Introduction
Erosion is the chemical dissolution of the tooth structure due to acids. A process
that reduces the mineral content of any tissue is called demineralization. The hardness
and strength of the tooth enamel is greatly influenced by demineralization and remineralization
processes. Due to the loss of the mineral content, dental erosion occurs.[1 ] It is a superficial phenomenon which eventually causes the dissolution of subsurface
layers. Due to the loss of mineralized content, the tooth becomes more susceptible
to the attack of bacteria leading to the initiation of caries, if not treated on time
can lead to the loss of the complete tooth structure.[2 ] Consumption of acidic beverages causes an acidic environment in the oral cavity
which leads to the thinning of enamel due to demineralization. The buffering activity
of saliva is also not effective as these acidic beverages have varying amounts of
resistance against it.[3 ]
[4 ] Not only extrinsic drinks but intrinsic acidic sources can also cause erosion. Bulimia
nervosa, anorexia nervosa, gastroesophageal reflux disease, etc., are a few examples
of intrinsic acid-producing conditions which lead to the demineralization of the tooth
structure. Acids in the mouth lower the pH and, thus, lead to the loss of minerals
from the tooth surface finally leading to the exposure of dentin resulting in sensitivity,
pain, and loss of tooth structure.[5 ]
[6 ]
Fruit juices, aerated drinks, and carbonated drinks are a major part of todays diet
globally. Also, the change in lifestyle habits of the general population, addiction
to video games, and long television hours have influenced a lot of people to consume
these drinks frequently for an extended time. Sedentary lifestyle habits allow the
carbonated drinks to remain in contact with the dental hard tissues for a longer period
leading to decreased salivary activity and loss of enamel at a very fast rate.[7 ]
[8 ]
Hence, the present study aims to evaluate the effect of acidic dietary beverages on
the macroscopic and microscopic structures of enamel and dentin. The objectives of
the study include (1) estimating the mean weight reduction in the tooth structure
on exposure to acidic beverages, (2) analyzing the surface characteristic changes
in enamel and dentin following exposure to acidic beverages, (3) examining the microscopic
changes in ground sections of enamel and dentin on exposure to acidic beverages.
Not many studies have used both macroscopic and microscopic techniques simultaneously
to study and demonstrate the effect of both acidic beverages and dietary preservatives
on the tooth (enamel and dentin). Information on the effect of dietary preservatives
has also been provided.
Materials and Methods
The study was conducted at the Department of Oral Pathology and Microbiology, Ramaiah
University of Applied Sciences, Bangalore, Karnataka, India. Verbal and written ethical
consent was obtained from the patients stating that following extraction their tooth/teeth
would be used for research purposes, and it was also reassured to patients that their
identity would not be revealed. The present study analyzed the microscopic and macroscopic
changes in the structure of enamel and dentin on exposure to acidic beverages with
the use of anterior and posterior extracted human teeth. The criteria for inclusion
were teeth requiring extraction for orthodontic reasons only which are intact without
restorations, fracture, or dental caries. Teeth extracted due to fracture, decay,
and failed restorations were excluded.
Sample Preparation : Twenty teeth specimens were allocated for each test group (nine test groups) and
10 teeth for one control group, a total of 190 teeth (180 test and 10 control) were
considered for analysis. The teeth were vertically split, using a diamond bur to expose
the enamel and dentin, into sections (each of these sections was weighed before and
after exposure). At each of the four-time intervals, 10 sections were taken out for
analysis, five were viewed under stereomicroscope and five were subjected to ground
section. Prior to the start of the experiment, the sliced specimens were weighed using
an electric precision balance and the pH of the acidic beverages was measured using
a digital pH meter (pHep, range 0.0–14.0, resolution 0.1 pH, accuracy at 20°C/68°F
is ± 0.1 pH). The pH levels of the nine test samples recorded were as follows: orange
juice (5.1), pineapple juice (4.4), lemon juice (4.2), Coca-Cola (3.5), Mountain Dew
(4.1), Red Bull (4.4), vinegar (3.5), apple cider (3.7), and tomato ketchup (4.6).
