Trial design
This is the protocol of a triple-blind randomized, controlled, parallel-group clinical trial. Two groups will be compared: subjects who will receive a Xylitol chewing gum with the polyol as the only sweetener (70% w/v), and those who will receive sugared gum containing a 23% (w/v) Maltitol. The flow-chart of the study design is displayed in figure 1.
The investigation will have an experimental period of one school year (approximately nine months in total). The study will gain the approval of all the schools’ authorities. Due to language problems and the low literacy rate of the population, parents or guardians verbal approval will be obtained for children’s participation.
The trial - Caries Prevention Xylitol in Children (CaPreXCh) - was registered with ClinicalTrial.gov (NCT04420780) and is currently in the no-recruiting phase. The Standard Protocol Items for Clinical Trials (SPIRIT) was used to guide the present protocol as detailed in online supplementary appendix (appendix 1).
The study should have be carried out from August 2021 to August 2024 in Zanskar Valley (Ladakh), but due to the persistence of the COVID-19 pandemic, it is not possible to predict the real beginning of the trial.
Participants, interventions and outcomes
Setting
The study will be conducted in the Zanskar Valley (Ladakh). School classes of subjects aged 5-14 years old will be randomly selected from a list of classes in the selected schools.
In 2018, the total schoolchildren population in the Zanskar Valley aged 5-17 years amounted to 2,407 children.
Eligibility: inclusion and exclusion criteria
The inclusion criteria will consider the following:
a) to be 5-14 years old;
b) to be in good general health;
The exclusion criteria will consider the following:
a) children who refuse to participate in the research; parents/guardians who refuse the participation of their children to the trial;
b) children who present systemic conditions or chronic diseases that require differentiated care and follow-up.
Preliminary epidemiological survey
A team of four dentists received training to diagnose caries lesions using the WHO-DMFT index for permanent teeth and the dmft for primary teeth. The team received training and inter-examiner reliability was assessed before the start of the study; sensitivity, specificity, percentage agreement and kappa statistics were recorded. Inter-examiner reliability ranged from 0.75 to 0.84 (K-Cohen) for sound teeth and from 0.82 to 0.88 for caries lesions. Intra-examiner reliability ranged from 0.82 to 0.90 for sound teeth and from 0.84 to 0.91 for caries lesions. Dental caries prevalence (dt/DT) and severity (number of lesions) was recorded for caries at the dentinal lesion level [11]. Every subject was examined using a plain mirror (Hahnenkratt, Königsbach, Germany) and the WHO CPI ballpoint probe (Asa-Dental, Milan, Italy), under standard light. No bitewing radiographs or fiber-optic trans-illumination were used.
An ad hoc prepared questionnaire assessed general health, eating habits, oral hygiene and the self-perception of oral conditions, based on previous surveys [12,13]. The height (cm) and the weight (Kg) were measured and the body mass index (BMI) was calculated. The waist circumference was also measured.
Caries was almost ubiquitarian with only 10.04% of caries-free children (dt/DT=0). Caries severity, in both primary and permanent dentitions was statistically significantly related to gender and waist circumference (p<0.01). This preliminary epidemiological survey will allow to design the intervention trial.
Interventions
After obtaining actual caries data, schools with similar numbers of schoolchildren (at least 300 subjects per school) will be selected for the preventive project. The participants will be randomized, taking as cluster the school class, allocating each class into one of the two groups of the study (Figure 1) Randomization will be performed and 2 groups will be created:
(1) the first group (Xyl) will receive sugar-free gums containing 70% (w/v) Xylitol as only sweetener;
(2) the second group (Pol) will receive reduced sugar-gums containing 23% (w/v) Maltitol.
All chewing gums will be produced and supplied by Perfetti Van Melle SpA (Lainate, Italy). All types of chewing gums will weigh 1.4 g each and will be identical in colour, shape and taste. The treatment will follow the school year calendar for a total of nine months of administration.
Clinical examination
Clinical examination will comprise an oral examination (caries index, bleeding on probing recording) and an evaluation of plaque pH fluctuation after sucrose challenge. Bleeding on probing will be used as a proxy of plaque presence, since there is a causal relationship between bleeding on probing and amount of plaque [14].
