title: Degradation of trans-polyisoprene over time following the analysis of root fillings removed during conventional retreatment.
abstract: OBJECTIVE
  To evaluate in vivo degradation of root filling materials over time.
  
  
  METHODS
  Thirty-six root filled teeth with or without periapical lesions were selected. Teeth with poor coronal restoration were not included. The teeth had been root filled 3-30 years previous and were scheduled for conventional retreatment. The association of root canal treatment, age, periapical lesion and root filling degradation was investigated. The filling material was removed from the root canal using files and no solvent. Trans-1,4-polyisoprene was isolated through solubilization of root filling remnants in chloroform followed by filtration and centrifugation. Gel permeation chromatography (GPC) and infrared spectroscopy (FT-IR) were utilized to study the occurrence and degree of degradation. The GPC and FT-IR data were collected for each sample and analysed statistically using the Kruskal-Wallis test.
  
  
  RESULTS
  Degradation of trans-1,4-polyisoprene was a slow process. The process was identified as an oxidation reaction through the production of carboxyl and hydroxyl groups. Compared with the control group, significant molar mass decrease was noted after 15 years (P = 0.0146) in teeth with no periapical lesions. However, in teeth associated with periapical lesions the number of years for significant degradation was reduced to 5 (P = 0.0009).
  
  
  CONCLUSIONS
  Polyisoprene degrades inside root canals as an oxidative process. The presence of periapical lesions was associated with a more rapid onset of degradation.
authors.affiliation: Department of Endodontics, University of Fortaleza, Fortaleza, Brazil. manigliaf@secrel.com.br
authors.forename: C
authors.initials: C
authors.lastname: Maniglia-Ferreira
authors.forename: J B A
authors.initials: JB
authors.lastname: Silva
authors.forename: R C M
authors.initials: RC
authors.lastname: de Paula
authors.forename: J P A
authors.initials: JP
authors.lastname: Feitosa
authors.forename: A A
authors.initials: AA
authors.lastname: Zaia
authors.forename: C C R
authors.initials: CC
authors.lastname: Ferraz
authors.forename: B P F A
authors.initials: BP
authors.lastname: Gomes
authors.forename: F J
authors.initials: FJ
authors.lastname: Souza-Filho
mesh_terms: D001711:Biotransformation; D002070:Butadienes / Q000737:chemistry*; D002850:Chromatography, Gel; D019232:Dental Restoration Failure; D006171:Gutta-Percha / Q000737:chemistry*; D045782:Hemiterpenes / Q000737:chemistry*; D006801:Humans; D010084:Oxidation-Reduction; D010420:Pentanes / Q000737:chemistry*; D010485:Periapical Periodontitis / Q000628:therapy; D019233:Retreatment; D012387:Root Canal Filling Materials / Q000737:chemistry*; D012389:Root Canal Obturation; D017550:Spectroscopy, Fourier Transform Infrared; D018709:Statistics, Nonparametric; D013997:Time Factors
chemical_list: D002070:Butadienes; D045782:Hemiterpenes; D010420:Pentanes; D012387:Root Canal Filling Materials; C005059:isoprene; D006171:Gutta-Percha