## 2 Materials and Methods  
### Data Source  
The PDATL questionnaire consists of nine questions assessing functional health (items one to four) and emotional/body image (items five to nine). The questionnaire uses a 5-point Likert scale to rate the items representing the frequency of the disturbance, \"never\", \"rarely\", \"sometimes\", \"often\", and \"very often\" corresponding to the numeric values 5, 4, 3, 2, and 1, respectively. It also includes the \"don't know\" option, which corresponds to the numeric value 6 [6]. The original English version of the questionnaire was adopted to the Greek language using the forward and backward translation methodology to utilize it as a documentation tool and further validate it as a summated rating scale to formulate a valuable tool in clinical settings [8]. The DASS-21 questionnaire was also employed to identify potential emotional states of depression, anxiety, and stress caused by tooth loss and denture-wearing. DASS-21 has been successfully adopted in the Greek language in a previous study [9]. Furthermore, the Distress Thermometer (DT), a visual analog scaleused by the National Comprehensive Cancer Network to screen distress in cancer patients, was applied to measure the overall impact of tooth loss and denture-wearing. DT measures distress directly on a 10-point scale ranging from \"no distress\" to \"severe distress\" and is available in Greek [10].  
Two nationwide samples were collected at baseline, and data were organized in two studies according to the study design followed in a previous research report [11]. The first sample was acquired from the Dental School at the National and Kapodistrian University of Athens (NKUA) (study 1-NKUA), and the second sample was acquired from the Dental School at the Aristotle University of Thessaloniki (AUTH) (study 2-AUTH). Calibrated interviewers (one interviewer for study 1-NKUA and two for study 2-AUTH) conducted telephone interviews following the questionnaire items. Since two calibrated examiners interviewed the participants in the AUTH data set, the Mann-Whitney non-parametric test was performed at a statistical level of \(\alpha\) = 0.05 to explore statistically significant differences between the two interviewers. The results showed that the distribution of items 1, 2, 3, 5, and 6, 7, 8 was not statistically significantly different between the two examiners, with corresponding \(p\)-values 0.81, 0.61, 0.90, 0.80, 0.40, 0.19, and 0.19, respectively. However, for items 4 and 9, the corresponding \(p\)-values were statistically significant (\(p<0.01\) and 0.04, respectively), indicating that the participants presented with a wide variation in \"discomfort/pain\" threshold levels, as well as in the \"difficult to relaxing\" perception when interviewed by the two different interviewers.  
Adult patients who responded positively to the study call from May 2021 to October 2021 and were successfully wearing dentures for at least one year were recruited for this study. The dentures were fabricated at the corresponding University clinical settings following the same fabrication procedures and construction protocol. All participants were ambulatory, living in the community, presented no mental illness, and came to the university clinical setting for rehabilitation with complete or removable dentures. NKUA and AUTH Schools of Dentistry Committees for Research Ethics approved the protocols of these studies (IRB# 455/25.01.2021 and 13/14.04.2021, respectively). All participants signed an informed consent according to the general recommendations of the Declaration of Helsinki.