Finite element analysis of maxillary incisor displacement during en-masse retraction according to orthodontic mini-implant position

Correlation Between Radiological Changes of the Temporomandibular Joint and Upper Cervical Vertebrae in Degenerative Joint Disease: A Cone-Beam Computed Tomography-Based Analytical Study

Objectives This study was conducted to assess the radiological changes of the temporomandibular joint (TMJ) and cervical vertebrae individually and their correlation in degenerative joint disease (DJD) using a cone-beam computed tomography (CBCT)-based approach. Methodology The study employed a cross-sectional, analytical retrospective design, analyzing one-year data. CBCT scans of 60 patients (120 TMJs) were assessed for degenerative changes using standardized imaging parameters. Eligibility criteria included full field-of-view CBCT scans, excluding those with craniofacial anomalies or prior orthodontic treatment. Radiological assessments of TMJs and cervical vertebrae were conducted by experienced radiologists using the Anjos Pontual method and novel grading system (TMJ Spine Degenerative Severity Index). Results The study included 60 CBCT scans (120 joints), with 31.7% males and 68.3% females. Participants were predominantly aged 31-60 years (58.3%). DJD findings for the right TMJ showed grade 1 changes in 55.0% and grade 2 in 31.7%, while the left TMJ had 46.7% grade 1 and 35.0% grade 2 changes. A strong positive correlation (0.704) was found between bilateral TMJ and cervical vertebrae changes. Age correlated significantly with TMJ alterations but not with cervical vertebrae changes. Conclusion This study demonstrated that there exists a positive association between the radiological changes of TMJ and cervical vertebrae in DJD with age, which can be detected in mild stage of severity on CBCT and can be of use in clinical correlation and application of optimal interventions ensuring better prognosis.

Three-dimensional volumetric evaluation of root resorption in maxillary anteriors following en-masse retraction with varying force vectors - a randomized control trial

BACKGROUND

Root resorption in orthodontics is associated with direction and magnitude of force application as primary etiological factors. Well-controlled trials that utilize three-dimensional segmentation to detect volumetric changes in tooth structure are required to assess the quantitative nature of root resorption.

OBJECTIVE

To assess the severity of root resorption (RR) during retraction of maxillary anteriors with three different force vectors (with and without skeletal anchorage) via cone-beam computed tomography (CBCT) superimpositions.

TRIAL DESIGN

Three-arm parallel randomized clinical trial (RCT).

MATERIALS AND METHODS

Forty-two (16 males, 26 females) patients, (17-28 years), in permanent dentition with bimaxillary protrusion were randomly allocated to three groups of 14 patients each using block randomization (1:1:1 ratio) and allocation concealment. En-masse anterior retraction post first premolar extractions was carried out with modified force vectors in the three groups based on anchorage type [Molar, Mini-implant and Infrazygomatic crest (IZC) bone screws]. Volumetric root loss and linear dimensional changes were blindly assessed on initial (T0) and final (T1, end of space closure) CBCT scans. Normality distribution of values was done using Shapiro-Wilk's test. ANOVA and Post-hoc Tukey HSD test were done to compare measurements between groups at significance levels (P < .05).

RESULTS

Forty patients were analysed (14, 14, and 12 in three groups). Significant volumetric loss was noted in all groups. Central incisors demonstrated a significant reduction in IZC group (81.5 ± 21.1 mm3 ) compared to conventional (50.1 ± 26.5 mm3 ) and mini-implant groups (76.1 ± 27.6 mm3 ). Canines demonstrated a significant reduction in mini-implant group (108.9 ± 33.9 mm3 ) compared to conventional (68.8 ± 42.5 mm3 ) and IZC groups (103.1 ± 29.1 mm3 ). Regarding linear parameters, central incisors and canines revealed significant root length reduction in both skeletal anchorage groups. Lateral incisors showed no significant changes between groups.

CONCLUSIONS

Intrusive force vectors generated during skeletally anchored retraction can predispose anteriors to an increased risk of resorption. Greater loss of root volume was noted in the centrals and canines when retracted with skeletal anchorage.

