April’s Tip

One month after placement of initial leveling arch wire (i.e., a .014 or .016 NiTi, CuNiTi), the patient returns to the office and laments; “I developed spaces between my front teeth and my overbite worsened.”
The following are reasons why:

1. The inherent properties of the SWA are leveling of the curve of Spee, slight distal moment on the last molar and labial moment (flaring) of incisors.
2. Expression of the tip (angulation), particularly in the maxillary arch (+11, +8, +4), precipitates labial moment on incisors (flaring).  The mandibular arch is less affected.
3. Maxillary cuspids are too vertical – this will increase the overbite.  The ideal angulation of the maxillary cuspid, for the bracket slot to be horizontal is +11 to +13 degrees.

The following are the remedies:

1. Annealing (heat treating) the end of the arch wire and placing crisp “bend-back” distally to the last banded molar. This will inhibit labial moment (flaring) of incisors (Bennett, McLaughlin)
2. By-passing maxillary incisors, until the bracket slot on the maxillary cuspids become horizontal (tip +11 to +13 degrees) (Bennett, McLaughlin)
3. Implementing the Storino Leash

Storino Leash

 Storino Leash is a short elastomeric chain stretched from cuspid to cuspid (5 links) or first bicuspid to first bicuspid (7 links), that sits incisal to the anterior brackets, without any engagement.  It was first invented by Dr. Daniela Storino from Brazil in 2006. The elastomeric chain serves two purposes: it de-torques the anterior teeth during leveling and it prevents incisor extrusion during up-righting.  It may be initiated on a .018 or a .016 x .022 SS arch wires.

The author’s observations, for practicality, are related to the maxillary arch:

1. If an extrusion and labial torque (flaring) of anterior teeth is required, just proceed with a leveling arch wire
2. If cuspids appear to be too vertical, bracket and level only posterior teeth including the cuspids and by-pass the incisors.  Lace back from the last banded molars to the cuspids.  When the slot on the cuspid bracket becomes horizontal, continue leveling the anterior teeth
3. For all cases, where you desire to prevent deepening the overbite and flaring, the author suggests:

• Annealing and crisp bend back the end of the arch wire
• Lace back from the cuspids to the last banded molars
• Place Storino Leash when you will progress at least to a .018 SS or Beta Titanium arch wire

References:

1. Bennett J. C., McLaughlin R. P.; Orthodontic Treatment Mechanics and the Preadjusted Appliance; 105
2. Journal Of Clinical Orthodontics, LVI, 5; 296
3. Palencar A. J., Personal PP presentations