Journal of Indian Society of Pedodontics and Preventive Dentistry
Journal of Indian Society of Pedodontics and Preventive Dentistry
                                                   Official journal of the Indian Society of Pedodontics and Preventive Dentistry                           
Year : 2019  |  Volume : 37  |  Issue : 2  |  Page : 146--150

Inhibitory effect of a resin coat-containing prereacted glass fillers on the enamel demineralization of the primary teeth: An in vitro pilot study


R Rabiabasree1, R Krishnakumar2, Anand S Prabhu2, N Sathyajith Naik3, KK Shashibhushan4, K Janarthanan2,  
1 Department of Paediatrics and Preventive Dentistry, Rajah Muthiah Dental College and Hospital, Annamalai University, Chidambaram, Tamil Nadu, India
2 Division of Pedodontics and Preventive Dentistry, Rajah Muthiah Dental College and Hospital, Annamalai University, Chidambaram, Tamil Nadu, India
3 Division of Pedodontics and Preventive Dentistry, Institute of Dental Sciences, Bareilly, Uttar Pradesh, India
4 Division of Pedodontics and Preventive Dentistry, Sharavathi Dental College, Shimoga, Karnataka, India

Correspondence Address:
Dr. R Rabiabasree
Department of Paediatrics and Preventive Dentistry, Rajah Muthiah College and Hospital, Annamalai University, Annamalai Nagar, Chidambaram - 608 002, Tamil Nadu
India

Abstract

Background: With an increasing interest in preventive strategies, pedodontics research is now more focused on developing newer materials and techniques to coat the primary teeth to prevent onset of new carious lesions. Aim: The aim of this study is to evaluate the inhibitory effect of prereacted glass (PRG) filler-containing resin coat on enamel demineralization of the primary teeth. Subjects and Methods: Eight de-rooted primary caries-free teeth sectioned into 4 mm × 4 mm were divided into either experimental group which received the PRG barrier coat or control group which was left uncoated. These were then immersed in acid buffer at pH 4.5 for 3 days. Mineral content was evaluated by scanning electron microscopy with energy dispersive X-ray analysis. Statistical Analysis: Data were collected and analyzed statistically using paired Student's “t” test, with a P < 0.05 being considered statistically significant. Results: When the calcium/phosphorous (Ca/P) ratio (wt%) which is indicative of the mineral content of enamel was compared, the values were higher for the experimental group than that for the control group and the association was statistically significant (P < 0.01). Conclusion: The higher Ca/P ratio of experimental group was suggestive of the ability of PRG barrier coat to inhibit enamel demineralization in the primary teeth.



How to cite this article:
Rabiabasree R, Krishnakumar R, Prabhu AS, Naik N S, Shashibhushan K K, Janarthanan K. Inhibitory effect of a resin coat-containing prereacted glass fillers on the enamel demineralization of the primary teeth: An in vitro pilot study.J Indian Soc Pedod Prev Dent 2019;37:146-150


How to cite this URL:
Rabiabasree R, Krishnakumar R, Prabhu AS, Naik N S, Shashibhushan K K, Janarthanan K. Inhibitory effect of a resin coat-containing prereacted glass fillers on the enamel demineralization of the primary teeth: An in vitro pilot study. J Indian Soc Pedod Prev Dent [serial online] 2019 [cited 2019 Oct 19 ];37:146-150
Available from: http://www.jisppd.com/text.asp?2019/37/2/146/261350


Full Text



 Introduction



Oral health is one of the essential dimensions to the quality of life.[1] In India, the trend indicates an increase in oral health problems, especially dental caries, which has been consistently increasing both in prevalence and in severity over the last five decades.[2] Children of all age groups are affected by dental caries and its treatment is restorative care, which may even include pulp therapy. These treatment options are not only expensive but also demanding for a child. The best option, which is more acceptable and economical for the children is, prevention.[3]

Several caries preventive strategies have been advocated including patient education, diet modifications, tooth brushing, systemic and topical fluorides, sealants, and antimicrobials[4] to the most recent sealing or infiltration of incipient enamel caries lesions with low viscosity light-curing resins.[5]

Coating materials make the enamel surface smooth and protect against bacterial retention in the incipient caries lesion. The esthetic advantage of coating materials is also preferable.[5]

Roberts et al. first remarked about the newly developed prereacted glass (PRG) ionomer filler technology.[6] The PRG barrier coat is a giomer dental material that contains surface PRG (S-PRG) filler, to which PRG technology had been applied. It is characterized by its bioactive functions because of the gradual release of multiple ions.[7]