LIMITATIONS

Small sample size and variations during CBCT acquisition.

HARMS

Low-dose CBCT scans were taken at T0 and T1 treatment intervals.

Comparing the Efficiency of Infrazygomatic Crest (IZC) Screws and Conventional Method for Anterior Retraction in Patients Undergoing Fixed Orthodontic Treatment for Class 2 Malocclusion: A Prospective Clinical Study

Introduction In orthodontic treatment for class 2 malocclusion, conventional approaches involve extracting the upper first premolars and using methods like en masse retraction and extra-oral or intra-oral distalization. However, these often result in unintended forces and adverse effects. Contemporary techniques, such as maxillary arch distalization with mini-implants like infrazygomatic crest (IZC) implants, offer superior outcomes. IZC implants provide a safe, flexible, and effective site for implant placement, achieving a remarkable 93.7% success rate. Power arms enable precise control, allowing orthodontists to apply controlled forces for optimal tooth movement. This study aims to compare cephalometric parameters pre and post treatment using IZC/buccal shelf (BS) screws and conventional retraction, assessing the efficiency of IZC screws in maintaining arch length during teeth retraction. Methods In a split-mouth study at Yenepoya Dental College, 40 orthodontic patients aged 18-35 were divided into control (premolar extraction, anterior retraction) and study (third molar removal, IZC screw distalization) groups. The control group used a nitinol spring/E chain for retraction, while the study group employed IZC screw-assisted en masse distalization. Regular reviews and adjustments occurred, with radiographs and study models assessed after six months for cephalometric parameters and arch length. Results A significant difference was found in U1-SN (degree), L1-Apog (in mm), L1-NB (degree), and L1-NB (in mm) of pretreatment records, whereas all other measurements showed statistically similar values between conventional and IZC groups. Improvement was higher with the conventional group when compared with IZC groups in these measurements due to the extraction of the first premolars rather than third molar extraction and distalization. However, the IZC group also showed statistically significant improvement in cephalometric parameters such as U1-SN (degree), L1-Apog (in mm), L1-NB (degree), and L1-NB (in mm). Conclusion  The statistical analysis of radiographic and cast measurements in both the maxilla and mandible demonstrated a significant efficiency of IZC screws in teeth retraction while preserving arch length compared to conventional methods. Nevertheless, to strengthen the findings of our study, additional clinical investigations on IZC screws are warranted.

Dental, skeletal and soft tissue changes after bimaxillary protrusion treatment with temporary anchorage devices using different retraction mechanics

BACKGROUND

Temporary anchorage devices (TADs), which are absolute anchorage, are used for retraction of the anterior teeth in cases of severe bimaxillary protrusion. There have been a number of studies regarding anterior tooth movement using TADs performed by simulation systems and actual treated materials with sliding mechanics. However, there are few studies regarding anterior tooth movement using TADs treated by loop mechanics The purpose of this study was to investigate the effect of TADs in anterior tooth movement using loop mechanics performed in actual cases of bimaxillary protrusion.

METHODS

This study was performed in 20 adult patients with severe bimaxillary protrusion treated with four bicuspid extraction with sliding or loop mechanics (n = 10 in each mechanics) using TADs. The skeletal and denture patterns, as well as the soft tissue profile from pre-treatment (T0) and post-treatment (T1) lateral cephalograms, were compared between sliding and closing loop mechanics.

RESULTS

The use of TADs is useful for retraction of anterior teeth without molar anchorage loss. in sliding and loop mechanics. The upper anterior teeth were less lingual tipped and lower anterior teeth were more upright resulting in less clockwise rotation of the occlusal plane in loop mechanics compared to sliding mechanics.

CONCLUSION

An oblique retraction force vector with a lower point of application causes less intrusion and more lingual tipping of upper anterior teeth as well as more clockwise rotation of the occlusal plane compared to a parallel retraction force vector.

Temporary anchorage devices and the forces and effects on the dentition and surrounding structures during orthodontic treatment: a scoping review

BACKGROUND

Temporary anchorage devices (TADs) offer the clinician an immediate temporary source of skeletal anchorage for a range of orthodontic interventions. It is important to understand forces involved in using TADs and the effects on the dentition and surrounding structures, to improve clinical outcomes.

