Risks and complications
Risks and complications can be divided into risks during surgery, risks and complications that occur in the first 6 months after the placement and long term risks and complications.
1. Risks and complications during implant surgery
Placement of dental implants is a surgical procedure and carries the normal risks of surgery. If additional surgical procedures are performed (sinus lift, bone graft etc.), they also carry the normal risks.
However, the risk of complications is considered to be very low - less than 5 percent, according to current statistics. Problems are rare and when they do occur, they are usually minor and easily treated.
Life-threatening events associated with dental implants are extremely rare but some severe bleeding may occur especially if large blood vessels are injured during surgery.
If such an accident should occur, treatment includes compression, vasoconstrictive medication, cautery or ligation of arteries. Most of the times, bleeding is kept under control.
Infection from bacteria is a common risk to any surgery. In modern days, less than 1% of the surgeries result in an infection and most of those infections are minor.
An infection at the implant site during surgery or in the early days after surgery can increase the risk of implant failure. Pre-op antibiotics reduce the risk of implant failure but have little impact on the risk of infection.
Proper oral hygiene after surgery is essential. A clean mouth will heal faster and the risk of infection is reduced if the mouth is not riddled with bacteria and food debris.
The most common issue is when the inferior alveolar nerve (located inside the mandible) is accidentally damaged during surgery. After surgery, patients may experience lingering pain, tingling and numbness in the teeth, gums, lips (mostly the lower lip) or chin for an undetermined time.
If the nerve damage is minor, patients will recover after a certain period of time.
important anatomic structures
that can be damaged during implant surgery
Sinus problems occur when dental implants placed in the upper jaw protrude into one of the sinus cavities. Careful planning and precise surgery execution are essential to avoid this accident.
panoramic film : a dental implant protrudes into the sinus cavity
Even if sinus complications do not occur in every case, these implants have a high risk of failure because of the insufficient bone support.
Lack of stability
An inability to place the implant in bone to provide stability of the implant (referred to as primary stability of the implant) increases the risk of failure to osseointegration.
Some research even suggests that the primary stability of the implant in bone is a more important determinant of success of implant integration, rather than a certain period of healing time.
Other accidents may occur during the surgical placement, but these are extremely rare : damage (and possible devitalization) of adjacent teeth or other surrounding structures, necrosis of the flap of tissue around the implant, mandibular fracture etc.
2. Risks and complications in the first 6 months
These complications occur in the first 6 months after implant placement. The most common complication is the failure to integrate.
Failure to integrate
An implant failure to integrate in the first 6 months can first be related to some general or local factors :
- general conditions such as uncontrolled diabetes, untreated osteoporosis, radiation exposure on the head and neck, etc
- improper oral hygiene
- heavy smokers or high alcohol consumption
- various accidents during surgery : infection, puncture of a sinus cavity, etc
However, latest research suggests that the most important factor is the primary implant stability.
For this, an implant needs to be surrounded by a healthy quantity of bone and it has to be placed in the bone to provide stability of the implant. Loosening implant posts have a higher risk of failure.
An implant is tested between 8 and 24 weeks to determine if it is integrated. The clinical sings to determine implant success are the absence of pain, mobility, infection and gingival bleeding.
The osseointegration status is then tested on radiographs and with specific devices (e.g. Periotest).
dental X-ray : implant failure to integrate
it is considered that a radiographic lucency In radiology, lucency is a darker region that is normally caused by soft tissues, air or liquid. It is the opposite of opacity which has a whiter shade and is caused by hard tissues (teeth, bone), metal or artefacts. Lucency around a dental implant signifies bone loss greater than 1.5 mm around a dental implant is a sign of failure
While there is significant variation in the rate that implants fail to integrate (due to individual risk factors), the approximate values are 1 to 6 percent.
3. Long term complications
Long-term implant failures may be caused by an improper design of the prosthetic restoration or by inappropriate care and maintenance. Regardless of the cause, implants fail due to either loss of bone around them or a mechanical failure of the implant.
There are also the risks associated with the prosthetic components which over time can wear off, chip, break or cause a lack of satisfaction on the part of the patient.
Peri-implantitis is a destructive inflammatory process affecting the soft and hard tissues surrounding an osseointegrated implant in function. Peri-implantitis is an infectious disease that can be caused by various factors :
- improper oral hygiene
- excessive mechanical load on the implant
- the status of the tissue surrounding the implant
- patients with diabetes
- heavy smokers
Diagnosis is based on changes of color in the gingiva, bleeding and probing depth of peri-implant pockets, suppuration etc. The X-ray shows gradual loss of bone height around the implant.
If peri-implantitis is diagnosed, treatment will depend on the amount of bone loss and the aesthetic impact of the implant in question.
The therapeutic approach can range from local debridements around the implant fixture, antibiotics, antiseptics, and ultrasonic and laser treatments to regenerative procedures using a bone graft.
Fracture of the implant
The fracture is a mechanical failure of the implant. Fractures may occur when implants are too short or too thin. The implant can fracture at various levels :
The fracture of the implant and abutment screw is a catastrophic failure and normally the fixture and the prosthetic components cannot be salvaged (image a).
When only the abutment fractures, the abutment and the crown would need replacement but the implant fixture can sometimes be salvaged (image b).
a : fracture of the implant
b : fracture of the abutment screws
The most common cause of gingival recession is gingivitis, an inflammatory disease of the gums mainly caused by an improper oral hygiene.
Recession of the gingiva leads to exposure of the metal abutment under a dental crown. In other situations, black triangles caused by bone loss and the retraction of the papilla appear between implants and natural teeth.
Some of these conditions may be improved with a soft tissue graft. Before any surgery, all causative agents have to be removed.
Prosthetic restoration risks
Besides the implants, there are the risks associated with the prosthetic components. First, poor aesthetics including a high smile line, poor gingival quality and missing papillae, difficulty in matching the form and shade of natural teeth may lead to a lack of satisfaction on the part of the patient (assuming the patient does not have unrealistic expectations).
Over time, prosthesis can wear off, chip, break, detach, change aesthetic appearance or suffer other complications. Many times, the implant fixtures will last longer than the prosthesis.
chipped porcelain restoration
Additionally, removable dentures and overdentures need regular maintenance.
Patients who wear implant supported prosthesis should ideally be free of pain or any other unpleasant signs, able to chew and taste and be pleased with the aesthetics.
Implants should be tested at least twice a year during regular checkups. Criteria for the success are the absence of pain, mobility, radiographic lucency (greater than 1.5 mm) around implants, the lack of suppuration or bleeding in the soft tissues, adequate function, and aesthetics in the prosthetic.