Miniscrew insertion sites of infrazygomatic crest and mandibular buccal shelf in different vertical craniofacial patterns: A cone-beam computed tomography study

Optimizing Infrazygomatic Miniscrew Insertion Parameters: Systematic Review and Meta-Regression Analysis of Bone Thickness by Insertion Height, Angulation, and Anatomical Position

Introduction: Infrazygomatic crest (IZC) miniscrews are widely used for skeletal anchorage in orthodontics. Despite their growing popularity, the optimal insertion parameters-such as height, angulation, and anatomical position-remain controversial, with existing studies offering inconsistent and fragmented data. Aim: To determine the optimal insertion position, height, and angulation of infrazygomatic miniscrews to maximize bone insertion using cone-beam computed tomography (CBCT) analysis and to investigate the influence of facial skeletal patterns on IZC bone morphology. Methods: This review was conducted according to the PRISMA 2020 guidelines. A comprehensive electronic search was performed across six databases: PubMed, Scopus, Web of Science, Cochrane, EBSCO, and Google Scholar. Studies reporting CBCT-based IZC bone thickness were included. A meta-analysis was conducted using a random-effects model, and meta-regression was applied to assess the relationship between insertion height, angulation, and bone thickness. The STROBE checklist was used to assess the quality of the included observational studies. Results: Seventeen studies comprising a total of 1840 CBCT-based measurements were included. The meta-regression revealed a significant inverse relationship between insertion height and bone thickness (β = -0.53; p < 0.001) and a positive correlation with angulation (β = 0.09; p < 0.001). The U67 region refers to the anatomical area between the maxillary first and second molars, adjacent to the infrazygomatic crest and zygomatic buttress, which with an insertion height of 9.9 mm and 80° angulation, demonstrated the highest mean cortical bone thickness (3.52 mm). There was no evidence of a significant association between facial pattern and bone thickness (p = 0.878). Conclusions: This review presents the first predictive model for IZC miniscrew placement based on meta-regression. The findings support the U67 site at 9.9 mm height and 80° angulation as the optimal insertion protocol. These data-driven guidelines provide clinicians with practical, evidence-based direction for improving miniscrew stability and minimizing complications.

Effect of multiple hook heights and positions during en masse maxillary distalization using infrazygomatic crest miniscrew- single and double points of force application: a finite element analysis study

BACKGROUND

This study aimed to simulate maxillary dentition distalization as one unit anchored to infrazygomatic crest (IZC) miniscrew using different hook positions and lengths.

MATERIALS AND METHODS

Eleven finite-element models (FEM) were constructed from a cone beam computed tomography scan of a patient with Class II malocclusion. Different force vectors to the IZC miniscrew were simulated using one point of force application either mesial to the canine or mesial to the first premolar, using different hook lengths (0, 2, 4, and 6 mm). In the novel approach, two point-force system was constructed using double-hook retraction in three conditions. The FEM yielded tooth displacement patterns and stress contour plots of the periodontal ligament.

RESULTS

When hooks were placed mesial to the canine, the incisor showed palatal translation with controlled palatal tipping at 0 and 2 mm, palatal bodily displacement at 4 mm, and palatal translation with torquing at 6 mm. In hooks mesial to the first premolar, the pattern showed palatal translation with torquing, except with the 0-mm hook where controlled palatal tipping occurred. Whereas, vertically, it shows extrusion at the 0- and 2-mm hooks mesial to the first premolar and intrusion with the remaining single hook simulations. The molar exhibited translation with controlled distal tipping at all hook lengths mesial to the canine and 0 mm mesial to the first premolar, while it demonstrated distal translation with torquing at 2-,4-, and 6-mm hooks mesial to the first premolar. Vertically, it showed extrusion with hooks mesial to the canine, which changed to intrusion with hooks mesial to the first premolar. In double-hook simulations, the incisor showed bodily displacement only with hooks mesial to the canine and second premolar, whereas the molar showed distal bodily movement with hooks mesial to the first and second premolars.

CONCLUSION

Hook height and position variations are crucial in the resultant displacement pattern. Accordingly, different force systems should be tailored individually based on the patient's initial malocclusion.