Exposure to Test Samples : The split specimens were placed in 200 mL of the following acidic beverages: commercially
available orange juice, lemon juice, pineapple juice, Coca-Cola, Mountain Dew, Red
Bull, apple cider, vinegar, and tomato ketchup. The tooth sections were removed from
these acidic beverages at an interval of 12, 24, 48, and 96 days for macroscopic and
microscopic analyses. The solutions were changed at each time interval. The teeth
in the control group were immersed in distilled water of pH 7.
Post-Exposure Weight Analysis : The specimens were weighed using a digital weighing balance, and the mean weight
loss before and after exposure was calculated.
Microscopy : The sectioned specimens were viewed under a stereomicroscope to assess and analyze
the degree of surface changes (roughness and discoloration). Ground sections of the
specimens (40–60 μm in thickness) were made using Arkansas stone, and these sections
were viewed under both bright field microscope and polarizing microscope. Under the
compound microscope, the parameters assessed were the changes in the integrity of
dentinal tubules and the striae of Retzius. The ground sections were prepared at each
time interval for analysis.
Parameters assessed under the polarizing microscope were the variation and concentration
of color with distribution of birefringence which corresponds to the demineralization
each specimen has undergone after the specific intervals of exposure to the individual
acidic beverages. A customized scoring criterion from 0 to 3 was developed based on
the severity of changes for the parameters analyzed ([Table 1 ]).
Interpretation and Statistical Analysis: The scores for each experiment conducted were tabulated. The difference in pre- and
post-exposure weights of specimens and different scores obtained under stereomicroscope,
bright field microscope, and polarizing microscope were tabulated and analyzed statistically
for significance. The scoring criteria designed are presented in the table. The test
extracts were labeled as follows: 1 = orange juice, 2 = pineapple juice, 3 = lemon
juice, 4 = Coca-Cola, 5 = Mountain Dew, 6 = Red Bull, 7 = vinegar, 8 = apple cider,
and 9 = tomato ketchup.
Table 1
Customized tri-microscopic scoring criteria for interpretation of macroscopic and
microscopic findings of demineralization changes caused by acidic beverages
Parameters
0
1
2
3
Discoloration
No
Mild
Moderate
Severe
Stereomicroscope
Surface irregularities
No roughness
Mild with grainy appearance
Moderate with craze lines
Severe with chalky/sandstone appearance
Compound microscope
Striae of Retzius
Distinct and regular
Faint and regular
Faint and irregular
Indistinct
Dentinal tubules
Distinct and continuous
Faint and continuous
Faint and discontinuous
Sparse
Polarizing microscope
Demineralization
Organized
Organized with irregular borders
Disorganized
Disorganized and patchy
Results
Control Teeth
The control sections did not show any mean weight change at any given time intervals.
No discoloration or surface irregularities were observed. The integrity of striae
of Retzius and dentinal tubules were well maintained. The polarizing microscope revealed
no patchy or demineralized areas. The birefringent colors were well organized and
uniform in distribution, ([Fig. 1A–P ]).
Mean Weight Reduction
For all nine extracts, the mean weight change at 48- and 96-day time intervals was
significantly higher compared with that at 12- and 24-day time intervals (p < 0.001), ([Table 2 ]). Vinegar (sample 7) showed the maximum reduction in weight compared with all other
extracts, and the weight reduction was significant between the 12- and 96-day exposure
as well. Apple cider also showed moderately high values for weight change followed
by lemon juice.
Discoloration After Exposure
The comparison of mean discoloration values between different test samples at 96-day
time interval indicated a significant difference in the mean discoloration values
between the nine study samples and between the samples and control (p < 0.001), ([Table 3 ]). Multiple comparisons between the extracts demonstrated that Coca-Cola, Mountain
Dew, and Red bull had maximum discoloration capacity when compared with pineapple
juice, lemon juice, and vinegar which showed the least mean discoloration scores (p < 0.001). This was followed by apple cider, tomato ketchup, and orange juice, ([Fig. 2 ]).
