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Unilateral posterior crossbite, one of the most frequent malocclusions, is often associated with functional lateral shift of the mandible. Although the effects of functional lateral shift on the mandible and temporomandibular joint have been examined in various animal experiments, cranial and maxillary changes have received less attention.The aim of this study was to investigate the effects of functional lateral shift on the craniofacial complex in growing rats.Eighty 5-week-old male Sprague-Dawley rats were randomly divided into an experimental group (n = 40), which received an oblique guide appliance that shifted the mandible to the left during closure, and a control group (n = 40). The rats were scanned by cone-beam computed tomography at 3 days and 1, 2, 4 and 8 weeks. The dimensions of the mandibular bone, condyle, maxilla and cranium were measured.The mandibles of rats in the experimental group were smaller than those of the rats in the control group and were asymmetrical. The condyles of the rats in the experimental group were thinner than those of the control rats. The condylar length on the ipsilateral side was shorter and wider than that on the contralateral side from 4 to 8 weeks. No significant differences in cranial length or height were observed between the experimental and control groups. The height of the upper first molar and alveolar bone on the contralateral side was significantly smaller than that on the ipsilateral side and in the controls from 4 to 8 weeks.Functional shift in the mandible produces morphological asymmetries in the mandible and maxillary region and may cause bilateral condylar degenerative changes.

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. The recent review article by Zonnenberg, Türp and Greene ‘Centric relation critically revisited – What are the clinical implications’? opens an important debate by addressing topics of central relevance in Dentistry, namely the relationship between occlusion and the condyle-to-glenoid-fossa position, and the need for diagnostic assessment and therapeutic alteration of the condylar position in orthodontic patients. Zonnenberg, Türp and Greene concluded that the mandibular condyle is correctly situated in most orthodontic patients. Thus, in their view, orthodontists can disregard this aspect during treatment, and rely on the plastic properties of the masticatory supporting structures, while aiming at finishing the cases in a good occlusal relationship. We think that this approach fails to consider that biological variation of the stomatognathic structures can also be pathological and that, as dental occlusion determines condylar relative position within the glenoid fossa, changes in the occlusion are likely to alter the original condylar-to-glenoid-fossa relation. Hence, we claim that whenever the occlusal relationship must be changed, the clinician should carefully monitor the condyle position and the mandibular function to prevent possible iatrogenic effects. To advance the discourse on the topic, we invite Zonnenberg, Türp and Greene to clarify their definition of ‘average patient’ and their interpretation of ‘full-mouth orthodontic and orthognathic treatment’, their understanding of ‘biologically acceptable condylar relationship’, their justification of maximum intercuspation as reference position, the extent to which they think it is safe to rely on the TMJ resilience, and finally their alternative to centric relation in the treatment of patients needing condylar repositioning. info:eu-repo/semantics/publishedVersion

Botulinum toxin type A (BoNTA) injection into the masticatory muscles has been widely used to treat a number of painful and nonpainful conditions; however, no systematic reviews have been performed on the long-term effect to the mandibular bone.Our systematic review aimed to evaluate the impact of botulinum toxin injection into the masticatory muscles on mandibular bone based.PubMed, Embase, Ovid, CINAHL and Web of Science were searched for human studies assessing mandibular bone after injection of BoNTA using computed tomography (CT) and cone beam CT (CBCT).Seven studies were eligible for review; five reported significant bony changes to one or more areas of the mandible. Most frequently affected were the condylar head, coronoid process and ramus. The most frequent changes were decreased bone volume, cortical thickness and cortical and trabecular density.This is the first systematic review to examine an association between BoNTA injection into the masticatory muscles and mandibular bone quality. Data were analysed from a limited number of studies with a small sample size, and the quality of the included studies was very low. While the majority of available evidence suggests BoNTA injection results in bony change, further study is required to confirm a dose-dependence effect and the impact of gender and age. High-quality trials should utilise a combination of software analysis and radiologist review, with longer-term follow-up to monitor for persistence of bony effect and clinical significance.

OBJECTIVE Certain malocclusions or unilateral tooth loss can lead to asymmetric functional load of the two mandibular sides during mastication and induce skeletal asymmetries to the condylar process of growing individuals. However, in adults, asymmetric function may have a different impact. The aim of the present study was to investigate three-dimensionally the effects of unilateral masticatory function on the condylar process morphology in growing and adult rats and the adaptive processes to differential condylar loading. MATERIALS AND METHODS Fifty-six growing and adult Wistar rats aged 4 and 26 weeks respectively were obtained. The maxillary right molars of the experimental animals were extracted and all animals were followed for 12 weeks. Three-dimensional images were obtained by an in-vivo microcomputed tomography (micro-CT) examination. The following measurements were studied: condylar process height, condylar base width, and condylar cross-sectional surface. RESULTS While no differences were found with regards to condylar process height and base width, the cross-section of the condyle on the extraction side did not increase during growth in the young rats. No such differences were found in adults. Young rats had statistically significantly shorter condylar height, base width and cross-sectional surface than the adult rats and showed significant growth of these structures during the experimental period. CONCLUSION Condylar height and base width growth are not hindered by reduced occlusal function, contrary to the average cross-sectional surface, which implies that the condyle form of growing individuals becomes thinner while maintaining its length, in the absence of occlusal stimuli. The condyle of adult rats with extractions is less affected by occlusion changes.

Mucopolysaccharidoses (MPS) are a group of rare metabolic diseases characterized by a wide spectrum of symptoms including progressive condylar resorption.The aim of this study was to quantify the severity of condylar involvement in MPS I individuals in comparison with a group of non-MPS individuals and to describe how condylar changes may vary among the different types of MPS.Fifty panoramic radiographs of MPS patients (13.4 ± 6.2 years) with MPS I (n = 14), MPS II (n = 2), MPS IV (n = 8) and MPS VI (n = 2) were compared with forty panoramic radiographs of non-MPS individuals. The severity of condylar resorption was evaluated using a qualitative score (grades 0-3) and using the ratio of condylar height to ramus height (CH: RH).All MPS I and VI individuals showed pronounced bilateral degenerative condylar resorption. In contrast, individuals with MPS II and IV exhibited heterogeneous findings. The quantification of condylar height to ramus height revealed that CH: RH was significantly decreased in MPS I as compared to that of non-MPS individuals (P .001). In contrast, the CH: RH ratios of MPS II and IV showed great variability.Mucopolysaccharidoses subtypes differ with regard to the severity of condylar resorption.

