ESTHETIC AND FUNCTIONAL PLANNING: clinical and digital resources

1. INTRODUCTION

The evolution of dentistry in recent decades has been rapid and remarkable. Every moment a new technique is described, mastered, and popularized. In the not-too-distant past, dental treatment consisted of seeking pain relief; often extracting the tooth was considered the most effective treatment. With the understanding of the importance of maintaining dentition for the correct functioning of the stomatognathic system and general health of the individual, dentistry focused on stopping the progression of caries, periodontal diseases, and occlusal disorders.

Contemporary dentistry seeks the preservation and restoration of teeth, periodontal tissues, and peri-implant tissues, with an appropriate relationship between the arches. The treatment philosophy should focus on the restoration of dentofacial function and esthetics to provide or restore the patient’s physical, mental, and social well-being, improving their quality of life.

Often dissociated, esthetics and function are integral parts of the same system. They must act synergistically to provide greater predictability and longevity to dental treatments.

Restorative materials have evolved to reproduce the characteristics of teeth accurately. However, periodontal and peri-implant tissues need a much higher dedication from the dental professional for their reconstruction; preservation is key to avoiding the need for future more invasive and sometimes less predictable procedures. Comprehensive understanding and reconstruction of the biological and functional characteristics of periodontal and peri-implant tissues is challenging and requires interaction between specialties to achieve the expected results. Nevertheless, it is necessary to be sensitive to achieve perfect harmonization of a smile.

In the field of esthetics, many subjective components are linked to ethnicity, belief, culture, age, and individuality. However, there are rules and parameters that, when observed, become a good starting point for the dentist to develop a clinical and digital plan of the rehabilitating treatments. Digital Smile Design (DSD) is a tool that facilitates the diagnosis of changes, planning, and interpersonal communication, guiding professionals to obtain more feasible results¹.

OBJECTIVES

At the end of the chapter the reader should be able to:

Understand the facial, dental, and periodontal aspects that guide esthetics in dentistry.
Identify the presence of esthetic changes and the need for multidisciplinary treatments to obtain the expected result.
Understand the importance of planning and communication with the patient and other professionals involved in treatment.

2. PLANNING BASED ON CLINICAL EVIDENCE

2.1. FACIAL ANALYSIS

When we refer to esthetics, we have to take into consideration that the concept of beauty is broad and generates diversity. Thus, we cannot generalize the criteria to be evaluated. However, there are essential elements that determine facial harmonies, such as planes, lines, and contours, as well as the eyes and smile. From these analyses, planning should take into account esthetic and functional parameters according to the patient’s needs.

The first analysis performed when observing the face is its outline (Figs 01A–C). The facial contour consists of the curves of the face and determines, for example, the support of the upper lip and its relationship with the lower lip and occlusal plane. Next, the field of vision usually shifts to two areas: the smile and the eyes. Other details, such as the nose and hair, are observed later.

01. A–G Facial contour: frontal view (A); mid-profile (B); and profile (C). Types of face: triangular (D); square (E); round (F); and oval (G).

The face can be classified into four different types: triangular, square, round, and oval (Figs 01D–G). The proportions between the various planes of the face (frontal and lateral) are important to define facial proportionality and esthetics². In addition, the face can also be divided into three thirds: upper, middle, and lower. A series of face planes were created to allow comparisons and provide guidance.

2.1.1. FACIAL PLANES

The facial planes consist of lines and contours and can be horizontal or vertical. The horizontal lines pass through different facial points, such as the pupils and the lip commissure (Fig 02). The parallelism between these lines generates harmony.

02. Horizontal lines and facial planes: interpupillary line (a); intercommissural line (b); and incisal plane (c).

The interpupillary line is a horizontal line drawn over the center of the eyes in the pupil. It should be parallel to the line of the labial commissures, the incisal plane, and the gingival line. This line makes it possible to evaluate the direction of the incisal line and gingival contour of the maxilla²^,³. A slight discrepancy between the interpupillary and the intercommissural line is not esthetically relevant. However, if it is a significant discrepancy, it should be corrected.

The incisal plane must follow the contour of the lower lip³; its relationship to the gingival contour of the upper teeth can diagnose mild, moderate, or severe inclination of the maxilla. Planning procedures to correct a gummy smile require evaluation between the planes/facial lines, the relationship between the middle and lower third of the face, and the length and mobility of the upper lip. This evaluation aims to avoid misdiagnosis and, consequently, treatment failure. It usually requires multidisciplinary interventions such as orthodontics, oral and maxillofacial surgery, periodontics, and even esthetic medicine/dentistry with botulinum toxin application or hyaluronic acid fillers.

