Densitometric analysis of experimentally produced periapical radiolucencies.

Artificial periapical lesions were created in a mounted dried human mandible. These lesions were radiographed by means of a reproducible projection technique. A penetrometer was projected on the same radiographs as the dental and bony structures. The developing process was standardized. The radiographs were evaluated by means of densitometric analysis. The densitometer readings of the dental and bony structures on the radiographs were converted to a millimeters-of-aluminum-equivalents scale by means of the densitometer readings of the penetrometer images on the same radiographs. The measurements on the radiographs were presented in graphs and isodensitometric images. Areas where bone was removed could be reproducibly distinguished by densitometric analysis from areas where no bone was removed. For this purpose, the densitometric analysis of periapical radiographs proved to very useful, whereas the interpretations of the same radiographs by ten dentists differed greatly.     

Deep circumflex iliac artery flap combined with a costochondral graft for mandibular reconstruction

Our aim was to use the deep circumflex iliac artery (DCIA) flap together with a costochondral graft as a safe and reliable bone flap for routine reconstruction of the mandibular body and the temporomandibular joint (TMJ). Five patients with benign tumours of the mandible had segmental mandibulectomy including the condyle, and this was reconstructed in one stage using the DCIA combined with a constochondral graft. The rib was inserted into the iliac crest as a whole transplant, and fixed to the proximal stump of the mandible with a prebent reconstruction plate according to a computer-aided design. The grafts healed uneventfully, and dental implants were inserted in 4 cases. During the 2-year follow-up these patients had good mandibular function, including mouth opening, force of bite, and occlusion. The radiographs showed good bony consolidation between the graft and the stump of the mandible and function of the TMJ.A DCIA flap combined with a costochondral graft is a safe and reliable way to provide not only a large bulk of bone to suit the mandible, but also good function of the TMJ in the absence of radiotherapy.     

Central neurilemmoma of the jaws. Review of literature and case report.

Neurilemmomas presenting as primary central bone tumors are extremely rare. Only 21 cases have been reported to have arisen in the jaws; all except for one have occurred in the mandible. The majority of these have been associated with the inferior dental nerve. A case of a central neurilemmoma arising in the anterior mandible is reported. Its probable origin is from one of the alveolar branches of the incisive nerve--an unusual site in the mandible. The radiographic features include expansion of cortical bone, resorption of roots of teeth, the presence of lace-like bony septa and a spotty calcification within the tumor. The treatment and the prognosis are briefly discussed.     

Histological assessment of bioengineered new bone in repairing osteoperiosteal mandibular defects in sheep using recombinant human bone morphogenetic protein-7

Numerous experimental studies have been published about osteoinductive bone morphogenetic proteins (BMPs). However, to our knowledge there has been no detailed histological study of a mandibular defect in a large mammal, reconstructed using BMPs. We describe here the histological features of rhBMP-7-induced bone in mandibular defects in sheep. METHODS: A 35 mm osteoperiosteal defect was created at the parasymphyseal region of the mandible in six adult sheep. The continuity of the mandible was maintained using a bony plate, and rhBMP-7 was applied on a type I collagen carrier. Bone labels were injected at selected time intervals during the follow-up period. The animals were killed after 3 months and bone samples were examined histologically, histomorphometrically, and by fluorescence microscopy. RESULTS AND CONCLUSIONS: We found a mixture of woven and lamellar bone that contained many cells with large nuclei. This had not reorganised to form cortical bone and the rhBMP-7-induced bone was more porous than the native bone. The newly-formed bone restored both endosteal and periosteal layers. rhBMP-7-induced bone was biocompatible and induced no ossification of soft tissue or abnormal growth of nearby vital structures. The mineral apposition rate was 1.98 microm/day (range 0.62-5.63 microm/day), a value close to that reported in humans. This suggests that BMPs have a limited effect in accelerating the rate of mineralisation, but promote the pre-mineralisation processes, and perhaps the formation of woven bone.     

