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 Table of Contents  
Year : 2020  |  Volume : 10  |  Issue : 3  |  Page : 129-133

Comparative evaluation of remineralising efficacy of bioactive glass agent and nano-hydroxyapatite dentifrices on artificial carious lesion in primary teeth: An in vitro study

Department of Pediatric and Preventive Dentistry, K M Shah Dental College and Hospital, Sumandeep Vidyapeeth, Vadodara, Gujarat, India

Date of Submission10-Aug-2020
Date of Decision15-Aug-2020
Date of Acceptance20-Aug-2020
Date of Web Publication22-Sep-2020

Correspondence Address:
Seema Bargale
Department of Pediatric and Preventive Dentistry, K M Shah Dental College and Hospital, Sumandeep Vidyapeeth, Vadodara, Gujarat
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/AIHB.AIHB_85_20

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Introduction: The phenomenon of reversal of incipient or early enamel caries forms an important part of prevention leading to apparent repair of the lesion. Recently, novel biomaterials such as the bioactive glass (BAGs) and nano-hydroxyapatite (n-HAP) crystal have been introduced as remineralising agents. Aim: This study aimed to evaluate and compare the remineralising efficacy of BAG agent and nano-hydroxyapatite (NHA) dentifrices on artificial carious lesion in primary teeth. Methodology: Thirty human extracted primary teeth were selected for the study, and the specimens were randomly divided into Group A: BAGs agent toothpaste group and Group B: n-HAP toothpaste group. The surface microhardness of the teeth was measured using a Vickers microhardness tester at the baseline and after demineralisation and remineralisation. The statistical analysis was done using independent t-test for intergroup comparison and paired t-test for intragroup comparison. Results: On intergroup comparison, microhardness differences of baseline to exposure to dentifrice between the two groups showed that microhardness differences of baseline to exposure to dentifrice were higher in Group B with a t value of −2.158 and was statistically significant (P < 0.001). On intragroup comparison of the mean values of baseline microhardness and microhardness after exposure to dentifrices, the mean values of baseline microhardness were higher in both the groups with a difference of 14.3 and 20.45 in Group A and Group B, respectively. Conclusion: Both BAG and NHA toothpastes were considered to be effective for the remineralisation of caries-like lesions of primary teeth. The remineralising efficacy of n-HAP toothpastes was found to be slightly higher than that of BAGs toothpastes, which was statistically significant.

Keywords: Bioactive glass, nano-hydroxyapatite, primary teeth, remineralisation, surface microhardness

How to cite this article:
Khandelwal JR, Bargale S, Dave BH, Poonacha K S, Kariya PB, Vaidya S. Comparative evaluation of remineralising efficacy of bioactive glass agent and nano-hydroxyapatite dentifrices on artificial carious lesion in primary teeth: An in vitro study. Adv Hum Biol 2020;10:129-33

How to cite this URL:
Khandelwal JR, Bargale S, Dave BH, Poonacha K S, Kariya PB, Vaidya S. Comparative evaluation of remineralising efficacy of bioactive glass agent and nano-hydroxyapatite dentifrices on artificial carious lesion in primary teeth: An in vitro study. Adv Hum Biol [serial online] 2020 [cited 2021 Apr 17];10:129-33. Available from: https://www.aihbonline.com/text.asp?2020/10/3/129/295845

  Introduction Top

Degree of saturation of oral fluids with respect to apatitic minerals governs the fundamental process of enamel demineralisation and remineralisation. The incipient or early enamel caries reversal phenomenon forms an important part of prevention, which guides to obvious lesion repair.[1]

Non-cavitated carious lesions that proceed maximally to the junction between dentin and enamel can indeed be stopped or even resolved with non-invasive cariostatic measures. This includes bioactive materials, manufactured from milk products which encourage enamel and dentin remineralisation under cariogenic conditions via the introduction of special remineralising agents.[2] Modern biomaterials such as nano-hydroxyapatite (n-HAP) and bioactive glass (BAGs) have recently been developed as remineralising agents.

