Translated Abstract
Background：
Modern oral implant therapy has been stepping into the orbit of the development of science since the the establishment of osseointegration in the 1970s, which indications have covered from edentulous or free toothless to all kinds of tooth missing. Oral planting artificial device was implanted and formed osseointegration in the alveolar process, to support and retain restoration, complete the missing tooth repair, which required enough bone volume to accommodate implant insertion. Under the efforts of the scholars all over the world in this field, with the development of implant material science and the improvement of the design, the implant success rate has been significantly increased, and more and more patients with missing teeth have been enjoying the benefits of it. However, in our country, the development of oral implant still facing with some problem such as large population and unbalanced medical condition. 1995 national epidemiological survey data showed that in 35 ~ 44 years old, toothless jaw accounted for 0.11%, the per capita lost teeth 0.88, in 65~74 - year - old group toothless jaw was 10.5% in the population, per capita lost teeth 9.86, which was mainly caused by periodontitis, and the prevalence and severity of periodontitis along with aging, which has serious damage to alveolar process, especially maxillary teeth area, combining with the maxillary sinus gasification, often leads to more lack of available bone height, which buried a hidden danger to plant treatment.In view of this, clinical application of sinus floor elevation have solved this problem in some extend.
According to Caldwell-Luc operative methods in 1980s, Boyne and James proposed lateral sinus floor elevation (LSFE) to augment bone volume, and many scholars has improved this technology; Tatum has put forward another minimally surgical trauma method, that was osteotome sinus floor elevation (OSFE) in 1986. The improvement of surgical technology had broken through the bottleneck of implant therapy in clinical applications. At present, the success of sinus floor elevation (SFE) has been recognition. Clinically, according to the residual bone height, different surgical operation was chose. If RBH≥3mm, LSFE and simultaneous implant (SI) is feasible, if RBH＜3mm, LSFE and stage implant is safe,which adds to the uncertainty of implant time. There is no discussion about OSFE, because of its no bone graft generally. For bone graft material, there are tissue engineering bone and autologous bone, bone substitutes, freeze-dried allograft, these materials are relatively expensive and antigenic problems may exist, except for autologous bone. The source of autogenous bone is limited and there might be additional surgical trauma. Meanwhile, there are unpredictable absorption rate. Review the literatures which suggest that no bone graft of SFE can observe new bone formation, and the sinus membrane has osteogenic potential. A problem comes out that the following implant scheme is feasible, there is no bone graft in LSFE, on the premise of good initial implant stability, select the implants of special surface processing and the rounded roots to support elevated sinus membrane and form a similar ＂tent＂ sample structure. If possible, patients can not only save the bone graft treatment costs, reduce the risk of infection, but also avoid secondary surgical trauma, shorten the clinic treatment time and total cost. For implant surface possessing and design, it is also a very good reference. Implant surface structure can be designed to adhesive a variety of osteoblast factor and cytokines, which can accelerate osteogenesis effect of the space.
Objective:
To improve beagles experimental model of the LSFE and SI.
To evaluate feasibility of the rounded root implant elevate sinus membrane and osteogenesis effect potential of the space.
Preliminary explore the relationship between membrane elevation height and osteogenesis effect potential of the space.
Method:
Under the general anesthesia, the modified experimental model of the LSFE and SI were established in 8 beagles, 16 months age. The fourth premolar (PM4) bilaterally in maxilla were extracted with special care. Lateral window were performed to elevation the sinus membrane. The palatal of the maxilla PM4’ distal-buccal root were elected as candidate site, where Osstem implant (South Korea) including ?4.0 mmxH8.5 mm and ?4.0mmxH10mm was inserted in 4 beagles, respectively, after trimming the bone platform. The right sinus was filled with autogenous bone as control group, whereas the lift sinus nothing (membrane elevation alone) as test group. ISQ value were measured postoperative immediately and 6 months. After 6 months, those specimens were obtained for CBCT/Micro CT scans and gross observation. Set up volume of interest, three-dimensional (3D) model of specimens were reconstruction to detect the new bone (NB), bone volume fraction (BV/TV, BVF), trabecular thickness (Tb.Th), trabecular number (Tb.N) and trabecular spacing (Tb.Sp) parameters to quantitative analysis. Finally, the specimens were made into 50μm thick hard tissue section without decalcification, fluorescent tags and Van Gieson staining, observing the osseointegration under optical microscope.
Results:
1.Animal experiment results
The modified model was feasible and effective. 16 implants were in good initial stability. ISQ averages 66. The wound healed well. During this experiment period, all animals had in good condition. There were no acute inflammations in oral wounds.
2.CBCT results
Preoperative CBCT image was done to analyse sinus anatomy structure and size, determine the surgical plan. Postoperative immediately image suggested that implant was in ideal position consisting with preoperative surgical design, and that bone graft area on the right side was filled with autogenous bone maintaining good elevate space, left only implant in the space with low density image. After 6months, CBCT showed that all around the implant bone were normal. There were no acute inflammations in sinus during the follow-up period.
3.ISQ results
The data of implants’ ISQ value postoperative immediately and 6 months in this study was normal distribution (P ＞ 0.05)by Skewness/Kurtosis test. Paired t-test and Stata 12.0 statistical software were used to analyse. Two groups of implant ISQ value had no statistical difference respectively. Finally, implant stability is good.
4. Micro - CT results
The image information were possessed by the VG Studio Max2.1 software, set up VOI, 3D model of specimens were reconstruction to detect and quantitative calculating the related parameters of bone around implant, including the bone trabecular and new bone formation parameters.
5. Histology results:
Observed under light microscope, tetracycline fluorescence labeling results showed that the new bone was strong green fluorescence belt. Obviously, VG staining showed that haversian system was visible, the disordered arrangement of trabecular bone. Red areas was mature bone tissue, yellow area was unmineralization osteoid bone . Two groups of implants have reached the normal osseointegration.
Conclusion:
1. The Beagles is ideal model of LSFE and SI. Sinus volume is (1979.98 + 129.20) mm3, has enough volume to accommodate implant and bone graft. The palatal-distal-point of PM4 is an ideal site for SI, in which corresponding to the palatal macroporous lateral bone plate, the bone thickness is (2.31 + 0.59) mm and eye shot is open, can avoid the interference of the distal first molars, all of which ensure the initial stability of the implant.
2. Traditional LSFE in dogs, the infraorbital neurovascular bundle is cut and ligated. In this study, the bundle is protected and postoperative restored, reducing the operation difficulty, alleviating the postoperative reaction. The study also shows that the rounded root implant, with good initial stability, elevate sinus membrane is feasible. There is no sinus membrane perforation during the follow-up period.
3. ISQ value and osteogenesis effect is no statistical difference between test group and control group. This result shows that active bone remodeling in elevated space and the membrane may have osteogenetic potential. New bone formation is confirmed by histology. Multi-factor analysis of variance showed that the osteogenetic potential of sinus membrane may related to the elevated height.
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