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Ectopic eruption of the second permanent molar is a tooth replacement disorder during adolescence. If not treated in time, it can cause hard tissue of the adjacent first molar resorption, early tooth loss, decreased chewing efficiency, and other serious malocclusions. Timely detection and treatment of ectopic eruption of the second permanent molar are of great significance in preventing malocclusions in adolescents and establishing normal occlusion relationships. However, current case reports on the ectopic eruption of the mandibular second molar are relatively rare and are mostly concentrated on surgical and orthodontic treatments, and long-term follow-up is lacking. This paper reports a case in which brass wire ligation was used to treat ectopic eruption of the mandibular second permanent molar, allowing the permanent teeth to erupt smoothly and establish a normal occlusion. The patient was observed for five years after the operation. The occlusion was stable, and the tooth root development, pulp vitality, and periodontal conditions were normal. This paper provides a clinical approach that is short in treatment duration, simple, and minimally invasive for young mandibular second permanent molars with moderate mesial inclination and partial eruption. This method is of importance in helping children establish physiological occlusion.

It is a basic prerequisite for the successful completion of endodontic treatment to thoroughly understand the root canal space anatomy. With the development of dental devices in dentistry, the root canal morphology of the mandibular first premolars can be presented in more detail. Before conducting root canal therapy on the mandibular first premolar with complex root canal morphology, it should be necessary to evaluate the potential difficulties and risks for making an appropriate treatment plan. The present paper reviews the research progress on the diversities of root canal morphology in mandibular first premolars in recent years, and then makes technologic recommendations based on the morphology diversities.

Copyright of China Journal of Oral & Maxillofacial Surgery is the property of Shanghai Jiao Tong University, College of Stomatology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of West China Journal of Stomatology is the property of Sichuan University, West China College of Stomatology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Journal of Oral & Maxillofacial Surgery is the property of Shanghai Jiao Tong University, College of Stomatology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of West China Journal of Stomatology is the property of Sichuan University, West China College of Stomatology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper is aimed to develop a computerized three dimensional system for displaying and analyzing mandibular helical axis pathways. Mandibular movements were recorded using a six-degrees-of-freedom ultrasonic jaw movement recording device. The three-dimensional digital models of the midface and the mandible were reconstructed and segmented from CT skull images. The digital models were then transformed to the coordinate system of mandibular motion data by using an optical measuring system. The system was programmed on the base of the Visualization ToolKit and Open Scene Graphics Library. According to the motion data, transformation matrices were calculated to simulate mandibular movements. Meanwhile, mandibular helical axis pathways were calculated and displayed three dimensionally by means of an eigenvalues method. The following parameters of mandibular helical axis were calculated: the rotation around instantaneous helical axis, the translation along it, its spatial orientation, its position and distance relative to any special reference point. These parameters could be exported to describe comprehensively the whole mandiblular movements. It could be concluded that our system would contribute to the study of mandiblular helical axis pathways.

Copyright of China Journal of Oral & Maxillofacial Surgery is the property of Shanghai Jiao Tong University, College of Stomatology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The application principle and procedure of reverse engineering and rapid prototyping techniques are introduced in this paper. The description is concentrated on the applications of the above techniques in medical field, especially in reconstructive surgery of mandibular bone defect.

Objective: To analyze occlusal contact areas on the working and nonworking sides during unilateral mastication., Methods: Eighteen subjects without any temporomandibular disorder (TMD) symptoms participated in the present study. The subjects were presented with 3 g gum for right masticating. Chewing movement was simulated using virtual craniofacial movement simulation system. Then occlusal contact areas were calculated at four selected moments during the closing phase in the third chewing cycle: the occurrence of occlusal contact, one third time, two thirds time, the intercuspal occlusion., Results: During the closing phase in the third chewing cycle, the total occlusal contact areas on working side increased from (9.3+/-0.4) mm2 to (39.2+/-1.2) mm2, and that on nonworking side increased from (2.3 +/-0.5) mm2 to (40.3+/-1.2) mm2. At the occurrence of occlusal contacts, occlusal contact areas of the first and second mandibular molars were on average (3.7+/-0.2) mm2 and (3.5+/-0.2) mm2 on working side, and (0.5+/-0.2) mm2 and (1.2+/-0.3) mm2 on nonworking side, respectively. However, when the mandible moved to the intercuspal position, their areas were sharply increased to (14.8+/-0.7) mm2 and (13.9+/-0.4) mm2 on working side, and (13.6+/-0.5) mm2 and (12.1+/-0.5) mm2 on nonworking side, respectively. In addition, nonworking-side contacts were observed for 12 subjects at the occurrence of occlusal contacts, and for all subjects at two thirds time., Conclusion: This paper provides a new method useful for analyzing occlusal contacts during functional movements. This study revealed the pattern of occlusal contacts during the closing phase in the chewing cycle. Moreover, it was confirmed that nonworking-side contacts occurred during unilateral mastication.

