# Modified Gingival Index (MGI) Classification Using Dental Selfies
## 2 Materials and Methods  
### Dataset  
The data used in this research study was collected between September 2019 and May 2020 at the Department of Community Dentistry Faculty of Dental Medicine, The Hebrew University--Hadassah School of Dental Medicine. The protocol was approved by Hadassah research ethics committee (IRB, 0212-18-HMO), and written informed consent was obtained from all participants. There was no compensation for participating. The participants were using the application developed by us, the iGAM app which is currently available on the Google Play store ([[https://play.google.com/store/apps/details?id=com.igmpd.igam](https://play.google.com/store/apps/details?id=com.igmpd.igam)]([https://play.google.com/store/apps/details?id=com.igmpd.igam](https://play.google.com/store/apps/details?id=com.igmpd.igam))). The application development process was described in a recently published article [21]. Following initial registration, the patient logs in, personal patient data (such as age, gender, etc.) is collected. In order to characterize the patient's interest in the app, the patient is prompted to fill out a questionnaire about dental knowledge and behaviors, including oral hygiene habits. Participants were instructed to photograph themselves once a week for 8 weeks. Nevertheless, not everyone completed the full experiment, as will be described shortly. In the app, the flash was set up to turn on automatically and to simultaneously initiate a 10-s timer, giving the participant time to position the camera. A sound indicated that the phone had started taking photographs, and another sound signaled the end of the photographing time. Seventy-five participants took part in this group study. The majority were male (74.7%), native to Israel (97.3%), Jewish (100%), \"single\" (50.7%), nonsmoker (74.7%), and did not take medications (85.3%), 41.3% indicated their occupation as \"student\" and 28% were \"secular\".  
Regarding the inclusion and exclusion criteria, the inclusion criteria are as follows: the subject must be 18 years or older, must understand Hebrew, and have a smartphone with the Android operating system. Exclusion criteria: as outlined [21] the app had several initial versions, and tested with different mouth openers. Once the app was stabilized, and the second generation \"optimal\" mouth opener was used [21], there were no other exclusion criteria, any subject who successfully used the app and uploaded a photo, their dental selfie was included in the dataset.  
We ended up with 44 participants. In total we collected 190 dental selfies. The distribution of participants by length of participation is shown in Figure 2. A total of 11 participated for one week, four for two weeks, eight participated for six weeks, and five participants completed all eight weeks of the trial period.  
Figure 2: The distribution of the 190 dental selfies—shows the number of participants per length of participation in our pilot study (number of weekly selfies sent using the app).  
For each of the 190 dental selfies, a dentist marked bounding boxes (see Figure 3) around the eight front-most teeth (see Figure 4 for the notation)--the four central incisors (upper right: 11, upper left: 21, lower left: 31 and lower right: 41) and four lateral incisors (upper right: 12, upper left: 22, lower left: 32 and lower right: 42)--and each bound area was cropped as a separate image. Producing a total dataset of 1520 single tooth (and surrounding gum) images.  
Next, Figures 5 and 6 illustrate the distribution of MGI scores--overall, and per tooth position, indicating healthy, mild or severe inflammation, as was determined by a single board-certified examiner dentist that was blind to the participants.  
Figure 4: The ISO 3950 Teeth notation system.  
Figure 3: A dental selfie (out of the 190 collected). The bounding box marked by the dentist around the upper right lateral incisor (tooth #12) shown outlined in black. (One of eight bounding boxes used to crop single tooth images from the selfie).