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| Author(s): |
Carolina Santezi Neto
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Araraquara. 2016-10-10. |
| Institution: | Universidade Estadual Paulista (Unesp). Faculdade de Odontologia. Araraquara |
| Defense date: | 2016-08-05 |
| Advisor: | Lívia Nordi Dovigo |
| Abstract | |
Formation of dental biofilm is the main factor associated to development of oral infections. Although topic antimicrobials, such as chlorhexidine (CHX), have been used to decontaminate the oral surfaces, they may promote adverse effects on hard and soft tissues as well as the possibility of promoting microbial resistance. Thus, the investigation of alternative antimicrobial treatments, such the Photodynamic Inactivation (PDI), is relevant to dental sciences. Previous research suggested that the curcumin (CUR) might be a promising photosensitizer for PDI, but there are some aspects that need to be better evaluated. The aim of this study was to assess the efficacy of CUR-mediated PDI against dental biofilms and the existence of possible negative effects of PDI on the properties of composite resins and dental surface. The research was divided into 3 consecutive studies. The study 1 aimed to evaluate the PDI efficacy using different CUR formulations (liquid – DMSO (dimethylsulfoxide) at 10%; eumulgin hydrogel, chitosan hydrogel and oleic acid hydrogel) on mono-species biofilm of Streptococcus mutans (UA 159 ATCC 700610; Sm), Lactobacillus casei (ATCC 4646; Lc) and Candida albicans (ATCC 90028; Ca) formed in vitro. Prior to the execution of the treatments, the photodegradation rate of each formulation in concentrations 20, 40, 60 and 80 µM was performed and the results showed that the chitosan hydrogel (R2=0,989) and oleic acid hydrogel (R2=0,976) were able to be used in the tests, both at 80 µM. Then, cell concentration of each species was standardized in order to the grow biofilm and the following treatment groups were tested for all formulations and evaluated species: C-L- (no CUR and light; negative control), C-L+ (no CUR and with light - 18J/cm2; blue LED), C+L- (with CUR and no light) and C+L+ (with both CUR and light; PDI). Data were analyzed descriptvely and inferential analysis (two-way ANOVA followed by Games Howell test) indicated that the effect of the formulation, treatment and the interaction between them was highly significant (p < 0,0001) for the three species tested, and the PDI groups mediated by the formulation of DMSO at 10% presented the best antimicrobial activity for all evaluated microrganisms (MOs). Among the hydrogel formulations, oleic acid hydrogel promoted antimicrobial effect, thus it was selected for conducting subsequent studies. Study 2 evaluated the effect of PDI-mediated CUR carried in a system called hydrogel oleic acid on the stability of color, hardness and surface roughness of specimens made of bovine enamel and composite resins. The treatment groups evaluated were CN (negative control), AcO (positive control) and PDI. Data were analyzed descriptively and then, inferential analysis (ANOVA mixed repeated measures followed by Sidak post-test for variables "color stability" and "microhardness"; Games and Howell for "surface roughness") was performed. However, to do the analysis for the “color stability" variable, it was considered only 2 moments of color measurement (immediately and 60 days after treatment). In the same way, the measurements for "hardness" and "surface roughness" were assessed prior to treatment and 60 days after performing them. To the "color stability" variable, the ANOVA results showed that the factors "time", "treatment", "resin" and "interaction between them" were significant (p ≤ 0.021) on the color change of resins, and, in general, this change was greater in the measurements assessed in time "60 days after the treatments". For the microhardness variable, except the factors "time x treatment" and "treatment", all others were significant (p < 0,001), showing that PDI for TPH and AML resins did not cause any deleterious effect on this property. On the other hand, for the resin Z350, the measurements performed at time "60 days after the treatment", showed a reduction in hardness values compared to the values found in CN and AcO groups, suggesting that PDI promoted a negative effect on the hardness. ANOVA showed no significance on factor "time" (p = 0.991), but it showed that the factors "surface", "treatment" and "treatment x area" was significant (p < 0.001). In addition, results showed that the surface roughness of TPH and Z350 resins did not change, while the AML was reduced after both treatments. Differently, for the specimens prepared with dental enamel, the three investigated variables did not suffer any negative effect after the treatments, and the factor “times” was the only one considered significant (p ≤ 0.002). Study 3, a pilot, evaluated the effectiveness of the PDI protocol previously established on multi-species biofilms formed on bovine enamel blocks in situ. For this, after approval by the ethics committee in research of this faculty, 7 volunteers were selected and impressions were taken for making intra-oral device. They also were instructed on the use of the device for biofilm formation (48 hours). Microbiological step consisted in removal of enamel blocks of the device, application of the treatments (C+L+ and C-L-) and quantification of viable cells in specific culture media for Sm, Lc, Candida spp and unspecific media for MOs general growth. The data were processed and inferential analysis (MANOVA followed by ANOVA by a factor) showed that the factor "treatment group" was highly significant (p <0.001) on Sm and general MOs viability. Thus, in conclusion, although the efficacy of PDI mediated by CUR in order to reduce biofilms formed in vitro has been established, the efficacy is directly related to the type of vehicle used for solubilization of the photosensitizer. Furthermore, the protocol "CUR at 80 µM carried by hydrogel oleic acid associated with fluence of 18J/cm2 with pre-irradiation time of 5 minutes" was effective for the quantitative reduction of Sm and MOs in general of the biofilms which grown in situ and showed no deleterious effect on color stability, hardness and surface roughness of tooth enamel. However, for some resins, negative effects on these properties were observed. Thus, the use of this protocol appears to be safe on surfaces of enamel, while for resins, a careful evaluation prior to use should be made. Thus, more investigations are necessary in order to better understand the findings. (AU) | |
| FAPESP's process: | 13/15770-6 - Efficacy of curcumin-mediated photodynamic inactivation against dental biofilms and evaluation of possible changes on the properties of composite resins and dental surface |
| Grantee: | Carolina Santezi Neto |
| Support Opportunities: | Scholarships in Brazil - Doctorate |