Thursday, December 6, 2012

Why Is It Better to Save a Natural Tooth?

A patient recently asked...

 I'm a healthy 47 year old male. My upper central incisor (#9) was struck (trauma). It cracked vertically to the gum line, and then cracked horizontally to the lateral edge (resulting in an inverted "L" shaped fracture).

My general dentist first tried applying a layer of bonding, which appeared to be acceptable both aestetically and structurally.

6 weeks later, severe pain started to develop. I went back to my dentists and he said that there is no sign of infection, but that the pain is likely from the nerve dying. We agreed that we should go with either a root canal + crown, or implant + crown.

As a mechanical engineer, I'm leaning towards the implant, because it seems more "fool proof", especially considering that the existing tooth has been structurally compromised down to the gumline.

But the one thing that still has me second-guessing the implant option is that endodontists and periodontists both seem to universally agree that "It's better to save the tooth whenever possible."

So I have to ask: WHY???

Why is it "better to save the natural tooth" if it is subject to future decay (in particular at the base of the crown) and is also subject to brittleness following the root canal?

As a mechanical engineer, I like the prospect of an inert metal or zirconium implant that is not subject to these potential future modes of failure.

Please share your insights in the context specific to my situation described above. Much appreciated. Thank you. 

While it may seem a simple solution to replace a tooth with an implant and then avoid future issues like decay or root fracture, there are some important reasons why the specialists are recommending preserving the natural tooth if possible.

Periodontal Ligament attaches the root to the bone
Teeth and implants are not the same. The main difference between a tooth and an implant is that a tooth has a periodontal ligament. This ligament attaches the root to the bone and acts as a shock absorber for the tooth.  Without a periodontal ligament, when you touch, tap or chew on the tooth, you cannot feel the tooth or how hard you are biting.

The sensory function of the periodontal ligament helps you know when something is wrong with your tooth. If the tooth is hitting too hard, the ligament senses it. If there is infection around the tooth, the ligament senses it. The sensory function of the periodontal ligament is very important to dental health.

The periodontal ligament also supports the surrounding bone. When the ligament (tooth) is removed, bone loss naturally follows. The periodontal ligament also is a home to multiple cell lines which support the bone such as: osteoclasts, osteoblasts, fibroblasts, cementoblasts, cementoclasts, and stem cells. The periodontal ligament allows the tooth to be moved through the bone (orthodontics).

The periodontal ligament has an important role with esthetics.  When the ligament is removed, and bone loss naturally occurs, gingival recession follows. This can change the esthetics of the tooth, especially in the anterior esthetic area.

The periodontal ligament also has an immunological purpose. The ligament and the gingival connective tissue fibers form a barrier to protect the bone from bacterial invasion.

There are times when the natural tooth cannot be saved.  If the root is fractured, then the tooth is not savable.  The endodontist is the most qualified specialist to determine if a root is fractured.  At Superstition Spring Endodontics, we use microscopes and focused field, high resolution CT scans to aid in the diagnosis of root fracture.

The periodontal ligament is the difference!

In these particular cases, a dental implant may be the ideal way to replace a missing tooth.  Marketing of dental implants by manufacturers has made this treatment options well known to the public, however, dental implants are not free of complications or need for revision (additional) treatment over time. By understanding the complications that can occur with implants, it will help to understand why specialists recommend, "saving the tooth if possible".

The ligament is a shock absorber
Many of the complications with dental implants can be associated with the lack of a periodontal ligament. Here are a few of the ways the lack of periodontal ligament can cause complications with dental implants.

The periodontal ligament is the shock absorber for your tooth.  Can you imagine driving a car without shocks? An implant, without a ligament, has no proprioception (sense of feeling). This means it is difficult for you to "feel" how hard the teeth are hitting together. Porcelain chipping, cracking and loosening of implant screws are all common complications with implants, mostly due to the lack of a periodontal ligament and the proprioception it provides.

Fortunately, with implants adjacent to natural teeth, you maintain proprioception from the adjacent natural teeth so your chewing can still feel the same. However, it is difficult to feel if the implant crown is hitting too hard, like you would with a natural tooth. Your dentist must be careful to get the implant crown adjusted just right, and will often times flatten the crown to prevent excessive force on the implant or make the biting contact light.

Bone loss over time is expected
The periodontal ligament transfers the force from the tooth to the bone. That constant transfer of force to the bone, keeps the bone functioning around the root.  When the periodontal ligament is gone, bone loss naturally follows. Some studies say that up to 0.2mm/yr of bone loss can be expected. There are theories as to why this occurs. Some think its simply the mechanical forces on the implant transferred to the bone that causes the recession.

Bone loss in anterior can cause esthetic defects
Loss of bone around an implant can cause unsightly changes in the anterior esthetic zone. While the implant may be functioning, esthetic failure is a well known complication with anterior implants.

Peri-implantitis is the growth of bacterial biofilms on the implant surface, causing chronic inflammation leading to bone loss.  Many people are not aware that an implant can get peri-implantitis, just like a tooth can get periodontitis, both of which can eventually lead to the loss of the implant/tooth.   The periodontal ligament plays an important role in the preservation of the bone around a tooth.

Historically, implants have been classified as "surviving" or "failed" based upon mobility of the implant. New implant studies have suggested that implant intervention may need to be done at earlier stages before too much bone loss has occurred.  It was proposed that surgical intervention may need to be done when an implant is considered "ailing" or "failing" rather than waiting until enough bone loss has occurred to consider it "failed".

In a recent study published in the Journal of Oral and Maxillofacial Implants, a comparative study between the success rates of implants and root canals revealed no significant difference in the two options and emphasized that treatment decisions should be made on factors other than outcomes.  In other words, neither of these treatment options can claim to be more successful than the other.  These treatments are different, and each has its own pro's and con's.

Implants have an important role in dentistry.  I routinely recommend implant placement for missing teeth or teeth that are too damaged to save. However, implants are not teeth and we should try to preserve our natural teeth if possible.

For more information on the longevity of implants vs. natural teeth, click here or here.


Tyler said...


How can you say "bone loss over time is expected" and then show a photo of three external hex smooth surface implants? In that system absolutely, but who is placing external hex smooth surface fixtures anymore?

With the internal conical connection, platform switching, and roughened surface bone loss is not expected when the surgical procedure is properly completed.

The Endo Blog said...

Thanks for your comment. The reason I showed the 3 external hex smooth surface implants, is because it's a 23 yr old implant. While the design and surface of implants continue to evolve, implant marketers conveniently overlook the crestal bone loss that will occur. It is my understanding that there is still some debate as to the cause of the crestal bone loss. It may be the torque/lateral forces on the implant, it could be the biofilm/microbial effect on the implant. But it generally accepted that crestal bone loss will occur.
My point is that without a periodontal ligament, an implant is not the same a tooth. When we do a root canal, we don't take the tooth out of occlusion or flatten the occlusion. We put it in function immediately, and expect the crestal bone to remain the same unless there is active periodontal disease. Implants and teeth are not the same, and should rarely be considered althernative treatments.