BAG is a composite of synthetic minerals that can effectively improve re-mineralisation, containing calcium, sodium, phosphorous and silica. The surface of the tooth is affixed and crystalline hydroxyl-carbonate apatite (HCA) is deposited continuously. Microscopic particles of BAG release thousands of mineral ions upon exposure to humidity, which contributes in the formation of a solid film of hydroxyapatite (HA) on the enamel and dentin surfaces. Not only does this ability fix initial carious lesions but it also eliminates tooth hypersensitivity.[3]

HA is the mineral crystalline form of calcium and phosphorus found in the enamel, dentin, cementum and bone. It is widely used in biology, medicine and dentistry due to its optimal characteristics, such as similarity to the mineral structure of hard tissues, biocompatibility and low solubility.[4] It has remineralising effects when applied to tooth enamel. The recent developments in nanotechnology have resulted in a drop in particle size and even shape modifications, resulting in highly bioactive compounds of calcium phosphate that have a higher penetration potential for the demineralised porosity region as remineralising agents.[5],[6]

n-HAP in the past few years has gained significant recognition in medicine and dentistry, and is considered among the most biocompatible and bioactive materials. Because of its chemical and structural similarities with enamel minerals, the application of n-HAP directly to biomimetic repair of the damaged enamel has gained a great deal of interest in dental science today.[7] In the 1980s, toothpaste containing HA (e.g., Apadent, Apagard and others) was first introduced and checked in Japan.

Considering the value and effectiveness of preventive measures against invasive approaches for the treatment of initial caries and the key problems associated with the use of fluoride, attempts have been made to use synthetic remineral agents as an alternative to fluoride. Thus, owing to the remineralising properties of nano-hydroxyapatite (NHA) and BAG and the significance of preventive and treatments, this study focuses to assess and compare the remineralising effects of NHA and BAGs dentifrices on artificial cavitation in primary anterior teeth using surface microhardness test.

  Methodology Top

This study was conducted as an experimental in-vitro study at the department of paediatric and preventive dentistry and was initiated after the approval of the ethical committee of the institute (SVIEC/ON/DENT/SRP/19010). A sample size of thirty human extracted teeth was selected by using the power calculation of α = 0.05 and 0.20, with 80% being the strength of the test. Teeth which were sound and non-carious and without any restoration, hypoplastic lesions, stains or white spot lesions were included in the study.

Specimen preparation

The selected teeth were adequately cleaned and placed in saline (0.9% solution for sodium chloride) before required for the study. A high-speed diamond disc was used to separate the crown and divide it into two parts [Figure 1]. Pumice polishing paste was used to paint the abraded surfaces. Specimens of thickness 100–150 μm were prepared. The samples were randomly divided into two groups: Group A with BAG toothpaste as test agent and Group B consisting of n-HAP toothpaste as test agent [Figure 2]. The baseline surface microhardness (SMH) of the teeth was measured using a Vickers microhardness tester by applying 25 g load for 5 s.
Figure 1: Sectioning of crown into two halves using a high-speed diamond disc.

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Figure 2: Group A: Bioactive glass toothpaste as the test agent and Group B: Nano-hydroxyapatite toothpaste as the test agent.

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Lesion formation/demineralising regimen

The demineralising solution containing 2.2 mM calcium chloride, 2.2 mM sodium phosphate and 0.05 M acetic acid was prepared, and the pH was adjusted with 1 M potassium hydroxide to 4.4. Each specimen was placed in 15 ml of solution of demineralisation for 48 h for the formation of incipient caries-like lesions.[8]

Once after the formation of cavitation, SMH testing was performed again. The SMH was measured using the same microhardness tester machine under similar conditions.

Dentifrice slurry preparation

Dentifrice slurry was prepared by suspending 12 g of the respective dentifrice in 36-ml deionised water to create a 1:3 dilution. The suspensions were thoroughly stirred with a stirring rod.

Remineralisation regimen

The specimens of each group were then coated with slurry of the toothpastes for 2 min and then immersed in artificial saliva for 10 days [Figure 3]. The artificial saliva contained KCl – 0.4 g/l, NaCl – 0.4 g/l, CaCl2·2H2O – 0.906 g/l, NaH2 PO4·2H2O – 0.690 g/l, Na2S·9H2O – 0.005 g/l, urea – 1 g/l and pH – 6.5.[9]
Figure 3: Remineralising regimen for Group A and Group B.

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Evaluation of specimens

The specimens were evaluated after the remineralisation regimen by Vickers surface microhardness tester machine by applying 25 g load for 5 s [Figure 4].
Figure 4: Surface microhardness evaluation using Vicker's Microhardness Tester.

