Peerapong Tua-Ngam

Investigation of Fluoride Release from Orthodontic Acrylic Plate

Objective: This study aimed to investigate fluoride release, flexural strength and surface characteristics of three orthodontic acrylic resins (A) blended with (1) sodium fluoride powder (NaF), (2) calcium fluoride powder (CaF2), and (3) glass ionomer cement powder (GIC). Material & Methods: Acrylic resin was blended with NaF, CaF2 , and GIC to make orthodontic acrylic plates. Each sample group was divided into subgroups at fluoride concentrations 5%, 10% and 20%. The acrylic resin was cured in a round stainless steel mold and kept in a bottle with 10 ml. deionized water then kept in an incubator at 37oC. The deionized water, changed every day, was tested for fluoride release up to six mo by Orion machine. For the flexural strength test, the samples were cured in a stainless steel mold, 64 mm. long, 10 mm. wide and 3.3 mm. high according to standard of ISO 20795-2 and testing was done up to 6 mo in deionized water. Scanning electron microscope determined surface characteristics after being blended. Results: Fluoride release was observed from orthodontic acrylic plates blended with NaF, CaF2 and GIC. The results of the A-NaF and the A- CaF2 group decreased fluoride level greatly at day 2, but the A-GIC group was observed at day 7. The A-NaF group and the A-GIC group could not detect fluoride level after mo 4 and 2, respectively. The A-CaF2 group found greater long term fluoride release than the A-NaF and the A-GIC group especially at 20% concentration (up to six mo). Significant differences (p<0.05) of fluoride release level (ppmF) among the A-NaF, A-GIC, and A-CaF2 groups at 5% concentration in every time point from day 1 to the mo 5, but not significant in mo 6 similar to the 10% concentration comparison. Whereas, comparing the 20% concentration among groups, significant differences (p<0.05) were found between groups in all periods of time (from the day 1 to mo 6). When comparing the different concentrations of 5%, 10%, and 20% in each group, significant differences (p<0.05) were found in every concentration at every time period of the A-GIC group from day 1 to mo 2, in the A-CaF2 group from day 1 to mo 6 and in the A-NaF group from day 1 to mo 4. Conclusion: Fluoride release was observed from orthodontic acrylic plates blended with NaF, CaF2 and GIC. The longest duration of fluoride release from orthodontic acrylic plates was found in the CaF2 group followed by the NaF and GIC groups. The flexural strength in every group decreased over time. This result implied that the flexural strength decreased during fluoride release. The acrylic surface was seen to be porous in every period of the fluoride release process.

Comparison of the Mechanical Properties of Three Commercial Orthodontic NiTi Round Archwires

To compare mechanical properties of three commercial NiTi orthodontic round wires, three commercial brands of NiTi round wire (Nic-China, Ormco-USA, and Smart-Thailand) with sizes 0.014’’, 0.016’’, and 0.018’’were studied. Five specimens each size of each brand were used to test mechanical properties; unloading force (N), spring back (mm), and yield strength (N/mm) with three-point bend test using an Instron Universal Testing Machine. Kolmogorov-Smirnov test and one-way ANOVA were employed to test the differences among groups with statistical difference at p<0.05.The average unloading force from lowest to highest were Ormco, Smart and Nic with 0.014”, Smart, Ormco and Nic with 0.016”and Smart, Nic and Ormco with 0.018”, respectively. The Nic brand had the highest value of unloading force, spring back, and yield strength in all wire sizes, except unloading force 0.018” Ormco and spring back 0.018” Smart. There were no statistically significant differences in unloading forces among all wire sizes. The three brands of commercial orthodontic NiTi wires presented similar unloading force, spring back, and yield strength properties. These mechanical properties are related to lower rates of deformation and are appropriate to be used in the initial phase of orthodontic treatment.

