A method for the patient- and site-specific assessment of microbial imbalances in periodontitis building on clinical and demographic parameters, comprising the steps of • identification and quantification of bacterial species using genetic workflows in samples obtained from periodontal pockets or saliva; • calculation of a microbial profile based on the quantity of one or several bacterial species associated with periodontitis or a ratio of the quantities of these bacteria; • using a reference database, modelling of the microbial profile as a function of a selection of relevant clinical and demographical parameters; • using a set of clinical and demographical parameters from a patient, calculation of the predicted value of the microbial profile via the aforesaid model; • comparison of the microbial profile between the predicted value and the patient value obtained in the laboratory to assess the relative imbalance of the local microbiome and based on this, recommend a site and/or patient-specific therapy, wherein said clinical information includes • local factors: pocket depth of the sampled site, bleeding-on-probing, tooth type, therapy stage selected from untreated, in active therapy and in supportive therapy, • systemic factors smoking status as well as diabetes status, said demographic information includes • age, • gender, and • optionally race and ethnicity, and wherein for modelling of the microbial profile, a linear mixed-effect model is used, which is based on molecular and clinical data from a reference database, wherein the model includes the microbial profile as the response variable and clinical parameters including pocket depth as explanatory variables. • identification and quantification of bacterial species using genetic workflows in samples obtained from periodontal pockets or saliva; • calculation of a microbial profile based on the quantity of one or several bacterial species associated with periodontitis or a ratio of the quantities of these bacteria; • using a reference database, modelling of the microbial profile as a function of a selection of relevant clinical and demographical parameters; • using a set of clinical and demographical parameters from a patient, calculation of the predicted value of the microbial profile via the aforesaid model; • comparison of the microbial profile between the predicted value and the patient value obtained in the laboratory to assess the relative imbalance of the local microbiome and based on this, recommend a site and/or patient-specific therapy, wherein said clinical information includes • local factors: pocket depth of the sampled site, bleeding-on-probing, tooth type, therapy stage selected from untreated, in active therapy and in supportive therapy, • systemic factors smoking status as well as diabetes status, • local factors: pocket depth of the sampled site, bleeding-on-probing, tooth type, therapy stage selected from untreated, in active therapy and in supportive therapy, • systemic factors smoking status as well as diabetes status, said demographic information includes • age, • gender, and • optionally race and ethnicity, • age, • gender, and • optionally race and ethnicity, and wherein for modelling of the microbial profile, a linear mixed-effect model is used, which is based on molecular and clinical data from a reference database, wherein the model includes the microbial profile as the response variable and clinical parameters including pocket depth as explanatory variables. <EOS>