Microscopic changes in the condyle and disc in response to distraction osteogenesis of the minipig mandible.

PURPOSE: Unilateral mandibular distraction osteogenesis (DO) has been shown to cause gross changes in the mandibular condyle and articular disc. The purpose of this study was to correlate histologic findings with these gross changes in a minipig distraction model. MATERIALS AND METHODS: Semiburied distractors were placed via submandibular incisions in 15 minipigs. Two unoperated animals served as controls. The protocol consisted of 0-day latency and rates of 1, 2, or 4 mm/day for a 12-mm gap. After the minipigs were killed (at 0, 24, or 90 days), ipsilateral and contralateral condyles and discs were harvested, decalcified, prepared for standard paraffin embedding, and evaluated to determine changes in 1) morphology and thickness of the articular cartilage and subchondral bone and 2) morphology of the disc. RESULTS: In control animals, there were no degenerative changes in the articular cartilage and underlying condylar bone; there were no significant differences in the mean articular cartilage thickness. The temporomandibular joint discs were normal. In experimental animals, distracted condyles showed increasing degenerative changes and mean articular cartilage thickness as the DO rate increased. The discs were thinner. These changes were present, but to a lesser degree, in the contralateral condyles. After 90 days, degenerative changes in the condyles and discs were reduced, after remodeling, except in the 4 mm/day DO group. CONCLUSIONS: Histologic changes in the condyles and temporomandibular joint discs in response to mandibular DO correlated with previously reported gross changes. These changes were greater at higher distraction rates and remodeling back to normal occurred in mandibular condyles distracted at 1 mm/day.     

牵张成骨延长一侧下颌骨对颞下颌关节的影响

目的：研究牵张成骨（DO）延长一侧下颌骨对双侧颞下颌关节（TMJ）的影响。方法：用DO技术将8只山羊的一侧下颌骨延长10mm，在牵张完成后第8和16周分别处死4只动物，取双侧关节作组织学和扫描电镜研究。结果：下颌一侧DO术后双侧髁状突发生适应性改建，髁突表面超微结构正常。结论：在适当的牵张条件下延长一侧下颌骨不会对TMJ造成病理性损害。     

颞下颌关节侧向咬合位与对刃位薄层塑化断面对照研究

目的:对比分析下颌对刃位、侧向咬合位颞下颌关节的运动解剖形态,为颞下颌关节病变提供解剖依据。方法:将8例新鲜尸头摆置成对刃位5例、下颌侧向咬合位3例,以颞下颌关节为中心,切割成8cm×8cm×10cm的标本块,利用生物塑化技术,制成斜矢状位、斜冠状位、轴位塑化断层标本共16套。下颌侧向咬合位工作侧、非工作侧关节形态改变与对刃位相对照。结果:下颌侧向咬合位工作侧,髁突在关节窝内向后、向上、向外移位,关节盘位置无变化,关节盘双板及后带受压;非工作侧,髁突向下、向前、向内侧移位,关节盘后带位置向下移位,无前移位,关节盘中带外侧位居上下关节面之间,明显受压变薄。结论:关节盘并非随髁突作同步同向运动。关节盘在髁突作滑动运动时发生移位;当转动运动、滑动运动复合出现时,关节盘发生移位;而在关节窝内发生的转动运动,关节盘不发生移位。     

Reconstruction of mandibular condyle by transport distraction osteogenesis: Experimental study in rhesus monkey.

PURPOSE: This study investigated histomorphologic changes in the newly formed condyle reconstructed by transport distraction osteogenesis through a nonhuman primate model. MATERIALS AND METHODS: Six adult rhesus monkeys were used in this study. Bilateral condyles and articular discs were extirpated, and the technique of transport distraction osteogenesis was carried out to reconstruct the condyles. X-ray and 3-dimensional (3D) computed tomography (CT) scanning films were taken at various intervals. Two monkeys were killed respectively at 4, 12, and 24 weeks after completion of distraction; the transport segments and the distracted calluses were harvested and processed for histologic examination. The original condyles removed at surgery served as normal control. RESULTS: Open bite was seen in all animals postoperatively and diminished at the end of distraction. Bone regeneration was perfect in the distraction gap between the transport disc and the pre-existing mandible. The bony transport disc gradually remodeled to a neocondyle that was similar to the original condyle in the appearances and structures. The head of neocondyle was covered with a fibrous cap, which might play the role of an articular disc. CONCLUSION: A neocondyle with functional shape can be created by transport distraction osteogenesis. This suggests that this technique is an alternative method for reconstruction of the mandibular condyle.     

