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Biomedical subjects

T Eliades

Publications and source records attributed to T Eliades.

At least 19 recordsLinked to original sources
PubMed2006

Maxillary incisor torque with conventional and self-ligating brackets: a prospective clinical trial.

OBJECTIVES: To test the hypothesis that the engagement mode of wire to bracket affects the buccolingual inclination of maxillary incisors in extraction and non-extraction treatment with self-ligating and conventional brackets. DESIGN: A randomized clinical trial employing a random distribution of variables among the studied populations. SETTING AND SAMPLE POPULATION: Private practice of one author. A total of 105 patients followed prospectively, were divided into two groups based on the inclusion of extraction in the treatment planning. These groups were further divided in two subgroups each, one receiving a self-ligating bracket and the other treated with a conventional Edgewise appliance of the same slot size and prescription. EXPERIMENTAL VARIABLE: Difference in the buccolingual inclination of maxillary incisors before and after treatment with the two appliances across the two treatment groups (extraction and non-extraction). OUTCOME MEASURE: Angular measurements of the Sella-Nasion and Nasion-A point to maxillary incisor axis. RESULTS: No difference was found in the mean difference of the two angles measured for the two bracket groups studied. CONCLUSION: Self-ligating brackets seem to be equally efficient in delivering torque to maxillary incisors relative to conventional brackets in extraction and non-extraction cases.

Adolescent↗
PubMed2005

In vitro degradation of polyurethane orthodontic elastomeric modules.

The objectives of this study were to investigate the structural characteristics of orthodontic polyurethane elastomeric modules and their changes produced by mechanical and chemical ageing. Three products were tested (Generation II, Dentaurum, Alastic). For each product four groups of modules were studied under the following conditions: as-received (A(0)); after 3 weeks stretching at 50% elongation in air (B(0)); after 3 weeks immersion in an ethanol/water solution (3:1 v/v) to induce accelerated ageing (A(1)); and after 3 weeks immersion in the ethanol/water solution at 50% elongation, as above (B(1)). The chains and the solution extracts were characterized by micro-MIR FTIR spectroscopy. Specimens of group B(0) exhibited changes in peak intensities relative to the control group (A(0)), attributed to molecular orientation of poly (methylene glycol) soft segments and chain extenders such as butanediol. Moreover, group B(0) showed differences in the omega(CH(2))b peak at 1364 cm(-1), attributed to oxidative degradation of alpha-methylene groups by formation of ester, carboxylic acid or aldehyde groups due to hydrogen abstraction. Comparison of A(1) and B(1) groups with the controls (A(0), B(0)) showed no major differences between their respective spectra, apart from the loss of the 1639 cm(-1) peak attributed to ethylene NN bis (stearamide) wax. However, comparison of the spectra of the extracts from the elongated modules with the extracts of the controls revealed differences in the concentration of alcohol and alkene groups. The structural changes identified were the same in all the products tested and may indicate degradation mechanisms that could potentially hold intraorally.

Elastomers↗
PubMed2004

Tensile properties of orthodontic elastomeric chains.

The purpose of this investigation was to assess the permanent elongation, tensile strength and toughness of elastomeric chains. Two types (open and closed chains, i.e. with and without an intermodular link) of three brands of elastomeric module yielding six groups were included in the study. Specimens with equal numbers of loops were measured and classified into four groups based on their ageing state: (a) as-received; (b) subjected to a 24 hour steady strain in air determined as 50 per cent of original length; (c) exposed intraorally for 24 hours; and (d) retrieved following 3 weeks of intraoral exposure. All specimens were subjected to tensile stress and their behaviour was analysed with three-way ANOVA and Tukey's multiple comparison test at alpha = 0.05 level of significance, with brand, type (open or closed chains), and treatment variables serving as discriminating variables. Modular geometry or design were found not to have significant effects on elongation, probably due to the substantial variation in chain shape, modular size, and link length among products of the same category. Similarly, no correlation was identified between specimen treatment and the tensile strength of elastomers. The toughness results were not consistent with the group rankings for tensile strength, probably because of variation in the elastic and plastic deformation of specimens upon loading.

Analysis of Variance↗
PubMed2003

Multi-technique characterization of retrieved bone cement from revised total hip arthroplasties.

