Mandibular Process Research Articles

Mesenchymal fibroblast growth factor receptor signaling regulates palatal shelf elevation during secondary palate formation.

Palatal shelf elevation is an essential morphogenetic process during secondary palate closure and failure or delay of palatal shelf elevation is a common cause of cleft palate, one of the most common birth defects in humans. Here, we studied the role of mesenchymal fibroblast growth factor receptor (FGFR) signaling during palate development by conditional inactivation of Fgfrs using a mesenchyme-specific Dermo1-Cre driver. We showed that Fgfr1 is expressed throughout the palatal mesenchyme and Fgfr2 is expressed in the medial aspect of the posterior palatal mesenchyme overlapping with Fgfr1. Mesenchyme-specific disruption of Fgfr1 and Fgfr2 affected palatal shelf elevation and resulted in cleft palate. We further showed that both Fgfr1 and Fgfr2 are expressed in mesenchymal tissues of the mandibular process but display distinct expression patterns. Loss of mesenchymal FGFR signaling reduced mandibular ossification and lower jaw growth resulting in abnormal tongue insertion in the oral-nasal cavity. We propose a model to explain how redundant Fgfr1 and Fgfr2 expression in the palatal and mandibular mesenchyme regulates shelf medial wall protrusion and growth of the mandible to coordinate the craniofacial tissue movements that are required for palatal shelf elevation.

Closed versus open treatment of mandibular condylar process fractures: A meta-analysis of retrospective and prospective studies.

The treatment of fractures of the mandibular process remains controversial, although there is a trend towards open reduction and internal fixation. This study compared open and closed treatments and assessed the results with a meta-analysis. A literature search of PubMed found eight studies that met the search criteria and were included in the meta-analysis. The studies increasingly suggest better results for open treatment, in terms of mouth opening, protrusion, laterotrusion, pain, and malocclusion. In the meta-analysis, the outcome was significantly better for laterotrusion and protrusion in patients treated by open reduction and internal fixation. Due to the different study protocols and lack of information on classification, follow-up time, and inclusion criteria, comparison of the studies remains difficult and further prospective, randomized studies should examine these issues.

Giant Cell Tumor of the Skull: Review of the Literature

Giant cell tumors (GCTs) are rare in the skull. The present report describes a case with a primary GCT located in the temporal bone and reviews the relevant literature. We also propose a treatment strategy for GCT of the skull. A 41-year-old man presented with headache and auditory disturbance. Radiologic images showed a lytic expansive extradural lesion originating primarily from the right temporal bone and expanding into the middle cranial fossa and the infratemporal fossa. A biopsy specimen of the lesion was obtained from the external auditory meatus. Total removal was performed with temporal craniectomy, mandibular condylar process removal, tympanoplasty, and mastoidectomy. The rate of recurrence of GCTs is related to complete resection and location of the GCT rather than to the degree of invasiveness. Some of the mononuclear cells and stromal cells in GCT express receptor activator of nuclear factor κ-β ligand (RANKL). Because inhibition of RANKL and bisphosphonate therapy might eliminate giant cells, this approach might be useful for recurrent or unresectable GCTs of the skull. Preoperative diagnosis by biopsy is important in determining the therapeutic strategy of GCTs. Complete resection is important to reduce the recurrence rate of GCTs in the skull.

