if the quantity and quality of alveolar bone for a dental implant is appropriate , then the prosthesis using an osseointegrated dental implant will have a favorable long - term result 12 . implant - supported restorations can be successful , even in atrophic jaws , using bone augmentation that includes bone graft and tissue regeneration techniques3 . among the various techniques , autogenous bone is believed to be the most effective bone graft material and is still regarded as the " gold standard " for augmentation procedures because of its osteogenic potential4 . in cases where large amounts of bone are required , autogenous bone is considered the best choice . autogenous bone can be harvested from sites such as the iliac crest , tibia , skull , or mandible56 . moreover , block bone can be harvested from intraoral sites , including the retromolar region , zygoma , maxilla , and mandible78 . intraoral harvesting has several advantages when compared with extraoral donor sites , such as proximity of the donor site to the recipient site , convenient surgical access , shorter operation time , lower morbidity of the donor site , and ease of performing the procedure in an outpatient or office environment . the intraoral surgical operation can be performed in the office under local anesthesia or in the operating room under general anaesthesia910 . several studies have shown that intramembranous bone grafts ( skull or mandible ) , compared to endochondral bone grafts ( iliac ) , have minimal resorption and better incorporation at the recipient sites1112 . microarchitectural features , such as the cortical / cancellous ratio , may affect the volumetric stability of the bone grafts in the craniofacial skeleton1314 . on computed tomography ( ct ) scans , the hounsfield unit ( hu ) is proportional to the degree of x - ray attenuation by the tissue . on cone - beam ct ( cbct ) , the degree of x - ray attenuation is shown by greyscale or voxel values . we calculated the volumetric changes using the grayscale of the harvested cortical bone and volume of interest ( voi ) using the computer program ez3d2009 ( vatech , yongin , korea ) . the aim of this study was to evaluate volumetric changes of bone reconstruction of severely atrophic jaws , using a block consisting of autogenous mandibular cortical bone prior to dental implant placement . in addition , the clinical success of dental implants placed at the grafted alveolar bone sites was also evaluated . a retrospective chart review of patients who underwent onlay graft surgery prior to dental implant placement was conducted . the patients included in this study were treated from march 2010 to april 2014 at the pusan national university dental hospital ( yangsan , korea ) . ninety - five patients ( 48 men and 47 women ) aged 19 to 72 years were included in the study . the graft sites were divided into three parts ; anterior and both posterior regions of one jaw . all patients included in the study were scheduled for onlay grafts and implantation using a two - stage procedure . personal information , such as age , sex , and grafting direction ( horizontal / vertical ) , location ( anterior / posterior or maxilla / mandible ) and whether or not sinus lift procedures were conducted , were collected from the patient records . all patients underwent an onlay bone grafting procedure using a mandibular bone block , consisting of buccal cortical bone from the posterior part of the mandibular body to the external oblique ridge . no patient had undergone any oncologic treatment , and there was no use of any allografts or xenograft materials . a cbct was taken before the grafting surgery ( t0 ) and after the grafting surgery ( t1 , within 3 days ) and just before the implant surgery ( t2 ) . dental implants were placed at recipient sites 5.50.8 months after grafting surgery in all cases . the authors used several dental implants , including a sand blasted with large grit and acid etched sand large acid ( sla ) surface , usii ( osstem , seoul , korea ) , solar ( shinhung , seoul , korea ) , and straumann slactive ( straumann ag , basel , switzerland ) . the authors observed the state of the dental implants and evaluated them clinically over 2.61.2 years . occlusion function , marginal bone loss ( by dental panorama ) , peri - implantitis , osseointegration of the fixture , and prosthetic problems were investigated at all dental implant sites . only 11 patients could not be evaluated with respect to their implant - based prosthetics . six patients were not seen again for personal reasons , and prosthetics were not yet completed for five patients . the authors used panoramic radiographs and standard dental films for long - term follow - up since cbct was not beneficial for patients , and taking a cbct solely for research purposes was not considered ethical . preoperative cbcts were used to evaluate the need for a bone graft with mandibular cortical bone in those patients who had a severe atrophic jaw . of these , 85 