Objective: This paper presents a new method of skeleton reconstruction for oblique facial clefts using autogenous bone of the mandibular outer table., Methods: In the operation, the mandibular outer table was harvested through the intraoral approach. Assisted with internal rigid fixation technique, the mandibular outer table was used to reconstruct the naso-orbital framework as inlay or onlay bone graft., Results: From 1993 to 2001, seven cases of oblique facial clefts were repaired with mandibular outer table bone graft. Postoperative follow-up for 6 months to 3 years demonstrated that the grafted bone healed well with the adjacent bones. No obvious bone resorption was observed. The facial appearance was improved greatly., Conclusions: The mandibular outer table, with similar bone density to the calvarium, is easy to harvest without donor site scar. The method is quite ideal for skeleton reconstruction of oblique facial clefts.

Objective: To evaluate the methods of orthognathic treatment for mandibular asymmetry., Methods: 110 cases of mandibular asymmetry had been treated in past thirteen years. The type of deformity, the management of the cases, and the effects of orthognathic treatment were summarized in this paper. Orthodontic therapy was taken before and after operation to keep the treatment effect., Results: According to the type of the asymmetry deformity, different methods were used. After treatment, all the patients obtained satisfactory facial appearances and oral function., Conclusion: It should be diagnosed before surgery whether the development of deformity is steady or not. If it is steady, the effects of orthognathic and orthodontic therapy will be satisfactory; if not, we should remove the affected condyles and simulataneously ameliorate facial appearance.

Purpose: To investigate the clinical and radiographic manifestations of malignant ameloblastoma of the jaw and methods for treatment., Methods: 10 consecutive cases of malignant ameloblastoma were treated in the Department of Oral and Maxillofacial Surgery, Ninth People's Hospital,Shanghai Second Medical University between 1991 and 2003. All the cases were proved to be malignant ameloblastoma by surgical pathology and followed up for 1 to 8 years. This paper reviewed the clinical manifestation, diagnosis and treatment of these 10 cases., Results: Among the 10 cases of malignant ameloblastoma, 5 were female, 5 were male ,aged from 22 to 60 years. 4 cases were located in the maxilla, and 6 cases in the mandible.All the patients underwent partial mandibulectomy or maxillectomy combined with modified radical neck dissection or supraomohyoid dissection with flap repair at the same time. The follow up outcomes were satisfactory both in appearance and function without recurrence., Conclusion: Malignant ameloblastoma is a kind of low degree malignant tumors. Diagnosis is made by pathology. Operation is the only radical method of therapy.

Precision registration of serial sections is an important step for 3-D image reconstruction. It directly affects the accuracy of the reconstructed result and parameter computation. This problem has been studied and demonstrated by many investigators, but the whole process has not yet reached good performance. In this paper, we discussed the registration of serial sections image of mandible and put forward a method of the soft registration-based transformation on the basis of the hard registration in consideration of the speciality of 3-D image reconstruction for the serial sections of mandible. Employing control points and using Affine Transformation and Extended Hough Transformation, we solved the problem of displacement on 3-D image reconstruction for serial secons and paved the way for reconstructing the mandible microstructure with reality. The results of experiments indicate that the 3D image reconstructed after registration has only a little distortion.

Mandible defects can be caused by many diseases, most commonly occurring in cranio-maxillofacial regions. With the development of orthopaedics, biomaterial and cell biology in these years, great improvements have been acquired in repair of mandible defects. This paper systematically reviewed the relevant research advances and applications, and showed the applied prospect of bone tissue engineering in this field.

Four types of 3D mathematical mode of the muscle groups applied to the human mandible have been developed. One is based on electromyography (EMG) and the others are based on linear programming with different objective function. Each model contains 26 muscle forces and two joint forces, allowing simulation of static bite forces and concomitant joint reaction forces for various bite point locations and mandibular positions. In this paper, the method of image processing to measure the position and direction of muscle forces according to 3D CAD model was built with CT data. Matlab optimization toolbox is applied to solve the three modes based on linear programming. Results show that the model with an objective function requiring a minimum sum of the tensions in the muscles is reasonable and agrees very well with the normal physiology activity.

