the expansion/contraction ratio of metal fillings is far greater than natural tooth structure creating tremendous destructive forces each time a temperature change occurs (cold and hot foods and drinks). This is a major reason of tooth fracture leading to eventual crowns.  Composite resin filling ratios are much closer to natural teeth.

These restorations are also technique sensitive, and require meticulous protocol for success. If done properly, they create a much better seal than the silver-mercury fillings and can better prevent decay (cavities) from occurring under the filling.  Of course, these fillings look better than the metal ones, but like the mercury controversy, this is almost a secondary consideration at this time, although not one to be ignored.

Dentistry has come a long way over the past few years.  We are fortunate to have these materials and techniques at our disposal and as in any growing field, the future is limitless.