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BACKGROUND: The incidence of mandibular first molar impaction is less than 0.01%, and there are no standard treatment guidelines. Orthodontic traction can be chosen as a treatment plan in some circumstances. One miniscrew in the mandibular ramus can offer sufficient anchorage for the traction of impacted mandibular molars. CASE DESCRIPTION: A 10-year-old boy had a completely labially positioned maxillary left canine and a deeply impacted mandibular left first molar associated with a dentigerous cyst. Using 2 palatal miniscrews for distalization, space was created to align the maxillary left canine. In addition, a miniscrew in the mandibular ramus facilitated the traction of the mandibular left first molar. After 3 years and 6 months of orthodontic treatment, the integrity of the dental arch was restored, and occlusal function was reestablished. PRACTICAL IMPLICATIONS: A ramus miniscrew is an effective and viable treatment option for the orthodontic traction of deeply impacted mandibular molars.

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A 20-year-old female patient with severe maxillary crowding and skeletal Class III malocclusion was successfully treated using an enhanced pendulum appliance. Camouflage treatment was chosen because the patient refused surgical intervention. Detailed examination and analysis revealed that labial inclination of the maxillary anterior teeth could provide the alignment space necessary after tooth extraction in the maxillary arch but it would not be beneficial esthetically and would increase the moment perpendicular to the tooth long axis as well as increase the risk of bone dehiscence. Therefore, lingual inclination of the mandibular anterior teeth was performed. To create space for aligning the maxillary arch, an enhanced pendulum appliance was utilized, in addition to premolar extraction. The enhanced pendulum appliance had one mesial and one distal helix on each spring, exerting opposing forces in the buccolingual direction and reducing the buccolingual inclination of the molars. In addition, miniscrews were integrated into the Nance arch of the enhanced pendulum appliance to provide skeletal anchorage, minimizing the reciprocal movement of anchorage teeth. This modification not only enhanced control over tooth movement but also improved treatment efficiency. During the entire treatment duration of 17 months, substantial improvement in facial and occlusal aspects were noted. Additionally, the patient retained these positive changes until the subsequent 2-year follow-up period.

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PURPOSE: The purpose of this study was to analyze the biomechanical effects of four different designs of frog appliances for molar distalization using finite element analysis. METHODS: A three-dimensional finite element model including complete dentition, periodontal ligament, palatine, and alveolar bone was established. Four types of frog appliances were designed to simulate maxillary molar distalization: tooth-button-borne (Type A), bone-borne (Type B), bone-button-borne (Type C), and tooth-bone-borne (Type D) frog appliances. A force of 10 N was applied simulating a screw in the anteroposterior direction. To assess the von Mises stress distribution and the resultant displacements in the teeth and periodontal tissues, geometric nonlinear theory was utilized. RESULTS: Compared to the conventional tooth-borne frog appliance (Type A), the bone-borne frog appliances showed increased first molar distalization with enhanced mesiolingual rotation and distal tipping, but the labial inclination and intrusion of the incisors were insignificant. When replacing the palatal acrylic button with miniscrews (Types B and D), more anchorage forces were transmitted from the first premolar to palatine bone, which was further dispersed by the assistance of a palatal acrylic button (Type C). CONCLUSIONS: Compared to tooth-borne frog appliances, the bone-borne variants demonstrated a clear advantage for en masse molar distalization. The combined anchorage system utilizing palatal acrylic buttons and miniscrews (Type C) offers the most efficient stress distribution, minimizing force concentration on the palatine bone.

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OBJECTIVES: To compare the mandibular posterior space available before treatment and the distance of molar distalization achieved after mandibular dentition distalization with microimplants. MATERIALS AND METHODS: A total of 66 Class I or III adult patients (mean age = 24.46 ± 4.89 years) who underwent molar distalization using microimplants were retrospectively included. The posterior space available distal to the second molar before treatment and the distance of distalization achieved after treatment were measured using axial cone-beam computed tomography images (0, 2, 4, and 6 mm apical to the second molar root furcation). Changes in lingual cortical thickness and molar root length after treatment were examined. Paired t-test or Wilcoxon signed-rank test was performed to compare measurements before and after treatment. Spearman correlation analysis was performed to assess the relationship between thinning of the cortical plate and root resorption. RESULTS: Achieved distalization distance was significantly greater than pretreatment posterior space available by 0.8 mm at all root levels (P < .001). The difference was greater toward the root apex level and greater in the Class III group than the Class I group. Lingual cortical thickness was significantly decreased after treatment along with resorption of the second molar distal root (P < .001). In addition, a positive correlation was found between thinning of the cortical plate and distal root resorption of the molar (P < .001). CONCLUSIONS: Achieved distalization distance of the mandibular molar using microimplants was greater than the pretreatment posterior space available. Thinning of the lingual cortex and root resorption were observed after distalization.

