Growth characteristics of ameloblastoma involving the inferior alveolar nerve: a clinical and histopathologic study

OBJECTIVE: Growth characteristics of ameloblastomas involving the inferior alveolar nerve were examined to determine the most appropriate surgical management of the nerve at the time of the surgical procedure. STUDY DESIGN: Clinical and histopathologic examinations were performed on 22 resected mandibles in which the inferior alveolar nerve was lying adjacent to, or contained within, the tumor. RESULTS: Patterns of tumor involvement of the nerve bundle were evaluated with respect to the presence of bone (11 patients) or connective tissue wall (7 patients) between the tumor and the nerve bundle, and tumor infiltration of perineural connective tissue (4 patients). Neither invasion into the nerve sheath nor invasion into the nerve itself by the ameloblastoma was detected. Tumor infiltration of the tissue surrounding the nerve was identified for the multicystic and solid types but not for the unicystic type. Presence of bone or connective tissue wall between the tumor and the nerve bundle was dominant in the unicystic and plexiform ameloblastomas, whereas tumor infiltration of the perineural tissue was frequently observed in ameloblastomas with the follicular pattern. CONCLUSION: The preservation of the inferior alveolar nerve may be possible in the management of the unicystic type of ameloblastoma. However, a more radical approach is necessary for treatment of multicystic or solid tumors, especially those exhibiting a follicular pattern.     

The growth characteristics of multilocular ameloblastomas. A histological investigation with some inferences with regard to operative procedures

The growth characteristics of multilocular ameloblastomas and the reaction of the surrounding tissues were studied by means of a histological examination of 31 surgical specimens. Infiltration of spongy bone was observed frequently whereas there was little tendency to invade cortical bone. The periosteum largely prevented extension of the tumour. However, in the region of the mucosa overlying the alveolar process apparent encapsulation was absent. There were indications that the infiltrative growth pattern exhibited by an ameloblastoma within spongy bone was due to secondary enclosure of tumour tissue by remodelled bone.     

Perineural infiltration of the inferior alveolar nerve in mandibular ameloblastomas

Our aim was to evaluate the histological association of mandibular solid and multicystic ameloblastoma with the inferior alveolar nerve, both in situ and in segments of the nerve that had been removed separately, to assess the feasibility of preserving the nerve during resection of mandibular ameloblastomas. In this prospective histological examination of 13 resected hemimandibulectomy specimens, we studied the proximity of tumour cells to the inferior alveolar nerve. In group 1 (n = 8) this association was examined with the nerve still within the mandibular segment after resection, while in group 2 (n = 5) the nerve was removed from the resected tumour and examined separately. Perineural and intraneural involvement of the ameloblastoma with the nerve was confirmed in 5 cases in group 1 and 2 cases in group 2. Tumour cells abutted the nerve directly in group 1. In group 2 tumour was removed with, and found within, the nerve. On this evidence we cannot recommend preservation of the inferior alveolar nerve during operation for large, advanced, mandibular ameloblastomas.     

Ultrasonic osteotomy as a new technique in craniomaxillofacial surgery

Ultrasound osteotomy is a new surgical technique used in dentistry to section hard tissues without damaging adjacent soft tissues. It was hypothesized that this could also be useful in craniofacial and orthognathic surgery. An ultrasonic device was employed in the following craniofacial surgical procedures: 144 Le Fort I osteotomies, 140 palatal expansions after Le Fort I osteotomies and 140 bilateral sagittal osteotomies; 2 Le Fort III osteotomies for treatment of Crouzon syndrome in two patients; 12 cases of unicortical calvarial bone grafting; removal of superior orbital roof in 25 cases of craniofaciostenosis; removal of external wall of the orbit in 10 cases of orbital cavity tumour; removal of anterior and posterior walls of the frontal sinuses in four cases of orbital cavity tumour. Integrity of soft tissues and surgical time were evaluated. Functional results were good without any soft-tissue damage being observed, but the overall operative time was increased. Ultrasound osteotomy is a new technical procedure that is advantageous for bone cutting in multiple situations, with minimal to no damage in adjacent soft tissues such as brain, palatal mucosa and the inferior alveolar nerve.     

