Mandibular Lateral Displacement Research Articles

Asymmetry in Class II subdivision malocclusion: Assessment based on 3D surface models.

There is currently no consensus in the literature whether the aetiology of a Class II subdivision is dental, skeletal or both. The aim of this study was to identify and quantify skeletal and dental asymmetries in Class II subdivision malocclusions. CBCTs from 33 Class II subdivision malocclusion patients were used to construct 3D volumetric label maps. Eighteen landmarks were identified. The original scan and associated 3D volumetric label map were mirrored. Registration of the original and mirrored images relative to the anterior cranial base, maxilla and mandible were performed. Surface models were generated, and 3D differences were quantified. Statistical analysis was performed. Anterior cranial base registration showed significant differences for fossa vertical difference, fossa roll, mandibular yaw, mandibular lateral displacement and lower midline displacement. Regional registrations showed significant differences for antero-posterior (A-P) mandibular length, maxillary roll, A-P maxillary first molar position, maxillary first molar yaw and maxillary first molar roll. Class II subdivision patients also show an asymmetric mandibular length as well as an asymmetric gonial angle. Moderate correlations were found between the A-P molar relationship and fossa A-P difference, mandibular first molar A-P difference, maxillary first molar A-P difference and maxillary first molar yaw. This study suggests that Class II subdivisions can result from both significant skeletal and dental factors. Skeletal factors include a shorter mandible as well as posterior and higher displacement of the fossa on the Class II side, resulting in mandibular yaw. Dental factors include maxillary and mandibular first molar antero-posterior asymmetry.

Evaluation of horizontal condylar angle in malocclusions with mandibular lateral displacement using cone-beam computed tomography.

To evaluate the horizontal condylar angle (HCA) in mandibular lateral displacement (MLD). HCA in MLD malocclusions were examined using cone-beam computed tomography data in subjects with MLD and control subjects. HCA in joints of control patients and contralateral side joints of MLD patients were not significantly different. The mean HCA on the shifted side was larger than on the contralateral side (P < .001) in the different HCA groups. HCA was significantly larger on the shifted side than on the contralateral side in skeletal Class I, Class II, and Class III groups (P < .001). (1) There was no statistically significant difference between HCA in control patients and on the contralateral side in MLD patients. (2) HCA was significantly larger on the shifted side than on the contralateral side. (3) HCA on the shifted side and the contralateral side in MLD Class I, Class II, and Class III are significantly different.

Three-dimensional morphological characterization of malocclusions with mandibular lateral displacement using cone-beam computed tomography

Objective: The purpose of this study was to evaluate the morphologic characteristics of MLD malocclusions using 3D imaging.Materials and methods: MLD characteristics were examined using CBCT data in 40 subjects. A 3D Cephalometric analysis was developed to describe the spatial position of the mandible and temporal bones.Results: Vertical dental heights were shorter and the posterior occlusal plane (POP) presented a steeper sagittal inclination on the shifted side (the side of the laterally displaced bony chin) than on the contralateral side. (p < 0.01). The MLD was related to a superiorly inclined POP Cant in the same direction (r = 0.82; p < 0.01). The shifted side condyle was dislocated medially and was smaller. Temporal bone sagittal inclination showed a more forward and medial inclination on the contralateral side (p < 0.01).Conclusions: A unilateral decrease in the vertical height of the dentition and the subsequent steeper occlusal plane inclinations correlated with (1) mandibular rotational displacement and condylar lateral displacement, (2) mandibular and condylar morphologic changes (3) changes in temporal bone position.

Orthodontics problems in pediatric and growing subjects

Results The presence of posterior crossbite was significantly greater in growing subjects with oral breathing thus confirming the influence of these factors on skeletal development with constriction of the whole palate. Unilateral posterior crossbite is often associated with mandibular lateral displacement that is clinically characterized by deviation of the chin, facial asymmetry, dental midline discrepancy, and high prevalence of internal derangement of the temporomandibular joint. Children with anterior openbite presented with a greater prevalence rate of sucking habits. Hyperdivergency is a risk factors for negative overbite in mixed dentition subjects. The test group had significantly smaller maxillary intermolar and intercanine widths and greater posterior transverse discrepancy. Class III malocclusion is a complex clinical entity that entail the contraction of the maxilla and a narrowing of the base of the nose in addition to an increased mandibular total length. Conclusions Treatment of orthodontic problems that do not improve with age may be started earlier to avoid worsening of the condition in permanent dentition. The objective of any treatment in pediatric subjects before eruption of all permanent teeth are to correct the skeletal discrepancy between the jaws and improve function and facial esthetics by allowing them to develop normally, to create an ideal overbite and overjet relationship, to align the anterior permanent teeth and reduce the chance of trauma to these teeth, to improve the width of the dental arches and to reduce the risk for extraction of permanent teeth and for surgery in severe cases. Morphologic and functional characteristics of unilateral posterior crossbite with mandibular lateral deviation should be clarified to correct and prevent this malocclusion. Children with mouth-breathing pattern and sucking habits showed a significant constriction of the maxillary arch and an increased palatal height when compared with control group. Early treatment of Class III malocclusion is able to produce significant and favorable longterm skeletal shape changes characterized by an anterior morphogenetic rotation of the mandible.

