Animal Experimental Study Of The Osteogenic Efficiency Of Maxillary Sinus Elevation Without Bone Transplantation

Background:Tooth loss in maxillary posterior area lead to bone resorption accompanied by osteoporosis, gasification of the maxillary sinus, and other factors always lead to insufficient bone available, which becomes the difficulties in oral implant. The concept of maxillary floor lifting was firstly termed by Tatum in1976. Boyne and James termed maxillary floor lifting through lower edge of vestibular sulcus incision later, and then it was accepted and became popular. Maxillary floor lifting was considered as a useful bone augmentation surgery.The maxillary floor lifting need to implant various bone grafting material in early times. Although autograft is the golden standard for bone graft, it has a problem associated with its uncertain absorptivity. With the development of maxillary sinus floor lifting, the innovation has been heavily focused on the bone grafting materials. Many studies compared diffierent bone grafting materials and agree on the necessary use of the materials. Scientists began to explore the maxillary sinus floor lifting surgery without grafting materials since1997, and they filled the lifting space with the blood clot instead of grafting materials. Ellegaard had tooth implantation in the posterior maxilla for24patients with periodontitis and38teeth involved maxillary sinus operation. Carefully separate the mucosa in the lateral wall of the maxillary sinus in fenestration and then place the implants through the alveolar bone routinely. Mucous membrane of maxillary sinus was supported by the implants that implanted into the maxillary sinus and therefore a close space was formed. The implant in this space was filled with blood clot. Reset the mucosal flap to the window area without a barrier membrane in the bone loss area. After5～6months, the implants began with functional loading. New bone formation was observed around the upper stage under the mucosa of the maxillary sinus, and35implants were observed with good osseointegration.In2002, Lundgren reported that obvious new bone formation was observed between the bone and mucosal of the maxillary sinus after removal of mucosal cyst and3months healing period. Then Lundgren performed maxillary floor lifting without filling into bone grafting materials for10patients, and a total of19implants were placed. A total of6-9mm bone height was increased after6-12months. There was no difference of new osseointegration between between this method and using substitute. New osseointegration was located the sinusal mucosa, so scientists inferred that the sinusal mucosa was able to induce bone forming.Laceration of mucosa or perforating the mucosa is the most common complication, especially in the condition that the mucosa is thin or there exist maxillary sinus septa of bone. If left untreated, it may lead to the infection of the maxillary sinus and even lead to more serious complication involve with eyes and brain. The treatment is different according to the size of perforation. For the small one, placing gelfoam or tissue patch in the defected area is enough. For the bigger damage, it is necessary to relax the mucosa and stitch1to2, then place the tissue patch with bone meal, and close the wound at last. But larger perforation always suspends the operation until the mucosa was completely healed2to3months later. Some scholars support to open other2holes in the lateral wall of the maxillary sinus and stitch through the holes tightly. In this way, the perforation site will be closed, and new bone formation can be seen.The maxillary sinus elevation surgery without bone transplantation underlines the maintaining of space in mucosa elevation. The space full of blood clot is an important part of obtaining expected bone formation. Then in the case of mucosal tearing, if mucous membrane is successfully elevated to maintain a space, whether there is new bone formation?If when mucosa menbrane is elevated when mucosa tearing or perforation, the space full of blood clot will form new bone, then if when mucosa menbrane experiences tearing or perforation, so that we have to terminate the operation,we can transform to maxillary sinus floor elevation surgery without bone transplantation.In the end,this operation can be completed with shortening the time of retreatment,in addition,the risk and costs of bone transplantation is reduced.ObjectivesOur study was to assess the osteogenesis in maxillary sinus floor elevation without bone transplantation and to evaluate the effect of titanium screws for space-maintaining when the the mucosa was teared or not.Material and Methods1.Experimental animal and MaterialSix healthy adult male Beagle dogs were12-14months old and12.2-14kg. They were purchased from Gaoyao Condar Laboratory animal science and technology co, LTD. The biochemical criterion of these dogs are normal, so they were no acute inflammation and no infectious diseases. And the dogs were feeding timing and quantitative by the sun Yat-sen university animal laboratory center. Titanium-screws:purchased from Xi’an in titanium nations biological material co, LTD. Type2.5mmx8mm.2.Methods2.1AnesthetizationThe6beagle dogs were preoperative fast for12hours and premedicated with penicillin (400thousand u/d) by intramuscular injection2hours before operation. Sumianxin and pentobarbital sodium were used as combined anaesthesia,which at first, sumianxin was intramuscular