Timing of dietary acid intake and erosive tooth wear: A case-control study

Abstract

Objectives

There is a lack of clinical data on the impact of timing of dietary acid intake and toothbrush abrasion when attempting to control erosive tooth wear progression. The aim of this study was to estimate the association of theoretical causative factors with erosive tooth wear to inform evidence-based guidelines.

Methods

Using case-control study design, 300 participants with dietary erosive tooth wear and 300 age-matched controls were recruited from the restorative clinics of King’s College London Dental Institute. A previously validated questionnaire was adapted to be interviewer-led and to assess frequency, timing and duration of dietary acid intake in addition to alternate drinking habits prior to swallowing. Timing of toothbrushing in relation to meals and dietary acid intake was investigated. Associations with erosive tooth wear were assessed in crude and adjusted logistic regression models.

Results

Fruit intake between meals (p < 0.001), but not with meals (p = 0.206), was associated with erosive tooth wear and contrasted with acidic drinks which maintained a strong association regardless of timing of intake (OR up to 11.84 [95% CI: 5.42–25.89], p < 0.001). Prolonged fruit eating and alternate drinking habits prior to swallowing (OR 12.82 [95% CI: 5.85–28.08] and 10.34 [95% CI: 4.85–22.06] respectively) were as strongly associated with erosive tooth wear as three or greater daily acid intakes (OR 10.92 [95% CI: 4.40–27.10]). Toothbrushing within 10 min of acid intake was not associated with erosive tooth wear following adjustments for dietary factors (OR 1.41 [95% CI: 0.82–2.42], p = 0.215]).

Conclusion

Significantly increased odds ratios were observed when acids were consumed between meals in this cohort of patients. Universal advice to delay brushing after meals may not be substantiated.

Clinical significance

Prevention should be focused on avoiding dietary acids between meals, eliminating habits which increase contact time with the acid and reducing daily intake of acidic drinks. Toothbrushing after meals was not associated with erosive wear. Toothbrushing immediately after an acid challenge requires further investigation.

Introduction

Erosive tooth wear is the chemical-mechanical cumulative loss of dental hard tissue not caused by bacteria . As the prevalence of erosive wear is increasing an increased focus on prevention may prolong the long term health of the dentition. However, the interactive role of dietary erosion and abrasion and the relative significance of each effect are currently undergoing academic debate . Preventive guidelines remain unclear and attention is urgently required to produce basic evidence-based preventive advice.

Frequency of dietary acid intake is hypothesised to be the most important risk factor in extrinsic tooth wear progression , and yet a clinical threshold of “safe” intake has yet to be established. Inherent protective mechanisms conferred by saliva, salivary pellicle and intra-oral ion reservoirs require depletion before dental mineral loss occurs . In addition, acid clearance and intra-oral pH stabilisation occur rapidly over 2–13 min . The frequency of daily acid intake which overrides the natural defences, is unclear from the literature. Previous case-control studies have investigated either acidic beverages or fruit in isolation but not the overall pattern of acid intake adjusting for confounding factors. The timing of acid intake may be important and to date has not been investigated epidemiologically. Additional foods present may buffer the acid . Increased salivary flow rates at mealtimes may also lower the erosive potential of the acid sufficiently to prevent demineralisation and irreversible tissue loss. However, the clinical significance of timing of acidic foods has yet to be clarified.

Furthermore, it has been suggested that salivary remineralisation after erosive challenges may confer significant protection from abrasion and therefore the timing of tooth brushing in relation to erosive challenges may be important in tooth wear progression . However, there is laboratory evidence to suggest that full remineralisation of eroded dental tissues may not be possible and a large European epidemiological study failed to observe clear patterns between timing of food intake and tooth brushing . Attention has been drawn to the low level of clinical evidence base behind these recommendations and the clinical significance of remineralisation time prior to abrasive forces may be relatively small . In addition, if the buffering capacity of meals is significant, insufficient demineralisation may have occurred to enable abrasive tooth wear. The relative importance of the interactions between frequencies of dietary acid intake with and between meals, prolonged contact time with the acid and toothbrush abrasion remains to be established.

