Postoperative mandibular stability after orthognathic surgery in patients with mandibular protrusion and mandibular deviation

Skeletal stability and temporomandibular joint (TMJ) signs and symptoms were analyzed in 23 patients in whom mandibular protrusion and mandibular deviation had been corrected using bilateral sagittal split ramus osteotomy (BSSRO group, n = 10) and unilateral SSRO and intraoral vertical ramus osteotomy (USSRO+IVRO group, n = 13). Miniplate fixation was used in SSRO but no fixation was used in IVRO. The ratio of condylar bony change was 30.4% (7/23) and all condylar bony changes were seen on the deviated side. All preoperative signs and symptoms of TMJ disorders (4/13 patients in the USSRO+IVRO group and 2/10 patients in the BSSRO group) disappeared after surgery. Comparing the USSRO+IVRO group and the BSSRO group, in patients without condylar bony change, the mandible in both groups was stable anteriorly and horizontally after surgery, even though there was a larger horizontal mandibular movement in the USSRO+IVRO group during surgery. Comparing patients with condylar bony change versus no condylar bony change in the USSRO+IVRO group, postoperative horizontal mandibular displacement was significantly larger in the condylar bony change group than in the no condylar bony change group. These results support the idea that USSRO+IVRO can be useful in correcting mandibular deviation as well as improving signs and symptoms of TMJ disorders. However, it also seems important to be aware of the possibility of horizontal mandibular relapse in patients with condylar bony change.     

Osteoma in mandibular condyle

A case of peripheral osteoma occurring in the mandibular ramus in a 26-year-old man is reported. Radiographic examination revealed a pedunculated, protruding globular, bone-like opaque mass around the notch of the right mandibular ramus. Histopathological examination showed a lamellar bone structure with irregular arrangement. Wide trabeculae, narrow interstitial areas, and many fibrovascular channels were detected by scanning electron microscopy. Thus, characteristic findings of a compact osteoma were obtained clinically and histopathologically.     

Bone availability for mandibular molar distalization in adults with mandibular prognathism

Objectives:To investigate the retromolar space available for molar distalization in patients with mandibular prognathism.Materials and Methods:Using cone-beam computed tomography, the posterior mandibular dimensions in 110 consecutive patients with Class I or Class III malocclusion were measured (mean age, 27.0 ± 7.1 years). The shortest linear distances from the distal root of the right mandibular second molar to the inner border of the mandibular cortex were measured at the level of root furcation and 2, 4, and 6 mm apical to the furcation along the sagittal line and the posterior line of occlusion. The retromolar distances were compared between the Class I and Class III malocclusion groups using general linear mixed models.Results:The retromolar space measured through the sagittal line showed no significant intergroup difference. Among the distances measured through the posterior line of occlusion, the space measured at depths 0 and 2 mm to the furcation were significantly greater in the Class III group than in the Class I group.Conclusions:Patients with Class III malocclusion have greater retromolar space for mandibular molar distalization along the posterior line of occlusion only at the level of the second molar furcation.     

Congenitally missing mandibular incisors and mandibular symphysis morphology

OBJECTIVE: To explore the association between congenital absence of permanent mandibular incisors and craniofacial and mandibular symphysis morphology in Japanese orthodontic patients. MATERIALS AND METHODS: A total of 27 girls with one or two congenitally absent mandibular incisors (group M) were selected and divided into group 1M (16 girls with the absence of one incisor) and group 2M (11 girls with the absence of two incisors). In addition, 20 other Japanese girls without hypodontia and with little or no mandibular incisor crowding were enrolled as a control (group C). Using the lateral cephalogram of each subject, 17 angular, 8 linear, and 3 area measurements were made for evaluation of craniofacial and mandibular symphysis morphology. The cephalometric data thus obtained were statistically analyzed and compared between the groups. RESULTS: A significantly greater retroclination of the retained mandibular incisors was found in group 1M than in group C. Groups 1M and M showed a significantly greater retroclination of mandibular alveolar bone than group C. Groups 2M and M exhibited a significantly smaller mandibular symphysis area than group C. CONCLUSION: The retroclination of the mandibular incisors and alveolar bone and the reduced mandibular alveolar bone area should be taken into consideration in planning orthodontic treatment on patients with congenitally missing permanent mandibular incisors.     

Analysis of head and mandibular tapping movements in patients with mandibular protrusion

The present study was conducted to investigate whether there was a functional coupling between the head and mandibular movements in ten patients with mandibular protrusion (MP) and ten control subjects with normal occlusion (Normal), using a six degrees-of-freedom measuring device. Single-peak waveforms were predominantly seen in both MP (98.2%) and Normal (99.3%). However, vertical displacements of the upper and lower incisor points (VD(UIP) and VD(LIP)) were all significantly larger in MP than those in Normal. The ratio VD(UIP)/VD(LIP) also increased more sharply with an increase in VD(LIP) in MP, compared to that in Normal. Mandibular rotation in MP was also significantly larger than that in Normal. The results showed that, in MP, the head moves more vertically in rhythmical coordination with mandibular movement during tapping. Finally, it may be that this larger vertical head movement is related to the greater condylar rotation in MP subjects.     