Histological evaluation of condylar hyperplasia model of rabbit following distraction osteogenesis of the condylar neck

Summary Condylar hyperplasia is the excessive unilateral growth of mandibular leading to facial asymmetry, occlusal disturbance, joint pain and dysfunction. The aim of this study is to evaluate the histological presence of temporomandibular joint in model of condylar hyperplasia by lengthening unilateral condylar neck of distraction osteogenesis. An extra oral distractor was employed to achieve unilateral condylar neck distraction (1·0 mm daily for 7 days). The experimental condylar necks were elongated by 7 mm compared to the contralateral. Eleven adult white rabbits were used. Eight rabbits were, respectively, sacrificed after the post‐distraction period (4 or 8 weeks). All animals were evaluated clinically and histomorphometrically. The condyles radiologically showed remodelling, flattening and sclerosis. In 4‐week group, thinning of the cartilage was evident, and the trabeculae were long, not multiply connected. A thin, dense fibrous layer covered all over the surface of cartilage. In 8‐week group, the cartilaginous layer was similar to thickness of the normal cartilage, but still thinner than control. However, the fibrous layers covering condyle manifested slight degenerative changes, and even depressions and erosions were seen in the cartilage and subchondral bone. The trabeculae showed denser and multiply connected. In 8‐week group, the cartilaginous thickness of surgical condyles was significantly thinner than the contralateral. This study indicates that unilateral distraction of condylar neck loads the condyles asymmetrically. Asymmetrical loads affect more on the surgical condyles than the contralateral, and after 8 weeks of the post‐distraction, condyle could recover from asymmetrical loads in some degree.     

Changes in parathyroid hormone-related protein and 3-dimensional trabecular bone structure of the mandibular condyle following mandibular distraction osteogenesis in growing rats.

PURPOSE: Distraction osteogenesis (DO) is commonly performed for mandibular reconstruction during the growth period. We tested the hypothesis that parathyroid hormone-related protein (PTHrP) in mandibular condylar cartilage and underlying trabecular bone in growing individuals undergo changes in response to distraction forces. MATERIALS AND METHODS: Forty-eight 6-week-old male Sprague-Dawley rats were used. Animals underwent unilateral mandibular distraction using a distractor that we devised, and unoperated animals were evaluated as controls. DO procedure was performed: 3 days' latency period, 0.4 mm/day rate, total 4.0 mm. Changes in cartilage morphology, PTHrP activity, and 3-dimensional trabecular bone structure changes measured by micro-computed tomography were examined at 0, 2, 4, and 6 weeks of consolidation. RESULTS: A marked irregularity was noted in the superior portion of the distracted side's condylar cartilage that resolved after distraction ceased. PTHrP was more strongly expressed in the hypertrophic layer of condylar cartilage on the distracted side than in controls, up to 6 weeks after the end of distraction. Subchondral trabecular bone volume, percent bone volume, and trabecular number in the superior and posterior regions of the condyle decreased significantly by 2 weeks after distraction. These parameters returned to normal in the posterior condyle, but not in the superior part of the condyle by 6 weeks following distraction. CONCLUSION: These results suggest that unilateral mandibular distraction in growing rats causes temporary morphologic alterations of trabecular bone structure on the distracted side accompanied by increased production of PTHrP in the mandibular condyle.     

运用输送盘牵张成骨术重建猴下颌髁突的实验研究

目的研究在猴颞下颌关节（TMJ）缺损动物模型上运用输送盘牵张成骨术重建髁突的可行性及其整复效果。方法选取6只成年恒河猴,手术截除其双侧关节髁突与关节盘,在下颌升支部行“L”形骨切开术,形成骨输送盘,并安置自行研制的牵张器。按每次0.4 mm,每次间隔12 h的牵张速率向上牵引输送盘至关节窝。牵张结束后第4、12、24周各处死2只动物。通过影像学分析和组织学检查评价输送盘改建与牵张间隙内新骨生成情况。以术中切除的髁突作为正常对照组。结果术后所有动物都有不同程度的咬合错乱,牵张结束后咬合基本恢复正常。骨输送盘形态基本接近正常髁突,其下方可见大量软骨细胞;牵张间隙内新骨生成良好。结论输送盘牵张成骨术可以重建一个形态和功能都基本接近正常的髁突,这种技术可以作为一种整复TMJ缺损的新方法。     

