FAILURES IN IMPLANTOLOGY

“Failure is the foundation of success” (Lao Tzu)

Introduction Regardless of the high reliability of implant therapy, the risks of complications and failures must be kept in mind. And even if the media presents this discipline as a miracle cure for edentulism, it is up to the dentist to assess the case and make the decision on implant treatment, but also to inform the patient, who must be aware that any surgical procedure presents a risk of complications, and even failure.

Post-operative effects These effects vary in their form and intensity for each patient depending on the type of procedure, we can have:
1. Pain: Damage to nerve endings located at the surgical site can cause post-operative pain.

These pains are generally well controlled by analgesic treatment administered immediately at the end of the procedure.

Hematomas: The appearance of hematomas is common, especially in this type of surgery requiring the detachment of large, full-thickness flaps. Their spontaneous resorption can take two to three weeks.
Inflammation and edema: Edema is a classic consequence of surgery; it is actually an endogenous reaction to the trauma caused by surgery.

A!! It is important to inform the patient that if the post-operative outcome seems to be worse than expected by their dentist, they should not hesitate to contact them quickly to detect any potential complications. The patient will be explained the post-operative recommendations to follow and how to respect the medication regimen.

Recommendations to the patient:

Keep the compress in your mouth for 10 to 15 minutes.
Rest : Avoid any tiring activity.
Pain : Preventive painkiller, within one hour of the procedure.
Bleeding : Slight bleeding that stains saliva is normal on the first day. Avoid hot drinks and mouthwash on the first day. If bleeding persists, clean the area with a dry compress, then bite on an unfolded compress for 30 minutes. Repeat several times if necessary.
To limit swelling : Apply an ice pack to the cheek for 5 to 7 minutes every hour for 4 hours following the procedure.
Fever : After surgery, a fever is common for 24 to 48 hours.
Oral hygiene : Do not brush the operated area for 7 days. From the next day, strict oral hygiene should be observed, using well-diluted mouthwashes.
Tobacco and/or alcohol are contraindicated for 2 weeks, because they:
- disrupt coagulation.
- delay healing.
- may be responsible for complications.
Removable prosthesis : It is strongly recommended not to wear your dental appliance for 2 to 3 weeks. Any compression in the area where the surgery was performed could compromise the prognosis of dental implants.

Success criteria in implantology:

The criteria for success in implantology involve mastering different parameters:

Patient related: General condition, Motivation, Oral hygiene.
The surgical procedure.
The properties of implant biomaterials , and the chosen prosthetic concept .

Implant success criteria:
- Lack of clinical mobility.
- Absence of peri-implant radiolucent image.
- stability of the peri-implant bone level.
- absence of pain, infection or neuropathy.
Prosthetic success criteria : A prosthetic treatment is successful if it does not show any of the following signs of failure:
- Changes to the treatment plan due to poorly positioned implants.
- The prosthetic creations were redone several times due to mechanical complications (unscrewing and fractures of the various components).
- An aesthetic result that is not satisfactory for the patient.
- Persistent phonetic difficulties.
- Hygiene and maintenance problems related to inadequate prosthetic design.
Therapeutic success criteria: To be considered a therapeutic success, the implant-supported prosthesis must meet several criteria:

Functional (chewing, phonation).
Psychological (absence of pain and discomfort, aesthetic result).
Physiological (achievement and maintenance of osseointegration, absence of tissue inflammation).

Failure to meet any of these criteria is considered a failure, even if the other conditions are met.

Complications and failures in implantology:
1. Intraoperative complications: a- Vascular complications
  - Intraoperative hemorrhage : may occur:
    - during soft tissue incision (inappropriate positioning of incisions).
    - during bone preparation of the implant site (hemorrhage due to injury to an artery or perforation of the lingual cortex).

Prevention : prevention of the risk of hemorrhage is based on:
- an appropriate surgical technique.
- knowledge of anatomy.
- clinical and radiological evaluation of bone.
- screening for blood clotting disorders.
- a wide approach allowing you to visualize and protect risk areas.

b- Nervous Complications

Lesion of the mandibular branch of the trigeminal nerve:

( Alveolodental nerve , lingual nerve and mental nerve.) This may involve: compression, contusion, stretching, partial or total section causing significant sensory disturbances (paresthesia, complete anesthesia, etc.)