The Evolution and Development of The Mandibular Coronoid Process in Mammals

The coronoid process of the mammalian dentary bone is an evolutionary novel structure reflecting the new role of the dentary in mammals as an attachment site for the muscles of mastication. Previous studies have shown that the size and shape of the coronoid is correlated to the bite force required by the adult animal, and is dependent upon the mechanical force acting upon it during development. However little is known about the developmental programme leading to the specification of the processWe demonstrate that the paired homeobox transcription factor Pax9 is expressed in the ossifying front of the future coronoid process, and that Pax9 expressing cells contribute to the coronoid process, but not the other mandibular processes. In Pax9 mutants the coronoid is absent, however the temporalis muscle, which attaches to it, develops normally. Histological and gene expression studies indicated that the muscle attachment site remains. Loss of the coronoid is therefore driven by changes in the intrinsic patterning of the bone. In contrast other mouse mutants lacking the coronoid, such as the Tbx1 null, loss of the coronoid is a consequence of the loss of the muscle acting on the developing bone. Changes to this structure can therefore be influenced by intrinsic and extrinsic factors. The relative size of the coronoid process varies considerably across mammals, with herbivores, such as the guinea pig having a reduced or absent coronoid, while carnivores can have extremely large coronoid processes. The contribution of genes such as Pax9 and Tbx1 to changes in size of this processes on other mammals have therefore also been investigated. Our data implicates cooption of Pax9 in to the osteogenic program of the dentary enabled the development of the coronoid process, a key component in the emergence of the novel jaw.

Facial development and alterations in FGF signaling in a mouse model of Crouzon Syndrome

Mutations in FgfR2 cause several craniosynostosis syndromes, including Crouzon Syndrome (CS), but knowledge of the specific mechanisms by which FGF effects morphogenesis is lacking. The gene CRISPLD2 is associated with non-syndromic cleft lip/palate. Preliminary data indicate it is a novel intracellular target of FGF signaling and alters facial morphology and fibroblast migration rates in vitro. Using a FgfR2W290R mouse model of CS, we investigated the development of the CS facial phenotype and how FGFR2 activity and CRISPLD2 dosage affect cell responses to extracellular FGF. Embryos at stages E9.5-E13.5 were genotyped, photographed, sectioned, and/or used for mouse embryonic fibroblast (MEF) cell lines. Facial shape was quantified using 2-D geometric morphometrics. Cell proliferation and apoptosis in facial primordia were assayed. MEF responses to extracellular FGF were assessed using pMEK expression and cell migration vectors. MEFs were infected with a CRISPLD2 virus (or control) and tests were repeated. At E10.5 (N=104), homozygous mutants (-/-) were rarer than expected, suggesting early embryonic lethality, and had significantly narrower faces and asymmetrical maxillary processes. This is surprising given the wider faces observed in CS patients and previously demonstrated in a chick embryo model. Facial shapes in +/- and +/+ embryos did not differ significantly after accounting for allometry from E9.5-E13.5. Preliminary results show increased apoptosis in the maxillary and mandibular processes of -/- embryos. We are currently analyzing cell proliferation results and performing in vitro analyses. This work will provide insight on how upstream and downstream modulators of FGF signaling regulate craniofacial form.

Patterning of mammalian heterodont dentition within the upper and lower jaws.

Mammalian heterodont dentition is differentiated into incisors, canines, premolars, and molars in the mesial-distal direction, in both the upper and lower jaws. Although all the lower teeth are rooted in the mandible, the upper incisors are rooted in the premaxilla and the upper canine and the teeth behind it are in the maxilla. The present study uncovers ontogenetic backgrounds to these shared and differing mesiodistal patterns of the upper and lower dentition. To this end, we examined the dentition development of the house shrew, Suncus murinus, instead of the rodent model animals because the dentition of this primitive eutherian species includes all the tooth classes, and no toothless diastema region. In the shrew, the upper incisor-forming region extended over the medial nasal prominence and the mesial part of the maxillary prominence. Consequently, the maxillary and mandibular prominences were in a mirror-image relationship in terms of the mesiodistally differentiated tooth-forming regions and of the complementary gene expression pattern, with Bmp4 in the mesial and Fgf8 in the distal regions. This suggests shared molecular mechanisms regulating tooth class differentiation between the upper and lower jaws. However, the premaxillary bone appeared within the mesenchyme of the medial nasal prominence, but grew distally beyond the former epithelial boundary with the maxillary prominence to form, finally, the incisive (premaxillary-maxillary) suture just mesial to the canine. Therefore, the developmental locations of the upper incisors are not inconsistent with the classical osteological criterion of the upper canine by comparative odontologists.

