# The Efficiency of Operating Microscope Compared with Unaided Visual Examination, Conventional and Digital Intraoral Radiography for Proximal Caries Detection

Authors: Ilkay Peker; Meryem Toraman Alkurt; Oya Bala; Bulent Altunkaynak
Journal: International Journal of Dentistry
 (2009)

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## Abstract

Objective.  The purpose of this study was to evaluate the efficiency of operating microscope compared with unaided visual examination, conventional and digital intraoral radiography for proximal caries detection.  Materialsand Methods. The study was based on 48 extracted human posterior permanent teeth. The teeth were examined with unaided visual examination, operating microscope, conventional bitewing and digital intraoral radiographs. Then, true caries depth was determined by histological examination. The extent of the carious lesions was assessed by three examiners independently. One way variance of analysis (ANOVA) and Scheffe test were performed for comparison of observers, and the diagnostic accuracies of all systems were assessed from the area under the ROC curve (Az). Results. Statistically significant difference was found between observers (P<.01). There was a statistically significant difference between operating microscope-film radiography, operating microscope-RVG, unaided visual examination-film radiography, and unaided visual examination-RVG according to pairwise comparison (P<.05). Conclusion. The efficiency of operating microscope was found statistically equal with unaided visual examination and lower than radiographic systems for proximal caries detection.


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## Body

## 1. Introduction

A variety of test  methods are
discussed for the  diagnosis of proximal tooth
surfaces. Adjuncts such as bitewing  radiography and  fiber-optic transillumination provide an
improvement to unaided vision. Unaided visual diagnosis had detected fewer than
50% of caries lesions on occlusal surfaces and even
fewer on proximal surfaces [1].It is not possible to detect only with unaided visual
examination in interproximal caries lesions; radiographs help for proximal
caries diagnosis and detection of their lesion depth [2, 3]. The combination of visual
inspection and bitewing radiographic images is accepted as a standard procedure
in proximal caries diagnosis [4]. However, proximal radiolucencies on
bitewing radiographs are not always indicative of clinical cavitation. The
deeper the radiolucency penetrates enamel and dentine, the higher the
probability of cavitation [5].Due to
difficulties in proximal caries detection, different methodologies were
investigated. Magnification is an accessible, commonly advocated aid to
diagnosis [6]. Recently, the new methods of magnifying visual aids such as
intraoral camera, magnification loops, and operating microscope are used for
caries diagnosis, restorative treatment decisions, root resection, and retrograde
canal preparation [7, 8]. Previous studies [9, 10] had investigated
the efficiency of operating
microscope for occlusal caries diagnosis, but there is insufficient
publication [5, 11] about  usage of this device for proximal caries
detection in dental literature.The purpose of this study was
to evaluate the efficiency of operating microscope
compared with unaided visual examination, conventional
and digital intraoral radiography for proximal caries detection by means of
receiver operating characteristic (ROC) curve analysis.


