Bracketless three-dimensional orthodontic treatment using coated nickel–titanium E-wires for mild–moderate anterior crowding: A case report with 6-month follow-up

Abstract

In recent years, interest in esthetics has increased considerably, resulting in a growing demand for invisible orthodontic appliances, particularly among adolescents and adults. Bracketless orthodontic treatment is an advanced orthodontic approach that uses coated archwires and composite resin, applied with precision using three-dimensional technology. This method may offer an effective alternative to conventional bracket-based systems in certain cases. This single-case report described a clinical case of skeletal and dental Class I malocclusion characterized by moderate lower dental crowding (4.5 mm); midline shift; a dental crossbite involving teeth 14, 15, and 25; and an increased mandibular incisor inclination (lower incisor to mandibular plane = 104°). This condition was managed using the three-dimensional bracketless orthodontic treatment technique. This technique represents an advanced esthetic approach designed for individuals who prioritize dental appearance. It may reduce anterior teeth proclination by acting from the lingual side and may shorten treatment duration in cases of mild to moderate crowding, ensuring faster and more efficient outcomes.

Introduction

Esthetic considerations are among the primary concerns for patients seeking orthodontic treatment.^1,2 Accordingly, various esthetic orthodontic techniques, including porcelain brackets, lingual orthodontics, and clear aligners, have been developed.^3–6 However, these approaches are often associated with high costs and several clinical limitations. ⁷

Lingual orthodontics offers a significant esthetic advantage, as the brackets are completely hidden from view. However, this technique has certain limitations, including difficulties in maintaining oral hygiene, potential speech disturbances, and patient discomfort or tongue irritation such as ulcerations. ⁸

In contrast, despite the significant increase in the use of clear aligners in recent years, the finishing stage often requires an excessive number of trays, thereby warranting a high level of patient compliance, with a recommended daily wear time of at least 22 h.^9,10

These factors have led to the development of innovative techniques, such as three-dimensional (3D) bracketless orthodontic treatment (3DBOT), aimed at providing discreet and esthetically pleasing orthodontic solutions.

The BOT initially addressed mild relapse of anterior teeth resulting from inadequate patient compliance with retainers following orthodontic treatment. This approach enables precise tooth movement via activatable orthodontic wires instead of the use of metal or ceramic brackets. ¹¹

Moreover, the 3DBOT method is an innovative approach distinguished by its ability to facilitate tooth movement in all three dimensions. In advanced 3D setup technology, a continuous archwire mechanism offers enhanced control over tooth protrusion, lingual positioning, arch shape, and planned expansion along with its discreetness and comfort.^12,13 Direct intraoral scanning and 3D printed models have been shown to produce clinically acceptable dimensional accuracy for orthodontic planning and transfer, supporting the use of digital setups in bracketless workflows. ¹⁴ Accordingly, recent studies on 3D-printed orthodontic components suggest potential for customized, time-efficient appliances in esthetic workflows. ¹⁵

Digital setups have demonstrated acceptable accuracy for moderate crowding corrections and can guide clinical interproximal reduction (IPR) and bonding point placement. ¹⁶

This approach eliminates the need for brackets and uses conventional composite resin to stabilize the archwire in its intended position. Therefore, it does not interfere with speech or complicate oral hygiene maintenance, and it offers a more passive and less demanding alternative treatment for patients.^12,13

The revolutionary BOT is a modern esthetic technique based on the concept of a labially invisible orthodontic appliance composed of nickel–titanium (NiTi) wires coated with a water-soluble material, which are bonded to the lingual surfaces of anterior teeth and to the occlusal surface for posterior teeth.^13,17

This coated E-wire (E-wire; Seoul, Korea) is a practical technique that uses a multilayer fiber coating made from poly-γ-glutamic acid (γ-PGA), a water-soluble substance used for coating orthodontic wires. This coating dissolves upon contact with water and is safe and easy to apply. Most importantly, it creates space around the orthodontic wire, forming a gap between the wire and the resin adhesive. This configuration facilitates essential sliding movement during effective orthodontic treatment.

