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.

Does a reduction of polymerization time and bonding steps affect the bond strength of brackets?

High bond strengths are required in order to avoid bracket failure during treatment while brackets should be removable. In addition, chair time should be kept at a minimum. Therefore, the aim of this study was to investigate any differences in bracket's bond strength to enamel by reducing the polymerization time and the steps of bonding procedure. Five hundred teeth were randomly allocated into 20 groups. The groups were established considering the investigated curing units (quartz-tungsten-halogen (QTH) and light-emitting diode (LED), each with two different polymerization times) and the used bonding agents (Clearfil SE Bond, Transbond Plus, Ideal1, iBond, and Transbond XT Primer following acid etching). The brackets were debonded using a shear-peel load and used to calculate the bond strength. The location of adhesive failure was registered by using the modified adhesive remnant index (ARI). The influence of the parameters curing unit, curing time, and bonding agent as well as their interaction products on bond strength showed that the bonding agent influenced the bond strength most followed by curing time. The parameter curing unit as well as all the generated interaction products of it showed a lower impact. Regarding the ARI, the bonding agent exhibited also the highest influence. Using a LED resulted in comparable bond strengths as the QTH curing device also at shorter exposure times. Additionally, the two-component self-etching primers showed similar bond strengths compared to the acid-etching method. Chair time can be reduced by using two-component self-etching primers and LED without decrease of bond strength.

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.

Pilot study on accuracy and dimensional stability of impression materials using industrial CT technology.

OBJECTIVE: Using computed tomography, scan impressions can be saved and edited as virtual data. The aim of this study was to evaluate the parameters influencing different impression materials and impression trays and their relevance with regard to accuracy and dimensional stability. MATERIALS AND METHODS: Two alginate impressions (Zhermack Hydrogum®5 and Kaniedenta Tetrachrom®) and a polyether impression (3MEspe Impregum™) were each combined with two acrylic trays (3M Espe Position Tray™ and Profimed Opti-Tray) and CT scanned immediately after impression at the Fraunhofer Institute Development Center for X-ray Technology (EZRT) in Fürth, Germany. Each impression was digitized 10 times on the same day, 3 times after 2 days and twice after 6 days, thus determining the dimensional stability of the various materials. An acrylic model was digitized with a high-resolution µCT research scanner to be used as a reference for assessing the accuracy of the impression materials. For graphic and statistical analysis, VGStudio Max® was used. RESULTS: Both alginate impressions were less dimensionally stable than the polyether impression material. The Zhermack Hydrogum®5 alginate impression resulted in more deviation (151 µm) after 6 days than the Kaniedenta Tetrachrom® impression. The polyether scans showed a mean deviation of 73 µm. The accuracy of both alginates was similarly precise (mean value: Hydrogum®5 0.129 ± 0.021 mm, Tetrachrom® 0.137 ± 0.002 mm). The type of tray had limited influence on the results of the alginate impressions, while the accuracy of the Impregum™ impression depended on the tray combination chosen. CONCLUSION: The accuracy of the alginate impressions is sufficient for clinical use in orthodontics and produced, with correct storage, acceptable results even after 2 days. Hydrogum®5 impressions proved to be slightly more accurate than the reference material but less dimensionally stable than the Tetrachrom® impressions. The 3M Espe Position Tray™ seemed to be more practical due to a better retentive effect compared to the Opti-Tray made by Profimed.