Magnetic Resonance Imaging and Its Effects on Metallic Brackets and Wires: Does It Alter the Temperature and Bonding Efficacy of Orthodontic Devices?

Orthodontic appliances and their diagnostic impact to brain MRI

OBJECTIVE

The aim of this study was to display and quantify signal loss artifacts in 1.5T and 3T brain MRI on a volunteer with different orthodontic appliances.

MATERIALS AND METHODS

In this experimental study, three different orthodontic appliances were examined on a 1.5T and a 3T MRI scanner in a healthy adult with normal dental occlusion: stainless-steel brackets paired with a nickel-titanium archwire; brackets, archwire, and stainless-steel molar bands; brackets, archwire, molar bands, and a stainless-steel trans-palatal archwire. Assessment of diverse anatomical structures, including different cerebral structures and blood vessels, was conducted using a six-point Likert scale.

RESULTS

Utilizing conventional stainless-steel brackets and a nickel-titanium archwire, with or without the inclusion of stainless-steel molar bands, all cerebral structures demonstrated satisfactory assessability with high diagnostic quality under both 1.5T and 3T MRI. For example, with an average rating of 85/85 for T2 and 77/85 for susceptibility-weighted imaging (SWI). Upon introduction of the stainless-steel trans-palatal archwire, additional artifacts were observed, predominantly manifesting in SWI (20/85), diffusion-weighted imaging (DWI) sequences (31/85), and phase contrast angiography (PCA) (17/20). Differences in artifact severity were mainly observed in the SWI and DWI sequences.

CONCLUSION

Based on the findings of this study, it is not imperative to entirely remove orthodontic appliances to achieve sufficient diagnostic quality in brain MRI. In instances where SWI or DWI sequences are necessitated, the removal of solely the trans-palatal stainless-steel archwire should be contemplated, given its straightforward execution.

CLINICAL RELEVANCE

These results highlight the potential to reduce injury risk during orthodontic appliance removal, expedite imaging procedures, and consequently accelerate diagnostic processes, particularly crucial in emergencies.

The Effect of MRI Exposure on the Shear Bond Strength and Adhesive Remnant Index of Different Bracket Types

Background/Objectives: Magnetic resonance imaging (MRI) is widely used in diagnostics, but its effects on orthodontic materials remain a concern. This study aimed to evaluate the impact of MRI exposure at 1.5 T and 3 T on the shear bond strength (SBS) and adhesive remnant index (ARI) of different orthodontic bracket types (metal, self-ligating, and ceramic). Methods: A total of 90 extracted human premolars were divided into three groups (control, 1.5 T, and 3 T MRI exposure). The three bracket types were bonded using Transbond XT adhesive and subjected to standardized polymerization. MRI scans were conducted using 1.5 T and 3 T machines with clinically relevant sequences. SBS was measured using a universal testing machine, and the ARI was assessed under a stereomicroscope. Statistical analysis was performed using Kruskal-Wallis and chi-square tests. Results: MRI exposure influenced SBS and the ARI differently across bracket types. Firstly, 3 T MRI exposure significantly reduced SBS in self-ligating (p = 0.017) and ceramic brackets (p = 0.014) compared to the control, whereas metal brackets showed no significant changes. ARI scores varied across MRI conditions, with metal and self-ligating brackets showing increased adhesive retention at higher field strengths. No significant differences were observed in ARI scores for ceramic brackets across MRI conditions. Conclusions: The clinical importance of understanding these results is that both patients and clinicians must be aware of inevitable changes that occur in SBS during MRI, since exposure to high-field MRI, particularly 3 T, may alter bond strength and adhesive failure characteristics.

Multibraided Fixed Retainers with Different Diameters after Magnetic Resonance Imaging (MRI): In Vitro Study Investigating Temperature Changes and Bonding Efficacy

OBJECTIVES

Orthodontists are often asked to remove fixed retainers before patients undergo magnetic resonance imaging (MRI). The present in vitro study was designed to analyze the heating and bonding efficacy of stainless steel multibraided fixed retainers after 1.5- and 3-tesla (T) MRI.

MATERIALS AND METHODS

A total of 180 human mandibular incisors were used to create 45 specimens of four teeth each, divided into nine groups. Handmade multibraided fixed retainers of three different sizes, defined by the diameter of the initial wire used (0.008″, 0.010″ and 0.012″), were tested. Three groups underwent MRI at 1.5 T, another three groups underwent MRI at 3 T and the last three groups did not undergo MRI. Temperature was assessed before and after MRI. Shear bond strength (SBS) and adhesive remnant index (ARI) were assessed after MRI for all groups. Data were statistically analyzed (p < 0.05).

