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. 2022 Jan-Feb;33(1):57-67.
doi: 10.1590/0103-6440202203878.

Ultrasound device as a minimally invasive approach for caries dentin removal

João Felipe Besegato  1 , Priscila Borges Gobbo de Melo  1 , Adilson César de Abreu Bernardi  2 , Vanderlei Salvador Bagnato  3 , Alessandra Nara de Souza Rastelli  1
Affiliations

Ultrasound device as a minimally invasive approach for caries dentin removal

João Felipe Besegato et al. Braz Dent J. 2022 Jan-Feb.

Abstract
in English, Portuguese

The aim of this study was to evaluate the efficacy of an ultrasound device and the dentin surface morphology after removal of the caries dentin lesions by removal rate and scanning electron microscopy (SEM). The Knoop hardness test on the bovine dentin blocks (n = 20, 4x4x2mm) was performed to standardize the samples and only those with 38 ± 2 KHN were included. The dentin blocks were submitted to induction of artificial caries lesions, using the bacterial model. Strains of Streptococcus mutans and Lactobacillus acidophilus were used for 7 days. The caries dentin lesion was removed for 1 min, according to two methods: G1 - carbide bur under low-speed rotation (control group) and G2 - ultrasound device under refrigeration. For the removal rate, the samples were weighed 3 times: T0 (before induction), T1 (after induction) and T2 (after removal). Morphology evaluation of the residual dentin surface was performed by SEM. Data normality was verified by Shapiro-Wilk test (p ≥ 0.240). T-test for independent samples was applied to evaluate the removal rate. A significance level of 5% was adopted. G2 provided lower removal rate than G1 (G1: 3.68 mg and G2 = 2.26 mg). SEM images showed different morphological characteristics between the groups. G2 showed absent of smear layer, while G1 showed a visible smear layer over the surface. We concluded that ultrasound device provides minimally invasive removal with residual dentin exhibiting open dentin tubules and no smear layer formation and no bacteria, which infer the removal of the infected tissue.

O objetivo deste estudo foi avaliar a eficácia de um dispositivo ultrassônico e a morfologia da superfície dentinária após a remoção da dentina cariada por meio da taxa de remoção e imagens de microscopia eletrônica de varredura (MEV). Foi realizado o teste de dureza Knoop nas amostras de dentina bovina (n = 20, 4x4x2mm) afim de padronizar as amostras e foram incluídas apenas aquelas com 38 ± 2 KHN. As amostras de dentina foram submetidas à indução de lesões artificiais de cárie, utilizando-se modelo biológico contendo cepas de Streptococcus mutans e Lactobacillus acidophilus durante por 7 dias. As lesões foram removidas por 1 min, de acordo com dois métodos: G1 - fresa esférica sob baixa rotação (grupo controle) e G2 - dispositivo ultrassônico sob refrigeração. Para a taxa de remoção, as amostras foram pesadas em três tempos: T0 (antes da indução), T1 (após a indução) e T2 (após a remoção). A avaliação morfológica da superfície residual da dentina foi realizada por MEV. A normalidade dos dados foi verificada pelo teste de Shapiro-Wilk (p ≥ 0,240). Teste T para amostras independentes foi aplicado para avaliar a taxa de remoção. Foi adotado nível de significância de 5%. G2 apresentou menor taxa de remoção que G1 (G1: 3,68 mg e G2 = 2,26 mg). As imagens de MEV mostraram características morfológicas diferentes entre os grupos. G2 mostrou ausência de smear layer, enquanto G1 mostrou grande quantidade de smear layer sobre a superfície. Com base neste estudo in vitro, o dispositivo de ultrassom promoveu remoção minimamente invasiva e dentina residual exibindo túbulos dentinários abertos e mínima formação de smear layer.

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Conflict of interest statement

The authors deny any conflict of interest in this paper.

Figures

Figure 1
Figure 1. Flowchart of the study.
Figure 2
Figure 2. System used to maintain the samples individually suspended in a 24-well culture plate during the artificial caries lesion development.
Figure 3
Figure 3. Ultrasound caries removal device.
Figure 4
Figure 4. Artificial dentin caries lesion and lesion depth at 5x (A) and 10x (B) magnification obtained by polarized light microscopy images. Arrows indicate caries-affected dentin.
Figure 5
Figure 5. Mean and standard deviation of the samples weight difference (mg) according to each evaluation time (n = 10). T0 - before the artificial caries lesion development; T1 - before the carious dentin removal; and T2 - after the carious dentin removal.
Figure 6
Figure 6. Representative SEM photomicrographs of control group (without artificial caries lesion development) at 200 (A), 1000 (B), 2000 (C) and 5000x (D) magnification.
Figure 7
Figure 7. Representative SEM photomicrographs of carbide bur (G1) at 200 (A), 1000 (B), 2000 (C) and 5000x (D) magnification. Arrows indicate smear layer covering the dentin tubules. Circles indicate dentin tubules exposure.
Figure 8
Figure 8. Representative SEM photomicrographs of ultrasound device group (G2) at 200 (A), 1000 (B), 2000 (C) and 5000x (D) magnification. Arrows indicate smear layer. Circles indicate dentin tubules exposure.
See this image and copyright information in PMC

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