Maxillary Protraction Via Bone Anchorage: A Straightforward Strategy for Complex Dilemmas - An Illustrative Case Report

Introduction

The orthodontic treatment of young individuals with skeletal Class III malocclusion presents challenges, mainly due to the prevalent reluctance among patients and their guardians to consider orthognathic surgery once growth is complete. The conventional approach to early treatment for skeletal Class III typically involves the use of a facemask. Unfortunately, this method which relies on teeth as anchor sources often results in undesired tooth movement and exhibits limited efficiency in bringing about skeletal changes.¹

To address these limitations, temporary anchorage devices such as mini-screws and mini-plates have become more common. These devices aim to minimize the dental effects associated with traditional facemask treatment while maximizing the skeletal impact. Various studies have explored alternative anchorage sources, including intentionally ankylosed deciduous canines and implants, to achieve effective maxillary traction.²

The most contemporary and efficacious modality involves the application of Class III elastics in tandem with bone-anchored maxillary protraction utilizing mini plates.³ This sophisticated technique introduced by Hugo-de-clerk in 2009 strategically places mini plates at the zygomatic base, apical to the maxillary molars and the anterolateral aspect of the mandible.⁴ In stark contrast to traditional facemask regimens, this approach engenders more profound skeletal transformations. Notably, its crowning merit lies in the capacity to administer traction throughout the diurnal cycle stands dependent on patient cooperation. Moreover, boneanchored maxillary protraction stands applicable to patients aged 11 years and beyond.^5,6

Thus, this case report aimed to describe the treatment protocol for a patient with Class III skeletal problem due to maxillary retrognathia using maxillo-mandibular bony anchorage with intermaxillary elastics.

Case Presentation

A 15-year-old female patient reported to the department with the chief complaint of lower teeth being forwardly positioned relative to upper teeth. The patient’s medical history revealed no systemic diseases that might impede orthodontic treatment.

Extra-oral examination

Concave profile with positive lip step and competent lips were noted as shown in Figure 1.

Intra-oral examination

Class I molar relationship on right side and Class III on left side, with reverse overjet of 3 mm as shown in Figure 1.

Cephalometric examination

The cephalometric analysis revealed Class III malocclusion due to maxillary retrusion with SNA of 75◦, SNB of 81º, ANB of -6º, mandibular plane angle of Go-Gn-SN of 24º, inclination angle of 80º.

The patient had upright maxillary incisors and retroclined lower incisors, U1 to SN was 102º and IMPA was 88º as shown in Table 1.

Treatment objectives

• To correct the maxillo-mandibular discrepancy by maxillary forward positioning
• To eliminate the negative overjet
• To level and align arches
• To obtain an ideal overbite and overjet
• To attain a pleasing profile and smile

Treatment alternatives

Diverse treatment approaches, such as employing an orthopedic appliance (Facemask), delaying intervention until the cessation of growth and subsequently undergoing orthognathic surgery, or utilizing mini plates and class III elastics to advance the maxilla, were recommended to achieve the treatment objectives.

Treatment progress

The patient and parents chose to undergo Bone Anchored Maxillary Protraction (BAMP) therapy for maxillary advancement. After obtaining informed consent, two pairs of bilateral orthodontic mini plates (SK Surgicals, India) were strategically placed in the canine region of the mandible and beneath the infra zygomatic crests of the maxilla, firmly anchored with titanium screws.³

The position for miniplate insertion was evaluated, and miniplates were inserted under local anesthesia (2% lidocaine with 1:100,000 epinephrine) by an oral and maxillofacial surgeon as shown in Figure 2.

Three weeks after the insertion of mini plates, a posterior bite plate was given in the lower arch followed by the use of inter-maxillary elastics in between the hooks of the mini plates on both sides. The elastic force was measured at six ounces as shown in Figure 2.

The patient was directed to employ intermaxillary elastics around the clock for 24 hours, excluding periods of having food and during maintenance of oral hygiene procedure, and to change the elastics daily on both sides.

After five months of orthopedic intervention, the patient achieved a 2 mm of ideal positive overjet, and the negative overjet was successfully resolved. Subsequently, active orthopedic therapy was concluded, and fixed orthodontic treatment commenced, incorporating a fixed MBT (0.022-in) mechanotherapy while maintaining the ongoing use of elastics (Figure 2).

After an 8-month duration of fixed orthodontic intervention, the optimal alignment of the dental midline, overjet, and overbite was successfully achieved, marking the completion of the orthodontic treatment as depicted in Figure 2. The total duration of treatment was 13 months. The retention phase was initiated with an upper ESSIX retainer and lower fixed lingual retainer along with intermaxillary elastics for nighttime wear.³

Discussion

This case demonstrates the clinical application of mini plates in the treatment of a 15-year-old female with maxillary deficiency.

Studies have demonstrated the substantial potential for maxillary forward movement through the application of maxillary advancement appliances. Recent findings suggest that certain sagittal changes can be attained until the onset of adolescence.⁷

However, it is essential to note that these appliances often lead to considerable discomfort and are aesthetically unappealing, resulting in diminished patient compliance. Additionally, the use of orthopedic appliances has been associated with skin abrasions, further complicating their tolerability.

Hugo-De-Clerk et al.,⁴ used the mini plates to protract the maxilla and called it bone-anchored maxillary protraction (BAMP).³ In broad terms, the potential for orthopedic advancement of the maxilla and midface improves with a younger patient demographic.⁵

The efficacy of Bone Anchored Maxillary Protraction (BAMP)³ treatment critically relies on the bone quality at the site of plate placement and the patient's diligent adherence to elastic usage, coupled with impeccable hygiene practices. Neglecting to consistently utilize elastics diminishes the authentic orthopedic benefits of the treatment. Plate stability can be compromised if the soft tissue around the implant gets infected.

Consequently, patients may opt to abstain from utilizing the appliance, and this lack of compliance could yield unsatisfactory results. A drawback associated with the use of a chin cup is retroclination of the lower incisors, brought about by the pressure exerted by the chin cup component on the lower lip and lower dentition. This undesirable lingual tipping may give rise to complications such as crowding. Conversely, mini-screws offer a promising avenue for addressing maxillary deficiency. Nevertheless, it is essential to recognize a limitation of mini-screws, as they may experience loosening, accompanied by erythema and mucosal irritation.

Hugo-de-clerk et al.⁸ has shown that the BAMP protocol does not restrain the growth of the mandible, but instead, it alters the direction of mandibular growth by closing the gonial angle and distalizing the posterior ramus and condyles. The glenoid fossa remodels to adapt to a new condylar position. While these findings are promising, long-term studies are necessary to evaluate the stability of this compensatory mechanism and the health of the temporomandibular joint complex.⁸

In this particular scenario, applying force directly to the teeth to rectify the skeletal problem would have unavoidably caused tooth displacement. The entire treatment process extended over 13 months. However, since the patient is 16 years old, with cervical vertebrae maturation index (CVMI)2 stage 5, and still has 5% to 10% of growth potential left, the surgical plates with inter-maxillary elastics will be maintained until the growth is completed.

In this case report, a patient with maxillary retrusion underwent effective treatment using the bone-anchored maxillary protraction method, serving as a substitute for conventional approaches involving both extraoral appliances and surgery. This method successfully addressed the sagittal discrepancy, leading to improved facial aesthetics for the patient. Importantly, the patient consistently followed the prescribed treatment plan. The use of mini plates emerged as a practical non-surgical option for managing Class III malocclusion, providing a viable alternative to surgical procedure.

Conflict of Interest

Nil