PRG filler is a xerogel. A ligand exchange mechanism within the prereacted hydrogel endows PRG fillers with the ability to release and recharge fluoride. The fluoride ion sustained release PRG filler can provide stable fluoride ion release for a long time. Even when dried and then dispersed in water, there can be a fluoride ion release. This is due to hydrolysis of the compounds through a ligand exchange that involves no compound dissociation. In conventional dental composition, it results in a disintegration of the compounds when dissolved in water. When PRG filler was dispersed in water, the fluoride ion concentration is in an equilibrium state such that the fluoride ion supply is replenished as it is consumed from the water and also has a characteristic feature of releasing fluoride ion sustainably without involving any compound disintegration.[8] Silicate and fluoride strongly induce remineralization of the dentin matrix. Strontium and fluoride also improve the acid resistance of teeth by converting hydroxyapatite to strontium apatite and fluorapatite.[9]

Sodium ions (Na+) released by PRG fillers are water soluble and induce the function of five other ions, namely aluminum (Al3+), borate (BO3−), silicate (SiO2−), fluoride (F−), and strontium (Sr2+) ions. Borate ion (BO3−) which is released has bactericidal activity, promotes bone formation, and prevents bacterial adhesion and antiplaque properties. The aluminum ions (Al3+) control hypersensitivity. Silicate ion (SiO2−) leads to the calcification of bone, whereas strontium ions (Sr2+) have a neutralization effect, act as acid buffer, promote formation of bone tissues, and improve acid resistance. Fluoride ions (F−) help in creation of fluorapatite crystals (formation of acid-insoluble crystals, caries prevention, antibacterial effect, and remineralization of decalcified lesions). PRG fillers alter the pH of the surrounding environment within a weakly alkaline range when they come into contact with water or acidic solutions.[9] Therefore, the filler could be advantageously incorporated into dental compositions which require fluoride ion release, in response to various application needs in dentistry.[6]

PRG barrier coat has been extensively used as a desensitizing material;[10],[11],[12] however, fewer studies[5],[7] exist on its ability to arrest caries for primary tooth enamel. Thus, the present study was conducted to determine the inhibitory effect of PRG filler-containing resin coat on the demineralization of the primary teeth enamel following immersion in demineralizing buffer solution with evaluation using scanning electron microscope with energy dispersive X-ray (SEM-EDX) analysis.

 Subjects and Methods



Eight primary teeth without any hypoplastic lesions, visible caries, and white spots on the tooth surface that were extracted for orthodontic reasons were collected for the present study.

The primary teeth which were collected and sectioned with an airotor (NSK Pana-Air S B2, Japan) following removal of the roots, dividing the crowns into mesial and distal half. Then, the specimens were ground using 600-grit emery sheet and polished. The polished surface area of the specimens were approximately 4 mm × 4 mm in dimension.[13]

The specimens were randomly divided into two groups, namely experimental group and control group with four specimens in each group. The enamel specimens of the experimental group were coated with PRG filler-containing resinous coating material, PRG barrier coat (Shofu Dental Corporation). The PRG barrier coat was manipulated as per the manufacturer's recommendation. The prepared mixture was applied onto the enamel surface within 2 min of mixing as there are chances for the material to become more viscous. Then, the enamel specimens were left untouched for 3 s and then cured by irradiation with a light activation unit (Woodpecker, LED.D Germany). The specimens were cured at a light intensity of 1000 MW/cm2 for 10 s at a distance not >6 mm between the light tip and the resin coat.[14] The enamel specimens in the control group were left uncovered. An acidic demineralizing buffer solution containing 2.2 mmol/L calcium chloride, 2.2 mmol/L sodium hydrogen phosphate, and 50 mmol/L acetic acid, adjusted to pH 4.5 with sodium hydroxide was prepared.[14] The enamel specimens were immersed individually in 10 ml of the prepared solution and were incubated for 3 days at 37°C. The demineralization buffer was changed every 24 h and the pH was measured using a pH meter, in accordance with Ma et al.[15] At the end of the 3rd day, the PRG barrier coat from the experimental group was carefully removed with a dental explorer from each enamel specimen.[10] All the enamel specimens in the study were polished and gold sputtered using a gold sputtering unit and were mounted on to a brass specimen stub using a carbon-based adhesive tapes. Then, they were subjected to SEM-EDX analysis at 15 kV,[12] to evaluate calcium and phosphorous content. The calcium and phosphorous contents were then converted into Ca/P ratio (wt %) from the obtained data. Since the data are in continuous scale, parametric tests of significance were employed to identify statistical significance. The mean Ca/P ratio (wt %) of the experimental and the study group was compared using paired Student's “t” test and a P < 0.05 was considered as statistically significant.