Condylar fractures account for a large proportion (20% to 52%) of mandibular injuries. The goal of treating these fractures is to restore the occlusion, thereby re-establishing the masticatory function as close as possible to the patient's pre-trauma state. The aim of this study was to compare the bite forces following unilateral condylar fractures treated by open reduction and internal fixation (ORIF) with those managed by the closed method.Patients with unilateral mandibular condylar fractures were divided into two groups (n = 20) using a simple randomization method. Patients in group I were treated by open reduction and internal fixation (ORIF) using titanium miniplates and screws. Patients in group II were treated by the closed method with inter-maxillary fixation. Patients in both groups were evaluated pre-operatively and then post-operatively at one week, one month and three months for maximum bite force achieved at the central incisor, premolar and molar regions.Pre-operative bite forces on the unaffected site were significantly higher than the affected site in both groups, whereas no significant difference was observed in bite forces between the unaffected and affected sites in both groups post-operatively. The bite forces achieved at both the unaffected and affected sites in the ORIF group were significantly higher than in the closed group.Maximum bite forces differed significantly when the treatment was done with the open method, and the patients treated with the open method needed less time to achieve the maximum bite forces, thereby making an earlier return to function.

BACKGROUND The current diagnostic criteria for temporomandibular disorders (TMD) do not require imaging for the diagnosis of degenerative joint disease (DJD) of the temporomandibular joint (TMJ) condyle, and there is a lack of data investigating the effectiveness of imaging modalities in predicting long-term TMJ DJD prognosis. OBJECTIVES To verify the association between initial bone scintigraphy results and long-term DJD bone changes occurring in the TMJ condyle on cone beam computed tomography (CBCT). METHODS Initial bone scintigraphy, panoramic radiography and CBCT results were analysed in relation to long-term (12 months) TMJ DJD bone change on CBCTs in 55 TMD patients (110 joints). Clinical and radiographic indices were statistically analysed among three groups (improved, no change, and worsened) based on long-term TMJ DJD prognosis calculated by destructive change index (DCI). RESULTS Neither the uptake ratio nor visual assessment results from initial bone scintigraphy showed a significant difference according to long-term condylar bone change groups. The cut-off value of bone scintigraphy uptake ratio was 2.53 for long-term worsening of TMJ DJD. Worsening of TMJ DJD was significantly associated with the diagnosis based on panoramic radiography (p = .011) and CBCT (p

Objective Incisors tubed prosthesis with bilateral anterior elevation (BAE) relation had been reported to stimulate the proliferative response in the mandibular condylar cartilage of mice, thus the prosthetic occlusion elevation had been proposed to treat cartilage degeneration. Currently, we aimed to detect the long-term effect of BAE on temporomandibular joints (TMJs). Materials and methods Twelve 6-week-old female mice were assigned to age-matched control and BAE groups (n = 6). Micro-CT images and the macro- and micro-morphology of the mandibular condyles were analyzed at 29 weeks. Results Compared with the age-matched controls, in BAE group, there were loss of subchondral cortical bone, and heavy loss of the subchondral trabecular bone at the superior sites of the TMJ condyles, but hyperostosis at the inferior sites as revealed by micro-CT images and histological slices. In BAE group, cartilage thickness and matrix area were increased with up-regulated expression of type II , type X collagen and Ki67, but the expression of cleaved caspase-3 was down-regulated (all, P Conclusion In addition to cartilage thickening, long-term BAE induces loss of the subchondral cortical bone and heavy loss of the underneath subchondral trabecular bone, but hyperostosis further underneath. Using BAE as a treatment remains double-edged.

Bone modelling evaluation is important for monitoring idiopathic condylar resorption (ICR) progress. To compare condylar modelling in ICR patients treated with or without stabilisation splints (SSs). Eighty-four condyles from 84 ICR patients were studied: 42 received SS therapy (SS group); 42 received conventional therapy (control group). Cone-beam computed tomography images at diagnosis (T0) and after at least 6 months (T1) were used for three-dimensional reconstruction. Volume differences between T0 and T1 (δV) were used to evaluate the amount of modelling. Percentage of growth area (PCT) was used to assess the condylar surface growth tendency. No significant change in condylar volume was found in the SS group, whereas that in the control group was significantly decreased at T1 (P

Objective The lateral pterygoid is vital in coordinating multidimensional jaw movements. Since a vector in three‐dimensional (3D) space is defined by two 3D points, the role of the lateral pterygoid in 3D jaw movements is defined by its origin and insertion. Reportedly, the lateral pterygoid is inserted into not only the pterygoid fovea but also into the medial surface of the condylar process. The objective was to investigate the morphological features of the region of the lateral pterygoid that inserted into the medial surface of the condylar process. Material and Methods Ten head halves of seven cadaveric donors were analyzed. In all specimens, the insertion area on the medial surface of the condylar process was measured based on microcomputed tomography images. Muscle fibers were separated into ≥50 small bundles, and positional relationships between the origins and insertions were investigated. Results Overall, 28.8 ± 5.0% of the insertion area of the lateral pterygoid was situated on the medial surface of the condylar process. Moreover, muscle fiber arrangement revealed that origins of the muscle bundles inserting into the medial surface in seven specimens posteriorly occupied the lateral plate of the pterygoid process longitudinally, whereas those in three specimens mainly occupied the posteroinferior portion. Conclusions Muscle bundle inserting on the medial surface of the condylar process had a broad insertion area and a distinct origin on the posterior region of the lateral plate of the pterygoid process. This muscle bundle could act as one of the significant subunits within the lateral pterygoid. Therefore, anatomical coordination mechanisms underlying jaw movement cannot be elucidated without considering this subunit.

Mandibular condylar cartilage is a representative secondary cartilage, differing from primary cartilage in various ways. Syndecan is a cell-surface heparan sulfate proteoglycan and speculated to be involved in chondrogenesis and osteogenesis. This study aimed to investigate the expression patterns of the syndecan family in the developing mouse mandibular condylar cartilage. At embryonic day (E)13.0 and E14.0, syndecan-1 and -2 mRNAs were expressed in the mesenchymal cell condensation of the condylar anlage. When condylar cartilage was formed at E15.0, syndecan-1 mRNA was expressed in the embryonic zone, wherein the mesenchymal cell condensation is located. Syndecan-2 mRNA was mainly expressed in the perichondrium. At E16.0, syndecan-1 was expressed from fibrous to flattened cell zones and syndecans-2 was expressed in the lower hypertrophic cell zone. Syndecan-3 mRNA was expressed in the condylar anlage at E13.0 and E13.5 but was not expressed in the condylar cartilage at E15.0. It was later expressed in the lower hypertrophic cell zone at E16.0. Syndecan-4 mRNA was expressed in the condylar anlage at E14.0 and the condylar cartilage at E15.0 and E16.0. These findings indicated that syndecans-1 and -2 could be involved in the formation from mesenchymal cell condensation to condylar cartilage. The different expression patterns of the syndecan family in the condylar and limb bud cartilage suggest the functional heterogeneity of chondrocytes in the primary and secondary cartilage.

