Variation in accessory mental foramen frequency and number in extant hominoids

Nerves providing sensation to the lower face and jaw exit the mandibular canal via the mental foramen. In humans, there are many documented occurrences of additional foramina (accessory mental foramina, AMFs) on the lateral mandibular surface that may also contain nervous structures. There are large discrepancies in the literature regarding how often AMFs occur in humans, and investigations of non-human hominoid AMFs are rare. Consequently, the causes of interspecific diversity in this variable have not been explored. This project seeks to compare the frequency and number of AMFs between males and females, and among human regional groups and hominoid subspecies and species, and to investigate possible causal factors for any differences identified. No significant differences were found between males and females in any group. Gorillas and orangutans had the highest percentages of individuals with AMFs and the highest mean number of foramina, while modern humans and siamangs had the lowest figures for these variables. Significant differences (p < .05) were found for the mean number of foramina between most pairs of species. The results also showed that species with mandibles that are larger overall, have a larger area anterior to mental foramen, and a longer mandibular canal typically present more AMFs. The strongest correlation was found between the mean number of mental foramina and mandibular canal length. We suggest that these results provide preliminary support for the hypothesis that increasing mandibular canal length increases the likelihood that that nerves will ramify, leading to greater frequencies of accessory mental foramina.     

Clinical and radiological outcomes after treatment of sagittal fracture of mandibular condyle (SFMC) by using occlusal splint in children

This study was designed to investigate the effects of occlusal splints in the treatment of sagittal fractures of the mandibular condyle in children. From January 1995 to December 2011, 37 sagittal fractures of the mandibular condyle in 30 patients aged 4–8 years old were included in this study. All the patients were treated with 1–2 mm occlusal splints in the molar region. The mouths of the patients were kept slightly open by the occlusal splints for 3–6 months, and we reviewed the clinical and radiological remodelling of the affected condyles after treatment. Excellent (n = 20) and good (n = 10) clinical outcomes were achieved with full radiological remodelling seen in 19 and partial remodelling in 11. Treatment with occlusal splints is effective in delivering good results and function with minimal morbidity in children with sagittal fractures of the condyle, while permitting ongoing remodelling and growth in the short term.     

Biomechanical evaluation of a new design titanium miniplate for the treatment of mandibular angle fractures

The optimal management of mandibular angle fractures remains controversial. The aim of this experimental study was to test the stability and resistance to mechanical force of a new titanium miniplate design. Thirty fresh sheep hemimandibles, sectioned at the angle region, were used to evaluate two plating techniques. One group received fixation via a new design single non-compression titanium miniplate and the second group via a six-hole straight non-compression titanium miniplate. A custom-made biomechanical test model was used for the samples. Each hemimandible was subjected to compressive and tensile forces using an Instron machine. The biomechanical forces (N) that caused 4-mm displacement or fixation loosening were compared. Comparison between the groups showed that fixation with the new design miniplate had more resistance to lateral compression forces than with a six-hole straight miniplate (P < 0.009). Moreover, the new design miniplate fixation displayed more resistance to vertical compression and tensile forces (P > 0.46 and P > 0.61, respectively). The study demonstrated that mandibular fracture fixation with the new design non-compression titanium miniplate offered greater resistance to lateral displacement forces and may also provide increased resistance to vertical compressive and tensile forces than a conventional six-hole straight miniplate.     

Mandibular reconstruction in the growing patient with unilateral craniofacial microsomia: a systematic review

The purpose of this systematic review is to provide an overview of the surgical correction of the mandible in unilateral craniofacial microsomia (UCM) performed in the growing patient, and its long-term outcome and stability. The following databases were searched: PubMed, Embase, Cochrane, and Web of Science. Articles reporting prospective and retrospective studies of patients not older than 16 years (N ≥ 4) who had undergone surgical correction of a craniofacial microsomia spectrum condition using grafts, osteotomies, distraction, or combinations of these, were reviewed. The period of follow-up was selected to be ≥1 year. After inclusion, the articles were evaluated on short- and long-term outcomes, relapse, and any increase in asymmetry following treatment. Thirty of 1611 articles were included in the qualitative synthesis. Analysis of the surgical mandibular correction of UCM showed that the outcome is not so much treatment-dependent, but patient-dependent, i.e. deformity gradation-dependent. The type I–IIa Pruzansky–Kaban patient had the best results with regard to minimal relapse and/or minimal increase in asymmetry. Single-stage correction of the asymmetry should be postponed until the permanent dentition stage. It can be concluded that in the treatment of the severely hypoplastic mandible, the patient will benefit from a multi-stage treatment protocol if indicated for functional or psychological problems.     

