## 4 Diagnosis of Dentin Hypersensitivity
### Assessment and Recording of Dentin Hypersensitivity  
When addressing DH, it is often necessary to document the severity of symptoms or the effectiveness of implemented treatments. The assessment of DH in clinical studies should always be regarded as subjective and reliant on the individual and distinct responses of each patient to various stimuli [36; 44]. The perception of pain stemming from a stimulus on the exposed dentin surface is influenced by a range of different factors unique to each patient, encompassing psychological, cultural, emotional, and socio-economic elements [36].  
Patients' responses tend to be more pronounced when exposed to sudden stimuli in contrast to anticipated ones. Furthermore, it is acknowledged that interactions with healthcare providers can trigger psychological effects in patients, potentially giving rise to phenomena such as the placebo, nocebo, and Hawthorne effects [36; 45; 46]. In particular, the placebo effect constitutes a multifaceted psychophysiological reaction caused by the administration of a sham treatment. Essentially, patients experience an improvement in their condition after interacting with their dentist and expecting positive outcomes following medical advice contributes to symptom amelioration [45; 47]. Conversely, the nocebo effect, which operates through negative expectations, can induce adverse side effects even within placebo treatments, shifting symptoms from positive to negative [48]. Currently, it is believed that, under normal circumstances, individuals are subject to varying degrees of susceptibility to the placebo effect, making it challenging to overlook or categorize those who respond positively.  
The Hawthorne effect represents another psychological facet in the patient-dentist interaction, wherein individuals alter or enhance aspects of their behavior in response to the perception of being observed [46]. These factors may provide insight into the scarcity of robust evidence or the presence of contradictory outcomes in clinical studies concerning the efficacy of different treatment options [49]. The potential for quantitatively assessing patients' sensitivity to external stimuli on the exposed dentin surface could offer a more precise determination of the problem's extent and assist in evaluating various treatment approaches in a more objective and dependable manner.  
Two distinct approaches for evaluating dentin sensitivity have been outlined. Firstly, sensitivity can be assessed based on the strength of the stimulus required to induce pain (stimulus-based assessment), and secondly, a subjective evaluation of the pain provoked by a specified stimulus is conducted (response-based assessment) [3; 50]. Response-based methods gauge the immediacy of pain following the application of a consistent, dependable, and repeatable stimulus. Normal stimuli such as probe pressure (tactile stimulus), cold, and evaporative air are frequently employed due to their easy control and reproducibility [51; 52]. Given that dentin sensitivity can vary in response to different stimuli, it is recommended to employ a minimum of two distinct stimuli during the examination to validate the outcome [3; 53]. Among these stimuli, probe (tactile) stimulation has been observed to be less effective than thermal and drying stimuli. When applying various stimuli, it is advisable to commence with the least intense stimulus initially [44; 50].