Dental implant complications and failure

In implantology, complications can be categorized according to when they occur:

Pre-operative complication:

Dental imlant placement is a very it is a procedure performed during the operation that leads to complications immediately or a few hours/days later,

1.Vascular complications

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pre-operative bleeding is most often due to improper angle or alignment of the incision, or during bone preparation of the surgical site.

1.1.1. During incisions

In particular, more bleeding is common when the incisions are placed far into the vestibule. It would be best to make them close to the muco-gingival line and at the limits of the alveolar crest.

1.1.2. During bone preparation

Arterial hemorrhages are most often encountered during the osseous preparation of the implant site, sometimes it can happen after the perforation of the lingual cortical, which can cause a complication called the floor of the mouth hematoma; indeed The placement of an implant in the anterior mandibular region must be done with care because this area is very vascularized. A fracture of the internal cortical bone during osteotomy or a tear in the lingual periosteum will result in a very high risk of hemorrhage. In implantology, the risk of lesion of the sublingual artery is maximum in the area of the canine and first premolar (maximum caliber). Similarly, a lesion of the submental artery can occur when the drills perforate the basilar rim.

1.1.3. Mucosal lesions

Several types of bleeding can be observed after surgery. They are classified according to their size: petechiae (<2 mm); purpura (2 to 10 mm); ecchymosis (>10 mm). They result from damage to the blood vessels and capillaries present in the mucous membranes and in the skin. These plaques can be  rounded or irregular , initially blue/red or purplish in color. In 2002, Goodacre et al. reported that approximately 24% of all implant sites had

ecchymosis.

There may also be the formation of a hematoma or contusion resulting from the rupture of a blood vessel wall and resulting in a collection of blood that is usually clotted in an organ, space or tissue. This collection can form a fairly hard lump.

1.2 Nerve complications

Neurosensitivity disorders and neuralgia may occur following implant surgery. Penetration into the lower alveolar canal or the chin foramen during osteotomy can lead to various nerve damage such as compression, tearing or nerve rupture. The buccal, lingual and chin nerves that travel through the tissues can also be damaged during the procedure by needle penetration during anesthesia, scalpel, nerve stretching or compression by instruments during the creation of the flap or its elevation.

A nerve injury results in different symptoms of increasing stage and severity depending on the severity of the injury to the nerve.

We distinguish between :

Paresthesias: abnormal sensitivity

Hypoesthesia: decreased sensitivity

Hyperesthesia: increased sensitivity

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Dysesthesia: unpleasant sensitivity (pain)

Anesthesia: complete loss of sensitivity.

1.2.1. Injury caused by anesthesia

An anesthesia needle can cause nerve damage either by its actual needle touching the nerve during the injection or by the anesthetic used. Studies have shown that patients have felt a sensation of electrical discharge at the time of anesthesia in cases where neurological disorders have appeared post-operatively , more recent studies by the same researcher have shown that neurological disorders are more serious with articaine 4%. A permanent lesion can occur in approximately 1 in 25,000 truncal anesthetics. When it occurs, most patients appear to recover completely, and 85% of them will recover completely within 8 to 10 weeks, and 5% will recover over a longer period of time, and 10% will be permanently injured.

1.2.2. Injury caused by the surgical procedure

Nerve damage during implant surgery is most often due to the preparation of the surgical site. A poorly placed scalpel incision, a flap that is too violently recurred, or an uncontrolled instrument that slips, are the most important risk factors and can have consequences ranging from a simple scrape of the nerve sheath to a clear, transverse injury to the nerve. In the latter case, nerve repair and a return to normal appear to be compromised.

1.2.3. Injury caused by nerve compression

Neurological disorders are not necessarily caused by direct nerve damage, but can be the result of compression of the tissues adjacent to the nerve (bone, soft tissue, nerve sheath), inducing juxtanerveous inflammation.

This overpressure on the nerve causes discomfort such as pain or paresthesia and disappears once the inflammation is reduced or the object of compression is removed (implant placed too close to the mandibular canal for example).

The use of larger diameter and shorter implants prevents this type of complication by keeping a safe distance from the nerve.

1.3 Technical complications

1.3.1. Instrumental  fracture

During preparation of the implant site, fracture of rotating instruments, especially small caliber ones, is always a possibility.

Instrument tips may break during the procedure, either due to fatigue or improper handling, which mainly reflects the application of excessive force to their working part.

In most cases they are left in place with no clinical consequences apart from being visible on routine x-rays. The explanation is that these instruments remain enclosed in the bone like an implant; since their volume is small, the host body can encapsulate them without clinical problems, however, an attempt must be made to extract them first.

It is impossible to prevent instrument fatigue. However, it is visible when cutting instruments become blunt, and it is wise not to use them; otherwise they need more force for the operation that leads to their breakage.

1.3.2. Swallowing and inhalation

During each step of the surgical procedure, the patient may ingest or inhale implant placement instruments or implant components. This can be a medical emergency, especially in the case of inhalation, which can lead to severe complications in the short or long term. The patient must be informed in such cases.

If the object is in the digestive tract, an X-ray check every two days should be performed until the material is expelled. The intervention of a gastroenterologist is necessary if the swallowed item is not in normal transit. He will then decide on a medical or surgical treatment depending on the complications and the type of object (size, sharp, prickly, etc.).

If the object is in the respiratory tract, there is a risk of perforation and pneumothorax.

