title: The bleeding site: a multi-level analysis of associated factors.
abstract: OBJECTIVE
  To evaluate the association between the probability of a sulcus/pocket to bleed on probing (BoP) and patient related as well as site-specific characteristics.
  
  
  METHODS
  Data from 88960 sites were retrospectively derived from the clinical record charts of 601 adult patients. BoP (positive/negative) had been recorded at the initial periodontal visit after probing pocket depth (PPD) assessment. To analyse the influence of patient-, tooth- and site-related factors on the probability for a site to be BoP+, a logistic, 3-level model was built with BoP as the binary outcome variable.
  
  
  RESULTS
  (i) The mean probability to be BoP+ for a site with PPD = 3 mm was 18%, and the log odds increased by 0.69 for each 1 mm increment in PPD; (ii) a significantly higher risk for BoP+ was observed for inter-proximal versus approximal surfaces, posterior teeth versus anterior teeth, females versus males, while a significantly lower risk was observed for smokers versus non-smokers; (iii) when controlling for the significant covariates, different BoP+ probabilities could still be observed among sites in patients with a different susceptibility to BoP.
  
  
  CONCLUSIONS
  The probability of a site to be BoP+ was associated with either site-specific (i.e. PPD, tooth aspect, tooth type) or patient-related factors (i.e. gender, smoking status).
authors.affiliation: Research Centre for the Study of Periodontal and Peri-Implant Diseases, University of Ferrara, Ferrara, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Farina
authors.forename: Cristiano
authors.initials: C
authors.lastname: Tomasi
authors.forename: Leonardo
authors.initials: L
authors.lastname: Trombelli
mesh_terms: D000328:Adult; D010520:Aggressive Periodontitis / Q000453:epidemiology; D000465:Algorithms; D055113:Chronic Periodontitis / Q000453:epidemiology; D015331:Cohort Studies; D048909:Diabetes Complications / Q000453:epidemiology; D004198:Disease Susceptibility / Q000453:epidemiology; D005260:Female; D005884:Gingival Hemorrhage / Q000453:epidemiology*; D005891:Gingivitis / Q000453:epidemiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010512:Periodontal Index; D010514:Periodontal Pocket / Q000453:epidemiology*; D015995:Prevalence; D011336:Probability; D012189:Retrospective Studies; D012307:Risk Factors; D012737:Sex Factors; D012907:Smoking / Q000453:epidemiology; D014070:Tooth / Q000473:pathology; D055815:Young Adult
keywords: gingival haemorrhage; gingival pocket; inflammation; periodontal disease; periodontal pocket