Search

The charismatic and diverse ornithischian dinosaurs exhibited some of the most extreme examples of cranial anatomy, inspiring decades of investigation into their muscular anatomy. Current ornithischian jaw muscle reconstructions, although parsimonious, pose concerns of small adductor muscles and caudally displaced insertions relative to mandibular proportions. Here, craniomandibular material of ornithischian genera spanning all subclades is reexamined for osteological correlates indicative of intracranial and oral soft tissues. M. adductor mandibulae externus (mAME) has traditionally been reconstructed as solely inserting along the caudal margin of the coronoid process for jaw closure. Here, a new mAME reconstruction is proposed in derived ornithischians, with the superficial-most mAME layer reconstructed as a rostrolabial expansion of muscle, exiting the cranium rostroventrally beneath a unique, laterally flaring jugal and inserting along the lateral surface of the coronoid process and its rostrally extending, shelf-like labial dentary ridge (LDR). Through previous dental microwear and morphological studies, ceratopsians, hadrosaurids, and ankylosaurs are known to have implemented a major palinal feeding component in their jaw motions, unlike other primarily basal ornithischians. This rostral fan-like extension of muscle in these derived clades would create a greater mandibular support system and mechanical advantage along the labial margin of the jaw, cradling the entire mandible while lifting it up into occlusion and retracting it. In hadrosaurids and ankylosaurs, this rostrolabially expanding muscle also acts in medial rotation of the dentaries about their long axes. With these new reconstructions, the notion of a novel, unparsimonious "cheek" muscle is rejected, with further discussion of plausible buccal soft tissues. Anat Rec, 2018. © 2018 Wiley Periodicals, Inc. Anat Rec, 303:347-362, 2020. © 2018 American Association for Anatomy.

Paget disease of bone (PDB) is a chronic progressive bone disorder characterized by localized increased bone turnover and focal areas of woven bone formation. Although skull involvement is common, PDB very rarely affects the mandible. This report describes the clinical and histologic findings in a 75-year-old patient with PDB involving the mandible. Microstructural analyses showed an altered quality of the bone microstructure and calcium depletion of the affected bone. Differential diagnosis of PDB affecting the mandible is discussed.

Purpose The mandible is an essential esthetic and functional component of the lower third of the face and its reconstruction has always been a challenge, especially after severe post-traumatic injuries. The purpose of the present report was to introduce a new approach of mandibular reconstruction in a patient who had lost the entire mandible except for the rami after being severely injured in a blast. Materials and Methods A new approach using a titanium mandibular rami implant technique was applied using computer-aided 3-dimensional virtual planning and rapid prototyping technology. A prosthetic component was supported by the mandibular implant, which achieved occlusion and dedicated function for the patient. Results This method offered precise adaptation of the implant and prosthesis and an easier surgical procedure, providing a shortened operation time, no donor site morbidity, and more predictable outcomes. Conclusion This new technique allows reconstruction of large-scale mandibular defects that is not possible by conventional surgical methods.

a b s t r a c t Introduction/objective: The fibula osteocutaneous free flap has been a workhorse for mandibu- lar reconstruction since Hidalgo's original description for its use for this purpose. The objective of this manuscript is to review the use of the fibula flap in mandibular reconstruc- tion and to answer some of the commonly held misconceptions as to why some surgeons view it as an inferior reconstructive option to the vascularized iliac crest flap. Materials/methods: Review of the literature as it relates to the use of the fibula free flap in mandibular reconstruction and the senior author's experience. Results: The bicortical nature of the fibula provides a stable platform for endosseous implant placement, thus allowing for comprehensive oral rehabilitation and improving the quality of life in reconstructed patients. The fibula osteocutaneous free flap, however, is the longest vascularized bone flap available, allowing for reconstruction of the entire mandible. Given these attributes, it would seem unlikely that doubts regarding the adequacy of the fibula free flap in mandibular reconstruction exists. However, the principal arguments challenging the use of the fibula osteocutaneous free flap are the lack of height of the reconstructed fibula compared to the native mandible, unreliable skin perforators to support a skin paddle, insufficient soft tissue coverage, and the presence of vascular anomalies which may preclude its use. These presumed shortcomings are circumvented with various proven techniques to increase fibular height and anatomic studies demonstrating the cutaneous perforator patterns. Conclusions: With these simple solutions in mind, the fibula osteocutaneous free flap will likely remain a workhorse for mandibular reconstruction, allowing for the reconstruction of virtually any oromandibular defect. It allows for both aesthetic, as well as, functional reconstruction of the mandible.