Augmentation of the rat mandible using guided tissue regeneration

The aim of the present study was to investigate whether it is possible to increase the height of the rat mandible at its inferior border using a bioresorbable membrane adapted to create a secluded space for ingrowth of bone tissue. The experiment was carried out in 18 rats. The mandibular ramus was exposed at both sides. A standardized titanium microimplant was then inserted in the naturally existing curvature at the inferior border of the mandible, serving as a fixed reference and space maker. The mandibular border on one side was covered with a polyhydroxybutyrate bioresorbable membrane, and the contralateral side, serving as control, received no membrane before closure of the wound. The membranes were placed in such a way that a space was created in the curvature between the membrane and the inferior border of the mandible. Macerated jaw specimens representing 6 months of healing demonstrated substantial amounts of bone formation in the curvature of the inferior border of the mandible, resulting in a flattening of the inferior border. Negligible amounts of bone formation had occurred in the control sides. Histological analysis demonstrated that. in 4 of 6 experimental specimens, the space created by the membrane was completely filled with new bone after 6 months of healing, but in some specimens soft tissue seemed to have migrated into the space through ruptures of the membrane or because of poor membrane adaptation at its lateral borders, thereby inhibiting bone formation. Only negligible bone formation had occurred at the control sides. It can be concluded that augmentation of the mandible can be accomplished using a bioresorbable membrane of polyhydroxybutyrate adapted to create a secluded space for ingrowth of bone tissue. but the membrane must be modified regarding its physical properties before clinical use in maxillofacial surgery.     

Impact of surface contamination of implants with saliva during placement in augmented bone defects in sheep calvaria

Our aim was to try and find out whether contamination with saliva during insertion of dental implants affects osseointegration in bone that has been augmented with different grafts. Six bony defects were created in each of the calvaria of six sheep, and then augmented with three different materials (autogenous bone, bovine bone, and resorbable biphasic ceramic bone substitute) After five weeks of healing, three implants contaminated with saliva (contaminated group) and three not contaminated (uncontaminated group) were placed in the centre of the augmented areas. For histomorphometric analysis, bone implant contact, bone area fraction occupancy, bone and material area, and bony area were measured after a healing period of five weeks. There was a significant difference between the contaminated and uncontaminated groups (p = 0.036) for bone implant contact only in the augmented areas, but there were no significant differences in bone area fraction occupancy, bone and material area, and bony area. We conclude that contamination with saliva during placement of dental implants can significantly compromise bone implant contact in augmented areas, but had no significant effect on the formation of bone in areas more distant from the surface of the implant. We suggest that salivary contamination should be avoided during placement of dental implants in augmented areas.     

Mechanical evaluation of mandibular defects reconstructed using osteogenic protein-1 (rhOP-1) in a sheep model: a critical analysis

Osteoinductive bone morphogenetic proteins (BMPs) have been used extensively in experimental and clinical orthopaedic research. It is a natural progression for these growth regulators to be tested in the craniofacial region. The aim of this investigation was to analyse the mechanical properties of the sheep mandibles reconstructed using recombinant human osteogenic protein type 1 (rhOP-1). A unilateral 35 mm osteoperiosteal continuity defect was created at the parasymphyseal region of the mandible in six adult sheep. The animals were sacrificed 3 months after surgery and mechanical properties of the regenerated bone at the operated sides (OS) were compared to the corresponding bone at the non-operated side (NOS). The regenerated tissue at the OS were then submitted for histological and histomorphometric analysis. Although all the animals achieved complete bony union, a wide range of mechanical properties was found. The rhOP-1-induced bone achieved a mean of 36% of the strength of the bone at the NOS (P < 0.05). The mean value of the stiffness of the OS was 24% of the NOS (P < 0.05). While half of the samples of the OS had 'weak' mechanical properties (9-25% strength compared to NOS) and a low stiffness (6-18%), the rest showed relatively higher strength (47-63%) and were stiffer (35-47%). Unlike the NOS, the operated sides failed under tensile stresses and cracks initiated at the superior border of the mandible. The wide mechanical variations suggest that further basic bone biology research is needed to provide better understanding of the cellular and molecular events which take place during the process of osteoinduction.     