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BACKGROUND: Desirable molar distalization by bodily movement is challenging and can be difficult to achieve. This study investigated changes in molar angulation (mesiodistal tipping), molar inclination (buccolingual torque) and rotation during distalization using clear aligner therapy (CAT). MATERIALS AND METHODS: This retrospective study included 38 cone beam computed tomographic images (CBCTs) taken for patients treated with molar distalization using CAT. The study evaluated pre- (T0) and post-treatment (T1) CBCTs of 19 adult patients (36.68 ± 13.50 years) who underwent maxillary molar distalization using Invisalign® aligners (Align Technology, Inc., San José, CA, USA) with a minimum of 2 mm distalization. Changes in maxillary molar tip, torque and rotation were measured for 61 molars (183 roots). Paired t-test was used to evaluate the differences between pre- and post-treatment readings. The level of significance was set at p ≤ 0.05. The reproducibility of measurements was assessed by the intraclass correlation coefficient (ICC). RESULTS: Molar angulation did not show significant change after distalization (p = 0.158) however, there was significant increase in buccal molar inclination (p = 0.034) and mesiobuccal molar rotation (p < 0.001). CONCLUSION: Molar distalization of 2 mm did not cause significant molar tipping. Maxillary molars showed significant buccal inclination (increased torque) and mesiobuccal rotation after distalization.

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Objectives: The purpose of this preliminary study was to determine the differences between planned and actual maxillary molar movements after the completion of treatment with an initial set of clear aligners including sequential maxillary molar distalization. Methods: The data records of 14 non-growing patients who completed orthodontic treatment with sequential maxillary molar distalization using clear aligners were retrospectively evaluated (n= 14, 4 males and 10 females, 33.61 ± 8.57 years). Data on planned tooth movements were obtained from ClinCheck software (ClinCheck Pro version 5.3). The amounts of actual tooth movements were obtained by performing superimposition of lateral cephalograms taken before and after treatment. The amounts of distal translation and tipping between planned and actual maxillary molar movements were compared with the paired Student's t-test. Results: The statistically significant differences between planned and actual translation movements of maxillary first and second molars were shown after completing treatment with the first series of aligners (p < 0.05). The average actual amount of molar distalization on maxillary first molars was less than the planned amount by 1.32 ± 0.42 mm. Similarly, the average actual amount of molar distalization on maxillary second molars was less than the planned amount by 1.57 ± 0.45 mm. The accuracy for molar distalization, namely, the percentage of actual distal translation to planned movement, was 40.11% for maxillary first molars and 35.39% for maxillary second molars. However, the difference between the planned and actual angulation movements was not significant (p > 0.05). Conslusions: In conclusion, the amounts of actual distal translation of maxillary molars through the utilization of clear aligners were significantly lower than planned. However, there were no statistically significant differences between the degrees of actual and planned molar angulation movement.