The purpose of this study was to assess the chemical composition, structure and degree of double bond conversion of retrieved bone cement from 29 total hip replacement revision arthroplasties, employing a multi-technique approach. Scanning electron microscopy revealed a porous cement surface, which replicated the characteristics of bone or femoral stem surface irregularities. Fourier transform infrared spectroscopy indicated that the retrieved bone cement samples were covered by a well-organized proteinaceous film rich in amides and alcohols, probably because of the adsorption of species from body tissues and fluids. X-ray fluorescence spectrometry showed the presence of potassium, sodium, calcium and phosphorus, implying the development of a mineralization process of the adsorbed biofilm. X-ray microtomography demonstrated a dense porous network in the bulk material comprised of macropores with a mean diameter >1 mm. FTIR analysis of the degree of double bond conversion of retrieved samples was in the order of 70%, similar to that of samples prepared in vitro in air, but 30% lower relative to their counterparts mixed in vitro and set in water. The effect of the adsorption of species onto bone cement surface on the reactivity of the material with the surrounding tissues and materials, is currently unknown. The results of this investigation reveal that the in vivo aging pattern of bone cements may involve alterations, which cannot be simulated under current in vitro protocols, emphasizing the necessity for adopting in vivo approaches including retrieval studies in assessing bone cement properties.

Journal Article↗
PubMed2002

Moisture-insensitive adhesives: reactivity with water and bond strength to wet and saliva-contaminated enamel.

The purpose of this study was to investigate the reactivity with water of a moisture-insensitive orthodontic primer (Transbond MIP), in conjunction with a no-mix orthodontic adhesive (Unite), and a moisture-insensitive adhesive (Smartbond), and to assess their bond strength to wet and saliva-contaminated enamel relative to the conventional application of the no-mix adhesive. The reactivity of the moisture-insensitive products with water was investigated by micro-multiple internal reflectance Fourier transform infrared spectroscopy (micro-MIR FTIR). Sixty premolars were divided into two groups of 30 teeth each and, on the buccal enamel surfaces, a standardized volume (0.1 ml) of water or fresh whole saliva was applied. Standard edgewise stainless steel brackets were then bonded to enamel surfaces as follows: (a) Unite, (b) Unite with the Transbond MIP, and (c) Smartbond. The brackets were debonded under shear force at a speed of 2 mm/min and the debonded enamel surfaces were subjected to fractographic analysis. The statistical analysis of the bond strength values was performed by two-way ANOVA with condition (water, saliva) and adhesive type serving as discriminating variables (n = 10, alpha = 0.05). The results of the fractographic analysis were evaluated by chi 2 test (alpha = 0.05). FTIR analysis showed that only Smartbond set in the presence of water. Application of water in Transbond MIP increased the extent of carboxyl ionization without inducing any setting reaction. Transbond MIP did not improve bond strength values when combined with the no-mix adhesive. Most adhesive-enamel condition combinations showed a trend to present lower bond strength in the presence of saliva; however, this was not confirmed statistically. Fractography of enamel and bracket base surfaces showed that Unite + Transbond MIP resulted in the most adhesive fractures (leaving no resin on enamel surface), whereas Smartbond presented the highest frequency of cohesive fractures (adhesive left on bracket and enamel surfaces).

Adhesives↗
PubMed2001

Impact factor. A review with specific relevance to orthodontic journals.

The aim of this article is to address the issues of impact factor and circulation with reference to dental and orthodontic journals by discussing various parameters including language, citations, nature of published articles, and scientific domain. Examples from the literature are provided to illustrate the variability of impact factors among periodicals, based on the publicity and scientific area covered, and the impact factor scores are presented together with the circulation of orthodontic periodicals.

Bibliometrics↗
PubMed2001

Intraoral aging of the inner headgear component: a potential biocompatibility concern?

