Effect of the addition of Chitosan and TiO2nanoparticles on antibacterial properties of an orthodontic composite in fixed orthodontic treatment: a randomized clinical trial study.

Due to the existing demands for methods independent of patient co-operation in preventing and overcoming the incidence of white spot lesions (WSLs) and caries in fixed orthodontic treatments, several studies have considered the modification of orthodontic composites using antimicrobial nanomaterials. In this regard, the aim of this study is to investigate the effect of the addition of chitosan nanoparticles (NPs) and TiO2NPs onStreptococcus mutans(S. mutans) counts and the enamel mineral content in fixed orthodontic patients. A double-blind randomized clinical trial study was carried out in 24 patients (i.e., 48 upper second premolars and 48 maxillary lateral incisors) who were candidates for fixed orthodontic treatment. In the case of the control group, the bracket was bonded to the tooth with an orthodontic adhesive (Transbond XT, 3M Unitek, USA) while, in the experimental group, the bracket was bonded to the tooth with Transbond XT containing 1% chitosan NPs and 1% TiO2NPs. For the maxillary lateral incisor and upper second premolar teeth, theS. mutanscounts around the brackets were measured, through the usage of real-time PCR, at the time points of 1 day, 2 months, and 6 months after bonding the brackets to the tooth. Furthermore, the enamel mineral content measurement was also performed around the brackets at 1 day, 2 months, and 6 months after bonding the brackets to the tooth. TheS. mutanscounts were analyzed using Friedman and Mann-Whitney U tests. The Repeated measures ANOVA test and Independent samples T-test were also applied, in order to evaluate the mineral content. According to the results, there was a significant reduction in theS. mutanscounts of experimental group at the time points of 1 day, 2 months, and 6 months in both maxillary lateral incisor and upper second premolar teeth. However, we did not observe any significant differences in the control group between the reports at 1 day, 2 months, and 6 months in both maxillary lateral incisor and upper second premolar teeth. The outcomes of this study indicate that, with regard to maxillary lateral incisor teeth, there were no significant differences between the results of the experimental group and control group at the time points of 1 day, 2 months, and 6 months. Furthermore, with respect to the upper second premolar teeth, no significant differences were observed between the two groups at 1 day and 2 months; however,S. mutanscounts were significantly lower in the experimental group than in the control group at the time point of 6 months. Moreover, our gathered data confirmed the absence of any significant differences between the experimental group and control group, in terms of enamel mineral content, at the time intervals of 1 day, 2 months, and 6 months. In conclusion, the incorporation of chitosan NPs and TiO2NPs in orthodontic composites induces an antibacterial property in the resultant adhesive to be used for fixed orthodontic treatment.

Incorporation of Chitosan Nanoparticles into a Cold-Cure Ortho-Dontic Acrylic Resin: Effects on Mechanical Properties.

Improvement of the antibacterial properties of acrylic resins, used in the construction of removable orthodontic appliances, is an important strategy to reduce the incidence of caries and oral diseases in orthodontic treatments. The addition of antimicrobial agents to acrylic resins is one of the effective methods to enhance the antimicrobial properties of these materials. However, one main concern is that modification of acrylic resin has negative effects on its mechanical properties. Recently, chitosan nanoparticles (NPs), as biocompatible and biodegradable polysaccharides with remarkable antimicrobial properties, have been used in different areas of dentistry and medicine. This study aimed to investigate the effects of adding chitosan NPs on the mechanical properties of a cold-cure orthodontic acrylic resin. The chitosan NPs were added to the acrylic resin in various weight percentages: 0% (control), 0.5%, 1%, 2%, and 4%. The flexural strength, compressive strength, Vickers microhardness, and impact strength measurements were performed for all five groups. The results showed that adding up to 1% (w/w) chitosan NPs to an acrylic resin had no significant negative effects on its flexural strength and compressive strength, while it decreased these parameters at weight percentages of 2% and 4% (w/w). The results also revealed that modification of acrylic resin with chitosan NPs up to 4% had no significant negative effects on the microhardness and impact strength of acrylic resin. In conclusion, the addition of chitosan NPs up to 1% (w/w) had no significant negative effects on the mechanical properties of cold-cure acrylic resin.

