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Table 3 Linear regressions with simplified plaque index or gingival index (both square root transformed) as dependent variable

From: Salivary levels of cariogenic bacterial species during orthodontic treatment with thermoplastic aligners or fixed appliances: a prospective cohort study

    Crude model Adjusted model
Outcome Factor Group b (95% CI) P b (95% CI) P
s-PlI* Appliance Brackets Referent   Referent  
Aligners − 1.11 (− 1.73 to − 0.48) 0.001 − 1.05 (− 1.55 to − 0.55) < 0.001
Age (per year)   NT   − 0.09 (− 0.23 to 0.06) 0.25
Gender Female NT   Referent  
Male    0.56 (0.01 to 1.11) 0.05
Time T0 Referent   Referent  
T1 − 0.59 (− 1.14 to − 0.05) 0.03 − 0.59 (− 1.14 to − 0.05) 0.03
T2 0.04 (− 0.65 to 0.72) 0.92 0.04 (− 0.65 to 0.72) 0.92
s-PlI at T0   NT   0.35 (0.12 to 0.58) 0.003
s-GI Appliance Brackets Referent   Referent  
Aligners − 1.23 (− 2.01 to − 0.45) 0.002 − 1.16 (− 1.89 to − 0.43) 0.002
Age (per year)   NT   NT  
Gender Female Referent   Referent  
Male NT   NT  
Time T0 Referent   Referent  
T1 − 0.09 (− 0.59 to 0.41) 0.72 − 0.09 (− 0.59 to 0.41) 0.72
T2 0.36 (− 0.36 to 1.07) 0.33 0.36 (− 0.36 to 1.07) 0.33
s-PlI at T0   NT   0.34 (0.04 to 0.64) 0.02
  1. *The following confounders had P ≤ 0.20 in initial separate models and were added in the adjusted model: age, gender, and s-PlI at T0. No significant interaction was found for time with appliance type (P = 0.08)
  2. The following confounder had P ≤ 0.20 in initial separate models and was added in the adjusted model: s-PlI at T0 (age and gender had P > 0.20 and were not added). No significant interaction was found for time with appliance type (P = 0.37)
  3. b unstandardized regression coefficient, CI confidence interval, NT not tested, s-GI simplified gingival index, s-PlI simplified plaque index