|Year : 2014 | Volume
| Issue : 2 | Page : 63-69
Comparative evaluation of antibacterial effect and physical properties of conventional glass-ionomer cement containing 1% chlorhexidine and 1% xylitol
AR Prabhakar, Sonali Agarwal, N Basappa
Department of Pedodontics and Preventive Dentistry, Bapuji Dental College and Hospital, Davangere, Karnataka, India
|Date of Web Publication||11-Sep-2015|
A R Prabhakar
Department of Pedodontics and Preventive Dentistry, Bapuji Dental College and Hospital, Davangere, Karnataka
Source of Support: Nil., Conflict of Interest: There are no conflicts of interest.
Context: The therapeutic procedures used in the treatment of caries do not always eliminate all the microorganisms. The persisting cariogenic bacteria can cause recurrent caries leading to failure of the restoration. Hence, incorporation of an agent with enhanced antimicrobial effect into the restorative material may be of paramount significance. Aim: To study the effect of 1% xylitol (XYL) (artificial sweetener) and 1% chlorhexidine (CHX) diacetate on antibacterial property against Streptococcus mutans and physical properties of conventional glass-ionomer cement (GIC). Settings and Design: An experimental in vitro intergroup randomized control trial. Materials and Methods: Study consisted of three test groups: Group 1 (conventional GIC), Group 2 (GIC + 1% XYL), and Group 3 (GIC + 1% CHX diacetate). A total of 135 samples were evaluated for antibacterial activity against S. mutans after 48 h and 7 days, and physical properties – compressive strength after 24 h and 7 days and setting time. Statistical Analysis: Multiple group comparison was made using one-way analysis of variance complemented by Tukey's post-hoc test, and intragroup comparison was made by Student's paired and unpaired t-test. Results: At the end of 48 h and 7 days, Group 3 exhibited highest antibacterial effect and Group 1 (control) showed the highest compressive strength after 24 h and 7 days, setting time was slightly prolonged for Groups 2 and 3. Group 2 and 3 exhibited a similar effect on physical properties. Conclusion: CHX diacetate displayed superior antibacterial activity, although both CHX and XYL affected the physical properties of conventional GIC to an equal extent.
Keywords: Antibacterial, atraumatic restorative treatment, chlorhexidine, glass-ionomer cement, xylitol
|How to cite this article:|
Prabhakar A R, Agarwal S, Basappa N. Comparative evaluation of antibacterial effect and physical properties of conventional glass-ionomer cement containing 1% chlorhexidine and 1% xylitol. Int J Oral Health Sci 2014;4:63-9
|How to cite this URL:|
Prabhakar A R, Agarwal S, Basappa N. Comparative evaluation of antibacterial effect and physical properties of conventional glass-ionomer cement containing 1% chlorhexidine and 1% xylitol. Int J Oral Health Sci [serial online] 2014 [cited 2019 Sep 20];4:63-9. Available from: http://www.ijohsjournal.org/text.asp?2014/4/2/63/165103
| Introduction|| |
Basic properties of dental materials for restorative treatment, such as mechanical, physical, and bonding properties, have been greatly improved as a result of numerous investigations, and many of the recent products in market exhibit excellent/acceptable clinical performance. Such improvement of restorative materials has contributed to the recovery of ideal anatomical form and function with less removal of tooth structure, leading the way to esthetic restorative treatments and minimal intervention dentistry. Accordingly, it is proposed that innovation of restorative materials in the new era could be directed toward a new dimension: Development of materials with "bio-active functions" to provide therapeutic effects.
As one bio-active function proposed for restorative materials is an antibacterial activity, it can be highlighted for the restorative treatment of caries. The ability to control bacteria would be advantageous to eliminate the risk of further demineralization and cavitation, since dental caries is an infectious disease, and eradication of cariogenic bacteria is an important principle.
One such area where restorative materials with enhanced antibacterial activity are being used is atraumatic restorative treatment (ART).
ART is one minimal intervention approach in which demineralized tooth tissues are removed using manual instruments, and the cavity, including adjacent pits and fissures, is restored using a filling material, usually a glass-ionomer cement (GIC). Since ART can be performed under circumstances where neither electricity nor local anesthesia is required, it is possible that insufficient carious tissues are removed in the process of cavity cleaning. Accordingly, improvement of filling materials to overcome the problems caused by incomplete removal of infected dentin will lead to an increase in the success rate of ART.
