title: Retention and stress distribution in distal extension removable partial dentures with and without implant association.
abstract: OBJECTIVE
  The present study aimed to evaluate the retention and stress distribution of conventional (C) RPD and compare to RPD associated to implant for support (IS) and retention (IR).
  
  
  METHODS
  Frameworks were cast from cp Ti (n=18) and Co-Cr alloy (n=18) by plasma and injected by vacuum-pressure. Conventional RPDs were compared to implant associated RPDs using a distal implant to support (IS) or to support and retain (IR) RPD. The specimens were subjected to insertion/removal cycles simulating 5 years of use and the retention force (N) was measured or evaluated. A mixed linear model was used to analyze the data (α=0.05). Photoelastic models were qualitatively examined for stress when an occlusal load of 15 kgf was applied over support teeth and RPD.
  
  
  RESULTS
  Retention force of IR RPDs is greater than IS and C RPDs for both cp Ti and Co-Cr alloy specimens. Retention force of cp Ti RPDs increased initially and was maintained throughout 5 years of simulation test while Co-Cr RPDs presented a decrease at the beginning of the test and had their retention force maintained throughout the test. Implant placement at residual alveolar ridge decreased stress around teeth, mainly in the first premolar. Stress concentration in the IS RPD is slightly greater than in the IR RPD.
  
  
  CONCLUSIONS
  The results suggest that implant placement at the distal extension improves retention and stress distribution of RPDs.
authors.affiliation: Department of Dental Materials and Prosthodontics, Dental School of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, Brazil. renata@forp.usp.br
authors.forename: Renata Cristina Silveira
authors.initials: RC
authors.lastname: Rodrigues
authors.forename: Adriana Cláudia Lapria
authors.initials: AC
authors.lastname: Faria
authors.forename: Ana Paula
authors.initials: AP
authors.lastname: Macedo
authors.forename: Maria da Gloria Chiarello
authors.initials: Mda G
authors.lastname: de Mattos
authors.forename: Ricardo Faria
authors.initials: RF
authors.lastname: Ribeiro
mesh_terms: D015921:Dental Implants; D003781:Denture Retention; D003832:Denture, Partial, Removable; D013314:Stress, Mechanical
chemical_list: D015921:Dental Implants