Dental Implants have evolved into the “gold standard” replacement option for missing teeth. The dental implant crown is widely accepted as the replacement option most like a natural tooth. Placement, healing and restoration with an implant crown are all predictable processes. A large volume of research supports the use of dental implants. However, there are several fundamental differences between dental implants and teeth that are not common knowledge amongst the general public. It is important that patients know as much about limitations with dental implants before pursuing this treatment option.
Below, I discuss differences between dental implant crowns and natural teeth and how these differences can affect the success of your implant treatment. I hope this information will provide patients with a foundation for deciding whether implants are right for them.
Dental Implants Vs. Teeth: Supporting Structures
The most important difference between a dental implant and your tooth root is that the dental implant is is in direct contact with bone, and it does not enjoy any cushioning from a periodontal ligament. Natural teeth do, however, enjoy this cushioning from the periodontal ligament and so they can tolerate much greater forces during chewing.
Dental implant crowns must have very minimal opposing tooth contact. If the implant crown is under excessive force during function then bone loss around the implant will occur. Adding to this challenge is the fact that opposing teeth can change position over time. It is common that 2 years or more after delivery, opposing tooth contact and related chewing forces on your implant crown will have increased. So your Dentist must be constantly checking biting forces on your implant crown and making necessary adjustments. Additionally, if you grind or clench your teeth when sleeping, your Kitchener Dentist will recommend a night guard to cushion and protect your teeth and implant crown. Unlike natural teeth, implant crowns require much greater attention and monitoring over time.
Dental Implants Vs. Tooth Roots: Shape & Form
If you take a look at the x-ray image on the left you will see a bright white screw and attached crown toward the bottom left. This is what a dental implant crown looks like in an x-ray.
You will likely notice that the shape of the implant, which supports a molar crown, is much thinner and with less flare than the molar tooth roots beside it. If you look at the natural teeth, their roots are thin at the tips and they flare out as they get closer to the tooth crown. So, the roots support almost all of the tooth crown directly above. The implant crown, in contrast, provides a very straight “root” without any flaring or contour. I think you will agree that roughly 75% of the implant crown has no direct support underneath.
This difference in implant shape provides the basis for some unfavourable mechanics during chewing. As forces change on the surface of the crown during chewing, a significant “seesaw” or lever effect becomes possible. This often leads to the characteristic bone loss crater seen around implants over time (see area above red curve in the image at left).
This bone loss will not compromise the implant. It does, however, underscore the importance of monitoring forces on the implant crown over time as a patient’s bite changes. Failing to do so will lead to more bone loss. It also suggests that designing an implant crown to minimize harmful lever forces is critically important to long term success.
If you minimize the front-back length of the implant crown above, you’ll have gaps between it and the neighbouring teeth. Those gaps will allow for constant food impaction, inflammation and bone loss over time. That is absolutely not an option. However, your Kitchener Dentist can minimize the width of the implant (that is, the tongue side to cheek side dimension). Most implant crowns have this design feature without patients being aware of it. This makes the crown much smaller compared to the natural tooth that it has replaced. If you have an implant crown, chances are it is providing you with significantly less chewing surface than you think. This might not be a deal-breaker for most people, but you should still be aware of it.
The shape of implant and crown also has an influence on how it must be cleaned. If you refer to the x-ray image above, you’ll notice the amount of dark space under the crown is large. Compared to a natural tooth, an implant crown is far more susceptible to food and plaque trapping under the gums. This implies that you should be flossing to clean this area with greater frequency (ideally 2-3 times a day). Additionally, manipulate your floss back-to-front and side-to-side within the gum pocket to sweep out food debris from underneath the crown. Cleaning around an implant crown is more technique-sensitive than cleaning around a natural tooth. Make sure you’re up to that challenge if you are considering dental implants.
Implant Crown Types
Once your jawbone has healed around your dental implant(s), it is time to restore them with a crown. Be aware that you will, in most cases, have 2 choices. Implant crowns can be attached to the dental implant by cement. The other option is to have a crown that you can screw into the threaded column inside your implant. In some cases, proper angulation cannot be achieved to enable a screw-retained implant crown. Here are strengths and weaknesses associated with each type of implant crown:
- Screw-retained implant crowns do not require use of messy cement. Excess cement can remain around the head of the implant causing chronic inflammation and bone loss. Care must be taken to diligently remove all excess cement and access to do so is difficult to achieve.
