*2.5. Microbiological Processing by Means of Next Generation Sequencing*

A randomly selected group of samples, from 50 subjects, 25 with periodontitis a 25 with periodontal health, were processed by means of Illumina® Sequencing (Illumina, San Diego, CA, USA) and the results have been published in a separate article [36].

## *2.6. Statistical Analysis*