## 2. Materials and Methods

The study was based on 48 extracted
human posterior permanent teeth, 24 molars and 24 premolars stored in a 5%
buffered formalin solution. No specimens exhibited any restoration on the
proximal surfaces. Organic and
inorganic debris were removed by an excavator and then the teeth were cleaned
by pumice and water slurry. Three mouth models were prepared with the teeth to
simulate the clinical condition. The models were fixed in a phantom head which
was adjusted to a dental unit during the sessions of unaided visual examination
and operating microscope assessment. The proximal surfaces coronal to the
cementoenamel-junction of the teeth were assessed by two specialists of oral
diagnosis and radiology and one specialist of
restorative dentistry of at least 10 years of experience independently. To
avoid observer fatigue, an interval of at least one week had separated each diagnostic
session.The models were
examined under a dental unit light, by using a dental mirror (size 5) and the air water syringe
of the dental unit without any magnification for unaided visual examination.
The clinicians evaluated the extent of the carious lesions in the proximal
surfaces of the teeth according to a 5-point rating scale
(Table1) [5].Table 1
Criteria used for evaluations.
ScoresVisual examination & operating
microscopeRadiographicHistological0No
lesionSoundSound1Enamel
opacity with smooth surfaceRadiolucency
in enamelCaries
in enamel2Enamel
opacity with rough surfaceRadiolucency
in dentino-enamel junctionCaries
in dentino-enamel junction3Cavitation
restricted to the enamelRadiolucency
in the outer half of the dentineCaries
in the outer half of the dentine4Cavitation
extending into dentineRadiolucency
in the inner half of the dentineCaries
in the inner half of the dentineThen the teeth
were examined using an operating  microscope 16x magnification (Moller-Wedel,
Dento 300, Wedel, Germany) according to the same scale. The
observers assessed the teeth adjusting the height of the operating stool at a
12 o’clock position. The position of operating microscope was not changed to
eliminate the position errors during
the examinations. Pictures captured on the computer monitor were recorded using
a video recorder.After unaided
visual and operating microscope examinations were completed, the teeth were
mounted in dental stone models 3 in a row (either 2 premolars and 1 molar or 1
premolar and 2 molars) with proximal surfaces in contact.Conventional
bitewing radiographs of the teeth were obtained using a specially designed
holder to provide standardized bitewing projection geometry in the buccolingual
direction, tangential to the proximal surfaces.
The object to film distance was approximately 0.5 cm and the
source-to-image receptor distance was 32 cm.
Size 2 Insight (Eastman Kodak Company, Paris, France) films with an exposure time of 0.16
seconds and CCX intraoral unit (Trophy, Instrumentarium, Tuusula, Finland) with focal spot of size 0.8 mm, operating at 70 kVp and 8 mA, with 2.5 mm of aluminum-equivalent filtration were used. One centimeter of
soft tissue equivalent material was used to simulate scatter radiation and beam
attenuation from facial tissues. All film radiographs were developed in
automatic film processor (Velopex, Extra-X, Medivance Instruments Ltd., London, UK, and NW107A) with freshly prepared solutions in the same
day.The CCD-based
system to be evaluated was the Radiovisiography (RVG, 2000 Model, Trophy
Radiologie, Paris, France).
Digital images were obtained with 32 cm sensor to focal spot distance with an exposure
time of 0.08 seconds under the same standardized conditions and were stored
using the RVG image management software.The film
radiographs were assessed using a masked light box and a 2x magnification X-viewer
(Luminosa, CSN Industrie, Cinisello
Balsamo, Italy)
by three clinicians independently in a quiet room with subdued ambient
lighting. Images from the digital system were displayed on a 17-inch monitor in
the same ambient lighting. Brightness and contrast features of the software
were not changed. The observers indicated their decision separately for each
interproximal side of the teeth by masking other side with the use of a black
cartoon.  They assessed the extent of the
carious lesions according to a 5-point rating scale (Table1) [12].After all
assessments were completed, the teeth were histologically prepared. The
proximal surfaces were first colored with a solution of propylene glycol with
added basic fucsin (0.5%) for 10 seconds and rinsed in tap water. Then, the
teeth were hemisectioned perpendicularly to the proximal surfaces from their
santral fossas by a diamond disc under water-cooling. Two sections were obtained,
each section was examined under stereomicroscope (Olympus SZ 60, Tokyo, Japan) with a 10x magnification. Two observers not
participating in the study both experienced in histological examination and
being blinded to the
radiographic appearance of the surfaces evaluated the sections by consensus
according to a 5-point confidence scale (Table1)
[12].Histological validation served as a “gold standard” for all
tested methods. One way variance of analysis (ANOVA) and pairwise comparisons
(Scheffe test) were performed for comparison of observers. The diagnostic
accuracies of the four diagnostic systems were assessed from the area under the
ROC curve (Az). Med-Calc (version 7.3) was used for ROC analysis. The
rating scales were dichotomized as “presence” or “absence” of caries during the
analysis. Score 0 in both radiographic and histological scales was detected as
absence of caries and the others were detected as presence of caries.  Az values were calculated for each
observer for each diagnostic method. The Az values were analyzed by
pairwise comparison of ROC curves. SPSS-version 13.0 for Windows was used for
all calculations.  The level of
statistical significance was α = 0.05.


