The possible occurrence of implant failure is a major issue for dental implantologists and knowledge to prevent and manage such scenarios is clinically essential. Implant failure can be diagnosed based on the clinical signs of infection such as hyperplastic soft tissues, suppuration, colour changes of the marginal peri-implant tissues, mobility of implant and gradual bone loss that can be seen in radiographs.

Criteria for Implant Success 

• The individual implant is immobile when tested clinically 
• No radiographic evidence of peri-implant radiolucency 
• Bone loss not>0.2mm annually 
• Gingival inflammation amenable to treatment 
• Absence of symptoms of infection and pain 
• Absence of damage to adjacent teeth 
• Absence of parasthesia, anesthesia or violation of the mandibular canal or maxillary sinus 

Warning Signs of Implant Failure 

• Fracture 
• Loss of osseointegration 
• Gingival enlargement  
• Pain 
• Infection and soft tissue sloughing 
• Mobility of implant body 
• Purulent exudates  
• Peri implant gingival recession 

Categories of Implant Failure 

• Biological failure 
• Mechanical failure 
• Iatrogenic failure 
• Adaption failure 

Factors Influencing Failure

Patient  Factors  

• Dentist must consider patient dependent criteria such as bone quality and quantity, oral and general health , patients oral habits.

Systemic  Factors 

• Diabetes 
• Osteoporosis- postmenopausal women 
• Osteopenic patients

Bone Quality 

• Type 1: Homogenous and compact bone 
• Type 2: Dense trabecular bone surrounded by thick layer of  compact  bone 
• Type 3: Thin layer of cortical bone surrounding a core of dense trabecular bone 
• Type 4: Has a core of low-density trabecular bone encased in thin cortical bone 

Poor bone quality leads to loss of osseointegration and implant failure.

• Type 1and 2 - favorable 
• Type 4 - increases the risk of  failure 

Oral  Hygiene  Status 

• Poor  oral hygiene – formation of oral biofilm 
• Dental implants have no periodontal ligament between their surface and alveolar bone – easy microbial plaque accumulation on the rough implant surface – elicit inflammatory process 

              If inflammatory process is not controlled around the implant – bone loss and failure 

Oral  Lesions  And  Oral Habits 

• Cysts, Mucosal lesions – contraindication 
• Patients with autoimmune diseases and those receiving immunosuppressive drugs - poor prognosis if the implant is placed 
• Bruxism
• Smoking 
• Periodontitis 

Implant  Design 

• Implant length, diameter, surface and core characteristics influence the success or failure of osseous implant 
• Range of the length of dental implants - 7-20mm 
• Longer implant - high success rates 
• Implant diameter contributes to higher bone-to-implant contact

Implant  Spacing/Number 

• Spacing  is  important  between  implant and natural tooth 
• Minimum separation -  3mm between natural tooth and implant is needed 
• 4-7mm - prevent bone necrosis 

Take Home Message

Although success rate of dental implants are high, they do fail. A lack of primary stability, surgical trauma, and infection seem to be the most important causes of early implant failure. Proper case selection, diagnosis, treatment planning, good surgical practices and regular maintenance by patients are crucial for successful outcomes.

 Article by Dr. Siri P.B.