 Results



In the SEM photomicrograph of the experimental group, the enamel surface had an orderly placed rod appearance and the enamel crystals were homogenously arranged with a clear outline [Figure 1]. However, in the control group, there were increased surface porosities and a clear destruction of the enamel surface resulting in significant depression and irregularities [Figure 2].{Figure 1}{Figure 2}

The calcium and phosphorous mineral content evaluation using SEM-EDX analysis showed higher values for the experimental group over the control group [Figure 3] and [Figure 4].{Figure 3}{Figure 4}

The mean Ca/P ratio (wt %) of the experimental group was 2.36 and the control group was 1.38 [Table 1]. When the control group was compared with the experimental group for the Ca/P ratio (wt %), the values were higher for the experimental group and the association was statistically significant (P = 0.01).{Table 1}

 Discussion



Although enamel is the most acid-resistant substance in the human body, it is constantly subjected to the presence of cariogenic plaque along with the presence of fermentable carbohydrates. The demineralization process happens when the environmental acidity (pH) drops below a certain level (critical pH).[16]

PRG fillers contain prereacted hydrogel, by a ligand exchange mechanism; it has an ability to release and recharge fluoride. Only limited studies has been reported on the efficacy of PRG filled-coating material in inhibiting demineralization for primary tooth enamel after an acidic challenge.[5],[7] Thus, the present study was conducted to evaluate the inhibitory effect of PRG filler-containing resin coat on enamel demineralization of the primary teeth.

Eight primary caries free teeth sectioned into 4 mm × 4 mm[13] were divided into either experimental group which received the PRG barrier coat or control group which was left uncoated. These were then immersed in acid buffer at pH 4.5 for 3 days.[15] The PRG barrier coat was carefully removed with a dental explorer from each enamel specimen of the experimental group.[10] All the enamel specimens of both the groups were then polished and gold sputtered using a gold sputtering unit and were mounted on to a brass specimen stub using a carbon-based adhesive tapes. The sputter, stub, and adhesive tape are made out of conductive material to conduct current produced by the electron beam away from the enamel specimen, thereby avoiding secondary electron scattering.[17] Then, they were subjected to SEM-EDX analysis at 15 kV.[12] The methodology followed was in accordance with Nakamura et al.[13] and Ma et al.[15] Data were collected and analyzed statistically using paired Student's “t” test with a P < 0.05 being considered statistically significant.

In the enamel samples of the experimental group, the enamel surface had an orderly placed rod appearance and the enamel crystals were homogenously arranged with a clear outline, while in the control group, there were increased surface porosities and a clear destruction of the enamel surface resulting in significant depression and irregularities.

It has been reported that the mean Ca/P ratio of the primary teeth enamel is 2.00 ± 0.3 (Bhaskar Das et al., 2016).[18] In the present study, the control group shows a mean Ca/P ratio of 1.3200 which is lower than the above figure, suggesting that the demineralization process has occurred. However, in the experimental group, the Ca/P ratio was 2.36 which presumably signifies a better degree of inhibition of demineralization. This was in accordance with Hegde and Moany, 2012,[19] Yumiko Hosoya et al., 2013,[10] and Kawasaki et al., 2014.[20] When the control group was compared with the experimental group for the Ca/P ratio (wt%), the association was statistically significant (P = 0.01).

A ligand exchange mechanism within the prereacted hydrogel endows S-PRG fillers with the ability to release and recharge fluoride. In addition to fluoride, S-PRG fillers released Al, B, Na, Si, and Sr ions. Strontium and fluoride also improve the acid resistance of teeth by converting hydroxyapatite to strontium apatite and fluorapatite.[10] The above mechanisms are the probable reasons which enable the PRG barrier coat material to inhibit demineralization in the present study.

 Conclusion



The presentin vitro study was carried out in an environment that simulates the complex oral cavity and the result demonstrated the inhibitory effect of PRG filler-containing resin coat on enamel demineralization of the primary teeth. As it takes only 20 s to apply, PRG barrier coat is useful in young children and could be particularly beneficial for children with limited cooperation.

Limitations

An oral cavity is affected by brushing and chewing which carries the possibility of a coated material on tooth getting worn out. However, the present study does not address the wear resistance of the material. Thus, it is recommended further studies be conducted to evaluate the wear resistance of the material, to determine its durability in an oral environment.

Acknowledgment

It is gratifying that I (R Rabiabasree) have been able to honor my well-wisher and my mentor Prof. Dr. R Krishnakumar, for his untiring, compassionate, selfless efforts, indispensable support, and motivation which brought out the best in me. My sincere thanks to Prof. Dr. DK Sugumaran, Prof. Dr. G Mohan, Prof. Dr. Syed Shaheed Ahamed, and Prof. Dr. Anand S Prabhu for their never ending support. My heartfelt thanks to my family and my friends Dr. S Praveen Kumar, Dr. C Shunmuga Sankari, Dr. R Amirtha Varshini, and Dr. M Nisha, who have emotionally supported me in all of my pursuits and thereby helped me to follow my dreams. Special mention to my senior Dr. Lokesh for his great ideas and my juniors, Dr. V Sandhiya and Dr. N Anushaa for their constant enthusiasm, valuable suggestions, cooperation, and help during my work.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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