Cephalometry without complex dedicated postprocessing in an oriented magnetic resonance imaging dataset: a pilot study.

OBJECTIVES: Magnetic resonance imaging (MRI) enables a 3D-volume-imaging without ionizing radiation. Therefore, it was the aim of this study to present a post-processing-free method for cephalometric analysis of a MRI-dataset and to examine whether there is a significant difference between cephalometric analysis of conventional 2D cephalograms and MRI scans. METHODS: One MRI scan each was performed on three cadaver heads using a 3T-MR-scanner. Cephalometric analysis was conducted directly on the 3D dataset. All reference points were projected onto a virtual sagittal plane that was perpendicular to the Frankfort horizontal plane. Double-sided points were averaged. Cephalometric angles were measured from the projected points. Results were compared with cephalometric measurements on conventional lateral cephalometric radiographs (LCRs). The cephalometric analysis was performed by five raters. RESULTS: 390-angle measurements were obtained. The inter-rater reliability was high [intraclass correlation coefficients (ICCs) ≥ 0.74 for all angles]. Differences between the measurements on the cephalograms and MRI scans ranged between -0.91° (-1.88°, 0.07°) and 0.97° (-0.63°, 2.57°) on average and were equivalent with respect to a margin of [-2°, 2°] in all angles except L1-Me-Tgo (Bonferroni-Holm-corrected P < 0.05 in all angles except L1-Me-Tgo). The best match was found for the SNA angle. CONCLUSION: The clinical comparability of the MRI- and LCR-based cephalometry could be stated. Using MRI in orthodontics would reduce radiation exposure and the risk of stochastic radiation damage, which is of importance especially in younger patients.

Impact of specific orthodontic parameters on the oral health-related quality of life in children and adolescents : A prospective interdisciplinary, multicentre, cohort study.

PURPOSE: The aim of the present study was to analyse the impact of specific orthodontic findings on oral health-related quality of life (OHRQoL) when taking into consideration age and psychological factors in children and adolescents. METHODS: In all, 250 children and adolescents with an indication for orthodontic diagnostics were recruited using a multicentre study design. Using validated and internationally acknowledged questionnaires, we assessed OHRQoL, health-related quality of life (HRQoL), self-esteem and behavioural problems. We also examined a selection of specific orthodontic findings using photos, model casts and cephalometric analyses, and investigated the impact of these parameters on OHRQoL using simple linear regression analyses. Thereafter, we added all the significant specific orthodontic and psychological parameters to a multiple linear regression model using a stepwise forwards selection procedure. RESULTS: We were able to identify different specific orthodontic findings that have a significant impact on OHRQoL. These were the type of lip closure, the position of the chin, the Little-index of the upper jaw, the overjet, the overbite and the ANB angle. Moreover, we were able to demonstrate that psychological and some specific orthodontic parameters have a significant impact on OHRQoL. CONCLUSION: Specific orthodontic findings have a significant impact on patients' perceived OHRQoL. Further longitudinal studies are required to investigate whether the treatment and correction of these malocclusions also improve the OHRQoL of children and adolescents.

Correlation between oral health-related quality of life and orthodontic treatment need in children and adolescents-a prospective interdisciplinary multicentre cohort study.

PURPOSE: Oral health-related quality of life (OHRQoL) is a construct for assessing the self-perceived oral health of patients. The aim of this study was to investigate the correlation between OHRQoL and orthodontic treatment need in consideration of demographic and psychological factors. PATIENTS AND METHODS: This multicentre study included 250 patients with an indication for orthodontic diagnostics. In cooperation with the Institute of Clinical Psychology at the University of Würzburg, validated and internationally acknowledged questionnaires were selected to assess OHRQoL (COHIP-G19) and health-related quality of life (HRQOL). Self-esteem and behavioural problems were taken into consideration as possible psychological factors. Orthodontic treatment need was assessed using the Index of Orthodontic Treatment Need-Dental Health Component (IOTN-DHC), the Index of Orthodontic Treatment Need-Aesthetic Component (IOTN-AC) and the Dental Aesthetic Index (DAI). Possible significant correlations between the collected parameters and OHRQoL were evaluated by means of linear regression analysis. RESULTS: Objective orthodontic treatment need (IOTN-DHC and DAI) was significantly correlated with OHRQoL. Further factors significantly influencing OHRQoL in children and adolescents were age, HRQOL, self-esteem and behavioural problems. CONCLUSIONS: Objective orthodontic treatment need significantly influences OHRQoL in children and adolescents. Further studies are required to investigate if OHRQoL may be improved by correcting misaligned teeth and jaws.

