Table 1.

The following key words, achieved by studies investigating either colorectal cancer or periodontitis or both of them [16,18,19,21,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41], were employed in the literature search and were logically combined with the boolean operators AND, OR, NOT.

	Key Words
(1)	gene AND human
(2)	cancer
(3)	carcinoma
(4)	2 OR 3
(5)	colon
(6)	colonic
(7)	rectal
(8)	CRC
(9)	5 OR 6 OR 7 OR 8
(10)	periodontitis
(11)	periodontal disease
(12)	periodontal inflammation
(13)	gingivitis
(14)	periodontal disruption
(15)	10 OR 11 OR 12 OR 13 OR 14
(16)	1 AND 4 AND 9 AND 15