Biomedical subjects

George Eliades

Publications and source records attributed to George Eliades.

At least 19 recordsLinked to original sources

PubMed2007

Assessment of bisphenol-A release from orthodontic adhesives.

INTRODUCTION: The aim of this study was to quantitatively characterize the bisphenol-A (BPA) released from orthodontic adhesives after artificial accelerated aging. METHODS: A chemically cured, no-mix adhesive and a visible light-cured adhesive were bonded to 40 stainless steel brackets divided in 2 groups of 20 brackets each. In total, 3 series of specimens were prepared for each adhesive-bracket group. All specimens were immersed in alcohol to induce accelerated aging. Samples of eluent removed from each group at 1 day and at 1, 3, and 5 weeks after aging were processed with high-pressure liquid chromatography; all assays were performed in triplicate, and the results were averaged. RESULTS: No trace of BPA was identified for either adhesive across all time intervals, implying that, if present, the amount of BPA did not exceed the detection limit of the analytical technique (0.1 ppm or 0.1 microg/L). CONCLUSIONS: BPA release from light-cured or chemically cured, no-mix adhesives did not reach the 0.1 ppm level. Estrogenicity assays are required to clarify the potential estrogenicity of adhesives, whereas formulation of benzoic ring-free, high molecular weight monomers might eliminate the concerns associated with the use of Bis-GMA.

Analysis of Variance↗

PubMed2006

Interfacial characteristics of adhesive luting resins and composites with dentine.

PURPOSE: To evaluate the interfacial characteristics of five adhesive resin luting agents with dentine including tensile bond strength, failure mode, extent of demineralisation, morphological changes and hybrid layer formation. MATERIALS AND METHODS: The products tested were Bistite II DC (BDC), C&B Super-Bond (CBM), M-Bond (MBD), Panavia-F (PAF) and Rely-X Unicem (RXU). For tensile bond strength measurements (TBS), metallic rods were bonded to standardised dentine surface areas (n=10), thermal-cycled (3000x 5-55 degrees C, 4 cycles/min) and debonded at 1mm/min crosshead speed. The failure mode was examined on dentine surfaces by LV-SEM (n=10), whereas the thickness of the hybrid layer by HV-SEM (n=4). FT-IR microscopy (n=4) and ESEM (n=4) were used to assess the extent of demineralisation and the morphological changes induced on dentine by the conditioning and priming treatments. RESULTS: TBS (MPa) values were BDC (13.01), MBD (9.19) and PAF (7.07) significantly different from CBM (4.79) and RXU (4.47). The percentage of debonded dentine area covered with resin showed the highest values in BDC (47.80) and MBD (38.12) significantly different from CBM (17.20), PAF (16.47), and RXU (16.50). The extent of demineralisation for CBM was 100%. No statistical differences were found among BDC (60.86%), MBD (60.22%) and PAF (51.99%). RUX (45.03%) showed the lowest value. CBM induced the most pronounced tubule funneling and intertubular dissolution, followed by PAF, BDC and MDB. RXU partially removed the smear layer without opening tubule orifices. The thickest hybrid layer was found in CBM (4.17microm) followed by MBD (2.39microm). No statistically significant differences were found between PAF (0.95microm) and BDC (1.12microm), whereas RXU showed no detectable hybrid layer. SIGNIFICANCE: Significant differences were found in the interfacial properties among the materials tested, that may lead to differences in their clinical performance.

Analysis of Variance↗

PubMed2006

3D-marginal adaptation versus setting shrinkage in light-cured microhybrid resin composites.

