机械扩张力作用下小鼠腭中缝成骨与破骨的研究

目的观察小鼠腭中缝在机械扩张力作用的不同阶段成骨与破骨现象,探讨两种现象在腭中缝机械力扩张骨改建过程中的意义。方法选用6周龄健康雄性C57BL/6小鼠90只,随机分成对照1d、3d、7d、14d、28d组和实验加力1d、3d、7d、14d、28d组,每组各9只。用两眼簧扩弓器施加扩张力(0.56N)于实验加力组小鼠的腭中缝。于加力后1d、3d、7d、14d、28d通过苏木素-伊红染色观察腭中缝组织形态学的改变,碱性磷酸酶染色(ALP)和抗酒石酸酸性磷酸酶染色(TRAP)观察腭中缝组织中成骨细胞与破骨细胞的变化。结果实验组1d紧邻腭骨的骨膜细胞ALP染色呈强阳性,7d实验组腭中缝明显被扩宽,缝边缘ALP染色呈强阳性。TRAP染色显示实验组第1天有破骨细胞活动而3d破骨细胞消失,7d实验组破骨细胞主要分布于鼻底侧且较第1天组多,14d实验组与7d相似而28d破骨细胞消失。结论对腭中缝施加扩张力能够促使成骨细胞与破骨细胞活化增殖,二者时间与空间的数量和分布差异导致了腭中缝扩张骨改建。     

大鼠正畸压力侧牙槽骨改建中RANKL和OPG mRNA的表达

目的研究破骨细胞核因子kB受体活化因子配基（receptor activator nuclear factor kappa B ligand,RANKL）及其伪受体骨保护因子（osteoprotegerin,OPG）的mRNA在大鼠正畸牙移动压力侧牙槽骨改建中的表达变化及时问分布特点。方法选用80只6周龄SD雄性大鼠建立正畸牙移动模型,分别在加力后2d、5d、7d、10d和14d各处死16只大鼠。HE染色观察大鼠牙周组织的形态学变化;TRAP染色计数压力侧牙槽骨组织中的破骨细胞数量;实时定量PCR方法检测RANKL和OPGmRNA的表达变化及时问分布特点。结果骨改建的最活跃期为正畸加力后的第7d,压力侧牙槽骨组织中的TRAP染色阳性破骨细胞计数随加力时间的增加而增加,第7d达到高峰,而后逐渐降低。压力侧牙槽骨组织中的RANKL和OPGmRNA表达水平均随加力时间的增加而增加,第7d达到高峰,而后均逐渐降低。结论RANKL和OPG mRNA表达的变化规律不仅与骨改建过程一致,而且也与TRAP染色阳性破骨细胞数量的变化规律一致。RANKL和OPG与正畸牙移动骨改建过程中破骨细胞的分化、形成和功能密切相关。     

川续断皂苷VI对大鼠正畸牙周组织改建影响的研究

［摘要］ 目的 探究局部注射川续断皂苷VI(ASD)是否通过促进大鼠正畸牙移动过程中破骨细胞分化而影响牙周组织改建。方法 选择40只6周龄雌性Wistar大鼠,随机分为4组（10只/组）：A组：空白对照组(局部注射生理盐水),B组：ASD低浓度组(局部注射5 mg/kg ASD),C组ASD高浓度组(局部注射10 mg/kg ASD),D组：前列腺素E2组(局部注射适宜浓度PGE2)。实验分别于第3、7、14、21及28天5个时间点处死2只大鼠,对大鼠上颌第一磨牙近中压力侧牙周组织进行TRAP染色以观察破骨细胞数及免疫组化以观察破骨细胞分化因子（ODF）表达情况。结果 从第3天到第21天,4组上颌第一磨牙近中压力侧TRAP阳性细胞的数目及ODF的表达随加力时间不断增多,第28天时出现下降。从第7天开始,与A组相比,实验组破骨细胞数量和ODF表达均增加,B组比C组、D组减少且有统计学差异,C组与D组无统计学差异。结论 局部注射ASD和适宜浓度的PGE2可有效促进压力侧牙周组织破骨细胞的分化,加快牙周改建。局部注射10 mg/kg ASD与PGE2效果基本相近,而稍低浓度ASD效果弱于PGE2和稍高浓度ASD。     

