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.

Superficial skin sensitivity impairment and skeletal stability after sagittal split ramus osteotomy.

Adjustable osteosynthesis miniplates are used to facilitate positioning of the mandible after bilateral sagittal split osteotomy (BSSO) to avoid skeletal relapse and occlusal discrepancies. The short Obwegeser BSSO reduces neurosensory disturbances. Adjustable osteosynthesis plates suited for the Obwegeser BSSO are not commercially available. This study tested adjustable miniplates for the short Obwegeser BSSO in advancement of the mandible and correction of facial asymmetry, assessing (1) sensitivity impairment of the lower lip and (2) skeletal stability.A prototype of L-shaped, 6-hole, 2.0-mm miniplate with 2 sliding holes was used. Five patients with facial asymmetry (group 1) and 10 patients with mandibular hypoplasia (group 2) were operated on. Sensitivity of the lower lip was quantified using the pain and thermal sensitivity test before the surgery (T0), 1 week after the surgery (T1), and 12 months after the surgery (T2). The length of the ascending ramus (group 1) and the corpus (group 2) was determined at T1 and T2 using cone beam computed tomographic scans and lateral skull radiographs, respectively.After the surgery, occlusion was adequate. There was no need for revisional surgery. At T2, no patient showed a pathologically reduced sensitivity of the lower lip. The length of the ascending ramus in group 1 and the length of the corpus in group 2 did not have statistically significant changes between T1 and T2.The current study revealed that the adjustable osteosynthesis plates especially designed for the short Obwegeser BSSO can be safely used for the advancement of the mandible and the correction of facial asymmetry, with a minimum risk for neurosensory disturbance and a high skeletal stability.

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.

Repeatability and reproducibility of landmarks--a three-dimensional computed tomography study.

The aim of this study was to investigate the repeatability and reproducibility of the placement of anthropological cephalometric landmarks on three-dimensional computed tomography (3D CT) cranial reconstructions derived from volume data sets. In addition, the influence of the observer's experience on the repeatability of landmark setting was also explored. Twenty patients without any craniofacial deformity (11 females and 9 males; age range 6.1-16 years) were selected retrospectively from CT volume data sets already available from 695 patients of Dental Clinic 3, Orthodontics of Erlangen University Hospital. The CT examination was performed with the SOMATOM Sensation64 (Siemens AG Medical Solutions, Erlangen, Germany). The program VoXim6.1 (IVS Solutions AG, Chemnitz, Germany) was used for 3D reconstruction of the volume data sets. A total of 28 landmarks were examined in the skeleton module of the program VoXim6.1. The randomly sorted data sets were analysed by two orthodontists and two postgraduate students. Each data set was analysed twice by each observer at an interval of 3 weeks. The analysis of variance regarding random effects was used to calculate the intraobserver and interobserver components of standard deviation (SD) of depiction of individual landmarks as measures of repeatability and reproducibility, respectively. Median intraserial SD and interserial SD of 0.46 mm (range: 0.14-2.00 mm) and 0.20 mm (range: 0.02-2.47 mm), respectively, were obtained depending on the landmark and plane. This study included systematic analysis of extreme values (outliers) in the assessment of the quality of measurements obtained. Descriptive statistics revealed qualitative differences in the depiction of different landmarks. The landmarks nasion and infradentale revealed a minor SD in all three spatial coordinates with the smallest SD for infradentale (SD = 0.18 mm) in the transverse plane. However, no systematic trend was identified with regard to the influence of the observer's level of experience affecting the repeatability of landmark positioning. Thus, the repeatability and reproducibility of placements of landmarks with 3D CT were found to be acceptable for a majority of anatomical positions.

Accuracy of anatomical landmark identification using different CBCT- and MSCT-based 3D images: an in vitro study.