生长期山羊囊内骨折复位术中保留髁突软骨的重要性及组织学研究

目的：通过组织学观察,探讨髁突囊内骨折内固定术中保留和切除髁突软骨对髁突生长发育的影响。方法：6个月龄山羊12只,随机分为实验组（n=8）和对照组（n=4）。实验组双侧髁突造成囊内骨折并同期行手术复位固定．一侧保留髁突软骨,另一侧切除髁突软骨。术后3个月、6个月处死动物,切取髁突标本行石蜡切片和硬组织切片观察骨折愈合和髁突生长情况。结果：实验组髁突骨折愈合良好,钛板被新生骨组织覆盖;HE染色显示．保留髁突软骨组,髁突软骨结构清晰,与正常对照髁突相同,软骨成骨活跃,髁突生长发育正常;切除髁突软骨组,髁突软骨层消失,表面为成熟的骨细胞覆盖,直接与关节盘的纤维组织相连,新生骨组织少见：硬组织切片显示,钛板与骨组织直接结合．未见组织渗出和排异反应。结论：手术复位髁突囊内骨折时保留髁突软骨,不会影响髁突的生长发育;损伤髁突软骨．会造成髁突与关节盘黏连．引起髁突生长发育障碍。     

Incisor and mandibular condylar movements of young adult females during maximum protrusion and lateratrusion of the jaw

This study evaluated the correlations between condylar translation and incisor movements during maximum protrusion and lateratrusion. The sample was 27 adult females (23--35 years old), selected for normal temporomandibular function, occlusion, and skeletal patterns. Condylar and mandibular central incisor movements [linear distances (LD) and curvilinear pathways (CP)] were recorded in three dimensions for 20 s with an optoelectric (Optotrak) jaw-tracking system while each participant performed multiple maximum protrusive and lateratrusive cycles. Masticatory analysis and multilevel statistical programs computed the three-dimensional movements of the incisors and condylar hinge axis during protrusion and lateratrusion. CP of the incisor point averaged 12.0 mm (9.3 mm LD) during protrusion, 13.0 mm (11.5 mm LD) during right excursion and 12.3 mm (11.0 mm LD) during left excursion. CP of the condyles averaged 11.9--12.9 (9.2--9.5 LD) mm during protrusion. During lateratrusion the contralateral condyles moved anteroinferiorly 11.6--14.1 mm (9.5--10.2 mm LD); the ipsilateral condyles moved posterolaterally 5.8-6.8 mm (2.3--2.5 mm LD). The left condyles demonstrated more movement than the right condyles during protrusion and than the contralateral condyles during laterotrusion. Relative variation, as measured by the coefficient of variation, was greater for the movements of the ipsilateral than contralateral condyles. Incisor movements were only moderately related to condylar movements between individuals and between replicates; LDs showed stronger correlations than CPs; and correlations were stronger for lateratrusion than protrusion. While incisor and condylar movements were not affected by repeated protrusion, incisor CP (approx. 0.2 mm/cycle) and LD (approx. 0.1 mm/cycle) increased significantly with repeated excursive movements to the left and right. It was concluded that (1) incisor protrusion and lateratrusion provide moderately reliable measures of condylar translation; (2) the linear distances that the incisors move during lateratrusion provide the best measure of contralateral condylar translation; and (3) condylar movements are not affected by repeated protrusion or lateratrusion.     

牵引成骨结合组织工程化软骨重建山羊髁突缺损的实验研究

目的：利用牵引成骨结合组织工程化软骨重建山羊髁突缺损。方法：12只山羊随机分为两组：实验组在下颌切迹下方作截骨线,切除一侧髁突及其颈部,左右随机。再于下颌支后缘形成转移盘,在转移盘的远中植入软骨细胞支架复合物。对照组在转移盘的远中仅植入支架。分别于牵引结束4、8、12周大体及组织学观察山羊髁突的形成情况。结果：牵引结束后4周,实验组山羊髁突已具备良好的外形,髁突表面覆盖软骨组织：对照组山羊新形成之髁突外形虽与正常髁突相似但表面无软骨层。12周时,实验组山羊髁突外形与正常髁突相似,表面仍有软骨层覆盖：而对照组山羊新形成的髁突外形虽与正常髁突相似,但表面仍无软骨层覆盖。结论：利用牵引成骨结合组织工程化软骨的方法不仅可以从外形上重建山羊髁突,而且在解剖结构上与正常髁突相似,为髁突正常功能的行使提供了良好的解剖学基础。     

Histomorphometric evaluation of short-term changes in masseter muscle after lengthening the rabbit mandible by distraction osteogenesis.