Fractional CO2 laser treatment for post-surgical lip scars in cleft lip and palate patients.

Post-surgical scars of cleft lip patients can lead to abnormal lip activity, which causes deficient maxillary growth. The aim of the present study was to assess the effect of laser therapy on the appearance and electrical activity of the upper lip in cleft lip and palate patients. Twelve patients with cleft lip and palate participated in this study. All patients had surgically repaired the cleft lip at the age of about 3-6 months. The lip scars underwent five fractional CO2 laser treatment sessions with a 4-week interval. Improvement of the quality of the skin texture was recorded according to quartile grading scale based on photographs taken before and 1 month after treatment. Patients' satisfaction survey was also recorded using Patient Scar Assessment Questionnaire (PSAQ) before and after laser therapy. Moreover, the EMG activity of the upper lip muscle was measured before and after treatment. According to dermatologists, the improvement of scar appearance ranged from 0.5 to 3, with a mean of 1.29 ± 0.86. Mean scores of the scar appearance (p < 0.001), symptoms (p = 0.003), and scar consciousness (p < 0.001) subscales of the PSAQ questionnaire had significantly increased after treatment. The EMG recording of the upper lip had decreased significantly after laser treatment at rest (p = 0.009) and maximum lip compression (p = 0.007). The fractional CO2 laser is an effective method for treating old scars of the cleft lip with a significant change in the opinion of patients about their scar appearance. Also, the therapy can help to reduce the EMG activity of the upper lip at rest.

Antimicrobial photodynamic therapy of Lactobacillus acidophilus by indocyanine green and 810-nm diode laser.

This study investigated the efficacy of photodynamic therapy (PDT) using EmunDo as a photosensitizer against Lactobacillus acidophilus. A gallium aluminum arsenide diode laser was used in this experiment (810 nm, CW). Standard suspensions of Lactobacillus acidophilus were divided into six groups by treatment: 1) EmunDo, 2) diode laser (100 mW, 90 s), 3) diode laser (300 mW, 30 s); 4) EmunDo + diode laser (100 mW, 90 s), 5) EmunDo + diode laser (300 mW, 30 s), 6) control (no treatment). Bacterial suspensions from each group were subcultured onto the surface of MRS agar plates immediately and 24 h after treatment, and the viable microorganisms of Lactobacillus acidophilus were counted. The data were analyzed by ANOVA and student's t-test at p < 0.05. There was a significant between-group difference in the number of Lactobacillus acidophilus colonies in cell cultures obtained at 24 h after treatment (p < 0.001). The viable counts were significantly lower in EmunDo and both PDT groups, as compared to the other groups (p < 0.05). In the control and laser-irradiated groups, the number of colonies increased significantly at 24 h compared to the immediately after treatment (p < 0.05), whereas in both PDT groups, the number of colonies showed a significant reduction after 24 h of therapy (p < 0.05). Under the conditions used in this study, L. acidophilus colonies were susceptible to PDT after sensitization with EmunDo and exposure to diode laser. These findings imply that PDT is capable to reduce cariogenic bacteria, potentially leading to more conservative cavity preparation.

Static and kinetic frictional forces of silica-insert ceramic brackets with coated archwires in artificial saliva.

BACKGROUND: During sliding mechanics, the frictional force (FF) is an important counterforce to orthodontic tooth movement. The purpose of this in vitro study was to investigate the static and kinetic FFs of S silica-insert ceramic (SIC) brackets with Teflon-coated (TC) and conventional S stainless steel (SS) archwires. MATERIALS AND METHODS: The target group of this study included 80 maxillary canine 0.022 inch slot SIC brackets. Forty SS brackets were used as the control. TC and conventional uncoated SS archwires of different dimensions (0.016, 0.018, 0.016 × 0.022, and 0.018 × 0.025 inch) were examined. All tests were carried out under artificial saliva injected condition. Scanning Electron Micrographs were prepared for two samples of coated and uncoated archwires. Analysis of variance and Tukey post hoc tests were used for statistical purposes (level of significance P < 0.05). RESULTS: SIC brackets showed significantly lower levels of FFs than SS brackets. TC archwires had greater frictional values than conventional uncoated ones. They also exhibited an unusual behavior of increasing kinetic FFs with time. Indentation and delamination of coating were obvious under scanning electron microscopy observations. CONCLUSION: From the standpoint of friction, SIC brackets may serve well, even better than SS brackets, in sliding mechanics. The coating layer of the archwires may delaminate and lost, causing an impediment to tooth movement.