The most important vertical lines to evaluate facial esthetics are the midline and the interincisal line (Fig 03). The first passes through the nasion and philtrum, and the second passes between the central incisors. There are reference points for drawing the facial midline (such as the glabella, tip of the nose, upper lip philtrum, and chin), which divides the face into two parts. This line helps in the evaluation, location, and orientation of the interincisal line; changes in it may compromise the balance of other facial structures, thus impairing esthetics⁴^–⁶. Coincidence of the facial midline and interincisal line occurs in 70.4% of the population⁷. Esthetically, the midline serves to assess the location and orientation of the interincisal line. The parallelism between them is more critical than their distance.

03. Vertical lines of the face: midline (a) and interincisal line (b).

The occlusal plane is determined by the incisal edges of the anterior teeth and the occlusal surfaces of the posterior teeth. The outline of the lips serves as a guide to determine the length and position of the teeth. Movement of the upper lip determines the smile line of the patient. The range of motion and amount of dental and gingival exposure will depend on several factors, such as the degree of muscle contraction, periodontal tissue level, skeletal conditions, and tooth shape and wear.

2.1.2. LIPS AND SMILE LINE

In general, with the upper lip at rest position, exposure of the central incisors ranges from 1 mm to 3 mm. Women usually expose more teeth than men; with aging the incisal edges of the maxillary central incisors become less visible because the natural process of tooth wear occurs, accompanied by decreased muscle tone and amplitude.

The lips define and structure the smile, besides delimiting the so-called esthetic zone. The lips can be broad, medium, or narrow in form⁷. They can also be classified according to gingival exposure into high, intermediate, or low smile line (Figs 04A–C). The high smile line reveals the full length of the maxillary anterior teeth, as well as a band of gingival tissue. If this gingival exposure is greater than 3 mm, the patient has a gummy smile. The intermediate smile line shows from 75% to 100% of the length of the maxillary anterior teeth and may show the gingival papillae. A low smile line exposes less than 75% of the maxillary anterior teeth, without exposure of gingival tissue. From an esthetic point of view, the intermediate smile line is the most pleasant⁷^–¹².

04. A–C Smile lines: low (A), exposure of less than 75% of the maxillary anterior teeth, no exposure of the gingival tissues; intermediate (B), exposure of 75–100% of the maxillary anterior teeth, may expose the papilla; high (C), exposure of the entire length of the maxillary anterior teeth, exposure of a band of gingival tissue.

A pleasant smile should expose the maxillary teeth and a small band of gingiva and papillae (Fig 05). Over time, muscle tone decreases and the gingival exposure tends to decrease, even leading to no exposure of the maxillary incisor crown in older patients, and that may become a complaint.

05. Exposure of maxillary central incisors, lateral incisors, canines, premolars and gingival tissue resulting in a pleasant smile.

The relationship between the incisal edge of the maxillary teeth and the lower lip usually occurs in three ways (Figs 06A–C). The first and most pleasant occurs when the incisal edges of the maxillary teeth follow the curvature of the lower lip when the patient smiles. The second occurs when the incisal edges are straight, giving the patient a straight smile. The third, when the incisal edges are reversed in relation to the lower lip, gives the patient an inverted or ‘sad’ smile.

06. A–C Relationship between the incisal edge of the maxillary anterior teeth and lower lip: the incisal edges follow the curvature of the lower lip (A); the incisal edges are aligned with the lower lip (B); the incisal edges are inverted in relation to the lower lip (C).

2.2. DENTAL ANALYSIS

2.2.1. SHAPE

The definition of a pleasant smile is that the maxillary central incisors are deemed the focal teeth due to their location in the dental arch, being the most dominant and visible. Thus, in esthetic rehabilitation, they should be the reference to determine the characteristics of the other teeth. The shapes of the maxillary central incisors are commonly classified as triangular, squared, and oval¹³^,¹⁴ (Figs 07A–C). The triangular shape of the maxillary central incisor is the most frequent, followed by the square and, less frequently, oval shape. For the complete assimilation of dental morphology, it is essential to have a detailed observation of all surfaces in different views. The incisal view allows the observation of morphological changes that occur from the facial to the proximal surfaces; lateral visualization allows the observation of the cervical, mid, and incisal planes (Figs 07D, E).