Assessment of Volume and Height of the Coronoid Process in Patients With Different Facial Types and Skeletal Classes: A Cone-Beam Computed Tomography Study

To determine the height and volume of the mandibular coronoid process (CP) by cone-beam computed tomography (CBCT) and to identify the presence of any correlations of these measurements with age, gender, facial type, and skeletal class. The sample consisted of 132 patients from a departmental routine patient base. After CBCT, CP height was determined using OnDemand 3D software (CyberMed, Seoul, Republic of Korea), and CP volume was obtained using ITK-SNAP 3.0 software (Cognitica, Philadelphia, PA). Measurements were subjected to analysis of covariance against facial type, skeletal class, gender, and age, with a significance level of 5%. CP height and volume were similar regardless of age, facial type, and skeletal class. However, the 2 measurements were statistically different regarding gender, with larger values for men than for women. These observations suggest that gender is the only factor influencing the height and volume of the CP.

Fracture of mandibular condyle—to open or not to open: an attempt to settle the controversy

To compare the outcome of the open method versus the closed method of treatment for mandibular condylar fracture. Fifty patients with fractures of the mandibular condylar processes were evaluated. All fractures were displaced, with a degree of deviation between the condylar fragment and the ascending ramus of 10 to 45 degrees (mediolaterally). The patients were randomly divided into two groups, with group 1 receiving open reduction internal fixation and group 2 receiving closed reduction. The follow-up was done over the period of 6 months. Statistically significant improvement was seen in group 1 compared with group 2 in terms of anatomic reduction of the condyle, shortening of the ascending ramus, occlusal status, and deviation on mouth opening. A statistically significant difference was seen in the patients treated with the open method, with improved temporomandibular joint functions and fewer short- and long-term complications compared with those treated with the closed method.

Fractures of the mandibular condyle – Open versus closed – A treatment dilemma

PurposeThe aim of this prospective randomized controlled study was to evaluate the superiority of open method of treatment of mandibular condylar fracture over closed method of treatment by comparing them. Methods and patientsOut of a total of 50 randomized patients fractures of the mandibular condylar process completed the study and were evaluated. All fractures were displaced, being either angulated between 10° and 45°. The follow-up examinations 1st day, 2nd day, 1st week, 2nd week, 6th week, and 6 months following treatment included clinical evaluation of functional and subjective parameters including visual analogue scale for pain and the interincisal mouth opening, malocclusion, deviation of mouth, range of motion, radiographic measurements were done. ResultsNo significant difference was found between the two groups in the maximal interincisal opening, range of movements and TMJ pain. However statistically significant difference was seen in the anatomic reduction of condyle, shortening of ascending ramus, occlusal status and deviation on mouth opening on immediate postoperative phase. ConclusionBoth treatment options for condylar fractures of the mandible yielded acceptable results. However, a statistically significant difference was seen in the anatomic reduction of the condyle and there was no deviation on maximum mouth opening in patients treated with open reduction and internal fixation which suggests its superiority over closed method.

Peripheral osteoma of condylar neck following trauma

Osteomas are solitary, benign, slow-growing osteogenic tumors that sometimes involve the craniofacial region, such as the paranasal sinuses, temporal bone, or jaw bones. They can be classified as central and peripheral osteomas. The peripheral osteoma of the mandible is relatively uncommon. Though most of the cases involving the mandible arise from the mandibular body, angle, condyle head, or coronoid process, we report one such case unusually arising from the anterior surface of the neck of the condyle, the pterygoid fovea region. We believe it is the first recorded case of an osteoma arising from the pterygoid fovea region.

