|Year : 2015 | Volume
| Issue : 2 | Page : 111-115
A study on gingival component of smile
Goutam Chakroborty, Tamal Kanti Pal, Abhijit Chakroborty
Department of Periodontics, Guru Nanak Institute of Dental Science and Research, Kolkata, West Bengal, India
|Date of Web Publication||3-Sep-2015|
Dr. Goutam Chakroborty
'Nirala' Anandanagar, Parbangla, Kolkata - 700 140, West Bengal
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: Esthetic enhancement of smile requires prior quantification of gingival component of smile. Hence, a study has been designed on randomly selected volunteers' and posed frontal smiling photographs were taken and analyzed through computer-aided ImageJ software. Aim: To determine the role of gingival component in designing a smile. Settings and Design: Present observational study includes one frontal photograph from each of 212 subjects who were attending the Department of Periodontics (examined during the study period) and then divided into three age groups (18-30, 31-40, and 41-50 years). Materials and Methods: Standardized frontal photographs with posed smile from 212 volunteers irrespective of age and sex were taken and the images were analyzed in computer by using ImageJ software. Statistical analysis used: Mean and standard deviation of intercommissural width (ICW), interlabial gap (ILG), and smile index (SI) during posed smiling were calculated for different sex. Comparison between male and female group were done by Mann-Whitney U test, and P-values were calculated for ICW, ILG, and SI. Spearman's rank correlation coefficients (rho) were calculated for SI and different components of central zone of smile. Results: Male group as compared to female group exhibited greater ICW and ILG, and there was existence of fair to good correlation between lip dynamics and different factors of smile. Conclusion: Present study indicates that different factors of central zone of smile havefair to good correlation with lip dynamics assessed by SI.
Keywords: Esthetic value, central papilla display, gingival display, image analysis, Image J Software, posed smile, smile index
|How to cite this article:|
Chakroborty G, Pal TK, Chakroborty A. A study on gingival component of smile. J Int Clin Dent Res Organ 2015;7:111-5
| Introduction|| |
Esthetic enhancement of smile requires prior quantification of different factors of smile. An esthetically pleasing smile depends on tooth size, shape, color, and position (visible tooth surface); amount of visible gingiva (gingival display); and the framing of the lips, with its movement (lip dynamics). 
Maxillary central incisors and the central papilla, because of their location in the midline and being the most prominent, are first noticeable in appearance.  Hence visibility of central papilla, adjacent teeth, and gingival display and their association with the smile line are considered to be the key esthetic factors in smile of any individual. 
To visualize and quantify the frontal smile, Ackerman et al.,  developed a ratio, called the smile index (SI) that describes the area framed by the vermilion borders of the lips during the social smile. The SI is determined by dividing the intercommissural width (ICW) by the interlabial gap (ILG) during smile. This ratio is helpful for comparing smiles among different individuals or across time in one individual. Smile is always influenced by person's age, sex, personality, and emotion; and it should essentially be a function of lip movement (lip dynamics) and there should be a harmonious relationship among visible tooth surface, gingival display, and lip dynamics. Lip dynamics can be assessed by evaluating smile line and SI. Gingival display and tooth display can be assessed by analyzing and comparing, the static frontal photographs of the patients on posed smile.
We are in need to quantify the gingival esthetics in an objective manner and then to analyze and search for much needed harmonious relationship that exists among the factors of central zone of smile. Spontaneous smile is natural and brings more esthetic value to our face, but it cannot be reproduced on demand, any analytical study involving the data acquired from spontaneous smiling may induce some unintentional error in the study analysis.
Therefore, an observational study is designed to find out relations of gingiva in quantifiable way to the constitutional factors of smile.
| Materials and Methods|| |
The observational study was carried out in the Department of Periodontics for the duration of 12 months. Primarily 2116 individuals attending the department of periodontics were examined during the study period. Only 212 individuals of different age and sex (who met the inclusion criteria) were scanned out of exclusion criteria and selected for the present study. It was explained to the potential subjects that this was a study on posed smile capturing only a small zone of face consisting only of lips, teeth, and part of gingiva.
Selection of subjects
Voluntary involvement in the study.
Complete permanent dentition.
Individuals of both sexes were included in the study.
Individuals with 18-50 years of age were included in the study.
Individuals of acceptable intellect and oral habits were included into the study.
Class 1 molar relation with no anterior crowding.
Missing teeth that could have been visible on smile.
Prosthodontic work on teeth visible in smile.
Inability to determine the natural head position (NHP; noncooperative patients)
Presence of any active periodontal diseases.
Presence of any craniofacial anomalies or other pathology.
Any previous orthodontic treatment or maxillofacial surgery.
Present study encompassing one frontal photograph from each of 212 subjects and then divided into three age groups (18-30, 31-40, and 41-50 years). Each frontal photograph was then observed and analyzed and data, thus generated, was statistically analyzed.