Morphological and Histological Changes in the Mandibular Condyle after Plate Removal in Experimental Models of Short- and Long-term Mandibular Lateral Displacement

Morphological and Histological Changes in the Mandibular Condyle after Plate Removal in Experimental Models of Short- and Long-term Mandibular Lateral Displacement

Morphologic, functional, and occlusal characterization of mandibular lateral displacement malocclusion

Mandibular lateral displacement (MLD) is clinically characterized by deviation of the chin, facial asymmetry, dental midline discrepancy, crossbite in the posterior region, and high prevalence of internal derangement of the temporomandibular joint. Morphologic and functional characteristics of MLD should be clarified to correct and prevent this malocclusion. We examined the morphologic features, occlusal scheme, and functional behavior of MLD in 116 patients. Facial morphology was examined with posteroanterior cephalograms, occlusion guidance on the articulator after face-bow transfer, and condylar movement with the condylograph. The superiorly inclined occlusal plane was associated with mandibular deviation in the same direction. The posterior occlusal plane on the shifted side was significantly steeper than that on the nonshifted side. Functional analysis of condylar movement showed a close relationship between the direction of MLD and the direction of condylar lateral shift during opening and closing, and protrusion and retrusion. The occlusal guidance inclination in the buccal segment of the nonshifted side was steeper than that in the shifted side. The results suggested that reduced vertical height of the dentition on 1 side induced mandibular lateral adaptation with contralateral condylar shift (asymmetry); this leads to condylar lateral shift during functional movement.

Editor's Comment and Q&A: Morphologic, functional, and occlusal characterization of mandibular lateral displacement malocclusion

Introduction Mandibular lateral displacement (MLD) is clinically characterized by deviation of the chin, facial asymmetry, dental midline discrepancy, crossbite in the posterior region, and high prevalence of internal derangement of the temporomandibular joint. Morphologic and functional characteristics of MLD should be clarified to correct and prevent this malocclusion. Methods We examined the morphologic features, occlusal scheme, and functional behavior of MLD in 116 patients. Facial morphology was examined with posteroanterior cephalograms, occlusion guidance on the articulator after face-bow transfer, and condylar movement with the condylograph. Results The superiorly inclined occlusal plane was associated with mandibular deviation in the same direction. The posterior occlusal plane on the shifted side was significantly steeper than that on the nonshifted side. Functional analysis of condylar movement showed a close relationship between the direction of MLD and the direction of condylar lateral shift during opening and closing, and protrusion and retrusion. The occlusal guidance inclination in the buccal segment of the nonshifted side was steeper than that in the shifted side. Conclusions The results suggested that reduced vertical height of the dentition on 1 side induced mandibular lateral adaptation with contralateral condylar shift (asymmetry); this leads to condylar lateral shift during functional movement.

Mandibular lateral translation during symmetric mandibular function in relation to patterns of intracapsular derangement of TMJ

PURPOSE: The purposes of this study were to examine the occurrence of different types of mandibular lateral translation (ΔYMLT) using condylography and magnetic resonance imaging (MRI), to investigate the relationship between ΔYMLT and the disunion pattern in intracapsular derangement patients with ΔYMLT, and to consider the three-dimensional therapeutic position of the condyle in the mandibular fossa. MATERIAL AND METHODS: Sixty-two patients with ΔYMLT, or side shift, during symmetrical mandibular movements were analyzed with computerized condylography and MRI to determine the occurrence of different types of MLT and the relationship between the ΔYMLT and the intracapsular derangement pattern. RESULTS: Of a total of 62 subjects, we classified 43 (69.4%), 12 (9.4%), and 7 (11.2%) of them as ΔYMLT type, closed lock type, and excessive condylar rotation type, respectively. There was a high prevalence of ΔYMLT for subjects who had one side antero-medial (including medial sideway) and the other side antero-lateral disk displacement. The directions of ΔYMLT and disk displacement coincided in 95.3% of cases; this means recapturing of the displaced disk by the condyle in lower joint translation. CONCLUSION: Results indicate that mandibular lateral displacement causes the condyle to be displaced in the same direction, and the disk displacement to the opposite side; hence it creates ΔYMLT in the disk displacement direction. On the basis of these findings, it is concluded that the ΔYMLT is a useful indicator for early detection of intracapsular derangement and that the ΔYMLT allows estimation of the therapeutic condylar position.

