Distalization of maxillary molars using temporary skeletal anchorage devices: A systematic review and meta‐analysis

Molar distalization in orthodontics: a bibliometric analysis

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.

Effectiveness of miniscrew-supported maxillary molar distalization according to temporary anchorage device features and appliance design: systematic review and meta-analysis

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.

Skeletal and dentoalveolar changes after total maxillary arch distalization using the casted palatal plate vs. buccal miniscrews: A randomized clinical trial

OBJECTIVES

To evaluate treatment changes after total maxillary arch distalization using the casted palatal plate compared with buccal miniscrews.

MATERIAL AND METHODS

This was a randomized, parallel, two-arm, single center trial. Participants were young adults with class II dental relationships and normal or horizontal growth patterns. The patients were treated with total distalization of the maxillary arch and were randomly allocated, according to the anchorage devices, between the plate group and the minivis group. The primary outcomes were sagittal, vertical and angular changes of molars and incisors, while the secondary outcomes were skeletal and soft tissue changes. Outcomes were evaluated on lateral cephalograms and blinding of outcome assessment was implemented. A multivariate analysis of Variance (MANOVA) tests were used and Bonferroni correction for multiple comparisons with P<0.001.

RESULTS

Forty patients (33 females and 7 males; mean age 20±3.1 years) where enrolled. A significant distalization of U6 was observed in both groups (4.33mm in the plate group and 1.88mm in the miniscrews group). It was combined with significant intrusion and non-significant distal tipping of the U6 in the plate group (1.85mm and 3.10°, respectively), while intrusion and distal tipping were non-significant in the miniscrew group (0.8mm and 2°, respectively). Both groups showed significant retraction and palatal inclination without vertical changes of U1. Only the plate group produced significant reduction of ANB and Wits. Upper and lower lips were retracted and the nasolabial angle increased significantly in both groups. There was no significant main effect of the appliance type on the comparison of treatment effects between the two groups (P=0.623). However, univariate comparisons showed that the plaque group showed greater distalization of the U6 (P<0.001).

CONCLUSIONS

Both the casted palatal plate and buccal miniscrews can be viable devices for total distalization of the maxillary arch in the treatment of class II patients. The casted plate may be considered when more extensive distalization is required.

Effective contribution ratio of the molar during sequential distalization using clear aligners and micro-implant anchorage: a finite element study

INTRODUCTION

This study aims to investigate the biomechanical effects of anchorage reinforcement using clear aligners (CAs) with microimplants during molar distalization. And also explores potential clinical strategies for enhancing anchorage in the sequential distalization process.

METHODS

Finite element models were established to simulate the CAs, microimplants, upper dentition, periodontal ligament (PDL), and alveolar bone. In group set I, the 2nd molars underwent a distal movement of 0.25 mm in group set II, the 1st molars were distalized by 0.25 mm after the 2nd molars had been placed to a target position. Each group set consisted of three models: Model A served as the control model, Model B simulated the use of microimplants attached to the aligner through precision cuts, and Model C simulated the use of microimplants attached by buttons. Models B and C were subjected to a series of traction forces. We analyzed the effective contribution ratios of molar distalization, PDL hydrostatic stress, and von Mises stress of alveolar bone.

RESULTS

The distalization of the 2nd molars accounted for a mere 52.86% of the 0.25-mm step distance without any reinforcement of anchorage. The remaining percentage was attributed to the mesial movement of anchorage teeth and other undesired movements. Models B and C exhibited an increased effective contribution ratio of molar distalization and a decreased loss of anchorage. However, there was a slight increase in the undesired movement of molar tipping and rotation. In group set II, the 2nd molar displayed a phenomenon of mesial relapse due to the reciprocal force produced by the 1st molar distalization. Moreover, the efficacy of molar distalization in terms of contribution ratio was found to be positively correlated with the magnitude of force applied. In cases where stronger anchorage reinforcement is required, precision cuts is the superior method.

CONCLUSIONS

The utilization of microimplants in conjunction with CAs can facilitate the effective contribution ratio of molar distalization. However, it is important to note that complete elimination of anchorage loss is not achievable. To mitigate undesired movement, careful planning of anchorage preparation and overcorrection is recommended.

Success rate of infrazygomatic crest mini-implants used for en-masse retraction of maxillary anterior teeth in first premolar extraction cases: A three-dimensional comparative prospective clinical trial between adolescents and young adults

BACKGROUND

The purpose of this study was to compare the success rate of infrazygomatic mini-implants between adolescents and young adults.

METHODS

A total of 60 subjects of different age groups ie, (group I [adolescents]: 12-18 years, mean age: 14.9 ± 2.9 years; group II [young adults]: 19-25 years, mean age = 21.9 ± 3.1 years) were assessed in the study. En-masse retraction of maxillary anterior teeth was carried out with extraction of upper first premolars with infrazygomatic crest (IZC) mini-implants as anchorage units. Clinical parameters such as success rate, soft tissue thickness, maximum insertion torque, maximum removal torque, pain response, soft tissue response, and cone-beam computed tomography parameters such as embedded angulation, penetration depth, thickness of bone on buccal and palatal aspect of mini-implant, and peri-implant bone density were evaluated.

