Stress distribution in the temporomandibular joint after mandibular protraction: A three-dimensional finite element study

Objective:To evaluate the stress patterns in temporomandibular joint (TMJ) during mandibular protraction at different horizontal advancements with constant vertical height in a construction bite using a three-dimensional finite element method.Materials and Methods:A three-dimensional computer-aided model was developed from the magnetic resonance imaging (MRI) of a growing boy (age 12 years) using MIMICS software (version 7.0, Materialise, Leuven, Belgium). Stresses with constant vertical opening of 5 mm changing the sagittal advancements from 0 mm to 5 mm and 7.5 mm were recorded. Differences in magnitude and pattern of stresses were compared.Results:The tensile stresses in the posterosuperior aspect of the condylar head and on the posterior aspect of the glenoid fossa migrated posteriorly with increased bite advancements. The location of tensile stresses changed in the condylar head and fossa on mandibular protraction of 5 mm to 7 mm.Conclusion:This study indicates that larger horizontal advancements of construction bites may not be favorable for tissues of TMJ. Clinical application necessitates study on an animal model.     

The three-dimensional assessment of dynamic changes of the proximal segments after intraoral vertical ramus osteotomy

Objectives: The aim of this study was to assess the positional changes of the proximal segments after intraoral vertical ramus osteotomy (IVRO).

Method: Fifteen patients underwent IVRO and were followed according to the authors’ unique postoperative management regimen. The analyses of the positions and angles of the proximal segments were performed on frontal and lateral cephalograms, which were taken before surgery (T1) and within 3 days (T2), at 4 weeks (T3), and later than 6 months after surgery (T4). The three-dimensional positions of the condylar heads were also assessed by CT images, which were taken before and 1 year after surgery.

Results: The proximal segments temporarily swung posteriorly and laterally with a center on the condylar head as a fulcrum point at T2 and T3, compared with T1, and they repositioned at T4. The condylar heads moved inferior approximately 2 mm with lateral rotation one year after surgery, as seen in the CT.

Discussion: The condylar heads changed their positions physiologically for newly established jaw movement after IVRO with the authors’ post-operative management regimen because the post-operative skeletal stability and the jaw function were good and stable using this method.     

Delayed hypoglossal nerve palsy following unnoticed occipital condyle fracture

Occipital condylar fractures (OCFs) are rare and difficult to diagnose. The routine use of computed tomography (CT) scan in traumatology has however now made their diagnosis easier, with an estimated frequency of 4 to 19% of craniospinal traumatized patients and 0.4 to 0.7% of all severe traumatized patients in emergencies. This paper describes a patient who was not diagnosed with OCF during his first hospitalization after a road accident. However, 15 days later a left sided hypoglossal nerve palsy occurred. In this case report, we underline that an examination of the cranial nerve is a quick and easy procedure to screen each head trauma patient for occipital foramen fractures. Also, careful attention must be paid to X-Rays, CT scans and magnetic resonance imaging of the craniocervical junction.     

Transmasseteric anterior parotid approach for condylar fractures: experience of 129 cases

We have evaluated the transmasseteric anterior parotid (TMAP) approach in the treatment of 163 condylar fractures in 129 patients. Ninety-five patients presented with unilateral, and 34 with bilateral, fractures. The inclusion criteria were patient's choice for open reduction and internal fixation, displaced unilateral condylar fractures with occlusal derangement, and displaced bilateral condylar fractures with anterior open bite. Mean (SD) maximum interincisal opening after 3 months was 44(5)mm. There were no differences in lateral movements during the reviews 6 weeks and 3 months postoperatively. Protrusive movement at the end of 3 months was 7(2)mm. All patients achieved functional occlusion identical to the pretraumatic occlusion and good reduction of the condyles. No patient developed temporary or permanent facial palsy, sialocele, salivary fistula, or Frey syndrome. The mean (SD) operating time was 46(11)min. The TMAP approach avoids the complications of incision of the parotid gland, minimises the risk of facial nerve palsy, and offers excellent access to the fractured condyle.     

Evaluation of Fractured Condylar Head Along the Sagittal Plane: Report of Three Cases

There are case reports of sagittal fractures of the condylar head leading to bifid condyle. However bifid condyles maybe found in patients with no history of trauma. A split in the saggital plane of the condyle is not visible with a lateral, oblique or panaromic radiographs but only with anteriorposterior, transorbital projections or CT scan of the temperomandibular joint. The chances of condyle being split in the sagittal plane may be due to the medial pole extending beyond the condylar neck, moreover the condyle is composed of cancellous bone covered by a thin layer of cortical bone. Here we are presenting three case reports of Saggital split condyles and stress the need for inclusion of these type of fractures in the classification of condylar fractures.     