PURPOSE: To comparatively evaluate the 3D-marginal adaptation to dentine versus shrinkage strain of two light-cured microhybrid resin composites. METHODS: Dentine cavities (Ø: 2 mm; h: 1 mm; n=2x4) were prepared, filled with a single layer of EsthetX and Premise resin composites, respectively, without any adhesive cavity pre-treatment, and light-cured for 40s at 750 mW/cm2. All the specimens were imaged by computerized X-ray microtomography. Sequential sections (n=11) at 8.09 pixel size were taken at top, middle and bottom sites of each restoration relative to the axial wall and the interfacial micro-void volume fraction (%VF) was calculated. Shrinkage strain (%S) and strain rate (%SR) of the composites were measured by the bonded-disc method (n=4). The results of %VF per material and restoration site were subjected to statistical analysis by 2-way ANOVA and Tukey's test, whereas the results of %S and %SR were analysed by t-test (p=0.05). Regression analysis was performed to determine correlations between %PF and %S, %S(R). RESULTS: The results of %VF at top (t), middle (m) and bottom (b) restoration sites were (%, mean+/-S.D.): EsthetX 0.84+/-0.11 (t), 0.80+/-0.32 (m), 6.74+/-5.12 (b), Premise 0.99+/-0.24 (t), 0.92+/-0.38 (m), 1.72+/-0.97 (b). The results of %S were (%, mean+/-S.D.): EsthetX 2.60+/-0.29, Premise 1.91+/-0.10 and of %SR were (%, mean+/-S.D.): EsthetX 1.47+/-0.04, Premise 1.18+/-0.02. %VF(b) of EsthetX showed the highest values within and between the testing groups (p<0.05). %S and %S(R) values of EsthetX were significantly higher from Premise (p<0.05). Strong positive correlations were documented between %VF(b)-%S (r=0.843) and %VF(b)-%SR (r=0.943). CLINICAL SIGNIFICANCE: The results confirmed a positive correlation between setting shrinkage and interfacial gap volume at bottom sites of light-cured microhybrid composite restoration due to differential shrinkage. Shrinkage strain rate seems to be a more sensitive factor in determining percentage volume of interfacial porosity at bottom restoration sites.

Analysis of Variance↗

PubMed2006

Orthodontic latex elastics: a force relaxation study.

The objectives of this study were to assess the force relaxation of latex elastics occurring within 24 hours of extension and to estimate the extension required to reach the reported force. Five specimens of various manufacturers' latex elastics size and force levels were mounted on a custom-made setup capable of monitoring force levels in real time with a continuous mode and without operator intervention. The percentage of force relaxation was estimated from the initial and 24-hour levels, and the results were analyzed with one-way analysis of variance and the Tukey test at alpha = 0.05 level of significance. The elastics showed force relaxation in the order of 25%, which consisted of an initial high slope component and a latent part of decreased rate. Most relaxation occurred within the first 3-5 hours after extension, regardless of size, manufacturer, or force level of the elastic. The overall as well as the initial relaxation curves were fitted to equations, which described the variation of force with time. Elastic extension to achieve the reported force was found to range between 2.7 and five times the original length. Latex elastics show force relaxation in the order of 25%, which consists of an initial high slope component and a latent part of decreased rate. Most relaxation occurs within the first 3-5 hours after extension, regardless of size, manufacturer, or force level of the elastic. The empirical rule of "3" shows remarkable variation, ranging from 2.7 to five.

Elasticity↗

PubMed2005

Light-cured or chemically cured orthodontic adhesive resins? A selection based on the degree of cure, monomer leaching, and cytotoxicity.

PURPOSE: The purpose of this study was to estimate the degree of cure and monomer leaching of a light-cured and a chemically cured (no-mix) adhesive and to assess their biologic properties. MATERIAL: The degree of cure of adhesive specimens prepared with a procedure identical to the clinical bonding process was assessed by infrared spectroscopy. The adhesives were then immersed in normal saline solution for 2 months, and the residual monomer leached from the adhesives was quantitatively and qualitatively analyzed by liquid chromatography. The effect of the immersion media on human gingival fibroblasts' viability and proliferation was also evaluated with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and deoxyribonucleic acid (DNA) synthesis assays, respectively. The results were analyzed by analysis of variance and Tukey test (alpha = .05). RESULTS: No difference was found between the 2 adhesives with respect to their degree of cure and the amount of triethylene glycol dimethacrylate released; no diglycidyl dimethacrylate monomer was detected in the eluent. However, significant qualitative changes in the composition of the substances eluted from the 2 adhesives were observed. CONCLUSIONS: Whereas no cytotoxic effect was shown for either immersion media, a moderate reduction in the DNA synthesis was obtained by both adhesives, implying a minor cytostatic effect. Further research is required to assess the long-term biologic properties of adhesives, including potential estrogenic action.

Analysis of Variance↗

PubMed2005

The effect of different light-curing units on fatigue behavior and degree of conversion of a resin composite.

