Treponema denticola is easily missed in a direct stain of a tooth or gum scraping because the cells are distorted by the staining procedure. Why can this bacterium be seen with negative staining?

Negative staining is a technique used to stain the micro-organism and their structure using the negative stain.

In negative stain, the samples are not stained but the background of the specimen is stained with the negative dyes like India ink and nigrosin.

When viewed under the microscope, the background appears dark and the samples appear white.

The principle behind this technique is that the bacteria surfaces are usually negatively charged and the dyes are acidic in nature which upon dissociation attains negative charge on themselves. the negative charge of the bacterial surface repels each other and the bacteria appear white.