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This study compares a new technique for teeth alignment to the conventional method. The teeth were aligned using an open-coil spring, i.e. simultaneous space opening and alignment, on round nickel-titanium (NiTi) archwires. The purpose of this 2-arm parallel trial (1:1 allocation ratio) was to evaluate the alignment efficiency of conventional and open-coil spring techniques in anterior crowding treatment.

In this clinical trial study, sixty-two non-extraction patients (70 dental arches: 24 upper arches and 46 lower arches) with ≥3mm of Little’s Irregularity Index (LII) were recruited in two groups based on the minimization method. Blinding was applicable for outcome assessment only. In one group, the teeth were aligned using an open-coil spring, whereas the alignment in the other group was done conventionally, (space opening on steel wires followed by alignment with an auxiliary NiTi wire). The alignment duration was the primary outcome that was investigated for survival analysis and alignment rate ratios, and levels of crowding were calculated with Cox proportional hazard regression. The pre- and post-treatment intercanine widths were also recorded as the secondary outcome. The chi-square and t-test were used to compare other variables between the groups. The level of statistical significance was set at P<0.05.

There was no significant difference in the alignment duration between the conventional (185.48±74.82 days) and open-coil (179.19±64.15 days) groups (P=0.725). No harm was detected using the mentioned methods.

The use of open-coil spring over brackets on NiTi or steel wires does not seem to affect anterior crowding treatment time.

Orthodontic patients are at an increased risk of caries due to difficulty in plaque control. Antimicrobial agents, such as fluoride and chlorhexidine, can be useful in preventing tooth demineralization. The present study aimed to determine the effect of fluoride and chlorhexidine gels and their mixture on the shear bond strength (SBS) of orthodontic brackets.

In this ex-vivo study, 70 premolars were divided into seven groups. The first group was considered as the control. The second, third, and fourth groups were first etched with 37% phosphoric acid and then pretreated with chlorhexidine, fluoride, and fluoride-chlorhexidine gels, respectively. The brackets were then bonded. In the fifth, sixth, and seventh groups, the enamel surface was etched after pretreatment, and then, the brackets were bonded. After mounting the teeth, SBS was measured using the Instron machine. Data were analyzed using one-way analysis of variance (ANOVA) and Tamhanechr('39')s T2 test (α≤0.05).

The mean SBS was 19.7 MPa in the control, 11.1±2.5 MPa in the second, 11.8±3.6 MPa in the third, 21±7.5 MPa in the fourth, 19.4±9 MPa in the sixth, and 14.1±6.7 MPa in the seventh group with no statistically significant differences. However, there was a statistically significant decrease in the mean SBS (8±5.2 MPa) of the fifth group (chlorhexidine before etching) compared to the control group (P=0.04).

The use of fluoride and chlorhexidine can be recommended to orthodontic patients because of antibacterial and anticaries properties and no significant decrease in the SBS of orthodontic brackets (except when chlorhexidine is used before etching).