The Pilot Study Of The Regulation Of Peri-implant Crestal Bone Loss During Unloaded Period

Objects: This paper is to investigate the regulation of crestal bone level of non-submerged implants at unloaded period and the change of the expression of Tartrate Resistant Acid Phosphatase (TRAP) , which is the marker of the osteoclast, in bone tissue surrounding titanium implants during this period. The function of the osteoclast in bone resorption and remodeling was discussed after implants placement.Methods: Four Beagles were used in this study, which were automatically allocated into group A and group B, two dogs for each group. Group A: (T) 12 non-submerged titanium implants with smooth surface were placed in the mandibular 3 months after the promolar were extracted. The standardized radiographics were taken immediately and each month afterimplants placement (totally five months). (2) After the anterior teeth of the maxilla and the promolar & the anterior teeth of mandibular were removed, implants were placed at different times, so we can get the implant specimens of different periods after dogs were killed. The implant specimens were sectioned, fixed in 4% paraformaldehyde for 24 hours at 4℃, decalcified with 10% EDTA ( at 4℃) at PH7.2, and embedded in paraffin wax, sectioned, HE stained. The osteoclast was identified by histochemical staining of the Tartrate-resistant acid phosphatase (TRAP) and taken count of the number. Group B: 12 non-submerged titanium implants that the surface was sand-blasted and acid-etched were placed in the mandibular 3 months after the promolar were removed. The standardized radiographics were takenimmediately and each month after implants placement (totally three months). The radiographics were scanned into computer, then used the calibration of the Photoshop 6.01 software to measure the level of the crestal bone. The distance from the top of the implant to the point of bone-implant interface was calibrated using the known implant length to the measured implant length. Data were expressed by means D, and were analyzed by the SPSS 10.0 software.Results: Group A; Crestal bone loss was 0.64mm one month after implants placement. The second month was 0.02mm and the 3th, 4th, 5th month were 0.04mm, 0.15mm, 0.24mm respectively. Bone loss of the first month among other months was statisticlly significant (p<0.05, ANOVA analysis). Group B: Crestal bone loss was 0.70mm one month after implants placement. The second month was 0.10mm and the 3th month were 0.07mm. Bone loss of the first month was statisticlly significant than the other months's (p<0.05, ANOVA analysis). The number of OC which located at the crestal bone surrounding the implant reached summit at 6, 9 days after implants placement, about 16.00?.37 and 16.75 .63 respectively, which had significantly difference among the other periods (pO.OOl, ANOVA analysis). The number of OC (9.50 .22) during implants placement to one month had significantly (pO.OOl, T test) increase as compared to the number one month later. Conclusions: Maxium bone loss was observed at first month after implants placement. The OC at the crestal bone surface around implants was mostly recruited and activated between implants placement to one month later this periods, which was in accord with the observation of X radiographic.