- Screw-retained implant crowns can be easily unscrewed and removed. This is convenient if your Kitchener-Waterloo Dentist needs access to the gum tissue around your implant. Removal of cement-retained implant crowns is much more difficult and often requires cutting through and destroying the crown itself.
- Cement-retained implant crowns are slightly more esthetic compared to screw-retained implant crowns. This is because, screw-retained crowns have a hole in the top to allow for screw insert. Once your Dentist torques in the crown, they use white dental filling material to seal the screw access hole. This filling material is less rich in appearance than the porcelain in your dental implant crown. Therefore, the sealed access hole on a screw-retained crown is somewhat noticeable.
Can Implants Fail?
Yes, they can. Patients tend to have the impression that a dental implant is forever (this is likely . It is certainly possible that an implant can last you for the rest of your life. But, be aware that this does not always happen. The failure rate is higher in individuals with systemic conditions that compromise healing (i.e. Diabetes). The failure rate is also very high in smokers.
Failure amongst prime candidates is usually due to implant placement in thin or weak bone. It could also result where an implant crown is under excessive functional force over a number of years. Given that a single implant crown can cost between $4,000 – $6,000, it is critical that patients fully understand failure rates. Moreover, they need to be told about maintenance challenges and limitations/shortcomings associated with dental implants.
Treatment Options: Dental Implant Crowns vs. Dental Bridges
Dental implants are often promoted as being superior to dental bridges. Implant crowns do offer some advantages:
- You can floss either side of an implant crown but you cannot floss between bridge teeth because of rigid connection between all teeth or “units”. You must instead irrigate under and around a bridge tooth with a plastic syringe or Waterpik.
- Implant crowns do not require a 1-2 mm reduction or “shaving down” of neighbouring teeth to accommodate the bridge’s retaining crowns/caps.
However, dental bridges do offer some advantages over implant crowns:
- Cost-efficiency. Replacing a lost tooth with a 3-unit or 3-tooth bridge costs approximately $3,000. Replacing the same tooth with a dental implant will cost between $4,500 and $6,000. Variation depends on the need for bone grafting prior to implant placement.
- Better contours and less food impaction. Larger and more complex gum pockets surround dental implant crowns. This is true when comparing implant crowns to both dental bridges and natural teeth. There is far less space under and around a bridge tooth. With less food and plaque collection, dental bridges typically enjoy less chronic inflammation and bone loss over time.
- Reinforcement of neighbouring teeth. If the teeth on either side of an extraction site are unrestored (meaning no fillings and no root canal treatment) or minimally restored (meaning small filling(s) and no root canal treatment), then shaving them down to accommodate retaining crowns needed to anchor a bridge is probably destructive. These teeth, in fact, do not need to be reinforced. However, when 1 or more teeth neighbouring an extraction site are heavily restored (with large dental fillings), cracked and/or root canal treated, there will be significant incidental benefit to the being reinforced by retaining crowns associated with a dental bridge. I would argue that, in this second scenario, the incidental strengthening of already compromised adjacent teeth makes a dental bridge worthy of consideration against a dental implant.
So, remember that the condition of other teeth can change how we look at different treatment options. The best solution for Patient A might not be the best solution for Patient B. It’s important to have a thorough discussion of available treatment options with your family dentist before embarking on restorative treatment. And don’t rush into a decision. Often times the best choices come from multiple discussions/consults and careful thought over a year or two.
Implant dentistry provides wonderful solutions for replacement of missing teeth. While expensive, many patients are very happy with their implant restoration(s). My goal with this article is to provide patients with a better understanding of the technical aspects of implant dentistry. This will enable them to make the best restorative decision for themselves. Ultimately, a thorough discussion with your Kitchener Dentist will give you the foundation necessary to make a great restorative decision. Remember that communication is one of the major keys to long-term treatment success!
Written by Dr. Kyle Hornby, Kitchener Dentist
This article is intended to promote understanding of and knowledge about general oral health topics. It is not intended to be a substitute for professional advice, diagnosis or treatment. Always seek the advice of your Dentist in Kitchener with any questions you may have regarding a dental condition or treatment.