title: Evaluation of resistance to displacement of metal posts with different lengths.
abstract: OBJECTIVE
  to evaluate the resistance to displacement of metal intraradicular retainers of different lengths by means of the shear test.
  
  
  METHODS
  Thirty-six maxillary central incisors were cross-sectioned at 16 mm from the root apex, endodontically treated and randomly divided into three groups that were treated as follows: G1 (control) preparation of 2/3 (10.6 mm) of the total root length; G2: preparation of 1/2 (8 mm) of the total root length and G3: preparation of 1/3 (5.3 mm) of the total root length. After canal preparation, a matrix was made of the coronal and radicular portions using Duralay to obtain metal intraradicular retainers. These retainers were cemented with zinc phosphate cement and subjected to the compression shear test in a Universal Test Machine (EMIC DL 2000) at a crosshead speed of 0.5 mm/minute. The results were subjected to statistical analysis by analysis of variance (ANOVA) and Newman- Keuls, which showed statistically significant difference (P < 0.01).
  
  
  RESULTS
  The means in Newtons and their respective standard deviations were: G1 = 972.05 (±81.36); G2 = 921.15 (±112.25); G3 = 686.66 (±113.02).
  
  
  CONCLUSIONS
  It could be concluded that metal retainers of 2/3 and 1/2 the length of the root portion showed higher resistance to displacement values when compared with the group that had been prepared for 1/3 of the root length.
authors: Department of Restorative Dentistry, Piracicaba Dental School, State University of Campinas, Piracicaba, Brazil.
authors: Ana Paula
authors: AP
authors: Farina
authors: Doglas
authors: D
authors: Cecchin
authors: Aloisio Oro
authors: AO
authors: Spazzin
authors: Fernanda de Carvalho Panzeri
authors: Fde C
authors: Pires-de-Souza
authors: Nereu Roque
authors: NR
authors: Dartora
authors: Marcelo Ferraz
authors: MF
authors: Mesquita
mesh_terms: D002484:Cementation / Q000379:methods; D003722:Dental Alloys / Q000737:chemistry*; D017267:Dental Prosthesis Design; D017268:Dental Prosthesis Retention; D003786:Dental Pulp Cavity / Q000473:pathology; D003799:Dental Stress Analysis / Q000295:instrumentation; D006801:Humans; D007180:Incisor / Q000473:pathology; D008422:Materials Testing; D011176:Post and Core Technique / Q000295:instrumentation*; D018915:Root Canal Preparation / Q000379:methods; D013314:Stress, Mechanical; D019553:Tooth, Nonvital / Q000628:therapy; D015036:Zinc Phosphate Cement / Q000737:chemistry
chemical_list: D003722:Dental Alloys; D015036:Zinc Phosphate Cement