In Vitro Investigation of the Dependency Between Abutment Length and Implant Stability Quotient (ISQ) for Stability Measurements on Bone Anchored Hearing Implant Systems.

Hypothesis: The investigation aimed at measuring the relation between abutment length and Implant Stability Quotient (ISQ) for stability measurements on two types of bone-anchored hearing implant systems.

Background: Measuring bone-anchored hearing implant stability using the ISQ has the inherent limitation that the measurement is dependent on the length of the abutment used on the implant. This dependency has not earlier been analyzed in depth. Therefore, ISQ measurements for different abutment lengths cannot be directly compared if a patient needs a change of abutment or when evaluating different patients in a scientific setting.

Methods: The dependency of ISQ on abutment length for Cochlear BI300 (Cochlear Nordic AB, Mölnlycke, Sweden) and Ponto Wide Implant (Oticon Medical AB, Askim, Swden) was measured using a temporal bone model and a plaster model. ISQ at abutment level was compared with the corresponding ISQ at implant level and results were analyzed by multiple linear regression.

Results: The ISQ dependency on abutment length was -3.5 ISQ/mm (95% CI: -3.7 to -3.4) (Cochlear BI300 implant) and -2.9 ISQ/mm (95% CI: -3.0 to -2.7) (Oticon Wide Implant).

Conclusion: The dependency of ISQ on abutment length for two types of bone-anchored hearing implant systems has been established empirically. This knowledge enables clinicians to continue monitoring the ISQ for a patient after a change of abutment and enables researchers to compare ISQ between patients in a clinical study.