Purpose: The aim of this investigation was to evaluate whether the placement of medical-grade calcium sulfate hemihydrate (MGCSH) in fresh extraction sockets might affect the quality of newly formed bone and influence crestal bone changes. Materials and Methods: Forty patients who needed maxillary single- tooth extraction followed by implant insertion were enrolled in the study. Alveoli were required to have four remaining intact walls. After tooth extraction, 22 patients received MGCSH in the extraction sockets (test group), and 18 received no grafting material (control group). At the time of extraction and 3 months later (at implant placement surgery), vertical and horizontal socket dimensions were measured. In addition, during implant placement, tissue specimens were harvested for histologic and immunohistochemical evaluations. Comparisons of test and control tissues were performed with the unpaired Student t test. Results: Vertical resorption of the buccal socket walls and reduction of the buccopalatal width were more pronounced at control sites than at MGCSH sites (1.2 mm versus 0.5 mm, and 3.2 mm versus 2.0 mm, respectively). Formation of 100% living trabecular bone with woven and lamellar arrangements was found in both test and control sections. The average trabecular bone area fraction was greater in the grafted specimens than in control specimens (58.8% versus 47.2%). In the test group, the average percentage of lamellar bone increased from 16.4% to 43.6% from the crestal to the apical region and was greater than in unfilled specimens (11.1% coronally, 22.2% apically; P .0001). Conclusions: MGCSH seems to be effective in accelerating the bone healing process and minimizing alveolar ridge resorption in intact fresh extraction sockets. Schlagwörter: bone healing, calcium sulfate, dental implant, human histology, socket preservation