Stereomicroscopic Analysis
The comparison of mean surface irregularities between different test samples at 96-day
time interval showed a significant difference in the mean scores between the nine
study samples and between samples and control (p < 0.001), ([Table 4 ]). Vinegar and apple cider showed maximum surface irregularities, loss of gloss and
roughness, followed by lemon juice, Coca-Cola, and Mountain Dew. Tomato ketchup did
not show any appreciable changes compared with normal, ([Fig. 3A–P ]).
Brightfield Microscopic Analysis
The mean values for integrity of striae of Retzius scores significantly increased
at 96-day time interval as compared with other time lines (p < 0.001), ([Table 5 ]), whereas the mean of integrity of dentinal tubules scores showed a significant
increase at 24 and 48-day time intervals itself, as compared with 12-day time interval
(p < 0.001). Maximum loss of integrity of striae of Retzius was observed in teeth exposed
to apple cider and vinegar, followed by Coca-Cola and Red Bull drink. Lemon juice
showed significant changes at 96 days. Orange juice and tomato ketchup did not show
any changes compared with normal, ([Fig. 4A–P ]).
Maximum loss of integrity of dentinal tubules was observed in teeth exposed to vinegar
and apple cider ([Table 6 ]). This was followed by Coca-Cola, Red Bull, Mountain Dew, and lemon juice with similar
values. Again, the least changes were induced by tomato ketchup, only at 96 days.
Polarizing Microscopic Analysis
The mean values for degree and pattern of demineralization scores significantly increased
at 96-day time interval as compared with other time lines for all test samples (p < 0.001) ([Table 7 ]). Demineralized areas were observed as patchy and haphazard areas of birefringence
with loss of stratification of colors in contrast to normal tooth where the birefringent
colors were stratified and arranged in an organized fashion. The degree and pattern
of demineralization were found to be high once again for vinegar and apple cider closely
followed by Red Bull and lemon juice. Coca-Cola and Mountain Dew had comparable values
at 96 days. The least changes were induced by tomato ketchup and orange juice, ([Fig. 5A-P ]).
Fig. 1 (A –P ): Photomicrographs of control sections of teeth. The integrity of striae of Retzius
and dentinal tubules were well maintained. The polarizing microscope revealed no patchy
or demineralized areas. The birefringent colours were well organized and uniform in
distribution.
Table 2
Comparison of mean weight change (in grams) between different extracts at 96-day time
interval using one-way ANOVA test followed by Tukey's post-hoc analysis
Test samples
N
Mean
SD
Min
Max
p -Value
Sig. Diff.
p -Value
Orange juice
10
0.040
0.019
0.01
0.07
<0.001*
E1 vs. E2, 7 and 8
<0.001*
Pineapple juice
10
0.120
0.026
0.08
0.16
E2 vs. E3, 4, 5, 6, 7, 8, and 9
<0.001*
Lemon juice
10
0.030
0.009
0.02
0.05
E3 vs. E4, 6, 7, and 8
<0.01*
Coca-Cola
10
0.060
0.014
0.04
0.08
E4 vs. E7, 8 and 9
<0.001*
Mountain Dew
10
0.040
0.019
0.01
0.07
E5 vs. E7 and 8
<0.001*
Red Bull
10
0.060
0.017
0.03
0.09
E6 vs. E7, 8 and 9
<0.001*
Vinegar
10
0.430
0.026
0.39
0.47
E7 vs. E8 and 9
<0.001*
Apple cider
10
0.210
0.020
0.18
0.24
E8 vs. E9
<0.001*
Tomato ketchup
10
0.020
0.009
0.01
0.03
–
–
Abbreviations: ANOVA, analysis of variance; E, extract; Max, maximum; Min, minimum;
SD, standard deviation, Sig. Diff., significant difference.
*denotes significant p -Values.
