Athanasios E. Athanasiou

In Vivo Aging of Orthodontic Alloys: Implications for Corrosion Potential, Nickel Release, and Biocompatibility

Despite the large number of studies investigating nickel release from orthodontic stainless steel and nickel-titanium alloys, there is a lack of conclusive evidence with respect to the composition and kinetics of the corrosive products released. The objective of this review is to address the critical issues of corrosion potential and nickel leaching from alloys by investigating the effect of intraoral conditions on the surface reactivity of the materials. After an overview of fundamentals of metallurgical structure of orthodontic alloys, we provide an analysis of corrosion processes occurring in vivo. We present recent evidence suggesting the formation of a proteinaceous biofilm on retrieved orthodontic materials that later undergoes calcification. We illustrate the vastly irrelevant surface structure of in vivo- vs in vitro-aged alloys and discuss the potential implications of this pattern in the reactivity of the materials. Finally, we present a comprehensive review of the issue of nickel release, based on three perspectives: its biologic effects, the methods used for studying its release, and nickel-induced hypersensitivity in orthodontic patients.

Alterations of hyoid bone position and pharyngeal depth and their relationship after surgical correction of mandibular prognathism

The present investigation studied changes of hyoid bone position and pharyngeal depth at the levels of the second and fourth cervical vertebrae and their relationships in mandibular prognathism patients who received combined orthodontic-surgical treatment. The material consisted of presurgical and 1-year postsurgical profile cephalograms of 52 adult orthognathic surgery patients (40 females and 12 males) who initially had mandibular prognathism and had undergone bilateral vertical ramus osteotomy through an extraoral incision in the retroangular area. Hyoid bone position and pharyngeal depth were assessed on the profile radiographs with 10 cephalometric variables. Paired t tests were used to evaluate the operative changes in all cephalometric parameters. The relationships between pairs of variables describing hyoid bone position and pharyngeal depth were assessed by means of Pearsons product-moment correlation analysis. Significant differences (p less than 0.01) were observed for the distances of the hyoid bone to the maxilla and the mandible. The distances of the hyoid bone with the anterior cranial base, the vertebral column, and the anterior pharyngeal wall, and the measurements representing pharyngeal depth exhibited no significant changes (p greater than 0.05). Moderate correlations were seen between (1) the depth of the pharynx at the fourth cervical vertebra and the hyosymphyseal distance (r = 0.34) and the distance between the point of the projection of the hyoid bone to the mandibular line with its posterior border (r = -0.34), and (2) the depth of the pharynx at the second cervical vertebra and the distance of the hyoid bone with the anterior pharyngeal wall at the level of the fourth cervical vertebra (r = -0.33).(ABSTRACT TRUNCATED AT 250 WORDS)

Factors affecting the duration of orthodontic treatment: a systematic review.

The aim of this study was to systematically investigate the literature for articles referring exclusively to the duration of orthodontic therapy and to explore the various factors that could affect this. A Medline search from 1990 to the first week of March 2005 was conducted, the Cochrane Database for Systematic Reviews was utilized, five orthodontic journals were hand searched, the abstracts of related articles were reviewed to search for any relevant studies that might have been missed, and the reference lists of the retrieved articles were hand assessed. Eligibility was determined by reading the reports identified by the search. The end result of this search provided 41 articles. Although there is a need for more conclusive research, the present review revealed several conclusions concerning the duration of orthodontic treatment: (1) there are indications that extraction treatment lasts longer than the non-extraction therapy; (2) age does not seem to play a role provided the patients are in the permanent dentition; (3) when Class II division 1 malocclusions are considered, there is evidence that the earlier the orthodontic treatment begins the longer its duration; (4) there is conflicting information regarding treatment duration within public health systems; (5) combined orthodontic-surgical treatment duration is variable and appears to be operator sensitive; (6) various factors, such as the technique employed, the skill and number of operators involved, the compliance of the patients, and the severity of the initial malocclusion, all seem to play a role; and (7) impacted maxillary canines appear to prolong treatment.

Clinical characteristics and properties of ceramic brackets: A comprehensive review

The aim of this article is to provide the clinician with an up-to-date comprehensive literature review concerning the clinical characteristics and properties of ceramic brackets. The article critically presents and discusses the various aspects of ceramic brackets with regard to the types, physical properties, bond strength, frictional resistance, base surface characteristics, debonding techniques and enamel fracture risks, enamel abrasion and wear, bracket fracture, and bracket recycling. The article contains also guidelines and criteria concerning the specific applications and use of ceramic brackets.

