Table 1. Descriptive data and statistics of all outcome parameters evaluated.
| Descriptive statistics |
Global test |
Post hoc test Δ force (F)/F+nicotine |
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|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Parameters Evaluated | Experimental conditions (n=7 per group) | M | SD | min. | max. | F/H/U | df1-2 (z) | P-value | r | P-value | 95% CI of ΔM | |
| Serology (after 14 days of OTM, nicotine bioavailability (cotinine) and systemic inflammation (IL-6)) | ||||||||||||
| IL-6—blood serum concentration in ng·mL−1 (n=4/grp.) | Control (PBS) | 0.9 | 0.7 | 0.1 | 1.7 | 17.407F | 2 | ***0.001 | 0.89 | **0.009T | 1.6–9.9 | |
| Orthodontic force | 3.7 | 0.8 | 2.5 | 4.3 | ||||||||
| Force+nicotine | 9.5 | 3.5 | 6.3 | 14.3 | ||||||||
| Cotinine—blood serum concentration in μg·L−1 (n=5/grp.) | Control (PBS) | 5.0 | 0.0 | 5.0 | 5.0 | 25.000U | 2.785z | **0.008 | 0.88 | **0.008U | 283.7–623.9 | |
| Force+nicotine | 458.8 | 137.0 | 258.0 | 569.0 | ||||||||
| CBCT (radiology, experiment A, OTM within 14/28 days, velocity of orthodontic tooth movement) | ||||||||||||
| First upper left molar M1—orthodontic tooth movement within 14/28 days (tipping, in °) | Control (PBS) | 14 days | −0.3 | 0.9 | −1.6 | 0.8 | 91.183F (group) 59.639F (time) | 2 (group) 1 (time) | ***<0.001 (group) ***<0.001 (time) | 0.91 (group) 0.88 (time) | ***<0.001T | 1.4–4.5 |
| 28 days | 0.0 | 1.5 | −1.8 | 2.0 | ||||||||
| Orthod. force | 14 days | 3.6 | 1.6 | 1.7 | 5.3 | |||||||
| 28 days | 6.3 | 1.5 | 4.1 | 7.8 | ||||||||
| Force+nicotine | 14 days | 6.1 | 1.2 | 4.5 | 7.9 | |||||||
| 28 days | 9.7 | 1.1 | 8.5 | 11.4 | ||||||||
| Second upper left molar M2—orthodontic tooth movement within 14/28 days (in mm) | Control (PBS) | 14 days | 0.0 | 0.0 | 0.0 | 0.1 | 125.398F (group) 219.362F (time) | 2 (group) 1 (time) | ***<0.001 (group) ***<0.001 (time) | 0.94 (group) 0.96 (time) | **0.004GH | 0.1–0.4 |
| 28 days | 0.0 | 0.1 | −0.1 | 0.1 | ||||||||
| Orthod. force | 14 days | 0.4 | 0.1 | 0.3 | 0.5 | |||||||
| 28 days | 0.7 | 0.1 | 0.6 | 0.8 | ||||||||
| Force+nicotine | 14 days | 0.6 | 0.1 | 0.5 | 0.7 | |||||||
| 28 days | 1.0 | 0.2 | 0.8 | 1.3 | ||||||||
| Third upper left molar M3—mesial drift within 14/28 days (in mm) | Control (PBS) | 14 days | 0.0 | 0.0 | 0.0 | 0.1 | 40.659F (group) 40.210F (time) | 2 (group) 1 (time) | ***<0.001 (group) ***<0.001 (time) | 0.83 (group) 0.83 (time) | **0.002T | 0.1–0.3 |
| 28 days | 0.0 | 0.1 | −0.2 | 0.2 | ||||||||
| Orthod. force | 14 days | 0.1 | 0.1 | 0.0 | 0.2 | |||||||
| 28 days | 0.3 | 0.1 | 0.2 | 0.5 | ||||||||
| Force+nicotine | 14 days | 0.2 | 0.1 | 0.2 | 0.3 | |||||||
| 28 days | 0.5 | 0.1 | 0.4 | 0.6 | ||||||||
| RT–qPCR (after 14 days of OTM, experiment B, inflammation and osteoclast activity within the dental-periodontal tissue) | ||||||||||||
| IL-1β—normalized relative gene expression (geNorm) | Control (PBS) | 0.04 | 0.03 | 0.02 | 0.10 | 42.52F,W | 2–7.301 | ***<0.001 | 0.92 | **0.002GH | 0.6–1.9 | |
