title: Influence of luting agents on time required for cast post removal by ultrasound: an in vitro study.
abstract: OBJECTIVE
  This in vitro study evaluated the influence of luting agents on ultrasonic vibration time for intraradicular cast post removal.
  
  
  METHODS
  After endodontic treatment, 30 roots of extracted human canines were embedded in resin cylinders. The post-holes were prepared at 10 mm depth and their impressions were taken using autopolymerizing acrylic resin. After casting procedures using a nickel-chromium alloy, the posts were randomly distributed into 3 groups (n=10) according to the luting material: G1- zinc phosphate (SS White) (control group), G2 - glass ionomer cement (Vidrion C; SS White), and G3- resin cement (C & B; Bisco). In G3, the adhesive procedure was performed before post cementation. After 24 h, the cement line was removed at the post/tooth interface using a fine diamond bur, and the ST-09 tip of an Enac ultrasound unit was applied at maximum power on all surfaces surrounding the posts. The application time was recorded with a chronometer until the post was completely dislodged and data were analyzed by ANOVA and Tukey's test (p<0.05).
  
  
  RESULTS
  The roots were removed from the acrylic resin and inspected to detect cracks and/or fractures. The means for G1, G2, and G3 were 168.5, 59.5, and 285 s, respectively, with statistically significant differences among them. Two G3 posts resisted removal, one of which developed a vertical fracture line.
  
  
  CONCLUSIONS
  Therefore, the cement type had a direct influence on the time required for ultrasonic post removal. Compared to the zinc phosphate and glass ionomer cements, the resin cement required a longer ultrasonic vibration time.
authors.affiliation: Department of Dentistry, Federal University of Valleys of Jequitinhonha and Mucuri, Diamantina, MG, Brazil.
authors.forename: Janir Alves
authors.initials: JA
authors.lastname: Soares
authors.forename: Manoel
authors.initials: M
authors.lastname: Brito-Júnior
authors.forename: Dimitri Ribas
authors.initials: DR
authors.lastname: Fonseca
authors.forename: Anielo Faleiro
authors.initials: AF
authors.lastname: Melo
authors.forename: Suelleng Maria Cunha
authors.initials: SM
authors.lastname: Santos
authors.forename: Nadia Del Carmen Soto
authors.initials: Ndel C
authors.lastname: Sotomayor
authors.forename: Neilor Mateus Antunes
authors.initials: NM
authors.lastname: Braga
authors.forename: André Luis
authors.initials: AL
authors.lastname: Faria e Silva
mesh_terms: D002858:Chromium Alloys; D003481:Cuspid; D017005:Dental Debonding / Q000379:methods; D003799:Dental Stress Analysis; D005899:Glass Ionomer Cements; D006801:Humans; D008422:Materials Testing; D011176:Post and Core Technique; D019279:Resin Cements; D013997:Time Factors; D014465:Ultrasonics; D014732:Vibration; D015036:Zinc Phosphate Cement
chemical_list: D002858:Chromium Alloys; D005899:Glass Ionomer Cements; D019279:Resin Cements; D015036:Zinc Phosphate Cement