The effect of different concentration of emodin nanoparticles, as an antibacterial agent, on the flexural resistance of acrylic resin used in orthodontics: An in vitro study.

OBJECTIVE: The aim of this study was to investigate the impact of emodin nanoparticles (n-Emo) on the flexural strength of acrylic resin used in orthodontics. METHODS: A total of 24 acrylic resin discs were prepared according to ISO:20795-1 and divided into four groups (n=6): 0% n-Emo, 0.5% n-Emo, 1% n-Emo, and 2% n-Emo. The flexural strength of each group was measured using the Universal Testing Machine. One-way analysis of variance (ANOVA) and Tukey tests were used to analyse the data. RESULTS: The highest flexural strength values were observed in the groups containing 0% and 0.5% concentrations of n-Emo, while the lowest mean flexural strength was recorded in the group containing 2% concentration of n-Emo. There were significant difference in flexural strength values between the groups containing 0% with those containing 1% and 2% concentrations (P=0.045, P=0.011, respectively), as well as between those containing 0.5% and 2% concentrations of n-Emo (P=0.041). CONCLUSIONS: The results of the study showed that the incorporation of n-Emo had a negative impact on the flexural strength of the acrylic resin utilized in orthodontics. Nonetheless, the mean flexural strength values of all groups fell within the normal range, implying that the addition of n-Emo did not jeopardize the mechanical properties of the acrylic resin. It is therefore conceivable that the use of n-Emo as an antimicrobial agent in acrylic resin could be a promising approach to reducing enamel demineralisation and dental caries, while preserving its mechanical properties. This study was approved by the ethics committee of the Tehran University of Medical Sciences (1401-2-398-54892).

Evaluation of antibacterial effect of the orthodontic composite containing propolis nanoparticles in rat as an animal model.

AIM: The present study aimed to assess the antimicrobial effects of orthodontic primer containing nano-propolis against the cariogenic bacteria in а rat model. MATERIALS AND METHODS: Transbond XT orthodontic primer containing 0%, 1%, 5%, and 10% nano-propolis was experimentally prepared in-house. The Wistar rats we used in the study were randomly divided into four groups and their oral cavities were colonized with Streptococcus mutans, Streptococcus sanguinis, and Lactobacillus acidophilus. After anesthetizing the rats, one drop (10 µL) of primer containing different concentrations of nano-propolis was applied to the labial surface of the maxillary incisor and light-cured. The orthodontic composite was applied on the primer and light-cured. One drop (10 µL) of primer containing the same concentrations of nano-propolis was again applied on the surface of composite and light-cured. The number of S. mutans, S. sanguinis, and L. acidophilus colonies in the saliva of rats was quantified at 24 h, at days 4 and 7 using plate counting. RESULTS: Primer containing 1%, 5%, and 10% of nano-propolis significantly reduced the S. mutans colony count at 24 h compared with the control group (p<0.05). At day 4, the mean S. mutans colony counts in the 5% and 10% nano-propolis groups were significantly lower than that in the control group (p<0.05). Primer containing 1%, 5%, and 10% (all (p<0.05) of nano-propolis significantly reduced the L. acidophilus at 24 hours. Also, at day 4 the mean L. acidophilus colony counts in the 5% and 10% nano-propolis groups were significantly lower than that in the control group (p<0.05). At 24 h and 4 days, the mean S. sanguinis colony count in the 1%, 5%, and 10% nano-propolis group was significantly lower than that in the control group (p<0.05). No significant difference was observed in the presence of all concentrations of nano-propolis at day 7 (p>0.05). CONCLUSIONS: Orthodontic primer containing nano-propolis significantly reduced the colony count of cariogenic bacteria in a rat model.

Evaluation and comparison of the effect of incorporating zinc oxide and titanium dioxide nanoparticles on the bond strength and microleakage of two orthodontic fixed retainer adhesives.

