Safe sites for orthodontic miniscrew insertion in the infrazygomatic crest area in different facial types: A tomographic study

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.

Temporary Anchorage Devices in Clear Aligner Therapy: A Systematic Review

This systematic review analyzed the combined use of aligners and orthodontic temporary anchorage devices (TADs) in orthodontic treatment. The aim was to evaluate the effectiveness, benefits, and potential challenges of integrating the use of miniscrews with aligners. This review was conducted according to the PRISMA statement, and the protocol was registered at PROSPERO under the ID CRD42024576712. A comprehensive search on PubMed, Scopus, and Web of Science was conducted to identify relevant papers involving patients treated with aligners and TADs, dating from 1 January 2004 to 17 July 2024. The electronic database search identified a total of 458 articles. After eligibility, 14 records were selected for qualitative analysis. The findings suggest that the combination of aligners and miniscrews significantly enhances treatment precision and control, especially in cases requiring complex tooth movements, such as intrusion, extrusion, and distalization. The use of miniscrews allows greater control of movement and stability. The integration of these two techniques presents challenges, such as the need for precise miniscrew placement and potential discomfort during insertion. However, there was high satisfaction due to the aesthetic and comfort benefits of aligners. Further research is desirable to delve deeper into the topic to optimize clinical outcomes.

Evaluation of Two Mini-implant Lengths in the Infrazygomatic Crest Region: A Randomized Clinical Trial

OBJECTIVE

  Temporary anchorage devices (TADs) have revolutionized fixed orthodontic appliance treatment through anchorage controlling in the clinic and play an essential role in resolving many complex cases. Due to the limited space, there is a risk of injury to the roots while using interradicular microimplants. Therefore, the infrazygomatic crest (IZC) area can be an alternative mini-implant insertion site in the maxillary arch. The aim of the study was to evaluate the primary stability, pain perception, sinus penetration, late stability, and failure rate with two mini-implant lengths in the IZC area.

MATERIALS AND METHODS

 Forty-eight mini-implants (Tusk Dental Co., Ltd., Canada) with two different lengths (length/diameter: 12/2 and 14/2 mm) were grouped by length (24 per group) and inserted bilaterally into the IZC area of 24 patients. The data were statistically analyzed, considering a significance level of p < 0.05.

RESULTS

 Sinus penetration prevalence did not differ significantly between 12-mm (54.2%) and 14-mm (62.5%) mini-implants (p > 0.05). Primary stability was significantly higher with the 14-mm mini-implants (p < 0.05). The failure rate did not differ significantly between the 12-mm (20.8%) and 14-mm (16.7%) mini-implants (p > 0.05).

CONCLUSION

 While the failure rate was similar between 12- and 14-mm mini-implants, the 14-mm mini-implants were more likely to damage adjacent structures. Therefore, shorter mini-implants should be preferred over longer mini-implants for most cases requiring IZC TADs.

TRIAL REGISTRATION ID

 ClinicalTrials.gov identifier: NCT06293872.

Cortical Bone Thickness and Morphology at the Infrazygomatic Crest Area in Growing Thai Patients with UCLP: A CBCT Study

ObjectivesTo determine and compare buccal cortical bone thickness and morphology (in terms of shape and height) at the infrazygomatic (IZ) crest in growing Thai patients with unilateral cleft lip and palate (UCLP) using cone-beam computed tomography (CBCT) with the ultimate goal of identifying potential sites that are suitable for the placement of miniplates.DesignProspective study.SettlingInstitutional research.PatientsTwenty-four Thai patients with non-syndromic complete UCLP with Class III skeletal discrepancy aged 10-14 years.InterventionsA total of 48 CBCT images captured the IZ crest. Five horizontal and six vertical reference planes were established in the IZ crest area.Main Outcome MeasureThe mean buccal cortical bone thickness of the cleft and non-cleft sides were 1.13 ± 0.45 mm and 1.15 ± 0.46 mm, respectively. The most frequently observed shape for the IZ crest was the external concave contour. There were no statistically significant differences in cortical bone thickness and shape distribution between the cleft and non-cleft sides. (P > .05).ResultsThe thickness of the buccal cortical bone increased anteriorly and superiorly from V + 0 and H + 0. The average height of IZ crest on the cleft side was 16.20 ± 1.59 mm and 16.78 ± 1.84 mm on the non-cleft side. Notably, significant differences were detected in terms of height between the cleft and non-cleft side and cortical bone thickness by gender (P < .05).ConclusionsThe IZ crest was found to provide sufficient support for the insertion of a miniplate, particularly in the superior and anterior regions, ensuring primary stability in growing Thai patients with UCLP.