Prevention:
- careful radiological examination
- Computer-generated surgical guides
- Soft tissue elevation must be done in an atraumatic manner.
- use safety stops when drilling
- It is advisable to respect a safety zone of 2 mm above the dental canal.
Damage to teeth adjacent to the implant: Breakage of the periodontal ligament of an adjacent tooth can also cause acute pain.

Involvement of the apex of a healthy adjacent tooth can lead to loss of sensitivity and

/ or pain similar to that of pulpitis.

Prevention: precise analysis of preoperative X-rays and the use of a surgical guide allowing the correct positioning of the implant in the 3 planes of space.

c- Technical complications:

Instrumental fractures : fracture of small-caliber rotating instruments.
- Prevention: use of good quality equipment and controlled back and forth movements in the axis of the drilling reducing the risk of fracture
Swallowing and inhalation: Swallowing an instrument or implant does not cause major complications; it is eliminated naturally. Inhaling an instrument, however, constitutes a medical emergency.
- Prevention: Placement of compresses or connection of certain instruments to parachutes.
Fenestration and dehiscence: Placing an implant in a deficient bone volume (< 6 mm) or in an incorrect axis can lead to fenestration or dehiscence.

These bone defects can be filled by simultaneous grafts

Prevention: These per-operative complications must be anticipated through meticulous radiographic analysis (scanner) and the use of small diameter implants.
Lack of primary stability: an implant that is not stable at the end of the procedure can compromise osseointegration; this may be due to:

a low density bone.
excessive tapping.
improper preparation of the implant site.
Prevention:
- removal of the unstable implant and its replacement with a longer and/or larger diameter implant if the width of the ridge allows it.
- The period of foster care is then increased.
- The use of self-drilling implants improves initial stability in the presence of low-density bone.

Immediate postoperative complications: a- Sensitivity disorders

Partial or total damage to the inferior alveolar-dental nerve is difficult for the patient to bear. The clinical picture may be one of subacute or chronic diffuse pain, locoregional sensitivity disorders (hypo or anesthesia of the lower lip and/or chin).

Treatment :

radiological analysis (CT).
removal of the implant or its displacement in the coronal direction.
in the case of canal compression, removal must be done before osseointegration of the implant.

On the other hand, in the presence of a partial lesion, sensory disorders regress spontaneously within a few months.

Infectious Complications:

Superinfection can interfere with osseointegration, sometimes leading to implant loss. This can be linked to external contamination or a prior infection of the implant site.

Prevention:

ATB preoperatively and postoperatively associated with rigorous asepsis.
Eradication of any infectious source before implant placement.
A radiographic check can confirm the absence or presence of peri-implant bone loss .

Sinus complications:

Perforation of the nasal or sinus cavities (partial penetration):

In a healthy sinus, an implant penetration of 1 to 2 mm remains asymptomatic if aseptic conditions are respected.
On the other hand, a breach of Schneider’s membrane can lead to sinusitis, fistula or oro-sinus communication. In this case, the patient should be referred to an ENT specialist.

Prevention/treatment:

It is necessary to ensure the total absence of sinus pathology using a CT scan which shows thickening of the Schneiderian membrane in the case of sinusitis. It is then necessary to have the patient treated by an O.RL doctor before considering implant placement, or to review the treatment plan with shorter, non-penetrating implants. When sinus surgery is performed in good bone and surgical conditions, checks often show bone growth at the apex of the implant.

Intrasinus expulsion of the implant:

Major complication of maxillary surgery. It occurs either during surgery or during the osseointegration phase.

Mucosal Complications

Wound opening: Following a suture break or wound dehiscence in the days following surgery; this requires emergency intervention to recreate the tissue seal and avoid any risk of infection, bone necrosis or pain.
Exposure of the cover screw : improper closure of the surgical site or insufficient burial of the implant.
Gingival abscess: resulting from incomplete screwing of the prosthetic abutments (healing or temporary) onto the implants, or from a forgotten suture. This results in the proliferation of granulation tissue, sensitivity or gingival hypertrophy.
Injuries and/or compression by the waiting prosthesis: The intrados must be cleared at the implant level and relining is carried out using a delayed-setting resin. Checks are regular to rebase the intrados and monitor the progress of healing.