Table 3
Comparison of mean discoloration values between different extracts at 96-day time
interval using one-way ANOVA test followed by Tukey's post-hoc analysis
Test samples
N
Mean
SD
Min
Max
p -Value
Sig. Diff
p -Value
Orange juice
10
1.90
0.32
1
2
<0.001a
E1 vs. E2, 3, 4, 5, and 7
<0.001a
Pineapple juice
10
0.00
0.00
0
0
E2 vs. E4, 5, 6, 8, and 9
<0.001a
Lemon juice
10
0.00
0.00
0
0
E3 vs. E4, 5, 6, 8, and 9
<0.001a
Coca-Cola
10
3.00
0.00
3
3
E4 vs. E6, 7, 8, and 9
<0.001a
Mountain Dew
10
3.00
0.00
3
3
E5 vs. E6, 7, 8, and 9
<0.001a
Red Bull
10
2.00
0.00
2
2
E6 vs. E7
<0.001a
Vinegar
10
0.00
0.00
0
0
E7 vs. E8
<0.001a
Apple cider
10
1.80
0.42
1
2
–
–
Tomato ketchup
10
1.80
0.42
1
2
–
–
Abbreviations: ANOVA, analysis of variance; E, extract; Max, maximum; Min, minimum;
SD, standard deviation, Sig. Diff., significant difference.
Fig. 2 Macroscopic view of discolored teeth. Coca-Cola showed maximum discoloration followed
by Mountain Dew and Red Bull drink. Tomato ketchup showed least discoloration followed
by orange juice (bluish tinge due to labeling ink used ).
Table 4
Comparison of mean Surface Irregularity values between different extracts at 96-day
time interval using one-way ANOVA test followed by Tukey's post-hoc analysis
Test samples
N
Mean
SD
Min
Max
p -Value
Sig. Diff
p -Value
Orange juice
10
1.00
0.47
0
2
<0.001a
E1 vs. E2, 4, 5, 7, and 8
<0.001a
Pineapple juice
10
2.80
0.42
2
3
E2 vs. E3, 4, 5, 6, and 9
<0.001a
Lemon juice
10
1.00
0.00
1
1
E3 vs. E4, 5, 7, and 8
<0.001a
Coca-Cola
10
2.00
0.00
2
2
E4 vs. E6, 7, 8, and 9
<0.001a
Mountain Dew
10
2.00
0.00
2
2
E5 vs. E6, 7, 8, and 9
<0.001a
Red Bull
10
1.00
0.00
1
1
E6 vs. E7 and 8
<0.001a
Vinegar
10
3.00
0.00
3
3
E7 vs. E9
<0.001a
Apple cider
10
3.00
0.00
3
3
E8 vs. E9
<0.001a
Tomato ketchup
10
0.90
0.32
0
1
–
–
Abbreviations: ANOVA, analysis of variance; E, extract; Max, maximum; Min, minimum;
SD, standard deviation, Sig. Diff., significant difference.
Fig. 3 Stereomicroscope photomicrographs of sectioned teeth immersed in (A –D ) apple cider and (E –H ) vinegar showed maximum surface irregularities, loss of gloss, and roughness at 48
days. Changes observed in (I and J ) Coca-Cola, (K ) lemon juice, and (L ) Mountain Dew at 48 days. (M and N ) Maximum changes induced by vinegar at 96 days. (O and P ) Tomato ketchup not exhibiting any noticeable changes.