Oculoauriculovertebral spectrum and maxillary sinus volumes : CT-based comparative evaluation.

OBJECTIVES: To evaluate, by comparing maxillary sinus volumes, how asymmetries related to oculoauriculovertebral spectrum (OAVS) affect upper-jaw development. METHODS: From pre-existing multislice spiral computed tomography (MSCT) datasets, we selected 20 cases of 11 female and 9 male patients aged 6.1-24 years who were clinically and radiographically symmetrical (group 1) plus 20 cases of 8 female and 12 male patients aged 5.7-23.9 years who had OAVS (group 2). After three-dimensional reconstruction of the datasets, the volumes of the left and right maxillary sinuses were calculated and compared based on patient groups and based on the sides affected or unaffected by OAVS. To this end, the OAVS patients were subdivided into a group in whom both external acoustic pores were radiographically present (group 2a) and a group in whom the pore on the affected side was congenitally missing (group 2b). RESULTS: Intrarater reliability was very high (0.997). Significantly larger volumes of the maxillary sinuses, amounting to a mean of 13.4 ml, were observed in the control group than in the asymmetric OAVS groups where the volumes averaged 9.8 ml or 10.3 ml, respectively (p = 0.03). No statistically significant differences in sinus volumes were found between the two OAVS groups (p = 0.557) and between the sides affected or unaffected by the OAVS (p = 0.8311 in group 2a and 0.4961 in group 2b). CONCLUSIONS: Overall, we found the volumes of both maxillary sinuses to be somewhat smaller in the asymmetric patients than in the symmetric control group. This might indicate that OAVS was associated with a mild generalized hypoplasia of the maxilla, but significantly different sinus volumes were not seen between the affected and unaffected sides.

Prevalence of temporomandibular disorders in patients with Hashimoto thyroiditis.

OBJECTIVES: Autoimmune thyroid disease (AITD), also known as Hashimoto thyroiditis (HT), is a degenerative inflammatory disease with high prevalence among women and has been associated with fibromyalgia and widespread chronic pain. The goal was to determine the frequency of temporomandibular disorders (TMD) in patients with HT. METHODS: In all, 119 women (age 19-60 years) were divided into a study (52 women diagnosed with HT) and a control (67 healthy individuals, of which 15 were excluded) group. Serum concentrations of thyroid-stimulating hormone (TSH), free triiodothyronine (fT3), free thyroxine (fT4), anti-thyroglobulin (Tg) and anti-thyroid peroxidase (TPO) antibody levels were measured. The temporomandibular jaw and muscles were examined using the German Society of Functional Diagnostics and Therapy guidelines. The Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) was used to assess TMD. Standardized questionnaires, incorporating epidemiological criteria, state and treatment of the thyroid disease, Helkimo Index (HI), and Fonseca Anamnestic Index (FAI), were filled out by all patients. RESULTS: The two groups did not differ in terms of demographic parameters or mandibular jaw mobility. Significantly higher levels of anti-TPO and anti-Tg were attested in all subjects of the HT group. Markedly elevated prevalence of TMD was found in the HT group. Muscle pain and stiffness were found in 45 (86.5%) subjects of the HT group (p < 0.001), of whom 33 (63.4%) also had disc displacement with reposition (p < 0.001). Whereas 50% of the control group showed no TMD symptoms, all subjects in the HT group had symptoms. CONCLUSIONS: A significantly elevated prevalence of TMD was found in patients with HT. Thus, patients with TMD who do not respond to therapy should be referred for thyroid diagnostic workup.

Oro-dental pathologies in acromegaly.