injection (0.08mL/kg),and then,until it work out,3%pentobarbital sodium(0.8mL/k)was intraperitoneal injection.After general anesthesia, skin preparation, sterilization and spreading towels were prepared as normal.2.2CBCT PhotographyA CBCT was taken to know the Maxillary sinus anatomy well, and then results and analysis of measurement provide imaging evidences for the experimental animal surgery..2.3Surgical ProcedureTrapezoidal incisions were performed from mesial part of second maxillary molar to distal part of first maxillary molar, and full thickness flaps were reflected to expose the outside wall of maxillary alveolar bone. A2cm×1cm rectangle cut bone was designed to lift bone block, under which a infraorbital neuraltube was exposed. The outside wall of maxillary sinus was exposed after the infraorbital neuraltube was ligatured, the outside wall was opened approximately6mm x8mm, and was taken out by bone-chesel, and then was put into normal saline. White mucous membrane of maxillary sinus was visible and was elevated carefully.2holes was drilled beside bone window, and titanium screws were twisted into holes to sustain space. In the end, the window walls were relocated, and flaps were sutured. The control group was mucosa breakage, of which the side was almost5mm.The part of breakage underwent no reatment and the mucousa was elevated in the same way as test groups to sustain space.3.Postoperetive CareHalf flow diet was provided after operation,and intramuscular injection of penicillin (800thousand u) was given for7days after surgery.4. All dogs were sacrificed after6monthsGross observation:to watch the condition of the lesion, new bone formation and the space the implants anchorage keep.Histological observations:maxilla was collected and then the sample were prepared, last the sample were place in10%formalin. Across gradient alcohol dehydration, dipping into the liquid investment, heating up to polymerization and accomplish embedding. After slicing and staining by toluidine blue, the sample can be observed by light-microscope.Results1.CBCT imaging results of maxillary sinus in Beagle dogsIt’s observed from CBCT that the shape of maxillary sinus in cross-section of Beagle dogs is long elliptic, while the buccolingual dimension was significantly longer than the mesiodistal dimension. The shape of coronary plane looked like a kidney, and the sag part was close to infraorbital neuraltube, and the shape of sagittal plane is irregular quadrangle. The mean mesiodistal dimeter of maxillary sinus in10beagle dogs is22.41mm±3.10mm, while the buccolingual dimeter is6.21mm±0.94mm, then the height is21.13mm±2.55mm. There is no obvious statistic difference in both sides.2.Observation of gross specimenThe postoperative healing in all experimental surgeries was uneventful and the animals demonstrated good health during follow-up period. Incisions healed well and mucous membrane showed no swollen and fester. All12maxillary sinus showed no obvious inflammation. The bone window healed well after sacrifice.24Titanium screws were located in the original position, but sinus mucosa was collapsed. In the12titanium screws in mucosa breakage group,11of them perforated tissue, but bone apophysis was found around8screws. While in the mucosa integrant group,10perforated and bone apophysis was found around8.3. Histological observationsFor hard tissue slices, we cuted the slices through the long axis of titanium screws, and used toluidine blue for staining, and then they were abserved under a light microscope. There was mineralized mature bone around titanium screws, but no intercellular substances and no new bone was observed.Conclusions1. It could be concluded that maxillary sinus in Beagle dogs was irregular from this study with Cone Beam Computed Tomography to observe maxillary sinus. It was oblong in cross section and the medial distal dimension of maxillary sinus was longer than the buccolingual dimension obviously. The shape of maxillary sinus was "Kidney type" at coronal plane with the depression adjacent to infraorbital neural tube but irregular quadrangle at sagittal plane. The mean values were obtained, including the mesiodistal and the buccolingual dimension and the height in order to provide a basis for how to perform surgery in Beagle dogs. It benefits avoiding faults due to operation blindness and decreasing complications, which was significant in the degree of guidance.2. The shape and volume of maxillary sinus in dogs is different from human beings. It is much deeper and lateral bone plate. Infraorbital neural tube are on their way before getting into maxillary sinus. The bottom floor of infraorbital neural tube is the lareral wall of maxillary sinus, as infraorbital nueves and blood vessel bundle runs in infraorbital neural tube, it should be ligatured carefully. As the maxillary sinus mucosa in dogs is thicker, the coefficient of operation is more difficulty. It is the reason that suture the mucosa over the bone is preferred than the volume of the space. Further animal experiment study is needed to ensure the consistent clinical results.3. In this study, the osteogenesis was not obvious in sinus lateral floor elevation and the mucosa was not tearing in Beagle dogs. Still the appliance of Tai nail as a device to keep the volume of space was doubted. Further study is needed to evaluate whether the operation is feasible and we are trying to design better equipments to keep the volume of space in our following research.