Abstract:

Objective To discuss the effects of superelastic nickel-titanium archwires （SENT） and heat-activated nickel-titanium archwires （HANT） on the initial alignment efficiency of mandibular anterior teeth and pain levels of the patients with extraction orthodontic treatment and non-extraction orthodontic treatment by using low-friction self-ligating brackets， and to provide the basis for the selection of the most suitable archwire in orthodontic clinical practice. Methods Eighty patients underwent fixed orthodontic treatment with self-ligating brackets were randomly assigned to SENT or HANT subgroups， and there were 40 patients in extraction orthodontic treatment group and 40 patients in non-extraction orthodontic treatment group. A single operator fully engaged a 0.014-inch straight archwire into the brackets.The patients， operators， and data measurers were all blinded；the initial clinical alignment efficiency of the archwires of the patients in various groups was observed， and the Little’s index was calculated； the visual analog scale （VAS） scores and pain perception of the patients in various groups were recorded 4 h after initial bonding of the appliances and every day before breakfast during the first week of orthodontic treatment； multivariate regression analysis was performed for the initial Little’s index， gender， and age， and the influence factors of pain in the patients was analyzed. Results There were no significant differences in age， gender， and initial Little’s index among the patients in extraction group and non-extraction group （P>0.05）. Compared with before treatment， the Little’s indexes of the patients in both HANT and SENT subgroups in non-extraction orthedontic treatment group were decreased 4 weeks after treatment，but the difference between groups was not significant （P>0.05）. Compared with SENT subgroup in non-extraction orthodontic treatment group， the Little’s index of the patients in HANT subgroup was decreased （P<0.05）. In extraction orthodontic treatment group， there were no significant differences in Little’s indexes of the patients between the HANT and SENT subgroups before and after treatment （P>0.05）. The pain perception peaked on the first day after initial bonding and gradually decreased to baseline levels.The patients in SENT and HANT subgroups in both extraction and non-extraction orthodontic treatment groups showed the similar patterns of pain change. There were no significant differences in the average VAS scores and maximum pain intensity scores between the patients in SENT and HANT subgroups at different time points （P>0.05）. The type of archwire had no significant effect on the degree of pain， while time significantly affected the degree of pain. The multivariate regression analysis results showed a significant correlation between initial Little’s index and maximum VAS scores of the patients in extraction orthodontic treatment group （b=0.359， P=0.033）. Gender and age did not affect the degree of pain of the patients in either group. Conclusion When applying low-friction self-ligating brackets for orthodontic treatment， the initial alignment efficiency with 0.014-inch HANT archwires is superior to 0.014-inch SENT archwires in non-extraction treatment group， while both archwires show the same efficiency in extraction patients. SENT and HANT archwires do not affect the initial degrees of pain of the orthodontic patients.

Key words: NiTi archwires, Alignment efficiency, Orthodontic pain, Self-ligating brackets, Little’s index