RESULTS

The success rate of IZC mini-implants in adolescents was found to be 96.6% and 98.3% in young adults respectively. There was no significant difference in success rate between the two groups. Intergroup comparison showed a significant difference (P < 0.05) in terms of maximum insertion torque, maximum removal torque, soft tissue thickness, cortical bone thickness, and peri-implant bone density values. Comparison between right and left side revealed a significant difference (P < 0.05) with regards to soft tissue response, soft tissue thickness, total bone thickness, cortical bone thickness, and peri-implant bone density.

CONCLUSIONS

There was no significant difference in the success rate of IZC mini-implants between adolescents and young adults. Thus, the use of IZC mini-implants can be recommended in adolescents for successful orthodontic treatment.

Effect of Molar Distalization on Condyle-Glenoid Fossa Relationship

Objective

It is essential to be aware of the potential effects of orthodontic treatment on tissues and anatomical structures associated with the masticatory system, especially the temporomandibular joint (TMJ). Little information is available about the consequences of molar distalization on the TMJ. Therefore, this study is aimed at investigating the changes of the condyle-fossa relationship after molar distalization using the distal jet appliance.

Materials and Methods

The sample consisted of twenty-five patients (mean age 20.4 ± 2.6) who underwent molar distalization by the distal jet appliance. CBCT scans were taken before (T0) and after (T1) the completion of the molar distalization. Joint spaces (anterior, superior, and posterior) and cephalometric vertical angles (SN.GOME and Björk sum) were measured and compared at T0 and T1.

Results

Superior and posterior joint spaces increased significantly after molar distalization (PS 0.29 mm, P < 0.001, SS 0.06 mm, P < 0.5). Vertical cephalometric angles also increased after molar distalization by the distal jet appliance (SN.GOME 0.92°, Björk 1.11°).

Conclusion

There was a statistically significant increase in the superior and posterior joint spaces after molar distalization. However, this increase may not be of clinical importance. The vertical dimension has also increased.

Three-dimensional analysis of the relationship between mandibular retromolar space and positional traits of third molars in non-hyperdivergent adults

BACKGROUND

The anatomical position of the mandibular third molars (M3s) is located in the distal-most portions of the molar area. In some previous literature, researchers evaluated the relationship between retromolar space (RS) and different classifications of M3 in three‑dimensional (3D) cone-beam computed tomography (CBCT).

METHODS

Two hundred six M3s from 103 patients were included. M3s were grouped according to four classification criteria: PG-A/B/C, PG-I/II/III, mesiodistal angle and buccolingual angle. 3D hard tissue models were reconstructed by CBCT digital imaging. RS was measured respectively by utilizing the fitting WALA ridge plane (WP) which was fitted by the least square method and the occlusal plane (OP) as reference planes. SPSS (version 26) was used to analyze the data.

RESULTS

In all criteria evaluated, RS decreased steadily from the crown to the root (P < 0.05), the minimum was at the root tip. From PG-A classification, PG-B classification to PG-C classification and from PG-I classification, PG-II classification to PG-III classification, RS both appeared a diminishing tendency (P < 0.05). As the degree of mesial tilt decreased, RS appeared an increasing trend (P < 0.05). RS in classification criteria of buccolingual angle had no statistical difference (P > 0.05).

CONCLUSIONS

RS was associated with positional classifications of the M3. In the clinic, RS can be evaluated by watching the Pell&Gregory classification and mesial angle of M3.

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.

Mandibular retromolar space in adults with different sagittal skeletal patterns

OBJECTIVES

To analyze the mandibular retromolar space among normal-divergent adult patients with different sagittal skeletal patterns by cone-beam computed tomography (CBCT).

MATERIALS AND METHODS

CBCTs of a total of 120 normal-divergent adult patients were investigated. Patients were categorized into the following three groups according to their ANB angle: skeletal Class I (48 patients), skeletal Class II (36 patients), and skeletal Class III (36 patients). Four different planes parallel to the mandibular occlusal plane were used to measure the retromolar space. The retromolar space was measured by two reference lines and then compared between different sagittal skeletal patterns groups. The incidence of root contact with the inner lingual cortex was compared among the three groups.

RESULTS

The retromolar space of the Class III patients was significantly larger than that of Class I patients and Class II patients. Compared with Class I and Class III patients, Class II patients had a smaller retromolar space and higher incidence of contact with the inner cortex of the mandible.

CONCLUSIONS

Class III patients had a larger retromolar space than Class I patients and Class II patients in four different planes. The mandibular retromolar space should be evaluated by CBCT in patients who need mandibular molar distalization.

