tooth extraction often results in alveolar ridge resorption with substantial reduction in height and width of the alveolar bone . the extent of resorption may be affected by several factors , for example , the number of bony socket walls , bone density , severity of periodontal bone loss , the presence of infection , and the absence of adjacent teeth . alveolar bone remodeling and resorption after tooth extraction is considerably greater at buccal plate than at lingual plate of both maxilla and mandible . in addition , it has been reported that 50% reduction in the bucco - lingual width of postextraction sites will occur after 12 months . decreased dimensions of the ridge may result in the insertion of shorter and narrower implant , which may influence long - term function and stability of the implant supported restoration . furthermore , it may inhibit the placement of an implant in a prosthetically and esthetically acceptable location . when immediate implant placement is not indicated , socket preservation is a method of choice used to minimize the dimensional changes in soft and hard tissues after tooth extraction . for this purpose , different graft materials and techniques have been introduced . a number of studies have used guided bone regeneration technique for ridge preservation and reported that the technique can preserve the ridge dimensions more predictably than natural healing does . however , using graft materials in extraction sockets can result in remaining nonvital graft particles , which may interfere with the normal healing process of sockets in which dental implants have to be inserted . it is not known whether implants inserted in residual graft particles will show long - term success or not , but most clinicians prefer placing implants into vital bone . therefore , a material which can preserve ridge dimension and also promote socket fill with vital bone will be the most acceptable one . the primary objective of this randomized clinical trial was to assess horizontal and vertical ridge changes following socket preservation using resorbable collagen membrane and two different graft materials ; deproteinized bovine bone mineral ( dbbm ) and demineralized freeze - dried bone allograft ( dfdba ) ; the second objective was to evaluate healing of the grafted sockets via histologic and histomorphometric analysis . the research protocol of this randomized controlled study was approved by the ethical committee of shahed university , tehran , iran , and was registered in iranian registry of clinical trials ( irct ) with registry code : irct2013080414270n1 . twenty - five teeth scheduled for extraction were selected in 25 patients ; 17 females and 8 males with mean age of 35.35 years ( age range from 21 to 62 years ) . patients were chosen from the individuals looking for tooth extraction and implant therapy at the departments of periodontology and implantology , faculty of dentistry , shahed university , tehran , iran they were included in this study based on the following criteria : 
 single rooted teeth with hopeless prognosisbuccal plate with 2 mm and more dehiscence or thickness < 1 mm . 
  single rooted teeth with hopeless prognosis buccal plate with 2 mm and more dehiscence or thickness < 1 mm . the exclusion criteria were consisted of any systemic disease or medication that interfered with bone healing ( such as diabetes , autoimmune diseases , prolonged corticosteroids therapy , or chemotherapy ) , smoking , allergic reaction , and current pregnancy . before entering the study , patients were given an explanation of the nature of the investigation and they signed an informed consent form . patients were randomly allocated to one of the treatment groups ( dfdba or dbbm ) by a computer - generated randomization list . a comprehensive periodontal examination was performed and oral hygiene instructions were given for all patients . periapical / panoramic radiographs , clinical photographs , and study cast were taken . in cases with abscess formation customized acrylic stents were fabricated on study casts to serve as fixed reference guides for measurement of vertical and horizontal dimensional changes of alveolar ridge . a narrow vertical notch was prepared on both sides of the stent along the midpoint of the extraction socket . the following clinical parameters were assessed : ( 1 ) horizontal measurement which was the distance from coronal border of buccal aspect to the coronal border of the lingual / palatal aspect of the alveolus or ridge at midpoint . this measurement was performed with a caliper to the nearest tenth of millimeter ; ( 2 ) vertical measurements , ( a ) the distance between the most coronal point of buccal side of the socket or ridge and the most apical end of the stent at the place of its notch , and ( b ) similar measurement at lingual / palatal aspect . following administration of local anesthesia , sulcular incision was made around tooth to be extracted and two adjacent teeth on buccal and palatal / lingual sides . on buccal side , two vertical incisions were made at mesial and distal papilla of the adjacent teeth . after full - thickness flap reflection on buccal and lingual sides , atraumatic tooth extraction using periotome was performed . sockets were debrided with curette to remove all granulation tissues