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What happens to a tooth once it has a cavity and subsequent restoration to repair this defect?

The life cycle of a tooth that has received a restoration is very predictable and has been well documented over the years.

The first area of decay for a tooth is usually the biting surface or proximal surface (i.e. between adjacent teeth). The initial restoration is small and usually free of sensitivity. As time goes by, the filling and surrounding tooth wear (from abrasion, acid erosion, thermal flexure, etc) and the filling fails. Moisture begins to penetrate the margins and recurrent decay develops. Most often, the restoration is not replaced in a timely manner because there are no symptoms with this process and the patient does not feel the treatment is necessary.

Once the patient decides they are ready for treatment, the old restoration is removed and a larger one placed to accomodate the damaged areas of the tooth. This means the width has increased, the depth has increased, the risk of sensitivity has increased (and the proximal surfaces are usually involved).

As the size of the resoration increases, so does the risk of fracture. Once recurrent decay develops around a filling of this stage, a fracture is inevitable. The fracture usually encompasses a large portion of the tooth and may encroach on the pulp tissue (nerve supply) of the tooth. 

Further recurrent decay will develop with time and, when left untreated, will lead to even further fracture and risk for root canal therapy. As this point the only restorative option for the tooth will be a crown. 

No restoration is permanent. Eventually the crown will require replacement. If the treatment has been delayed and even more tooth structure is lost, then the tooth may no longer be restorable and require extraction. 

This doesn't sound very good, does it?! There are ways to prevent the progression from simple filling to extraction. The single most important thing is routine hygiene maintenance to keep restoration margins free of long-standing plaque and calculus debris. Routine radiographic and visual assessment of the restorations is necessary to detect failing restorations. Timely replacement of restorations can dramatically reduce the increase in size from one restoration to the next. 

Choosing the right filling material can also improve the life-span of a restored tooth. Once the filling size has progressed to greater than 1/2 the intercuspal width or a cusp requires replacement, then a CEREC onlay, 3/4 crown or crown are the most durable and long-lasting options. They will reduce the risk of fracture dramatically! 

If a tooth gets to the stage where root canal therapy, periodontal surgery and a new crown are required, one has to consider the long-term prognosis for the tooth. In some cases the prognosis will be good. In others, the prognosis may be guarded at best. At this point, replacement of the tooth with an implant-supported crown may be the best option. Implant treatment most closely resembles the original tooth and has an excellent pronosis - if cared for, they may last a lifetime.

A patient presented with discomfort on the lower left side due to pulpitis of tooth 3-5. The tooth had been previously restored with a very large and deep composite restoration. The depth of the decay and trauma associated with removing it caused an irreversibe inflammatory response in the tooth known as pulpitis. This tooth required immediate endodontic treatment to remove the inflammed pulp tissue and resolve the discomfort.

Traditionally, this treatment is completed using chemical irrigation of the canal system to ensure the organic tissue and bacteria have been removed from the system. Some chemicals can be dangerous and difficult to use. Also, there is little guarantee that the chemicals introduced into the space can completely reach the apex of the tooth without passing beyond the tooth into the periapical tissues.

At Basinview Dental Centre, Dr. Luke Haslam does not use chemical irrigation to complete root canal disinfection, but rather uses laser energy applied by the Waterlase iPlus. With this system, root canals are cleaned and shaped using traditional instrumentation (hand and rotary endodontic files; stainless steel and/ or nickel titanium). The irrigatant used is simply distilled water - zero complication if any water passes beyond the tooth apex. Once the canal has been shaped as desired, a special laser tip is inserted into the canal space. Once the canal is shaped properly, this tip can be placed into position to allow laser energy to disinfect the tooth apex. Laser energy is applied in a series of passes throughout the canal system until the desired disinfection is achieved - for some teeth, this may merely take 30 seconds!

There is no discomfort or chemical smell. The laser will remove organic debris and bacteria 1000um laterally from the main canal.  This means far greater penetration of disinfection than chemical systems into lateral canals, fins, isthmuses and apical deltas. These areas are a common cause of root canal failure - the chemical disinfection simply can not remove was it can not touch.

The root canal completed for this patient clearly shows a complex apical delta - there are at least 5 openings at the apex of this tooth. The laser disinfection allowed for these areas to be easily cleansed prior to obturation which allowed the gutta percha filling to flow into these areas. This will greatly improve the patient's chance of success with this treatment. 

The patient noted no post-operative discomfort and has been symptom free since the treatment was completed 4 months ago. The patient has scheduled to have a full coverage crown placed on this tooth to complete the treatment for this tooth.

The Dreaded "Root Canal"

November 01, 2012 | Posted Endodontics

The "root canal" is the most misunderstood dental procedure. Many of you have probably heard people refer to a difficult task by saying, "It was worse than having a root canal" or "I would rather have a root canal than...".

How did this procedure get such a negative connotation when it has such a positive result?

Part of the problem is that most patients are unaware of what this procedure actually is. Another problem is that most often, when a "root canal" treatment is required, the patient is in pain. When a person experiences pain, their judgement and even their personality can be affected.  Combine the negative connotation of a "root canal" and a patient in pain and then it becomes difficult for a patient to see beyond the immediate need to remove pain and see the importance of saving their tooth. Dr. Haslam has actually removed this term from the office vocabulary; we no longer refer to this procedure as a "root canal", but rather as an endodontic treatment (its true name) or by describing it as "removing the pulpal tissue from the tooth". By doing this, the patient has the chance to see the treatment as it is rather than as it has been percieved to be.

What is an endodontic procedure and when is it necessary?

When a tooth receives a trauma that causes irreversible damage to the vital tissue inside the tooth, the vital tissue must be removed to prevent pain and infection in and around the tooth. This procedure is known as endodontics. The trauma may be from an impact injury, a deep cavity (carious lesion), severe periodontal disease, excessive wear from acid erosion, bruxism (parafunction), tooth fracture, dramatic thermal injury, etc. Any of these situations may cause the vital tissues inside the tooth to be irreversibly inflammed. As the tissue inflammation increases, the pressure inside the tooth increases and this is felt as a "toothache". Often, it is described as a throbbing sensation that increases in intensity with time. If left untreated, this pain can become severe. Eventually, the vital tissues inside the tooth will become necrotic and at this point, infection begins. This infection is often very localized to the periapical region of the tooth, until it spreads to the surrounding soft tissues resulting in an abscess.

To treat the tooth, local anesthetic is applied just as when a basic restoration is to be completed. The tooth is isolated with a rubber dam and then the pulp of the tooth is accessed using a dental bur. The pulp tissue is cleaned out if the pulp chamber and then the canals inside each root using small cleaning instruments and a disinfecting solution. The canal spaces are then sealed using a plastic filling material (gutta percha) and sealant and the tooth is restored with an appropriate filling material.

This procedure has a 97% success rate! So why does everyone fear the "root canal"?

In the past, the techniques, instruments and even anesthetics were not even comparable to those of today. Most often, an endodontic treatment is completed in less than an hour! There is no pain during the procedure and any tooth pain prior to the procedure is immediately resolved. If there was infection prior to the procedure, it will quickly resolve following treatment and very rarely will a precautionary course of antibiotcs be required. Most often, patients will comment after the procedure, "That wasn't anything like I had expected. I didn't feel anything" or they are simply amazed when the procedure is completed.

Let's look forward to the new treatments and technologies of the future that will make these procedures even faster and more comfortable and avoid thinking back to the old days when these procedures gained their negative connotations.

Dr. Luke Haslam

Basinview Dental Centre