BACKGROUND: An adhesive with both proper mechanical and antimicrobial properties seems to be beneficial. We aimed to investigate the effect of zinc oxide (ZnO) and titanium dioxide (TiO2) nanoparticles (NPs) on bond strength and microleakage of two different fixed retainer adhesives. METHODS: In this in vitro experimental study, 168 extracted human incisors were randomly divided into six groups of 28 (eight double-tooth specimens for the bond strength test and 12 specimens for the microleakage test). In three groups: Transbond XT (3M Unitek, Monrovia, CA) without NPs, with 1% ZnO NPs and with 1% TiO2 NPs were applied. The other three groups included Ortho Connect Flow (GC orthodontics, Tokyo, Japan) composite with the same order to bond a 0.175-inch multistrand wire to the lingual surfaces of the teeth. The bond strength was measured using the Universal Testing Machine, and the adhesive remnant index was reported using a stereomicroscope (Nikon, SMZ800, Tokyo, Japan). The dye-penetration method was used to determine the microleakage. RESULTS: For bond strength, there was no significant difference among groups. For microleakage, there was no significant difference between GC and Transbond XT groups. However, in subgroups of Transbond XT, the addition of TiO2 NPs increased the microleakage significantly in comparison with ZnO and control groups (P = 0.011). There was no significant statistical difference between the groups in terms of residual adhesives (P = 0.166). CONCLUSIONS: Through the incorporation of 1% TiO2 and ZnO NPs into the fixed retainer adhesive, the bond strength was maintained within the clinically acceptable range. The addition of TiO2 NPs to Transbond XT significantly increased the percentage of microleakage.

Evaluation of the flexural strength of orthodontic acrylic resin incorporated with propolis nanoparticles: an in vitro study.

AIM: Nanopropolis has become the subject of interest in medicine and dentistry as a natural product due to its outstanding properties, particularly antimicrobial activity. This study aimed at investigating the effect of nanopropolis on flexural strength of polymethyl methacrylate (PMMA).

Concerns and Problems of Orthodontic Patients during the COVID-19 Pandemic.

OBJECTIVES: We aimed to find the main concerns of patients undergoing active orthodontic treatments and their orthodontic treatment-related (OTR) problems during the coronavirus disease-2019 (COVID-19) pandemic. MATERIALS AND METHODS: A researcher-made questionnaire addressing several aspects of the effects of COVID-19 pandemic on treatment was distributed among 181 orthodontic patients receiving active treatment. Anxiety, concern, problems, and willingness to attend orthodontic appointments and to undergo other dental procedures was questioned. The correlation of gender, age, COVID-19-related anxiety and OTR anxiety was statistically analyzed. Patient satisfaction level with different aspects of dental-clinic performance was also evaluated. RESULTS: The participants included 117 females and 64 males, of which 94% adhered to the pandemic restrictions. The mean COVID-19-related- and OTR-anxiety were 51.7% and 52.7%, respectively. Higher COVID-19-related anxiety was significantly correlated with higher OTR anxiety (P<0.001). There was an inverse correlation between general COVID-19-related anxiety and OTR anxiety and willingness to attend orthodontic appointments (P<0.05). A positive insignificant (P=0.07) correlation existed between age and willingness to attend appointments. The main concern was prolongation of treatment and the most common problem was irritation of oral soft tissues by appliances. The majority (65.3%) were willing to attend their orthodontic appointments. Orthognathic surgery (62%) had the highest while, dental restorations and radiography had the lowest refusal rates (9.9%). CONCLUSION: COVID-19 pandemic significantly affected orthodontic treatment. The level of COVID-19-related anxiety was moderately high and patients were concerned about the impact of lockdown on their orthodontic treatment outcome. Young adults demonstrated higher levels of stress than other age-groups.

Antibacterial properties of an acrylic resin containing curcumin nanoparticles: An in vitro study.

Background. Microbial accumulation is still a significant problem with removable acrylic appliances. This study aimed to assess the antimicrobial properties of a self-cured acrylic resin containing curcumin nanoparticles (CNPs). Methods. This in vitro study used 48 acrylic discs containing 0.5%, 1%, and 2% CNPs. The antimicrobial properties of the discs against Streptococcus mutans, Streptococcus sanguinis, Lactobacillus acidophilus, and Candida albicans were evaluated using disc agar diffusion (DAD), eluted component, and biofilm inhibition tests. The growth inhibition zones were measured, and the colonies were counted after 1, 3, and 7 days. Results. DAD test showed that none of the curcumin nanoparticle concentrations caused growth inhibition zones for any microorganisms. All the concentrations were effective against all four microorganisms in the biofilm inhibition test except 0.5% for L. acidophilus. In the eluted component test, solutions containing 2% concentration had maximum growth inhibition of all the groups at all time intervals. An increase in curcumin nanoparticle concentration from 0.5% to 1% was effective only against C. albicans. Conclusion. Generally, CNPs in all concentrations were effective against the biofilms of all four microorganisms assessed in this study. Therefore, incorporating 2% CNPs into acrylic resin seems suitable for clinical use.

Effect of nano-zinc oxide and nano-chitosan particles on the shear bond strength of dental composites used as orthodontic adhesive.

