LINGUAL ORTHODONTICS USING THE LIGHT WIRE BRACKET, PART 2

Elyakim Mizrahi, BDS, DORTH RCS, FDS RCS, MSc, PhD.


www.lingualnews.com Vol 2 No 2 November 2004

Introduction
My rationale for using the Light Wire bracket, the laboratory and clinical procedures involved are presented in a series of two articles. Part 1 describing the pre clinical laboratory procedures has been submitted. Part 2 describes clinical aspects of the lingual technique using the light wire bracket.

Clinical aspects of treatment
The basic diagnosis and treatment planning is the same as for conventional labial treatment with special attention given to anchorage considerations¹ and to the type of palatal surface available for bonding, eg, porcelain or metal backed crowns. The decision to extract or not, is based on the dictates of the case bearing in mind the conventional considerations given to the degree of crowding, skeletal base discrepancy, soft tissue profile analysis and long-term stability.
As with conventional labial techniques, anchorage may be reinforced by the incorporation of mini implant screws.²
Patients who select lingual orthodontics as the treatment of choice, are a special group who have heightened levels of self consciousness and have specific expectations. It is essential to make the patient aware of the possible limitations of the treatment plan and to try to marry their expectations with the anticipated final result. 

Although it is not always possible, it is advisable to follow the three stages of Begg treatment adhering to the objectives of each stage.
Stage 1: Alignment of incisors, reduce overjet and overbite, and correct the molar relationship.
Stage 2: Close residual spaces either by further retraction of the anterior segment, or by maintaining the position of the anterior teeth and moving the posterior segment mesially.
Stage 3: Correct anterior root torque, correct root angulations and maintain corrected incisor and molar relationship.

Archwires
Selection will be dependant on the malocclusion and the irregularity of the teeth. With irregular teeth, start with the lightest 0.012 or 0.014 Nickel-titanium archwire and change to 0.016 steel, plain or with intermaxillary hooks as soon as possible. The intermaxillary hooks (circles) may be placed either between the canine and premolar or between the canine and lateral incisor teeth. (Figure 1) Change to 0.018 steel for stage. ³

Fig 1: The intermaxillary hooks (helices) may be placed either between the canine and premolar or between the canine and lateral incisor teeth

Mechanics
Archwires should be pre-bent either on study models or photocopies of study models showing the dental arch. Place canine/premolar and molar offsets as required.

It is essential to understand that in cases with an increased overjet, as with conventional labial light wire technique, the six anterior teeth will be retracted en masse as one unit. The archwire used for this stage will be 0.016 inches high tensile stainless steel sliding in a palatal tube 0.036 inches in diameter. With this combination of dimensions there is minimal friction and the anterior segment will retract under the influence of very light forces. The overjet and overbite will reduce rapidly. Care should be taken not to over retract the anterior segment. The forces may be generated by either class II or class I intra oral elastics, coil springs or elastomeric modules. It the maxillary first molar on its own is subjected to class I elastic traction and an anchorage bend, there is a risk that it may rotate and tip in an undesirable fashion.  However, with the archwire sliding through both the first and second molar tubes, a very stable anchorage unit is created. While the archwire is still free to slide distally with minimal friction, the molars cannot tip or rotate individually. When necessary, depending on the dictates of the malocclusion, both the upper and lower arches may incorporate either anchorage bends or an increased or reverse curve of Spee.

Auxiliary Springs
Auxiliary springs are an essential component of this technique, they are used for correcting rotations, expansion between either individual or groups of teeth, and they can be used for root torque and root uprighting.  They may be used at any stage of treatment and more importantly, they can be inserted and removed without disturbing or removing the main archwire. Most of the springs have been designed by Dr Andre Hugo.^3,4

Rotating spring (Figure 2)
Rotating teeth with the lingual technique without encroaching on the labial surface, is a difficult procedure. Conventional rotating springs may be used in the maxillary arch, unfortunately it is not possible to use them on mandibular incisors. This rotating spring was designed by Dr Andre Hugo,^3,4 it is efficient and can be used in either the maxillary or mandibular arch, it can be inserted and removed without removing or adjusting the main archwire. The tooth must be tied to the archwire in such a manner so as not to inhibit the rotation. For mesio-palatal/lingual rotation, the tie should be on the mesial and conversely for disto-palatal/lingual rotation the tie should be to the distal of the bracket. The vertical post is inserted into the vertical slot of the bracket, and the loop slides in between the archwire and the tooth surface. The spring is activated by hooking the horizontal arm onto the main archwire. To avoid dislodgement, the horizontal arm can also be ligatured to the archwire.

Uprighting springs (Figure 3)
Uprighting springs are made from 0.010 inch (mini uprighting spring) 0.012, or 0.014, high tensile stainless steel. They can be inserted either from the gingival or incisal aspect. They are essential for uprighting teeth on either side of an extraction site, and for correcting mesiodistal angulation of anterior teeth. Modified palatal uprighting spring designed by A Hugo ^3,4 are inserted from the incisal and are designed to avoid any impingement from opposing teeth during occlusion.

Fig 2: Rotating spring

Fig. 3 Uprighting springs

Torquing auxiliary (Figure 4)
Palatal torquing auxiliary springs are generally used in stage 3. They were designed by A Hugo and modified by Z Webber3,4 and may be used with most bracket systems including the edgewise technique. They are inserted and removed without removing or adjusting the main archwire. With the incorporation of a small circle at the central loop, it is possible to tie the spring to the main archwire and so control the position of the horizontal bar of the auxiliary so that it acts as close as possible to the incisal edge of the tooth.

Summary
As with any technique, there are advantages as well as disadvantages. The main advantages are: the small bracket size, which maximises the inter-bracket distance and the minimal friction between archwire and bracket, which allows tooth movement under the influence of very light forces.  The main disadvantage is the need to incorporate auxiliary springs to carry out the necessary root movements.

Fig. 4 Torquing auxilliary

Fig 5 Clinical case: J M Class II (2)

REFERENCES
1. Geron S, Vardimon A. Six anchorage keys used in lingual orthodontics sliding mechanics. World Journal of Orthodontics.(2003) 4:258-265.
2. Park HS. The skeletal cortical anchorage using titanium microscrew implants. Korean Journal of Orthodontics. (1999) 29:699-705.
3.Hugo A, Weber Z and Reyneke J. Lingual Orthodontic Manual (2002) Personal contact.
4. Mizrahi E. Orthodontic Pearls, Published by Taylor Francis, 11 New Fetter Lane ,London EC4P 4EE. ISBN  184184 252 4. Chapter 10 (2004)

Dr E Mizrahi.
128 Woodford Avenue.
Gants Hill.
IG2 6XA. ESSEX
UK
Tel 020 8551 9336
Kimmizrahi@aol.com

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Adult and Lingual Orthodontics
EDITORS:
Dr. Silvia Geron D.M.D., M.Sc
Dr. Rafi Romano D.M.D., M.Sc
Dr. Pablo Echarri D.M.D., M.Sc