Open Journal of Stomatology, 2013, 3, 440-446 OJST
http://dx.doi.org/10.4236/ojst.2013.38073 Published Online November 2013 (http://www.scirp.org/journal/ojst/)
Evaluation of an oral moisture-checking device for
screening dry mouth*
Yosuke Fukushima1#, Tetsuya Yoda1, Shoichiro Kokabu1, Ryuichiro Araki2, Tsubasa Murata3,
Yoshimasa Kitagawa3, Ken Omura4, Shuji Toya5, Kayoko Ito6, Saori Funayama6, Hiroshi Iwabuchi7,
Kazuhiro Asano8, Yutaka Imai8, Akihide Negishi9, Satoshi Yokoo9, Goichi Matsumoto10, Eiro Kubota10,
Hideki Watanabe11, Mikio Kusama11, Kojiro Onizawa12, Takuya Goto12, Seiji Nakamura13,
Ryuichi Nakazawa14, Kiyoshi Harada14, Takashi Fujibayashi10
1Department of Oral and Maxillofacial Surgery, Faculty of Medicine, Saitama Medical University, Saitama, Japan
2Community Health Science Center, Saitama Medical University, Saitama, Japan
3Oral Diagnosis and Medicine, Department of Oral Pathobiological Science, Graduate School of Dental Medicine, Hokkaido Univer-
sity, Sapporo, Japan
4Oral Surgery, Department of Oral Restitution, Division of Oral Health Sciences, Graduate School, Tokyo Medical and Dental Uni-
versity, Tokyo, Japan
5Oral and Maxillofacial Surgery, Dry Mouth Clinic, The Nippon Dental University Niigata Hospital, Niigata, Japan
6Division of Gereatric Dentistry, Niigata University Medical & Dental Hospital, Niigata, Japan
7Department of Dentistry and Oral Surgery, Tochigi National Hospital, Tochigi, Japan
8Department of Oral and Maxillofacial Surgery, Dokkyo Medical University School of Medicine, Tochigi, Japan
9Department of Stomatology and Oral Surgery, Gunma University Graduate School of Medicine, Maebashi, Japan
10Department of Oral and Maxillofacial Surgery, Kanagawa Dental College, Yokosuka, Japan
11Department of Oral and Maxillofacial Surgery, Jichi Medical University, Tochigi, Japan
12Department of Oral and Maxillofacial Surgery, Institute of Clinical Medicine, University of Tsukuba, Tsukuba, Japan
13Section of Oral and Maxillofacial Oncology, Division of Maxillofacial Diagnostic and Surgical Sciences, Faculty of Dental Science,
Kyushu University, Fukuoka, Japan
14Department of Oral and Maxillofacial Surgery, Division of Medicine, Interdisciplinary Graduate School of Medicine and Engi-
neering, University of Yamanashi, Kofu and Tamaho, Japan
Received 18 August 2013; revised 20 September 2013; accepted 2 October 2013
Copyright © 2013 Yosuke Fukushima et al. This is an open access article distributed under the Creative Commons Attribution Li-
cense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
Objective: This multicenter clinical study was to
assess the clinical usability of an oral moisture-
checking device in detecting the dry mouth patients
and evaluating the optimal measurement site.
Materials and Methods: The study group comprised
250 patients with dry mouth and 241 healthy
volunteer subjects at 13 medical centers. This device
was used to measure the moisture degrees of the
lingual mucosa and the buccal mucosa. Subjective
oral dryness, objective oral dryness, and saliva flow
rates were also compared between the two groups.
For statistical analysis, receiver-operating chara-
cteristic analysis was performed to calculate the area
under the curve (AUC). Results: The moisture degree
of the lingual mucosa was significantly lower in the
dry mouth group (27.2 ± 4.9) than that in the healthy
group (29.5 ± 3.1, AUC = 0.653). When a lingual
mucosa moisture degree of 31.0 or higher was defined
as normal, less than 27.0 as dry mouth, and 27.0 to
less than 31.0 as borderline zone of dry mouth, both
the sensitivity and the specificity for the diagnosis of
dry mouth were close to 80%. Conclusion: These
results suggest that the oral moisture-checking device
is a usable screening device for dry mouth.
Keywords: Dry Mouth; Oral Moisture-Checking Device;
ROC Analysis
1. INTRODUCTION
*On June 2, 2010, Mucus® received manufacturing and marketing ap-
p
roval as a body composition analyzer, a class II controlled medical
device (medical device approval number: 22200BZX00640000) by
Ministry of Health, Labour and Welfare, Japan. We have no financial
conflict of interest.