BACKGROUND: This study aimed to evaluate the effect of the combination of zinc oxide nanoparticles (NPs) and chitosan NPs on the shear bond strength (SBS) of composites used for orthodontic bonding. METHODS: Four groups of composites (n = 10), containing 0%, 1%, 5%, and 10% w/w NP fillers, respectively, were used to bond brackets to the surfaces of 40 intact bovine incisors. After 1000 rounds of thermal cycling at 5°C-55°C, all specimens were mounted in acrylic blocks. The SBS was tested using a universal testing machine, and the adhesive remnant index scores were registered using a stereomicroscope. Data were statistically analyzed using a 1-way ANOVA and the Kruskal-Wallis test. RESULTS: The highest value of mean SBS was found in the control group, and the lowest value was found in the group with composite containing 10% NPs. The adhesive remnant index did not differ significantly among the groups (P = 0.823). CONCLUSIONS: Incorporation of 1% and 5% zinc oxide and chitosan NPs had no effect on the SBS of composite, and the obtained SBS values were similar to that of the control group.

Evaluation of antimicrobial properties of nano-silver particles used in orthodontics fixed retainer composites: an experimental in-vitro study.

Background. The present study evaluated the antimicrobial efficacy of composite resins containing nano-silver (NAg) particles used in fixed orthodontic retainers. Methods. Nano-composite resin samples with 1%, 2%, and 5% concentrations of NAg were prepared. The antimicrobial effectiveness of NAg was assessed against Streptococcus mutans, Streptococcus sanguis, and Lactobacillus acidophilus by the biofilm inhibition test (three-day-old biofilms), eluted components test (on days 3, 15, and 30), and disk-diffusion agar test after 48 hours. Measures of central tendency and index of dispersion were used to determine colony-forming units. Kruskal-Wallis test and Mann-Whitney U test were also used. Results. The biofilm inhibition test showed a significant decrease in the colonies of S. mutans (87.64%, 96.47%, and 99.76% decrease), S. sanguis (98.13%, 99.47%, and 99.93% decrease), and L. acidophilus (81.59%, 90.90%, and 99.61% decrease) at 1%, 2%, and 5% concentrations of Nag, respectively, compared to the control groups. The colony-forming unit (CFU)/mL of tested microorganisms continuously decreased with increased NAg concentration. In the eluted component test, no significant differences were noted in the 3rd, 15th, and 30th days between the different concentrations of Nag-containing composite resin disks and control samples. According to the disk-diffusion agar test, there was no growth inhibition zone for the composite resin disks containing 1% and 2% concentrations of Nag. However, the growth inhibition zone was seen with a 5% concentration, with a diameter of 9.5±0.71 mm for S. mutans, 8.5±0.71 mm for S. sanguis, and 8±1.41 for L. acidophilus. Conclusion. The incorporation of NAg into composite resins has antibacterial effects, possibly preventing dental caries around fixed orthodontic retainers.

Shear Bond Strength of Self-Adhesive Composite Containing TiO2 and SiO2 Nanoparticles with an Additional Etching Step for Orthodontic Brackets Bonding to Enamel.

INTRODUCTION: Recently, nanoparticles such as nano-TiO2 have been added to some dental materials for enhancing dental carries prevention due to their antibacterial activity. AIM: This study aimed to assess the shear bond strength of a self-adhesive composite containing TiO2 and SiO2 nanoparticles for orthodontic bracket bonding. MATERIALS AND METHODS: This in vitro, experimental study was done on 70 extracted human premolars divided into 7 groups. Six groups of Vertise Flow self-adhesive composite samples were prepared: without any nanoparticles, with 0.5% and 1% TiO2 nanoparticles, 0.5% and 1% SiO2 nanoparticles, and 1% mixture of TiO2 and SiO2 nanoparticles so that nano-hybrid composites were prepared. Metal brackets were bonded with these samples as well as Transbond XT as the control group. The shear bond strength of the brackets to enamel was measured using a universal testing machine. The adhesive remnant index (ARI) score was also determined by a stereomicroscope. Data were analyzed by one-way ANOVA, Tukey's test and Kruskal-Wallis test. RESULTS: The shear bond strength of the groups was significantly different (p=0.000). Pairwise comparisons revealed that the bond strength of Transbond XT group was significantly higher than others (p<0.05), followed by the 1% TiO2 group with significant differences with Vertise Flow and 0.5% TiO2 groups. The lowest value belonged to Vertise Flow with no nanoparticles. The ARI scores was different in the control group (p=0.000). CONCLUSIONS: Adding TiO2 and SiO2 nanoparticles to Vertise Flow self-adhesive composite not only did not adversely affect its shear bond strength, but also slightly increased it. Overall, the self-adhesive nano-hybrid composite containing TiO2 and/or SiO2 nanoparticles, following an additional etching step would be acceptable for bracket bonding and can be used clinically to benefit from the antimicrobial activity of these nanoparticles.

