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Determining Reliability and Validity of the Modified Gingival Index when Reviewed in an Image-based Survey Format
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- Author / Creator
- Heron, Samantha
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Gingivitis affects 50-90% of the Canadian adult population, with the accumulation of dental plaque being the most common cause. Clinically, gingivitis is characterized by red, swollen gums, bleeding upon stimulation, and a loss of stippled, knife-edged margins. Gingivitis will not necessarily develop into periodontal disease, but gingivitis always precedes periodontitis. Gingivitis can be diagnosed by inserting an instrument into the gingival sulcus to measure a bleeding response, performing tissue biopsies or by analyzing gingival crevicular fluid, however, in clinical research, the Modified Gingival Index (MGI) is a commonly used method for assessing the gingiva without performing invasive periodontal probing. The MGI is used to determine the inflammatory status of the gingiva by performing only a visual examination. A score of zero to four is provided for each tooth based on the physical appearance of the gingival surfaces and ranges from healthy (zero) to severe gingivitis (four). Although the MGI classification is a frequently used measure for diagnosing gingival disease, it is unclear whether the index is reliable and valid for research use when the gingiva of subjects is provided via an image-based survey format.
A total of 72 participants were recruited from the general dental hygiene clinic as well as the dental and dental hygiene student population of the School of Dentistry in the Kaye Edmonton Clinic at the University of Alberta. Anterior intraoral photographs of the subjects' teeth and gingiva were taken and used to create an online image-based survey administered through REDCap. Dentists, dental hygienists, and non-clinician researchers were asked to evaluate each photo by assigning a score based on the MGI definitions.
A cumulative logistic mixed-effects regression model was used to determine if one job type was more or less likely to assign a higher or lower MGI score to each subject. McFadden's pseudo-R2 was calculated from the regression model to establish the effect of job type and years of practice in assigning MGI scores. Krippendorff's alpha was used to determine reliability within- and across-groups of reviewers, and the ordinal alpha measured internal consistency of the index.
Overall, the results of this study indicate there is no consistency or agreement among dentists, dental hygienists, and non-clinical researchers when classifying the health of the gingiva based on the MGI criteria. This suggests that the MGI may not be a reliable or valid research instrument when subjects are presented in an image-based survey. The lack of agreement among reviewers suggests that the visual component of classifying gingival inflammation based on colour, contour, consistency, and texture may not be sufficient as when a bleeding component is included. Furthermore, the classification of severity of gingival inflammation may not be appropriate as the reviewers did not agree in assigning mild, moderate, or severe scores. -
- Subjects / Keywords
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- Graduation date
- Fall 2019
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- Type of Item
- Thesis
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- Degree
- Master of Science
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- License
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.