title: An in vitro assessment of circumferential grooves on the retention of cement-retained implant-supported crowns.
abstract: BACKGROUND
  Crowns cemented on short implant abutments may have insufficient retention.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the effect of circumferential grooves on the retention of cemented cast copings on implant abutments.
  
  
  METHODS
  Sixty similarly-shaped implant abutments were divided into 4 groups (n=15): without grooves, with 1 groove, with 2 grooves, and with 3 grooves. Fifteen identical NiCr cast copings were prepared to fit all 60 abutments. The castings were cemented to each group of abutments with a noneugenol provisional cement (Tempbond NE) and a zinc phosphate cement (Harvard). After thermal cycling and storage for 6 days in a water bath, retention tests were conducted with a tensile testing machine (Instron) (5 mm/min) and retentive forces were recorded. Data were subjected to 1 way-ANOVA, Tukey's (HSD) test, and repeated measures ANOVA (α=.05).
  
  
  RESULTS
  For the noneugenol temporary cement, group retention values were increased according to the number of grooves (P<.001). For the zinc phosphate cement, the first groove increased the retention by approximately 60% (P<.001). The retentive values were higher for the zinc phosphate cement than the provisional cement. The influence of the grooves depended on the type of cement used (P<.001). Cement remnants were found primarily on the castings for provisional cement and for the plain abutments cemented with zinc phosphate cement. Remnants were found primarily on the abutments for the grooved abutments cemented with zinc phosphate cement.
  
  
  CONCLUSIONS
  The addition of circumferential grooves to implant abutments increased the retention of cement-retained castings. For zinc phosphate cement, 1 groove was as effective as several, whereas for the provisional cement, the retention increased gradually with additional grooves.
authors: Department of Oral Rehabilitation, The Maurice and Gabriela Goldschleger, School of Dental Medicine, University of Tel Aviv, Israel. lewins@post.tau.ac.il
authors: Israel
authors: I
authors: Lewinstein
authors: Liat
authors: L
authors: Block
authors: Zachi
authors: Z
authors: Lehr
authors: Zeev
authors: Z
authors: Ormianer
authors: Shlomo
authors: S
authors: Matalon
mesh_terms: D002484:Cementation / Q000379:methods; D002858:Chromium Alloys / Q000737:chemistry; D003442:Crowns; D000044:Dental Abutments; D003738:Dental Cements / Q000737:chemistry*; D017267:Dental Prosthesis Design; D017268:Dental Prosthesis Retention; D019094:Dental Prosthesis, Implant-Supported; D003799:Dental Stress Analysis / Q000295:instrumentation; D006801:Humans; D008422:Materials Testing; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013718:Tensile Strength; D013997:Time Factors; D014867:Water / Q000737:chemistry; D015034:Zinc Oxide / Q000737:chemistry; D015036:Zinc Phosphate Cement / Q000737:chemistry
chemical_list: D002858:Chromium Alloys; D003738:Dental Cements; C474196:Tempbond NE; D014867:Water; D015036:Zinc Phosphate Cement; D015034:Zinc Oxide