Which of the following factors is important in determining implant success?

Bone quality is indeed a crucial factor in determining the success of dental implants. The condition and density of the bone into which the implant is placed significantly influence the ability of the implant to integrate properly with the surrounding bone. High-quality bone provides better stability and support for the implant, enhancing the chances of osseointegration, which is the process by which the implant becomes securely attached to the bone.

While patient age and type of prosthesis can play a role in the overall treatment plan and long-term outcomes, they do not directly impact the biological integration of the implant as bone quality does. For instance, older patients may have different healing capacities, and the choice of prosthesis affects function but not the initial success of the implant itself. Therefore, the most pivotal factor out of those listed is bone quality, as it directly relates to the implant's stability and longevity.