Post-implant complications and failures (late):
Failures of osseointegration (biological failure)

Checking the osseointegration of the implant after a healing period of 2 to 3 months is the decisive step in the treatment as a whole.

The absence of osseointegration of the implant can be observed in several ways:

incorrect sound on percussion : a “dull” sound is a sign of fibrous interposition at the bone/implant interface.
implant mobility: implant mobilization can be tested during the various screwing and unscrewing maneuvers of the healing screw.
pain during unscrewing and screwing maneuvers : even if the implant cannot be moved.
Significant peri-implant bone loss .
Etiology of loss of osseointegration
- Heating of the bone (> 47°C).
- External contamination or prior infection of the implant site.
- Excessive bone compression.
- Lack of vascularization of the bone.
- Insufficient blocking of the implant.
- Premature loading of the implant.
Prevention: Respecting the basic principles of osseointegration helps limit primary failures.

Aesthetic failure

Aesthetic complications occur mainly in the maxilla, they are less visible in the mandible, and are especially apparent in fixed prostheses.

🡺 Aesthetic problems in single tooth loss:

Unfavorable crown length: The presence of a prosthetic crown that is too long at the end of an implant treatment constitutes a serious aesthetic detriment to the gummy smile. The causes associated with this are very varied:
1. Poor positioning of the implant in the vestibulo-palatal direction.
2. Incorrect positioning of the implant in the vertical direction.
Inadequate emergence profile: The emergence profile is a fundamental parameter which acts directly on the coronal morphology and which contributes to the construction of an aesthetic implant prosthesis.

1. Poor choice of implant diameter.

Wrong choice of intermediate element.
Incorrect positioning of the implant in the vertical direction.
Poor positioning of the implant in the vestibulo-palatal direction.

Visible cervical limit: The cervical limit of a supra-implant prosthesis must be located a maximum of 2 to 3 mm below the gum. This requirement must be met vestibularly for anterior teeth and maxillary premolars when the smile line is high. Aesthetic problems related to the cervical limit appear to be dependent on many factors:
1. Incorrect positioning of the implant in the vertical direction.
2. Wrong choice of intermediate element.
3. Transparency of the metal through the gum.
Absence of papillae: Their absence results in the appearance of “black holes” that cannot be satisfactorily eliminated by a prosthetic device. The development and maintenance of a papilla depends on several factors :

Surgical factors:

Existence of bone tissue at the interdental level : The presence of interdental bone peaks constitutes the best guarantee concerning the presence of papillae at the end of the prosthetic treatment.

Presence of a minimum space of 1.5 mm in the mesio-distal direction between the tooth and the implant : In order to provide sufficient mesio-distal space for the development and maintenance of the interdental papillae. It is then necessary to choose an implant whose neck dimensions allow the minimum space of 1.5 mm to be preserved for each papilla.

Prosthetic factors:
- Lateral compression at the stage of the temporary prosthesis : It is necessary to favor the ideal emergence shape of the temporary crown which exerts a certain compression of the peri-implant gum at the level of the interdental space. This compression will guide the development of the papillae in the embrasures.
- Emergence profile: The prosthetic objective is to copy the shape of the emergence profile of homologous teeth.
- Distance between alveolar ridge and prosthetic contact point : Tarnow et al. (1992) Complete papilla regeneration can be achieved if this distance is less than or equal to 5 mm . When the distance is 6 mm, the papilla regenerates in 56% of cases. In the presence of an alveolar ridge-contact point distance greater than 7 mm , papillary regeneration is only 27% . It is therefore imperative to judiciously position the prosthetic contact point during temporization at a distance from the alveolar ridge less than or equal to 5 mm.