Successful management and stability of maxillary class II dentoalveolar protrusion with extractions of upper second and lower third molars, using en-masse distalization and vertical control with bone miniscrews: Adult case report with 7-year follow-up

This case report describes the successful long-term management of a 19-year-old female patient presenting with a skeletal Class II pattern, mild anterior open bite, and mandibular retrognathia. The orthodontic treatment approach involved the distal movement of the maxillary and mandibular dentitions through the extraction of the maxillary second molars and mandibular third molars, combined with the use of extra-alveolar infrazygomatic crest (IZC) and buccal shelf (BS) miniscrews for anchorage. The treatment outcome achieved a stable, well-aligned dentition with ideal intercuspation and an improved facial profile. The 7-year post-treatment records demonstrated a stable occlusion and satisfactory facial aesthetics, confirming the long-term stability of this treatment approach. This case report supports that en-masse distalization of the entire dentition by extracting the upper second molars and lower third molars, coupled with bone miniscrew anchorages, can be a favourable alternative to the conventional premolar extraction approach for the correction of borderline Class II malocclusions.

Optimal sites for mini-implant insertion into the infrazygomatic crest according to different craniofacial morphologies: A cross-sectional cone-beam computed tomography study

INTRODUCTION

The infrazygomatic bone crest and other extraalveolar regions represent a viable option for the placement of temporary anchorage devices when distalizing the maxillary arch. This approach allows for the movement of the dentition without concern for potential collisions among dental structures. Nevertheless, it is of the utmost importance to conduct a thorough examination of the anatomy of this region before the placement of mini-implants to prevent potential injuries, such as maxillary sinus perforations. The objective of this study was to quantify the depth of the infrazygomatic crest and evaluate its correlations with age, gender, skeletal classification, and vertical pattern.

METHODS

The study sample of this cross-sectional, retrospective study consisted of 201 cone-beam computed tomography scans collected from patients treated at the Master's program in orthodontics at the University of Valencia and at a private dental clinic. The cone-beam computed tomography scans were collected for 5 years, from January 2017 to May 2022. The total and intraalveolar lengths were defined and measured at 3 points: the distal roots of the maxillary second molars, the distal roots of the maxillary first molars, and the mesial roots of the maxillary first molars. These measurements were taken on both the right and left sides using the Carestream 3D Imaging System (Atlanta, Ga).

RESULTS

The total length (TL) at the mesiobuccal level of the first molars was found to be significantly longer on both sides (P = 0.001). The intraalveolar length exhibited statistically significant differences between the right and left sides, with those of the left side exhibiting greater length (P <0.001). The normodivergent patterns demonstrated lower TL values than hypodivergent (P = 0.006) and hyperdivergent patterns (P = 0.033).

CONCLUSIONS

A statistically significant inverse relationship was observed between the distance from the cementoenamel junction to the vestibular bone crest and the total and intraalveolar lengths in the studied regions. The TL was greatest in the region of the mesiobuccal root of the maxillary first molars, followed by the region of the distal root of the second molars, and finally, the region of the distobuccal root of the maxillary first molars. Patients with normodivergent patterns exhibited the lowest total infrazygomatic ridge height.

Three-dimensional quantitative temporomandibular joint changes in skeletal class I malocclusion treated with extraction and non-extraction protocols: a comparative study of fixed orthodontic appliances and clear aligners

OBJECTIVE

This study aimed to evaluate the positional and morphological changes in the temporomandibular joint (TMJ) in adult patients with skeletal Class I malocclusion treated with fixed orthodontic appliances (FAs) and clear aligners (CAs), both with and without premolar extractions.

METHODS

This retrospective study involved 120 adult patients divided into non-extraction and extraction groups, each further subdivided equally into those treated with FAs and CAs. Cone beam computed tomography (CBCT) was used to assess the TMJ measurements before (T0) and after treatment (T1). Statistical analyses were conducted to compare the mean changes in intra- and inter-groups. A significance level of p ≤ 0.05 was considered.

RESULTS

In the non-extraction group, specifically in FAs, significant increases were observed in TMJ parameters; anteroposterior condylar position (APCP) and mediolateral condylar inclination (MCI). Conversely, significant decreases were noted in vertical condylar position (VCP) and vertical condylar inclination (VCI). In the extraction group, significant increases were noted in APCP and anterior joint space (AJS), while posterior joint space (PJS) and anteroposterior condylar joint position (APCJP) decreased. For inter-group comparisons, the extraction group showed significant increases in APCP in FAs compared to CAs, and a significant decrease in APCJP in FAs compared to CAs.

CONCLUSION

FAs significantly impact condylar positions and joint spaces, especially in extraction cases. Monitoring TMJ parameters during orthodontic treatment is crucial to ensure positive outcomes and prevent TMJ disorders (TMDs). These findings may guide the selection of orthodontic appliances based on individual malocclusion characteristics.

