Miniscrews for orthodontic anchorage: a review of available systems

Evaluation of safe areas for miniscrew use according to various skeletal anomalies with CBCT

OBJECTIVES

We aimed to determine safe areas to apply miniscrews in the interradicular region of the maxilla and mandible in individuals with various sagittal skeletal malocclusions.

MATERIALS AND METHODS

Cone beam-computed tomography images of 159 individuals were used. Individuals were divided into three groups: Class I, Class II, and Class III. In the sagittal plane, 3-6-9-mm apical sections were determined from the alveolar crest apex. The buccal cortical bone thickness, interradicular distance, and buccolingual bone distances were measured.

RESULTS

In the buccal cortical bone thickness, we observed statistically significant differences between the classes except for the 1-1 region in the maxilla and all regions and sections in the mandible (p < 0.05). The differences in the buccolingual bone distance between classes were statistically significant, except for the 3-mm and 6-mm sections in the 3-4 and 4-5 regions of the maxilla, the 9-mm sections in the 1-2 and 2-3 regions, the 6-mm and 9-mm sections in the 3-4 region, and the 6-mm section in the 4-5 regions of the mandible (p < 0.05). The differences in the interradicular bone distance were statistically significant between the classes in all regions and sections of the mandible except the 6-mm sections in the 1-2 region and in all sections of the maxilla except the 6-mm sections in the 3-4 region (p < 0.05).

CONCLUSIONS

We observed significant differences in the buccal cortical bone thickness, interradicular bone distance, and buccolingual bone distance among individuals.

CLINICAL RELEVANCE

Understanding the anatomy of interradicular regions and preventing complications.

Feasibility of mini-implant insertion between mesial and distal buccal roots of a maxillary first molar: A cone-beam computed tomography imaging study

INTRODUCTION

Mini-implant insertion in the maxillary posterior region can be influenced by anatomic limitations, thus increasing the failure rate. We explored the feasibility of a new implantation site: the region between the mesial and distal buccal roots of the maxillary first molar.

METHODS

Cone-beam computed tomography data from 177 patients were collected from a database. The maxillary first molars were morphologically classified by analyzing the angle and morphology of the mesial and distal buccal roots. Next, 77 subjects were randomly selected from the 177 patients to measure and analyze the hard-tissue morphology in the maxillary posterior region.

RESULTS

We devised the Morphological Classification on the Mesial and Distal Buccal Roots of Maxillary First Molar (MCBRMM), divided into 3 types: MCBRMM-I, II, and III. In all subjects, MCBRMM-I, II, and III accounted for 43%, 25%, and 32%, respectively. At 8 mm from the mesial cementoenamel junction of maxillary first molars, the interradicular distance between the maxillary first molar's mesiodistal buccal roots of MCBRMM-I was 2.6 mm, showing an upward trend from the cementoenamel junction to the apex. The distance from the buccal bone cortex to the palatal root was >9 mm. The buccal cortical thickness was >1 mm.

CONCLUSIONS

This study provided a potential site for mini-implant insertion in the maxillary posterior region: the alveolar bone of maxillary first molars in MCBRMM-I.

Tooth Complications after Orthodontic Miniscrews Insertion

Orthodontic miniscrews (OM) are widely used in modern orthodontic clinical practice to improve skeletal anchorage and have a high safety profile. A complication at the time of OM insertion is tooth root perforation or periodontal ligament trauma. Rarely, OM injury can cause permanent damage, such as ankylosis, osteosclerosis, and loss of tooth vitality. The aim of this work was to analyze potential risks and dental complications associated with the use of OMs. A search of the PubMed, Cochrane, Web of Science, and Scopus databases was conducted without a time limit using the keywords "orthodontic mini-screw" and "dental damage", resulting in 99 studies. After screening and eligibility, including articles obtained through a citation search, 13 articles were selected. Four studies revealed accidental injuries caused by OM. Most of the damage was localized at the root level and resolved spontaneously with restorative cement formation after prompt removal of the OM, while the pain disappeared. In some cases, irreversible nerve damage, extensive lesions to the dentin-pulp complex, and refractory periapical periodontitis occurred, requiring endodontic and/or surgical treatment. The choice of insertion site was the most important element to be evaluated during the application of OMs.

