Introduction
Pulp stones are discrete calcifications appearing within the pulp of the healthy,
diseased and/or, even, the unerupted teeth. They may exist freely within the pulp
tissue or, may be attached to, embedded in dentin.[1 ] Despite several microscopic and histochemical studies, the exact cause of pulp calcifications
remains largely unknown; however, several conditions have been claimed to predispose
to pulp stone formation, such as age, genetic predisposition, low-grade, persistent
insults to the vital tissue, circulatory disturbances, and inductive interaction between
the pulp tissue and the epithelium, although, in many instances, there is no clear-cut
or defined etiology behind such degenerative changes, eventually leading to pulp calcifications.
The latter category of changes where the etiology is not discernible is included as
idiopathic calcifications.[2 ]
[3 ]
[4 ]
[5 ]
Numerous studies have also shown an association between the formation of pulp stones
and atheromatous plaques in the vessels.[6 ]
[7 ]
[8 ] Likewise, Edds et al suggested that 74% of patients with reported cardiovascular
disease had detectable pulp stone formations, while only 39% of patients without a
history of cardiovascular disease had pulp stones.[9 ] There is also evidence that hypercalcemia, gout and renal lithiasis are predisposing
factors to pulp calcifications.[10 ] The mechanism of apatite formation, also recognized as pathological biomineralization,
behind dental pulp stone formation is hypothesized to be similar to joint calcifications,
and renal calculi seen as the regressive changes observed in tissues as aging happens.[11 ]
Kajander et al and Ciftcioglu et al also stated that nanobacteria known to produce
biologic apatite over their cellular covering are responsible for dental pulp stone
formations, just like renal calculi and other calcified tissues, leading to a hypothesis
that this might be explained as a common factor between calcifications seen in the
aging or traumatized pulp tissues and atheromatous plaques seen in the ischemic heart
diseases (IHDs).[12 ]
[13 ]Furthermore, osteopontin, a constituent of atherosclerotic plaque, apparently plays
a role in plaque calcification, as it is produced by macrophages which, in turn, play
a key role in the initiation of calcific changes seen in other necrotic tissues of
the body as part of regressive, dystrophic changes attracting calcium, including the
renal and carotid artery calcifications.[14 ]
[15 ]
[16 ]
IHDs have been recorded as the leading cause of morbidity worldwide, wherein arteriosclerosis
is the most common cause of IHDs, including stable and unstable angina, myocardial
infarction (MI), cerebrovascular diseases such as stroke and peripheral artery disease
(PAD), which is also known as peripheral vascular disease (PVD). The high prevalence
and associated mortality of IHDs, thus, mandates the need for early markers that can
help diagnose the condition at an early enough stage, so that preventive measures
can be adopted before a frank clinical disease sets in.[17 ]
Sufficient evidence exists in the literature which indicates that patients with IHDs
show higher degree of pulp calcifications.[18 ]
[19 ] Localized pulp calcifications are a normal part of the aging process of the tooth
physiology, although pulp stones extending to the entire dentition, especially in
younger age groups, are infrequent and need further evaluation to predict the risk
of other associated diseases, including IHDs in the presence of compounding risk factors.[20 ] The present study was planned to estimate the prevalence of pulp stones in patients
diagnosed with/or undergoing treatment for IHDs.
