ESEM ANALYSIS OF ENAMEL SURFACE MORPHOLOGY ETCHED WITH ER,CR:YSGG LASER AND PHOSPHORIC ACID: IN VITRO STUDY

Objectives: The aim of the present study was to evaluate the etching pattern of Er,Cr:YSGG and conventional etching on prepared samples of human enamel by environmental scanning electron microscope (ESEM).
Materials and Methods: Forty five freshly extracted human upper premolars were used; the teeth had been extracted for orthodontic reasons and were collected and stored in a solution of 0.1% (wt/vol) thymol. The teeth were mounted vertically in a self-cure acrylic cylinder. One clinician prepared all the teeth, in each tooth, a 4x4 mm area was treated in middle third of the buccal surface. The teeth were divided into three groups according to type of etching techniques (n=15).Group(A): enamel etched with 37% phosphoric acid for 30 s, thoroughly rinsed with distilled water for 60 s and gently air dried.; Group (B): enamel was irradiated with Er,Cr:YSGG laser ablated with an energy output of 4.5 watt/30hz and Group (C):enamel was irradiated with Er,Cr:YSGG laser ablated with an energy output of 4.5 watt/20hz. In group b & c Er,Cr:YSGG laser (2.78 μm wavelength) used for 15 sec at 45degree angulations working distance 5mm on a square size 4x4mm on buccal surface. Micro-morphological changes of enamel surface were evaluated using an environmental scanning electron microscope at X250 & X1500 magnification.
Results: In this study, laser with 30 Hz reveals a definite change in the surface of the enamel, most of the enamel prisms are interrupted showing an irregular outline. However laser with 20 Hz showed the ultra-structural appearance of enamel nearly similar to that of conventionally etched enamel with 37 percent phosphoric acid.
Conclusion: Within the limits of this in vitro study, both conventional acid etching & laser 20 Hz etching showed nearly similar effect on enamel surface, so the laser-etching can be successfully used as an alternative to the conventional acid-etch. On the other hand laser 30 Hz etching failed to induce an effect on enamel surface comparable to that of acid etching and therefore can’t be used as substitute for the conventional acid –etch.