Literature reveals that only chlorhexidine (CHX) has been widely incorporated in GIC and all the studies have shown an increase in the antibacterial effects in vitro, however, the physical properties of the cement have been adversely affected.
Medicinal plants have been used for centuries and have become part of complementary medicine worldwide because of their potential health benefits. Xylitol (XYL) a five carbon sugar (polyol) is a natural sweetener found in xylan-rich plants, trees, fruits, and vegetables. The cariostatic and therapeutic effects of XYL have been attributed to both microbiologic and physiochemical actions of XYL. The majority of oral bacteria cannot utilize XYL. XYL leads to inhibition of acid production, and most of the oral streptococci have also been found to be inhibited by it. It has been found to specifically interfere with the metabolism and adherence of Streptococcus mutans and possibly of lactobacilli also. This inhibition occurs due to the formation of XYL-5-phosphate, which is toxic to the organism but not to humans.
Thus, the present study is a modest attempt to explore the influence of addition of XYL – a natural safe traditional phyto extract and to study its effect on the antibacterial and physical properties (compressive strength and setting time) of conventional GIC.
| Materials and Methods|| |
The present study is an in vitro design; ethical approval had been obtained for the same from the Institutional Review Board (Ref No: BDC/Exam/256/2014-15).
Preparation of experimental material, that is, glass-ionomer cement with 1% xylitol and glass-ionomer cement with 1% chlorhexidine diacetate
- Group 1 (control): Fuji IX GIC
- Group 2: To obtain a concentration of 1% w/w of XYL in GIC, 0.15 g of XYL was added to 14.85 g of GIC Fuji IX powder
- Group 3: To obtain a concentration of 1% w/w of the CHX diacetate, 0.15 g of CHX diacetate was added to 14.85 g of GIC Fuji IX powder.
The resultant mixture was thoroughly triturated in a mortar and pestle to obtain the powder for each of the test groups.
This study was conducted in three parts:
- Part I: Evaluation of antibacterial activity against S. mutans after 48 h and 7 days
- Part II: Evaluation of compressive strength after 24 h and 7 days
- Part III: Evaluation of setting time.
Part I: Evaluation of antibacterial activity
The antibacterial activity of the unset cement specimens was evaluated using the agar inhibition test in a laminar airflow unit.
A loopful of S. mutans inoculum from the lyophilized culture was transferred to 10 ml of brain heart infusion (BHI) broth. The resultant broth with S. mutans was incubated for 24 h. After a 24 h incubation period, a loopful of S. mutans was spread onto a BHI agar plate and left for 30 min.
Five wells were made on the agar plate with the help of cork borer (Fisher Scientific, UK). Two such agar plates were prepared (total of 10 wells for each group).
Powder and liquid of each experimental group were mixed (according to the manufacturer's instructions), then placed into the wells made in the agar plates inoculated with the bacterial strain as described previously. The plates were then incubated at 37°C ± 0.5°C for 48 h and the diameters of zones of inhibition produced around the specimens were measured. The size of inhibition zones were calculated by subtracting the diameter of the specimen from the total diameter of the specimen (diameter of cement sample + diameter of inhibition zone).
The specimens were then left in the same plates for 3 more days in the incubator (total of 5 days) and then transferred to freshly inoculated plates and left there for 48 h more to obtain the inhibition zones for day 7. As mentioned above, the zones of inhibition around the specimens were measured for S. mutans.
Part II: Evaluation of compressive strength
Brass molds of a standardized size, that is, 4 mm diameter × 6 mm long were used to prepare specimens. Powder and liquid were mixed according to the manufacturer's instructions. Molds were filled with the respective restorative materials. The ends of each sample were ground flat using wet 600 grit silicon carbide paper, then removed from the molds and stored in 100% relative humidity for 60 min. The specimens were then stored in distilled water for 24 h and 7 days prior to testing. The specimens were tested using a Universal testing machine at a crosshead speed of 1 mm/min. Each specimen was placed with the flat ends between the plates of the testing machine, and the compressive load was applied along the long axis of the specimen. The compressive strength (C), measured in megapascals (MPa), was calculated using the following formula: C =4P/πD2 (where P is the maximum force applied in Newtons (N) and D = diameter of the specimen).
Measurement of compressive strength was done twice, that is, once after 24 h and again after 7 days. A total of ten samples were tested for each of the groups.
