青春期大鼠下颌功能性前伸后翼外肌的超微结构改变

目的观察青春期大鼠下颌功能性前伸后翼外肌的超微结构变化。方法青春期雄性Sprague-Dawley大鼠40只,随机分为4个实验组和4个对照组,每组5只。实验组配戴固定的前伸下颌矫治器。对照组不配戴矫治器。分别于下颌前伸3 d、7 d、14 d、28 d处死实验组和对照组大鼠。取大鼠左右侧翼外肌,制作电镜标本,透射电镜下观察翼外肌的超微结构变化。结果下颌前伸3天时,实验组大鼠翼外肌肌细胞内部分肌丝溶解;下颌前伸7 d和14 d时,肌丝方向紊乱,肌小节宽度不规则。下颌前伸3 d、7 d和14 d时,翼外肌肌细胞内肌丝间及肌膜下线粒体增多、形态改变。下颌前伸7 d和28 d时,翼外肌肌细胞内肌浆网多见。下颌前伸28 d时,翼外肌肌细胞内肌丝方向基本一致。结论青春期大鼠下颌功能性前伸后翼外肌的超微结构发生改建。     

Movement of the mandibular condyle and activity of the masseter and lateral pterygoid muscles during masticatory-like jaw movements induced by electrical stimulation of the cortical masticatory area of rabbits

We examined the functional role of the lateral pterygoid muscle (LP) and the masseter muscle (MS) in the movement of the mandibular condyle in masticatory-like jaw movements induced by electrical stimulation of the cortical masticatory area of urethane-anaesthetised rabbits. EMGs of the LP and MS were recorded along with video images of the mandibular condyle movement filmed with a high-speed CCD camera at a time resolution of 8 ms. The time required for the contractile force of the MS and LP to emerge as bite force or jaw movement was determined by direct electrical stimulation to respective muscles: 32.8+/-1.5 ms for the MS and 34.3+/-2.9 ms for the LP. The LP on the working side showed biphasic activity not only in the jaw-opening phase but also in the middle occlusal phase. It is assumed that the MS on the working side begins to exert actually the maximum mechanical influence on the bite force 32.8 ms after its EMG peak in the early occlusal phase. Such development of the mechanical effect of the MS during middle occlusal phase is appeared to be involved in stabilization of the condyle in the middle occlusal phase. Approximately 25 ms (25.1+/-2.5 ms) after the peak of mechanical influence of the MS, the mechanical influence of the working-side LP activity reached maximum in the late stage of the occlusal phase. This LP mechanical influence seems to be functionally associated with an antero-inferior movement of the working side condyle in the late stage of the occlusal phase that is coincident with a movement of the incisal point towards the balancing side across the midline.     

Trueness and precision of digital impressions obtained using an intraoral scanner with different head size in the partially edentulous mandible

Purpose

It remains unclear whether digital impressions obtained using an intraoral scanner are sufficiently accurate for use in fabrication of removable partial dentures. We therefore compared the trueness and precision between conventional and digital impressions in the partially edentulous mandible.

应用穿颊器口内入路微创治疗下颌骨角和升支骨折

目的:观察口内和穿颊的手术入路处理下颌骨角部和升支骨折,并用小钛板坚强内固定的疗效。方法:对2004-01~2005-07间18例连续的下颌骨角部和升支骨折患者,用穿颊器经过颊部小切口联合口内切口复位内固定。随机选取同时期的另外20例同类型骨折患者,仍按照传统口外入路行手术切开复位内固定,2组间进行对比。结果:用口内和穿颊入路患者中有1例内固定术后骨折处仍有小幅动度,还需辅以颌间固定;口外入路行内固定手术的患者中有2例需行术后颌间固定。没有术后感染发生,没有出现需要行切开引流或需取出固定物的病例。结论:通过口内和穿颊入路行坚强内固定适用于不伴有严重错位或粉碎性骨折的下颌骨角部和升支部骨折的病例。     

Evaluation of mandibular volume using cone-beam computed tomography and correlation with cephalometric values

Objective:To investigate the association between maxillofacial morphology and mandibular bone volume in patients with skeletal malocclusion.Materials and Methods:Subjects were 118 adult Japanese (58 males and 60 females). Skeletal malocclusion was classified, based on cephalometric analysis, into skeletal Classes I (−1° ≤ ANB < 4°), II (ANB ≥ 4°), and III (ANB < −1°). Using cone-beam computed tomography and three-dimensional image analysis software, the dental crowns and mandible were separated, with only the mandible extracted. This was then reconstructed as a three-dimensional model, from which the mandibular volume was measured.Results:No significant difference in mandibular volume was noted among skeletal Classes I, II, and III, nor was there any significant correlation between mandibular volume and the ANB, SNB, or mandibular plane angles. There was occasional and limited correlation between mandible volume and gonial angle and certain cephalometric distance parameters.Conclusion:We conclude that proper understanding of the three-dimensional maxillofacial morphology requires not only cephalometric radiographic tracings but also high-resolution analysis of the mandibular area, width, and volume.     