Trichorhinophalangeal syndrome type 1 (TRPS1; Online Mendelian Inheritance in Man #190350) is an autosomal dominant disorder caused by mutations in TRPS1. We report a Thai male with TRPS1 who carried a c.1842C>T (p.Arg615Ter) mutation. He had 15 supernumerary teeth, double mental foramina, hypoplastic mandibular condyles with slender condylar necks and unique ultrastructural hair findings. Body hair was absent. The hair in the area of a congenital melanocytic nevus had a greater number of hair cuticles than normal. Occipital hair had abnormal hair follicles and cuticles. The scale edges of the hair cuticles were detached and rolled up. Hypoplastic mandibular condyles with slender condylar necks, double mental foramina and the rolled up edges of hair cuticles have not been reported in patients with TRPS1.

Temporomandibular joint disc displacement is common in the world's population and could be associated with bone and functional characteristics of the temporomandibular joint. The aim of these study was to analyse the association between temporomandibular joint disc position evaluated by magnetic resonance imaging (MRI) and the inclination of the mandibular condyle evaluated by computed tomography (CT). One hundred and seventy temporomandibular joints (TMJ) were retrospectively analysed. The temporomandibular disc position was evaluated by MRI and classified into three types: normal (N), disc displacement with reduction (DDWR) and disc displacement without reduction (DDWoR). The mandibular condyle measurements evaluated by CT included horizontal, sagittal and coronal inclination. ANOVA followed by post hoc Tukey's test was used to evaluate the interaction between condylar inclination and disc position. There was an association between disc position and the horizontal and sagittal condylar inclination (P .05). There are statistically significant differences in the mean of horizontal and sagittal inclination of the mandibular condyle between the DDWoR and the other disc positions (P = .002 and P = .004). Disc position was not statistical associated with coronal inclination of condyle (P .05). These results indicate that the inclination of the mandibular condyle may be different in TMJ with various disc position. A more medial horizontal inclination and a more posterior sagittal inclination of the mandibular condyle are associated with DDWoR.

The articulator is a prerequisite device for the analysis of occlusion and prosthodontic treatment, and it is required to simulate patient jaw movements. This article describes the technique to obtain sagittal condylar inclination (SCI) using cone beam computed tomography (CBCT) data and intraoral scan of the protrusive interocclusal position. The SCI can be used on a virtual articulator in a computer-aided design software, and it can assist in the fabrication of prosthesis which is harmonious with the mandibular movement of individual patient.

Objectives To detect whether early growth response 1 (EGR1) in peripheral blood leucocytes (PBLs) indicates temporomandibular joint (TMJ) osteoarthritis (OA) lesions. Materials and methods Egr1 mRNA expression levels in PBLs were detected in eight malocclusion patients without temporomandibular disorder (TMD) signs and 16 malocclusion patients with clinical TMD signs with (eight) or without (eight) imaging signs of TMJ OA. Twelve 6-week-old rats were randomized to a control group and a unilateral anterior crossbite (UAC) group and were sampled at 4 weeks. The Egr1 mRNA expression levels in PBLs and protein expression levels in different orofacial tissues were measured. Results Patients with TMD signs with/without TMJ OA diagnosis showed lower Egr1 mRNA expression levels in PBLs than patients without TMD signs. The lower Egr1 mRNA expression was also found in the PBLs of UAC rats, which were induced to exhibit early histo-morphological signs of TMJ OA lesions. In subchondral bone of UAC rats, EGR1 protein expression was decreased, co-localization of EGR1 with osterix or dentin matrix protein-1 was identified, and the number of EGR1 and osterix double-positive cells was reduced (all p Conclusion Egr1 reduction in PBLs potentially indicates subchondral bone OA lesions at an early stage.

OBJECTIVE We aimed to develop a mouse model predominating in a proliferative response in the articular cartilage of the temporomandibular joints. MATERIALS AND METHODS Bilateral anterior elevation of occlusion was developed by installing metal tubes onto the incisors of mice with edge-to-edge relation to prevent tooth wear, leading to an increase in the vertical height of the dental occlusion with time. Morphological changes and expression changes in Cyclin D1, Aggrecan, and type II and type X collagen in the mandibular condylar cartilage were detected. In addition, cells were isolated from the mandibular condylar cartilage and exposed to cyclic tensile strain (CTS). RESULTS Compared with age-matched controls, the tooth length was longer at 3 weeks, 7 weeks, and 11 weeks in BAE mice (p

Objective Anterior disk displacement (ADD) is a most common subtype of temporomandibular disorders (TMD), which is promoted by chondrocytes apoptosis. However, the signaling pathways that trigger apoptosis are still unknown. The aim of this study was to investigate the expression of endoplasmic reticulum (ER) stress-related proteins in the condylar cartilage of rabbits following ADD. Methods Sixty healthy adult rabbits were randomly assigned to the experimental and sham-operated control groups (n = 12). The experimental rabbits were subjected to surgical ADD in the right temporomandibular joints. The production of ER stress-related proteins C/EBP homologous protein (CHOP), glucose-regulated protein 78 (GRP78), cleaved caspase-3, and caspase-12 in cartilage was evaluated by immunohistochemistry, quantitative real-time PCR, and Western blot analysis. Results Our results showed that the expression of CHOP, GRP78, cleaved caspase-3, and caspase-12 increased significantly along with degenerative changes in cartilage after ADD. Conclusion These results indicate that the ER stress pathway is activated in ADD cartilage and might promote the development of TMD.

Arthrocentesis has an effect of washing out inflammatory products that accumulate in the joint compartment of a dysfunctional temporomandibular joint (TMJ). The procedure removes inflammatory cytokines, which are pain-causing substances, for early reduction of TMJ pain and quick recovery of jaw function, thus increasing the possibility of a successful rehabilitation. The aim of this study was to investigate the relationship between arthroscopy synovitis grade in patients with unilateral high condylar fractures and concentrations of the pro-inflammatory cytokines tumour necrosis factor (TNF)-alpha as well as of matrix metalloproteinases (MMPs) in washed-out synovial fluid (SF) samples obtained from those patients. A total of 26 patients with unilateral high condylar fractures who underwent arthrocentesis for a therapeutic purpose were examined. SF samples were collected before performing arthroscopy to determine synovitis grade. The detection rates and concentrations of TNF-alpha and MMPs were determined, and their association with synovitis grade was analysed. TNF-alpha was detected in 23 and MMP-3 in 22 of the TMJs. There was a correlation between synovitis grade and concentration of TNF-alpha in the fracture group. Furthermore, the concentrations of TNF-alpha and MMP-3 were significantly higher as compared to the control group, comprised of TMJs on the non-fracture side of the same patients, while a correlation was also noted between TNF-alpha concentration and synovitis grade in the fracture group. The present findings may provide a biological/biochemical rationale for arthrocentesis as a reasonable treatment modality for high condylar fractures.