A Study of Various Forms of Mandibular Coronoid Process in Determination of Sex

The coronoid process of the mandible is gaining vital importance as a graft material in reconstructive craniomaxillofacial surgeries and as a non metric skull variant in assessment of age, sex, race and species. Hence the present study was taken to assess the different forms of the coronoid process existing in Indian adult population on both sides and to assess the feasibility of using this knowledge in identification of sex. The study includes 50 male and 50 female mandibles which were collected from various medical colleges. The various presentations of coronoid process were observed and broadly classified, on both the sides. Statistical analysis was calculated using Chi-square test. Hook shaped coronoid process was the most predominant type (61.5%) followed by triangular (14%) and rounded (12.5%) types. About 12% belonged to the miscellaneous type. Hook shape coronoid process was significantly higher in the females. The other shapes did not show any significant gender variation. From the present study it was inferred that the structural changes at the coronoid process of mandible help oneself to distinguish the gender of the individual.

両側筋突起および咬筋腱膜切除後に生じた臼歯部開咬の1例

A 45-year-old man was referred to our hospital because of limitation of mandibular movement. He was given a diagnosis of hyperplasia of the mandibular coronoid process and masticatory muscle tendonaponeurosis hyperplasia. Bilateral coronoidectomy and aponeurectomy of the masseter muscles were performed via an oral approach. Posterior open bite was noted 3 days after the operation. Magnetic resonance imaging of both temporal mandibular joints showed displacement of the left condyle as well as joint effusion at the posterosuperior joint space. A splint and pumping manipulation were applied, and the patient was given a nonsteroidal anti-inflammatory drug. The left posterior open bite nearly completely improved with no negative impact on the patient’s quality of life 1 year 9 months after the operation.

A prosthodontist can play a vital role in management team of maxillofacial fractures in young patient: A clinical report

The aim of this case report is to present the treatment method used for a 6-year-old boy patient with a history of mandibular fracture due to fall from rooftop 2 days back. Treatment principles of this patient differ from that of an adult due to concerns regarding mandibular growth processes and dentition development. The goal of this fracture treatment is to restore the underlying bony architecture to its preinjury position in a stable fashion as noninvasively as possible and with minimal residual esthetic and functional impairment.

Mandibular coronoid fractures, how rare?

To study the rarity of mandibular coronoid process fractures and treatment strategies based on the displacement of these fractures. A retrospective study of 11 cases of coronoid process fractures among 307 treated cases from 2008 to 2013 was conducted. Six patients were treated conservatively and 5 underwent ORIF with associated fractures. A statistical analysis of the data obtained after subjective and objective evaluation was done. The incidence of coronoid process fractures was 3.58% of all mandibular fractures analyzed. There was no statistically significant difference found between two treatment modalities, but differences in maximum interincisal opening (MIO) and pain in the postoperative period were significant. We recommend that linear coronoid fractures with minimal displacement can be managed with conservative treatment. For patients with significant displacement of coronoid process, limited mouth opening or concomitant mid-face or lower-face fractures, rigid internal fixation is recommended.

Segmented therapies in orthodontics

Segmental osteotomies offer a versatile option for conventional orthodontic surgery. Basically any single tooth or groups of teeth can be repositioned surgically. Segmental osteotomies have been used to correct bimaxillary protrusion, anterior open bite, transverse maxillary deficiency, distal position of mandibular dentoalveolar process, mandibular anterior crowding and in cleft care for various purposes. Advantages of using segmental osteotomies include shorter treatment time then moving the teeth orthodontically. The technique makes treatment possible also in cases with reduced anchorage, since surgical repositioning of segments does not place demand in anchorage. There is generally accepted rule concerning segmental osteotomies: The distance a dentoalveolar segment can be moved surgically is not more than can be done orthodontically. That means that the tooth movement limits presented in the envelope of discrepancy (Proffit 1997) apply equally to dentoalveolar segmental osteotomies and orthodontics. The main limiting factor is the resistance of soft tissues. Distraction osteogenesis is a treatment method that not only expands bony structures but also initiates a sequence of adaptive soft tissues changes termed distraction histogenesis. Then a question can be made if segment reposition by distraction osteogenesis would allow larger movements than orthodontics only, i.e. beyond orthodontic limits. From the orthodontic point of view it must be realized that no pre-surgical coordination of the entire dental arches like in conventional orthognathic surgery is made, but dental arches are aligned in segments. Preoperative orthodontics often includes preparation of spaces for osteotomies and postoperative uprighting of the tipped teeth. Because of the change in the traditional orthognathic surgery close collaboration between surgeon and orthodontist is extremely important already in the planning phase of the treatment utilizing segmented therapy.