OBJECTIVES: The aim of this study was to investigate the effect of different light-curing units and irradiation modes on the mechanical fatigue strength and degree of conversion of a restorative resin composite. METHODS: Conventional halogen, plasma arc and blue LED light-curing units were used for polymerization of a resin composite (Tetric) Ceram, Ivoclar, Vivadent, Liechtenstein). Initial fracture strength (FS) and flexural fatigue limit (FFL) as well as degree of conversion (DC) were measured. The FFL was determined under cyclic loading for 10(5) cycles in terms of a staircase approach. The specimens were stored for 14 days in 37 degrees C distilled water prior to testing. The curing efficiency was observed with Fourier transform infrared micromultiple internal reflectance spectroscopy. The measurements were carried out at 0.5 and 2.5 mm distance from the directly irradiated surface after 14 days storage in dark and dry conditions at 37 degrees C. RESULTS: The highest FS, FFL and DC were observed from high energy curing devices and from extended curing intervals. The conventional halogen light exhibited the most homogenous in-depth curing efficiency along with a low loss of mechanical resistance under cyclic fatigue. SIGNIFICANCE: Evaluation of flexural fatigue limit and curing efficiency correlate in terms of decreased mechanical strength due to insufficient light-curing intervals or light intensities. Initial promising fracture strengths do not correlate with a clinically more relevant fatigue loading and with the in-depth degree of conversion, both accounting for a significantly reduced strength performance.

Analysis of Variance↗

PubMed2005

Comparative assessment of the roughness, hardness, and wear resistance of aesthetic bracket materials.

OBJECTIVE: The purpose of this study was to assess critical properties of orthodontic aesthetic bracket materials. METHOD: Samples of polycarbonate, poly(oxy)methylene, ultra high molecular weight polyethylene (UHMWPE), and polycrystalline alumina raw material used from bracket manufacturing were subjected to: (a) profilometry for the determination of Ra, Rq, Rmax and Rz roughness parameters; (b) Vickers hardness (HV50) testing; and (c) wear resistance determined by the scratch test. The results were analyzed with one-way ANOVA and Tukey multiple comparisons test at alpha=0.05 level of significance. RESULTS: The UHMWP and alumina specimens showed the highest roughness values for all parameters. The highest hardness, amongst the polymeric raw materials, was obtained from the poly(oxy)methylene appliances. Differences were also noted between the polycarbonate raw material of different manufacturers implying an effect from the manufacturing process. With the exception of alumina, the highest wear resistance was found for the poly(oxy)methylene specimens. SIGNIFICANCE: The results of this study reveal the variability among aesthetic plastic bracket raw materials, their reduced hardness and wear resistance relative to alumina as well as the inappropriateness of UHMWPE as alternative bracket material.

Aluminum Oxide↗

PubMed2005

Surface characterization of modern resin composites: a multitechnique approach.

PURPOSE: To characterize the surface properties of some modern resin composites employing a series of physicochemical methods. METHODS: Specimens from three microhybrid (Palfique Estellite-PE, Z250 Filtek-ZF, Tetric Ceram-TC) and one nanofilled (Supreme Filtek-SF) conventionally photo-cured resin composites polished with Soflex disks were studied for the following properties: Surface chemical composition and degree of C=C conversion (FTIR), surface energetics (contact angles), surface texture (AFM), surface roughness (AFM, stylus profilometry) and gloss (60 degrees-, 20 degrees-angle specular gloss). RESULTS: Polar and non polar molecular groups were identified in all products including NH and CONH (SF, ZF, TC). SF and ZF demonstrated higher conversion than PE and TC (P< 0.05). No significant differences (P> 0.05) were found in critical surface tension, total work of adhesion and its polar and dispersion components, the latter being the highest in all products. AFM showed the smoothest surface texture in PE. The ranking of Sa, Sq, Ra and Rz roughness parameters was PE ZF>TC, P< 0.05) were more sensitive than 60 degree-angle measurements (PE, SF>TC, P< 0.05) in revealing gloss differences. A positive correlation was found between Sa and Ra and a negative one between Sa and 20 degree-angle gloss.

Adhesiveness↗

PubMed2004

Effect of loading rate on bond strength.

The purpose of this study was to examine the effect of loading rate on the bond strength of brackets bonded to enamel. Forty premolars were used and brackets were bonded with a chemically cured or a light-cured adhesive, mounted on a testing machine, and debonded under shear stress at two loading velocities: a standard 1 mm/min, and a fast 200 mm/min which better approximates the actual jaw velocity during chewing. Bond strength results (N) were analyzed with two-way analysis of variance (loading rate, adhesive) (alpha = 0.05). An increased loading rate resulted in decreased bond strength, probably due to the induction of a stiff body response and elimination of the viscoelastic properties of the resin. The results indicated a similar effect on both chemically cured and light-cured adhesives, thus emphasizing the need for standardized test conditions in bond strength protocols. The implication of loads generated during chewing must be considered when estimating the long-term survival of the bond.

