title: An automatic robotic system for three-dimensional tooth crown preparation using a picosecond laser.
abstract: BACKGROUND
  Laser techniques have been introduced into dentistry to overcome the drawbacks of traditional treatment methods. The existing methods in dental clinical operations for tooth crown preparation have several drawbacks which affect the long-term success of the dental treatment.
  
  
  OBJECTIVE
  To develop an improved robotic system to manipulate the laser beam to achieve safe and accurate three-dimensional (3D) tooth ablation, and thus to realize automatic tooth crown preparation in clinical operations.
  
  
  METHODS
  We present an automatic laser ablation system for tooth crown preparation in dental restorative operations. The system, combining robotics and laser technology, is developed to control the laser focus in three-dimensional motion aiming for high speed and accuracy crown preparation. The system consists of an end-effector, a real-time monitor and a tooth fixture. A layer-by-layer ablation method is developed to control the laser focus during the crown preparation. Experiments are carried out with picosecond laser on wax resin and teeth.
  
  
  RESULTS
  The accuracy of the system is satisfying, achieving the average linear errors of 0.06 mm for wax resin and 0.05 mm for dentin. The angle errors are 4.33° for wax resin and 0.5° for dentin. The depth errors for wax resin and dentin are both within 0.1 mm. The ablation time is 1.5 hours for wax resin and 3.5 hours for dentin.
  
  
  CONCLUSIONS
  The ablation experimental results show that the movement range and the resolution of the robotic system can meet the requirements of typical dental operations for tooth crown preparation. Also, the errors of tooth shape and preparation angle are able to satisfy the requirements of clinical crown preparation. Although the experimental results illustrate the potential of using picosecond lasers for 3D tooth crown preparation, many research issues still need to be studied before the system can be applied to clinical operations.
authors.affiliation: State Key Lab of Virtual Reality Technology and Systems, Beihang University, Beijing, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.forename: Dangxiao
authors.initials: D
authors.lastname: Wang
authors.forename: Yuru
authors.initials: Y
authors.lastname: Zhang
authors.forename: Lei
authors.initials: L
authors.lastname: Ma
authors.forename: Yuchun
authors.initials: Y
authors.lastname: Sun
authors.forename: Peijun
authors.initials: P
authors.lastname: Lv
mesh_terms: D003442:Crowns; D004867:Equipment Design; D006801:Humans; D007834:Lasers; D012371:Robotics / Q000295:instrumentation*; D019246:Tooth Preparation / Q000295:instrumentation* / Q000379:methods*
keywords: layer-by-layer ablation; picosecond laser; robotic system; tooth crown preparation