Optimizing the Anatomical Location and Procedural Parameters for Miniscrew Placement in the Infrazygomatic Region- A CBCT Study

This study evaluates the integration of anatomical and procedural guidelines to develop realistic protocols for successful miniscrew insertion in the infrazygomatic crest (IZC) region, using CBCT measurements. A total of 720 measurements were collected from 30 adult patients, focusing on the upper first molar (U6) region. A grid system was created in the sagittal plane, including 12 reference points around the U6, with horizontal and vertical measurement points. A 12-mm virtual IZC miniscrew was inserted at each reference point, with the angle adjusted for 1 mm of sinus penetration and 5 mm of projection beyond the bone surface. Insertion success was defined as maintaining a minimum 0.5 mm safe distance from the roots, classified as system-compatible (SC), while root contact (RC), failure to achieve sinus penetration (SF), or sinus perforation (SP) exceeding 1 mm were classified as failures. No significant differences were found among the reference regions (p > 0.05). The 15 mm-U6MB region, with an insertion angle of 41.22°±8.67° apically and 12.36°±2.48° mesially, had the highest success rate of 55.0 %. The 15 mm-U6DB region, while aligning with the guidelines, had a higher incidence of root proximity (56.9 %). At the 17 mm region, sinus perforations exceeded 1 mm in 96.8 % of cases. The recommended placement height of 15 mm above the POP, with a 40° apical and 10° mesial angle at U6MB, offers the best balance of stability and safety, in line with literature guidelines. This study provides clinicians with evidence for effective miniscrew placement, ensuring stability while avoiding critical anatomical structures.

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.

Success rate and factors affecting stability of infrazygomatic miniscrew implants: a systematic review and meta-analysis

BACKGROUND

The infrazygomatic miniscrew implants (IZC-MSI) serve as innovative temporary anchorage devices placed parallel to the roots of molars in the infrazygomatic crest region, leveraging their extra-radicular location to support the en masse distalization and intrusion of the maxillary dentition. The efficacy and stability of these screws are crucial for their application in contemporary orthodontic practices.

OBJECTIVES

This systematic review aimed to estimate the success rate and factors affecting the stability of IZC-MSI.

SEARCH METHODS

An electronic search was conducted on 7 February 2024 across the following databases: PubMed, Scopus, EMBASE, and Cochrane databases without any restriction on language and time of publication.

SELECTION CRITERIA

The review included clinical trials (both randomized and non-randomized) and retrospective cohort studies that utilized infrazygomatic miniscrew anchorage for orthodontic tooth movement in human participants.

DATA COLLECTION AND ANALYSIS

The proportion of success rate was calculated and factors affecting stability (patient and implant-related factors) such as age, sex, implant position, and loading characteristics were subjected to subgroup analysis and meta-regression. The quality assessment of studies was done using the Cochrane risk-of-bias tools for randomized (RoB 2.0) and non-randomized trials (ROBINS-I).

RESULTS

Fourteen studies (n = 1683 IZC-MSI) were included in the meta-analysis revealing a 92% success rate of IZC-MSI (C.I. 87%-95%; prediction interval: 66%-99%; I2 = 80%). Studies with sample size > 100 presented a 94% success rate (C.I. 91%-96%; I2 = 63%) and moderate heterogeneity. Meta-regression analysis revealed no significant relation between age and success rate. Significant heterogeneity was observed in the subgroup analysis of host-, implant- and other related risk factors affecting stability and limited correlation was found. The risk-of-bias assessment revealed high risk in five, moderate in five, and low in four studies.

CONCLUSIONS

IZC-MSI have shown a good success rate for their clinical application. Although some factors appear to influence IZC-MSI stability, the majority of them necessitate additional investigation due to the low quality of evidence. Furthermore, high-quality studies are needed to confirm the results of this meta-analysis and address other important factors such as operator's experience, insertion torque, and sinus penetration that could not be analysed due to limited data.

REGISTRATION

CRD42024469048.

Automatic Segmentation of the Jaws Used in Guided Insertion of Orthodontic Mini Implants to Improve Their Stability and Precision

Background and Objectives: With the goal of identifying regions with bicortical bone and avoiding root contact, the present study proposes an innovative technique for the simulation of the insertion of mini orthodontic implants using automatic jaw segmentation. The simulation of mini implants takes place in 3D rendering visualization instead of Multi-Planar Reconstruction (MPR) sections. Materials and Methods: The procedure involves utilizing software that automatically segments the jaw, teeth, and implants, ensuring their visibility in 3D rendering images. These segmented files are utilized as study models to determine the optimum location for simulating orthodontic implants, in particular locations characterized by limited distances between the implant and the roots, as well as locations where the bicortical structures are present. Results: By using this method, we were able to simulate the insertion of mini implants in the maxilla by applying two cumulative requirements: the implant tip needs to be positioned in a bicortical area, and it needs to be situated more than 0.6 mm away from the neighboring teeth's roots along all of their axes. Additionally, it is possible to replicate the positioning of the mini implant in order to distalize the molars in the mandible while avoiding the mandibular canal and the path of molar migration. Conclusions: The utilization of automated segmentation and visualization techniques in 3D rendering enhances safety measures during the simulation and insertion of orthodontic mini implants, increasing the insertion precision and providing an advantage in the identification of bicortical structures, increasing their stability.