| Orthodontic force | 0.42 | 0.22 | 0.16 | 0.75 | ||||||||
| Force+nicotine | 1.65 | 0.57 | 0.71 | 2.26 | ||||||||
| IL-6—normalized relative gene expression (geNorm) | Control (PBS) | 0.01 | 0.01 | 0.00 | 0.02 | 32.93F,W | 2–7.301 | ***<0.001 | 0.90 | ***<0.001GH | 0.6–1.5 | |
| Orthodontic force | 0.47 | 0.17 | 0.29 | 0.74 | ||||||||
| Force+nicotine | 1.53 | 0.39 | 1.03 | 2.05 | ||||||||
| IL-8-equivalent (CXCL1)—normalized rel. gene expression (geNorm) | Control (PBS) | 0.09 | 0.05 | 0.03 | 0.17 | 78.85F,W | 2–7.379 | ***<0.001 | 0.87 | **0.002GH | 0.4–1.6 | |
| Orthodontic force | 0.89 | 0.27 | 0.62 | 1.23 | ||||||||
| Force+nicotine | 1.90 | 0.49 | 1.18 | 2.64 | ||||||||
| CTSK—normalized relative gene expression (geNorm) | Control (PBS) | 0.04 | 0.01 | 0.04 | 0.05 | 33.103F,W | 2–7.421 | ***<0.001 | 0.90 | ***0.001GH | 2.1–5.6 | |
| Orthodontic force | 0.31 | 0.10 | 0.19 | 0.49 | ||||||||
| Force+nicotine | 4.15 | 1.53 | 2.35 | 6.44 | ||||||||
| CLCN7—normalized relative gene expression (geNorm) | Control (PBS) | 0.03 | 0.01 | 0.02 | 0.04 | 67.400F,W | 2–7.603 | ***<0.001 | 0.93 | **0.007GH | 0.5–2.4 | |
| Orthodontic force | 0.34 | 0.06 | 0.27 | 0.41 | ||||||||
| Force+nicotine | 1.79 | 0.79 | 0.92 | 3.00 | ||||||||
| Histomorphometry and Histochemistry (M2 distobuccal root, after 14 days of OTM, experiment C, OIIRR and osteoclast activity) | ||||||||||||
| TRAP+ area in % in PDL per mm2 root area (TRAP density) | Control (PBS) | 3.8 | 2.1 | 1.0 | 6.9 | 33.692F,W | 2–11.0 | ***<0.001 | 0.90 | **0.002GH | 4.7–17.7 | |
| Orthodontic force | 10.1 | 2.9 | 5.1 | 13.9 | ||||||||
| Force+nicotine | 21.3 | 5.4 | 14.6 | 30.1 | ||||||||
| Relative dentine root resorption in % | Control (PBS) | 0.0 | 0.0 | 0.0 | 0.0 | 18.491H | 2 | ***<0.001 | 0.95 | ***0.001U | 4.4–9.9 | |
| Orthodontic force | 2.6 | 0.5 | 2.0 | 3.4 | ||||||||
| Force+nicotine | 9.7 | 2.3 | 6.9 | 13.5 | ||||||||
CBCT, cone-beam computed tomography; CI, confidence interval; df, degrees of freedom; F, test statistic of one-way/mixed (CBCT) ANOVA; GH, Games–Howell post hoc test; H, test statistic of two-sided Kruskal–Wallis H-test; IL, interleukin; M, arithmetic mean; max., maximum; min., minimum; n, number of animals; OTM, orthodontic tooth movement; OIIRR, orthodontically induced inflammatory root resorption; P, significance value; r, effect size (Pearson’s correlation coefficient); PDL, periodontal ligament; PBS, phosphate-buffered saline; RT–qPCR, reverse transcription quantitative real-time; PCR, polymerase chain reaction; SD, standard deviation; T, Tukey’s Highly Significant Difference post hoc test; TRAP, tartrate-resistant acid phosphatase; U, test statistic of two-sided Mann–Whitney U-test; W, Welch test corrected ANOVA; z, standardized test statistic; ΔM, difference of arithmetic means of group force (2) and group force+nicotine (3).
Gene expression was normalized via the reference genes PPIB/YWHAZ (combination). Bold values are indicate P values, which are statistically significant (P≤0.05). */**/***P≤0.05/0.01/0.001.