title: Effect of a fluoride varnish on the margin leakage and retention of luted provisional crowns.
abstract: BACKGROUND
  Provisional crowns cemented with provisional luting agents are susceptible to washout, margin leakage, and secondary caries when placed for a prolonged period.
  
  
  OBJECTIVE
  This study was conducted to determine the effect of combining a varnish containing 2.26% NaF with 2 provisional luting agents on the margin leakage and retention of provisional crowns.
  
  
  METHODS
  Acrylic resin provisional crowns were fabricated for 8 shoulder-prepared molars. The eight provisional (N=24) crowns were luted individually with Temp-Bond (TB), Freegenol (FG), or Duraphat (DU). Specimens were thermocycled 500 times (5 degrees and 60 degrees C) with a 1-minute dwell time, stored in 100% relative humidity at 37 degrees C for 6 days, and then immersed in a 0.5% Gentian violet solution for 24 hours. Seven days after cementation, a removal test of the crowns (shear retention test) was conducted with a universal testing machine at a crosshead speed of 5 mm/min. Retention was determined as the maximum recorded force needed for crown dislodgment. DU varnish was applied to the inner surface of the dislodged crowns with no removal of the cement layer TB, FG (N=16). The crowns were relined with a 0.5-mm layer of acrylic resin and luted with a combination of luting agent and DU (TB, FG) N=16. No luting agent (NC) served as the control (N=8). Results were analyzed with the Wilcoxon matched-pairs signed-ranks test. Leakage at the margins was assessed with a 4-level dye penetration scale, and statistical differences were identified with a chi(2) test. All hypothesis testing was conducted at the 95% level of confidence.
  
  
  RESULTS
  The mean 7-day retention forces were as follows: 44.5 N (Temp-Bond), 51.6 N (Freegenol), and 35.9 N (Duraphat). There were no significant differences among these values. Duraphat combined with Freegenol decreased the retention of provisional crowns, but Duraphat combined with Temp-Bond increased the retention of provisional crowns by 69-145%. Duraphat alone and in combination with both provisional luting agents significantly reduced margin leakage (P<.05). The least margin leakage was evident when the provisional crowns were luted with Duraphat alone.
  
  
  CONCLUSIONS
  With regard to retention and margin leakage, the results of this study suggest that Duraphat varnish can be successfully used as provisional luting agent for single provisional crowns.
authors.affiliation: The Maurice and Gabriela Goldschleger School of Dental Medicine, Department of Oral Rehabilitation, Tel Aviv University, Israel. lewins@post.tau.ac.il
authors.forename: Israel
authors.initials: I
authors.lastname: Lewinstein
authors.forename: Nitzan
authors.initials: N
authors.lastname: Fuhrer
authors.forename: Yehuda
authors.initials: Y
authors.lastname: Ganor
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D002327:Cariostatic Agents / Q000737:chemistry*; D002484:Cementation; D016009:Chi-Square Distribution; D004396:Coloring Agents; D016001:Confidence Intervals; D003442:Crowns; D001840:Dental Bonding; D003738:Dental Cements / Q000737:chemistry*; D003763:Dental Leakage / Q000145:classification*; D017268:Dental Prosthesis Retention; D003794:Dental Restoration, Temporary; D005054:Eugenol / Q000737:chemistry; D005460:Fluorides, Topical / Q000737:chemistry*; D005840:Gentian Violet; D006801:Humans; D007764:Lacquer; D016555:Matched-Pair Analysis; D008422:Materials Testing; D012969:Sodium Fluoride / Q000737:chemistry; D018709:Statistics, Nonparametric; D013314:Stress, Mechanical; D013816:Thermodynamics; D015034:Zinc Oxide / Q000737:chemistry; D015035:Zinc Oxide-Eugenol Cement / Q000737:chemistry
chemical_list: D000180:Acrylic Resins; D002327:Cariostatic Agents; D004396:Coloring Agents; D003738:Dental Cements; D005460:Fluorides, Topical; C078077:Freegenol; D015035:Zinc Oxide-Eugenol Cement; C023807:sodium fluoride topical preparation; D005054:Eugenol; C076899:Temp-Bond; D012969:Sodium Fluoride; D005840:Gentian Violet; D015034:Zinc Oxide