Evaluation of the alignment efficiency of nickel-titanium and copper-nickel-titanium archwires in patients undergoing orthodontic treatment over a 12-week period: A single-center, randomized controlled clinical trial

Abstract

Objective: The aim of this trial was to compare the alignment efficiency and intermaxillary arch dimension changes of nickel-titanium (NiTi) or copper-nickel-titanium (CuNiTi) round archwires with increasing diameters applied sequentially to the mandibular arch.

Methods: The initial alignment phase of fixed orthodontic treatment with NiTi or CuNiTi round archwires was studied in a randomly allocated sample of 66 patients. The NiTi group comprised 26 women, 10 men, and the CuNiTi (27℃) group comprised 20 women, 10 men. The eligibility criteria were as follows: anterior mandibular crowding of minimum 6 mm according to Little's Irregularity Index (LII), treatment requiring no extraction of premolars, 12 to 18 years of age, permanent dentition, skeletal and dental Class I malocclusion. The main outcome measure was the alignment of the mandibular anterior dentition; the secondary outcome measure was the change in mandibular dental arch dimensions during 12 weeks. Simple randomization (allocation ratio 1:1) was used in this single-blind study. LII and mandibular arch dimensions were measured on three-dimensional digital dental models at 2-week intervals.

Results: No statistically significant difference was observed between NiTi and CuNiTi according to LII (p > 0.05). Intercanine and intermolar arch perimeters increased in the CuNiTi group (p < 0.001). Inter-first premolar width showed a statistically significant interaction in week × diameter × application (p < 0.05).

Conclusions: The effects of NiTi and CuNiTi round archwires were similar in terms of their alignment efficiency. However, the intercanine and intermolar arch perimeters, and the inter-first premolar width changes differed between groups.

Keywords: Copper-nickel-titanium; Nitinol; Three-dimensional digital dental cast analysis; Wire.

Figure 1. The appliances used in this study. A, Nickel-titanium (NiTi) group before treatment; B, NiTi group after treatment; C, copper-nickel-titanium (CuNiTi) group before treatment; D, CuNiTi group after treatment; E, F, Essix retainer with acrylic bite block.

Figure 2. Dental arch measurements. A, Little's Irregularity Index. a, The distance between the mesial tip of the left canine and the distal point of the left lateral incisor; b, the distance between the mesial point of the left lateral incisor and the distal point of the left central incisor; c, the distance between the mesial point of the left central incisor and the mesial point of the right central incisor; d, the distance between the distal point of the right central incisor and the mesial point of the right lateral incisor; e, the distance between the mesial tip of the right canine and the distal point of the right lateral incisor. B, Intermolar and intercanine arch perimeters on mandibular dental models. Intermolar arch perimeter (solid line), the distance in millimeters from the mesial dental contact of the left first molar to the mesial dental contact of the right first molar through the dental arch. Intercanine arch perimeter (dashed line), the distance in millimeters from the mesial contact of the left canine to the mesial dental contact of the right canine through the dental arch. C, Interdental and interalveolar arch widths on mandibular dental models. 1, The linear distance between the cusp tips of the right and left canines; 2, the linear distance between the buccal cusp tips of the right and left first premolars; 3, the linear distance between the buccal cusp tips of the right and left second premolars; 4, the linear distance between the mesiobuccal cusp tips of the right and left first molars; 5, the linear distance between the fossa of the first molars; 6, the linear distance between the alveolar bases of the right and left canines; 7, the linear distance between the alveolar bases of the right and left first premolars; 8, the linear distance between the alveolar bases of the right and left first premolars; 9, the linear distance between the alveolar bases of the right and left first molars.

Figure 3. Flow diagram showing patient selection during the study.

Figure 4. The arch forms of nickel-titanium (NiTi) and copper-nickel-titanium (CuNiTi) archwires used in this study.