The expressions of IGF‐1, BMP‐2 and TGF‐β1 in cartilage of condylar hyperplasia

Summary Condylar hyperplasia is a complex post‐natal growth abnormality of the mandible and condyle, which leads to facial asymmetry. We investigated the distributions of insulin‐like growth factors (IGF‐1), bone morphogenetic protein‐2 (BMP‐2) and transforming growth factor‐β1 (TGF‐β1) in cartilage of condylar hyperplasia and revealed relationships between age and the cartilaginous thickness. Twenty patients with condylar hyperplasia were divided into four histopathological types. The cartilaginous thickness and age in different histological types were analysed, and the localizations of IGF‐1, BMP‐2 and TGF‐β1 were detected by immunohistochemistry analysis. The cartilaginous thickness of condylar hyperplasia significantly increased. The cartilaginous thickness of type III was significantly thicker than type I and type II, Bivariate correlation revealed a significant correlations between age and the cartilaginous thickness (r = 0·68, P = 0·01). However, the expressions of IGF‐1, BMP‐2 and TGF‐β1 were the strongest in type I. In almost all types of condylar hyperplasia, the presence of IGF‐1 and BMP‐2 was found mainly in the proliferative chondrocyte layer and the hypertrophic chondrocyte layer, and only a few in the calcified chondrocyte layer. The presence of TGF‐β1 widely distributed from the fibrous articular surface to the calcified cartilage. These findings suggest that the proliferative activity of cartilage in condylar hyperplasia is strongly associated with age and cartilaginous thickness. Therefore, the four pathological types of condylar hyperplasia seem more likely to be four discontinuous stages.     

髁突骨软骨瘤与髁突增生患者的CT表现特点分析

目的:比较下颌骨髁突骨软骨瘤和单侧下颌骨髁突增生的CT表现特点。方法:对2005—2010年上海交通大学医学院附属第九人民医院口腔颌面外科收治的下颌骨髁突骨软骨瘤11例和单侧下颌骨髁突增生8例患者的CT影像学资料进行评价,评价指标包括病变髁突大小、病变范围以及病变周围软硬组织改变。结果:11例下颌骨髁突骨软骨瘤病例CT显示肿瘤与病变髁突无明显分界(8/11)或与患侧髁突有蒂相连(3/11);肿瘤骨皮质及骨髓腔均与患侧髁突相续,瘤体表面均有特征性薄层软骨帽覆盖,瘤体外周密度通常高于中心;瘤体周围均有薄层软组织包绕。患侧颞骨关节面表面均有明显矿化,且因受瘤体压迫改建而较对侧平坦,患侧关节上、下腔间隙较对侧明显变窄;肿瘤生长方向不尽相同。8例单侧下颌骨髁突增生病例CT显示髁突颈部和(或)下颌支延长,髁突形状改变;增生的髁突外周骨皮质均有不同程度的骨化,硬化层厚度较对侧大;骨髓腔密度较不均匀。结论:CT检查能有效提供病变髁突及其周围软硬组织情况,为鉴别诊断下颌骨髁突骨软骨瘤和单侧下颌骨髁突增生提供良好的依据。     

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。     

Osseous alterations in the condylar head after unilateral surgical directional change in rabbit mandibular condyles: Preliminary study

The purpose of this study was to investigate bony changes in the mandibular condyle when the surface not normally subjected to masticatory forces was subjected to functional loading using a unilateral surgical experiment. Fifteen male New Zealand white rabbits, divided into two groups, were used. Oblique vertical body osteotomies of the mandible and counterclockwise rotation (CCWR) of the proximal segment (PS) [six with 1 mm (group I), six with 3 mm (group II)] were performed on the right side. Osseous changes of condyles were analyzed using micro-computed tomography and histological evaluation four weeks postoperatively. The comparison was performed between condyles on the right and left sides. Since the left condyle (control) might be affected by the operation on the right side, the results were also compared with the healthy control (group III, n = 3, 6 condyles). CCWR of the PS led to osteoporotic changes of the condyle including significantly reduced bone volume and bone mineral density (p < 0.05), thin and small number of trabeculae (p < 0.05). In addition, thinning of condylar cartilage and reduced density of cartilaginous cells were observed. However, these changes were not affected by the amount of CCWR of the PS.     