Table 5
Comparison of mean integrity striae of Retzius values between different extracts at
96-day time interval using one-way ANOVA test followed by Tukey's post-hoc analysis
Test samples
N
Mean
SD
Min
Max
p -Value
Sig. Diff
p -Value
Orange juice
10
0.90
0.32
0
1
<0.001a
E1 vs. E3, 4, 6, 7, 8, and 9
<0.001a
Pineapple juice
10
1.00
0.00
1
1
E2 vs. E3, 4, 6, 7, 8, and 9
<0.001a
Lemon juice
10
1.90
0.32
1
2
E3 vs. E5, 7, 8, and 9
<0.001a
Coca-Cola
10
1.90
0.32
1
2
E4 vs. E5, 7, 8, and 9
<0.001a
Mountain Dew
10
0.90
0.32
0
1
E5 vs. E6, 7, 8, and 9
<0.001a
Red Bull
10
1.90
0.32
1
2
E6 vs. E7, 8, and 9
<0.001a
Vinegar
10
3.00
0.00
3
3
E7 vs. E9
<0.001a
Apple cider
10
3.00
0.00
3
3
E8 vs. E9
<0.001a
Tomato ketchup
10
0.00
0.00
0
0
–
–
Abbreviations: ANOVA, analysis of variance; E, extract; Max, maximum; Min, minimum;
SD, standard deviation, Sig. Diff., significant difference.
Fig. 4 Bright field microscope photomicrographs showing loss of integrity of striae of Retzius
at 96 days. Polarized microscopy photomicrographs of the same sections showing loss
of stratification of birefringent colours, patchy and haphazard birefringence. Apple
cider (A–B), vinegar (C–D), coca–cola (E–F), red bull drink (G–H), mountain dew (I–J),
lemon juice (K–L). No significant changes observed in orange juice (M–N) and tomato
ketchup which show good integrity of striae of Retzius with uniform and stratified
distribution of birefringent colours (O–P).
Fig. 5 Bright field microscope photomicrographs showing loss of integrity of dentinal tubules
at 96 days. Polarized microscopy photomicrographs of the same sections showing loss
of stratification of birefringent colours, patchy and haphazard birefringence. Apple
cider (A–D), vinegar (E–F), Coca–cola (G–H), red bull drink (I–J), mountain dew (K–L).
No significant changes observed in tomato ketchup (m–n) and orange juice (O–P) which
show good integrity of dentinal tubules and striae of Retzius with uniform and stratified
distribution of birefringent colours.
Table 6
Comparison of mean integrity of dentinal tubules between different extracts at 96-day
time interval using one-way ANOVA test followed by Tukey's post-hoc analysis
Test samples
N
Mean
SD
Min
Max
p -Value
Sig. Diff
p -Value
Orange juice
10
1.00
0.00
1
1
<0.001a
E1 vs. E3, 4, 5, 6, 7, and 8
<0.001a
Pineapple juice
10
1.00
0.00
1
1
E2 vs. E3, 4, 5, 6, 7, and 8
<0.001a
Lemon juice
10
1.90
0.32
1
2
E3 vs. E7, 8 and 9
<0.001a
Coca-Cola
10
2.00
0.00
2
2
E4 vs. E7, 8 and 9
<0.001a
Mountain Dew
10
1.80
0.42
1
2
E5 vs. E7, 8 and 9
<0.001a
Red Bull
10
1.90
0.32
1
2
E6 vs. E7, 8, and 9
<0.001a
Vinegar
10
3.00
0.00
3
3
E7 vs. E9
<0.001a
Apple cider
10
3.00
0.00
3
3
E8 vs. E9
<0.001a
Tomato ketchup
10
0.80
0.42
0
1
–
–
Abbreviations: ANOVA, analysis of variance; E, extract; Max, maximum; Min, minimum;
SD, standard deviation, Sig. Diff., significant difference.
