9
A Synthesis Between Neuroimaging and Oral Healthcare
9.1 Assessment of Individual Differences in Brain–Stomatognathic Axis
9.1.1 Introduction
Medicine is the science of assessment, so is dentistry. Either the diagnosis of oral diseases or the evaluation of treatment efficacy depends on a valid and reliable assessment of clinical symptoms and signs. For example, a periodontist evaluates the outcome of periodontal treatment according to the degree of the periodontal recession and bone loss, which is quantified using validated tools, such as periodontal probes and X‐ray imaging. At present, most of the dental assessments applied at the chairside focus on intraoral conditions, such as tooth decay and the depth of the periodontal pocket. As discussed in Section 1.4, a heavy focus on assessing intraoral conditions reflects the dominancy of the OB (i.e. oral‐to‐behaviour) framework of dental treatment. According to the OB framework, dentists can restore patients’ oral functions as long as the structural deficits in the mouth are fixed. However, clinical and neuroimaging evidence suggests that feeding behaviour is associated with not only the stomatognathic system but also the brain, as shown in Chapters 4–6. Therefore, to fully assess individual profiles of oral structure and function, we may consider adopting an integrative assessment, which consists of both the assessment of oral conditions and the brain‐behavioural factors related to feeding behaviour. In this chapter, we propose a pragmatic framework of the integrative assessment, the brain–stomatognathic integrative assessment (BSIA). We first highlight the major aims of the BSIA and outline the components of the BSIA. Finally, recent examples of a preliminary attempt of the BSIA are discussed.
9.1.2 What Does the BSIA Aim for?
Consider the following three hypothetical figures. Patient A is 75 years old farmer, fully dentated. The patient has been working on the farm for more than 40 years and having a balanced diet. Patient B is a 57 years old stockbroker, fully dentated. The patient usually consumes just a piece of energy bar for a meal due to a busy schedule. Finally, Patient C is a 54 years old scientist and enthusiastic vegetarian, fully dentated. The patient has just been diagnosed with mild cognitive impairment (MCI) two months ago. When facing the three patients, dentists will quickly notice that they are fully dentated, with different ages, occupations, lifestyles or eating habits. However, dentists will also notice that the same oral condition (i.e. being fully dentated) does not guarantee an equal capability of feeding. For example, Patient A is older than the other two patients but may be superior to the others in physical fitness, partly due to the rural way of life. Patient B and Patient C are both office workers, which demand a great degree of mental effort. However, Patient C suffers from MCI at a younger age. The effect of such an early decline in cognitive abilities on oral health and feed behaviour should be carefully monitored in the long run. In sum, to predict the trajectory of changes in individual oral functions, one needs to consider not only the current oral status but also the brain‐behavioural factors related to feeding behaviour. Both the aspects are considered as the critical elements in the BSIA. In the following sections, we further elaborate on two major aims for the BSIA in clinical oral healthcare: prediction and classification.
9.1.2.1 Prediction of Long‐term Changes in Oral Functions
Dentists need to evaluate not only patients’ current intraoral conditions, but also how their oral conditions may change in the near future. Predicting treatment outcomes is important for periodontal, orthodontic and prosthetic therapies, which need to be followed up and evaluated for months or years. Therefore, one of the primary aims of the BSIA is to predict how individual oral function and feeding behaviour will change in the long run. According to the BSIA, the prediction should be made according to the current status of individual health, and this ‘current status’ includes not only the oral conditions but also the general physical and mental conditions of patients. The role of physical and mental conditions is highlighted especially for older people because better physical and mental conditions suggest a better ‘reserve’ that helps them to cope with the challenges caused by ageing (or age‐related diseases) (Cabeza et al. 2018).
Figure 9.1 Major aims of brain–stomatognathic integrative assessment (BSIA). (a) Prediction of long‐term changes in oral functions. Individual differences in brain reserve and cognitive reserve may play a key role in their susceptibility to diseases. The BSIA, which includes the assessment of cognitive functions of older people, would help to predict the future condition of individual oral health. (b) Classification of patients with different risks of oral diseases. The BSIA helps to classify the patients for their risk of oral diseases and the prognosis of treatment, based on a full‐scale assessment of general physical and mental status.
Individual differences in brain reserve and cognitive reserve may play a key role in their susceptibility to diseases (Barulli and Stern 2013) (Figure 9.1a). For example, Patient C in our previous case has been diagnosed with MCI. Even the patient has good oral health at present, the deficits in brain and behaviour, which may be associated with MCI, may impair the patient’s ability to maintain oral health in the future. For example, if MCI progresses into dementia, chronic periodontitis may be more likely to develop because the patient becomes gradually unable to maintain oral care. Therefore, the BSIA assesses individual brain‐behaviour factors that reflect the status of brain and cognitive reserve, which would be helpful for predicting the change of individual oral function and feeding behaviour.