Management of Post-orthodontic White Spot Lesions and Subsequent Enamel Discoloration with Two Microabrasion Techniques.

STATEMENT OF THE PROBLEM: Demineralization of enamel adjacent to orthodontic appliances frequently occurs, commonly due to insufficient oral hygiene. PURPOSE: The aim of this study was to compare two microabrasion techniques on improving the white spot lesions as well as subsequent enamel discoloration. MATERIALS AND METHOD: Sixty extracted premolar teeth without caries and hypoplasia were selected for this study. White spot lesions were artificially induced on the buccal surface of each tooth. Teeth were randomly assigned to three treatment groups, each treated with pumice powder as the control, microabrasion with 18% HCl, and microabrasion with 37% H3PO4. Subsequently, the three groups were daily immersed for five minutes in a tea-coffee solution for a period of one week. Colorimetric evaluation was done before and after formation of white spot lesions, after microabrasion, and after immersion in the colored solution; then the color differences (∆E) were calculated. Statistical analysis was performed by multiple measurement analysis and the Tukey's test. RESULTS: This study showed that ∆E between the stages of white spot formation and microabrasion for H3PO4 was more than other groups and for the pumice powder group it was less than the others. Furthermore, there was a significant difference between ∆E of the three study groups (p= 0.017). Additionally, ∆E after placing the teeth in the colored solution and microabrasion was the highest for the HCl group and the lowest for the pumice powder group. There was also a significant difference between the three groups (p= 0.000). CONCLUSION: Pumice powder alone had similar effects as 18% HCl on removing the white spot lesions. Nevertheless, 18% HCl makes the enamel susceptible for subsequent color staining more than the other microabrasion methods.

Evaluation of the cytotoxicity of fiber reinforced composite bonded retainers and flexible spiral wires retainers in simulated high and low cariogenic environments.

OBJECTIVES: The aim of this study was to evaluate the cytotoxic effects of fiber reinforced composite bonded retainers in comparison with flexible spiral wires (FSWs) under high and low cariogenic-simulated environments using human oral fibroblasts. MATERIALS AND METHODS: Four types of bonded retainers were evaluated: (1) reinforced with glass fibers: Interlig (Angelus), (2) reinforced with polyethylene fibers: Connect (Kerr), (3) reinforced with quartz fibers: Quartz Splint UD (RTD), and (4) FSW. Twenty specimens of each sample group were prepared with the same surface area and halved. Next, half of them were placed in a high cariogenic environment 60 min in 10% lactic acid 3 times a day and remained in Fusayama Meyer artificial saliva for the rest of the day) and the other half were placed in a low cariogenic environment 20 min in 10% lactic acid 3 times a day and remained in Fusayama Meyer artificial saliva for the rest of the day) for 1, 7 and 30 days. Cell viability was assessed by MTT assay. Data were analyzed using SPSS software (α =0.05). RESULTS: During the 1(st) month, cytotoxicity reduced gradually. In the low cariogenic-simulated environment, the cytotoxicity of all of the groups were reported to be mild at day 30 and the difference between them was significant (P = 0.016). In the same period in the high cariogenic-simulated environment, the cytotoxicity of Connect and Quartz Splint was mild, and they had lower cytotoxicity than the other groups. Meanwhile, Interlig had moderate (52%) and FSW had severe cytotoxicity (22%) and the difference between the groups was also significant (P = 0.000). CONCLUSIONS: FSW retainers are not recommended in those at high-risk for dental caries. However, in those at low-risk, there is no difference from the standpoint of cytotoxicity.

Microleakage and shear bond strength of orthodontc brackets bonded to hypomineralized enamel following different surface preparations.

