Considerations preliminary to the application of early and immediate loading protocols in dental implantology

In oral implantology, a 3-6 month stress-free healing period is presently a ccepted as a prerequisite to achieve bone apposition without interposition of a fibrous scar tissue. This protocol was introduced by Branemark and co- workers in 1977. The aim of the present paper is to review the reasons that led Branemark and collaborators to require long delayed loading periods. I t is shown that the requirement for long delayed loading periods was drawn from the initiation and development periods of their original clinical tria l. Demanding conditions were met involving simultaneously: 1) patients with poor bone quality and quantity, 2) non-optimized implant design, 3) short implants, 4) non-optimized surgical placement, 5) nonoptimized surgical pro tocol and 6) biomechanically non-optimized prosthesis. Extrapolation of the requirement for long healing periods from these particular conditions to m ore standard situations involving refined surgical protocols and careful pa tient selection might be questioned. Albeit premature loading has been inte rpreted as inducing fibrous tissue interposition, immediate loading per se is not responsible for fibrous encapsulation. It is the excess of micromoti on during the healing phase that interferes with bone repair. A threshold o f tolerated micromotion exists, that is somewhere between 50 mu m and 150 m u m. It is suggested that loading protocols might be shortened through 2 di fferent approaches. The first way would be to decrease stepwise the delayed loading period for free-standing implants below the presently accepted 3-6 months of healing. The second way would be to identify immediate loading p rotocols that are capable of keeping the amount of micromotion beneath the threshold of deleterious micromotion. Immediate loading protocols for impla nts-retained overdentures and fixed bridges are reviewed. It is shown that successful premature loading protocols require a careful and strict patient selection aimed to achieve the best primary stability. These various proto cols need to be further documented in order to assess their predictability.