En-Mass Retraction of Maxillary Anterior Teeth with Severe Proclination and Root Resorption-A Case Report

Molar distalization has been a validated method to correct dental sagittal relationships and create space to relieve mild to moderate crowding. In the current case report, an adult female patient had a mild skeletal Class III relationship and dental Class III molar relationship. Four premolars and one lower incisor were extracted during the previous two rounds of orthodontic treatments, and the maxillary anterior teeth were left with severe proclination and root resorption. Limited by the available teeth, extraction was not an option for her. Thus, molar distalization with TADs was the best option used in the treatment to address her chief complaint. In addition, a proper bite opening was performed to eliminate occlusion trauma. Utilizing the mid-palatal TADs, the maxillary central incisors were retracted 7.9 mm and retroclined 33 degrees, and the molar distalization was achieved as much as 8 mm. The cross-section slices of CBCT images confirmed the proper retraction of maxillary incisors and well-positioned roots in the alveolar bone. Moreover, the root resorption was not worsened from the treatment. Clinically, the maxillary anterior teeth were preserved esthetically and functionally. This case report illustrates that with proper diagnosis and treatment mechanics, significant tooth movement can be achieved even on extremely proclined maxillary incisors with severe root resorption.

Correction of an adult Class III malocclusion through regaining of orthodontic space and an implant restoration

This case report describes the interdisciplinary treatment of a 23-year-old female with Class III malocclusion and a missing maxillary left second premolar. Treatment alternatives were discussed, and the selected treatment plan was presented to illustrate a way to gain space for the premolar implant restoration and correct Class III relationship through maxillary molar retraction followed by maxillary total arch protraction with a palatal temporary skeletal anchorage device. Esthetic anterior alignment and functional occlusal rehabilitation was achieved, and facial balance was maintained at the end of treatment. CLINICAL SIGNIFICANCE: Implant restoration in conjunction with regaining orthodontic space by a team of multidisciplinary dental specialists presents an effective treatment solution to permanent tooth agenesis. Class III malocclusion can be treated with a combination of maxillary protraction and mandibular retraction using temporary skeletal anchorage devices. The versatility of modified palatal C-plates presents greater clinical application when related side effects are controlled with solid understanding of their biomechanics.

The effect of third molars on maxillary molar distalisation using a miniscrew-supported 3D® maxillary bimetric distalising arch

Objectives: The aim of the present study was to investigate the effect of third molars on the efficiency and biomechanics of a novel miniscrew-supported 3D® Maxillary Bimetric Distalising Arch (3D-MBDA).

Methods: Twenty-three patients, whose third molars were either extracted at the beginning of treatment (Group 1, n =11) or retained (Group 2, n =12), were included in the study. Lateral cephalometric films and dental casts, taken at the beginning (T0) and at the end of upper molar distalisation (T1), were analysed to study the differences between groups.

Results: Crown distalisation of the first molars was similar between the groups; however, root distalisation, both at the trifurcation and apex levels, intrusion at the mesiobuccal cusp tip, and the distalisation rate were significantly higher in Group 1. The resultant tipping of the first molars in both groups was mesially-directed, unlike the usual distal tipping. The second molars distalised more, displaced less vestibularly and rotated mesiobuccally in Group 1, whereas they demonstrated a significantly higher vestibular displacement and distobuccal rotation in Group 2. The mean distalisation time was significantly shorter in Group 1 when compared to Group 2. The miniscrew success rate was 95.5% for Group 1 and 91.7% for Group 2.

Conclusion: The miniscrew-supported 3D-MBDA was found to have greater effects on root distalisation and the final inclination of the molars. The third molars were associated with limited root movement, unfavourable displacement of the second molars, as well as a slower distalisation rate. Therefore, the extraction of third molars prior to distalisation is recommended, especially when the miniscrew-supported 3D-MBDA is the appliance choice.

Comparison of treatment effects from total arch distalization using modified C-palatal plates versus maxillary premolar extraction in Class II patients with severe overjet

INTRODUCTION

This study aimed to compare the skeletodental and soft tissue changes with total arch distalization using a modified C-palatal plate (MCPP) and maxillary first premolar extraction treatment in Class II malocclusion patients with severe overjet.

SETTING AND SAMPLE POPULATION

The sample consisted of 46 adult patients who had Class II Division 1 malocclusion with severe overjet; 25 of them received non-extraction treatment with MCPPs (age, 22.5 ± 7.2 years), and 21 received maxillary first premolar extraction treatment (age 23.4 ± 6.5 years).

METHOD

A total of 26 variables were measured on pre- and post-treatment lateral cephalograms. To evaluate the differences between pretreatment and post-treatment in each group, t tests and Wilcoxon rank-sum tests were used. To compare the amount of change between the two groups, MANOVA test was used.

RESULTS

The overjet was significantly reduced in the MCPP and extraction groups by 4.8 mm and 5.4 mm, respectively. However, the two groups had no significant difference in the sagittal, vertical and angular changes of the maxillary incisors. In addition, regarding soft tissue changes, the MCPP and extraction groups showed an increased nasolabial angle of 7.5° and 9.4°, decreased upper lip to the true vertical line of 1.8 mm and 2.2 mm, respectively (P < .001).

CONCLUSIONS

There was no significant difference in the skeletal changes between the MCPP and extraction groups, and the reduction in overjet was similar in the groups. These results suggest that MCPP might be a viable treatment option for total arch distalization in Class II malocclusion patients with severe overjet.