Residual Force of Orthodontic Elastomeric Ligature

Objectives:The study aimed to compare the residual forceoflocally produced Thai orthodontic elastomeric ligatureswith 2 commercial brands.Materials and Methods: The study compared Thai clear and blue orthodontic elastomeric ligatures with clear and blue commercial brands[Unitek (USA) and W&H (China)]. The dimensional characteristics of the ligatures (i.e., inner diameter, outer diameter and cross-section thickness) were measured. Then initial extension force was measured. After that, the residual force was determined at day 1and repeated on day 2,3,4,5,6,7,14,21, and 28 andthe percentage of residual force wascalculatedaccording to ISO 21606:2007. The data were analyzed with Two-way ANOVA and multiple linear regression (p<0.05). Results: Thai ligatures had significantly greater inner diameter(clear 1.22 mm, blue 1.21 mm) and cross-section thickness (clear 0.78 mm, blue 0.79 mm) in both colors when compared with Unitek and W&H brands. Thai ligatures had no significant difference in cross-section thickness between clear and blue.Thai clear ligatures hadthe highest initial extension force(2.30 N). Thai ligatures showed similar force decay patterns as other brands, rapidly decreasing the first day, gradually decreasing over 7 days and remaining nearly constant until 28 days.However, both clear and blue Thai elastomeric ligatures had significantly less outer diameters (clear 3.12 mm, blue 3.15mm). Thai blue ligatures had the lowest initial extension force (1.96 N).TheThai clear and blue demonstrated less percentage of residual force in the first day (clear 53.00%, blue 50.66%) and28 days (clear, 37.69%, blue, 37.00%) butthey were clinically acceptable. In general, clear ligatures exhibited a greater percentage of residual force than blue ligatureamong the 3 brands. Conclusion:Thai orthodontic elastomeric ligature properties are comparable to commercially available brands and acceptable for clinical application.

Cytotoxicity of Three Light-Cured Orthodontic Adhesives

Objective: The aim of this study was to evaluate the cytotoxic effects of three commercial light-cured orthodontic adhesives.Materials and methods: The potential cytotoxic effects of three types of orthodontic adhesives, Grengloo, Green Glue, and Transbond XT, were tested on L929 cell culture. The cell line was grown in 96-well tissue culture plates (1x105 cells/mm3). Thin resin discs weighing 0.4, 0.6, 0.8, 0.8, and 0.8 gram of each material were prepared and aged for 1, 3, 6, 8, and 10 days, respectively, in Minimum Essential Medium (MEM) at 37°C with 5% CO2 at 100% humidity. Cell viability was assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay according to ISO 10993-5: 2009 (E). The differences among the groups was statically analyzed by independent paired t-test (α = 0.05).Results: After 1 day of storage, all adhesive systems showed cytotoxic effects. However, ageing tended to considerably reduce the cytotoxicity of Green Glue. Grengloo was essentially non-cytotoxic day 3 onwards, while Green Glue and Transbond XT exhibited potential cytotoxicity at all times of the experiment. Conclusion: All tested light-cured orthodontic adhesives had cytotoxic potential during the first day. Grengloo had the highest cell viability, whereas, Green Glue had the lowest.

Mechanical and Physical Properties of Various Types of Dental Floss

To compare maximum load, percentage of elongation, physical characteristics of 4 types of dental floss: (1) Thai Silk Floss (silk, waxed), (2) Oral B® Essential Floss (nylon, waxed), (3) Experimental Floss Xu (nylon, unwaxed), (4) Experimental Floss Xw (nylon, waxed). Four types of floss were tested (n=30) with a Universal Testing Machine (Instron®). Each sample (30 cm long, 5 cm segment) was fixed, and pulled apart with load cell of 100 N and a test speed of 100 mm/min. Physical characteristics were investigated by digital microscope under 2.5×10 magnification, and scanning electron microscope under 1×100 and 5×100 magnification. The size of the filaments was measured in micron (μm) and the fineness was measured in Denier. For mechanical properties, the maximum load and the percentage of elongation were presented as mean ± SD. The distribution of the data was calculated by the Kolmogorov-Smirnov test. One-way ANOVA and multiple comparison (Tukey HSD) were used to analyze the differences among the groups with the level of a statistical difference at p < 0.05. The maximum load of Floss Xu, Floss Xw, Oral B and Thai Silk were 47.39, 46.46, 25.38, and 23.70 N, respectively. The percentage of elongation of Oral B, Floss Xw, Floss Xu and Thai Silk were 72.43, 44.62, 31.25, and 16.44%, respectively. All 4 types of dental floss showed statistically differences in both the maximum load and percentage of elongation at p < 0.05, except for maximum load between Floss Xw and Floss Xu that showed no statistically significant difference. Physical characteristics of Thai silk revealed the most disintegrated, the smallest, and the least fine filaments. Floss Xu had the highest maximum load. Oral B had the highest percentage of elongation. Wax coating on Floss X increased the elongation but had no significant effect on the maximum load. The physical characteristics of Thai Silk resulted in the lowest mechanical properties values.

