Maxillary Central Incisors Relative to Upper Lip

When beginning with esthetics, the first step is an appraisal of the position of the maxillary central incisors relative to the upper lip ( Fig. 21-1 ). This assessment is made with the patient’s upper lip at rest. Using a millimeter ruler or periodontal probe, the clinician determines the position of the incisal edge of the maxillary central incisor relative to the upper lip. The position of the maxillary central incisor can either be acceptable or unacceptable. An acceptable amount of incisal edge display at rest depends on the patient’s age. Previous studies have shown that with advancing age, the amount of incisal display decreases proportionately. For example, in a 30-year-old patient, 3 mm of incisal display at rest is appropriate, whereas in a 60-year-old patient, the incisal display could be 1 mm or less. The change in incisal display with time probably relates to the resiliency and tone of the upper lip, which tends to decrease with advancing age.

This 35-year-old woman was missing her maxillary incisors. The incisal edge of her maxillary prosthesis was 2 mm from her upper lip at rest (A), and the gingival margins of the prosthetic teeth were at the level of the upper lip when smiling (B). She had an Angle Class III molar relationship (C) and maxillary retrognathism (D). She had severe wear of the posterior teeth, and the level of the maxillary posterior teeth was positioned too far coronally (B and C) . Before Le Fort surgery, her entire dentition was provisionalized. The maxillary posterior interocclusal space was opened (E) to provide space for restorations (F) . Orthodontic bracketing facilitated the finishing of the occlusion (G). Using the maxillary incisor position and the posterior occlusal plane as guides not only improved the occlusion (H), but also resulted in ideal smile esthetics after restoration (I).

If the incisal edge display is inadequate ( Fig. 21-2 ), a primary objective of interdisciplinary treatment may be to lengthen the maxillary incisal edges. This objective can be accomplished with restorative dentistry, orthodontic extrusion, or orthognathic surgery ( Fig. 21-2 ). Choosing the correct procedure will depend on the patient’s facial proportions, existing crown length, and opposing occlusion. If the incisal edge display is excessive, an objective of treatment may be to move the maxillary incisors apically by equilibration, restoration, orthodontics, or orthognathic surgery. The treatment decision will depend on the patient’s existing anterior occlusion and the facial proportions.

This 61-year-old woman’s chief esthetic complaint was that she did not show her teeth when speaking and smiling. She had a short lower facial height (A), and the maxillary incisal edges of her anterior bridge were 2 mm above the level of the upper lip at rest (B). As a result, she showed very little of her maxillary incisors on smiling (C). Both maxillary and mandibular osteotomies were used to rotate her maxilla and mandible downward in the anterior aspect to lengthen her lower facial height (D and E) and produce a much more esthetic smile (F). Her posterior facial height was not lengthened in order to maintain her vertical dimension of occlusion.

Maxillary Dental Midline

The second aspect of esthetic tooth positioning to be evaluated is the maxillary dental midline. Recent studies have shown that laypeople do not notice midline deviations of up to 3 or 4 mm if the long axes of the teeth are parallel with the long axis of the face. Therefore the most important relationship to evaluate may be the mediolateral inclination of the maxillary central incisors. If the incisors are inclined by 2 mm to the right or left ( Fig. 21-3 ), laypeople regard this discrepancy as “unesthetic.” A canted midline can be corrected with orthodontics or restorative dentistry. Usually the decision depends on whether the maxillary incisors will require restoration.

This adult woman was dissatisfied with her smile. Her maxillary central incisors were inclined to her left (A), and the incisal edges had been abraded, producing a flat incisal edge relationship (B). To change the tooth inclination, the maxillary brackets were placed at an angle to the worn incisal edges, but perpendicular to the long axis of the roots (C). As the roots uprighted, the worn incisal edges became more apparent (D). Her general dentist added composite to the incisal edges during orthodontics (E) to restore the teeth to their normal size and proportion (F).