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  Results Top

Data collected were entered into a computer and analysed using the SPSS software version 25 (SPSS Inc., IBM, Chicago). Result on continuous measurements were presented as mean ± standard deviation, and results on categorical measurements were presented in number (%). Paired t-test was used for intragroup comparison and independent t-test for intergroup analysis.

Surface micohardness evaluation

[Table 1] shows intragroup comparison; the means values of microhardness in Group A (BAG toothpaste) at baseline, after carious lesion formation and after exposure to dentifrices were 360.63 ± 5.78, 270.65 ± 5.23 and 346.31 ± 6.31, respectively. It was found that there was increase in microhardness values from artificial carious lesion formation to the exposure of dentifrices with a difference of 75.65 and was statistically significant with P < 0.001.
Table 1: Intragroup comparison of micro hardness value differences at each interval

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The mean values of microhardness in Group B (n-HAP toothpaste) at baseline, after carious lesion formation and after exposure to dentifrices were 341.73 ± 5.07, 256.54 ± 5.1 and 321.28 ± 6.48, respectively. It was found that there was an increase in microhardness values from artificial carious lesion formation to the exposure of dentifrices with a difference of 64.74 ± 8.59 and was statistically significant with P < 0.001.

[Table 2] shows intergroup comparison; the microhardness difference from artificial carious lesion formation to the exposure to dentifrices was higher in Group B (n-HAP toothpaste) with a mean value of − 64.74 ± 8.59 than Group A with a mean value of − 75.66 ± 5.96 and was statistically significant with P < 0.001.
Table 2: Intergroup comparison of microhardness value differences at each interval

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From the results, negative value indicates increase in SMH, which shows better remineralising efficacy of Group B (n-HAP toothpaste).

  Discussion Top

The cycle of demineralisation of the enamel relies on the pH and composition of the teeth with calcium, phosphate and fluoride. Such factors define the saturation level of minerals. Therefore, a state of subsaturation may lead to the dissolution of HA crystals in the tooth and to the diffusion of calcium and phosphate ions onto the enamel surface.[10] A hypersaturation of the ions on the enamel surface can cause HA crystals to re-deposit, known as remineralisation of the enamel, and perhaps lead to the formation of an intact surface layer on the enamel surface.[11]

Calcium and phosphate ions have a role in the process of demineralisation/remineralisation that has been well recognised. The organic content of saliva also plays an important role in this regard. In our research, the artificial saliva was prepared using both organic and mineral compounds in order to simulate the clinical setting as much as possible. An increased surface microhardness signifies remineralisation, and demineralisation is indicated by a decreased surface microhardness.

BAG is a synthetic composite of minerals consisting of calcium, sodium, phosphorus and silica. It releases crystalline HCA with a mineral-like composition identical to the human tooth. BAG releases ions into its surroundings following immersion in an aqueous surrounding. The sodium ions present in calcium sodium formulation are replaced with hydrogen ions by bioactive phosphosilicate glass and therefore pH increases. The calcium and phosphate ions eventually aggregate and form a thin coating on the tooth surface filled with calcium phosphate. This ionic reservoir will inhibit the demineralisation cycle and improve remineralisation by shielding the enamel from cariogenic conditions.[10] The hydrogen cations in a wet environment and sodium ions are replaced in the particles, enabling the release of calcium and phosphate ions in this material. These reactions occur within seconds. Calcium and phosphate ion release occurs for as long as the substance is in a humid environment. The local pH increases temporarily as a result of sodium release. The calcium and phosphorous ions released from a BAG agent, along with calcium and phosphate ions in the saliva, form a coating of calcium phosphate on the tooth surface as a consequence of their temporary rises in pH. This layer becomes HCA, structurally and chemically resembling biological apatite, by the continuous deposition of calcium and phosphorus.[12]

In our study, application of BAG toothpaste significantly increased the microhardness from artificial carious lesion formation to the exposure of toothpaste. These properties of BAG were proved in previous studies conducted by Palaniswamy et al.,[13] who evaluated the remineralising potential of BAG and Casein phosphopeptide amorphous calcium phosphate (CPP-ACP) on early enamel lesions and found that BAGs and CPP-ACP both acted as novel agents to repair and prevent demineralisation, while BAG proved to be more effective for early remineralisation. Similar results were found in a study conducted by Mony et al.,[14] who evaluated NovaMin's capacity to remineralise a demineralised lesion caused experimentally comparing with sodium fluoride dentifrice in extracted premolars. It was found that NovaMin proved as effective as fluoride in enhancing the Ca/PO4 ratio and hardness of a demineralised enamel.