#Corresponding author.
In general, oral dryness is objectively evaluated by ex-
aminations of salivary flow rates by techniques of stimu-
lated whole salivary collection (SWSC) such as the

Y. Fukushima et al. / Open Journal of Stomatology 3 (2013) 440-446 441
chewing gum test and the Saxon test or unstimulated
whole salivary collection (UWSC) such as spitting me-
thod, or by assessing salivary gland secretory function by
salivary gland scintigraphy. These methods indirectly
estimate oral dryness on the basis of the salivary flow
rate and salivary gland function, but do not evaluate oral
mucosal dryness (moisture degree) directly.
An oral moisture-checking device has been developed
recently by adapting a skin moisture sensor suitable for
oral mucosa. This device measures the moisture content
of the surface of oral mucosa on the basis of electrostatic
capacity. In 2002, a prototype model was developed, and
possibilities for clinical use have been reported [1-3].
Subsequently, several improvements were made, in-
cluding the use of smaller device sensors, the introduc-
tion of a spring to ensure that pressure is uniformly ap-
plied, and changing the shape of the handle and labeling.
The improved oral moisture-checking devices in third-
generation are now available. Measurements can now be
obtained in about 2 seconds, causing minimal stress and
discomfort to subjects in examinee [4,5]. However, the
physiological borderline value classifying patients with
dry mouth from normal subjects has not been established
yet. In addition, although the moisture contents of the
tongue and buccal mucosa are usually measured, the op-
timal site for measurement remains unclear. The purpose
of this multicenter clinical study is to assess the clinical
usability of an oral moisture-checking device in detecting
the dry mouth patients and evaluating the optimal meas-
urement site.
2. SUBJECTS AND METHODS
The study group comprised subjects with dry mouth (dry
mouth group) and those without dry mouth (healthy
group) who were enrolled at the following 13 participat-
ing medical centers: Hokkaido University Hospital, Jichi
Medical University Hospital, Dokkyo Medical Univer-
sity Hospital, Tochigi National Hospital, Gunma Univer-
sity Hospital, Tsukuba University Hospital, Saitama
Medical University Hospital, Tokyo Medical and Dental
University Hospital, Kanagawa Dental College Hospital,
Niigata University Medical and Dental Hospital, Nippon
Dental University Niigata Hospital, Yamanashi Univer-
sity Hospital, and Kyushu University Hospital.
2.1. Inclusion Criteria for Dry Mouth Group
Subjects in the dry mouth group were adults who were
subjectively aware of mouth dryness and had a diagnosis
of dry mouth according to the criteria proposed by the
Japanese Society for Oral Mucous Membrane [6] (i.e.,
subjects who have objective symptom of dry mouth with
decreased salivary flow rates in SWSC ≤10 mL/10 min-
utes on the chewing gum test or ≤2 g/2 minutes on the
Saxon test, or UWSC ≤1.5 mL/15 minutes, or subjects
with decreased salivary gland function on salivary gland
scintigraphy). These examinations were performed at the
day or within 1 week before or after the measurement of
oral moisture degree with an oral moisture-checking de-
vice. During this period, no changes were allowed in
factors with potential effects on mouth dryness, such as
modifications of treatments, drugs, or environmental
factors. However, if patients were receiving saliva-sti-
mulating agents such as cevimeline hydrochloride hy-
drate, pilocarpine hydrochloride or some other treatments
such as salivary gland massage, the aforementioned ex-
aminations were obtained on the same day as measure-
ment with an oral moisture-checking device. Persons
who routinely used oral moisturizers and those who were
considered unsuitable for the study by the investigator
were excluded.
2.2. Inclusion Criteria for Healthy Group
Subjects in the healthy group were adult volunteers with
no subjective awareness of mouth dryness who had SWSC
rate of >10 mL/10 minutes on the chewing gum test.
Persons who had a diagnosis of dry mouth or Sjögren’s
syndrome, abnormalities of the oral mucosa, or burning
mouth syndrome, and those who were considered un-
suitable for the study by the investigator were excluded.
The enrollment period was from October 2009 through
May 2010. The target sample size determined with pre-
liminary power analysis was 250 for both dry-mouth and
healthy groups. Subjects were consecutively assigned to
two groups according to the above mentioned criteria.