and periradicular lesions [ figure 1 ] . the periosteum of buccal flap was incised ; this would allow coronal advancement of facial flap and a tension - free primary closure . acrylic stent was placed on neighboring teeth , and then measurements were recorded as described before [ figures 2 and 3 ] . extraction sockets were divided into two treatment groups randomly and were grafted with dfdba ( cenobone ; tissue regeneration corporation , kish island , iran ) or dbbm ( bio - oss ; geistlich pharma ag , wolhusen , switzerland ) . collagen membrane ( bio - gide ; geistlichpharma ) was trimmed and placed over the grafted socket and alveolar bone in both groups [ figure 4 ] . buccal and lingual / palatal flaps were approximate using interrupted simple loop and vertical mattress sutures . postsurgical medication consisted of amoxicillin 500 mg every 8 h for 1 week , 400 mg ibuprofen every 6 h , if needed , and 0.2% chlorhexidine mouth rinse twice a day for 3 weeks . patients scheduled for dental implant surgery 4 - 6 months after the first surgery . at this stage , full - thickness buccal and palatal / lingual mucoperiosteal flaps were elevated . an osseous core ( 2 mm  6 mm ) was obtained from the center of the grafted socket using a trephine with a 2 mm inner and 3 mm outer diameter . the socket was grafted with demineralized freeze - dried bone allograft and trimmed collagen membrane covered the socket and buccal bone . for histological and histomorphometrical evaluation , the harvested bone specimens were fixed in 10% buffered formalin then decalcified in 10% formic acid for 2 days . the blocks were processed and sectioned in 4 m thick serial longitudinal sections through central part of core specimens , then stained with hematoxylin and eosin . histomorphometric analysis was performed under optic microscopy ( magnification 40 ) with image analysis software ( iranian histomorpho meter , ihmm , version 1.0 , sbmu , iran ) . at least three randomly selected fields , 1 per section for each patient were used to calculate the percentage of lamellar bone and woven bone , and residual graft particles . in addition , the number and percentage of sockets with different amount of inflammation and two types of bone marrow ( fibro - vascular or fatty - vascular / fibrous ) were assessed [ figures 58 ] . newly formed bone ( nb ) and residual graft particles ( gp ) were present ( 40 ) . newly formed bone ( nb ) and residual graft particles ( gp ) were present ( 40 ) . calcifying osteoid ( o ) in close contact with residual graft particles ( gp ) of deproteinized bovine bone mineral ( 400 ) . residual graft particles ( gp ) of demineralized freeze - dried bone allograft in the proximity of the fatty vascular connective tissue ( 400 ) . in this study , shapiro - wilk and levene 's tests were used to assess the normal distribution of the values and equality of variances , respectively . statistical significance of differences between two treatment groups for horizontal and vertical measurements , woven and lamellar bone , and residual graft particles were analyzed using t - test and mann - whitney u - test . for comparing qualitative variables ( bone marrow and inflammation ) between two groups , type i error was set at 0.05 and all analyses were done using spss version 18 ( spss inc . , chicago , il , usa ) . a comprehensive periodontal examination was performed and oral hygiene instructions were given for all patients . periapical / panoramic radiographs , clinical photographs , and study cast were taken . in cases with abscess formation customized acrylic stents were fabricated on study casts to serve as fixed reference guides for measurement of vertical and horizontal dimensional changes of alveolar ridge . a narrow vertical notch was prepared on both sides of the stent along the midpoint of the extraction socket . the following clinical parameters were assessed : ( 1 ) horizontal measurement which was the distance from coronal border of buccal aspect to the coronal border of the lingual / palatal aspect of the alveolus or ridge at midpoint . this measurement was performed with a caliper to the nearest tenth of millimeter ; ( 2 ) vertical measurements , ( a ) the distance between the most coronal point of buccal side of the socket or ridge and the most apical end of the stent at the place of its notch , and ( b ) similar measurement at lingual / palatal aspect . following administration of local anesthesia , sulcular incision was made around tooth to be extracted and two adjacent teeth on buccal and palatal / lingual sides . on buccal side , two vertical incisions were made at mesial and distal papilla of the adjacent teeth . after full - thickness flap reflection on buccal and lingual sides , atraumatic tooth extraction using periotome was performed . sockets were debrided with curette to remove all granulation tissues and periradicular lesions [ figure 1 ] . the periosteum of buccal flap was incised ; this would allow coronal advancement of facial flap and a tension - free primary closure . acrylic stent was placed on neighboring teeth , and then measurements were recorded as described before [ figures 2 and 3 ] . extraction sockets were divided into two treatment groups randomly and were grafted with dfdba ( cenobone ; tissue regeneration corporation , kish island , iran ) or dbbm ( bio - oss ; geistlich pharma ag , wolhusen , switzerland ) . collagen membrane ( bio - gide ; geistlichpharma ) was trimmed and placed over the grafted socket and alveolar bone in both groups [ figure 4 ] . buccal and lingual / palatal flaps were approximate using interrupted simple loop and vertical mattress sutures . postsurgical medication consisted of amoxicillin 500 mg every 8 h for 1 week , 400 mg ibuprofen every 6 h , if needed , and 0.2% chlorhexidine mouth rinse twice a day for 3 weeks . patients scheduled for dental implant surgery 4 - 6 months after the first surgery . at this stage , full - thickness buccal and palatal / lingual mucoperiosteal flaps were elevated . an osseous core ( 2 mm  6 mm ) was obtained from the center of the grafted socket using a trephine with a 2 mm inner and 3 mm outer diameter . the socket was grafted with demineralized freeze - dried bone allograft and trimmed collagen membrane covered the socket and buccal bone . for histological and histomorphometrical evaluation , the harvested bone specimens were fixed in 10% buffered formalin then decalcified in 10% formic acid for 2 days . the blocks were processed and sectioned in 4 m thick serial longitudinal sections through central part of core specimens , then stained with hematoxylin and eosin . histomorphometric analysis was performed under optic microscopy ( magnification 40 ) with image analysis software ( iranian histomorpho meter , ihmm , version 1.0 , sbmu , iran ) . at least three randomly selected fields , 1 per section for each patient were used to calculate the percentage of lamellar bone and woven bone , and residual graft particles . in addition , the number and percentage of sockets with different amount of inflammation and two types of bone marrow ( fibro - vascular or fatty - vascular / fibrous ) were assessed [ figures 58 ] . section from a deproteinized bovine bone mineral site specimen . newly formed bone ( nb ) and residual graft particles ( gp ) were present ( 40 ) . section from a demineralized freeze - dried bone allograft site specimen . newly formed bone ( nb ) and residual graft particles ( gp ) were present ( 40 ) . calcifying osteoid ( o ) in close contact with residual graft particles ( gp ) of deproteinized bovine bone mineral ( 400 ) . residual graft particles ( gp ) of demineralized freeze - dried bone allograft in the proximity of the fatty vascular connective tissue ( 400 ) . in this study , shapiro - wilk and levene 's tests were used to assess the normal distribution of the values and equality of variances , respectively . statistical significance of differences between two treatment groups for horizontal and vertical measurements , woven and lamellar bone , and residual graft particles were analyzed using t - test and mann - whitney u - test . for comparing qualitative variables ( bone marrow and inflammation ) between two groups , type i error was set at 0.05 and all analyses were done using spss version 18 ( spss inc . , chicago , il , usa ) . five patients refused to continue the research protocol due to lack of compliance with the scheduled appointments and did not take part in the implant placement surgery . twenty patients ( 14 women , 6 men , mean age 35.5 , and age range 21 - 62 years ) completed the study . horizontal measurements revealed that in dfdba group , 29.75%  2.61 reduction in ridge width occurred between baseline and 4 - 6 months postsocket preservation . similarly , dbbm group showed 28.58%  1.82 reduction in ridge width from baseline to final . the difference in ridge width between baseline and postextraction was statistically significant in each group , but there was no statistically significant difference between two groups in this regard ( p = 0.878 ) . vertical measurements at baseline and 4 - 6 months postsurgery showed 1.29  0.68 mm ( 23.91%  4.55 ) and 1.1  0.17 mm ( 18.02%  1.58 ) reductions in ridge height at buccal aspect in dfdba and dbbm groups , respectively . these values were 0.41  0.38 mm ( 7.84%  2.3 ) and 0.35  0.34 mm ( 5.83%  1.71 ) at lingual side [ table 2 ] . the differences in vertical height reduction between baseline and postextraction were statistically significant in each group . although this reduction was greater in both buccal and palatal / lingual sides in dfdba group than in dbbm group , there were no statistically significant differences in these values between two groups . horizontal measurement ( mm ) for demineralized freeze - dried bone allograft and deproteinized bovine bone mineral groups at baseline and 4 - 6 months postsocket preservation vertical measurements ( mm ) for demineralized freeze - dried bone allograft and deproteinized bovine bone mineral groups at baseline and 4 - 6 months postsocket preservation all sections showed bone formation that included lamellar bone and woven bone [ table 3 ] . the average amount of lamellar bone was higher in dfdba group than in the dbbm group , but the difference was not statistically significant ( p = 0.101 ) . new bone with increased osteoblastic activity was observed in intimate contact with dbbm particles [ figure 7 ] . there were no statistically significant differences between the two groups with respect to the types of bone marrow [ table 4 ] ( p = 0.141 ) . the amount of inflammation was higher in