PURPOSE: Oro-dental pathologies (ODP) such as enlargement of the tongue, mandibular prognathism, and spaced teeth are characteristic features of acromegaly. Their frequency of occurrence during the course of the disease is largely unresolved. Purpose of this study was to assess ODP and oro-dental treatments in patients with acromegaly with regard to the length of the diagnostic process, tumor histology, and quality of life (QoL). METHODS: Single-center retrospective survey study using questionnaires on dental symptoms, diagnostic process, and treatment in patients with acromegaly operated on a growth hormone-secreting pituitary adenoma. The association between ODP and QoL was assessed using the Short-Form 36 (SF-36) Health Survey. RESULTS: 145/314 patients completed the questionnaires. 80.7% were affected by any ODP, most frequently enlargement of the tongue (57.9%), spaced teeth (42.8%), mandibular growth (24.1%), and mandibular prognathism (22.1%). ODP were significantly more frequent in patients with sparsely vs. densely granulated adenomas (p = 0.045). Early diagnosis within 2 years was associated with significantly fewer ODP than later diagnosis (68.5 vs. 87.2%, p = 0.009). Treatments included dental crowns (16.6%), dental bridges (12.4%), dental implants (9.7%), dental prostheses (3.4%), orthodontal (i.e., braces, 6.9%), and surgical correction of the teeth (2.1%). Physical QoL was significantly lower in patients with ODP than in those without (p = 0.014). CONCLUSION: In our large series of patients, four of five patients were affected by ODP at any time during the course of the disease. The results highlight the importance of early identification and treatment of oro-dental problems in patients with acromegaly as hallmarks of the disease.

Determination of the mesio-distal tooth width via 3D imaging techniques with and without ionizing radiation: CBCT, MSCT, and µCT versus MRI.

Objective: The purpose of this study was to estimate the feasibility and accuracy of mesio-distal width measurements with magnetic resonance imaging (MRI) in comparison to conventional 3D imaging techniques [multi-slice CT (MSCT), cone-beam CT (CBCT), and µCT]. The measured values of the tooth widths were compared to each other to estimate the amount of radiation necessary to enable orthodontic diagnostics. Material and Methods: Two pig skulls were measured with MSCT, CBCT, µCT, and MRI. Three different judges were asked to determine the mesio-distal tooth width of 14 teeth in 2D tomographic images and in 3D segmented images via a virtual ruler in every imaging dataset. Results: Approximately 19% (27/140) of all test points in 2D tomographic slice images and 12% (17/140) of the test points in 3D segmented images showed a significant difference (P ≤ 0.05). The largest significant difference was 1.6mm (P < 0.001). There were fewer significant differences in the measurement of the tooth germs than in erupted teeth. Conclusions: Measurement of tooth width by MRI seems to be clinically equivalent to the conventional techniques (CBCT and MSCT). Tooth germs are better illustrated than erupted teeth on MRI. Three-dimensional segmented images offer only a slight advantage over 2D tomographic slice images. MRI, which avoids radiation, is particularly appealing in adolescents if these data can be corroborated in further studies.

Effects of enamel sealing on shear bond strength and the adhesive remnant index : Study of three fluoride-releasing adhesives in combination with metal and ceramic brackets.

OBJECTIVES: Selected combinations of materials were used to create tooth-adhesive-bracket complexes to evaluate shear bond strength (SBS) and the adhesive remnant index (ARI) with regard to enamel sealing. METHODS: Four adhesive systems also appropriate for use as enamel sealants were combined with four bracket types, resulting in 16 adhesive-bracket combinations, each of which was tested on 15 permanent bovine incisors. Sealant-adhesives included two recently introduced fluoride-releasing systems (Riva bond LC® and go!®), one established primer (Opal® Seal™), and one commonly used adhesive as control (Transbond™ XT). Brackets included two metal (discovery® by Dentaurum and Sprint®) and two ceramic (discovery® pearl and GLAM®) systems. After embedding the bovine teeth, bonding the brackets to their surface, and storing the resultant samples as per DIN 13990-2 with modifications, an SBS test was performed by applying the shear force directly at the bracket base in an incisocervical direction. Then the ARI scores were determined. RESULTS: Discovery® + Transbond™ XT yielded the highest (47.2 MPa) and GLAM® + go!® the lowest (17.0 MPa) mean SBS values. Significant differences (p < 0.0001) were found between metal and ceramic brackets of the same manufacturers (Dentaurum and Forestadent). Our ratings of the failure modes upon debonding predominantly yielded ARI 0 or 1. The high SBS values and low ARI scores observed with discovery® + Transbond XT™ were reflected in a high rate of enamel fracture, which occurred on 11 of the 15 tooth specimens in this group. CONCLUSIONS: All sealant-bracket combinations were found to yield levels of SBS adequate for clinical application. SBS values and ARI scores varied significantly depending on which sealant-brackets were used.