PURPOSE: Structural changes in muscles may affect the process during and after distraction osteogenesis (DO) of the mandible. However, the response of the masticatory muscles is still not well defined after gradual lengthening of the mandible. In this experimental study, short-term structural changes in masseter muscles of the rabbits are evaluated after mandibular DO. MATERIALS AND METHODS: Left mandibles of 10 New Zealand rabbits were lengthened by DO for 7 days in the rate of 1 mm/day. Mandibles of all animals were removed at the end of the consolidation period. Muscle biopsy samples of distracted and contralateral sides were histopathologically investigated, and histomorphometric results were statistically analyzed. RESULTS: Atrophy, hypertrophy, regeneration, and concomitant mild interstitial edema and fibrosis were found more evident in experimental side biopsy samples 30 days after distraction. Histomorphometric analysis revealed a statistically significant decrease in the mean regions of masseter muscle fibers of the distracted sides compared with the control sides (P <.05). CONCLUSION: This experimental study showed that the structure of masseter muscle is influenced during and shortly after mandibular distraction osteogenesis. Atrophic changes of the ipsilateral masseter muscles may be regarded as regenerative response that occurs during and shortly after distraction period.     

Three-dimensional finite element analysis of the mandible and temporomandibular joint on simulated occlusal forces before and after vertical ramus elongation by distraction osteogenesis

Distraction osteogenesis has recently become a mainstay for treatment of mandibular hypoplasia. Thorough knowledge about changes in the temporomandibular joint (TMJ) and the surrounding parts of the mandible and the skull after mandibular distraction is still lacking. The purpose of the current study was to investigate the stress distribution in the mandible and the TMJ before and after skeletal correction by intraoral unilateral vertical mandibular ramus distraction, using a finite element (FE) model. The FE models were based on computed tomography scans and magnetic resonance imaging scans of a patient with unilateral hypoplasia of the right mandibular ramus caused by juvenile idiopathic arthritis. The character of stress distribution in the mandible and TMJ before and after skeletal correction by 15 mm of vertical distraction of the mandibular ramus was analyzed quantitatively and compared during centric occlusion. Before the distraction osteogenesis treatment, the condyles, articular discs, and glenoid fossa regions are loaded with a different stress pattern. The affected right condyle, disc, and fossa are loaded diffusely and externally in comparison with the anterior and with centralized loading on the normal left side. After unilateral mandibular distraction osteogenesis, the load became more centric and symmetrical. The results suggest that correction of the mandibular deformity by distraction osteogenesis tends to normalize the stress patterns in the TMJ.     

Alterations of morphology and microdensity in the condyle after mandibular osteodistraction in the rat.

PURPOSE: In this study, we examined the effects of mandibular distraction osteogenesis on the morphology and the microdensity of the rat condyle. Materials and Methods: One hundred twenty-nine rats were allocated to 4 experimental groups (n = 32 or 33). Each received unilateral mandibular ramus osteotomy and distraction device placement. After a 3-day latency, these were distracted once a day for 5 days. The slow distraction group was distracted a total of 1 mm (0.2 mm/d); the moderate group, 2 mm (0.4 mm/d); the rapid group, 3 mm (0.6 mm/d); and the sham group, no distraction (0.0 mm/d). Eight to 9 rats in each group were sacrificed at each of 4 time points after device placement (6, 10, 24, and 38 days). Baseline data were obtained 3 days after osteotomy and device placement without distraction from an additional 10 rats. Radiographs of the hemimandibles were scanned and measured to evaluate changes in condylar size (height, width, and area), angulation, and bone microdensity converted to equivalent bone thickness using a stepwedge. The wet weights of masseter muscle were measured at the time of harvest. RESULTS: 1) Muscle weight gains over time were significantly lower in the treated than the untreated sides throughout the consolidation period (P <.001). 2) Condylar size and angulation on the untreated side increased postoperatively, whereas there was a significant reduction of these parameters (P <.01 to.001) on the treated side at 24 and/or 38 days. 3) Condylar microdensity significantly increased on the untreated side at 24 and 38 days (P <.05 to.01) but not on the treated side. 4) Faster or larger distraction caused more severe size reduction and more upright condylar angulation, prevented an increase in bone microdensity on the treated side, especially during the consolidation periods (P <.05 to.01), and retarded increase in muscle weight, whereas a slower distraction rate showed few negative, and even some positive effects. 5) Correlations in size, angulation, and microdensity between right and left condyles became less significant over time. 6) There were positive correlations between muscle weight and condylar size, angulation, and microdensity. CONCLUSION: An increased rate of mandibular distraction has significant negative effects on condylar morphology and microdensity.     