07. A–E Incisor shapes: triangular (A), squared (B), and oval (C). Incisal view (D) – allows the observation of morphological changes that occur from the facial to the proximal surfaces. Proximal view (E) – allows the observation of the cervical, mid, and incisal planes.

The flat area on the facial surface of the central incisor is primarily responsible for the reflection of light and, consequently, for the appearance of the teeth. It may vary in shape, size, and location (Figs 08A–D). The concept of proportionality suggests that the upper central incisors have a height/width ratio of 10:8 or 80% (Figs 09A–C). However, when this ratio is slightly changed (Figs 10A–D) in the order of 10:7.5 (75%) or 10:8.5 (85%), an esthetically pleasing arrangement remains¹³^,¹⁴.

08. A–D Light reflection area on the anterior teeth (A). These characteristics should be reproduced in esthetic restorations (B). The flat area is principally responsible for light and tooth appearance; it is the area between the facial line angles (red lines) (C). Between the proximal surfaces and line angles is an area called the proximal transition (D). Ceramic crown done during the Clinical Prosthesis Course at FAESA with supervision of Prof George Alves (B–D).

09. A–C Concept of proportionality: the maxillary central incisor should have a height to width ratio of 10:8 or 80%.

10. A–D Alteration in the dental proportion and asymmetry between homologous teeth (A). Surgical procedure performed to intentionally keep the discrepancy in the gingival contour (B). Appearance after tissue healing (C) and immediately after restorative therapy (D). Surgical procedure: Dr Fausto Frizzera; restorative procedure: Dr Marco Masioli.

2.2.2. TEXTURE (MACRO- AND MICROMORPHOLOGY)

Surface texture is a significant factor in the appearance of teeth because it creates different forms of light reflection (Figs 11A, B). Two types of texture are considered: (1) horizontal, which consists of horizontal perikymata that tend to disappear with wear of the facial surface of the teeth; (2) vertical, consisting mainly of developmental lobes and grooves on the facial surface. The incisal edge usually has three lobes (mesial, central, and distal) and two interposed grooves (mesial and distal) ¹⁴.

11. A, B Surface texture of teeth in a young (A) and an elderly (B) patient. Textures tends to disappear with age and wear of the buccal surface. Images provided by Dr Matheus Bandéca.

The texture of teeth changes over time because of enamel wear due to physiological activity. Texture can be associated with age. In young patients, teeth have more surface texture; in middle-aged patients, surface characteristics are less pronounced and usually more polished; and in elderly patients, surface characteristics are slight. Also, a higher degree of polishing usually occurs due to toothbrush abrasion, eating, and lip action¹⁴.

Although there is a correlation between age and surface shine, this may vary from person to person, being influenced by physiological factors, degree of tooth mineralization, eating habits, and oral hygiene.

It is important not to confuse texture with surface shine. Some teeth may present little texture and high shine, just as other teeth may have heavy texture and high shine¹³.

2.2.3. INTERDENTAL RELATIONSHIP

The interdental relationship is as essential as the individual assessment of each tooth. Therefore, contact between the central incisors, symmetry, position of the incisal edges, width, contact points, and embrasures should be taken into consideration for the treatment plan of esthetic rehabilitations.

After the individual evaluation, the relationship between the central incisors and the other teeth, and with the face, should be verified. Ideally, the contact between the maxillary central incisors should be linear, straight, and transverse to the horizontal plane and coincident with the midline of the face (Figs 12A–C).However, even in cases where it is not possible to match the facial midline with the dental midline, contact between the maxillary central incisors should always be parallel to the facial midline.

12. A–E Types of contact between the maxillary central incisors: aligned to the horizontal plane (A); not aligned to the horizontal plane (B); absence of contact between the maxillary central incisors with presence of a diastema (C). Symmetry (D) and asymmetry (E) between homologous teeth.

Anterior homologous teeth should have symmetry in a frontal view (Figs 12D, E). The closer to the midline, the more desirable this symmetry. Thus, the maxillary central incisors should be as symmetrical as possible. Symmetry in the other teeth is desirable; however this need decreases as the teeth move away from the midline¹³.