Part III: Evaluation of setting time
The setting time was evaluated for the following three groups:
The net setting time is the time measured from the end of mixing until the material sets. The test was undertaken in a climatic condition of 37°C, using a Vickers needle (300 g, 1.12 mm) with a flat end that was plane and perpendicular to the long axis of the needle. Five specimens per group were prepared in a brass mold, having an inner diameter of 10 mm and 1 mm thickness and positioned on mixing pad paper and then filled to a level surface with mixed GIC. The upper surface was made flat by pressing down with a glass slide. The assembly comprising mold, foil, and cement was placed on the vicat apparatus.
The indenter was carefully lowered vertically into the surface of the cement every 15 s. The net setting time was recorded as the time that elapsed between the end of mixing and time when the needle failed to make a complete circular indentation in the cement.
For the evaluation of antibacterial activity, multiple group comparison was made using one-way analysis of variance (ANOVA) complemented by Tukey's post-hoc test and intragroup comparison was made by Student's paired t-test. For the evaluation of compressive strength, group-wise comparison was made using one-way ANOVA complemented by Tukey's post-hoc test and intragroup comparison was made by Student's unpaired t-test. For setting time, the intergroup comparison was made using one-way ANOVA.
| Results|| |
All the groups depicted higher mean antibacterial activity after 48 h which declined significantly after 7 days.
[Table 1a] and [Table 1b] shows the mean values of inhibition zones obtained for the various groups after 48 h and 7 days and the significance of the difference between the groups. Highest mean antibacterial activity was shown by Group 3 that is, GIC + 1% CHX [Figure 1].
|Table 1a: Descriptive statistics showing intragroup comparison of the inhibition zones (mm) produced by the control and the test groups against Streptococcus mutans nd of 48 h 7 days|
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|Table 1b: Descriptive statistics showing intergroup comparison of the inhibition zones (mm) produced against Streptococcus mutans at the end of 48 h and 7 days|
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|Figure 1: Intragroup comparison of the inhibition zones (mm) produced against Streptococcus mutans after 48 h and 7 days|
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Compressive strength values increased after 7 days for all the groups compared to that after 24 h. Group 1 showed the highest mean compressive strength, however, the difference in compressive strength values of Group 2 and Group 3 was comparable [Table 2a], [Table 2b] and [Figure 2].
|Table 2a: Descriptive statistics showing intragroup comparison of compressive strength values after 24 h and 7 days|
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|Table 2b: Descriptive statistics showing intergroup comparison of mean difference in compressive strength values after 24 h and 7 days|
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|Figure 2: Intragroup comparison of the compressive strength values (megapascals) at the end of 24 h and 7 days|
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Setting time was found to be slightly prolonged for Groups 2 and 3 [Table 3] and [Figure 3].
|Table 3: Descriptive statistics showing intergroup comparison of setting time|
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| Discussion|| |
Globally, dental caries ranks amongst the most prevalent diseases of humans. Realization that dental caries is reversible in the initial stages and a dynamic biochemical event at a micron level, has changed the way the profession recognizes the caries process. In communities with few dental facilities and care providers, alternative measures for treating caries are often used, one such alternative therapy being ART, wherein minimal cavity preparation using only hand instruments followed by restoration of the cavity with an adhesive filling material, such as GIC is done.
However, although it is believed that hand excavation is capable of removing most of the infected dentin; research has shown that bacteria remain even after complete hand excavation within the tubuli of affected dentin, and thus necessitating further research directed specifically toward uplifting the level of asepsis achieved before cavity restoration. In this regard, enhancing the antibacterial effect of the restorative cement might be looked upon as a plausible solution.
Various investigators have attempted to enhance the antibacterial effect of GIC (restorative cement most commonly employed for ART) by incorporating various synthetic and natural chemical substances with inherent antibacterial effect but, however, none of them has been successful without jeopardizing the physical properties of the cement which in turn adversely speaks upon the longevity of the restoration.,,,
Investigators highly recommend the usage of the CHX diacetate, particularly between 1% and 5% final concentrations to obtain optimum antibacterial effects without jeopardizing the basic physical properties of the GICs.,,, According to Takahashi et al., antibacterial effect was not dose dependent, however, incorporation of CHX diacetate at concentrations 2% or higher, significantly decreased the compressive strength, bond strength to dentin, and setting time of the cement. Hence, a concentration of <2% that is, 1% of CHX diacetate was selected in the present study, as a proven gold standard to which we could compare the efficacy of a relatively unexplored natural antibacterial agent-XYL.