The following variables were evaluated: subjective
oral dryness, objective oral dryness, SWSC rates on the
chewing gum test, UWSC rates on the spitting method,
and oral moisture degree as measured with the testing
oral moisture-checking device. A self-administered ques-
tionnaire was used to assess subjective oral dryness.
Each patient was requested to grade oral dryness at the
time of measuring oral moisture degree as follows: no
sensation of mouth dryness (0 points), mild mouth dry-
ness (1 point), moderate mouth dryness (2 points), and
severe mouth dryness (3 points). Objective oral dryness
was evaluated by the examiner who measured mois-
ture-checking device as follows: none (0 points), mild (1
point), moderate (2 points), and severe (3 points). Mu-
cus®, oral moisture-checking devices* (serial numbers,
301722 to 301726, 301731, 301733 to 301736, 301741,
301744 to 301754, 301756 to 301758, and 301760; Life
Co., Ltd., Saitama, Japan) were used to measure oral
moisture degree (Figure 1). To eliminate the effects of
stimulants such as food, water, speech, and stress on the
measurements, the subjects in examinee were requested
to physically rest and mentally relax for about 5 minutes

Y. Fukushima et al. / Open Journal of Stomatology 3 (2013) 440-446 442
Figure 1. Oral moisture-checjing device.
before measurement [5]. A disposable cover which was
made by polyethylene was applied to the sensor for each
subject. This coverage of the sensor has been proven not
to disturb the calibration of the device. The measurement
sites were the center of the lingual mucosa about 10 mm
from the tip of the tongue and the right buccal mucosa
about 10 mm from the corner of the mouth (Figures 2(a)
and 2(b)). The sensor was manually applied to the meas-
urement sites at a pressure of about 200 g, as practiced
beforehand with a manometer. To eliminate outliers, oral
mucosal wetness was measured continuously 3 consecu-
tive times. The median was used as a representative
value [4]. We examined the following variables: oral
moisture degree according to measurement site, partici-
pating medical centers, cut-off values according to
measurement sites, correlations of oral mucosal dryness
with other measured variables, and the presence or ab-
sence of adverse events at the time of measurement of
oral moisture degree.
Receiver-operating characteristic (ROC) analysis, un-
paired t-tests, Pearson correlation coefficients, and
Spearman correlation coefficients (Medcalc version 11.3
for Windows) were used for statistical analysis. As for
ROC analysis, the area under the ROC curve (AUC) was
calculated, and the value providing the best balance be-
tween sensitivity and specificity was used as a cut-off
point. P values of less than 5% were considered to indi-
cate significant differences.
In this study, all subjects received thorough explana-
tions about the contents of examinations, methods in-
cluding the measurement, the need for examinations and
the measurement, associated risks, freedom to give or
withdraw consent, protection of privacy and personal
information, anticipated benefits, and alternative exami-
nations that were available. All subjects signed informed
consent forms. The ethical approval of this study was
obtained by the Institutional Review Board of Saitama
Medical University (approval number: 09-015-1), as well
as by the institutional review boards of each participating
medical center.
3. RESULTS
1) Demographic characteristics of subjects
The study group comprised 250 subjects with dry
mouth (35 men and 215 women) and 241 healthy sub-
jects with no evidence of dry mouth (117 men and 124
(a)
(b)
Figure 2. Measurement of oral moisture degree of the lingual
mucosa and buccal mucosa; (a) Lingual mucosa; (b) Buccal
mucosa.
women) who were enrolled at 13 medical centers (A to
M) (Table 1). Mean age was 65.0 years in the dry mouth
group and 50.5 years in the healthy group.
2) Oral moisture degree according to the measurement
site and medical center
Oral moisture degree of the lingual mucosa was sig-
nificantly lower in the dry mouth group (27.2 ± 4.9
[mean ± standard deviation]) than in the healthy group
(29.5 ± 3.1, p < 0.001). Oral moisture degree of the buc-
cal mucosa did not differ significantly between the dry
mouth group (31.2 ± 3.7) and the healthy group (31.3 ±
2.6). In both groups, oral moisture degree of the buccal
mucosa was significantly higher than that of the lingual
mucosa (p < 0.001 in the both groups) (Table 2).
The data from 9 centers (A to I) had enough sample
sizes needed for statistical comparison between the 2

Y. Fukushima et al. / Open Journal of Stomatology 3 (2013) 440-446 443
Table 1. Number of patients according to each medical center.