RESULTS

After 1.5 T exposure, no significant temperature increase from T0 to T1 was observed in any of the groups (p > 0.05). Regarding the 3 T groups, a significant difference from T0 to T1 was found for all the groups (p < 0.05). Temperature changes were not clinically relevant, as they were less than 1 °C for all groups except for group 3 (ΔT0-T1: 1.18 ± 0.3 °C) and group 6 (ΔT0-T1: 1.12 ± 0.37 °C). Furthermore, there were no significant differences between the temperature variations associated with different wire diameters (p > 0.05).

CONCLUSIONS

No significant changes in SBS or ARI were found (p > 0.05).

CLINICAL SIGNIFICANCE

Since overheating was irrelevant and adhesion values did not change, the tested devices were concluded to be safe for MRI examinations at 1.5 T and 3 T.

New Materials and Techniques for Orthodontics

Orthodontics is a specialty of dentistry dealing with the prevention, diagnosis, and treatment of mispositioned jaws and teeth [...].

Effect of Magnetic Resonance Imaging at 1.5 T and 3 T on Temperature and Bond Strength of Orthodontic Bands with Welded Tubes: An In Vitro Study

Magnetic resonance imaging (MRI) is a widely used diagnostic technique. Patients wearing orthodontic devices are often requested to remove their appliances before an MRI exam, even when the exam involves anatomical areas far from the head, in order to prevent the heating and detachment of the appliances. The present report aims to evaluate changes in temperature and adhesive forces of molar bands after MRI at two different strength outputs. Sixty stainless steel molar bands were bonded on permanent human upper molars using two different cements: Unitek Multi-Cure Glass Ionomer Band Cement (3M Unitek, Monrovia, CA, USA) and Transbond Plus Light Cure Band Adhesive (3M Unitek). Appliances were subjected to MRI with two different strengths (1.5 Tesla and 3 Tesla). Tubes and band temperature was measured before and after MRI. Subsequently, the shear bond strength (SBS) test was calculated. Data underwent statistical analysis (p < 0.05). After MRI, molar bands exhibited significant heating, even though not clinically relevant, with a temperature increase ranging between 0.48 °C and 1.25 °C (p < 0.05). SBS did not show significant differences (p > 0.05). The present study suggests that, under MRI, the molar bands tested are safe; therefore, their removal could be not recommended for non-head and neck MRI exams. Removal would be necessary just in artifact risk areas.

MRI compatibility of orthodontic brackets and wires: systematic review article

BACKGROUND

Before the magnetic resonance imaging (MRI) examination fixed orthodontic devices, such as brackets and wires, cause challenges not only for the orthodontist but also for the radiologist. Essentially, the MRI-safe scan of the fixed orthodontic tools requires a proper guideline in clinical practice. Therefore, this systematic review aimed to examine all aspects of MRI-safe scan, including artifact, thermal, and debonding effects, to identify any existing gaps in knowledge in this regard and develop an evidence-based protocol.

METHODS

The Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) statement was used in this study. The clinical question in "PIO" format was: "Does MRI examination influence the temperature of the orthodontic devices, the size of artifacts, and the debonding force in patients who have fixed orthodontic bracket and/or wire?" The search process was carried out in PubMed, PubMed Central, Scopus, and Google Scholar databases. The search resulted in 1310 articles. After selection according to the eligibility criteria, 18 studies were analyzed by two reviewers. The risk of bias was determined using the Quality In Prognosis Studies tool.

RESULTS

Out of the eligible 18 studies, 10 articles examined the heating effect, 6 were about the debonding effect, and 11 measured the size of artifact regarding brackets and wires. Considering the quality assessment, the overall levels of evidence were high and medium. The published studies showed that heating and debonding effects during MRI exposure were not hazardous for patients. As some wires revealed higher temperature changes, it is suggested to remove the wire or insert a spacer between the appliances and the oral mucosa. Based on the material, ceramic and plastic brackets caused no relevant artifact and were MRI-safe. Stainless steel brackets and wires resulted in susceptibility artifacts in the orofacial region and could cause distortion in the frontal lobe, orbits, and pituitary gland. The retainer wires showed no relevant artifact.

CONCLUSIONS

In conclusion, the thermal and debonding effects of the fixed orthodontic brackets and wires were irrelevant or resoluble; however, the size of the artifacts was clinically relevant and determined most significantly the feasibility of fixed brackets and wires in MRI examination.

Microleakage beneath orthodontic brackets in high field magnetic resonance imaging (MRI) AT 1.5 & 3 tesla

OBJECTIVES

The aim of the present study was to evaluate the effects of 1.5 T and 3 T MRI on the adhesion between the orthodontic brackets and the teeth by evaluating the microleakage between theenamel, adhesive and brackets interfaces.

