Comparative Evaluation of Microhardness of Two Different Remineralizing Pastes - An In vitro study

Keywords

Remineralizing Agents ; Casein Phosphate - Amorphous Calcium Phosphate ; Enamel Caries.

Introduction

Dental caries is a process that takes place on any tooth surface where the dental plaque is accumulated for a long period. Initial caries progression may be prevented by suitable surface treatment[ 1]. This issue signifies the current concept regarding remineralization and demineralization of the tooth surface[2].

The first step in the remineralization process is demineralization, which regulates and reverses the decay process. Demineralization happens as acidogenic bacteria reduce the pH of the calculus. The remineralization process starts when Ca+2 and PO4 ions in saliva raise the pH of calculus. Therefore, demineralized lesions are remineralized. However, when the demineralization is equal to or higher than remineralization, decay occurs [3].

The level of Ca+2 and PO4 in the saliva has a big impact on the buffer ability of the saliva. When fluoride ions are present in the saliva, the rate of remineralization increases. As a result, research focused on the role of fluoride in preventing caries and reversing the decay or demineralization phase. In recent in vivo and in vitro studies, the effect of fluoride on remineralization and demineralization has been researched [4]

One of the most effective remineralizing agents for caries prevention is fluoride. Nonetheless, there have been several concerns posed about fluorosis and fluoride intake in general. Fluoride replacements such as CPP-ACP and nano-hydroxyapatite (NHA) have been suggested in recent years due to their anticariogenic properties.[5,6]. Earlier studies have shown that the application of a CPPs toothpaste and sodium fluoride (Colgate Neutrafluor 9,000 ppm) (NaF) can provide significant additional prevention of enamel demineralisation when resin-modified glass ionomer cement (RMGIC) is used for bonding molar tubes for orthodontic patient as preventive actions[7]. An in vitro study to evaluate the remineralisation of incipient enamel lesions by the topical application of Casein Phosphopeptide- Amorphous Calcium Phosphate (CPP-ACP) using laser fluorescence and scanning electron microscope showed high scores of remineralisation[8] .

Micro hardness and roughness are two of the important properties of materials and associated with loss or gain of mineral content in tooth structure[9]. An ideal toothpaste should remove unwanted surface deposits and stains with minimal influence on the enamel, dentine and restorations [10]. Thus, the effects of such products on properties of enamel and restorative materials are important [11]. It is one of the important properties of the materials which correlates with strength, proportional limit and wear resistance [12].

Therefore, due to a continuous (daily) therapeutic recommendation for using these products, it is relevant to assess the effects of these toothpastes on properties such as microhardness and its remineralisation property. This is an in-vitro study that aims at evaluation of the microhardness and the remineralising property of 3 different remineralising toothpastes.Previously our team has a rich experience in working on various research projects across multiple disciplines (Govindaraju and Gurunathan 2017; A. Christabel et al. 2016; Soh and Narayanan 2013; Mehta et al. 2019; Ezhilarasan, Apoorva, and Ashok Vardhan 2019; Campeau et al. 2014; Kumar and S 2016; S. L. Christabel 2015; Kumar and Rahman 2017; Sridharan, Ramani, and Patankar 2017; Ramesh et al. 2016; Thamaraiselvan et al. 2015; Thangaraj et al. 2016; Ponnulakshmi et al. 2019; “Fluoride, Fluoridated Toothpaste Efficacy and Its Safety in Children - Review” 2018) Now the growing trend in this area motivated us to pursue this project.

Materials and Methods

It was an in vitro study conducted in the month of November 2020 – February 2021 in the city of Chennai, Tamil Nadu.

Ethical Approval

The study was registered with the Institutional Review Board of the Saveetha Institute of Medical and Technical Sciences, Chennai, Tamil Nadu, India. Ethical approval was obtained from the Institutional Review Board of the SIMATS.

Sampling Method

Sixteen freshly extracted sound teeth, extracted for therapeutic reasons, were used. Teeth with any caries or white spot lesions were excluded. The teeth were decoronated and the crown portions were divided into two segments of one buccal and one palatal half using a diamond disc mounted on a contra-angle handpiece. Enamel samples were fixed on the self-cure acrylic mold with the enamel surface exposed. These samples were stored in deionized water until further use.

Group A: GC Tooth Mousse

Group B: Enafix

Group C: Colgate Total

Remineralisation was carried out using the brushing stimulator. After multiple cycles of remineralization, the surface microhardness of the specimens was determined using Vickers microhardness testing machine.