Is the mandibular buccal shelf anatomy related to craniofacial morphology? A cross-sectional CBCT study

BACKGROUND

The placement of Temporary Anchorage Devices (TADs) in the mandibular buccal shelf area is a common option for distalizing the lower arch. Therefore, the study of bone thickness and depth in this area is mandatory before planning TAD insertion. The aim of this study was to quantify the width and depth of the mandibular buccal shelf structure and examine its associations with sex, age, skeletal class and vertical pattern.

MATERIAL AND METHODS

A cross-sectional study was carried out on cone beam computed tomographies obtained from 91 patients. The bone thickness was evaluated in the mandibular buccal shelf area 5 and 8 mm apical to the cement-enamel junction (CEJ), and the bone depth was measured 4 mm buccal to the CEJ at the level of the distal root of the mandibular first molar and the mesial root of the mandibular second molar using the InVivoDental 6.0 software.

RESULTS

The depth and thickness of the bone increased in distal areas, and the thickness was greater at 8 mm. No differences were found between sex or skeletal class. Bone thickness decreased with age, and it was significantly lower in hyperdivergent patients.

CONCLUSIONS

The thickness of the bone was higher in distal and deeper areas, and the depth was greater in distal areas. The hyperdivergent facial pattern and age were negatively associated with bone thickness.

Effect of maxillary molars distalization using clear aligners and fixed orthodontic appliances on the positional and dimensional temporomandibular joint parameters: a three-dimensional comparative study

OBJECTIVE

The use of clear aligners (CAs) for orthodontic treatment has substantially increased in recent decades. However, limited empirical evidence exists regarding their potential effects on the temporomandibular joint (TMJ). The aim of this study was to assess the effect of maxillary molar distalization on the positional and dimensional TMJ parameters between CAs and conventional fixed orthodontic appliances (FAs) in skeletal class II malocclusion.

METHODS

This is a retrospective cohort study examined 70 adult patients with skeletal class II malocclusion with similar baseline characteristics based on American Board of Orthodontics (ABO) discrepancy index scores. The patients were treated by maxillary distalization movement by CAs or FAs, of which there were two equal groups of 35 patients were included in each group. CBCTs on TMJs were performed before and after treatment through Anatomage Invivo Dental 6.0. The measured parameters included inclination, position, condyle and articular fossa dimensions, and the volumetric joint spaces.

RESULTS

In both groups, linear measurements of the maxillary molar position revealed significant improvement after treatment (P < 0.001). Regarding TMJ parameters, intra-group comparisons revealed significant changes in FA group in the anterioposterior condylar inclination and condylar position across the three planes. Additionally, the pretreatment-centric condylar position in the glenoid fossa was 45.7% and 40% in the CA and FA groups, respectively. After treatment, these percentages changed to 51.4% and 31.4%, respectively. In inter-group comparisons, significant changes were noted in the mediolateral condylar position, which was more inward in the FA group than the CA group.

CONCLUSION

The FA group had more significant dimensional and positional changes in the mandibular condyle than the CA group; nevertheless, the changes are considered clinically negligible.

Biomechanical analysis of total arch maxillary distalization using infrazygomatic crest miniscrews: a finite element analysis study

AIM

To evaluate the maxillary incisors and canine's immediate movement tendency using three different power arms (PA) height levels during total arch maxillary distalization supported on infrazygomatic crest (IZC) miniscrews according to finite element analysis (FEA).

METHODS

Three finite element models of the maxilla were developed based on CBCT imaging of a teenage male patient presenting a Class II Division 1 malocclusion in the early permanent dentition. Maxillary complex, periodontium, orthodontic accessories, IZC miniscrews and an orthodontic wire were digitally created. The PAs were placed between canines and lateral incisors and projected at 4, 7, and 10 mm height distances. After that, distalization forces were simulated between PA and IZC miniscrews.

RESULTS

The anterior teeth deformation produced in the FEA models was assessed according to a Von Mises equivalent. The stress was measured, revealing tendencies of initial maxillary teeth movement. No differences were found between the right and left sides. However, there was a significant difference among models in the under-stress areas, especially the apical and cervical root areas of the maxillary anterior teeth. More significant extrusion and lingual tipping of incisors were observed with the 4 mm power arm compared to the 7 mm and 10 mm ones. The 10 mm power arm did not show any tendency for extrusion of maxillary central incisors but a tendency for buccal tipping and intrusion of lateral incisors.

