Abstract: Abstract： Objective To explore the better and mature technique of immediate implantation.Methods Animal experiments:Nine rural adult mongrel dogs were used in this study.Self-contrast was adopted.Mandibular third and fourth premolars were extracted bilaterally on all animals.Each premolar had two roots which were medial root and distal root.The implants with the same diameter as extraction sockets were placed into right mandibular third,fourth premolar distal extraction sockets and left mandibular third,and fourth premolar medial extraction sockets (Sim group); The implants with the smaller diameter than extraction sockets were placed into left mandibular third and fourth premolar distal extraction sockets.The space around the defects was filled with Bio-oss(Bio group).The dogs were killed randomly at 1st month,2nd months,3rd months after surgery.The tissue samples were stained with HE for histological examination and bone histomorphometric parameters were measured to quantify the change of new bone around titanium implants and to observe the changes of implant-bone interface.Results The success rate of Sim group was higher than that of Bio group.The bone plate of sim group was better in continuity,thicker and surrounded by a large number of osteoblasts.At 1st month after surgery,contact length fraction (CLF),bone ingrowth fraction (BIF) in Sim group have significantly increased compared with those in Bio group (P＜0.05).At 2nd,3rd months after surgery,contact length fraction (CLF),bone ingrowth fraction (BIF) in Sim group slightly increased compared with Bio group,but there was no significant difference between two groups (P＞0.05).Conclusions Using root-shaped implants with the same diameter as extraction sockets could accelerate osseointegration,and the CLF was higher than that in the defects around implants covered with Bio-oss.

Key words: pure titanium implant, osseointegration, immediate implant, Bio-oss, dog