Table 6. Multivariate Cox proportional hazards model for the analysis of potential risk factors associated with implant failure.

Factors			Hazard ratio	95% CI	P value
Potential risk factors associated with implant failures
	Bone status (regenerated bone)		0.870	0.169–4.491	0.868
	Age		1.061	0.981–1.146	0.138
	Smoking		10.653	2.472–45.913	0.002a)
Risk factor of smoking associated with implant failure
	Comparison with subgroup 1
		Subgroup 2	10.872	2.039–57.962	0.005b)
		Subgroup 3	0.906	0.091–8.990	0.933
		Subgroup 4	9.094	0.827–100.054	0.071

CI: confidence interval, subgroup 1: nonsmokers in the native bone group, subgroup 2: smokers in the native bone group, subgroup 3: nonsmokers in the regenerated bone group, subgroup 4: smokers in the regenerated bone group.

^a)In comparison with nonsmokers, smokers had a 10.7 times higher risk for implant failure, with a statistically significant difference (P<0.05); ^b)In comparison with subgroup 1, subgroup 2 had a 10.9 times higher risk for implant failure, with a statistically significant difference (P<0.05).