Medical center Dry mouth group Healthy group
A 16 69
B 39 24
C 25 24
D 27 20
E 25 16
F 27 13
G 23 15
H 20 18
I 18 15
J 25 2
K 0 17
L 2 8
M 3 0
Total 250 241
Table 2. Oral moisture degree (mean ± SD) according to
measurement site.
Dry mouth groupHealthy group P value
Lingual mucosa 27.2 ± 4.9 29.5 ± 3.1 p < 0.001
Buccal mucosa 31.2 ± 3.7 31.3 ± 2.6 n.s.
P value p < 0.001 p < 0.001
groups. The oral moisture degree of the lingual mucosa
differed significantly between the dry mouth group and
healthy group in 4 centers (B, D, F, and G). The oral
moisture degree of the buccal mucosa differed signifi-
cantly between the groups in only 2 centers (D and G)
(Tables 3 and 4).
3) Cut-off points according to measurement site
At the lingual mucosa, AUC calculated by ROC analy-
sis was 0.653 (Figure 3). The best balance between sen-
sitivity and specificity was achieved at a cut-off point of
29.3, with sensitivity and specificity of 67.6% and 58.9%,
respectively. A cut-off point of 30.9 had sensitivity of
80.8% and specificity of 32.0%. A cut-off point of 27.1
had sensitivity of 39.2% and specificity of 81.3% (Table
5).
At the buccal mucosa, AUC calculated by ROC analy-
sis was 0.520 (Figure 4). A cut-off point of 32.9 pro-
vided the best balance between sensitivity and specificity,
with sensitivity of 74.7% and specificity of 34.8% (Ta-
ble 6).
4) Correlation of oral moisture degree with other
measured variables
Table 3. Mean oral moisture degree of the lingual mucosa ac-
cording to medical center.
Medical centerDry mouth group Healthy group P value
A 28.8 ± 5.3 28.9 ± 3.7 n.s.
B 26.8 ± 4.7 31.1 ± 2.1 p < 0.001
C 28.2 ± 3.8 28.3 ± 3.0 n.s.
D 27.3 ± 3.8 30.3 ± 0.6 p < 0.001
E 27.8 ± 5.1 30.6 ± 3.4 n.s.
F 28.1 ± 4.6 31.8 ± 3.5 P = 0.0078
G 25.4 ± 3.0 29.8 ± 2.4 p < 0.001
H 27.5 ± 5.5 29.7 ± 2.8 n.s.
I 25.8 ± 6.2 28.3 ± 3.3 n.s.
Table 4. Mean oral moisture degree of the buccal mucosa ac-
cording to medical center.
Medical centerDry mouth group Healthy group P value
A 31.2 ± 3.4 31.2 ± 2.5 n.s.
B 31.6 ± 2.5 32.5 ± 2.0 n.s.
C 32.7 ± 2.8 29.5 ± 3.6 n.s.
D 28.6 ± 2.9 31.4 ± 0.9 p < 0.001
E 33.6 ± 3.3 32.8 ± 2.6 n.s.
F 32.9 ± 4.6 33.4 ± 1.6 n.s.
G 28.6 ± 2.4 30.4 ± 1.6 P = 0.0046
H 32.2 ± 2.3 31.9 ± 2.1 n.s.
I 28.0 ± 5.6 29.2 ± 2.9 n.s.
02040 60 80100
False positive rate (100% - specificity)
AUC = 0.653
0
20
40
60
80
100
Positive rate (sensitivity)
Figure 3. Receiver-operating characteristic curve for the lin-
ual mucosa. g

Y. Fukushima et al. / Open Journal of Stomatology 3 (2013) 440-446 444
Table 5. Cut-off values for the lingual mucosa.
Cut-off value Sensitivity 95%CI Specificity 95%CI Positive likelihood ratio Negative likelihood ratio
30.9 80.8 75.4 - 85.5 32 26.1 - 38.2 1.19 0.6
29.3 67.6 61.4 - 73.4 58.9 52.4 - 65.2 1.65 0.55
27.1 39.2 33.1 - 45.6 81.3 75.8 - 86.0 2.1 0.75
0 20 4060 80 100
False positive rate (100% - specificity)
AUC = 0.520
0
20
40
60
80
100
Positive rate (sensitibity)
Figure 4. Receiver-operating characteristic curve for the lbuc-
cal mucosa.
