Polarized osteoclasts form the sealing zone and the ruffled border on bone surfaces. The sealing zone is detected as the actin ring (AR). The ruffled border is formed within the AR. Using dentin and osteoclasts formed in mouse cultures, we reported that polarized osteoclasts put tartaric acid resistance acid phosphatase (TRAP) on dentin, which was easily identified as the TRAP-mark. The position of TRAP-marks corresponded to that of ARs (Bone 49:1331, 2011). Here we examined how osteoclasts recognize dental implants by measuring ARs andTRAP-marks.
Methods:
Osteoclasts were obtained form mouse cultures. Osteoclasts were cultured on dentin, titanium (Ti), hydroxyapatite-coated Ti (HA-Ti), and sintered hydroxyapatite (sHA). Polarization of osteoclasts on the different substrates was evaluated by measuring of ARs and TRAP-marks. Effects of calcitonin on AR andTRAP-mark formation were also examined.
Results:
Osteoclasts formed ARs on Ti, HA-Ti and sHA as well as dentin. The size of ARs was small on dentin and HA-Ti, and large on Ti and sHA. Osteoclasts left TRAP-marks on HA-Ti, sHA and dentin. Moreover, ARs and TRAP-marks disappeared in response to calcitonin. Thus, osteoclasts polarized on Ti, HA-Ti and sHA as well as on dentin.
Conclusions:
Osteoclasts polarized on Ti, HA-Ti and sHA as well as dentin, suggesting that osteoclasts recognize Ti, HA-Ti, and sHA as bone. It is also suggested that osteoclasts may resorb HA of HA-Ti directly.