This case report presents a single clinical case illustrating the application of a 3DBOT technique using coated NiTi E-wires for the alignment of mild to moderate anterior crowding.

Case report

A medically fit male in his late teens presented to the Department of Orthodontics and Dentofacial Orthopedics at the Faculty of Dentistry, Damascus University in November 2024, with the chief complaint of crooked teeth. The patient exhibited good oral health, had no deleterious oral habits, and strongly preferred an esthetically driven treatment plan. The patient did not have a history of any systemic disease, and no relevant family medical history was reported.

This study was approved by the Institutional Review Board and the Ethics Review Committee of Damascus University (Approval Number: DN-02092024-328/1-10-2024). Written informed consent was obtained from the patient. The reporting of this case report conforms to Case Report (CARE) guidelines. ¹⁸

Extraoral examination revealed a convex facial profile, with a profile angle measuring 209°. The nasolabial angle was obtuse at 124°, whereas the labiomental angle was elevated at 143°. Assessment from the frontal view indicated an asymmetrical dolichofacial pattern, characterized by an increased lower facial third. The patient’s lips were competent and displayed a normal length and shape. Upon smiling, the smile line appeared asymmetrical. No occlusal cant was observed. The upper dental midline was in alignment with the facial midline, whereas the lower dental midline deviated 1 mm to the right. (Figure 1)

Figure 1.

Pretreatment extraoral photographs.

Intraoral examination revealed good oral hygiene, and all permanent teeth were fully erupted except for the third molars. The patient presented a Class I molar and canine relationship bilaterally. The malocclusion was complicated by the following: (a) moderate crowding in the lower arch; (b) mild crowding in the upper arch; (c) a dental crossbite involving teeth 14, 15, and 25; (d) an overjet of 1 mm; and (e) an overbite of 16% (1.5 mm). (Figure 2)

Figure 2.

Pretreatment intraoral photographs. (a) Right lateral; (b) frontal; (c) left lateral; (d) maxillary occlusal; and (e) mandibular occlusal.

Dental cast assessment revealed that both the upper and the lower arches displayed a U-shaped configuration. The maxillary arch showed asymmetry in the transverse plane, attributed to the palatal inclination of the upper premolars, which resulted in a dental crossbite involving teeth 14, 15, and 25. Similarly, the mandibular arch exhibited asymmetry in the anterior segment, predominantly due to a lack of space, which resulted in crowding of the anterior teeth and a normal curve of spee.

Space analysis conducted with a digital caliper revealed moderate crowding of 4.5 mm in the lower arch and mild crowding of 1.5 mm in the upper arch. According to Tonn’s analysis, a 0.5 mm increase in the size of the lower incisors compared with the upper incisors was observed, reflecting a 75% ratio. The anterior Bolton analysis indicated an 80.49% ratio, suggesting an increased mesiodistal width of the lower anterior teeth. Finally, the overall Bolton ratio was calculated at 94.36%, indicating a general excess in the size of mandibular teeth (Figure 3).

Figure 3.

Pretreatment scanning study model. (a) Right lateral; (b) frontal; (c) left lateral; (d) maxillary occlusal; and (e) mandible occlusal.

The panoramic radiograph demonstrated symmetry in the condyles and ramus, average bone level, and average root length. All permanent teeth were fully erupted, except for the lower third molars, which were partially erupted. In the upper arch, the upper left third molar (UL8) was congenitally missing, whereas its contralateral (UR8) remained unerupted (Figure 4).

Figure 4.

Pretreatment panoramic radiograph.

