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The Cox proportional hazards model for 6- and 12-month observation periods.
| Coefficient β | Hazard ratio | 95% CL | p | |
|---|---|---|---|---|
| Ceramic brackets (6 months) | 1.00 | 1.00 | ||
| Metal brackets (6 months) | −1.752 | 0.173 | 0.039–0.775 | 0.022 |
| Ceramic brackets (12 months) | 1.00 | 1.00 | ||
| Metal brackets (12 months) | −1.913 | 0.148 | 0.034–0.650 | 0.011 |