If the patient does not present any symptoms, Mr. Bert (46) advises, in order to reduce the psychological impact of this incident, to complete the procedure. To do so, always double the amount of material required. This precaution must also be taken in the case of the possible aspiration of a component by the assistant. For my part, I think it is more prudent to interrupt the intervention and take care of it immediately.

1.3.4. Damage to adjacent teeth

Teeth that are adjacent to an implant site may be damaged during or after the procedure. Too close proximity of the tooth to the implant may cause heating of the peripheral bone, ligament or cut the vascularization. All of these lesions can cause severe pain.

When the implant is placed, patients complain of severe pain, sensitivity to hot and cold is present in the causal tooth, and edema may occur. These symptoms may be immediate or delayed. X-ray examination reveals a radiolucent area around the apex of the tooth fairly soon after the procedure.

1.3.5. Primary instability

Primary stability can be defined as the degree of mechanical anchorage established after the implant has been placed in its site. It reflects the ability of the implant to withstand axial, lateral and rotational forces. According to Albrektsson (1986), this primary stability is a fundamental parameter for successful osseointegration. In fact, immobilization of the implant in the first instance will allow secondary stability to be obtained as a result of bone neoapposition in direct contact with the implant. If the primary stability of the implant is not satisfactory, then the bone-implant interface will undergo persistent micro-movements which, if they are too large, may lead to fibrointegration of the implant, indicating implant failure. The determination of bone density and the choice of a suitable surgical technique and implant material are parameters involved in primary stability.

The implant must be perfectly immobilized at the end of the procedure. A mobile implant necessarily leads to fibrointegration. There are several reasons why the primary stability of implants may be insufficient:

  • Over-preparation of the site with back-and-forth movements, important during drilling
  • After excessive tapping
  • Implantation in low density type IV bone
  • Extraction protocol – immediate implantation.
  • Elliptical or imprecise path followed during drilling.

This complication can also occur during implant placement immediately after tooth extraction when the available bone beyond the apex is not of sufficient height.

1.4. Bone complications :

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1.4.1. Heating of the bone

Bone heating during the drilling of the implant bed is one of the primary causes of failure in implantology. This will be caused by the frictional forces created by the insertion of the drill into the bone. In 1983, Ericsson and Albrektsson showed that the maximum temperature not to be exceeded in order to achieve satisfactory healing and bone remodeling is 47°C for one minute. If the temperature or time of exposure is higher then a necrotic zone will result showing no signs of repair after 100 days. The damaged area will then form fibrous tissue that will cause fibrointegration of the implant. A pain on the 3rd day post-operatively signs a very reserved prognosis as for the perenniality of the implant.

To control this heating it is necessary to use instruments:

  • New instruments with a maximum cutting efficiency.
  • adapted to the bone density (different between maxilla and mandible).
  • well irrigated (external and internal irrigation) with refrigerated saline.
  • at a rotation speed adapted to the drilling sequence.
  • regularly de-fouling during drilling.

1.4.2. Perforation of the inferior cortex of the mandible

According to Mark Bert, An anterior mandibular resorption with a bone height  between the two chin holes, less than or equal to the length of the implant will automatically lead to the perforation of the lower cortex. It is always preferable to drill the lower edge of the mandible rather than letting the implant protrude from the bone crest because of the risk of premature loading by the intrados of the prosthesis . Wesseling and Coll (1990) report a failure rate of 4.7% of implants perforating the lower edge of the mandible and that the postoperative outcome is not increased by this perforation, provided that it remains within reasonable limits (up to 1mm maximum).Nevertheless, the prevention of these perforations is paramount.

1.4.3. Bone table fracture

Mandibular fractures caused by implant placement or removal are often due to implantation in an atrophied mandible with a bone height of less than 10mm (Lamas et al, 2008) . However, this complication remains rare, but the patient should be warned of the risk. The placement of four or more implants, or large diameter implants in an atrophied mandible may weaken the bone and lead to fracture at the time of surgery or later. Indeed, the concentration of stress in a weakened area such as an osteotomy site or an area undergoing osseointegration can lead to a spontaneous fracture without trauma. This complication is very serious and is accompanied by pain, edema with or without fluctuation, altered occlusal relationships and mobility of the mandible or not.

1.5. Sinus and nasal complications

1.5.1 Partial intrusion of the implant and perforation of the sinus or nasal cavity

The placement of implants in contact with the sinus membrane is a commonly used technique. In a healthy sinus, a minimum penetration of the implant (less than 2 mm) is asymptomatic if the conditions of asepsis are respected, the same as for the nasal cavity. The Schneider’s membrane covering the sinus floor has the property of lifting a few millimeters without perforating itself, thus allowing long-term bone neoformation at the apex of the implant. However, too much penetration of an implant into the sinus wall can lead to serious complications (implant migration, infection…).

1.5.2. Total intrusion of the implant into the sinus cavity

When the implant is placed in the sinus region, there is a high risk of total intrusion of the implant itself or an instrument into the sinus cavity. This complication is often followed by bad local and loco-regional consequences, hence the interest of removing the implant while being as conservative as possible.

Reported sinus complications are rare. They are mainly sinusitis, haemosinus, and fistulae or oral-sinus communications

Frequently, insufficient sub-sinusal bone volume contraindicates the use of endosseous implants. However, surgical techniques such as sinus elevations and sinus fillings are used to consider the placement of implants. These poorly conducted techniques can interfere with the anatomical integrity of the sinuses and their physiology.

 

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