Masticatory muscles are closely involved in mastication, pronunciation, and swallowing, and it is therefore important to study the specific functions and dynamics of the mandibular and masticatory muscles. However, the shortness of muscle fibers and the diversity of movement directions make it difficult to study and simplify the dynamics of mastication. The purpose of this study was to use 3-dimensional (3D) simulation to observe the functions and movements of each of the masticatory muscles and the mandible while chewing. To simulate the masticatory movement, computed tomographic images were taken from a single Korean volunteer (30-year-old man), and skull image data were reconstructed in 3D (Mimics; Materialise, Leuven, Belgium). The 3D-reconstructed masticatory muscles were then attached to the 3D skull model. The masticatory movements were animated using Maya (Autodesk, San Rafael, CA) based on the mandibular motion path. During unilateral chewing, the mandible was found to move laterally toward the functional side by contracting the contralateral lateral pterygoid and ipsilateral temporalis muscles. During the initial mouth opening, only hinge movement was observed at the temporomandibular joint. During this period, the entire mandible rotated approximately 13 degrees toward the bicondylar horizontal plane. Continued movement of the mandible to full mouth opening occurred simultaneously with sliding and hinge movements, and the mandible rotated approximately 17 degrees toward the center of the mandibular ramus. The described approach can yield data for use in face animation and other simulation systems and for elucidating the functional components related to contraction and relaxation of muscles during mastication.

Osteopetrosis is a rare congenital (autosomal type) disorder of the skeletal system. Several variants have been described in the literature with grossly variant prognosis and clinical behaviour. Several reports of intractable osteomyelitis of the jaw bones secondary to osteopetrosis, particularly the mandible, have been published widely. However, there is no published report of the complete mandible sequestrating de novo, in the literature. An overview of this spectrum of sclerotic bone disease, its presentation in the oro-facial region, the diagnostic challenge it poses and the management dilemma it offers to the maxillofacial surgeon is discussed and a protocol for managing this disease effectively is presented. A clinical illustration of the complexities of management of osteopetrosis-induced osteomyelitis of jaw bones is demonstrated with a very rare case in which the entire mandible had sequestrated.

Introduced two decades ago, the free fibula flap has only recently been applied to reconstruction of the segmental mandibular defect. Hayden’s description of a neurosensory capability combined with enough bone to reconstruct an entire mandible with potential for osseointegration offers excellent functional rehabilitation. Together, with minimal donor site morbidity and the advantages of simultaneous, two-team surgery, the neurocutaneous free fibula has become our “workhorse” flap for optimal reconstruction of challenging oromandibular defects.

The stress distribution in an edentulous mandible provided with two implants in the interforaminal region was calculated by means of three different finite element models. The implants were connected with a bar or remained solitary. The first model was a three-dimensional representation of the entire mandible, the second model of the interforaminal region of this same mandible, whilst the third model was a two-dimensional representation of the interforaminal region. The differences in stress distribution around the connected implants and the solitary implants between these three models were analysed. It can be concluded that for a parameter study the stress distribution around the dental implants following from a three-dimensional finite element model of only the interforaminal region of an edentulous mandible can be used. For such studies therefore, benefit can be gained from the advantages of reduced modelling and calculation time.

