title: Rapid and selective removal of composite from tooth surfaces with a 9.3 µm CO2 laser using spectral feedback.
abstract: OBJECTIVE
  Dental composite restorative materials are color matched to the tooth and are difficult to remove by mechanical means without excessive removal or damage to peripheral enamel and dentin. Lasers are ideally suited for selective ablation to minimize healthy tissue loss when replacing existing restorations, sealants, or removing composite adhesives such as residual composite left after debonding orthodontic brackets.
  
  
  METHODS
  In this study, a carbon dioxide laser operating at 9.3-µm with a pulse duration of 10-20-microsecond and a pulse repetition rate of ∼200 Hz was integrated with a galvanometer based scanner and used to selectively remove composite from tooth surfaces. Spectra of the plume emission were acquired after each laser pulse and used to differentiate between the ablation of dental enamel or composite. Microthermocouples were used to monitor the temperature rise in the pulp chamber during composite removal. The composite was placed on tooth buccal and occlusal surfaces and the carbon dioxide laser beam was scanned across the surface to selectively remove the composite without excessive damage to the underlying sound enamel. The residual composite and the damage to the underlying enamel was evaluated using optical microscopy.
  
  
  RESULTS
  The laser was able to rapidly remove composite from tooth buccal and occlusal surfaces with minimal damage to the underlying sound enamel and without excessive heat accumulation in the tooth.
  
  
  CONCLUSIONS
  This study demonstrated that composite can be selectively removed from tooth surfaces at clinically relevant rates using a CO(2) laser operating at 9.3-µm with high pulse repetition rates with minimal heat deposition and damage to the underlying enamel.
authors.affiliation: University of California, San Francisco, San Francisco, California 94143-0758, USA.
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Chan
authors.forename: Krista
authors.initials: K
authors.lastname: Hirasuna
authors.forename: Daniel
authors.initials: D
authors.lastname: Fried
mesh_terms: D003188:Composite Resins; D003813:Dentistry / Q000379:methods; D006801:Humans; D066298:In Vitro Techniques; D054020:Lasers, Gas; D013499:Surface Properties; D013997:Time Factors; D014070:Tooth
chemical_list: D003188:Composite Resins