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INTRODUCTION: With the popularity of clear aligners, the sequential distalization protocol has been more commonly used for molar distalization. However, the amount of molar distalization that can be achieved, as well as the accompanying side effects on the sagittal dimension, are unclear. METHODS: Registered with PROSPERO (CRD42023447211), relevant original studies were screened from seven databases (MEDLINE [PubMed], EBSCOhost, Web of Science, Elsevier [SCOPUS], Cochrane, LILACS [Latin American and Caribbean Health Sciences Literature], and Google Scholar) supplemented by a manual search of the references of the full-reading manuscripts by two investigators independently. A risk of bias assessment was conducted, relevant data were extracted, and meta-analysis was performed using RStudio. RESULTS: After the screening, 13 articles (11 involving maxillary distalization, two involving mandibular distalization) met the inclusion criteria. All studies had a high or medium risk of bias. The meta-analysis revealed that the maxillary first molar (U6) mesiobuccal cusp was distalized 2.07 mm [1.38 mm, 2.77 mm] based on the post-distalization dental model superimposition, and the U6 crown was distalized 2.00 mm [0.77 mm, 3.24 mm] based on the post-treatment lateral cephalometric evaluation. However, the U6 mesiobuccal root showed less distalization of 1.13 mm [-1.34 mm, 3.60 mm], indicating crown distal tipping, which was validated by meta-analysis (U6-PP angle: 2.19° [1.06°, 3.33°]). In addition, intra-arch anchorage loss was observed at the post-distalization time point (U1 protrusion: 0.39 mm [0.27 mm, 0.51 mm]), which was corrected at the post-treatment time point (incisal edge-PTV distance: -1.50 mm [-2.61 mm, -0.39 mm]). CONCLUSION: About 2 mm maxillary molar distalization can be achieved with the sequential distalization protocol, accompanied by slight molar crown distal tipping. Additional studies on this topic are needed due to the high risk of bias in currently available studies.

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Objective: To examine the areas of the maxillary tuberosity (MT) (coronal, apical, width, and height) with respect to the presence or absence of the third molar to establish possible anatomical limitations for molar distalization. Methods: A total of 277 tuberosities were evaluated through sagittal computed tomography (CT) images, divided for measurement into coronal (free of bone), apical (area of influence of the maxillary sinus), and tuberosity (bony area) zones, and stratified by the presence or absence of the third molar, sex, and two age subgroups. Mann-Whitney U test was used to compare the groups considering the third molar. Results: The medians of the width and height of the tuberosity decreased significantly in the absence of the third molar (P < 0.001). The apical area also showed differences, with negative values in the absence of the third molar and positive values in the presence of the third molar (P < 0.001). However, no differences were observed for the coronal area (P > 0.05). Conclusions: In the absence of the third molar, the size of the MT, represented by its width and height, was smaller and negative values (decrease) were observed for the maxillary sinus. The sagittal CT provides useful information regarding the amount of bone tissue available for distalization and relationship of the second molar with respect to the maxillary sinus, which allows individualizing each case in relation to the amount and type of movement expected.

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OBJECTIVES: The biomechanics in achieving molar distalization may differ between fixed appliances and clear aligners in the control of tooth movement. The objective of this study was to compare the treatment effects between clear aligners (CA) and fixed appliances (FA) in patients treated with miniscrew-assisted molar distalization. METHODS: The sample consisted of 46 subjects with mild-to-moderate crowding. A total of 22 patients treated with clear aligners (age, 25.66 ±â€…6.11 years old) and 24 patients treated with fixed appliances (age, 24.04 ±â€…4.95 years old) for miniscrew-assisted molar distalization were included in this study. The dental and skeletal changes were evaluated by the pre- and post-treatment lateral cephalograms. RESULTS: Significant changes were found with the vertical variables SN-OP angle (2.24 ±â€…3.22°, P < .05) and SN-MP angle (0.73 ±â€…1.15°, P < .05) for the FA group when compared with the CA group (SN-OP angle 0.41 ±â€…2.26° and SN-MP angle -0.21 ±â€…1.38°, P > .05). Both treatment groups achieved a 2-3 mm. molar distalization with significant intrusion of the upper molars. The CA group showed significantly less distal tipping of molars (U6^PP angle -2.29 ±â€…3.29° and L6^MP angle -2.92 ±â€…2.49°, P < .05) compared to the FA group (-5.24 ±â€…4.28° and -5.53 ±â€…5.03°, P < .05). In addition, significant retraction and lingual inclination of the upper and lower incisors were found in both groups. LIMITATIONS: The changes of tooth position were evaluated by 2D lateral cephalograms, not 3D measurements. CONCLUSIONS: Compared to fixed appliances, clear aligners seemed to have better control of vertical dimension and distal tipping of molars in patients treated with miniscrew-assisted molar distalization.