9.1.2.2 Classification of Patients with Different Risks of Oral Diseases
In addition to predicting the progression of individual oral health, classifying oral health conditions between patients is another key domain in clinical practice. From the point of preventive dentistry, it is important to classify patients with a high risk of some diseases before serious symptoms develop (Figure 9.1b). As noted in the previous section, in older people, the susceptibility of functional impairment is associated with their reserve in physical and mental conditions (Barulli and Stern 2013; Cabeza et al. 2018). Therefore, one of the major aims of the BSIA is to assess these physical and mental factors, and the individual risk of having poor oral health can be estimated according to these factors. As shown in our hypothetical cases, the BSIA may help prosthodontists to classify Patient A and Patient B for their ability of food intake after installing a denture. Upon missing teeth, Patient B, who is weaker in physical fitness and eats energy bars only, may have more difficulty in maintaining normal feeding compared to Patient A, who has a better physical reserve (e.g. strength) and uses to taking a variety of foods. The focus of the BSIA also echoes recent advancements in precision medicine, which highlights that the strategies of disease prevention and treatment should take individual variability into account (Collins and Varmus 2015). In order to achieve the ‘precision’ in diagnosis and treatment, the psychosocial aspects of patient behaviour, such as the interaction between lifestyle and environment would play a key role. This is especially critical to feeding behaviour, which is highly associated with both the environmental (e.g. the way of food processing) and personal (e.g. masticatory functions) factors. According to the BSIA framework, whether or not patients can adapt themselves to environmental and bodily changes and maintain the adequate ability of feeding is a critical factor for evaluating their susceptibility to oral diseases.
9.1.3 Components of the BSIA
The BSIA framework proposed here consists of assessments for three domains (Table 9.1). (i) Assessment of the structural integrity of the stomatognathic system, which includes the ‘conventional’ items of an oral examination, such as examination of teeth, periodontal conditions, oral mucosa and the temporomandibular joint. (ii) Assessment of stomatognathic functions, which includes ‘functional tests’ that evaluate the performance of individual oral functions, including swallowing, mastication and speech. Notably, nutritional status should also be included. (iii) Assessment of the ‘reserves’ for patients to functionally adapt to oral diseases. The assessment of ‘reserves’ focuses on the brain‐behavioural factors, which reflect patients’ abilities to cope with the challenge from diseases (e.g. tooth loss or periodontitis) so that normal feeding can be maintained. The ‘reserves’ to be assessed include biological features, such as the cortical thickness of the brain and the general status of body composition (e.g. muscle mass and strength), and behavioural features, such as one’s general cognitive abilities (Barulli and Stern 2013; Cabeza et al. 2018).
Table 9.1 Proposed components of the brain–stomatognathic integrative assessment (BSIA).
| The BSIA domain | Components | Venue | |
|---|---|---|---|
| Hospital/clinic | Institution/home | ||
| Stomatognathic structure | Oral conditions (e.g. dentition and mucosal health) | Visual inspection/intraoral scanning | Recorded by an intraoral scanner/photographing |
| Stomatognathic function | Jaw conditions (e.g. mouth opening and deviation) | Visual inspection/jaw movement tracking | Recorded by video |
| Swallowing (e.g. RSST) | Visual and tactile inspection | Recorded by video | |
| Mastication (e.g. cutting ability) | Quantified using the sieve method | Recorded by photographing | |
| Mastication (e.g. mixing ability) | Quantified using the approaches of image analyses | Recorded by photographing | |
| Nutritional status | Paper‐and‐pen test | Electronic test | |
| Physical and mental reserves | Biological reserves (e.g. muscle mass) | ||
| Behavioural reserves (e.g. cognitive tests) | Paper‐and‐pen test | Electronic test | |
Notes: RSST: repetitive saliva swallowing test.
Figure 9.2 Key elements for implementing the brain–stomatognathic integrative assessment. (a) The multidisciplinary investigation can be undertaken in a hospital, where different departments are in charge of different assessments. Critically, the results of an assessment from one discipline (e.g. the score of cognitive tests from neurologists) are distributed for the use of other disciplines (e.g. dentistry). For example, the cognitive performance of older patients, as assessed by neurologists, is available for prosthodontists to evaluate if patients can adapt well to their new dentures. (b) In contrast to the hospital setting, a home‐based assessment can be facilitated by the use of teledentistry approaches and digital technology. For example, in long‐term care institutes or at home, patients can record their own oral status by photographing (via a smartphone). The image record may include a photo about their intraoral conditions (e.g. bleeding gum) or performance of oral functions (e.g. the food bolus after chewing). The images are sent to the cloud storage service for further analysis. A preliminary assessment is performed automatically by machine‐learning‐based algorithms, and critical problems (e.g. a poor oral mixing ability) are screened and forwarded to dental professionals for further evaluation.
9.1.4 How Does the BSIA Work? Some Practical Issues for Consideration
A critical challenge for the BSIA framework is its multidisciplinary nature. Because it consists of assessments from different fields, patients may need to visit different doctors for different assessments, which becomes very time‐consuming and increases patients’ financial burden. Moreover, for the residents living in long‐term care institutes, particularly older people and patients with special needs, it would be practically impossible for them to have multiple medical/dental visits just for the assessments. In the following sections, we discuss these challenges and propose potential solutions to the challenges.
9.1.4.1 Integration of Assessment Outcomes
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