The position and course of the mandibular canal.

Twenty-nine human cadaver mandibles were dissected longitudinally and cross-sectionally for determination of the precise location of the inferior alveolar nerve, artery, and vein. The neurovascular bundle was located in contact with, or very close to, the lingual cortical plate until it reached the mental foramen. Anterior to the mental foramen, the neurovascular bundle was not a distinct entity and was located close to the labial cortical plate. In the body of the mandible, the neurovascular bundle was located about one centimeter above the mandibular inferior border. The distance from the lateral border of the neurovascular bundle to the external surface of the buccal plate was usually half a centimeter in the molar and premolar regions. The mandibular canal was usually formed by a thin bony plate that, grossly, had more of an appearance of trabecular bone; in only a few mandibles was there a thin layer of cortical bone.     

Growth characteristics of large mandibular ameloblastomas: report of 5 cases with implications for the approach to surgery

The aim of this study was to establish surgical guidelines based on the growth pattern of ameloblastomas in relation to the possible infiltration of the cortical bone, the inferior alveolar nerve, the periosteal layer and the surrounding soft tissues. Five male patients with voluminous mandibular ameloblastomas were treated by means of radical surgery. Ameloblastomas showed an invasive growth pattern in the cancellous bone with small tumour nests at a maximum distance of 5mm away from the bulk of the tumour. Expansive and invasive growth in the Haversian canals was observed. There was no invasion of the inferior alveolar nerve. The mucoperiosteal layer was invaded but not perforated. No invasion was observed in the surrounding soft tissues of the periosteum and in the skin tissue. A local resection with a surgical margin of spongious bone of 1cm is suggested. When the tumour is radiologically closer than 1cm to the inferior border of the mandible, a continuity resection is mandatory. A conservative approach concerning the inferior alveolar nerve is suggested. Removal of an excess of perimandibular soft tissue is not indicated. The overlying attached mucosal surface should however be excised together with the underlying bone.     

开窗减压引流术治疗下颌骨巨大囊性病变

目的 评估开窗减压引流术在下颌骨巨大囊性病变治疗中的临床应用价值.方法 回顾分析4 例下颌骨巨大囊性病变（角化囊性瘤1 例、多囊型成釉细胞瘤2 例、单囊型成釉细胞瘤1例）,均行开窗减压引流术,临床随访行全颌曲面断层片检查,进行颌面部影像对比分析.结果 4例下颌骨巨大囊性病变囊腔均缩小、新骨形成、颌骨形态恢复,避免了下颌骨切除,牙颌功能保留,无下唇麻木,其中2 例已二期手术刮除残余囊壁,随诊1 年无复发.结论 开窗减压引流术,最大限度保留下颌骨形态和功能,是治疗下颌骨大型囊性病变的微创方法.     

Radiological analysis of maxillary artery relationships to key bony landmarks in maxillofacial surgery

The maxillary artery (MA) is a key structure at risk of injury in numerous oral and maxillofacial surgical (OMS) procedures. Knowledge of safe distances from this vessel to surgically familiar bony landmarks could improve patient safety and prevent catastrophic haemorrhage. Distances between the MA and bony landmarks on the maxilla and mandible were measured using CT angiograms on 100 patients (200 facial halves). The vertical height of the pterygomaxillary junction (PMJ) was mean (SD) measurement of 16 (3) mm. The MA enters the pterygomaxillary fissure (PMF) a mean (SD) distance of 29 (3) mm from the most inferior point of the PMJ. The mean (SD) shortest distance between the MA and medial surface of the mandible was 2 (2) mm (with the vessel directly contacting the mandible in 17% of cases). The branchpoint (bifurcation of the superficial temporal artery (STA) and MA) was directly in contact with the mandible in 5% of cases. The mean (SD) distances between this bifurcation point and the medial pole of the condyle were 20 (5) mm and 22 (5) mm, respectively. A horizontal plane through the sigmoid notch perpendicular to the posterior border of the mandible is a good approximation of the trajectory of the MA. The branchpoint is usually within 5 mm of this line and inferior in 70% of cases. Surgeons should take note that both the branchpoint and the MA contact the surface of the mandible in a significant number of cases.     