Single stage surgery for contouring the prominent mandibular angle with a broad chin deformity: En-bloc Mandibular Angle-Body-Chin Curved Ostectomy (MABCCO) and Outer Cortex Grinding (OCG)

BackgroundVarious surgical options are reported to address the Asian 'squared face', characterized by a prominent mandibular angle (PMA) associated with an oversized chin deformity; but shortcomings lie in the requirement of multi-stage procedures with the risk of further revision surgery. We have developed a single-stage “Mandibular Angle-Body-Chin Curved Ostectomy (MABCCO) and Outer Cortex Grinding (OCG)” surgical technique to shorten the period of the surgical treatment and minimize the inherent surgical risks in the multi-staged procedures.MethodsA retrospective study involving patients (n = 36) presented with prominent mandibular angle and an oversized chin who underwent the operation described from 2010 to 2012 with at least 12 months of follow-up. The surgical and aesthetic outcomes were evaluated through clinical assessment, photography, imaging analysis including preoperative and post-operative patient satisfaction rates.ResultsAll the patients were satisfied with the improvement in their appearance following surgery; specifically the 'smoothness' of the mandibular inferior border with no 'second mandibular angle'. The width of the mandible was reduced with G–G distance reduced from 119.9 mm ± 3.9–109.7 mm ± 3.5 (p < 0.05). A significant preoperative and post-operative gonial angle (G-A) was found at the left (110.7° ± 9.6 vs 139.9° ± 11.5, p < 0.05) and right side of mandible (111.3° ± 10.7 vs 140.7° ± 11.8, p < 0.05). There was no iatrogenic inferior alveolar nerve or mental nerve injury and a stable aesthetic outcome beyond the first year.ConclusionWe demonstrated favourable surgical and aesthetic outcomes with our single-stage en-bloc curved osteotomy surgical technique to reshape the prominent mandibular angle with a broad chin deformity with no increased in surgical risks but a high satisfaction rate and stable outcomes.     

口腔颌面部锥形束CT结合微创拔牙技术在下颌阻生第三磨牙拔除中的临床应用

目的研究口腔颌面部锥形束CT(CBCT)检查结合牙体分割微创拔牙技术在下颌阻生第三磨牙(IMTM)拔除中的临床应用。方法选取2018年1月至2019年5月四川省攀枝花市中心医院诊断为IMTM的97例(155颗)拔牙患者为研究对象。术前CBCT明确IMTM与周围重要组织的关系,术中采用转角高速涡轮机夹持长臂裂钻分割牙体,以微创的方式分块拔除IMTM。记录拔牙时间、患者满意度、术中及术后并发症等指标。采用t检验比较男、女间拔牙时间的差异,采用方差分析比较不同阻生牙类型及不同年龄段组间拔牙时间的差异。结果CBCT结果显示67.7%(105/155)的下颌管位于IMTM根尖的颊侧、22.6%根尖下方、9.7%舌侧,其中24.5%<1 mm;24颗(15.5%,24/155)IMTM根尖区舌侧骨板缺如,56颗牙(36.1%,56/155)<1 mm。IMTM以近中、垂直及水平向阻生最为常见,平均拔牙时间分别是(24.3±1.1)min,(15.6±1.2)min,(29.7±1.8)min,差异有统计学意义(F=23.85,P<0.001);术中8颗牙(5.2%,8/155)下颌管暴露,无1例舌侧骨板损伤致牙根移位。术后3例少量出血,1例发生干槽症,无1例发生下唇麻木,患者满意度在95.5%以上。结论CBCT应作为IMTM拔除前常规的影像学检查手段。高速涡轮机牙体分割微创拔牙技术适用于各类IMTM拔除,具有创伤小、临床效率高、并发症少、患者满意度高等优点。     

成人骨性Ⅲ类错牙合患者正畸去代偿前后下切牙区牙槽骨形态特征的CBCT研究

目的比较正畸去代偿前后严重的成人骨性Ⅲ类错牙合患者下切牙区牙槽骨形态变化情况。方法对15例接受正畸-正颌联合治疗的严重成人骨性Ⅲ类错牙合患者(男9例,女6例,平均年龄23.6岁),分别在治疗前(T0期)和正颌手术前1个月(T1期)进行CBCT摄片。分别测量正畸前及术前正畸结束时下切牙区牙槽骨形态,包括牙槽骨厚度、牙槽骨附着高度、牙根长度等指标。相关数据采用SPSS15.0统计软件进行配对t检验。结果正畸去代偿前后的比较结果显示:1正畸去代偿以后下切牙唇倾度增大,根尖点距舌侧骨皮质距离变小(P<0.01);2牙槽骨厚度未见明显改变;3唇舌侧牙槽骨附着高度矫治后均有降低,尤其是舌侧牙槽骨附着高度降低显著(P<0.01);4牙根长度测量未见明显改变。当下切牙进行较大范围的唇向倾斜运动时,牙根向舌侧骨皮质靠近,牙槽骨附着高度进一步降低。结论在成人骨性Ⅲ类错牙合的矫治中,由于需要在不良的牙槽骨形态中移动下切牙,必须密切关注其牙周组织状况、牙槽骨形态变化以及牙根与牙槽骨的关系,选择恰当的矫治方案,减少下切牙过度地唇舌向移动,避免不良反应的发生。