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Effectiveness of Riboflavin and Rose Bengal Photosensitizer Modified pharmaceuticals Article Effectiveness of Riboflavin and Rose Bengal Photosensitizer Modified Adhesive Resin for Orthodontic Bonding Ali Alqerban 1,2 1 Department of Preventive Dental Sciences, College of Dentistry, Dar al Uloom University, Riyadh 45142, Saudi Arabia; [email protected] 2 Department of Preventive Dental Sciences, College of Dentistry, Prince Sattam Bin Abdulaziz University, Al-Kharj 11942, Saudi Arabia Abstract: This study aimed to evaluate the effect of riboflavin (RF) and Rose Bengal (RB) photo- sensitizer modified adhesive resin on the degree of conversion (DC), and antimicrobial capacity after bonded to tooth surface. Different concentrations of RB and RF were prepared by homoge- nization method. An ultraviolet light source A (UVA) (375 nm wavelength, 3 mW/cm2 power) was used for 30 min irradiation. FTIR was performed for control and test adhesives to analyze the DC. Antibacterial testing was performed using the MTT assay. Metal brackets were bonded using the modified adhesives and subjected for SEM examination. The surfaces of teeth and metal brackets were examined at ×10 magnification for assessing adhesive remnant index (ARI) after PDT, 24 h and thermocycling. For DC, control group, 0.1% RB and RF after PDT showed the highest value. SEM imaging indicated lowest growth of Streptococcus mutans over 0.5% of RB-PDT and RF-PDT as compared to the control group. The MTT assay outcomes reported that the activity of S. mutans substantially decreased with the addition of a high amount of either RB or RF (p < 0.01). Mean ARI scores showed a significant difference between all groups. This study concluded that 0.1% of either RB or RF after PDT can be used for bonding orthodontic brackets to the tooth surface with substantial antibacterial properties. Keywords: cross-linking agents; fluorescent dyes; oxidation reduction; photochemistry; photosensi- Citation: Alqerban, A. Effectiveness tizing agents; protein conformation; Rose Bengal of Riboflavin and Rose Bengal Photosensitizer Modified Adhesive Resin for Orthodontic Bonding. Pharmaceuticals 2021, 14, 48. 1. Introduction https://doi.org/10.3390/ph14010048 With the advancement of dentistry and patient knowledge, orthodontic therapy Received: 17 December 2020 has gained popularity amongst the general population. The therapy is done to provide Accepted: 1 January 2021 treatment for misaligned teeth that involves the use of orthodontic wires and brackets. Published: 10 January 2021 The brackets used can either be metal or ceramic in origin [1,2]. Although orthodontic treatment assists in creating skeletal and dental improvement, this treatment modality is Publisher’s Note: MDPI stays neu- also responsible for creating an environment that favors bacterial growth [3–5]. tral with regard to jurisdictional clai- The factors responsible for the increased development of bacterial biofilm include the ms in published maps and institutio- application of orthodontic appliances close to the soft tissue structures, malaligned teeth, nal affiliations. and improper oral hygiene maintenance [6]. The abundance of bacterial biofilm can lead to the development of oral health problems that include plaque-induced gingivitis, white spot lesions, and oral malodor (bad breath) [7–10]. The most common treatment modality used to tackle this problem addresses the repeated application of scalers (manual or ultrasonic). Copyright: © 2021 by the author. Li- censee MDPI, Basel, Switzerland. In adjunct to this, the patients are also advised to follow strict oral hygiene protocols [11]. This article is an open access article To improve oral health care and patient satisfaction, dentists and scientists have been distributed under the terms and con- working together to establish treatment protocols that benefit on a larger scale. One such ditions of the Creative Commons At- protocol that is being readily used in dentistry as an established therapeutic regimen is tribution (CC BY) license (https:// a photodynamic therapy (PDT) [12–17]. This treatment involves three main components, creativecommons.org/licenses/by/ which include laser light (specific wavelength), nascent or free oxygen, and photosensitizer 4.0/). (PS). The procedure for this treatment is initiated by the application of laser light on the dye Pharmaceuticals 2021, 14, 48. https://doi.org/10.3390/ph14010048 https://www.mdpi.com/journal/pharmaceuticals Pharmaceuticals 2021, 14, 48 2 of 11 Pharmaceuticals 2021, 14, 48 2 of 11 which include laser light (specific wavelength), nascent or free oxygen, and photosensi- tizer (PS). The procedure for this treatment is initiated by the application of laser light on the dye molecules. These dye molecules absorb the coherent light and transform a dormantmolecules. singlet