ABSTRACT: A precision 3-dimensional (3D) head model can be fabricated by integrating a digital dental model into a maxillofacial 3D image. The integration requires accurate registration of 2 image modalities. The aims of this study were to determine the registration errors for implementation of laser-scanned dental images into cone-beam computed tomography (CBCT) scan data and to examine the influence of the registration area on the accuracy of registration.
The CBCT scans were obtained from 30 adults, and the maxillofacial 3D images were reconstructed. Maxillary and mandibular dental casts were taken from the same subjects and scanned with a 3D laser scanner. The laser-scanned maxillary and mandibular dentition images were incorporated into the CBCT images of each arch in 3 ways according to the registration area: only the buccal surfaces, only the lingual surfaces, and both the buccal and lingual surfaces. Surface-based registration was performed by using an iterative closest point algorithm, and its errors were evaluated by measuring the 3D Euclidean distances between the surface points on the 2 images.
The registration errors ranged from 0.27 to 0.33 mm. The mandibular arch did not show significant differences in registration errors according to the selected area for the registration. The maxillary arch, however, showed significant differences according to the registration area. When the lingual surfaces only were used for registration, the errors were greater than for the other 2 methods. The errors were least when both the buccal and lingual surfaces were used for registration.
The results of this study indicate that accuracy in the integration of laser-scanned dental images into the maxillofacial CBCT images increases when a broad area is used for registration.
American journal of orthodontics and dentofacial orthopedics: official publication of the American Association of Orthodontists, its constituent societies, and the American Board of Orthodontics 10/2011; 140(4):585-91. · 1.33 Impact Factor
ABSTRACT: To develop a hard coating for stainless surfaces based on silver (Ag)-platinum (Pt) alloys.
Ag-Pt alloys, which have high degree of biocompatibility, excellent resistance to sterilization conditions, and antibacterial properties to different bacteria, are associated with long-term antibacterial efficiency. Approximately 1.03-µm to 2.34-µm-thick coatings, as determined by scanning electron microscopy, were deposited on stainless surfaces by the simultaneous vaporization of both metals (Ag and Pt) in an inert argon atmosphere. The coating was done by physical vapor deposition. Microorganisms and eukaryotic culture cells were grown on these surfaces.
The coatings released sufficient Ag ions when immersed in phosphate-buffered saline and showed significant antimicrobial potency against Streptococcus mutans and Aggregatibacter actinomycetemcomitans strains. At the same time, human gingival fibroblast cells were not adversely affected.
Ag-Pt coatings on load-bearing orthodontic bracket surfaces can provide suitable antimicrobial activity during active orthodontic treatment.
The Angle Orthodontist 08/2011; 82(1):151-7. · 1.21 Impact Factor
ABSTRACT: To investigate the mechanisms through which mechanical stress and lipopolysaccharide treatment modulate osteoblastic differentiation in periodontal ligament cells.
Cells were treated with lipopolysaccharide and/or mechanical strain applied with a Flexercell Strain Unit. Protein expression and mRNA were analyzed by Western blotting and reverse transcription-polymerase chain reaction, respectively.
When lipopolysaccharide was co-applied with mechanical strain, the increase in the expression of bone morphogenetic protein-2, bone morphogenetic protein-7, and Runx2 mRNA seen with mechanical strain alone was restricted, but heme oxygenase-1 expression was further enhanced. Furthermore, pretreatment with an inhibitor of heme oxygenase-1 or inhibitors of p38, mitogen-activated protein kinase, JNK, phosphoinositide 3-kinases, protein kinase G, and nuclear factor kappaB restricted osteogenic differentiation induced by the application of lipopolysaccharide and mechanical strain.
These results suggest that orthodontic force-induced osteogenesis in alveolar bone is inhibited by the accompanying periodontal inflammation via the upregulation of heme oxygenase-1 expression. Thus, the heme oxygenase-1 pathway could provide a possible therapeutic strategy to improve bone formation in orthodontic treatment.
The Angle Orthodontist 07/2010; 80(4):552-9. · 1.21 Impact Factor
ABSTRACT: The purpose of this study was to investigate various factors associated with initial miniscrew stability for the prediction of the success rate.
A total of 378 miniscrews in 154 patients were examined by reviewing their charts. Potential confounding variables examined were age, sex, jaw (maxilla or mandible), placement site, tissue mobility (firm or movable tissue), type, length, and diameter of the miniscrew, and the number of previous operations. The outcome variable of this study was initial stability, defined as the stability of the miniscrew from placement to orthodontic force application. We used the generalized estimating equations method to estimate the influence of each factor on stability for the correlated outcomes of each patient.
The overall success rate was 83.6% for all miniscrews (316 of 378). After adjusting for the type of miniscrew, the relative success rate in the mandible was 0.48 times that in the maxilla but without statistical significance (crude odds ratio = 0.52, P = 0.13; adjusted odds ratio = 0.48, P = 0.09). There was no statistically significant association of any factors in this model with respect to initial stability.
These results suggest that initial stability cannot be guaranteed or predicted. For this reason, any treatment plan should consider the possibility of failure.
American journal of orthodontics and dentofacial orthopedics: official publication of the American Association of Orthodontists, its constituent societies, and the American Board of Orthodontics 09/2009; 136(2):236-42. · 1.33 Impact Factor
ABSTRACT: The purpose of this study was to investigate factors affecting lip-line canting by using musculoskeletal analyses.
Fifty-six adults with lip-line canting were selected as subjects. They were divided into 3 groups according to the changes of lip line during smiling: increasing (group I), decreasing (group D), and minimal (group M). Lip-line canting at rest was correlated to craniofacial morphology and muscular activity: Regarding craniofacial morphology, various craniofacial measurements in lateral and frontal cephalograms were used, including inclination of the tongue blade placed across both first molars. The zygomaticus major was the focus of the measurement of muscular activity affecting lip-line canting, and its activity during smiling was evaluated by using a needle electrode.
In group I, lip-line canting at rest showed a significant correlation with the right-left (R/L) difference of muscular activity, but no significant correlation with the measurements of craniofacial morphology. In group D, lip-line canting showed a positive correlation with the measurements of craniofacial morphology, such as the inclination of the tongue blade, and a negative correlation with the R/L difference of muscular activity. In group M, lip-line canting showed no significant correlation with the R/L difference of muscular activity, but a significant correlation with inclination of the tongue blade.
The results indicate that lip-line canting is caused by craniofacial morphology when the change of lip-line canting during smiling is minimal, whereas lip-line canting is affected by the R/L difference of muscular activity in addition to craniofacial morphology when the cant of lip line markedly changes during smiling. The findings suggest that the cause of lip-line canting can be identified easily by the change of canting during smiling, without complicated musculoskeletal analyses.
American journal of orthodontics and dentofacial orthopedics: official publication of the American Association of Orthodontists, its constituent societies, and the American Board of Orthodontics 10/2007; 132(3):278.e7-14. · 1.33 Impact Factor