| Abstract|| |
Introduction: Remineralization as a treatment procedure has received a lot of attention both from clinicians as well as researchers. The objective of this study was to assess the effect of Remin Pro® on enamel microhardness after bleaching the teeth with McInnes bleaching agent using Vickers microhardness tester.
Materials and Methods: In this study, freshly extracted ten central incisors were taken which were subjected to baseline indentation by using Vickers microhardness indenter and then McInnes bleaching solution was applied for 5 min to demineralize these teeth. Remin Pro a newer remineralizing agent was applied for 7 days, which showed an increase in microhardness at the end of 7 days.
Results: The values were subjected for statistical analysis using paired t-test. All the samples showed a decrease in the microhardness after bleaching with McInnes solution. The decrease in mean hardness from baseline to demineralization was found to be statistically significant (P < 0.001). However, remineralizing the same tooth with Remin Pro for 7 days, showed an increase in hardness, which was found to be statistically significant (P < 0.05).
Conclusion: McInnes bleaching agent decreases the microhardness of enamel and Remin Pro® used in the study causes an increase in the microhardness of bleached enamel.
Keywords: Demineralization, McInnes bleaching agent, remineralization, Remin Pro®
|How to cite this article:|
Kamath U, Sheth H, Mullur D, Soubhagya M. The effect of Remin Pro® on bleached enamel hardness: An in-vitro study. Indian J Dent Res 2013;24:690-3
Currently, treatment modalities available to treat discolored teeth include laminates, porcelain jacket crown and bleaching. Of these bleaching is popular, as it is least invasive, least expensive and simple to use. 
|How to cite this URL:|
Kamath U, Sheth H, Mullur D, Soubhagya M. The effect of Remin Pro® on bleached enamel hardness: An in-vitro study. Indian J Dent Res [serial online] 2013 [cited 2019 Sep 22];24:690-3. Available from: http://www.ijdr.in/text.asp?2013/24/6/690/127612
The technique was first described in 1877 as whitening of teeth. Later in 1916, Dr. Walter Kane used hydrochloric acid to remove fluorosis stains. In 1937, Ames used an alternative technique using the hydrogen peroxide instead of hydrochloric acid to remove fluorosis stains. , McInnes successfully bleached the teeth with endemic fluorosis, wherein he used five parts 30% hydrogen peroxide, five parts 36% hydrochloric acid and one part ethyl ether. ,
Significant amount of mineral loss has been noted due to increased frequency of acid exposure in bleaching, which tends to alter the total demineralization/remineralization amounts. , Various methods have been used to analyze tooth demineralization/remineralization. These include microradiography to measure mineral loss/gain, indirect measures like iodine permeability and surface microhardness. 
Remin Pro® (VOCO GmbH) is a newer remineralizing water-based cream which contains hydroxyapatite, fluoride and xylitol. Hydroxyapatite fills eroded enamel, fluoride seals dentinal tubules and xylitol acts as an antibacterial agent. It has been recommended for the management of dentinal hypersensitivity, to prevent enamel demineralization and to promote remineralization of enamel subsurface lesions. 
The present study was undertaken to investigate the influence of McInnes bleaching agent on enamel microhardness and subsequent remineralization by Remin Pro® on bleached enamel surface using Vickers hardness indenter.
| Materials and Methods|| |
Various materials and equipment used in the study are shown in [Table 1].
Ten freshly extracted, sound central incisors were selected and their roots were removed. Then, each tooth crown was embedded in self-cured acrylic resin molds, with the labial surface leveled on top and lying flat and parallel to the horizontal plane. Mounted samples were stored in artificial saliva to prevent dehydration. The baseline microhardness measurements were taken on the labial surface by means of a Vickers indenter with 100 g of force for 30 s by focusing at × 10 objective lens [Figure 1], two indentations on each sample away from edge were made and the average of two readings were taken as baseline microhardness measurement.
Preparation of bleaching agent and its application
Freshly prepared McInnes bleaching solution consists of a mixture of 1 ml of 36% hydrochloric acid, 1 ml of 30% hydrogen peroxide and 0.2 ml of anesthetic ether which is mixed in the ratio of 5:5:1. It was applied to the enamel surface using a cotton applicator for 5 min. Then, the samples were washed with deionized water and blotted dry using absorbent paper and again the microhardness of the enamel surfaces was measured with the Vickers indenter as previously. Then again the samples were stored in artificial saliva for next 24 h to prevent dehydration.
Remineralization process using Remin Pro®
Remin Pro® paste was applied with cotton applicator on the enamel surface of samples for 3 min [Figure 2] washed with deionized water and stored in artificial saliva every day for 7 days. At the end of 7 days, the samples were washed with deionized water and blotted them dry using absorbent paper. Again the microhardness of the enamel surfaces was measured with the Vickers indenter as previously.
Then, the obtained data was subjected to statistical analysis.