One of the most important sources of ideas for development, investigation, and application of biomedical materials has always been the surgeon who has the ultimate responsibility for implementing the medical device in the treatment of his/her patients. But while all surgeons care about advancing the materials, methods, and instruments for treatment of their patients, it is only a very few who have the education/training, talent, and commitment to envisage the most promising innovations. Sadly, one such surgeon, Dr Philip Boyne, Emeritus Professor of Oral and Maxillofacial Surgery in the School of Dentistry at Loma Linda University, died on 9 June 2008. Details of his life can be found elsewhere: (www.legacy.com/pe/Obituaries.asp?Page=LifeStoryPrint&PersonID=111344176). Dr Boyne was the compleat academic surgeon. Much of his 20-year career in the Navy, which ended in 1968, was spent at the Naval Research Institute at the Bethesda Naval Hospital, and all of his subsequent years were at universities: University of California at Los Angeles, University of Texas in San Antonio, and Loma Linda University. Throughout his professional life Dr Boyne dedicated himself to finding new solutions for oral and maxillofacial problems, and most of these solutions involved biomedical materials. He played substantial roles in the development of anorganic bone as a bone graft substitute material and a collagen membrane for guided tissue regeneration. To the end, he was actively participating in the development of biomedical materials for other oral and maxillofacial applications. Dr Boyne was one of the first surgeons to regularly attend biomaterials meetings and to publish in biomaterials journals. In these ways he shared his knowledge, experience, and ideas with the biomaterials community. He was generous in making his time available to young investigators, and unselfish in encouraging them to pursue their own ideas. It was his presentation at one of the early biomaterials meetings (Clemson University's Fourth Annual Symposium on Biomaterials, held in Clemson, South Carolina on 3–7 April 1972) that inspired me, at the time three months into my first faculty position at Clemson University. He reviewed his work treating patients with total mandibulectomies, a condition that I did not even know existed. As anybody would be, I was immediately struck by the horrific situation of losing one's entire mandible, and I could feel the hopelessness that the patients must have been experiencing. But Dr Boyne then proceeded to demonstrate how he reconstructed the mandibles using bone graft contained in a titanium meshwork molded to the shape of the lost bone. My horror was replaced by wonder at what could be achieved in regenerating tissue and relieving human suffering, and the central role that biomaterials played in the process. Ten years later, as I was researching various strategies in the development of bone graft substitute materials I again came in contact with Dr Boyne, having come across the many studies he had performed on bone graft materials while he was at the Naval Research Institute in the 1950s and 60s. He unselfishly shared his ideas and provided encouragement. One of Dr Boyne's most important traits as an investigator, and collaborator, was his honesty in reporting the negative as well as positive outcomes of the materials and procedures that he was studying. He was always thinking about what he was doing, and was indefatigable in seeking improvements in treatment options. Perhaps such determination is not difficult to understand in a person who would run marathons barefooted (nine of them at Boston). My remembrance of Dr Boyne is not unique. He served as a source of ideas and inspiration for decades of students, residents, and senior as well as junior investigators working on various aspects of biomedical materials. His passing makes us ever more appreciative of the importance of a team approach to multidisciplinary problems such as those encountered in the application of materials to the solution of medical problems. We can only hope that he and his like are adopted as role models by young surgeons.

Objective: To evaluate displacement and stress distribution on craniofacial structures associated with fixed functional therapy. Materials and Methods: A finite element model of the human skull was constructed from sequential computed tomography images at 2-mm intervals using a dry adult human skull. In this study, linear, four-nodal, tetramesh and triangular shell elements were used with six degrees of freedom at each of their unstrained nodes: three translations (x, y, and z) and three rotations (around the x-, y-, and z-axes). Results: The entire mandible moved anteroinferiorly. Maximum displacement was observed in the parasymphyseal and midsymphyseal regions. The pterygoid plate was displaced in a posterosuperior direction. The anteroinferior displacement of the mandibular dentition was most pronounced in the incisor region, while the maxillary dentition was displaced posterosuperiorly. The entire dentition experienced tensile stress except for the maxillary posterior teeth. Tensile stress was also demonstrated at point A, the pterygoid plates, and the mandible, and minimal compressive stress was demonstrated at anterior nasal spine. Maximum tensile stress and von Mises stresses occurred in the condylar neck and head. Conclusion: Fixed functional therapy causes a posterosuperior displacement of the maxillary dentition and pterygoid plate and thus can contribute to the correction of Class II malocclusion. The displacement was more pronounced in the dentoalveolar region as compared to the skeletal displacement. All dentoalveolar structures experienced tensile stress, except for anterior nasal spine and the maxillary posterior teeth.