Assessment of facial soft-tissue profiles based on lateral photographs versus three-dimensional face scans.

OBJECTIVES: The purpose of this study was to compare two-dimensional (2D) lateral photographs versus three-dimensional (3D) face scans in analyzing facial profiles using Schwarz's concept of the jaw profile field (JPF) in its original 2D and in a modified 3D version. In addition, the distribution of the facial profile types described by Schwarz were examined. MATERIALS AND METHODS: Of 75 adult volunteers recruited specifically for this study, we obtained both photographs (Nikon D 300S; Nikon, Düsseldorf, Germany) and scans (FaceSCAN3D Scientific Photolab 60 Hz; 3D-Shape, Erlangen, Germany) in a standardized setting. Four raters analyzed the pertinent measurements using image analysis software (Onyx Ceph 3; Image Instruments, Chemnitz, Germany). Statistical analysis was conducted using the R suite environment (v. 3.2.1; R Foundation for Statistical Computing, Vienna, Austria). RESULTS: Intraobserver reliability was substantial for two raters (κ = 0.61-0.8), moderate for one (κ = 0.41-0.60), and almost perfect for one (κ = 0.81-1.00). As for interobserver reliability, we observed moderate agreement between the two basic technologies tested, but internal agreement was only moderate even within the 2D view modes (average κ = 0.51) versus almost perfect within the 3D view modes (κ = 0.84-0.94). Forward-slanting anteface was clearly the most common (43.27%) and straight retroface the least common (0.3%) diagnosis. Only a minority of patients (18.38% of women and 16.15% of men) had straight as opposed to slanting profiles. CONCLUSIONS: Given our findings of acceptable agreement between 3D scanning and 2D lateral photography, in combination with almost perfect internal agreement between different 3D view modes, it appears useful to adapt Schwarz's method of facial profile assessment for clinical use in 3D virtual environments.

Landmarks of the Frankfort horizontal plane : Reliability in a three-dimensional Cartesian coordinate system.

OBJECTIVES: The goal was to investigate whether the three-dimensional (3D) reliability of the landmarks defining the Frankfort horizontal plane (FH) can be enhanced by reducing variance with the help of nearby anatomical structures. METHODS: Twenty multislice computed tomography (MSCT) datasets of evidently symmetrical patients (11 female and 9 male patients, 6.1-16 years old) were selected from 695 datasets archived at our department. In the 3D reconstructions, we located the anthropometric landmarks orbitale and porion, then these were modified with the help of frontomalare temporale, radiculare and the most anterior border of the left and right external acoustic pore. The resultant orbitale* and porion* reference points for the Frankfort horizontal plane were then compared to the original landmarks. Statistical analysis was performed. RESULTS: The superior reliability in the sagittal y-axis and in the transversal x-axis of the new reference points was confirmed. Based on the covariance matrices, the mean maximum standard deviation (square root of the maximum eigenvalue) in the direction of maximum variance was reduced from 0.77/0.94 mm to 0.47/0.48 mm for left/right orbitale, and similar reductions from 0.85/0.92 mm to 0.29/0.30 mm were noted for left/right porion (p < 0.001 for all four points). Vertical reliability did not improve further. CONCLUSIONS: The modifications significantly reduced the variance of the orbitale and porion landmarks, thus, clearly increasing the three-dimensional reliability. Hence these optimized reference points are better suited to construct the FH, which arguably is an important spatial reference plane in orthodontics.

Three-dimensional CT evaluation of oculoauriculovertebral spectrum patients use of Katsumata's asymmetry index.