Use of Stafne's mandibular defect in improving retention of mandibular complete dentures

In 1942, Stafne was the first to report radiographic findings of "static bone cavities" situated near the angle of the mandible. The typical radiographic appearance of Stafne's mandibular defect is a radiolucency below the inferior alveolar canal, between the mandibular premolars and the angle of the mandible. Stafne's mandibular defect ranges from 10 mm to 30 mm in diameter. The size has been shown to be remarkably constant in diagnosed lesions followed over time. In the majority of cases, the lesion is symptomless. Routine surgical exploration is not indicated. It is suggested that the lesion is a radiographic rather than a pathological entity; therefore, consideration was given to making use of these anatomical retentive areas in a prosthetic manner. In this article, a literature review of Stafne's mandibular defect is presented and attempts to improve the retention and stability of the lower complete dentures by using this anatomical entity are described.     

Impact of impacted mandibular third molars in mandibular angle and condylar fractures

Previous retrospective analyses prove that impacted mandibular third molars (M3s) increase the risk of angle fractures and decrease the risk of concomitant fractures to the condyle. The authors have attempted to verify these relationships and identify the underlying mechanism of injury. A retrospective cohort was designed for patients attending the Division of Oral and Maxillofacial Surgery from January 2001 till October 2008. The primary predictor variable was M3. The secondary predictor variables were: M3 position, classified using the Pell and Gregory system; angulation, classified using Shiller's method; and the number of visible dental roots. The outcome variables were angle and condyle fractures. Hospital charts and radiographs were used to determine and classify these variables. The study sample comprised 1102 mandibular fractures in 600 patients. For patients injured by moderate traumatic force resulting in two fractures of the mandible, the presence/absence of impacted M3s played an important role in angle/condylar fractures. Patients with impacted M3s were three times more likely to develop angle fractures and less likely to develop condylar fractures than those without impacted M3s. This study provides clinical evidence to suggest that the removal of unerupted mandibular third molars predisposes the mandible to condyle fractures.     

儿童骨性下颌偏斜患者的牙弓形态及颌骨对称性分析

目的：研究骨性下颌偏斜儿童的牙弓形态,并对颌骨对称性进行分析。方法：选择13例骨性下颌偏斜患者作为研究对象,在模型上以腭中缝为参考标准,测量两侧的牙弓宽度,分析其对称性;在X线片上测量两侧下颌升支高度、下颌体长度及下颌骨综合长度,并进行统计分析。结果：骨性下颌偏斜患者的牙弓形态存在明显的不对称,偏斜侧的牙弓宽度明显大于对侧（P〈0.05）;偏斜侧下颌升支高度和下颌体综合长度明显小于对侧（P〈0.05）,而两侧下颌体长度无明显差异（P〉0.05）。结论：骨性下颌偏斜患者的下颌骨存在明显不对称,牙齿也出现了不同程度的代偿,在临床正畸治疗中,应进行综合分析。     

Spontaneous mandibular regeneration: another option for mandibular reconstruction in children?

Treatment for conditions of the mandible may require resection of the affected segment, and this may need reconstruction. There are case reports of spontaneous regeneration of segments of excised mandibles that resulted in reduced or no need for reconstruction, and we present four such cases. The age at presentation ranged from 6 to 12 years. In all cases the periosteum was preserved during resection. All patients showed evidence of spontaneous regeneration, both clinically and radiographically, between 3 and 5 months after resection. The planned delayed reconstruction meant that these patients either did not need any bony reconstruction, or needed less than had originally been anticipated. Such regeneration is mostly reported in children, and is thought to be the result of an intact periosteal layer. In patients having planned mandibular resections, where the periosteum is preserved, some spontaneous regeneration should be anticipated and final reconstruction delayed until this is complete.     

细长型髁突增生病下颌骨及下颌神经管位置CT形态学研究

目的应用CT进行细长型髁突增生病（HE）下颌骨解剖学及下颌神经管形态学研究,为临床治疗提供参考。方法对19例HE患者进行多层CT扫描,采用Mimics 10.0软件进行三维重建,在不同断面重建图像,进行下颌神经管、下颌孔和骨皮质测量,并与无下颌骨病变的对照组进行比较。结果在第一磨牙中心长轴断面的舌侧、第二磨牙中心长轴的颊侧及上缘、磨牙后区中心至下颌角连线断面的颊侧、上缘及下缘、下颌孔下缘下5 mm处水平位断面的舌侧、前缘及后缘,2组下颌神经管外缘距下颌骨表面距离的差异具有统计学意义（P<0.05）;在第一磨牙颊侧和下缘,2组下颌骨骨皮质厚度的差异具有统计学意义（P<0.05）;2组下颌孔至下颌升支前缘及下颌骨下缘距离的差异具有统计学意义（P<0.05）。结论细长型髁突增生病骨皮质厚度从下颌第一磨牙到下颌升支在各个方向均逐渐减小。与正常颌骨相比,下颌神经管在下颌第二磨牙及磨牙后区偏颊侧并靠上方,下颌孔在升支内侧较靠前并偏低。     

