title: [Influence of retention-form design on the retention of resin-bonded fixed partial dentures].
abstract: OBJECTIVE
  To evaluate the influence of retention-form design of resin bonded fixed partial dentures (RBFPDs).
  
  
  METHODS
  Forty-five metal replicas of posterior metal RBFPDs were divided into 3 groups(n=15):C shape(control group), C shape + axial groove, C shape + pin hole. All the replicas were luted with Panavia F cement and subgroup of 5 specimens were subject to 70 N compressive load cycling for 0 cycles, 240,000 cycles , and 1,200,000 cycles respectively .Half of the cycles was on the central fossa of the pontics and half on the buccal inclined surface of the lingual cusp. Forces for dislodgment of the specimens were applied along the long axis of the abutment at a cross head speed of 1.0 mm /min. The separation forces were recorded as maximum retention force at the time of dislodgement.
  
  
  RESULTS
  Separation forces of the C shape group (566.82+/-71.59 N)<axial groove group(656.07+/-137.29 N)<C shape + pin hole group (791.40+/-141.22 N) without compress load cycling . After 240,000 cycles, C shape group (539.37+/- 88.26 N) <axial groove group(599.19+/-82.38 N) <C shape + pin hole group (710.98+/-165.73 N). After 1 200 000 cycles, axial groove group(307.93+/-46.09 N) <C shape group (365.79+/-61.78 N) <C shape + pin hole group (505.04+/-125.53 N). The mean retention force was related to the design of the retention force and the fatigue cycles(P<0.001). When the fatigue cycles factor was controlled, separation force of the C shape + pin hole was greater than C shape + axial groove group and C shape group(P<0.05). The difference of C shape + axial groove group and C shape group was not significant (P>0.05). After 1,200,000 cycles, the retention force of the RBFPDs decreased significantly (P<0.001).
  
  
  CONCLUSIONS
  To compare with axial groove, the design of pinhole retention form was conduced to the improvement of the retention force and durability of RBFPDs.
authors.affiliation: Department of Prosthodontic, Peking University School and Hospital of Stomatology, Beijing 100081, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Yang
authors.forename: Ya Dong
authors.initials: YD
authors.lastname: Yang
authors.forename: Hai Lan
authors.initials: HL
authors.lastname: Feng
mesh_terms: D001840:Dental Bonding; D003738:Dental Cements; D003799:Dental Stress Analysis; D016379:Denture, Partial, Fixed, Resin-Bonded; D006801:Humans
chemical_list: D003738:Dental Cements