Treatment of Class II Malocclusion Crowding using Self−Ligating Brackets and MPA IV - A Case Report

INTRODUCTION

Self-ligating brackets have been suggested to replace the conventional ligation methods of elastomeric and stainless steel ligatures to increase clinical efficiency. Consistent archwire engagement throughout orthodontic treatment and elimination of the need for frequent visits for the replacement of ligatures are the main advantages of this new ligation mode¹. Additionally, due to the unique bracket-archwire engagement methods and the resulting increased intra-slot wire play, a reduction in the magnitude of the generated forces may be achieved.

These brackets, referred to as “low-friction” brackets as they utilize lighter forces to move teeth because there is much less friction in the system to overcome. Currently self−ligating brackets can be divided into active – with a spring clip, that presses actively against the archwire, and passive ones with a slide. This brings several other favourable features including the elimination of potential cross-contamination with elastic ligatures, supposed reduced risk for enamel decalcification from the elimination of the retentive site for plaque accumulation, hypothetically reduced friction in sliding mechanics, and assumed low-magnitude forces resulting in fewer side effects.^2-8

The Mandibular Protraction Appliance introduced by Carlos M. Coelho has proven to be effective during approximately 10 years of clinical use. This fourth (MPA IV) version seems to be as efficient as its antecedents, but is much more practical to construct, easy to manipulate and comfortable for the patient.¹²

CASE REPORT

A 13-year-old male patient reported to the Department of Orthodontics and Dentofacial Orthopaedics with chief complaint of irregularly placed upper and lower front teeth. 

On examination the patient had Angle's Class II division 1 malocclusion, upper and lower anterior crowding, unilateral posterior cross bite with overjet of 3mm and 50% overbite, an apparently mesoprosopic facial form and potentially competent lips with inter-labial gap of 3 mm, convex profile, deep mentolabial sulcus and retrusive chin with normal lower anterior facial height and naso-labial angle.

The functional analysis showed normal speech pattern, oronasal breathing with an adult swallowing pattern. The path of closure of mandible was normal without any deviation.

Cephalometric analysis revealed class II skeletal base with normal maxilla and retrognathic mandible, average growth pattern with proclined and protruded upper and lower anteriors, protruded upper and lower lip(Table 1).

Hand wrist radiograph revealed a Fishman's skeletal maturity stage 3 and absence of adductor sesamoid indicating 65-85% growth remaining. Cervical Vertebrae Maturation Index (Hassal and Farman) revealed acceleration stage of growth.  

The treatment goal was to correct upper and lower anterior crowding, achieve Angles class I molar relation, improve skeletal relation with correction of profile and lip incompetency.

Treatment was planned involving therapeutic extraction of upper and lower bilateral first bicuspids, space gained was utilized for correction of protrusion and crowding. 

Levelling and aligning was done in both arches utilizing Tenbrook 0.018 slot passive self-ligating brackets taking advantage of reduced friction. Once the mandible was unlocked mandibular advancement was planned using Mandibular Protraction Appliance IV which can be fabricated by the clinician himself to inhibit maxilla growing sagittally, move maxillary molars backward and can stimulate the growth of mandible.

Treatment Progress

Pre Adjusted Self ligating appliances were bonded in both dental arches and superelastic Nickel-Titanium [NiTi] arch wires followed by rigid 017 × 025 S.S was used. Complete alleviation of crowding was achieved within 6 months. Once decrowding and space closure was achieved case was revaluated for amount of overjet and fixed functional appliance i.e. MPA IV was placed with advancement by 6 mm. The Mandibular Protraction Appliance (MPA) evolved in the mid-1990s in an effort to mimic fixed functional appliances for the correction of Class II malocclusions that patients could not easily remove, and that clinicians could make without laboratory expense or additional inventory. It functions much like a Herbst appliance but uses smaller tubes and rods and these attach to the maxillary first molar headgear tube and the mandibular edgewise archwire. Correction of class II molar relationship to class I molar relationship by using MPA-IV was achieved in 8 months. Settling of occlusion was done using 3/16” red elastics on 0.010 multi-stranded archwire. Finishing and detailing was done. The total treatment time was 18 months. After the treatment, ANB is decreased remarkably by 30, SNB increased 3° with increase in effective mandibular length, mandibular plane angle increased 2° the mandible protruded significantly, mandibular retrognathia facial type was corrected remarkably, overjet reduced to 2mm with normal overbite (Table I)

Appliance was debonded and Begg's retainer was placed in upper and lower arch. Patient was instructed to wear retainer full time for 1 year. Routine follow up visits were scheduled every 2 months.

DISCUSSION

Class II can be corrected with 4 methods:

1) growth modification, 2) teeth movement, camouflaging maxilla disproportion (orthodontic camouflage), 3) combination of both methods, 4) orthognathic surgery in conjunctive orthodontic−surgical treatment.^9,10  

Treatment of the presented case started during pubertal spurt; furthermore, parameters of cephalometric radiogram and the positive result of functional test called for growth modification. Growth adaptation should be performed with removable functional appliances in children and adolescents with mixed dentition. However, in adolescents who have their permanent dentition, in post-adolescents, and in young adults, the fixed functional appliance is usually indicated.

Conventionally, treatment of Class II with co-existing crowding requires evaluation of incisor placement in their basal bones, as well the assessment of the profile−type, prior to choice of either extraction or non−extraction approach. In patients with crowding it is necessary to unlock the presenting malocclusion in order to facilitate advancement of mandible. Passive type of Self ligating brackets has an advantage in achieving rapid correction of crowding due to their reduced friction during levelling and aligning of the arches. The treatment of Class II division 1 malocclusion usually involves extractions: removal of two upper premolars followed by canine distalization and en masse retraction which requires maximum anchorage as done in this case. First premolar extraction in lower arch was done to create space for decrowding. Once dental relation improved mandibular advancement undertaken using fixed functional appliance to take advantage of the benefits of the period of growth, in order to obtain the harmony of facial skeleton growth.

Furthermore, in comparison to an “early” treatment approach (early adolescence/mixed dentition), “late” treatment (late adolescence/permanent dentition) can more easily accomplish a stable post treatment cuspal interdigitation, preventing a relapse. Additionally, the retention time can be reduced since the residual growth period (with a possible unfavourable growth pattern) is relatively short.¹¹

CONCLUSION

Self-ligating brackets and MPA -IV seems a promising, effective and well−tolerated modern treatment modality. The low−friction system shortens the active treatment time. Excluding of ligatures also facilitates proper oral hygiene. MPA-IV is one type of new fixed functional orthodontic appliance which can bring about a desired effect and is easy to make, didn't depend on patients' compliance, comfortable, can be worn for the whole day(24hours/day) to achieve successful results. For class II malocclusion characterized by mandibular retrognathia, on one hand, MPA-4 can stimulate or accelerate mandibular growth and inhibit maxilla growth, modify the unacceptable skeletal relationships; on the other hand, MPA-4 can move maxillary molars backward and move mandibular molars forward, so it can correct class II molar relationships.