Statistical Analyses

The collected data was tabulated into Microsoft office Excel 2013 transferred to SPSS version 26.0 software (SPSS, Chicago, IL, USA) for statistical analysis. This data was analyzed statistically using the paired t test to evaluate differences in the values obtained pre and post cycle and to see if the results were statistically significant. The baseline data was evaluated and compared against the post cycle values for all the 3 remineralising toothpastes. The confidence interval was set at 95%.

Results

The result showed there has been a statistically significant difference in the microhardness among the three samples. Microhardness results per sample and treatment are shown below in Table 1. All tooth samples underwent statistically similar levels of demineralisation and remineralization. The various p values found for group A (0.096), group B (0.542), group C (0.003). None of the values were statistically significant.

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Figure 1:

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Figure 1: Sample Preparation For Groups A,B And C. Mounted Samples On Die Stone.

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Figure 2:

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Figure 2: Brushing Simulator.

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Figure 3:

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Figure 3:Vickers Hardness Tester.

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Figure 4:

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Figure 4:Vickers Hardness Tester (Measurement Of Sample).

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Table 1:

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Table 1 :The above table showing the baseline and post cycle values before and after microhardness testing for the total (16 samples ) which were grouped as Group A , Group B , Group C . Mean , Standard deviation values were interpreted and Statistical analysis was done using Anova , t-test and Post -hoc tests were calculated and P value was interpreted.

Discussion

Hardness is a surface property of a material that shows its resistance against permanent deformation. Vickers hardness is a type of microhardness test which is commonly used to evaluate surface microhardness of brittle and restorative materials [12, 28–31].

Many commercially available ones contain ingredients that may have adverse effects on the surface of restorations and teeth[32]. Little information was available about the adverse effects of some of these new dentifrices [10]. Fluoridated toothpastes have been used extensively and their anti-cariogenic properties have been evaluated through laboratory, clinical and epidemiological studies[ 33]. The increased use of these toothpastes suggests that a more accurate assessment of their effectiveness is needed. Micro hardness determination can provide indirect evidence of demineralization and remineralization in dental hard tissues[34].

The goal of this project was to evaluate the in vivo effects of a novel mouthwash on enamel recovery after demineralization by simulating an artificial intra-oral exposure by using the brushing stimulator. The results showed significantly higher microhardness values following application of the toothpastes.

About the fact that GC tooth mousse supplies calcium and phosphate ions for remineralization, the microhardness was mild. According to Galbiatti et al., after CCP-ACP application, non-homogeneous deposits with adherent irregularities were developed and settled as globular structures .These globular structures occupy the interprismatic cavities and surround the prisms partly[35]. These findings were consistent with the study done by Ferrazzano, 2011[36].

A study by Newby[37] stated that 1150 ppm NaF test dentifrice and Crest Cavity Protection (1100 ppm NaF) protected enamel specimens greater than the fluoride-free placebo. In another study by HatipogluNaF toothpastes significantly increased the microhardness of the lesions (p<0.001) when compared to control groups and revealed a mineral precipitation band on the surface layer of all samples[38].

Haghgoo et al[39] (2014) compared between NHA and NaF mouthwashes and found no difference in the remineralizing effect. However, surface microhardness and tooth remineralization significantly increased. They used the remineralizing agent in the form of a mouthwash. In an in vivo analysis, Najibfard et al[40] (2011) compared 10% and 5% NHA, as well as a mixture of 10% NHA + 1100 ppm NAF. The findings of the microradiographs revealed that the toothpastes tested had similar remineralizing effects. Our findings revealed that toothpaste from group C has a greater remineralizing effect. However, by using the Vickers microhardness tester to measure the remineralizing effect of agents, researchers should be mindful of the method's drawbacks and the limitations of extrapolating in vitro effects to the clinical environment. This procedure is not capable of completely simulating oral conditions.

Our institution is passionate about high quality evidence based research and has excelled in various fields (JayaseelanVijayashreePriyadharsini 2019; Pc, Marimuthu, and Devadoss 2018; Ramesh et al. 2018; Ramadurai et al. 2019; Sridharan et al. 2019;Ezhilarasan, Apoorva, and Ashok Vardhan 2019; Mathew et al. 2020; Samuel 2021; R et al. 2020; Chandrasekar et al. 2020; J. VijayashreePriyadharsini, SmilineGirija, and Paramasivam 2018)

Conclusion

All the three toothpastes showed remineralising potential and there was an increase in the overall microhardness but the values were not statistically significant. Future research should concentrate on assessing the possible impacts of synthetic CPPs in order to develop a new prevention approach focusing on the use of these bio-active concepts in personal hygiene products to mitigate cariogenicity.

Acknowledgement

The authors thank the institution for their support and contribution.