ORIGINAL ARTICLE
Photographic and videographic assessment of the smile: Objective and subjective evaluations of posed and spontaneous smiles Joan F. Walder,a Katherine Freeman,b Mitchell J. Lipp,c Olivier F. Nicolay,c and George J. Cisnerosd Northampton, Mass, Delray Beach, Fla, and New York, NY
Introduction: Esthetic considerations play an increasingly important role in patient care, and clinicians need a methodology that includes imaging techniques to capture the dynamic nature of the smile. Photographs of the posed smile are routinely used to guide diagnosis and treatment, but there is no standardized and validated method for recording the dynamic smile. The purposes of this study were to (1) determine whether a posed smile is reproducible, (2) compare visual and verbal cues in eliciting a smile, and (3) compare the diagnostic value of videography and photography in evaluating a patient's smile. Methods: The smiles of 22 subjects were simultaneously photographed and videotaped on 2 separate occasions. For objective comparisons, measurements of the smile were obtained from 8 3 10 color still photographs and selected digitized video images. A panel consisting of a layperson, an oral surgeon, an orthodontist, and a prosthodontist subjectively assessed the reproducibility of the smile, posed vs spontaneous smiles, and the diagnostic value of video vs still images. Results: Objective measurements showed that the posed smile can be reliably reproduced, whether captured by videography or still photography. However, subjectively, the panel members detected differences between the posed smiles taken on different days 80% of the time. The clinician panel members expressed a strong preference for videography over photography and for the spontaneous over the posed smiles. Conclusions: This study emphasizes the need to continue to investigate and standardize the methods of eliciting and recording a smile of diagnostic quality. (Am J Orthod Dentofacial Orthop 2013;144:793-801)
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s part of a facial esthetic evaluation, the clinician studies lip function and posture. During this evaluation, the patient is often asked to smile, and a split-second image of that dynamic action is captured on a still photograph. This photograph, used as part of the diagnostic process to determine a course of treatment, remains as a permanent record in the patient’s chart. If we want to depend on a still photograph to reflect the esthetics of a patient’s smile, it is necessary to capture a true representation of that smile. For instance, if the photo was taken a few seconds earlier
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Private practice, Northampton, Mass. President and founder, Extrapolate, LLC, Delray Beach, Fla. Clinical associate professor, Department of Orthodontics, College of Dentistry, New York University, New York. d Professor, Department of Orthodontics, College of Dentistry, New York University, New York. All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest, and none were reported. Address correspondence to: George J. Cisneros, Department of Orthodontics, College of Dentistry, New York University, 345 E 24th St, New York, NY 10010; e-mail, [email protected]. Submitted, April 2013; revised and accepted, July 2013. 0889-5406/$36.00 Copyright Ó 2013 by the American Association of Orthodontists. http://dx.doi.org/10.1016/j.ajodo.2013.07.012 b c
or later, would it show the same smile? If a different directive was used to elicit a smile, would it trigger the same response? Would videography rather than photography provide a more effective diagnostic impression? Previous studies have qualitatively and quantitatively addressed the movement of a smile.1-5 Studies in the psychology literature have found that people are better able to detect posed emotion from motion photography than from still photography.6,7 Nonetheless, the dental literature is surprisingly lacking in its discussion of the dynamic nature of the smile as it relates to the methods used to elicit, record, and reproduce it and how it reflects our patients' esthetics. The aims of this study were to investigate the potential variability in current methods of evoking a smile for analysis and to evaluate the relative diagnostic value of videography vs photography in capturing a dynamic event. It is necessary to be critical of the tools used to determine a treatment plan and to make great efforts to standardize them. MATERIAL AND METHODS
Twenty-two subjects volunteered to participate in the principal portion of this study. They were students, 793
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faculty, and staff from Manhattan College, Bronx, New York. The only exclusionary criteria were visible developmental or traumatic abnormalities of the face or facial musculature, and missing anterior teeth. The subjects were simultaneously photographed and videotaped on 2 days. All participants signed informed consents but were not told that we were looking for possible reproducibility of the smile or any other information that would bias their responses. The position of each subject's head was standardized by a head holder designed specifically for this study. The holder positioned the head with a 3-point contact in both the vertical and horizontal dimensions: 2 ear rods were placed in the external auditory meati and a pad on the forehead. A series of black rectangular markers, 1 inch long and 1 inch apart, were placed on the head holder and captured in the photographs to correct for any alteration in magnification from image to image. The head holder was fastened to a stand, which held it in a constant position vertically and horizontally. The height of the chair was adjusted to accommodate for the subjects' variations in height. Measurements of the horizontal and vertical positions of the forehead pad were taken with a millimeter ruler at the first session, and the head holder was reset to these same measurements for each subsequent session. Two cameras were arranged so that each subject could be photographed and videotaped simultaneously. For the 2 cameras to be used simultaneously, thus capturing the same smile, it was necessary to set up isosceles triangles between the subject and each camera mounted on tripods (Fig 1). The centers of the 2 camera lenses were placed 4 ft 7 in from the anterior portion of the head holder and 2.25 in from the center (a line extended from the midsagittal plane of the subject setup). This made an angle of 2.34 from the midsagittal plane of the subject to the center of each camera lens, creating a negligible distortion as determined by an optical error analysis. For the still photography, at each session, 2 photographs of the subject were taken. The first photograph was prompted by a verbal directive and the second by a visual directive. The verbal directive was “give me a nice, big smile, one that shows your teeth.” A poster board with color photographs of 6 people smiling broadly was used for the visual directive, and the subjects were told to “smile like the people in the photographs.” The verbal directive was uniformly given first to prevent the subjects from relying on the memory of the visual image when presented with the verbal command. The frontal photographs were taken by the same operator (J.F.W.) using a Pentax K-1000 camera (Asahi Optical, Tokyo, Japan) with a 90-mm F/2.8 macro lens (Sigma, Tokyo, Japan) mounted on a tripod, 35-mm Kodachrome
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ISO 64 slide film (Eastman Kodak, Rochester, NY), and a standardized camera-to-source distance of 4 ft 7 in. All 88 slides, which resulted from the 22 subjects being photographed 2 times at the 2 separate sessions each, were then converted into 8 3 10 color copies via a Kodak 1550 Plus printer (Eastman Kodak) for analytical purposes. The still images shown to the panel were cropped to include only a standardized border beyond the vermilion of the lips. For the videography, a Panasonic Palmcorder VHSC video camera (Matsushita Electric Corporation of America, Osaka, Japan) mounted on a tripod was manually focused to show a close-up, full-face view of each subject. VHS-C film was used. The object-to-source distance was also 4 ft 7 in. The video camera was turned on before the verbal directive and remained on throughout the entire session. Randomly, 1 image from the video footage (either the verbal or the visual smile from either day 1 or 2) was selected for each subject to use for comparison with the still images. The apex or height of each of the 22 randomly selected smiles was determined by agreement of 2 evaluators (J.F.W. and G.J.C.). In the case of a disagreement, a third evaluator was used. The apex of a smile was defined as the frame in which the smile was the largest. To measure the video images, the apices of the smiles were converted into 35-mm slides and then into 8 3 10 color copies, using the Kodak 1550 Plus. The Media Suite Pro video-editing program (Avid Technology, Tewksbury, Mass) was used to create a videotape of each subject’s smile to be viewed by the panel. In 13 of the 22 subjects, the video camera was able to capture an unsolicited spontaneous smile. The smiles were deemed spontaneous by 2 evaluators viewing the unedited video footage using the following criteria: (1) there was no cue by the photographer to smile before the smile and (2) the subject appeared relaxed and was conversing with the photographer. Two examiners, with a third examiner consulted when there was a difference of opinion between the 2 original evaluators, also selected the apices of these spontaneous smiles. The apices of these smiles were then converted into 8 3 10 color copies with the Kodak 1550 Plus. For an objective assessment and comparison of the still and video-derived images described above, measurements were taken twice by the same operator (J.F.W.) with a vernier caliper to the nearest 0.1 mm, then averaged (Fig 2). A panel of 4 people was selected to provide subjective assessments of the smiles. The panel included a prosthodontist (rater 1), an orthodontist (rater 2), a layperson (rater 3), and an oral surgeon (rater 4). The panel portion of this study was divided into 4 parts. Part 1 addressed the issue of reproducibility of
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Fig 1. Scaled diagram of equipment configuration: subject/headholder at the apex and 2 cameras at each base of the isosceles triangles. A 2.34 angle was created from the midsagittal plane of the subject to the center of each camera lens for negligible distortion of images.