The influence of pre- and intraoperative positioning of the condyle in the centre of the articular fossa on the position of the disc in orthognathic surgery. A magnetic resonance study

OBJECTIVE: We investigated the changes in the temporomandibular joint (TMJ) after bilateral sagittal split osteotomy of the mandible for orthognathic surgery and the influence of positioning of the condylar process in the centre of the articular fossa before and during the operation for preventing changes in the TMJ postoperatively. STUDY DESIGN: A total of 28 patients with mandibular retrognathism had bilateral sagittal split osteotomies for mandibular advancement. In one group of 14 patients (28 TMJ), the condyles were placed in the centre of the articular fossa before and during the operation, and in the other group they were not. Differences on magnetic resonance imaging (MRI) were calculated and the results were evaluated. RESULTS: The main differences were found at maximal mouth opening. 15/28 TMJs (54%) that had not been positioned changed the position of the disc from physiological to anterior disc derangement with and without reduction postoperatively. In the 28 that had been positioned, changes were found in only 3 TMJs (11%) postoperatively. CONCLUSIONS: Fixing the condylar process in the centre of the articular fossa intraoperatively before bilateral sagittal split osteotomy is a factor in preventing postoperative structural changes in the temporomandibular joint.     

双侧下颌牵张成骨对转化生长因子β1在颞下颌关节髁突表达的影响

目的　研究狗的双侧下颌牵张成骨中颞下颌关节髁突的形态改变及转化生长因子β1(TGF-β1)在髁突的 表达。方法　16只狗随机分为4组,每组4只,分别为牵张6 d组、牵张后固定2周组、牵张后固定8周组及正常对 照组。各实验组的牵张频率均为1 mm/d,1次/天。对每组动物的髁突标本进行苏木精-伊红染色及TGF-β1的免 疫组化染色观察。结果　苏木精-伊红染色可见实验组动物的髁突纤维软骨早期有不同程度的损伤,增殖带、肥 大带细胞增生活跃,软骨钙化层及其深层软骨成骨活跃;TGF-β1阳性染色主要定位在肥大带细胞胞浆、周围基质和 成骨反应活跃处的成软骨细胞、成骨细胞及周围基质。牵张后固定2周时这种改建修复现象最明显,8周时逐渐恢 复至正常对照组的表现。结论　双侧下颌牵张成骨对颞下颌关节髁突影响主要表现为髁突纤维软骨组织形态学 的改变和软骨、骨的改建活动,但随着固定时间的延长这种改变逐渐修复。     

Effect of mandibular distraction osteogenesis on temporomandibular joint after previous irradiation and hyperbaric oxygenation

The purpose was to evaluate the effect of mandibular distraction osteogenesis (DO) on condylar cartilage after radiotherapy and hyperbaric oxygenation (HBO). Unilateral DO was performed on low- and high-dose irradiated rabbits with or without accompanying HBO, and non-irradiated animals. High-dose irradiated animals were given irradiation in the temporomandibular joint (TMJ) equivalent to 50 Gy in 25 fractions. Low-dose irradiated rabbits received scattered irradiation of 10% of that of high-dose irradiated animals. After radiotherapy, some of the animals were given HBO 18 times at 2.5 ATA for 90 min/day. One month after completion of radiotherapy, distraction osteotomy with distractor placement was performed. After a latency period, distraction was started at the rate of 1 mm/day, continued for 2 weeks, and the regenerate was allowed to consolidate for 1 month. Condyles of non-operated rabbits served as controls. Histological changes were more evident on the distracted than on the non-distracted side. In distracted, non-irradiated animals, condylar cartilage changes were minor and probably clinically insignificant. In irradiated rabbits, condylar cartilage changes on the lengthened side were severe, and often cartilage was either totally or partially sealed off by bone. Condylar heads were morphologically deformed. Even low doses of irradiation resulted in notable changes on the operated side, and HBO did not prevent disadvantageous effects.     

