When Curt Lemon died, O'Brien found it difficult to be sad because he didn't know him well, and what he knew he didn't like all that much. Lemon played the role of the tough soldier, and often took it too far. He would pull off stunts, and once painted his whole body and wore a ghost mask and then went trick-or-treating to villagers on Halloween and wouldn't stop bragging about it after. O'Brien thought Lemon's opinion of himself was too high "for his own good." Or perhaps his opinion was too low, and that's what he was trying to change. O'Brien says it's easy to get sentimental about those who have died, so instead he'll tell a quick story about Lemon.
O'Brien remarks that it was difficult to mourn Curt Lemon's death because he didn't like him that much and felt like he was overcompensating for either low self esteem or puffing himself up with too big of an ego. But, with this line of thinking, O'Brien says that it would be easy to start waxing poetic about Lemon's good qualities, so instead it's better to tell a fast story that explains the kind of man Curt Lemon was.
In February, the Company worked in an area called the Rocket Pocket (called this because the enemy used it occasionally to launch rockets to the airfield in Chu Lai). For the Company, though, this stop was a two-week vacation: it was along the sea, felt like a resort outside, and it was quiet. One afternoon an Army dentist was sent in by the higher ups to check out everyone's teeth. He lectured everyone oral hygiene and then set up in a small tent where everyone had to go in for a personal exam. It wasn't a fancy set-up: battery-powered drill, canvas cot, bucket of seawater to rinse, a suitcase filled with different instruments. The dentist seemed only concerned with getting his duties done quickly.
The contrast between this place that is used by the enemy as a source for rockets to kill Americans versus how the American soldiers see it as a place akin to a resort shows how the landscape of war is so different for all parties involved. One man's area to fear death is another to feel at peace. But this peace has to be interrupted by bureaucracy—even in war it's mandated that the men all be seen by a dentist. It's darkly comic, because healthy teeth won't save you in battle.
As everyone sat waiting their turn, Curt Lemon began to get tense. Someone asked what was wrong, and he said in high school he'd had some bad experiences with dentists that he equated to torture. He didn't mind the blood and pain of combat, even enjoyed it, but dentists creeped him out. He said he wouldn't let anyone touch his teeth.
Even though Lemon is completely fine with the gore and death of combat, he can't handle someone else touching his teeth—which is a morbid, bizarre predisposition. He's more comfortable with shooting someone dead than seeing the dentist.
When Lemon was called in, though, he went. But he fainted before the dentist touched him. Four soldiers, O'Brien included, had to lift him up onto the cot. When he came around he looked shy, like he'd been caught doing something terrible. He refused to say anything to anyone.
Even though he says he won't let anyone touch his teeth, he follows orders and sees the dentist. When he faints and wakes up, he's immediately embarrassed and ashamed of how this will affect his macho reputation.
The rest of the day he sat alone beneath a tree, staring at the dentist's tent in a daze. Every once in a while, he could be heard cursing. O'Brien notes that others would have laughed it off, but it was "too much" for Lemon: "The embarrassment must've turned a screw in his head."
The shame and embarrassment start to drive Lemon up a wall, and he curses himself for his fear. The embarrassment becomes so much that he is compelled to act.
In the night, Lemon went to the dentist's tent and woke him up. He told him he had a horrible toothache. The dentist couldn't find anything wrong with Lemon, but Lemon insisted. Finally the dentist shot Lemon with Novocain and pulled out a completely healthy tooth. O'Brien says it was surely painful, but the next morning Lemon was "all smiles."
By getting a perfectly healthy tooth pulled, he feels he keeps his reputation intact and shows that he's brave up against anything. This eliminates his embarrassment, and he sees it as settling the score against himself after he fainted. That it is totally irrational doesn't matter.