The lateral cephalometric radiograph indicated a skeletal Class I relationship in the sagittal plane, with an A point–Nasion–B point angle (ANB) measurement of 4° and a Wits appraisal of 1 mm. In vertical dimension, a slight posterior rotation of the mandible was observed, reflected by an Nasion–Sella to Gonion–Menton (NS-GoMe) angle of 40°. The intermaxillary angle (MM) was measured at 26°, and the Björk sum was recorded at 400°, suggesting a normal growth pattern. Regarding incisor inclinations, the upper incisors exhibited normal angulation (upper incisor to Nasion–Sella (U1–NS) = 110°, upper incisor to Nasion–A line (U1–NA) = 21°, U1 to NA = 4 mm), whereas the lower incisors were proclined and bodily displaced (lower incisor to mandibular plane (L1–GoMe) = 104°, lower incisor to NB (L1–NB) = 35°, L1 to NB = 7 mm). The interincisal angle (L1–U1) was 121°. (Figure 5)

Figure 5.

Pretreatment lateral cephalometric X-ray.

Treatment planning

The treatment objective was to eliminate posterior dental crossbite by correcting the axial inclinations of the upper premolars. In addition, the mild crowding in the upper arch and moderate crowding in the lower arch were corrected through IPR. The discrepancies identified in both the Bolton and Tonn analyses were addressed. This plan also included rectifying the deviation of the lower dental midline, with maintenance Class I canine and molar relationships.

Treatment method

Impressions of the upper and lower dental arches were obtained using a condensation silicone impression material (Bonasil® C-Silicone Impression Mass Set, DMP Dental; Greece).

The resulting dental casts were subsequently scanned using Scanner Maestro (Dental Wings; Canada) to create digital models.

Each model was imported into 3Shape Ortho Analyzer software, where the teeth requiring alignment were repositioned based on the necessary amount of IPR for each tooth to achieve the desired outcome (Figure 6). This process, documented in a specialized form, produces a digital setup of both the upper and lower dental arches after the alignment of the teeth.

Figure 6.

Amount of interproximal stripping.

Selection of the printing modality and post-processing affects model accuracy and clinical transfer. Prior comparisons of printing technologies inform the choice of resin and printer settings. ¹⁹ In addition, recent studies on 3D-printed orthodontic components suggest the potential for customized, time-efficient appliances in esthetic workflows. ¹⁵ Accordingly, printer technology selection influences model accuracy and should be reported to ensure reproducibility. ¹⁹

A 3D Printer Riton (Riton 3D; China) was then employed to create a physically printed model from this digital representation via resin material DentraTec resin (DentraTec; Germany) (Figure 7).

Figure 7.

The digital model printed with a resin material.

After digital alignment of the anterior teeth, the wire was positioned on the printed resin model within the central fossae of the posterior teeth and aligned neutrally along the lingual surfaces of the anterior teeth. The distance between the incisal edge and the wire was subsequently recorded and clinically transferred using a bracket positioning gauge with a marker (Ormco; Switzerland).

Direct bonding technique

First, IPR was performed using a stripping strip, with the amount of reduction measured via an IPR gauge.

The bonding process was initiated with the posterior teeth, where the wire was bonded to the central fossae, followed by the anterior teeth, where the bonding points were precisely determined based on the previously measured distances on the resin model.

Bonding protocol

Enamel surfaces were etched using 37% phosphoric acid, followed by application of a bonding agent (Bond, Ivoclar Vivadent; Germany). A medium-viscosity flowable composite (Tetric EvoFlow, Ivoclar Vivadent; Germany) was then used to bond the wire. Light curing was performed in continuous mode using an light emitting diode (LED) curing unit (SMLColor; Guangxi, China) for 20s per bonding point, with the curing tip positioned as close as possible to the composite (<1 mm).

NiTi wire surface morphology and ion release after intraoral exposure can influence clinical performance and biocompatibility. These factors should be considered when using coated wires. ²⁰ Additionally, intraoral thermal fluctuations alter NiTi mechanical behavior and may affect the deactivation profile of coated wires used in bracketless systems. ²¹

The coated E-wires were sequentially replaced, starting with a 0.012 NiTi-coated E-wire (RA-012U and RA-012L) (Figure 8), followed by a 0.014 NiTi-coated E-wire (RA-014U and RA-014L) (Figure 9), once the initial wire had sufficiently deactivated and returned as closely as possible to its original shape. All wires were supplied by E-wire (Seoul, Korea).