We describe a novel method of estimating reduced bone mineral density (BMD) from dental panoramic tomograms (DPTs) which show the entire mandible. Careful expert width measurement of the inferior mandibular cortex has been shown to be predictive of BMD in hip and spine osteopenia and osteoporosis. We have implemented a method of automatic measurement of the width by active shape model search, using as training data 132 DPTs of female subjects and tested on a test data set of 606 DPTs of female subjects whose BMD has been established by dual-energy X-ray absorptiometry. We demonstrate that the sensitivity of the automatic method to osteoporosis is equivalent to that of expert manual measurement.

Quantitative computed tomography (QCT) was completed in 34 subjects between the ages of 9 and 33 years with symmetrical mandibles in order to investigate the three-dimensional cortical bone mineral density (BMD) distribution in the mandible. The number and distribution of the pixels were determined at three levels: (1) representing the entire mandibular bone; (2) the cortical bone at 60% above the baseline defined as the segmentation level (around 1050 mg/cm3) and representative of only cortical bone; and (3) the highest mineralized cortical bone (>1250 mg/cm3). The geometrical distribution of the highest mineralized areas was evaluated by three-dimensional reconstruction of the images. The total number of pixels for the entire mandible increased significantly at each time point represented at four increasing ages groups (9-11 years of age, 12-14 years of age, 15-17 years of age, and >18 years of age). The male and female subjects had a similar total number of pixels for the entire mandible before the age of 11, but the male subjects showed a significantly larger total number of mandibular pixels after that age. Comparison of the number of pixels for pure cortical bone (60% segmentation level) and the highest mineralized cortical bone indicated a significant increase with maturation with the greatest change occurring between the 13-year and 16-year age groups. However, the ratio of cortical bone/total bone increased at a more rapid rate in the male subjects and reached a plateau by the 16-year age group, showing distinct differences in mineralization of the mandible between the sexes.

The Panoramic Radiograph Panoramic radiography displays the mandible and maxilla, which are curved structures, on flat, easily viewed images [ I ]. The technique is extraoral (as opposed to an intraoral technique. in which the film to be exposed is placed inside the patient’s mouth). Patients remain stationary, and the film and X-ray tube rotate around them. We use a 6 x I 2 inch film and a 70-kV technique with a phototimer. One advantage of panoramic radiography is that a survey of the entire mandible and maxilla can be obtained on one film and with one exposure. Disadvantages include geometric distortion. lack of fine detail, and numerous artifacts that require care to interpret. With experience. many of these disadvantages are overcome. However, supplementary imaging techniques may be required. Panoramic radiography can prove helpful in planning CT or MR imaging studies. Congenital Variants and Common Developmental Abnormalities Unerupted Teeth Adult patients often have unerupted teeth (21. Such teeth can occur at almost any site in the jaws but are especially common adjacent to molars (Fig. I).

A case of chronic osteomyelitis of mandible involving both temporomandibular joints with a pathologic fracture as a complication of neglected pulpal infection is described. The predisposing factor that causes so wide spreading of the infection almost certainly is a nutritional deficiency.

