Basically, he misdiagnosed a simple issue, and when he finally figured it out, he did poor, incomplete work to fix it. In the end, I lost a tooth and thousands of dollars.
I needed multiple visits to solve a problem he essentially caused through incompetence. All the while, his staff was giving me mistaken information about insurance coverage, and I spent an unnecessary fortune on an issue he wasn't even talented enough to fix.
When he realized how badly he'd screwed up, he was clearly worried I'd claim malpractice, and turned from "Mr. Friendly" to "Mr. Icy."
The problem was not "solved" until I went to another dentist, who described Yap's shoddy work and warned me I'd eventually lose the tooth because Yap had weakened it so much. It's a few years later, and the tooth just had to be pulled.
Some people on this site like him, and I can see why; he has a big ego, a deep confident voice, a salesmen's style of persuasion, and he makes his staff behave in a very polite and proper way. The problem is that he and his staff are error-prone mediocrities.
I'm not litigious, but I wish I'd sued. His incompetence not only cost me money and a tooth, but pain, suffering, time, and worry, but the whole time, he only cared about himself.
Front desk:
Hygiene rating:
I know this doctor: 5 years
out of 