Benign fibrous histiocytoma: report of case

Benign fibrous histiocytoma is a rare and usually painless oral neoplasm found in adults that may affect either soft tissue or bone typically noted in their fifth decade. This case was found in a 32 year-old Caucasian male who presented with a fairly well circumscribed unilocular radiolucent lesion extending from the mandibular right first incisor to the left first premolar and reaching the inferior mandible on a panoramic radiograph. A bony window was created and the intrabony lesion was curetted. Multiple sections revealed a cellular tumor composed of uniform spindle-shaped cells arranged in a prominent whorled or storiform pattern. Scattered xanthoma cells, multinucleated giant cells, lymphocytes, and deposits of hemosiderin were noted throughout the lesional stroma. Although malignant fibrous histiocytoma of the bone is relatively well known, benign fibrous histiocytoma of the bone is very rare.     

Temporoparietal osteofascial flap for head and neck reconstruction.

PURPOSE: This article describes the use of the temporoparietal osteofascial flap (TOF) for reconstruction of bony defects in the midface and mandible. PATIENTS AND METHODS: We reviewed the demographics, etiology, indications, surgical technique, radiographic evaluation, and final outcome of 11 patients with upper or lower jaw defects who underwent reconstruction using the TOF between 1994 and 1999. RESULTS: The TOF was used to reconstruct a defect of the mandible in 7 patients, the hard palate in 2 patients, the maxilla in 1 patient, and the zygoma in 1 patient. The defect was a result of tumor resection in 9 patients and of trauma in 2 patients. The defect size ranged from 3 to 6 cm. Ten flaps (91%) were successful and 1 flap failed. There was 1 donor site complication (small dural tear) that was repaired immediately without sequelae. One patient had osseointegrated dental implants placed in the bone with good results. Exploration of the construction area was performed in 1 patient 13 months after surgery because of recurrent tumor. It showed a fully integrated bone flap. CONCLUSION: This vascularized calvarial bone flap can be used for the reconstruction of small to medium-sized defects of the maxilla and lateral mandible with good functional and cosmetic results. It can be performed without special microvascular expertise and with minimal donor site morbidity. A full-thickness bone flap can support osseointegrated dental implants.     

Atherosclerotic changes of the inferior dental artery correlated with those of the carotid bifurcation and the abdominal artery

50 corpses from adults aged 20 to 75 have been used in order to study the atherosclerotic lesions occurring in typical regions (bifurcation of the common carotid artery and the abdominal aorta) and their relationship to atherosclerotic changes in the inferior alveolar artery. Histological analysis revealed that atherosclerotic alterations of the inferior alveolar artery may appear sometimes earlier than it would be expected on the ground of age. Intima cell proliferation and thickening of elastic elements in the middle layer of the arterial wall, the first signs of atherosclerosis, were found already at the beginning of the third decade of life when the signs of this process in the typical regions were not yet evident. Atherosclerosis affects essentially the functional capacity of the inferior alveolar artery. The development of atherosclerosis in the wall of this artery favours an hypovascularization of the mandible, which must be of certain importance in every operative procedure in oral surgery, especially in those inducing a severe and long traumatism in bone and soft tissues, such as dental implantations.     

