Sustainable orthodontic management of bilateral maxillary canine agenesis with miniscrew-assisted total mesialization moving beyond prosthodontic solutions

INTRODUCTION

The congenital absence of permanent maxillary canines is exceedingly rare, with a reported global prevalence of approximately 0.30%, highest in Asia and lowest in Europe and South America.^[1] This condition, though uncommon, has a substantial impact on both oral function and facial esthetics. While hypodontia can occur in syndromic and non-syndromic forms, the isolated agenesis of maxillary canines in otherwise healthy individuals is particularly unusual.^[2,3]

Management strategies typically rely on either prosthodontic replacement (implants or bridges) or orthodontic space closure using premolar substitution.^[4-7] Each approach has its own biomechanical and aesthetic challenges, particularly in patients who present with an ideal skeletal profile and no need for anterior retraction. In such cases, prosthodontics often becomes the default option. This case report presents a previously undocumented treatment of a 24-year-old non-syndromic patient with bilaterally missing permanent maxillary canines and retained deciduous predecessors. The case illustrates the successful use of miniscrew-assisted total mesialization to achieve full space closure without prosthetic replacement.

CASE REPORT

A 24-year-old Chinese Malaysian woman presented with concerns about retained deciduous canines (53, 63) in the maxillary arch and an unesthetic smile. The patient also reported a composite restoration on the mesial aspect of tooth 21. Her medical history was unremarkable, with no trauma or syndromic conditions.

Clinical examination showed an orthognathic profile with a normodivergent facial pattern and competent lips. Intraoral assessment identified mild generalized papillary enlargement without inflammation, along with firmly retained deciduous canines (53, 63). The patient had a full complement of teeth except for the missing maxillary canines (13, 23) and third molars. The maxillary arch appeared symmetrical with approximately 6 mm of spacing and no clinical bulge associated with the absent canines, while the mandibular arch showed 2.5 mm of spacing and bilateral lingual tori. Occlusal analysis revealed a Class I molar relationship with a 3 mm overjet and 4 mm overbite, and both upper and lower dental midlines aligned with the facial midline. Radiographic evaluation through a dental panoramic tomogram confirmed the congenital absence of 13, 23, and third molars and the presence of deciduous maxillary canines with intact roots. Cephalometric analysis indicated a Class I skeletal pattern with a hypodivergent pattern, upright maxillary incisors, proclined mandibular incisors, and mildly protrusive lips [Figure 1].

Close

Figure 1:

(a-h) Pre-treatment photographs of a 24-year-old patient with a presenting concern regarding the retention of baby canines in the maxillary arch and unesthetic look owing to the diminutive size of 53 and 63. (i) The panoramic radiograph revealed missing 13, 23, and all 8s. The roots of 53 and 63 are intact with no signs of resorption. (j) The lateral cephalography analysis revealed a Class I skeletal base relationship with hypodivergent facial pattern.

Export to PPT

Treatment progress

The treatment commenced with bonding of self-ligation brackets (Empower 2, American Orthodontics, USA) from second molar to second molar in the maxillary arch, beginning alignment with 0.014” NiTi wires and progressing to 0.017” × 0.025” stainless steel (SS) wire for stabilization. After about 5 months, the retained deciduous canines were extracted to facilitate space closure. At the outset, the miniscrews (1.6 × 8 mm, Jeil Medical Corporation, Taiwan) were self-drilled at the infra-zygomatic crest (IZC) areas bilaterally. A custom cantilever arm attached to a miniscrew head on either side, that extended anteriorly juxtaposed to the canine area, allowed application of elastic pull force (4.5 Oz) to facilitate group mesial movement bilaterally. After a month, as the patient reported discomfort with the right miniscrew with inflammation, it necessitated its removal and replacement of the miniscrew interradicular between # 12 and 22 for application of Class 1 elastics from the custom-made hooks attached to the miniscrew head. After about 8 months, approximately 3–4 mm of mesial movement had been achieved, with ongoing adjustments with NiTi coil springs/elastics to improve efficiency and address asymmetrical space closure [Figure 2]. The boot loops functioned as segmental torque control elements rather than as retraction mechanisms. By incorporating boot loops in the maxillary archwire, the anterior segment was biomechanically reinforced as a controlled unit, allowing the expression of palatal root torque on the maxillary incisors. This configuration effectively counteracted the reciprocal forces generated during posterior teeth group mesialization, preventing unwanted incisor flaring or retroclination. Consequently, the anterior teeth remained positionally stable while posterior segments underwent controlled mesial movement.

Close

Figure 2:

Progress photographs (a-i) demonstrating group mesialization of the maxillary posterior teeth and space closure in the mandibular arch. (a-c) A 12 mm NiTi closed coil spring was activated to deliver continuous force, with boot loops incorporated to control torque (palatal root torque for the maxillary anterior teeth). (f-g) Elastic thread was used intermittently to produce a trampoline effect, enhancing the mesializing forces.

