Howard accidentally revealed he has gay sex?

On the show last week Howard was recounting a story how he went to the dentist and they were able to tell he recently had given oral sex....

I'm not one to question Howard's sexuality, but I was under the impression that dentists are able to tell this only when it involves giving fellatio? Something about the penis hitting the soft palette of your mouth or something?

No judgement, but did Howard just inadvertently reveal something he didn't mean to?