The reinnervation of teeth after segmental osteotomy has been investigated using electrophysiological techniques in 6 cats. An osteotomy which divided the entire mandible was carried out bilaterally. The anterior segment was repositioned anteriorly by 5 mm and in 3 animals bone grafts were inserted at the osteotomy sites. A jaw opening reflex could be evoked by stimulation of 9 of the 12 denervated canine teeth by 9 weeks after the osteotomy. 12 weeks after the operation, recordings were made from the denervated teeth, the inferior alveolar nerve central to the osteotomy, and from nerves supplying adjacent tissues. The results were compared with those of previous experiments in which the anterior segment was not repositioned. Regenerating inferior alveolar nerve fibres re-innervated 18 of the 24 teeth denervated by osteotomy without bone grafting and 21 of the 24 teeth denervated by osteotomy with bone grafting. These fibres were few in number and had decreased conduction velocities. Pulpal fibres were also present in the ipsilateral mental and lingual nerves and the contralateral inferior alveolar, mental and lingual nerves. There was very little difference in the reinnervation of the teeth after osteotomy without repositioning the segment, after repositioning the segment without bone grafting or after repositioning with bone grafting.

A trial study was conducted comparing the standard "four view" mandibular series and pantomography for th evaluation of mandibular trauma. During the six-month trial period a series of 17 patients with a total of 24 mandibular fractures was compiled. The pantomographs were more easily interpreted than the standard views because overlapping structures were blurred and spatial orientation was clear. In eight of the 17 patients the fractures were more clearly visualized by pantomography. Because the entire mandibule was seen so well on the pantomographs, no special views were required. Eleven patients had single fractures, which are in fact quite common.

A REVIEW of the opinions expressed during the last fifty to eighty years concerning the nature and treatment of distoclusion will lead one to the conclusion that these opinions have been subject to constant change and that purely mechanical considerations regarding the form and manufacture of appliances have carried more weight than differential diagnosis or pathogenic knowledge. I will not go into the details of this repeated change in suggestions for treatment, but I would like to point out that from an exchange of correspondence between Angle and Oppenheim2 in 1929, which was published in American and German professional journals, it becomes evident that during the later years of his life Angle, too, was convinced of the need to classify distoclusion cases according to their various characteristics in order to obtain a, clearer idea of the type of treatment that should be employed. In other words, Angle also required a differential diagnostic examination. The method of treatment must be correlated to the result of this examination, which can be carried out by studying the relationship between the face and the jaws by means of photographs or teleradiographs. If we consider the various methods of t,reatment, it can be said that, on the whole, with the methods which have been in use up to now, alveolar movement of the teeth to correct occlusal anomalies was generally considered a more reliable way to obtain a durable result than movement of the entire mandible. Kingsley ‘sz8 method of “jumping the bite” proved to be reliable only in distoclusion cases which were not too pronounced and which did not exceed onehalf of one premolar in breadth. All other methods relying on the aid of an extraoral anchorage (headgear) or inter-maxillary elastics compensated for the occlusal anomaly chiefly through alveolar movements of the teeth. With these methods the movements are usually distributed between both dental arches, with a distal movement of the upper teeth and a corresponding alveolar mesial movement of the lower teeth. Functional orthopedics (1989) brought into the treatment of distoclusion a new development which must be considered extremely valuable. In this

Because most radiologists have had little experience with mandibular injuries, it is imperative, in cases of suspected fracture, that the roentgenographic examination of the mandible provides a clear demonstration of the entire mandible. Visualization of the condylar process is particularly important, since a poorly functioning temporomandibular joint is the usual result of an undiagnosed and hence untreated fracture. Numerous recent standard radiography textbooks do not mention the Chamberlain-Towne projection among the views for visualizing the mandible, 9, 14 However, this projection offers a very effective way of demonstrating the condylar region and the temporomandibular joint proper, supplementing the usual posteroanterior and oblique views of a routine mandible examination. Laminagraphy is helpful in certain cases, but with the inclusion of a Chamberlain-Towne projection in the routine examination it has usually not been necessary.