Export to PPT

After about 18 months into treatment, the lower arch was bonded, and customized mechanics like boot loops and bull loops were employed for controlled retraction under torque control. Despite mild gingival inflammation, progress continued with archwire upgrades and interproximal reduction in the lower arch to facilitate tooth movement and incisor inclination improvement. Patient concerns about maxillary midline aesthetics were addressed through incremental composite adjustments, and keyhole loop mechanics were employed to act as a stress breaker between the anterior and posterior segments for detailing and finishing [Figure 3]. Keyhole loop design increases the effective wire length and reduces the load–deflection rate at the segment junction, allowing selective flexibility and controlled force dissipation. This configuration limits the transmission of unwanted moments and forces from posterior finishing mechanics to the anterior segment, thereby protecting incisor position. Consequently, the anterior and posterior segments could be detailed independently, permitting precise occlusal refinement while maintaining anterior tooth stability. Minor first-order bends were performed in the lower arch to perfect tooth positions, aligning with the patient’s preferences for a balanced outcome.

Close

Figure 3:

Progress photographs (a-c) demonstrating the mechanics of keyhole loops as stress breakers between anterior and posterior segments that allow for fine detailing and finishing. Short E-chain engaged between 12 and 22 further to mild interproximal reduction between 11 and 21. (d-f) Predebond photographs demonstrating socked-in occlusion.

Export to PPT

Treatment result

The patient finished with a Class II molar relationship, bilateral, and the first premolars substituted well for the maxillary canines with adequate functional excursions. Overjet and overbite are still within normal limits [Figure 4]. Cephalometric superimposition shows mesialization of the maxillary molars, retraction of mandibular incisors, and minimal retroclination of maxillary incisors [Figure 5]. Gingivectomy was performed to harmonize the gingival contours, and thermoplastic retainers were fabricated to maintain the results. Post-treatment follow-ups confirmed stable occlusion and patient satisfaction, with 24/7 retainer use for the first 1-year post-debond toward long-term stability. This comprehensive approach, combining meticulous biomechanics with patient-centered adjustments, successfully addressed the challenges of congenitally missing canines while achieving both functional and esthetic goals. At the 19-month retention check, the occlusion remained stable, and facial appearance was most pleasing [Figure 6]. There was no evidence of a relapse, and the patient was advised to continue nighttime retainer wear.

Close

Figure 4:

(a-h) Post-treatment photographs demonstrating a well-balanced harmonious smile aesthetics with maxillary first premolars substituting missing canines. The inter-arch relationship demonstrated an optimal outcome with normal overjet and overbite and adequately interdigitated Class II molar relationship. (i) The panoramic radiograph revealed adequate root parallelism and alveolar bone height. (j) The lateral cephalograph revealed maintenance of Class I skeletal base relationship with adequate inter-incisal angle (128°).

Export to PPT

Close

Figure 5:

Superimposition of the lateral cephalograms at pretreatment (black) and post-treatment (red).

Export to PPT

Close

Figure 6:

(a-h) Photographs at 19 months into retention. No evidence of relapses and good interdigitation maintained.

Export to PPT

DISCUSSION

This case report details the successful orthodontic treatment of an adult patient with a Class I malocclusion, congenitally missing maxillary canines, retained deciduous maxillary canines, and an orthognathic facial profile. The treatment involved mesialization of the buccal segment teeth utilizing fixed mechanotherapy and miniscrew anchorage from the buccal aspect. This approach, though challenging, resulted in a comprehensive, sustainable biological outcome, clinical feasibility, and long-term stability.

While premolar substitution for missing canines is well-documented in cases requiring anterior retraction,^[4,5,7] this report presents a case of miniscrew-anchored total mesialization of four posterior teeth bilaterally. This technique substituted maxillary first premolars as canines in a Class I patient, achieving prosthodontic-free rehabilitation without compromising facial aesthetics. Common problems when maxillary first premolars substitute for canines include crown morphology mismatch (shorter crown height, different cusp form), torque differences (premolars are naturally more palatally inclined), functional guidance issues during lateral excursions, and gingival margin discrepancies. However, these issues were anticipated but did not become clinically significant in this patient. This was due to controlled bodily mesialization under miniscrew anchorage, preventive torque control, selective soft-tissue refinement, and acceptance of group function rather than strict canine guidance. Consequently, the premolars integrated harmoniously without compromising esthetics, function, or periodontal health.

Although some reports describe the successful mesial movement of one or two molar teeth,^[8,9] this case is unique in demonstrating a well-coordinated mesial tooth movement of 4 posterior teeth bilaterally without significant anterior tooth movement. The results were achieved optimally while meticulously maintaining root parallelism and bone integrity. To the best of our knowledge and based on literature reviews, no prior case in the literature has reported such a large-scale and multiple tooth movement in the mesial direction.