Maxillary Incisor Inclination and Posterior Occlusal Plane

Once the correct incisal edge position and midline relationship of the maxillary incisors has been established, the next step is to evaluate the labiolingual inclination of the maxillary anterior teeth. Are they acceptable, proclined, or retroclined? When orthodontists evaluate labiolingual inclination, they rely on cephalometric radiographs to determine tooth inclination. However, general dentists do not use cephalograms. Another method of assessing the inclination of the maxillary anterior teeth is to evaluate the labial surface of the existing maxillary central incisors relative to the patient’s maxillary posterior occlusal plane. Generally, the labial surface of the maxillary central incisors should be perpendicular to the occlusal plane ( Fig. 21-4 ). This relationship permits maximum direct light reflection from the labial surface of the maxillary central incisors, which enhances their esthetic appearance. If teeth are retroclined ( Fig. 21-5 ) or proclined ( Fig. 21-6 ), correction may require either orthodontics or extensive restorative dentistry and possibly endodontics to establish a more ideal labiolingual inclination.

The esthetic position of the maxillary incisal edges in this 52-year-old man was ideal relative to the upper lip (A). He had a significant malocclusion with anterior crossbite (B) and an Angle Class III posterior relationship in centric occlusion (C). With his condyles centered in the glenoid fossae, his maxillary and mandibular incisors were in an end-to-end anteroposterior relationship. His maxillary arch and the position of the maxillary posterior occlusal plane were ideal (D). His primary problem was the proclination of the mandibular incisors relative to the normally positioned maxillary incisors (E). His treatment involved nonsurgical orthodontics to retract the mandibular incisors and correct the crossbite (F). By maintaining the ideal relationship of the maxillary incisors during orthodontics (G), not only does he have good occlusion (H), but his incisal edge position and smile esthetics are ideal (I).

This 54-year-old man had a deep anterior overbite (A) and retroclined maxillary incisors (B). His occlusion was Angle Class I, but skeletally he had bimaxillary retrusion of both dental arches (C). The position of the maxillary incisors was at the level of the upper lip (C), which is normal for his age. The overbite problem was caused by overeruption of the mandibular incisors, which had also been abraded significantly (D). Initially these teeth were built up with composite (E) so that brackets could be placed on these teeth (F) to intrude them into the alveolus (G). This permitted the general dentist to restore these teeth (H) after the deep overbite had been corrected (I).

This 52-year-old woman had short maxillary incisors that were positioned in an end-to-end relationship with the mandibular incisors (A). As a result, these teeth had worn significantly (B). Her general dentist could not restore these teeth because of her lack of overjet and because her maxillary incisal edge was at the level of the upper lip (C). Normal overjet for her age is 1 to 2 mm below the level of the upper lip. A diagnostic wax-up (D) showed that one lower incisor could be extracted to create the necessary overjet. To provide restorative space and the correct tooth proportions, the maxillary incisors were intruded (E and F) during orthodontics. This space allowed the dentist to restore length and proper proportion to the maxillary anterior teeth (G), but still create the proper overbite relationship (H) and improve her upper lip–to–incisal edge relationship after restorative treatment (I).

The next step is to evaluate the maxillary posterior occlusal plane relative to the ideal location of the maxillary incisal edge. The maxillary incisal edge will be level with the posterior occlusal plane (see Fig. 21-4 ), coronal to the posterior occlusal plane (see Fig. 21-1 ), or apical to the posterior occlusal plane (see Fig. 21-2 ). Correcting the posterior occlusal plane position will require orthognathic surgery (see Figs. 21-1 and 21-2 ) and/or restorative dentistry. The amount of tooth abrasion, the patient’s vertical facial proportions, and the position of the alveolar bone will help to determine the correct solution of posterior occlusal plane discrepancies.

After the position of the maxillary central incisal edges have been determined, the incisal edges of the maxillary lateral incisors and canines, as well as the buccal cusps of the maxillary premolars and molars, can be established ( Fig. 21-7 ; see Fig. 21-4 ). The levels of these teeth generally are determined by their esthetic relationship to the lower lip when the patient smiles. If the patient has an asymmetric lower lip, it may be more prudent to use the interpupillary line as a guide in establishing the posterior occlusal plane.

