Analysis of Various Smile Parameters Using Digital Photography: An Observational Study

INTRODUCTION

Poets, painters, writers through the centuries have described a smile as an asset to humans and have emphasized that nothing can be more attractive in a personality than having a beautiful smile. The smile parameters can be based on proportions and parameters like the divine proportion or the golden ratio.¹ Cosmetic dentistry is a multidisciplinary approach to esthetically rehabilitate a patients’ smile. An informed, structured, and disciplined approach is required to assess, diagnose, and restore esthetic problems. The esthetic elements can be drawn into a pleasing arrangement to create a beautiful smile.² Knowledge of the smile parameters of a population would certainly help us in rehabilitating the local population, be it replacing a single tooth or an entire mouth. Many have classified smile one among them is by Ackerman et al. who classified smile into a social smile/posed smile and the enjoyment smile/unposed smile/Duchenne smile depending on the voluntary and involuntary action of orofacial muscles.¹

Prosthodontics is a branch where lies a delicate amalgamation of scientific principles and creative, artistic capability. With the increasing demands of the patient for an esthetic smile, a thorough and rigorous knowledge about esthetic principles is a must for prosthodontists. Through prosthodontics, one can design various types of smiles depending on facial types.

Generally, a normal photograph and casts are used for evaluating smile parameters. But the normal static photographs can be very vague, cannot provide proper evaluation of smile parameters in depth. And evaluating smile parameters through casts is also not feasible as it does not have an amalgamation of hard and soft tissue. Like our mere existence in the universe is based on quantum physics, the digital field is no exception. Digital gadgets like computers, lasers, camera lenses, etc., all of these work on this basic principle. The cameras used earlier have come a long way with improvements in lens, pixels, etc. Thus, at present, the digital world has so much to offer from which we can benefit to rehabilitate our patients. As smile rehabilitators, our ultimate aim should be to make use of our clinical knowledge and expertise, as well as the digital or the technical support to give our patients the best that they deserve. Dental photography offers the dental professional an array of the possibility of visual reconstruction of the various stages of treatment.³ Therefore, digital photographs have come into the picture, where it provides better efficacy and is nowadays easily available in the market. The disadvantage lies as it is not cost-effective. The present study was undertaken to know the smile parameters of a sample population using the photographs captured in a digital single-lens reflex (DSLR) camera with the intention that the results would help us in prosthodontic rehabilitation of the local population.

MATERIALS AND METHODS

Using a convenient sampling technique, a sample size of 120 (60 males and 60 females) was drawn who were selected among the patients visiting the Department of Prosthodontics of the School of Dentistry, Krishna Institute of Medical Sciences Deemed University, Karad, Maharashtra. All patients were informed about the study procedure in their mother tongue and made aware of the experimental design. The study subjects were approached, explained about the study, and their consent was taken.

Inclusion criteria for this study include patients within the range of 18–25 years with a healthy periodontium, complete permanent dentition excluding 3rd molars, class I molar relation with no anterior crowding. Exclusion criteria include patients with any prosthodontic and/or restorative work on teeth visible in a smile, undergone/undergoing orthodontic treatment or maxillofacial surgeries, presence of any periodontal disease, presence of any craniofacial anomalies or other pathologies.

Ethical clearance was obtained from the University’s Ethical Committee (KIMSDU/IEC/04/2016). The photographs of the participants were captured using DSLR [Single-lens reflex digital camera (NIKON D3500)] with AF-P 18 to 55 mm VR lens, lens mount NIKON F mount (with AF contact). Both close-up and facial photographs were captured. The close-ups were taken both during natural and forced smiles. Standardization of the images was done as per Liébart et al. criteria by positioning the head in the Frankfort horizontal plane and capturing the picture from a distance of 30 cm to include the lateral commissures of the mouth, the teeth, gingiva, and the philtrum of the upper lip.⁴ All the pictures were photographed and evaluated by a single investigator to maintain standardization total of 240 photographs of 120 patients were taken wherein a natural smile photograph and a forced smile photograph (i.e., 2 photographs of each patient) were taken of all participants in this study.

The five parameters considered in the present study are:

• Smile arc

  To mark the smile arc, a curve was drawn touching the incisal edges of the upper anterior teeth on the photograph when the subject was instructed to smile naturally. The smile arc was evaluated as positive or negative depending on whether the arc was convex (Fig. 1A) or concave (Fig. 1B) and straight (Fig. 1C)

• Gingival visibility

  The amount of gingiva visible on a natural smile and forced smile were recorded. Further, the gingival visibility was divided as type I (Fig. 2A), type II (Fig. 2B), type III (Fig. 2C), type IV (Fig. 2D) according to Liebert et al. classification.⁴

• Facial and dental midline

  All the photographs were evaluated for a correlation between the facial and the dental midline. This was done using Adobe Photoshop CS3 version 10.0.⁵ A line was drawn to mark the facial midline through the nasion, tip of the nose, philtrum, and pogonion and compared with the dental midline which is drawn between the two central incisors. The facial midline was evaluated as ideal (Fig. 3) or canted. The dental midline was evaluated as ideal (Fig. 4A), shift to the right (Fig. 4B), or shift to the left (Fig. 4C).