Structured abstract Objectives: To investigate hypoxia‐inducible factor 1‐alpha (HIF‐1α) and vascular endothelial growth factor (VEGF) expression under altered loading, and to explore the relationship between loading and hypoxia in the mandibular condylar cartilage of young rats. Setting and sample population: Eighty Sprague‐Dawley rats. Material and methods: The reduced loading group was fed soft food, and their incisors were cut to avoid occlusal contact. The increased loading group was fed hard food and had forced jaw‐opening. Ten rats from each group (n = 10) were sacrificed at 12, 24, 48, and 96 hours after initiation of the experiment. Pimonidazole hydrochloride (Hypoxyprobe‐1, HP‐1) was used as a hypoxia marker to confirm the hypoxic state. Hypoxic chondrocytes as indicated by HP‐1, HIF‐1α and VEGF protein expressions were recognized by immunohistochemical detection. HIF‐1α and VEGF mRNA expressions were detected by semi‐quantitative RT‐PCR. Results: Hypoxyprobe‐1 was confined in the upper layers of cartilage, and was most strongly expressed in the weight‐bearing area of TMJ at 12 and 96 hours. Staining of HIF‐1α and VEGF was most strongly expressed in the chondrocytes of the fibrous and proliferative layer at all time points. Furthermore, expressions were also displayed in the hypertrophic and calcified layers at 48 and 96 hours. The expressions of HIF‐1α and VEGF mRNA were higher in the increased loading group than in the reduced loading group at 48 and 96 hours (P < 0.05). Conclusion: Mechanical loading seems to directly induce weight‐bearing area hypoxia followed by new vessel formation, which indicates that these factors are related and important for the development of cartilage.

Objective To study the effects of intermittent parathyroid hormone (PTH [1-34]) on the mandibular condylar cartilage (MCC) and subchondral bone in adult female mice. Materials and methods Twenty-two, 20-week-old female mice were used for in vivo experiments. The experimental mice (n=11) received daily intraperitoneal injections of PTH [1-34] for 3 weeks, while control mice (n=11) received intraperitoneal injections of 0.9% saline solution. Mice were euthanized and then micro-computed tomography (micro-CT); histology and immunostaining were carried out to assess the response. Results Intermittent PTH [1-34] led to early MCC breakdown and surface irregularities. Micro-CT analyses indicated that PTH [1-34] treatment led to increased bone volume fraction, tissue density and trabecular thickness, while decreasing the trabecular spacing. Histological analyses showed decreased proteoglycan secretion, increased bone turnover (TRAP staining) and increased mineralization. Furthermore, PTH [1-34] treatment showed increased apoptosis of the cells. Our immunohistochemistry showed increased expression of pSMAD158 in the MCC and subchondral bone with PTH administration, whereas sclerostin (SOST) expression was decreased. Conclusions Intermittent PTH [1-34] results in early mineralization of the MCC, which may result in cartilage degeneration. Our results identified a novel mechanism by which PTH [1-34] induces alteration in the microarchitecture of the MCC and the subchondral bone.

Objective We experimentally compared the effects of compressive and tractional mechanical stress on the temporomandibular joint (TMJ) of rabbits to assess the etiology of progressive condylar resorption. Materials and methods We performed a cortical osteotomy using custom-made devices that were lengthened by 0.25 mm every 12 h for 1 week after surgery. During this time, the rabbit TMJ was under compressive or tractional mechanical stress. The samples in each group were examined using micro-computed tomography and histological staining. Results Scores for the area of bone resorption were higher in the compressive group than in the tractional group. Moreover, scores for the depth of bone resorption were higher in the compressive group than those in the tractional group. We observed a significantly higher prevalence of resorption in the subcondylar bone in the compressive group than in the tractional group. There were substantially more cells that were positive for tartrate-resistant acid phosphatase in the compressive group than in the control and tractional groups. Conclusions The outcomes here suggest that excessive mechanical stress, particularly compressive mechanical stress, may significantly affect morphological bone change findings in the TMJ.

Structured AbstractObjectives This study sought to investigate the three-dimensional (3D) changes in anteroposterior, vertical and mediolateral positions and orientations of the mandibular condyle as well as joint space parameters following maxillary first premolar extraction and incisor retraction in skeletal Class II patients. Setting and Sample Population Thirty patients were treated by orthodontic maxillary first premolar extraction at the Faculty of Oral and Dental Medicine, Cairo University, Egypt. Materials and Methods Cone beam computed tomography (CBCT) analysis was performed in patients pre- and post-treatment. Sixty joints were evaluated based on the volumetric images, and the following 3D measurements were evaluated: (i) mandibular condylar position relative to the cranial base and the joint itself, (ii) condylar inclination and (iii) anterior, posterior, superior and medial joint spaces. Results There was a statistically significant (P≤.05) posterior positioning of the condyle relative to the vertical plane. The distance increased significantly from 5.77 to 6.82 mm as this plane is anterior to the mandibular condyle. There was an increased anterior joint space (from 3.10 to 3.90 mm) and decreased posterior joint space (from 2.78 to 2.23 mm) following treatment. No changes were observed in mediolateral and vertical condylar positions. Conclusions Posterior positioning of the condyle after orthodontic extraction and incisor retraction may occur, but its clinical significance requires further assessment in future studies.

The presence of body posture changes among patients with temporomandibular disorders (TMD) has been a controversial topic in dentistry. Based on that, the aim of this study was to assess postural features of pain-free subjects with internal derangement of the temporomandibular joint (TMJ), viz. disc displacement, when compared to subjects with normal disc position. A total of 21 subjects with unilateral, pain-free TMJ disc displacement (DD) and 21 subjects without any TMD signs of symptoms were assessed for body posture changes by means of posturographic evaluation of several body segments and postural balance reactions through the centre of mass during jaw movements using a balance platform. Posturographic measurements showed the absence of any significant differences between the two groups in any of the outcome parameters. Similarly, all balance platform responses to mandibular movements were not different between groups. There are no significant differences in body posture between subjects with and without unilateral disc displacement in the temporomandibular joint. Such observations, indicating a well-preserved postural balance in the presence of TMJ internal derangement, put into serious question the potential influence of TMJ disorders on whole body posture and viceversa.