ROOT COVERAGE PROCEDURE IN A SINGLE AND DEEP RECESSION USING STRAUMANN MUCODERM^®

In a pleasant smile, the incisal edge of the maxillary lateral incisors is, on average, 1 mm more apically than the edge of the central incisors. The incisal edges of the canines are in the same plane or slightly more apical than the incisal edges of the central incisors.

The interdental contact of the maxillary anterior teeth descends from the canine toward the central incisors (Fig 13). The contact between the canine and lateral incisor is more apical than the contact between the lateral and central incisors. The contact between the central incisors is more incisal than the contact between the lateral and central incisors. These contact points are usually tight unless there is a mesiodistal discrepancy of the crown, with the presence of diastemata between the teeth¹⁵^,¹⁶. The position of the interdental contact is related to the position of the tooth in the arch and its morphology¹⁷. In a buccal or lingual view, it is possible to observe the gingival and incisal embrasures. The gingival embrasure, which houses the interdental papilla, is delimited by the contact point, adjacent teeth, and bone crest. The incisal/occlusal embrasure is delimited by the contact point, incisal angles, and by an imaginary line from the end of each incisal angle.

13. Contacts between anterior teeth (lateral view).

The analysis of the incisal embrasure is a crucial Factor for the planning of esthetic rehabilitation of anterior teeth. The pattern of the shape produced by the incisal embrasures and separations between the maxillary anterior teeth with the darker background of the mouth helps to define a pleasant smile. The spaces between the embrasures follow a pattern that begins between the central incisors and progresses distally. Incisal embrasures increase in size and volume as they move away from the midline¹⁸ (Figs 14 and 15A–F).

14. The incisal embrasure between the central and lateral incisors should be bigger than the incisal embrasure between the central incisors. The same aspect as the incisal embrasure between the canine and lateral incisor should be bigger than the incisal embrasure between the lateral and central incisors.

15. A–F The shape of the embrasures and the interproximal contact should be considered because they influence the smile esthetics (A, B). Diagnostic wax-up of the patient with the appropriate shape of incisal embrasures can be used to visualize a greater harmony between the anterior teeth (C). The result obtained with the wax-up allows performing a mock-up, where a putty matrix is made from the waxed model. Then, bis-acrylic resin is dispensed into the matrix (D) and then positioned into the patient’s mouth (E). After the resin cures, the matrix and excess are removed. The dentist and patient can evaluate the proposed changes in the of anterior teeth (F). Restorative procedure: Dr Mateus Tonetto.

2.2.4. DENTAL AXIS

The inclinations (facial-lingual positioning) and angles (mesiodistal positioning) of the anterior teeth correspond to the dental axis. The anterior and posterior teeth present a positive angulation of the buccal axis of the clinical crown, that is, the occlusal portion of the buccal axis is positioned more mesially to the gingival portion. These angles should increase from the maxillary central incisors toward the maxillary canines. The opposite happens with the inclinations, which decrease from the maxillary central incisors toward the canines¹⁵^,¹⁶ (Figs 16A, B and 17A, B). The long axis or direction of the anterior teeth in an esthetic smile follows a progression as it moves away from the midline. When the maxillary anterior teeth are angled mesially, the overall esthetic impact is a harmonious relationship with the lower lip curvature¹⁹.

16. A, B Adequate (A) and inadequate (B) angulation; note the right maxillary lateral incisor.

17. A, B Adequate (A) and inadequate (B) inclination of the maxillary anterior teeth.

The inclination of the maxillary incisors can be assessed by analyzing the buccal surface of the existing maxillary central incisors relative to the patient’s maxillary posterior occlusal plane. The buccal surface of the maxillary central incisors should be perpendicular to the upper occlusal plane (Figs 18A–C). This ratio allows maximum direct light reflection from the buccal surface of the maxillary central incisors, which improves their esthetic appearance²⁰. If the teeth are reclined or inclined, esthetics may be impaired and require correction.

18. A–C Maxillary central incisor with the facial surface perpendicular to the maxillary occlusal plane (A); note the central incisor dominance (B) and adequate light reflection (C).

2.2.5. DOMINANCE AND REGRESSIVE APPEARANCE PROPORTION

Dominance refers to the fact that the maxillary central incisors should be the dominant teeth and most visible when smiling. The curvature of the dental arch shows less of the teeth in the distal position. The less a tooth is visible, the less its importance on the smile. The maxillary central incisors, because of their position in the center of the arch, should appear as the widest and whiter ones and, consequently, are the predominant teeth in the frontal aspect (Fig 19A).