OBJECTIVECeramic brackets debonding by Nd:YAG laser is based on the thermal effect of laser, which may cause injury of the pulp tissue. In this study, the histological changes of pulp tissue that subjected to Nd: YAG laser irradiation with different power and time were observed.

METHODS20 New Zealand rabbits were included in this study. Ceramic brackets were bonded to the 4 incisors as routine. The ceramic brackets of left upper teeth that debonded mechanically were used as control group, while the brackets of right upper, left lower and right lower incisors were debonded by laser with 3 W 3 s (group A), 2 W 5 s (group B) and 5 W 2 s (group C) energies, respectively. The teeth were pulled out at 5 minutes, 1 day, 3 days, 1 week and 1 month after the debonding operations. Slides prepared from the pulp tissues of the debonded teeth were used to evaluate the injury of laser.

RESULTSIn comparison with the control group, pulp tissue of teeth that exposed to laser with different energy for 5 minutes showed mild capillary dilation. One day later, group A, B and C showed moderate capillary dilation, and group C also showed moderate infiltration. At 3 days, inflammation was disappeared in group B, whereas capillary dilation was found in group A. Hemorrhage and inflammation cells infiltration were found in group C. At 1 week, alleviation of capillary dilation was found in group A but not in group C. One month later, inflammation disappeared in group A, while pulp tissue in group C showed mild edema and capillary dilation.

CONCLUSIONNd:YAG laser of high energy may cause injury of the pulp tissue during debonding. Laser energy of 3 W 3 s could effectively debond ceramic brackets without irreversible pulp injury.

Animals ; Ceramics ; Dental Debonding ; Dental Pulp ; Lasers ; Lasers, Solid-State ; Orthodontic Brackets ; Rabbits

OBJECTIVETo explore the possibility of pulsed Nd:YAG laser-aided debonding for removing orthodontic metal brackets and to compare the method with the conventional mechanical debonding method.

METHODSFifty healthy premolars extracted for orthodontic purpose were randomly divided into five groups (10 teeth in each group). There were four experimental groups and one control group. Every tooth was bonded with bracket. Laser was used to irradiate the teeth in experimental groups with different electric currents (13.0, 13.5, 14.0, 14.5 A). During the irradiation, the brackets received 4.9 N of force until the brackets off. The time needed for debonding and the temperature change of the pulp cavity were recorded. The teeth in control group were debonded using mechanical method. The adhesive remnant index (ARI) was calculated using stereomicroscope and imagetool software. All samples were examined with a scanning electron microscope.

RESULTSThe time taken between the four groups were (67.70 ± 7.18), (35.90 ± 4.28), (24.90 ± 3.76), (6.90 ± 2.33) s, highly statistical difference was found in the time needed for debonding (P < 0.01). The temperature in the pulp cavity among the four groups were (20.97 ± 3.10), (12.75 ± 3.14), (8.99 ± 2.47), (2.91 ± 1.88)°C, and statistical differences were found in temperature change of the pulp cavity (P < 0.05). ARI of three experimental groups and the control group were (8.55 ± 5.02)%, (15.42 ± 7.37)%, (5.55 ± 3.79)%, (13.72 ± 6.69)%, and (74.36 ± 29.44)%. The enamel surface of the control group was coarse with deep scratchs. The enamel surface was smooth and clean in the experimental groups.

CONCLUSIONSPulsed Nd:YAG laser-aided debonding for removing metal brackets was feasible. Laser-aided debonding was better than conventional mechanical debonding method. The method reduced the damage to the enamel surface.

Dental Debonding ; methods ; Dental Enamel ; Humans ; Lasers, Solid-State ; Orthodontic Brackets

OBJECTIVEThe aim of this study was to investigate the effect of short enamel etching time on bonding strength.

METHODS80 healthy premolars were randomly divided into two equal groups, one was etched for 15 seconds, the other for 60 seconds, after normally bonding Edgewise brackets, the tooth specimen was stored in water at room temperature for 24 hours. An MTS NEW810 100KN testing machine was used to examine the shear force.

RESULTSAlthough the bonding strength for 15 seconds etching time was weaker than that for 60 seconds, the means of the bonding strength in 15 seconds group reached 5.8625 MPa.

CONCLUSIONEtching for 15 seconds could provide enough bond strength for orthodontic practice. Furthermore, the adhesive remained on tooth after debonding was less by comparison with 60 seconds etching group, therefore brackets could be removed easily and the work efficiency could be increased in clinic by means of 15 seconds etching time.

Acid Etching, Dental ; methods ; Dental Bonding ; Dental Debonding ; Dental Enamel ; injuries ; ultrastructure ; Humans ; Orthodontic Brackets ; Orthodontics, Corrective ; Stress, Mechanical ; Surface Properties ; Tensile Strength ; Time Factors

OBJECTIVETo investigate the bond strengths of customized titanium bracket manufactured by selective laser melting.

METHODSEighty human premolars which had been extracted for orthodontic purpose were collected and divided randomly (by random table) into two groups (customized bracket group and 3M bracket group, 40 molars in each group). The 35% phosphoric acid was used for etching and the brackets were bonded with 3M Unitek bonding adhesive. All bonded specimens were placed in saline for 24 hours at room temperature and were tested on DWD3050 electronic testing machine to determine the shear bond strength and tensile bond strength. After debonding, the adhesive remnant indexes (ARI) were recorded.

RESULTSThe shear bond strengths of customized brackets was 6.80 (6.20, 8.32) MPa, which was significantly lower than that of the 3M brackets [10.46 (9.72, 11.48) MPa] (Z = -3.463, P < 0.05). And the tensile bond strengths of customized brackets was (6.93 ± 1.21) MPa, which was significantly higher than that of the 3M brackets [(5.88 ± 1.23) MPa] (t = 2.81, P < 0.05). No significant difference was found in the ARI between two different kinds of the brackets.

CONCLUSIONSThe shear bond strength and tensile bond strength of both kinds of brackets were enough for clinic application.

Acid Etching, Dental ; Adolescent ; Bicuspid ; Child ; Composite Resins ; chemistry ; Dental Bonding ; methods ; Dental Debonding ; Dentin-Bonding Agents ; chemistry ; Humans ; Lasers ; Orthodontic Brackets ; Phosphoric Acids ; chemistry ; Random Allocation ; Shear Strength ; Tensile Strength ; Titanium