Material and Methods
The present study consisted of 300 subjects within an age range of 25 to 65 years
who were divided into two groups: study group consisting of 150 patients, including
113 males and 37 females, and 150 age- and sex-matched healthy controls. The control
group consisted of subjects who had no significant medical history and in whom the
risk of IHDs was ruled out on the basis of the absence of any predisposing risk factors,
including a previous history of any chest discomfort or a positive family history
for cardiovascular disease and related investigations, as per the cardiologist’s opinion,
while patients who were either recently diagnosed with/or under treatment for IHDs
were included in the study group. The patients who had a known history of other systemic
illnesses including gout and renal disorders or, who were undergoing treatment for
the same, had radiotherapy treatment in the past were excluded from the study. Furthermore,
pregnant females and those who were unwilling to participate in the study were also
excluded from the study, apart from subjects with possible dental causes of pulp stone
formation, including subjects with crowns and bridges, extensive carious lesions or
deeply placed restorations, subjects with history of orthodontic treatment, those
afflicted with bruxism, and subjects who presented with severe attrition and previous
history of trauma. The study protocol and its significance were explained in detail
to each subject and a written, informed consent was obtained from all before their
inclusion into the study. The structure and plan of the study was sent to the Ethics
Committee of the Institution before the start of the study and their approval sought
via. Institutional Ethics Committee Letter approval no SDDC/IEC/01–37–2019. Pulp stones
were imaged using bitewing radiography ([Figs. 1 ] and [2 ]) following conventional technique, while paralleling technique was used under standard
conditions for standardization and reproducibility. The equipment used for taking
bitewing radiographs was wall-mounted, very high-frequency DC (300 kHz), Carestream
(Kodak) dental X-ray machine (Carestream Dental LLC, 3625 Cumberland Blvd. Ste. 700
Atlanta, GA) operating at 60 KVp tube voltage and 7 mA tube current, with a focal
spot of 0.7 mm and focal length of 8 inches. The radiographic films used were Carestream
(Kodak) E-Speed, size 2 dental films (31 mm into 41 mm), while an XCP-Rinn film holder
(Dentsply DeTrey GmbH, De-Trey-Straße 1, 78467 Konstanz, Germany) was used for taking
radiographs.
Fig. 1 Posterior bitewing radiograph revealing pulp stones/calcifications within pulp chambers
of 1st and 2nd molars.
Fig. 2 Posterior bitewing radiograph revealing pulp stones/calcifications within pulp chambers
of 1st and 2nd molars in another patient.
Evaluation of Bitewing Radiographs
All the radiographs were checked by three radiographers while the interexaminer variability
was tested. The radiographs were examined using a magnifying glass in a darkened room,
with the help of a light box, an even, diffuse light source, and peripheral light
blocked to determine the presence of pulp chamber narrowing as well as pulp stones
in the pulp chambers. Narrowing of pulp chamber was defined as a notable reduction
in the size of pulp chamber, while pulp stones were identified as discrete, radiopaque
masses inside the pulp chambers of the teeth and determined as present or absent.
The results obtained were put to statistical analysis while interexaminer variability
was ruled out through replicate observations in all samples.
Statistical Analysis Used
Statistical analysis was done using IBM SPSS Statistics for Windows version 21 (IBM
Corp, Armonk, USA), while independent t -test and Chi-square test were used to check the prevalence of pulp stones in the
study and control groups, based on their gender-, arch-, region- and side-wise distribution.
p < 0.05 was considered statistically significant.
Results
The patients with IHDs exhibited 100% prevalence of pulp stones and the difference
was found to be statistically significant ([Table 1 ]), although there was a significant difference in the mean number of pulp stones
observed in the study and control groups, with the study group revealing 2217 pulp
stones against 639 pulp stones observed in the control group (p < 0.001) ([Table 2 ]). Furthermore, no significant difference was found in relation to the gender predilection
in both the groups ([Table 3 ]). Again, although the results were not found to be statistically significant on
comparison of the study and control groups, maxillary arch and posterior teeth were
predominantly affected in both the groups ([Tables 4 ] and [5 ]). On analyzing the arch-wise prevalence of the total number of pulp stones in the
study and control groups, there was a 51.33% involvement of the maxillary arch in
the study group against 58.67% in the control group, while the prevalence of pulp
stones was found to be 48.67% and 41.33% in case of mandibular arch in the study and
control groups, respectively ([Table 4 ]). The posterior teeth too showed a clear predilection for pulp stones, although
the results were not found to be statistically significant when compared in relation
to the study and control groups. On analyzing the region-wise prevalence of total
number of pulp stones in the study and control groups, 87.33% of the posterior teeth
were found to be afflicted with pulp stone formation against 12.67% in case of the
anterior teeth. Similar results were obtained in the control group, wherein 86.00%
of the posterior teeth revealed pulp stones on radiographic examination against the
anterior teeth, which revealed a mere 14.00% prevalence of pulp stones in the control
group ([Table 5 ]). The results in relation to the predilection for the side of the jaw affected were
found to be statistically insignificant in the present study (p > 0.05) ([Table 6 ]).