单侧后牙长期缺失后髁突形态的锥形束CT研究

目的采用锥形束CT（CBCT）研究单侧后牙长期游离缺失对双侧髁突形态的影响。方法收集30例单侧后牙长期游离缺失患者和30例正常对照者的CBCT图像,应用Mimics 15.0软件测量双侧髁突体积、面积、线距及骨密度,对测量结果进行统计学分析。结果缺牙侧的髁突体积、髁顶体积及其骨密度明显小于非缺牙侧（P<0.05）;髁突横截平面的面积及其骨密度大于非缺牙侧（P<0.05）。结论单侧后牙长期游离缺失后,双侧髁突均发生适应性改建,缺牙侧髁突小于非缺牙侧。     

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.     

Condyle and mandibular bone change after unilateral condylar neck fracture in growing rats

Unilateral fracture of the condylar neck in immature subjects might lead to mandible asymmetry and condyle remodelling. A rat model was used to investigate mandibular deviation and condylar remodelling associated with condyle fracture. 72 4-week-old male rats were randomly divided into three groups: an experimental group (unilateral transverse condylar fracture induced surgically), a sham operation group (surgical exposure but no fracture), and a non-operative control group (no operation). The rats were killed at intervals up to 9weeks after surgery, and outcomes were assessed using various measures of mandible deviation, histological and X-ray observation, and immunohistochemical measures of expression levels of connective tissue growth factor (CTGF) and type II collagen (Col II). The fracture led to the degeneration of mandibular size, associated with atrophy of fractured condylar process. Progressive remodelling of cartilage and increasing expression levels of CTGF and Col II were found. The authors conclude that condylar fracture can lead to asymmetries in mandible and condyle remodelling and expression of CTGF and Col II in condylar cartilage on both the ipsilateral and the contralateral sides.     

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目的研究发育期SD大鼠髁状突颈部骨折对下颌髁状突软骨细胞中上游刺激因子1(USF1)表达的影响。方法本研究于2011年7—9月在昆明医科大学口腔医学院研究所完成。选择4周龄雄性SD大鼠12只,其中6只大鼠用于制作下颌单侧髁状突颈部骨折动物模型,6只大鼠为对照。分别在术后1、3、5周时处死大鼠,取出骨折侧、骨折对侧以及空白对照的髁状突软骨。采用免疫组织化学方法检测髁状突软骨细胞中USF1表达情况。结果术后1周,骨折对侧空白对照组与骨折侧的USF1表达有显著性差异(P<0.01);术后3周,空白对照组与骨折侧USF1表达有显著性差异(P<0.01)。骨折侧术后3周、5周与术后1周USF1表达有显著性差异(P<0.01)。结论单侧髁状突颈部骨折引起应力变化,使患侧髁状突软骨细胞中USF1表达异常,进而影响髁状突的生长发育。     

High condylar shave of the temporomandibular joint with preservation of the articular soft tissue cover: an experimental study on rabbits

The high condylar shave has the disadvantage of removing the articular soft tissue cover together with the underlying condylar bone. In an attempt to overcome this disadvantage, we elevated the articular soft tissue cover, shaved the condylar head, and replaced the articular soft tissue cover in its original position in nine adult rabbit temporomandibular joints. On the contralateral joints, the same amount of bone was shaved together with the articular soft tissue cover. The rabbits were killed after 3 months, and the condyles were macroscopically and histologically evaluated. All condyles were covered with an articular soft tissue layer in the area operated on. This surface was smoother when the articular soft tissue cover was preserved. Histologically, the subarticular layer of cartilage cells was continuous in the joints with preservation of the articular soft tissue cover but was frequently interrupted in the joints where this cover was removed. The incision made in the posterior part of the articular surface for elevating the articular soft tissue cover frequently caused a deformity of the condyle and an interruption of the subarticular layer of cartilage. The results suggest that preservation of the articular soft tissue cover on the mandibular condyle might be one way to improve the postoperative morphology after high condylar shave. The technique in its present state has obvious drawbacks and should be further refined before it is considered for clinical application.     