• Gingival zenith pattern

  Horizontal lines on the gingival zenith of central, lateral incisors, and canines were marked as shown in Figure 5 to know the gingival zenith patterns.

• Relationship between the smile arc and lower lip

The relationship between smile arc and lower lip curvature was drawn depending on whether there was a gap between the incisal edges of the upper incisors and the lower lip (Fig. 6A) or there was light contact of maxillary incisal edges with lower lip (Fig. 6B).

In the present study, the sample size considered according to the convenient sampling technique was 120 (N). Statistical analysis was performed using SPSS software, version 23. The mean and standard deviation (SD) were calculated for age. Frequency and percentage were calculated for gender and other parameters. Chi-square test and Fisher’s exact test were used to check the association between gender and various parameters. Comparison between two groups (male and female) for various parameters was done by non-parametric Mann–Whitney “U” test. The p value of 0.05 was considered to be statistically significant.

RESULTS

Table 1 shows the age distribution in the study population, respectively. Among males N (60), 85.0% (N = 51) of them had convex smile arc. Among females N (60), 78.3% (N = 47) of them had convex smile arc. Within the genders when the smile arc was compared using the Mann–Whitney “U” test, 81.7% (N = 98) of the study population had convex smile arc (Table 2) which was statistically insignificant (p = 0.429).

Gingival visibility according to Liebert et al. assessed for normal and forced smiles in both genders.⁴ Results obtained for gingival visibility for both forced and normal smiles in both genders had a higher percentage of type II type of gingival visibility. When the gingival visibility was compared in both the genders for forced smile 53.3% (N = 64) had type II type of gingival visibility (Table 3) which was statistically insignificant (p = 0.979). And for normal smile 52.5% (N = 63) had type II (Table 3) which was statistically insignificant (p = 0.802). From the results, it can be conveniently drawn that the majority of the population had type II type of gingival visibility. However, it is interesting to note that there was not even a single study subject who had a type I gingival visibility score for both normal and forced smiles.

In 39 of the males, i.e., 65.0% and 38, i.e., 63.3% of the female study subjects, the dental midline was found to deviate to the right. When the Mann–Whitney “U” test was applied to compare the midline deviation within the genders in 77, i.e., 64.2% of the study subjects the dental midline was found to deviate to the right. The results obtained were statistically insignificant (p = 0.624). With the data it can be concluded that the majority of the study population the midline is deviated to the right side, followed by the dental midline coinciding with the facial midline, and in the least number of study subject’s midline was found to deviate to the left side (Table 4).

Among the males N = 50, 83.3% followed the ideal zenith pattern. Among the females N = 48, 80.0% of them followed the zenith pattern. When the zenith pattern was compared within the genders in the study population using Mann–Whitney “U” test about N = 98, 81.7% followed the zenith pattern (Table 5) which was statistically insignificant (p = 0.814). With these data, it can be said that about 80% of the study population followed the ideal zenith pattern. When the relationship between the incisal edges of upper anteriors and lower lip was evaluated in the male study population, N = 43, 71.1% and N = 51, 85.0% of females had incisal edges of upper anteriors touching the lower lip which directly relates to the positive smile arc. When this relation was studied between the genders using Fisher’s exact test in N = 94, 78.3% of the study population the lower lip was in contact with upper anteriors (Table 5) which was statistically insignificant (p = 0.120).

DISCUSSION

A pleasing smile can be created by arranging various esthetic components in harmony.¹ The dental discrepancies are evaluated differently by laypeople, general dentists, and restorative dentists.⁶

Multiple photographic views (e.g., facial, sagittal) facilitate the smile analysis.⁷ A dentist should always look forward to an ideal goal that would lead him toward proper diagnosis and treatment planning for smile rejuvenation.⁸ Clinical photography has become an important part of standard dental practice.⁹

The area of presentation of a smile lies in-between the upper and lower lips. Our teeth and the gingival mesh are an integral part of the smile. The lip thickness, inter-commissural width, inter-labial gap, smile index (width/height), and gingival architecture are the soft tissue definitive for the area of presentation of a smile.¹⁰ The various parameters of the smile that were assessed in this study are discussed below.

CONCLUSION

Within the limitations of the present study, it can be concluded that the various smile parameters assessed can be used to rehabilitate the smile of dentate patients, partially dentate, and/or can help rehabilitate an edentulous mouth. The present study was done to evaluate some aspects of the dento-labial-gingival complex using photographs. Knowledge of smile design, coupled with new and innovative dental technologies, allows dentists to diagnose, plan, create, and deliver esthetically pleasing new smiles.

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