Research design and ethical considerations
The Medical Ethics Committee of Mazandaran University of medical sciences approved this randomized, double-blind clinical trial (Moral code: IR.MAZUMS.REC.1396.10438). All patients entered the study after receiving adequate explanations about the treatment of the disease, possible complications, the therapeutic process, and signing the consent form. The present study was registered as a retrospective study.
Participants and selection criteria
Based on the study of Babaei et al., with a mean and standard deviation of the ulcer diameter on the 7th day, 1.29 ± 0.66 in the interventional group and 0.60 ± 0.69 in the control group, a confidence level of 95%, a test power of 90%, and for the two-way test, by using the formula for comparing the two means in the G-power software. The sample size of the present study was determined to be 44 patients (22 patients in each of the interventional and control groups) [13].
Patients with recurrent aphthous stomatitis aged 20–40 years who were referred to the Oral Diseases Department of Sari dental clinic in October 2018 and had a history of minor aphthous ulcers in their lips and buccal mucosa were selected based on the inclusion criteria of the study. Patients were randomly allocated to the intervention group (N = 22) or the control group (N = 22). The head nurse of the medical center (someone other than the analyzers and evaluators) registered the participants and gave them medicine (cinnamaldehyde mucoadhesive tablets or placebo). The duration of the intervention was seven days.
The inclusion criteria of this study were patients who had minor recurrent aphthous stomatitis in their lips and buccal mucosa, no systemic diseases, no use of immunosuppressive medicines for at least one month, and no use of dentures and antibiotics. Also, pregnant women, who could not use mucoadhesives patches, patients with syndromes that aphthous-like lesions are one of their manifestations (Behcet's syndrome), smokers, and individuals who could not continue the study due to personal or social reasons, were excluded [13].
Developing the pharmaceutical product
10-mg cinnamaldehyde mucoadhesive tablets were developed with different proportions of adhesive polymers (such as Carbopol HPMC K4M) alone and mixed. The pharmaceutical drug and polymer were mixed. After complete mixing, the magnesium stearates were added, and the tablets were made using direct compression. Evaluation of changes in weight, hardness, erosion, tensile strength, and value determination were measured by spectrophotometry. The number of active compounds in the tablets after 0.5, 1, 1.5, 2, 3, and 4 h was determined by ultraviolet spectrophotometry in at least three samples.
The mucoadhesive strength of the evaluated formulations was determined using a sodium alginate gel; to do so, a spool and a string attached to the tablet were used. After the tablet touched the gel surface, the amount of force needed to separate the tablet from the gel surface was measured by pouring water into the bottom of the string container. After calculating the weight force applied to detach the tablet, the weight was multiplied by the gravity acceleration. Based on the tablet surface area, the adhesion force per area unit was determined in N/m2.
The present study is a continuation of an animal study conducted at Mazandaran University of Medical Sciences [24], in which the safety and efficacy of cinnamaldehyde were examined on Wistar rats. In the present study, cinnamaldehyde 98% was purchased from Merck–Germany. Based on the quality approvals as well as the approval of the ethics committee of Mazandaran university of medical sciences, the authors examined cinnamaldehyde patches on humans in the present study.
It should be noted that each patient was assured about the safety of the cinnamaldehyde patches before they were enrolled in the present study and was informed about the previous study that was performed on rats [24]. After the completion of the clinical trial, none of the patients showed any particular side effects or allergies to the cinnamaldehyde patches.
Study protocol
The examiner and the patients were blinded. All patients in the two groups were blinded and asked to refer to the clinic within the first 24 h after the appearance of the aphthous lesions. This period was considered as the baseline (day zero). In the first group, patients were taught how to use three mucoadhesive patches and were asked to use them daily in the morning, afternoon, and night. Each individual was asked to avoid eating and drinking for 30 min after using the patches. In the control group, the same was done with a placebo. Patients were clinically examined on days 0, 3, 5, and 7 to evaluate the pain intensity and healing of the ulcers. The examiner was blinded and was unaware of the medication each patient was receiving. Metal calibers were used to determine the diameter of the ulcers and the surrounding inflammatory zone (by millimeters) [13]. Patients were also asked to select the pain intensity according to the Visual Analogue Scale (VAS) criteria. This scale consists of a 10-cm line in which zero indicates no pain and ten indicates the maximum pain. The patient marked a point representing their pain on this scale and used the numeral scale (e.g., from one to ten) to estimate the pain intensity. Patients were asked to report the VAS 3 times a day after each meal. Usually, pain stimulation in the oral cavity reaches its maximum after mechanical and chemical stimulation. Eating and chewing stimulate the oral mucosa by mechanical stimuli caused by the presence of food particles as well as chemical stimuli derived from the presence of acids, spices, and salt in the food. Therefore, the measurement of pain during meals can accurately reflect the overall pain of the oral mucosa. Patients with a pain score of 1 and ulcer size of less than 1 mm were considered to be healed [25].
Data analysis
Data analysis was performed using the SPSS-20 statistical software; notable that the analyzer was blinded. Variables were described by percentage, mean and standard deviation. Fisher's exact test was used to compare the gender variable between the two groups. The mean age was compared between the two groups using an independent sample t-test, and quantitative variables of normal distribution were evaluated using the Shapiro Wilk test. The Friedman test was used to examine the time intervals in the two groups, and the Mann–Whitney test was used to compare the two groups at different measurement times. The Generalized Estimation Equation (GEE) test was used to compare the time trend of changes in the inflammatory zone diameter and pain intensity between the two groups.