## 3. Results

The status of the 96 proximal
surfaces of the teeth were assessed. Histological examination of the teeth
confirmed that 61 (63.54%) of the proximal surfaces were caries free, whereas
35 (36.46%) of proximal surfaces determined caries lesions of different depths.
The numbers of
proximal surfaces for each score according to the histological examination are
shown in Table2.Table 2
Histological examination of the teeth.
ScoresNo. of tooth surfacesPercent (%)Score 06163.54Score 133.12Score 21212.5Score 322.09Score 41818.75Statistically significant difference was found
between three observers at 99% confidence interval (P  < .01)
according to ANOVA. Scheffe test from pairwise comparisons was performed to determine
which observers were different. No statistically significant difference was
found between 1st and 2nd observers (P  < .05) and there was statistically
significant  difference between both 1st and 3rd observers and 2nd and 3rd observers
(P  < .01)
(Table 3).Table 3
Results of Scheffe test.
ObserversGroupsMean differenceStandard errorP   valueAsymptotic 95% confidence intervalLower boundUpper bound12−0.0570.089.811−0.270.1630.531(*)0.089.0000.310.75210.0570.089.811−0.160.2730.589(*)0.089.0000.370.8131−0.531(*)0.089.000−0.75−0.312−0.589(*)0.089.000−0.81−0.37* The mean difference is significant at the
0.05 level.Two ROC curves are illustrated. The first ROC
curve (Figure1) is illustrated by considering
assessments of 1st observer due to no statistically
significant difference between 1st and 2nd observers and the second ROC curve (Figure
2) is illustrated for 3rd observer. Areas under
the ROC curve (Az) and standard errors are
shown in Table 4 and analysis of Az values are shown in
Table 5.Table 4
TheAz values
and standard errors for 1st  and 3rd observers.
Test result variable (s)AreaStd. error (a)Asymptotic 95% confidence intervalLower boundUpper bound1st ObserverUnaided visual examination0.6500.0600.5460.745Operating microscope0.6500.0600.5460.744Film radiography0.8000.0500.7060.875RVG0.7930.0510.6980.8693rd ObserverUnaided visual examination0.5330.0620.4280.635Operating microscope0.5330.0620.4290.636Film radiography0.7730.0520.6770.853RVG0.7600.0540.6620.841Table 5
Pairwise comparisons ofAz values.
PairwiseDifference between areaStd. error (a)P   valueAsymptotic 95%confidence intervalLower boundUpper bound1st ObserverOperating microscope-unaided
visual examination0.0000.051.996−0.0990.099Operating microscope-film radiography0.1500.072.0360.0100.291Operating microscope-RVG0.1430.072.0480.0010.285Unaided visual
examination-film radiography0.1500.072.0380.0090.291Unaided visual examination-RVG0.1430.073.0500.0000.285Insight-RVG0.0070.054.896−0.0990.1133rd ObserverOperating microscope-unaided
visual examination0.0010.036.984−0.0700.071Operating microscope-film radiography0.2400.078.0020.0870.393Operating microscope-RVG0.2260.078.0040.0740.379Unaided visual
examination-film radiography0.2410.078.0020.0880.394Unaided visual examination-RVG0.2270.078.0030.0750.380Film radiography-RVG0.0140.047.772−0.0780.106Figure 1
ROC curve for 1st observer.Figure 2
ROC curve for 3rd observer.For both 1st and 3rd observers, no statistically significant difference was
found between operating microscope-unaided visual examination and film radiography
(Insight)-RVG in 95% confidence interval according to pairwise comparison (P < .05). There was a statistically
significant difference between operating microscope-film radiography, operating
microscope-RVG, unaided visual examination-film radiography, unaided visual
examination- RVG in 95% confidence interval according to pairwise
comparison (P < .05) for both 1st and 3rd observers.


