Table 3.
Multi-level mixed effects linear regression models predicting Little's Irregularity Index
| Model 1 | Model 2 | Model 3 | |
|---|---|---|---|
| Initial LII | 0.599* | 0.056 | 0.055 |
| Female | 0.241 | 0.257 | 0.317 |
| Age | 0.059** | 0.051** | 0.043 |
| Ethnicity | |||
| African | -0.798 | -0.585 | -0.609 |
| Asian | -0.191 | -0.167 | -0.279 |
| Other | -0.574 | -0.651 | -0.683 |
| Mandible | -0.092 | 0.007 | 0.009 |
| Test center | |||
| Test center 1 | -0.194 | 0.139 | -0.008 |
| Test center 2 | 0.025 | 0.349 | -0.082 |
| Test center 3 | -0.275 | -0.152 | -0.183 |
| Treatment time | -0.032* | -0.032** | -0.032** |
| LII (second) | 0.048* | 0.048* | |
| Treatment time (second) | 0.000*** | 0.000*** | |
| Treatment time × initial LII | -0.006**** | -0.006**** | |
| Device | -0.881*** | ||
| Constant | -0.749 | 0.591 | 1.584** |
| RI_Patient_Constant | 0.089 | -0.102 | -0.133 |
| RI_Arch_Constant | -0.550 | -0.351 | -0.358 |
| RI_Res_Constant | 0.483* | 0.357* | 0.355* |
| Chi square | 508.554 | 716.377 | 730.174 |
NS: 314 time intervals nested within 136 arches nested within 90 patients. * p < 0.001, ** p < 0.10, *** p < 0.05, **** p < 0.01.