Table 7
Comparison of mean demineralization values between different extracts at 96-day time
interval using one-way ANOVA test followed by Tukey's post-hoc analysis
Test Samples
N
Mean
SD
Min
Max
p -Value
Sig. Diff
p -Value
Orange juice
10
1.00
0.00
1
1
<0.001a
E1 vs. E3, 4, 5, 6, 7, and 8
<0.001a
Pineapple juice
10
1.00
0.00
1
1
E2 vs. E3, 4, 5, 6, 7, and 8
<0.001a
Lemon juice
10
2.80
0.42
2
3
E3 vs. E4, 5 and 9
<0.001a
Coca-Cola
10
1.90
0.32
1
2
E4 vs. E6, 7, 8, and 9
<0.001a
Mountain Dew
10
1.80
0.42
1
2
E5 vs. E6, 7, 8, and 9
<0.001a
Red Bull
10
2.90
0.32
2
3
E6 vs. E9
<0.001a
Vinegar
10
3.00
0.00
3
3
E7 vs. E9
<0.001a
Apple cider
10
3.00
0.00
3
3
E8 vs. E9
<0.001a
Tomato ketchup
10
1.00
0.00
1
1
–
–
Abbreviations: ANOVA, analysis of variance; E, extract; Max, maximum; Min, minimum;
SD, standard deviation, Sig. Diff., significant difference.
To summarize the results, vinegar showed the maximum weight change post-exposure.
Coca-Cola and Mountain dew showed the highest mean discoloration scores compared with
other test samples. Vinegar and apple cider showed maximum surface irregularities
and roughness viewed under stereomicroscope. Vinegar and apple cider were found to
induce maximum changes in striae of Retzius and dentinal tubules. Maximum degree and
pattern of demineralization were also observed for vinegar and apple cider under polarizing
microscope.
Discussion
India's soft drink consumption has grown by 87% in the past 9 years, and the net increase
in the next 3 years is expected to be approximately 7%. Statistics show that the per
capita consumption of soft drinks was 4.1 L in 2018 and is expected to be 4.6 L by
2021.[9 ] Citric, phosphoric and carbonic acids are the three main dietary acids present in
these soft drinks. Additionally, acetic acid is present in preservatives like vinegar
and apple cider. Hence, the aim of this study was to analyze the relative cumulative
effect of erosivity for the selected acidic beverages with an emphasis on dietary
preservatives. These data will allow a ranking for the most erosive acidic beverages
for diet counseling.
Unfavorable changes due to chronic exposure of teeth to acidic beverages do not correlate
with a single drink consumption but denote a cumulative effect of consumption of these
dietary acids on a daily basis, i.e., deleterious effects seen in teeth exposed to
acidic beverages for 15 minutes per day for 96 days through in vitro studies correspond to the detrimental changes that would be observed after 25 years
in individual's life time who consumes the beverage with the same frequency and duration.[7 ]
[10 ]
[11 ]
[12 ]
[13 ]
Commercially available fruit juices and carbonated drinks were considered for this
study since they adequately represent the diet habits of the current young generation.
To our knowledge, the effect of acidic beverages on both the enamel and dentin at
macroscopic and microscopic levels has not been analyzed yet in the same study. The
effect of dietary preservatives on enamel and dentin is also not established. The
present study has addressed the above concerns making it unique.
The acidic challenge preceded by food consumption on enamel erosion and discoloration
different drinks impose on tooth color are challenging aspects to overcome.[14 ]
[15 ]
In the current study, the discoloration potentials of various acidic beverages were
scored and analyzed by using a customized scoring criterion in comparison with normal
control. It was found that Coca-Cola, Mountain Dew, and Red Bull had maximum discoloration
capacity. The discoloration caused by these agents can be attributed to the coloring
agent present in these drinks. The key ingredients of Coca-Cola include carbonated
water, sugar (sucrose or high-fructose corn syrup (HFCS), caffeine, phosphoric acid,
and class 4—caramel color 150d /E150d. The ingredient responsible for staining is
the class 4—caramel color 150d/E150d which is a dark brown coloring agent.[16 ] Mountain Dew is composed of carbonated water, HFCS, concentrated orange juice, citric
acid, natural flavors, sodium benzoate, caffeine, sodium citrate, erythorbic acid,
gum arabic, ethylenediaminetetraacetic acid, brominated vegetable oil, and tartrazine.