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Fig 2. Objective measurements of still and video-derived images: A, commissure to commissure; B, vermilion border to vermilion border*; C, inferior border of the upper lip to superior border of the lower lip*; D, maxillary incisal edge to the inferior border of the upper lip*; E, maxillary incisal edge to the vermilion border of the upper lip*; F, maxillary incisal edge to the interpupillary line*; G, intercanthal distance. Also measured was the 1-in marker on the head holder to determine the change in magnification. *Measured at midpoint of commissure to commissure distance.
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3. the smiles using still photography. Part 2 compared the diagnostic value of the 2 media: videography and still photography. With video technology, parts 3 and 4 provided comparisons of spontaneous and posed smiles. All 4 panel members were shown parts 1, 3, and 4, whereas part 2 was shown to the professional members of the panel only because it required a comparison of the diagnostic value of video vs still images. The following is a description of the 4 parts shown to the panel.
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Still photographs day 1 vs day 2. By random selection, either the verbal or the visual set of still photographs was selected for each subject to be shown to the panel. The randomly selected smile photos were cropped to display only a standardized border just beyond the vermilion border of the lips so as not to distract the panel with other facial features and extraneous details such as hairstyle and makeup. Each panel member independently was asked to determine whether he or she thought that the 2 smiles were the same. Twenty-six sets of smiles were projected next to each other on a screen. To ascertain the validity of each panel member’s responses, 4 of the 26 sets of photographs reviewed were actually duplicates, with the same pictures shown side by side. Still photography vs videography. The 22 randomly selected smiles were then shown to the 3 professional members of the panel in both the video and still formats. This provided a subjective comparison of the clinical value of the still and video smiles. The panel members were asked to fill out a form that asked 2 questions: (1) which is more useful diagnostically, the still photo, the video footage, or no preference? and (2) do you have any comments regarding preference? Posed vs spontaneous smiles (uncropped). The 4 panelists were shown the series of full-faced posed smiles along with their spontaneous counterpart, both obtained from the video footage. They were asked to select the most diagnostically useful image. “Diagnostically useful” was defined as the smile that appeared to be the most natural, the one that seemed to best represent the subject’s unsolicited smile. The layperson was told to select the smile that appeared most natural. Posed vs spontaneous smiles (cropped). The 4 panelists were also shown the series of spontaneous
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variable measured ðmmÞ 3 25:4 mm ð1-inch markerÞ length of marker in still image ðmmÞ
(Equation 1)
variable measured ðmmÞ 3 intercanthal distance as measured in still images ðmmÞ intercanthal distance ðmmÞ
(Equation 2)
variable measured ðmmÞ 3 intercanthal distance as measured in spontaneous images ðmmÞ intercanthal distance ðmmÞ
(Equation 3)
smiles along with their posed counterparts, with both images cropped to display only a standardized border beyond the vermilion of the lips. The panel members were asked to select the most diagnostically useful image. Once again, “diagnostically useful” was defined as the smile that appeared to be the most natural, the one that seemed to best represent the subject’s unsolicited smile. The layperson was told to select the smile that appeared most natural. The raw data were standardized to account for magnification differences between the images measured. For the data sets comparing still images only, the measured length of the 1-in marker (25.4 mm) in the image was used to adjust for changes in magnification. The formula used in these cases is shown in Equation 1. We were unable to use the 1-in marker as a standard measure for the video-derived images because the reproduced quality tended to blur the marker edges. Instead, the intercanthal distance was used for each subject because the data sets compared in this section were all taken at the same time, and thus there was no concern for change in head position or camera angulation. The formula used to standardize the data set that compared the video-derived images with the still images is shown in Equation 2. The formula used to standardize the data set that compared the apices of the video-derived spontaneous smiles and the video-derived posed smiles is shown in Equation 3. Statistical analysis
A power analysis was performed to determine the number of subjects required for this investigation. The maximum change in the width of a smile (commissure to commissure) considered by the principal investigator
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of this study (J.F.W.) to be diagnostically acceptable was measured on 4 subjects. At 2 times, each subject was asked to begin at his or her broadest smile and then to slowly reduce the smile until the examiner thought that the smile no longer had diagnostic quality. The change in width was found to average 4 mm. The full range of the smile was also measured; it averaged 13 mm. Using these estimates, we calculated that 22 subjects (11 men, 11 women) were required for the comparison between the different smiles obtained in this study, for a type I error of .05 and a 2-tailed test with 80% power. All analyses performed on the objective measurements were done using the standardized data. The differences between days 1 and 2 were tested for significance using either a paired t test or the Wilcoxon signed rank test, depending on whether the assumptions of normality were met for the t test. The same approach was used to assess the significance of the following: (1) the differences between the still and video images, (2) the differences between the verbal and visual cues in the still photographs, and (3) the differences between the spontaneous and posed smiles taken from the video. Tests of significance were 2-tailed, with a type I error of .05. An intraclass correlation coefficient (ICC) for the repeated measurements was computed to determine reliability. RESULTS
A total of 22 subjects (11 women, 11 men) participated in this study. They were between the ages of 20 and 49, with average ages of 24.7 years for the men and 27.2 years for the women. The average length of each subject’s videotaped session was about 57 seconds, with a range of 35 to 90 seconds. The videotape segments averaged 49 seconds for the women (range, 35-65 seconds) and 65 seconds for the men (range, 45 -90 seconds).
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Table I. Objective comparisons of smiles elicited on day 1 vs day 2 (n 5 22) Verbal Objective measurement (mm) Commissure to commissure Vermilion upper lip to vermilion lower lip Superior lower lip to inferior upper lip Upper incisal edge to inferior upper lip Upper incisal edge to vermilion upper lip Upper incisal edge to interpupillary line Intercanthal distance
Mean difference* 0.9 0.4 0.5 0.4 0.5 0.6 0.1
Visual
Range* 8.9 9.0 9.1 5.1 4.3 6.4 3.8
Significance NS NS NS NS NS NS NS
Mean difference* 1.5 0.2 0.3 0.1 0.3 0.1 0.2
Range* 10.6 10.8 9.1 4.2 5.6 5.8 3.2
Significance S NS NS NS NS NS NS
NS, No statistically significant difference; S, statistically significant difference at the alpha \0.05 level. *Standardized data.
