EFFECT OF LASER ETCHING ON BONDING AND DEBONDING OF ORTHODONTIC BRACKETSE

Abstract

Objectives: Comparing effect of surface enamel conditioning when irradiated with Er,Cr:YSGG laser versus typical phosphoric acid etching on shear bond strength of orthodontic brackets and their effect on esthetics of enamel surfaces after debonding. Methods: Forty freshly extracted premolars were used in this study. Sample was divided into two groups (n=20), group I; enamel etched with 37% phosphoric acid (3M Unitek, Monrovia, USA) for 15 s. Group II; enamel was irradiated with Er,Cr:YSGG laser ablated with an energy output of 4.5 watt/20hz (2.78 μm wavelength) used for 15 sec. Orthodontic brackets (NU-EDGE.022” ROTH RX.TP orthodontics) were bonded to enamel surface of all specimens (Feltik Supreme XT Flowable, 3M/ESPE). The teeth were placed in Lloyd universal testing machine at crosshead speed of 0.5 mm/minute, and the shear force to remove the brackets was recorded. The bracket bases and enamel surfaces were examined after debonding under a light stereomicroscope at 20 x magnification and the adhesive remnant index (ARI) scores were assigned to each specimen. Statistical analysis was conducted using SPSS. The SBS data were compared with an unpaired t test. Statistical significance for both tests was defined as p < 0.05. The distributions of ARI scores were compared with an unpaired t test. Results: A higher shear bond strength mean value was recorded in acid etching group (14.71±0.82) Mpa, where unpaired t test revealed that the difference between groups was statistically significant (P<0.0001). Higher (ARI) mean value was recorded in laser etching group (2.3±0.47), where unpaired t test revealed that the difference between groups was statistically significant (P<0.0001). Conclusions: Er:YAG laser is capable of obtaining optimal bond strength for orthodontic brackets when used as a surface conditioning agent though have lower bond strength, In addition, it leaves the enamel with a rougher surface upon debonding versus typical acid etching techniques.