OBJECTIVE

To examine and qualitatively synthesize literature on the forces involved with the use of TADs and the effects on the dentition and surrounding structures in orthodontic tooth movement, to provide better understanding of the complex interactions and the clinical implications.

SEARCH METHODS

Electronic databases searched included: Cochrane Library [including Central Register of Controlled Trials (CENTRAL)], Embase via OVID, Pubmed, and Scopus. Study screening and selection were conducted in duplicate.

SELECTION CRITERIA

Studies selected were clinical studies, simulation studies (computer or laboratory-based), or animal studies with no restriction over gender, age, study type (excluding case reports), or setting. Studies focusing on the forces involved with the use of TADs in orthodontic treatment and their effects on the dentition and surrounding structures were included.

DATA COLLECTION AND ANALYSIS

A data charting form was piloted and refined. Data charting was performed independently and in duplicate. This consisted of key fields with predetermined options and free text. The extracted data were collated, and a narrative synthesis conducted.

RESULTS

The results from 203 included studies were grouped into seven TAD based interventions combining the clinical, simulation, and animal studies. They were: En masse retraction of anterior teeth, intrusion, movement of a single tooth, orthopaedic interventions, distalisation, maxillary expansion and other types. The forces involved with the use of TADs, and their effects on the dentition and surrounding structures, were presented in descriptive and tabular formats.

LIMITATIONS

This review restricted study language to English. Formal appraisal of the quality of evidence is not a required feature of scoping reviews, as per the PRISMA-ScR guidelines, however it was evident that a proportion of clinical studies were of high risk of bias and low quality and therefore any proposed changes the reader may consider to their clinical practice should be contextualized in light of this.

CONCLUSIONS

Across the seven types of TAD based interventions the effects on the dentition and surrounding structures are described providing a better understanding of the complex interactions. A guide to the level and direction of forces in each type of intervention is provided to aid clinicians in achieving high quality outcomes.

IMPLICATIONS

There is a need to validate future FEA simulation studies by comparing to clinical data. It is also recommended that future scoping reviews incorporate a formal critical appraisal of studies to facilitate the translation of the results into clinical practice. Development of a standard set of terms for TADs is recommended to facilitate future research.

REGISTRATION

Registration of a scoping review is not possible with PROSPERO.

FUNDING

None to declare.

Comparative evaluation of displacement and stress distribution pattern during mandibular arch distalization with extra and inter-radicular mini-implants: a three-dimensional finite element study

OBJECTIVE

To compare the initial stress distribution and displacement on mandibular dentition using extra and inter-radicular mini-implants for arch distalization, by means of finite element analysis.

METHODS

For this study, two finite element models of the mandible were designed. The models consisted of periodontal ligament (PDL) and alveolar bone of all teeth until second molars. In the Case 1, bilateral extra-radicular buccal-shelf stainless steel mini-implants (10.0-mm length; 2.0-mm diameter) were placed between first and second permanent molars. In the Case 2, bilateral inter-radicular stainless steel mini-implants (10.0-mm length; 1.5-mm diameter) were placed between second premolar and first permanent molar. Power hook was attached between canine and first premolar at a fixed height of 8mm. In the two cases, 200g of distalization force was applied. ANSYS v. 12.1 software was used to analyze and compare von Mises stress and displacement in the mandibular dentition, PDL and bone.

RESULTS

Higher stresses were observed in mandibular dentition with the inter-radicular implant system. The amount of von Mises stress was higher for cortical bone (85.66MPa) and cancellous bone (3.64MPa) in Case 2, in comparison to cortical bone (41.93MPa) and cancellous bone (3.43MPa) in Case 1. The amount of arch distalization was higher for mandible in Case 1 (0.028mm), in comparison to Case 2 (0.026mm).

CONCLUSION

Both systems were clinically safe, but extra-radicular implants showed more effective and controlled distalization pattern, in comparison to inter-radicular implants, in Class III malocclusion treatment.