Fully digital fabrication of an occlusal device using an intraoral scanner and 3D printing: A dental technique

This dental technique describes a fully digital method for fabricating occlusal devices using a complete-arch intraoral scan and 3D printing. The maxillary and mandibular arches of a healthy, fully dentate volunteer were digitized using an intraoral scanner. A second scan and modified recording of the centric relation enabled a virtual arrangement of the maxillary and mandibular arches, both in centric relation and in the desired vertical dimension of occlusion. An occlusal device was subsequently designed virtually and fabricated from a light-polymerizing acrylic resin using a 3D printer. The occlusal device was tested for fit, occlusion, and patient-friendly handling. As only minor occlusal corrections were required, the fully digital procedure described is suitable for the fabrication of occlusal devices.     

The role of the inferior head of the human lateral pterygoid muscle in the generation and control of horizontal mandibular force

The aim was to test the hypothesis that the inferior head (IH) of the human lateral pterygoid muscle (LP) is involved in the generation and fine control of horizontal isometric mandibular force. Although previous studies provided some evidence for this, they had limitations that necessitate a re-examination. In eight participants, electromyographic (EMG) activity was recorded from the IHLP unilaterally, as well as bilateral surface recordings from the masseter (M) and anterior temporalis (AT), and the submandibular group of muscles (SUBM), during the generation of horizontal isometric mandibular force in a direction contralateral to the side of the IHLP recording. Isometric force at 5–8 mm open from the intercuspal position was exerted on a transducer (attached by a bar to the upper teeth) by a rod attached to the lower teeth. Participants tracked a target on a video screen that required 5-s holding periods at each 100 gwt (0.98 N) between 400 gwt (3.92 N) and 800 gwt (7.84 N). The mean of multi-unit EMG activity from all muscles during the most stable 2-s force-holding periods increased significantly with each force increment (GLM repeated measures: P<0.0001). When normalized, the multi-unit data from the IHLP exhibited the steepest rate of increase. The mean firing rates of 21 IHLP single motor units (SMUs) significantly increased with force (GLM repeated measures: P<0.0001). Two SMUs fired in advance of force onset, which suggests a role in force initiation. There were close associations between fluctuations in force and in IHLP SMU firing rates and multi-unit activity, but a similar correspondence was not as clear for the other recorded jaw muscles. These findings suggest that the IHLP is important in the generation and fine control of contralaterally directed, horizontal jaw forces.     

Use of an occlusal splint and intraoperative imaging with an intraoral approach in the management of mandibular subcondylar fractures

IntroductionTo evaluate the feasibility of safely managing subcondylar fractures using an original surgical procedure combining an intraoral approach, the use of a custom-made occlusal overlay splint, and intraoperative imaging.Materials and methodsCondylar fragment was freed from surrounding soft tissues, was laterally exposed to the ramus, and a miniplate was fixed in place for osteosynthesis. An overlay splint maintaining the dental occlusion was used to facilitate reduction and stabilization during fixation. Intraoperative monitoring by cone-beam computed tomography (CBCT) was performed before completing the fixation.ResultsBetween November 2018 and June 2019, 10 patients were treated using this procedure. The median length of the proximal condylar fragment was 29 mm (range 24–39 min). Five patients had an associated mandibular fracture. The median duration of the condylar fracture surgery was 54.5 min (range 38–79 min). All patients had satisfactory reduction and osteosynthesis with no complications.ConclusionIt is feasible to safely manage subcondylar fractures with this surgical procedure that could facilitate open reduction using intraoral approaches. Occlusal splints maintain downward pressure on the rami bilaterally and symmetrically, helping to anatomically reposition condylar process fractures. Intraoperative imaging is used to monitor this step.     

