Patients with dental anxiety only develop anxiety and fear about dental treatments. Patients with severe dental anxiety have difficulty cooperating with dental treatments, and can only complete dental treatments through general anesthesia, or even abandon treatments. Dexmedetomidine is a potent, highly selective α2-adrenoceptor agonist, which provides good anxiolytic, sedative and analgesic effects and is commonly used in anesthesiology and intensive care medicine departments, routinely intravenously. In recent years, intranasal administration of dexmedetomidine has also been reported for pediatric dentistry and adult alveolar surgery, showing good sedative and analgesic effects. However, these studies have problems such as single surgical types, small sample size, and few indicators analyzed. Therefore, the evaluation of intranasal administration of dexmedetomidine is still not comprehensive enough. Besides, the anxiolytic effect of dexmedetomidine for dental anxiety has not been reported yet. This project plans to carry out a randomized, double-blinded, placebo-controlled, two-stage clinical trial. We will firstly explore a reasonable dose, and secondly verify it with placebo as the control. We plan to measure the object indicators, including the NTI value, plasma cortisol, interleukin-6, blood pressure and heart rate, and to assess the subjective indicators using scales and questionnaires, thus comprehensively evaluating the effectiveness, safety and feasibility of the anxiolytic effect of intranasal dexmedetomidine for severe dental anxious patients, and preliminary exploring its mechanism additionally. We intend to help severe dental anxious patients completing dental treatments.

Inclusion Criteria:

1. Fully understand the purpose and significance of this trial, voluntarily participate in this clinical trial, and voluntarily sign an informed consent form;
2. Age 18 to 65 years old, regardless of gender;
3. Diagnosed by a dentist and needs dental treatment;
4. Can be immediately arranged for dental treatment after being evaluated by the clinician as having no contraindications;
5. Graded as severe dental anxious (obtained using the MDAS modified dental anxiety scale);
6. After controlling the symptoms of infection if with symptoms of acute/systemic infection, and can be arranged immediately after meeting the indications for dental treatments;
7. BMI is 18.5 kg/m2~25 kg/m2;
8. After resting for 30 min, the SBP < 180 mmHg, the DBP < 110 mmHg, and the 60≤HR ≤ 120 bpm;
9. For women who have not been menopausal or who have been under 1 year of menopause, a pregnancy test (blood or urine pregnancy test) should be performed during the screening period, and then the study and administration should be carried out after the pregnancy test is negative during the screening period.

Exclusion Criteria:

1. Subjects who are not considered by the researcher to be suitable for nasal drops (such as severe rhinitis, nasal malformations, etc.);
2. Subjects with a history of severe arrhythmias such as type II or above AV block or a history of cardiac insufficiency;
3. Subjects with a history of myocardial infarction or unstable angina in the 6 months before the screening period;
4. Subjects with a history of ischemic stroke or transient ischemic attack (TIA);
5. Subjects with poor blood pressure control after drug therapy (hypertension: SBP≥180 mmHg, and/or DBP≥110 mmHg, or hypotension: SBP <90 mmHg and/or DBP≤50 mmHg);
6. Subjects with psychiatric disorders (such as schizophrenia, anxiety, depression, etc.) and cognitive dysfunction, or have a history of epilepsy, or previous abuse of psychotropic drugs and narcotic drugs;
7. Subjects with a history of difficult airway disease or possibility, such as obstructive sleep apnea syndrome;
8. Randomly, within 1 year of random, a history of drug abuse, a history of drug abuse and a history of alcohol abuse, i.e., a subject who drank more than 2 units of alcohol per day on average (1 unit = 360 ml of beer or 45 ml of liquor or 150 ml of wine with an alcohol content of 40%);
9. Subjects who received selective alpha2-adrenoceptor agonists or antagonists within 14 days of randomization;
10. Those who are allergic to dexmedetomidine hydrochloride or items used in stomatology;
11. Pregnant or nursing women;
12. Those who have a birth plan within 30 days before the screening period and half a year after the end of the trial, and are unwilling or unable to take effective contraception measures;
13. Other circumstances in which the investigator determines that the subject is not suitable to participate in this study.

All of the data will be shared after publication of the paper of this trial

The data will become available after the publication of the paper about this trial

IPD will be accessed by the Data and Safety Monitoring Committee and all researchers in related fields