种植体植入后牙槽骨破骨细胞的活性变化

目的:动态观察种植体植入后不同时间段周围牙槽骨破骨细胞的数目、活性的表达变化规律.方法:选用6只成年雄性Beagle犬作为实验动物,随机选择双侧下颌第二前磨牙及第四前磨牙共计24个牙位,分别以12个牙位作为实验组和对照组,检侧种植体植入后3、7、15、30、60和90 d种植体周围牙槽骨破骨细胞的活性变化.取犬下颌骨进行大体标本观察,拍摄X线片,取种植体周围骨组织进行HE染色,观察破骨细胞的形态学变化,并进行定量组织学分析,对照组拔牙窝的检测方法相同.采用SPSS13.0软件包对数据进行统计学分析.结果:破骨细胞的表达活性在种植体植入后第7天达到高峰,而后随时间延长逐渐降低,实验组破骨细胞的活性表达显著活跃于对照组.结论:破骨细胞性骨吸收最为活跃的时间在种植体植入后的第7天左右.     

不同愈合时间下挤压植入种植体对Beagle犬骨界面改建的组织形态学测定

目的：研究不同愈合时间下挤压植入微种植体对其周围骨界面改建的影响。方法：采用自身对照原则,将36枚微种植体植入6只成年Beagle犬上颌后牙区。左右各植入3枚种植体,一侧为实验组以骨挤压植入,对侧为对照组。每侧随机分配植入不同愈合时间（2周,4周和8周）的种植体,取带有种植体骨标本制备不脱钙的超硬组织切片,采用组织形态学定量测定的方法,对钛种植体骨界面改建过程进行动态观察,从定量的角度分析其变化的差异。结果：实验组与对照组种植体骨接触率均随愈合时间的延长而增加。实验组愈合2周,4周时种植体骨接触率明显高于对照组,8周时趋于一致。实验2周组与8周组种植体骨接触率表现出显著性差异,对照2周组与4周组存在显著性差异。结论：愈合早期骨挤压可以提高种植体骨整合率,提示需要早期加载的微种植体以骨挤压术式植入可提高种植体稳定一I生。     

高植入扭力对微型种植体-骨界面愈合的组织学影响

目的:探讨高植入扭力对种植体-骨界面组织愈合的影响。方法:将36枚微型种植体以(14±1)Ncm及(11±1)Ncm的扭力植入4只Beagle犬的下颌牙槽骨,观察7 d及28 d的组织学、组织形态测量学及扫描电镜变化。结果:14 Ncm组植入后7 d界面密骨质有重度微损伤,28 d骨界面仍有许多碎骨屑。而11 Ncm组7 d骨质轻度微损伤,28 d骨愈合良好。2组种植体-骨结合率(BIC)无显著差异(P0.05),7 d时,2组种植体-骨密度(BD)值差异无统计学意义(P0.05),但28 d时,11 Ncm组BD值明显高于14 Ncm组(P0.05)。结论:适度扭力植入种植体的骨界面损伤小、愈合快,而过高植入扭力可造成骨界面严重微损伤,影响骨组织愈合。     

破骨细胞过氧化物酶体增殖因子活化受体gamma敲除对腭中缝扩张后骨新生和骨重建的影响

目的 探讨破骨细胞过氧化物酶体增殖因子活化受体gamma(PPAR-g)敲除对腭中缝扩张(MSE)后骨新生和骨重建的影响.方法 将雄性对照野生型小鼠(WT)和破骨细胞PPAR-g敲除小鼠(KO)分为如下4组,WT+假手术,WT+ MSE,KO+假手术,KO+ MSE.术后14天处死,采用HE染色、抗酒石酸酸性磷酸酶(TRAP)染色、以及实时荧光定量PCR方法研究破骨细胞PPAR-g敲除对腭中缝扩张后骨新生和骨重建的影响.结果 KO+MSE组新骨形成面积较WT+ MSE组增加,细胞总数增多,但是破骨细胞计数较WT+ MSE组减少,破骨细胞分化相关基因(cFos,Calcr,Car2,Ctsk,和Mmp9)的表达显著下降.结论 破骨细胞PPAR-g敲除可以促进腭中缝扩张(MSE)后骨新生和骨重建.在腭中缝扩张后的骨重建过程中,PPAR-g是调控破骨细胞分化和骨新生的一个重要分子.     