Table 1
Number of subjects showing pulp stones in study and control groups
Group
With pulp stone
%
Without pulp stone
%
Total
χ2 -Value
p -Value
Study group
150
100.00
0
0.00
150
15.7890
< 0.001
Control group
135
90.00
15
10.00
150
Total
285
95.00
15
5.00
300
Table 2
Comparison of study and control groups with mean number of pulp stones by independent
t-test
Group
Number (%)
Mean
SD
t-Value
p -Value
Abbreviation: SD, standard deviation.
Study group
2217 (96.24%)
14.78
5.64
25.4998
< 0.001
Control group
639 (27.59%)
4.26
1.06
Table 3
Gender-wise prevalence of total number of pulp stones in study and control groups
Group
Males
%
Females
%
Total
χ2 -Value
p -Value
Study group
113
75.33
37
24.67
150
0.2770
0.5990
Control group
109
72.67
41
27.33
150
Total
222
74.00
78
26.00
300
Table 4
Arch-wise prevalence of total number of pulp stones in study and control groups
Group
Maxillary arch
%
Mandibular arch
%
Total
χ2 -Value
p -Value
Study group
77
51.33
73
48.67
150
1.6301
0.2020
Control group
88
58.67
62
41.33
150
Total
165
55.00
135
45.00
300
Table 5
Region-wise prevalence of total number of pulp stones in study and control groups
Group
Posterior region
%
Anterior region
%
Total
χ2 -Value
p -Value
Study group
131
87.33
19
12.67
150
0.1155
0.7340
Control group
129
86.00
21
14.00
150
Total
260
86.67
40
13.33
300
Table 6
Side-wise prevalence of total number of pulp stones in study and control groups
Group
Right side
%
Left side
%
Total
χ2 -Value
p -Value
Study group
74
49.33
76
50.67
150
0.1201
0.7290
Control group
77
51.33
73
48.67
150
Total
151
50.33
149
49.67
300
Discussion
When pathological calcification occurs in nonviable tissues, it is known as dystrophic
calcification, and it may occur despite normal serum levels of calcium. In contrast,
the deposition of calcium salts in vital tissues is known as metastatic calcification,
and it almost always reflects some degree of derangement in normal calcium metabolism,
leading to hypercalcemia.[21 ]
Dental pulp calcifications date back to the year 1921 when they were first mentioned
by Norman and Johnson as dental pulp nodules, a term which was later modified to dental
pulp stones or denticles.[22 ] Pulp calcifications are usually reported as incidental findings on intraoral radiographs
as discrete, radiopaque bodies enclosed within the pulp chambers or root canals, with
a wide variation in the numbers seen.[23 ]
Kronfeld and Boyle classified pulp stones histologically into true and false forms,
wherein the true pulp stones are more irregular in shape and are lined by odontoblasts
and thus composed of dentine, whereas false pulp stones are constituted by the degenerating
cells of the pulp, which calcify as a part of the process of dystrophic calcification,
attracting calcium despite normal serum levels.[23 ]
[24 ]
[25 ] There is another category of pulp calcifications too, the diffuse or amorphous type
which is seen in close association with the blood vessels.[23 ]
Cardiologists have confirmed the role of calcium phosphate crystals in generating
inflammation within the arteries and also playing a major role in acute MIs, leading
to sudden death of the patients. The base of all calcifications including joint calcifications,
renal calculi, atherosclerotic plaques, as well as pulp stones is made up of calcium
phosphate crystals that elicit an acute immunological response as well as the eventual
sequel, leading to widespread morbidity and mortality.[11 ]
At the ultrastructural level, various studies on pulp stones have also reported similarity
in the nature of pulp stones and calcifications observed in various other tissues
in the body. Ninomiya et al found an even distribution of type I collagen throughout
the pulp stones, while osteopontin was found to play an integral role in the process
