OBJECTIVE To study effects of the modified sandblasted surface of titanium implants, developed by authors, on the bone healing process. METHODS Osteoblasts were derived from the 5th passage of human fetal osteoblasts after primary isolation. Alkaline phosphatase (ALP) activities and protein contents of cellular layers, and osteocalcin contents in culturing medium were employed as criteria to evaluate osteogenic functions and differentiation of osteoblasts. The ALP activity was assayed utilizing the kinetic method, the protein content utilizing the Coomassie's method, and the osteocalcin content utilizing the radioimmune assay (RIA) method. Values of all criteria were divided by the corresponding cell numbers of different groups at a respective time point for the purpose of standardization. Samples were assigned to three groups-the modified sandblasted surface group, the smooth surface group and the blank control group, The culture was ended at, 4 days and 13 days. RESULTS At 4 days of culture, the modified sandblasted surface group showed a superiority to the smooth group with respects to the ALP activity [(17.390 +/- 1.595) nmol PNP x min(-1) x 10(-6) cells vs. (10.978 +/- 1.879) nmol PNP x min(-1) x 10(-6) cells] and protein content [(152.7 +/- 16.3) micro g/10(6) cells vs. (58.0 +/- 5.9) micro g/10(6) cells] of cellular layers and the osteocalcincontent [(43.0 +/- 6.1) ng/10(6) cells vs. (24.9 +/- 6.0) ng/10(6) cells] in culturing medium. Till the 13th day of culture, no differences were detected. CONCLUSIONS It is cytologically proved that the modified sandblasted surface can accelerate the bone healing process of implants though the improvement of osteoblastic functions and differentiation.