Assessment of Bond Strength between Metal Brackets and Non-Glazed Ceramic in Different Surface Treatment Methods

Objective: The aim of this study was to evaluate the bond strength between metal brackets and non-glazed ceramic with three different surface treatment methods.Materials and Methods: Forty-two non-glazed ceramic disks were assigned into three groups. Group I and II specimens were etched with 9.5% hydrofluoric acid. Subsequently in group I, silane and adhesive were applied and in group II, bonding agent was used only.In group III, specimens were treated with 35% phosphoric acid and then silane and adhesive were applied. Brackets were bonded with light-cured composites. The specimens were stored in water in room temperature for 24 hours and then thermocycled 500 times between 5°C and 55°C.Results: The difference of tensile bond strength between groups I and III was not significant(P=0.999). However, the tensile bond strength of group II was significantly lower than groups I, and III (P<0.001). The adhesive remnant index scores between the threegroups had statistically significant differences (P<0.001).Conclusion: With the application of scotch bond multi-purpose plus adhesive, we can use phosphoric acid instead of hydrofluoric acid for bonding brackets to non-glazed ceramic restorations

The Effect of Different Methods of Fluoride Administration at Different Concentrations on the Load-Deflection Properties of Rhodium-Coated Niti Archwires

Background and Objective: Fluoride compounds are widely used for the control of dental plaque. Considering the effect of different fluoride compounds on the mechanical properties of orthodontic wires, this study was conducted to analyze the effect of different methods of fluoride administration at different concentrations on the load-deflection properties of rhodium-coated NiTi orthodontic archwires. Methods: This clinical trial was conducted on 30 patients aged between 15 and 25 years referring to Babol University of Medical Sciences due to dental crowding and didn't have vertical skeletal defects. 0.016-inch Rhodium-Coated A-NiTi wire was placed on patients' maxillary brackets. Patients were randomly divided into three groups of ten: The control group used only fluoride toothpaste, the second group used fluoride toothpaste with sodium fluoride mouthwash (0.05%) and the third group used fluoride toothpaste with Acidulated Phosphate Fluoride gel (1.23% APF). After six weeks, the values of unloading force (N), yield strength (N/m2) and stiffness (N/m) of the wires were obtained using a three-point bending test. Findings: The mean unloading force and stiffness of the second group wires were higher than that of the other groups and in the first group, they were higher than the control group in all values, but no significant differences were found between the groups. There was a significant difference between the yield strengths of different groups (p=0.038). The mean yield strength in the second group was higher than the other groups (0.94±0.16 N/m2) and was significantly different from the control group (0.75±0.19 N/m2) (p=0.030). Conclusion: According to this study, method of fluoride administration does not affect the unloading force and stiffness but the yield strength of rhodium-coated NiTi archwires increases with an increase in the fluoride concentration

Evaluation of the Effects of Low-Level Laser Therapy on the Rate of Relapse of Mandibular Incisors after Fixed Orthodontic Treatment: A Randomized Controlled Trial

Background and Objective: Stability is one of the major issues in orthodontics. The purpose of this study is to investigate the effect of Low-Level Laser Therapy on the rate of relapse of mandibular incisors. Methods: This Single-blinded Randomized Controlled Trial consisted of twenty patients (aged 12-18 years) seeking orthodontic treatment. The subjects were divided into two groups with randomly permuted blocks (n=10): experimental and control groups. The Little’s irregularity index was measured on plaster models prior to treatment using American Board of Orthodontic Measuring Gauge. After unraveling of initial crowding, archwires on mandibular anterior segments of both groups were removed. The experimental group received Low-Level Diode Laser at 808 nm wavelength, 250 mW power, 4J energy and continuous wave mode, on coronal third of lower central and lateral incisors and canines’ roots for sixteen seconds three times a week, within a four-week period. The relapse rate was quantified on each plaster model using Little’s irregularity index at the end of first (T1), second (T2), third (T3), and fourth (T4) weeks. Findings: The study population consisted of twenty patients aged 12-18 years who had 5-9 mm crowding and proper oral hygiene. At T1, the relapse rate was 0 mm and 0.05±0.15 mm in experimental and control group, respectively, which was not statistically significant (p=0.343). Over the following weeks, however, there was statistically significant difference between the relapse rate of the two groups (p=0.003). The mean rate of relapse percentage was 4.48±4.31 mm in experimental and 12.06±5.52 mm in control group, which was significantly lower in Low-Level Laser Therapy group. Conclusion: The application of Low-Level Laser Therapy at 808 nm wavelength on mandibular incisors during orthodontic retention phase may slow down the relapse rate. Therefore, it could be considered as an effective adjunct to reduce immediate relapse