Effects of different distalization directions and methods on maxillary total distalization with clear aligners: a finite element study

OBJECTIVES

To analyze the effects of maxillary tooth distalization by clear aligner (CA) treatment with variations in the angular direction of the distalization force, presence of attachments, and force-application method used.

MATERIALS AND METHODS

A finite element model containing alveolar bone, dentition, and periodontal ligament was constructed. Analytical model groups were as follows: (1) distalization with buttons (without attachments), (2) buttons on canines (with attachments), (3) precision cuts on the canines (without attachments), and (4) precision cuts on the canines (with attachments). A distalization force of 1.5 N was applied to the button or precision cut at -30°, -20°, -10°, 0°, 10°, 20°, and 30° to the occlusal plane.

RESULTS

As the direction of force approached +30°, the dentition inclined posteriorly. The posterior movement pattern was significantly influenced by the presence of an attachment and the direction of force, rather than the area where the force was applied. Distal inclination was dramatically reduced with attachments. A disengagement or deformation of the CA may reduce the distalization efficiency of the dentition or move the dentition in an inappropriate direction.

CONCLUSIONS

Attachments for efficient distalization by the CA are necessary. The use of miniscrews in the direction of force parallel to the occlusal plane is more advantageous than the use of Class II elastics. Due to CA deformation, distalization with the button on the canines can be more effective for distal movement of the maxillary dentition.

Efficiency of maxillary total arch distalization using temporary anchorage devices (TADs) for treatment of Class II-malocclusions: A systematic review and meta-analysis

OBJECTIVES

To evaluate the treatment effects and post-treatment stability of the maxillary total arch distalization using TADs during the non-extraction treatment of class II malocclusions.

MATERIALS AND METHODS

Study involved an electronic search followed by hand searching for randomized and non-randomized clinical studies about maxillary total arch distalization using TADs. After data extraction and risk of bias assessment, meta-analysis was performed for dental, skeletal and soft tissue changes using the Generic-inverse variance approach by use of the mean difference and random-effect model.

RESULTS

In total, 1788 articles were identified, 88 full texts were screened and 22 studies were found eligible; 17 of them were included in the quantitative analysis. The means of distalization/distal tipping of the maxillary first molar were 4mm/3.17° in adults, 3.95mm/1.61° in adolescents after treatment with the Modified C-Palatal plate (MCPP), while they were 2.44mm/2.91° with the inter-radicular mini-screws. Both MCPP's treatment in adults and inter-radicular mini-screws resulted in significant intrusion of U6 (1.64 and 0.75mm, respectively), while insignificant extrusion of U6 was resulted in adolescents treated by MCPP. MCPP appliances resulted in palatal inclination/extrusion of maxillary incisors U1 (6.77°/2mm in adults, 7.46°/3.14mm in adolescents). In contrast, inter-radicular mini-screws resulted in less palatal less amount of palatal inclination/insignificant intrusion of U1 (2.42°/0.14mm). MCPP treatment also resulted in significant changes in the skeletal measurements (SNA, ANB, occlusal and mandibular planes). Insignificant differences were found between subgroups in the retraction amount of maxillary incisors, as well as the upper and lower lips. In the follow-up of adolescents treated with MCPP, a significant amount of mesial movement, mesial tipping, and extrusion (2.94mm, 2.84°, and 3.94mm, respectively) was found. However, skeletal and occlusal corrections of the Class II relationship were maintained.

CONCLUSIONS

Maxillary total arch distalization using TADs can be an effective and stable treatment procedure. However, RCTs or prospective cohort studies are highly recommended to establish a clinical evidence regarding their efficiency.

Torque control of maxillary anterior teeth with the double J retractor and palatal miniscrews during en masse retraction

A double J retractor (DJR) and palatal miniscrews were used to retract maxillary anterior teeth after failure of buccal posterior miniscrews. The line of action passing through the center of resistance of the maxillary anterior teeth and the moment generated by the palatal miniscrews via torquing springs successfully controlled the overbite and incisor torque during space closure. The DJR and palatal miniscrews work well with labial fixed appliances to address bimaxillary protrusion.

