title: Effect of acetyl resin retentive arms on the retentive force of circumferential clasps: an in vitro study.
abstract: OBJECTIVE
  To compare and to evaluate the stability of the retentive force of cobalt-chromium (Co-Cr) circumferential clasps (control) to those with an acetyl resin retentive arm.
  
  
  METHODS
  Sixteen specimens with a couple of circumferential clasps were made using Co-Cr over a metal model providing 0.25 mm undercuts. Eight specimens were fabricated without the anterior retentive arm, which was made later using acetyl resin (Dental D). Insertion and removal simulation test was performed through 7250 cycles. The retentive force was recorded in Newtons (N) for periods corresponding to 0, 1, 2, 3, 4, and 5 years. The data were subjected to ANOVA and Tukey test to compare periods and to Student's t test to compare groups (α=0.05).
  
  
  RESULTS
  Mean (SD) is presented for Co-Cr and resin groups, respectively: 8.09(3.05) and 2.79(1.57) in period 0; 10.48(4.25) and 3.32(1.92) in 1 year; 10.09(4.15) and 3.47(1.81) in 2 years; 9.87(4.30) and 3.46(1.87) in 3 years; 9.46(3.93) and 3.27(1.59) in 4 years; 9.63(3.79) and 3.41(1.59) in 5 years. There were significant differences for Co-Cr between periods of 0 and 1 (p<0.001), 0 and 2 (p<0.01) and 0 and 3 (p<0.05). In the resin group, no significant differences were found between periods (p>0.05). Comparisons between the groups showed statistical differences for all tested periods: 0 (p=0.0012), 1 (p=0.0013), 2 (p=0.0019), 3 (p=0.0031), 4 (p=0.0027) and 5 years (p=0.0014).
  
  
  CONCLUSIONS
  Acetyl resin retentive arms, even if only in the anterior clasps, can significantly reduce the retentive force, but this force remained stable after 5 years of simulated use.
authors: Department of Stomatological Sciences, School of Dentistry, Federal University of Goiás, Goiânia, GO, Brazil.
authors: Érica Miranda
authors: ÉM
authors: de Torres
authors: Iane Inarde
authors: II
authors: de Siqueira Damasceno
authors: Bruna Aguiar
authors: BA
authors: do Amaral
authors: Renata Cristina Silveira
authors: RC
authors: Rodrigues
authors: Adriana da Fonte Porto
authors: Ada F
authors: Carreiro
authors: Ricardo Faria
authors: RF
authors: Ribeiro
mesh_terms: D002858:Chromium Alloys; D016734:Dental Clasps; D003779:Denture Design; D003781:Denture Retention; D003832:Denture, Partial, Removable; D012117:Resins, Synthetic
chemical_list: D002858:Chromium Alloys; D012117:Resins, Synthetic