title: The effect of ultrasonic instruments on the quality of preparation margins and bonding to dentin.
abstract: BACKGROUND
  Ultrasonic instruments have recently been developed for finishing crown preparations. They are successful in accessing difficult areas on the preparation margin, but their effects on the dentin surface and on bond strength are contradictory.
  
  
  OBJECTIVE
  The aim was to evaluate the condition of crown preparation margins finished using new ultrasonic instruments and to assess their effects on dentin bond strength.
  
  
  METHODS
  Characteristics of tooth surfaces prepared using two different ultrasonic protocols were compared; Perfect Margin Shoulder (PMS) (PMS 3, Satelec, Merignac, France) 1, 2, and 3 (complete finishing) versus PMS 1 and 2 (partial finishing). They were assessed using scanning electron microscopy (SEM) and surface roughness analysis. Bonding of composite resin to dentin surfaces prepared with the complete PMS kit was compared with dentin surfaces prepared with finishing diamond burs, using micro-tensile testing.
  
  
  RESULTS
  SEM images revealed a clear difference between the two preparation sequences (PMS 1, 2 versus PMS 1, 2, and 3). Surfaces finished using the PMS tips 1, 2, and 3 appeared continuous, even, and smooth compared with PMS tips 1 and 2 only. The additional use of the PMS 3 uncoated tip enhanced smear layer removal. There was no significant difference when comparing the surface roughness obtained with the PMS 1, 2, and 3 protocol with the PMS 1 and 2 only (p > 0.05). Micro-tensile bond strength was not significantly different between the surfaces prepared with the ultrasonic instruments and the surfaces prepared with the diamond burs (p > 0.05).
  
  
  CONCLUSIONS
  The use of the complete PMS finishing kit (PMS 1, 2, and 3) produced better quality finishing lines than PMS 1 and 2. The use of ultrasonic instruments to prepare dentin resulted in comparable bond strengths to the use of diamond burs.
  
  
  CONCLUSIONS
  The extremely precise preparation margin possible with ultrasonic instruments improves the quality and accuracy of crown preparations, which may lead to better impressions and closer adaptation of restorations. The complete set of three Perfect Margin Shoulder instruments is recommended, which can produce comparable bond strengths to preparations with rotary instruments.
authors.affiliation: Department of Oral Rehabilitation, University of Otago School of Dentistry, Dunedin, New Zealand.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Ellis
authors.forename: Vincent
authors.initials: V
authors.lastname: Bennani
authors.forename: David
authors.initials: D
authors.lastname: Purton
authors.forename: Nicholas
authors.initials: N
authors.lastname: Chandler
authors.forename: Bronwyn
authors.initials: B
authors.lastname: Lowe
mesh_terms: D002484:Cementation / Q000379:methods; D003442:Crowns; D003748:Dental Equipment; D018772:Dental Marginal Adaptation; D017267:Dental Prosthesis Design; D017220:Dentin-Bonding Agents; D006801:Humans; D008855:Microscopy, Electron, Scanning; D011476:Prosthodontics / Q000295:instrumentation / Q000379:methods; D015203:Reproducibility of Results; D013499:Surface Properties; D019231:Tooth Preparation, Prosthodontic / Q000295:instrumentation*; D014465:Ultrasonics
chemical_list: D017220:Dentin-Bonding Agents