Antimicrobial Properties of Acrylic Resin Incorporated with Propolis Nanoparticles.

Objectives: One of the main problems with polymethyl methacrylate (PMMA) used for the fabrication of oral removable appliances is plaque accumulation due to surface porosities. Incorporation of antimicrobial agents in this material might help tackle this problem. The aim of this study was to evaluate the antimicrobial activity of PMMA acrylic resin incorporated with propolis nanoparticles (PNPs). Materials and Methods: Antimicrobial properties of acrylic resin incorporated with PNPs were assessed against Streptococcus mutans (S. mutans), Streptococcus sanguinis (S. sanguinis), Lactobacillus acidophilus (L. acidophilus) and Candida albicans (C. albicans). Acrylic discs were fabricated in four groups: A control group without PNPs and three experimental groups containing 0.5%, 1% and 2% concentrations of PNPs. Disc agar diffusion (DAD) test was performed to determine the antimicrobial effects of PNPs by measuring the microbial growth inhibition zones on Muller-Hinton agar plates. The eluted components test evaluated the viable counts of microorganisms in liquid medium after 24 and 72h. Finally, biofilm inhibition test assessed the efficacy of PNPs for inhibition of biofilm formation. P<0.05 was considered significant. Results: The acrylic discs failed to produce microbial inhibition zones in the DAD test. Discs containing 1% and 2% nanoparticles showed anti-biofilm effects on all four microbial species. The colony counts of all microorganisms significantly decreased following exposure to liquids containing nanoparticles after 24 and 72h in eluted component test. Conclusion: PMMA acrylic discs incorporated with PNPs presented some antimicrobial properties against S. mutans, S. sanguinis, L. acidophilus, and C. albicans. Objectives: One of the main problems with polymethyl methacrylate (PMMA) used for the fabrication of oral removable appliances is plaque accumulation due to surface porosities. Incorporation of antimicrobial agents in this material might help tackle this problem. The aim of this study was to evaluate the antimicrobial activity of PMMA acrylic resin incorporated with propolis nanoparticles (PNPs). Materials and Methods: Antimicrobial properties of acrylic resin incorporated with PNPs were assessed against Streptococcus mutans (S. mutans), Streptococcus sanguinis (S. sanguinis), Lactobacillus acidophilus (L. acidophilus) and Candida albicans (C. albicans). Acrylic discs were fabricated in four groups: A control group without PNPs and three experimental groups containing 0.5%, 1% and 2% concentrations of PNPs. Disc agar diffusion (DAD) test was performed to determine the antimicrobial effects of PNPs by measuring the microbial growth inhibition zones on Muller-Hinton agar plates. The eluted components test evaluated the viable counts of microorganisms in liquid medium after 24 and 72h. Finally, biofilm inhibition test assessed the efficacy of PNPs for inhibition of biofilm formation. P<0.05 was considered significant. Results: The acrylic discs failed to produce microbial inhibition zones in the DAD test. Discs containing 1% and 2% nanoparticles showed anti-biofilm effects on all four microbial species. The colony counts of all microorganisms significantly decreased following exposure to liquids containing nanoparticles after 24 and 72h in eluted component test. Conclusion: PMMA acrylic discs incorporated with PNPs presented some antimicrobial properties against S. mutans, S. sanguinis, L. acidophilus, and C. albicans.

An in vitro evaluation of the effects of nanoparticles on shear bond strength and antimicrobial properties of orthodontic adhesives: A systematic review and meta-analysis study.

INTRODUCTION: Biofilm accumulation around orthodontic brackets and composite is a common complication of orthodontic treatment. OBJECTIVE: A systematic review and meta-analysis were done to find out whether the association of nanoparticles with the orthodontic adhesives compromises its properties and whether there are exceptional nanoparticles exhibiting excellent antimicrobial potential against cariogenic bacteria along with remarkable mechanical properties. MATERIALS AND METHODS: Electronic databases were searched using the following keywords; orthodontic or orthodontics and antimicrobial or antibacterial and adhesive and nanoparticles and shear bond strength. Thirteen studies were included and meta-analysis was performed. RESULTS: The results indicated no drastic changes in mechanical properties (0.812, 95% CI [0.750, 0.861], P=0.000). The Ag-HA, Cur, Cur-ZnO, and TiO2 in concentration≥1% showed a statistically significant difference, where the control groups had higher shear bond strength. Nine studies assessed the antimicrobial properties of nanoparticles. 1 wt% Cu and 5 wt% TiO2 not only did not affect shear bond strength but also showed more antimicrobial activity against Streptococcus mutans. The analysis demonstrated the absence of heterogeneity (Q value=44.014; df (Q)=12; and I2=72.736) in shear bond strength of orthodontic adhesives with nanoparticles, with low risk of bias. CONCLUSIONS: Adding≤5 wt% antimicrobial nanoparticles to an orthodontic adhesive is less conducive to microbial growth than unmodified adhesive and does not influence bracket-enamel bond strength.