Data and patterns of transverse dentofacial structure of 6- to 15-year-old children: a posteroanterior cephalometric study.

The aims of the present cross-sectional investigation were to provide normative data of selected dentofacial posteroanterior cephalometric measures and to describe the patterns of transverse dentofacial structure. The material comprised the P-A cephalograms of 588 Austrian schoolchildren (157 girls and 431 boys, who were 6 to 15 years old). All subjects were healthy, presented various types of occlusions, and did not receive orthodontic or orthopedic therapy. In studying the P-A cephalograms, 8 linear and 2 angular variables, as well as 10 ratios were used. The results of the study revealed that all skeletal widths and all ratios representing relations between the various breadths of the facial skeleton and the interorbital width demonstrated an increase when the measurements at the initial and final ages of 6 and 15 years, respectively, were compared. However, the maxillary intermolar width during the period from 9 to 12 years did not present any increase, and the mandibular intermolar width remained approximately the same during the whole observation period. The transverse dentoalveolar relationship in the incisal region remained very symmetric during aging. The standard deviations of most cephalometric variables were small when they were compared with their corresponding mean values. The present data are of value for the diagnosis of various types of dentofacial anomalies, for monitoring growth of persons or groups of corresponding age and race, and for comparison with other studies.The aims of the present corss-sectional investigation were to provide normative data of selected dentofacial posteroanterior cephalometric measures and to describe the patterns of transverse dentofacial structure. The material comprised the P-A cephalograms of 588 Austrian schoolchildren (157 girls and 431 boys, who were 6 to 15 years old). All subjects were healthy, presented various types of occlusions, and did not receive orthodontic or orthopedic therapy. In studying the P-A cephalograms, 8 linear and 2 angular variables, as well as 10 ratios were used. The results of the study revealed that all skeletal widths and all ratios representing relations between the various breadths of the facial skeleton and the interorbital width demonstrated an increase when the measurements at the initial and final ages of 6 and 15 years, respectively, were compared. However, the maxillary intermolar width during the period from 9 to 12 years did not present any increase, and the mandibular intermolar width remained approximately the same during the whole observation period. The transverse dentoalveolar relationship in the incisal region remained very symmetric during aging. The standard deviations of most cephalometric variables were small when they were compared with their corresponding mean values. The present data are of value for the diagnosis of various types of dentofacial anomalies, for monitoring growth of persons or groups of corresponding age and race, and for comparison with other studies.

Soft-tissue and dentoskeletal profile changes associated with mandibular setback osteotomy

The aims of the present retrospective cephalometry study were (1) to describe the interrelationships of the soft-tissue and dentoskeletal profiles after total mandibular setback osteotomies and (2) to detect whether there were any cephalometric variables that could contribute to an accurate prediction of the surgical effect on the soft-tissue profile. The presurgical and postsurgical lateral cephalograms of 50 consecutively treated patients (37 females and 13 males) were used; these patients had received combined orthodontic-surgical management of mandibular prognathism by means of a bilateral vertical ramus osteotomy with an extraoral approach. At the time of surgery, their ages ranged from 17 to 41 years. Lateral cephalograms with the teeth in habitual occlusion taken before and approximately 1 year after surgery were available for all patients. A computerized cephalometric appraisal, named profile analysis, was developed and used, including variables corresponding to sagittal and vertical relationships of skeletal and soft-tissue profiles, incisal relationships, soft-tissue thickness, and lip morphology. The statistical elaboration of the data was made by means of paired t test, Pearsons product-moment coefficient correlation, and multiple regression analyses. The assessment of the results disclosed that considerable facial changes and improvement took place after the surgical procedure. The skeletal and soft-tissue facial profiles were straightened and the posture of the lips was improved. The normal incisal relationship achieved became influential on the soft tissues overlying both incisors and led to a better lip competence and posture. Posterior movement at points B and Po was accompanied by reductions ranging from 91% to 103% of the corresponding soft tissues. The presence of both significant correlation coefficients (p less than 0.05) and high r square values (greater than 0.70) in the multiple regression analysis for the osseous tissue variables N-B and N-Po, alone or together with the overjet and S-N-B angle, respectively, reflected their high prediction value with regard to the sagittal relationship of the lower lip, its thickness, and the soft-tissue thickness at the chin area. The findings of Pearsons product-moment coefficient correlation also indicated that the operative changes of the thickness of the upper lip, the lower lip, and the soft tissue at the chin region are influenced by the initial preoperative thickness of the area.

