Adjunctive Orthodontic Treatment Protocol

All patients fulfilling the above eligibility criteria were subject to adjunctive orthodontic treatment using pre-adjusted fixed appliance (0.022-inch slot system, MBT, 3M Unitek, Monrovia, CA, USA), which was provided by the same experienced operator (Y.Y.). Individual treatment plans and goals were made via discussion between orthodontists and periodontists and then finalized with patients’ approval. Accordingly, orthodontic forces were delivered to teeth for designated movement. A standardized archwire protocol at the initial treatment stage was employed considering its effect on orthodontic pain [22 (link),35 (link),43 (link)], specifically, with a 0.014-inch thermal nickel–titanium (NiTi) wire (G&H Orthodontics, Franklin, IN, USA) for the first two months, followed by a 0.016-inch thermal NiTi wire (G&H Orthodontics, Franklin, IN, USA) for one month. By then, most teeth had achieved a preliminary alignment. Subsequently, 0.018-inch, 0.017 × 0.025-inch NiTi archwires (G&H Orthodontics, Franklin, IN, USA), and 0.017 × 0.025-inch stainless steel archwires (G&H Orthodontics, Franklin, IN, USA) were sequentially administered to the patients depending on individual circumstances. After anticipated treatment outcomes were achieved, fixed appliances were removed, and orthodontic treatment entered the retention phase with immediate delivery of polyvinyl chloride retainers and fixed-lingual retainers (0.0215-inch multistranded wire) attached to the anterior teeth.