In orthodontic treatment, fixed or movable devices are applied to correct the position of the teeth. For higher-quality treatment, most orthodontists prefer the use of fixed devices. Adhesives, including composites and cement, are applied to attach the bracket to the tooth. The success rate of orthodontic treatment with fixed devices depends on the quality and stability of the employed connecting materials [1]. The cause of rapid demineralization is the presence of large and persistent amounts of cariogenic microbes around the brackets and braces, i.e., improperly attached to the tooth [7]. The most important of which are Streptococcus mutans and Streptococcus subrinus [8]. To prevent caries and insufficient research concerning types of cement used in orthodontics, we aimed to apply the antibacterial properties of 3 common orthodontic types of cement (glass ionomer, zinc phosphate, & polycarboxylate) on two common cariogenic bacteria (Streptococcus mutans & Subrinus).

 The present laboratory study used the standard strains of Streptococcus mutans (1601 PTCC) and Streptococcus sobrinus (1290 PTCC) to evaluate the relevant antimicrobial effects. The sample size was estimated to be 5 samples per cement. Despite 6 types of cement, a total of 60 samples were studied. The bacteria were cultured for 24 hours at 37°C in 2 mL of Brain Heart Infusion broth and reached the half McFarland standard. The direct Contact Test method was used to evaluate the antibacterial properties of cement [16]. The bacterial base suspension was placed in a container, containing agar; the test substance was added to the dish. The antibacterial effect prevents the growth of bacteria around the test substance and creates an aura of non-growth; the diameter of which indicates the intensity of this effect. With sterile punching, the wells of the same size were generated in Himedia environments, and the bacteria were cultured with a sterile swab in a grass culture medium. The wells were then covered with 50 μL of the desired cement. The plates were incubated at 37°C. On days 2 and 5, the diameter of the no-growth halo around each well was measured with a digital caliper. Analysis of Variance (ANOVA) and t-test were used to analyze the obtained data.

 This study applied 60 media, including 30 Streptococcus mutans and 30 for Streptococcus subrinus. In each group, 10 media for zinc phosphate cement (5 media for Iranian zinc phosphate cement & 5 media for Foreign zinc phosphate cement), 10 culture media for polycarboxylate cement (5 Iranian polycarboxylate cement media & 5 media foreign polycarboxylate cement), and 10 culture media were used for glass ionomer cement (5 culture media for Iranian glass ionomer cement & 5 culture media for foreign glass ionomer cement). In this study, the diameter of the growth inhibition zone around the types of cement in both culture media remained unchanged between days 2 and 5 (Tables 1 & 2; Figure 1). 








 In both culture media types, containing Streptococcus mutans and Subrinus bacteria, a significant difference was observed in the culture media between the 3 groups of cement concerning the diameter of the growth inhibition zone around them (P<0.000). The following results were obtained by paired-wise comparing the culture media of the two studied bacteria:
 There was a significant difference in culture media (P<0.000) containing mutants except for internal zinc phosphate and external zinc phosphate (P=0.586) as well as between Iranian zinc phosphate and Iranian glass ionomer (P=0.179). In culture media containing Sobrinus bacteria, there was no significant difference between foreign zinc phosphate and Iranian glass ionomer (P=0.168); however, in other cases, there was a significant difference (P<0.000).

The present study findings indicated that the highest antibacterial effect was related to glass ionomer, zinc phosphate, and polycarboxylate, respectively. 
The highest growth inhibition zone was observed around the cement of the culture media, containing mutans and sobrinus, respectively, related to glass ionomer cement, zinc phosphate, and polycarboxylate cement, in sequence. The mean general and discrete growth aura around the studied cement in culture media, containing sobrinus was larger than culture media containing mutans, i.e., significant. Consistent with the results of previous studies by Mota [10], Eick [21], and Slutsky [23], the antibacterial property of glass ionomer was higher than that in other types of cement and short-lived. Daugela [26] also stated that zinc phosphate suggested the strongest antibacterial activity, compared to other cement immediately after mixing. Their obtained data were inconsistent with those of our study; this discrepancy may be due to differences in the methods and materials used in the experiments. According to the current study results, the antibacterial effect of types of cement on the bacterium Subrinus is much greater than that of mutans. Compared with domestic and foreign production cement, in Mutans culture medium, foreign glass ionomer of Iranian type presented better results. Besides, in the culture medium of Subrinus, foreign glass ionomer and zinc phosphate were better. There was no difference between polycarboxylate in both culture media. As a result, these data can be generalized to specific brands in this study.
According to the achieved findings, the antibacterial effects of glass ionomer are more than those of the other two types of cement. Additionally, the antibacterial effects of the studied types of cement on Subrinus were stronger than those of Mutans.

The present study was approved by Babol University of Medical Sciences (Code: MUBABOL.REC.1391.7).

This study was extracted from the PhD. dissertation of the first author at the Department of Orthodontics, School of Dentistry, Babol University of Medical Sciences, Babol.

The authors met the standard criteria of the International Committee of Medical Journal Publishers (ICMJE) and contributed equally to the writing of the article.

The authors declared no conflicts of interest.

The authors appreciate the contribution of the Dental Materials Research Center of Babol University of Medical Sciences to this study.
 

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