Factors influencing the patterns of invasion of the mandible by oral squamous cell carcinoma

The pattern of tumour invasion of the mandible depends on the extent of invasion. Both the width (P=0.02) and depth (P=0.01) in patients with an invasive or infiltrative pattern of disease were greater than in tumours showing the less aggressive erosive pattern in which the tumour mass is separated from the resorbing bone by a connective-tissue layer. Evidence in this study suggests that the erosive pattern develops through a mixed pattern to the invasive pattern of disease as the tumour progresses through the bone. The invasive pattern of disease was evident at a much shallower depth in the molar region of the mandible (mean 9 mm), with a decreased ratio of alveolar to basal bone, than in the premolar and parasymphyseal region (mean 25 mm) (P=0.02). The hypothesis to explain this phenomenon is that the more superficial alveolar bone responds by resorbing in advance of the tumour, but the basal bone is unable to respond in the same way and becomes widely infiltrated. The attached mucosa with its firm collagen attachment to bone is proposed as the main route of tumour entry into the mandible in both dentate and edentulous mandibles.     

The histologic pattern of bone invasion by squamous cell carcinoma of the mandibular region.

Surgical specimens from 16 nonirradiated patients with carcinoma of the mandibular region who had undergone resection of the mandible were investigated histologically to evaluate the presence, pattern and extent of bone involvement. Thirteen of the 16 carcinomas had invaded the mandibular bone. Two main patterns of growth were identified: seven carcinomas had infiltrated nonuniformly into the bone and six tumours had advanced as a compact front. Direct invasion from the oral mucosal tumour could be verified in 12 cases. Extension of four of these 12 tumours in bone clearly exceeded their dimension in the overlying mucosa. Carcinoma tissue in the mandibular canal, at a distance from the major tumour extension, was seen in two cases, whereas the periodontal ligament spaces were invaded only when there was a direct contiguous invasion by the tumour. The grade of histologic differentiation of the carcinoma did not definitely correlate with the frequency, pattern or extension of bone involvement. The results indicate that large tumour size, location on the mandibular alveolar ridge and clinical fixation to the mandibular bone predispose to, but are not prerequisites for bone invasion. Taken together, this study has shown that prediction of the presence and extent of bone involvement of the carcinoma located in the mandibular region is difficult on clinical grounds.     

Inferior alveolar nerve transposition--an in vitro comparison between piezosurgery and conventional bur use

An in vitro comparison between a new ultrasound-based piezoelectric device and a conventional bur was performed for lateralization or transposition of the inferior alveolar nerve to evaluate the effects on soft and hard tissue. Transposition of the inferior alveolar nerve was performed in the cadaver mandibles of 10 sheep: the left nerve was uncovered with a saline-cooled diamond-coated spherical bur (2000 rpm), and the right nerve was uncovered with the piezoelectric device mounted with a spherical diamond tip. The surface, the zone of bone defect, and the nerve were examined by light microscopy and laser microscopy. Bone treated with the rotary bur showed significantly smoother surfaces and shallower defect zones (50 microm) in comparison with the piezoelectric device (150 microm). Lesions of the epineurium and an increased amount of bone particles were found in the lesions prepared with the piezoelectric device. In vitro preparation with the piezoelectric device was more invasive to the bone than was a conventional diamond bur. Touching the inferior alveolar nerve resulted in roughening of the epineurium without affecting deeper structures. The degree of injury was lower than when using the conventional rotary bur.     

Surgical treatment of maxillary nerve injuries. The infraorbital nerve

Although inferior alveolar and lingual nerve injuries appear to occur more often, there are undoubtedly cases of ION injury that require evaluation and possible surgical intervention by the oral and maxillofacial surgeon. Patients with ION injuries will require a neurosensory examination for the determination of the level of sensory impairment, or the localization of pain of peripheral origin (centrally mediated pain will not benefit from peripheral nerve surgery). The surgical management of ION injury might be as relatively simple as decompression of the nerve by reduction of a zygomatic complex fracture, or may require extensive mobilization of the nerve and surrounding soft tissue and bone to allow for primary anastomosis or a nerve autograft. In specific instances, improvement in ION sensory function or alleviation of pain within the distribution of the ION can be expected.     

Inferior alveolar nerve transposition with involvement of the mental foramen for implant placement

Inferior Alveolar Nerve (IAN) transposition is an option for prosthetic rehabilitation in cases of moderate or even severe bone reabsorption for patients that do not tolerate removable dentures. The aim of the present report is to describe an inferior alveolar nerve transposition with involvement of the mental foramen for implant placement. The surgical procedure was performed under local anesthesia, by the inferior alveolar, lingual and buccal nerve blocking technique. Centripetal osteotomy was performed, and bone tissue was removed, leaving the nerve tissue free in the foramen area. After that, transsection of the incisor nerve was performed, and lateral osteotomy was started from the buccal direction, toward the trajectory of the IAN. The procedure was concluded, by making use of a delicate resin spatula to manipulate the vascular-nervous bundle. The drilling sequence for placing the dental implants was performed, and autogenous bone was harvested using a bone collector attached to the surgical suction appliance. After the implants were placed, the bone tissue previously collected during the osteotomies and drilling processes was placed in order to protect the IAN from contact with the implants. The surgical protocol for inferior alveolar nerve transposition, followed by implant placement presented excellent results, with complete recovery of the sensitivity, seven months after the surgical procedure.     