Tartrazine is a synthetic lemon yellow azo dye primarily used as a food colorant which
is primarily responsible for the staining of teeth in Mountain Dew.[17 ] Red Bull energy drink contains caffeine, taurine, B vitamins (B3, B5, B6, and B12),
and simple sugars (sucrose and glucose) in a buffer solution of carbonated water,
baking soda, and magnesium carbonate.[18 ] Caramel produced by ammonia process along with riboflavin is a common food coloring
agent used in Red Bull energy drink responsible for staining.[19 ]
Erdemir et al 2016, in a recent study, demonstrated that energy drinks had a risk
of causing discoloration due to their wide variety of ingredients. Varying amounts
of caffeine, guarana extract, taurine, and ginseng are the main ingredients of energy
drinks which are responsible for discoloration.[20 ] The mean loss of weight in the tooth structure can be attributed to the degree of
the demineralization. In the present study, the maximum mean weight loss was observed
with respect to vinegar followed by apple cider.
The explanation for the above result is that vinegar typically contains 5 to 20% acetic
acid by volume. Usually, the acetic acid is produced by the fermentation of ethanol
or sugars by acetic acid bacteria resulting in a lowered pH.[21 ] Apple cider is fermented juice from crushed apples and contains lactic acid, succinic
acid, and acetic acid. Bacteria and yeast are added to the liquid to start the alcoholic
fermentation process, which converts the sugars to alcohol. In a second fermentation
step, the alcohol is converted into vinegar by acetic acid-forming bacteria (Acetobacter
species). Acetic acid and malic acid combine to give vinegar its sour taste and a
lowered pH.[22 ]
Red Bull energy drink showed the maximum mean loss of weight among the carbonated
drinks. The above results can be attributed to the pH of the acidic beverages used;
vinegar had the lowest pH resulting in maximum mean loss followed by apple cider.
Red Bull energy drink has 27 g of sugar per can. Taurine, or 2-aminoethanesulfonic
acid, is an amino acid naturally made in the human body. Found in the lower intestine
and a major component of bile, taurine is an antioxidant that helps to move minerals
through the system and generate nerve impulses. Each can of Red Bull contains 1,000 mg
of taurine.[23 ] These components can significantly lower the mineral component of hard tissues.
A study conducted by Mathew et al 2017 weighed enamel before and after immersion in
different beverages. The mean weight reduction by orange juice was 21% followed by
Red Bull (13%), Pepsi (11%), lemon juice (16%), apple juice (16%), coffee (3%), and
green tea (3%). This demonstrated the erosive potential of these beverages.[24 ]
Although the mean loss of weight denotes the demineralization, it is a quantitative
value and does not describe the effects of these beverages individually on the enamel
and dentin. To assess the erosivity of these drinks on the enamel and dentin, the
current study used advanced microscopic methods.
The changes in the surface of the tooth structure also determine the strength and
longevity of the tooth. These surface changes in the teeth specimens were observed
using a stereomicroscope. Loss of gloss and roughness of the tooth structure cause
more plaque accumulation and, hence, lead to demineralization, decay, and poor oral
hygiene.[25 ] In the present study vinegar and apple cider showed maximum surface irregularities,
loss of gloss and roughness, followed by lemon juice, Coca-Cola, and Mountain Dew.
Grando et al 1996 reported the erosion caused in vitro by cola-type and guarana-type beverages (the latter is a soft drink sold in Brazil)
and a canned lemon juice on the enamel of human deciduous teeth. Stereomicroscopic
analysis showed loss of gloss and an alteration in the normal color of enamel, with
irregular loss of dental tissue in variable degrees. The loss of gloss and roughness
was directly proportional to the incubation time.[26 ] Both regular and sugar-free sodas also contain acids that have a demineralizing
effect. With each sip of soda, a damaging reaction that lasts for approximately 20 minutes
is initiated.[27 ]
The present study used ground sections with thickness between 60 and 70 µm under 10x
and 40x magnification. The parameters assessed with respect to the enamel and dentin
were the integrity of striae of Retzius and dentinal tubules, respectively. Striae
of Retzius was chosen since it represents the deposition of enamel and the enamel
rods, which is the main component that determines the integrity of the enamel. Dentinal
tubules were assessed since the integrity of the dentin is dependent on the configuration
of these tubules. The present study is the first of its kind to analyze and correlate
integrity of striae of Retzius and dentinal tubules with demineralization. Both parameters
were given scores based on their appearance under the microscope. Maximum loss of
integrity of striae of Retzius was observed in teeth exposed to apple cider and vinegar,
followed by Coca-Cola. Lemon juice showed significant changes at 96 days. Although
few studies have evaluated the effect of acidic beverages on human teeth, the current
study for the first time has also evaluated the effect of dietary preservatives, the
erosive effects of which are often neglected.