Objective Chondrogenesis and endochondral ossification in mandibular condyle play crucial roles in maxillofacial morphogenesis and function. Circadian regulator brain and muscle arnt‐like 1 (BMAL1) is proven to be essential for embryonic and postnatal development. The goal of this study was to define the functions of BMAL1 in the embryonic and postnatal growth of mandibular condylar cartilages (MCC). Materials and Methods Micro‐CT, TUNEL staining and EdU assay were performed using BMAL1‐deficient mice model, and in vitro experiments were performed using rat chondrocytes isolated from MCC. RNA sequencing in mandibular condyle tissues from Bmal1 ‐/‐ mice and the age‐matched wild‐type mice was used for transcriptional profiling at different postnatal stages. Results The expression levels of BMAL1 decrease gradually in MCC. BMAL1 is proved to regulate sequential chondrocyte differentiation, and its deficiency can result in the impairment of endochondral ossification of MCC. RNA sequencing reveals hedgehog signalling pathway is the potential target of BMAL1. BMAL1 regulates hedgehog signalling and affects its downstream cascades through directly binding to the promoters of Ptch1 and Ihh, modulating targets of hedgehog signalling which is indispensable for endochondral ossification. Importantly, the short stature phenotypes caused by BMAL1 deficiency can be rescued by hedgehog signalling activator. Conclusions Collectively, these results indicate that BMAL1 plays critical roles on chondrogenesis and endochondral ossification of MCC, giving a new insight on potential therapeutic strategies for facial dysmorphism.

Biomarkers of temporomandibular joint (TMJ) osteoarthritis (OA) remain unknown. The objective was to detect whether molecular biomarkers from peripheral blood leucocytes (PBLs) engage in TMJ OA lesions. Thirty‐four six‐week‐old Sprague Dawley rats were used. The top upregulated gene ontology categories and gene‐fold changes in PBLs were detected by a microarray analysis comparing rats that received 20‐week unilateral anterior crossbite (UAC) treatment with age‐matched controls (n = 4). Twenty weeks of UAC treatment had been reported to induce TMJ OA‐like lesions. The other twenty‐four rats were randomly placed in the UAC and control groups at 12‐ and 20‐week time points (n = 6). The mRNA expression levels of the selected biomarkers derived from the microarray analysis and their protein expression in the alveolar bone and TMJ were detected. The microarray analysis indicated that the three most highly involved genes in PBLs were Egr1, Ephx1 and Il10, which were confirmed by real‐time PCR detection. The increased protein expression levels of the three detected molecules were demonstrated in cartilage and subchondral bone (P

BACKGROUND The temporomandibular joint (TMJ) disc plays a role in joint movement and in load absorbance and distribution. An experimental unilateral anterior crossbite (UAC) prosthesis induces mandibular condylar cartilage degeneration in rats. However, the changes in the articular disc are still unknown. OBJECTIVE To describe changes in the TMJ discs of UAC rats. METHODS The discs of fifty-four Sprague-Dawley rats, equally distributed into a UAC group and an age-matched sham-operated control group at 4, 12 and 20 weeks (n = 9), were evaluated by gross and histomorphological observation and by detection at the mRNA or protein expression levels of the markers related to the matrix elements. RESULTS No macro- or micro-morphological differences were observed between groups. However, there were catabolic degradative changes at the molecular level in the UAC group, showing a significant reduction in the mRNA and/or protein expression levels of many molecules. The reduction became worse with time (P

Masseter muscle function influences mandibular bone homeostasis. As previously reported, bone resorption markers increased in the mouse mandibular condyle two days after masseter paralysis induced with botulinum toxin type A (BoNTA), followed by local bone loss.This study aimed to evaluate the bone quality of both the mandibular condyle and alveolar process in the mandible of adult mice during the early stage of a BoNTA-induced masseter muscle atrophy, using a combined 3D histomorphometrics and shape analysis approach.Adult BALB/c mice were divided into an untreated control group and an experimental group; the latter received one single BoNTA injection in the right masseter (BoNTA-right) and saline in the left masseter (Saline-left). 3D bone microstructural changes in the mandibular condyle and alveolar process were determined with high-resolution microtomography. Additionally, landmark-based geometric morphometrics was implemented to assess external shape changes.After 2 weeks, masseter mass was significantly reduced (P-value0.001). When compared to Saline-left and untreated condyles, BoNTA-right condyles showed significant bone loss (P-value0.001) and shape changes. No significant bone loss was observed in the alveolar processes of any of the groups (P-value0.05).Condyle bone quality deteriorates at an early stage of BoNTA-induced masseter muscle atrophy, and before the alveolar process is affected. Since the observed bone microstructural changes resemble those in human temporomandibular joint degenerative disorders, the clinical safety of BoNTA intervention in the masticatory apparatus remains to be clarified.

Temporomandibular joint dislocation refers to the dislodgement of mandibular condyle from the glenoid fossa. Anterior and anteromedial dislocations of the mandibular condyle are frequently reported in the literature, but superolateral dislocation is a rare presentation. This report outlines a case of superolateral dislocation of an intact mandibular condyle that occurred in conjunction with an ipsilateral mandibular parasymphysis fracture. A review of the clinical features of superolateral dislocation of the mandibular condyle and the possible techniques of its reduction ranging from the most conservative means to extensive surgical interventions is presented.

Structured Abstract Objectives To measure the lengths of the force and resistance arms, in order to calculate the mechanical advantage and muscular work of the human temporalis muscle (TM) in brachyfacial (BR) and dolichofacial (DO) subjects. Setting and Sample Population Mandibles from 49 subjects of both genders (BR n = 9; DO n = 40) from the collection of the Laboratory of Human Anatomy at Universidade de Santa Cruz do Sul, Rio Grande do Sul, Brazil, were analyzed. Material and Methods The distance between the condylar process and the coronoid process (insertion site of the TM) represented the length of the force arm (LFA) of the TM. The distance between the condylar process and the mental protuberance represented the length of the resistance arm (LRA). Thus, the mechanical advantage of the TM was obtained using the following ratio: LFA/LRA, while the muscular work (LRA/LFA) of the TM was obtained using the inverse of this ratio. Results When compared with the DO, the parameters of the BR are significantly greater, as shown by the LFA (6.0%) and mechanical advantage (8.2%; p = 0.0078). By contrast, our results show that in the DO, the LRA was 2.4% longer and the muscular work was 10.4% greater (p = 0.0087). Conclusion The mechanical advantage of the TM in BR subjects is significantly greater than in DO subjects. Moreover, this greater mechanical advantage may explain, at least in part, the higher incidence of temporomandibular dysfunctions in BR subjects.