The reason for operating on patients with mandibular prognathism is to improve the facial appearance and the functional efficiency of the jaws. In edentulous patients the operation is justifiable in order to improve the relation between the upper and lower alveolar processes, thus making it possible to construct more efficient and better-fitting dentures. In edentulous patients the methods of immobilization of the jaws and postoperative care become more difficult unless adequate splints are made prior to operation. Preference is given to cutting through the ascending rami and pushing back the entire mandible to its new position. The main reason for this procedure is that it gives greater masticating surfaces since no teeth have to be sacrificed. The operative procedure described in this paper provides for greater surface contact of the fragments, which prevents nonunion.

This paper has dealt with the use of occipital force for the correction of the anteroposterior malrelationship of Class II, Division 1 malocclusion. Six treated cases of Class II, Division 1 were reported. At no time has mandibular anchorage with Class II intermaxillary elastics been used during active treatment. The correction of the anteroposterior malrelationship of the dental arches was accomplished by means of occipital force applied directly to the maxillary arch. Of the six cases presented, three were treated in the mixed dentition and three in the permanent dentition. An appraisal of the results showed: (1) In all of the cases the maxillary arch was moved posteriorly except the one in which the occipital force was applied in the intercanine area. (2) This posterior movement of the maxillary arch brought about a correct occlusal relationship between the maxillary and mandibular teeth without any expansion in the dental arches except in the one case in which the occipital force was applied in the intercanine area. (3) The marked improvement in facial balance that resulted from this method of treatment seems to have been due to a readjustment of the various component parts of the dentofacial complex. (4) Several factors may be operative either individually or jointly to produce this change in the dentofacial complex. In some cases the posterior movement of the maxillary arch produced a compensatory adjustment of the surrounding parts to the mandible. In other cases, there was little posterior movement of the maxillary arch. The entire change was due to a repositioning of the entire mandible to the changed occlusal plane of the maxillary arch. Again in other cases the corrected occlusion and facial change was the result of a combined posterior movement of the maxillary arch and a repositioning of the mandible. Rotations of the entire mandible were not unusual. In closing, I wish to emphasize that the application of occipital force as presented in this paper was designed to test the efficacy of this force and to evaluate the changes produced by it in the dentofacial complex. This made it essential to omit the use of mandibular appliances wherever feasible. In my usual method of treatment of Class II, Division 1, while occipital force replaces intermaxillary force for the correction of the anteroposterior malrelationship of the dental arches, a mandibular appliance is part of the assemblage.

A simple procedure for examining roentgenographically the entire mandible and the maxilla, with the exception of the midline area, has been explained. Several illustrations have been included for purposes of clarification.

• The management of osteoradionecrosis of the mandible remains controversial. Involvement of large areas of the mandible or the entire mandible with osteoradionecrosis may result in severe functional disability and cosmetic deformity. Pain, trismus, difficulty with speech and eating, and a malodorous wound are all problems that must be corrected. Local forms of therapy may be inadequate in the treatment of extensive osteoradionecrosis, and more aggressive surgical management is required. The extent of surgical intervention depends on the individual case. However, preservation of function and avoidance of disfigurement are important goals in the treatment plan. From both a functional and cosmetic standpoint, surgical management can be effective in achieving satisfactory rehabilitation goals. ( Arch Otolaryngol 1982;108:179-183)

The total rehabilitation of the patient with loss of the mandible remains one of the most difficult reconstructive problems. This is especially true where the bony loss is massive and there are unfavorable local soft tissue circumstances resulting from either radiation or scarring. The ideal solution would allow reconstitution of the entire mandible, providing osseous union even in a scarred tissue bed. Having created a semblance of normal mandibular anatomy, it would allow for rehabilitation of speech, swallowing, and mastication. Ideally, the surgical procedure would have a low rate of failure and would result in minimal donor site deformity. Alloplastic implants, homologous bone grafts, and autologous bone grafts have limited application in these cases. Microvascular free tissue transfers of bone and soft tissue have broadened the horizons of reconstruction, but these techniques are limited primarily to unilateral or modest bilateral problems, and substantial donor site deformity is associated with many of them. There is also significant risk of failure with microvascular techniques, especially when the recipient site is affected by previous radiation or scarring.