These state dye to molecules an excited absorb triplet the state. coherent The excited light and molecules transform then a dormant react with singlet the freestate molecular to an excited oxygen triplet to form state. a highly The excited toxic product molecules called then reactive react with oxygen the freespecies molecular (ROS). Theseoxygen species to form further a highly facilitate toxic product an irreversible called reactive oxidative oxygen movement species (ROS).in the Thesebacterial species cell composition,further facilitate which an irreversible ultimately oxidativeleads to bacterial movement cell in death the bacterial [18–20]. cell Various composition, types of which pho- tosensitizersultimately leads are toused bacterial to treat cell oral death diseases [18–20 including]. Various methylene types of photosensitizers blue, toluidine areblue, used in- docyanineto treat oral green, diseases and includingmany others. methylene Rose Bengal blue, (RB) toluidine and riboflavin blue, indocyanine (RF) have been green, exten- and sivelymany others.used for Rose medical Bengal applications. (RB) and riboflavin RB and (RF)Rf bot haveh act been as extensivelycross-linking used agents. for medical These photosensitizerapplications. RB-like and agents Rf both act act as as inhibitors cross-linking of collagen agents. degradation, These photosensitizer-like after the destructive agents activityact as inhibitors of the acid of-based collagen bacteria, degradation, such as afterStreptococcus the destructive mutans ( activityS. mutans of) the[21]. acid-based bacteria,According such as toStreptococcus the authors’ mutans knowledge,(S. mutans no study)[21]. exists in the database that evaluated RB andAccording RF as photosensitized to the authors’ knowledge,proteins and no modified study exists inside in the the database orthodontic that evaluatedadhesive resin.RB and Therefore, RF as photosensitized this laboratory proteins study aimed and modified to characterize inside the and orthodontic evaluate the adhesive effect of resin. RB andTherefore, RF photosensitized this laboratory orthodontic study aimed adh toesive characterize resin on degree and evaluate of conversion, the effect and of RBantimi- and crobialRF photosensitized capacity bonded orthodontic to the tooth adhesive surface. resin on degree of conversion, and antimicrobial capacity bonded to the tooth surface. 2. Results 2. Results The FTIR spectra of the powders riboflavin and rose Bengal are presented in Figure 1A. The FTIR spectra of the powders riboflavin and rose Bengal are presented in Figure1A . Characteristic peaks at 1576 cm−1, 1652 cm−1, and 1728 cm−1 are noted. The spectrum at 1728 Characteristic peaks at 1576 cm−1, 1652 cm−1, and 1728 cm−1 are noted. The spectrum −1 cmat 1728 indicates cm−1 indicatesC=O stretching C=O stretching frequency frequency of riboflavin. of riboflavin. In the components, In the components, the aromatic the −1 −1 C=Caromatic stretching C=C stretching mode of moderiboflavin of riboflavin appears appears at 1576 at cm 1576 and cm− 11652and cm 1652 cm(indicated−1 (indicated with −1 pointers).with pointers). Rose-Bengal Rose-Bengal possesses possesses important important peaks at peaks 456 c atm 456 which cm− indicates1 which indicatesC-I bonding, C–I −1 −1 −1 atbonding, 952 cm at for 952 C cm-C− stretching1 for C–C stretchingvibration, vibration,and 1335 andcm 1335and cm1613−1 cmand 1613for C=C cm− stretching1 for C=C vibrationstretching and vibration C=O stretching and C=O stretchingvibration, vibration,respectively. respectively. After incorporating After incorporating these powders these inpowders orthodontic in orthodontic adhesives, adhesives, the ascribed the peaks ascribed were peaks evident were forming evident strong forming bonds strong with bonds the resinwith thematrix. resin The matrix. degree The of degree conversion of conversion was plotted was for plotted the area for on the the area spectrum on the spectrum ranging betweenranging between1608 cm− 16081 to 1640 cm− cm1 to−1 1640(Figure cm −1B).1 (Figure 1B). FFigureigure 1. FTIRFTIR spectra spectra of of ( (AA)) riboflavin riboflavin (black (black spectrum) spectrum) and and rose Rose Bengal Bengal (red (red spectrum) spectrum) powder powder.. Characteristic Characteristic peaks peaks at 1576at 1576 cm cm−1, 1652−1, 1652 cm−1 cm, and−1 ,1728 and cm 1728−1 are cm noted.−1 are The noted. spectrum The spectrum at 1728 cm at− 17281 indicates cm−1 C=Oindicates stretching C=O stretchingfrequency of frequency riboflavin. of Inriboflavin. the components, In the components, the aromatic the C=C aromatic stretching C=C mode stretching of riboflavin mode ofappears riboflavin at 1576 appears cm−1 and at 1576 1652 cm cm−−11 and(indicated 1652 cmwith−1 (indicatedpointers). Rose with-Bengal pointers). possesses
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