Preliminary study on a miniature laser manipulation robotic device for tooth crown preparation.

Background: The existing methods in dental clinical operations for hard tissue removal have several drawbacks which affect the long-term success of the dental treatment.

Methods: In this paper, we introduce a miniature robotic device called LaserBot, which can manipulate a femtosecond laser beam to drill/burr a decayed tooth to realize clinical tooth crown preparation. In order to control the 3D motion of the laser focal point on the surface of a tooth, three miniature voice-coil motors with optical grating rulers are utilized to drive the 2D pitch/yaw rotation of a vibration mirror and 1D translation of a protruding optical lens. This method can provide high-resolution control of the laser beam. In order to maintain the small size of the robot, a parallel five linkage mechanism combined with a slider-rocker mechanism is developed to realize 2D pitch/yaw rotation of the vibration mirror.

Results: Experiment results show that the movement range and resolution of the laser beam point can meet the requirement of typical dental operations. The size of the working end of the device that enters the mouth is 25 × 22 × 57 mm (height × width × length), which is small enough to be mounted on any tooth. The average repeatability error of the laser focal point is about 40 µm. Ablation experiments on wax-resin material and on tooth validate that a femtosecond laser can be used for tooth ablation.

Conclusions: The developed robotic device achieved precise 3D motion control of a laser focal point and is small enough to be used in the narrow workspace of the oral cavity. Limitations of the prototype have been identified, and quantified specifications are identified for designing the next generation prototype.