Tensile Bond Strength of Metal Bracket Bonding to Glazed Ceramic Surfaces With Different Surface Conditionings

Objective: The objective of this study was to compare the tensile bond strength of metal brackets bonding to glazed ceramic surfaces using three various surface treatments.Materials and Methods: Forty two glazed ceramic disks were assigned to three groups. In the first and second groups the specimens were etched with 9.5% hydrofluoric acid (HFA). Subsequently in first group, ceramic primer and adhesive were applied, but in second group a bonding agent alone was used. In third group, specimens were treated with 35% phosphoric acid followed by ceramic primerand adhesive application. Brackets were bonded with light cure composites. The specimens were stored in distilled water in the room temperature for 24 hours and thermocycled 500 times between 5°C and 55°C. The universal testing machine was used to test the tensile bond strength and the adhesive remenant index scores between three groups was evaluated. The data were subjected to one-way ANOVA, Tukey and Kruskal-Wallis tests respectively.Results: The tensile bond strength was 3.69±0.52 MPa forfirst group, 2.69±0.91 MPa for second group and 3.60±0.41 MPa for third group. Group II specimens showed tensile strength values significantly different from other groups (P<0.01).Conclusion: In spite of limitations in laboratory studies it may be concluded that in application of Scotch bond multipurpose plus adhesive, phosphoric acid can be used instead of HFA for bonding brackets to the glazed ceramic restorations with enough tensile bond strength

Evaluation of the Effects of Low-Level Laser Therapy on the Rate of Relapse of Mandibular Incisors after Fixed Orthodontic Treatment: A Randomized Controlled Trial

Background and Objective: Stability is one of the major issues in orthodontics. The purpose of this study is to investigate the effect of Low-Level Laser Therapy on the rate of relapse of mandibular incisors. Methods: This Single-blinded Randomized Controlled Trial consisted of twenty patients (aged 12-18 years) seeking orthodontic treatment. The subjects were divided into two groups with randomly permuted blocks (n=10): experimental and control groups. The Little’s irregularity index was measured on plaster models prior to treatment using American Board of Orthodontic Measuring Gauge. After unraveling of initial crowding, archwires on mandibular anterior segments of both groups were removed. The experimental group received Low-Level Diode Laser at 808 nm wavelength, 250 mW power, 4J energy and continuous wave mode, on coronal third of lower central and lateral incisors and canines’ roots for sixteen seconds three times a week, within a four-week period. The relapse rate was quantified on each plaster model using Little’s irregularity index at the end of first (T1), second (T2), third (T3), and fourth (T4) weeks. Findings: The study population consisted of twenty patients aged 12-18 years who had 5-9 mm crowding and proper oral hygiene. At T1, the relapse rate was 0 mm and 0.05±0.15 mm in experimental and control group, respectively, which was not statistically significant (p=0.343). Over the following weeks, however, there was statistically significant difference between the relapse rate of the two groups (p=0.003). The mean rate of relapse percentage was 4.48±4.31 mm in experimental and 12.06±5.52 mm in control group, which was significantly lower in Low-Level Laser Therapy group. Conclusion: The application of Low-Level Laser Therapy at 808 nm wavelength on mandibular incisors during orthodontic retention phase may slow down the relapse rate. Therefore, it could be considered as an effective adjunct to reduce immediate relapse