Antimicrobial Efficacy of Silver Nanoparticles Incorporated in an Orthodontic Adhesive: An Animal Study.

OBJECTIVES: This study assessed the antimicrobial efficacy of silver nanoparticles (AgNPs) incorporated in Transbond XT orthodontic adhesive used in rats. MATERIALS AND METHODS: Transbond XT orthodontic adhesive containing 0%, 1%, 5% and 10% AgNPs was experimentally produced. Twenty-eight male Wistar rats were randomly divided into four groups (n=7) of control (0% AgNPs), 1% AgNPs, 5% AgNPs and 10% AgNPs. After anesthetizing the rats, one drop (10 µm) of the adhesive was applied on the central incisor, and light-cured for 20 s. Transbond XT composite (1×1×1 mm) was also applied. Another 10-µm drop was applied over it, and light-cured for 40 s. Biofilm test was carried out, and the number of colony forming units (CFUs) of Streptococcus sanguinis (S. sanguinis), Streptococcus mutans (S. mutans) and Lactobacillus acidophilus (L. acidophilus) in the saliva of rats was counted at baseline and 24 h after the application of adhesive. The data were analyzed using one-way ANOVA and Tukey's test. RESULTS: In presence of 5% and 10% AgNPs, S. sanguinis and L. acidophilus counts were significantly lower than those in the control and 1% AgNP groups (P<0.05). The S. mutans colony count was significantly lower in presence of all concentrations of AgNPs compared with the control group (P<0.05). The S. mutans colony count in 10% AgNP group was significantly lower than that in 1% and 5% AgNP groups (P<0.05). CONCLUSION: Silver nanoparticles have dose-dependent antimicrobial effects; 5% concentration is the minimum concentration of AGNPs with optimal antimicrobial efficacy against all strains evaluated in this study.

Antibacterial Effects of Orthodontic Primer Harboring Chitosan Nanoparticles against the Multispecies Biofilm of Cariogenic Bacteria in a Rat Model.

INTRODUCTION: Microbial biofilm accumulation around orthodontic brackets and composite is a common complication of fixed orth-odontic treatment. This study assessed the antibacterial effects of orthodontic primer containing chitosan nanoparticles (CNPs) against the multispecies biofilm of cariogenic bacteria in а rat model. MATERIALS AND METHODS: Transbond XT orthodontic primer containing 0%, 1%, 5%, and 10% CNPs was experimentally prepared. The Wistar rats were randomly divided into four groups (n=7) of control (0% CNPs), 1%, 5% and 10% CNPs. The oral cavities of the rats were infected with cariogenic bacteria. After anesthetizing the rats, 1 drop (10 µL) of primer with different concentrations of CNPs was applied to their central incisor and light-cured for 20 seconds. Transbond XT orthodontic adhesive (2 × 2 mm) was applied on the primer. Another drop (10 µL) of primer was applied and light-cured for 40 seconds. The number of Streptococcus mutans, Streptococcus sanguinis, and Lactobacillus acidophilus colonies in the saliva of rats was quantified at 24 hours, 4 days and 7 days. RESULTS: Adding 1% (p=0.005), 5% (p<0.001) and 10% (p<0.001) of CNPs to orthodontic primer significantly reduced the S. mutans colony count at 24 hours compared with the control group. At 24 hours, the mean S. sanguinis colony counts in the 5% (p=0.04) and 10% (p=0.02) CNP groups were significantly lower than that in the control group. Also, at 4 and 7 days, the mean colony counts in the 5% and 10% CNP groups were significantly lower than that in the control group (p<0.05). At 24 hours and 4 days, the mean L. acidophilus colony count in the 10% CNP group was significantly lower than that in the control group (p<0.05). At 7 days, rats with failed adhesive showed a significantly higher count of all three bacteria compared with rats with adhesive (p<0.05). CONCLUSIONS: The addition of 5% CNPs to orthodontic primer significantly decreased the colony count of cariogenic bacteria in rats.

Evaluation of the Effect of Propolis Nanoparticles on Antimicrobial Properties and Shear Bond Strength of Orthodontic Composite Bonded to Bovine Enamel.