The effect of intraoral aging of biomaterials on the modification of their surface properties has mostly been unknown. The purpose of this study was to investigate and characterize surface alterations of retrieved inner face-bow headgear components. Specimens were prepared from 3 areas of retrieved headgear wires: inner-outer face-bow soldered junction, buccal segment, and projection entering the buccal tube. Specimens from as-received headgear wires that matched the brand and size of the retrieved wires were also fabricated; all specimens were then subjected to multitechnique characterization. Optical microscopy revealed extensive biofilm islands of amorphous precipitants and accumulated microcrystalline particles. Micro-multiple internal reflectance Fourier transform infrared spectroscopy investigation of the retrieved wire samples demonstrated the presence of a proteinaceous biofilm, the organic constituents of which were mainly amide, alcohol, and carbonate. Scanning electron microscopy and radiographic microanalysis showed that the elemental species precipitated on the material surface were mainly calcium and phosphorus, forming calcium-phosphorus precipitates with thicknesses reaching 300 microm, whereas radiograph fluorescence spectrometry provided evidence of integument calcification through identification of calcium and phosphorus peaks. The clinical implication of the aging pattern that was identified relates to the potential protective role or induction of disintegration by the biofilm adsorbed on the wire that affected the biocompatibility of the alloy. Whereas further investigation is suggested for the clarification of the effect of intraoral aging on ionic release, the results of this study emphasize the necessity for the incorporation of in vivo approaches, including retrieval analyses, in the study of the biologic performance of orthodontic materials.

Adolescent↗
PubMed2001

Comparison of enamel colour changes associated with orthodontic bonding using two different adhesives.

The purpose of this study was to evaluate the enamel colour changes associated with bonding of brackets with a no-mix (one-phase) adhesive resin (Unite) and a glass-ionomer adhesive (GC Fuji Ortho). Thirty recently extracted premolars were used in the investigation. Black rectangular pieces of adhesive tape with a 3-mm diameter window were used to standardize the enamel surface intended for analysis. The teeth were divided into two groups of 15 teeth each, brackets (Starfire TMB) were bonded with the two adhesives, and the enamel surfaces were colourimetrically evaluated at three time intervals: (a) before bonding (baseline), (b) following debonding and cleaning, and (c) after artificial photo-ageing for 24 hours. The CIE colour parameters (L*, a*, b*) were recorded and averaged for each material, interval group, and the corresponding colour differences (delta E) were calculated. The results were statistically analysed using two-way ANOVA repeated measures, and Scheffé multiple range test at alpha = 0.05 level of significance. All differences noted exceeded the threshold for clinical detection (delta E = 3.7). The highest differences were recorded for the baseline-debonding interval for both adhesives used. No difference was found with respect to delta E between etching-mediated and no etching-mediated bonding implying that the debonding cleaning process involving adhesive grinding may be more invasive relative to acid etching with regard to enamel colour alterations.

Acid Etching, Dental↗
PubMed2001

Enamel colour changes following whitening with 10 per cent carbamide peroxide: a comparison of orthodontically-bonded/debonded and untreated teeth.

The purpose of this study was to determine if a colour difference exists between teeth that had orthodontic appliances bonded to and debonded from them and untreated controls subjected to whitening with 10 per cent carbamide peroxide. The sample consisted of 20 pairs of first and second premolars extracted for orthodontic reasons. The contralateral surfaces were divided into an experimental and control group. The experimental group underwent orthodontic bonding/debonding procedures. Both groups were subjected to 4 hour whitening and 20 hour hydration sessions for 30 days. The L*a*b* colour system was chosen to evaluate any colour change and these changes were calculated by determining the delta E from the L*a*b* values using a colorimeter. Colour change readings were taken before and after each 4 hour whitening. Additional readings were taken at 48 hour intervals for 30 days following the cessation of active whitening. The results were analysed using statistical (ANOVA) and graphical analyses (alpha = 0.05). A colour change difference of 2 CIELAB units was set as being clinically significant. A mean clinical colour difference was found for enamel surfaces subjected to orthodontic bonding/debonding of attachments relative to control sites after whitening. Bonding and debonding procedures resulted in a significant colour difference between orthodontic bonded and control sites at the end of the active period, which became insignificant at the end of the 30 day period of monitoring. Both the control and debonded sites responded to whitening; however, the control sites responded initially to a greater extent; the orthodontic debonded sites did not respond until after 2 weeks of continuous whitening. After the 2 week period the improved response of the debonded sites decreased the colour difference between the two groups.

Algorithms↗
PubMed2000

The inappropriateness of conventional orthodontic bond strength assessment protocols.