The aim of this study was to investigate the interrelationship between dietary acid intake, tooth brushing after acid intake and erosive tooth wear. It was hypothesised that the frequency, timing (between meals) and duration of acid intake are positively associated with erosive tooth wear whereas delaying brushing after meals is negatively associated with erosive tooth wear.

Materials and methods

This was a single-centre, frequency-matched, case-control study. The study protocol was approved by West of Scotland Research Ethics Service (Reference 14/WS/0015) and written informed consent was obtained from all participants. The present study adheres to the Strengthening the Reporting of Observational Studies (STROBE) statement and is registered at clinicaltrials.gov (Identifier number: NCT02449434).

Participants

Participants (n = 600) aged 18 years or older, were recruited between May 2014 and March 2016 following referral by their general dental practitioners (GDP) for erosive tooth wear (cases, n = 300) or general treatment (controls, n = 300) to the restorative clinics at King’s College London Dental Institute. All participants had a minimum of 20 teeth (10 in each jaw). Participants were excluded if they had missing anterior teeth, anterior crowns/bridges or cavitated caries on more than one tooth. A history of eating disorders or gastro-oesophageal reflux, bruxism or prescribed xerostomic/heartburn medication, pregnancy, involvement in other research within the past 30 days or inability to speak or understand the English language also excluded the participant from this study. Bruxism was diagnosed from the clinical appearance, signs and symptoms of attritive tooth wear; those with flattened surfaces without erosive lesions were excluded.

According to a pilot study and a previous study within our group , a minimum sample size of 490 participants (245 in each group) was needed. This calculation assumed the proportion of adults with high dietary acid intake (3+ times/day) was 55% among cases and 40% among controls (expected odds ratio of 2.25), case-control ratio of 1-to-1, 90% statistical power and 95% significance level.

Data collection

Data collection procedures were identical for cases and controls. The Basic Erosive Wear Examination (BEWE) index graded tooth wear on the buccal, occlusal and palatal/lingual surfaces of each tooth excluding third molars and was used to differentiate the groups. This ordinal scale graded tooth wear from 0 to 3 (0 = no wear, 1 = early surface loss, 2 = surface loss < 50% or specific defect, 3 = surface loss > 50%). Teeth with restorations involving >50% of the tooth, traumatised or carious teeth were excluded from the assessment. Teeth were examined under good lighting in a dental chair but without magnification. A sextant BEWE score was calculated by recording the highest score from any surface in each sextant. The cumulative BEWE score was calculated by summing each sextant BEWE score within the range from 0 to 18 . A trained and calibrated dentist carried out all clinical examinations. Inter-examiner and intra-examiner Kappa scores, calculated on duplicate examinations of 30 patients against a calibrated BEWE expert (DB), were 0.85 and 0.75 respectively.

Erosive tooth wear cases were defined as those with a BEWE score of 12 or higher and at least one score of 3 in a sextant whereas controls were defined as those with a BEWE score of 10 or lower and no score of 3 on any surface of any tooth (clinically classified as no or mild erosive tooth wear). Controls were age-matched on a 1:1 ratio with cases. Frequency matching was used, to yield controls with the same distribution over six age groups (18–25, 26–35, 36–45, 46–55, 56–65 and 66+ years). Cases that could not be matched were excluded from the study.

After recruitment, a trained interviewer questioned participants on potential risk factors for erosive tooth wear using an adapted version of a previously validated questionnaire . Participants were asked about the frequency, timing (with meals or between meals) and duration of consumption of fruits, fruit drinks, carbonated beverages and other acidic drinks , the type of holder (cup, glass, bottle, can), whether they had a habit of retaining drinks in their mouth (sipping, swishing or holding) prior to swallowing, whether they reported to brush within 10 min of consuming something acidic and any associated symptomatology (i.e. sensitive teeth). Total daily frequency of acid intake was estimated as the sum of fruit (apples, citrus, grapes, berries and any other fruit) and acidic drinks (carbonated drinks, fruit drinks, any other acidic drinks e.g. fruit teas, wine). For timing, total daily frequency of acid intake was separated into four indicators, daily frequency of fruit intake with and between meals and daily frequency of acidic drink intake with and between meals. Duration of a single acid intake was divided into three categories (<5 min, 5–10 min and ≥10 min). Questions were standardised and participants were given the opportunity to clarify questions, ensuring comprehension before answering. Each questionnaire lasted between 5 and 10 min.