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.

Treatment for Severe Class II Open Bite Using a Bonded Hyrax Expander, IZC Mini-Implants, and MEAW Technique in an Adolescent Patient

This case report describes the successful 3D treatment of a patient with a narrow maxilla and a severe class II open bite using a combination of a bonded hyrax expander, infrazygomatic crest mini-implants, and the multiloop edgewise arch-wire (MEAW) technique. A 14-year-old female with a thumb-sucking habit in childhood, presented with a severe open bite, a convex profile, and an obtuse nasolabial angle. Diagnosis revealed a skeletal Class II open bite with moderate crowding in the maxillary and mild crowding in the mandibular arch. Treatment objectives included eliminating the open bite, achieving normal overbite and overjet, and improving upper incisor visibility. Treatment involved the use of a bonded rapid palatal expansion device, mini-implants for maxillary intrusion, fixed appliances, vertical elastics, and a MEAW. Treatment results showed resolution of the open bite, improvement in overbite and overjet, achievement of Class I molar and canine relationships, and improved upper incisors visibility. Fixed appliances were used for the whole 22-month therapy period, and post-treatment records demonstrated that the treatment's objectives were met.

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.

Clinical analysis of successful insertion of orthodontic mini-implants in infrazygomatic crest

BACKGROUND

The insertion positions of mini-implant in infrazygomatic crest has been reported, but due to the anatomical variation, the precise location of this site is not clear yet. This study used cone-beam computed tomography (CBCT) to analyze the position and angle of mini-implants successfully inserted in the infrazygomatic crest, with the goal of providing reference data for clinical practice.

METHODS

CBCT was used to image 40 mini-implants and their surrounding tissues in adult orthodontic patients who successfully underwent mini-implant insertion in the infrazygomatic crest. The insertion positions and angles of mini-implants were measured, and the thicknesses of buccal and palatal bone adjacent to the mini-implants were also recorded. Then, we proposed the position and implantation angle for infrazygomatic crest insertion. According to the position and angle, the cortical bone thickness and distance to the root of another 54 randomly selected infrazygomatic crests were recorded to verify its feasibility.

RESULTS

In the coordinate system, the implantation position of the 40 successful mini-implants was (-0.4 ± 2, 8.2 ± 2.5) and the implantation angle between the long axis of the mini-implant and horizontal reference plane was 56.4° ± 7.7°. The bone thicknesses on buccal and palatal sides of infrazygomatic crest adjacent to mini-implants were 4.1 ± 2.5 mm and 7.2 ± 3.2 mm, respectively, and the cortical bone thickness was 2.4 ± 0.6 mm. Among 54 infrazygomatic crests, 75.9% of them met the safety and stability requirements. When the implantation height was increased by 1, 2, and 3 mm, the proportions of implants that met requirements for success were 81.5%, 90.7%, and 94.4%, respectively. But, the proportions of eligible implants were limited at implantation angle increases of 5° and 10°.

CONCLUSIONS

Using the long axis of the maxillary first permanent molar (U6) as the vertical reference line, mini-implants could be safely inserted in the infrazygomatic crest at a distal distance of 0.4 mm and height of 8.2 mm from the central cementum-enamel junction of U6, with an implantation angle of 56.4°. The success rate increased when the implant height increased, but the proportion of eligible implantation was limited with the increase of implantation angle.

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.

Success rate of infrazygomatic miniscrews considering their design and insertion techniques. A review

Miniscrews offer the possibility of performing dental movements, minimizing unwanted side effects and enhancing effectiveness. Extra-alveolar miniscrews are ideal as they provide excellent primary stability and avoid anatomical structures. However, in some cases the primary stability is lost before achieving the success of the mechanics used and thus, the most likely causes of failure should be determined. The purpose of this review was to analyze the success rate of infrazygomatic miniscrews, considering their design and the insertion techniques used. Data collection of this literature review was carried out by searching PubMed, Wiley, Google Scholar sites, SCIELO, Elsevier and Dialnet for publication made from 2003 to June 2022. The search was carried out on June 10th, 2022 and the following keywords were used; infrazygomatic crest, miniscrews, anchorage and stability. Different topics were analyzed and discussed highlighting their clinical relevance. After analyzing the 798 articles, 566 were excluded. The remaining articles were re-analyzed and 153 articles were excluded for the title or abstract and 33 articles were excluded for the methodology. Finally, 46 items remained. After thoroughly analyzing all the articles included, this study concluded that the alloy of the miniscrew (stainless steel or titanium), perforation of the maxillary sinus and the placement area (adhered mucosa or mobile mucosa) do not influence the survival of the miniscrew. The evidence also indicates that the percentage of failure is lower in infrazygomatic compared to intraradicular miniscrews. Orthodontists can confidently and safely include infrazygomatic miniscrew in different orthodontic procedures.