Background Temporomandibular joint (TMJ) osteoarthritis(OA)characterized with cartilage degen-eration is associated with inflammation. High mobility group box chromosomal protein-1(HMGB-1)is a potent mediator of inflammation and the trigger of OA. The expression of HMGB-1 in TMJ OA was uncovered, but the role of HMGB-1 in TMJ cartilage degeneration is not fully understood. In this study, the regulation of HMGB-1 in TMJ condylar cartilage was revealed. Methods A complete Freund's adjuvant (CFA)-induced TMJ inflammation animal model was employed and the expression of HMGB-1 was detected at 1st, 2nd, and 6th weeks by immunohistochemistry. TMJ condylar chondrocytes were incubated with IL-1β (10 and 40 ng/ml) at 24, 48, and 72 h, and the translocation and protein level of HMGB-1 were evaluated by immunofluorescence and Western blot. Result Nuclear HMGB-1 staining was predominantly located in chondrocytes of both the fibrosis and proliferative zones in healthy TMJ. 1st week and 2nd week after CFA injection, immunoreaction could be detected in the cytoplasms of HMGB-1-positive cells and cartilage matrix especially in hypertrophic zone. At 6th week after CFA injection, cartilage matrix expression was disappeared and the cytoplasm expression of HMGB-1 was very weak in hypertrophic zone. HMGB-1 was translocated from the nucleus to the cytoplasm at 48 h after incubated with IL-1β (10 ng/ml and 40 ng/ml). The protein level of HMGB-1 was increased after stimulation and had a peak at 48 h. Conclusion HMGB-1 might be associated with TMJ inflammation and OA. Insight into the role of HMGB-1 in TMJ inflammation is helpful to add the new knowledge into the pathogenesis of TMJ OA.

Structured Abstract Objectives To investigate how displacements of maxillo-mandibular structures are associated with each other at splint removal and 1 year post-surgery following 1-jaw and 2-jaw surgeries for correction of Class III malocclusion. Setting and Sample Population Fifty patients who underwent surgical correction with maxillary advancement only (n = 25) or combined with mandibular setback (n = 25) were prospectively enrolled in this study. Methods Cone-beam computed tomographies were taken pre-surgery, at splint removal and at 1 year post-surgery. Three-dimensional cranial base superimpositions and shape correspondence were used to measure the outcomes from pre-surgery to splint removal (surgical changes) and splint removal to 1 year post-surgery (post-surgical adaptations). Pearson's correlation coefficients were used to evaluate the association between the regional displacements. Results Both surgery groups presented mandibular clockwise rotation with surgery and post-surgical adaptive counterclockwise rotation. In patients treated with maxillary advancement only, the surgical changes of the maxilla were significantly correlated with chin changes. The amount and direction of chin autorotation were significantly correlated with right and left ramus autorotation. Right and left condylar displacements were significantly correlated. One year post-surgery, adaptive displacements and bone remodeling of both rami were correlated with the chin and condylar changes. For the 2-jaw group, the few correlations between the positional and remodeling changes in the anatomic regions of interest observed due to the surgery were different than those observed after post-surgical adaptations, suggesting that these changes occurred independently. Conclusion Our results indicate that surgical displacements and post-surgical adaptations are often correlated in one-jaw surgery and are, in general, independent in two-jaw surgery.

The mandible has a property to flex inwards around the mandibular symphysis with change in shape and decrease in mandibular arch width during opening and protrusion of the mandible. The mandibular deformation may range from a few micrometres to more than 1 mm. The movement occurs because of the contraction of lateral pterygoid muscles that pulls mandibular condyles medially and causes a sagittal movement of the posterior segments. This movement of mandible can have a profound influence on prognosis and treatment outcome for various restorative, endodontics, fixed, removable and implant-related prosthesis. The review unfolds the causes, importance and clinical implications of median mandibular flexure in oral rehabilitation. This review also highlights the appropriate preventive measures and techniques that should be adopted by clinicians to minimise the effect of flexural movement of the jaw during oral rehabilitation. This would not only help clinicians to achieve a good prosthesis with accurate fit and longevity but also maintain the health of the surrounding periodontal or periimplant gingival tissues and bone.

The purpose of this study was to investigate stress on poly-L-lactic acid (PLLA) plates with a thickness of 1.4 mm and titanium plates with a thickness of 1.0 and 1.4 mm placed for mandibular symphyseal fractures with or without conservatively treated, unilateral condylar fractures using finite element analysis. The symphyseal fracture region was defined by the following three conditions: the defect, the callus, and the contact condition. Stress on the plates was analyzed by an applying occlusal force of 478.1 N on the first molar of the non-condylar fracture side. In the model of isolated symphyseal fracture, the maximal stresses were below the material strength in all plate types and conditions. In the models with condylar fracture, the maximal stresses on these plates were much higher than those in the models of isolated symphyseal fracture, especially for the defect condition. Although the maximal stresses on all types of plates in the contact condition were below the material strengths, some of those in the defect condition were higher than these strengths. These results suggest that a PLLA plate can theoretically withstand stress under good reductions of symphyseal fractures, even for condylar fractures; however, both the PLLA plate and titanium miniplate may be at risk of fracture under poor reduction.

Temporomandibular joint (TMJ) displays a high remodelling capability. The current purpose was to investigate the differences between mandibular condylar remodelling responses of growing mice to installation and removal of unilateral anterior crossbite (UAC) prosthesis. Twenty-four mice were divided into one mock control group and two UAC groups. Unilateral anterior crossbite was created by installing a pair of prosthesis to left-side maxillary and mandibular incisors. Unilateral anterior crossbite was removed in removal group at 3 weeks but remained in UAC group. Temporomandibular joints were sampled at 7 weeks. Changes in condylar cartilage and subchondral bone were assessed by histology and in vivo micro-CT. Real-time PCR and immunohistochemistry were performed to evaluate expression changes in ADAMTS-5, MMP-3, MMP-9, MMP-13, IL-1, TNF-α, OPG and RANKL. Statistical analysis was performed at α = 0.05. Temporomandibular joint cartilage degradation was induced by UAC as previously reported but was reversed by removal of UAC. The dropped cartilage thickness, chondrocyte number and collagen II-positive area, the increased expression levels of Adamts-5, Mmp3, 9, 13, Tnf-α and Il-1β in cartilage, the decreased ratio of OPG/RANKL in both condylar cartilage and subchondral bone, the loss of TMJ subchondral bone and the increase in the TRAP-positive cells in subchondral bone were all reversed in the removal group (P < 0.05). The growing mouse TMJ condyle displays a high remodelling capability which can be degenerative and rehabilitative, respectively, in response to placement and thereafter removal of the aberrant prosthesis. Eliminating aberrant prosthesis is helpful to promote the degraded condyle to recover.

