Effect of the timing of second molar bonding on the duration of the mandibular arch levelling: a randomized clinical trial.

Dritsas, Konstantinos; Alharbi, Majed; Kouvelis, Georgios; Kloukos, Dimitrios; Gkantidis, Nikolaos (2022). Effect of the timing of second molar bonding on the duration of the mandibular arch levelling: a randomized clinical trial. European journal of orthodontics, 44(2), pp. 203-209. Oxford University Press 10.1093/ejo/cjab046

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This study investigated the effect of the timing of second molar bonding on the time required for the levelling of the mandibular dental arch.


Single-centre two-arm parallel randomized clinical trial using random permuted blocks. Allocation concealment was achieved through sealed envelopes. There was blinding in outcome assessment, but not of patient or operator.


Thirty-six patients (12-18 years old) with mild to moderate crowding and fully erupted mandibular second molars were assigned randomly (1:1 ratio) in two groups. Group A started fixed orthodontic treatment by bracket bonding in both jaws. Initial wire was 0.014" NiTi. Lower second molar tubes were bonded at the time of 0.016" x 0.022" NiTi wire placement. Group B was same as Group A, but second lower molars were bonded at the first appointment. Placement of the 0.017" x 0.025" stainless steel wire in the mandibular arch was considered the primary endpoint of the trial, indicating the completion of the levelling phase. The days required from bonding to the endpoint comprised the main outcome. Non-parametric statistics were applied.


There were two dropouts in each group. The compared groups had similar baseline characteristics regarding age, sex, overjet, overbite, space in the dental arch, average Curve of Spee (CoS), and maximum CoS. Group A tended to require more days for levelling (median: 203 days) than Group B (median: 168 days). However, this difference was not statistically significant (P = 0.128). From the tested occlusal factors, only initial overjet was found to be moderately associated with the days required to complete levelling of the mandibular arch (r = 0.45, P = 0.009).


In the frame of the current study, the duration of the levelling phase of orthodontic treatment with fixed appliances was not affected by the timing of second molar inclusion in the appliance. Future research could aim in cases with deep CoS to generalize the present findings and in larger sample sizes.

Item Type:

Journal Article (Original Article)


04 Faculty of Medicine > School of Dental Medicine > Department of Orthodontics

UniBE Contributor:

Dritsas, Konstantinos, Alharbi, Majed Mohammad A, Kloukos, Dimitrios (B), Gkantidis, Nikolaos


600 Technology > 610 Medicine & health




Oxford University Press




Renate Imhof-Etter

Date Deposited:

15 Jul 2021 11:54

Last Modified:

29 Mar 2023 23:37

Publisher DOI:


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