Biomedical subjects

Theodore Eliades

Publications and source records attributed to Theodore 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

Orthodontic journals with impact factors in perspective: trends in the types of articles and authorship characteristics.

INTRODUCTION: The purposes of this study were to analyze the types of articles and their authorship characteristics in the 3 orthodontic journals with impact factors--American Journal of Orthodontics and Dentofacial Orthopedics (AJODO), Angle Orthodontist (AO), and European Journal of Orthodontics (EJO)--during 2 intervals of 5 years each (1993-1997 and 1998-2002) and to assess the changes in their contents during these periods. METHODS: The results of 3004 article entries were analyzed with the Pearson chi-square test, and the examination of the variability of the parameters studied among journals and across the 2 time intervals was performed at the 0.05 level of significance. RESULTS AND CONCLUSIONS: Significant differences were found between the journals with respect to the research component of articles (higher in the EJO) and case reports (higher in the AJODO and the AO). For each journal, differences were also identified between the 2 time intervals, with multi-authored papers and multiple affiliations appearing more frequently in the second interval. The contributions of articles from the United States and Canada to the AJODO and the AO were statistically higher than to the EJO. A similar trend was found for articles from Europe, which comprise more than 70% of the content of the EJO. An increased contribution of articles from East Asia and Oceania was noted in the second time interval, which reached almost 100% of the previous time frame. The potential sources of variation in the studied parameters are discussed.

Authorship↗

PubMed2006

Orthodontic materials research and applications: part 1. Current status and projected future developments in bonding and adhesives.

The purpose of this opinion article, to be presented in 2 parts, is to project immediate future developments expected in orthodontic materials research and applications. Analysis of the material is structured around 2axes: presentation of evidence summarizing the current status in various fields, and formulation of a hypothesis for short-term future developments. This first part of the article deals with advances and developments in bonding to enamel. Projected adhesive developments include greater use of high-energy lamps for polymerization in light-cured systems, universal application of molar tube bonding, widespread use of self-etching primers, broader acceptance of glass ionomers in their conventional and modified modes, and elimination of 2-phase adhesives in favor of no-mix and light-cured adhesives. Long-term future adhesive applications might also include biomimetic approaches, adopting mechanisms used by living organisms to adhere to surfaces.

Biomimetic Materials↗

PubMed2006

Failure rate of self-ligating and edgewise brackets bonded with conventional acid etching and a self-etching primer: a prospective in vivo study.

The purpose of this study was to comparatively assess the failure rate of self-ligating and edgewise brackets bonded with a self-etching adhesive and conventional phosphoric acid in patients followed for 12 months of active treatment. Sixty-two patients with complete permanent dentitions, similar treatment plans, and mechanotherapy were selected for the study. GAC Microarch edgewise brackets and ORMCO Damon2 brackets were bonded using a split mouth design, using the 3M Transbond Plus Self-etching primer (SEP) and Transbond XT paste; and conventional acid etching, with Orthosolo primer and Enlight paste, applied at an alternate sequence so that the adhesives were equally distributed on the maxillary and mandibular right and left quadrants. Data analysis was conducted with the use of logistic regression modeling. No difference in failure incidence was noted for either bracket-adhesive and mandibular or maxillary arch combinations, whereas a statistically significant difference was shown for right-sided appliances. On the basis of the results of this study, bonding of self-ligating brackets with SEP does not demonstrate higher probability for failure relative to standard bonding procedures and conventional brackets.

Acid Etching, Dental↗

PubMed2006

Porcelain surface roughness, color and gloss changes after orthodontic bonding.