One of the ultimate goals for orthodontic treatment is to establish an esthetic, healthy, stable and efficient occlusion. Currently, however, most of the criteria are limited to static occlusion, with little attention to dynamic occlusion. During the therapy, the orthodontists may sometimes find the maximum intercuspation (MI) is remarkably inconsistent with the centric relation (CR), or the mandibular positions are different before and after the therapy. These definitely will influence the stability of the treatment, or even the health of temporomandibular joint (TMJ) and stomatognathic system. The functional occlusion theory emphasizes that the displacement of TMJ in the glenoid fossa is the reason for the inharmony between MI and CR, and the relapse. What is more, this theory also gives the orthodontists the ways to evaluate the relationships among the MI, CR and TMJ. In this paper, we will introduce the contents and methods of the functional occlusion theory. [ABSTRACT FROM AUTHOR]

Objective: The paper reviewed the effectiveness and reliability of skin paddles of free fibula flaps in the reconstruction of maxillofacial defects., Methods: Fifty-five consecutive free fibula osteocutaneous flap transfers performed from June 21, 1999 to October 31, 2000 were reviewed. The skin paddles of each flap were analyzed in terms of surgical design, blood supply, size, reconstruction location, and survival., Results: Fifty-seven skin paddles were used for the 55 free fibula flaps (double skin paddles for 2 flaps), 37 were nurtured by one perforator, 18 by two and two by 3 perforators. Twenty-eight skin paddles were used for intraoral reconstruction, 7 for extraoral reconstruction, 1 for both intraoral and extraoral reconstruction, 2 for soft tissue augmentation, and the remaining 19 were simply used as window for monitoring the blood flow of fibula flap. One free fibula flap with one skin paddle was lost because of venous thrombosis, and the other 54 flaps survived completely, with 100% survival of 56 skin paddles., Conclusion: The skin paddle of free fibula flap is safe and reliable. It can be used for all kinds of soft tissue reconstruction, as well as window for monitoring the blood flow of fibula flap after operation.

Obstructive sleep apnea and hypopnea syndrome (OSAHS) is characterized by obstruction of upper airway and respiratory disturbance, excessive daytime sleepiness and tiredness. The possible causes are obesity, hypertension, and upper airway malformations, etc. The location and degree of upper airway structure narrowing in patients have been investigated in many ways, such as X-ray, multi-slices spiral computed tomography, etc. With multi-planar reconstruction technique, 3-dimensional construction of upper airway can be established which shows the delicate changes of the upper airway structure. Mandibular advancement device is known as an effective treatment on mild and moderate OSAHS. By advancing the mandible forward, it can increase the space of upper airway, especially the oropharyngeal space. This paper reviewed the methods of investigating on OSAHS and the change of upper airway structure in OSAHS patients treated with mandibular advancement device. Supported by Combined Research Fund of Bureau of Health, Yunan Province and Kunming Medical College (Grant No. 2009CD205). [ABSTRACT FROM AUTHOR]

Objective: To explore the methods of orthognathic treatment for the developmental mandibular asymmetry to simultaneously achieve satisfactory facial appearance and oral functions and to prevent recurrence of the deformity., Methods: 37 cases of developmental mandibular asymmetry have been treated in past seven years. The type of the deformity, the management of the cases, and the effects of therapy were summarized in this paper., Results: According to the type of the asymmetric deformity, different means were used. After treatment, all the patients obtained satisfactory facial appearance and oral function., Conclusions: During the orthognathic treatment, it is important to simultaneously ameliorate facial appearance and achieve good oral function. It should be diagnosed before surgery whether the development of the deformity is steady or not. The correction of skeleton and soft tissues must be performed by stages.

Objective: This paper presents a new method of osteotomy for the prominent mandibular angle (PMA)., Methods: Two modifications have been made to the conventional procedures. The first is the one-stage curved osteotomy of the mandibular angle. The second is non-resection of the masseter muscle. The surgical procedure has been performed through an intraoral approach with a direct field of vision., Results: From December 1996 to December 1997, a total of thirty-eight patients suffering from PMA have been operated on by this method with satisfactory results. The follow-up is 3 to 12 months., Conclusion: This method is a very simple and ideal procedure with much less complications for surgical treatment of PMA.

