# Optimization of Image Capture Distance for Facial Thermograms in Dentistry
## 1 Introduction  
Population demographics reveal that the number of elderly persons is increasing all over the world. Aging has certain implications on society on the health, economic, and psychosocial fronts [1, 2, 3]. An aging society implies that older adults will become the major stake holders in the community and will be more frequent in all interactions in everyday life. Older adults frequently present with a set of health problems that are unique to this segment in the population, collectively known as \"geriatric syndromes\" [4]. Often, they present with a multimorbid status including polypharmacy, cognitive impairment, possible physical handicaps, frailty, and most importantly, are usually dependent for their activities of daily living (ADLs) [5, 6, 7, 8]. Another pertinent demographic aspect that needs to be kept in mind is that natural teeth are being retained to an advanced age [9, 10, 11]. Although natural teeth retention in old age is beneficial, there may be certain issues because of it in this frail cohort [12, 13, 14]. Maintaining oral health is complex in elders with severe cognitive and/or physical impairments. Bad oral hygiene is a common finding in care-dependent, institutionalized older adults [15]. Low plaque control increases the oral bacterial loads, augmenting the incidence of coronal/root caries and/or periodontal problems [16, 17, 18, 19, 20, 21, 22]. Untreated caries and periodontal conditions result in oral infections causing pain, and may eventually result in tooth loss, thus compromising the Oral Health-Related Quality of Life (OHRQoL) [23, 24, 25]. It is difficult to screen for oral health problems early in cognitively impaired elders becausethey cannot communicate properly about their pain/discomfort, or they may exhibit care-resistant behavior. Frequently, the oral condition is evident only after it has progressed to a visible and/or a palpable swelling. This could be avoided if an efficient, easy, innovative tool system for screening oral conditions in non-communicative dependent frail older adults existed. This might assist in the identification of acute oral health problems appropriately and result in the provision of the necessary dental care, preventing any complications. Changes in body temperature are considered as reliable indicators for diagnosing medical conditions. Thermograms are images that capture the heat distributions in tissues, structures, and regions using an infrared camera. Medical infrared thermography (MIT) is a non-invasive test that is helpful in making medical diagnoses by detecting heat patterns. These heat patterns are converted into electrical signals and visualized as an image. MIT is employed in medicine mostly for diagnostic purposes, observing treatment progress, for research, and in veterinary medicine [26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44]. The application of thermography in dentistry has been limited and has been generally employed primarily for the diagnosis of chronic orofacial pain and temporomandibular disorders [45; 46; 47; 48; 49], for studying inferior alveolar nerve deficits [50; 51; 52; 53], and also as a complimentary tool detecting patients at risk for stroke [54]. Recently, other applications of thermography in dentistry include diagnosing burning mouth syndrome [55; 56; 57] and peripapical lesions [58], as well as the assessment of the surgical removal of retained roots [59] have been cited in the literature. MIT might be a novel innovative tool that could be of interest in the screening of oral diseases in cognitively declined elders. Its advantage lies in the fact that it is a non-invasive, painless, procedure that can be performed without contact, therefore limiting all factors that may result in precipitating noncompliant behavior from a care-resistant cognitively declined patient. Thermography has not yet been validated for the screening of oral disorders in cognitively declined individuals and no clear guidelines or methodology for this purpose have yet been defined in the literature.