of calcification, as it was found in the peripheral areas of pulp stones.[15 ] Likewise, Hirota et al also found similar occurrence of osteopontin in their immunohistochemical
study on atherosclerotic plaque and urinary stones.[26 ]The said observations from various studies, thus, hypothesized a relationship between
the occurrence of pulp stones and the calcifications observed in various other tissues
of the body, including the arterial plaques as well as the renal calculi (nephrolithiasis),
gall bladder stones (cholelithiasis), and various degenerative joint diseases (DJDs),
proposing pulp stones to be a part of the systemic biomineralization process affecting
many tissues of the body.[10 ]
[13 ]
[26 ]
[27 ]
[28 ]
Recently, it was also reported that calcified nanoparticles located in the cytolysosome
could invade human dental pulp tissue through a receptor-mediated endocytosis and
can be one of the important reasons behind dental pulp stone formation.[12 ] Yang et al also detected vacuole containing these calcified nanoparticles, which
indicated the cell's tendency for crystal deposits, inferring that the existence of
calcified nanoparticles might promote calcification as crystallization of the nuclei
leads to the formation of biogenic apatite structures.[29 ]Similarly, Chen et al have also shown the relation of calcified nanoparticles/nanobacteria
in the induction of renal calculi (nephrolithiasis).[30 ]Zeng et al, too, elaborated the role of these calcifying nanoparticles (CNPs), also
called nanobacteria, for pathological calcifications.[31 ]
Furthermore, pulp stones vary in size, ranging from microscopic particles to large,
discrete masses that almost completely obliterate the pulp chamber. Among them, only
the larger pulp stones are radiographically apparent, while those that are either
small in size or relatively less calcified and in the initial stages of calcification
are not routinely detected by the conventional radiological procedures of diagnostics.[16 ]
[28 ]
[32 ]
[33 ] Thus, the true prevalence of pulp stones is always likely to be a little higher
than the results obtained from radiographic evaluations, although radiographs are
considered to be the only means of evaluating the pulp stones in a noninvasive manner
in the clinical settings.[34 ]
The radiographic differentiation between pulp stone and pulpal sclerosis was demonstrated
by Gauz and White who explained that early pulpal sclerosis is a degenerative process
that precedes the formation of frank pulp stones and is not demonstrable radiographically,
while diffuse pulpal sclerosis, on the other hand, produces a generalized calcification
throughout a large area of pulp chamber or pulp canal.[35 ] Pulp stones are discrete calcifications appearing within the pulp, which may be
seen as a definite single or multiple radiopaque structures within the pulp chamber
or canals. Similar results were obtained in the study conducted by Willman who examined
164 teeth from patients of different age groups and found a histological evidence
of pulp calcifications in 87.2% of the teeth examined against 14% of the teeth wherein
pulp stones could be detected radiographically.[36 ]
Most of the prevalence studies have identified pulp stones using radiographic criteria
in concordance with the one used in the present study. In the present study, it was
found that pulp stones were prevalent in 100% of the patients with IHDs in accordance
with the study conducted by Ranjitkar et al who examined the prevalence of pulp stones
in the Australian population and found the same in 46% of the subjects and 10% of
the teeth examined in the study.[34 ] Also, the said study observed subjects in the control group also to be afflicted
with pulp stones similar to the findings of the present study, although the total
number of pulp calcifications observed were lesser in number in the control group
as compared with the study group.
