Canine extrusion with a vertical tube supported cantilever spring
A buccally impacted canine is most commonly encountered and is usually positioned near the root of an adjacent tooth and mesial to its normal position [Figure 1]. One of the challenges of such vertical tooth movement is prevention of unwanted side effects on the molar.
Cantilever springs are simple and efficient orthodontic appliances, with a wide variety of clinical uses. Biomechanically, cantilevers are able to produce statically determinant force systems, giving the clinician the opportunity to deliver qualitatively and quantitatively precise forces. A cantilever spring consists of 2 arms, the fixed and free end. The fixed end is inserted into a bracket or a tube, and the free end applies a point contact and does not engage a bracket slot or tube.
A 0.019” × 0.025” stainless steel archwire was placed in the maxillary arch, and a vertical tube was soldered to it between the premolars [Figure 2]. A 0.017” × 0.025” titanium-molybdenum alloy cantilever spring of 3 mm helix was fabricated with two arms [Figure 3]. The vertical arm, i.e., the fixed end of cantilever spring, was inserted into the soldered vertical tube and cinched [Figure 4], and the horizontal arm which is at 90° to the vertical arm was activated to in the incisal direction by closing the helix and forcefully engaging into the bracket bonded on the impacted canine [Figures 4 and 5]. This cantilever spring exerted 50 g of force for canine extrusion as measured with a force gauge [Figures 6 and 7].
This spring was shown to be an effective means of aligning buccally impacted maxillary canines [Figures 4 and 5]. Final alignment and leveling of canine was performed using 0.019” × 0.025” stainless steel wire. The residual space closure was done using active tie backs [Figure 8]. Post treatment intraoral photograph showing well aligned maxillary canine in the arch [Figure 9].
This spring can be easily fabricated and activated at chair side for extrusion of a single tooth to avoid the unwanted effects on the molar and can also be used when an auxiliary molar tube is not available.