surgeries were performed under local anesthesia . in order to improve patient comfort , conscious sedation with midazolam was used in these surgeries from march 2010 to october 2011 at the pusan national university dental hospital . another sedative agent , dexmedetomidine ( precedex ; hospira , lake forest , il , usa ) , was used for surgeries performed in november 2011 . another nine patients were treated under general anesthesia due to long operative times required for multiple recipient sites or patients ' demands . lidocaine with epinephrine ( 1:100,000 epinephrine ) was administered locally to reduce pain and bleeding . harvesting the mandibular block bone was initiated with linear incision over the lower external oblique ridge . after reflection of the full - thickness flap and exposure of the mandibular body bone , the osteotomy was completed with copious irrigation . one part of the harvested bone was ground into small particles using a bone crusher.(fig . 1 ) the harvested block bone was positioned as an onlay using the " lag screw " technique in order to stabilize the bone block15 . the authors fixed the block bone and surrounded it with particulate cortical bone mixed with fibrin sealant ( tisseel ; baxter healthcare gmbh , wien , austria ) . then , a bioresorbable collagen membrane ( ossguide ; bioland , cheonan , korea ) was used for covering the grafted bone . for increased bone volume and tension ( full - coverage onlay ) , elongation of the buccal flap was achieved through a small incision and dissection of the periosteum.(fig . b ) antibiotics were given preoperatively 30 minutes before and postoperatively for approximately one week intravenously and by mouth . the donor site used was the mandibular buccal cortical bone from the body of the mandible . the authors assumed that the harvested cortical bone was the same as the adjacent non - harvested cortical bone on the grayscale range . therefore , the authors established the grayscale range of the harvested cortical bone by measuring the grayscale of the adjacent cortical bone . the authors enclosed the grafted bone in a rectangular parallelepiped , namely , the voi in the ez3d2009 program setting . this program is able to calculate the volume of grafted bone by integrating the materials corresponding to the determined grayscale range . for the onlay graft , it is not difficult to draw lines for the voi because the grafted bone is not surrounded by recipient bone.(fig . 3 ) the mann - whitney u test was used for statistical analysis in order to identify differences due to sex . the one - way anova test was used for onlay direction in the same manner . scheffe 's test combined with one - way anova was used to identify differences due to age . the kruskal - wallis test was used for the recipient location , and the student 's t - test was used for the sinus lift procedures . all statistical analyses were performed using ibm spss statistics 21.0 ( ibm co. , armonk , ny , usa ) . a retrospective chart review of patients who underwent onlay graft surgery prior to dental implant placement was conducted . the patients included in this study were treated from march 2010 to april 2014 at the pusan national university dental hospital ( yangsan , korea ) . ninety - five patients ( 48 men and 47 women ) aged 19 to 72 years were included in the study . the graft sites were divided into three parts ; anterior and both posterior regions of one jaw . all patients included in the study were scheduled for onlay grafts and implantation using a two - stage procedure . personal information , such as age , sex , and grafting direction ( horizontal / vertical ) , location ( anterior / posterior or maxilla / mandible ) and whether or not sinus lift procedures were conducted , were collected from the patient records . all patients underwent an onlay bone grafting procedure using a mandibular bone block , consisting of buccal cortical bone from the posterior part of the mandibular body to the external oblique ridge . no patient had undergone any oncologic treatment , and there was no use of any allografts or xenograft materials . a cbct was taken before the grafting surgery ( t0 ) and after the grafting surgery ( t1 , within 3 days ) and just before the implant surgery ( t2 ) . dental implants were placed at recipient sites 5.50.8 months after grafting surgery in all cases . the authors used several dental implants , including a sand blasted with large grit and acid etched sand large acid ( sla ) surface , usii ( osstem , seoul , korea ) , solar ( shinhung , seoul , korea ) , and straumann slactive ( straumann ag , basel , switzerland ) . the authors observed the state of the dental implants and evaluated them clinically over 2.61.2 years . occlusion function , marginal bone loss ( by dental panorama ) , peri - implantitis , osseointegration of the fixture , and prosthetic problems were investigated at all dental implant sites . only 11 patients could not be evaluated with respect to their implant - based prosthetics . six patients were not seen again for personal reasons , and prosthetics were not yet completed for five patients . the authors used panoramic radiographs and standard dental films for long - term follow - up since cbct was not beneficial for patients , and taking a cbct solely for research purposes was not considered ethical . preoperative cbcts were used to evaluate the need for a bone graft with mandibular cortical bone in those patients who had a severe atrophic jaw . a total of 95 patients had grafting surgery . of these , 85 surgeries were performed under local anesthesia . in order to improve patient comfort , conscious sedation with midazolam was used in these surgeries from march 2010 to october 2011 at the pusan national university dental hospital . another sedative agent , dexmedetomidine ( precedex ; hospira , lake forest , il , usa ) , was used for surgeries performed in november 2011 . another nine patients were treated under general anesthesia due to long operative times required for multiple recipient sites or patients ' demands . lidocaine with epinephrine ( 1:100,000 epinephrine ) was administered locally to reduce pain and bleeding . harvesting the mandibular block bone was initiated with linear incision over the lower external oblique ridge . after reflection of the full - thickness flap and exposure of the mandibular body bone , the osteotomy was completed with copious irrigation . one part of the harvested bone was ground into small particles using a bone crusher.(fig . 1 ) the harvested block bone was positioned as an onlay using the " lag screw " technique in order to stabilize the bone block15 . the authors fixed the block bone and surrounded it with particulate cortical bone mixed with fibrin sealant ( tisseel ; baxter healthcare gmbh , wien , austria ) . then , a bioresorbable collagen membrane ( ossguide ; bioland , cheonan , korea ) was used for covering the grafted bone . for increased bone volume and tension ( full - coverage onlay ) , elongation of the buccal flap was achieved through a small incision and dissection of the periosteum.(fig . b ) antibiotics were given preoperatively 30 minutes before and postoperatively for approximately one week intravenously and by mouth . the donor site used was the mandibular buccal cortical bone from the body of the mandible . the authors assumed that the harvested cortical bone was the same as the adjacent non - harvested cortical bone on the grayscale range . therefore , the authors established the grayscale range of the harvested cortical bone by measuring the grayscale of the adjacent cortical bone . the authors enclosed the grafted bone in a rectangular parallelepiped , namely , the voi in the ez3d2009 program setting . this program is able to calculate the volume of grafted bone by integrating the materials corresponding to the determined grayscale range . for the onlay graft , it is not difficult to draw lines for the voi because the grafted bone is not surrounded by recipient bone.(fig . the mann - whitney u test was used for statistical analysis in order to identify differences due to sex . the one - way anova test was used for onlay direction in the same manner . scheffe 's test combined with one - way anova was used to identify differences due to age . the kruskal - wallis test was used for the recipient location , and the student 's t - test was used for the sinus lift procedures . all statistical analyses were performed using ibm spss statistics 21.0 ( ibm co. , armonk , ny , usa ) . the recipient sites were divided into three parts for each jaw ( anterior , left posterior , and right posterior ) . there were 69 maxillary sites and 59 mandibular sites that were grafted with mandibular block bone in this retrospective study . the patients consisted of 66 women and 62 men , and the average age was 49.1 years . each patient had an average of 1.35 recipient sites . with the exception of 11 patients who did not have final prosthetics placed on their implant fixtures , or had not come to our hospital for implantation , 84 patients had 267 implants placed in their onlay - grafted sites . three infections occurred at the recipient sites less than a week after the grafting surgery . in one case , granulation tissue was found on the recipient site 2 months after surgery , and the tissue was curetted . the authors compared the residual graft rate with age , sex , graft direction ( horizontal / vertical ) , graft location ( anterior / posterior , maxilla / mandible ) , and whether or not the sinus lift procedure was conducted . for the analysis of differences due to age shown in table 1 , a significant difference was only observed between a and b , which corresponds to patients in their 30s and 50s , respectively . in other words , differences due to age and sex were not statistically significant according to this study.(table 2 ) statistically significant esdifferences were found for grafting direction . horizontal onlay grafts were more stable than vertical or vertical plus horizontal grafts in graft volume.