Table II. Objective comparisons of verbally vs visually prompted smiles (n 5 22) Day 1 Objective measurement (mm) Commissure to commissure Vermilion upper lip to vermilion lower lip Superior lower lip to inferior upper lip Upper incisal edge to inferior upper lip Upper incisal edge to vermilion upper lip Upper incisal edge to interpupillary line Intercanthal distance
Mean difference* 0.5 1.0 1.2 0.4 0.1 0.1 0.1
Day 2
Range* 11.6 3.2 13.4 6.2 6.3 1.8 1.8
Significance NS NS NS NS NS NS NS
Mean difference* 1.0 0.4 0.4 0.4 0.3 0.2 0.3
Range* 14.2 13.6 11.8 7.6 7.7 3.6 1.7
Significance NS NS NS NS NS NS S
NS, No statistically significant difference; S, statistically significant difference at the alpha \0.05 level. *Standardized data.
We considered the reproducibility of the posed smile. The results of the objective data are given in Table I; for the most part, no statistically significant differences were found between the smile measurements taken on day 1 and day 2. The exception was the difference in commissure to commissure distance between the visually commanded smile on day 1 and the visually commanded smile on day 2. The mean difference in this instance was 1.51 mm, with a standard deviation of 2.93 mm and a range of 10.57 mm. No statistically significant differences were found when the verbally directed smiles of day 1 were compared with the visually directed smiles of day 1 (Table II). The only statistically significant difference in measurement was found between the intercanthal distances recorded on the verbally directed smiles on day 2 and the visually commanded smiles on day 2. The mean difference was 0.30 mm with a standard deviation of 0.49 mm and a range of 1.73 mm. For the results of subjective data, the ICC for agreement among the raters in comparing the still images taken on day 1 with the still images on day 2 was 0.52842; that was “moderate” agreement. The ICC for this same group without the duplicates (identical slides)
was 0.28763; this was considered “fair” agreement. The relative frequencies of the same subject's smiles on days 1 and 2 classified as the same or different for the panel members were tabulated to assess the reproducibility of the smiles within raters. The 2 smiles were determined to be different 95% of the time by rater 1, 73% of the time by rater 2, 64% of the time by rater 3, and 95% of the time by rater 4. Overall, the panel determined the smiles to be different in 83% of the cases. In addition, when the layperson’s responses were omitted from the distribution, 88% of the smiles were determined to be different. Raters 1, 2, and 3 were able to identify all 4 duplicates, and rater 4 recognized 3 of the 4 duplicates. We also compared the videography with the still photography. For the results of the objective data, when comparing the still photographs with the videography, 3 measurements had statistically significant differences: (1) the commissure to commissure distance, (2) the maxillary incisal edge to the vermilion border of the upper lip distance, and (3) the maxillary incisal edge to the interpupillary line distance (Table III). The average magnitude of the difference in the commissure to commissure distance was 1.19 mm; the video distance was smaller, with a standard deviation of 1.28 mm and a
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Table III. Objective comparison of smiles captured by videography vs still photography (n 5 22)
Table IV. Objective comparison of posed vs spontaneous smiles (n 5 13)
Mean Objective measurement (mm) difference* Range* Significance Commissure to commissure 1.2 4.8 S 0.2 6.6 NS Vermilion upper lip to vermilion lower lip Superior lower lip to inferior 0.0 2.7 NS upper lip Upper incisal edge to inferior 0.1 1.8 NS upper lip Upper incisal edge to vermilion 0.5 2.2 S upper lip Upper incisal edge to 1.5 2.6 S interpupillary line
Mean Objective measurement (mm) difference* Range* Significance y Commissure to commissure 0.1 22.6 y Vermilion upper lip to vermilion 0.7 8.2 lower lip y Superior lower lip to inferior 0.1 6.5 upper lip y Upper incisal edge to inferior 0.4 4.1 upper lip y Upper incisal edge to vermilion 0.1 5.2 upper lip y Upper incisal edge to 1.4 24.2 interpupillary line
S, Statistically significant difference at the alpha\0.05 level; NS, no statistically significant difference. *Standardized data.
*Standardized data; ysample size (n) was insufficient to reach significance.
Fig 3. The professional panel preferred the video to still images 68% of the time. The individual preferences were as follows: 63%, 63%, and 77% preference for the video by raters 1 (prosthodontist), 2 (orthodontist), and 4 (oral surgeon), respectively.
range of 4.76 mm. The mean difference in the maxillary incisal edge to the vermilion border of the upper lip was 0.50 mm; the video distance was smaller again, with a standard deviation of 0.66 mm and a range of 2.24 mm. The mean difference in the interpupillary line to the maxillary incisal edge was 1.47 mm (video smaller), with a standard deviation of 0.78 mm and a range of 2.64 mm. In the results of the subjective data, the agreement among raters for the comparison of the video footage with the still images was not statistically significant. Using a frequency distribution, overall, the panel preferred the video 68% of the time, the still images 23% of the time, and had no preference 9% of the time (Fig 3). The preferences were 63%, 63%, and 77% for the video by raters 1, 2, and 4, respectively (rater 3, the layperson, was excluded from this portion of the panel). We compared the spontaneous and posed smiles. The objective data showed no statistically significant differences in the measurements of the spontaneous and posed smiles from the video footage (Table IV). However, this study was not designed with sufficient
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Fig 4. The spontaneous smile was preferred 75% of the time overall. When limited to the professional panel members, this preference increased to 79%. The individual preferences were as follows: 85%, 77%, 62%, and 77% preference for spontaneous smiles by raters 1, 2, 3, and 4, respectively.
power to address this issue. The number of subjects (13) in this section was insufficient, and thus inferences drawn from this might be limited. The results of the subjective data showed that agreement among raters with regard to the comparison of the spontaneous smiles with the posed smiles was statistically significant for the cropped images (ICC, 0.17149: “slight” agreement) and not statistically significant for the uncropped images. A frequency distribution showed the following (Fig 4). The spontaneous smile was preferred 85% of the time by rater 1 (prosthodontist), 77% of the time by rater 2 (orthodontist), 62% of the time by rater 3 (layperson), and 77% of the time by rater 4 (oral surgeon). Overall, the panel preferred the spontaneous to the posed smile 75% of the time. When the layperson’s responses were omitted from the distribution, the spontaneous smile was selected 79% of the time. When the images were cropped, the panel’s preference for the spontaneous smiles declined to 67%.
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DISCUSSION
In this study, we found that whether recorded with a video or a still camera, prompted with a visual or a verbal cue, or taken on day 1 or 2, the posed smile could be reliably reproduced. Greater reproducibility was obtained with objective measures; however, as noted by the panel members, the eye of the diagnostician might be more critical than objective measures. The literature has addressed many aspects of the smile, but only a few studies have even touched on the aspect of the reproducibility of the smile.1,2 Peck et al3 coached their subjects before taking smile records and found that they were “easily able to attain a reproducible maximum smile.” However, prior methods used to determine smile reproducibility have been ambiguous or determined by visual inspection alone, and were not a specific aim of the studies. The psychological literature has often attributed specific characteristics to the posed smile.8-11 By imparting specific attributes to the posed smile, this implies that the posed smile is consistent. Johnson and Smith12 suggested that their smile measurements could not be considered precise because they did not use a device to limit head position or correct for magnification changes. After reviewing the literature, we decided to use a head holder to apply stringent control over the changes in measurements that can occur with head position changes. However, for clinical purposes, the use of a head holder while taking diagnostic photographs or video of a patient might hinder the patient’s ability to smile naturally by restricting his or her ability to respond normally. The reproducibility of natural head position has been shown to be within a clinically acceptable range of 2 .13 Perhaps accurate information could be obtained from facial photography or videography if the patients were allowed to hold their head in a more natural manner. Further investigation comparing facial images taken in natural head position with facial images taken when the subject is placed in a head holder would address this issue more definitively. Analysis of the smiles by the panel members showed that there might be subtleties about a smile that cannot be measured objectively. More than 80% of the time, the panel could distinguish between the smiles taken on different days. When the data were limited to the professional panel members, the ability to discriminate between the 2 smiles increased, suggesting that the practitioner’s eye might be more discriminating than objective measures for diagnosis and treatment planning.
