A thesis submitted to the College of Dental Medicine of Nova Southeastern University of the degree of Master of Science in Dentistry. ABSTRACT The significance of this research was to identify the optimal techniques to remove ceramic orthodontic appliances in order to prevent tooth-enamel fracture, pain, and esthetic complications. Discomfort and pain are common occurrences during orthodontic appliance removal. In debonding (bracket removal) appointments, less force, measured as reduced shear bond strength (SBS) is preferable because greater force creates more discomfort and pain. In a previous study, 24.3% of patients reported pain when metallic brackets were removed using a ligature-cutting plier, compared to 12.8% of patients reporting pain when a lift-off instrument was employed. These previous findings demonstrate the need to investigate new debonding removal methods which have less SBS to help reduce the pain experienced by orthodontic patients. Some recent studies have reported that orthodontic bracket debonding causes inevitable damage to the enamel surface. The debonding of ceramic orthodontic brackets can increase the risk of enamel damage. The application of heat to help debond a bracket can increase the temperature of the pulp chamber; this could injure pulp cells and threaten the long term vitality of the affected tooth. The purpose of this in-vitro study was to evaluate the safety and effectiveness of using a diode laser for the debonding of ceramic brackets in relation to the amount of debonding force required, the risk of direct force impact on enamel, and the risk of causing an adverse temperature increase inside the pulp chamber. The central hypothesis I investigated was that using a diode laser would facilitate the debonding of ceramic brackets by decreasing the SBS, increase the adhesive remnant index (ARI), and avoid causing an adverse temperature increase in the pulp chamber. I investigated these parameters with the goal of establishing an effective and safe protocol for debonding ceramic brackets. At present no guidelines exist, I recognized that guidelines are needed for using a diode laser to debond brackets in relation to the power level and duration of lasing. This study tested two types of ceramic brackets; a monocrystalline bracket called Radiance and polycrystalline ceramic bracket called Clarity. These brackets were selected because they are widely available and in common use. The experimental brackets were monocrystalline and polycrystalline: the laser power settings and lasing times were; negative control (not lased), lased at 2.5 watts for 3 and 6 seconds, and lased at 5.0 watts for 3 and 6 seconds. The diode laser treatments had little effect on the debonding SBSs for the removal of the Radiance monocrystalline brackets. Alternatively, the debonding of the Clarity polycrystalline brackets with laser treatment using 2.5 watts for 6 seconds, 5.0 watts for either 3 seconds or 6 seconds reduced the SBS. The debonding of the Radiance monocrystalline brackets with laser treatment using 2.5 watts for 3 seconds, and 5.0 watts for 6 seconds increased the ARI. The debonding of the Clarity polycrystalline brackets with laser treatment using 2.5 watts for 6 seconds, 5.0 watts for 3 seconds and 6 seconds increased the ARI. The increase in pulp chamber temperature likely to cause thermal injury to the pulp cells was measured against Zack and Cohen¡¯s in vivo standards (2.2¢ªC and, 5.5¢ªC).30 When compared to the 2.2¢ªC standard; the debonding of Radiance monocrystalline brackets with laser treatment using 2.5 watts for 3 seconds were within the standard, and the debonding of Clarity polycrystalline brackets using 2.5 watts for 3 seconds was cooler. When compared to the 5.5¢ªC standard, the debonding of Clarity polycrystalline brackets using 2.5 watts for 6 seconds was cooler. The research results showed that using a diode laser for debonding at 2.5 watts for 6 seconds decreased the SBS for Clarity polycrystalline brackets (reduced the force needed for debonding), increased ARI for Clarity polycrystalline brackets (increased adhesive on enamel), and did not increase the pulp chamber temperature by an injurious amount. The difference in the debonding SBS, ARI and pulp chamber temperatures of the two bracket types probably arose because of the difference in the designs of the two bracket pads. My research results demonstrate the long-term need to design brackets with pads which can be removed easily with a diode laser, leave more adhesive on enamel, and that do not cause injurious temperature increases within the pulp chamber. My research results also demonstrate why guidelines for bracket debonding using diode lasers are needed, which limit the power setting and lasing times. The debonding of brackets using diode lasers could benefit orthodontic patients and become more common if it can reduce the risk of tooth fracture, lower the sensation of pain, reduce the amount of enamel damage, and maintain the vitality of teeth in future studies.