OBJECTIVES: To evaluate patients with oculoauriculovertebral spectrum (OAVS) malformations based on Katsumata's asymmetry index and to assess the usefulness of the scores thus obtained in identifying degrees and sites of asymmetry. METHODS: Multislice spiral computed tomography (MSCT) datasets of 8 female and 12 male OAVS patients aged 5.7-23.9 years were retrospectively analyzed. After three-dimensional reconstruction, central and bilateral anatomical landmarks were identified within a coordinate system defined by the sella, nasion, and dens axis. MSCT datasets of 20 clinically symmetrical patients were used to define the cutoff values for asymmetry. Based on the mean asymmetry scores and their standard deviations, the severities and sites of asymmetry were evaluated and processed for visual presentation in charts. RESULTS: Both interrater (ICC 0.7070-0.9984) and intrarater (FVU 0.0014-0.2930) reliability was very high. The calculated asymmetry scores added up to mean values and standard deviations that were higher by factors of around 1.5-2.5 than reported by Katsumata et al. More anatomical landmarks were rated as asymmetric in OAVS patients showing unilateral agenesis of an external acoustic pore than in OAVS patients without such agenesis: in the former patients, statistically significant asymmetries compared to the control group were present at the L1M (coronal pulp cavity of the lower first molar), CoP (coronoid process), and Co (condylion superius) landmarks, whereas the latter group showed such significant asymmetries at the CoP and Co landmarks. Likewise, more patients with unilateral agenesis showed asymmetries at the level of the maxilla. Highly variable severities of asymmetry were found in both subgroups of OAVS patients. CONCLUSION: Katsumata's asymmetry index can yield well-structured and illustrative views of landmark distribution, thus, suitably allowing for qualitative asymmetry evaluation of OAVS cases and identification of the skeletal regions involved.

MRI vs. CT for orthodontic applications: comparison of two MRI protocols and three CT (multislice, cone-beam, industrial) technologies.

OBJECTIVES: To examine the relative usefulness and suitability of magnetic resonance imaging (MRI) in daily clinical practice as compared to various technologies of computed tomography (CT) in addressing questions of orthodontic interest. METHODS: Three blinded raters evaluated 2D slices and 3D reconstructions created from scans of two pig heads. Five imaging modalities were used, including three CT technologies-multislice (MSCT), cone-beam CT (CBCT), and industrial (µCT)-and two MRI protocols with different scan durations. Defined orthodontic parameters were rated one by one on the 2D slices and the 3D reconstructions, followed by final overall ratings for each modality. A mixed linear model was used for statistical analysis. RESULTS: Based on the 2D slices, the parameter of visualizing tooth-germ topography did not yield any significantly different ratings for MRI versus any of the CT scans. While some ratings for the other parameters did involve significant differences, how these should be interpreted depends greatly on the relevance of each parameter. Based on the 3D reconstructions, the only significant difference between technologies was noted for the parameter of visualizing root-surface morphology. Based on the final overall ratings, the imaging performance of the standard MRI protocol was noninferior to the performance of the three CT technologies. CONCLUSIONS: On comparing the imaging performance of MRI and CT scans, it becomes clear that MRI has a huge potential for applications in daily clinical practice. Given its additional benefits of a good contrast ratio and complete absence of ionizing radiation, further studies are needed to explore this clinical potential in greater detail.

Shear bond strength of brackets on restorative materials: Comparison on various dental restorative materials using the universal primer Monobond® Plus.

OBJECTIVE: The purpose of this work was to analyze surfaces consisting of different restorative materials for shear bond strength (SBS) and failure patterns of metal and ceramic brackets. Bonding involved the use of a universal primer (Monobond® Plus, Ivoclar Vivadent). MATERIALS AND METHODS: Six restorative materials were tested, including one composite resin (Clearfil Majesty™ Posterior, Kuraray Noritake Dental), one glass-ceramic material (IPS Empress® Esthetic, Ivoclar Vivadent), one oxide-ceramic material (CORiTEC Zr transpa Disc, imes-icore), two base-metal alloys (remanium® star, Dentaurum; Colado® CC, Ivoclar Vivadent), and one palladium-based alloy (Callisto® 75 Pd, Ivoclar Vivadent). Bovine incisors served as controls. Both metal and ceramic brackets (discovery®/discovery® pearl; Dentaurum) were bonded to the restorative surfaces after sandblasting and pretreatment with Monobond® Plus. A setup modified from DIN 13990-2 was used for SBS testing and adhesive remnant index (ARI)-based analysis of failure patterns. RESULTS: The metal brackets showed the highest mean SBS values on the glass-ceramic material (68.61 N/mm(2)) and the composite resin (67.58 N/mm(2)) and the lowest mean SBS on one of the base-metal alloys (Colado® CC; 14.01 N/mm(2)). The ceramic brackets showed the highest mean SBS on the glass-ceramic material (63.36 N/mm(2)) and the lowest mean SBS on the palladium-based alloy (38.48 N/mm(2)). Significant differences between the metal and ceramic brackets were observed in terms of both SBS values and ARI scores (p < 0.05). Under both bracket types, fractures of the composite-resin and the glass-ceramic samples were observed upon debonding. Opaque restorative materials under metal brackets were found to involve undercuring of the adhesive. CONCLUSIONS: Monobond® Plus succeeded in generating high bond strengths of both bracket types on all restorative surfaces. Given our observations of cohesive fracture (including cases of surface avulsion) of the composite-resin and the glass-ceramic samples, we recommend against using these material combinations in clinical practice.