Mandibular invasion of lower gingival carcinoma in the molar region: its clinical implications on the surgical management

The spread pattern of a tumour and its extent in the mandible are important in the management of gingival cancer. Sixteen patients with gingival squamous cell carcinoma (SCC) involving the mandible in the molar region were included in this study. Resection specimens of the mandibular bone and adjacent cancer were histologically analysed to identify the type and characteristics of invasion and were compared with the radiological features. Our results showed that the actual width of invasion was underestimated to a greater extent than the actual depth of invasion. For horizontal aspects, four dentate cases had horizontal intramedullary spread underneath intact mucosa or cortical bone extended from the main foci of tumour that infiltrated through the occlusal surface. For vertical aspects, nerve invasion took place in only one of 16 specimens, while five cases showed downward infiltration beyond the inferior alveolar canal without nerve involvement, so that the pattern of tumour spread was mostly transmedullary rather than perineural in previously non-irradiated cases. These cases with deep infiltration showed the infiltrative type of invasion in the dentate mandible. And when the tumour was related with previous dental extractions or curettage, it tended to be more extensive than what was predicted from an imaging point of view. These pathological and clinical features affecting the tumour spread should be considered in the management of gingival SCC in the molar region.     

下齿槽神经缺失大鼠下颌骨牵张成骨牵张期蛋白质组学分析

目的：探讨用蛋白质组学iTRAQ技术分析下齿槽神经缺失大鼠下颌骨牵张成骨牵张期新生组织蛋白表达的改变.方法：6只大鼠随机分为2组,实验组为下齿槽神经缺失大鼠下颌骨牵张成骨,对照组为正常大鼠下颌骨牵张成骨,均进行单侧下颌骨牵张,速率：0.2mm/12h,牵张期为10d,下颌骨牵张成骨牵张期第10d取材.将取材的新生骨组织标本进行理化性分析、蛋白质提取及蛋白质定量检测.应用iTRAQ技术对蛋白质样本进行检测,寻找及鉴定差异蛋白.结果：应用iTRAQ技术质谱鉴定出置信度95％的蛋白315种,共鉴定出差异蛋白146个,其中上调≥1.5倍的39个,下降≤0.8倍的58个.结论：感觉神经系统在牵张成骨的成骨过程中起到一定调控作用.筛选出多种下齿槽神经缺失下颌骨牵张成骨牵张期新骨形成相关的差异蛋白,为进一步验证感觉神经缺失对下颌骨牵张成骨新骨形成相关蛋白质奠定了基础.     

A survey of tumours of the jawbones in Hong Kong Chinese: 1963-1982

A total of 114 tumours of the jawbones was confirmed in a survey of 204,583 surgical specimens in Chinese in the University Department of Pathology, Hong Kong from 1963-1982. Odontogenic tumours totalled 82 of which 62 per cent were ameloblastomas. Thus, odontogenic tumours, in particular ameloblastomas, are relatively common in Chinese. In the 51 cases of ameloblastoma, the mean age at presentation in females was significantly younger than in males. Pathological analysis of the ameloblastomas showed the following: (1) connection of tumour epithelium with oral mucosal epithelium suggests a better prognosis; (2) basaloid pattern in the tumour may prognostically indicate a more aggressive biological behaviour; (3) neoplastic infiltration of the grossly normal bone surrounding the tumour mass was frequent; (4) ameloblastomas not uncommonly contained cysts lined by innocuous-looking epithelium; (5) a significant proportion of ameloblastomas appeared grossly as thin-walled unilocular cysts. The implications of these findings in the diagnosis and treatment of ameloblastoma are emphasized.     