The purpose of this study was to evaluate the alteration in surface characteristics after orthodontic debonding of two types of porcelain systems commonly used in prosthetic dentistry. For this purpose, porcelain specimens were fabricated from low-fusing (n = 20) and high-fusing (n = 20) porcelain. The baseline surface roughness, color, and gloss were evaluated using profilometry, color shade index, and gloss study. All specimens were bonded with brackets and debonded using a testing machine at a rate of 0.1 mm/minute crosshead speed. The porcelain surfaces were polished using a 12-fluted carbide composite removal bur (low-fusing, n = 20; high-fusing, n = 20). In addition, half of each porcelain group was further polished using a series of Sof-Lex discs (low-fusing, n = 10; high-fusing, n = 10). The postdebond porcelain surface characteristics roughness, color, and gloss were reevaluated and compared with baseline measurements. The results were analyzed with two-way analysis of variance and Tukey multiple comparisons test, with porcelain type (low-fusing or high-fusing) and polishing protocol (carbide bur or carbide bur and discs) serving as discriminate variables at alpha = 0.05 level of significance. Bonding and debonding increased all roughness parameters tested; however, no change was revealed between the two polishing protocols. Similarly, gloss and color index changes were significantly altered after resin grinding, regardless of the polishing method used. No difference was identified between the two porcelain types with respect to roughness, color index, or gloss. Orthodontic bonding alters the porcelain surfaces, and postdebond polishing does not restore the surface to the prebond state.

Analysis of Variance↗

PubMed2006

Force to debond brackets from high-fusing and low-fusing porcelain systems.

The purpose of this study was to test the hypothesis that porcelain surface finishing, ie, low- and high-fusing porcelain, has an effect on the amount of force required to debond orthodontic brackets. A total of 20 high-fusing and 20 low-fusing porcelain specimens were prepared, polished, and bonded with standard edgewise brackets using a suggested porcelain bonding protocol. The brackets were debonded with a universal testing machine at shear mode. Resin removal was performed using two methods: a multifluted carbide bur with and without the use of Sof-Lex polishing discs. Representative specimens were studied under a scanning electron microscope before and after debonding to assess the surface morphology and potential surface damage. Statistical analysis with a t-test revealed that there was no difference between the two porcelain treatments on the force to debond values and no qualitative differences were observed on the porcelain surface between the two resin clean-up methods. From a clinical perspective, the practitioner can bond ceramic restorations without previous knowledge of the porcelain type used.

Dental Bonding↗

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↗

PubMed2006

A comparative assessment of the failure rate of molar tubes bonded with a self-etching primer and conventional acid-etching.

OBJECTIVES: Comparative assessment of the failure rate of molar tubes bonded to first and second molars with a self-etching primer and conventional acid-etching. MATERIAL AND METHODS: Four hundred forty-four molar tubes (246 first molar tubes and 198 second molar tubes) were bonded, using a split-mouth design, on 62 patients (23 male, 39 female; mean age 13.7 years) with the 3M Transbond Plus self-etching primer combined with Transbond XT paste; or with conventional acid-etching, Orthosolo primer, and Enlight adhesive paste. First-time failures were recorded over a period of 15 months. RESULTS: Bond failure per adhesive system, arch (maxilla-mandible), quadrant (left, right) and tooth (first or second molar) were studied. Statistical analysis using logistic regression modeling (alpha = .05) showed that the overall failure rate for the first and second molar tubes was 11% (8% with self-etching primer and 13% with conventional acid-etching). No significant difference was found between the 2 bonding methods. Tooth location and type showed statistically significant associations. Mandibular tubes showed a 3:1 probability for failure compared to maxillary tubes. Right-sided tubes demonstrated 3 times more failures when compared to left-sided tubes, and second molar tubes showed a 3-fold increase in failure. CONCLUSION: Molar tube bonding with self-etching primer shows similar success rates to conventional acid-etching, whereas the mandibular right second molar presents the highest failure incidence.

Acid Etching, Dental↗

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

Intraoral aging of orthodontic materials: the picture we miss and its clinical relevance.