Comparative study of image quality and radiation dose of cone beam and low-dose multislice computed tomography--an in-vitro investigation.

OBJECTIVES: The aim of this study was to evaluate the image quality and dose exposition of different cone-beam computed tomography (CBCT) and low-dose multislice spiral CT (MSCT) scanners. MATERIALS AND METHODS: A human cadaver head was examined with three MSCT and five CBCT scanners. The radiation dose was measured using an Alderson RANDO phantom. Standard protocols were used to obtain the CBCT data. For the MSCT devices, the tube voltage and tube current were modified to obtain acceptable image quality while keeping the radiation dose as low as possible. The image quality of MSCT and CBCT devices was determined by examining the enamel-dentin and dentin-pulp interface and the periodontal ligament space of 22 teeth. RESULTS: Inter- and intra-observer agreement was found for the different groups of raters. CBCT systems were rated superior to MSCT devices in terms of image quality for all dental structures. The differences in image quality among the studied CBCT and MSCT scanner groups did not turn out to be significant but were significant between CBCT and MSCT devices. The organ dose varied considerably between the different CBCT and MSCT devices. The differences concerning the organ dose were notably pronounced in the area of the eye lens. CONCLUSIONS: The tested devices exhibited significant differences with respect to the organ dose. The variance was particularly pronounced in the CBCT devices. With a dose exposition equal or lower than the CBCT, the image quality in the MSCT devices was judged to be significantly worse.

Three-dimensional volume tomographic study of the imaging accuracy of impacted teeth: MSCT and CBCT comparison--an in vitro study.

The aim of this study was to analyze the imaging accuracy of cone beam computed tomography (CBCT) data sets compared with multislice spiral computed tomography (MSCT) data sets in determining the exact mesiodistal width of unerupted porcine tooth germs and to compare the radiologically obtained results of width measurements with the actual mesiodistal dimension of the tooth germs. In MSCT and CBCT data sets, the largest diameter of 24 tooth germs was determined with the aid of the mesial and distal contact points. The reference method used was mesiodistal width measurement using sliding callipers after the tooth germs had been osteotomized. Accuracy and precision were ascertained with difference plots and a one-way model II analysis of variance with random effects. Analysis of accuracy revealed marked differences between the measuring methods in the difference plot: slightly higher mean values were measured by MSCT and markedly lower values by CBCT than by the reference method (calliper); the mean deviation was significantly greater for CBCT. The width of the confidence interval in the comparison of CBCT versus clinical measurements is more than 4 times higher than in the comparison of MSCT versus clinical values. Precision analysis found that repeatability was twice as high with CBCT as with clinical measurement, whereas MSCT and clinical measurement differed only slightly. The mesiodistal width of displaced teeth can be determined by MSCT but also by CBCT. MSCT is superior to CBCT in determining tooth width; the difference was statistically significant (P = 0.05).

Retrieval analysis of different orthodontic brackets: the applicability of electron microprobe techniques for determining material heterogeneities and corrosive potential.

OBJECTIVE: The objective of this study was to investigate the applicability of micro-analytical methods with high spatial resolution to the characterization of the composition and corrosion behavior of two bracket systems. MATERIAL AND METHODS: The surfaces of six nickel-free brackets and six nickel-containing brackets were examined for signs of corrosion and qualitative surface analysis using an electron probe microanalyzer (EPMA), prior to bonding to patient's tooth surfaces and four months after clinical use. The surfaces were characterized qualitatively by secondary electron (SE) images and back scattered electron (BSE) images in both compositional and topographical mode. Qualitative and quantitative wavelength-dispersive analyses were performed for different elements, and by utilizing qualitative analysis the relative concentration of selected elements was mapped two-dimensionally. The absolute concentration of the elements was determined in specially prepared brackets by quantitative analysis using pure element standards for calibration and calculating correction-factors (ZAF). RESULTS: Clear differences were observed between the different bracket types. The nickel-containing stainless steel brackets consist of two separate pieces joined by a brazing alloy. Compositional analysis revealed two different alloy compositions, and reaction zones on both sides of the brazing alloy. The nickel-free bracket was a single piece with only slight variation in element concentration, but had a significantly rougher surface. After clinical use, no corrosive phenomena were detectable with the methods applied. Traces of intraoral wear at the contact areas between the bracket slot and the arch wire were verified. CONCLUSION: Electron probe microanalysis is a valuable tool for the characterization of element distribution and quantitative analysis for corrosion studies.