应用无机活性诱导元素支架材料行下齿槽神经切除后神经管骨重建治疗复发性三叉神经痛的初步报告

目的对复发性第Ⅲ支三叉神经痛患者行下齿槽神经管开窗并行下齿槽神经全切除、神经管内置入无机活性诱导元素,利用其成骨特性以治疗复发性三叉神经痛的疗效分析。方法选择下牙槽神经撕脱术后复发病例18例,用球形磨钻磨除下颌第一前磨牙至下颌角下牙槽神经管周围骨质,形成直径约2cm的长条形骨窗,完整切除下齿槽神经,磨钻选磨,置入无机活性诱导材料。对患者术后随访至少2年,并对本手术方法治疗下齿槽神经痛的疗效进行评价。结果患者切口均Ⅰ期愈合,术后未出现水肿、感染等并发症。6例患者术后7 d内有余痛不止,1周后疼痛基本消失,X线连续观察2年下齿槽神经管成骨效果良好。结论本手术方法可以有效治疗复发性第Ⅲ支三叉神经痛,副作用是下齿槽神经切断造成的局部麻木。     

Hemimandibulectomy and therapeutic neck dissection with radiotherapy in the treatment of oral squamous cell carcinoma involving mandible: a critical review of treatment protocol in the years 1994–2004

This retrospective non-randomized 10-year follow-up study compared 147 patients with squamous cell carcinoma (SCC) of the oral cavity requiring hemimandibulectomy, treated by surgical resection, therapeutic neck dissection and radiotherapy. The 5-year survival rates were compared related to localization, size of the tumour, infiltration of locoregional lymph nodes, distant metastases, histopathological grading, radicality of surgery, and invasion of tumour into the mandible. Occurrence of tumour relapse and its localization was studied. The mean 5-year survival rate was 26%. Patients with SCC of the mandibular alveolar process had higher rates; the lowest rates occurred in SCC of the buccal mucosa. Survival rate was significantly lower with insufficient resection of the tumour (85% relapse). An important number of patients with radical resection died within 3 months of surgery. In almost 55% of the mandibles tumour was not present. In 5% of infiltrated mandibles, dissemination into inferior alveolar nerve was proven. Decreasing survival rate was seen with increasing size of tumour and higher histological grade. Therapeutic neck dissection significantly reduces survival rate and increases the percentage of lymph node relapse. Elective neck dissection should be performed in SCC requiring hemimandibulectomy. Primary reconstruction should reverse the high percentage of postoperative complication arising from increased radicality.     

Mandibular invasion of squamous cell carcinoma: factors determining surgical resection of mandible using computerized tomography and histopathologic study

Aim  

Carcinoma of the mandibular region can be considered as an important, distinct entity associated with special problems relating to diagnosis, evaluation of extension, planning of treatment, surgical techniques, treatment result and prognosis. The study was aimed to assess the accuracy of computerized tomography in demonstrating mandibular invasion, to assess the role of anatomic structures like cancellous spaces, the inferior alveolar nerve and periodontal spaces in spread of carcinomas in the mandible and to determine the spread of tumour within the mandible and the resection procedure to be carried.     

Maxillofacial deformities in neurofibromatosis

Four patients with neurofibromatosis are described: all displayed the feature of an increased depth of the sigmoid notch probably due to an expansive growing neurofibroma of the inferior alveolar nerve. One patient had a local neurofibroma with an invasive growth pattern and only this patient shows hyperplasia of the bone. The suggestion is made, contrary to what is found in the literature, that only the invasive growth type gives rise to hyperplasia and this type is always concomitant with a localized form of neurofibromatosis.     

Mobilization of the inferior alveolar nerve with simultaneous implant insertion: a new technique. Case report

For reconstruction of an atrophied posterior mandible, different therapeutic options have been proposed, such as autologous bone grafting, guided bone regeneration for vertical ridge augmentation, and inferior alveolar nerve (IAN) mobilization with simultaneous implant placement. The possible dehiscence of soft tissues covering the surgical zone makes the first and second techniques unpredictable. Moreover, two surgical sites are necessary and a long treatment time is required (about 12 months). With IAN mobilization, only one surgical intervention is required and the total treatment time is shorter (about 6 months). However, this technique risks irreversible damage to the IAN, with consequent functional alterations. Current studies have shown extreme variability in the examination of functionality of the neurovascular bundle after its mobilization. This variability can be attributed both to the methodology used for the tests, which evoke subjective answers from the patient, and to the surgical procedure, which is highly dependent on operator technique. Nerve damage can be the result of an overstretched mucoperiosteal flap in the premolar area to achieve optimal visibility of the surgical zone. This article reports a case in which a new surgical approach to IAN mobilization is performed using a specifically engineered device for simplified bone surgery (Mectron Piezosurgery). This device enables the surgeon to cut hard tissue without injuring the soft tissues. Therefore, there is a lower risk of damaging the IAN, and it is possible to reduce overstretching of the mental nerve by creating a smaller bone window and using an apicocoronal inclination of instruments to capture the neurovascular bundle.     