HA is the main component of enamel that gives a luminous white look and prevents diffuse reflection of light through the closure of the small pores of enamel surface. HA is also a crucial calcium and phosphate source, which is very important to remineralise demineralised enamel surfaces. Indeed, a large prevalence of calcium phosphate salts is an inorganic part of all the mineralised tissues in the human bodies. Certain inorganic materials such as calcium carbonates and sulphates are also found in smaller quantities; HA in particular accounts for 60%–70% and 90%, respectively, in bone and enamel weight. Nanotech interest has recently emerged in various fields, creating interesting and imminent applications in n-HAP dentistry with crystals of 50–1000 nm in size. n-HAP is highly capable of interacting with proteins and plaque and bacterium fragments while in toothpastes. This potential is due to the size of nanoparticles, which significantly increases the surface area that proteins can bind to. The Sangi Co. Ltd in 1978, had the idea to create toothpaste which could restore the tooth enamel, which contains n-HAP (Apadent) for the first time, which is used in our study.[15]

In our study, NHA significantly remineralised the artificial carious lesion. These findings were similar to a study done by Swarup and Rao,[16] who compared the effects of synthetically processed HA particles in the remineralisation of early enamel lesions compared to 2% sodium fluoride and found that the surface morphology of the n-HAP group was close to that of the biological enamel, an increase in mineral content (Ca/P ratio) compared to 2% sodium fluoride.

When the remineralising efficacy of BAGs and n-HAP was compared, specimens of n-HAP group showed an increased SMH values, which was statistically significant. These results were contradictory to the previous study conducted by Haghgoo et al.,[17] who compared the remineralising effects of NovaMin (BAG agent) and NHA on caries-like lesions in primary teeth and found that the mean SMH was found to be higher in the teeth treated with NovaMin toothpaste than in the teeth treated with NHA. However, this difference was not statistically significant.

The results of the current study demonstrate that both non-fluoridated novel remineralising agents i.e., BAG and NHA, enhanced the SMH values after artificial demineralisation, thus proving effective for remineralisation. However, n-HAP was proved to be better than BAGs dentifrice, which could be due to its ability of gradual deposition of the mineral that precipitates and nucleates in the dark zone of demineralisation, thereby offering complete biomimetic regeneration of the lost enamel crystallites.

One possible imitation of the current study can be the differences in artificially stimulated and natural biological condition such as the use of artificial saliva.

  Conclusion Top

Based on the data obtained from the present study, the potential for remineralisation was shown both by BAG and n-HAP toothpastes, but remineralisation of samples treated with n-HAP toothpaste was found to be higher. Hence, in the present study, n-HAP toothpaste showed enhanced remineralisation and therefore can be expected to be efficient in children under high risk who have not achieved healthy oral hygiene behaviours. Children often have the habit of swallowing the paste while brushing their teeth everyday. It may be considered to be one of the benefits of BAG and n-HAP toothpaste over fluoride-containing paste, making it acceptable and safe to be used as a toothpaste of choice for young children.

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Conflicts of interest

There are no conflicts of interest.

  References Top

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Vahid Golpayegani M, Sohrabi A, Biria M, Ansari G. Remineralization effect of topical NovaMin versus sodium fluoride (1.1%) on caries-like lesions in permanent teeth. J Dent (Tehran) 2012;9:68-75.  Back to cited text no. 3
Huang SB, Gao SS, Yu HY. Effect of nano-hydroxyapatite concentration on remineralization of initial enamel lesion in vitro. Biomed Mater 2009;4:341-44.  Back to cited text no. 4
Adams LK, Lyon DY, McIntosh A, Alvarez PJ. Comparative toxicity of nano-scale TiO2, SiO2 and ZnO water suspensions. Water Sci Technol 2006;54:327-34.  Back to cited text no. 5
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Mehta R, Nandlal B, Prashanth S. Comparative evaluation of remineralization potential of casein phosphopeptide-amorphous calcium phosphate and casein phosphopeptide-amorphous calcium phosphate fluoride on artificial enamel white spot lesion: Anin vitro light fluorescence study. Indian J Dent Res 2013;24:681-9.  Back to cited text no. 8
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  [Figure 1], [Figure 2], [Figure 3], [Figure 4]

  [Table 1], [Table 2]


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