title: Prognosis of double crown-retained removable dental prostheses compared with clasp-retained removable dental prostheses: A retrospective study.
abstract: OBJECTIVE
  The present study compared the clinical prognosis of double crown-retained removable dental prostheses (D-DRPs) with that of clasp-retained removable dental prostheses (C-RDPs).
  
  
  METHODS
  Clinical records of 201 patients who had received 52 D-RDPs with 144 abutment teeth (D-teeth) and 199 C-RDPs with 399 abutment teeth (C-teeth) at the Prosthetic Dentistry Clinic in Hokkaido University Hospital between April 2005 and June 2015 were analyzed. Survival and complication probabilities of the two types of prostheses and abutment teeth were evaluated using the Kaplan-Meier method and compared using the log-rank test. Cox regression analysis was used to determine the impact of covariates on abutment teeth survival and complications such as gender, age, type of retainer, Eichner classification, jaw, type of tooth, endodontic therapy performed, type of edentulous space, and presence of opposing teeth.
  
  
  RESULTS
  Statistical analysis showed no significant differences between the two types of prostheses in terms of prostheses survival, prostheses complication, and abutment teeth survival. However, a significant difference was observed for complications of abutment teeth. Decementation was the most frequent cause of failure, which occurred in 76.9% of D-teeth and 28.3% of C-teeth. Patient's age, jaw, endodontic therapy performed, and type of edentulous space affected the survival of abutment teeth, whereas the type of retainer and edentulous space affected complications of abutment teeth.
  
  
  CONCLUSIONS
  The prognosis of both types of prostheses was considered to be acceptable. Although D-RDP had lower complication-free rates for abutment teeth, most of the observed complications were decementation, which was considered to be reparable.
authors.affiliation: Department of Oral Functional Prosthodontics, Division of Oral Functional Science, Graduate School of Dental Medicine, Hokkaido University, Kita 13, Nishi 7, Kita-ku, Sapporo, 060-8586, Japan. Electronic address: ishikei@den.hokudai.ac.jp.
authors.forename: Keita
authors.initials: K
authors.lastname: Ishida
authors.affiliation: Clinical Research and Medical Innovation Center, Hokkaido University Hospital, Kita 14, Nishi 5, Kita-ku, Sapporo, 060-8648, Japan.
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Nogawa
authors.affiliation: Department of Oral Functional Prosthodontics, Division of Oral Functional Science, Graduate School of Dental Medicine, Hokkaido University, Kita 13, Nishi 7, Kita-ku, Sapporo, 060-8586, Japan.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Takayama
authors.affiliation: Department of Oral Functional Prosthodontics, Division of Oral Functional Science, Graduate School of Dental Medicine, Hokkaido University, Kita 13, Nishi 7, Kita-ku, Sapporo, 060-8586, Japan.
authors.forename: Masayasu
authors.initials: M
authors.lastname: Saito
authors.affiliation: Department of Oral Functional Prosthodontics, Division of Oral Functional Science, Graduate School of Dental Medicine, Hokkaido University, Kita 13, Nishi 7, Kita-ku, Sapporo, 060-8586, Japan.
authors.forename: Atsuro
authors.initials: A
authors.lastname: Yokoyama
mesh_terms: D000368:Aged; D003442:Crowns; D000044:Dental Abutments; D016734:Dental Clasps; D003832:Denture, Partial, Removable; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D012189:Retrospective Studies
keywords: Abutment teeth; Clasp; Clinical study; Dental prostheses; Double crowns