This study being the first of its type wherein an attempt to incorporate XYL into a restorative material was to be experimented, selection of an appropriate concentration of the medicament was a big challenge.
XYL has been shown to be effective in the prevention of caries when consumed in quantities as little as 8 g/day. The range of commercially available products containing 4 g of XYL or higher per serving has expanded in recent years. According to Söderling et al. concentrations of XYL as low as 1% was also successful in achieving around 70% of S. mutans inhibition, thus, providing the researchers with a more practical concentration gradient that could be incorporated into GIC, and similarly was followed by us wherein a concentration of 1% XYL was selected to be incorporated into GIC.
The unset cement specimens were assessed for their antibacterial activity after 48 h and 7 days. All the groups exhibited significant antibacterial activity, however, CHX DA incorporated GIC (Group 3), displayed the highest inhibitory effect compared to its counterparts. The decreased antibacterial activity exhibited by XYL group in comparison to CHX DA group could probably be attributed to the fact that XYL used was a natural nonsynthetically derived phytoextract with probable impurities as well. Whereas CHX DA tested was a 100% pure commercially available synthetically prepared form. Hence, the authors hope that a more standardized and pure preparation of the XYL extract would probably further enhance its antibacterial effect, and probably a higher concentration might also prove to be beneficial.
The zones of inhibition produced on the 7th day were considerably smaller as compared to that produced after 48 h for all the test groups. This decline in antibacterial activity could be attributed to the concomitant decline in the available concentrations of the chemicals viz., XYL, CHX DA, and possibly fluoride ions from GIC also. This decline in antibacterial activity over extended periods of time has been invariably reported by the previous researchers as well.,
Another exploratory domain of the present study was to study the effect of these chemical additives on the physical properties (compressive strength and setting time) of GIC. To be acceptable clinically, modified materials must provide superior antimicrobial activity without compromising the physical properties. ART procedure is commonly employed for the restoration of posterior teeth which are subjected to heavy occlusal forces, and the ability of the restoration to best withstand these occlusal forces can be judged by their compressive strength.
Most of the assays were performed after storage periods longer than 24 h. It is important to compare the physical properties of GIC between periods of 1 and 24 h or more because their final setting is achieved after 24 h, and they usually present lower strength values during the first hours. Keeping this in mind, different time duration of 24 h and 7 days was selected in the present study.
Results of the present study depicted that although the 7th day compressive strength values were significantly greater as compared to that after 24 h for all the groups, addition of 1% w/w of CHX diacetate and XYL produced significant yet similar decline in the compressive strength of the cement as compared to the control (GIC) both after 24 h and after 7 days. Similar results had been obtained by Botelho  in his study, wherein the effect of addition of various chemical agents (CHX hydrochloride, cetylpyridinium chloride, cetrimide, and benzalkonium chloride) to GIC at various concentration ratios and their effect on the antibacterial and physical properties of the cement was done.
Group 2 and 3 showed similar mean setting time values = 4.3 ± 0.1 which was found to be in accordance with the previous studies conducted by Deepalakshmi et al.
The possible reason for decrease in the physical properties can be attributed to cationic salts, which hamper the setting reaction of the polyacrylic acid glasses, thereby extending the setting time, due to an interfered proton attack and leaching of ions from the glasses. Also, since neither CHX nor XYL contribute to the structure of GIC, which in turn could have weakened the scaffold and could have compromised the physical properties-compressive strength and setting time. In addition, the slight modification in powder/liquid ratios by adding CHX diacetate and XYL may have also influenced the compressive strength and setting time.
However, both CHX diacetate and XYL showed considerable increase in the antibacterial activity of the GIC following incorporation in amounts as minimal as 1%, CHX diacetate having an upper hand but the fact that XYL is a natural, safe, traditional phyto extract with absolutely no side effects that cannot be overlooked. Also, literature extensively reports of its remineralization capabilities, thus, XYL incorporated restorative materials not only may exhibit an elevated antibacterial activity but would help in the remineralization of the residual softened dentin residue which is not exhibited by any of the synthetic chemical antibacterial agents.
| Conclusion|| |
Within the limitations of the present study, it may be concluded that the incorporation of XYL into GIC may be considered as a safe alternative to the incorporation of synthetic harmful chemicals. Although a single concentration of 1% was tested in the present study, incorporation of higher concentrations of XYL should also be explored to obtain the maximum antibacterial effect.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1a], [Table 1b], [Table 2a], [Table 2b], [Table 3]