Dental Implant Failure: Reasons and Prevention

Discuss implant failures and precautions that need to be taken.

Implants have become most successful treatment modality in the treatment of partially and completely edentulous patients. Even with the success rates more than 70%, as stated by Brånemark and Misch after detailed clinical study, there exist a failure at various levels of the treatment procedure.

Classification of implant failure

Two main types – Types due to etiology and according to types of failure

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Etiology

• Host factors
  • Prevailing medical and dental status
  • Psychology
  • Habits
• Surgical procedure
  • Pre-surgical
    • Infected implant sites
    • Inadequate mineralization of grafts
  • Stage 1 surgery
    • Inappropriate flap design
    • Improper implant angulations
    • Insufficient primary stability
    • Excess pressure and overheating of bone
    • Teeth–implant space
    • Implant contamination
  • Stage 2 surgery
    • Improper loading protocol
    • Local and systemic entrusted factors
• Implant selection
  • Implant dimensions
  • Mismatch of bone and implant type
  • Number of implants
  • Improper implant design and system
• Prosthodontic factors
  • Increased cantilever
  • Implants–natural teeth connection
  • Prosthesis design
    • Absence of passive fit of prosthesis
    • Improper abutment fit interface
    • Improper prosthesis design
    • Improper occlusal design.
• Periodontal factors
  • Peri–implantitis
  • Improper oral health maintenance

Type of failure

• Esthetics failure
  • Gingival esthetics failure
  • Restoration factors
  • Implant factors
• Osseointegration failure
• Functional and psychological problems.

Etiological Factors

The implant failures can be subdivided into factors caused due to host or patient, surgical failure, improper implant selection and prosthetic factors.

Host/Patient Factor

• Prevailing medical and dental status of patient
• Psychology
• Habits.

Contraindications for implants
Pregnancy, granulocytopenia, long-term steroid use, diabetes, hemophilia, Ehler–Danlos syndrome, Marfan’s syndrome, osteoradionecrosis, renal failure, organ transplants, anticoagulant therapy, Crohn’s disease, fibrous dysplasia, Paget’s disease and osteoporosis. Systemic complications delay healing phase or bone repair mechanisms in the implant site.

Patient psychology
The patient has to be educated and motivated to maintain the oral hygiene.

Habits
Such as pan chewing, smoking and other parafunctional habits can cause increased forces on implants and local ischemia.

Surgical failures

Presurgical and surgical failure.

Presurgical

Infected implant sites – with periodontal infections, endodontic lesions, infected socket and dental pathologic conditions

Inadequate mineralization of graft – Implants fail to integrate in immature grafts. It is ideal to wait till all the woven bone matures to lamellar bone that can have better implant prognosis.

Factors that can contribute to the failure of implant in stage 1 surgery are:

• Inappropriate flap design –  Improper flap design can lead to decrease in nutrients reaching implant site and blood supply, infection and tissue ischemia. Proper flap closure ensures better healing and surgical prognosis
• Improper implant angulations – It is advisable to have straight implant and abutment for favorable prognosis since the implants are designed for axial forces
• Insufficient primary stability – Precision osteotomy reduces the implant mobility and facilitates faster healing
• Excess pressure and overheating of bone – The use of excessive pressure and heat can damage the bone cell by forming a barrier layer between the implant and healthy bone causing osseointegration failure
• Teeth–implant space – Minimum of 1 mm space is required between teeth and implant to maintain ideal bone health
• Implant contamination – Improper sterilization protocol during surgical procedure, broken manufacture seal and oral cavity contamination.

Factors causing failure in Stage 2 surgery

Improper loading protocol
Adequate healing time has to be provided before loading the implant.

Local and systemic factors
The protocol measures for stage 2 surgery as removal of cover screw with adequate tissue relief, infection free zone and adequate keratinized gingiva should be maintained for the success of implant.

Implant selection

Bone support, bone type, number, type and size of the implants play a vital role in implant success. The precautions followed in implant selection to prevent implant failure are:

• The length and width of implant has to be sufficient to support the superstructure
• In possible limits, increased number of implants has to be placed to support the restoration for uniform stress distribution
• Selection of a proper implant system according to available clinical situation for better success of implant
• Mismatch of system can compromise the implant health and success.

Prosthetic factors

Factors influencing the prosthetic design are:

• Reduced number of implants can cause a cantilever design with undue forces on the supporting implant. A minimal of 8 mm cantilever is the permissible limit with increased number of implants
• The preferred design is to avoid implant connection to natural teeth, if connected can cause overload and mismatched resiliency
• A lack of passive fit of prosthesis at the abutment interface.

Periodontal factors

Peri-implantitis
Is the postoperative failure arising due to Gram negative bacteria. Retrograde peri-implantitis can be caused due to micro fracture of bone, infection from adjacent teeth or early loading. Preventive care has to be followed during the various procedures to avoid retrograde peri-implantitis.

Improper oral maintenance
Can lead to wider problems from tissue loss to bone loss which in turn affects esthetic and function.

Types of failure

Esthetic failure can be further subdivided into:

• Gingival esthetics – papilla esthetics, contour and form of gingiva around the restoration
• Restoration esthetics – color, emergence profile, size, form and type of restoration
• Implant esthetics – thread exposure, angulations of implants, bone resorption

Undue care is taken during treatment planning, surgical stage and during fabrication of restoration to avoid esthetic failures.

Lack of osseointegration can be due to:

• Bone grafting issues
• Surgical and prosthetic factors
• Functional and psychological problems.

Treatment options for management of implant failure:

• Nonsurgical
  • Topical treatments and oral medicaments
  • Removal of occlusal interferences
  • Debridement
  • Repair of prosthesis.
• Surgical
  • Resective and regenerative surgery
  • Implant removal.

Appropriate procedures have to be selected depending on the clinical situation and type of failure. Careful evaluation procedures are done and suitable management protocol is done to correct the failures.