Author's Notes: Because I obviously have no self-control and couldn't stop mentally picturing this scene, I whipped this up real quick. Inspired by a text post by edwwardelric on tumblr.

Disclaimer: None of this is mine, not even the idea.

Out with the Old

Nudging gently with the tip of his tongue, Ed assessed with the damage done to his tooth. It had been bordering on wobbly for the better part of the past few days, hindering his ability to eat certain foods at worst and sparking sharp flares of pain when he least expected it. The thing had been irritating and distracting, but there had been little he could do about it beyond waiting. Besides, it wasn't that painful, he reasoned; he'd been through a lot worse. He could manage to tough it out.

It probably hadn't helped matters that he'd gotten into it with some ruffians trying to extort a small town alchemist and managed to get punched right in the jaw. How the asshole hadn't managed to knock the loose tooth right out of Ed's mouth was both mystifying and frustrating. Now the damn thing just seemed to be hanging by a thread, a silent mocking reminder of his childhood.

After all, Ed was on the cusp of losing the last of his baby teeth, and he wanted it gone. He was a State Alchemist now, a Major in the Amestris military, for Truth's sake. He couldn't have any baby teeth. That was absurd. He was an adult. The stupid tooth was the line between him being a kid and him being a man.

Presently, Ed was rather distracted prodding the loose tooth with his tongue to really pay attention to what was going on around him. He stood there, eyes not entirely focused on what was before him, trying to get a feel for the tooth without flinching whenever he hit a nerve, hands hung loosely at his side. The accursed thing hurt worse than the shiner beginning to rim his left eye. It was so annoying, perhaps even more annoying that the asshat sitting in front of him.

"Fullmetal, are you even listening to me?"

Ed snapped his eyes back forward and pressed his tongue to the roof of his mouth. Colonel Mustang sat before him, casually leaning back in his plush chair and drumming his fingers on his desk. A bored expression hung on his face, betrayed by the hint of irritation in his eyes. The man had been talking seemingly non-stop while Ed tried to rid himself of the last vestiges of his childhood.

"Don't damage property; the building was about to fall down anyways. Don't get into fights that I can't handle – which I can, and Al was with me. The government isn't a cleaning service that fixes things whenever I make a mess; then you shouldn't use me as your street cleaning service. Be more careful. Blah, blah, blah. I heard you the first ten debriefings."

It took a small amount of willpower not to cringe when he spoke, as it managed to make the tooth wiggle a little more in his mouth. Why wouldn't the damn thing just come out? It had to be stubborn, of course. That last thread it was hanging onto so obstinately had to be the most sensitive nerve in his body. It reminded him of whenever Winry and Pinako connected his automail to his nerves – basically not fun at all.

"If you're going to act like a petulant child, Fullmetal, then I'm going to treat you like one." Mustang narrowed his dark eyes at him. "Am I going to have to ground you? I can't imagine you'd be good behind a desk, but if that's what it takes to curb your destructive temper tantrums and juvenile behavior in the field, I'll pass down the order."

"You're my commanding officer, not my dad," Ed snapped. "And I'm not a child!"

The tooth flared in pain seemingly in response. His own body was betraying him. He almost growled.

"You're twelve years-old," Mustang responded. The man had wondered out loud on more than one occasion if it had been a mistake to bring someone so young into the military. Not for any moral reasons, of course. He just didn't think that Ed had a mature enough temperament to be a military officer. That always managed to rile Ed up.

"I'm an alchemy prodigy," Ed shot back. The truth was, no matter his age, the military would never have let Ed go due to his skills, and Mustang had known that, hence why he'd been the one to recruit Ed so quickly.

Mustang scoffed and leaned forward, peering at him closely. There was a hint of a smirk on his face. "You probably haven't lost all your baby teeth yet. State Alchemist or not, you're still a child."

Positively seething, Ed gripped his hands into fists at his side, damn near trembling. There was no way the asshole could have known what Ed was suffering through right now, and yet Mustang struck a nerve as painful as the one in his mouth. If he hadn't known Ed's plight then, Mustang certainly did now, a light of smug recognition gleaming in his eyes as he leaned back in his seat.

Well, Ed couldn't handle that.

Somehow summoning all the power that rage could give him, Ed shoved his fingers into his mouth. It helped using his automail hand, as he couldn't feel the tooth and flinch away with his flesh one. Growling awkwardly around his hand and cursing the blasted thing to high hell and back alongside Mustang, Ed yanked as hard as he could on the tooth, pulling it right out. It hurt almost worse than when he'd been punched in the face and it had been knocked loose. A bit of blood spurted out onto his white glove as well. But the sharp pain slowly began to fade away as triumphant relief began to flood into him.

Ed held his last baby tooth high in the air for one second, announcing his victory to the room, before chucking it with all his strength at Mustang.

The Colonel just barely managed to dodge it, ducking to the side in a quick flash that looked suspiciously practiced. He probably had a lot of things thrown at him by scorned women that he used or something. The man somehow managed to look affronted when he sat back up straight in his seat.

"There, you bastard!" Ed proclaimed, pointing a finger at him and baring his teeth at the other man like he was some sort of animal. "I'm not a kid anymore!"

Mustang glanced down at where the tooth sat on the floor, then back up at Ed. A rather thoughtful expression crossed his face, only to turn into a full blown smirk. "Why, Fullmetal, you look so threatening with that gap-toothed smile."

Clamping his mouth shut, Ed slid his tongue around and right through the small gap where the wobbly tooth had once been. It was right in the front of his mouth on this bottom jaw. Until the other tooth grew in, he would be left with a gap. Mustang's implication was horribly correct. Ed was going to look like some adorable…child until the last of his adult teeth grew in.

Letting out a frustrated yell, Ed threw his hands in the air, turned on his heels, and stormed out of the office. Everyone on Mustang's team, save for Lieutenant Hawkeye, looked a little nervous. Even Al in his suit of armor managed to appear anxious, rattling about as he stood up.

"Everything okay, boss?" Second Lieutenant Havoc asked as he swiveled around in his chair.

Ed merely grunted in response. He didn't want to admit that he was terrified of opening his mouth to say anything, lest any of the men see the offending gap in his teeth. He liked these guys well enough and thought that they could possibly be trusted, but the few times he'd crossed paths with men in the military, they weren't exactly friendly to a kid who they thought was an up-jumped alchemy nerd.

"It seems as if our Edward Elric is one step closer to being a man today," Mustang declared from the doorway of his office. Ed jerked around to see the smug bastard leaning against the threshold, holding up Ed's tooth in his fingers. He froze on the spot and glowered. The other men blinked in confusion. "You sure you don't want this, Fullmetal? I hear if you put it under the pillow, the Tooth Fairy will give you money. You might need that to pay for your mess in the Clarkstown village if the government doesn't cover it."

"You're going to need the money when I bust your perfect teeth!" Ed exclaimed, waving a fist at him.

"Such a frightening sight." Mustang smiled.

Hawkeye sighed. "Sir, could you possibly refrain from harassing Edward? It's immature."

Mustang cast her a hurt look. Ed stuck his tongue out at him.

"Oh, Brother, you lost your last baby tooth!" Al clapped his hands together. "That's good news. Now you can eat again without being in pain."

No, it was most certainly not childish of Ed to chase his little brother out of the office and through the hallways of the Eastern military headquarters, not with Mustang calling out after him to turn in his revised report on the morrow and not to use alchemy to fight Al. Adults had disagreements all the time and with that stupid tooth gone, Ed was officially an adult.