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Letters to the Editor

Dear Editor

The article on ‘Choosing a pre-adjusted orthodontic appliance prescription for anterior teeth’ by E. Thickett, N. G. Taylor, and T. Hodge,¹ is a well thought out and of value to all orthodontists who use pre-adjusted edgewise systems. The authors have ‘thought out of the box’ and have nicely elucidated various modifications of bracket positioning to tackle certain tricky clinical situations that an orthodontist routinely encounters.

Although we agree with most of the modifications mentioned in the article (and were already using some of them), we wish to share our approach to handling some of the situations cited, and to seek clarification on certain points.

1. (i) When an upper central incisor is missing and the treatment plan involves moving a lateral incisor into the former’s space, the authors mention that they bond a contralateral central incisor bracket onto the lateral incisor in such a fashion that the tooth’s root moves mesially and the crown distally (Thickett et al., Figure 6).¹ The authors claim that this provides an optimal emergence profile and avoids the problem of retention from a mesiogingival margin of a restoration.

However, we feel that the traditional method of centring the lateral incisor in the space of the central incisor (without changing the angulation) is better than the authors’ modification. If the lateral incisor assumes the angulation that the authors suggest, the occlusal forces will not be transmitted along its long axis and a large distal restoration will be more prone to failure than small restorations on its mesial and distal aspects.

(ii) On closer observation of Thickett et al. Figure 6,¹ we suspect that the bracket on the lateral incisor is not of a contralateral central incisor but of a contralateral lateral incisor. We wish to know which bracket exactly the authors have used.

2. In the case of Class III camouflage (Thicket et al., Figure 4),¹ the authors suggest the use of contralateral canine brackets to tip the canine crowns distally. To achieve the same objective, we prefer to use the designated bracket on the designated canine but slightly angulating it to get the desired amount of crown tipping. This method will leave the power arm distally which will be better from a biomechanical point of view, if we need to use it.

3. In the case of Class III camouflage, the authors suggest inverting the incisor bracket for labial root torquing. Although Subtelny,² Catania,³ and Goldin⁴ advocated this kind of labial root torque in Class III patients, they have used it for skeletal correction (maxillary protraction) in growing individuals, and not for camouflage. We think that if we invert the brackets on upper central incisors, especially MBT brackets, we get an effective torque of –17°. We suspect that inducing such an amount of negative torque may cause root resorption and dehiscence. So, we would like to know if the authors have used these MBT brackets without any problems.

References

1 Thickett E, Taylor NG, Hodge T. Choosing a pre-adjusted orthodontic appliance prescription for anterior teeth. J Orthod 2007; 34: 95–100.[Abstract/Free Full Text]

2 Subtelny JD. Oral respiration: facial maldevelopment and corrective dentofacial orthopedics. Angle Orthod 1980; 50: 71–80.[Medline]

3 Catania JA, Cohen BD, Deeney MR. The use of labial root torque and the tie-forward technique in the treatment of maxillary skeletal retrusion and severe arch length discrepancy. Am J Orthod Dentofacial Orthop 1990; 98: 12–18.[CrossRef][Medline]

4 Goldin B. Labial root torque: effect on the maxilla and incisor root apex. Am J Orthod Dentofacial Orthop 1989; 95: 208–19.[CrossRef][Medline]

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