Likewise, in relation to IHDs, Edds et al reported 74% of the patients with IHDs to
be afflicted with pulp stones, while Khojastepour et al reported 68.2% of the patients
with known cardiovascular diseases (CVD) and 28.2% of subjects without CVD having
pulp stones.[7 ]
[9 ] Ezoddini-Ardakani et al, also, observed 67.3% of the teeth in patients with IHDs
having pulp calcifications.[14 ]Nayak et al, although, recorded a little lesser prevalence of pulp stones in their
study compared with these studies, confirming an increased prevalence of pulp stones
in patients with known systemic diseases, primarily CVD, observing the prevalence
of pulp stones in hypertensive patients to be 15.85% higher than in the normal subjects
included.[8 ]
As far as the overall prevalence of pulp stones in the samples studied is concerned,
al-Hadi Hamasha and Darwazeh found pulp stones in 51% of the radiographs and 22% of
the teeth examined in 814 Jordanian adults.[33 ] Ravanshad et al also reported pulp stones in 46.9% of the adult Iranian population
included in their study.[2 ]On similar lines, Sisman et al examined bitewing radiographs of 469 Turkish patients
and found 57.6% prevalence of pulp stones in the sample included and 15% prevalence
among the teeth examined.[37 ] Likewise, Tamse et al evaluated full mouth radiograph of 300 patients and reported
pulp stones in 20.7% of the radiographs examined.[38 ] Baghdady et al assessed 515 Iraqi subjects and recorded 19% of the teeth with pulp
stones.[39 ] Similarly, Gulsahi et al, in their study, found pulp stones in 12% of the subjects
and 5% of the teeth examined.[40 ]Nayak et al, in a study on Indian population, examined 1432 teeth and found 9.35%
prevalence of pulp stones.[8 ]
Contrary to the findings of these studies, Hill stated that of the subjects examined
between 50 to 70 years, 66% of the subjects exhibited pulp stones without a known
evidence or history of other systemic diseases, similar to the finding of the study
conducted by Khojastepour et al.[3 ]
[7 ] The results of the present study also suggested an equal predisposition of both
the sexes for the development of pulp stones, although few studies have reported a
female preponderance toward the same and observed pulp stones to be more common in
females than in males.[34 ]
[38 ]
[41 ] Furthermore, Ranjitkar et al also suggested an increasing prevalence of pulp stones
with age, a finding which was in accordance with the results obtained in the present
study.[34 ]
Also, both the groups in the present study showed a higher prevalence of pulp stones,
wherein another notable finding in the present study was that in relation to the maxillary
teeth, which seemed to have a definite predilection toward the development of pulp
stones. The results of the present study revealed 51.33% of maxillary teeth to be
afflicted with pulp stones against 48.67% of the mandibular teeth in the study group.
Likewise, 58.67% of the maxillary teeth were found to have pulp stones against 41.33%
of the mandibular teeth in the control group, showing a clear predilection of the
maxillary teeth toward pulp stone formation against the mandibular teeth. This was
in accordance with the study conducted by Nayak et al who reported significantly higher
number of pulp stones in the maxilla (12.36%) than in the mandible (5.95%) and in
similar other studies conducted by Ranjitkar et al, Sisman et al and Turkal et al,
who also confirmed similar findings with the results obtained from their studies.[8 ]
[34 ]
[37 ]
[42 ]
The present study also evidenced more number of pulp stones in the posterior teeth
than anterior teeth, in accordance with the results of the studies conducted by Gulsahi
et al, with around 87.33% of posterior teeth afflicted with pulp stones in the study
group against 12.67% of the anterior teeth.[40 ]Similarly, in the control group, the corresponding values were 86.00% in case of
posterior while 14.00% in case of anterior teeth, with a plausible explanation for
this being the rich blood supply in the posterior teeth. al-Hadi Hamasha and Darwazeh
had also put forth a hypothesis based on the observations made from their study that
since posterior teeth were the largest, the rich blood supply in their pulp tissue
would increase their probability for more calcifications observed.[33 ]
Thus, according to the results obtained in the present study, which were largely in
line with the previous similar studies conducted in the past, the present study mandated
for further studies to be conducted in line with the present study, so as to seek
a definite correlation between the occurrence of pulp stones with other systemic diseases,
as have been hypothesized to have a similar etiology behind the calcifications seen
in them. Similar conclusions were drawn in the study conducted by Ozkalayci et al
who had also suggested that a careful radiographic workup and a multidisciplinary
approach in patients with an increased prevalence of pulp stones are of utmost significance
to predict the possibility of other associated systemic disorders that might have
predisposed the subjects to have this kind of a subtle change, seen in the pulp tissues,
which is a less critically acclaimed clinical entity.[43 ]
Conclusions
The findings of the present study suggested a positive correlation between pulp stones
and IHDs, highlighting the significance of dental radiographic examination, which
may lead to the possible early detection of IHDs. Such a screening can easily be employed
as a public health measure and further investigations planned, including a series
of clinical and biochemical tests to rule out the risk for frank IHDs, perhaps, many
years before the actual symptoms of vascular disease set in.