正畸牙移动压力侧牙槽骨中cathepsin K、RANKL和OPG mRNA及蛋白的表达

目的检测大鼠正畸牙移动压力侧cathepsinK、RANKL和OPGmRNA及蛋白表达变化及时间分布特点。方法选用80只6周龄SD雄性大鼠建立正畸牙移动模型,分别在加力后2d、5d、7d、10d和14d各处死16只大鼠。HE染色观察牙周组织的形态学变化。TRAP染色计数压力侧牙槽骨中的破骨细胞数量。免疫组化方法定位及相对定量检测cathepsinK、RANKL和OPG蛋白表达变化及时间分布特点。Real—timePCR检测cathepsinK、RANKL和OPGmRNA表达变化及时间分布特点。结果骨改建的最活跃期为正畸加力后的第7d。压力侧牙槽骨中的TRAP染色阳性破骨细胞计数随加力时间的增加而增加,第7d达到高峰,而后逐渐降低。压力侧牙槽骨中的cathepsinK、RANKL和OPGmRNA及蛋白的表达水平均随加力时间的增加而增加,第7d达到高峰,而后均逐渐降低。结论cathepsinK、RANKL和OPGmRNA及蛋白表达的变化规律不仅与骨改建过程一致,而且也与TRAP染色阳性破骨细胞数量的变化规律一致。cathepsinK、RANKL和OPG与正畸牙移动骨改建过程中破骨细胞的分化、形成和功能密切相关。     

大鼠正畸牙移动压力侧牙槽骨中cath K mRNA表达的研究

目的研究组织蛋白酶K（cathepsin K,cath K）mRNA在大鼠正畸牙移动压力侧牙槽骨中的表达变化及时间分布特点,探讨正畸牙移动中牙周改建的分子生物学机制。方法选用80只6周龄SD雄性大鼠建立正畸牙移动模型,分别在加力后2d、5d、7d、10d和14d处死动物各16只,HE染色观察牙周组织改建的变化,TRAP染色计数压力侧破骨细胞数量;实时定量PCR（real-time quantitative PCR）检测cath K mRNA表达变化及时间分布特点。结果cath K mRNA表达随加力时间的增加而增加,在加力后的第7天开始下降。这与牙周组织形态学的变化以及TRAP染色阳性破骨细胞数目的变化规律相一致。结论在生物机械力的诱导下,cathK参与了正畸牙移动骨改建过程中有机基质的降解,cath K mRNA随正畸加力时间的增加出现规律性变化。     

RANKL和OPG在种植体周围软组织及骨组织的表达变化

目的：研究破骨细胞核因子κB受体活化因子配基（receptor activator nuclear factor kappa B ligand,RANKL）及其伪受体骨保护因子（osteoprotegerin,OPG）在非负荷期种植体周围软组织和骨组织中的表达变化及时间分布特点。方法：选用6只1-2岁龄左右的雄性Beagle犬建立种植义齿动物模型,分别观测种植体植入后3d、7d、15d、30d、60d和90d,种植体周围的骨改建情况。取种植体周围软组织进行实时荧光定量PCR,取犬下颌骨进行大体标本观察拍摄X线片,取种植体周围骨组织进行免疫组化染色,检测RANKL和OPG随时间的表达变化及分布特点。结果：骨改建的最活跃期为种植体植入后的第7d,种植体周围软组织中的RANKL和OPG mRNA及骨组织中的RANKL和OPG均随种植体植入时间的增加而增加,第7d达高峰,而后均逐渐降低。RANKL和OPG在种植体周围软组织及骨组织中的表达变化规律一致。结论：OPG和RANKL能在种植体周围软组织中表达,且变化规律与种植体周围骨组织改建过程一致。种植体周围组织可以通过OPG/RANKL系统参与破骨细胞的形成,调节骨质吸收,影响骨组织代谢微环境。     

外源性β-NGF对骨缺损区骨形成和改建的调节作用

目的：探讨β-NGF对骨缺损区新骨形成和改建的影响。方法：利用手术方法建立大鼠颅骨骨缺损模型,采用微渗透泵于骨缺损区局部持续导入外源性β-NGF。通过H-E染色、Gomori改良三色染色技术,检测术后3、7、14、21和28 d不同时间点骨缺损区的新生骨量,探讨β-NGF对骨缺损区新骨形成和改建的影响。应用Image-Pro Plus 6.0软件对骨缺损区中兴趣区域的新骨形成进行半定量测定,采用SPSS 19.0软件包对所得数据进行统计分析。结果：成功建立大鼠颅骨骨缺损局部持续导入β-NGF给药模型。H-E染色结果显示,导入β-NGF侧（实验组）与无β-NGF导入侧（对照组）均有新骨形成。Gomori改良三色染色结果发现,21、28 d时,实验组与对照组的新骨形成呈现明显增加,且实验组的新骨形成量显著多于对照组（P<0.05）, 28 d时的成熟骨量实验组显著多于对照组（P＜0.05）。结论：骨缺损区导入外源性β-NGF可能会促进新骨形成与骨改建。     