The aim of this paper was to study the reproducibility of the positions of hinge-axis of mandibular retruded small open-closed movements, and the positional relationship between the hinge-axis and condyles. Fourteen normal students were tested by a six degrees of freedom mandibular movement recorder MT1602 (Germany). The result showed that: the hinge-axis could not be exactly repeated and movable instantaneous centers of rotation (ICR) were recorded. These rotation centers distributed almost evenly around the condyles, the mean distance from these rotation centers to condyle centers was about 8.83 +/- 5.65 mm.

When severe mandibular hypoplasia accompanying obstructive sleep apnea syndrome (OSAS) were treated by the orthognathic surgery, the results were quite successful not only in patients' profile, occlusion and functions, but also in the subjective and objective evaluations related to OSAS. The paper summarizes the methods and surgical procedures of treating OSAS with orthognathic surgery through the diagnoses and treatment of a group cases suffering from severe mandibular hypoplasia accompanying OSAS. Severe mandibular hypoplasia can cause not only the deformity and the disorder of occlusion, but also the OSAS. The advancements of mandible and hyoid with orthognathic surgery can improve the patients'prfile, occlusion and expand the patency of upper airway, so it can cure OSAS.

The paper deals with quantitative study of bone healing in goat after unilateral oblique osteotomy of the mandibular ramus. Bone histomorphometry combined with tetracycline bone labelling and gamma monophoton absorptiometry were used to assess the rate of the new bone formation and its degree of mineralization during the healing process. The result showed that if the articular capsule and the lateral pterygoid muscle were remained and attached, the quantity of new trabaculae and the rate of bone healing in the inferior part of proximal fragment were less than those in the superior part (P < 0.05). There was a bone healing delay in the inferior part of proximal fragment.

Since 1987, the authors have performed mentoplasty for congenital mandibular deformities in 46 patients with the assistance of X-ray pantomoscanning. Mandibular deformities include: 1) Bilateral hyperplasia of mandibular angles and massetter hypertrophy; 2) Retrognathia or micrognathia; 3) Asymmetric mandibular deformity. In this paper, following problems are discussed: 1) The advantages of an extraoral approach in mentoplasty; 2) The importance of the X-ray pantomoscanning; 3) The specific feature of asymmetric chin; 4) The improvement of the silicon implant used in mentoplasty; 5) Evaluation of the composite operative result.

The geometric similarity and mesh dividing of finite element models directly create an effect on the results of analysis when a theoretical stress analysis is performed by the use of finite element method. The model is routinely established by means of sectioning the specimen. In this paper, a series of plane section CT images of the teeth and mandible, an image analysis system and a specially designed software for modeling three-dimensional finite element were used to establish a three-dimensional finite element model. It is a new preprocessing method for finite element applications in the field of oral biomechanism. The technique is characterized by the advantages of high similarity of the model to specimens and no damage to specimens; it is simple and easy. The images and figures can be repetitively used.

In this paper, 31 cases with lower jaw defects (disarticular of TMJ, 9; conservation of TMJ, 8; defects of mandibular arch, 14) were immediately reconstructed following tumor-surgery with plate, and combined with bone graft for some of cases. Results demonstrated the remarkable clinical value of this method in improving post-operation function and facial deformities, even though there exist problem such as healing, occlusion and loose of plate. In addition, the key technique procedures were discussed involving in operation.

This paper is to study the mandibular border movement showing in three different direction observations, mandibular tapping movement showing in two different direction observations and the mandibular movement of two types of foods by using D-SGG which is an accurate and convenient measurement system of mandibular movement tracks. The results are as follows: 1. a normal ranges of the mandibular border movement are made and the variations of the ranges are quite small in normal subjects, no significant difference is found. 2. the variations of mouth opening are greater in tapping movement than in border movement. The distributions of the tracks of tapping movement are about 4.0 mm, but the coefficient of variation is considerable. 3. The quality and quantity of test foods effect the ranges of mouth opening in chewing movement.

In this paper, we determined and compared the strength limits of mandible, ilium, skull and rib. The results showed that in the light of simple physics, ilium and skull may be suitable sources of bone for mandibular transplant, but the rib may be unsuitable for transplant.

This paper presents our study on the bias axis elastic properties of the human mandible. The elastic coefficients were determined by the composite materials mechanical testing methods. From these values the "technical constants" were calculated to be: EL = 18.823GPa, ET = 12.777GPa, GLT = 5.564GPa, vLT = 0.302, vTL = 0.205. Variation of elastic constants of the human mandible with the orientation to its long axis was investigated. A brief description of the variation law is given. The bias axis stress-strain relationship of the human mandible is established. The data indicate that the human mandible is a living, anisotropic and nonhomogeneous composite biomaterial. Its mechanical properties have a close relation to its location, orientation and structure.

