How to rehabilitate two converging implants in the premolar and molar region?

Rehabilitation of Converging Implants in Premolar and Molar Region

For rehabilitation of two implants placed in premolar and molar region that converge occlusally, the use of angled abutments is the most effective approach to correct the angulation and achieve proper prosthetic alignment. 1

Understanding the Challenge

• Converging implants (also called tilted or angulated implants) present a prosthetic challenge due to their non-parallel alignment, which can complicate the path of insertion for the final restoration 1
• Tilted implant placement is often intentional to avoid anatomical structures like the maxillary sinus, but can also result from surgical limitations or bone anatomy constraints 1

Prosthetic Solutions

Primary Approach: Angled Abutments

• Use custom or pre-fabricated angled abutments to correct the convergence and create a common path of insertion for the final restoration 1
• Angled abutments can compensate for implant angulation discrepancies up to 35-40° and allow for proper prosthetic alignment 1
• Select abutment angulation based on the degree of implant convergence to create parallel restorative platforms 1

Secondary Approaches:

• Screw-retained restorations with angled screw channels:

  • Modern CAD/CAM technology allows for screw access holes to be angled up to 25-30° from the implant axis 2
  • This approach maintains retrievability while accommodating implant convergence 2

• Individual crowns vs. splinted restoration:

  • For moderately converging implants, individual crowns may be possible with appropriate angled abutments 3
  • For severely converging implants, a splinted restoration may provide better biomechanical distribution of forces 2

Clinical Considerations

• Occlusal forces management:

  • Design occlusal surfaces with narrow, flat occlusal tables to reduce lateral contacts and minimize off-axis loading 4
  • Ensure proper occlusal adjustment to prevent overloading of the prosthesis, which could lead to mechanical complications 5

• Material selection:

  • For converging implants, high-strength materials like zirconia or metal-ceramic restorations are recommended to withstand potential stress concentration 2
  • Consider the use of resilient abutment materials to absorb some of the off-axis loading 2

• Maintenance protocol:

  • Implement regular follow-up to monitor for complications like screw loosening, which occurs in approximately 7% of posterior implant restorations 3
  • Evaluate for cement retention issues, which can affect up to 22% of cemented posterior implant restorations 3

Potential Complications and Management

• Biomechanical complications:

  • Converging implants may create unfavorable stress distribution, potentially leading to component failure or bone loss 5
  • Regular radiographic monitoring is essential to detect early peri-implant bone loss 5

• Prosthetic complications:

  • Abutment screw loosening is a common complication that may require retightening or replacement 3
  • Loss of cement bond may occur more frequently with angled abutments due to non-axial forces 3

Pitfalls to Avoid

• Avoid excessive cantilever designs when restoring converging implants, as this can magnify biomechanical complications 1
• Don't underestimate the importance of proper occlusal scheme - ensure adequate clearance and avoid heavy lateral contacts 4
• Avoid cement excess in subgingival areas, which is more challenging to remove with angled abutments and can lead to peri-implantitis 2

By following these guidelines, converging implants in the premolar and molar region can be successfully rehabilitated with predictable long-term outcomes.