Subjective oral dryness and objective oral dryness
were measured in all 491 participating subjects. At the
lingual mucosa, the correlation coefficients of oral mois-
ture degree with subjective oral dryness and objective
oral dryness were −0.320 and −0.350, respectively, indi-
cating weak negative correlations (p < 0.05). At the buc-
cal mucosa, oral moisture degree did not correlate with
either subjective oral dryness or objective oral dryness.
Among the 491 subjects, salivary flow rates were
measured by SWSC of the chewing gum test in 472 sub-
jects, and UWSC in 211. At the lingual mucosa, the cor-
relation coefficients of the oral moisture degree with
SWSC and UWSC were 0.25 and 0.34, respectively,
indicating weak positive correlations (p < 0.05). At the
buccal mucosa, however, oral moisture degree did not
correlate with saliva flow rates (Table 7).
5. Presence or absence of adverse events at the time of
measuring oral moisture degree
During the study period, there were no adverse events
caused by the use of the oral moisture-checking device.
4. DISCUSSION
This oral moisture-checking device measures electro-
static capacity on the basis of impedance generated by
connecting high-frequency waves supplied by a 5-volt
battery to plus and minus comb-shaped electrodes de-
picted on the surface of a 7.2 mm2 sensor. The electro-
static capacity reflects not only the water content of the
oral mucosal surface, but also the intramucosal water
content to a depth of about 50 µm. The numerical data
are expressed as 3-digit numbers, ranging from 0.00 to
99.8. The value strongly correlates positively with the
actual gravimetric moisture percentage, with a correla-
tion coefficient of 0.99, and is a relative measure of wa-
ter content, rather than the actual moisture percentage.
Even if technical difficulties occur, such as damage to an
insulator, only a limited site is exposed to a maximum
electric current of 8.9 µA and the effect on the human
body is nearly negligible.
The sensor has a square surface. Accurate measure-
ments cannot be obtained unless the surface of this sen-
sor comes in close contact with the mucosal surface.
Therefore, a flat surface of an adequate size is needed at
the measurement site of the oral mucosa. The lingual
mucosa and the buccal mucosa have been used as meas-
urement sites [1-4]. These sites were also used for meas-
urement in the present study. The moisture degree of the
buccal mucosa was significantly higher than that of the
lingual mucosa in both the dry mouth group and healthy
group. Disabato-Mordarski et al. reported that the thick-
ness of the moisture coating of the oral mucosa is site-
specific, strongly suggesting that the moisture degree
differs depending on the site of measurement [7]. Taka-
hashi et al. similarly reported that the moisture degree of
the buccal mucosa tended to be higher than that of the
lingual mucosa in patients with subjective oral dryness
[2]. One of the reasons for this difference is that the
measurement site of the buccal mucosa is near the pa-
rotid papilla. Secreted saliva may thus be directly meas-
ured. Takahashi et al. found that the moisture degrees
differed significantly between patients with dry mouth
and healthy subjects in both the lingual mucosa and the
buccal mucosa [2]. In our study, however, the moisture
degree of the buccal mucosa did not differ between the
groups. Moreover, the moisture degrees of the buccal
mucosa were nearly the same in the dry mouth group
(31.2 ± 3.7) and the healthy group (31.3 ± 2.6). When the
results were analyzed according to medical centers, the
moisture degree of the tongue was lower in the dry
mouth group at all centers, whereas the moisture degree
of the buccal mucosa was higher in the dry mouth group
than in the healthy group at 3 centers. In addition, the
moisture degree of the buccal mucosa did not signifi-
cantly correlate with subjectve oral dryness, objective i

Y. Fukushima et al. / Open Journal of Stomatology 3 (2013) 440-446 445
Table 6. Cut-off values for the buccal mucosa.
Cut-off value Sensitivity 95%CI Specificity 95%CI Positive likelihood ratio Negative likelihood ratio
33.7 81.7 76.3 - 86.4 26.4 21.0 - 32.3 1.11 0.69
32.9 74.7 68.7 - 80.1 34.8 28.9 - 41.1 1.15 0.73
28.3 12.5 8.6 - 17.3 80.4 74.9 - 85.1 0.64 1.09
Table 7. Relation between oral moisture degree and measured variables.