The daily consumption of apple cider vinegar seems to be trending among celebrities,
especially women as the most popular oral supplement for weight reduction.[28 ] The health benefits of apple cider vinegar have been well documented in inducing
weight loss in obese individuals. A recent study by Khezri et al 2018 has shown that
apple cider vinegar intake along with a restricted diet helps in decreasing body weight
plasma triglycerides and basal metabolic index.[29 ]
Individuals consuming apple cider vinegar remain exposed to erosive damage to the
enamel, greater damage is inflicted when consumed at night as the buffering action
of saliva is absent. A case reported in 2012 strongly suggests that erosive tooth
wear is easily induced by the daily consumption of apple cider vinegar.[30 ] The results of the current study serve as a word of caution for those frequently
consuming apple cider vinegar.
The configuration of the striae of Retzius and dentinal tubules determines the orientation
of the hydroxyapatite crystals of the enamel and dentin.[31 ] A change in this configuration results due to chronic exposure of the tooth structures
to acidic beverages resulting in demineralization. As both enamel and dentin have
inherent crystalline properties, their histological features are better visualized
under a polarizing microscope than transmitted light microscopy since structures such
as crystals and collagen fibers have the property to split polarized light into two,
a phenomenon known as birefringence.[32 ]
[33 ] Hence, the degree of demineralization of the apatite crystals can be determined
by the appearance of the enamel and dentin under the polarizing microscope.
Demineralization was observed as patchy and haphazard areas of birefringence with
loss of stratification of colors. The degree and pattern of demineralization was found
to be high once again for vinegar and apple cider closely followed by Red Bull and
lemon juice. Coca-Cola and Mountain Dew had comparable values at 96 days. Literature
review has shown that no study has employed polarizing microscopy to evaluate the
demineralization of enamel and dentin by acidic beverages. White et al 2001 compared
polarized microscopy findings of root caries and erosion of root structure caused
by corrosive acids and stated that histological pattern of two zones of opposite birefringence
is seen in all categories of erosive demineralization.[34 ] These zones of differing birefringence in dentin represent different degrees of
mineralization of collagen.
Conclusion
This present study is unique as it has utilized three different types of microscopes,
i.e., bright field microscope, stereomicroscope, and polarizing microscope with additional
assessment parameters of weight loss and discoloration making the analysis comprehensive.
We can conclude that vinegar and apple cider are the most detrimental dietary preservatives.
Among the acidic beverage's lemon juice was the most harmful to the hard tissues.
Coca-Cola and Mountain Dew were found to be potent demineralizing agents among the
aerated drinks followed by red bull. Tomato ketchup showed significantly least weight
change, surface irregularities, demineralization, dentinal tubules, and striae of
Retzius changes. Thereby, we can infer that tomato ketchup shows the least detrimental
effect on hard tissues.
With reference to the present study, oral health educators can reinforce important
practices to frequent acidic beverage consumers such as decreasing the time that the
beverage remains in the mouth and decreasing the frequency of consumption of these
acidic beverages in a day. The use of regular fluoride application to convert the
hydroxyapatite crystals to fluorapatite crystals will make the teeth resilient to
demineralization.[33 ] The use of buffering agents and mouth rinses after consumption of acidic beverages
can also be advocated that will help neutralize the acidic pH in the oral cavity.