Injury of the inferior alveolar nerve after overfilling of the root canal with endodontic cement: a case report

The inferior alveolar nerve (IAN) contains mainly sensory fibers. Within the mandibular canal, the IAN runs forward in company of the inferior alveolar artery, and together they are called the inferior alveolar neurovascular bundle. Disturbances of the IAN and mental nerve will predominantly give sensitivity symptoms in the soft tissue of the lower lip and chin. We present a case report of endodontic overfilling involving the mandibular canal. A 52-year-old woman was seen in our outpatient clinic for pain and numbness in the left lower lip and chin, which developed following an endodontic treatment for her mandibular left second premolar. The panoramic radiograph showed radiopaque material in the inferior alveolar canal region, with an extension from the left canine to the second premolar. This case report shows an unusual complication of mandibular second premolar root canal overfilling. The patient underwent treatment with corticosteroids, and after 2 months, the clinical examination revealed an improved clinical situation with a disappearance of the hypoesthesia but with a persistence of the pain. After 4 months, the pain had almost entirely disappeared. In conclusion, even if in our case no surgical treatment was used and although spontaneous resorption has been described for some materials, early surgical exploration with removal of the material and decompression of the IAN is suggested, irrespective of the material used, because the severity of nerve damage can increase with the duration of the injury.     

Influence of bone invasion and extent of mandibular resection on local control of cancers of the oral cavity and oropharynx

The aim of this paper was to evaluate the influence of bone invasion on treatment outcome among patients with cancers of the oral cavity and oropharynx and to determine whether or not outcome was influenced by the extent of mandibular resection. A review of 127 prospectively documented patients who were treated with marginal or segmental resection for oral (n = 110) and oropharyngeal (n = 17) cancers was undertaken. There were 97 males and 30 females with a median age of 61 years. Clinical T stages were: T1 17 patients, T2 33, T3 22, T4 55. Median followup was 4 years. A total of 94 patients underwent marginal resections and 33 underwent segmental resections. Histological bone invasion was present in 17 patients (16%) in the marginal resection group and 21 patients (64%) in the segmental group (P<0.05). Soft tissue surgical margins were positive in 11 patients (12%) in the marginal group and in seven patients (21%) in the segmental group (P=not significant). Local control did not correlate significantly with T stage, the extent of mandibular resection or the presence of histological bone invasion, but was significantly influenced by positive soft tissue margins (P<0.01). Among patients with bone invasion, the local control rate was higher following segmental resection when compared to marginal resections (87% vs 75%) but this was not statistically significant. Survival was significantly influenced by positive soft tissue margins but not bone invasion or the type of resection. We conclude that bone invasion alone did not predict for local control or survival rates among patients with oral and oropharyngeal cancers. Involved soft tissue margins were highly predictive of local recurrence and decreased survival. Conservative resection of the mandible is safe as long as marginal mandibulectomy does not lead to compromise of soft tissue margins. Segmental resection should be reserved for patients extensive bone invasion or those with limited invasion in a thin atrophic mandible.     

Soft tissue recurrent ameloblastomas also show some malignant features: A clinicopathological study of a 15-year database

Background

To investigate the clinicopathological features of six cases of soft tissue recurrent ameloblastoma and explore the role of increased aggressive biological behavior in the recurrences and treatment of this type of ameloblastomas.

Material and Methods

In this study, we retrospectively reviewed recurrent ameloblastomas during a 15-year period; six cases were diagnosed as soft tissue recurrent ameloblastoma. The clinical, radiographic, cytological and immunohistochemical records of these six cases were investigated and analyzed.

Results

All the six soft tissue recurrent ameloblastomas occurred after radical bone resection, and were located in the adjacent soft tissues around the osteotomy regions. In Case 4, the patient developed pulmonary metastasis, extensive skull-base infiltration and cytological malignancy after multiple recurrences and malignant transformation was diagnosed. In the other five cases, although there were no cytological signs are sufficient to justify an ameloblastoma as malignant, some malignant features were observed. In Case 1, the tumor showed moderate atypical hyperplasia and the Ki-67 staining percentage was 40% positive, which are strongly suggestive of potential malignance. In Case 5, the patient developed a second soft tissue recurrence in the parapharyngeal region and later died of tumor-related complications. All the remaining three patients showed cytology atypia of varying degrees and high expression of PCNA or Ki-67, which confirmed active cell proliferation.

Conclusions

Increased aggressiveness is an important factor of soft tissue recurrence. An intraoperative rapid pathological examination and more radical treatment are suggested for these cases. Key words: Ameloblastoma, soft tissue recurrence, aggressive biological behaviour.