基于配准技术的微创牙种植导向模板的制作方法及应用

目的设计制作精确的微创牙种植导向模板,以指导医生准确地手术定位。方法对行种植手术的患者下颌骨进行CT扫描,依据CT数据构建三维牙颌模型,并利用Simplant专业种植软件在三维模型的基础上进行模拟种植,确定种植体的位置和深度。对牙颌石膏模型进行数字化扫描,通过曲率配准技术将石膏模型和CT三维模型进行对齐,确定种植体设计位置与牙颌扫描模型的关系,根据种植体位置,在牙颌石膏数字化模型上利用3-Matic软件完成导向模板的设计,最后利用快速成型技术制作导向模板。结果通过配准技术将CT数据与牙颌数字化数据相融合,设计出的微创导板定位精确,在无需切开口腔黏膜的情况下依然能够很好地为医生在实际种植时提供导向。结论将三维配准技术应用于种植领域,结合Simplant模拟种植和快速成型等技术制作的微创种植导向模板定位准确,实现了手术的微创性与精确性,值得临床推广使用。     

The use of fresh frozen allogeneic bone for maxillary and mandibular reconstruction.

The use of fresh frozen bone (FFB) alone, or in combination with autogenous bone (AB), for bony augmentation of the maxilla and mandible in preparation for dental reconstruction with endosseous implants has been studied. Ten patients received FFB +/- AB for augmentation of a severely atrophic mandible (n = 6) or for reconstruction of a jaw defect secondary to trauma or tumor resection (n = 4). Average follow-up was 26.3 +/- 5.4 months. At the time of implant placement, the bone grafts were found to be firm in consistency, well incorporated, and well vascularized in all 10 patients. Twenty-nine endosseous implants were placed an average of 8.3 +/- 3.1 months following bone grafting. One implant failed and was replaced, and one implant remains buried as a nonfunctional unit. All patients have been restored prosthetically by means of 28 of the 29 implants. This preliminary study indicates that FFB may be used alone or in combination with autogenous bone for augmentation or reconstruction of the atrophic maxilla and mandible. The resultant ridge is adequate to support loaded endosseous implants. A potential disadvantage is the minimal risk of disease transmission.     

Clinical application of a new compact CT system to assess 3-D images for the preoperative treatment planning of implants in the posterior mandible A case report

When treatment planning before placing dental implants in the posterior region of the mandible, the locations of the inferior alveolar nerve and mental foramen need to be ascertained, as they determine the bone height available and the implant length selected. The purpose of this study was to introduce the clinical application of a newly developed compact computed tomography system (Ortho-CT) to assess three-dimensional (3-D) images for the preoperative treatment planning of implants in the posterior region of the mandible. To evaluate the 3-D images, we scanned using the Ortho-CT system the mandible with a radiopaque template placed in the posterior region. The Ortho-CT images provided excellent information for evaluating the morphology of the mandible, and for showing the location of the inferior alveolar nerve, mental foramen and the relationship of the template to the bone. We consider that Ortho-CT is a useful aid to preoperative treatment planning of implant therapy in the mandible.     

Dental implant therapy in the treatment of an oroantral communication after exodontia

A new technique in which a dental implant was the ultimate therapy for the treatment of an oroantral communication (OAC) that was created subsequent to the extraction of a maxillary first molar is described. A search of the English-speaking literature has not revealed implant therapy as part of documented modalities for the treatment of an OAC created following dental extraction. The OAC was closed by a sandwich technique that uses two resorbable membrane materials (Bio-Gide, Osteohealth, Shirley, NY) that surround a bone substitute (Bio-Oss, Osteohealth). This procedure, together with additional onlay grafting with the same bone substitute, was used also to regenerate subantral bone to enable the subsequent placement of an endosseous implant after 12 months. An 8-month postoperative radiograph showed creation of a new maxillary sinus bony floor and subantral bone of good quality, and height that can permit the placement of an endosseous dental implant.