Dental arch changes in postretention in Class II division 1 extraction cases

OBJECTIVE The purpose of this study is to evaluate the postretention stability of the dental arches in Class II division 1 patients treated with four bicuspid extractions and the edgewise technique. MATERIALS AND METHODS A digital caliper was used to analyze the dental casts from 29 Class II division 1 malocclusion patients with skeletal type II (14 males, 15 females; ages ranging from 10.2-18.0 years), treated with four bicuspid extractions and the edgewise technique. Intercanine width, intermolar width, arch length, irregularity index, overjet and overbite were evaluated at three times: pretreatment (T1), posttreatment (T2) and postretention (T3) (mean: 4.15 years). Students t-tests were used to compare the pretreatment-posttreatment, posttreatment-postretention and pretreatment-postretention. Significance was determined at P<0.05. RESULTS The results of the study are listed as: (1) The upper and lower intercanine widths significantly increased (P<0.05) between T1-T2 and decreased between T2-T3. However, no significant changes were observed between T1-T3; (2) The upper and lower intermolar widths significantly decreased (P<0.05) between T1-T2, between T2-T3 and between T1-T3, except for the upper intermolar width between T2-T3 which showed no significant change; (3) The upper and lower arch lengths significantly decreased (P<0.05) at posttreatment and postretention due to the closure of extraction spaces. Both the upper and lower arch lengths significantly decreased between T1-T2, T2-T3, and T1-T3, except for the upper arch length between T2-T3, which showed no significant change; (4) The irregularity index was significantly improved after treatment. However, there was a slight increase in incisor irregularity at postretention. At postretention, 75.86% of the patients had mild crowding, 20.68% had moderate crowding, 3.48% had severe crowding; (5) The overjet and overbite significantly decreased (P<0.05) between T1-T2 and increased between T2-T3. CONCLUSION The changes in the dental arches were small at postretention with a tendency to return towards their original position. The overall stability of Class II division 1 extraction cases is relatively good.

Initial Tensile and Residual Forces of Pigmented Elastomeric Ligatures from Various Brands

This study aimed to investigate the initial tensile and residual forces of pigmented elastomeric ligatures (clear, pink, and metallic) from three commercial brands – Brand 1 (USA), Brand 2 (USA), and Brand 3(China). Twelve elastomeric ligatures of each brand and color were evaluated for initial tensile and residual forces after stretching for 28 days at 37°C by a Universal Testing Machine. The results showed that the highest initial tensile force was 14.78 N, 20.71 N, and 15.1 N for the metallic color of Brand-1, pink color of Brand -2, and metallic color of Brand -3, respectively. There were significant (p<0.05) differences in the initial tensile force of each brand, except clear and metallic color of Brand-1 & 3 and pink color of Brand-2 & 3. Similarly, among the pigmented ligatures from each brand, significant (p<0.05) differences were observed in the initial tensile force, except metallic color of Brand-1 & 3. Brand-3 had the highest residual force after 28 days, whereas the loss of force was 80-90% in Brand-1 & 2 and 20-30% in Brand-3. There were also significant (p<0.05) differences in the residual forces in each color and brand, except metallic color of Brand-1. In conclusion, there were significant differences in the initial tensile and residual forces among the three pigmented elastomeric ligatures of the three commercial brands.

L929 cell cytotoxicity associated with experimental and commercial dental flosses

This aim of the study was to investigate the cytotoxicity of two commercial and two experimental dental flosses. Two commercial, Oral B® Essential Floss (nylon-waxed) and Thai Silk Floss (silk-waxed), and two experimental, Floss X (nylon-waxed) and Floss Xu (nylon-unwaxed) dental flosses were used. The cytotoxic assay was performed by using cell cultures (L929) which were subjected to cell viability test with methyl-tetrazolium. Each floss specimen (0.4 g) was placed in 1 ml of Minimum Essential Medium at 37°C with 5% CO2 at 100% humidity in an incubator for 24 hours. After incubation, the cell mitochondrial activity was evaluated for detecting viable cells using optical density as per the guidelines of ISO 10993-5:2009(E). Cytotoxic effects were evaluated by measuring percentage of cell viability at 3 points of time- 5 mins, 30 mins, and 1 hr. The results showed that two commercial dental flosses and Floss X had cell viability about 90% at the three time points; however, the experimental Floss Xu presented 80% cell viability at 5 min and <70% cell viability at 30 min and 1 hr. The results concluded that the commercial dental flosses and the experimental dental floss with wax tested in this study were acceptable for clinical use.

