title: Synergic effect of salivary pH baselines and low pH intakes on the force relaxation of orthodontic latex elastics.
abstract: BACKGROUND
  Latex elastics are still in common use due to their low cost and high flexibility to improve sagittal discrepancies or interdigitation of teeth. Mechanical properties of elastics are influenced by several environmental factors such as pH changes. This study evaluated similar latex elastics to define the influence of synergic effect of intermittent low pH and various baselines pH of saliva.
  
  
  METHODS
  Four groups of latex elastics (3-M Unitek, 3/16 inch) were tested (n= 15 in each group). Two groups of elastics were immersed in two tanks of artificial saliva with different pH levels of 7 and 5, and two groups were immersed in two tanks of artificial saliva with intermittent drop of pH to 4. The force was measured when the elastics were stretched to 25 mm. These measurements were taken in 0, 4, 8, 12, 24, 36, and 48 h for each group. Repeated measures analysis of variance (RMANOVA) andpost-hocTukey's test were used to assess the findings. The level of significance was 0.05%.
  
  
  RESULTS
  The interaction between pH and time analyzed with RMANOVA showed no significant differences (P> 0.05) except in 36 h (P= 0.014). The Tukey's analysis showed that each comparison between any two groups did not indicate significant differences (P> 0.05) except between Groups 1 and 3 and between Groups 2 and 3 (P< 0.05).
  
  
  CONCLUSIONS
  No significant correlation was seen between fluctuation of pH and force degradation in latex elastic band except in 36 h.
authors.affiliation: Department of Orthodontics, Orthodontic Research Center, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Shabnam
authors.initials: S
authors.lastname: Ajami
authors.affiliation: Department of Orthodontics, Orthodontic Research Center, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Amin
authors.initials: A
authors.lastname: Farjood
authors.affiliation: Department of Orthodontics, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Mahbubeh
authors.initials: M
authors.lastname: Zare
keywords: Orthodontic appliances; latex; orthodontic