Bone remodeling in immediately loaded and unloaded titanium dental implants: a histologic and histomorphometric study in humans

Remodeling is thought to prevent microdamage accumulation caused by repetitive loading and to increase the fatigue life of bone. The bone remodeling rate (BRR) is the period of time needed for new bone to replace the existing bone and to allow for the adaptation of bone to its environment. BRR is expressed as a percentage or volume of new bone within a specific time period. The aim of the present study was to evaluate bone remodeling events on submerged and immediately loaded dental implants. Twelve patients with edentulous mandibles participated in this study. All patients were rehabilitated with fixed mandibular prostheses, with 10 dental implants per patient. An additional implant was inserted in the most distal posterior mandibular jaw region. In 6 patients, these additional implants were loaded with a fixed provisional prosthesis the same day of the implant surgery and loaded. In the other 6 patients, the additional implants were left submerged and not loaded. After 6 months, all the additional implants were retrieved with a trephine. The percentage of woven and lamellar bone, number of osteoclasts and osteoblasts, and percentage of bone labeled by tetracycline at 0.5 mm and 2 mm from the implant surface were evaluated. The percentage of lamellar bone, number of osteoblasts, and percentage of bone tetracycline labeling was significantly higher in the loaded implants than in the unloaded implants (P =.0001). Also in the loaded implants, the percentage of woven and lamellar bone, number of osteoclasts and osteoblasts, and percentage of bone tetracycline labeling was significantly higher at 0.5 mm than at 2 mm from the implant surface (P =.0001). No such differences were found in unloaded implants (P =.377). In conclusion, we found that (1) loading appeared to stimulate bone remodeling at the interface, (2) a higher percentage of lamellar bone was found in loaded implants, (3) the percentage of bone labeling was higher at the interface of loaded implants, (4) no differences were found in the BRRs between immediately loaded and unloaded implants, and (5) immediate loading had not interfered on the lamellar bone formation at the interface and had not produced formation of woven bone at the interface.     

蛇床子素对大鼠正畸牙牙周组织改建的影响

目的 探讨灌服蛇床子素对大鼠正畸牙移动过程中牙周组织改建的影响。方法 72只8周龄雄性SD大鼠随机分3组,高浓度（40 mg/kg）、低浓度（20 mg/kg）蛇床子素组和对照组。建立大鼠正畸牙移动模型,分别灌服蛇床子素溶液和等量溶剂,加力7、14、21、28 d后分批处死,获取包含上颌磨牙的上颌骨,测量第一磨牙近中移动距离。分别采用H-E、抗酒石酸酸性磷酸酶染色观察牙周组织变化及对破骨细胞进行计数,采用SPSS 20.0软件包对数据进行统计学分析。结果 加力后7、14、21、28 d,上颌第一磨牙近中移动距离逐渐增大。加力第7天,低浓度组与对照组无显著差异（P>0.05）,其余各时间点实验组牙移动距离均较对照组显著增加（P<0.05）;高浓度组与低浓度组之间也有显著差异（P<0.05）。组织学观察可见,张力侧成骨细胞出现,实验组较对照组明显。压力侧破骨细胞计数于加力第7天达到高峰,与对照组有显著差异（P<0.05）,高浓度组较低浓度组多,且有显著差异(P<0.05);加力第14天,3组均减少,实验组仍较对照组多,有显著差异（P<0.05）,高、低浓度组间无显著差异（P>0.05）;21 d和28 d时继续减少,组间无显著差异（P>0.05）。结论 灌服蛇床子素能加快正畸牙移动,在早期阶段增加牙周组织中破骨细胞数量,加快牙周组织改建,其作用受剂量影响。     

