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.
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.[show_img]697-jco-img-1.jpg[/show_img]
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.
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.
After two months, the posterior open bite had closed significantly. The transpalatal arch had continued to open the anterior bite.
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.
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.