Defining Implant Success, Survival, and Failure

Introduction

In dental implantology, not every implant that remains in place is truly a success. Understanding the difference between implant success, survival, and failure is essential for accurate clinical evaluation and proper patient care.

This article explores a consensus reached by experts during the ICOI Pisa Conference, providing a standardized classification system for assessing implant health. The goal is to help clinicians make informed decisions based on defined clinical criteria, not just whether the implant is still in the mouth.

Beyond Implant Survival Rates

Traditionally, implant studies report survival rates—meaning whether the implant is still in the mouth. However, survival alone doesn’t reflect the implant’s health or function. An implant causing pain, with bone loss, or mobility may still be counted as “surviving,” even if it’s failing clinically.

Instead, the ICOI Pisa Consensus introduced a four-tier classification that differentiates between true success, satisfactory and compromised survival, and failure.

Implant Success Criteria

The ICOI defines implant success as the ideal clinical condition. This includes:

• No pain during function or palpation
• No mobility
• Less than 2 mm of crestal bone loss since implant placement
• No history of exudate or infection

The time factor also matters:

• Early success: 1–3 years in function
• Intermediate success: 3–7 years
• Long-term success: Over 7 years

Success is not just about survival but stability, patient comfort, and prosthetic function.

Evaluating Clinical Health Indicators

Pain and Sensitivity

Pain on chewing or palpation often signals problems with implant fit, tissue inflammation, or nerve impingement. Any implant that causes persistent discomfort during function is not successful.

Mobility

Healthy implants show no clinical mobility under up to 500g of force. Mobility suggests a loss of bone contact and typically indicates failure.

Radiographic Bone Loss

Marginal bone loss is a key marker of implant health. The consensus recommends measuring bone loss from the initial placement rather than from previous follow-ups. Bone loss is categorized in 1 mm increments.

• <2 mm = success
• 2–4 mm = satisfactory survival
• 4 mm but <50% of implant length = compromised survival
• 50% = failure

Probing Depths

Routine probing is not recommended unless there are symptoms. However, pocket depths >5–6 mm with bleeding, exudate, or inflammation may suggest peri-implant disease.

Understanding Peri-Implant Disease

Peri-implantitis involves inflammation and bone loss around a functioning implant. It may result from bacteria or mechanical overload. Once bone is lost and oxygen tension drops, anaerobic bacteria may accelerate the destruction.

Signs of active disease include:

• Persistent exudate
• Bone loss beyond 4 mm
• Pocket depths over 7 mm
• Bleeding on probing

The ICOI Health Scale for Implants

The ICOI developed a four-tier scale for categorizing implants:

Group I – Success (Optimum Health)

• No pain or tenderness
• No mobility
• ≤2 mm bone loss
• No exudate
• Prognosis: Excellent

Group II – Satisfactory Survival

• No symptoms
• No mobility
• 2–4 mm bone loss
• No exudate
• Prognosis: Good to very good

Group III – Compromised Survival

• No mobility, but >4 mm bone loss
• Increased probing depths
• May have exudate or bleeding
• Bone loss <50% of implant
• Prognosis: Guarded

Group IV – Failure

• Pain, mobility, or >50% bone loss
• Persistent exudate
• Implant removed or unable to restore
• Prognosis: Non-salvageable

Conclusion

Defining implant outcomes as either “success” or “failure” oversimplifies a complex clinical picture. The ICOI Pisa Consensus provides a more nuanced framework for implant assessment, promoting better clinical judgment and treatment planning.

Pain, mobility, progressive bone loss, and peri-implant infection are key red flags that must not be overlooked—even when the implant remains in place.

For consistent evaluation, clinicians should adopt this four-level scale to guide decisions and ensure optimal long-term outcomes for patients.

The original article published by: 

Carl E. Misch, DDS, MDS, Morton L. Perel, DDS, MScD, Hom-Lay Wang, DDS, MScD, Gilberto Sammartino, MD, DDS, Pablo Galindo-Moreno, DDS, PhD, Paolo Trisi, DDS, Marius Steigmann, Dr. Med, Alberto Rebaudi, MD, DDS, Ady Palti, DDS, Michael A. Pikos, DDS, D. Schwartz-Arad, DMD, PhD, Joseph Choukroun, MD, Jose-Luis Gutierrez-Perez, MD, PhD, DDS, Gaetano Marenzi, DMD, DDS, and Dimosthenis K. Valavanis, MD, DDS, DMD