Effect of archwire stiffness and friction on maxillary posterior segment displacement during anterior segment retraction: A three-dimensional finite element analysis

Objective: Sliding mechanics using orthodontic miniscrews is widely used to stabilize the anchorage during extraction space closure. However, previous studies have reported that both posterior segment displacement and anterior segment displacement are possible, depending on the mechanical properties of the archwire. The present study aimed to investigate the effect of archwire stiffness and friction change on the displacement pattern of the maxillary posterior segment during anterior segment retraction with orthodontic miniscrews in sliding mechanics. Methods: A three-dimensional finite element model was constructed. The retraction point was set at the archwire level between the lateral incisor and canine, and the orthodontic miniscrew was located at a height of 8 mm from the archwire between the second premolar and first molar. Archwire stiffness was simulated with rectangular stainless steel wires and a rigid body was used as a control. Various friction levels were set for the surface contact model. Displacement patterns for the posterior and anterior segments were compared between the conditions. Results: Both the anterior and posterior segments exhibited backward rotation, regardless of archwire stiffness or friction. Among the conditions tested in this study, the least undesirable rotation was found with low archwire stiffness and low friction. Conclusions: Posterior segment displacement may be unavoidable but reducing the stiffness and friction of the main archwire may minimize unwanted rotations during extraction space closure.ope

The Correlations between Temporomandibular Joint Symptoms and Magnetic Resonance Imaging Findings in German Patients

Purpose: The purpose of this study was to evaluate the correlation between the clinical symptoms of temporomandibular disorder and findings in the magnetic resonance imaging (MRI). Materials and Methods: Clinical data and MRI images were collected from a total of 240 German patients. Clinical symptoms were briefed as joint clicking, crepitus and pain. MRI findings were further defined according to the condyle position, condyle degeneration, disc positon, disc degeneration and the presence of osteophyte/sclerosis/synovitis. Hypermobility was separately recorded. Correlation analysis between parameters was performed. Result: Joint clicking had a positive correlation with unilateral disc degeneration, osteophyte, sclerosis and synovitis. Crepitus had a significant correlation with bilateral osteophyte. Pain was not correlated with any MRI findings except hypermobility. Conclusion: Selective correlations between the MRI findings and clinical symptoms were elucidated. The results of this study imply that condyle-disc deformities could be advanced without pain, and that joint clicking and crepitus could be clinical symptoms of condyle-disc degeneration.ope

Change of arch dimension using two different expansion modalities in adults-MARPE and continuous archwire: a pilot study

Considering the high prevalence, transverse control in adult patients presenting relatively narrow maxillary width is a challenging issue. This study compared the pattern of arch expansion induced by either miniscrew-assisted rapid palatal expander (MARPE) or continuous archwire engaged on self-ligating brackets. Age-matched adults groups(N=15 each) were treated with respective appliance. In both groups, all intercanine, interpremolar, and intermolar widths increased, and significantly greater change was noted in the intermolar region. Buccal tipping was minimal in both groups. Subsequent arch length increase, lingual tipping of incisors and distal tipping of molars were also found in both groups. According to the results, it can be concluded that the MARPE induced generally more arch expansion, particularly in the intermolar width, indicating that the adults showing buccal crossbite of the molars may have to undergo expansion via MARPE prior to arch alignment using continuous archwire.ope

A new concept for the cephalometric evaluation of craniofacial patterns (multiharmony).

Orthodontists commonly specify the alignment of the teeth and jaws by means of a set of k angles and their relationship with each other. Each individual can thus be visualized as a point in k-dimensional space. Individuals regarded as having an ideal occlusion and well-balanced face, form a cloud of points that is termed the 'norm' population. Individuals far from the cloud require orthodontic intervention. In this study, a method is presented--the multiharmony method (MHM), which assists in treatment planning. With multiple regression analysis, the expected value that each angle should take in a norm individual when the remaining angles are given is estimated. The residual difference between the measured angle and its expected value then indicates the deviation from a harmonic appearance in the respective angle. The MHM was applied to a data set of 134 Korean individuals identified as the norm population (Class I, mean age: 19.6 years) and to 87 patients (Class III, mean age: 21.2 years). From the number and size of the residuals, the two populations could be separated almost completely. Almost all patients showed residuals larger than any residual in the norm population (sensitivity: 99 per cent), whereas 90 per cent of all norm individuals showed no extreme residuals. The MHM can also be used to assist in visualizing different treatment effects, thereby assisting the orthodontist in choosing the best course of treatment for each patientope

Miniscrew-assisted rapid palatal expansion for managing arch perimeter in an adult patient