Evaluation of methodology and quality characteristics of systematic reviews in orthodontics

Systematic reviews (SRs) are published with an increasing rate in many fields of biomedical literature, including orthodontics. Although SRs should consolidate the evidence-based characteristics of contemporary orthodontic practice, doubts on the validity of their conclusions have been frequently expressed. The aim of this study was to evaluate the methodology and quality characteristics of orthodontic SRs as well as to assess their quality of reporting during the last years. Electronic databases were searched for SRs (without any meta-analytical data synthesis) in the field of orthodontics, indexed up to the start of 2010. The Assessment of Multiple Systematic Reviews (AMSTAR) tool was used for quality assessment of the included articles. Data were analyzed with Students t-test, one-way ANOVA, and linear regression. Risk ratios (RR) with 95% confidence intervals were calculated to represent changes during the years in reporting of key items associated with quality. A total of 110 SRs were included in this evaluation. About half of the SRs (46.4%) were published in orthodontic journals, while few (5.5%) were updates of previously published reviews. Using the AMSTAR tool, thirty (27.3%) of the SRs were found to be of low quality, 63 (57.3%) of medium quality, and 17 (15.5%) of high quality. No significant trend for quality improvement was observed during the last years. The overall quality of orthodontic SRs may be considered as medium. Although the number of orthodontic SRs has increased over the last decade, their quality characteristics can be characterized as moderate.

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.

Reporting characteristics of meta-analyses in orthodontics: methodological assessment and statistical recommendations

Ideally meta-analyses (MAs) should consolidate the characteristics of orthodontic research in order to produce an evidence-based answer. However severe flaws are frequently observed in most of them. The aim of this study was to evaluate the statistical methods, the methodology, and the quality characteristics of orthodontic MAs and to assess their reporting quality during the last years. Electronic databases were searched for MAs (with or without a proper systematic review) in the field of orthodontics, indexed up to 2011. The AMSTAR tool was used for quality assessment of the included articles. Data were analyzed with Students t-test, one-way ANOVA, and generalized linear modelling. Risk ratios with 95% confidence intervals were calculated to represent changes during the years in reporting of key items associated with quality. A total of 80 MAs with 1086 primary studies were included in this evaluation. Using the AMSTAR tool, 25 (27.3%) of the MAs were found to be of low quality, 37 (46.3%) of medium quality, and 18 (22.5%) of high quality. Specific characteristics like explicit protocol definition, extensive searches, and quality assessment of included trials were associated with a higher AMSTAR score. Model selection and dealing with heterogeneity or publication bias were often problematic in the identified reviews. The number of published orthodontic MAs is constantly increasing, while their overall quality is considered to range from low to medium. Although the number of MAs of medium and high level seems lately to rise, several other aspects need improvement to increase their overall quality.

Comparison of velopharyngeal growth patterns between cleft lip and/or palate patients requiring or not requiring pharyngeal flap surgery.

This investigation compares the patterns of velopharyngeal growth in cleft lip and/or palate patients. Those who had velopharyngeal competence and acceptable speech are compared with those who presented with velopharyngeal incompetence requiring pharyngeal flap surgery or prosthesis later. Lateral cephalograms of 30 cleft palate only (CPO), 35 unilateral cleft lip and palate (UCLP), and 20 bilateral cleft lip and palate (BCLP) children of the Lancaster Cleft Palate Clinic were studied. These records were taken at 6 month intervals during the first 2 postnatal years and annually thereafter up to 6 years of age. Soft tissue landmark points in the velopharyngeal region were digitized. Length and thickness of the soft palate and height and depth of the nasopharynx were measured. Evaluation of the growth curves of these four cephalometric variables indicated only two significant differences between children who later required pharyngeal flap surgery and those who did not. These differences were found in the growth in length of the soft palate of the CPO group and in the growth in depth of the nasopharynx of the BCLP group. Based on the present cephalometric data, it is impossible to predict at an early age those cleft lip and/or palate patients who will later require pharyngeal flaps.