The subjects will be examined using a mouth mirror, a ball ended probe and artificial light. Caries registration will be performed with regard to the first and second primary, and first and second permanent, molars. The International Caries Detection and Assessment System (ICDAS) will be use to record caries at tooth level as initial, moderate or severe lesions, the number of filled teeth and the missing teeth for caries [15,16]. Initial caries lesion can be defined as a primary lesion, which has not reached the stage of an established lesion with cavitation (ICDAS score 1 and 2). Moderate caries lesions are defined as white or brown spot lesion with localized enamel breakdown or an underlying dentine shadow without visible dentine exposure (ICDAS score 3 and 4). Severe caries lesions are defined as distinct cavity in opaque or discoloured enamel with visible dentine (ICDAS score 5 and 6) [9,15,16]. The bleeding on probing score, as the percentage of periodontal sites bleeding, will be registered in all subjects.
Plaque-pH measurements
Interproximal-plaque pH will be evaluated using pH indicator strips [17,18], which measure a pH value in the range of 4.0–7.0 (Spezialindikator, pH range 4.0–7.0; Merck, Darmstadt, Germany). The strips determine changes in plaque pH, discriminating differences at the level of 0.2–0.5 pH units and they are easy to use. The strips will be cut into 4 pieces (approx. 2 mm in width) in order to get a strip that could be easily inserted into the interproximal space, held in situ for 10 s and its colour compared to the colour index scheme supplied by the manufacturer.
For each subject, 3 measurements will be carried out in 2 sites, between the 2nd premolar or the 2nd primary molar, if present, and the 1st molar right and left of the upper jaw. Measurements will be performed before and at 2, 5, 10, 15, and 20 min after a mouth rinse with 10% sucrose.
Calibration of the examiners
Four dentists will be trained and calibrated by a benchmark examiner. Baseline training will consist of one-day theoretical course, followed by examination of extracted teeth, plus a session of photographs. After two days of the theoretical course, a clinical training will be performed. Twenty children will be examined and re-examined after 72 h. Inter-examiner reliability with the benchmark examiner will be evaluated using fixed-effects analysis of variance and intra-examiner reproducibility assessed as the percentage of agreement using Cohen’s kappa statistic [11].
Sample size
The sample size calculation was performed based on the primary outcome of the randomized clinical trial (caries increment at enamel and dentinal level). The calculation considered the results of a 3-year period [7,8]. It was also taken into account an increment of approximately 10% of the sample due to some changes in the prevalence of the disease. Thus, estimating a level of significance of 0.05 with a power of 80% and a caries prevalence of about 90% [6], the number of participants was set to 409 subjects (Kelsey method), based on a 10% absolute difference between the groups, using a two-tailed test [19].
Treatment
The subjects will be instructed to chew a total of 6 pellets for 5 min divided into 3 intakes a day (2 in the morning, 2 after the midday meal and 2 in the afternoon) [7,8].Thus, the total daily intake of Xylitol in the Xyl group will be 5.8 g, whist, in the Pol group, the amount of administered Maltitol will be 1.9 g. Subjects will be instructed to use the chewing gum immediately after the main meals and snacks.Parents/guardians will not be requested to make changes in dietary and oral hygiene habits of their children. Tooth brushing will not be allowed for at least 1 h after the chewing gum use. All subjects will receive a fluoridated toothpaste containing 1,450 mg/g NaF and a manual toothbrush, which will be substituted every 3 months throughout the entire experimental period (3 years). All children will be instructed to brush their teeth twice a day (after breakfast and dinner) for 2 min using vertical movements [20].
In order to evaluate the success of the administration of chewing gum at school, teachers will receive one month at a time the chewing gums necessary for that period of time and will distribute the blister packs to their school class. Children will have to return their empty blister pack when receiving that for the following month. This procedure will be repeated for all experimental (chewing) period (1-year school calendar/9 months).
Outcomes
The primary outcome will be the caries increment measured both at enamel and dentinal level. The secondary outcomes will be the differences obtained comparing caries increment and the variation of plaque pH in relation to the treatment used. Furthermore, a cost- effectiveness analysis will be performed using as outcome the measurement of quality-adjusted life years (QALY) [21].
