Table 3.

Relationship between each variable and development of ORN (multivariate analysis)

Variable		p-value	Hazard ratio	95% confidence interval
Periapical lesion at the start of RT	(−) vs. (+)	<0.001	3.722	2.076–6.674
Severe periodontal disease at the start of RT	(−) vs. (+)	0.006	2.818	1.351–5.880
Tooth extraction after RT	(−) vs. (+)	0.023	2.145	1.110–4.147

Abbreviations: ORN: osteoradionecrosis; RT: radiotherapy.