Purpose Matrix metalloproteases (MMPs) are tissue-remodeling enzymes that function during the remodeling process, such as in immune-inflammatory diseases. Metalloprotease-2 (MMP-2) and metalloprotease-9 (MMP-9) are gelatinases that degrade several types of extracellular matrix collagen. It is hypothesized that in temporomandibular joint (TMJ) dysfunction, MMP-2 and MMP-9 expression levels may be elevated. Therefore, the objective of this study is to determine the association of MMP-2 and MMP-9 expression with temporomandibular joint dysfunction using an immunohistochemical approach to evaluate the joint disk. Material and Methods A total of 45 human temporomandibular joint samples were collected, with 36 samples in the test group (patients with anterior disk displacement with reduction (n = 29) and without reduction (n = 7)) and nine samples in the control group. The immunostaining of the TMJ disks was statistically compared between the groups (P

Tissue engineering potentially offers new treatments for disorders of the temporomandibular joint which frequently afflict patients. Damage or disease in this area adversely affects masticatory function and speaking, reducing patients’ quality of life. Effective treatment options for patients suffering from severe temporomandibular joint disorders are in high demand because surgical options are restricted to removal of damaged tissue or complete replacement of the joint with prosthetics. Tissue engineering approaches for the temporomandibular joint are a promising alternative to the limited clinical treatment options. However, tissue engineering is still a developing field and only in its formative years for the temporomandibular joint. This review outlines the anatomical and physiological characteristics of the temporomandibular joint, clinical management of temporomandibular joint disorder, and current perspectives in the tissue engineering approach for the temporomandibular joint disorder. The tissue engineering perspectives have been categorized according to the primary structures of the temporomandibular joint: the disc, the mandibular condyle, and the glenoid fossa. In each section, contemporary approaches in cellularization, growth factor selection, and scaffold fabrication strategies are reviewed in detail along with their achievements and challenges.

Jaw-closing movements are basic components of physiological motor actions precisely achieving intercuspation without significant interference. The main purpose of this study was to test the hypothesis that, despite an imperfect intercuspal position, the precision of jaw-closing movements fluctuates within the range of physiological closing movements indispensable for meeting intercuspation without significant interference. For 35 healthy subjects, condylar and incisal point positions for fast and slow jaw-closing, interrupted at different jaw gaps by the use of frontal occlusal plateaus, were compared with uninterrupted physiological jaw closing, with identical jaw gaps, using a telemetric system for measuring jaw position. Examiner-guided centric relation served as a clinically relevant reference position. For jaw gaps ≤4 mm, no significant horizontal or vertical displacement differences were observed for the incisal or condylar points among physiological, fast, and slow jaw-closing. However, the jaw positions under these three closing conditions differed significantly from guided centric relation for nearly all experimental jaw gaps. The findings provide evidence of stringent neuromuscular control of jaw-closing movements in the vicinity of intercuspation. These results might be of clinical relevance to occlusal intervention with different objectives.

The effect of unilateral anterior crossbite on the remodelling of mandibular condyle needs to be investigated. This study aimed to investigate the effects of experimentally created unilateral anterior crossbite on the remodelling of mandibular condyle and explore the changes in the expression of relevant transcription factors and growth factors. The experimental unilateral anterior crossbite was created in 6-week-old female growing rats by bonding metal tubes to the left pairs of incisors. Remodelings of mandibular condylar cartilage was assessed histologically at 2, 4 and 8 weeks. Protein and mRNA levels of Sox9, runt-related transcription factor 2 (Runx2), Osterix (Osx), transforming growth factor beta 1 (TGFβ1), transforming growth factor beta receptor 2 (TGFβr2) and type X collagen (ColX) were investigated by immunohistochemistry and real-time PCR, while alkaline phosphatise (ALP) by histochemistry and real-time PCR. Decreased ratio of hypertrophic cartilage layer was noticed in the 4w experimental group versus controls. At all the time points, the expression of Sox9 and ALP increased but that of TGFβ1 and TGFβr2 decreased in experimental groups (P < 0·05). The expression of Runx2, Osx and Col X increased at 2w, but decrease at 4w (P < 0·05). The results that obvious cartilage degradation and altered expression of related transcription factors and growth factors were detected in the mandibular condyles of the experimental group suggested that the present unilateral anterior crossbite plays an adverse role in the TMJ, and thus leading to the degenerative endochondral ossification.

Temporomandibular joint (TMJ) disorders predominantly afflict women of childbearing age, suggesting a role for female hormones in the disease process. In long bones, estrogen acting via estrogen receptor beta (ERβ) inhibits axial skeletal growth in female mice. However, the role of ERβ in the mandibular condyle is largely unknown. We hypothesize that female ERβ-deficient mice will have increased mandibular condylar growth compared to wild-type (WT) female mice. This study examined female 7-day-old, 49-day-old, and 120-day-old WT and ERβ knockout (KO) mice. There was a significant increase in mandibular condylar cartilage thickness as a result of an increased number of cells, in the 49-day-old and 120-day-old female ERβ KO compared with WT controls. Analysis in 49-day-old female ERβ KO mice revealed a significant increase in collagen type X, parathyroid hormone-related protein (Pthrp), and osteoprotegerin gene expression and a significant decrease in receptor activator for nuclear factor κ B ligand (Rankl) and Indian hedgehog (Ihh) gene expression, compared with WT controls. Subchondral bone analysis revealed a significant increase in total condylar volume and a decrease in the number of osteoclasts in the 49-day-old ERβ KO compared with WT female mice. There was no difference in cell proliferation in condylar cartilage between the genotypes. However, there were differences in the expression of proteins that regulate the cell cycle; we found a decrease in the expression of Tieg1 and p57 in the mandibular condylar cartilage from ERβ KO mice compared with WT mice. Taken together, our results suggest that ERβ deficiency increases condylar growth in female mice by inhibiting the turnover of fibrocartilage.

To describe pediatric costochondral graft reconstruction of the absent mandibular condyle and to report the short-term and long-term outcomes and complications associated with performing this procedure in young children.Case series with a retrospective chart review.Pediatric otolaryngology clinic and tertiary children's hospital in a metropolitan area.All children treated for an absent mandibular condyle with a costochondral graft at Children's Hospitals and Clinics of Minnesota were identified from 2002 through 2011, and a retrospective chart review was performed.Ten patients aged 3 to 11 years were identified. The most common diagnosis, in 8 of 10 patients, was oculo-auriculo-vertebral syndrome. Three of the patients had a tracheostomy, of which 1 was decannulated following condylar reconstruction. Functional improvement, defined as improved symmetry, chewing, or better oral opening, was observed in 8 of 10 patients. Five patients have required no further surgeries to date, with a mean follow-up time of 3.9 years. Severe overgrowth of the graft was noted in 1 case, and partial or complete resorption of the graft was also noted in 3 cases. Overgrowth occurred after 5.7 years, whereas resorption occurred after an average of 2.5 years.Costochondral grafts are an excellent surgical treatment option for children with severe mandibular malformations. Short-term results show particular improvement in function and mandibular alignment. The mean follow-up time with no revision surgery was substantial and indicates that rib grafting is a good addition to the armamentarium of treatment for this patient population.