Data analysis

All analyses were performed in the Statistical Package for Social Sciences version 22 for Windows (IBM Corporation, Armonk, New York, USA). Cases and controls were compared in terms of their demographic and clinical characteristics, using the Chi-square test for categorical variables and the t -test for continuous measures. Cases and controls were also compared in terms of risk factors (total daily acid intake, fruit intake with meals, fruit intake between meals, acidic drink intake with meals, acidic drink intake between meals, duration of fruit and acidic drink consumption, brushing within 10 min of acid intake and alternate drinking habits) using the Chi-square test. Variables to be included in the logistic regression model were manually selected based upon prior theory and the research hypothesis. The variables included were: the frequency of fruit and acidic drink consumption with meals and between meals, duration of consumption, brushing after acid intake and alternate drinking habits prior to swallowing.

Using the presence or absence of severe erosive wear (cases and controls) as the dependent variable, the unadjusted, sex-and-age-adjusted and fully adjusted associations of the included variables with erosive tooth wear were estimated using unconditional binary logistic regression and reported using odds ratios (OR). As frequency matching does not require the use of conditional logistic regression during analysis , age (in the pre-defined groups), was included as a potential confounder.

Materials and methods

This was a single-centre, frequency-matched, case-control study. The study protocol was approved by West of Scotland Research Ethics Service (Reference 14/WS/0015) and written informed consent was obtained from all participants. The present study adheres to the Strengthening the Reporting of Observational Studies (STROBE) statement and is registered at clinicaltrials.gov (Identifier number: NCT02449434).

Participants

Participants (n = 600) aged 18 years or older, were recruited between May 2014 and March 2016 following referral by their general dental practitioners (GDP) for erosive tooth wear (cases, n = 300) or general treatment (controls, n = 300) to the restorative clinics at King’s College London Dental Institute. All participants had a minimum of 20 teeth (10 in each jaw). Participants were excluded if they had missing anterior teeth, anterior crowns/bridges or cavitated caries on more than one tooth. A history of eating disorders or gastro-oesophageal reflux, bruxism or prescribed xerostomic/heartburn medication, pregnancy, involvement in other research within the past 30 days or inability to speak or understand the English language also excluded the participant from this study. Bruxism was diagnosed from the clinical appearance, signs and symptoms of attritive tooth wear; those with flattened surfaces without erosive lesions were excluded.

According to a pilot study and a previous study within our group , a minimum sample size of 490 participants (245 in each group) was needed. This calculation assumed the proportion of adults with high dietary acid intake (3+ times/day) was 55% among cases and 40% among controls (expected odds ratio of 2.25), case-control ratio of 1-to-1, 90% statistical power and 95% significance level.

Data collection

Data collection procedures were identical for cases and controls. The Basic Erosive Wear Examination (BEWE) index graded tooth wear on the buccal, occlusal and palatal/lingual surfaces of each tooth excluding third molars and was used to differentiate the groups. This ordinal scale graded tooth wear from 0 to 3 (0 = no wear, 1 = early surface loss, 2 = surface loss < 50% or specific defect, 3 = surface loss > 50%). Teeth with restorations involving >50% of the tooth, traumatised or carious teeth were excluded from the assessment. Teeth were examined under good lighting in a dental chair but without magnification. A sextant BEWE score was calculated by recording the highest score from any surface in each sextant. The cumulative BEWE score was calculated by summing each sextant BEWE score within the range from 0 to 18 . A trained and calibrated dentist carried out all clinical examinations. Inter-examiner and intra-examiner Kappa scores, calculated on duplicate examinations of 30 patients against a calibrated BEWE expert (DB), were 0.85 and 0.75 respectively.