The purpose of this article is to examine the soundness of conventional orthodontic bonding assessment methods. A classification of bond strength studies is proposed with the testing environment (in vivo, in vitro, and ex vivo), loading mode (shear, tensile, and torsion), and bonding substrate (enamel, restorative, and prosthetic materials) serving as discriminating variables. Inconsistencies throughout the various stages of research protocols are analysed. These include the following: tooth selection, storage, and preparation; bonding; testing; and data analysis with regard to the clinical applicability of the reported information, as well as the scientific integrity of the testing procedure. Contradictory models may partially account for the considerable variability noted for reported bond strength values of different orthodontic bonding systems. Such discrepancies may also explain the conflicting evidence reported on the failure characteristics of the components of the bonding system in different trials examining the efficacy of nominally identical materials. A novel approach to study the fatigue life of materials is proposed to understand the processes occurring prior to bond failure. Mock research data manipulation is also utilized to illustrate the correct statistical treatment of findings, and recommendations for future research are made to ensure scientific soundness and clinical applicability of data.

Analysis of Variance↗
PubMed2000

Surface characterization of retrieved NiTi orthodontic archwires.

The structure and morphological condition of retrieved NiTi orthodontic archwires was evaluated and any possible alterations in the surface composition of the alloy following 1-6 months in vivo were characterized. NiTi wires (GAC, German Orthodontics, ORMCO) of various cross-sections were collected through a retrieval protocol and were subjected to multi-technique characterization. Optical microscopy revealed islands of amorphous precipitants and accumulated microcrystalline particles. Micro MIR-FTIR investigation of the retrieved samples demonstrated the presence of a proteinaceous biofilm, the organic constituents of which were mainly amide, alcohol, and carbonate. Scanning electron microscope and X-ray microanalysis showed that the elemental species precipitated on the material surface were Na, K, Cl, Ca, and P, forming NaCl, KCl, and Ca-P precipitates. Increased intra-oral exposure was consistently associated with the presence of a mature film, while evidence of alloy delamination, pitting, and crevice corrosion, as well as a notable reduction in the alloy grain size was observed. Intra-oral exposure of NiTi wires alters the topography and structure of the alloy surface through surface attack in the form of pitting or crevice corrosion or formation of integuments. Further in vivo research is required to resolve the implications of the described ageing pattern in the corrosion resistance of the alloy, the potential for nickel leaching, as well as bracket-archwire friction variants.

Alcohols↗
PubMed2000

Degree of cure of orthodontic adhesives with various polymerization initiation modes.

The purpose of this study was to estimate the degree of cure (DC) of a light-cured, and a two- and a one-phase (no-mix) chemically-cured, as well as a dual-cured commercially available orthodontic adhesive resin. Forty stainless steel brackets were divided into four groups of 10 brackets each, and the bracket bases were covered with a standardized volume of adhesive. They were then pressed firmly onto a yellowish background surface of 75 per cent reflectance covered with cellulose film to facilitate detachment of the system and recovery of the set material. The visible light- and dual-cured adhesives were photopolymerized by irradiation from the incisal and cervical edges of the bracket for 10 seconds each, while another group of ceramic brackets was used to assess the differential interference of transparent relative to opaque material in the DC. Micro-multiple internal reflectance Fourier transform infrared spectroscopy was employed for the estimation of the DC of the adhesives (alpha = 0.05, n = 10), utilizing a method proposed previously. The dual-cured product demonstrated the highest DC followed by the light-cured combined with the ceramic bracket, and the no-mix and the chemically-cured adhesives. The combination of the metallic bracket with the light-cured product resulted in a DC comparable with that of the chemically-cured material.

Analysis of Variance↗
PubMed1999

Multitechnique characterization of articular surfaces of retrieved ultrahigh molecular weight polyethylene acetabular sockets.

The articular surfaces of 10 retrieved ultrahigh molecular weight polyethylene acetabular sockets were studied by optical microscopy, X-ray fluorescence spectrometry, multiple internal reflectance FTIR spectroscopy, scanning electron microscopy, and wavelength dispersive X-ray microanalysis. The results revealed characteristic wear patterns including polishing, scratching, pitting, cratering, folding, shredding, burnishing, cracking, embedding of particles, and development of acquired biofilms with various degrees of mineralization. The biofilms formed were mainly of proteinaceous origin, and mineralized regions were composed of calcium phosphates with carbonate impurities. The crystallinity of the polyethylene at the articular surfaces was enhanced compared to the bulk, which was possibly due to the cold work produced in vivo. The mineralized regions were classified into two groups based on the grey levels of the backscattered images obtained. The high-contrast regions that were mainly composed of Ca and P with traces of Al and Si were associated with bone fragments; the low-contrast regions composed of K, Na, Ca, Mg, Si, Al, Fe, Cl, and P were associated with acquired biofilm calcification, which implies the active engagement of biofilms in the long term performance of acetabular sockets in vivo.

