Dental Implants – What Determines Success and Failure
Dental implants are presented to patients as perfect or near perfect replacements to their missing teeth. Rarely are they informed of the risks and counseled on the failure rates. The procedures can have serious consequences and is not perfect. Implants can and do fail. Patients need to be thoroughly informed about the risks and understand that dental implants can fail. With proper planning, implant placement is very predictable, safe and creates a functional and esthetic result for patients.
Dental Implants have come a long since their inception in the 1950’s. Dental implant technology is changing at an incredibly fast rate. As each new technology is adapted, dental implant success usually improves. Occasionally a technology comes into the marketplace that is mostly great marketing and either doesn’t not improve the success or actually hinders it. Fortunately that doesn’t happen very often.
So what makes dental implants fail ? There are a number of factors that lead to an increased risk of dental implant failure. Unfortunately some of the risks are not avoidable and that is why dental implants are about 90-95% successful based on various studies (the number is actually closer to 95%). As with long bone fractures, even with the best approximation of the fracture and great immobility, some fractures simply aren’t healed when the cast is removed. Either a non-union occurs (meaning no healing ever really started) or a fibrous union occurs (where instead of bone between the two sides of the fracture you have scar tissue). Depending on the type and where the fracture is and the patient, non-unions and fibrous unions occur about 5% of the time. That is similar to the failure rate of dental implants.
The same principles of healing from a fracture are congruent with the healing of an implant. You need good approximation of the bone to the implant surface and a period of immobility to have a successful osseointegration of the implant. Osseointegration means the bone accepted the implant and incorporates itself around the implant. As you can see, the failure rate of implants is similar to the rate of fractures not healing properly. You can get failure of the bone to osseointegrate (similar to non-unions) and instead of bone around an implant you get a fibrous encapsulation (similar to the fibrous union in bone fractures).
However certain conditions that increase the risk of implant failure are poorly controlled diabetes, some bone metabolic and congenital disorders, certain medications like glucocorticoids (prednisone), immunosupressants and bisphosphonate medications (Zometa, Fosamax, Actonel, Boniva, etc.) Additionally, smoking and poor hygienic habits can lead to an increased risk of implant failure. People with these disorders and/or on these medications should bring those to the attention of their implant surgeon so a treatment plan can be tailored to fit their needs and their medical conditions.
There are other factors that can lead to an increase in dental implant failure. Implants can fail early on in the healing phase or late. Early failures would be defined as any time before osseointegration occurs (healing phase) or at the time the crown is affixed to the implant. Late failure is defined as any time after the implant with the tooth is under function.
Factors that can cause early failure are:
This type of failure occurs shortly after the implants are placed. They can be caused by:
- overheating the bone at the time of surgery (usually due to lack of good irrigation)
- too much force when they are placed (too tight fitting implants can actually cause bone to resorb)
- not enough force when they are placed (too loose fitting implants don’t stay immobile and don’t heal properly)
- contaminated implant
- contaminated osteotomy
- epithelial cells in osteotomy site (connective tissue or scar tissue fills the socket around the implant instead of bone)
- poor quality of bone
- excessive forces during osseointegration (during healing the implant is under function, is mobile and therefore bone doesn’t affix to the implants)
- poor compliance with post operative medication and/or instructions
- other rare reasons like implant rejection from a titanium alloy allergy.
Late failures typically include poor hygiene from the patient. Patients’ often lose teeth because of poor care and the habit continues for some despite the implant surgery. Sometimes the implant is simply overloaded. Some patients have higher bite forces and may have needed more implants to distribute the forces more harmoniously. Lateral forces can cause implants to fail late. Implants, as well as teeth, like to be loaded straight up and down–called axially. When teeth and especially implants are loaded tangentially or laterally, they weaken the bone around themselves and begin to fail. The other factor is a poorly planned implant placement, improper implant placement and/or a poorly designed prosthetic tooth, teeth or device. There are therefore lots of reasons implants can fail. Some are controllable and avoidable and some are not. So how can a patient best insure their odds and minimize their risk of implant failure? The biggest help patients can do is stay compliant with the medications and instructions before and after the procedure. The second is taking this opportunity to stop smoking.
However the most controllable factor in ensuring the best chance of success is finding the right surgeon and restorative dentist. Find an implant surgeon who has had great success. Oral Surgeons, Periodontists and General Dentists with advanced Post Graduate training comprise this specialty area. Implants are usually done as a team. Make sure that not only your implant surgeon is qualified, but also just as important is the qualifications of the dentist restoring the implant (putting the tooth on the the implant). Ask lots of questions. Ask to see photographs of before and after photos and inquire about testimonials from other patients.
Implantology (placement of implants) is a very technically sensitive procedure. The success stems from proper planning of the case and the training, skill and experience are also key factors in the success of the procedure. While training is indeed important, evidence of substantial experience, especially within your interest area… can be even more important. Inquire if your surgeon is board certified and how long they have been placing implants and if the regular work or at least communicate with restorative dentist.
Prior to having the implant placed, the surgeon should explain everything to you. If you feel that you did not receive adequate information then wait until you are ready and completely informed. Find good information to help educate yourself. You can find more about dental implants by clicking here or by checking out this site for great information.