The purpose of this editorial is to systematically analyze the variety and potency of various aging variables affecting the morphology, structure, and mechanical properties of polymeric and metallic orthodontic materials. The effects of aging on the longevity of the bond strength and mechanotherapy were analyzed: aging-induced plasticization of resin adhesives might lead to bond failure at forces of magnitude lower than those sustained at the initiation of treatment. Standard in vitro methodologies cannot show this effect, and thus laboratory bond strength protocols require modification to become clinically meaningful. Also, the force transferred from an activated archwire to a preadjusted bracket slot, as well as friction during free sliding, seems to be affected by the intraorally induced alteration of materials. Although the effect of intraoral environmental conditions on the superelastic properties of nickel-titanium (Ni-Ti) archwires and coil springs requires further research to establish the true spectrum of effects, it has been suggested that intraoral temperature variations might transiently affect their properties and that the fracture resistance of used Ni-Ti wires is reduced. Clinical implications are discussed for (1) in vivo-aged elastomeric ligatures and chains, which can be postulated to express much higher creep than their in vitro-aged counterparts; (2) the largely unknown effect of aging on the spring component of self-ligated brackets and the associated effect on ligation force; and (3) the intraorally induced alterations in the structural conformation of Invisalign appliances (Align Technology, Santa Clara, Calif). The objective of future research efforts in the field of orthodontic materials should include the development of clinically relevant methodologies. A clear definition of limitations of laboratory experimental configurations might be instrumental in confining the clinical impact of research findings to their actual extent.

Biofilms↗

PubMed2005

A comparative in vivo assessment of the long-term failure rate of 2 self-etching primers.

INTRODUCTION: The purpose of this study was to comparatively assess the failure rate of brackets bonded with 2 self-etching adhesives after 14 months of treatment. METHODS: Twenty-two patients with complete permanent dentitions, and similar treatment plans and mechanotherapies, were selected for the study. Four hundred twenty-three brackets were bonded by using a split-mouth design, with Transbond Plus Self-Etching Primer (3M Unitek, Monrovia, Calif) or One-Step Self-Etching Primer (Reliance, Itasca, Ill). These self-etching primers were applied alternately so that they were equally distributed on the maxillary and mandibular right and left quadrants. RESULTS: Failure rates were recorded for 14 months and analyzed with the chi-square test at alpha = 0.05 level of significance. Overall total failure rates were 0.94%, for Transbond Plus and 8.10% for One-Step. Although significantly more failures were found for the mandibular arch, no difference was identified in failure rate between anterior and posterior teeth. The results of this study suggest that care should be taken in ensuring the compatibility of retainers with adhesives.

Acid Etching, Dental↗

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

Advanced orthodontic education: evolution of assessment criteria and methods to meet future challenges.

The achievement of academic and research institutes has increasingly become the subject of ranking by independent organizations. This trend has educational and economic implications, which may pertain to attracting students and endowments as well as allocating of funds to specific educational components. The aims of this article were to discuss the reliability and soundness of the existing academic ranking methods and to propose guidelines for the quantitative assessment of advanced orthodontic programs. This criteria-driven assessment assigns weight factors for the basic components of orthodontic education and provides a template for clarifying the standing of programs. Moreover, a combination of program and individual assessment is proposed to monitor the implementation of educational criteria and assess their effectiveness.

Accreditation↗

PubMed2005

Long-term clinical failure rate of molar tubes bonded with a self-etching primer.

The purpose of this study was to assess the long-term in vivo failure rate of tubes bonded to first and second molars with a self-etching primer (SEF). A total of 810 molar tubes (414 first molar and 396 second molar) were bonded on 135 patients (56 male, 79 female; mean age 14 years) with the 3M Transbond Plus Self Etching Primer. The first-time failures of the tubes were recorded for a mean period of 26 months (range 23-29 months). Failure rates per jaw (maxilla-mandible), tooth (first and second molar), and quadrant (left, right) were analyzed with the chi(2) at alpha = 0.05 level of significance. Significant differences were found in the failure rate between first and second molars (9.66% vs 20%, respectively) as well as maxillary and mandibular molars (7.5% vs 21%, respectively). The combined, total failure rate for first and second molars was 14.80%. No difference was found between male and female failure rates for the molar tubes. First-molar tubes bonded with an SEF may show failure rates comparable with those reported in the literature for tubes bonded with conventional acid etching.

Adolescent↗

PubMed2005

Metallurgical characterization of orthodontic brackets produced by Metal Injection Molding (MIM).