Introduction: Etiology of dental crowding may be related to arch constriction in diverse dimensions, and an appropriate manipulation of arch perimeter by intervening in basal bone discrepancies cases, may be a key for crowding relief, especially when incisors movement is limited due to underlying pathology, periodontal issues or restrictions related to soft tissue profile. Objectives: This case report illustrates a 24-year old woman, with maxillary transverse deficiency, upper and lower arches crowding, Class II, division 1, subdivision right relationship, previous upper incisors traumatic episode and straight profile. A non-surgical and non-extraction treatment approach was feasible due to the miniscrew-assisted rapid palatal expansion technique (MARPE). Methods: The MARPE appliance consisted of a conventional Hyrax expander supported by four orthodontic miniscrews. A slow expansion protocol was adopted, with an overall of 40 days of activation and a 3-month retention period. Intrusive traction miniscrew-anchored mechanics were used for correcting the Class II subdivision relationship, managing lower arch perimeter and midline deviation before including the upper central incisors. Results: Post-treatment records show an intermolar width increase of 5 mm, bilateral Class I molar and canine relationships, upper and lower crowding resolution, coincident dental midlines and proper intercuspation. Conclusions: The MARPE is an effective treatment approach for managing arch-perimeter deficiencies related to maxillary transverse discrepancies in adult patients.ope

Bimaxillary Total Arch Intrusion in Lingual Orthodontics for Hyperdivergent Class II Face with Asymmetry and Lip Protrusion

Hyperdivergent Class II face is accompanied by a convex profile, while it is usually characterized by upright upper and/ or lower incisors. Thus, it is important to precisely maintain an axis of upper incisors during retraction. Particularly, axis control of upper incisors is more difficult in lingual orthodontics. Unlike in the buccal appliance, traction force pushes the wire out of horizontal slot in the lingual appliance, so sufficient moment for torque control of incisors may not be obtained. Therefore, excessive overtorque should be placed on the archwire for making same amount of moment and accomplishing incisor translation. Furthermore, to correct lip protrusion and lip incompetency in this patient, bimaxillary total arch intrusion and maximum retraction of incisors was also treatment objective to improve soft tissue problems. This case report demonstrates satisfactory results through bimaxillary total arch intrusion with translation of upper incisors and intrusion of lower incisors using palatal/lingual miniscrews and continuous arch with additional torque for axis control of incisors in lingual orthodontics.ope

Orthodontic Repositioning of Subapically Transposed Tooth in a CLP Patient

Eruption disturbances such as an impaction complicate orthodontic treatment because soft-tissue and hard-tissue considerations must be taken into account. Treatment is further complicated when such eruption disturbances occur in a growing patient. Extraction of impacted teeth can be an option that carries the weight of additional prostheses and bony defects, whereas exposure or luxation followed by orthodontic traction can preserve the patient's teeth and bony structure with improved esthetics. Therefore, an accurate diagnosis is needed in establishing an efficient and effective force system to achieve the desired tooth movements with few unwanted sequelae. This case report describes the process of differential diagnosis with the aid of 3-dimensional imaging in constructing a force-driven system, using the centers of resistance as reference points, to successfully bring a pair of impacted maxillary canines into alignment in an adolescent boy.ope

A Sequential Approach for an Asymmetric Extraction Case in Lingual Orthodontics

To resolve the dental asymmetries, it is important to determine the treatment midline with facial midline as a reference and the anchorage value at each quadrant. Then the correction of midline and molar key should be conducted from the initiation of treatment. Therefore, the simulation of desired tooth movement prior to treatment is an essential part of orthodontic diagnosis. Moreover, considering that many adult patients have various degree of periodontal breakdown, a strategic tooth movement in order not to cause undesired round tripping is utmost important. Recently, virtual simulation have been developed and introduced to visualize three-dimensional desirable tooth movement to achieve treatment goals. In this report, we present a sequential approach for an asymmetric extraction case involving torque control with a lever arm in lingual orthodontics.ope

전치부 개교를 동반한 골격성 III급 안면비대칭 환자의 선수술 시 Virtual Set-up Model 을 이용한 수술교합 분석

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A Simultaneous Mobilization of Four Impacted Upper Incisors in a Case of an Adolescent Patient with Cleidocranial Dysplasia (CCD)

Introduction: Cleidocranial dysplasia (CCD) is often attended by a considerable number of supernumerary teeth combined with impaction of sometimes all permanent teeth. To help these patients obtain an esthetically pleasing and functional dentition, eruption of an appropriate number of permanent teeth should ideally be brought about, while all other teeth should be removed. The simultaneous traction of several neighboring teeth into the same direction is associated with biomechanical challenges. This report illustrates how these difficulties were solved in a specific treatment case. Findings and diagnosis: A 9-year-old boy presented with delayed tooth eruption. Major concern of the patient was the edentulous maxillary anterior segment. Clinical manifestation was confined to all deciduous canines and molars in both jaws and to the permanent mandibular central incisors. Radiographic examination revealed the impaction of all remaining permanent teeth as well as 20 supernumerary teeth and four third-molar buds. Cephalometric analysis revealed a tendency for skeletal class III in conjunction with a horizontal growth pattern. Treatment progress and outcomes: Utilizing a custom-planned appliance, four completely impacted maxillary incisors could be moved to esthetically and functionally acceptable positions within 8 months. The appliance used was supported exclusively by the maxillary deciduous teeth and the palate. Thanks to biomechanical considerations, the position of the anchor teeth could be fully preserved. Conclusions: Simultaneous mobilization of multiple teeth requires a customized approach that does justice to each patient’s individual situation. Meticulous treatment planning can prevent adverse effects even without the use of skeletal anchorage methods.ope