Erosive tooth wear cases were defined as those with a BEWE score of 12 or higher and at least one score of 3 in a sextant whereas controls were defined as those with a BEWE score of 10 or lower and no score of 3 on any surface of any tooth (clinically classified as no or mild erosive tooth wear). Controls were age-matched on a 1:1 ratio with cases. Frequency matching was used, to yield controls with the same distribution over six age groups (18–25, 26–35, 36–45, 46–55, 56–65 and 66+ years). Cases that could not be matched were excluded from the study.

After recruitment, a trained interviewer questioned participants on potential risk factors for erosive tooth wear using an adapted version of a previously validated questionnaire . Participants were asked about the frequency, timing (with meals or between meals) and duration of consumption of fruits, fruit drinks, carbonated beverages and other acidic drinks , the type of holder (cup, glass, bottle, can), whether they had a habit of retaining drinks in their mouth (sipping, swishing or holding) prior to swallowing, whether they reported to brush within 10 min of consuming something acidic and any associated symptomatology (i.e. sensitive teeth). Total daily frequency of acid intake was estimated as the sum of fruit (apples, citrus, grapes, berries and any other fruit) and acidic drinks (carbonated drinks, fruit drinks, any other acidic drinks e.g. fruit teas, wine). For timing, total daily frequency of acid intake was separated into four indicators, daily frequency of fruit intake with and between meals and daily frequency of acidic drink intake with and between meals. Duration of a single acid intake was divided into three categories (<5 min, 5–10 min and ≥10 min). Questions were standardised and participants were given the opportunity to clarify questions, ensuring comprehension before answering. Each questionnaire lasted between 5 and 10 min.

Data analysis

All analyses were performed in the Statistical Package for Social Sciences version 22 for Windows (IBM Corporation, Armonk, New York, USA). Cases and controls were compared in terms of their demographic and clinical characteristics, using the Chi-square test for categorical variables and the t -test for continuous measures. Cases and controls were also compared in terms of risk factors (total daily acid intake, fruit intake with meals, fruit intake between meals, acidic drink intake with meals, acidic drink intake between meals, duration of fruit and acidic drink consumption, brushing within 10 min of acid intake and alternate drinking habits) using the Chi-square test. Variables to be included in the logistic regression model were manually selected based upon prior theory and the research hypothesis. The variables included were: the frequency of fruit and acidic drink consumption with meals and between meals, duration of consumption, brushing after acid intake and alternate drinking habits prior to swallowing.

Using the presence or absence of severe erosive wear (cases and controls) as the dependent variable, the unadjusted, sex-and-age-adjusted and fully adjusted associations of the included variables with erosive tooth wear were estimated using unconditional binary logistic regression and reported using odds ratios (OR). As frequency matching does not require the use of conditional logistic regression during analysis , age (in the pre-defined groups), was included as a potential confounder.

Results

Table 1 shows the demographic and clinical characteristics of cases and controls. There were no significant differences in age between the two groups, but there were significantly more females among controls (p = 0.003). The mean BEWE score, used to differentiate the groups, was 15.0 for cases and 6.3 in controls. An increased proportion of cases reported to have dental sensitivity compared to controls (55% versus 42%, p < 0.001).

Table 1
Comparison of demographic and clinical characteristics of participants.
Characteristics Cases Controls p value a
Gender, n (%) 0.003
Men 162 54% 125 42%
Women 138 46% 175 58%
Age groups, n (%) 1.000
18–25 years 31 10% 33 11%
26–35 years 67 22% 67 22%
36–45 years 68 23% 66 22%
46–55 years 66 22% 66 22%
56–65 years 44 15% 44 15%
66+ years 24 8% 24 8%
Age in years 0.788
Mean ± SD 44.07 ± 14.17 43.76 ± 14.71
Range 18–74 18–75
BEWE score <0.001
Mean ± SD 15.01 ± 2.30 6.27 ± 2.79
Range 12–18 0−10
Self-reported sensitivity, n (%) <0.001
No 134 45% 194 58%
Yes 166 55% 106 42%
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Jun 19, 2018 | Posted by in General Dentistry | Comments Off on Timing of dietary acid intake and erosive tooth wear: A case-control study
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