Purpose: To study the stability of the microscrew implant anchorage under different loading force and different timing and observe the integration of the implant to the bone.
Methods: Thirty-six titanium alloy microscrew implants were implanted into three dogs' maxilla and mandible. The implants were divided into two groups: one with immediate implant loading and the other with delayed implant loading. In the delayed loading group, the microscrew implants that were implanted into the right maxilla and mandible were unloaded temporarily. Four weeks later, these dogs, together with the immediate loading group, whose microscrew implants were implanted into the left maxilla and mandible, were loaded at the same time. The mesial screw was unloaded. Two distal screws were loaded with force: 1.96N on the maxilla, and 3.92N on the mandibular. After 12 weeks, the dogs were sacrificed. The specimen were fixed and decalcified. Subsequently, immunohistochemical stain for BMP-2 was employed. The specimen were assessed with image analysis system to analyze the average grey scale. The data were analyzed using Student's t test and one-way ANOVA with SPSS 10.0 software package.
Results: BMP-2 staining showed that there was significant difference between the immediate loading group(1.96N,3.92N), delayed loading group(1.96N,3.92N) and non-loading group at average gray value (P<0.05). But there was no significant difference between the immediate loading group and delayed loading group (P>0.05).
Conclusions: Both the immediate and the delayed implant loading can strengthen the attachment and integration of the implant to the bone. The timing of the loading force has no significant impact on the stabilization of the microscrew implants.