Preliminary Study On The Best Time For Delayed Immediate Implantation

Purpose Since the titanium implant system has been created by professor Branemark, it has become one of the major methods to repair the missing tooth. The traditional dental implant restoration requires complete bone healing in dental extraction wounds after alveolar ridge form is good in order to carry out dental implant placement, which requires 3 to 12 months. During this time, absorption of the alveolar bone occur obviously. Therefore, the immediate implantation came into being. However, due to implant and alveolar bone intramural larger gap, most of the immediate implantation after tooth extraction need bone grafting. But most patients with trauma or severe periodontal disease are suitable for neither immediate bone grafting after tooth extraction nor immediate implanting. For these cases, we can use the delayed immediate implantation. This study aimed to find the peak period of osteoblast cell activity through animal experiment to help seek the best time for the delayed immediate implantation. In clinic, delayed immediate implantation (14days after tooth extraction), immediate implantation, and conventional method of implant technique were compared in bone density and alveolar bone height in certain parts of the peri-implant, thus to find whether there are significant differences in the three kinds of implanting methods.Methods The animal experiments: four adult mongrel dogs which have been quarantined were chosen as the experimental objects. After the experimental dogs are anaesthetized completely, 12 anterior teeth were extracted from jaws of each dog and the alveolar wall was protected as much as possible. Then the sockets were closed by suture. Penicillin was given intramuscularly for every dog for 3 days to prevent infection. Specimens were harvested according to the order as follows: The 7th day after the tooth extraction, cut the right maxillary alveolar bone around dental sockets of the 1st experimental dog, cut the left maxillary alveolar bone around dental sockets of the 2nd experimental dog, cut the left mandibular alveolar bone around dental sockets of the 3rd experimental dog, cut the right side of mandibular alveolar bone around dental sockets of the 4th experimental dog; The 14th day after the tooth extraction, cut the left maxillary alveolar bone around dental sockets of the 1st experimental dog, cut the left mandibular alveolar bone around dental sockets of the 2nd experimental dog, cut the right mandibular alveolar bone around dental sockets of the 3rd experimental dog, cut the right side of maxillary alveolar bone around dental sockets of the 4th experimental dog; the 21st day and 28th day, the four dogs'alveolar bone were cut per day in different quadrants, with each quadrant including three teeth. The specimens are disposed by HE staining, Masson staining, and detect the alkaline phosphatase activity in all the specimens.In clinic,6 implants were chosen to be treated with delayed immediate implantation,12 implants with immediate implantation, and 12 implants with conventional implantation. Bone density and height of alveolar bone in specific parts around the implant were compared by X-ray 3 months after the implanting operation to see whether there are significant differences in the three kinds of implanting methods.Results (1) There are a large number of spindle-shaped osteoblasts in the histological sections of the 14th day, it indicates that the osteoblasts which are participating in the new bone formation are increasing significantly, so the rate of the new bone formation is accelerating; In the Masson staining sections, the scope of immature bone tissue which is stained in green in 14th day is larger than in the 7th day.(2) ALP activity index of the 14th day is significantly higher than that in other groups at all times (P<0.05);(3) In clinic, there is no statistically significant difference in bone mineral density around the implants among the three methods (P>0.05);(4) There is no statistically significant difference in the alveolar bone height at the neck of the implants among the three methods (P>0.05).Conclusion 1 The activity of osteoblasts during the 14th day is significantly higher than that in other periods. The result suggests that 14 days after extraction may be the best time for delayed immediate implantation.2 In the premise of strictly controlled indications, there is no statistical difference in the alveolar bone absorption among the delayed immediate implantation, the immediate implantation, and the conventional implantation.3 There is no statistical difference in the bone mineral density around the implants among the delayed immediate implantation, the immediate implantation and the conventional implantation.4 The result of delayed immediate implantation was satisfactory, but more research and even a longer time follow-up is needed to see long-term effects.