In vivo spectral guided removal of composite from tooth surfaces with a CO₂ laser

Dental composites are used as restorative materials to replace tooth structure after the removal of caries, shaping, covering teeth for esthetic purposes and as adhesives. Dentists spend more time replacing existing restorations that fail than they do placing new restorations. Tooth colored restorations are difficult to differentiate from the surrounding tooth structure making them challenging to remove completely without incidental removal of healthy tooth structure. Previous studies have demonstrated that CO₂ lasers in conjunction with spectral feedback can be used to selectively remove composite from tooth surfaces. In addition, we assembled a system feasible for clinical use that incorporates a spectral feedback system, scanning system, articulating arm and a clinical handpiece and subsequently evaluated the performance of that system on extracted teeth. The purpose of this study was to test this system in vivo to demonstrate its efficacy relative to dental clinicians. Eight test subjects with premolar teeth scheduled for extraction for orthodontic reasons had bilateral premolars prepared with small occlusal cavity preparations and filled with dental composite. The laser scanning system was used to remove the composite from one of the preparations and a dental handpiece was used to remove the composite from the other. Cross polarization optical coherence tomography was used to measure the volume of the preparation before and after composite placement and removal. There was no significant difference in the loss of enamel and residual composite between the laser and the handpiece. This study demonstrated that a computer controlled spectral guided CO₂ laser scanning system can be used in vivo to selectively remove composite from tooth surfaces.