(table 1 ) graft location partially affected volumetric stability.(table 1 ) for the maxilla , the residual rate was higher than the mandible , but the difference was not statistically significant . for the anterior jaw , statistical analyses showed that less grafted bone was lost as compared with the posterior jaw . for cases where onlay graft surgery was performed at the same time as the sinus lift procedure on the posterior maxilla , the volumetric stability of the bone was poorer than without the sinus lift , but the difference was not statistically significant.(table 3 ) two hundred sixty - seven implants were placed on 111 onlay - grafted sites . approximately 24.414.3 months after implant - placing surgery , only 3 of the 267 implants had undergone mild marginal bone loss ( under 2 mm , vertically ) ; however , these implants did not have peri - implantitis or mobility . although the follow - up period was short , all implant - based prosthetics were clinically successful until november 2014 . a previous volumetric study showed that a significant amount of resorption of bone grafts occurred during the first 6 months following surgery . furthermore , these authors concluded that the initial loss of bone grafts subsides after 6 months and does not significantly continue after 12 months16 . therefore , in the current study , the authors placed implants 4.30.8 months after bone graft surgery . 4 ) several investigators who compared two - dimensional images from standard radiographs with data obtained from ct scans showed widely varying results ; underestimations of 21% and overestimations of 18% were observed17 . this result was attributed to a correlation between the bone height and the total volume of resorption and enlargement , as well as the distortion of standard radiographic imaging17 . therefore , the current authors calculated three - dimensional ( 3d ) volumetric changes for 4.2 months . several clinical and radiological studies have used ct scans to gain sectional information ; however , the methods used for obtaining the actual measurements are not universal ; they vary according to different software programs18 . the precision of the maxillary sinus volume calculated by ct was reported to be more than 95%19 . the accuracy of cts in estimating the volume of grafted bone has proved to be almost 100%20 . although analysis of the volume of grafted bone by ct scans appears to be precise in the literature , the actual volumetric measurements of each grafted site can have some source of error , depending on the method used for calculation . it is impossible to detect and distinguish a particular patient 's existing bone from the grafted areas18 . fortunately , we selected onlay - graft cases only , not inlay - grafts ; therefore , the authors could distinguish grafted bone from recipient bone . if the gap between the grafted bone and the recipient bone is narrow , it is difficult to draw lines for the voi . furthermore , even though the recipient bone is included in the voi , unless it corresponds to the determined grayscale range , the program does not calculate it as a meaningful volume . therefore , we formed a hypothesis that the grayscale range the of grafted bone is almost the same as that of the adjacent bone not harvested . it may be accurate to apply this hypothesis to ct at t1 , but the grayscale range of grafted bone may diminish over time . further studies are required in order to understand the change in the pattern of the grayscale range for grafted cortical bone during the remodeling period . hu were utilized in order to standardize the density in the ct , and air and water have been used to analyze lesions in other medical fields . cbct , which was used in this study as an imaging system , has many advantages over ct , including lower levels of radiation exposure , shorter acquisition times , cost - effectiveness , and submillimeter resolution21 . in ct scans , the hu is proportional to the degree of x - ray attenuation by the tissue . in cbct , the degree of x - ray attenuation is shown by the grayscale ( voxel value ) . strong correlations between the grayscales of cbct and hus of ct scans have been shown22 . several authors reported that membranous bone grafts maintain their volume to a greater extent compared with endochondral bone grafts232425 . one possible explanation for this result could be that bone grafts of membranous origin have higher cortical bone quality than those of endochondral origin . in addition , cortical bone grafts maintain their volume better than cancellous bone grafts , independent of embryogenic origin1314 . cancellous bone grafts can revascularize much more quickly than cortical bone ; however , cortical bone is much stronger26 . therefore , the authors utilized several operative techniques to maintain revascularizing ability and the microarchitecture of cancellous bone . capillary ingrowth , perforation of existing cortical bone , and tamping particulate cortical bone around cortical bone are important factors to consider in this assessment . as shown in fig . 