Adhesiveness↗

PubMed2004

Characterization and cytotoxicity of ions released from stainless steel and nickel-titanium orthodontic alloys.

The purpose of this study was to qualitatively and quantitatively characterize the substances released from orthodontic brackets and nickel-titanium wires and to comparatively assess the cytotoxicity of the ions released from these orthodontic alloys. Two full sets of stainless steel brackets of 20 brackets each (weight 2.1 g) and 2 groups of 0.018 x 0.025 Ni-Ti archwires of 10 wires each (weight 2.0 g) were immersed in 0.9% saline solution for a month. The immersion media were analyzed with inductively coupled plasma-atomic emission spectroscopy (ICP-AES), and the ionic content was statistically analyzed with 1-way analysis of variance (ANOVA). Human periodontal ligament fibroblasts and gingival fibroblasts were exposed to various concentrations of the 2 immersion media; nickel chloride was used as a positive control for comparison purposes. The cytotoxic or cytostatic activity of the media was investigated with the MTT and the DNA synthesis assays. The results of the cytotoxicity assay were analyzed with 2-way ANOVA and the Tukey test with solution and concentration variants as discriminating variables (alpha=0.05). The results indicated no ionic release for the nickel-titanium alloy aging solution, whereas measurable nickel and traces of chromium were found in the stainless steel bracket-aging medium. Concentrations of the nickel chloride solution greater then 2 mM were found to reduce by more than 50% the viability and DNA synthesis of fibroblasts; however, neither orthodontic materials-derived media had any effect on the survival and DNA synthesis of either cells.

Adult↗

PubMed2004

Structural conformation and leaching from in vitro aged and retrieved Invisalign appliances.

The objectives of this study were to investigate the structure of Invisalign appliances (Align Technology, Santa Clara, Calif) after intraoral exposure, and to qualitatively and quantitatively characterize the substances leached from the aligners after accelerated in vitro aging. Samples of Invisalign appliances were randomly selected from 10 patients before intraoral placement and after retrieval, and the prepared specimens were subjected to (1) bright-field optical reflection microscopy to study the surface morphology; (2) Fourier transform infrared microspectroscopy to characterize the in vivo changes in molecular composition induced on appliance surfaces, (3) scanning electron microscopy and energy dispersive X-ray microanalysis to identify the elemental composition of integuments formed on the surface, and (4) Vickers hardness (HV 200) testing. Another set of reference and retrieved appliances was subjected to artificial aging for 2 weeks, and the extracts were subjected to gas chromatography-mass spectroscopy. The retrieved appliances demonstrated substantial morphological variation relative to the as-received specimens involving abrasion at the cusp tips, adsorption of integuments, and localized calcification of the precipitated biofilm at stagnation sites. Buccal segments of retrieved appliances showed an increase in hardness, which might be attributed to mastication-induced cold work; however, the clinical implication of this effect on mechanotherapy is unknown. In vitro aged and retrieved appliances were found to leach no traceable amount of substances in an ethanol aging solution.

Adsorption↗

PubMed2004

Titanium orthodontic brackets: structure, composition, hardness and ionic release.

OBJECTIVES: The aim of the present study was to investigate the composition, morphology, bulk structure and ionic release of two brands of titanium orthodontic brackets: Orthos2 (Ormco, USA) and Rematitan (Dentaurum, Germany). METHODS: Five specimens of each group were examined with computerized X-ray microtomography, to reveal the morphology and structure of brackets, whilst resin-embedded and metallographically polished specimens were subjected to SEM/EDS analysis and Vickers microhardness measurements. Brackets were also maintained in 0.9% saline for 2 months and the ionic release in the immersion medium was determined with Inductively Coupled Plasma Atomic Emission Spectroscopy. The results of the hardness and ionic release measurements were statistically analyzed with two-way ANOVA and Tukey's test (alpha = 0.05). RESULTS: Orthos2 brackets consisted of two parts, the base (commercially pure Ti grade II) and the wing (Ti-6Al-4V alloy), joined together by laser welding, producing large gaps along the base-wing interface. The base was of lower hardness (Hv = 145), than the wing (Hv = 392) and incorporated a standard foil base-mesh pad. Rematitan brackets consisted of commercially pure Ti grade IV, with a single-piece manufacturing pattern of virtually identical hardness (p > 0.05) at the base and wings, featuring a laser-etched base-mesh pad. The hardness of the Rematitan brackets was significantly lower than the hardness of the Orthos2 wings, but double the hardness of the Orthos2 base. Released Ti levels were below the threshold level (1 ng/ml) of analysis for both materials, whilst traces of Al (3 ppm) and V (2 ppm) were found in the immersion media for Ti-6Al-4V alloy. SIGNIFICANCE: The structural and hardness differences found may influence the torque transfer characteristics from activated archwires to the brackets and the crevice corrosion potential at the base-wing interface (Orthos2). The detection of Al and V in the immersion medium (Orthos2) may imply a different biological response from the two types of Ti brackets.