OBJECTIVES: We aimed to investigate the effects of propolis nanoparticles (prpNPs) on antimicrobial property and shear bond strength (SBS) of orthodontic composite bonded to bovine enamel. MATERIALS AND METHODS: Sixty bovine teeth were randomly divided into five groups (n=12). PrpNPs were prepared at concentrations of 0% (control), 1%, 2%, 5%, and 10% in Transbond XT composite to bond stainless steel brackets to the teeth. SBS between brackets and teeth was measured using a universal testing machine. After debonding, the adhesive remnant index (ARI) on bracket bases was measured. In the microbial test, composites with the aforementioned concentrations of prpNPs were cured in metal discs. The bacteria included Streptococcus mutans (S. mutans), Streptococcus sanguinis (S. sanguinis), and Lactobacillus acidophilus (L. acidophilus), and antimicrobial effects of prpNPs were investigated by anti-biofilm, disc agar diffusion and eluted component tests. RESULTS: The 10% prpNPs group showed the lowest SBS. Colony growths of S. mutans and S. sanguinis at all concentrations (except for 1%) was significantly lower than the control group. L. acidophilus colony growth was significantly reduced at 5% and 10% concentrations. Growth inhibition zone developed at 2%, 5%, and 10% concentrations for S. mutans and S. sanguinis. The lowest numbers of S. mutans and S. sanguinis colonies at all concentrations were observed on day 15. L. acidophilus colonies decreased significantly at all concentrations (except for 1%) until day 30. CONCLUSION: Nano propolis has a significant antimicrobial effect at 2% and 5% concentrations, and the SBS is maintained within the acceptable clinical range.

Effect of TiO2 nanoparticles incorporation on antibacterial properties and shear bond strength of dental composite used in Orthodontics.

INTRODUCTION: Plaque accumulation and bond failure are drawbacks of orthodontic treatment, which requires composite for bonding of brackets. As the antimicrobial properties of TiO2 nanoparticles (NPs) have been proven, the aim of this study was to evaluate the antimicrobial and mechanical properties of composite resins modified by the addition of TiO2 NPs. METHODS: Orthodontics composite containing 0%, 1%, 5% and 10% NPs were prepared. 180 composite disks were prepared for elution test, disk agar diffusion test and biofilm inhibition test to collect the counts of microorganisms on three days, measure the inhibition diameter and quantify the viable counts of colonies consequently. For shear bond strength (SBS) test, 48 intact bovine incisors were divided into four groups. Composites containing 0%, 1%, 5% and 10% NPs were used for bonding of bracket. The bracket/tooth SBS was measured by using an universal testing machine. RESULTS: All concentration of TiO2 NPs had a significant effect on creation and extension of inhibition zone. For S. mutans and S. sanguinis, all concentration of TiO2 NPs caused reduction of the colony counts. Composite containing 10% TiO2 NPs had significant effect on reduction of colony counts for S. mutans and S. sanguinis in all three days. The highest mean shear bond strength belonged to the control group, while the lowest value was seen in 10% NPs composite. CONCLUSIONS: Incorporating TiO2 nanoparticles into composite resins confer antibacterial properties to adhesives, while the mean shear bond of composite containing 1% and 5% NPs still in an acceptable range.

Effect of TiO2 nanoparticles incorporation on antibacterial properties and shear bond strength of dental composite used in Orthodontics

ABSTRACT Introduction: Plaque accumulation and bond failure are drawbacks of orthodontic treatment, which requires composite for bonding of brackets. As the antimicrobial properties of TiO2 nanoparticles (NPs) have been proven, the aim of this study was to evaluate the antimicrobial and mechanical properties of composite resins modified by the addition of TiO2 NPs. Methods: Orthodontics composite containing 0%, 1%, 5% and 10% NPs were prepared. 180 composite disks were prepared for elution test, disk agar diffusion test and biofilm inhibition test to collect the counts of microorganisms on three days, measure the inhibition diameter and quantify the viable counts of colonies consequently. For shear bond strength (SBS) test, 48 intact bovine incisors were divided into four groups. Composites containing 0%, 1%, 5% and 10% NPs were used for bonding of bracket. The bracket/tooth SBS was measured by using an universal testing machine. Results: All concentration of TiO2 NPs had a significant effect on creation and extension of inhibition zone. For S. mutans and S. sanguinis, all concentration of TiO2 NPs caused reduction of the colony counts. Composite containing 10% TiO2 NPs had significant effect on reduction of colony counts for S. mutans and S. sanguinis in all three days. The highest mean shear bond strength belonged to the control group, while the lowest value was seen in 10% NPs composite. Conclusions: Incorporating TiO2 nanoparticles into composite resins confer antibacterial properties to adhesives, while the mean shear bond of composite containing 1% and 5% NPs still in an acceptable range.