兔下颌角骨外板磨除术后咬肌不同处理方式与骨的适应性研究

目的:通过对兔下颌角骨外板磨除术后咬肌不同处理方式与骨的适应性相关指标的测定,比较咬肌不同处理方式与下颌骨变化的差异,为下颌角肥大手术方式的选择提供依据.方法:雌性家兔50只,3个月龄,分为2组,每组25只.左侧为手术侧,第1组行下颌角骨外板磨除术后将咬肌与翼内肌缝合,第2组行下颌角骨外板磨除术后咬肌不做缝合固定.每组在术后第1、2、4、8、12周时分别处死5只动物,手术侧咬肌称重,切取手术侧部分骨组织连同其上部分咬肌作病理切片,行HE染色,光镜下观察细胞形态,在200倍镜下用HJ-YG病理诊断分析系统测量肌小节长度和肌细胞面积,用游标卡尺测量下颌骨的厚度.采用SPSS 13.0软件包对数据进行统计学分析.结果:术后第4、8、12周,第2组咬肌重量减轻,与第1组相比有显著性差异(P＜0.05).术后4、8、12周,第2组下颌骨厚度未增加,第1组下颌骨厚度增加,有显著性差异(P＜.05).术后1、2、4周,第2组肌小节长度较第1组短,有显著性差异(P＜0.05).术后8、12周,第2组肌细胞面积较第1组小,有显著性差异(P＜0.05).结论:兔下颌角骨外板磨除术后肌小节长度、咬肌细胞面积、骨细胞等发生了适应性改建,尤其是游离咬肌后咬肌失去张力,其附着点上移,致使其发生明显萎缩.下颌骨愈合后厚度不增加.     

经口内入路切除下颌骨良性肿瘤及同期血管化腓骨肌瓣精确重建下颌骨

目的： 首次介绍口内入路行下颌骨良性肿瘤切除和显微血管吻合的腓骨肌瓣即刻精确重建的经验。方法： 2018年1月—3月,对我科收治的4例下颌骨良性肿瘤患者行经口内入路的下颌骨节断性切除及显微血管吻合的腓骨肌瓣即刻重建术。3例术前行虚拟手术计划设计,并行钛板数字化压模成型。术中先在口内颊部显露面动、静脉并保护,按截骨导板完成下颌骨节断性切除和腓骨瓣塑形、钛板固定后,用导航验证重建下颌骨的位置。显微镜下将腓动脉与面动脉作端-端吻合,腓静脉与面静脉用微血管吻合器Coupler吻合。术后常规采用手提超声多普勒监测血管血流信号;术后1周复查全景片,检查重建下颌骨的位置。结果： 4例患者均顺利完成经口内入路的下颌骨节断性切除、腓骨重建,其中3例顺利完成口内显微血管吻合,1例因术区瘢痕、面静脉不理想而引至下颌下吻合。术后超声多普勒监测显示血流信号正常,口内及供区伤口均一期愈合。术中导航及术后全景片显示重建的下颌骨位置理想,咬合关系正常,面部外形对称,无面瘫及开口受限。结论： 经口内入路行下颌骨良性肿瘤的节断性切除及腓骨肌瓣精确重建和口内显微血管吻合是完全可行的,能够达到口外入路同样的效果,同时口外无瘢痕。     

双种植体-杆卡固位覆盖义齿修复下颌无牙颌的临床应用

颏孔间双种植体固位的杆卡固定覆盖义齿能够为无牙颌患者提供良好的固位与稳定,临床工作中应根据患者的客观条件合理应用。本文依据杆卡附着体特点及修复空间的要求,探讨并归纳颏孔间双种植体-杆卡固定覆盖义齿修复的诊疗步骤,并附以病例说明。     

Evaluation of mandibular transverse widths in patients affected by unilateral and bilateral cleft lip and palate using cone beam computed tomography

Objective:To evaluate the mandibular dental, alveolar, and skeletal transversal widths in patients affected by unilateral (UCLP) and bilateral (BCLP) cleft lip and palate and to compare the findings with a well-matched normal occlusion sample using cone beam computed tomography images.Materials and Methods:The study sample consisted of 75 patients divided into three groups: the UCLP (29 patients; mean age: 15.40 ± 3.22 years), BCLP (18 patients; mean age: 15.54 ± 3.72 years), and normal occlusion (28 patients; mean age: 15.82 ± 2.11 years) groups. Mandibular dental (intercanine and -molar), alveolar (intercanine and -molar), and skeletal (bigonial width) transversal measurements were performed three-dimensionally and analyzed using the one-way variance analysis and post hoc Tukey tests.Results:Patients affected by UCLP and BCLP had statistically significantly lower intercanine alveolar widths (P < .05 and P < .001, respectively) and larger intermolar (P < .001 and P < .05, respectively) and intermolar alveolar widths (P < .001) compared with the normal occlusion group. Furthermore, the patients affected by UCLP and BCLP had similar mandibular dental, alveolar, and skeletal transversal widths (P > .05).Conclusion:The UCLP and BCLP groups showed statistically significantly smaller values for intercanine alveolar widths and larger values for intermolar dental and alveolar widths compared with the normal occlusion group. This shows the importance of using individualized archwires according to the pretreatment arch widths of the patients affected by UCLP and/or BCLP.