A notable aspect of this case is that the extensive bilateral mesialization was achieved solely through buccal miniscrew anchorage, without any palatal appliance engagement. Conventionally, cases requiring large-scale posterior mesialization rely on dual-arch anchorage systems, such as palatal miniscrews or transpalatal bars, to counteract rotational moments and maintain transverse control. However, by carefully selecting miniscrew positions and directing forces parallel to the occlusal plane, sufficient anchorage and three-dimensional control were achieved without the need for additional palatal hardware. This simplified approach minimized patient discomfort, improved oral hygiene access, reduced appliance complexity, and eliminated the potential soft tissue irritation often associated with palatal devices. It also underscores that, with meticulous biomechanical planning and precise force vector control, complete group mesialization can be predictably achieved using a buccal-only anchorage system, a strategy that appears underrepresented in the current literature.

Group mesialization, particularly the coordinated movement of entire buccal segments, is a biomechanically complex and less frequently employed orthodontic approach compared to molar distalization, which has been more extensively studied and documented. Mesialization encounters greater resistance due to tight interproximal contacts, occlusal forces, and the natural curvature of the dental arch, which introduces additional friction and binding as the archwire must navigate sharper anterior bends.^[10] Frank and Nikolai demonstrated that friction significantly increases when sliding teeth around such curves, making force control and appliance design critical.^[11] Furthermore, posterior anchorage systems such as miniscrews or elastics, which apply pulling forces toward the anterior, tend to increase wire deflection and demand more precise mechanics to avoid excessive tipping. Unlike distalization, mesialization pushes teeth into regions of greater soft tissue constraint, such as tongue, buccal mucosa, and active musculature, and traverses anatomical zones with thinner alveolar bone, where movement may be slower and biologically unpredictable.^[12] The differing alveolar bone characteristics in the canine and posterior regions of the maxillary arch play a crucial role in orthodontic biomechanics.^[13] These factors necessitate the use of low-friction mechanics (e.g., self-ligating brackets) and enhanced anchorage reinforcement (e.g., miniscrews or miniplates) to maintain control.^[10] Finally, altering the posterior occlusion through mesialization introduces additional challenges in coordinating inter-arch relationships, further limiting its routine use in space closure.

In the present report, self-ligation brackets and sliding mechanics with a 0.017” × 0.025” SS archwire provided sufficient clearance for tooth movement and group mesialization. A 0.017” × 0.025” SS archwire was selected as the working wire for posterior group mesialization to balance controlled sliding with three-dimensional stability. In extensive mesialization, posterior teeth must traverse the increased curvature of the anterior arch, where larger-dimension wires such as 0.019” × 0.025” SS are more prone to early binding and notching. The slightly undersized wire delayed binding, reduced wire deflection, and allowed efficient bodily movement of the posterior segment.

In such complex scenarios, miniscrews are indispensable for predictable tooth movement. Their strategic placement offered absolute anchorage, facilitating controlled bodily tooth movement without compromising periodontal support. Our findings corroborate previous studies on the effectiveness of miniscrew anchorage in orthodontic tooth movement.^[14] Furthermore, precise wire bending and customized loops (e.g., keyhole loops, bull loops) were crucial for fine-tuning tooth positions, ensuring proper root alignment and optimal occlusal contacts. Biomechanically, the force was applied parallel to the occlusal plane and slightly above the level of the brackets. In the present case, the IZC was intentionally selected as the anchorage site due to its dense cortical bone, safe distance from dental roots, and its ability to permit force application above the occlusal plane. However, anterior miniscrew positioning distal to the lateral incisor roots can also provide biomechanically effective anchorage for posterior mesialization when appropriately planned. Such placement allows force application closer to the occlusal plane and can generate comparable mesializing vectors, particularly in cases where IZC placement is contraindicated or not well tolerated.

A custom cantilever arm was attached to the miniscrew head and extended anteriorly toward the canine region, allowing the force vector to be directed nearly parallel to the occlusal plane (approximately 0 to −5°). This design minimized occlusal plane rotation and facilitated controlled bodily mesialization of the posterior segment rather than individual tooth movement. Kawamura et al. analyzed tooth movement during mesialization of the whole maxillary dentition and noted that the occlusal plane rotated counterclockwise with the force angle of 0°.^[15] In the present case, as a result of the cantilever wire assembly supported by miniscrews, a simulated almost force angle of about 0 to −5° and minimal occlusal plane changes.

Posterior teeth mesialization was achieved using low, continuous forces (4.5 oz), with periodic reactivation using elastomeric chains or NiTi coil springs and close monitoring for asymmetry. These mechanics allowed predictable group mesialization while maintaining three-dimensional control throughout treatment. Elastomeric thread or elastic thread demonstrates a low load–deflection rate and elastic recovery, allowing force delivery to persist despite tooth movement and force decay. When used intermittently, repeated stretching and relaxation of the elastic produces cyclic force renewal rather than a single static activation. This stretch–recoil behavior is analogous to a “trampoline effect,” whereby force is repeatedly regenerated in the same direction, enhancing mesializing efficiency while maintaining forces within a biologically acceptable range.

CONCLUSION

This case report describes the successful orthodontic management of an adult with Class I malocclusion and congenitally missing canines using miniscrew-assisted mechanics. Precise biomechanics enabled mesialization of posterior segments while preserving root parallelism and bone integrity, offering a biologically sustainable alternative to prosthetics through meticulous planning and patient cooperation.