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Updated: Mar 17, 2026
Author Spotlight: Establishing an Accurate Microhardness Testing Protocol for Craniofacial Tissues
Published on: April 26, 2024
Relationship between analysis of laser speckle image and Knoop hardness on softening enamel
Nelson H Koshoji1, Renato A Prates2, Sandra K Bussadori2
1Dep. of Biophotonics, Universidade Nove de Julho (UNINOVE), São Paulo, Brazil; School of Engineering, Universidade Nove de Julho (UNINOVE), São Paulo, Brazil.
Background:
In this study is presented the correlation between laser speckle images and enamel hardness loss.
Methods:
In order to shift the enamel hardness, a dental demineralization model was applied to 32 samples of vestibular bovine teeth. After they were cleaned, cut and polished, the samples were divided into 4 groups and immersed in 30ml of a cola-based soft drink for 10, 20, 30 and 40min twice a day for 7 consecutive days with half the surface protected by two layers of nail polish. Each sample was analyzed by Knoop hardness and laser speckle imaging.
Results:
Pearson's correlation analysis demonstrated that the laser speckle image technique presents a strong correlation with the hardness loss of the enamel (r=0.7085, p<0.0001). This finding is corroborated by Blend & Altman analysis, in which the data presented a constant behavior throughout the whole interval. For both analyses, more than 95% of the data is within the confidence interval, as expected.
Conclusion:
This work demonstrates, for the first time to our knowledge, an empirical model for correlating laser speckle images with the loss of tooth enamel hardness.