Retrieval analysis of different orthodontic brackets: the applicability of electron microprobe techniques for determining material heterogeneities and corrosive potential

OBJECTIVE: The objective of this study was to investigate the applicability of micro-analytical methods with high spatial resolution to the characterization of the composition and corrosion behavior of two bracket systems. MATERIAL AND METHODS: The surfaces of six nickel-free brackets and six nickel-containing brackets were examined for signs of corrosion and qualitative surface analysis using an electron probe microanalyzer (EPMA), prior to bonding to patient's tooth surfaces and four months after clinical use. The surfaces were characterized qualitatively by secondary electron (SE) images and back scattered electron (BSE) images in both compositional and topographical mode. Qualitative and quantitative wavelength-dispersive analyses were performed for different elements, and by utilizing qualitative analysis the relative concentration of selected elements was mapped two-dimensionally. The absolute concentration of the elements was determined in specially prepared brackets by quantitative analysis using pure element standards for calibration and calculating correction-factors (ZAF). RESULTS: Clear differences were observed between the different bracket types. The nickel-containing stainless steel brackets consist of two separate pieces joined by a brazing alloy. Compositional analysis revealed two different alloy compositions, and reaction zones on both sides of the brazing alloy. The nickel-free bracket was a single piece with only slight variation in element concentration, but had a significantly rougher surface. After clinical use, no corrosive phenomena were detectable with the methods applied. Traces of intraoral wear at the contact areas between the bracket slot and the arch wire were verified. CONCLUSION: Electron probe microanalysis is a valuable tool for the characterization of element distribution and quantitative analysis for corrosion studies.

Burnout, depression and depersonalisation--psychological factors and coping strategies in dental and medical students.

BACKGROUND: Previous studies found that stress, depression, burnout, anxiety, and depersonalisation play a significant role amongst dental and medical students. We wanted to examine if students of the University of Erlangen-Nuremberg also would report elevated values as can been found in similar publications. Furthermore, particularly coping strategies were investigated. METHODS: The data collection took place in April 2008 including 182 dental and medical students of the 4th and 5th academic year at the University of Erlangen-Nuremberg. Demographic data and the following screening instruments were used: Maslach Burnout Inventory (MBI), Cambridge Depersonalisation Scale (CDS-9), Hospital Anxiety and Depression Scale (HADS), Brief COPE. RESULTS: Descriptive statistics showed higher pathological values in dental students than in medical students. The difference was especially pronounced on the depersonalisation scale (CDS-9), with 20.4% of the dental students, but only 5.5% of the medical students showing scores above a cut-off of 19. The scores decreased in the course of 3 semesters of dentistry. The students with elevated values showed a higher degree of dysfunctional coping. CONCLUSION: Our results obtained with the screening instruments are in line with the results of previous investigations of other authors and point out the importance of this issue. It might be useful to develop programs teaching dental students more adaptive coping strategies before their first patient contact.

3D CT based rating of unilateral impacted canines.

OBJECTIVE: The aim of this study was to develop a reference system for multislice computed tomography (MSCT) images to determine of the location of impacted teeth in metric terms. STUDY DESIGN: The CT data of 17 patients with unilateral impacted maxillary canines were selected retrospectively from existing MSCT data sets. In a reference coordinate system, defined by anterior nasal spine (ANS), posterior nasal spine (PNS), and A-point, the axis length and the inclination of the canines were determined and impacted and non-impacted canines were compared. RESULTS: There were significant differences between the impacted and non-impacted canines (p ≤ 0.0003) for all inclinations and the lengths in the x- and z-axes. The measurement of the inclination and sections of the impacted and non-impacted canine tooth axes showed sufficient repeatability and reproducibility. CONCLUSION: The coordinate system proved to be suitable for the exact metric localization of impacted teeth.