髁状突骨折与颞下颌关节强直的相关性研究

目的：阐述髁状突骨折与颞下颌关节强直发生可能的机理及临床工作中怎样预防由髁状突骨折造成颞下颌关节强直的发生。方法：收集近两年来就诊于我院口腔科的颞颌关节强直患者80例进行临床回顾性研究。研究其主要的疾病类型以及病因分类。结果：对80例患者的疾病类型研究发现颞下颌关节强直以髁突颈部残端与关节窝骨性融合的可能性最大占73．75％,病因研究比较发现外伤是造成颞下颌关节强直的主要病因占71．25％。组间的数据比较具有明显的差异（P＜0．05）,具有统计学意义。结论：髁状突骨折是导致颞下颌关节强直的主要因素。     

髁突囊内骨折开放手术的临床疗效

目的探讨髁突囊内骨折开放手术治疗的临床疗效。方法选择2015年1月至2018年7月安徽医科大学第一附属医院收治的27例35侧髁突囊内骨折的患者,所有患者均行开放手术,术后3个月行临床疗效及影像学评估。结果 35侧髁突囊内骨折中,26侧行骨折内固定治疗,9侧行骨折碎块摘除术。3个月后,患者临床治愈率达81. 48%,髁突骨折侧的影像学治愈率达88. 57%。结论髁突囊内骨折的开放手术有较好的临床疗效和应用价值。     

下颌骨髁突骨软骨瘤的影像学诊断及疗效评价

目的：探讨下颌骨髁突骨软骨瘤的诊治经验,恢复髁突正常的解剖形态和生理功能。方法：对1998—2008年收治的14例下颌骨髁突骨软骨瘤患者的诊治进行评价,指标包括影像学检查确诊率（X线、3D-CT及MRI）、开口度、咬合关系及术区感觉。根据检查指标进行临床诊断及手术效果评价。结果：X线、3D-CT和MRI的确诊率分别为57.1%、66.7%和87.5%。3D-CT和MRI检查能更清晰地反映肿物情况,为手术提供良好的指导。14例患者均行手术治疗,术后效果良好。结论：MRI和3D-CT检查是诊断下颌骨髁突骨软骨瘤的最佳方法,能较好地观察肿物的范围及位置关系,为手术提供良好的依据,而X线检查在下颌骨髁突骨软骨瘤的诊断中具有重要价值。     

不对称性颌间牵引对成年SD大鼠颞下颌关节软骨下骨组织形态的影响

目的 通过观察不对称牵引引起的成年SD大鼠髁突软骨下骨组织形态学变化,了解关节外不对称机械应力对髁突软骨下骨的影响.方法 选用10周龄雄性SD大鼠220只（随机分为轻力组104只、重力组104只、对照组12只）,实验组动物使用关节外固定加力装置,分别施加0.39、1.18 N,加力28 d拆除加力装置.在3、7、14、28、31、35、42、56 d取得标本,对髁突软骨的形态、骨小梁密度进行观察分析并进行统计学处理.结果 正常髁突软骨下骨骨小梁连续,与髁突表面垂直以顺应髁突的力学环境,在负荷加载后出现骨小梁形态和排列变化,密度发生相应波动.结论 髁突软骨下骨在外力刺激下,出现排列和骨小梁密度的变化以适应变化的机械应力环境.     

自体喙突移植重建下颌髁突的实验研究

目的:研究运用自体喙突移植重建髁突的可行性及其整复效果。方法:选取12只成年雄性山羊,手术截除右侧髁突与关节盘,取同侧喙突以L型钛板固定在下颌升支。分别在术后第4、12、24周各处死4只动物。通过大体观察、三维CT分析和组织学检查等方法评价自体喙突移植后的形态学和组织学变化。结果:所有动物术后咬合基本正常。术后4周可见喙突再生,术后24周时自体喙突形态基本接近正常髁突。新生髁突表面有较厚的致密纤维结缔组织覆盖,其下方的组织结构类似正常髁突表面的关节软骨。结论:自体喙突移植可以重建一个形态和功能都基本接近正常的髁突,因此这种技术可以作为一种整复TMJ缺损的新方法。