Histological evaluation of the temporomandibular joint after bilateral vertical ramus mandibular distraction in a canine model

The aim of this pilot study was to histologically evaluate the effect of bilateral vertical mandibular distraction osteogenesis (DO) on the temporomandibular joint (TMJ) in a canine model. Eight male beagle dogs underwent DO, with the placement of single-vector internal distractors. One unoperated animal served as control. After a latency period of 7 days, distraction was performed at a rate of 1 mm a day for an average of 12 days. The animals were divided into two groups (n = 4) and sacrificed after one or two months of consolidation. Eighteen TMJs were prepared for histological evaluation. Control TMJs surfaces were smooth, with no irregularities and trabecular bone was thick and multiply connected. In the one-month group, thinning of the trabecular bone was evident. The trabeculae were long, not multiply connected, parallel to each other and perpendicular to the articular surface. Although overall fibrous-cartilaginous tissues covering the TMJs were maintained with no signs of degenerative changes, one condyle from the one-month group had depressions and erosions of the fibro-cartilage layer and subcortical bone. In the two-month group, overall bone and cartilage architecture was more similar to the control specimens. This study indicates that, in the short term, gross changes can occur in the TMJ after bilateral mandibular vertical ramus distraction. These changes seem to be a process of biological adaptation to the pressure and functional changes secondary to surgery and distraction. However, long-term studies are needed to confirm whether the changes are completely reversible.     

下颌骨髁状突即刻再植的实验研究

为髁状突即刻再植的临床应用提供理论依据。方法　以日本大耳白兔为实验对象 ,切下右侧髁状突后行即刻再植术。左侧作为对照。术后分期处死动物 ,观察骨的愈合、髁状突及关节盘形态和组织学的改变。结果　再植髁状突骨愈合良好。再植髁状突早期有异常的形态学的改变 ,其生长发育受到一定的影响 ,但无关节粘连和强直 ,所有动物可行使正常的咀嚼功能。结论　髁状突即刻再植术可选择性地用于颞下颌关节重建。     

状突冷冻再植后颞下颌关节改变的实验研究

目的 :为颞下颌关节肿瘤的治疗及关节重建提供一定的理论依据。材料和方法 :对 16只未成年日本大耳白兔的右侧髁状突施行了冷冻再植术。术后所有动物正常存活 ,第 2、4、8、12周分别处死 4只动物。采用常规组织学、扫描电镜及微血管显像等对髁状突和关节盘进行观察。结果 :组织学检查发现随着血供逐渐恢复 ,失去活力的骨被新骨“爬行替代” ,而髁状突软骨的结构未完全恢复 ;扫描电镜检查证明了关节盘下腔面的表面结构基本正常 ,实验后期髁状突的表面较光滑 ,但无明显胶冻样物 ;微血管显像显示冷冻再植髁状突逐渐再血管化。 16只动物中有 3只的手术侧颞下颌关节发生轻度粘连。结论这些结果证明 :髁状突冷冻再植在颞下颌关节重建时有应用的可行性。     

Experimental model of distraction osteogenesis in edentulous rats

Distraction osteogenesis (DO) is a surgical technique producing bone lengthening by distraction of the fracture callus. Although a large number of experimental studies on the events associated with DO of craniofacial skeleton have been reported, the few employing rat mandibular bone DO used complicated designs and produced a small volume of newly formed bone. Thus, this study aims to present an original experimental model of mandibular DO in edentulous rats that produces a sufficient quantity and quality of intramembranous bone. Eight male Wistar rats, weighing 75 g, underwent extraction of lower molars. With rats weighing 350 g, right mandibular osteotomy was performed and the distraction device was placed. The distraction device was custom made using micro-implants, expansion screws, and acrylic resin. Study protocol: latency: 6 days, distraction: ? turn (0.175 mm) once a day during 6 d, consolidation: 28 d after distraction phase, sacrifice. DO-treated and contralateral hemimandibles were dissected and compared macroscopically and using radiographic studies. Histological sections were obtained and stained with H&E. A distraction gap filled with newly formed and mature bone tissue was obtained. This model of mandibular DO proved useful to obtain adequate quantity and quality of bone to study bone regeneration.