Early vertical correction of the deep curve of Spee

Even though few technological advancements have occurred in Orthodontics recently, the search for more efficient treatments continues. This paper analyses how to accelerate and improve one of the most arduous phases of orthodontic treatment, i.e., correction of the curve of Spee. The leveling of a deep curve of Spee can happen simultaneously with the alignment phase through a method called Early Vertical Correction (EVC). This technique uses two cantilevers affixed to the initial flexible archwire. This paper describes the force system produced by EVC and how to control its side effects. The EVC can reduce treatment time in malocclusions with deep curves of Spee, by combining two phases of the therapy, which clinicians ordinarily pursue sequentially.

Keywords:
Curve of Spee; Biomechanics; Overbite.

Authorship

Renato Parsekian Martins

Private practice and part-time Faculty, Universidade Estadual Paulista (UNESP), Department of Pediatric Dentistry, School of Dentistry, Araraquara, São Paulo, Brazil. Visiting professor, Jacksonville University School of Orthodontics, Jacksonville, Florida, USAUniversidade Estadual PaulistaBrazilAraraquara, São Paulo, BrazilPrivate practice and part-time Faculty, Universidade Estadual Paulista (UNESP), Department of Pediatric Dentistry, School of Dentistry, Araraquara, São Paulo, Brazil. Visiting professor, Jacksonville University School of Orthodontics, Jacksonville, Florida, USA

Contact address: Renato Parsekian Martins Rua Carlos Gomes 2158, Araraquara/SP - CEP: 14.801340 E-mail: dr_renatopmartins@hotmail.com

" The author reports no commercial, proprietary or financial interest in the products or companies described in this article.

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Figures

Figures (9)

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Figure 1
A) Beginning of the alignment phase with a 0.014-in NiTi archwire. B) After two months of treatment, a 0.016 x 0.022-in NiTi archwire was placed.

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Figure 2
Conventional treatment of a deep curve of Spee using a contemporary edgewise technique with 0.018-in MBT prescription brackets. A, B, C) 0.014-in NiTi archwires initially placed. D, E, F) Treatment progress after 0.014-in and 0.016 x 0.022-in NiTi archwires were used and replaced by 0.016 x 0.022-in stainless steel archwires. The flexible NiTi archwires produced a minimum vertical correction. G, H, I) Treatment progress, with flattened curve of Spee and improved vertical relationship.

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Figure 3
The rationale of a reverse curve NiTi archwire used for vertical correction. The green line depicts an estimated 3-mm activation when a flat archwire is placed, whereas the yellow line shows the increased vertical activation caused if a reverse curve is placed to the archwire. The reverse curve would produce twice the intrusive force of the flat wire.

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Figure 4
Treatment of the lower deep curve of Spee with reverse curve NiTi archwires on 0.018-in slot brackets. A) A 0.014-in NiTi archwire with reverse curve is placed along a bite raise to avoid contacts of the lower brackets with the upper teeth. B) After a two-month progress, a 0.016 x 0.022-in NiTi archwire with reverse curve is placed. The deflection of the archwire is similar to that of the 0.014-in wire, which was not capable of flattening the curve of Spee. C) After six months of total treatment time, a 0.016 x 0.022-in NiTi archwire with reverse curve is tied-in. The curve of Spee and the archwire are flat and the first molars are overcorrected, but the overbite correction is confounded by abrasion of the bite raise. D) After one year of total treatment, the 0.016 x 0.022-in stainless steel archwire has almost corrected the curve of Spee.

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Figure 5
Two 0.017 x 0.025-in beta-titanium intrusion base archwires can be inserted into the slots of the brackets over a flexible archwire to assist leveling. Because the force system in indeterminate, they might not produce intrusion if an incorrect activation is placed, e.g., an anterior bend intending to cause intru sion of the incisors might actually cause extrusion.

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Figure 6
A base archwire can be tied over the main archwire instead of being inserted to the brackets. In this case, the force system is determined and more predictable.

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Figure 7
Correction of a deep curve of Spee during alignment using the early vertical correction (EVC). A, B, C) The flattening of the curve of Spee is managed with two 0.017 x 0.025-in stainless steel cantilevers while the flexible 0.014-in NiTi archwire allows proper alignment. D, E, F) Two-month progress photographs of the improved vertical relationship. The correction of the curve of Spee occurred faster than the alignment of the teeth, which is still incomplete. The absence of change in the AP relationship points towards no extrusion of the molars.

