2.1

Study design

This study was a randomized controlled clinical trial conducted on 22 children suffering from acute lymphoblastic leukemia (ALL) aged between 4 and 6 years old. They were recruited from Hematology-Oncology Department of Children’s Hospital of Damascus University. The trial was approved by the Research Ethics Committee of Faculty of Dentistry of Damascus University and was registered at the Australian New Zealand Clinical Trials Registry (ANZCTR) ( trial id: ACTRN12618001931268 ), after having Universal Trial Number (UTN) U1111-1223-9672 .

Sample size was calculated according to previous similar study using the G*Power software (v. 3.1) (Franz Faul, Universität Kiel, Germany). The significant level was set at 0.05 and statistical power of study was set at 90%. It was estimated that 20 patients were required to demonstrate an effect size (0.85). Total sample size was raised by 20% to avoid any possible dropout of participants (24 patients).

The trial was a triple blinded one in which the patients, guardians, administrators and the investigators have no idea about the preventive agent they are used.

As computer-based methods for randomization are more reliable and easier to use than manual methods. Therefore, a random allocation list was carried out using https://www.randomizer.org/ .

This triple blinded randomized controlled clinical trial was designed and conducted according to the CONSORT statement over a period of 12 months from May 2018 to May 2019.

Inclusion Criteria of participants:

• 1.

  Children with acute lymphoblastic leukemia aged between 4 and 6 years.

• 2.

  Children have not received chemotherapy or radiotherapy before sampling.

• 3.

  Children have intact oral mucosa.

Exclusion criteria of participants:

• 1.

  Known sensitivity to olive oil.

• 2.

  Presence of any gingival or oral ulceration or mucositis.

• 3.

  Taking of any antiviral or antifungal therapy and/or any other agents for oral mucositis (OM) before enrollment in the study.

2.2

Clinical procedure

A signed informed consent was obtained from one guardian of each patient before the study.

Enrolled patients were in the high-risk group of Acute Lymphoblastic Leukemia to ensure that all participants will receive the same protocol of chemotherapy. All patients who fulfilled the inclusion criteria were randomly assigned into one of two groups, 12 children each.

Group 1: olive oil taken directly from a local distributor in Syria. It was stored in dark containers at room temperature through the study phase.

Group 2: Sodium bicarbonate 5% solution as a control group.

Regardless of the preventive agent used, all participants started the application two days before the induction of chemotherapeutic drugs. According to American Academic of Pediatric Dentistry (AAPD), children were instructed to brush their teeth before each application . Topical application was done two times daily by a sterilized disposable spongeous stick ( Fig. 1 ). Preventive agents were supplied in 200 ml glass containers that were colored with some attractive drawings in order to help in blinding ( Fig. 1 ).

Spongeous sticks and glass containers used.

For each application, a new stick was immersed into one of the agents and 5 ml was applied to tongue, buccal mucosa, lips and hard palate by the help of the Hospital’s nurses who have been informed that participants are not allowed to eat or drink for 1 h after the application .

A checklist paper posted in each participant’s room and the nurses did two checks every day (one check for each application) in order to monitor adherence of participants to the intervention.

2.3

Follow-up evaluations

The follow-up was done once weekly for eight weeks (during the induction and consolidation phases of chemotherapy) by two experienced external blinded investigators (Oral Medicine specialists).

Although there are many scales to quantify the injury of oral mucosa, the most common used one is the World Health Organization (WHO) grading scale, which combines clinical features with the patient’s ability to eat or drink . This scale classify oral mucositis (OM) as shown in Table 1 .

The investigator assessed (OM) according to (WHO) oral mucositis (OM) grading scale. The follow-up was done weekly to assess if the intervention delayed (OM) appearance also.

Figs. 2–5 show (OM) grades according to (WHO) grading scale as presented in participants of the present study.

Grade (1) OM- 6 years old-male- 3rd week of chemothaerpay-olive oil group.

Grade (2) OM- 4 years old-male- 6th week of chemothaerpay-olive oil group.

Grade (3) OM- 4 years old-female- 4th week of chemotherapy-sodium bicarbonate group.

Grade (4) OM- 5 years old-male- 4th week of chemotherapy-sodium bicarbonate group.

2.4

Statistical analysis

After using Kolmogorov–Smirnov test to determine if data were molded by a normal distribution, the test showed that data are not distributed normally. Therefore, Mann-Whitney U test was used to determine if there was a statistically significant difference between olive oil group and sodium bicarbonate group.

In this study, the level of significance (p-value) was set at 0.05 and the statistical analysis was performed using the IBM SPSS software v. 23 (IBM Corp., Armonk, USA).

Intra-examiner reproducibility and inter examiner reliability for (OM) diagnosis was calculated by cohen’s kappa test. The kappa for intra-examiner agreement and inter examiner reliability was 0.90.