In Genesis 49:12, "teeth whiter than milk" signify the Celestial Spiritual [milk] in the Lord's Natural [teeth], where Judah is here representing the Lord. (Arcana Coelestia 2184-2185).

In Psalms 3:7; 37:12, 58:6; Matthew 8:12, teeth signify the lowest natural things in man: in the genuine sense, their truths, in the opposite sense, their falsities. So the gnashing of teeth signifies the collision of falsities with truths. (Arcana Coelestia 4424[3])

In Exodus 21:27, this signifies truth in the natural, here the ultimate, which is the sensuous. (Arcana Coelestia 9062)

The tooth signifies the corporeal proprium, which is the lowest degree of man. (Arcana Coelestia 10283[12])

'Teeth,' as in Genesis 49:12, in the genuine sense, signify the natural level of life. Any hard part of the body, like bones and cartilage, corresponds to the truths and goods of the lowest natural level. 'Teeth' signify the outer edges of the life of the natural self, or the sensory level. There is a natural sensory will, and a natural sensory understanding. When the sensory levels are separated from the interior of the mind, their supposed truths are really mere falsities, and do violence to truths and destroy them. This situation appears in many passages, because sensory people do not see any truth in its own light, but engage in reasoning and altercations about everything... These altercations are heard in the hells as the gnashing of teeth. Viewed in itself, this is the collision of falsity and truth. This is the meaning of 'gnashing of teeth' in Matthew 8:12, 13:42, 50, 22:13, 24:51, 25:30, and Luke 13:28.

(Odkazy: Apocalypse Revealed 435)

6238. 'As Reuben and Simeon will they be mine' means that they will be truth and the good of truth. This is clear from the representation of 'Reuben' as faith in the understanding, and the truth of doctrine by means of which one is able to arrive at the good of life, dealt with in 3861, 3866, thus in general truth that belongs to the understanding; and from the representation of 'Simeon' as faith in the will, consequently truth realized in action, which is the good of faith or the good of truth, dealt with in 3869-3872, 4497, 4502, 4503, 5626, 5630, thus in general good which belongs to the new will. The things that Ephraim and Manasseh represent are clearly similar to all this.

[2] But since Reuben profaned what he represented, 4601, and Simeon polluted what he represented, 4497, 4501, 4507, on account of which they were cursed, see verses 3-7 of the next chapter, they lost their birthright and Joseph's sons Ephraim and Manasseh were acknowledged as the firstborn in place of them, 1 Chronicles 5:1. Nevertheless what Reuben and Simeon represented remained with them, for it makes no difference what the character of the person who serves to represent something is like, 665, l097 (end), 4281. That is to say, the representation of faith in the understanding remained with Reuben, and the representation of faith in the will with Simeon. But what resided with Ephraim was the representation of the Church's understanding, and what resided with Manasseh was the representation of the Church's will.