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To truly analyze an action, it seems logical that one would require a tool to capture the dynamic nature of that action. Nonetheless, the prevailing clinical question in this study was whether the practice of orthodontics requires a technique that can record the entire dynamic range of the smile, or whether it is sufficient to rely on the standard still photographs for diagnostic information. Are diagnostic photographs providing sufficient information about the smile or would videography be a better diagnostic tool? For those interested in information regarding the height of the smile alone, a still photograph might be sufficient, assuming that the photographer has captured the apex of the smile. However, we found video to be the method of choice by the clinicians. The panel members’ comments supporting the preference for video were the following: (1) “the whole range of the smile was visible,” (2) “it provided a record of muscle function and strain,” (3) “it showed whether the smile was guarded or not,” (4) “it revealed swallowing patterns,” (5) “it demonstrated lip posture and competence,” and (6) “it provided 2 views—the patient at rest and the patient smiling.” Previous studies have found that still images of a dynamic action are more difficult for the viewer to correctly analyze. A fixed representation of a facial expression can remove many of the cues for interpretation of that expression.14 As the panel members suggested, they preferred to see the entire range of the smile because it gave them significantly more information than did the still images. Certainly, as Bruner and Tagiuri15 maintained, a millisecond of exposure surely cannot represent clinical observations. Unlike past studies of facial esthetics, we attempted to specifically address the diagnostic value of obtaining videographic records of the smile. Few studies have touched on the smile as a dynamic action; however, for the most part, it has been in relation to dental and gingival display at maximum smile. Their focus was a fixed point at the height of the smile.1,2,16,17 Studies in the plastic and reconstructive surgery literature have evaluated smile dynamics and the soft-tissue changes that occur when the face moves from rest to maximum smile.3-5 These studies do recognize the value of closely evaluating the smile as a dynamic action. The video footage seemed to provide a reliable representation of the subject’s level of comfort during the photographic or videographic sessions. In several instances, the still image shown to the panel members appeared to depict a relaxed person giving a relaxed smile. However, when the video footage of this same smile was viewed, it became obvious that the person was not at all
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comfortable, and the smile was forced. Videography might give practitioners insight into how patients feel about their appearance or smile that can be missed in a hectic clinical examination or the still photographs taken by auxiliary staff. The panel members were less likely to select the spontaneous smile when the images were cropped, removing all other cues of facial expression. Duchenne18 described the use of 2 facial muscles to distinguish a deliberate smile from a spontaneous smile: “The first (zygomatic major) obeys the will but the second (orbicularis oculi) is only put in play by the sweet emotions of the soul; the .fake joy, deceitful laugh, cannot provoke the contraction of the latter muscle.” In 1980, Ekman et al10 confirmed Duchenne’s observations, finding that most people cannot voluntarily contract the outer portion of the orbicularis oculi and thus do not exhibit this action in a deliberate smile. A significant aim of this study was to begin to finetune our methods of eliciting and capturing smiles. Two behavioral patterns recognized in this study are worthy of discussion: (1) variations in response to the verbal and visual cues, and (2) sex differences in eliciting a posed smile. Although these findings were not specifically pinpointed in this study, they are of interest to practitioners because they might help to better elicit smiles from patients. The principal investigator (J.F.W.) observed that 45% of the subjects responded more easily to the verbal command, whereas only 18% seemed to smile more readily when shown the visual cue. The remainder had no preferences. The visual cue appeared to be confusing for many subjects. When the investigator provided the visual cue, several subjects asked “What do you mean?” or “Do you want me to imitate the smiles?” A few others needed to hear the instructions again. Studies have found individual variations in the responses to verbal and visual cues.19 Perhaps it would be beneficial to provide both verbal and visual commands. It was harder to elicit a posed smile from the men than from the women. Five of the 11 men (45%) had difficulty smiling on command, but only 1 of the 11 women (9%) had difficulty responding to the command. A subject was considered to have difficulty smiling on command if he or she did not respond with a facial expression that resembled a smile or did not appear to respond at all to the command as judged by the principal investigator and another impartial observer. The average length of the video footage used to capture the smiles of the men (65 seconds; range, 45-90 seconds) was longer than the average length of the video footage needed for the women (49 seconds; range, 35-65 seconds). Part of this discrepancy might be because all sessions were
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directed by and all images were photographed by a women (J.F.W.); thus, the men might have felt more inhibited to respond than did the women. Interestingly, although it took the men longer to smile, there was no difference in the number of male subjects (7 of 11) compared with the female subjects (7 of 11) who showed a spontaneous smile in the video footage. This would seem to imply that men might not necessarily smile less frequently than women in all situations, but they might be less able to “pretend” to smile.20-22 CONCLUSIONS
This study emphasizes the need to continue to investigate and standardize the methods of eliciting and recording a smile of diagnostic quality. The following are our specific conclusions. 1. 2.
3. 4. 5.
Posed smiles can be reliably reproduced as measured objectively, but, subjectively, differences were noted. When the entire face is visible, practitioners can detect important differences between posed and spontaneous smiles. However, this ability is decreased when only the smile is shown. Spontaneous smiles are preferred to posed smiles by professional diagnosticians. Videography provides diagnostic information that cannot be obtained with still photography alone. Video images are preferred to still images by professional diagnosticians.
ACKNOWLEDGMENTS
We thank Graham Walker for his guidance and assistance; Hugh Gilmore for his video-editing wizardry; and the highly perceptive panel members for their enthusiasm and remarkable attention to detail.
REFERENCES 1. Rigsbee OH III, Sperry TP, BeGole EA. The influence of facial animation on smile characteristics. Int J Adult Orthod Orthognath Surg 1988;3:233-9. 2. Peck S, Peck L, Kataja M. The gingival smile. Angle Orthod 1992; 62:91-100. 3. Rubin LR. The anatomy of a smile: its importance in the treatment of facial paralysis. Plast Reconstr Surg 1974;53:384-7. 4. Rubin LR, Mishriki Y, Lee G. Anatomy of the nasolabial fold: the keystone of the smiling mechanism. Plast Reconstr Surg 1989; 83:1-8. 5. Paletz JL, Manktelow RT, Chaban R. The shape of a normal smile: implications for facial paralysis reconstruction. Plast Reconstr Surg 1994;93:784-91. 6. Kozel NJ, Gitter AG. Perception of emotion: differences in mode of presentation, sex of perceiver, and role of expressor. CRC Report 1968;18:1-61.
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7. Dusenbury D, Knower FH. Experimental studies on the symbolism of action and voice: a study of the specificity of meaning in facial expression. Q J Speech 1938;24:424-35. 8. Chaurasia BD, Goswami HK. Functional asymmetry in the face. Acta Anat 1975;91:154-60. 9. Campbell R. Asymmetries in interpreting and expressing a posed facial expression. Cortex 1978;14:327-42. 10. Ekman P, Roper G, Hager JC. Deliberate facial movement. Child Dev 1980;51:886-91. 11. Ekman P, Hager JC, Friesen WV. The symmetry of emotional and deliberate facial actions. Psychophysiology 1981;18:101-6. 12. Johnson DK, Smith RJ. Smile esthetics after orthodontic treatment with and without extraction of four first premolars. Am J Orthod Dentofacial Orthop 1995;108:162-7. 13. Moorrees C, Kean M. Natural head position: a basic concept for the analysis of cephalometric radiographs. Am J Phys Anthropol 1958; 16:213-34. 14. Ekman P, Friesen W. Universal and cultural differences in the judgments of facial expressions of emotion. J Pers Soc Psychol 1987; 53:712-7.