Effects of Rigid and Nonrigid Connections between the Miniscrew and Anchorage Tooth on Dynamics, Efficacy, and Adverse Effects of Maxillary Second Molar Protraction: A Finite Element Analysis

Introduction

Direct, rigid indirect, and nonrigid indirect absolute anchorages using temporary anchorage devices (TADs, mini-implants/miniscrews) can provide promising opportunities for challenging, yet common, orthodontic tooth movements such as molar protraction. Rigid rectangular wire and ligature wire are the most common methods of attaching a tooth to a miniscrew in indirect anchorages. We aimed to provide a comparison of the rigidity of the connecting wire in terms of stress on the miniscrew, the anchorage loss, and the risk of root resorption using finite element analysis (FEA).

Methods

The maxillary right second molar was protracted into the proximal space at a 150 g load (1) using direct absolute anchorage with a tapered miniscrew implanted between the premolar roots and using indirect absolute anchorage with the second premolar reinforced by the miniscrew through (2) a rigid stainless steel (SS) wire or (3) a nonrigid SS ligature wire (4) at different elastic moduli. Stresses and displacements of 4 models' elements were measured. The risk of external root resorption was evaluated.

Results

Connecting the tooth to the miniscrew using rigid full-size wire (model 2) compared to ligature (model 3) can give better control of the anchorage (using the ligature wire, the anchorage loss is 1.5 times larger than the rectangular wire) and may reduce the risk of root resorption of the anchorage unit. However, the risk of miniscrew failure increases with a rigid connection, although it is still lower than with direct anchorage. The miniscrew stress when using a ligature is approximately 30% of the rigid model using the rectangular wire. The miniscrew stress using the rectangular wire is approximately 82.4% of the miniscrew stress in the direct model. Parametric analysis shows that the higher the elastic modulus of the miniscrew-tooth connecting wire in the indirect anchorage, the less the anchorage loss/palatal rotation of the premolars/and the risk of root resorption of the anchorage teeth and instead the stress on the miniscrew increases.

Conclusions

Direct anchorage (followed by rigid indirect anchorage but not nonrigid) might be recommended when the premolars should not be moved or premolar root resorption is a concern. Miniscrew loosening risk might be the highest in direct anchorage and lowest in nonrigid indirect anchorage (which might be recommended for poor bone densities).

Frequency of Using Miniscrew Anchorage by the Iranian Orthodontists

AIM: In recent years, miniscrews are extensively used for anchorage in orthodontic treatments. This study aimed to assess the frequency of using miniscrew anchorage by the Iranian orthodontists in 2020. MATERIALS AND METHODS: This descriptive, cross-sectional study evaluated 70 Iranian orthodontists. After obtaining their written informed consent, a questionnaire was emailed to them. The validity of the questionnaire was confirmed by four faculty members and its reliability was determined to be 75% by calculating the Cronbach’s alpha after administering it among 40 orthodontists. Data were analyzed using SPSS version 22. RESULTS: Of 97 administered questionnaires, 70 were filled out and returned (response rate=72.16%) by 42 males and 28 females. Of participants, 62.3% reported using miniscrews in their practice. Furthermore, 96.6% of the orthodontists reported that they would place the miniscrews by themselves. The majority of orthodontists (98.3%) were completely or relatively satisfied with the efficacy of miniscrews, and 93.5% recommended the use of miniscrews to their colleagues. Factors such as poor expertise in miniscrew insertion, doubts about its advantages, high cost, and time-consuming placement were the main reasons for reluctance of some orthodontists in using miniscrews. CONCLUSION: Considering the high efficacy of miniscrews for orthodontic treatment and high satisfaction level of Iranian orthodontists with miniscrews, their application is expected to rise by the Iranian orthodontists after eliminating the existing limitations against their widespread use.

Orthodontic temporary anchorage devices: A qualitative evaluation of Internet information available to the general public

INTRODUCTION

The evaluation of online information regarding orthodontic temporary anchorage devices (TADs) is lacking despite the increase in their use by orthodontists. This cross-sectional study aimed to investigate the quality of information regarding TADs available on the Internet to the general public.

METHODS

Two search terms ("orthodontic temporary anchorage device" and "orthodontic miniscrew") were entered separately into a total of 5 search engines. The DISCERN instrument, Journal of the American Medical Association (JAMA) benchmarks, and Health on the Net Foundation Code of Conduct were used to evaluate the quality of information contained within Web sites that satisfied the inclusion and/or exclusion criteria. Web site readability was assessed via the Simple Measure of Gobbledygook and Flesch Reading Ease Score tools. Descriptive statistical analyses and Cohen's kappa intrarater reliability tests were performed.