This 61-year-old man was dissatisfied with the esthetic appearance of his teeth. He had an Angle Class II malocclusion with a deep anterior overbite (A) and mandibular retrusion (B). His maxillary incisal edges were ideally positioned to the upper lip at rest for his age (B), and the posterior occlusal plane was at the appropriate level relative to the anterior teeth (C). The deep anterior overbite was caused by the mandibular incisor position (D). He had significant wear of the posterior teeth (E), which required restoration before orthodontics to place appliances on the teeth. A diagnostic wax-up (F) provided the guide for the restorative dentist before treatment and permitted ideal restoration of these teeth (G) after orthodontics and mandibular advancement to reposition the mandibular incisors relative to the maxillary arch. This change produced an ideal overbite and overjet (H) with excellent smile esthetics (I).

Gingival Levels

The next step in the process of determining the esthetic relationship of the maxillary anterior teeth is to establish the gingival levels. The current gingival levels should be assessed relative to the projected incisal edge position. The key to determining the correct gingival levels is to determine the desired tooth size relative to the projected incisal edge position ( Fig. 21-8 ). Remember, the incisal edge is not positioned to create the correct tooth size relative to the gingival margin levels. Using the gingiva as a reference to position the incisal edges is risky, because gingiva can move with eruption or recession. Thus the ideal gingival levels are determined by establishing the correct width/length ratio of the maxillary anterior teeth, the desired amount of gingival display, and symmetry between right and left sides of the maxillary dental arch.

This 62-year-old physician was dissatisfied with his smile esthetics and showed no maxillary incisal edge at rest (A) because of significant wear of the maxillary incisors (B). The tooth wear resulted from the end-to-end relationship of the maxillary and mandibular incisors (B). These teeth needed to be restored (C and D) , but the mandibular incisors were in the way. A diagnostic wax-up (E) showed that extraction of one mandibular incisor would produce sufficient overjet (F), so that the maxillary incisors could be lengthened (G) and not only produce good anterior occlusion (H), but also improve this patient’s smile esthetics (I).

If the existing gingival levels will produce a tooth that is too short relative to the projected incisal edge position, the gingival margins must be moved apically ( Fig. 21-9 ). This adjustment can be accomplished with gingival or osseous surgery ( Fig. 21-9 ), orthodontic intrusion, or orthodontic intrusion and restoration (see Figs. 21-6 and 21-9 ). The key factors that determine the most appropriate method of correction are the sulcus depth, location of the cementoenamel junction relative to the bone level, amount of existing tooth structure, root/crown ratio, and shape of the root. In some situations, surgical crown lengthening of the maxillary incisors (see Fig. 21-9 ) is more appropriate to establish the correct gingival levels. In other situations, orthodontic intrusion (see Fig. 21-6 ) and restoration of the incisal edge are more appropriate.

This 35-year-old woman was uncomfortable with the uneven lengths of her maxillary anterior teeth (A). To determine the solution, a periodontal probe was used to push through the soft tissue attachment down to bone (sounding) over the right lateral (B) and central (C) incisors. This showed that the cementoenamel junctions were at the level of the bone (altered active eruption). This relationship was confirmed when a gingival flap was elevated (D). The bone was moved 2 mm from the cementoenamel junction (E). After healing there was still a discrepancy between the right and left incisor crown lengths (F). This difference was caused by uneven wear of the incisal edges and was corrected with intrusion of the right maxillary anterior teeth (G) to permit restoration of the incisal edges (H), which completed the correction of her uneven maxillary anterior tooth length (I).

The next step in the process of establishing the correct esthetic position of the maxillary anterior teeth is to assess the papillary levels relative to the overall crown length of the maxillary central incisors. Research has shown that the average ratio is about 50% contact and 50% papilla. If the contact is significantly shorter than the papilla, it usually indicates moderate to significant incisor abrasion, which tends to shorten the crowns and therefore shortens the contact between the central incisors. If the contact is significantly longer than the papilla, the gingival contour or scallop over the central incisors might be flat, which could be caused by altered passive or altered active eruption of the teeth. Gingival or osseous surgery or orthodontic intrusion or extrusion ( Fig. 21-10 ) may be necessary to correct the level of the papillae between the maxillary anterior teeth.

This 42-year-old woman was dissatisfied with the esthetic appearance of her maxillary anterior teeth. She was missing her maxillary left lateral incisor (A), and the three remaining incisors had been restored with crowns. These teeth had short roots and had been treated endodontically (B).

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