超声波加速正畸牙移动的实验动物研究

目的:在大鼠正畸模型中,对第一磨牙牙周组织施加超声波振动,观察超声波是否能加速正畸牙移动。方法:选用30只SD大鼠,建立以中切牙为支抗,移动单侧第一磨牙的正畸模型,分为常规正畸组和超声波振动组。于加力第7、14、28天测量牙移动距离,HE染色,trap染色破骨细胞计数,Masson染色观察第一磨牙牙周组织的变化。结果:牙周组织接受超声波振动刺激后,大鼠第一磨牙在第7、14、28天移动速率显著高于常规正畸组(P<0.05);同时可观察到超声波振动组中TRAP阳性的破骨细胞显著多于常规正畸组(P<0.05)。而Masson染色则显示,在加力第7天,常规正畸组和超声波振动组中,皆出现新生骨;但第14天时,前者新骨形成更加明显;直到第28天超声波后者出现更大规模的成骨反应。结论:超声波显著、并持续地增加牙周组织内破骨细胞形成数量,此效应可能导致了大鼠正畸模型的牙齿移动的加速,成功建立超声波加速正畸牙移动的实验动物模型。     

不同年龄段小鼠下颌前导后髁突骨骼改建差异的研究

目的：：观测小鼠间歇性下颌前导后髁状突的形态学变化,比较不同年龄段的组织改建差异,为下颌前导的矫治时机和策略提供理论依据。方法：在4周龄和8周龄BABL/c雌鼠上建立间歇性下颌前导模型,于下颌前导后的14 d和28 d取颞下颌关节标本行Trap染色、Godener三色染色、微型计算机断层扫描( Micro-CT)技术来研究髁突破骨细胞及成骨细胞变化和骨骼形态学变化。结果：28 d时4周龄组相对于28 d时8周龄组,骨体积分数( BV/TV)和骨小梁厚度( TB. Th)减小,骨小梁间距(TB. Sp)增大(P<0.05)。骨小梁数量(TB. N)无明显差异(P>0.05)。14 d时4周龄组相对于14 d时8周龄组以及14 d时4周龄组相对于28 d时4周龄组,每视野中破骨细胞和成骨细胞数升高(P<0.05)。结论：小鼠导下颌向前与髁突骨骼改建有密切联系,不同年龄段差异显著。     

Damon3自锁托槽与普通金属托槽对牙齿垂直移动影响的实验研究

目的:探讨自锁托槽和普通直丝弓托槽使牙齿受压低力作用时牙周组织改建的差异.方法:以比格犬右侧侧切牙为研究对象,分别用Damon3自锁托槽与MBT金属托槽压低牙齿,观察加力7 d,14 d,28 d后两组犬牙周组织和牙槽骨改建情况.结果:对于被压低的牙齿,自锁托槽组骨吸收活跃,破骨细胞较多.结论:实验结果提示自锁托槽系统能够形成更加活跃的骨改建.     

增龄因素对鼠正畸牙牙周组织骨保护素及其配体表达的影响

目的:比较幼年鼠和成年鼠在正畸牙移动中牙周组织骨保护素(OPG)及其配体(OPGL)表达的不同比值,探讨增龄因素对正畸骨改建影响的分子机制。方法:制备大鼠正畸牙齿移动模型,于牙齿移动1d、3d、5d、7d、10d、14d及14d后去除正畸力1周后取材,免疫组化检测牙周组织OPG和OPGL的表达。结果:①.牙齿移动3d时,幼年鼠压力侧OPGL的表达明显增强;而成年鼠此时OPGL的表达没有幼年鼠明显。②.牙齿移动5d和7d时,幼年鼠和成年鼠OPGL的表达均成强阳性,破骨细胞多。③.牙齿移动10d、14d时,幼年鼠和成年鼠OPGL的表达逐渐减弱。④.14d时去除正畸力至21d时发现幼年鼠和成年鼠OPGL均已成弱阳性表达,幼年鼠可见部分成骨细胞。结论:在正畸力的作用下,OPGL与OPG的表达比值与年龄关系密切,增龄因素引起的牙周组织内OPGL/OPG表达变化可能是导致成年正畸特点的分子机制之一。     

Tissue responses resulting from tooth movement surgically assisted by corticotomy and corticision in rats

