Artificial tooth selection: Could digital photographs be helpful?
Stipetic J, Celebic A, Nola P, Petricevic N, Knezovic-Zlataric D, Baucic I, Baucic-Bozic M.
Department of Prosthodontics, School of Dental Medicine, University of Zagreb, Croatia
INTRODUCTION: Adequate choice of dimensions of artificial teeth is difficult without pre-extraction records. Many various methods and anatomical landmarks have been
used to aid in the selection and placement of artificial teeth for complete dentures (1-8), but none of them seem to be fully accurate. The patient's old photographs have also been
recommended (9,10). Wehner et al. (9) and Bindra et al (10) described a method of calculating dimensions of maxillary central incisor by measurements made on pre-extraction
photograph and on the patient by substituting in the following equation: calculated central incisor’s width = actual interpupillary distance x photographic width of central incisor/
photographic interpupilar distance. However, the quality of an old photograph has been questioned for this purpose. Recent development of digital photography and wide use of
personal computers and their low cost have made these techniques and equipment available to wide public.
AIM OF THE STUDY: to study possibility of calculating the width of a missing central incisor using digital photographs.
SUBJECTS AND METHODS: Fifty one dentate subjects, 18-48 years (30 females and 21 males) participated and gave a written consent. Digital photographs were
obtained (digital camera: Fuji Finepix A310 3.1 Megapixel 3x Optical/2.9x Digital Zoom) on an adjustable tripod (Manfrotto Tripod Digi MN714SHB) in a portrait mode. The
tripod was adjusted in the height of the subject’s tip of nose. Four photographs were made: from a distance of 35 cm, 70 cm, 1 m and 1.5 m (Figure 1). Images were transferred to a
personal computer in JPEG format. Microsoft Office Paint program was used to stretch or reduce an image and to cut and enlarge any part of an image, so that a full size of a face
could fit to an A4 size paper (29.7 cm x 21 cm) (Figure 2). After that, images were printed in color (A4 laser printer: Xerox Phaser 6250N; resolution 2400 dpi). The width of the
maxillary left incisor (MLI) and interpupilar distance were measured on participants prior to photography by a caliper with a precision of 0.1 mm (MEBA, Zagreb, Croatia). The
interpupilar distance was measured between the centers of pupils (IPD), which had been marked on a wooden spatula while each subject was looking at the object at least four
meters distant from the eyes. Afterwards the same measurement was repeated on each of the four images on, printed on a A4 size paper. To calculate the width of MLI the
following equation was used: MLIcalculated = photographic width of MLI x IPD / photographic IPD. Intraobserver and interobserver variability was assessed for both, clinical and
photographic measurements. Three different observers measured ten subjects and their photographs in two different occasions. There was no significant difference between the two
occasions (t test for dependent samples; p>0.05) and between three different observers (one way ANOVA; p>0.05). Maximum difference between three observers in two time
intervals was 0.8 mm for interpupilar distance, 0.2 mm for the width of MLI, 0.2 for the interpupilar distance on photographs and 0.1 mm for the width of MLI on photographs.
These values were within acceptable limits clinically. Finally, one observer completed all the measurements. Statistical analysis was made using SPSS 12.0 for Windows (Chicago,
Illinois) (one sample Kolmogorov-Smirnov test, descriptive statistics t test for dependent samples).
10
VARIABLE
t
p
Measured MLI value : calculated MLI value - 35 mm
-3.813
<0.001
Measured MLI value : calculated MLI value - 70 mm
-1.55
0.127
Measured MLI value : calculated MLI value - 1 m
0.299
0.766
Measured MLI value : calculated MLI value – 1.5 m
0.437
0.664
x
SD
9
8
7
mm
6
5
4
3
2
Figure 2. Images stretched or reduced in
Figure 1. Photographs from different
camera : object distances (35 cm, 70 cm,
1 m and 1.5 m)
size, cut and enlarged in the Paint Microsoft
Office Program, so that a full size of a face
could fit to A4 size paper (29.7 cm x 21 cm)
1
0
Central left
maxillary incisor
Calculated from
Calculated from
image from 35 cm image from 70 cm
Calculated from
image from 1 m
Calculated from
image from 1,5 m
x
8,347
8,7608
8,4206
8,3166
8,2865
SD
0,803
0,9237
0,825
0,9332
1,2452
Figure 3.
TABLE 1. T test for dependent samples between actual maxillary central
incisor value (MLI) and calculated MLI values from images made with a
digital camera from 35 cm distance, 70 cm distance, 1 m distance and 1.5 m
distance; t = t value; df = degree of freedom; p = p value
RESULTS : The calculated tooth width from 4 different photographs are in Figure 3. The width of MLI calculated from a 35 cm distance was bigger than the actual width,
which is a tendency to overestimate the actual width. The dependent t test between calculated MLI width (35 cm, 70 cm, 1 m and 1.5 m distance) and the actual MLI width are in
the Table 1. The difference was significant from a 35 cm distance (p<0.05), while there was no significant differences from a 70 cm, 1 m and 1.5 m distance (p>0.05). Paired
intercorrelations (r) were: MLI : MLI 35 cm=0.605; MLI : MLI 70 cm = 0.914; MLI : MLI 1 m = 0.657; MLI : MLI 1.5 m = 0.608; (p <0.05), the highest (0.914) between the
actual MLI width and the MLI width calculated from a 70 cm distance. Percentage of calculated MLI values that fell within ± 0.3 mm; ± 0.5 mm and ± 1 mm range of the actual
MLI values are shown in the Table 2.
DISCUSSION: Bindra et al.(10) described a technique of calculating the width of a central incisor from a
% within
% within ±0.5 % within ±1
pre-extraction photograph. However, he stated that it is of value only when the photograph is a full-face portrait of
±0.3 mm
mm
mm
DISTANCE
sufficient size with visible frontal teeth, which is not often available. Nowdays digital photography has been
available for wide public and the study was made with the idea that general practitioners can store digital images
35 cm
33.3
45.1
82.4
of each patient in a PC together with other personal data and status. The aim was to check the accuracy of
70 cm
66.7
86.3
100
calculating central maxillary incisor’s width from various camera-object distances. The camera used in this study
1m
37.3
64.7
88.2
was not a professional one and no knowledge of how to obtain professional photographs was needed. The program
1.5 m
17.6
41.2
76.5
Paint is a part of “Microsoft Office” package, available to wide public. Our results showed that images from a
TABLE 2. Percentage of calculated MLI values that fit within ± 0.3
distance of 35 cm were inaccurate (probably distorted; manufacturer’s manual: the focus range was: 2.0 ft to
mm; ± 0.5 mm and ± 1 mm range from the actual MLI values
infinity, Macro: 0.3ft. - 2.6ft). The highest correlation with actual MLI width was 0.914 from a 70 cm distance.
However, the distance of 1 m was also acceptable. The length of a central incisor was not calculated in this study, for the reason that longer maxillary incisors ars necessary in
dentures to compensate for bone resorption. Clinical relevance of the results also showed that the distance of 70 cm revealed the best results (Table 2) . However, better digital
cameras, with better optical and digital characteristics would give even better results.
CONCLUSION: Obtaining digital photographs is of proven value in calculating the width of a maxillary central incisor. The
photographs using a simple, not expensive and non-professional digital camera (3.2 Mpix) should be taken from a distance 70 cm to 1 m.
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