Experimental Research On Postextraction Site Preservation Applied In The Mandible Premolars Of Beagles

Object: Prosthetic methods conventionally applied clinically include removable prosthesis, fixed prosthesis, and implant prosthesis which enjoys unparallel advantages. But favorable bone conditions in the host site are vital to realize the integration of the implant and bone. Applying postextraction site preservation is to prevent and reduce disuse atrophy and absorption of alveolar ridge, making the height, width, and density of the alveolar ridge bone mass meet the requirements of anaphase implant. While applying GBR in clinical research can dramatically increase bone density, there are not much methods for GBR to prevent the reduction of height and width of alveolar ridge and to help reduce the bone density on the host site. Besides, the longest observation duration for fundamental research is 24 weeks, with no indication of the completion of metabolism and reconstruction, and of the stability of alveolar bone. This experiment is aimed to discuss the differences of height, width, bone density and times between host sites preserved and not preserved, hoping to provide some references for clinical alveolar bone physiological atrophy and implant site preservation through specifying the mechanism and time regularity of alveolar physiological atrophy by animal experiment.Method: To choose 12 healthy adult Beagles, extract mandible premolars on both sides, and carry out GBR immediately on one side and suture the other side for spontaneous recovery as control side. To put to death of 4 dogs respectively in the 3, 6 and 9 months after extraction. To take intact mandibles of two of the dogs for CT scan 3-D reconstruction, measure the height and width of the remaining alveolar bone and conduct dual energy x-ray absorptionmetry to measure extraction wound bone density; and to take bones from the extraction wound of other two dogs for dye light microscope observation, electron microscope observation and immunol histochemistry observation.Result: Compared with the control group, in the experimental group,the height and width of the remaining alveolar bone was relatively high, and the bone density was apparently high. Light microscope and electron microscope observations showed that the speed and duration of new bone formation of the experimental group was obviously faster than that of the control group. In the 9th month, the new bone tissue of the experimental group became denser in the extraction wound. Immunol histochemistry indicated that the experimental group served much better than the control group in terms of preventing osteoclasts'differentiation and activation, curbing bone absorption, facilitating the multiplication, differentiation and gathering of bone cells, evoking bone formation, and accelerating new bone formation.Conclusion: The experiment shows, spontaneous recovery after extraction suffers serious bone mass loss and the new bone is loose and poorly calcified. Site preservation can effectively prevent from physiological atrophy of the alveolar bone after extraction, forming new bone tissues and preserving the remaining alveolar bone as many as possible. And the dense new bone would provide favorable site conditions for anaphase implant. It also shows that the 9th month after extraction is the optimal time for anaphase implant.