Abstract
BackgroundAlthough preformed archwires with a variety of arch forms are currently commercially available, the effects of variation in the shape of these archwires on the orthodontic force at each tooth are not well understood. Therefore, we evaluated the forces delivered by various types of commercially available preformed nickel–titanium alloy (NiTi) archwires in a simulated mandibular dental arch.MethodsSixty-three types of 0.019 × 0.025-inch preformed NiTi archwires from 15 manufactures were selected for analysis. The intercanine width (ICW) and intermolar width (IMW) of each archwire were measured at the mean canine and first molar depths of 30 untreated subjects with normal occlusions. Each archwire was placed in a multi-sensor measurement system simulating the mandibular dental arch of subjects with normal occlusions, and orthodontic forces in the facial-lingual direction at the central incisors, canines, and first molars were measured. Correlations between the ICW, IMW, and ICW/IMW ratio of archwires and the delivered forces were analyzed. The archwires were classified into the following four groups according to the ICW and IMW: Control group, ICW and IMW are within the means ± standard deviations of the normal ranges; Ovoid group, narrow ICW and IMW; Tapered group, narrow ICW; and Square group, narrow IMW. The forces were compared among these groups for each tooth.ResultsSignificant correlations between the measured archwire width and force to each tooth were found, except between IMW and forces at the central incisors and canines. Significant differences in the forces were found among all groups, except between the Ovoid and Tapered groups at all teeth and between the Ovoid/Tapered and Control groups at the first molar. Significantly greater orthodontic forces in the facial direction were delivered at the central incisors by the archwires in the Ovoid and Tapered groups when compared with the archwires in the other groups.ConclusionThese findings suggest that there is a possible risk of a clinically significant level of unfavorable orthodontic force being delivered to the mandibular incisors in labial inclination when using a preformed archwire with an ICW that is narrower than the dental arch.
Highlights
The dental arch form is a key element for achieving stable orthodontic treatment results, and related factors such as occlusal relationship, oral habits, and the positional relationship of the teeth with the basal bone have been widely investigated [1]
Significant negative correlations were observed between the intercanine width (ICW) and the orthodontic force delivered at the incisors and first molars (Fig. 4A, C), and a significant positive correlation was observed between the ICW and the orthodontic force delivered at the canines (P < 0.01) (Fig. 4B)
A significant negative correlation was observed between the intermolar width (IMW) and the orthodontic force delivered at the first molars (P < 0.01) (Fig. 5C)
Summary
The dental arch form is a key element for achieving stable orthodontic treatment results, and related factors such as occlusal relationship, oral habits, and the positional relationship of the teeth with the basal bone have been widely investigated [1]. Felton et al [11] found that only two of 17 kinds of tested preformed archwires closely fit the dental arch forms of 30 subjects with untreated normal occlusions, which covered about 44% of the natural diversity of Class I orthodontic patients in the USA. Bhowmik et al [15] found that 15 kinds of preformed archwires were wider at both the canine and second molar widths than the average dental arches of subjects with normal occlusions in India. Oda et al [14] found that, on average, 20 kinds of preformed archwires available in Japan were significantly narrower than the dental arch form for Japanese subjects with untreated normal occlusions for both the canine and first molar. We evaluated the forces delivered by various types of commercially available preformed nickel–titanium alloy (NiTi) archwires in a simulated mandibular dental arch
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