dbbm group than in dfdba group [ table 5 ] , but the difference was not statistically significant ( p = 0.653 ) . the mean percentage of vital bone for dbbm group was 18.76%  3.54 and for dfdba group it was 34.49%  3.19 . there was statistically significant difference in total bone between groups ( p = 0.004 ) . dfdba - treated sockets showed 6.06  1.02% of residual graft particles whereas dbbm - treated sockets contained 12.77%  1.85 residual graft particles . mean percentage of lamellar and woven bone type of bone marrow in demineralized freeze - dried bone allograft and deproteinized bovine bone mineral groups the amount of inflammation in two study groups histomorphometric data ( percentage of new bone and residual graft materials ) in two study groups all sections showed bone formation that included lamellar bone and woven bone [ table 3 ] . the average amount of lamellar bone was higher in dfdba group than in the dbbm group , but the difference was not statistically significant ( p = 0.101 ) . new bone with increased osteoblastic activity was observed in intimate contact with dbbm particles [ figure 7 ] . there were no statistically significant differences between the two groups with respect to the types of bone marrow [ table 4 ] ( p = 0.141 ) . the amount of inflammation was higher in dbbm group than in dfdba group [ table 5 ] , but the difference was not statistically significant ( p = 0.653 ) . the mean percentage of vital bone for dbbm group was 18.76%  3.54 and for dfdba group it was 34.49%  3.19 . there was statistically significant difference in total bone between groups ( p = 0.004 ) . dfdba - treated sockets showed 6.06  1.02% of residual graft particles whereas dbbm - treated sockets contained 12.77%  1.85 residual graft particles . mean percentage of lamellar and woven bone type of bone marrow in demineralized freeze - dried bone allograft and deproteinized bovine bone mineral groups the amount of inflammation in two study groups histomorphometric data ( percentage of new bone and residual graft materials ) in two study groups the present randomized clinical trial compared dbbm with dfdba in ridge preservation following tooth extraction . dbbm ( bio - oss ) is deproteinized bovine bone mineral with high osseoconductive property proved by clinical and histologic studies . animal studies have demonstrated that the process of demineralization exposes bone morphogenic proteins which have the potential to induce the differentiation of local uncommitted connective tissue cells into osteoblasts . in this 4 - 6 months study , the average loss of alveolar width was 2.26  0.51 mm ( 28.58% ) for the dbbm and 2.3  0.64 mm ( 29.75% ) for the dfdba group , but the intergroup difference was not statistically significant . used dbbm and collagen membrane to preserve extraction sockets and reported alveolar ridge changes were less in the treated group ( 1.04  1.08 mm ) than control group ( 4.48  0.65 mm ) . their study includes premolar and molar teeth , and augmentation was performed without flap elevation . gholami et al . showed 1.07 mm loss of ridge width in nonmolar sockets filled with dbbm , but their study was different from ours in the way they included the teeth that had complete socket walls . 's investigation that showed mean reduction in the buccolingual dimension of 1.39  0.57 mm in dbbm group . the reason for this difference could be attributed to utilizing socket plug technique and molar and premolar extracted sockets . showed that ridge preservation using freeze - dried bone allograft and collagen membrane resulted in less alveolar ridge loss compared to extraction alone ( 1.2  0.9 mm vs. 2.6  2.3 mm ) . . showed in their study on nonmolar teeth 0.5  0.8 mm loss of ridge width in both bio - oss and collagen membrane group and dfdba in a putty carrier group . in the present study , height of the alveolar ridge decreased in buccal and lingual / palatal sides of preserved sockets in both groups , dfdba group experienced a 1.29 mm loss in buccal sides , whereas dbbm group showed reduction of 1.1 mm . more bone loss occurred in the buccal than in the lingual / palatal side following tooth extraction . nevins et al . evaluated the fate of buccal plate in maxillary anterior teeth by comparing pre- and post - extraction computed tomography scans they showed a vertical resorption of 2.42  2.58 mm in sockets grafted with bio - oss , while it was 5.24  3.72 mm in control group . in addition , vance et al . reported 0.3  0.7 mm vertical loss in dfdba and 0.7  1.2 mm vertical gain in bio - oss groups . the more positive outcome obtained by dbbm may be related to its low resorption rate , enabling the graft to act as a scaffold for longer time . van der weijden et al . showed that spontaneous healing following tooth extraction resulted in average reduction of 3.87 mm in width and 1.67 mm in height of alveolar ridge . based on systematic reviews , when socket augmentation is performed , ridge dimensions can be preserved to some extent . the results seem to depend on the type of materials and technique used and on the condition of the socket . many studies performed on intact sockets included molar teeth that have thick buccal and lingual plates while many conducted on sockets with bony defects . flap closure over the augmented socket is another issue