Mechanical environment for lower canine T-loop retraction compared to en-masse space closure with a power-arm attached to either the canine bracket or the archwire

OBJECTIVES

To assess the mechanical environment for three fixed appliances designed to retract the lower anterior segment.

MATERIALS AND METHODS

A cone-beam computed tomography scan provided three-dimensional morphology to construct finite element models for three common methods of lower anterior retraction into first premolar extraction spaces: (1) canine retraction with a T-loop, (2) en-masse space closure with the power-arm on the canine bracket (PAB), and (3) power-arm directly attached to the archwire mesial to the canine (PAW). Half of the symmetric mandibular arch was modeled as a linear, isotropic composite material containing five teeth: central incisors (L1), lateral incisor (L2), canine (L3), second premolar (L4), and first molar (L5). Bonded brackets had 0.022-in slots. Archwire and power-arm components were 0.016 × 0.022 in. An initial retraction force of 125 cN was used for all three appliances. Displacements were calculated. Periodontal ligament (PDL) stresses and distributions were calculated for four invariants: maximum principal, minimum principal, von Mises, and dilatational stresses.

RESULTS

The PDL stress distributions for the four invariants corresponded to the displacement patterns for each appliance. T-loop tipped the canine(s) and incisors distally. PAB rotated L3 distal in, intruded L2, and extruded L1. PAW distorted the archwire resulting in L3 extrusion as well as lingual tipping of L1 and L2. Maximum stress levels in the PDL were up to 5× greater for the PAW than the T-loop and PAB methods.

CONCLUSIONS

T-loop of this type is more predictable because power-arms can have rotational and archwire distortion effects that result in undesirable paths of tooth movement.

Characteristics and Dynamics of Full Arch Distalization Using Transpalatal Arches with Midpalatal and Interradicular Miniscrews as Temporary Anchorage Devices: A Preliminary Finite Element Analysis

INTRODUCTION

Miniscrews have proved quite effective in fixed orthodontic treatment. They can be placed in areas like palatal interradicular zones or midpalatal suture. Despite the value of these methods and their ever-increasing use, their characteristics are not assessed before when implanted in palatal interradicular areas or in the midpalatal suture. We aimed to assess, for the first time, the dynamics of full arch distalization using such miniscrews.

METHODS

A 3D model of maxilla with all permanent dentition was created from a CT scan volume. Tissues were segmented and differentiated. Afterward, miniscrews and appliances were designed, and the whole model was registered within a finite element analysis software by assigning proper mechanical properties to tissues and orthodontic appliances. The full arches were distalized using transpalatal arches with miniscrews as anchorage devices (in two different models). The extents of stresses and patterns of movements of various elements (teeth, miniscrews, appliances, tissues) were estimated. Results and Conclusions. Comparing the two models, it is obvious that in both models, the stress distribution is the highest in the TPA arms and the head of the miniscrew where the spring is connected. In comparison with the displacement in the X-axis, the "mesial in" rotation is seen in the first molar of both models. But there is one exception and that is the "mesial out" rotation of the right second molar. In all measurements, the amount of movement in Model 2 (with palatal interradicular miniscrews) is more than that in Model 1 (with midpalatal miniscrew). In the Y-axis, more tipping is seen in Model 2, especially the anterior teeth (detorque) and the first molar, but in Model 1, bodily movement of the first molar is more evident. Along the Z-axis, the mesial intrusion of the first molar and the distal extrusion of this tooth can be seen in both models. Again, the displacement values are higher in the second model (with interradicular miniscrews). In comparison with micromotion and stress distribution of miniscrews, in Model 1, maximum stress and micromotion is observed at the head of the miniscrew where it is attached to the spring. Of course, this amount of micromotion increases over time. The same is true for Model 2, but with a lower micromotion. As for the amount of stress, the stress distribution in both miniscrews of both models is almost uniform and rather severe.