Systematic status of the caridean families Gnathophyllidae Dana and Hymenoceridae Ortmann (Crustacea: Decapoda): a further examination based on molecular and morphological data

The four palaemonoid (sub)families Anchistioididae, Gnathophyllidae, Hymenoceridae, and Pontoniinae are similar in morphology, and all live in marine habitats. Their systematic relationships are controversial. In this study, we used sequences from a mitochondrial ribosomal gene (16S rRNA) and three nuclear genes (H3, NaK, and enolase) to explore the phylogenetic relationships of these four taxa. Our tree based on 43 species belonging to 28 genera shows that Gnathophyllidae and Hymenoceridae are nested within Pontoniinae. This result is consistent with evidence from larval morphology. The defining characteristics of Gnathophyllidae and Hymenoceridae, a vestigial or missing mandibular incisor process and a broadened third maxilliped, can also be found in Pontoniinae; conversely, on the basis of published species descriptions, gnathophyllids and hymenocerids meet most of the defining characteristics of Pontoniinae. The peculiar form of the third maxilliped in gnathophyllids and hymenocerids might be the result of adaptive evolution, as these particular features are also present in pontoniines. According to our phylogenetic tree, Anchistioididae are more remote from Pontoniinae, which is consistent with the distinct morphological differences in the pleopods. The pontoniine genera analyzed (together with Gnathophyllidae and Hymenoceridae) are divided into two clades. The members of Clade I exhibit primordial characteristics similar to those of the Palaemoninae, and might be direct descendants of the ancestor of the Pontoniinae; members of Clade II are more specialized.

Histopathological evaluation of the effects of variable extraoral dry times and enamel matrix proteins (enamel matrix derivatives) application on replanted dogs' teeth.

The extra-alveolar dry period and storage medium in which the tooth was kept prior to replantation remain the critical factors affecting the survival and regeneration of the damaged periodontium. When the replantation is delayed, replacement root resorption is the most common complication following replantation of an avulsed tooth. The aim of this histological study was to evaluate the periodontal healing of replanted dogs' teeth after 20 min (short) and 60 min (long) extraoral dry time with and without the application of enamel matrix proteins. Eighty mature premolar roots (40 teeth) maxillary and mandibular premolars were extracted, the root canals were accessed, instrumented, and filled using a lateral condensation technique, and the access cavity was restored with amalgam. Each root was randomly assigned to one of experimental groups: Groups I and II: Roots were replanted after an extraoral dry time of 20 min. In group II, Emdogain(®) (Biora, Malmo, Sweden) was applied directly to the external root surface with complete coverage. Groups III and IV: Roots were replanted after an extraoral dry time of 60 min. In group IV, Emdogain(®) was applied to the whole external root surface before replantation. Roots that replanted within a total extraoral dry time of 10 min were used as negative controls, while those replanted after 90 min of extraoral dry time were assigned as positive controls. After 4 months, the dogs were euthanized, and the maxillary and mandibular processes were processed for histology and microscopically evaluated. Statistical analysis showed no significant differences (P = 0.1075) among the experimental groups. The results of this study show that 20 min of extraoral dry time is as detrimental to the PDL cells as 60 or 90 min of extraoral dry time, with avulsed dogs' teeth, even when replanted with an inductive material such as EMD. This study provides strong evidence in relation to the threshold of the extraoral dry time of avulsed teeth, suggesting that the extraoral dry time threshold of PDL cell viability is significantly less than that which current guidelines promote.

Functional analysis of SPECC1L in craniofacial development and oblique facial cleft pathogenesis.