RESUMO Introdução: o acúmulo de placa e as descolagens de braquetes são algumas desvantagens presentes no tratamento ortodôntico, no qual se requer o uso de materiais compósitos para a colagem dos braquetes. Objetivo: tendo em vista que as propriedades antimicrobianas das nanopartículas (NPs) de TiO2 já foram confirmadas, o objetivo do presente estudo foi avaliar as propriedades antimicrobianas e mecânicas de resinas compostas modificadas pela adição de NPs de TiO2. Métodos: compósitos ortodônticos contendo 0%, 1%, 5% e 10% de NPs foram preparados. Cento e oitenta discos de compósito foram preparados para o teste de eluição, o ensaio de difusão em ágar por disco, e o ensaio de inibição da formação de biofilme, para se calcular as contagens de microrganismos ao longo de três dias, medir o diâmetro da inibição e, consequentemente, quantificar as contagens de colônias viáveis. Para o teste de resistência da colagem ao cisalhamento (SBS), 48 incisivos bovinos intactos foram divididos em quatro grupos, nos quais os compósitos contendo 0%, 1%, 5% e 10% de NPs foram utilizados para colagem dos braquetes. A SBS da interface braquete/dente foi medida em uma máquina universal de ensaios. Resultados: todas as concentrações de NPs de TiO2 apresentaram efeito significativo na formação e na extensão da zona de inibição. Para o S. mutans e o S. sanguinis, todas as concentrações de NPs de TiO2 causaram redução na contagem das colônias. O compósito contendo 10% de NPs de TiO2 apresentou uma diminuição significativa na contagem de colônias de S. mutans e S. sanguinis durante os três dias. A média mais alta da SBS foi observada no grupo controle, enquanto o valor mais baixo foi observado para o compósito com 10% de NPs. Conclusões: a incorporação de nanopartículas de TiO2 nas resinas compostas lhes conferiu propriedades antibacterianas, e o valor médio da SBS das resinas contendo 1% e 5% de NPs apresentou-se dentro de uma faixa aceitável.

Evaluation of the antibacterial activity of a conventional orthodontic composite containing silver/hydroxyapatite nanoparticles.

BACKGROUND: One of the most important complications of fixed orthodontic treatment is the formation of white spots which are initial carious lesions. Addition of antimicrobial agents into orthodontic adhesives might be a wise solution for prevention of white spot formation. The aim of this study was to evaluate the antibacterial properties of a conventional orthodontic adhesive containing three different concentrations of silver/hydroxyapatite nanoparticles. METHODS: One hundred and sixty-two Transbond XT composite discs containing 0, 1, 5, and 10 % silver/hydroxyapatite nanoparticles were prepared and sterilized. Antibacterial properties of these composite groups against Streptococcus mutans, Lactobacillus acidophilus, and Streptococcus sanguinis were investigated using three different antimicrobial tests. Disk agar diffusion test was performed to assess the diffusion of antibacterial agent on brain heart infusion agar plate by measuring bacterial growth inhibition zones. Biofilm inhibition test showed the antibacterial capacity of composite discs against resistant bacterial biofilms. Antimicrobial activity of eluted components from composite discs was investigated by comparing the viable counts of bacteria after 3, 15, and 30 days. RESULTS: Composite discs containing 5 and 10 % silver/hydroxyapatite nanoparticles were capable of producing growth inhibition zones for all bacterial types. Results of biofilm inhibition test showed that all of the study groups reduced viable bacterial count in comparison to the control group. Antimicrobial activity of eluted components from composite discs was immensely diverse based on the bacterial type and the concentration of nanoparticles. CONCLUSIONS: Transbond XT composite discs containing 5 and 10 % silver/hydroxyapatite nanoparticles produce bacterial growth inhibition zones and show antibacterial properties against biofilms.

Antimicrobial properties of poly (methyl methacrylate) acrylic resins incorporated with silicon dioxide and titanium dioxide nanoparticles on cariogenic bacteria.