In this paper, a vascular casting method using methylmethacrylate was adopted. Satisfactory samples were obtained and electron microscope observations were carried out on periosteum microvasculature of infant mandibular ramus. There were significant differences in the density and arrangement of periosteal microvascular in various regions. In muscular attached region, the blood vessels showed a high density and bundle-like arrangement parallel with the direction of muscular fibers. In nonmuscular attached region, the blood vessels showed a marked low density and an irregular net-like arrangement. Between muscular bundles small arteries into periosteum were seen. Around the mandibular foramen the vessels of the periosteum formed a high density region. The clinical application of the above mentioned results were discussed.

The postoperative recurrence of ameloblastoma is common. However, ectopic recurrence in clinical operations is rare. A case of ectopic recurrence of ameloblastoma in the bucca region of the mandible after 15 years is presented in this paper. The causes of the ectopic recurrence were analyzed based on relevant literature. [ABSTRACT FROM AUTHOR]

[Objectives] To investigate whether the stag beetle Dorcus hopei -coexists male trimorphism due to their remarkable variation in mandible and elytra length, and if so, to determine the relative success of each morph in mate competition. [Methods] 90 male specimens were classified into three putative morphs on the basis of mandible and elytra length. Male mating behavior was then filmed using an infrared camera and the relative competitive advantage of each morph assessed by measuring how long each took to approach female. [Results] a α-type males have well-developed mandibles (14.70-18.84 cm long) and elytra (22.14-25.86 cm long), whereas γ-type males have rudimentary mandibles (4.88-8.99 cm long) and elytra (15.42-19.40 cm long), and β -type males are intermediate in mandible (11.67-15.99 cm) and elytra (19.24-23.77 cm) length. α males spent more time in close proximity to females than β and γ males, and α males spent more time in close proximity to females than γ males. When γ males coexisted with other two male morphs, they always took more time to approach females. The observations implied the males at a disadvantage might benefit indirectly from the strong competition between two advantaged males.. [Conclusion] Our results suggested that the males of D. hopei are trimorphic, with three distinct male morphs simultaneously present in the population. Morphs could be ranked in terms of competitive superiority as follows: α > β > γ. We speculated that y males as the less strong type would gain opportunities by drawing on the competition between two competitive morphs.. Further studies will be needed to understand the mating behavior and tactics among three male morphs. This is the first report of male trimorphism in the Chinese stag beetle. Our findings provide insights into the understanding and knowledge of multiple phenotypes coexisting within the same species. [ABSTRACT FROM AUTHOR]

Copyright of China Journal of Oral & Maxillofacial Surgery is the property of Shanghai Jiao Tong University, College of Stomatology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Journal of Oral & Maxillofacial Surgery is the property of Shanghai Jiao Tong University, College of Stomatology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A new procedure, intraoral vertical ramus osteotomy (IVRO) becomes more and more popular in correction of mandibular prognathism recently. Simplified operation, decreased bleeding and mild reaction after operation are the advantages of this procedure. 32 cases of mandibular prognathism corrected by intraoral vertical ramus osteotomy were reported in this paper. Modifications for avoiding fracture and displacement of proximal segment, the main complication and indications of IVRO were discussed.

The purpose of this study was to assess the validity of the data supported by MKG by testing the accuracy of both the raw data and corrected data of it by means of precise measurements throughout the entire range of functional mandibular movements. This paper also presents a computer processing which can correct the geometric divergence and has the same effect of MKG analyzer.

Chondromyxoid fibroma is a rare benign tumor originated from cartilage. It mainly occurs in the metaphysis of long bones in children and young people. And it rarely occurs in the retromandibular fossa. This paper reported a case with chondromyxoid fibroma in the mandibular fossa. The potential histopathologic source, clinical manifestations, diagnosis, several differential diagnosis and treatment were discussed. [ABSTRACT FROM AUTHOR]

The ameloblastoma mainly occurs in the mandible, rarely seen in the soft tissues. This paper reported 1 case of mandibular gingival peripheral ameloblastoma, and discussed its treatment based on literature review. [ABSTRACT FROM AUTHOR]

Osteoid Osteoma is rare in mandibular condyle. A case of osteoid osteoma in the condyle was reported in this paper. The clinical manifestation, radiographic characteristic, pathologic diagnosis were discussed. Nidus is the key in diagnosing osteoid osteoma, and the final diagnosis is based on pathological findings. [ABSTRACT FROM AUTHOR]