Subjective oral dryness
(N = 491)
Objective oral dryness
(N = 491)
SWSC
(N = 472)
UWSC
(N = 211)
Correlation coefficient −0.32* −0.35* 0.25* 0.34*
Lingual mucosa
95%CI −0.38 to 0.22 −0.43 to -0.27 0.16 to 0.33 0.21 to 0.45
Correlation coefficient 0.01 −0.02 −0.03 0.11
Buccal mucosa
95%CI −0.08 to 0.10 −0.10 to 0.07 −0.12 to 0.06 −0.03 to 0.24
oral dryness, the results of SWSC and UWSC. These
findings suggest that the lingual mucosa is better suited
than the buccal mucosa for the measurement of moisture
degree by the oral moisture-checking device.
Overall, the mean moisture degree of the lingual mu-
cosa differed significantly between the dry mouth group
and healthy group, but when the results were analyzed
according to centers, significant differences were found
at only 4 of the 9 centers. These results may have been
caused by problems such as measurement bias of the
device itself, technical bias of using the device and selec-
tion bias in subject enrollment among the centers. As for
measurement conditions, oral moisture degree (dryness)
might be influenced by factors immediately before
measurement, such as drinking water, prolonged conver-
sation during interviews, and extreme tension. To elimi-
nate these factors, subjects should physically rest and
mentally relax for about 5 minutes before measurement
[5]. Our study was conducted in accordance with this
recommendation. However, some bias may have still
existed. The optimal measurement pressure of the sensor
of an oral moisture-checking device is 200 g. If the sen-
sor is applied to the lingual mucosa at a pressure of 300 g,
the value measured by the moisture-checking device
would increase by 1.1 times on average [4]. In our study,
we measured the moisture degree after practicing appli-
cation of the sensor at a pressure of 200 g. However, we
do not have exact evidence whether oral moisture degree
was actually measured at a uniform pressure in all sub-
jects. Outliers might occur if the contact angle of the
sensor is not vertical to the mucosal surface. To avoid the
occurrence of outliers, the median value of 3 or 5 meas-
urements should be used [4]. In our study, we used the
median of 3 measurements, but all outlying values may
not have been eliminated.
Oral moisture degree thus may not have been meas-
ured appropriately in some subjects. However, the AUC
of the ROC curve for the lingual mucosa was 0.653 in-
cluding these values. This value is comparable to that of
the diagnostic accuracy of creatine kinase for myocardial
infarction [8]. These results indicate that the oral mois-
ture-checking device may be a usable tool for the ex-
amination of dry mouth. However, when a cut-off point
of 29.3, providing the best balance between sensitivity
and specificity, was used for diagnosis, the sensitivity
and specificity were only 67.6% and 58.9%, respectively.
Therefore, a differential diagnosis between dry mouth
and non-dry mouth might be difficult by using cut-off
point of 29.3. Taken together, the present oral mois-
ture-checking devices should be considered as a screen-
ing device, and a borderline range between dry mouth
and non-dry mouth should be established. In our study,
the cut-off value providing a sensitivity of at least 80%
was 30.9 (sensitivity, 80.8%), indicating that dry mouth
will not be diagnosed in about 2 of 10 patients with this
condition. The cut-off value with a specificity value of at
least 80% was 27.1 (specificity, 81.3%), indicating that
dry mouth is misdiagnosed in less than 2 of 10 healthy
subjects. If a moisture degree of 27.0 to 31.0 is defined
as borderline zone for diagnosing dry mouth, a value of
more than 31.0 as normal, and a value of less than 27.0
as dry mouth, the sensitivity and specificity are close to
80%, making the oral moisture-checking device to be a
usable screening tool for dry mouth.
Conventionally, dry mouth was diagnosed mainly on
the basis of symptoms and salivary flow rates on the
chewing gum test and other examinations. Osailan et al.
showed that mucosal wetness of the anterior tongue cor-
relate with UWSC in dry mouth patients [9]. Won et al.
reported that moisture of the oral cavity depends on the
USWC, is not always decreased at least in some patients
[10].

Y. Fukushima et al. / Open Journal of Stomatology 3 (2013) 440-446 446
In our study, only a weak correlation was obtained at
the lingual mucosa. However, saliva flow rates are
merely an index of salivary gland function. Needless to
say, decreased secretion of saliva may lead to dry mouth.