The use of SPECT to evaluate growth cessation of the mandible in unilateral condylar hyperplasia

In unilateral condylar hyperplasia, for surgical intervention to be effective, the status of condylar bone growth has to be assessed correctly. Previously this assessment relied on serial clinical observations. This study aimed to evaluate the MDP-SPECT method of assessing condylar growth in unilateral condylar hyperplasia. Twenty-six MDP-SPECT of the mandible had been performed; 21 were diagnosed as condylar hyperplasia and five as non-mandibular disease. Three isotope parameters: isotope counts, pixel counts and counts per pixel were summed for each condyle per subject. The percentage difference in isotope uptake of the three parameters between the two condyles was calculated as the ratio of the combined counts of the two sides. These differences significantly correlated with each other (Pearson r=0.78-0.98) and with the clinical status of bone growth (Spearman rho=0.72-0.86). There was a significant difference for the count per pixel between the 'growing' condyle (transaxial, T: 15.05+/-7.14, coronal, C: 12.29+/-7.88), the 'no further growth' condyle (T: 5.22+/-4.08, C: 5.67+/-3.88) and the 'normal' condyle (T: 0.82+/-0.76, C: 1.34+/-0.66). This method was able to separate 'active growth' from 'growth cessation' of the condyle by a single MDP-SPECT of the mandible. However, further studies are needed to confirm this finding.     

不同咀嚼压力对幼兔髁突软骨成骨的影响研究

目的：分析生长发育期不同咀嚼模式下兔髁突软骨成骨形态学的差异,研究咀嚼压力对幼兔髁突生长发育的影响和作用机制。方法：选取15天龄的未断奶幼兔16只,随机分为硬食组和软食组各8只,硬食组提供颗粒饲料,软食组提供由同种颗粒饲料碾磨而成的粉末状饲料。幼兔28天龄断奶,分别于28天龄、33天龄肌肉注射四环素、钙黄绿素,38天龄处死幼兔。制作硬组织切片,荧光显微镜观察,独立t检验分析比较两组髁突软骨成骨厚度,骨形态学参数。结果：硬食组的软骨成骨厚度、骨小梁相对体积、骨小梁数量、骨小梁厚度均大于软食组（P<0.05）,硬食组骨小梁分离度小于软食组（P<0.05）。相同时间硬食组骨形成沉积率[（3.25±0.02）μm / d ]大于软食组[（2.37±0.02）μm / d ]。结论：生长期软食组幼兔的髁突软骨成骨能力较硬食组弱,咀嚼负荷力是影响髁突软骨成骨生长的重要因素。     

Effects of estrogen on the condylar cartilage of the rat mandible in organ culture.

PURPOSE: The effects of estrogen on bone have been well documented. However, very little is known about the regulatory role of estrogen on cartilage and, in particular, the secondary cartilage of the mandibular condyle. The aims of this study were to determine whether estrogen receptors are present in the condylar cartilage of the rat mandible and to assess the effect of varying 17beta-estradiol (E2) concentrations on the proteoglycan content of this tissue. MATERIALS AND METHODS: Mandibular condyles of 16 female Sprague-Dawley rats were resected. Eighteen of these condyles were divided into three groups and the condylar cartilage was removed and placed in organ culture for 4 days with media containing different concentrations of estrogen: 10(-11) mol/L, 10(-8) mol/L, and 10(-6) mol/L. The cartilage then was analyzed for proteoglycan content along with six specimens not passed through the organ culture. Six intact mandibular condyles also were resected and placed in organ culture with the same varying E2 concentrations, and the condylar cartilage was analyzed for estrogen receptors along with two condyles not passed through the culture system. RESULTS: Estrogen receptors were evenly distributed within the chondroblastic and hypertrophic zones in the control group and the group with 10(-11) mol/L E2. With E2 concentrations of 10(-8) mol/L and 10(-6) mol/L, there was a qualitative decrease in hypertrophic chondroblasts, thickness of the condylar cartilage, and a significant decrease in proteoglycan content. CONCLUSIONS: This study shows the presence of estrogen receptors in the secondary cartilage of the rat mandibular condyle. Estrogen has the potential to cause a decrease in extracellular matrix and thickness of this cartilage.     

