Journal of Orthodontics & Endodontics

Keywords

Smile; Digital video; Malocclusion; Lip length; Lip thickness

Background

The most common reason for seeking orthodontic treatment is to improve dentofacial esthetics. It is now accepted that modern orthodontic treatment requires a shift away from Angle’s paradigm of achieving ideal occlusion to the more esthetically focused soft tissue paradigm that is based on the patient’s overall benefit [1,2].

According to Hulsey, “Smile is one of the most effective means by which people convey their emotions.” [3] Majority of orthodontic literature and diagnosis is based on patient’s profile and lips at rest while analyzing a static photograph and / or lateral cephalogram [4-17]. The reason that smiles had not been readily studied in the past could be due to the difficulty in capturing a reliable, repeatable smile [1,2,18]. Although these orientations provide an adequate amount of diagnostic information, they do not contain all of the information needed for smile visualization and quantification. The records needed for contemporary smile visualization and quantification can be divided into 2 groups: static and dynamic. The dynamic recording of smile can be accomplished with digital Videography. Videography allows us to capture standardized/reproducible smile, thus minimizing the error when studying one snapshot. Digital video and computer technology enables the clinician to record anterior tooth display during speech and smiling at the equivalent of 30 frames per second. The videos are recorded in standardized fashion with the camera at a fixed distance from the subject [1,2]

The smile is a result of the interaction of various components that form the smile, and we need to understand the principles which are involved in creating a balance between the teeth and soft tissues [19].

Esthetic of smile depends on relationship between the teeth and lips and the way that lips and soft tissue frame the smile. A pleasant smile also depends on the quality and beauty of the dental elements and their harmonious integration. Dental components of the smile include the size, shape, color, alignment, and crown angulation (tip) of the teeth; the midline; and arch symmetry [20,21].

There are indications that there are differences in facial movements between the genders [22] Modern psychological research indicates that men and women possess different smile behavior [23].

This study is carried out to check malocclusion and gender related changes in upper lip length and thickness on smiling.

Materials and Methods

Participants

The present study was conducted on 120 subjects randomly selected from the students and staff of faculty of dentistry in Hama University. It was explained to the subjects that this was a study on lip movements involving a short questionnaire followed by a (5- 10 second) video clip capturing only a small part of the face (chin to nose). Video graphic records of these 120 subjects, who willingly consented to participate in the study, were taken to study the perioral zone at rest and on smiling.

The subjects were divided into three groups, namely, group 1 (class I), group 2 (class II div1), group 3 (class II div2), with each group containing 20 males and 20 females.

Inclusion criteria:

• Age range between 18 and 28 years.

• No active orthodontic treatment

Selection Criteria for the Class-II Sample: Class II div 1:

• Bilateral Class-II Buccal segments "molar and canine" with convex facial profile.

(The skeletal classification was not considerable)

• Proclination of maxillary front teeth with an overjet of > 4 mm.

Class II div 2:

• Bilateral Class-II Buccal segments "molar and canine". (The skeletal classification was not considerable)

Exclusion criteria:

• Missing tooth visible on smiling

• Prosthodontics /Restorative work on tooth/ teeth visible on smiling

• Gross facial asymmetry

• Visible periodontal disease, caries, excessive dental attrition

• history of orthodontic treatment

• Lip irregularities, or history of lip surgery.

Smile Recording and Measurements

The subjects were explained that this was a study on smile involving a 5- to 10-second video clip of a small part of the face. An informed consent was obtained from each subject who agreed to participate in the study voluntarily.

A video camera (SONY DSC-H200) was set on the tripod 4 feet from the subject. The subjects were seated on the adjustable stool and instructed to hold the head in natural head position by looking straight into an imaginary mirror. If head position required correction, the researcher helped the subject into natural head orientation. The camera lens was adjusted to be parallel to the apparent occlusal plane and the camera focused only on the mouth (from nose to chin) so that the person could not be identified. Included in the capture area (frame) were 2 rulers with millimeter markings. The rulers were secured in a cross configuration so that if the subject accidentally rotated 1 ruler, the other could be used to analyze the frame. The relaxed lip position was achieved by asking the subject to lick the lips and then swallow. Then, the subjects were instructed to say ‘‘Subject number __’’ and then smile.

Recording began 1 second before the subject started speaking and ended after the smile.

The video clip was downloaded to a computer (LG RD590) and uploaded to ScenalyzerLive (version 4.0, Andreas Winter, Vienna, Austria), a video-editing software program. Each frame was analyzed, and 2 frames were captured for the study. Each frame was then analyzed, and finally two frames were selected for the study. The first frame represented the subjects’ lips at rest or relaxed lip position, and the second frame represented the subjects’ natural unstrained posed smile. The widest commissureto commissure posed smile frame was selected as one of 10 or more frames showing an identical smile. Thus, the selected smile image represented a sustained and hence repeatable smile position.

Each frame was opened in Adobe Photoshop 6.0 (Adobe Systems, San Jose, Calif) and adjusted by using the millimeter ruler in the frame. Calibration of the software was done in accordance with the previous study of Desai et al [7].

