title: Evaluation of selective calculus removal by a fluorescence feedback-controlled Er:YAG laser in vitro.
abstract: OBJECTIVE
  To evaluate the removal of subgingival calculus and dental hard tissues depending on the threshold level of a fluorescence feedback-controlled Er:YAG laser.
  
  
  METHODS
  Twenty teeth with calculus on the root surface were treated with an Er:YAG laser. Laser settings were 140 mJ and 10 Hz. The initial fluorescence threshold level of 5 [U] was reduced at intervals of 1 [U] for every laser treatment. Areas of residual calculus (RC) were evaluated using a surface analysis software. Loss of dental hard tissues was assessed by histomorphometric analysis of undecalcified ground sections.
  
  
  RESULTS
  Using a threshold value of 5 [U], the median amount of RC was 11% (0-78%). By lowering the threshold levels, the amount of RC decreased [level 1 [U]: 0% (0-26%)]. The laser-treated root surfaces revealed a statistically significant reduction of the cementum thickness [median: 80 microm (0-250)] compared with the non-treated opposite side [median: 90 microm (30-250)] (p<0.05).
  
  
  CONCLUSIONS
  The amount of RC following laser irradiation depends on the fluorescence threshold level for a feedback-controlled Er:YAG laser. It might be suggested that this laser system may be used with a threshold level even lower than 5 [U] without removing a clinically relevant amount of root cementum.
authors.affiliation: Department of Periodontology, Operative and Preventive Dentistry, University of Bonn, Bonn, Germany. felix.krause@uni-bonn.de
authors.forename: Felix
authors.initials: F
authors.lastname: Krause
authors.forename: Andreas
authors.initials: A
authors.lastname: Braun
authors.forename: Olivier
authors.initials: O
authors.lastname: Brede
authors.forename: Jörg
authors.initials: J
authors.lastname: Eberhard
authors.forename: Matthias
authors.initials: M
authors.lastname: Frentzen
authors.forename: Søren
authors.initials: S
authors.lastname: Jepsen
mesh_terms: D000538:Aluminum Silicates; D003728:Dental Calculus / Q000473:pathology / Q000532:radiotherapy*; D003739:Dental Cementum / Q000473:pathology / Q000528:radiation effects; D004867:Equipment Design; D004871:Erbium; D005246:Feedback; D005453:Fluorescence; D006801:Humans; D053685:Laser Therapy; D014092:Tooth Root / Q000473:pathology / Q000528:radiation effects; D015019:Yttrium
chemical_list: D000538:Aluminum Silicates; D015019:Yttrium; D004871:Erbium