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Objective To assess pain intensity levels during orthodontic therapy of Class II malocclusion patients undergoing skeletally anchored maxillary molar distalization assisted with different micro-osteoperforation (MOP) approaches. Methods Twenty-seven patients (12 males and 18 females) with a mean age of 16.1 ± 0.3 years were randomized into three equal groups (n=9): Group 1 comprised MOPs on buccal surface, Group 2 comprised MOPs on buccal and palatal surface, and Group 3 comprised the control or no-MOP group. The patients underwent maxillary molar distalization using skeletally anchored distal jet appliance assisted with or without MOPs. The MOPs were applied repeatedly on the buccal and buccal and palatal sides, or no MOP (control). Pain intensity was assessed using a 10 cm visual analog scale after each device activation at 24, 48, 72 hours, and at seven days. Data were analyzed using one-way ANOVA and repeated measures ANOVA for non-paired and paired means. Results Both approaches of buccal and buccal and palatal application of MOPs showed statistically significant (p< 0.01) higher levels of pain intensity after the first activation at 24 hours. Nevertheless, pain intensity levels decreased significantly in both MOP groups and between the two activations. Conclusion The repeated application of MOPs on either the buccal side only or on both buccal and palatal sides during maxillary molar distalization did not affect the levels of pain experienced; however, these levels were reported to be higher than that obtained in the control group. Moreover, it is observed that these pain levels tend to gradually reduce to mild levels over the subsequent days.

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BACKGROUND: To compare dentofacial effects of distalization with miniscrew-supported pendulum and infrazygomatic crest miniscrews. METHODS: The study included 36 patients whose lateral cephalometric radiographs were obtained before (T0) and after (T1) distalization. Patients were divided into two groups according to the treatment methods: 1) distalization with miniscrew-supported pendulum (MSP) (n = 19; 14 girls and 5 boys; mean age 16.9 ± 1.46 years) and 2) distalization with infrazygomatic crest (IZC) miniscrews (n = 17; 8 girls and 9 boys; mean age 17.0 ± 1.68 years). Dental, skeletal and soft tissue measurements were performed on lateral cephalograms taken from individuals. RESULTS: A significant molar distalization was achieved both in the MSP group (3.52 ± 0.76 mm at 8.71 ± 2.02 months) and the IZC group (3.5 ± 0.74 mm at 9.7 ± 2.5 months) (P < 0.001 for both). Premolar distalization was significantly lower in the MSP group (1.73 ± 1.09 mm) than in the IZC group (2.81 ± 0.79 mm) (P < 0.01). Significant molar tipping was observed in both groups (P < 0.001), while no significant difference was found between the groups (P > 0.05). Retrusion of maxillary incisors were significantly higher in the IZC group (2.75 mm) than in the MSP group (0.98 mm) (P < 0.01). A significant difference was found between the two groups with regard to the changes in overjet and overbite (P < 0.05). CONCLUSIONS: Both distalization methods were found to be effective in achieving a Class I molar relationship in patients with Class II malocclusion.

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Distalization is one of the most useful movements in orthodontic treatments. The aim of this systematic review is to analyze the effectiveness of lower molar distalization using clear aligner therapy (CAT). An electronic search was made from January 2012 to October 2022 using PubMed, Scopus, and LILACS databases without language limitations. This systematic review followed the Preferred Reporting Items for Systematic reviews and Meta-Analyses checklist. The search strategy resulted in 151 studies. A screening was performed to remove duplicates, and all the studies that did not respond to our questions for the title or abstract. Three studies underwent full text analysis. From the evaluation of the studies included in this review, it is possible to state that lower molar distalization is a clinical solution, but it is not a full bodily movement. CAT can provide more specifically a distal tipping movement. This is confirmed analyzing the discrepancy between expected movement and obtained movement. CAT can be considered a valid therapeutic option in patients with dental class III malocclusion, but it is obtained as a tipping movement instead of a body movement. Over-correction should be considered during the planning of the therapy.

