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Demetrios J Halazonetis

Publications and source records attributed to Demetrios J Halazonetis.

15 recordsLinked to original sources
PubMed2005

The spontaneous smile in dynamic motion.

INTRODUCTION: The purpose of this study was to record and analyze the dynamic nature of spontaneous smiles. METHODS: Fifteen children (9 girls and 6 boys; average age, 10.5 years) were filmed with a hidden camera while they watched a funny cartoon video. Spontaneous smiles were recorded, and the video frames were digitized. Time-graphs of the measurements were constructed, and plots of the movement of the mouth points were drawn. RESULTS: Facial measurements showed that the upper lip elevated by 28%, relative to the rest position, and the mouth increased in width by 27%. The corners of the mouth moved laterally and superiorly at an angle of approximately 47 degrees . Time analysis showed that the smiles developed in a staged fashion. The first stage (attack phase) was the shortest, lasting an average 500 ms. It was followed by a sustaining phase that included waxing and waning. The smile ended with a fade-out stage. The second and third stages were of variable duration and could be interrupted by the attack phase of a subsequent smile. CONCLUSIONS: The dynamics of the spontaneous smile and the findings of this study raise concerns about the validity of a single photographic capture for esthetic assessment and treatment planning.

Adolescent↗
PubMed2005

Condyle and fossa shape in Class II and Class III skeletal patterns: a morphometric tomographic study.

INTRODUCTION: The purpose of this investigation was to study the shapes of the condyle and the glenoid fossa in patients with Class II Division 1, Class II Division 2, and Class III malocclusions. METHODS: Axially corrected tomograms of 189 patients were used (109 Class II Division 1, 47 Class II Division 2, and 33 Class III). Five points on the condyle and 7 on the outline of the fossa were digitized. Size was assessed by the centroid size of each structure, and measurements of shape were made by principal component analysis of the Procrustes residuals. RESULTS AND CONCLUSIONS: Inspection of the principal components of shape showed that shape variability of the condyle was mainly related to inclination of the condylar head; shape variability of the fossa was related to inclination of the eminence and fossa height. Centroid size was correlated to age in the Class III group only. Condylar and fossa shapes were found to be different between the groups; the Class III group had a more elongated and anteriorly inclined condylar head and a wider and shallower fossa. In the Class III group, the condyle was closer to the roof of the fossa. The 2 Class II divisions differed only in the position of the condyle in the fossa, which was situated more anteriorly in the Class II Division 1 group.

Adolescent↗
PubMed2005

From 2-dimensional cephalograms to 3-dimensional computed tomography scans.

Computed tomography is entering the orthodontic specialty as a mainstream diagnostic modality. Radiation exposure and cost have decreased significantly, and the diagnostic value is very high compared with traditional radiographic options. However, 3-dimensional data present new challenges and need a different approach from traditional viewing of static images to make the most of the available possibilities. Advances in computer hardware and software now enable interactive display of the data on personal computers, with the ability to selectively view soft or hard tissues from any angle. Transfer functions are used to apply transparency and color. Cephalometric measurements can be taken by digitizing points in 3-dimensional coordinates. Application of 3-dimensional data is expected to increase significantly soon and might eventually replace many conventional orthodontic records that are in use today.

Algorithms↗
PubMed2004

Morphometrics for cephalometric diagnosis.

This article demonstrates morphometric methods by applying them to an orthodontic sample. A total of 150 pretreatment cephalograms of consecutive patients (84 female, 66 male) were traced and digitized. Fifteen points were used for the analysis. The tracings were superimposed by the Procrustes method, and shape variability was assessed by principal component analysis. Approximately 70% of the total sample variability was incorporated in the first 5 principal components. The most significant principal component, accounting for 29% of shape variability, was the divergence of skeletal pattern; the second principal component, accounting for 20% of shape variability, was the anteroposterior maxillary relationship. It is recommended that Procrustes superimposition and principal component analysis be incorporated into routine cephalometric analysis for more valid and comprehensive shape assessment.

Cephalometry↗
PubMed2002

Estimated natural head position and facial morphology.

Estimated natural head position, or natural head orientation (NHO), has been proposed as a preferred reference position for assessing facial morphology. However, because this position is subjectively defined by the orthodontist, it could be influenced by facial form, which would be an undesirable attribute. The aim of this study was to assess whether NHO is influenced by facial morphology. Lateral photographs of 14 patients were used. Each was warped to produce 2 new images, with the chin positioned backwards or forwards relative to the original (+/-2 degrees change of the soft tissue N-Pg line). All 42 images were placed in circular frames and shown to 7 experienced orthodontists, who were asked to orient them to NHO. Image orientation between the 3 chin positions was measured and compared. The results showed that NHO depended on chin position. Images with protrusive chins were positioned with the head rotated more downwards (Frankfort plane 3.10 degrees relative to horizontal) than were images with retrusive chins (Frankfort plane 4.98 degrees ). The difference in head orientation measurements was half of the difference in chin position (1.88 degrees for a chin change of 4 degrees ). These findings call into question the validity of NHO for diagnosis because it depends on the same factor it aims to assess. Use of NHO would result in underestimating the true skeletal relationships.

Adolescent↗