**3. Components of the smile**

Medical practitioners may describe the smile as a status of the orofacial complex where muscles of the facial expression are harmonized. Muscles such as the frontalis, orbicularis oculi, orbicularis oris, zygomaticus major, risorius, platysma and depressor anguli oris are working in harmony to provide various facial expressions [3]. A common mistake is considering the oral complex as the only item composing the smile, though midfacial muscles such as the zygomaticus major and minor originate from the midface and hence affect the general character and smile. The muscles around the orbital complex are critical to facial expression as a reflection of youth and beauty when lacking heavy wrinkles [4]. Hence, the components of a smile can be evaluated according to different factors namely:


**Anatomical components**: The smile is composed of the upper lip, the maxillary bone, the maxillary teeth, and the gingival tissue envelope [5, 6].

**The upper lip** represents the area from the point subnasal to the upper lip stomion which varies between 18-22mm (Figure 1) [5]. The width of the lip is composed of mucosa, orbicularis muscle, fat, and skin, which varies between individuals in height and thickness. However, the extension of muscles into the surrounding structures such as the nose can affect the nasal shape when smiling. A lot of patients have their nasal tips turned downward when they smile, or have the alae of the nose extremely widen or flare, which can be unsightly [7].

bit more challenging if the patient is known to have a repaired cleft lip, previous lip trauma,

Other situations where patients visit clinics with a clear demand of what can make them feel happier, such as piercing or cheek dimples can be linked to the patient's own personal satisfaction. On other occasions, clients may be confused, and complain of resenting their profile pictures without clear understanding of their problem needing correction. It is well known, that in the current era of cosmetic revolution and subspecialty care and techniques, continuous evaluation and research regarding the principles of "smile management" are evolving. Therefore, practitioners should keep in mind that proper training in the field, careful case selection, and inter-specialty communication can provide the best results with the least

A smile is expressed as a form of one's feature reflecting pleasure and happiness usually shown by upturning the corners of the mouth [1]. It can be presented in a static state mostly during taking pictures, or can be as part of a dynamic state during articulation. However, the personal self-evaluation can be more complicated due to the era of advanced social networking. Hence,

Medical practitioners may describe the smile as a status of the orofacial complex where muscles of the facial expression are harmonized. Muscles such as the frontalis, orbicularis oculi, orbicularis oris, zygomaticus major, risorius, platysma and depressor anguli oris are working in harmony to provide various facial expressions [3]. A common mistake is considering the oral complex as the only item composing the smile, though midfacial muscles such as the zygomaticus major and minor originate from the midface and hence affect the general character and smile. The muscles around the orbital complex are critical to facial expression as a reflection of youth and beauty when lacking heavy wrinkles [4]. Hence, the components

**Anatomical components**: The smile is composed of the upper lip, the maxillary bone, the

it is not surprising that critics of smiles and perfectionism are increasing [2].

of a smile can be evaluated according to different factors namely:

maxillary teeth, and the gingival tissue envelope [5, 6].

or secondary facial deformity [2].

192 A Textbook of Advanced Oral and Maxillofacial Surgery Volume 2

possible complications.

**2. Definition of smile**

**3. Components of the smile**

**a.** Anatomical components

**b.** Smile lip line

**c.** Dental smile lines

**d.** Facial character

**Figure 1.** Lateral cephalometric analysis showing the lip form and position. Nasolabial angle (Cm-Sn-Ls), mentolabial sulcus depth (Si to Li-Pog'), maxillary incisor exposure (Stms-1). Upper lip protrusion (Ls to Sn-Pog'), lower lip protru‐ sion (Li to Sn-Pog'), vertical lip-chin ratio (Sn-Stms/Stmi-Me'), interlabial gap (Stms- Stmi). [5]

**The maxillary bone and teeth** constitute the second and third parts. The maxilla extends from the subnasal down to the alveolar component housing the teeth. The width of the smile is correlated with the width of the maxilla, as transverse deficiency will lead to narrow V-shaped maxillary arch and a wide buccal corridor which is not pleasant, and vice versa. While in the vertical dimension, maxillary excessive growth will lead to over expression of gum and teeth during smiling or a gummy smile; while extreme maxillary bone vertical deficiency will lead to absence of teeth and gingival show at static or dynamic orofacial states reflecting an unpleasant aging character. Evaluation of the maxillomandibular complex is accomplished via clinical and radiographic modalities clarified later in this chapter [5].

**The gingival architecture** is the fourth factor. Gingival recession exposing more tooth structure and roots is as unpleasant as gingival overgrowth -leading to short clinical crowns. As the crown shape, including height, width, curvature, and alignment have an important role [3], once the dental smile arc line is upturned posteriorly it will reflect better cosmetic results compared to a flat or downturned arc line. [6] Hence, a defect in a single component or inappropriate harmony between each can provide patients with unpleasant smiles. Therefore it is very critical to diagnose the major contributor to the disharmony and formulate the best management plan accordingly.

**Smile lip line:** This is divided into high, moderate or low horizontal smile lines according to the magnitude of upper lip coverage of the maxillary anterior teeth when static and smiling. [6] A high lip line refers to a smile showing the maxillary anterior teeth and part of the gingival tissue, while a low lip line shows 0-2mm of the anterior teeth. A high smile line is considered to be a challenging factor when rehabilitating the anterior maxilla. As any defect in the crown or gingival tissue can be disclosed; unlike patients with moderate or low smile lines (Figure 2).

**Dental smile line** (smile arc): This pertains to maxillary teeth from the incisor going along to the 1st molar and describes the best cosmetic relation as evaluated by an expert restorative dentist.[4,6] A smooth transition of dental lines, alignment, shape, and color can provide pleasant smiles. The dental smile line is an imaginary line drawn from the incisal edges of the maxillary anterior teeth and following the upper lip inferior border curvature. It can be flat, upturned, or downturned. These lines do have more fine details that a specialist restorative dentist can analyze. [3, 4, 6] The fine dental line details are beyond the scope of the chapter.
