***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: BACKGROUND Various maxillary sinus floor augmentation techniques using bone grafts and bone substitutes are frequently used to enable placement of dental implants in the posterior maxilla . A previous case report demonstrated the possibility of promoting bone formation in the sinus by lifting the membrane without using a grafting material . However , the predictability of the technique is not known . PURPOSE The aim of this study was to investigate whether sinus membrane elevation and the simultaneous insertion of titanium implants without additional grafting material constitute a valid technique for bone augmentation of the maxillary sinus floor . MATERIAL S AND METHODS The study group comprised 10 patients in whom a total of 12 maxillary sinus floor augmentations were performed . A replaceable bone window was prepared in the lateral sinus wall with a reciprocating saw . The sinus membrane was dissected , elevated superiorly , and sutured to the sinus wall to create and maintain a compartment for blood clot formation . One to three dental implants were inserted through the residual bone and protruded at least 5 mm into the maxillary sinus . The bone window was replaced and secured with the overlying mucosa . Bone height was measured directly at each implant site at the time of insertion . Resonance frequency analysis ( RFA ) was performed on each implant at the time of initial placement , at abutment surgery , and after 12 months of functional loading . Computed tomography ( CT ) was performed in the immediate postoperative period and 6 months later , prior to exposure of the implants . RESULTS A total of 19 implants ( Brånemark System , TiUnite , Nobel Biocare AB , Gothenburg , Sweden ) in lengths of 10 to 15 mm were placed , with an average residual bone height of 7 mm ( range , 4 - 10 mm ) . All implants remained clinical ly stable during the study period . Comparisons of pre- and postoperative CT radiography clearly demonstrated new bone formation within the compartment created by the sinus membrane elevation procedure . RFA measurements showed mean implant stability quotient values of 65 , 66 , and 64 at placement , at abutment connection , and after 12 months of loading , respectively . CONCLUSIONS The study showed that there is great potential for healing and bone formation in the maxillary sinus without the use of additional bone grafts or bone substitutes . The secluded compartment created by the elevated sinus membrane , implants , and replaceable bone window allowed bone formation according to the principle of guided tissue regeneration . The precise mechanisms are not known , and further histologic studies are needed . Sinus membrane elevation without the use of additional graft material was found to be a predictable technique for bone augmentation of the maxillary sinus floor Lifting of the sinus floor is a st and ard procedure for bony augmentation that enables dental implantation . Although cultivated skin and mucosal grafts are often used in plastic and maxillofacial surgery , tissue-engineered bone has not achieved the same success . We present the clinical results of dental implants placed after the insertion of periosteum-derived , tissue-engineered bone grafts in sinus lifts . Periosteal cells were isolated from biopsy specimens of periosteum , resuspended and cultured . The cell suspension was soaked in polymer fleeces . The cell-polymer constructs were transplanted by sinus lift 8 weeks after harvesting . The patients ( n=35 ) had either one or both sides operated on . Seventeen had a one-stage sinus lift with simultaneous implantation ( 54  implants ) . In 18 patients the implants were inserted 3 months after augmentation ( 64 implants ) . Selected cases were biopsied . A control group ( 41 patients : one stage=48 implants , two stage=135 implants ) had augmentation with autologous bone only . They were followed up clinical ly and radiologically for at least 24 months . Both implants and augmentation were significantly more successful in the control group . Failure of augmentation of the tissue-engineered bone was more common after large areas had been augmented . Eleven implants were lost in the study group and only one in the control group . Lifting the sinus floor with autologous bone is more reliable than with tissue-engineered transplants . Although lamellar bone can be found in periosteum-derived , tissue-engineered transplants , the range of indications must be limited Platelet-rich plasma is an autologous source of platelet-derived growth factor and transforming growth factor beta that is obtained by sequestering and concentrating platelets by gradient density centrifugation . This technique produced a concentration of human platelets of 338 % and identified platelet-derived growth factor and transforming growth factor beta within them . Monoclonal antibody assessment of cancellous cellular marrow grafts demonstrated cells that were capable of responding to the growth factors by bearing cell membrane receptors . The additional amounts of these growth factors obtained by adding platelet-rich plasma to grafts evidence d a radiographic maturation rate 1.62 to 2.16 times that of grafts without platelet-rich plasma . As assessed by histomorphometry , there was also a greater bone density in grafts in which platelet-rich plasma was added ( 74.0 % + /- 11 % ) than in grafts in which platelet-rich plasma was not added ( 55.1 % + /- 8 % ; p = 0.005 ) Purpose : Various sinus augmentation procedures , using bone substitutes , have been used to place  dental implants in the atrophic posterior