It really seems to me that dentists guess whether one needs clindamycin or amoxicillin for infection. why no bacterial testing done to really know?

Protocol: Antibiotic therapy follows a time tested methodology to eradicate dental infections. The usual antibiotics that are used almost always work. A culture takes time and costs money and is used when traditions methods are not effective. It's just not necessary for the average tooth infection, no more than a CAT scan is necessary for every ache and pain.