Alloys↗

PubMed2004

Nickel content of as-received and retrieved NiTi and stainless steel archwires: assessing the nickel release hypothesis.

This study assesses the nickel content of as-received and retrieved stainless steel and NiTi archwires alloys. New and used brand-matched, composition-matched, and cross section-matched archwires were subjected to scanning electron microscopy and energy-dispersive electron probe microanalysis. Elemental analysis was performed on three randomly selected areas, and the nickel content, expressed as ratios of Ni/Ti (in NiTi wires) or Ni/Fe (in stainless steel), was statistically analyzed with a t-test (alpha = .05). No changes were detected with respect to Ni content ratios between as-received and retrieved NiTi or stainless steel wires, suggesting an absence of nickel release. Wear and delamination phenomena on the wire surface and the formation of galvanic couple between the stainless steel wires and bracket brazing materials intraorally may modify the corrosion susceptibility of the wire alloys in clinical conditions.

Corrosion↗

PubMed2004

Color stability of orthodontic adhesive resins.

Color alteration of adhesive during treatment and after debonding may be implicated in long-term enamel discoloration. The aim of this study was to assess the color stability of light-cured and chemically cured adhesives subjected to artificial photoaging. Disk-shaped specimens of adhesives were colorimetrically evaluated before and after artificial photoaging using an ISO-recommended protocol. The measurement variable was the color change (deltaE) of adhesives induced by artificial, accelerated photoaging. The deltaE values derived from the two color recordings for the materials at pre- and postaging intervals were statistically analyzed with a one-way analysis of variance (ANOVA), with the adhesive brand serving as a discriminating variable. Differences among groups were further investigated using the Tukey multiple comparisons test (alpha = .05). To establish the statistical significance of the difference of the deltaE values of each adhesive and the deltaE threshold for clinical detection, a paired t-test was used (P = .05). All adhesives exhibited color change, which in some cases exceeded the clinically detectable color change limit. The extent of the color alterations of aged bonding systems may contribute to enamel discoloration after treatment.

Analysis of Variance↗

PubMed2004

Enamel surface roughness following debonding using two resin grinding methods.

The purpose of this study was to assess quantitatively the roughness of the enamel surface following debonding using two resin removal methods. The enamel surface of 30 premolar crowns was covered with black tape with a 3 mm window on the middle buccal third to standardize the area of analysis. The initial enamel surfaces were subjected to profilometry, registering four roughness parameters (Ra, Rq, Rt and Rz). The brackets were bonded to the plaster-embedded enamel surfaces with a chemically cured, no-mix adhesive, and debonded after 1 week. Resin removal in half of the specimens was performed with an eight-bladed carbide bur, and in the other half with an ultra-fine diamond bur, both attached to a high speed hand piece; a second profilometric measurement was made after resin removal. Finishing of all surfaces was achieved with Soflex discs and a third registration of roughness followed. The duration of each resin removal protocol was also recorded. The results were analysed with two-way ANOVA and the Newman-Keuls test with the two resin grinding modes and the three intervals serving as discriminating variables (n = 15). For the duration results, a one-way ANOVA was used. Significant differences (P < 0.05) were observed with respect to enamel roughness parameters between the two resin grinding methods used, while there was no consistent roughness-reducing effect of finishing with Soflex discs. Resin removal with a diamond bur was achieved in approximately half the time compared with the eight-bladed bur. The increase in most roughness variables induced by the debonding procedures was not reversed at the end of the finishing stage, regardless of the resin removal protocol used, suggesting an irreversible effect on enamel texture.