Aged↗
PubMed1999

Structural conformation of in vitro and in vivo aged orthodontic elastomeric modules.

The objectives of this study were to investigate the structural characteristics of open and closed elastomeric modules in the as-received condition, and following (a) 24-hour in vitro loading determined as a 50 per cent extension relative to their original length; (b) 24-hour intra-oral exposure; (c) 3-week intra-oral exposure. Ten specimens of each type (open and closed) of the three brands of elastic chains were included in the study (total of 60). All specimens were subjected to (a) optical transmission microscopy utilizing phase contrast and polarized light modes, (b) micro MIR FT-IR spectroscopy, and (c) scanning electron microscopy and electron probe X-ray microanalysis. Stretched elastomers demonstrated a honeycomb pattern of filament detachment corresponding to strained areas. The chains possessing a well-differentiated inter-modular link presented higher strain concentration gradients located in the link. Phase contrast imaging revealed that the stress adsorption mechanism of these materials involved macromolecular chain orientation and elongation co-axially to the applied load. The specimens retrieved after 24 hours had acquired a proteinaceous film rich in alcohol groups with minimal evidence of phosphate mineralization, while the 3-week retrieved specimens presented precipitation of Ca- and P-forming calcium phosphates. The high protein content of the biofilm organized on the surface of these materials, as well as the calcification pattern found, were similar to a non-specific mechanism of film adsorption of biomaterials exposed to body fluids. The results have clinical implications for aspects of retraction control through sliding mechanics with the use of elastomeric ligatures, and the potential detrimental effects on dental and periodontal tissues such as decalcification and gingival inflammation, respectively. In addition, the experimental protocols adopted for the in vitro study of the force decay of elastomerics should be modified to include parameters pertinent to adsorption phenomena and calcification processes documented to occur in vivo.

Biofilms↗
PubMed1996

Orthodontic-surgical correction of a Class II, Division 2 malocclusion.

The incorporation of the total subapical osteotomy as an alternative surgical technique to augment standard bilateral sagittal split osteotomy in facilitating establishment of the profile objectives in the surgical-orthodontic treatment of a patient with skeletal sagittal discrepancy, is presented in this case report. Esthetic considerations, as well as risks involved in this type of a combined surgical approach, are also discussed.

Adult↗
PubMed1995

Polymerization efficiency of chemically cured and visible light-cured orthodontic adhesives: degree of cure.

The use of light-cured orthodontic adhesives in combination with the new generation of ceramic brackets has become popular from an esthetic standpoint. The purpose of this article was to evaluate the degree of cure (DC) of selected light-cured and chemically cured adhesives bonded to ceramic and stainless steel brackets. The optical properties of eight types of brackets (single-crystal alumina, polycrystalline alumina, polycrystalline allumina with polycarbonate base, and stainless steel) were evaluated by diffuse visible light transmittance spectroscopic analysis. The degree of cure (DC) of a visible light-cured orthodontic adhesive bonded to these brackets under direct (20 seconds through the bracket) and indirect (2 x 10 seconds from the incisal and cervical edges of the bracket) irradiation was measured by micro-MIR FTIR spectroscopy. Brackets bonded to a chemically cured, two-paste orthodontic adhesive were used as a control group. According to the results the single-crystal alumina brackets showed the highest diffuse transmittance values at 468 nm followed by polycrystalline alumina and polycarbonate-base alumina types. Direct irradiation resulted in low DC values that were strongly correlated to the diffuse transmittance measurements at 468 nm (r = 0.73, p < 0.05). Indirect irradiation manifested significantly higher DC values than direct irradiation in the stainless steel bracket group, which yielded values comparable to those found in some indirectly irradiated polycrystalline bracket groups.

Acrylic Resins↗