maxilla . The aim of this article is to evaluate the possibility of new bone formation in the maxillary sinus without a bone graft . Material s : Ten patients without significant sinus pathosis were selected for this study . The bony window was prepared in the lateral wall using the ultrasonic piezoelectric bone surgery device ( Surgybone , Silfradent srl , Sofia , Italy ) . The sinus membrane was elevated superiorly and implants were placed simultaneously to maintain the space under the sinus membrane for new bone formation . As the methods of sealing the lateral access window of the sinus , patients were divided into 2 groups . Nonresorbable membrane was used to seal the lateral access window of the maxillary sinus after implant placement in 5 cases ( group A ) . Replaceable bony window was used to seal the lateral wall of the sinus in another 5 cases ( group B ) . Computed tomograms were taken immediately before and after surgery , at the uncovering of the implant , and after a 6 month healing period . A bone biopsy was taken on the previous bony window area to evaluate new bone formation . Results : A total of 21 implants in lengths of 10 to 15 mm ( mean , 13 mm ) were placed , with an average residual bone height of 5 mm ( range , 1–9 mm ) . All implants remained stable during the study period in clinical evaluations . New bone formation and new sinus floors were found in radiographic and histologic evaluations . Conclusions : The human study showed the capacity of new bone formation in the maxillary sinus with membrane elevation only and simultaneous implant placement beyond the original sinus floor . New bone formation without additional bone graft in the maxillary sinus is revealed from the clinical , radiographic , and histologic results , but furthermore long-term studies are needed to confirm this The aim of this study was to evaluate the effect of platelet-rich plasma ( PRP ) on early and late bone healing after autogenous maxillary sinus grafting . Eleven patients were subjected to sinus augmentation with particulated autogenous bone bilaterally  with the addition of PRP in one side . Platelet counts in baseline whole blood and PRP were registered . Biopsies were taken in the grafted bone of the sinus area with trephine at 3 months ( nine patients ) and simultaneously a micro-implant was installed in the same region . The micro-implants with surrounding bone were retrieved by biopsy at 6 months ( seven patients ) . Undecalcified cut and ground sections were histomorphometrically analysed . Quantification of new and old bone in all biopsies was performed . The results of this histological study showed that significantly more new bone was formed at PRP-treated sites compared to controls after 3 months of healing . After 6 months , this effect could no longer be observed . This is in accordance with previous studies showing that PRP has a rather low regenerative capacity but may influence the early phase of bone healing . The additional value of PRP in autogenous bone grafts in the maxillary sinus is question able PURPOSE The purpose of this prospect i ve study was to evaluate the safety and effectiveness of recombinant human morphogenetic protein-2 ( rhBMP-2 ) on an absorbable collagen sponge ( ACS ) compared with an autogenous bone graft when used for 2-stage maxillary sinus floor augmentation . The study assessed new bone formation , placement integration , and functional loading after 6 months and long term for 2 years . MATERIAL S AND METHODS A total of 160 subjects were r and omized , enrolled , and followed from January 1999 to February 2004 at 21 centers in the United States . The subjects with less than 6 mm of native bone height were treated with 1.50 mg/mL rhBMP-2/ACS or with an autograft . The height and density measurements were quantified by computed tomography scans . Core biopsies were obtained at dental implant placement and used for histological analysis . Safety was evaluated by oral examinations , radiographs , serum chemistries , and hematology . RESULTS A significant amount of new bone was formed by 6 months postoperatively in each group . The mean change in bone height in the rhBMP-2/ACS subjects was 7.83 + /- 3.52 mm versus 9.46 + /- 4.11 mm for the bone graft subjects . At 6 months after dental restoration , the induced bone in the rhBMP-2/ACS group was significantly denser than that in the bone graft group . No marked differences were found in the histologic parameters evaluated between the 2 groups . The new bone was comparable to the native bone in density and structure in both groups . The success rate for the rhBMP-2/ACS group was 79 % ( 64 of 81 subjects ) , and 201 of 251 implants placed in the bone graft group and 199 of 241 implants placed in the rhBMP-2/ACS group were integrated , retained , and functional at 6 months after loading . No adverse events were deemed related to the rhBMP-2/ACS treatment . The autograft group was noted to have a 17 % rate of long-term parasthesia , pain , or gait disturbance related to the bone graft harvest . CONCLUSIONS The results of our multicenter , r and omized , prospect i ve , clinical trial have shown the effectiveness and safety of rhBMP-2/ACS compared with bone graft for sinus floor augmentation . The study 's primary endpoint was exceeded , and the implants placed in rhBMP-2/ACS and bone graft groups performed similarly after functional loading 
    Output:
    
All investigated studies show high implant survival rates for the graftless technique .
The technique is considered to be cost-effective , less time-consuming , and related to lower morbidity since no bone harvesting is needed