Laser Conditioning: A Preferred Option over Conventional Acid Etching for Orthodontic Bonding

An article published in October 2020 by Piradhiba et al, ¹ with purpose to evaluate the demineralization resistance and the shear bond strength of enamel surfaces after erbium, chromium: yttrium–scandium–gallium-garnet (Er,Cr:YSGG) laser etching (2 W/15 Hz, 2 W/25 Hz) and to compare them with conventional acid etching for orthodontic bonding.

The article was very informative, innovative, and of great knowledge but we have come across certain doubts. Kindly respond for the same.

In “Results” (p. 3) it was stated that if P-value was <.05, then it is considered to be statistically significant. However, in Table 2 (p. 3, under “Phosphorus Variable”) when laser-etched 2 W/15 Hz compared with 2 W/25 Hz group, the P-value (.034) was known to be statistically significant whereas it was mentioned in manuscript as statistically insignificant. Kindly explain.

In the article (p. 4), as mentioned (under “Assessment of Shear Bond Strength”) the result of ARI score between the groups were not statistically significant (>.05). However if we look at Table 5 (p. 4) the P-value has not been stated. Therefore how can we declare that whether it was statistically significant or not?

Moreover, as per Table 5 under the laser etched group 2 W/15 Hz, adhesive remnant index (ARI) score of 3 has not been mentioned which was considered as 0, whereas in chi-square test the score cannot be equal to 0 in any box of contingency table. Kindly explain how chi-square has been done if the score were not mentioned.

As per the article, 60 extracted pre-molars teeth were selected for the study which were further divided into 2 equal parts (30 each) with random allocation to test 2 different parameters (demineralization resistance and shear bond strength).

However, for demineralization resistance of these 30 selected teeth were further assigned into 3 different groups. Therefore kindly explain why randomization of these 30 selected teeth has not been done; where it was needed most as statistical test ANOVA was performed among them?

According to article, 2790 nm wavelength of Er,Cr:YSGG laser was used to etch the enamel. However to create microporosities in enamel for better bonding 2780 nm wavelength ² is used. Kindly explain the need for 2790 nm wavelength to etch the enamel while it has been used to cut hard tissue, not to create microporosities.