Effect of low masticatory function on condylar growth: a morphometric study in the rat.

The aim of this study was to estimate the influence of functional alterations on the size of the mandibular condyle and to elucidate in detail, by means of histomorphometric analysis, the effect of changing the consistency of the diet on different portions of the condylar cartilage in growing rats. Forty growing rats were randomly divided into 2 groups. One group received the normal hard diet for rats; the other group received a standardized soft diet. The experimental period was 28 days. Ten animals from each group were used for gross morphometric analysis; the other 10 animals were used for histologic analysis of the condyle. The morphometric analysis of the condylar cartilage was based on the 25th, 50th, and 75th percentiles of the mediolateral sections of the condyles. The sections were divided into 3 parts: the anterior, intermediate, and posterior part; 4 measurements were performed in each. Significant differences were found in the condylar length and width between the groups, the soft diet group having a smaller condyle. The histomorphometric analysis of cartilage thickness showed significant differences between the 2 groups, being thinner in the anterior part and thicker in the posterior part of the condyle in the soft diet group. These routine histologic findings cannot explain the gross morphologic differences in the condylar size between the groups; this means that increased condylar cartilage thickness is not necessarily evidence of increased condylar growth. The results from this study indicate that a low masticatory function leads to decreased growth of the condyle and changes in the thickness of the cartilage. This may be the effect of an alteration in the stress distribution in the temporomandibular joint area, because of the absence of large masticatory forces.     

In vivo morphometric analysis of inflammatory condylar changes in rat temporomandibular joint

Oral Diseases (2011) 17 , 499–507 Objective: Injection of complete Freund’s adjuvant (CFA) into the temporomandibular joint (TMJ) causes acute swelling around the joint and subsequent morphological alterations in the condyle. We aimed to evaluate changes in the three‐dimensional architecture of the condyle induced with CFA. Materials and methods: The CFA was injected into the unilateral TMJ of rats and morphological changes in the condyle were assessed repeatedly for 14 days by in vivo micro‐CT. Results: Osseous abnormalities of condyle were first observed at 3–5 days after CFA injection on the tomographic images, and the condylar deformation became more obvious thereafter. Among 12 condyles examined at 14 days postinjection, osteophytosis was observed in all of the specimens and bone erosion coexisted in five condyles. None of the saline‐treated condyles showed architectural changes. Significant changes were detected in the mesiolateral and rostrocaudal widths of the CFA‐treated condyles at 10–14 days postinjection (P < 0.01). The extent of both condylar bone formation and resorption was greater in the CFA‐injected TMJs than in saline‐injected TMJs (P < 0.05). Conclusion: These results indicate that CFA causes dynamic morphological changes in the condyle and that our experimental approach will provide new insights into the subacute inflammatory processes in the TMJ.     

Can electrocautery of the mandibular condyle effectively treat condylar hyperplasia?

This study aims to introduce and evaluate a novel technique to treat unilateral condylar hyperplasia (UCH) by electrocauterization of the mandibular condyle via an intraoral approach.Patients suffering from unilateral condylar hyperplasia (UCH) were included in this study. All patients underwent electrocauterization of the affected condyle. An intraoral incision on the anterior border of the mandibular ramus was made to expose the external surface of the ramus and access the anterior border of the condylar head. A hole was then drilled into the condyle and cauterization was performed; six patients also received orthognathic surgery during the procedure. Patients underwent careful clinical assessment and radiological evaluation including panoramic view, lateral and posteroanterior cephalometry, cone-beam computed tomography (CBCT) and scintigraphy to assess condylar growth for a period of 12–24 months. Ten patients (5 male and 5 female) with active UCH type 1B or 2A were included in this study with a mean age of 20.7 years (range, 18–21.7 years). At the 12-month postoperative assessment, clinical evaluation showed stable dental occlusion with no midline shift; scintigraphy showed persistently reduced cellular activity, and computed tomography scans revealed no degeneration in either of the condyles with complete healing of the drilled holes.Within the limitations of this study it seems that the proposed treatment approach might be an alternative to previously established protocols.     