Smile capture method
Several frontal photographs of individual's face on posed smiling were taken at NHP with the help of a digital single lens reflex camera (Canon EOS 1100D) mounted on a tripod stand, and posed smiling image having maximum lip expansion and tooth and gingival display with unstrained facial expression was selected for the study.
- The camera (Canon EOS 1100D) was mounted on a tripod stand with the lens and positioned parallel to the true perpendicular of the face in NHP.
- The camera was raised to the level of subject's lower facial third.
- Posed frontal photograph taken from 3" distance, using same type of illumination.
Standardization of image
- A millimeter scale was photographed from 3" distance using Canon EOS 1100D camera.
- Image of the millimeter scale taken from the three feet distance was transferred to computer (Dell-INSPIRON N5050), and then opened with ImageJ Launcher software by clicking 'file' menu and then opened.
- The image was magnified upto 100% with the help of 'magnifying tool' from the ImageJ tool bar in the computer.
- A straight line was drawn and measured the distance on the scale of 10 mm. This showed the pixels value for 10 mm distance.
- Then 'menu bar' option was selected and 'analyze menu' was clicked, then 'set scale' sub menu was selected. The 'set scale' dialog box appeared which showed the distance in pixels as 112.
- Known distance and unit of the length were set as 10 mm and millimeter, respectively.
- Next the 'Global set' check box was ticked and 'OK' button was clicked. That showed the linear measurement of 10 mm distance in pixel count which was 112.
- When this standardization was used for any further linear measurement, the value shown by the tool bar as length was 10 times of the actual value. So by dividing the value (depicted by the tool bar as length) by 10 we got the original value of the object.
The photographs taken in the camera were transferred to computer (Dell Inspiron N5050). The images received from the camera were analyzed in computer using Image J software in following ways:
- First a working frame was prepared involving the smiling zone.
- ICW was measured by measuring the distances from outermost corner of the mouth from one side to other [Figure 1].
|Figure 1: Measurements taken for intercommissural width (ICW; green line) and interlabial gap (ILG; red line) for calculation of smile index (SI)|
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- ILG was measured by measuring the distance between midpoints of the upper and lower lips, when they were relaxed at posed smiling [Figure 1].
- SI was calculated by dividing the ICW by ILG [Figure 1].
- Papilla heights were measured at different visible maxillary teeth by measuring the distances from the tip of the interdental papilla to the smile line [Figure 2].
- Teeth display were measured by measuring the cervico-occlusal distances from the zenith points (where it was visible) or tentative positions of zenith points to incisal or occlusal limits of tooth display [Figure 3].
- Gingival display were measured by measuring the distances from the zenith points to the vermilion border of upper lip [Figure 3].
- Data obtained were exported to excel worksheet for analysis.
| Results|| |
Data obtained from image analysis by ImageJ software were transferred to excel sheet and then analyzed by Statistica version 6 (Tulsa, Oklahoma: StatSoft Inc, 2001).
Mean and standard deviation of ICW and ILG during posed smiling were calculated for different sex. SI was calculated by dividing the ICW by ILG for each sample and mean, and standard deviation of SI during posed smiling for different sex was calculated.
Comparison between male and female group were done by Mann-Whitney U test, and P-values were calculated for ICW, ILG, and SI. The mean; standard deviation; and P-values for ICW, ILG, and SI according to sexis given in [Table 1].
|Table 1: Mean, standard deviation, and P-values for intercommissural width, interlabial gap, and smile index according to sex|
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Comparisons of mean for ICW, ILG, and SI of male and female groups are shown in [Figure 4].
|Figure 4: Comparison of mean for ICW, ILG, and SI of male and female groups|
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Male group as compared to female group exhibited greater ICW and ILG, and lesser SI on posed smile. Statistically highly significant sex-related difference was noted in ICWs on posed smile between male and female, and significant sex-related difference was noted in ILGs on posed smile between male and female.
Evaluation of relations between SI and central papilla display (SI-PH11_21)
In this study, all the variables were found to be not normally distributed, and hence were subjected to nonparametric measure of statistical dependence between two variables. So for correlation analysis between SI and central papilla display (SI-PH11_21), Spearman's rank correlation coefficients (rho) were calculated. The Spearman's coefficient of rank correlation (rho) for SI-PH11_21 was −0.536 [Table 2], which indicated that a good negative linear correlation existed between SI and central papilla display on posed smile (SI-PH11_21). The relationship was explained by scattered diagram [Figure 5]a.