that was varying in different studies . for histologic and histomorphometric evaluation , bone was harvested from implant sites with trephine bur . to be ensured that specimens were obtained from grafted portion of sockets not the native bone , a narrow trephine with 2 mm internal diameter and 3 mm external diameter the mean amount of new bone for dfdba group was 34.49% which was in line with froum et al . and wood et al . studies , they showed 34.7% and 38.4% new bone in socket grafted with dfdba . in our study , the mean amount of new bone for dbbm was 18.76% which was significantly less than dfdba group . calasans - maia et al . demonstrated a mean value of 19.3% ( 22.6 ) new bone formation in socket grafted with bio - oss after a 24-week healing period which was in line with our study . artzi et al . in a 9 months study reported 46% bone formation using same material . differences in the amount of bone formation between studies could be due to different follow - up time . in our research , the amount of new bone in dfdba group ( 34.49% ) was more than dbbm group ( 18.76% ) . the difference may be attributed to low resorption rate of dbbm and demineralized nature of dfdba . chan et al . in a systematic review reported that the mean percentage of vital bone in natural healing sockets was 38.5% , the use of dfdba did not affect the amount of vital bone formation , and dbbm showed conflicting results . vance et al . who augmented sockets with dfdba in a carrier ( carboxymethylcellulose and calcium sulfate ) or dbbm presented 61  9% vital bone in dfdba group versus 26  20% in the dbbm group after 4 months . they have explained that higher percentage of vital bone in dfdba group may be related to earlier and greater vascular and cellular growth in porous structure of the carrier material . in the present work , residual graft particles in dfdba group ( 6.06% ) were less than dbbm group ( 12.77% ) , which is in agreement with other studies . however , the amount of residual dbbm ( 12.77% ) was still significantly less than the mentioned amount by zitzmann et al.(40% ) for successful implant placement . the residual particles of dbbm were in contact with both new bone and osteoid [ figure 7 ] , this is in agreement with other studies . the incorporation of the dbbm particles with new bone provide a dense scaffold for further bone deposition and a good support for dental implants . furthermore , dbbm graft particles are known to be resorbed and replaced with bone slowly , which means that the graft material takes part in bone remodeling . the results of this 4 - 6 months study exhibited that from the clinical point of view , both dfdba and dbbm covered by collagen membrane have similar effects on horizontal and vertical bone resorption of extraction sockets . histomorphometrically , the percentage of new bone formation in dfdba group was more than dbbm group while dbbm was associated with higher residual graft particles . the authors of this manuscript declare that they have no conflicts of interest , real or perceived , financial or non - financial in this article . the authors of this manuscript declare that they have no conflicts of interest , real or perceived , financial or non - financial in this article .
background : alveolar ridge preservation could be performed immediately following tooth extraction to limit dimensional changes of alveolar process due to bone resorption . the aim of this study was to compare the clinical and histologic outcomes of socket preservation using two different graft materials ; deproteinized bovine bone mineral ( dbbm ) and demineralized freeze - dried bone allograft ( dfdba ) with absorbable collagen membrane.materials and methods : twenty extraction sockets in 20 patients were randomly divided into 2 treatment groups : 10 sockets were augmented with dbbm and collagen membrane whereas 10 sockets were filled with dfdba and covered by collagen membrane . 
 primary closure was achieved over extraction sockets by flap advancement . 
 horizontal and vertical ridge dimensional changes were assessed at baseline and after 4 - 6 months at the time of implant placement . for histological and histomorphometrical analysis , 
 bone samples were harvested from the augmented sites with trephine during implant surgery . 
 all data were analyzed using spss version 18 ( =0.05).results : clinical measurements revealed that average horizontal reduction was 2.3  0.64 mm for dfdba and 2.26  0.51 mm for dbbm . mean vertical ridge resorption at buccal side was 1.29  0.68 mm for dfdba and 1.1  0.17 mm for dbbm . 
 moreover , mean vertical ridge reduction at lingual site was 0.41  0.38 mm and 0.35  0.34 mm for dfdba and dbbm , respectively . 
 no significant differences were seen between two groups in any of those clinical parameters . 
 histologic analysis showed statistically significant more new bone deposition for dfdba compared to dbbm ( 34.49  3.19 vs. 18.76  3.54 ) ( p < 0.01 ) . 
 residual graft particles were identified significantly more in dbbm ( 12.77  1.85 ) than dfdba ( 6.06  1.02).conclusion : based on the findings of this study , both materials have positive effect on alveolar ridge preservation after tooth extraction , but there was more new bone formation and less residual graft particles in dfdba group than in dbbm group .