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Objective: To investigate the effect of micro-implant anchorage combined with a clear aligner on the efficiency of mandibular molar distalization and the protection of anterior teeth anchorage, provide reference for clinical scheme design. Methods: This is a prospective study. Seventeen patients who were treated in the Orthodontics Department of the Hospital of Stomatology affiliated to Fujian Medical University from 2019 to 2021 and used Invisalign clear aligners to move mandibular molars distally were included and divided into two groups according to anchorage types: Group-A and Group-B. Group-A (ten cases) were treated without micro-implant anchorage, while Group-B (seven cases) were treated with micro-implant anchorage nails for enhanced anchorage. The effect of micro-implant anchorage on crown and root distal movement of mandibular molars and the difference in three-dimensional movement between mandibular molars and mandibular central incisors were analyzed. Results: The crown distalization efficiency of mandibular first and second molars in Group-B was 68.66% and 71.02%, respectively, which were higher than those in Group-A(p<0.05). The mandibular central incisors in Group-A showed labial displacement and a small amount of elongation, while those in Group-B showed less anchorage loss(p<0.05). In Group-A, the crown was tilted in the distal direction and moved in the buccal direction during mandibular molar distalization(p<0.05). While in Group-B, the crown was tilted in the distal directio (p<0.05) and the mandibular second molar was depressed(p<0.05). Conclusion: In the process of mandibular molar distalization assisted by micro-implant anchorage combined with a clear aligner, better protects the anchorage of the mandibular central incisor and improves the efficiency of the molar crown distalization.

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OBJECTIVE: This study aimed to evaluate the impact of molar teeth distalization movement by clear aligners on changes in the alveolar bone thickness and orthodontically induced inflammatory root resorption (OIIRR) in maxillary molars using conebeam computed tomography (CBCT). MATERIALS AND METHODS: Three-dimensional CBCT scans of 35 adult patients (one hundred forty maxillary molars) with pre-designed selection criteria and a mean age of 24.4 ± 7.1 years were included. The measured parameters, including alveolar bone thickness for maxillary molars and root resorption (OIIRR), were analyzed using pre-and post-treatment CBCT (T0 and T1, respectively) with Invivo 6.0 software. RESULT: Post-treatment, relevant statistically significant changes included deposition of bone in the average palatal surface of the 1st molars. The reduction of bone was seen in the average buccal surface of the first molars and both surfaces of the second molars. Regarding root length after treatment, the average maxillary 1st molar roots showed significant OIIRR (p < 0.001). CONCLUSION: Clear aligner treatment could effectively reduce the incidence of alveolar bone thickness reduction and OIIRR in treating Class II malocclusions compared to conventional braces, as shown in previous studies. This research will aid in fully grasping the benefits of clear aligners.

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Aim: To investigate the effects of low-level laser therapy (LLLT) on pain reduction in orthodontic patients during molar distalization. Materials and methods: Twenty patients requiring bilateral maxillary first molar distalization were randomly assigned to two groups: the intervention group (mean age 15.61 ± 1.03 years) received multiple LLLT after every activation of the distalizing appliance (immediately and on the 3rd, 7th, and 14th days) and the control group (mean age 15.64 ± 1.08 years) who did not receive LLLT. Patients reported pain levels every day for 7 days following activation of the appliance using an 11-point numeric rating scale (NRS), then the pain experience of both the intervention and control groups was compared using Mann-Whitney U test. Results: The mean pain scores on the 1st day were higher in the intervention group (9.27 ± 1.01) compared to that of the control group (8.80 ± 1.03). However, the mean pain scores of the intervention group (6.55 ± 1.29, 4.00 ± 1.26, 2.55 ± 1.29, 0.91 ± 1.04, 0.00 ± 0.00 and 0.00 ± 0.00, respectively) were lower than the control group (7.40 ± 1.90, 5.60 ± 2.07, 4.20 ± 1.99, 2.80 ± 1.93, 1.60 ± 1.58 and 0.40 ± 0.84, respectively) from the 2nd to the 7th day. All the differences were not statistically significant except on the 6th day (P-value = 0.003). The peak pain level was experienced by both groups on the 1st day, followed by a statistically significant gradual decrease in pain levels. Patients in the intervention group reported a shorter overall duration of pain. Conclusion: Although LLLT, with the used parameters, reduced the overall duration of pain experience following maxillary first molar distalization, it was not effective during peak pain levels.