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15. Bruner JS, Tagiuri R. The perception of people. In: Lindzey G, editor. Handbook of social psychology. Reading, Mass: AddisonWesley; 1954. p. 634-54. 16. Janzen EK. A balanced smile—a most important treatment objective. Am J Orthod 1977;72:359-72. 17. Tjan AH, Miller GD, The JG. Some esthetic factors in a smile. J Prosthet Dent 1984;51:24-8. 18. Duchenne B. The mechanism of human facial expression or an electro-physiological analysis of the expression of the emotions (translated by A. Cuthbertson) (originally published in 1862). New York: Cambridge University Press; 1990. 19. Smith TL, Eason RL. Effects of verbal and visual cues on performance of a complex ballistic task. Percept Mot Skills 1990;70(3 Pt 2):1163-8. 20. Korzenny BA, Korzenny F, Rota G. Women’s communication in Mexican organizations. Sex Roles 1985;12:867-76. 21. Hinsz-Verlin B, Tomhave JA. Smile and (half) the world smiles with you, frown and you frown alone. Pers Soc Psychol Bull 1991;17: 586-92. 22. Briton NJ, Hall JA. Gender-based expectancies and observer judgements of smiling. J Nonverbal Behav 1995;19:49-65.
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Photographic and videographic assessment of the smile: Objective and subjective evaluations of posed and spontaneous smiles Joan F. Walder,a Katherine Freeman,b Mitchell J. Lipp,c Olivier F. Nicolay,c and George J. Cisnerosd Northampton, Mass, Delray Beach, Fla, and New York, NY
Introduction: Esthetic considerations play an increasingly important role in patient care, and clinicians need a methodology that includes imaging techniques to capture the dynamic nature of the smile. Photographs of the posed smile are routinely used to guide diagnosis and treatment, but there is no standardized and validated method for recording the dynamic smile. The purposes of this study were to (1) determine whether a posed smile is reproducible, (2) compare visual and verbal cues in eliciting a smile, and (3) compare the diagnostic value of videography and photography in evaluating a patient's smile. Methods: The smiles of 22 subjects were simultaneously photographed and videotaped on 2 separate occasions. For objective comparisons, measurements of the smile were obtained from 8 3 10 color still photographs and selected digitized video images. A panel consisting of a layperson, an oral surgeon, an orthodontist, and a prosthodontist subjectively assessed the reproducibility of the smile, posed vs spontaneous smiles, and the diagnostic value of video vs still images. Results: Objective measurements showed that the posed smile can be reliably reproduced, whether captured by videography or still photography. However, subjectively, the panel members detected differences between the posed smiles taken on different days 80% of the time. The clinician panel members expressed a strong preference for videography over photography and for the spontaneous over the posed smiles. Conclusions: This study emphasizes the need to continue to investigate and standardize the methods of eliciting and recording a smile of diagnostic quality. (Am J Orthod Dentofacial Orthop 2013;144:793-801)
A
s part of a facial esthetic evaluation, the clinician studies lip function and posture. During this evaluation, the patient is often asked to smile, and a split-second image of that dynamic action is captured on a still photograph. This photograph, used as part of the diagnostic process to determine a course of treatment, remains as a permanent record in the patient’s chart. If we want to depend on a still photograph to reflect the esthetics of a patient’s smile, it is necessary to capture a true representation of that smile. For instance, if the photo was taken a few seconds earlier
a
Private practice, Northampton, Mass. President and founder, Extrapolate, LLC, Delray Beach, Fla. Clinical associate professor, Department of Orthodontics, College of Dentistry, New York University, New York. d Professor, Department of Orthodontics, College of Dentistry, New York University, New York. All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest, and none were reported. Address correspondence to: George J. Cisneros, Department of Orthodontics, College of Dentistry, New York University, 345 E 24th St, New York, NY 10010; e-mail, [email protected]. Submitted, April 2013; revised and accepted, July 2013. 0889-5406/$36.00 Copyright Ó 2013 by the American Association of Orthodontists. http://dx.doi.org/10.1016/j.ajodo.2013.07.012 b c
or later, would it show the same smile? If a different directive was used to elicit a smile, would it trigger the same response? Would videography rather than photography provide a more effective diagnostic impression? Previous studies have qualitatively and quantitatively addressed the movement of a smile.1-5 Studies in the psychology literature have found that people are better able to detect posed emotion from motion photography than from still photography.6,7 Nonetheless, the dental literature is surprisingly lacking in its discussion of the dynamic nature of the smile as it relates to the methods used to elicit, record, and reproduce it and how it reflects our patients' esthetics. The aims of this study were to investigate the potential variability in current methods of evoking a smile for analysis and to evaluate the relative diagnostic value of videography vs photography in capturing a dynamic event. It is necessary to be critical of the tools used to determine a treatment plan and to make great efforts to standardize them. MATERIAL AND METHODS
Twenty-two subjects volunteered to participate in the principal portion of this study. They were students, 793
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faculty, and staff from Manhattan College, Bronx, New York. The only exclusionary criteria were visible developmental or traumatic abnormalities of the face or facial musculature, and missing anterior teeth. The subjects were simultaneously photographed and videotaped on 2 days. All participants signed informed consents but were not told that we were looking for possible reproducibility of the smile or any other information that would bias their responses. The position of each subject's head was standardized by a head holder designed specifically for this study. The holder positioned the head with a 3-point contact in both the vertical and horizontal dimensions: 2 ear rods were placed in the external auditory meati and a pad on the forehead. A series of black rectangular markers, 1 inch long and 1 inch apart, were placed on the head holder and captured in the photographs to correct for any alteration in magnification from image to image. The head holder was fastened to a stand, which held it in a constant position vertically and horizontally. The height of the chair was adjusted to accommodate for the subjects' variations in height. Measurements of the horizontal and vertical positions of the forehead pad were taken with a millimeter ruler at the first session, and the head holder was reset to these same measurements for each subsequent session. Two cameras were arranged so that each subject could be photographed and videotaped simultaneously. For the 2 cameras to be used simultaneously, thus capturing the same smile, it was necessary to set up isosceles triangles between the subject and each camera mounted on tripods (Fig 1). The centers of the 2 camera lenses were placed 4 ft 7 in from the anterior portion of the head holder and 2.25 in from the center (a line extended from the midsagittal plane of the subject setup). This made an angle of 2.34 from the midsagittal plane of the subject to the center of each camera lens, creating a negligible distortion as determined by an optical error analysis. For the still photography, at each session, 2 photographs of the subject were taken. The first photograph was prompted by a verbal directive and the second by a visual directive. The verbal directive was “give me a nice, big smile, one that shows your teeth.” A poster board with color photographs of 6 people smiling broadly was used for the visual directive, and the subjects were told to “smile like the people in the photographs.” The verbal directive was uniformly given first to prevent the subjects from relying on the memory of the visual image when presented with the verbal command. The frontal photographs were taken by the same operator (J.F.W.) using a Pentax K-1000 camera (Asahi Optical, Tokyo, Japan) with a 90-mm F/2.8 macro lens (Sigma, Tokyo, Japan) mounted on a tripod, 35-mm Kodachrome
