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New statistical method to analyze three-dimensional landmark configurations obtained with cone-beam CT: basic features and clinical application for rapid maxillary expansion.

Gamble J, Lagravère MO, Major PW, Heo G - Korean J Radiol (2012)

Bottom Line: A method using tools from persistent homology and dimensionality reduction is presented and used to identify variability between the subjects.The analysis was in agreement with previous results using conventional methods, which found significant differences between treatment groups and the control, but no distinction between the types of treatment.This method of analysis allows entire configurations to be considered as a whole, and does not require specific inter-landmark distances or angles to be selected.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada.

ABSTRACT

Objective: To describe a statistical method of three-dimensional landmark configuration data and apply it to an orthodontic data set comparing two types of rapid maxillary expansion (RME) treatments.

Materials and methods: Landmark configurations obtained from cone beam CT scans were used to represent patients in two types (please describe what were two types) of RME groups and a control group over four time points. A method using tools from persistent homology and dimensionality reduction is presented and used to identify variability between the subjects.

Results: The analysis was in agreement with previous results using conventional methods, which found significant differences between treatment groups and the control, but no distinction between the types of treatment. Additionally, it was found that second molar eruption varied considerably between the subjects, and this has not been evaluated in previous analyses.

Conclusion: This method of analysis allows entire configurations to be considered as a whole, and does not require specific inter-landmark distances or angles to be selected. Sources of variability present themselves, without having to be individually sought after. This method is suggested as an additional tool for the analysis of landmark configuration data.

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Related in: MedlinePlus

Outline plot based on lowest, middle and highest 10% of β2 coordinates, centred on second molar region. Configuration of landmarks representing second molar is largest in mean shape corresponding to subjects with smallest coordinate values (shown in red). This means those subjects have second molars that are not fully erupted.
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Figure 12: Outline plot based on lowest, middle and highest 10% of β2 coordinates, centred on second molar region. Configuration of landmarks representing second molar is largest in mean shape corresponding to subjects with smallest coordinate values (shown in red). This means those subjects have second molars that are not fully erupted.

Mentions: One of the most interesting results was in the first β2 coordinate, where the analysis uncovered something that the researchers were not looking for. When looking at the inter-landmark distances that had strongest correlation with the first β2 coordinate (Fig. 10), and the plots of the mean shapes for the lowest, middle and highest 10% of coordinate values (Fig. 11), the landmarks most heavily involved were all related to the first and (especially) second molars. When looking specifically at the second molar region on the outline plot (Fig. 12), it can be seen that the subjects with lowest coordinate values had substantially higher root apex and pulp chamber landmarks in the second maxillary molars. Since the alveolar bone landmark is defined as being directly lateral to the root apex, the bone pertaining to this specific area is farther from the root apex compared to other teeth, resulting in the set of second molar landmarks appearing to have a much larger configuration. This type of configuration corresponds to unerupted second molars. Subjects with larger embedded coordinate values tend to have second molars that are more fully erupted (with lower root apex and pulp chamber landmarks, and alveolar bone landmarks much closer to the root apex). This coordinate displays variability between the subjects in degree of second molar eruption, but to determine whether there were any differences between the groups or over time, a repeated measures ANOVA was performed using the first β2 coordinate. Overall, time was seen to be significant (p = 0.015), but there were no significant differences between groups at any of the time points, and no time*group interaction was found. A profile plot of the first β2 coordinate for the three groups over time is shown in Figure 13. The general increasing trend over time, along with no obvious differences between the control and treatment groups, indicates that the changes seen were due to natural tooth eruption and not treatment effects.


New statistical method to analyze three-dimensional landmark configurations obtained with cone-beam CT: basic features and clinical application for rapid maxillary expansion.

Gamble J, Lagravère MO, Major PW, Heo G - Korean J Radiol (2012)

Outline plot based on lowest, middle and highest 10% of β2 coordinates, centred on second molar region. Configuration of landmarks representing second molar is largest in mean shape corresponding to subjects with smallest coordinate values (shown in red). This means those subjects have second molars that are not fully erupted.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3303895&req=5

Figure 12: Outline plot based on lowest, middle and highest 10% of β2 coordinates, centred on second molar region. Configuration of landmarks representing second molar is largest in mean shape corresponding to subjects with smallest coordinate values (shown in red). This means those subjects have second molars that are not fully erupted.
Mentions: One of the most interesting results was in the first β2 coordinate, where the analysis uncovered something that the researchers were not looking for. When looking at the inter-landmark distances that had strongest correlation with the first β2 coordinate (Fig. 10), and the plots of the mean shapes for the lowest, middle and highest 10% of coordinate values (Fig. 11), the landmarks most heavily involved were all related to the first and (especially) second molars. When looking specifically at the second molar region on the outline plot (Fig. 12), it can be seen that the subjects with lowest coordinate values had substantially higher root apex and pulp chamber landmarks in the second maxillary molars. Since the alveolar bone landmark is defined as being directly lateral to the root apex, the bone pertaining to this specific area is farther from the root apex compared to other teeth, resulting in the set of second molar landmarks appearing to have a much larger configuration. This type of configuration corresponds to unerupted second molars. Subjects with larger embedded coordinate values tend to have second molars that are more fully erupted (with lower root apex and pulp chamber landmarks, and alveolar bone landmarks much closer to the root apex). This coordinate displays variability between the subjects in degree of second molar eruption, but to determine whether there were any differences between the groups or over time, a repeated measures ANOVA was performed using the first β2 coordinate. Overall, time was seen to be significant (p = 0.015), but there were no significant differences between groups at any of the time points, and no time*group interaction was found. A profile plot of the first β2 coordinate for the three groups over time is shown in Figure 13. The general increasing trend over time, along with no obvious differences between the control and treatment groups, indicates that the changes seen were due to natural tooth eruption and not treatment effects.

Bottom Line: A method using tools from persistent homology and dimensionality reduction is presented and used to identify variability between the subjects.The analysis was in agreement with previous results using conventional methods, which found significant differences between treatment groups and the control, but no distinction between the types of treatment.This method of analysis allows entire configurations to be considered as a whole, and does not require specific inter-landmark distances or angles to be selected.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada.

ABSTRACT

Objective: To describe a statistical method of three-dimensional landmark configuration data and apply it to an orthodontic data set comparing two types of rapid maxillary expansion (RME) treatments.

Materials and methods: Landmark configurations obtained from cone beam CT scans were used to represent patients in two types (please describe what were two types) of RME groups and a control group over four time points. A method using tools from persistent homology and dimensionality reduction is presented and used to identify variability between the subjects.

Results: The analysis was in agreement with previous results using conventional methods, which found significant differences between treatment groups and the control, but no distinction between the types of treatment. Additionally, it was found that second molar eruption varied considerably between the subjects, and this has not been evaluated in previous analyses.

Conclusion: This method of analysis allows entire configurations to be considered as a whole, and does not require specific inter-landmark distances or angles to be selected. Sources of variability present themselves, without having to be individually sought after. This method is suggested as an additional tool for the analysis of landmark configuration data.

Show MeSH
Related in: MedlinePlus