Pattern of osteogenesis during onlay bone graft healing.

OBJECTIVE: The aim of this paper was to analyze how healing occurs between onlay bone graft and the mandible cortex. STUDY DESIGN: Autologous and allogeneic corticocancellous bones, harvested from the ilium wing, were grafted at each mandible side of 40 rabbits. One side received platelet-rich plasma (PRP). Killings occurred at 3, 7, 14, 28, and 56 days. Tissues were stained by hematoxylin-eosin and toluidine blue. New bone area was measured at different regions of sections stained with toluidine blue. Wilcoxon test was used to analyze differences among regions and Bonferroni test to analyze the influence of PRP, graft nature, and days. RESULTS: Osteogenesis was higher at the lateral region (P < .05). PRP tended to improve bone neoformation, which was higher at the allogeneic graft. Statistical significance among the different categories of variables-grafts, use of PRP, and days of observation-did not have a linear behavior. A linear behavior of statistical tests was not detected. Bone new formation increased until the 14th day (P < .05). CONCLUSIONS: Onlay grafts heal due to osteogenesis which occurs at the lateral region and between the cortex and host mandible. Allogeneic grafts and PRP tend to improve bone formation.

Evaluation of factors that can modify platelet-rich plasma properties.

OBJECTIVE: The aim of this article is to discuss a protocol for obtaining platelet-rich plasma (PRP) and evaluate which factors, derived from its preparation method and from whole blood, modify PRP cytometry and coagulation time. STUDY DESIGN: Whole blood, harvested from 50 rabbits, was centrifuged at 300g for 10 minutes. Supernatant was recentrifuged at 5000g for 5 minutes. PRP was clotted with calcium chloride. Whole blood and PRP cytometry were obtained through automatic measurement. The amount of erythrocyte- and platelet-poor plasma drawn from whole blood was measured. Hematocrit, platelet and leukocyte count, mean corpuscular volume (MCV) and mean platelet volume (MPV), mean, standard deviation, and median were also calculated at whole blood and PRP. PRP coagulation time was also analyzed. Mean values between groups were analyzed using Student t test. Correlations were evaluated using Pearson's correlation coefficient. The significance level was set at P < .05. A linear regression was performed to investigate the relationship among the correlated variables. RESULTS: From whole blood, 2.68 mL of erythrocytes and 5.72 mL of platelet-poor plasma (PPP) were removed. PRP platelet count was 2,324,080 cells/microL. Whole blood hematocrit influenced the amount of cells and PPP removed, as well as PRP platelet count. PRP platelet count was dependent on whole blood hematocrit and platelet count, and does not interfere in PRP coagulation time. A linear interaction was confirmed between the variables that presented significant Pearson correlation. CONCLUSIONS: The protocol evaluated produces a good PRP. Whole-blood parameters can predict PRP features. Whole-blood hematocrit is an important variable for PRP preparation and PRP cytometry characterization. PRP platelet count is dependent upon whole-blood platelet count.