Expression of integrinα5β1, focal adhesion kinase and integrin-linked kinase in rat condylar cartilage during mandibular lateral displacement

Integrins are cell-surface mechanochemical sensors and transducers involved in various cellular processes in combination with extracellular ligands. The aim of this study was to investigate the effect of mechanical stress on the expression of integrinα5β1 and its downstream kinases, focal adhesion kinase (FAK) and integrin-linked kinase (ILK), in condylar cartilage during mandible lateral shift in young rats. Sixty 4-week-old male Wistar rats were divided at random into five control groups and five experimental groups. All rats in the experimental groups were fitted with a resin plate to functionally displace the mandible 2 mm to the left (ipsilateral side). The rats were killed 1, 3, 7, 14 and 28 days after attachment of the appliance. Serial 6-μm sagittal sections were cut through the condylar head and processed for immunostaining of integrinα5β1, FAK and ILK. The results were quantified using an image analysing system. Integrinα5β1 expression in the superior–posterior region of the condylar cartilage on the ipsilateral side increased from 3 to 14 days compared with the contralateral side, with an intermediate level of expression in the control groups. Expression of FAK and ILK was similar to integrinα5β1 expression, and they were also upregulated on the ipsilateral side compared with the contralateral side at the early stages of the experiment. The different mechanical loading on the two sides of the condylar cartilage led to different expression patterns of integrinα5β1, FAK and ILK, which may correlate with the different morphological and histological changes seen between sides during mandibular lateral shift.

The effect of occlusal alteration and masticatory imbalance on the cervical spine.

The characteristics of mandibular lateral displacement include lateral inclination of the occlusal plane and the differences between the right and left masticatory muscles. The aims of this investigation were to compare the mandibular stress distribution and displacement of the cervical spine using three-dimensional finite element models (3D FEM) to simulate masticatory movements and to clarify the association between morphological and functional characteristics and head posture. A symmetrical standard model was produced (model-A). Model-B had higher masticatory muscle strength on the left side, model-C had symmetrical masticatory muscle strength but the occlusal plane was inclined upwards towards the right and model-D had the occlusal plane inclined upwards towards the right with higher masticatory muscle strength on the left side. Model-A showed a completely symmetrical stress distribution pattern, while in model-B there was an uneven distribution in the mandible with higher stress on the left side. In addition, the stress distribution in the cervical spine was asymmetrical, showing displacement to the right. Model-C showed a similar mandibular tendency to model-B but the opposite tendency in the cervical spine. In model-D, the mandibular stress distribution was markedly asymmetrical, but almost symmetrical in the cervical spine with markedly decreased lateral displacement. These results suggest that lateral inclination of the occlusal plane and imbalance between the right and left masticatory muscles antagonistically act on displacement of the cervical spine, i.e. the morphological and functional characteristics in patients with mandibular lateral displacement may play a compensatory role in posture control.

Dental asymmetry in temporomandibular disorders

In our previous study, it was reported that facial asymmetry due to mandibular lateral displacement (MLD) was significant in patients with temporomandibular disorders (TMD). In this study, dental asymmetry in TMD patients was investigated by means of PA cephalogram and study model. Lateral deviation of the midline of the mandibular occlusal table (PA-mid) and right-left difference of the molar relationship (Molar-Diff.) were examined, and their relationship with MLD was studied. PA-mid and Molar-Diff. were significantly correlated with MLD. In most cases, displaced side of the midline of the lower occlusal table was coincident with that of the mandibular skeletal midline. These results suggest that in TMD patients asymmetries in occlusal relationship of the midline of the mandibular teeth and molars were mainly due to a mandibular skeletal asymmetry and not merely due to a dental malposition on the alveolar basal bone. Many cases had a more distal occlusal relationship of the first molar on mandibular displaced side compared with that on the opposite side. A high incidence of Class II relationship was found (61.8% as a whole) and more remarkable on the mandibular displaced side. Midline discrepancy and right-left difference of the molar relationship seem to be important occlusal characteristics in patients with TMD.

Facial asymmetry in temporomandibular joint disorders.

In order to investigate skeletal deviation in patients with internal derangement of the TMJ, facial asymmetry was examined by the frontal cephalogram and compared with a control group of asymptomatic subjects. It was demonstrated that mandibular lateral displacement in the patients was significantly greater than that in the controls. The degree of displacement was significantly related to the cant of the frontal occlusal plane and the frontal mandibular plane, indicating the reduced vertical dimension of the posterior occlusal level and the ramus height on the mandibular displaced side. It is concluded that facial asymmetry due to mandibular lateral displacement is a relatively common problem in patients with internal derangement of TMJ. The cant of the frontal occlusal plane seems to be an important occlusal characteristic related to temporomandibular joint dysfunction.

Aninvestigationintotherelationshipbetween, teporoandibulardisorders and mandibular lateral displacement in patients with malocclusion

Aninvestigationintotherelationshipbetween, teporoandibulardisorders and mandibular lateral displacement in patients with malocclusion