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Am J Orthod Dentofacial Orthop. 2017 Oct;152(4):451-457. doi: 10.1016/j.ajodo.2017.05.019.

Comparison of in-vivo failure of single-thread and dual-thread temporary anchorage devices over 18 months: A split-mouth randomized controlled trial.

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Department of Orthodontics, Riphah International University, Islamabad, Pakistan. Electronic address:
Department of Orthodontics, Gandhara University, Peshawar, Pakistan.
Department of Orthodontics, Riphah International University, Islamabad, Pakistan.



The purpose of this study was to compare the in-vivo failure rates of single-thread and dual-thread temporary anchorage device (TAD) designs over 18 months.


Thirty patients with skeletal Class II Division 1 malocclusion requiring anchorage from TADs for retraction of maxillary incisors into the extracted premolar space were recruited in this parallel group, split-mouth, randomized controlled trial. A block randomization sequence was generated with Random Allocation Software (version 2.0; Isfahan, Iran) with the allocations concealed in sequentially numbered, opaque, sealed envelopes. A total of 60 TADs (diameter, 2 mm; length, 10 mm) were placed in the maxillary arches of these patients with random allocation of the 2 types to the left and the right sides in a 1:1 ratio. All TADs were placed between the roots of the second premolar and the first molar and were immediately loaded. Patients were followed for a minimum of 12 months and a maximum of 18 months for the failure of the TADs. Data were analyzed blindly on an intention-to-treat basis.


Four TADs (13.3%) failed in the single-thread group, and 6 TADs (20%) failed in the dual-thread group. The McNemar test showed an insignificant difference (P = 0.72) between the 2 groups. An odds ratio of 1.6 (95% confidence interval, 0.39-6.97) showed no significant associations among the variables. Most TADs failed in the first month after insertion (50%).


The failure rate of dual-thread TADs compared with single-thread TADs is statistically insignificant when placed in the maxilla for retraction of the anterior segment. Registration: The trial was not registered before commencement.


The protocol was not published before the trial.

[Indexed for MEDLINE]

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