title: The effect of different surface preparation techniques on the survival probabilities of orthodontic brackets bonded to nanofill composite resin.
abstract: OBJECTIVE
  To analyze the survival probabilities of different surface preparation techniques for bonding brackets to nanofill composite resin.
  
  
  METHODS
  In vitro, laboratory study.
  
  
  METHODS
  Mahidol University, Bangkok, Thailand.
  
  
  METHODS
  Thirty-five nanofill composite resin specimens/group were subjected to four surface preparation techniques as follows: (1) sandblast using aluminium oxide powder of 90 microm; (2) abrasion using diamond bur; (3) hydrofluoric acid etching for 2 min; and (4) 37% orthophosphoric acid etching for 30 s. Plastic conditioner was applied then brackets were bonded. Shear bond strength tests were carried out on a universal testing machine.
  
  
  METHODS
  Shear bond strength (MPa) and debonding force (N) were analyzed using Weibull analysis.
  
  
  RESULTS
  The maximum stress and debonding force levels with a 95% probability of survival ranking from highest to lowest were: (1) sandblast group (4.2 MPa, 45.5 N); (2) diamond bur group (2.2 MPa, 25.3 N); (3) orthophosphoric group (1.9 MPa, 19.8 N); and (4) hydrofluoric group (0.8 MPa, 10.9 N). There was a significant difference in the adhesive remnant index scores between the surface preparation techniques (chi squared P<0.001).
  
  
  CONCLUSIONS
  Bonding orthodontic brackets to nanofill composite resin materials may result in lower bond strengths and special surface preparation techniques might be required to avoid increased numbers of bond failures. Surface treatment with sandblasting followed by plastic conditioner could increase the survival probability. The use of a diamond bur, orthophosphoric etching or hydrofluoric etching cannot be recommended.
authors.affiliation: Nita Viwattanatipa, Mahidol University, Bangkok, Thailand. Nitaviw@hotmail.com
authors.forename: Nita
authors.initials: N
authors.lastname: Viwattanatipa
authors.forename: Walaitip
authors.initials: W
authors.lastname: Jermwiwatkul
authors.forename: Rochaya
authors.initials: R
authors.lastname: Chintavalakorn
authors.forename: Nuntinee
authors.initials: N
authors.lastname: Nanthavanich
mesh_terms: D020906:Air Abrasion, Dental; D003188:Composite Resins; D001840:Dental Bonding; D045662:Dental Etching / Q000379:methods*; D003799:Dental Stress Analysis; D018130:Diamond; D016013:Likelihood Functions; D008855:Microscopy, Electron, Scanning; D053761:Nanocomposites; D016910:Orthodontic Brackets; D011897:Random Allocation; D033081:Shear Strength; D013499:Surface Properties; D016019:Survival Analysis
chemical_list: D003188:Composite Resins; D018130:Diamond