RESULTS

Thirty-one Web sites were evaluated. Most were authored by orthodontists (77.4%) and originated from the U.S. (38.7%). The mean (standard deviation [SD]) DISCERN score was 41.87 (8.45) out of 80, with a range of 27-57. Intrarater reliability testing for DISCERN scores was excellent (0.84). Four Web sites achieved all 4 JAMA benchmarks, and 2 achieved none. Referencing of content sources throughout the Web sites scored least via DISCERN (mean 1.49 out of 5 per Web site [SD, 0.77]) and JAMA (19.35% of Web sites). One Web site contained the Health on the Net Foundation Code of Conduct seal. The mean (SD) Simple Measure of Gobbledygook score was 8.75 (1.25), with a range of 6.5-11.3. The mean (SD) Flesch Reading Ease Score was 59.81 (7.17), with a range of 47.6-73.8.

CONCLUSIONS

The quality of information related to TADs on the Internet is moderate. The usefulness of the information may be further reduced because it was beyond the readability of the average member of the general public. Web site authors should consider the use of additional expertise, quality of information tools, and readability formulas to ensure high-quality and easily readable content.

Safe regions of miniscrew implantation for distalization of mandibular dentition with CBCT

Background

To assess the anatomy of the mandibular buccal shelf (MBS) with cone-beam computed tomography (CBCT) and to identify the region of miniscrew implantation for the distalization of mandibular dentition.

Materials and methods

The MBS was assessed in 80 patients at four regions as follows: (i) between the buccal root of the mandibular second premolar and the mesiobuccal root of the first molar (L5_b–L6_mb), (ii) between the mesiodistal root of the first molar (L6_mb–L6_db), (iii) between the distobuccal root of the first molar and the mesiobuccal root of the second molar (L6_db–L7_mb), and (iv) between the mesiodistal roots of the second molar (L7_mb–L7_db). The buccal alveolar bone thickness, the narrowest inter-radicular space at the buccal side of the roots, and the distance between the implantation site and the mandibular neural tube were measured at horizontal planes of 3, 5, 7, and 9 mm from the alveolar crest.

Results

The buccal alveolar bone thickness increased from the premolar to the molar and from the crest edge to the mandibular roots. The L7_mb–L7_db region had the thickest buccal alveolar bone of 7.61 mm at a plane of 9 mm. The buccal inter-radicular spaces were smallest in the L7_mb–L7_db region and greatest in the L6_db–L7_mb region. The distances from the implantation site to the mandibular neural tube at planes of 3, 5, 7, and 9 mm were all > 13 mm from the L6 region to the L7 region.

Conclusions

The L6_db–L7_mb region should be the first choice for miniscrew implantation in the MBS for the distalization of mandibular dentition.

Biological Effects of Anodic Oxidation on Titanium Miniscrews: An In Vitro Study on Human Cells

This controlled in vitro study compared the effects of varying the thickness of a TiO₂ layer on cellular activity using commercially available miniscrew samples with identical surface features to derive information with direct clinical impact. Titanium grade V plates with four different thicknesses of TiO₂ layer/color were used: absent/gray (Control group), 40–50 nm/pink (Pink group), 130 nm/gold (Gold group) and 140 nm/rosé (Rosé group). In vitro experiments used Saos-2 cells and included cell growth analysis, phospho-Histone H3 and procollagen I staining, cell viability analysis, and a cell migration assay at 12, 24, 40 and to 48 h. Few differences were seen among the groups, with no clear behavior of cellular activity according to the TiO₂ thickness. The Control group showed a greater cell count. Phospho-Histone H3 staining was similar among the groups and procollagen I staining was greater in the Rosé group. Cell viability analysis showed a significant difference for live cell counts (greater in the Rosé group) and no difference for the dead cell counts. The cell migration assay showed a delay for the Rosé group up to 40 h, where full repopulation of cell-free areas was obtained at 48 h. The results suggest that the TiO₂ layers of the commercial miniscrews have minimal biological effects, including cytotoxicity, with possibly negligible or minimal clinical implications.