Letters From Our Readers
To: Editor, The Angle Orthodontist
Re: Response to: Anchorage condition during canine retraction using transpalatal arch with continuous and segmented arch mechanics. The Angle Orthodontist. 2016;86:380–385.
Thank you for your letter to the editor. Please find below each comment presented in the letter, followed by the authors' response in italics:
I found this paper to be very interesting. However, I wonder if you could explain why the T-loop was designed to have the loop positioned off-center to the mesial, rather than to the distal? Placing the loop mesially would increase the alpha moment and thus enhance anchorage of the anterior segment, which was not the desired intent.
Authors response:
It is true that the T-loop was located off center to the mesial to bypass the second premolar, since the wire was inserted into the first molar tube (Figure 1, C), and to leave wire distal to the loop for enough range of activation. However, this was compensated for by a larger bend (60°) for the posterior segment than the anterior segment (35°) to create the required moment-to-fore ratio and to enhance the posterior anchorage. After the first activation, the T loop became more distally and the Beta moment is expressed more where maximum anchorage is produced in the posterior segment than in the anterior segment
Also, the study compared T-loop mechanics to continuous wire space closure using sliding mechanics. Can you comment on whether you think friction of the continuous wire played any role in the differences you saw between the two outcomes?
Authors response:
Yes, friction in the continuous arch mechanics could have played a role in the differences between the two outcomes. This was mentioned in the discussion section.
If the beta bend placed in the T-loop was meant to preserve anchorage in the T-loop group, were there any steps taken to conserve anchorage in the continuous wire patients? Perhaps a better comparison would have been accomplished using only patients treated with T-loops but between those with and those without posterior anchorage bends.
Authors response:
Other than the TPA, there was no other steps taken to conserve anchorage in the continuous wire patients. The comparison between segmented arch mechanics with or without posterior anchorage bends is actually a future work planned to be performed soon.
Thank you.
Adel Alhadlaq
Thamer Alkhadra
Tarek El-Bialy