下颌切牙及下颌第一前磨牙根管形态的体外研究

目的:采用透明标本法观察下颌切牙、下颌第一前磨牙根管系统的类型和特点.方法:选取根尖发育完全,牙根完整,未进行过牙髓治疗的离体下颌切牙120个、下颌第一前磨牙156个,开髓、去髓,注入墨水,制成透明标本.观察根管数目,按Vertucci分类法对根管系统进行分类,测量多根管牙根管分叉处至釉牙骨质界的距离.结果:下颌切牙、下颌第一前磨牙多根管的发生率分别为28.2%、30.9%,多根管以1-2型为主,多数在根管中段出现分叉.结论:下颌切牙、下颌第一前磨牙根管系统复杂,了解其形态特征有利于避免遗漏根管.     

Evaluation of mandibular infiltration versus mandibular block anaesthesia in treating primary canines in children

Objective.  The objectives of this study were to determine the effectiveness of mandibular infiltration compared with mandibular block in treating primary canines in children and to relate the effectiveness to the type of treatment performed.
Methods.  A total of 89 children, 6–9 years old, requiring identical treatment on contralateral mandibular canines were selected. The split mouth study design was used. The anaesthetic used in both techniques was 2% lidocaine solution with 1 : 80,000 epinephrine. Dental procedures included class III, IV, and V restorations, formocresol pulpotomies, and extractions. Child's pain reaction and behaviour for each anaesthesia technique and the type of treatment were rated at certain intervals of treatment using sounds, motor, and ocular changes indicating pain and the Frankl Behaviour Rating Scale. Evaluations were made upon injection, probing, rubber dam placement, and during tooth preparation and extraction.
Results.  No statistically significant difference was found between the two anaesthetic techniques for either pain or behaviour at all evaluation intervals ( P  > 0.05), during the performance of restorations, pulpotomies, or during extractions.
Conclusions.  Mandibular infiltration anaesthesia is as effective as mandibular block for restoration, pulpotomy, and extraction in primary canines. The mandibular infiltration anaesthesia was not significantly less painful than the mandibular block.     

Intraoral multistage mandibular angle ostectomy: 10 years' experience in mandibular contouring in Asians

In Asia, a round face rather is more acceptable than a square face. Intraoral mandibular angle ostectomy is a common aesthetic procedure for correcting a prominent mandibular angle. However, an operation of sheer straight-lined prominent mandibular angle resection would sometimes create extramandibular angles or palpable bone steps in the margin of mandibular body and produce unnatural lower one-third facial appearance, especially for a square and disproportional mandibular angle even extending to the middle mandibular body. This article describes the method of multistage mandibular angle ostectomy to produce a natural lower one-third facial contour. This method mainly focused on the posterior area of mandibular ostectomy by intraoral approach, although it has modifications. Mandibular contouring is realized first through bone cutting from antegonial notch posteriorly upperward, reaching to the middle ramus of the mandible near the earlobe; second ostectomy followed along mandible lower part is to get rid of extramandibular angle according to the preoperative design; sometimes necessarily, third ostectomy creates a smooth mandibular contour. From January 2000 to January 2010, 379 patients were operated on, and satisfactory results were achieved. Thus, this procedure could avoid excessive bone cutting, extramandibular angles, unnatural appearance, and palpable bone steps.     

Champy plates in mandibular surgery

Champy plates are becoming more and more accepted for the fixation of simple mandibular fractures, fixation of middle face fractures and fixation after Le Fort osteotomies. This area of indication can be extended by their use in cases of complicated mandibular fractures, fixation of bone graft, and immediate reconstruction following removal of mandibular tumours. Experience shows that Champy plates have the following advantages over other methods: the plates are small, flexible, easily adaptable and the monocortical screws allow a rapid surgical application. Some examples are presented.     

Bifid mandibular canal in Japanese

The location and configuration of mandibular canal variations are important in surgical procedures involving the mandible, such as extraction of an impacted third molar, dental implant treatment, and sagittal split ramus osteotomy. We report 3 Japanese patients with bifid mandibular canals using panoramic radiograph and multi-slice helical computed tomography (CT) images. In 2 of the 5 sides, the bifid mandibular canal was suggested on panoramic radiograph. The bifid mandibular canal had a short and narrow upper canal toward the distal area of the second molar in 4 sides, and a short and narrow lower canal toward the distal area of second molar in 1 side, as revealed on reconstructed CT images. Since the location and configuration of mandibular canal variations are important in surgical procedures involving the mandible, they should be carefully observed using reconstructed CT images.