Pulpal blood flow changes and pain scores related to using Superelastic 0.018-inch Nickel Titanium as the first orthodontic alignment archwire: a prospective clinical trial

Abstract Background Optimal orthodontic force results in maximum rate of tooth movement without tissue damage. Even though starting orthodontic treatment with a thicker archwire may shorten treatment duration, the evidence on the effect of using 0.018-inch NiTi as the first alignment archwire on pulpal blood flow (PBF) status is still scarce. Objectives to record PBF changes and pain scores associated with using 0.018-inch NiTi as the first alignment archwire during fixed orthodontic treatment. Methodology Patients were selected from subjects attending postgraduate orthodontic teaching clinics at Jordan University of Science and Technology. In total, forty healthy patients who exhibited mild lower arch crowding were included. A split-mouth trial design was used. Each patient received two archwire sizes at one time joined in the midline by crimpable hook and applied in the lower arch. Patients were assigned into one of two groups based on archwire sizes used. Group 1: 0.014-inch and 0.018-inch NiTi (Six males, 14 females aged 19.4±1.33 years) and Group 2: 0.016-inch and 0.018-inch NiTi (Seven males, 13 females aged 19.6±1.45 years). The archwire size group was randomly allocated with a 1:1 allocation ratio. A Laser Doppler Flowmeter was used to measure PBF at different time intervals (T0-T5). Pain scores were recorded using a visual analogue scale (VAS). A repeated measures ANOVA and a post-hoc Bonferroni comparison tests were conducted to examine differences at the different time points before and during orthodontic alignment. Results For all studied archwire sizes, PBF decreased 20 minutes after their placement. Most PBF changes occurred within 24hours and continued to decrease until 72 hours after archwire placement where the maximum reduction was reached. Eventually, normal values were reverted within 1 month. PBF changes were similar between all alignment – groups. Conclusions Initial orthodontic alignment with 0.018-inch NiTi does not cause irreversible changes to pulpal vasculature or produces higher pain scores.

# 摘要
## 背景
最佳正畸力可实现牙齿移动的最大速率且不造成组织损伤。尽管采用较粗弓丝启动正畸治疗可缩短治疗周期，但关于以0.018英寸镍钛（NiTi）弓丝作为初始排齐弓丝对牙髓血流量（PBF）影响的相关证据仍较为匮乏。
## 研究目的
记录固定正畸治疗中，以0.018英寸镍钛（NiTi）弓丝作为初始排齐弓丝时的牙髓血流量变化及伴随的疼痛评分。
## 研究方法
研究对象选自约旦科技大学正畸研究生教学门诊的就诊患者。最终纳入40名存在轻度下牙列拥挤的健康受试者。本研究采用分口试验设计：每位患者同时在下颌牙弓内植入两种弓丝，二者在中线处通过压接式挂钩连接。根据弓丝尺寸将患者随机分为两组，分配比例为1:1。组1：0.014英寸与0.018英寸镍钛（NiTi）弓丝（6名男性，14名女性，年龄19.4±1.33岁）；组2：0.016英寸与0.018英寸镍钛（NiTi）弓丝（7名男性，13名女性，年龄19.6±1.45岁）。采用激光多普勒血流仪（Laser Doppler Flowmeter）在不同时间点（T0-T5）测量牙髓血流量，采用视觉模拟评分法（VAS）记录疼痛评分。通过重复测量方差分析及Bonferroni事后比较检验，分析正畸排弓阶段前后不同时间点的组间差异。
## 结果
所有受试弓丝植入后20分钟，牙髓血流量均出现下降。多数牙髓血流量变化发生于植入后24小时内，并持续下降至植入后72小时达到最大降幅，最终于1个月内恢复至基线正常水平。两组的牙髓血流量变化趋势无显著差异。
## 结论
采用0.018英寸镍钛（NiTi）弓丝开展初始正畸排弓治疗，不会对牙髓脉管系统造成不可逆改变，亦不会引发更高的疼痛评分。