Sample
Three- and five-year-old children attending pre-school were invited to participate in this prospective cohort study designed using a multi-stage cluster sampling technique. Representations of both locality of residence and school type were considered in order to incorporate all socio-economic bands.
The three-year-old cohort, identified as the (3 – 5) group, was re-examined two years later while the five-year-old cohort, identified as the (5 – 8) group was re-examined three years after the initial screening visit. The difference in the screening time was due to the restricted number of examiners and scribes involved in this project.
The selection criteria included:
Inclusion Criteria:those children resident on the Islands all their lives and who turned three or five years old in that calendar year.
Exclusion Criteria:Children exhibiting enamel defects associated with loss of tooth tissue. Children who did not return a signed consent form were also excluded.
Ethical Approval
A detailed research protocol was prepared abiding to all the requirements as stated in the World Medical Association Declaration of Helsinki – Ethical Principles for Medical Research Involving Human Subjects, WMA General Assembly, 2008. The protocol was submitted for consideration, guidance and approval to the Faculty of Dental Surgery Research Ethics Committee and subsequently to the University of Malta Research Ethics Committee (UREC MD 31/2013). The study was also registered with the Local Data Protection Officer.
Approval was also sought from the relevant authorities in the three school streams. (State schools, Church schools and Independent schools). Additional signed parental consent was also sought after having distributed information sheets to all parents/legal guardians at least three weeks prior to the school visit.
Calibration of examiners
Training and calibration of examiners and scribes in the use of the Basic Erosive Wear Examination (BEWE) Index(35)and in periodontal diagnosis and charting was carried out by internationally renowned researchers in the fields. The examiners included four dental surgeons; the scribes were two dental hygienists. Training and calibration programs organised by the Faculty of Dental Surgery, University of Malta, included seminars, discussions, simulation lab sessions and clinical sessions over several days. Training in the use of The International Caries Detection and Assessment System (ICDAS) was carried out individually via the eLearning programme portal provided by the ICDAS Foundation(36). Further calibration sessions were carried out involving duplication of examination of clinical cases in order to assess intra- and inter-examiner reliability.
Clinical Examination
Examinations were held on school premises during school hours. A portable dental unit (D-13600 Denta-Trolley, BPR Swiss-Switzerland) provided compressed air. A Daray X200LED mobile examination light provided a standardised source of light delivering 8,000 lux at 1m and 32,000 lux at 0.5m (Daray Lighting Ltd., Leighton Buzzard, Luton, UK). Individually wrapped sterile packs containing a front surface reflecting mirror and a ball-ended WHO CPITN-E (Community Periodontal Index of Treatment Needs) probe were available for each participant. Data were recorded by trained scribes onto number coded data input sheets. The children were examined in a supine position by examiners wearing personal protective equipment. Repeat examinations of two randomly selected children were carried out at each school visit to check intra-examiner reproducibility. Participants were screened for erosive tooth wear and dental caries. They were also charted for the presence of plaque, calculus, dental traumatic injuries and soft tissue lesions. Each child needing treatment was given a referral note.
Indices.
Erosive tooth wear - The Basic Erosive Wear Examination (BEWE) Index was used to score an index value per participant (Bartlett et al. 2008). The BEWE Index examines all surfaces of all teeth (excluding third molars) and records the highest score (0-3) for each sextant which scores then contribute to the individual’s cumulative score (0 – 18). For the purpose of this study, participants were assigned to an erosion experience category according score: BEWE 1 – scores 0 - 2, no risk; BEWE 2 – scores 3 - 8, low risk; BEWE 3 – scores 9 - 18, medium - high risk.
Outcome measurement was always blinded to or independent of any knowledge of the predictors under consideration.
Dental Caries – The International Caries Assessment and Detection System (ICDAS)(36)was utilised as a system for detecting and classifying carious lesions present.
The BASCD Plaque Score employed was that according to the BASCD (British Association for the study of Community Dentistry)(37)criteria. Scores for each tooth were as follows: 0 – no plaque present, 1 – little plaque visible on probing, 2 – substantial amount of plaque visible to the naked eye, 9 – no assessment possible. Calculus was scored as either 0 – no calculus present or 1 – calculus present.
Salivary Parameter Testing
Salivary testing was carried out using the Saliva-Check BUFFER™ kit (GC Corp., USA). This test assessed the participants’ salivary flow, pH and buffering capacity. Provided manufacturer instructions were followed. Samples were taken during the above-described clinical examination. Unstimulated salivary flow rate was measured by everting the lower lip, blotting it dry with tissue and observing the mucosa under good light. The timing for the formation of droplets of saliva to appear at the orifices of the minor salivary glands was noted. If droplets took less than 60 seconds to appear, salivary flow was recorded as ‘normal’. If droplets took more than 60 seconds to form salivary flow was recorded as ‘slow’. Buffering capacity was assessed by removing a Buffer test strip from the foil packaging and placing on an absorbent tissue with its test side up. Using the pipette provided sufficient saliva was drawn from the patient’s mouth and a drop of saliva was dispensed on each of the three test pads. The strip was immediately turned 90ºonto its side to allow excess saliva to flow onto the absorbent tissue. This was done to prevent excess saliva from swelling on the test pad and possible affecting the accuracy of the result. At the end of the clinical examination the test pad was evaluated and the buffering capacity result was calculated by referring to the conversion table provided, and adding up and the points according to the colour change of each pad. A combined total score of 0 – 5 was recorded as a Very Low buffering capacity, a score of 6 – 9 was recorded as a Low buffering capacity and a score of 10 – 12 was recorded as a Normal/High buffering capacity. Salivary pH was measured by dispensing a drop of saliva on a pH test strip provided and allowing it to rest for 10 seconds. The colour change of the strip was compared with the testing chart made available and a reading was taken as either highly acidic (pH 5.0 – 5.8), moderately acidic (pH 6.0 – 6.6) or healthy saliva (pH 6.8 – 7.8).