Figure 8.

A coated 0.012 NiTi E-wire was bonded to the upper and lower arches after precise determination of the supposed points on the lingual surfaces of the anterior teeth. NiTi: nickel–titanium.

Figure 9.

A 0.014 Niti E-wire was applied to the upper and lower arches 6 weeks after the initial wire placement. NiTi: nickel–titanium.

The water-soluble coating material dissolves upon exposure to moisture; therefore, adequate isolation was maintained during the bonding procedure. After completion of bonding, a direct stream of water was applied using a three-way air–water syringe, resulting in immediate dissolution of the coating material. This created a space between the wire and the composite resin, thereby allowing free movement of the wire.

The criteria for wire activation and deactivation were as follows. The wire was bonded sequentially from the mesial to distal surfaces of each tooth. A controlled couple moment was applied to each tooth, as required in bracketless orthodontic mechanics, allowing tooth movement in the direction of the applied force with simultaneous rotation around its center of resistance. Wire replacement was performed once sufficient deactivation and shape recovery were achieved.

Treatment results

The facial esthetics at the end of treatment were pleasing. The dental crossbite was corrected. The lower dental midline was aligned. Crowding in both arches was resolved, with good alignment of the upper and lower teeth, normal overbite and overjet, and good interdigitation. Class I molar and canine relationships were maintained, and the case was completed within 12 weeks of active treatment (Figure 10). Upon smiling, the smile line appeared symmetrical (Figure 11).

Figure 10.

The total active treatment was 12 weeks, the dental crossbite was corrected, the lower dental midline was aligned, the crowding in both arches was resolved, and the case was completed with Class I molar and canine relationships.

Figure 11.

Pretreatment extraoral photographs.

Posttreatment lateral cephalometric X-ray

Posttreatment lateral cephalometric changes in the dental measurements were as follows: the upper incisors exhibited no significant alterations, with upper incisor to palatal plane (U1–SPP) measuring 110°, U1–NA at 21°, and U1 to NA measuring 4 mm. In contrast, the lower incisors showed notable changes, with L1–GoMe recorded at 100°, L1–NB at 31°, and L1 to NB at 6 mm. The interincisal angle (U1–L1) was measured at 123° (Figure 12) (Table 1).

Figure 12.

Posttreatment lateral cephalometric X-ray image.

Table 1.

Pre- and posttreatment lateral cephalometric measurements.

Measurement	Pretreatment	Posttreatment
U1–SPP (°)	110°	110°
U1–NA (°)	21°	21°
U1–NA (mm)	4 mm	4 mm
L1–GoMe (°)	104°	100°
L1–NB (°)	35°	31°
L1–NB (mm)	7 mm	6 mm
U1–L1 (°)	121°	123°

U1–SPP: upper incisor to palatal plane; U1–NA: upper incisor to Nasion–A line; L1–GoMe: lower incisor to mandibular plane; L1–NB: lower incisor to Nasion–B line; U1–L1: Interincisal angle.

Measurement reliability was confirmed by re-evaluation performed by an independent examiner who was not involved in the patient’s clinical treatment.

Intraexaminer reliability was confirmed by remeasuring the parameters after 1 week, demonstrating acceptable measurement consistency.

No significant skeletal changes were observed throughout the treatment in the sagittal plane; however, an increase by only 2 degrees in the vertical plane was noted.

The superimposition of the pre- and posttreatment lateral cephalograms, performed using WebCeph software, demonstrated a reduction in the proclination and protrusion of the mandibular incisors following treatment (Figure 13).

Figure 13.

The superimposition of the pre- and posttreatment lateral cephalograms.