METHODS

Fifty-eight extracted human premolars which were received a standard bracket bonding procedure were randomly divided into three groups; control group (n = 20; no MRI), 1.5 T MRI group (n = 19; 20 min MRI exposure of 1.5 T) and 3 T MRI group (n = 19; 20 min MRI exposure of 3 T). The teeth were kept in distiled water for 2 weeks, and thereafter subjected to 500 thermal cycles. Then specimens were sealed with nail varnish, stained with 0.5% basic fuchsin for 24 h, sectioned and photographed under a stereomicroscope. Microleakage was scored with regard to the adhesive-enamel and bracket-adhesive interfaces at the occlusal and gingival levels. Statistical analysis was accomplished by Kruskal-Wallis and Bonferroni-Dunn tests.

RESULTS

All of the groups exhibited statistically similar microleakage scores in the adhesive-enamel interface along occlusal margins (p>0.05, p = 0.331). The mean microleakage scores along gingival margins in the 3 T MRI group was significantly higher compared to the control group both in the adhesiv-enamel and bracket-adhesive interfaces (p<0.05, p = 0.019 and p = 0.020 respectively). The microleakage scores along the gingival margins were also significantly higher than the occlusal margins in the 3 T MRI group (p<0.05, p = 0.029).

CONCLUSIONS

3 T MRI may weaken the adhesion between the enamel and the stainless steel orthodontic brackets.

The intraoral permeability measurement as a screening for artifact formation by orthodontic products in MRI

AIM

Metal dental products lack precautionary statements regarding MR compatibility due to an exemption in the labelling obligation. Hence, it is difficult for radiologists to decide whether to remove fixed metal objects in patients prior to MRI. A solution could be the direct determination of the magnetic permeability (µ_r) as a decisive material-related predictor of artifact formation and other interactions. Thus, the applicability of an industrially used measurement device as a screening instrument and the relevance of the manufacturer's application restrictions in vitro and in vivo were tested.

METHODS

Precision and trueness were tested using self-made test objects with different dimensions and different permeability. To clarify whether the measurement results are affected by the remanence (B_R) induced in the objects, 28 brackets of different materials were exposed to a weak and a strong external magnetic field and the magnetic flux density before and after these exposures was compared. The clinical test was performed on a volunteer with an orthodontic appliance experimentally composed of brackets with different levels of magnetic permeability (µ_r). Validity and intra- and interrater reliability were calculated using two rater groups consisting of four dentists and four medical-technical radiology assistants (MTRA), respectively.

RESULTS

With coefficients of variation below 0.14%, precision was excellent regardless of object surface and size. Trueness was high on objects with µ_r ≤ 1.002, and decreased with increasing µ_r, for which size-dependent correction factors were calculated. Intra- and interrater reliability and validity were excellent and independent of professional intraoral manipulation experience.

CONCLUSIONS

The permeability measurement allows for a valid and reliable determination of the magnetizability of intraoral metal objects. When used as a screening tool to detect nonartifact-causing objects, no correction factor needs to be calculated. For the first time, it offers radiologists a decision support for the selective removal of only the highly permeable components of the multiband apparatus.

In Vitro Study of Shear Bond Strength in Direct and Indirect Bonding with Three Types of Adhesive Systems

This study aimed to compare the shear bond strength (SBS) and adhesive remaining index (ARI) using one conventional and two novel adhesive systems with clinical step reduction and direct and indirect bonding. A sample of 72 human premolars were divided into six groups of 12 samples. The first three groups (G1, G2, G3) were bonded with a direct technique, while the remaining groups (G4, G5, G6) were bonded by the indirect technique. Groups G1 and G4 used conventional acid-etching primer composite (XT); groups G2 and G5 used self-etching bonding (BO), and groups G3 and G6 had an acid-etching treatment followed by a self-adhesive composite (OC). All groups were exposed to thermocycling. Shear bond strength was analyzed with a universal test machine, and the ARI was examined with 4× magnification. The results showed statistically significant differences between the three adhesive systems. The highest strength values were observed in the XT group G1 (13.54 ± 4 MPa), while the lowest were shown in the BO G2 samples (5.05 ± 2 MPa). There was no significant difference between the direct or indirect bonding techniques on the three compared groups. The type of primer and bonding material significantly influenced the SBS. Values with self-etching bonding were below the minimum recommended for clinical use (5.9-7.8 MPa). There was no difference between indirect and direct bonding techniques. The lowest ARI scores (0-1) were observed in both self-etching and BO groups. Further clinical studies are needed to compare in vivo results.