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ISO 64 slide film (Eastman Kodak, Rochester, NY), and a standardized camera-to-source distance of 4 ft 7 in. All 88 slides, which resulted from the 22 subjects being photographed 2 times at the 2 separate sessions each, were then converted into 8 3 10 color copies via a Kodak 1550 Plus printer (Eastman Kodak) for analytical purposes. The still images shown to the panel were cropped to include only a standardized border beyond the vermilion of the lips. For the videography, a Panasonic Palmcorder VHSC video camera (Matsushita Electric Corporation of America, Osaka, Japan) mounted on a tripod was manually focused to show a close-up, full-face view of each subject. VHS-C film was used. The object-to-source distance was also 4 ft 7 in. The video camera was turned on before the verbal directive and remained on throughout the entire session. Randomly, 1 image from the video footage (either the verbal or the visual smile from either day 1 or 2) was selected for each subject to use for comparison with the still images. The apex or height of each of the 22 randomly selected smiles was determined by agreement of 2 evaluators (J.F.W. and G.J.C.). In the case of a disagreement, a third evaluator was used. The apex of a smile was defined as the frame in which the smile was the largest. To measure the video images, the apices of the smiles were converted into 35-mm slides and then into 8 3 10 color copies, using the Kodak 1550 Plus. The Media Suite Pro video-editing program (Avid Technology, Tewksbury, Mass) was used to create a videotape of each subject’s smile to be viewed by the panel. In 13 of the 22 subjects, the video camera was able to capture an unsolicited spontaneous smile. The smiles were deemed spontaneous by 2 evaluators viewing the unedited video footage using the following criteria: (1) there was no cue by the photographer to smile before the smile and (2) the subject appeared relaxed and was conversing with the photographer. Two examiners, with a third examiner consulted when there was a difference of opinion between the 2 original evaluators, also selected the apices of these spontaneous smiles. The apices of these smiles were then converted into 8 3 10 color copies with the Kodak 1550 Plus. For an objective assessment and comparison of the still and video-derived images described above, measurements were taken twice by the same operator (J.F.W.) with a vernier caliper to the nearest 0.1 mm, then averaged (Fig 2). A panel of 4 people was selected to provide subjective assessments of the smiles. The panel included a prosthodontist (rater 1), an orthodontist (rater 2), a layperson (rater 3), and an oral surgeon (rater 4). The panel portion of this study was divided into 4 parts. Part 1 addressed the issue of reproducibility of
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Fig 1. Scaled diagram of equipment configuration: subject/headholder at the apex and 2 cameras at each base of the isosceles triangles. A 2.34 angle was created from the midsagittal plane of the subject to the center of each camera lens for negligible distortion of images.
1.
Fig 2. Objective measurements of still and video-derived images: A, commissure to commissure; B, vermilion border to vermilion border*; C, inferior border of the upper lip to superior border of the lower lip*; D, maxillary incisal edge to the inferior border of the upper lip*; E, maxillary incisal edge to the vermilion border of the upper lip*; F, maxillary incisal edge to the interpupillary line*; G, intercanthal distance. Also measured was the 1-in marker on the head holder to determine the change in magnification. *Measured at midpoint of commissure to commissure distance.
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3. the smiles using still photography. Part 2 compared the diagnostic value of the 2 media: videography and still photography. With video technology, parts 3 and 4 provided comparisons of spontaneous and posed smiles. All 4 panel members were shown parts 1, 3, and 4, whereas part 2 was shown to the professional members of the panel only because it required a comparison of the diagnostic value of video vs still images. The following is a description of the 4 parts shown to the panel.
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Still photographs day 1 vs day 2. By random selection, either the verbal or the visual set of still photographs was selected for each subject to be shown to the panel. The randomly selected smile photos were cropped to display only a standardized border just beyond the vermilion border of the lips so as not to distract the panel with other facial features and extraneous details such as hairstyle and makeup. Each panel member independently was asked to determine whether he or she thought that the 2 smiles were the same. Twenty-six sets of smiles were projected next to each other on a screen. To ascertain the validity of each panel member’s responses, 4 of the 26 sets of photographs reviewed were actually duplicates, with the same pictures shown side by side. Still photography vs videography. The 22 randomly selected smiles were then shown to the 3 professional members of the panel in both the video and still formats. This provided a subjective comparison of the clinical value of the still and video smiles. The panel members were asked to fill out a form that asked 2 questions: (1) which is more useful diagnostically, the still photo, the video footage, or no preference? and (2) do you have any comments regarding preference? Posed vs spontaneous smiles (uncropped). The 4 panelists were shown the series of full-faced posed smiles along with their spontaneous counterpart, both obtained from the video footage. They were asked to select the most diagnostically useful image. “Diagnostically useful” was defined as the smile that appeared to be the most natural, the one that seemed to best represent the subject’s unsolicited smile. The layperson was told to select the smile that appeared most natural. Posed vs spontaneous smiles (cropped). The 4 panelists were also shown the series of spontaneous
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variable measured ðmmÞ 3 25:4 mm ð1-inch markerÞ length of marker in still image ðmmÞ
(Equation 1)
variable measured ðmmÞ 3 intercanthal distance as measured in still images ðmmÞ intercanthal distance ðmmÞ
(Equation 2)
variable measured ðmmÞ 3 intercanthal distance as measured in spontaneous images ðmmÞ intercanthal distance ðmmÞ
(Equation 3)
smiles along with their posed counterparts, with both images cropped to display only a standardized border beyond the vermilion of the lips. The panel members were asked to select the most diagnostically useful image. Once again, “diagnostically useful” was defined as the smile that appeared to be the most natural, the one that seemed to best represent the subject’s unsolicited smile. The layperson was told to select the smile that appeared most natural. The raw data were standardized to account for magnification differences between the images measured. For the data sets comparing still images only, the measured length of the 1-in marker (25.4 mm) in the image was used to adjust for changes in magnification. The formula used in these cases is shown in Equation 1. We were unable to use the 1-in marker as a standard measure for the video-derived images because the reproduced quality tended to blur the marker edges. Instead, the intercanthal distance was used for each subject because the data sets compared in this section were all taken at the same time, and thus there was no concern for change in head position or camera angulation. The formula used to standardize the data set that compared the video-derived images with the still images is shown in Equation 2. The formula used to standardize the data set that compared the apices of the video-derived spontaneous smiles and the video-derived posed smiles is shown in Equation 3. Statistical analysis
A power analysis was performed to determine the number of subjects required for this investigation. The maximum change in the width of a smile (commissure to commissure) considered by the principal investigator
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of this study (J.F.W.) to be diagnostically acceptable was measured on 4 subjects. At 2 times, each subject was asked to begin at his or her broadest smile and then to slowly reduce the smile until the examiner thought that the smile no longer had diagnostic quality. The change in width was found to average 4 mm. The full range of the smile was also measured; it averaged 13 mm. Using these estimates, we calculated that 22 subjects (11 men, 11 women) were required for the comparison between the different smiles obtained in this study, for a type I error of .05 and a 2-tailed test with 80% power. All analyses performed on the objective measurements were done using the standardized data. The differences between days 1 and 2 were tested for significance using either a paired t test or the Wilcoxon signed rank test, depending on whether the assumptions of normality were met for the t test. The same approach was used to assess the significance of the following: (1) the differences between the still and video images, (2) the differences between the verbal and visual cues in the still photographs, and (3) the differences between the spontaneous and posed smiles taken from the video. Tests of significance were 2-tailed, with a type I error of .05. An intraclass correlation coefficient (ICC) for the repeated measurements was computed to determine reliability. RESULTS
A total of 22 subjects (11 women, 11 men) participated in this study. They were between the ages of 20 and 49, with average ages of 24.7 years for the men and 27.2 years for the women. The average length of each subject’s videotaped session was about 57 seconds, with a range of 35 to 90 seconds. The videotape segments averaged 49 seconds for the women (range, 35-65 seconds) and 65 seconds for the men (range, 45 -90 seconds).
