Journal of Clinical Orthodonics
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CASE REPORT

Correction of Open Bite with Elastics and Rectangular NiTi Wires

Various types of elastics-- Class II, Class m, box, triangular, zig-zag, criss-cross, diagonal, and others--provide the clinician with the ability to correct both anteroposterior and vertical discrepancies. Superelastic nickel titanium (NiTi) rectangular wires allow control of torque from the onset of treatment.1

In open-bite cases and in orthognathic cases such as a mandibular advancement of a deep-bite patient (where extensive postsurgical orthodontics must often be used to work against the return of the deep bite2), the combination of a lower rectangular NiTi archwire, an upper stainless steel archwire, and vertical elastics may prove useful.

The NiTi wire is flexible enough to allow extrusion in the lower bicuspid area while preserving torque control. Significant vertical correction can be obtained by combining the NiTi wire with the stiffer stainless steel wire and vertical elastics.3

The following case demonstrates the use of such a technique to close a posterior open bite.

Case Report

[show_img]697-jco-img-0.jpg[/show_img]

A 16-year-old female presented with a 4mm posterior open bite, a borderline anterior open bite, an impacted maxillary canine, and a bilateral edge-to-edge posterior crossbite. The treatment objective was to close the open bite solely by extruding the maxillary dentition, without undesirable extrusion or tipping of the lower arch.

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A Roth .018" twin bracket system was selected. After initial uncovering of the impacted canine, a light (100g) NeoSentalloy rectangular NiTi archwire was placed in the upper arch, and an .016"X.016" stainless steel archwire in the lower. Light triangular vertical elastics were worn full-time, helping to bring the exposed canine into the arch. A transpalatal arch, designed to correct the posterior crossbite, initially opened the bite further.

[show_img]697-jco-img-2.jpg[/show_img]

After one month, a heavy (300g) NeoSentalloy upper archwire was placed. This stabilized the upper arch while allowing it to move as a unit when pulled by the elastics against the much stiffer lower archwire.

[show_img]697-jco-img-3.jpg[/show_img]

After two months, the posterior open bite had closed significantly. The transpalatal arch had continued to open the anterior bite.

[show_img]697-jco-img-4.jpg[/show_img]

After six months, there was visible improvement in the anterior relationship as the posterior crossbite was almost entirely corrected. The light elastics continued to be worn full-time.

[show_img]697-jco-img-5.jpg[/show_img]

After eight months, a harmonious occlusion had been achieved. Final detailing is to be accomplished with upper and lower .016"X.022" stainless steel archwires. Even with another six to eight months of finishing, the case will be completed ahead of schedule.

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Fig. 1 Forces and moments produced by bends in three different locations.
Fig. 2 Lingual root torque produced by twisting rectangular wire for insertion into anterior bracket slots.
Fig. 3 A. Center bend. Note wire-bracket angles compared to straight wire and angulated brackets. B. Resilience of activated wire. C. Two offcenter bends used to produce same force as center bend.
Fig. 4 Center bends used for root paralleling in extraction treatment.
Fig. 5 Center bends used for root divergence in case with midline diastema.
Fig. 6 Simultaneous divergence of all incisor roots with two sectional wires.
Fig. 7 Two off-center bends used to parallel roots at extraction site.
Fig. 8 A. Cantilever bend placed one-third of distance between brackets, resulting in long section and short section. B. Resilience of wire results in no angle at right bracket.
Fig. 9 Cantilever bend used in anterior segment with continuous overlay arch.
Fig. 10 Cantilever intrusion of canine, with archwire placed under canine bracket wings.
Fig. 11 A. Off-center bend. B. Resilience of activated wire responsible for counterclockwise moment.
Fig. 12 Off-center tipback bend at molar.
Fig. 13 Off-center toe-in bend.
Fig. 14 Simultaneous rotation of molars and correction of crossbite.
Fig. 15 A. Center bend used to rotate second molar, which now requires buccal movement. B. Center bend converted to off-center bend by removing first molar ligature, creating buccal force.
Fig. 16 Off-center bend placed for canine retraction becomes center bend after space closure.
Fig. 17 Parallel (step) bend.
Fig. 18 Two examples of step bends. A. Canines bonded. B. Canines not bonded.
Fig. 19 Step bend used to increase posterior transverse dimension.
Fig. 20 In step-down arch, increased archwire length does not increase vertical deflection.
Fig. 21 A. Increased vertical deflection from use of tipback bend. B. Load-deflection ratio is one-fourth of original value. C. Half-length cantilever requires four times as much force for activation as cantilever twice as long with only one unit of vertical deflection.
Fig. 22 A. Center bend and step bend. Brackets on right involve opposite angular relationships. B. Cantilever bend. As bend moves left, wire-bracket angle on right rotates counterclockwise. C. Bracket slot moves from original angular position to final angular position, opposite original. D. Zero point, with archwire forming no angle with bracket slot.

DR. CHRISTIAN SANDER DMD, PD

DR. CHRISTIAN SANDER DMD, PD

DR. W. EUGENE ROBERTS DDS, PhD

DR. W. EUGENE ROBERTS DDS, PhD

DR. FRANZ GUNTER SANDER DMD

DR. FRANZ GUNTER SANDER DMD

DR. FRANZ MARTIN SANDER DMD, PD

DR. FRANZ MARTIN SANDER DMD, PD

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