Measurements on Rest Frame (Figure 1)

1. Upper lip length- from subnasale to stomion superius

2. Upper lip thickness- vertical distance from the most superior point of cupid’s bow to the most inferior portion of the tubercle of the upper lip

Measurements on Smile Frame (Figure 2)

1. Upper lip length- subnasale to stomion superius

2. Upper lip thickness- vertical distance from the most superior point of cupid’s bow to the most inferior portion of the tubercle of the upper lip

The measurements were made on rest and the posed smile photograph as shown in Figures 1 and 2 and Table 1.

Table 1: Measurement Used in the Study.

Statistical Analysis

Minitab® 15 (Minitab Inc, State College, PA, USA) was used to perform the statistical analysis. With alpha set at 5%, Data were summarized as mean 6 SD. Groups were compared by two-factor (class of malocclusion and sex) analysis of variance (ANOVA) using general linear models. If the ANOVA showed statistical significance, the Bonferroni post hoc test was done to determine which groups were significant from the others.

Results

The results are shown in Tables 2 through 7.

Table 2: Descriptive Statistics and Significance of Mean Differences of Rest Position Measurements Between Males and Females.

At rest position, The Class I subjects possessed higher values of upper lip length followed by Class II div2 then Class II div1, this difference was significant (P < .05) between (Class I, II div1, 2) and non-significant between (class II div1, II div2).(Table 3)

Table 3: Comparisons of Rest Position Measurements Between the five Groups With in Males and Within Females.

At smile position, The Class II div2 subjects possessed higher values of upper lip length followed by Class II div1 then Class I, this difference was significant (P < .05) between (Class I, II div1, 2) and non-significant between (class II div1, II div2) (Table 5). The upper lip length was significantly higher in males compared with females in all groups at both rest and smile positions. (Table 2, 4)

Table 4: Descriptive Statistics and Significance of Mean Differences of Smile Measurements Between Males and Females.

Table 5: Comparisons of smile Position Measurements Between the five Groups Within Males and Within Females.

The Class I subjects – at rest position - possessed higher values of upper lip thickness followed by Class II div2 then Class II div1, this difference was significant (P < .05) between (Class I, II div1), and (class II div1, II div2) and non-significant between (class I, II div2) (Table 3).but at smile position, The Class I subjects possessed higher values of upper lip thickness followed by Class II div2 then Class II div1, this difference was not significant (P > .05) between all groups (Table 5).

There was no significant difference between males and females in all groups at both rest and smile positions. (Table 2, 4)

Change in upper lip length and thickness was significantly higher (P < .05) in class I compared with class II div1,2 ,and significantly higher (P < .05) in class II div2 compared with class II div1 (Table 7) .

Table 6: Descriptive Statistics and Significance of Mean Differences of changes of Measurements Between Males and Females.

Table 7: Comparison of the changes of Measurements Between the five Groups Within Males and Within Females.

Change in upper lip length was significantly higher (P < .05) in males compared with females in all groups, and Change in upper lip thickness was significantly higher (P < .05) in males compared with females in class II div1 (Table 6).

Discussion

The smile plays an important part in orthodontic diagnosis and treatment planning

The selection of the two frames used in this study was based on the reproducibility of the two expressions. Several studies12–14 have concluded that the rest position of the lips and posed smile are the reproducible expressions

An important aspect to consider when evaluating smile is the effect of malocclusion and gender on changes of upper lip length and thickness.

The study showed that upper lip length -at rest position- in class I was higher compared with other groups that come in accordance with Rakosi [24] who mentioned that Class II have shorter upper lip than that of Class I subjects.

The upper lip length - at smile position- in class II div1 was higher compared with class I, II div2 and this may due to lack of lips' elasticity in patients with class II of malocclusion, this result come in agreement with Islam et al [25] who mentioned that Both the upper and lower lips in the smile of patients in the Class II division 1 group were positioned downward.

Change in upper lip length in class II div1,2 was less than class I, and This results was consistent with the idea that protrusion of upper incisors in class II cases causes decreasing of the lips' elasticity and the muscles' ability to raise the upper lip. According to Islam et al ²⁵ the upward movement of the upper lip in Class II division 1 group was smaller in comparison with the class I group.

The study showed a significant difference between class II div1 and class II div2 in upper lip thickness and in change of upper lip thickness. This result comes in agreement with Tanic et al [26]

Who mentioned that the upper lip thickness was higher in class II div2 compared with class II div1.

On the basis of the results and back to Tables (2,4) for overall sample, Class I and IIdiv1,2, a significant sex difference had been seen for upper lip length with males possessed higher value at 0.05 level of probability. Al–T’aani [27] stated that Helman found that the upper lip length show significant difference between two sexes.

The vertical changes in upper lip length and thickness were significantly higher in males compared with females; these results come in agreement with Chetan et al [28] who mentioned that Males have more vertical movements whereas females have more horizontal movements during smile.

Conclusions

From present study we may conclude that:

• Upper lip length at rest and smile was higher in class I compared with other groups.

Changes in upper lip length and upper lip thickness were higher in class I.

• Upper lip in the smile of patients with Class II division 1 was positioned downward.

• The upward movement of the upper lip (changes in length and thickness) was smaller in Class II div 1compared with the other groups.

• Males have more vertical movements during smile.

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