title: Effect of clasp design on retention at different intervals using different abutment materials and in a simulated oral condition.
abstract: OBJECTIVE
  The purpose of this study was to compare the retention of circlet (E) clasps and back-action clasps against three abutment surface materials during long-term simulation of attachment and detachment.
  
  
  METHODS
  Forty-eight test models were constructed by placing premolars (natural abutments or metal dies) inside metal blocks to test different abutment retention surface materials (sound enamel, composite resin, and glass-ceramic; 16 each). The models were duplicated into investment models for construction of circlet (E) and back-action clasps. Removal and insertion cycling of clasps was carried out for 250, 500, 1000, 2000, 4000, 8000, and 16,000 cycles. The retention of each clasp was measured before cycling and after each interval. Data were analyzed using 1-way-ANOVA, 2-way-ANOVA, and Mann-Whitney U tests.
  
  
  RESULTS
  No significant differences in retention of either clasp were found between the three abutment material surfaces; however, there was a significant decrease in retention force of the circlet (E) clasp between 1000 and 2000 cycles but not of the back-action clasp.
  
  
  CONCLUSIONS
  (1) The back-action clasp maintains its retention force for a longer period than the circlet (E) clasp. (2) Composite resin contouring of teeth provided retention comparable to enamel and a ceramic material.
authors.affiliation: Department of Oral and Maxillofacial Rehabilitation, King Abdulaziz University, Faculty of Dentistry, Jeddah, Saudi Arabia; Department of Prosthodontics, Al Azhar University, Faculty of Dentistry, Cairo, Egypt.
authors.forename: Mohamed A
authors.initials: MA
authors.lastname: Helal
authors.forename: Osama A
authors.initials: OA
authors.lastname: Baraka
authors.forename: Mohamed E
authors.initials: ME
authors.lastname: Sanad
authors.forename: Yasser
authors.initials: Y
authors.lastname: Al-Khiary
authors.forename: Klaus
authors.initials: K
authors.lastname: Ludwig
authors.forename: Matthias
authors.initials: M
authors.lastname: Kern
mesh_terms: D002516:Ceramics / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D017076:Computer-Aided Design; D000044:Dental Abutments; D016734:Dental Clasps / Q000145:classification; D003743:Dental Enamel / Q000033:anatomy & histology; D003764:Dental Materials / Q000737:chemistry*; D017267:Dental Prosthesis Design; D017268:Dental Prosthesis Retention / Q000295:instrumentation*; D003799:Dental Stress Analysis / Q000295:instrumentation; D006801:Humans; D008422:Materials Testing; D013314:Stress, Mechanical; D013499:Surface Properties
chemical_list: D003188:Composite Resins; D003764:Dental Materials; C420128:Spectrum composite resin; C023506:Glass ceramics
keywords: CAD/CAM; Clasp; ceramic; composite; enamel; retention