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Figure 8
Clinical application of the EVC with 0.017 x 0.025-in beta-titanium cantilever over a 0.014-in NiTi archwire. The cantilever causes an apical deflection of the archwire mesial to the canine bracket, minimizing extrusion of the incisors. Obs.: The upsidedown bracket bonded to maxillary canine substituting the lateral incisor aims to reverse the direction of its torque.

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Figure 9
Force diagram of the EVC cantilever with its preactivated shape shown in gray. It produces an intrusive force of 80 gf anteriorly, an extrusive force of 80 gf posteriorly and a crown-distal tipping tendency of 2000 gF.mm in the molars.

Figure 1 A) Beginning of the alignment phase with a 0.014-in NiTi archwire. B) After two months of treatment, a 0.016 x 0.022-in NiTi archwire was placed.

Figure 2 Conventional treatment of a deep curve of Spee using a contemporary edgewise technique with 0.018-in MBT prescription brackets. A, B, C) 0.014-in NiTi archwires initially placed. D, E, F) Treatment progress after 0.014-in and 0.016 x 0.022-in NiTi archwires were used and replaced by 0.016 x 0.022-in stainless steel archwires. The flexible NiTi archwires produced a minimum vertical correction. G, H, I) Treatment progress, with flattened curve of Spee and improved vertical relationship.

Figure 3 The rationale of a reverse curve NiTi archwire used for vertical correction. The green line depicts an estimated 3-mm activation when a flat archwire is placed, whereas the yellow line shows the increased vertical activation caused if a reverse curve is placed to the archwire. The reverse curve would produce twice the intrusive force of the flat wire.

Figure 4 Treatment of the lower deep curve of Spee with reverse curve NiTi archwires on 0.018-in slot brackets. A) A 0.014-in NiTi archwire with reverse curve is placed along a bite raise to avoid contacts of the lower brackets with the upper teeth. B) After a two-month progress, a 0.016 x 0.022-in NiTi archwire with reverse curve is placed. The deflection of the archwire is similar to that of the 0.014-in wire, which was not capable of flattening the curve of Spee. C) After six months of total treatment time, a 0.016 x 0.022-in NiTi archwire with reverse curve is tied-in. The curve of Spee and the archwire are flat and the first molars are overcorrected, but the overbite correction is confounded by abrasion of the bite raise. D) After one year of total treatment, the 0.016 x 0.022-in stainless steel archwire has almost corrected the curve of Spee.

Figure 5 Two 0.017 x 0.025-in beta-titanium intrusion base archwires can be inserted into the slots of the brackets over a flexible archwire to assist leveling. Because the force system in indeterminate, they might not produce intrusion if an incorrect activation is placed, e.g., an anterior bend intending to cause intru sion of the incisors might actually cause extrusion.

Figure 6 A base archwire can be tied over the main archwire instead of being inserted to the brackets. In this case, the force system is determined and more predictable.

Figure 7 Correction of a deep curve of Spee during alignment using the early vertical correction (EVC). A, B, C) The flattening of the curve of Spee is managed with two 0.017 x 0.025-in stainless steel cantilevers while the flexible 0.014-in NiTi archwire allows proper alignment. D, E, F) Two-month progress photographs of the improved vertical relationship. The correction of the curve of Spee occurred faster than the alignment of the teeth, which is still incomplete. The absence of change in the AP relationship points towards no extrusion of the molars.

Figure 8 Clinical application of the EVC with 0.017 x 0.025-in beta-titanium cantilever over a 0.014-in NiTi archwire. The cantilever causes an apical deflection of the archwire mesial to the canine bracket, minimizing extrusion of the incisors. Obs.: The upsidedown bracket bonded to maxillary canine substituting the lateral incisor aims to reverse the direction of its torque.

Figure 9 Force diagram of the EVC cantilever with its preactivated shape shown in gray. It produces an intrusive force of 80 gf anteriorly, an extrusive force of 80 gf posteriorly and a crown-distal tipping tendency of 2000 gF.mm in the molars.

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Early vertical correction of the deep curve of Spee

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[1] Contact address: Renato Parsekian Martins Rua Carlos Gomes 2158, Araraquara/SP - CEP: 14.801340 E-mail: dr_renatopmartins@hotmail.com