Participant timeline
The study should have be recruiting patients from August 2021 to September 2021, nevertheless, as previous described, COVID-19 doesn't allow at the moment to make predictions about it. Each subject will be enrolled for 36 months, estimating 9 months (one school year) of treatment and 27 months of follow-up. The study phases are presented in Figure 2.
Recruitment
The recruitment will occur in Zanskar Valley (Ladakh), in Padum city.
Assignment of interventions
Allocation: sequence generation and concealment mechanism
The random list will be generated using a computer program (Microsoft Excel for Mac version 16.37); a school-class-based randomization will be carried-out by G.C.in permuted blocks of 2 or 4 classes with a random variation of the blocking number and 2 groups will be created [22].
The two types of chewing gums will both be supplied in plain white containers coded as ‘green’ or ‘blue’. The code will be sealed by an independent monitor and not broken until the statistical analysis will be finalized.
Implementation
All examinations of the children enrolled will be carried-out by calibrated dentists.The clinical examination of the enrolled sample will be recorded at baseline (t0), will be repeated after 12 months since the start of the chewing gum administration period (t1), after another 12 months period (t2) and finally after further 12 months (t3) (24 months from the end of the chewing gum use). (Figure 2)
Blinding
The study will have a triple-blind design: children, parents/guardians and teachers responsible for the treatment, dentists who will evaluate the outcomes and the statistician who will analyse data will be blinded to the allocation group of the participants.
Data collection, management, and analysis
The follow-up assessments will be performed by calibrated blinded dentists. The clinical data will be recorded on electronic sheets organized on PageMaker and then transferred into Microsoft Excel Software. Data will be cleaned, deleting those revealing the participants’ identities and they will be shared in a public repository at the moment of the submission of the manuscripts.
Data on caries will be recorded considering the tooth as unit of analysis; the net caries increment for initial, moderate and severe caries level, using ICDAS (Δ-initial, Δ-moderate and Δ-severe), will be calculated in primary and permanent molars. Differences between groups in terms of caries increment will be evaluated using the nonparametric Mann–Whitney U test. Data analysis will be conducted through Kaplan-Meyer graphs to evaluate caries increment. A comparison of the methods will be carried-out with Cox regression with shared frailty. The calculation of sensitivity, specificity and accuracy will consider the results obtained with the indices and the classification of caries lesion presence of by the proposed reference standard.The cost-effectiveness ratio will also be verified, considering as effectiveness the prevention of the primary outcome. For all tests, two-tailed analyses will be used, considering a level of significance of 5%. The quality-adjusted life-year index (QALY) will be calculated to assess the value of the preventive intervention [23]. To determine QALYs, the utility value associated with a given state of health by the years lived in that state will be calculated. A year of life lived with no caries increment will be worth 1 QALY (1 year of life × 1 Utility value) [24].
Analyses will be performed using the statistical package Stata 16.0 (Stata Corp, College Station, USA).
Monitoring
Data monitoring
An independent regulation of data collection, management and analysis will be applied independently by the authors.
Harms
The procedures performed offer minimal risk to patients’ oral health. Side effects of the administration of both chewing gums will be assessed by means of a questionnaire administered to the participants’ parents after 3 months from the beginning of the experimental period and a second time at the end of the administration period.
Auditing
Data will be stored by one of the authors of the study. Data will be weekly inspected. The inconsistencies will be verified, corrected and registered.
Ethics and dissemination
Research ethics approval, Consent and Assent
No official Ethical committee is present in the area of the survey. The study proposal was already submitted to the authorities of the Zanskar Tibetan Hospital Health Care & Sowa Rigpa Research Institute and its coordinator, the Lama Zopta, for their approval. Approval will also be asked to each school involved in the survey. Due to language difficulties and the population’s low literacy rate, verbal approval will be obtained for children’s participation by their parents or guardians.
Confidentiality
Participants will be coded with identification numbers to guarantee confidentiality during data analysis. Participants’ files will be stored in a secure room in theDepartment of Restorative, Preventive and Pediatric Dentistry, University of Bern.
Access to data
Clinical trial data will be granted full access via public repository after acceptance of the manuscript.
Ancillary and post-trial care
Parents/guardians of the children participating in the trial will receive information about the children’s oral status.
Dissemination policy
A full report of the findings will be prepared and submitted in full length through national and international journals, newsletters and via website.