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OBJECTIVES: The study endeavors to undertake a bibliometric analysis on molar distalization, with the objective of illuminating its evolutionary trajectory, current status, and prognosticating future research hotspots and trends. MATERIAL AND METHODS: A comprehensive exploration of the literature on molar distalization was carried out by conducting a search in the Web of Science (WOS) core database of the University of Hong Kong Electronic Library. The search for topic terms employed included "molar distalization," "molar distalisation," "move molar distally," "molar distal movement," and "molar backwards." The search results were subsequently subjected to meticulous analysis using CiteSpace software. This analysis encompassed various facets such as the citation count; the geographical distribution of the countries, institutions, and journals responsible for publishing the articles; the distribution of the authors; the utilization of keywords within the articles; and the analysis of references. RESULTS: A total of 516 articles were included in the analysis. The top 5 countries in terms of the number of published papers were the United States (USA), South Korea, Turkey, Italy, and Germany, and the top 5 institutions in terms of the number of published papers were Kyung Hee University, A.T. Still University of Health Sciences, Catholic University of Korea, Seoul St. Mary's Hospital, and Universidade de Sao Paulo. The top 5 authors in terms of the number of published papers were Park, Kook, Bayome, Janson, and Lee. There was little cooperation overall. The top 3 journals in terms of the most published related articles were all orthodontic-related journals. After molar distalization and anchorage, the most frequently used keywords were distalization, movement, and pendulum appliance. Kinzinger GSM is the most frequently cited author in references, and one of his articles also has the highest centrality score in references. CONCLUSIONS: As the tides of time shift and scholars display an ever-growing dedication to unraveling the intricacies of this therapeutic modality, the realm of molar distalization has undergone notable advancements in technology. Initially, the traditional appliance suffered from aesthetic drawbacks and discomfort. However, contemporary iterations of the appliance have transcended these limitations, boasting enhanced elegance and convenience while concurrently elevating their efficacy. Nevertheless, limitations of current appliances, including their durability and propensity for recurrence post-treatment, continue to necessitate further advancement. Hence, the ongoing scientific inquiry aims to delve deeper into refining treatment modalities and fabricating cutting-edge appliances within this realm. CLINICAL RELEVANCE: This study holds the potential to significantly enhance the ability of orthodontists to devise treatment protocols and offer state-of-the-art clinical recommendations, thereby empowering them to deliver advanced and refined orthodontic interventions.

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OBJECTIVES: To evaluate the effectiveness of distalizing maxillary first molars (U6) by temporary anchorage devices (TADs) according to their location (palatal, buccal, and zygomatic), their number, and appliance design. MATERIALS AND METHODS: An electronic search of maxillary molar distalization with TADs was done through April 2023. After study selection, data extraction, and risk-of-bias assessment, meta-analyses were performed for the extent of distalization, distal tipping, and vertical movement of U6 using the generic inverse variance and random-effects model. The significance level was set at 0.05. RESULTS: Forty studies met the inclusion criteria: 4 randomized controlled trials (RCTs), 13 prospective studies, and 23 retrospective studies (total of 1182 patients). Distalization of the U6 was not significantly greater (P = .64) by palatal (3.74 mm) and zygomatic (3.68 mm) than by buccal (3.23 mm) TADs. Distal tipping was significantly higher (P < .001) in nonrigid (9.84°) than in rigid (1.97°) appliances. Vertical movement was mostly intrusive and higher but not significantly different (P = .28) in zygomatic anchorage (-1.16 mm). CONCLUSIONS: Distalization of U6 with TADs can be an effective and stable treatment procedure, especially when performed with rigid palatal appliances. However, further RCTs or prospective cohort studies are strongly recommended to provide more clinical evidence.