|Figure 5: Scattered diagram indicating the linear relationship on posed smile (a) between SI and central papilla (SI-PH11_21), (b) between SI and gingival display at the zenith of maxillary right central incisor (SI-GD11), (c) between SI and gingival display at the zenith of maxillary left central incisor (SI-GD21), (d) between SI and tooth display of maxillary right central incisor (SI-TD11), (e) between SI and tooth display of maxillary left central incisor (SI-TD21)|
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|Table 2: Spearman's rank correlation coefficients for different paired parameters|
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Evaluation of relations between SI and gingival display at the zenith points of maxillary right and left central incisors (SI-GD11 and SI-GD21)
The Spearman's coefficient to rank correlation (rho) for SI and gingival display at the zenith points of maxillary right and left central incisors (SI-GD11, SI-GD21) were −0.473 and−0.417, respectively [Table 2], which indicated that a fair negative linear correlations existed between SI and gingival display at the zenith points of maxillary right and left central incisors (SI-GD11 and SI-GD21). The relationship was explained by scattered diagram [Figure 5]b and c.
Evaluation of relations between SI and tooth display of maxillary right and left central incisors (SI-TD11 AND SI-TD21)
The Spearman's coefficient to rank correlation (rho) for SI and tooth display of maxillary right and left central incisors (SI-TD11 and SI-TD21) were −0.567 and −0.453, respectively [Table 2], which indicated that a good negative linear correlations existed between SI and tooth display of maxillary right central incisors (SI-TD11), while a fair negative linear correlations existed between SI and tooth display of maxillary left central incisors (SI-TD21). The relationship was explained by scattered diagram [Figure 5]d and e. The Spearman's rank correlation coefficients (rho) for each pair of relations are given in the [Table 2].
| Discussion|| |
Since smile is essentially a dynamic act, direct measurement of different constitutional factors of smile is practically impossible. For quantification of factors related to esthetics, individual's frontal smile should be captured first, either by videographic methods or by static photographs. There are many studies on smile, anterior dental display, and smile esthetics in the literature, almost all used static pictures. ,,
Spontaneous smile brings more esthetic value to our face, but it cannot be reproduced on demand. Any analytical study involving the data acquired from spontaneous smiling may induce some unintentional error in the study analysis. Moreover to capture a spontaneous smile from individual's face either one has to still the smile by hidden camera or has to induce spontaneous smile by some previously known provocation factors, both of which seems unrealistic and unethical. Present study involves static frontal photographs of posed smile taken by digital SLR camera, hence chances of unintentional error is negligible. For quantification of gingival esthetics; different approaches, ranging from simple to sophisticated one, were employed in the dental literatures. Desai et al.,  made an analysis of dynamic smile by using videography (capturing images at 30 frames per second) and computer software. Sachdeva et al., made a study to evaluate the role of smile in overall facial esthetics, by capturing the static photograph, of posed smile of the 100 normal subjects from Himachal Pradesh and then analyzed by using the Microsoft Office Picture Manager software. 
In maximum cases, individual's frontal smile was taken along with the previously calibrated measuring instruments or framework for standardization of the image obtained. The standard and the authenticity of smiling image obtained in such a way might be jeopardized by incorporation of measuring instruments.
Present study is unique in this regard. No measuring instruments were incorporated during smile capture. Standardization of image was made separately. It shows ICW was 72.64 mm for males and 68.43 mm for females, and ILG was 13.88 mm for males and 12.23 mm for females. The mean value of ICW was significantly higher in males as compared to females. The mean value of ILG was also significantly higher in males as compared to females. These are in accordance with the study conducted by Sachdeva et al.  Ackerman and coworkers introduced SI as a soft tissue determinant of a smile. The SI is the smile width divided by the smile height. By evaluating SI, the lip dynamics can also be ascertained. In various dental literatures, different determinants of smile and their influences on smile were assessed. To the best of our knowledge, this is the first report of its kind as far the papillary display in the smile is concerned.
Present study tries to unfold this arena. As a matter of fact, the central zone of smile consisting of central papilla, and adjacent teeth, because of their location, bears the key esthetic factors in smile of any individual.  Therefore, assessment of the relations between:
- SI and central papilla display,
- SI and gingival display at the zenith points of maxillary right and left central incisors (SI-GD11, SI-GD21), and
- SI and tooth display of maxillary right and left central incisors (SI-TD11, SI-TD21) has been made in the present study.
As a whole, present study clearly indicates that different constitutional factors of central zone of smile have fair to good correlation with lip dynamics assessed by SI. The exposure of the teeth during smile varies from person to person; concomitantly amount of gingiva in a smile also varies. To design a smile we need to determine the amount of part to be exposed along with the exposure of the teeth. The current procedure described in this article can predictably determine the correct amount of gingival show with the proportional exposure of teeth. This can easily relate the clinical benefit in designing a smile. In conclusion it can be stated that gingival component of smile can predictably be assessed quantitatively, which in turn can be utilized in designing a smile predictably. This newer modality of assessing proportion of tissue can better be utilized in designing a smile in the field of esthetic dentistry.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2]