🡺 Aesthetic problems in complete edentulism:

Aesthetic problems in non-removable screw-retained prosthesis of the stilt type

In the mandible In the mandible There are few aesthetic problems with this type of bridge given the non-visibility of the pillars when smiling.
In the maxilla On the other hand, this type of rehabilitation has led to numerous failures which have very largely limited its indication to the maxilla, due to:
- Inadequate support of the upper lip due to bone resorption

significant centripetal movement not compensated in the horizontal plane by a false vestibular gum.

The visibility of metal components is inevitably revealed by a short upper lip or a gummy smile.
Aesthetic problems in fixed, sealed or screw-retained prostheses: Aesthetic problems in fixed, sealed or screw-retained prostheses are mainly encountered in the maxilla. The causes associated with them are as follows:

Presence of implants at the embrasures : the implant emergence point in the mesiodistal plane is crucial for prosthetic construction. It must be located opposite a prosthetic element so that the emergence profiles simulate the natural. The reference elements are no longer anatomical but prosthetic. The ideal position of the implants is ensured by a surgical guide.
Emergence of screws on the vestibular surfaces : Centripetal maxillary bone resorption often requires a palatal angulation giving a vestibular axis to the prosthesis screw. The creation of a bridge directly screwed onto the implants requires having the screw heads visible on the vestibular surface of the incisors and canines, which is aesthetically unacceptable.

Different solutions are proposed, including:

the use of angled pillars
The sealed implant system makes it possible to avoid these drawbacks and obtain aesthetically acceptable teeth.

Absence of papillae: Restoring a complete maxillary edentulism with an implant-supported fixed bridge does not replace the lost interdental papillae because the edentulous ridges are generally flat and not scalloped. Some authors advocate surgical periodontal rearrangements to replace the lost interdental papillae.
Collapse of lip support: An upper lip not supported by adequate gingival volume or by a resin gingiva is an aesthetic failure

Any decision to implant in the maxilla must be preceded by the fitting of a mounting on a resin base plate without false gum, in order to assess the support of the lip which will be validated by the practitioner and the patient.

Unfavorable crown length : Significant vertical bone resorption can affect the aesthetic result if the smile line is high, as the prosthetic teeth will appear longer. A gummy smile may lead us to prescribe bone grafts or the wearing of removable false gums to avoid the effect of long teeth in the jaw.
Functional failure

Phonetic problems : Difficulty pronouncing certain letters (S and T in particular) is common with maxillary implant-supported bridges. Air passage between the prosthetic restoration and the palate can create major phonetic difficulties.
Solution :
- A phonetic adaptation period of 3 months is often sufficient.
- If phonetic problems persist, prosthetic modifications are necessary: the installation of a false gum.

Food retention: Macro-foods get stuck under the extension elements, in the inter-implant spaces or under the false resin gum.
Occlusal problems : The presence of screws on the occlusal surfaces and their orifice hinders the achievement of harmonious and correctly distributed contacts to guide axial forces and also disrupts the harmony of sliding in propulsion and lateral movements.

The sealed prosthesis allows for the establishment of an adequate occlusal morphology.

Lingual discomfort: In the case of long-standing, uncompensated posterior mandibular edentulism, the patient may experience lingual discomfort following the insertion of the prosthesis. This discomfort usually disappears after a few weeks of adjustment.

Mechanical failure

In covering prosthesis:

Fracture of the prosthetic base Reinforcement of the prosthetic base must be systematic when connecting the female attachments in the removable prosthesis that we want to stabilize.
Fracture of the removable antagonist prosthesis Here again, the reinforcement of the antagonist prosthesis with a cast chrome-cobalt grid must be included in the initial estimate given to the patient.
Implant fracture This therapeutic option remains contraindicated by some authors given that the axis of the occlusal forces of the antagonist teeth is not located in the long axis of the implants, which generates significant mechanical constraints.
- In fixed prosthesis
Fracture of the frame: The fracture site can be located:

At the span level, that is to say between two pillars. This case is very rare. It is essentially linked to a major casting defect
At the level of an extension of the reinforcement . This much more frequent accident is linked either to an extension that is too long, or to an undersizing of the reinforcement section.
Other factors may be involved, such as casting defects and occlusal overloads leading to fatigue fracture.
Loosening the abutment screw : The screw joint represents the weak link in the system. These are therefore the first elements of the system to suffer the consequences of abnormal stress on the implant system.