Three-Dimensional Finite Element Analysis on En-Masse Retraction of the Maxillary Anterior Teeth With Quantitative Combined Loading Control

This study aims to elucidate the biomechanical effects of combined loading of maxillary anterior and posterior implants using the sliding method on en-masse retraction of the anterior teeth and to quantify the loading ratio (LR) of anterior and posterior implants to achieve controlled retraction of the maxillary anterior teeth. A three-dimensional finite element model of the maxilla-upper dentition appliance was constructed. Implants were placed on the distal (A) and mesial (B) sides of the lateral incisors as well as on the mesial (C) side of the first molar and different amounts of force were loaded between the implants using 2- or 5-mm traction hooks. The labiolingual movement of the anterior teeth was recorded and the relationship between the LR of the implants and the movement of the central incisors was evaluated. With 2-mm traction hooks, the central incisors exhibited a translation tendency during retraction at lower A/C and B/C LR and labial or lingual crown inclination at higher values. With 5-mm traction hooks, the central incisors, lateral incisors, and canine teeth exhibited a labial crown inclination. The results of this study suggest that 2-mm traction hooks can cause labial crown inclination, translation tendency during retraction, or lingual crown inclination of the central incisors due to alterations in the LR of the anterior and posterior implants. The central incisors only exhibited labial crown inclination during combined loading of the anterior and posterior implants when 5-mm traction hooks were used.

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.

Can interfaces at bracket-wire and between teeth in multi-teeth finite element model be simplified?

OBJECTIVE

Finite element (FE) method's correctness depends heavily on modeling method. This study aimed at determining whether the interfaces at bracket-wire and between teeth can be simplified for multi-teeth FE analysis.

METHOD

A three-dimensional FE model of a mandible was created from cone-beam computed tomography scan. Due to symmetry, only a half of the mandible was modeled, which consisted of five teeth (first premolar extraction and only first molar), brackets and archwire, periodontal ligament (PDL), cortical bone, and cancellous bone. All the bone, teeth, and PDL were considered to be isotropic and linear. The En-masse retraction case was simulated. A detailed model, which has contact elements between the bracket and archwire and between teeth, was developed to allow relative motion at the interfaces. A model with simplified interfacial conditions, which does not allow the relative motion, was also created. The stresses and displacements as results of the treatment on these two models were calculated and compared.

RESULTS

The stress and displacement distributions from the detailed model were more close to reality based on the expected displacement pattern of the clinical case than from the simplified model. The maximum stresses from the two methods were also different. The highest stress from the detailed model is twice as high as from the simplified model.

CONCLUSIONS

The detailed model provides much more reasonable results than the simplified model. Thus, the simplified model should not be used to replace the detailed model if the stress magnitude and highest stress location are the expected outcomes.

Finite Element Analysis of Stress in Maxillary Dentition during En-masse Retraction with Implant Anchorage

The goal of this study was to investigate how the height of the archwire hook and implant anchor affect tooth movement, stress in the teeth and alveolar bone, and the center of resistance during retraction of the entire maxillary dentition using a multibracket system. Computed tomography was used to scan a dried adult human skull with normal occlusion. Three-dimensional models of the maxillary bone, teeth, brackets, archwire, hook, and implant anchor were created and used for finite element analysis. The heights of the hook and the implant anchor were set at 0, 5, or 10 mm from the archwire. Orthodontic force of 4.9 N was systematically applied between the hook and the implant anchor and differential stress distributions and tooth movements observed for each traction condition. With horizontal traction, the archwire showed deformation in the superior direction anterior to the hook and in the inferior direction posterior to the hook. Differences in traction height and direction resulted in different degrees of deformation, with biphasic movement clearly evident both in front of and behind the hook. With horizontal traction of the hook at a height of 0 mm, all the teeth moved distally, but not with any other type of traction. At a height of 5 mm or 10 mm, deformation showed an increase. The central incisor showed extrusion under all traction conditions, with the amount showing a reduction as the height of horizontal or posterosuperior traction increased. The center of resistance was located at the root of the 6 anterior teeth and entire maxillary dentition. The present results suggest that it is necessary to consider deformation of the wire and the center of resistance during en-masse retraction with implant anchorage.

