‘M’ mechanics for midline diastema correction in mixed dentition

Background

A maxillary midline diastema is a self-correcting anomaly, which is present in the mixed dentition period that manifests as a space between the two central incisors and is corrected on eruption of permanent maxillary canines. But certain conditions such as tooth material and jaw size discrepancies, midline pathologies such as supernumerary teeth, high labial frenal attachment, habits, peg laterals, congenitally missing lateral incisors tend to retain the diastema even after eruption of permanent canines.1 Based on the linear measurement of diastema, a wide range of prevalence of 98% in children aged 6 years old, 49% in 11 years old and 7% in 12–18 years old has been reported.2 The prevalence rate in adults is 1.6%–2.4%.3

Closure of retained midline diastema is usually done in the permanent dentition period and includes identification and removal of the aetiology, followed by various modalities which includes orthodontic tooth movement, restorative procedure with aesthetic resin composites, prosthetic management based on the age of the patient.4

This report is on a novel technique of management of midline diastema in the mixed dentition period with an indication of its retention in permanent dentition using ‘M’ spring.

Case presentation

A male patient of middle childhood reported with irregularly erupted upper front teeth. It was his first dental visit and his medical history was non-significant. The extraoral examination showed a straight profile, a mesoprosopic facial type and competent lips. The intraoral examination revealed the child was in mixed dentition period and examination of maxillary anterior region showed the presence of two supernumerary teeth: a mesiodens in relation to 11, 21 and a supplemental teeth present in relation to 21, 22 on the palatal aspect (figure 1). Occlusal status was found to be Angle’s class I molar relationship and flush terminal plane relationship bilaterally. The midline diastema was found to be 6 mm. The other findings were the presence of caries in the primary molars and deep stained pits and fissures in permanent molars.

Figure 1

Intraoral hard tissue image.

Investigations

An OPG was advised which revealed the absence of no other impacted supernumerary teeth. Based on clinical and radiographic examination, the following treatment plan was proposed:

• Extraction of two supernumerary teeth followed by assessment of midline space.

• Oral prophylaxis followed by placement of pit and fissure sealant in permanent molars.

• Restoration of all carious primary molars.

Differential diagnosis

Not applicable.

Treatment

The case was started with extraction of two supernumerary teeth under local anaesthesia after obtaining consent from the parent. The patient was recalled after a week and healing of the extraction site was satisfactory (figure 2). The midline space was measured as 5 mm with reduction of 1 mm of space following extraction. Space closure was planned using a 2×4 appliance and ‘M’ spring. Prior to be commencement of orthodontic treatment, oral prophylaxis and placement of pit and fissure sealants were performed. The treatment was initiated by bonding preadjusted MBT brackets 0.022’’×0.028’’ on the labial surfaces of 12, 11, 21, 22 and banding the upper permanent first molar using bands with buccal tubes. The initial arch alignment was done with 0.012’’, 0.014’’ and 0.016’’ round NiTi with an interval of 2 weeks for each wire followed by placement of ‘M’ spring.

Figure 2

Postextraction healing after a week.

Construction and placement of ‘M’ spring is done in such a way that M spring was made out of 0.016’’ rectangular AJ Wilcock stainless steel wire. M spring was designed with three helices of 3 mm in diameter, two at the periphery and one at the centre. Labial loops were positioned 5–6 mm above the bracket slot and designed to be out of contact with the labial sulcus and other delicate soft tissues. Activation is done by giving a 45° inward bend to the active arm so that it completely rests in the maxillary bracket slot. After activation, modules are placed to stabilise the spring in the bracket slot (figure 3).

Figure 3

Placement of M spring following arch alignment.

Outcome and follow-up

The patient was reviewed every week. At the end of 4 weeks, a clinical space closure of 4 mm was achieved and 1 mm of space was left for spontaneous closure at the time of eruption of permanent canines. M spring was removed and rectangular 0.016’’ stainless steel wire was given for retention (figure 4) for 2 weeks followed by debonding the 2×4 appliance.

Figure 4

Retention using rectangular SS wire. SS, stainless steel.