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)

435. And their teeth were like lions' teeth. This symbolically means that matters of the senses, which constitute the lowest elements of the natural self's life, appeared to them to have power over all else.

Teeth symbolize the lowest elements of the natural self's life, which are called sensual, as discussed in no. 424 above. These sensual elements are of two kinds, one having to do with the will, the other with the intellect. Sensual elements having to do with the will are symbolized by women's hair, as said just above in no. 434; and sensual elements having to do with the intellect are symbolized by teeth. The latter, which is to say, sensual people caught up in falsities by conviction, appear to themselves to have power over everything, so that they cannot be overcome. Therefore the locusts' teeth, which symbolize such sensual elements, were like lions' teeth - a lion symbolizing power (no. 241).

That teeth symbolize the lowest elements of a person's life - those elements called sensual - and that when these are divorced from the interior levels of the mind, they are caught up in nothing but falsities and attack truths and destroy them, can be seen from the following passages:

With my soul I lie down among lions...; their teeth are a spear and arrows... (Psalms 57:4)

O God, destroy their teeth in their mouth! Turn aside the molars of the young lions... (Psalms 58:6)

...a nation has come up against My land, strong..., its teeth the teeth of a lion, and it has the molars of a fierce lion. (Joel 1:6)

...O Jehovah..., You have broken the teeth of the impious. (Psalms 3:7)

...a beast (came up from the sea), terrible, dreadful, and exceedingly strong, which had huge iron teeth; it was devouring and breaking in pieces... (Daniel 7:3, 7).

Blessed be Jehovah, who has not given us as prey to their teeth. (Psalms 124:6)

Since sensual people do not see any truth in its own light, but reason and argue about everything as to whether it is so, and since these altercations in the hells sound outside the hells like the gnashing of teeth, which regarded in itself is a colliding of falsity and truth, it is apparent what the gnashing of teeth symbolizes in Matthew 8:12; 13:42, 50; 22:13; 24:51; 25:30, and Luke 13:28; and in some measure what to gnash with the teeth symbolizes in Job 16:9, Psalms 35:15-16; 37:12; 112:10, Micah 3:5, and Lamentations 2:16.