Evaluation of the effects of miniscrew incorporation in palatal expanders for young adults using finite element analysis

Objective

The aim of this study was to evaluate the stress distribution and displacement of various craniofacial structures after nonsurgical rapid palatal expansion (RPE) with conventional (C-RPE), bone-borne (B-RPE), and miniscrew-assisted (MARPE) expanders for young adults using three-dimensional finite element analysis (3D FEA).

Methods

Conventional, bone-borne, and miniscrew-assisted palatal expanders were designed to simulate expansion in a 3D FE model created from a 20-year-old human dry skull. Stress distribution and the displacement pattern for each circumaxillary suture and anchor tooth were calculated.

Results

The results showed that C-RPE induced the greatest stress along the frontal process of the maxilla and around the anchor teeth, followed by the suture area, whereas B-RPE generated the greatest stress around the miniscrew, although the area was limited within the suture. Compared with the other appliances, MARPE caused relatively even stress distribution, decreased the stress on the buccal plate of the anchor teeth, and reduced tipping of the anchor teeth.

Conclusions

The findings of this study suggest that the incorporation of miniscrews in RPE devices may contribute to force delivery to the sutures and a decrease in excessive stress on the buccal plate. Thus, MARPE may serve as an effective modality for the nonsurgical treatment of transverse maxillary deficiency in young adults.

Maxillary Corticotomies With Bone-to-Bone Retraction and Mandibular Segmental Osteotomy for Correcting an Anterior Double Protrusion

BACKGROUNDS

This article presents maxillary corticotomies with bone-to-bone retraction and anterior segmental osteotomy (ASO) as an alternative to 2-jaw orthognathics in the bimaxilary protrusion patient with partially anchylosed maxillary anterior tooth.

METHODS

The 18-year-old male, complaining of anterior protrusion, with a trauma history to the maxillary central incisor, and requesting rapid treatment, was treated with maxillary corticotomies in 2 stages and ASO in the mandible. The mandibular ASO and palatal corticotomy were done under local anesthesia and 2 weeks later, labial corticotomy followed. The anterior segment was retracted bodily using buccal C-tubes and a combination of the C-lingual retractor and palatal C-plate.

RESULTS

Due to a concern about ankylosis of the maxillary right central incisor, retraction of the anterior bone/tooth segment was chosen over any attempt to move teeth through the bone. After bone-to-bone retraction, the remaining extraction space was closed by protraction of posteriors. The total treatment period was 18 months. There was good retraction of the anterior segment and retrusion of the lips.

CONCLUSIONS

A combination of maxillary corticotomies with skeletal anchorage for bone-to-bone retraction and a mandibular ASO under local anesthesia might be an alternative treatment option for excellent profile change in a short treatment period.

Maxillary anterior en masse retraction using different antero-posterior position of mini screw: a 3D finite element study

Background

Nowadays, mini screws are used in orthodontic tooth movement to obtain maximum or absolute anchorage. They have gained popularity among orthodontists for en masse retraction of anterior teeth after first premolar extraction in maximum anchorage cases. The purpose of this study was to determine the type of anterior tooth movement during the time when force was applied from different mini screw placements to the anterior power arm with various heights.

Methods

A finite element method was used for modeling maxillary teeth and bone structure. Brackets, wire, and hooks were also designed for modeling. Two appropriate positions for mini screw in the mesial and distal of the second premolar were designed as fixed nodes. Forces were applied from the mini screw to four different levels of anterior hook height: 0, 3, 6, and 9 mm. Initial tooth movement in eight different conditions was analyzed and calculated with ANSYS software.

Results

Rotation of anterior dentition was decreased with a longer anterior power arm and the mesial placement of the mini screw. Bodily movements occurred with the 9-mm height of the power arm in both mini screw positions. Intrusion or extrusion of the anterior teeth segment depended on the level of the mini screw and the edge of the power arm on the Z axis.

Conclusions

According to the findings of this study, the best control in the sagittal plane during anterior en masse retraction was achieved by mesial placement of the mini screw and the 9-mm height of the anterior power arm. Where control in the vertical plane was concerned, distal placement of the mini screw with the 6-mm power arm height had minimum adverse effect on anterior dentition.