Table 4.

Results of the Cox Bi- and Multivariable Regression for the Identification of Factors Important for the Survival of Brackets^a

Factor	Category	Bivariable		Multivariable
		HR (95% CI)	P	HR (95% CI)	P
Gender	Female	Referent		NT
	Male	1.00 (0.73–0.38)	.98	NT
Age	Per year	1.00 (0.92–1.08)	.93	NT
Jaw	Mandible	Referent		Referent
	Maxilla	1.30 (0.99–1.69)	.06	1.30 (1.00–1.70)	.05
Deepbite	No	Referent		NT
	Yes	1.24 (0.91–1.67)	.17	1.14 (0.85–1.52)	.38
Crossbite	No	Referent		NT
	Yes	0.89 (0.58–1.37)	.60	NT
Anterior crowding	No	Referent		NT
	Yes	0.92 (0.63–1.34)	.66	NT
Mouth side	Left	Referent		NT
	Right	1.15 (0.88–1.51)	.30	NT
Tooth	Central incisor	1.72 (1.05–2.83)	.03	1.74 (1.06–2.87)	.03
	Lateral incisor	1.87 (1.15–3.05)	.01	1.89 (1.16–3.08)	.01
	Canine	Referent		Referent
	First premolar	1.43 (0.85–2.40)	.17	1.45 (0.86–2.43)	.16
	Second premolar	3.22 (2.04–5.08)	<.001	3.19 (2.03–5.03)	<.001
Tooth category	Posterior, canines-premolars	Referent		NT
	Anterior, incisors	0.98 (0.74–1.28)	.86	NT
Bracket type	SSCL	Referent		Referent
	CeramicCL	1.64 (1.15–2.32)	.006	1.62 (1.14–2.29)	.007
	SSSL	0.79 (0.54–1.15)	.21	0.80 (0.55–1.18)	.26
	Ni-freeSL	0.96 (0.58–1.60)	.89	1.01 (0.60–1.69)	.98
Extraction case	No	Referent		NT
	Yes	0.85 (0.51–1.42)	.54	NT
Auxiliary appliances used	No	Referent		NT
	Yes	1.00 (0.57–1.75)	1.00	NT
Missed appointment	Per appointment	1.03 (0.98–1.09)	.24	NT
Hygiene warning received	No	Referent		NT
	Yes	0.99 (0.73–1.35)	.96	NT

^aResults are given as hazard ratios with their 95% confidence intervals. HR indicates hazard ratio; CI, confidence interval; NT, not tested; SS, stainless steel; _CL, conventionally ligated; _SL, self-ligated.