Surface Characteristics, Chemical Composition and Ni Release of NiTi Wire in Different pH

Objective: To study the surface characteristics, chemical composition and Ni release from simulated standard fixed orthodontic appliance ligated with two differently priced nickel titanium (NiTi) archwires in artificial saliva at pH 5.14 and 6.69 for 4 weeks at 37oC. Materials and Methods: Two commercial NiTi rectangular wire (Ormco and Smart), 0.016 x 0.022 in size were studied. Their surface characteristics were evaluated: surface morphology by scanning electron microscope, surface roughness by surface roughness tester and grain structure analysis by optical microscope. Their chemical composition was analyzed by an energy dispersive X-ray spectrometer (EDC). For Ni release, twenty-eight simulated standard fixed orthodontic appliance samples sets, each set corresponding to one half-maxillary arch were used. Sample sets were divided in 2 groups (14 sets per group). The first group was ligated with Ormco NiTi archwires (USA) and the second with Smart NiTi archwires (China) with elastomeric ligatures. Half sets of each group were immersed in 50 ml artificial saliva at pH 5.14, and the other half at pH 6.69. Ni release was quantified with the use of flame atomic absorption spectrophotometry. Statistical analysis of variance was determined on days 1, 4, 7, 9, 14, 21 and 28 comparing Ni release between the groups and t-test was determined the difference between pH 5.14 and pH 6.69. Results: The suface morphology showed striations along the longitudinal axes. The Ormco NiTi wire had more surface roughness than Smart NiTi wire and the diameter of grain sizes were 2-8 μm. The chemical composition of the two NiTi wires was Ni, Ti, Cu, Al, and Cr but there was difference in the percentage of elements. Both Ormco NiTi and Smart NiTi wires continuously increased Ni release at time intervals at both pH levels. The Ormco NiTi wire had more Ni release at pH 6.69 than pH 5.14 but Smart NiTi wire had more Ni release at pH 5.14 than 6.69. At 4 weeks, the Ni release of one half-maxillary arch was 1.221 ppm (1221 μg/l) at pH 5.14, 1.267 ppm (1267 μg/l) at pH6.69 for Ormco NiTi wire and 2.175 ppm (2175 μg/l) at pH 5.14, 0.676 ppm (676 μg/l) at pH 6.69 for Smart NiTi wire. No significant difference was found in Ni release from Ormco and Smart NiTi wires at pH 5.14. At pH 6.69, no significant difference was found in Ni release from Ormco NiTi wires while Smart NiTi wire showed significant difference (p <0.05) on days 14, 21 and 28. Conclusion: Ni release depends on surface characteristics and chemical composition of archwires and pH.

Properties of Three Commercial Orthodontic Round Stainless Steel Wire

Objective: This study aimed to determine and compare the diameter, mechanical properties (tensile strength: flexural strength, flexural modulus of elasticity, 0.2% yield strength and springback: three point bending test: bending stiffness and 0.1mm. offset bending force) and chemical properties (composition and corrosion resistance) of three commercial orthodontic round stainless steel wires. Materials and Method: The samples of this study are three commercial brands of orthodontic round stainless steel wires, Highland (USA), Dentaurum (Germany) and W&H (China), 0.016 inch and 0.018 inch in size. The diameter was measured by micrometer and the mechanical properties were analyzed with tensile strength and three point bending test by Universal Testing Machine according to ISO 15841:2006. The composition was evaluated by Energy Dispersive X-ray Spectrometer (EDS) and the corrosion resistance was analyzed by a potentiodynamic polarization technique according to ISO 10271:2001. The data were analyzed with the Kolmoforov-Smith test, One-way ANOVA and Tukeys test. Results: There were significant differences (p<0.05) in diameter of the three commercial brands of orthodontic round stainless steel wires in both size except 0.016 in diameter between Dentaurum and Highland stainless steel wire. In terms of tensile strength, there were significant differences (p<0.05) in the flexural strength, flexural modulus of elasticity and springback in each variable, except W&H stainless steel wire with flexural strength in 0.016 and 0.018 wire size and springback in 0.018 wire size. However, in 0.2% yield strength, there was no significant difference in each brand and size except Dentaurum and Highland stainless steel in 0.018 wire size. For the three point bending test, there were significant differences (p<0.05) in bending stiffness and 0.1mm. offset bending force of each brand and size except 0.1mm. offset bending force between Dentaurum and Highland stainless steel in 0.016 wire size. In terms of chemical properties, there were the same elements but difference was found in percentage of each element, and W&H stainless steel had the least corrosion resistance. Conclusion: There were significant differences among three commercial orthodontic stainless steel wires in diameters, mechanical properties and chemical properties which will produce different force on each wire during tooth movement. All three brands, however, are acceptable for orthodontic use. The orthodontist should be aware of these differences in using stainless steel for orthodontic treatment.