Belief in and rejection of a relationship of occlusion and temporomandibular joint (TMJ) condyle-fossa position with normal and abnormal function are still contentious issues. Clinical opinions can be strong, but support in most published data (mostly univariate) is problematic. Distribution overlap, low sensitivity and specificity are a common basis to reject any useful prediction value. Notwithstanding, a relationship of form with function is a basic tenet of biology. These are multifactor problems, but the questions mostly have not been analysed as such. This review moves the question forward by focusing on TM joint anatomic organisation as the multifactor system it is expected to be in a closed system like a synovial joint. Multifactor analysis allows the data to speak for itself and reduces bias. Classification tree analysis revealed useful prediction values and usable clinical models which are illustrated, backed up by stepwise logistic regression. Explained variance, R(2), predicting normals from pooled TMJ patients was 32·6%, sensitivity 67·9%, specificity 85·7%; 37% versus disc displacement with reduction; and 28·8% versus disc displacement without reduction. Significant osseous organisational differences between TM joints with clicking and locking suggest that this is not necessarily a single disease continuum. However, a subset of joints with clicking contained characteristics of joints with locking that might contribute to symptom progression versus resistance. Moderately strong models confirm there is a relationship between TMJ osseous organisation and function, but it should not be overstated. More than one model of normals and of TM derangement organisation is revealed. The implications to clinical decision-making are discussed.

The articular disc of the temporomandibular joint is a constant structure in mammals. According to Parsons' report in 1900, however, it is absent in four animals: the armadillo, two kinds of monotremes and the Tasmanian devil. Thereafter, no research was performed to confirm this observation. The aim of this study was to determine by anatomical and histological examination whether the Tasmanian devil has an articular disc in its temporomandibular joint. Six fresh frozen corpses and one dry skull of Tasmanian devils were obtained from the School of Zoology, University of Tasmania. The corpses were dissected and the morphology of the temporomandibular joint was carefully observed by gross anatomical and histological examination. The structure of the temporomandibular joint of the dry skull was examined macroscopically and by micro-computed tomography. In all cases, absence of the articular disc in the Tasmanian devil temporomandibular joint was morphologically confirmed. The surface layer of both the condyle and the glenoid fossa comprised a thick fibrous tissue. Micro-computed tomography revealed dense and fine trabecular bone in the condyle. The thick fibrous tissue covering the condyle and high-density trabecular bone in the condyle might play a role in absorption against powerful mastication and heavy loading of the Tasmanian devil temporomandibular joint.

Parafunctional habits, such as prolonged clenching and bruxism, have been associated with dysfunctional overloading in the temporomandibular joint (TMJ). In this study, stress distributions in the TMJ were analysed during prolonged clenching, using three-dimensional finite element (FE) models of the TMJ with and without disc displacement. The aim of this study was to investigate stress distribution of the cartilaginous tissues in the TMJ with and without disc displacement. Finite element models were developed on the basis of magnetic resonance images from two subjects with and without anterior disc displacement. Condylar movements recorded during a 5-min clenching were used as the loading condition for stress analysis. In the asymptomatic model, the highest von Mises stresses were located in the lateral area (4·91 MPa) of the disc surfaces, and after 5-min clenching, the higher stresses were still located at the lateral area (3·65 MPa). In all the cartilaginous tissues, 30-50% of stress reduction occurred during 5-min clenching. In contrast, the von Mises stress in the cartilaginous tissues of the symptomatic model with disc displacement was markedly lower, compared with the asymptomatic model. However, in the condylar cartilage, stress relaxation during clenching was not recognised. Furthermore, relatively high stresses were observed in the retrodiscal tissues throughout clenching. The present results indicate that disc position could be involved in the stress distribution of the TMJ components during prolonged clenching.

To test the strength of internal fixation of mandibular condyle fractures repaired with titanium miniplates versus titanium intramedullary implants.Prospective laboratory experimentation in urethane mandible models and human cadaveric mandibles.Materials testing laboratory at an academic medical center.Osteotomies of the mandibular condyle were created in 40 urethane hemimandible models and 24 human cadaveric specimens. Half of the samples in each group were repaired with traditional miniplates, and the other half were repaired with intramedullary titanium implants. Anteroposterior and mediolateral loads were applied to the samples, and the displacement was measured with reference to the applied force.Titanium intramedullary implants demonstrated statistically significant improved strength and stiffness versus miniplates in the urethane model experimental groups. Despite frequent plastic deformation and mechanical failures of the miniplates, a 1.6-mm-diameter titanium intramedullary pin did not mechanically fail in any of the cases. Intramedullary implantation failures were due to secondary fracture of the adjacent cortical bone or experimental design limitations including rotation of the smooth pin implant.Mechanical implant failures that were encountered with miniplate fixation were not seen with titanium intramedullary implants. These intramedullary implants provide stronger and more rigid fixation of mandibular condyle fractures than miniplates in this in vitro model.

Growth of the mandibular condylar cartilage (MCC) is reviewed as a function of genetic and epigenetic factors. The growth centers around the differential spatial concentration of the chondrocytes, influence of growth factors like TGF-β and heterogeneity in the number of IGF receptors, control the action of IGF. Besides these factors, growth of the mandibular condyle is influenced by differential response of chondrocytes as a function of their source/ageing, which in turn is regulated by TGF-β, BMPs and IGFs. While IGF-1 promotes proteoglycan synthesis and survival of the chondrocytes to maintain cartilage homeostasis, TGF-β synergistically catalysed the effect of IGF-1, while BMPs catalysed proteolysis as and when physiologically needed. To understand these processes, role of IGF-1 and its six receptors is at the center to a number of physiological processes being regulated by its mode of application for the growth and differentiation. Probing deeper, biological functions of IGFs seemed to depend on their level of free status rather than bound status to respective IGF-binding proteins (IGF-BPs), considered prerequisite to modulate their biological functions. Genetic regulation of their secretion has thrown light on their insulin-like structural homology, level and response in osteo-arthritis (OA), rheumatic arthritis (RA) and diabetes type-II. Biochemistry and spatial distribution of IGF receptors in different domains exerts control on IGF-1 activities. In ultimate analysis, IGF-axis conserved during the evolution to regulate cell growth and proliferation affect nearly every organ in the body as judged from the techniques determining skeletal maturity and decision making dependent on it for orthodontic, orthognathic/orthopedic and dental implant applications.