CONCLUSION

The maxillary incisors and canines have different immediate movement tendencies according to the height of the anterior point of the en-masse distalization force application. Based on the PA height increase, a change from lingual to buccal tipping and less extrusion tendency was observed for the incisors, while the lingual tipping and extrusion trend for canines increased.

An evaluation of bone depth at different three-dimensional paths in infrazygomatic crest region for miniscrew insertion: A cone beam computed tomography study

Objective

To investigate the difference and distribution of bone depth at different three-dimensional simulated paths to help optimize the insertion path for miniscrew placement in the infrazygomatic crest.

Methods

Cone beam computed tomography scans of 80 adults (38 males and 42 females; mean age, 27.0 years) were assessed. For each subject, bone depth of 81 simulated insertion paths at different insertion points and three-dimensional angulations was measured in 160 infrazygomatic crests; the differences were evaluated using the adjusted Friedman test. The bone deficiency ratio for each path was calculated. Distributions of measurements were analyzed and reported as specially designed colormaps.

Results

Bone depth increased, and bone deficiency ratio reduced mesially to distally (P < 0.001), apically to coronally (P < 0.01), and at a greater gingival and distal inclination (P < 0.05). The maximum bone depth (10.72 mm) was observed 13 mm above the maxillary occlusal plane in the mesiobuccal root of the maxillary second molar. The minimum bone depth (3.4 mm) was observed 17 mm above the maxillary occlusal plane in the distobuccal root of the maxillary first molar. No bone deficiency was detected at the paths of 13 mm above the maxillary occlusal plane at a gingival inclination of 70° and distal inclination of 30° in the mesiobuccal root of the maxillary second molar. The highest bone deficiency ratio is present 17 mm above the maxillary occlusal plane at a gingival inclination of 60° and a distal inclination of 0° in the distobuccal root of the maxillary first molar (89/160).

Conclusion

Insertion paths located at 13 mm above the maxillary occlusal plane in the mesiobuccal root of the maxillary second molar were optimal. A gingival inclination of 70° and a distal inclination of 30° could be beneficial. The distobuccal root of the maxillary first molar region or above the 17 mm insertion plane may not be recommended.

Current status of the biomechanics of extra-alveolar miniscrews

Temporary skeletal anchorage devices such as miniscrews are frequently used nowadays. Compared to miniplates, miniscrews are much less expensive and technically easier to place and remove; they are popular and can be easily placed by an orthodontist. Extra-alveolar miniscrews offer benefits compared to inter-radicular miniscrews, such as reduced risk of root damage and the lack of interference with the mesiodistal tooth movement. They are particularly useful for addressing anchorage loss issues and enabling specific tooth movements such as total arch maxillary and mandibular retraction, posterior distalization, molar protraction, molar intrusion, occlusal plane control, and midline correction. The present paper discusses the current biomechanics principles related to the use of extra-alveolar miniscrews placed in the infrazygomatic and mandibular buccal shelf.

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.

Should Cone-Beam Computed Tomography Be Performed Prior to Orthodontic Miniscrew Placement in the Infrazygomatic Crest Area?-A Systematic Review

There is no unequivocal scientific consensus for the temporary anchorage device (TAD) positioning in the infrazygomatic crest area (IZC). The two principal aims of this systematic review were to assess bone availability in the IZC and to establish both the target site and the need for cone-beam computed tomography (CBCT) prior to miniscrew placement. The study was performed following PRISMA guidelines (PROSPERO: CRD42023411650). The inclusion criteria were: at least 10 patients, three-dimensional radiological examination, and IZC assessment for the TAD placement. ROBINS-I tool and Newcastle-Ottawa Scale were used for quality evaluation. No funding was obtained. The study was based on the information coming from: PubMed, Google Scholar, Web of Science Core Collection, MDPI, Wiley, and Cochrane Libraries. The last search was carried out on 1 August 2023. Fourteen studies were identified for analysis. A narrative synthesis was performed to synthesize the findings of the different studies. Unfortunately, it is not possible to establish the generally recommended target site for IZC TAD placement. The reasons for this are the following: heterogeneity of available studies, inconsistent results, and significant risk of bias. The high variability of bone measurements and the lack of reliable predictors of bone availability justify the use of CBCT for TAD trajectory planning. There is a need for more high-quality studies aiming three-dimensional bone analysis of the IZC.