Oblique facial clefts, also known as Tessier clefts, are severe orofacial clefts, the genetic basis of which is poorly understood. Human genetics studies revealed that disruption in SPECC1L resulted in oblique facial clefts, demonstrating that oblique facial cleft malformation has a genetic basis. An important step toward innovation in treatment of oblique facial clefts would be improved understanding of its genetic pathogenesis. The authors exploit the zebrafish model to elucidate the function of SPECC1L by studying its homolog, specc1lb. Gene and protein expression analysis was carried out by reverse-transcriptase polymerase chain reaction and immunohistochemistry staining. Morpholino knockdown, mRNA rescue, lineage tracing and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling assays were performed for functional analysis. Expression of specc1lb was detected in epithelia juxtaposed to chondrocytes. Knockdown of specc1lb resulted in bilateral clefts between median and lateral elements of the ethmoid plate, structures analogous to the frontonasal process and the paired maxillary processes. Lineage tracing analysis revealed that cranial neural crest cells contributing to the frontonasal prominence failed to integrate with the maxillary prominence populations. Cells contributing to lower jaw structures were able to migrate to their destined pharyngeal segment but failed to converge to form mandibular elements. These results demonstrate that specc1lb is required for integration of frontonasal and maxillary elements and convergence of mandibular prominences. The authors confirm the role of SPECC1L in orofacial cleft pathogenesis in the first animal model of Tessier cleft, providing morphogenetic insight into the mechanisms of normal craniofacial development and oblique facial cleft pathogenesis.

Diagnostic model of anterior open bite--a new way to predict skeletal type: a cross-sectional study.

The aim of this study was to determine a differential diagnostic model for anterior open bite (AOB) in children in order to predict evolution with growth in cases of skeletal or dysfunctional dysplasia. The sample was composed of 128 subjects divided into 2 groups according to overbite values: a control group with normal occlusion and 2.5 ± 1mm overbite, and an AOB group with a negative overbite. Measurements of hyoid bone position, gonial angle, SN/Go-Gn, FMA, height of alveolar processes, upper lip height, height of the anterior nasal spine to stomion superior, upper incisor and menton, antegonial notch, symphysis anatomy, condyle anatomy, convexity, facial axis, lower oropharyngeal area and curve of Spee were obtained for all subjects, based on lateral cephalometric radiographs and lateral photos. All data were analyzed, and multivariate logistic regression was applied. The area under the receiver operating characteristic (ROC) curve was calculated for the models obtained by logistic regression, in order to evaluate them. Statistical analysis was performed in IBM(®) SPSS(®) Statistics version 21.0. The results demonstrated that the AOB model was capable of predicting skeletal anterior open bite with an accuracy of 93%. The seven variables selected were: lower face height (LFH), height of mandibular alveolar process, antegonial notch, symphysis direction, symphysis thickness, gonial angle and facial axis. Measurements of facial morphology made it possible to construct a model able to differentiate, with a small margin of error, between the two distinct forms of AOB: skeletal and dysfunctional.

One-Stage Treatment to Osteochondroma of the Coronoid Process and Secondary Facial Asymmetry With Coronoidectomy and Reduction Malarplasty: A Case Report and Literature Review

This study summarizes the literature concerning osteochondroma of the mandibular coronoid process and presents a case of 1-stage treatment for this condition and concomitant facial asymmetry. A 20-year-old man presented with osteochondroma of the mandibular coronoid process. Radiologic images showed a mushroom-shaped coronoid growth inside the zygomatic arch with outward expansion. Coronoidectomy and reduction malarplasty were performed in 1 stage. The literature on osteochondroma of the mandibular coronoid process since 1943 was reviewed concerning etiology, pathogenesis, clinical characteristics, diagnosis, and treatment. At 20-month follow-up, the patient achieved markedly improved joint function and a symmetric facial appearance after excision of the osteochondroma. Coronoidectomy combined with simultaneous reduction malarplasty could be an alternative and promising method to treat osteochondroma of the coronoid process with secondary facial asymmetry.