The aim of this study was to investigate the bonding base surface morphology, alloy type, microstructure, and hardness of four types of orthodontic brackets produced by Metal Injection Molding technology (Discovery, Extremo, Freedom, and Topic). The bonding base morphology of the brackets was evaluated by scanning electron microscopy (SEM). Brackets from each manufacturer were embedded in epoxy resin, and after metallographic grinding, polishing and coating were analyzed by x-ray energy-dispersive spectroscopic (EDS) microanalysis to assess their elemental composition. Then, the brackets were subjected to metallographic etching to reveal their metallurgical structure. The same specimen surfaces were repolished and used for Vickers microhardness measurements. The results were statistically analyzed with one-way analysis of variance and Student-Newman-Keuls multiple comparison test at the 0.05 level of significance. The findings of SEM observations showed a great variability in the base morphology design among the brackets tested. The x-ray EDS analysis demonstrated that each bracket was manufactured from different ferrous or Co-based alloys. Metallographic analysis showed the presence of a large grain size for the Discovery, Freedom, and Topic brackets and a much finer grain size for the Extremo bracket. Vickers hardness showed great variations among the brackets (Topic: 287 +/- 16, Freedom: 248 +/- 13, Discovery: 214 +/- 12, and Extremo: 154 +/- 9). The results of this study showed that there are significant differences in the base morphology, composition, microstructure, and microhardness among the brackets tested, which may anticipate significant clinical implications.

Cobalt↗

PubMed2005

Premolar bracket position revised: proximal and occlusal contacts assessment.

AIM: To assess the effect of conventional bracket slot vertical position (4 mm from incisal edge) on crown spatial orientation relative to adjacent and opposing teeth through proximal contact balance and occlusal contacts assessment. MATERIAL AND METHODS: Forty patients were divided into two groups; in the first group, brackets were bonded 4 mm from the intact incisal edge; in the second group, bracket position was determined individually by transferring the maximum embrasure difference to the bracket slot height difference. The difference of proximal contacts between premolars and molars was measured. Bite registration with the use of articulating paper was also performed on all patients. Traces indicating contact between premolar maxillary lingual cusps and opposing mandibular fossa of the first and second premolars were evaluated. Differences with respect to the distribution of unbalanced proximal contacts and negative contacts between the two bonding schemes were analyzed with the chi-square test at P = .05 level of significance. RESULTS: Aligning the bracket slot with the center of the clinical crown (FA point) consistently produced unbalanced proximal contacts in excess of 1 mm, as well as increased absence of occlusal contacts. CONCLUSION: Positioning the bracket slot on the center of the premolar crown may result in marginal ridge discrepancy between the premolars and molars and lack of occlusal contacts with opposing dentition. This may be due to the height difference noted between the buccal and lingual cusp of the premolars, as well as variation in molar tube or band placement. Functional occlusal analysis should be integrated in the finishing stages of treatment to facilitate proper premolar crown position.

Adolescent↗

PubMed2005

Ethics and fraud in science: a review of scientific misconduct and applications to craniofacial research.

The purpose of this article is to review and discuss the occurrence of fraud in biomedical research and analyze the definition, origin, and various forms of scientific misconduct. Fraud in research most often involves reporting data for which no records of experiment or population are present; manipulating research materials, equipment, or procedures to arrive at the desirable result; adding, changing, or omitting results, which positively or negatively relate to the hypothesis that the research intends to test; and incorporating ideas, statements, procedures of others' work without permission and appropriate credit to the source. The etiologic factors contributing to this deviant behavior, and measures taken by relevant bodies to eliminate this phenomenon are discussed. Ethical and integrity aspects of craniofacial research are explored and a set of criteria to facilitate rigorous assessment of the integrity of clinical and basic research protocols is proposed. These include (1) an integrity-focused training of researchers to adhere to specific laboratory procedure and tactics which discourage fraud; (2) appointment of external reviewers to detect unusual and suspicious experimental process or data patterns; and (3) encouragement of multicenter trials. Although it is widely recognized that the sole determinant of scientific misconduct is the individual investigator's integrity, a number of precautions may effectively reduce the prevalence of this event, which may affect the status and trends of biomedical research in general.

Bioethical Issues↗

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↗