40 P C S O B U L L E T I N • W I N T E R 2 0 0 9

USING TORQUE ADJUSTMENTS MANDIBULAR INCISORS TO

CLASS II CORRECTION

BY STEPHEN L. GOLD, DDS, MPH (LARKSPUR, CA). EDITED BY DR. EARL JOHNSON (MILL VALLEY, CA)

EARL’S

did not fully account for the slot play between a bracket and a retraction arch wire.

The maxillary central torque prescription may be +15° but if the slot play is too high, insufficient torque is delivered by a flat unadjusted wire. In this case, the arch wire needs to have ad-ditional torque added to augment the torque of the pre-adjusted brackets.

A common problem during the initial leveling of the mandibu-lar arch is for the mandibular incisor crowns to excessively incline facially, reducing the horizontal overjet space. In many cases, adding buccal root torque to the lower incisors while leveling the lower arch will keep the incisors in an upright posi-tion, and gain available overjet space.

Some clinicians may not understand that increasing lingual root torque (labial crown inclination) of the upper incisors actu-ally increases both arch length and overjet. Dr. Larry Andrews, in his book, “The Six Keys to Occlusion,” measured dental casts pre and post protrusive angulation of incisors to prove that the arch lengths are increased by increasing incisor inclination. If the upper incisor crowns tips are proclined facially one mil-limeter and the lower incisor crown tips are reclined lingually 1mm, 2mm of additional anterior overjet space is created. This often creates enough space to finish moving the maxillary cupids into perfect Class I occlusion instead of, without addi-tional overjet, leaving them a 0.5mm or 1mm forward towards a Class II relationship.

Maintaining adequate anterior overjet (during orthodontic correction of Class II malocclusions) is necessary to achieve an ideally interdigitated posterior occlu-sion. Transitional anterior overjet provides the necessary space to allow retraction

of all the maxillary teeth distally during Class II correction. If the crowns of the mandibular incisors prematurely occlude against the lingual surfaces of the maxillary incisors, a barrier is formed, making it impossible to move the maxillary teeth sufficiently distal to achieve a full Class I molar and cuspid relationship.

Four methods to increase existing anterior overjet space are:

· Reproximate the mandibular anteriors

· Open an over-closed bite

· Torque the maxillary incisor crowns facially

· Torque the mandibular incisor crowns lingually

· Create/leave space between the upper anteriors.

Since inadequate lingual root torque is a common problem dur-ing maxillary incisor retraction, the preferable tactic, in most cases, is to add lingual root torque to the maxillary incisors, which will flare their crowns more labially. A likely reason for under-torqued incisors is the use of a torque prescription that

OF THE MAXILLARY AND INCREASE OVERJET DURING

41W I N T E R 2 0 0 9 • P C S O B U L L E T I N

USING TORQUE ADJUSTMENTS MANDIBULAR INCISORS TO

CLASS II CORRECTION

EARL’S PEARLS

Some orthodontists believe the only way to achieve a proper Class I relationship, in the case of a maxillary anterior arch length deficiency, is to create space around the lateral incisors in preparation for a crown widening prosthetics. Before resort-ing to this solution, the clinician should confirm that upper incisor inclination (torque) is correct. Torque correction will most often solve the problem of inadequate overjet.

SMALL LATERALS

In a case with small maxillary laterals (but not so small that they need crowns to make them look esthetically pleasing), increasing the facial inclination of the upper incisor crowns may allow one to close any remaining space around the lateral incisors without requiring prosthetic buildups on the laterals.

LOWER INCISOR EXTRACTIONSince torquing incisors can change the arch length, it also has implications for treating lower arch length discrepancies. While finishing a three lower incisor case (with a shortage of tooth material), consider proclining the lower incisor crowns and reclining the upper incisor crowns lingually. This will reduce anterior overjet and allow a better posterior sagittal occlusion. This strategy both increases the lower arch circum-ference and decreases the upper arch circumference.

BIOMECHANICS – TWO TACTICS1. To close excess space in the maxillary arch, use a closing loop wire with the loops placed distal to the laterals and lingual root

torque added to the incisors. Allow the lingual root torque to work on the incisors,increasing overjet space and then activate the closing loops to close the excess space between the teeth while maintaining the increased torque. Lingual mandibular incisor crown torque may also be needed to create sufficient horizontal overjet.

2. Avoid the discomfort associated with placing torqued arch wires by reducing torquing forces. Use two arch wires in each arch, utilizing molar brackets with double tubes. Place a maxil-lary rectangular SS utility arch wire with lingual incisor root torque that bypasses the bicuspids and cuspids. In the second molar tube, place a NiTi round arch wire into just the buccal segments, bypassing the incisor brackets, and tie it loosely to hold it to the SS wire in the anterior brackets.

FINAL THOUGHTSDecreasing deep overbites and reproximating teeth are widely practiced methods for creating additional anterior overjet to permit achievement of a full correction of a Class II malocclu-sion. This article encourages practitioners to add facial crown torque to the upper incisors and lingual crown torque to the lower incisors as an additional way to create room for complete correction into a solid Class I occlusion.

OF THE MAXILLARY AND INCREASE OVERJET DURING