4 , these techniques could make some of the bone between the grafted cortical bone and existing bone similar to the materials surrounded by the sinus membrane and sinus floor , and thus , allowing for the formation of new bone . von arx and buser27 performed horizontal ridge augmentation using autogenous block grafts covered with anorganic bovine bone mineral ( abbm ) and a bioabsorbable collagen membrane in the atrophic jaw . their study demonstrated successful horizontal ridge augmentation with high predictability . a mean initial crest width of 3.06 mm was measured . at re - entry , the width was 7.66 mm , with a calculated mean gain of horizontal bone thickness of 4.6 mm . after 5.8 months , only minor surface resorption of 0.36 mm was observed from augmentation to re - entry . we used a similar technique , but we selected a particulate block bone in place of abbm . significant amounts of resorption of the bone graft take place during the first 6 months after the grafting surgery . furthermore , initial loss of bone grafts subsides after 6 months and does not significantly continue after 12 months16 . thus , 4.2 months ( average period from t1 to t2 in this study ) is not too short to evaluate volumetric changes . moreover , implants protect the graft from continuous resorption vertically in areas without implants , where resorption has been prolonged such that implant fixture threads are no longer engaged in bone28 . thus , it is not a good idea to wait for full remineralization and revascularization of the grafted bone . in this study , no grafted block bone had fallen out during the 4.2 0.8 months after the surgery when the implant fixture was inserted . following implant - placing surgery , volumetric calculation by the method used in this study is almost impossible , or very inaccurate , because the titanium fixture causes many artifacts on the cbct scan image , and the borders that distinguish grafted bone from residual bone gradually become more ambiguous . therefore , implant - based prosthetics were evaluated clinically and on conventional radiographic films . only 3 implants out of the 267 total had undergone mild marginal bone loss after 24.414.3 months . the success rate was 98.8% . in this study , age , sex , grafting direction and location , and whether or not the sinus lift procedure was used , were factors selected that can affect volumetric change . vertical onlay - grafts were more susceptible to strong tension because of direction and were more likely to be uncovered by the gingiva , owing to inadequate flap length compared with the horizontal only - grafts . the reason that the anterior part of the jaw maintained more grafted bone than the posterior part is that the former had more horizontal onlay - grafts than the latter . these results are universally accepted ; however , more data and further studies are needed to determine volumetric stability , when viewed as a varying factor . the high residual rate ( 74.6% ) of the grafted bone and the perfect survival rate of dental implants on grafted bone makes our bone grafting technique ( using mandibular block bone and supplementary particulate bone ) a reliable method . long - term 3d volumetric studies after implant - placement surgery require exclusive software that are optimized for the calculation of the 3d volume , due to artifacts and distortion from metal and difficulties distinguishing grafted bone from existing bone .
objectivesthe purpose of this study was to estimate the volumetric change of augmented autobone harvested from mandibular body cortical bone , using cone - beam computed tomography ( cbct ) and three - dimensional reconstruction . 
 in addition , the clinical success of dental implants placed 4 to 6 months after bone grafting was also evaluated.materials and methodsninety - five patients ( 48 men and 47 women ) aged 19 to 72 years were included in this study . 
 a total of 128 graft sites were evaluated . 
 the graft sites were divided into three parts : anterior and both posterior regions of one jaw . 
 all patients included in the study were scheduled for an onlay graft and implantation using a two - stage procedure . 
 the dental implants were inserted 4 to 6 months after the bone graft . 
 volumetric stability was evaluated by serial cbct images.resultsno major complications were observed for the donor sites . 
 a total of 128 block bones were used to augment severely resorbed alveolar bone 
 . only 1 of the 128 bone grafts was resorbed by more than half , and that was due to infection . 
 in total , the average amount of residual grafted bone after resorption at the recipient sites was 74.6%8.4%.conclusionvolumetric stability of mandibular body autogenous block grafts is predictable . 
 the procedure is satisfactory for patients who want dental implants regardless of atrophic alveolar bone .