Development of a novel dismantlable adhesive for orthodontic use triggered by thermal stimulation

This study aimed to develop a novel orthodontic adhesive material whose bond strength decreases under external stimuli for easy removal. Stearyl acrylate (SA) and methyl acrylate (MA) copolymerization gels with monomer ratios of 1:1 (SA/MA(1:1) gel) or 3:1 (SA/MA(3:1) gel) were synthesized and added to 4-methacryloxyethyl trimellitate anhydride/methyl methacrylate-tri-n-butyl borane resin (4META resin) at 30 wt% (4META resin-30% SA/MA(1:1) gel, 4META resin-30% SA/MA(3:1) gel). The thermal and mechanical properties of obtained adhesive were characterized. Bond strength was measured by shear testing at room temperature and at elevated temperatures (50 °C). Transition temperatures of 4META resin-30% SA/MA (1:1) gel and 4META resin-30% SA/MA (3:1) gel were 37.9 °C and 41.6 °C respectively from differential scanning calorimetry measurement. The shear strength of 4META resin, 4META resin-30%SA/MA(3:1) gel, and 4META resin-30%SA/MA(1:1) gel was 8.0 MPa, 8.4 MPa, and 7.1 MPa at room temperature and 6.0 MPa, 3.9 MPa, and 4.7 MPa at 50 °C. In 4META resin containing the copolymerized gel, Young's modulus and tensile strength, as well as shear strength, decreased significantly when the measurement temperature was set to 50 °C from room temperature. A novel adhesive that reduces bond strength by half or less upon temperature stimulation was successfully developed using SA and MA copolymer gels.