title: Factors influencing the removal of posts.
abstract: Root canal retreatment in teeth restored with intraradicular posts has attracted interest due to the difficulties of their removal without weakening, perforating or fracturing the remaining root structure. The use of ultrasonic devices has been suggested by some authors to facilitate post removal, reducing the possibility of fractures or root perforations. The purpose of this study was to determine the efficacy of cast posts removal by ultrasonic device regarding post length, adaptation of post to root canal walls and cement type.
  
  
  METHODS
  Seventy-seven single rooted endodontically treated teeth restored with cast posts were included to this study. Post removal was processed with ultrasonic and time for this was recorded. The length and width of the post, quality of post adaptation, type of cement were evaluated according to radiographic findings and clinical records.
  
  
  RESULTS
  Mean value of time needed for post removal was 14.15 (SD +/- 8.57) minutes. A strong correlation was observed between the time of post removal and post length (r=0.620, p=0.000). The mean time required for the removal of posts cemented with zinc phosphate was 11.36 min (SD +/- 5.84) and for the posts cemented with resin modified glass-ionomer was 15.37 min (SD +/- 3.83). Statistically significant difference in the time needed for the posts cemented with different cements was observed (p = 0.002). The mean time needed for the post removal with the inappropriate adaptation was 10.1 min (SD +/- 6.0) and the time for the post with appropriate adaptation was 15.7 min (SD +/- 8.9). Statistically significant difference between these two groups was observed for the time of posts removal (p = 0.003). According to the results of linear regression model test, 50% of variation in time needed to remove posts was explained by following variables: post length, post adaptation and the cement type. The total regression model was highly significant (p = 0.000).
  
  
  CONCLUSIONS
  The time taken for post removal depended on post length, its adaptation in the root canal and on the type of luting cement. Root fractures are unlikely to occur with good case selection.
authors.affiliation: Institute of Odontology, Faculty of Medicine, Vilnius University, Zalgirio 115, Vilnius, Lithuania.
authors.forename: Vytaute
authors.initials: V
authors.lastname: Peciuliene
authors.forename: Jurate
authors.initials: J
authors.lastname: Rimkuviene
authors.forename: Rasmute
authors.initials: R
authors.lastname: Maneliene
authors.forename: Rolandas
authors.initials: R
authors.lastname: Pletkus
mesh_terms: D017267:Dental Prosthesis Design; D020878:Device Removal / Q000295:instrumentation*; D005899:Glass Ionomer Cements; D006801:Humans; D016014:Linear Models; D011076:Polycarboxylate Cement; D011176:Post and Core Technique; D019279:Resin Cements; D019233:Retreatment; D012390:Root Canal Therapy; D013997:Time Factors; D014465:Ultrasonics; D015036:Zinc Phosphate Cement
chemical_list: D005899:Glass Ionomer Cements; D011076:Polycarboxylate Cement; D019279:Resin Cements; D015036:Zinc Phosphate Cement