## 4. Discussion

The efficiency of operating
microscope was compared with unaided visual examination, film and digital
intraoral radiography for proximal caries detection according to ROC analysis
in this study.Recently, many
researchers have advocated the use of ROC analysis to assess diagnostic methods
for the detection of dental caries [13]. Validity of ROC analysis can be
assessed by increasing the number of tooth surfaces, increasing the rating
scale, and uniform distribution of caries depths [14]. In this study, the
sample was relatively large, 5-point rating scale was used, and the distribution
of caries depths was not
uniform. Area under the ROC curve (Az value) gives useful
information to measure accuracy of a diagnostic system [15]. The highest Az values belonged to film radiography and RVG for all observers. The Az values of unaided visual examination and operating microscope were equal and
lower than the radiographic methods.A diagnostic
tool should be reliable and valid. Interobserver reliability is an important
factor for this aim [16]. On the
other hand, training and experience of
observers may affect intra-
and interobserver agreements [17].
Syriopoulos et al. [18] emphasized
that diagnosis of the radiologists was significantly closer to actual lesion
depth than that of general practitioners. Two of the observers were the
specialists of oral diagnosis and radiology, the
other observer was a specialist of restorative dentistry of at least 10 years
of experience in this study. No statistically significant difference was found
between the two specialists
of oral diagnosis and radiology for all diagnostic
systems (P < .05), but there was a statistically
significant difference between the specialist of restorative dentistry and the
specialists of oral diagnosis and radiology (P < .05). The Az values were found to be 0.800, 0.793, and 0.650 for film radiography, RVG, and both
unaided visual examination and operating microscope, respectively, according to
assessments of 1st observer. The Az values were
found to be 0.773, 0.760, 0.533 for film radiography, RVG, and both unaided
visual examination and operating microscope, respectively, according to
assessments of 3rd observer in this study. The Az values of 1st observer were higher than 3rd observer for all diagnostic
methods. This condition may be due to the fact that the specialists of oral diagnosis and radiology were more experienced than other specialists about
diagnostic and radiographic methods.Due to difficulty of proximal caries
diagnosis with only visual examination, the combination of visual
inspection and bitewing radiographic images is accepted as a standard procedure
in proximal caries detection [5, 19].
Machiulskiene et al. [20] reported that
the clinical examination alone detected about 60% of the total number of proximal
cavitated dentin lesions, and bitewing examination detected about 90% of these
lesions. But they emphasized that the clinical examination is a more effective
method in noncavitated enamel lesions. In this study, the radiographic methods
were better than clinical examinations for proximal caries diagnosis in
conformity with previous studies [19, 21].The positioning of operating microscope is the most common
difficultness. The operator should be careful and not change the position as far
as possible. It was reported that the ideal operator zones are in the 7 to 12
o’clock positions for right-handed operators, and 5 to 12 o’clock for left ones. The clinicians
should conform these suggestions to use operating microscope effectively [22].
The researchers studied at 12 o’clock position and not changed the
position of operating microscope during the examinations in this study.Currently, magnifying visual aids such as magnification
eyeglasses, stereo microscope [23], and also digital imaging [24] with
magnification are used in proximal caries detection in some studies and they
reported that these methods are effective. However, Haak et al. reported that
prism loupe or surgical microscope does not improve the ability to diagnose
proximal caries [25]. In this study,
the efficiency of operating microscope was evaluated by comparing with unaided visual
examination, film and digital intraoral radiography for proximal caries
detection according to ROC analysis. No statistically significant difference
was found between operating microscope and unaided visual examination (P < .05), and there was a statistically
significant difference between operating microscope and both two radiographic
systems (P < .05).In conclusion, the efficiency of operating microscope
was found statistically equal with unaided visual examination and lower than
film and digital intraoral radiography according to ROC analysis. Because the
operating microscope is expensive and requires equipment and operator experience,
according to the results of this in vitro study it can be said that use of this
device would not improve to make an accurate diagnosis of proximal caries
lesions. However, the accuracies of diagnostic methods with magnifying visual
aids should be investigated and clinical usefulness of these methods in dental
practice should be discussed in vitro and in vivo with several studies in which
the numbers of
samples are larger and rating scales are increased by comparing conventional
methods for proximal caries detection.



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