The data were analyzed by paired t-test.
| Results|| |
The mean value of hardness at baseline was found to be 304.00 ± 4.42 (standard deviation [SD] = 4.42) and after demineralization by using bleaching agent, there was a reduction in the hardness value, which was 294.70 ± 4.18 (SD = 4.18). The decrease in mean hardness from baseline to demineralization was found to be statistically significant (P < 0.001) [Table 2].
After remineralization mean value hardness increased to 304.10 ± 8.29 (SD = 8.29), which was found to be statistically significant (P < 0.05) [Table 3] and [Figure 3].
|Table 3: Comparison of hardness at remineralization from demineralization |
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| Discussion|| |
McInnes bleaching agent has been specifically recommended for the treatment of teeth with endemic fluorosis and has gained popularity in clinical set up because of its superficial nature, easy manipulation and its quality of being less expensive. ,
The effects of bleaching on microhardness of enamel are related to their pH and the strong oxidizing effect of hydrogen peroxide on enamel, which leads to alteration of the enamel matrix. , Hydrogen peroxide diffuses through the enamel and dentin releasing free radicals. These reactive oxygen molecules and hydrogen peroxide ions convert the long chained dark colored chromophores into light colored chromophores. This effect can be enhanced by lowering the pH of the bleaching agent, which alters the mineral composition, hence decreasing enamel and dentin microhardness. 
Various methods have been used for analyzing tooth demineralization and remineralization, which includes both direct and indirect techniques. The key in utilization of indirect methods is the realization that they measure properties, which may change with mineral content variations, but are not equivalent to mineral gain or loss.
Hardness of enamel can be measured by many techniques, including spherical, Knoop or Vickers indenters. In the Vickers hardness test, a diamond in the shape of a square-based pyramid is pressed into the polished surface of a material under a specific load. The test is suitable for determining the hardness of very brittle materials, such as tooth structure.  The average hardness value for enamel is in the range from 270 to 350 KHN range or from 250 to 360 VHN range. In this study, the microhardness values were in the range from 285 to 317 VHN, which was within the standard range.
One of the factors, which may alter the hardness, was preparation of specimens, because any tilt or not flat surface may yield a too large indentation and thus a smaller Vickers hardness measurement. Hence two indentations were made to avoid any operational bias and then the average of these two indentations was taken for statistical analysis.
We used artificial saliva for storing the specimens in between bleaching cycles as studies have shown that by doing this there is a slight increase in microhardness after demineralization. ,
Various techniques for neutralizing the effect of bleaching are the use of baking soda, prophylactic paste containing fluoride, acidulated phosphate fluoride gel and use of copious amount of water.  In the present study Remin Pro® (VOCO GmbH) has been used, which is commercially available.
Remin Pro® (VOCO GmbH) is a water-based cream, which contains hydroxyapatite, fluoride and xylitol. Hydroxyapatite fills the superficial enamel lesions and the tiniest irregularities that arise from erosion. Fluoride gets converted to fluorapatite when it comes in contact with saliva; thus, strengthens the tooth and renders it more resistant to acid attacks. Xylitol reduces the harmful effects of bacteria and their metabolic product lactic acid.
Previous studies have shown that, there was no much change in microhardness immediately after the first cycle of bleaching with McInnes bleaching solution. On the contrary in our study, there was a significant amount of reduction in microhardness after the first cycle of bleaching. , It may be due to variation in specimen preparation, preparation of McInnes bleaching solution or Vicker microhardness indenter.
With the use of Remin Pro® (VOCO GmbH) after bleaching, there was a considerable increase in microhardness, which was comparable with other leading brands, like GC tooth mousse. , This may be due to the presence of 1450 ppm fluoride, which is 61% higher than other brands available today (900 ppm fluoride present in GC tooth mousse plus).
In summary, McInnes bleaching agent used in this study caused a significant decrease in the enamel microhardness (294.70 ± 4.18, SD = 4.18), when compared with the baseline values (304.00 ± 4.42, SD = 4.42). However subsequent remineralizing by Remin Pro® for 7 days caused recovery in the microhardness (304.10 ± 8.29, SD = 8.29), which was almost equal or slightly more than the baseline value.
This study was conducted with a small number of samples utilizing in vitro conditions. Application to the general population requires further research and analysis.
| Conclusion|| |
From the above study it can be concluded that,
- McInnes bleaching agent causes a decrease in the microhardness of enamel by causing enamel demineralization
- Remin Pro® used in the study causes an increase in the microhardness of bleached enamel.
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Department of Conservative and Endodontics, Dr. Syamala Reddy Dental College and Hospital, Bangalore, Karnataka
Source of Support: Grants – Author; Equipment –Vickers Micro indenter,
Metallurgic Laboratory, Bangalore. Drugs – Author; Statistical Help –
Mr. Thejasvi Venkateshmurthy, Statistician, Bangalore, India, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3]