Computed Tomographic Evaluation of Buccal Shelf Dimensions in South Indian Patients With Sagittal Skeletal Class III Malocclusion: A Retrospective Study

Background Computed tomographic evaluation of mandibular buccal shelf region in skeletal class III malocclusion cone beam computed tomography (CBCT) studies have been reported to have great alteration in the thickness of mandibular buccal shelf region owing to the different growth patterns and ethnic variations. The aim of this study was to determine the total and cortical bone thickness in the mandibular buccal shelf (MBS) region for extra-alveolar mini-screw placement in South Indian patients with sagittal skeletal class III malocclusion. Material and methods This retrospective computed tomographic study consisted of archived files of the Dravidian population with class III skeletal base that met the eligibility criteria. The total bone and cortical bone thickness of the buccal shelf regions were evaluated in relation to three anatomical sites at various depths and angulations. One-way ANOVA and Tukey honestly significant difference (HSD) post hoc tests were used for statistical analysis. Pearson correlation coefficient was performed to compare if any relation existed between bone thickness and the growth pattern. Results The maximum bone thickness in the buccal shelf region in our study was found at the distal portion of the second molar root, 8-12 mm from its cementoenamel junction (CEJ) and at 30-45 ° angulation (p-value<0.005). There was a positive correlation between the hypo-divergent growth pattern and the thickness of the bone. Conclusion Based on the sites recorded, the preferred site for mini screw placement in Class III patients is the distobuccal cusp region with respect to the second molar at a depth of 8-12 mm and at angulation of 30-45 °. There was a moderate correlation with hypo-divergent growth patterns, suggestive of a wider and thicker mandibular buccal shelf region in these subjects.

Bone thickness and height of the buccal shelf area and the mandibular canal position for miniscrew insertion in patients with different vertical facial patterns, age, and sex

OBJECTIVES

The objectives of this article were the following: (1) to analyze bone thickness and height (BTH) of the buccal shelf area (BS) quantitatively in four different potentially eligible sites for miniscrew insertion; (2) to compare and contrast BTH and the changes in spatial position of the inferior alveolar nerve canal (IANC); and (3) to assess differences with age among vertical facial patterns (hypodivergent, normodivergent, and hyperdivergent) and sex.

MATERIALS AND METHODS

Cone-beam computed tomography scans of 205 individuals (110 women and 95 men) were divided into groups according to age, vertical facial pattern, and sex. The BTH of the BS and the BTH to the IANC were measured in the mesial and distal roots of the first and second molars.

RESULTS

BTH progressively increased in a posterior direction (P < .001), while BTH to the IANC increased and decreased (P < .001) for thickness and height, respectively, in the same direction in all age groups, for the three different vertical facial patterns, and in both sexes. Women showed significantly less BTH to the IANC (P < .002). Hypodivergent patients had greater BTH (P < .024) and a smaller bone height to the IANC (P < .018) only in the first molar region. Patients over 40 years of age had lower bone height in the second molar area (P < .003).

CONCLUSIONS

The ideal place for BS miniscrew insertion is the region of the distal root of the second molars, regardless of facial pattern, sex, and age. The BS in women has less BTH and less BTH to the IANC.

Total arch maxillary distalization using infrazygomatic crest miniscrews in the treatment of Class II malocclusion: a prospective study

OBJECTIVES

To evaluate treatment effects in Class II patients using infrazygomatic crest (IZC) miniscrews (MS).

MATERIALS AND METHODS

A prospective sample of 25 adolescents (14 females and 11 males; mean age: 13.6 ± 1.5 years) who underwent maxillary dentition distalization treatment with IZC MSs were recruited. Lateral cephalograms and digital models at the beginning of treatment (T1) and after Class II molar correction (T2) were obtained. To compare cephalometric and digital model changes, paired t-test and Wilcoxon test were used. A significance level of 5% was used.

RESULTS

All patients achieved Class II molar correction over a mean period of 7.7 ± 2.5 months. The IZC MS therapy provided 4 mm of distalization; there was 1.2 mm of intrusion of the first molar with 11.2° distal tipping. The maxillary incisors were retracted 4.7 mm and tipped lingually 13.4°. Overjet and overbite showed a reduction of 3.6 mm and 2.4 mm, respectively. The occlusal plane rotated clockwise 2.8°. The upper lip was retracted by 1 mm and the nasolabial angle increased 5.1°. There was an increase in the interpremolar and intermolar distances.

CONCLUSIONS

Total arch distalization of the maxillary dentition using IZC MS was effective in the treatment of Class II malocclusions.