Association between maxillary lateral incisors' root volume and palatally displaced canines: An instrumental variables approach to the guidance theory
To evaluate association and causation between maxillary lateral incisors' (MxI2) apical root volume (ARV) and palatally displaced canines (PDC). In a retrospective cross-sectional study, computed tomography scans of 179 patients with unilateral PDC were analyzed. MxI2 root length and volume on...
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Published in | The Angle orthodontist Vol. 88; no. 6; pp. 719 - 725 |
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Main Authors | , , , , , , |
Format | Journal Article |
Language | English |
Published |
United States
Edward H. Angle Society of Orthodontists
01.11.2018
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Subjects | |
Online Access | Get full text |
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Summary: | To evaluate association and causation between maxillary lateral incisors' (MxI2) apical root volume (ARV) and palatally displaced canines (PDC).
In a retrospective cross-sectional study, computed tomography scans of 179 patients with unilateral PDC were analyzed. MxI2 root length and volume on the impaction and eruption side were measured. A mixed logit model was used to infer the association between ARV and PDC and an instrumental variables approach to interpret causality.
MxI2 root length on the impaction side was shorter in 42%, equal in 33% and longer in 25% of the patients. ARV amounted for 13.5% of total root volume on the impaction and 14.9% on the eruption side. Reduced ARV was significantly associated with the impaction side ( P < .001). The causal effect of ARV on PDC in the instrumental variable approach amounted to less than half of the association in a standard noncausal approach.
An association between PDC and reduced MxI2 root length and volume was confirmed. However, the lack of causality did not allow the researchers to draw a conclusion as to whether a reduced ARV is causing PDC or resulting from it; this should be considered in etiologic theories. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 Professor, Division of Oral Surgery, University Clinic of Dentistry, Medical University of Vienna, Vienna, Austria. Professor, Division of Radiology, University Clinic of Dentistry, Medical University of Vienna; and Department of Diagnostic Radiology, Division of Osteoradiology, General Hospital, Medical University of Vienna, Vienna, Austria. Resident, Division of Dental Student Training and Patient Care, University Clinic of Dentistry, Medical University of Vienna, Vienna, Austria. Research Fellow, Karl Donath Laboratory for Hard Tissue and Biomaterial Research, Statistics, Medical University Vienna, Vienna, Austria. Professor and Department Chair, Division of Orthodontics, University Clinic of Dentistry, Medical University of Vienna, Vienna, Austria. Resident, Division of Orthodontics, University Clinic of Dentistry, Medical University of Vienna, Vienna, Austria. |
ISSN: | 0003-3219 1945-7103 |
DOI: | 10.2319/020818-107.1 |