Early loading on oral implants to promote osseointegration has not been consistently successful, partly because mechanisms for force-induced healing bone morphogenesis are ill-understood. Objectives: This study hypothesizes that functional loading can enhance osseointegration by proper stimulation of pre-osteoblasts in early healing stage. Methods: Seventeen Sinclair pigs were used and divided into experimental (load, 12 pigs) and control (non-load, 5 pigs) groups. Each group was divided into subgroups for non-loaded implant healing times of 1, 2 or 4 months. For the experimental pig, one smooth titanium threaded implant was placed in the mandible unilaterally. After the specified healing periods, the implant was loaded uni-axially for an additional five months. The force 6.5 N was controlled using an intra-oral hydraulic device (Ko et al., 2002). Cyclic loads (1 Hz) were applied for 10 minutes each day. Radiography and micro-computer tomography were used to assess osseointegration at the end of the experiments. For the control pig, the implant was inserted and allowed to heal for the same 1, 2 or 4 months as for the experimental group. An additional 5 months of non-loaded healing time was added. All procedures were approved by the University of Minnesota (9910A22661). Results: The preliminary results showed that early loading (1-month healing) significantly reduced crestal bone loss and promoted osteogenesis at the deep implant-bone interface (P<0.05). The dense trabeculae aligned predominantly parallel to the direction of maximum principal stress (tensile), suggesting that early daily loading activated cellular response to elicit an adaptive remodeling. Cell appearances, percent osteoid, and tissue strains of the healing tissue at the time when loading starts were assessed and compared among different healing times. Conclusions: This is the first time a controlled-load has been shown to profoundly enhance osseointegration for an early loaded dental implant. (Supported in part by Whitaker Foundation and MDRCBB)

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