AIM: To assess the effects of adding nano-titanium dioxide (nano-TiO2) and nano-silicon dioxide (nano-SiO2) and their mixture to poly (methyl methacrylate) (PMMA) to induce antimicrobial activity in acrylic resins. MATERIALS AND METHODS: Acrylic specimens in size of 20 mm × 20 mm × 1 mm of 0.5% and 1% of nano-TiO2 (21 nm) and nano-SiO2 (20 nm) and their mixture (TiO2/SiO2 nanoparticles) (1:1 w/w) were prepared from the mixture of acrylic liquid containing nanoparticles and acrylic powder. To obtain 0.5% and 1% concentration, 0.02 g and 0.04 g of the nanoparticles was added to each milliliter of the acrylic monomer, respectively. Antimicrobial properties of six specimens of these preparations, as prepared, were assessed against planktonic Lactobacillus acidophilus and Streptococcus mutans at 0, 15, 30, 45, 60, 75, and 90 min follow-up by broth dilution assay. The specimens of each group were divided into three subgroups: Dark, daylight, or ultraviolet A (UVA). The percent of bacterial reduction is found out from the counts taken at each time point. STATISTICAL ANALYSIS: Data were analyzed using one-way analysis of variance and Tukey's post hoc analysis. RESULTS: Exposure to PMMA containing the nanoparticles reduced the bacterial count by 3.2-99%, depending on the nanoparticles, bacterial types, and light conditions. Planktonic cultures of S. mutans and L. acidophilus exposed to PMMA containing 1% of TiO2/SiO2 nanoparticles showed a significant decrease (P < 0.001) (98% and 99%, respectively) in a time-dependent manner under UVA. The S. mutans and L. acidophilus counts did not significantly decrease in PMMA containing 0.5% nano-TiO2 and PMMA containing 0.5% nano-SiO2 in the dark. No statistically significant reduction (P > 0.05) was observed in the counts of S. mutans and L. acidophilus in PMMA without the nanoparticles exposed to UVA. CONCLUSIONS: PMMA resins incorporated with TiO2/SiO2 nanoparticles showed strong antimicrobial activity against the cariogenic bacteria.

Effect of Addition of Curcumin Nanoparticles on Antimicrobial Property and Shear Bond Strength of Orthodontic Composite to Bovine Enamel.

OBJECTIVES: This study sought to assess the effect of curcumin nanoparticles (curcNPs) on antimicrobial property and shear bond strength (SBS) of orthodontic composite to bovine enamel. MATERIALS AND METHODS: In this in vitro, experimental study, 1%, 5% and 10% curcNPs were added to Transbond XT composite. Stainless steel brackets were bonded to 48 sound bovine incisors in four groups (n=12) using composite containing 0% (control), 1%, 5% and 10% curcNPs. The bracket-tooth SBS was measured by a universal testing machine. The adhesive remnant index (ARI) score was calculated after debonding using a stereomicroscope. Also, 180 discs were fabricated of the four composites; 108 were subjected to eluted component test, 36 were used for disc diffusion test and 36 were used for biofilm test to assess their antimicrobial activity against Streptococcus mutans, Streptococcus sanguinis and Lactobacillus acidophilus. RESULTS: The highest and lowest SBS belonged to control and 10% curcNP groups, respectively. The difference in SBS was significant among the four groups (P=0.008). The SBS of control group was significantly higher than that of 10% curcNPs (P=0.006). The four groups were not significantly different in terms of ARI score (P>0.05). Growth inhibition zones were not seen in any group. In biofilm test, the colony counts of all bacteria significantly decreased by an increase in percentage of curcNPs. Colony count significantly decreased only at 30 days. CONCLUSIONS: At 1% concentration, curcNPs have significant antimicrobial activity against cariogenic bacteria with no adverse effect on SBS. However, insolubility of curcNPs remains a major drawback.

Three-dimensional analysis using finite element method of anterior teeth inclination and center of resistance location.

OBJECTIVE: To locate the centre of resistance of consolidated units of four and six anterior teeth during retraction. METHODS: Twelve three-dimensional (3D) models were designed in SolidWorks of the anterior segment with four and six teeth and their supporting structure. A proper force system was applied in each model to retract the teeth bodily. The exact location of the centre of resistances (CRes) was determined. It was found that the path of CRes change in four-tooth and six-tooth units according to the anterior teeth torque. RESULTS: A posterior shift of the CRes by increasing the inclination of teeth was shown. However, vertical position has a fluctuant behaviour. First it moves apically, then it moves incisally. Furthermore, results suggest that in en masse retraction, translation can be achieved with a smaller amount of moment-to-force ratio than in four-incisor retraction. In other words, for bodily retraction of anterior incisor segments, we should apply force in a more apical position. CONCLUSION: Different anterior torques between 7 and 35 degrees, cannot affect the CRes position dramatically. The area of CRes shifting is 0.92 mm (anterioposteriorly) x 0.74 mm (superior-inferiorly) in the six-tooth unit in the teeth model and 0.85 mm (anterioposteriorly) x 0.82 mm (superior-inferiorly) in the teeth and bone model. In the four-tooth model, the area of CRes shifting is 0.97 mm (anterioposteriorly) x 0.93 mm (superior-inferiorly) in tooth model and 0.77 mm (anterioposteriorly) x 0.87 mm (superior-inferiorly) in the teeth and bone model.