ABSTRACT
The combination of digital image correlation (DIC) and scanning electron microscopy (SEM) enables to extract high resolution full field displacement data, based on the high spatial resolution of SEM and the sub-pixel accuracy of DIC. However, SEM images may exhibit a considerable amount of imaging artifacts, which may seriously compromise the accuracy of the displacements and strains measured from these images. The current study proposes a unified general framework to correct for the three dominant types of SEM artifacts, i.e. spatial distortion, drift distortion and scan line shifts. The artifact fields are measured alongside the mechanical deformations to minimize the artifact induced errors in the latter. To this purpose, Integrated DIC (IDIC) is extended with a series of hierarchical mapping functions that describe the interaction of the imaging process with the mechanics. A new IDIC formulation based on these mapping functions is derived and the potential of the framework is tested by a number of virtual experiments. The effect of noise in the images and different regularization options for the artifact fields are studied. The error in the mechanical displacement fields measured for noise levels up to 5% is within the usual DIC accuracy range for all the cases studied, while it is more than 4 pixels if artifacts are ignored. A validation on real SEM images at three different magnifications confirms that all three distortion fields are accurately captured. The results of all virtual and real experiments demonstrate the accuracy of the methodology proposed, as well as its robustness in terms of convergence.
ABSTRACT
This randomized controlled trial aimed to evaluate the duration and outcome quality of orthodontic treatment with a customized fixed appliance system versus a noncustomized system. Patients ( n = 180) were randomized and received orthodontic treatment with the Insignia customized orthodontic system or the Damon Q noncustomized orthodontic system. The allocation sequence was concealed using identical, sequentially numbered, opaque, sealed envelopes. Patients with nonextraction treatment plans were treated by 2 equally experienced orthodontists. Pretreatment and posttreatment plaster casts were made for each patient, and the models were rated using the Peer Assessment Rating (PAR) score. Planning time, treatment duration, and numbers of loose brackets, visits, and complaints were recorded. The examined null hypothesis was that the customized appliance system was not associated with significantly ( P < 0.05) shorter treatment duration compared to a noncustomized appliance. We analyzed 85 patients in the customized group and 89 in the noncustomized group. Treatment duration was 1.29 ± 0.35 y in the customized group and 1.24 ± 0.37 y in the noncustomized group. In the customized group, the PAR score was 23.32 ± 9.15 pretreatment and 5.38 ± 3.75 posttreatment. In the noncustomized group, the PAR score was 21.84 ± 7.95 pretreatment and 5.93 ± 3.58 posttreatment. None of these outcomes significantly differed between groups. On the other hand, the orthodontist had a significant effect on treatment duration, quality of treatment outcome, and number of visits ( P < 0.05). A higher PAR score pretreatment was associated with increased treatment duration, posttreatment PAR, and number of visits ( P < 0.05). Compared to the noncustomized group, the customized group had more loose brackets, a longer planning time, and more complaints ( P < 0.05). The customized orthodontic system was not associated with significantly reduced treatment duration, and treatment quality was comparable between the 2 systems ( ClinicalTrials.gov : NCT01268852).