Analysis of Variance↗

PubMed2004

Effect of sodium hypochlorite treatment on the molecular composition and morphology of human coronal dentin.

PURPOSE: The aim of the present study was to evaluate the deproteination potential of 5% aqueous NaOCl solution applied by rubbing action on the molecular composition and morphology of smear-layer covered and acid-etched human coronal dentin surfaces. MATERIALS AND METHODS: Paired specimens (n = 4 x 2 per group) of acid-etched (Group A) and smear-layer covered (Group B) human coronal dentin surfaces were sequentially treated with the NaOCl solution for time intervals ranging from 5 s to 120 s and analyzed by reflectance FTIR microspectroscopy and tapping mode atomic force microscopy. The changes in the mineral (v4 P-O stretching vibrations) to matrix (C = O stretching vibrations of amide I) peak area ratios and in the Ra roughness parameter were used to quantify the effect of treatment. Two-way ANOVA and Dunn's tests were used to assess the differences within each group and between groups (a = 0.05). RESULTS: In both groups, NaOCl treatment reduced organic matrix (amide I, II, III peaks), but did not affect carbonates and phosphates. In group A, the rate of deproteination was slow, and reached a peak value after 120 s. Tubule orifices became visible after 40 s of treatment; after 120 s, excessive porosity was detected, with Ra values presenting no statistically significant difference from group B. In group B after 10 s, the extent of deproteination was enhanced, reaching a plateau between 30 s and 60 s, and attaining a maximum after 120 s. Tubule diameter, intertubular porosity, and Ra were increased; intertubular dentin area was reduced. For both groups after 40 s of treatment, the mineral to matrix ratio recorded was similar to smear-layer-free sectioned dentin. CONCLUSION: The results of the present study imply that deproteination of mineralized or acid-etched dentin surfaces within a clinically relevant time frame may provide methods for bonding to dentin alternative to conventional technique-sensitive dentin hybridization.

Acid Etching, Dental↗

PubMed2004

Plastic brackets: hardness and associated clinical implications.

AIM: To assess the Vickers hardness of plastic brackets, after in vitro aging. The morphology and structure of corresponding retrieved brackets were also studied to assess the reliability of in vitro set-up in imposing effects comparable to intraoral aging. MATERIALS AND METHODS: Four types of plastic brackets were selected. Specimens were immersed in a buffer solution to induce artificial aging; brackets of two groups were retrieved after orthodontic treatment. The wings of brackets were subjected to Knoop hardness testing, and scanning electron microscopy was employed to study the morphology and microstructure of retrieved brackets. The results were statistically analyzed by two-way analysis of variance and Tukey test (alpha = 0.05). RESULTS: Differences were identified between the brands of brackets, but not between the new and in vitro-aged appliances. The retrieved appliances showed significant reduction in hardness when compared with their as-received counterparts. Evidence of degradation was seen in the retrieved appliances. CONCLUSIONS: The inability of ex vivo experimental configuration to simulate clinical conditions is stressed; several clinical implications related to torque control, friction, and tie-wing strength of brackets are discussed.

Buffers↗

PubMed2003

Characterization of as-received, retrieved, and recycled stainless steel brackets.

AIM: The purpose of the present study was to investigate the composition and to assess the microhardness and structure of as received, retrieved, and recycled stainless steel brackets. MATERIALS AND METHODS: New, used, and recycled brand-, slot size-, and prescription-matched appliances were subjected to scanning electron microscopy (SEM), energy dispersive (EDS) electron probe microanalysis, metallographic analysis, and Vickers microhardness testing. Elemental analysis was performed on randomly selected bulk material base and wing areas. Basic metal content and microhardness results were statistically analyzed using a two-way ANOVA and the Tukey test, with treatment (as received, retrieved, and recycled) and bracket region (base, wing) serving as discriminating variables (alpha = 0.05). RESULTS: The results showed that there was no alteration in the bulk composition of the brackets among the three conditions. In contrast, differences were noted between bracket base and wing with respect to elemental composition among all groups, implying that the base and wings were manufactured from different alloys. The metallographic etching identified no difference in grain structure between the bracket base and wing components for all groups, regardless of treatment. Vickers microhardness demonstrated significant differences in hardness between base and wing for all groups and between recycled and retrieved states for the wing component.

Electron Probe Microanalysis↗