In sealed prosthesis , this complication is anticipated by:

The creation, on the lingual face of the cap, of a notch calibrated to a crown remover.
the use of a polycarboxylate cement, which breaks under impact, removes the crown.
Given the impossibility of loosening, this is a major complication requiring the destruction of the cap to access the screw.
Fracture of prosthesis or abutment screws : Fracture of a prosthesis screw does not compromise the future of the prosthetic restoration, since in the event of failure, the abutment can be removed and replaced. On the other hand, fracture of an abutment screw inside the implant must be managed with great care. It is not recommended to use ultrasound on the internal thread of the implant because it risks creating burrs that prevent the screw from rising.

Tips:

A straight probe, applied firmly to the screw and rotating in the direction of unscrewing, can be used to remove the fractured screw.
A new, coarse-grained cutter is inserted into an old turbine not connected to the unit.

*Causes of screw loosening and fractures*
*Single tooth loss*	*Multiple edentulism*
Wrong direction of occlusal force Implant inclination Poor adjustment of occlusal contacts and sliding Inadequate choice of implant diameter Implant offset from the center of the prosthetic crown Significant height of the prosthetic restoration Poor tightening of screws Nature of the abutment screw	Extension Poor adaptation of the framework Poor tightening of the screws Insufficient number and poor distribution of implants

– Poor adaptation of the prosthetic infrastructure

Damage to the internal thread of the implant The internal thread of the implant can be distorted by a healing screw forced into an imperfect axis, this thread becomes damaged and unusable.
Loosening of cemented prostheses: Clinical studies show that prosthetic complications are relatively limited in cemented prostheses. The main cause of loosening is the low height of the abutments (3 to 4 mm) in the posterior sectors.
Fracture of cosmetic material: Occlusion problems, bruxism and parafunctional habits are the main factors responsible for the fracture of cosmetic materials.
Implant fracture: This is the most serious prosthetic complication because it can jeopardize the entire prosthetic restoration. The vast majority of implant fractures occur in the posterior region where occlusal forces are much greater. The fracture resistance of an implant increases with the diameter of the implant (The 5 mm diameter implant is three times more resistant than the standard implant (3.75 mm). The 6 mm implant is six times more resistant to fracture ).

Gingival complications from prosthetic causes: Several problems to know:
- Gingival inflammation due to alteration of the implant surface, penetration of microbes along the implant components or following poor removal of excess cement in the peri-implant sulcus.
- Fistula
- Gingival hyperplasia
Bacterial complication

Inflammatory complications of infectious origin, mucositis and peri-implantitis appear more and more frequently, both due to the considerable increase in the number of implants placed each year and the lengthening of the observation period.

The term peri-implant mucositis is used to describe reversible inflammatory reactions affecting the peri-implant soft tissues.

The term peri-implantitis describes an inflammatory process that affects the peri-implant tissues and which results in particular in the more or less significant loss of bone support.

The main risk factors for the onset of peri-implantitis are:

history of periodontal disease.
poor oral hygiene.
tobacco consumption.

Preventive treatment

Primary prevention, before implant placement, involves the search for risk factors (unbalanced diabetes, smoking, neutropenia, etc.) and a history of oral infections (treatment of neighboring teeth, elimination of infectious foci, periodontal preparation).
If the implant replaces a non-vital tooth, the risk of peri-implantitis is increased. Therefore, careful curettage/rinsing of the extraction site must be performed before any implant procedure.
Secondary prevention (after the start of operation) involves maintaining a healthy periodontium, using maintenance sessions, and respecting occlusion rules .

Conclusion

The best way to manage failure is to avoid it, and this is achieved by applying preventive measures involving a complete pre-implant assessment, a carefully considered treatment plan, good training of the practitioner and their ability to most accurately assess their level of skills, and rigorous maintenance.

The practitioner who, faced with a complication, does not know how to manage the situation is then at fault. It therefore seems essential to know how to manage the unexpected and to have considered an alternative solution with the patient, from the initial treatment plan .

Finally, we remind you that it is important to put things into perspective, because therapeutic failure remains rare.

Bibliography

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