Archive for July 2014
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.