title: Noise rich in low frequency components, a new comorbidity for periodontal disease? An experimental study.
abstract: BACKGROUND
  Exposure to noise rich in low frequency components induces abnormal proliferation of extracellular matrix and collagens. The previous studies have shown alterations in the periodontium of both humans and animals. Our objective was the evaluation of collagens I, IV and V of the periodontium of Wistar rats exposed to noise rich in low frequency components.
  
  
  METHODS
  5 groups (each with 10 animals) were exposed to continuous low frequency noise (LFN). The LFN, from previously recorded white noise, frequency filtered and amplified, was applied in growing periods of 1, 3, 5, 9 and 13 weeks, in order to characterize the alterations with exposure time. A control group of ten animals was kept in silence. These animals were used in groups of 2 as aged-matched controls. After exposure, sections were obtained including teeth, alveolar bone and periodontium and observed after immunollabeling for collagens I, IV and V.
  
  
  RESULTS
  A significant increase in collagen I was observed in exposed groups (P < 0.001) (Kruskal-Wallis test). Post-hoc comparisons (Mann-Whitney test with Bonferroni correction) showed an increase in collagen I in animals exposed for 3 weeks or more (P < 0.001). The same test was applied to collagen V where significant differences were found when comparing control and exposed groups (P ≤ 0.004). The t-test for independent samples was applied to collagen type IV where no significant differences were found (P = 0.410), when comparing to the control group.
  
  
  CONCLUSIONS
  As in other organs, we can observe fibrosis and the newly formed collagen is likely to be "nonfunctional", which could have clinical impact.
  
  
  CONCLUSIONS
  Noise may constitute a new comorbidity for periodontal disease.
authors.affiliation: Center for Interdisciplinary Research Egas Moniz, CiiEM, Portugal.
authors.forename: José João Baltazar
authors.initials: JJ
authors.lastname: Mendes
authors.affiliation: Center for Interdisciplinary Research Egas Moniz, CiiEM, Portugal.
authors.forename: Pedro Miguel Antunes
authors.initials: PM
authors.lastname: Oliveira
authors.affiliation: Center for Interdisciplinary Research Egas Moniz, CiiEM, Portugal.
authors.forename: José Américo Almeida
authors.initials: JA
authors.lastname: de Brito
authors.affiliation: Abel Salazar Biomedical Sciences Institute, Portugal.
authors.forename: Artur Manuel Perez
authors.initials: AM
authors.lastname: Neves Águas
authors.affiliation: Center for Interdisciplinary Research Egas Moniz, CiiEM, Portugal.
authors.forename: José António Mesquita
authors.initials: JA
authors.lastname: Martins Dos Santos
keywords: Fibrosis; low frequency noise; periodontal disease; periodontium