Objective:To compare the histological responses in corticotomy- and corticision-assisted tooth movement.Materials and Methods:Ninety Wistar rats were divided into three groups: C (control—tooth movement only), CT (tooth movement + corticotomy), and CI (tooth movement + corticision). Surgeries were performed on the vestibular and lingual cortical bone of the maxillary first molar. Tooth movement was carried out with nickel-titanium closed coil springs having a force of 30 g. The rats were sacrificed at 3, 14, and 28 days. To evaluate the number of osteoclasts and amount of root resorption, a tartrate-resistant acid phosphatase stain was used. Hematoxylin and eosin staining was performed for areas of hyalinization, and the organic bone matrix was stained with picrosirius.Results:The CT group showed a greater number of osteoclasts than did the C group on day 3 (P < .05). At the same time point, the CT and CI groups showed a delayed onset of organic bone matrix remodeling and a lower incidence of root resorption than did the C group (P < .05). There were also fewer hyalinization areas in the CI group than in the C group on day 3 (P < .05).Conclusions:Corticotomy effectively increased bone resorption during the early stages of tooth movement, but this increase was not observed for corticision. The surgical procedures did not accelerate organic bone matrix remodeling. Corticotomies and corticisions decreased the risk of root resorption only during the early stages of movement. Corticision reduced the level of hyalinization, while corticotomy did not.     

Microvascular response in the periosteum following mucoperiosteal flap surgery in dogs: angiogenesis and bone resorption and formation

BACKGROUND: When surgical stress reaches the periosteum, bone resorption and formation that occur as a periosteal response are closely related to angiogenesis and hemodynamics. Thus, we investigated bone remodeling in the healing process after mucoperiosteal flap surgery, focusing our attention on the microcirculation. METHODS: Mucoperiosteal flap surgery was performed on 12 adult beagle dogs. The periosteal vascular plexus was observed on days 7, 14, 21, and 28 after surgery, using three different techniques: in histological specimens into which India ink was injected into blood vessels, under a light microscope; in ultrathin sections, using a transmission electron microscope; and in acryl plastic-injected vascular corrosion cast specimens, under a scanning electron microscope. RESULTS: On day 7 after surgery, the interstitum of the elevated mucoperiosteal vascular plexus was filled with sinusoidal new blood vessels. Bone resorption by osteoclasts was observed around these new blood vessels and many highly permeable fenestrations were present in the vascular endothelium. On day 14 after surgery, sinusoidal new blood vessels were more markedly developed and some regions exhibited glomeruluslike morphology consistent with bone resorption cavities. Activated osteoblasts were present around these new blood vessels and highly permeable vesicles, which were considered to be possible vesiclo-vacuolar organelles (VVOs) and caveolae, were noted in the vascular endothelium. On days 21 and 28 after surgery, the mucoperiosteal vascular plexus was dissected through regression of endothelial cells and fibroblasts and reconstructed into a rough mesh structure, and simultaneously the bone surface became smooth. CONCLUSION: The morphology of the mucoperiosteal vascular plexus changed with bone metabolism and these changes contributed to transport of substances involved in periodontal repair.     

A mouse model of mandibular osteotomy healing

The purpose of this study was to establish a novel mouse model of membranous osteotomy healing. By applying this model to transgenic mice or using in situ hybridization techniques, we can subsequently investigate candidate genes that are believed to be important in membranous osteotomy healing. In the current study, 20 adult male CD-1 mice underwent a full-thickness osteotomy between the second and third molars of the right hemimandible using a 3-mm diamond disc and copious irrigation. Compo-Post pins were secured into the mandible, 2 mm anterior and posterior to the osteotomy. After the soft tissues were reapproximated and the skin was closed, an acrylic external fixator was attached to the exposed posts for stabilization. The animals were killed on postoperative day number 7, 10, 14, and 28 (n=5 animals per time point). The right hemimandibles were decalcified and embedded in paraffin for histologic evaluation or immunohistochemistry localizing osteocalcin. At 7 days after the osteotomy, early intramembranous bone formation could be seen extending from either edge of the osteotomized bone. By 10 days, an increasing number of small blood vessels could be seen within and around the osteotomy. At 14 days, the bone edges were in close approximation, and by 28 days the callus had been replaced by actively remodeling woven bone in all specimens examined. Immunohistochemistry demonstrated that osteocalcin expression correlated temporally with the transition from a soft to a hard callus. Furthermore, osteocalcin was spatially confined to osteoblasts actively laying down new osteoid or remodeling bone. This study describes a novel mouse model of membranous osteotomy healing that can be used as a paradigm for future osteotomy healing studies investigating candidate genes critical for osteogenesis and successful bone repair.