If oral mucosal wetness is preserved, mouth dryness may
not necessarily develop. On the other hand, even if saliva
flow is enough, xerostomia induced by excessive oral
vaporization can occur. Because the oral moisture-
checking device measures the amount of moisture not
only on the oral mucosal surface, but also in the epithet-
lium of the oral mucosa, it provides a more accurate
measure of the moisture status (dryness) of the oral mu-
cosa than dose saliva flow rate. Therefore, the oral
moisture-checking device may be usable as a screening
device of the moisture status (dryness) of the oral mu-
cosa. The oral moisture-checking device can be used to
provide one of standard measures of the moisture status
(dryness) of the oral mucosa. With further improvements,
such devices are expected to be widely used for the ob-
jective assessment of dry mouth.
5. CONCLUSION
The oral moisture degree in patients with dry mouth
group and normal subjects group was measured and sta-
tistically analyzed. The moisture degree of the lingual
mucosa showed significant differences between the groups,
whereas that of the buccal mucosa did not. On ROC
analysis, the AUC is 0.653 for the lingual mucosa and
0.520 for the buccal mucosa. For the lingual mucosa,
when a moisture degree of more than 31.0 is defined as
normal, less than 27.0 as dry mouth and 27.0 to 31.0 as
borderline zone of dry mouth, both the sensitivity and the
specificity are close to 80%. These results suggest that
this moisture-checking device is usable as a screening
device for dry mouth.
6. ACKNOWLEDGEMENTS
We are grateful to Life Co., Ltd. for kindly providing us with the oral
moisture-cheking devices.
REFERENCES
[1] Yamada, H., Nakagawa, Y., Nomura, Y., Yamamoto, K.,
Suzuki, M., Watanabe, N.Y., Saito, I. and Seto, K. (2005)
Preliminary results of moisture checker for mucus in di-
agnosing dry mouth. Oral Diseases, 11, 405-407.
http://dx.doi.org/10.1111/j.1601-0825.2005.01136.x
[2] Takahashi, F., Koji, T. and Morita, O. (2006) Oral dry-
ness examination: Use of an oral moisture checking de-
vice and modified cotton method. Prosthodontic Reserch
and Practice, 5, 26-30. http://dx.doi.org/10.2186/prp.5.26
[3] Murakami, M., Nishi, Y., Kamashita, Y. and Nagaoka, E.
(2009) Relationship between medical treatment and oral
dryness diagnosed by oral moisture-checking device in
patients with maxillofacial prostheses. Journal of Prost-
hodontic Research, 53, 67-71.
http://dx.doi.org/10.1016/j.jpor.2008.08.010
[4] Fukushima, Y., Kokabu, S., Kanaya, A., Hori, N.,
Tateyama, T., Sato, T., Sakata, Y., Kobayashi, A., Araki,
R., Yanagisawa, H. and Yoda, T. (2007) Experimental
examination of appropriate measurement method of oral
moisture checking device. Japanese Society for Oral
Mucous Membrane, 13, 16-25.
[5] Fukushima, Y., Yoda, T., Araki, R., Hori, N., Kokabu, S.,
Yakata, Y. and Kobayashi, A. (2009) Experimental ex-
amination of temporal variations of the moisture degree
of the oral mucosa in ordinary persons. Japanese Society
for Oral Mucous Membrane, 15, 15-21.
http://dx.doi.org/10.6014/jjomm.15.15
[6] Committee for the Classification on Terminology of Japa-
nese Society for Oral Mucous Membrane (2008) Classi-
fication of xerostomia (dry mouth). Japanese Society for
Oral Mucous Membrane, 14, 86-88.
[7] Disabato-Mordarski, T. and Kleinberg, I. (1996) Meas-
urement and comparison of the residual saliva on various
oral mucosal and dentition surfaces in humans. Archives
of Oral Biology, 41, 655-665.
http://dx.doi.org/10.1016/S0003-9969(96)00055-6
[8] Peirce, J.C. and Cornell, R.G. (1993) Integrating stratum-
specific likelihood ratios with the analysis of ROC curves.
Medical Decision Making, 13, 141-151.
http://dx.doi.org/10.1177/0272989X9301300208
[9] Osailan, S., Pramanik, R., Shirodaria, S., Challacombe,
S.J. andProctor, G.B. (2011) Investigating the relation-
ship between hyposalivation and mucosal wetness. Oral
Diseases, 17, 109-114.
http://dx.doi.org/10.1111/j.1601-0825.2010.01715.x
[10] Won, S., Kho, H., Kim, Y., Chung, S. and Lee, S. (2001)
Analysis of residual saliva and minor salivary gland se-
cretions. Archives of Oral Biology, 46, 619-624.
http://dx.doi.org/10.1016/S0003-9969(01)00018-8