OBJECTIVE: The aim of this study was to evaluate the reproducibility of anatomical landmarks and the accuracy of different cone-beam CTs (CBCTs/DVTs) and a multislice spiral CT (MSCT) scanner. METHODS: A human, fresh-frozen cadaver head was scanned with four CBCTs (Accuitomo 3D, 3D eXam, Pax Reve 3D, Pax Zenith 3D) and one MSCT (SOMATOM Sensation 64) scanner. The three-dimensional (3D) reconstruction of the volume data sets and location of the anthropometric landmarks (n=11), together with linear (n=5) and angular (n=1) measurements were carried out by three examiners using the program VoXim® 6.1. The measurements were taken twice at a 14-day interval. Descriptive analyses were made and the standard deviations were used to compare differences in the accuracy of landmark identification. RESULTS: The descriptive statistics showed distinct differences in the reference points in the three axes of the coordinate system. Because of anatomical and morphological factors, the pogonion and gnathion reference points displayed higher standard deviations when set on the transverse plane (SD(CBCT) Pog: 0.66-1.57 mm; SD(MSCT) Pog: 0.14-1.09 mm; SD(CBCT) Gn: 1.05-1.77 mm; SD(MSCT) Gn: 0.20-0.85 mm), thus showing less accuracy. However, standard deviations on the sagittal and vertical planes were smaller. Genion, anterior nasal spine and infradentale had very low standard deviations on all three planes. The distance (Mfl-Mfr) and angle (Krl-Krr-Ge) revealed significantly smaller standard deviations in the MSCT (SD(CBCT) Krl-Krr-Ge: 0.51-0.75 mm; SD(MSCT) Krl-Krr-Ge: 0.22 mm). CONCLUSION: The CBCT devices evaluated in this study are suitable for taking exact 3D measurements of anatomical structures and meet all requirements for 3D cephalometric analysis.

Comparison of the spatial landmark scatter of various 3D digitalization methods.

AIM: The aim of this study was to compare four different three-dimensional digitalization methods on the basis of the complex anatomical surface of a cleft lip and palate plaster cast, and to ascertain their accuracy when positioning 3D landmarks. MATERIAL AND METHODS: A cleft lip and palate plaster cast was digitalized with the SCAN3D photo-optical scanner, the OPTIX 400S laser-optical scanner, the Somatom Sensation 64 computed tomography system and the MicroScribe MLX 3-axis articulated-arm digitizer. First, four examiners appraised by individual visual inspection the surface detail reproduction of the three non-tactile digitalization methods in comparison to the reference plaster cast. The four examiners then localized the landmarks five times at intervals of 2 weeks. This involved simply copying, or spatially tracing, the landmarks from a reference plaster cast to each model digitally reproduced by each digitalization method. Statistical analysis of the landmark distribution specific to each method was performed based on the 3D coordinates of the positioned landmarks. RESULTS: Visual evaluation of surface detail conformity assigned the photo-optical digitalization method an average score of 1.5, the highest subjectively-determined conformity (surpassing computer tomographic and laser-optical methods). The tactile scanning method revealed the lowest degree of 3D landmark scatter, 0.12 mm, and at 1.01 mm the lowest maximum 3D landmark scatter; this was followed by the computer tomographic, photo-optical and laser-optical methods (in that order). CONCLUSIONS: This study demonstrates that the landmarks' precision and reproducibility are determined by the complexity of the reference-model surface as well as the digital surface quality and individual ability of each evaluator to capture 3D spatial relationships. The differences in the 3D-landmark scatter values and lowest maximum 3D-landmark scatter between the best and the worst methods showed minor differences. The measurement results in this study reveal that it is not the method's precision but rather the complexity of the object analysis being planned that should determine which method is ultimately employed.

Enamel Demineralization during Fixed Orthodontic Treatment - Incidence and Correlation to Various Oral-hygiene Parameters.

OBJECTIVE: To investigate the incidence of white spot lesions (WSLs) around brackets and molar bands during orthodontic therapy, and establish whether a correlation to indices of dental and gingival health, fluoride application and oral hygiene could be demonstrated. PATIENTS AND METHODS: Fifty-three patients with fixed orthodontic appliances were included at random in this study at the Department of Orthodontics of Erlangen-Nuremberg University. Dental health (DMFS), plaque index, papillary bleeding index, sulcus probing depth (SPD), gingival recession (GR), clinical attachment level (as sum of SPD and GR), oral hygiene, and fluoride use were evaluated. WSLs were graded from intraoral photographs taken before and after treatment. RESULTS: 97.5% of teeth before and 73.6% after treatment were free of WSLs. Of all teeth, 24.9% developed new WSLs or a rise in their number. New or more numerous WSLs were more common in upper and lower premolars (34.4%) and front teeth (28.1%) than molars (11.8%). WSL incidence during therapy correlated with clinical attachment level, and the oral hygiene and fluoride-use scores. CONCLUSIONS: Despite improvements in materials and preventive efforts, orthodontic treatment continues to carry the considerable risk of enamel demineralization. Each patient's prophylactic efforts, including fluoride use, are of paramount importance in preventing WSLs.