Intraoral images taken after a 6-month follow-up showed no signs of relapse, with good stability maintained. (Figure 14). Retention was achieved via a vacuum-formed retainer (VFR) immediately after removal of the wires to maintain alignment following mild–moderate anterior crowding.^22–24

Figure 14.

Intraoral images of the patient after 6-month follow-up.

Discussion

This case of malocclusion, characterized by mild to moderate crowding in the dental arch, was selected after obtaining patient consent to evaluate the initial effects of the BOT technique in relatively mild cases. Previous studies have indicated that this technique should be the preferred option for tooth alignment when esthetics are a primary concern for the patient. ¹¹

Digital setups have demonstrated acceptable accuracy for moderate crowding corrections and can guide clinical IPR and bonding point placement. ¹⁶ In parallel, 3D imaging and digital planning have progressively expanded clinical options for esthetic and minimally invasive orthodontic approaches. ²⁵ Furthermore, 3D assessment methods provide objective measures for soft-tissue changes and support the use of digital workflows in esthetic orthodontic planning. ²⁶

Characterization of the crystalline and mechanical properties of NiTi archwires is essential for interpreting clinical responses to coated wires. ²⁷

3DBOT allows the orthodontist to predict, in advance, the amount of IPR and the labial inclination of the anterior teeth, thereby increasing patient confidence by providing a clear expectation of the treatment outcome. The technique does not interfere with speech, minimally affects oral hygiene, and requires very little patient compliance, making it a more passive and less demanding alternative.^11,12,17 However, although BOT effectively controls the tipping of the teeth in mild to moderate cases, it does not provide full control over tipping and torque in more complex cases.

This technique focuses on the use of only one or two wires, thereby eliminating the need for gradual wire replacement. A coated E-wire was employed to create a space between the wire and the resin adhesive, which facilitates the necessary sliding movement during orthodontic treatment.

Digital tooth alignment was used to generate a digital model. This procedure is supported by robust evidence demonstrating its accuracy, effectiveness, and reliability.^28,29

Following digital alignment, bonding points were identified on the resin model, as this technique has been shown in studies to yield clinically acceptable outcomes for precise clinical transfer. ³⁰

A reduction in the proclination of the lower incisors was observed in the dental measurements on the posttreatment lateral cephalometric X-ray. This change may be attributed to the application of force from the lingual side, which is positioned closer to the center of resistance of the anterior teeth. This directional force likely influences the control of lower incisor proclination during alignment, similar to the mechanisms observed in lingual orthodontic techniques. ³¹

The duration of treatment was 3 months, likely due to mild to moderate crowding and the application of force from the lingual surface, which was positioned closer to the center of resistance. This approach is effective in managing anterior dental crowding and may contribute to reduced treatment time, thereby potentially accelerating orthodontic tooth movement.

VFRs were selected because they offer an optimal balance between esthetics and cost, making them a preferred option for many patients, particularly when esthetic concerns are paramount. The patient was instructed to wear the VFR full-time during the first 6 months, followed by nighttime wear, to allow for spontaneous eruption and settling of the posterior teeth, thereby improving interdigitation.

Adverse effects

The patient was instructed to report any side effects, including pain, discomfort, swelling, speech difficulties, challenges with oral hygiene, or difficulties in chewing. Initially, the patient experienced moderate speech difficulties, which gradually diminished as he adapted to the appliance during the first week. Additionally, mild dental pain was reported, although it was considered tolerable.

Conclusion

The 3DBOT technique is an advanced esthetic approach designed for individuals who prioritize dental appearance. It may reduce anterior teeth proclination by acting from the lingual side and may shorten treatment time in cases of mild to moderate crowding, ensuring faster and more efficient outcomes.

To enhance the generalizability of the findings and validate the conclusions drawn from this clinical case report, we recommend conducting a randomized controlled trial (RCT) with a control group to compare the effectiveness of the bracketless technique with conventional orthodontic methods, thereby supporting and confirming these preliminary findings.