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

PURPOSE: Distraction osteogenesis (DO) is a commonly used technique for mandibular lengthening, but changes in the temporomandibular joint have not been well documented. The purpose of this study was to evaluate the effect of DO, at varying rates, on the mandibular condyle and articular disc. 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/d for a 12-mm gap. After the animals were killed (0, 24, or 90 days), ipsilateral and contralateral condyles and discs were harvested and evaluated to determine changes in 1) condylar form and size, 2) condylar surface, and 3) the articular disc. RESULTS: Articular surfaces of the condyles in control animals were smooth, with no irregularities or erosions. In animals undergoing distraction, ipsilateral condyles showed increasing changes in morphology and AP dimension, and surface contour irregularities as the DO rate increased. These changes were present, but to a lesser degree, in the contralateral condyles. Articular discs of both ipsilateral and contralateral sides showed variable thinning at the medial aspect at end DO. After 90 days, changes in the condyles and discs were reduced by remodeling except in the 4 mm/d DO groups. CONCLUSIONS: Results of this preliminary study indicate that gross changes occur in condyles and discs after unilateral mandibular DO. These changes are more severe at faster distraction rates (4 mm/d) and tend to resolve during neutral fixation when a rate of 1 mm/d is used.     

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。     

Comparison of different analytical methods used for analyzing SPECT scans of patients with unilateral condylar hyperactivity

This study aimed to compare different analytical methods and identify the optimal analysis method to distinguish patients with unilateral condylar hyperactivity (UCH) from those with inactive condyles. Single-photon emission computed tomography (SPECT) scans of patients with progressive and nonprogressive mandibular asymmetry (each group, n = 26), were analyzed using the region of interest technique. Sensitivity, specificity and receiver operating characteristic (ROC) curves were calculated for the different analytic methods. The ROC curve illustrates that UCH can be diagnosed significantly better by determining the percentile bone activity in both condyles. The area under the curve (AUC) of the percentile comparison between the affected and contralateral condyles was 0.93 ± 0.04, that for the condyle/clivus ratio was 0.75 ± 0.07 and for the condyle/cervical spine (CS) ratio 0.57 ± 0.08. Sensitivity for the condyle/clivus ratio was 65% and specificity 61%. Sensitivity for the condyle/CS ratio was 85% and specificity 31%. For the percentile difference of the condyles, sensitivity and specificity were 88%. For UCH patients, direct comparison of bone activity between the affected and contralateral condyle in SPECT scans is the analysis method of choice. Comparison of condylar bone activity to reference bone activity does not have additional value in the diagnosis of UCH.     

Changes in growth and morphology of the condyle following mandibular distraction in minipigs: overloading or underloading?

OBJECTIVE: Loading of temporomandibular tissues during mandibular distraction may cause changes in condylar growth and cartilage thickness. This study examines the effects of distraction on the condyle in a large animal model by explicitly measuring growth and in vivo loading. DESIGN: Unilateral mandibular distraction was carried out on 20 growing minipigs divided into three groups. One group underwent distraction but not consolidation, whereas the other two groups were allowed a period of consolidation of either 1 or 2 weeks. Animals received fluorochrome and 5-bromo-2'-deoxyuridine (BrdU) labelling and masticatory strain was measured from the condylar neck. Condylar strain was also recorded in an age-matched sample of eight animals that received no distraction surgery. Immunohistochemical procedures were used to identify dividing prechondroblasts and histological analysis was used to measure mineral apposition rate, count dividing cells, and measure the thickness of condylar cartilage. RESULTS: Strain magnitude, particularly compressive strain, was much larger on the non-distraction side compared to the distraction side condyle. Compared to normal loading levels, the distraction side condyle was underloaded whereas the condyle on the intact side was overloaded. Mineral apposition and cartilage thickness were greater on the distraction side condyle compared to the opposite side. Differences between the sides were most pronounced in the group with no consolidation and became progressively reduced with consolidation time. CONCLUSIONS: Increased mineralisation and cartilage thickness on the distraction side condyle are associated with reduced, not increased loading, perhaps because of disruption of the distraction side masseter muscle.     

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.