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Table I. Objective comparisons of smiles elicited on day 1 vs day 2 (n 5 22) Verbal Objective measurement (mm) Commissure to commissure Vermilion upper lip to vermilion lower lip Superior lower lip to inferior upper lip Upper incisal edge to inferior upper lip Upper incisal edge to vermilion upper lip Upper incisal edge to interpupillary line Intercanthal distance
Mean difference* 0.9 0.4 0.5 0.4 0.5 0.6 0.1
Visual
Range* 8.9 9.0 9.1 5.1 4.3 6.4 3.8
Significance NS NS NS NS NS NS NS
Mean difference* 1.5 0.2 0.3 0.1 0.3 0.1 0.2
Range* 10.6 10.8 9.1 4.2 5.6 5.8 3.2
Significance S NS NS NS NS NS NS
NS, No statistically significant difference; S, statistically significant difference at the alpha \0.05 level. *Standardized data.
Table II. Objective comparisons of verbally vs visually prompted smiles (n 5 22) Day 1 Objective measurement (mm) Commissure to commissure Vermilion upper lip to vermilion lower lip Superior lower lip to inferior upper lip Upper incisal edge to inferior upper lip Upper incisal edge to vermilion upper lip Upper incisal edge to interpupillary line Intercanthal distance
Mean difference* 0.5 1.0 1.2 0.4 0.1 0.1 0.1
Day 2
Range* 11.6 3.2 13.4 6.2 6.3 1.8 1.8
Significance NS NS NS NS NS NS NS
Mean difference* 1.0 0.4 0.4 0.4 0.3 0.2 0.3
Range* 14.2 13.6 11.8 7.6 7.7 3.6 1.7
Significance NS NS NS NS NS NS S
NS, No statistically significant difference; S, statistically significant difference at the alpha \0.05 level. *Standardized data.
We considered the reproducibility of the posed smile. The results of the objective data are given in Table I; for the most part, no statistically significant differences were found between the smile measurements taken on day 1 and day 2. The exception was the difference in commissure to commissure distance between the visually commanded smile on day 1 and the visually commanded smile on day 2. The mean difference in this instance was 1.51 mm, with a standard deviation of 2.93 mm and a range of 10.57 mm. No statistically significant differences were found when the verbally directed smiles of day 1 were compared with the visually directed smiles of day 1 (Table II). The only statistically significant difference in measurement was found between the intercanthal distances recorded on the verbally directed smiles on day 2 and the visually commanded smiles on day 2. The mean difference was 0.30 mm with a standard deviation of 0.49 mm and a range of 1.73 mm. For the results of subjective data, the ICC for agreement among the raters in comparing the still images taken on day 1 with the still images on day 2 was 0.52842; that was “moderate” agreement. The ICC for this same group without the duplicates (identical slides)
was 0.28763; this was considered “fair” agreement. The relative frequencies of the same subject's smiles on days 1 and 2 classified as the same or different for the panel members were tabulated to assess the reproducibility of the smiles within raters. The 2 smiles were determined to be different 95% of the time by rater 1, 73% of the time by rater 2, 64% of the time by rater 3, and 95% of the time by rater 4. Overall, the panel determined the smiles to be different in 83% of the cases. In addition, when the layperson’s responses were omitted from the distribution, 88% of the smiles were determined to be different. Raters 1, 2, and 3 were able to identify all 4 duplicates, and rater 4 recognized 3 of the 4 duplicates. We also compared the videography with the still photography. For the results of the objective data, when comparing the still photographs with the videography, 3 measurements had statistically significant differences: (1) the commissure to commissure distance, (2) the maxillary incisal edge to the vermilion border of the upper lip distance, and (3) the maxillary incisal edge to the interpupillary line distance (Table III). The average magnitude of the difference in the commissure to commissure distance was 1.19 mm; the video distance was smaller, with a standard deviation of 1.28 mm and a
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Table III. Objective comparison of smiles captured by videography vs still photography (n 5 22)
Table IV. Objective comparison of posed vs spontaneous smiles (n 5 13)
Mean Objective measurement (mm) difference* Range* Significance Commissure to commissure 1.2 4.8 S 0.2 6.6 NS Vermilion upper lip to vermilion lower lip Superior lower lip to inferior 0.0 2.7 NS upper lip Upper incisal edge to inferior 0.1 1.8 NS upper lip Upper incisal edge to vermilion 0.5 2.2 S upper lip Upper incisal edge to 1.5 2.6 S interpupillary line
Mean Objective measurement (mm) difference* Range* Significance y Commissure to commissure 0.1 22.6 y Vermilion upper lip to vermilion 0.7 8.2 lower lip y Superior lower lip to inferior 0.1 6.5 upper lip y Upper incisal edge to inferior 0.4 4.1 upper lip y Upper incisal edge to vermilion 0.1 5.2 upper lip y Upper incisal edge to 1.4 24.2 interpupillary line
S, Statistically significant difference at the alpha\0.05 level; NS, no statistically significant difference. *Standardized data.
*Standardized data; ysample size (n) was insufficient to reach significance.
Fig 3. The professional panel preferred the video to still images 68% of the time. The individual preferences were as follows: 63%, 63%, and 77% preference for the video by raters 1 (prosthodontist), 2 (orthodontist), and 4 (oral surgeon), respectively.
range of 4.76 mm. The mean difference in the maxillary incisal edge to the vermilion border of the upper lip was 0.50 mm; the video distance was smaller again, with a standard deviation of 0.66 mm and a range of 2.24 mm. The mean difference in the interpupillary line to the maxillary incisal edge was 1.47 mm (video smaller), with a standard deviation of 0.78 mm and a range of 2.64 mm. In the results of the subjective data, the agreement among raters for the comparison of the video footage with the still images was not statistically significant. Using a frequency distribution, overall, the panel preferred the video 68% of the time, the still images 23% of the time, and had no preference 9% of the time (Fig 3). The preferences were 63%, 63%, and 77% for the video by raters 1, 2, and 4, respectively (rater 3, the layperson, was excluded from this portion of the panel). We compared the spontaneous and posed smiles. The objective data showed no statistically significant differences in the measurements of the spontaneous and posed smiles from the video footage (Table IV). However, this study was not designed with sufficient
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Fig 4. The spontaneous smile was preferred 75% of the time overall. When limited to the professional panel members, this preference increased to 79%. The individual preferences were as follows: 85%, 77%, 62%, and 77% preference for spontaneous smiles by raters 1, 2, 3, and 4, respectively.
power to address this issue. The number of subjects (13) in this section was insufficient, and thus inferences drawn from this might be limited. The results of the subjective data showed that agreement among raters with regard to the comparison of the spontaneous smiles with the posed smiles was statistically significant for the cropped images (ICC, 0.17149: “slight” agreement) and not statistically significant for the uncropped images. A frequency distribution showed the following (Fig 4). The spontaneous smile was preferred 85% of the time by rater 1 (prosthodontist), 77% of the time by rater 2 (orthodontist), 62% of the time by rater 3 (layperson), and 77% of the time by rater 4 (oral surgeon). Overall, the panel preferred the spontaneous to the posed smile 75% of the time. When the layperson’s responses were omitted from the distribution, the spontaneous smile was selected 79% of the time. When the images were cropped, the panel’s preference for the spontaneous smiles declined to 67%.
