Patient selection

This study is a prospective clinical study and the protocol was approved by the Ethics Committee of Dalian Stomatological Hospital (Ethics Review No. DLKQLL2021027). Forty patients with clinically and histopathologically diagnosed OLP were selected, who presented to the department of Periodontics and Oral Mucosa Disease of Dalian Stomatological Hospital from December 2021 to December 2022, all lesions with erosions. There were 9 male patients and 31 female patients, the duration of the disease ranged from 18 months to 54 months, and the sites of lesions were mainly located in the oral mucosa of the buccal, gingival and lingual margins.

Inclusion criteria: (1) patients with a clinical and histopathological diagnosis of OLP (according to WHO diagnostic criteria [15]); (2) patients with an erosive type of OLP according to Andreasen classifification [2]; (3)without skin lesions; (4) no local stimulation; (5) no previous treatment of OLP at least 3 months.

Exclusion criteria: (1) with epithelial dysplasia; (2) using drugs that can cause lichenoid lesions; (3) patients with systemic diseases, such as haematopoietic diseases, malignant tumours, etc.; (4) pregnant or lactating women; (5) inability to attend follow-up appointments.

Study design

The sample size calculation was performed using G*Power Software. The mean values, as well as the SD, were taken from the study performed by Diana et al. [16]. The α error was set at 5%, and the β error was set at 80%. According to G*Power, a sample of 17 patients per group will be required. In order to prevent sample drop-outs during follow-up, we planned to increased the enrollment by 20%, and at the end of the study, we retained 20 participants per group, which met the experimental requirements. All the patients agreed to join the experimental study, and we randomly divided the patients into two groups: the Er: YAG group and the TA group (Fig. 1) by drawing cards.

The Er: YAG group was treated with pulsed Er: YAG laser irradiation. The specific parameters were set as follows: energy: 50 mJ, frequency: 10HZ, water set to 0/8 − 6/8, working tip: 1.3 mm*14 mm. The treatment was performed in non-contact mode, and the erosive area of the lesion was irradiated uniformly at a distance of 3 mm from the erosive wound until fresh wounds were exposed. Sterile gauze was pressed to stop bleeding, and the irradiation was performed once a week until the erosive area disappeared completely, no more than 10 times in total.

Patients in TA group were treated with TA(Australian American Pharmaceutical Factory, China, 5 g/branch) for local application. After cleaning hands, patients were instructed to dry the saliva in the lesion area with sterile cotton swabs, and then take appropriate amount of ointment with a cotton swab or finger to evenly apply to the erosive area at one time. Patients were instructed not to eat or gargle within 30 minutes after medication, 3 times a day, until the erosion area disappeared completely, for a maximum of 30 days.

After the treatment, all patients were instructed to gargle with 2% sodium bicarbonate solution for 5 minutes three times a day until the erosion area disappeared completely. The patients of the two groups were revisited at 1 week, 2 weeks, 1 month and 3 months after treatment, and the clinical indicators of the two groups were collected and recorded. In this study, the operation of all patients was carried out by the same doctor, data collection was carried out by another doctor(Fig. 2), and statistics of data were completed by another staff member, who could not distinguish the experimental group from the control group.

Fig. 1Fig. 2

Information collection form

Clinical assessmentPain

Visual Analogue Scale(VAS) [17]was used to evaluate the pain degree of the two groups of OLP patients at the first visit and each follow-up visit. A 10-cm-long line was drawn on a blank sheet of paper and marked uniformly on the line at 1-cm intervals from 0 to 10. The left end of the line was marked with the number 0, indicating no pain, and the right end of the line was marked with the number 10, indicating severe pain. The 0–10 indicated that the degree of pain increased in turn, and the patients were asked to mark the line according to their pain status.

Lesion area

A periodontal probe was used to measure the area of erosion in centimeters(cm). The area of each lesion was calculated by measuring the distance between the furthest points adjacent to the healthy mucosa in the width and length of the lesion. If there are multiple erosive lesions in the same patient, the total area of erosive lesions should be measured separately and calculated, and then divided by the number of lesions to take the average value of the area of erosive lesions.

Clinical signs

The lesions were evaluated according to Thongprasom sign scores [18]:

Score 0 No lesion;

Score 1 Mild white striae only;

Score 2 White striae with erythematous area less than 1 cm2;

Score 3 White striae with erythematous area more than 1 cm2;

Score 4 White striae with erosive area less than 1 cm2;

Score 5 White striae with erosive area more than 1 cm2.

Function

Assess the patient’s masticatory function, swallowing function, fluid intake and altered taste sensation [19]:

Score 0: no difficulty;

Score 1: mild difficulty;

Score 2: moderate difficulty;

Score 3: severe difficulty;

Score 4: inability to perform a specific function.

Recurrence rate

To assess the recurrence rate of cured patients in both groups. The recurrence rate (%) = number of recurrences/number of cured patients x 100%.

Statistical analysis

SPSS 26.0 statistical software was used to analyse the data. The count data were expressed as n(%) by χ2 test, measurement data were expressed as (\(\bar\)± s), t-test for normal distribution, rank sum test for non-normal distribution, and the statistical significance of the difference was considered as P < 0.05.