Is it true that it takes 3 months longer for posterior upper dental implants to oseointegrate than lower molar quadrant dental implants in most cases?

Not necessarily: I leave the implants for a minimum of three months before uncovering, sometimes longer. Your surgeon may feel differently based on experience and your specific situation. Lets them explain their rationale.

No: Typically it takes 100 days for integration to occur. Of course there are exceptions. Maxillary bone (upper jaw) is less dense and usually there is less primary stability as measured by placement torque resistance. However, bone grows as bone grows. No specific extra time needed for upper as a general rule. We restore both arches at the same time and take our final impressions at about 100 days.

It is true: When compared to compact bone (mandible) spongy bone (maxilla) has less density and hardness is not a stable base for primary fixture fixation.

Yes: Maxillary bone is softer than mandibular, it is recommended to wait a little longer in the upper Maxillary vs the mandible

Not really: It takes the same amount of tome for bone to fill and integrate in both jaws. Structurally, however, bone in lower jaw is denser than in upper no matter how long you wait.