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BACKGROUND:The reciprocal force generated by the molar distalization with clear aligners can lead to anchorage loss.The effect of arch shapes and missing second premolars on anchorage has not been reported. OBJECTIVE:To analyze the effect of arch shapes and missing second premolars on anchorage during molar distalization with clear aligners using the finite element method. METHODS:Cone-beam CT data from an adult male were acquired from the database to establish the maxilla-upper dentition-periodontium-rectangular attachment-clear aligner model.The distal movement amount designed on the bilateral second molars was set to 0.25 mm.First,there were two groups in the study:second premolar bilateral presence and absence groups.Then,four subgroups in each group were created:tapered arch,ovoid arch,square Class Ⅱ Division 1 arch,and Class Ⅱ Division 2 arch groups.The Ansys software was used to calculate the displacement of the anchorage tooth and the stress of the periodontal ligament. RESULTS AND CONCLUSION:Mesial tipping and extrusion of first molars and premolars,labial inclination and intrusion of anterior teeth occurred during the upper second molar distalization with clear aligners.When the bilateral second premolars were missing,the mesial displacement of first molars increased significantly while that of first premolars and anterior teeth decreased in all groups.The square Class Ⅱ Division 1 arch group showed the least anterior labial inclination,while the tapered arch group showed the most.There was no significant difference between the ovoid arch group and the tapered arch group.Moreover,the magnitude of tipping in the square Class Ⅱ Division 2 arch group was slightly higher than that in the Class Ⅱ Division 1 arch group.The stress of the periodontal ligament of the anchorage teeth was concentrated on the cervical and apical regions of the teeth.And the lowest stress level was detected in the square arch group.Compared with the other groups,the stress on the labial cervical area of the periodontal ligaments was also significantly relieved in the square arch group.To conclude,the square arch is more favorable in terms of anterior anchorage control and periodontal ligament stress distribution.Anterior labial inclination efficiency can be increased in cases of Class Ⅱ Division 2 by designing the anterior labial inclination in conjunction with molar distalization.If the second premolar is missing during molar distalization,it is not conducive to opening up the space in the area of the missing tooth.

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BACKGROUND:Previous studies have shown that clear aligners can achieve molar distalization effectively,but it is not yet clear how the vertical dimensions change in patients with different vertical craniofacial patterns after molar distalization. OBJECTIVE:To evaluate the effect of molar distalization with clear aligners on occlusal vertical dimension in different vertical craniofacial patterns. METHODS:Forty patients(13 cases of Class Ⅰ malocclusion,20 cases of Class Ⅱ malocclusion,and 7 cases of Class Ⅲ malocclusion)were selected,including 13 cases in the high angle group,17 cases in the average angle group,and 10 cases in the low angle group.Among them,the age ranged from 10 to 53 years,with an average of 28.5 years.All patients were subjected to clear aligners for molar distalization.Lateral cephalometric films were taken before and after treatment.Cephalometric measurements,including the sagittal and vertical indicators of teeth and jaws,were measured by the same orthodontist,and each indicator was measured 3 times and averaged. RESULTS AND CONCLUSION:After orthodontic treatment,the crowded dentition was corrected,the overbite and overjet were back to normal and the lateral profile was improved significantly in all 40 patients.The GoGn-SN in the high angle group decreased by 0.4°,while the GoGn-SN in the average and low angle groups increased by less than 1°,the ANS-Me in the three groups increased by less than 1 mm.There was no statistically significant difference before and after treatment.There was a statistically significant decrease in the U6-PP in the low angle group by 0.47 mm(P<0.01).The L1-MP and the U1-SN in the average angle group significantly decreased by 0.83 mm(P<0.05)and by 6.46°(P<0.001),respectively.In conclusion,molar distalization with clear aligner treatment can control the vertical dimension effectively,prevent clockwise mandibular rotation,and maintain the lower face height.Patients with high angle can also undergo invisible orthodontics to distal molars.The realization rate of the anterior tooth intrusion movement by using clear aligners is insufficient,and the intrusion design should be increased to prevent the elongation phenomenon in anterior teeth.

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OBJECTIVES: To evaluate the biomechanical system of molar distalization with clear aligner therapy (CAT) combined with angel button using interradicular mini-implants (IRMIs) with varying elastic forces. MATERIALS AND METHODS: FE models including maxilla, complete maxillary dentition, periodontal ligaments (PDL), composite attachments, mini-implants (MI), and dedicated orthodontic aligner, were constructed. Three groups were created in accordance with the sagittal position of MI. Elastic forces (0 N,1 N,1.5 N,2 N) were applied. RESULTS: CAT without elastics caused labial tipping and intrusion of the anterior teeth. Initial labial tipping and the von Mises stress of the maxillary anterior teeth decreased as the elastic forces increased.

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