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DISCUSSION
In this study, we found that whether recorded with a video or a still camera, prompted with a visual or a verbal cue, or taken on day 1 or 2, the posed smile could be reliably reproduced. Greater reproducibility was obtained with objective measures; however, as noted by the panel members, the eye of the diagnostician might be more critical than objective measures. The literature has addressed many aspects of the smile, but only a few studies have even touched on the aspect of the reproducibility of the smile.1,2 Peck et al3 coached their subjects before taking smile records and found that they were “easily able to attain a reproducible maximum smile.” However, prior methods used to determine smile reproducibility have been ambiguous or determined by visual inspection alone, and were not a specific aim of the studies. The psychological literature has often attributed specific characteristics to the posed smile.8-11 By imparting specific attributes to the posed smile, this implies that the posed smile is consistent. Johnson and Smith12 suggested that their smile measurements could not be considered precise because they did not use a device to limit head position or correct for magnification changes. After reviewing the literature, we decided to use a head holder to apply stringent control over the changes in measurements that can occur with head position changes. However, for clinical purposes, the use of a head holder while taking diagnostic photographs or video of a patient might hinder the patient’s ability to smile naturally by restricting his or her ability to respond normally. The reproducibility of natural head position has been shown to be within a clinically acceptable range of 2 .13 Perhaps accurate information could be obtained from facial photography or videography if the patients were allowed to hold their head in a more natural manner. Further investigation comparing facial images taken in natural head position with facial images taken when the subject is placed in a head holder would address this issue more definitively. Analysis of the smiles by the panel members showed that there might be subtleties about a smile that cannot be measured objectively. More than 80% of the time, the panel could distinguish between the smiles taken on different days. When the data were limited to the professional panel members, the ability to discriminate between the 2 smiles increased, suggesting that the practitioner’s eye might be more discriminating than objective measures for diagnosis and treatment planning.
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To truly analyze an action, it seems logical that one would require a tool to capture the dynamic nature of that action. Nonetheless, the prevailing clinical question in this study was whether the practice of orthodontics requires a technique that can record the entire dynamic range of the smile, or whether it is sufficient to rely on the standard still photographs for diagnostic information. Are diagnostic photographs providing sufficient information about the smile or would videography be a better diagnostic tool? For those interested in information regarding the height of the smile alone, a still photograph might be sufficient, assuming that the photographer has captured the apex of the smile. However, we found video to be the method of choice by the clinicians. The panel members’ comments supporting the preference for video were the following: (1) “the whole range of the smile was visible,” (2) “it provided a record of muscle function and strain,” (3) “it showed whether the smile was guarded or not,” (4) “it revealed swallowing patterns,” (5) “it demonstrated lip posture and competence,” and (6) “it provided 2 views—the patient at rest and the patient smiling.” Previous studies have found that still images of a dynamic action are more difficult for the viewer to correctly analyze. A fixed representation of a facial expression can remove many of the cues for interpretation of that expression.14 As the panel members suggested, they preferred to see the entire range of the smile because it gave them significantly more information than did the still images. Certainly, as Bruner and Tagiuri15 maintained, a millisecond of exposure surely cannot represent clinical observations. Unlike past studies of facial esthetics, we attempted to specifically address the diagnostic value of obtaining videographic records of the smile. Few studies have touched on the smile as a dynamic action; however, for the most part, it has been in relation to dental and gingival display at maximum smile. Their focus was a fixed point at the height of the smile.1,2,16,17 Studies in the plastic and reconstructive surgery literature have evaluated smile dynamics and the soft-tissue changes that occur when the face moves from rest to maximum smile.3-5 These studies do recognize the value of closely evaluating the smile as a dynamic action. The video footage seemed to provide a reliable representation of the subject’s level of comfort during the photographic or videographic sessions. In several instances, the still image shown to the panel members appeared to depict a relaxed person giving a relaxed smile. However, when the video footage of this same smile was viewed, it became obvious that the person was not at all
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comfortable, and the smile was forced. Videography might give practitioners insight into how patients feel about their appearance or smile that can be missed in a hectic clinical examination or the still photographs taken by auxiliary staff. The panel members were less likely to select the spontaneous smile when the images were cropped, removing all other cues of facial expression. Duchenne18 described the use of 2 facial muscles to distinguish a deliberate smile from a spontaneous smile: “The first (zygomatic major) obeys the will but the second (orbicularis oculi) is only put in play by the sweet emotions of the soul; the .fake joy, deceitful laugh, cannot provoke the contraction of the latter muscle.” In 1980, Ekman et al10 confirmed Duchenne’s observations, finding that most people cannot voluntarily contract the outer portion of the orbicularis oculi and thus do not exhibit this action in a deliberate smile. A significant aim of this study was to begin to finetune our methods of eliciting and capturing smiles. Two behavioral patterns recognized in this study are worthy of discussion: (1) variations in response to the verbal and visual cues, and (2) sex differences in eliciting a posed smile. Although these findings were not specifically pinpointed in this study, they are of interest to practitioners because they might help to better elicit smiles from patients. The principal investigator (J.F.W.) observed that 45% of the subjects responded more easily to the verbal command, whereas only 18% seemed to smile more readily when shown the visual cue. The remainder had no preferences. The visual cue appeared to be confusing for many subjects. When the investigator provided the visual cue, several subjects asked “What do you mean?” or “Do you want me to imitate the smiles?” A few others needed to hear the instructions again. Studies have found individual variations in the responses to verbal and visual cues.19 Perhaps it would be beneficial to provide both verbal and visual commands. It was harder to elicit a posed smile from the men than from the women. Five of the 11 men (45%) had difficulty smiling on command, but only 1 of the 11 women (9%) had difficulty responding to the command. A subject was considered to have difficulty smiling on command if he or she did not respond with a facial expression that resembled a smile or did not appear to respond at all to the command as judged by the principal investigator and another impartial observer. The average length of the video footage used to capture the smiles of the men (65 seconds; range, 45-90 seconds) was longer than the average length of the video footage needed for the women (49 seconds; range, 35-65 seconds). Part of this discrepancy might be because all sessions were
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directed by and all images were photographed by a women (J.F.W.); thus, the men might have felt more inhibited to respond than did the women. Interestingly, although it took the men longer to smile, there was no difference in the number of male subjects (7 of 11) compared with the female subjects (7 of 11) who showed a spontaneous smile in the video footage. This would seem to imply that men might not necessarily smile less frequently than women in all situations, but they might be less able to “pretend” to smile.20-22 CONCLUSIONS
This study emphasizes the need to continue to investigate and standardize the methods of eliciting and recording a smile of diagnostic quality. The following are our specific conclusions. 1. 2.
3. 4. 5.
Posed smiles can be reliably reproduced as measured objectively, but, subjectively, differences were noted. When the entire face is visible, practitioners can detect important differences between posed and spontaneous smiles. However, this ability is decreased when only the smile is shown. Spontaneous smiles are preferred to posed smiles by professional diagnosticians. Videography provides diagnostic information that cannot be obtained with still photography alone. Video images are preferred to still images by professional diagnosticians.
ACKNOWLEDGMENTS
We thank Graham Walker for his guidance and assistance; Hugh Gilmore for his video-editing wizardry; and the highly perceptive panel members for their enthusiasm and remarkable attention to detail.
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