OBJECTIVES: This study investigated the effects of several conditioning methods on shear bond strength (SBS) and microleakage of orthodontic brackets bonded to demineralized enamel. STUDY DESIGN: One hundred premolars were selected and immersed in a cariogenic solution for 12 weeks. The teeth were randomly assigned into 5 groups. In groups 1 and 2, the teeth underwent acid etching for 30 and 120 seconds, respectively. In group 3, a combination of laser and acid etching was employed. A self-etch primer (SEP) was applied in group 4 and in group 5, the teeth were exposed to acidulated phosphate fluoride (APF) for 4 minutes before etching. After bracket bonding, the teeth were immersed in methylen blue for 12 hours and then were mounted in acrylic resin. SBS was determined with an Instron Universal Testing Machine and the amount of microleakage under the brackets was assessed under a stereomicroscope. RESULTS: The lowest SBS was related to the SEP group and the highest one was observed in the specimens prepared by APF+acid etching. There was a significant difference in SBS (p=0.009), but not in microleakage (p=0.971) of the study groups. The SBS of the specimens treated with SEP was significantly Lower than the other groups, which were not significantly different from each other. The SEP group displayed a higher frequency of bond failure at the enamel-adhesive interface. CONCLUSIONS: Enamel preparation with SEP provided the lowest SBS among the groups. All groups showed some degree of microleakage. There was no significant correlation between SBS and microleakage. Key words:Bond strength, microleakage, bonding, self-etch primer, Er:YAG laser.

Effects on shear bond strength and the enamel surface with an enamel bonding agent.

INTRODUCTION: The purpose of this study was to evaluate the shear bond strength of orthodontic brackets and the effect of an enamel bonding agent (EBA) on enamel surface after debonding. METHODS: Seventy-five extracted maxillary premolars were collected and randomly divided into 3 groups of 25. The enamel cracks were surveyed with a stereomicroscope. In the first group, 1 layer of EBA was applied before the adhesive resin. In the second group, 2 layers of EBA were used; in the third group, no EBA was used. Bonding was followed by incubation for 48 hours at 37 degrees C and thermocycling for 1000 cycles. Debonding was performed with a shear force. The surfaces of the teeth were evaluated, and the length, depth, direction of cracks, and adhesive remnants on the enamel surface were recorded. Data were analyzed by using analysis of variance and paired samples t tests. RESULTS: There were no significant differences between the shear bond strengths (P = 0.341) of the 3 groups, or in the direction, length, and depth of the cracks before and after debonding (P > 0.05). There was a significant increase in the number of cracks after debonding in the 3 groups (P < 0.05). The evaluation of adhesive remaining on the surface of the teeth indicated that most bond failures occurred at the resin-bracket interface. CONCLUSIONS: The use of EBA does not enhance bond strength or provide greater protection to the enamel surface during debonding.

Comparison between the external gonial angle in panoramic radiographs and lateral cephalograms of adult patients with Class I malocclusion.

The external gonial angle is an important angle of the craniofacial complex. It is significant for the diagnosis of craniofacial disorders. Lateral cephalogram and orthopantomograms can be used to determine this angle. In this study, we compared the external gonial angle determined from the two mentioned radiographs in Class I patients. We collected the radiographs of 70 patients with Angle's Class I (22 men and 48 women). The patients' age ranged from 15-30 years with a mean age of 18.24 years. The data gained were statistically evaluated by t-test. The following results were obtained. The mean value of the gonial angle in the lateral cephalogram was 125.00 degrees (men, 124.9 degrees and women, 125.04 degrees ) and in the orthopantomogram was 124.17 degrees (men 123.68 degrees , women 124.39 degrees ). The difference between these rates was 0.83 degrees (men 1.22 degrees , women 0.64 degrees ) and not significant (P = 0.406). Based on the obtained results, we can conclude that panoramic radiography can be used to determine the gonial angle as accurately as a lateral cephalogram. In addition, we can determine the right and left gonial angles of a patient in the orthopantomogram without interferences due to superimposed images of anatomical structures in a lateral cephalogram. For determination of the gonial angle, an orthopantomogram may be a better choice than a lateral cephalogram.