Height and Weight Measurements – Body Mass Index (BMI)
Anthropometric measurements were carried out and recorded using a portable stadiometer (SECA 214 portable Stadiometer) and portable digital scales (SECA 875 flat scales). Children were asked to remove their school shoes and were measured wearing their uniforms. Participants were instructed to hold the Frankfort plane parallel to the ground during measurements. BMI was then calculated as weight divided by the square of the height (Kg/m2). The calculated BMI values were divided into four categories (Thinness, Normal, Overweight and Obesity) according to the International Obesity Task Force (IOTF) cut-off values.(38)Cut-off points at the mid-year value (3.5 years and 5.5 years) were utilized as recommended when carrying out epidemiological studies including age groups of one year width(38).
Parent Questionnaires
A piloted and sequentially refined questionnaire in both English and Maltese was distributed to parents/legal guardians of all participants. Instructions were clear and an example was provided. A combination of both closed and open-ended questions were included. The response category ‘don’t know’ was included where appropriate. Responses for closed questions were converted to numerical format and responses to open-ended questions were summarised into categories. This allowed for entry into IBM SPSS and statistical analysis.
The questionnaire was designed to enquire about predictors for erosive wear as identified by literature review. These included questions about sociodemographic factors, oral health habits, dietary habits and general health factors. Sociodemographic variables included gender, age, locality and duration of residence, parental educational level (divided into 4 levels: Primary School level, Secondary School level, Post-Secondary School level and Tertiary level), and parental job type (4 subdivisions: Professional, Clerical/Business, Manual labourer and Unemployed). Oral hygiene related questions enquired about the frequency (never, less than once a day, once a day, two or more times a day) and timing (before breakfast, after breakfast, after lunch, before bed and other times) and technique of brushing (horizontal, vertical, circular or a combination of all), the type of brush (manual or electric) used, type of toothpaste (adult with fluoride, adult without fluoride, children’s with fluoride, children’s without fluoride, whitening toothpaste) and amount of toothpaste used (smear, smaller than pea-sized, pea-sized full length of toothbrush head or over flowing) and whether the child rinses after brushing. Dietary habits related questions included questions related to the drink consumed most on a daily basis and after sports activities and at night, the temperature of the drink, swallowing habits (swishing, retaining in the mouth, none), timing of drinking (sipping over a period of time, in one episode) and the use of a straw. Parents were then presented with a chart listing twenty-eight food and drink items and were asked to select the frequency of consumption of their child for each item on a scale of ‘more than four times a day’, 2 – 4 times a day’, ‘once a day’, ‘1 – 2 times a week’, ‘less than once a week’ and ‘never’. General health related questions enquired about use of medications, asthma and its treatment, hospitalisation, gastro-oesophageal reflux disease, history and duration of vomiting and symptoms of dry mouth. The distributed questionnaires were number coded per participant to match the data input forms. An identical copy of the questionnaire was redistributed to the same cohorts at the follow-up visit.
Data Analysis
Tests for normality were run for all the variables. The data collected was both of a continuous and categorical nature. Descriptive statistics were carried out in order to describe the characteristics of the sample including Average Cumulative scores, Percentage scores of BEWE experience categories and incidence figures. The Chi-square test for independence was used to explore the relationship between the frequencies for categorical demographic variables scored.
The Wilcoxon signed rank test was conducted to evaluate the temporal effect on the frequencies of consumption of dietary constituents (2 years in the (3 – 5) cohort and 3 years in the (5 – 8) cohort). The relationship between the change in BEWE scores and the change in food frequencies was investigated using the Spearman Rank Order correlation test. A Mann-Whitney U test was conducted to compare the change in BEWE scores over time for the twenty-six bivariate categorical variables including age, gender, asthma diagnosis, reflux symptoms and grinding habits. Kruskall-Wallis tests allowed comparison of scores of changes in BEWE scores over time across the remaining 55 categorical variables representing demographic factors, oral hygiene habits and dietary habits. The relationship between change in BEWE scores and all the continuous variables was investigated using Spearman Rho correlation coefficient Test. These variables included results for BMI, number of siblings, deft scores, buffering capacity scores and salivary pH.
The dependent variable was increment in erosive tooth wear in the preschool aged child. Risk indicators/factors and predictor variables were employed, as allowed by risk prediction models. This was done in an effort to maximise sensitivity and specificity. Risk indicators/factors included demographic data (age and gender), behavioural data (oral hygiene practices and dietary habits), and biologic factors (salivary flow/buffering capacity). Predictor variables included baseline BEWE scores for erosive tooth wear and baseline deft scores for caries diagnosis.
Two prognostic prediction models were developed from the data collected from this prospectively collected cohort. The models were developed using the Generalised Linear Model function – one for each age cohort. This allowed the simultaneous analysis of multiple variables including a mixture of categorical and continuous variables. Those variables that showed a statistically significant relationship with a difference in BEWE cumulative score over time together with those up to a significance level of p = 0.1 were utilised to develop two risk prediction models. A forward procedure was performed adding and retaining predictors with p<0.05 in the model. The sensitivity and specificity of the model was calculated and the model was evaluated by Receiver Operating Characteristics (ROC) analysis. A BEWE cumulative score of 9 was taken as a cut-off value.
Statistical tests were carried out using SPSS 20.0 software (IBM Company, Chicago, IL, USA). Statistical significance for all tests was set at p<0.05.