[Fluid shear stress increases the Ca2+ concentration in bone-marrow derived osteoclast-like cells].

OBJECTIVE: To study the change of Ca2+ density in cultured osteoclast-like cells in response to fluid shear stress. METHODS: Laser scanning confocal microscope and fluorescent probe were used to detect the free Ca2+ in osteoclast-like cells before and after undergoing fluid shear stress. The images were analyzed and compared with image software. RESULTS: At 37 degrees C the free Ca2+ in osteoclast-like cells could be labelled effectively with 10 micromol/L Fluo-3/AM. Compared with contol group, the average intensity of Ca2+ fluorescent signal in osteoclast-like cells undergoing fluid shear stress increased significantly. CONCLUSION: The Cal2+ concentration in bone-marrow derived osteoclast-like cells is sensitive to fluid shear stress, which suggests osteoclast-like cells modulate their function in response to fluid shear stress through the change of free Ca2+ concentration.

[A three-dimensional finite element analysis on relationship between abutment undercut and retentive arm width of cast cobalt-chromium three-arm clasp].

OBJECTIVE: To analyze the stress distribution on cast retentive clasp arms in dislodging denture, and to discuss the deepest undercuts of the second mandibular premolar (abutment) for cobalt-chromium alloy cast clasps with different widths. METHODS: Three-dimensional finite element models of the abutment with different depths of undercuts and retentive arms with different widths were set up. Dynamic displacement load (3 mm/s) was exerted on the middle of the retentive arms to analyze the stress in retentive arms while they were being removed from the abutment. RESULTS: The peak stress in retentive arms was positively correlated to the undercuts displaced by clasp tips, and those were not obviously related to the undercuts displaced by the middle of retentive arms. When width/thickness of retentive arms was 3, the increase of peak stress of retentive arms with similar locations of clasp tips was significantly related to the increase of the arm width. The deepest undercuts of the second mandibular premolar for cobalt-chromium alloy cast retentive arms with different widths of 1.8 mm, 1.6 mm, and 1.4 mm were 0.25 mm, 0.30 mm, and 0.35 mm respectively. CONCLUSIONS: When width/thickness of the retentive clasp arm is fixed, the wider the arm is, the smaller depth it should be placed on the undercut of abutment. Retentive clasp arms with different widths should be placed on different depths of undercuts in order to prevent their permanent deformation.