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Risk Factors

Risk factors for implant failure can be grouped into local, systemic and behavioural aspects (Lang and Lindhe, 2015).

 

Local Risk Factors

  • Poor Oral Hygiene: Poor oral hygiene significantly increases the risk of secondary implant failure due to peri-implantitis. Ensuring high standards of oral hygiene is critical for implant success (Tecco et al., 2017).
  • History of Periodontal Disease: Patients with untreated periodontitis have a reduced implant survival rate. The same factors that increase periodontitis risk also heighten the risk of implant failure. Effective periodontal treatment must be completed before implant placement (Sousa et al., 2016; Chrcanovic et al., 2014b).

History of periodontal disease should also be taken into account. It must be controlled and oral health maintained before dental implant treatment due to the lower implant survival rate associated with patients with untreated periodontitis. A patient with a history of developing periodontitis may have an increased risk of developing peri-implantitis.

  • Endodontic Infections: Infections in adjacent teeth can lead to retrograde peri-implantitis. Ensuring endodontic health is vital before proceeding with implant placement (Ramanauskaite et al., 2016).
  • Parafunction and Excessive Loading: Overloading at the implant-bone interface can lead to bone loss and technical complications. Occlusal adjustments may be necessary to prevent excessive loading (Salvi and Bragger, 2009). Occlusal conditions and loading should be considered as ‘overloading’ at the implant-bone interface may result in bone loss.

 

Systemic Risk Factors

  • Smoking: Smoking impairs immune response and wound healing, significantly increasing the risk of implant failure and complications such as peri-implantitis. Smoking cessation is strongly recommended as part of the treatment plan (Chrcanovic et al., 2015d). History of periodontal disease should also be taken into account. It must be controlled and oral health maintained before dental implant treatment due to the lower implant survival rate associated with patients with untreated periodontitis. A patient with a history of developing periodontitis may have an increased risk of developing peri-implantitis.
  • Diabetes: While well-controlled diabetes patients have similar implant survival rates to non-diabetic patients, poorly controlled diabetes is associated with higher marginal bone loss, wound healing problems, and increased infection risk. Effective diabetes management is crucial for successful implant therapy (Annibali et al., 2016; Chrcanovic et al., 2014a).
  • Bisphosphonates and Medication-Related Osteonecrosis of the Jaw (MRONJ):
    • Pathophysiology: MRONJ is associated with the use of bisphosphonates and other antiresorptive and antiangiogenic medications, impairing osteoclast and endothelial cell function, and disrupting normal bone turnover and healing. Inflammation and infection also contribute to MRONJ development (Katsarelis et al., 2015; Lombard et al., 2016).
    • Medications and Risk: Oral antiresorptive medications have a lower MRONJ incidence (1 in 10,000 to 1 in 100,000), while intravenous formulations have a significantly higher risk (1 in 10 to 1 in 100). MRONJ is more common in the mandible and in areas with thin mucosa (Dodson, 2015; Brock et al., 2011).
    • Clinical Recommendations: Dental implant treatment is generally not recommended for patients receiving intravenous bisphosphonates or those on long-term oral bisphosphonates. This is considered a relative contraindication requiring careful evaluation. Bone grafting and sinus lift procedures are also discouraged (Chrcanovic et al., 2016a; Scully et al., 2006).
  • Radiotherapy:
    • Risk Factors: Implants in irradiated bone face higher risks due to compromised healing and potential complications such as osteoradionecrosis. The decision to place implants in irradiated bone should be made cautiously, considering the overall health of the patient and the specific effects of radiation on bone (Butterworth et al., 2016).
    • Indications: According to UK National Multidisciplinary Guidelines, implants can be considered for patients undergoing resection for head and neck cancer if there is a good prognosis for both cancer and implant treatment. They are indicated to retain a fixed prosthesis or support a removable prosthesis, especially when there is poor tissue support and dry mouth (Butterworth et al., 2016).
  • Immunosuppression: Patients undergoing immunosuppressive therapy or with systemic diseases face higher risks of implant failure. Implants can still be successful with well-managed conditions and strict maintenance protocols. Immunosuppression is typically a relative contraindication (Gay-Escoda et al., 2016).
  • Chemotherapy: Chemotherapy can delay wound healing and increase susceptibility to infections, although some agents do not significantly impact implant survival. It is considered a relative contraindication, requiring close monitoring and management (Chrcanovic et al., 2016b; Kovacs, 2001).
  • Anticoagulants: Patients on oral anticoagulants with an INR of 2-4 generally do not face significantly higher bleeding risks with dental implants. However, those with severe liver disease, thrombocytopenia, or bleeding disorders require special management and coordination with a haematologist (Madrid and Sanz, 2009; Renton et al., 2013).
  • Metabolic Bone Disease: There is no significant difference in implant survival rates between patients with and without osteoporosis. However, osteoporosis can increase peri-implant bone loss (de Medeiros et al., 2017). Careful monitoring and management are required for patients with metabolic bone diseases.
  • Mucosal and Autoimmune Disorders:
    • Scleroderma: Patients with scleroderma may have restricted mouth opening and stiff lips, making access and maintaining good oral hygiene challenging. Rigorous maintenance is required for these patients.
    • Systemic Lupus Erythematosus (SLE): Patients with SLE may be susceptible to bacteraemia, making antibiotic cover advisable. Implant survival rates in patients with mucosal diseases like oral lichen planus, Sjögren’s syndrome, and systemic sclerosis are comparable to those without mucosal diseases (Reichart et al., 2016).
  • Haematological and Lymphoreticular Disorders: Conditions such as agranulocytosis, cyclic neutropenias, leucocyte adhesion deficiency (LAD), and aplastic anaemia can increase susceptibility to periodontitis. While there are no well-controlled studies on implant success in these conditions, implants may be placed during the control or remission phase of the disease with strict postoperative maintenance (see Chapter 43).
  • Genetic Disorders: Genetic disorders such as Down’s syndrome and Papillon–Lefevre syndrome can lead to early tooth loss due to infection susceptibility. Dental implants may have a lower survival rate in these patients, and effective postoperative care and long-term maintenance are essential (Limeres Posse et al., 2016; Nickles et al., 2013).

 

Summary

Absolute contraindications for dental implants involve conditions that directly impede successful integration or pose significant health risks. Relative contraindications, such as controlled diabetes or long-term bisphosphonate use, require careful evaluation and management to mitigate risks and optimise outcomes. Proper assessment and tailored treatment planning are essential for achieving successful results in dental implant therapy.

 

Behavioural Risk Factors

  • Poor Compliance: Failure to maintain proper oral hygiene and regular dental visits can increase the risk of implant complications and failure.
  • Unrealistic Expectations: Lack of understanding and poor communication about the treatment can lead to dissatisfaction and complications.
  • Substance Abuse: Alcohol and drug abuse can impair patient cooperation and affect the success of implant treatment.
  • Psychiatric Issues: Psychiatric or psychological conditions can impact a patient's ability to cooperate with treatment. However, patients with medically controlled depression can generally undergo implant treatment successfully.