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)

5071. The reason why the expression 'cursed' is used of those on the left and why their punishment is called 'eternal fire' in the following statements -'Then He will also say to those on the left, Depart from Me, O cursed ones, into eternal fire prepared for the devil and his angels' and 'these will go away into eternal punishment' - is that they have turned away from good and truth and have turned towards evil and falsity. 'Cursing' in the internal sense of the Word means a turning away, 245, 379, 1427, 3570, 3584. The eternal fire into which they were to depart is not material fire, nor is it a tormented conscience, but a craving for evil. For cravings like this in a person are spiritual fires which consume him during the life of the body and torment him in the next life. Because of these fires burning within them, the inhabitants of hell use dreadful methods to torture one another.

[2] Eternal fire is clearly not material fire; and the reason it is not a tormented conscience is that none who are governed by evil have any conscience; and those who have had no conscience during their lifetime cannot have any in the next life. But the reason eternal fire is a craving is that the entire fire of life in a person is fuelled by his loves, a heavenly fire by the love of what is good and true, a hellish fire by the love of what is evil and false. Or what amounts to the same, a heavenly fire is fuelled by love to the Lord and love towards the neighbour, and a hellish fire by self-love and love of the world. Anyone can see, if he stops to think, that all the fire or heat burning within a person is fuelled by his loves. This also explains why love is called spiritual heat and why in the Word fire and heat have no other meaning, 934 (end), 1297, 1527, 1528, 1861, 2446, 4906. The fire of life in the evil is also such that when they feel very strong cravings, a kind of fire is also burning in them, which inflames them with an intense and furious desire to torment others. But the fire of life in the good is such that when a higher level of affection exists with them, a kind of fire is alight in them too. But this fire inflames them with a loving and zealous desire to do good to others.