Aesthetic evaluation of profile incisor inclination

European Journal of Orthodontics 33 (2011) 228–235 doi:10.1093/ejo/cjq059 Advance Access Publication 17 August 2010 © The Author 2010. Published by Oxford University Press on behalf of the European Orthodontic Society. All rights reserved. For permissions, please email: Aesthetic evaluation of profile incisor inclination Nathalie Ghaleb, Joseph Bouserhal and Nayla Bassil-Nassif Department of Orthodontics, Faculty of Dental Medicine, Medical Sciences Campus, Saint-Joseph University, Beirut, Lebanon Correspondence to: Dr Nayla Bassil-Nassif, Department of Orthodontics, Faculty of Dental Medicine, Medical Sciences Campus, Saint-Joseph University, Damas Street, PO Box 11-5076, Riad El Solh, Beirut 11072180, Lebanon. E-mail: Introduction The smile as an important feature in daily life should be of interest to orthodontists. It is an essential asset for psychosocial adaptation: people with beautiful teeth and smiles are considered more attractive, more intelligent, and more popular with the opposite gender (Shaw et al., 1985; Beall, 2007). There are a number of reports in the orthodontic literature concerning the frontal view of the smile, whereas the lateral view is still unexplored. Sarver and Ackerman (2003) focused their treatment planning on analysis of the smile in all dimensions: in the profile view, the incisor inclination is of importance. Kerns et al. (1997) found that profile and frontal views of the same smile were not similarly rated for aesthetic appeal: the profile views were rated higher than the frontal views of the same smile. These findings suggest that orthodontists should consider both frontal and lateral views when planning and assessing orthodontic treatment (Sarver and Proffit, 2005). From an aesthetic viewpoint, Schlosser et al. (2005) found it preferable to either leave a normally protrusive maxillary dentition in its original position or advance rather than retract the maxillary anterior teeth. On the other hand, among the factors that negatively influence the smile and give the face an ‘old’ appearance, is lingual inclination of the upper incisors as a result of loss of torque (Lamarque, 1999). Several cephalometric standards have been introduced to assess the attractiveness of the face; yet it has been shown that good facial harmony can exist within a wide range of cephalometric values (Peck and Peck, 1970; Moss et al., 1995), and even a well-treated orthodontic case in which the final records meet every criterion of the American Board of Orthodontics for successful treatment may not produce an aesthetic smile (Schabel et al., 2008). Beside, professional opinions regarding evaluation of smile aesthetics may not coincide with the perceptions and expectations of laypeople (Johnston et al., 1999; Kokich et al., 1999; Thomas et al., 2003; Roden-Johnson et al., 2005; Parekh et al., 2006). Ideally, the buccal face of the maxillary incisors should be vertical and parallel to the frontal plane of the face (Philippe, 1987). The purposes of this study were 3-fold: (1) to evaluate the impact of maxillary incisor inclination on the aesthetics of the profile view of a smile, (2) to determine the most aesthetic inclination in the profile view of a smile and to correlate it with facial features, and (3) to determine if dentists, orthodontists, and laypeople appreciate differently incisor inclination in smile aesthetics. Subject and methods Subject An undergraduate female dental student (age 22 years) was chosen from the Faculty of Dental Medicine at Saint-Joseph The objectives of this study were to evaluate (1) the impact of maxillary incisor inclination on the aesthetics of the profile view of a smile, (2) to determine the most aesthetic inclination in the profile view of a smile and correlate it with facial features, and (3) to determine if dentists, orthodontists, and laypeople appreciate differently incisor inclination in smile aesthetics. A smiling profile photograph of a female subject (22 years of age) who fulfilled the criteria of soft tissue normative values and a balanced smile was obtained. The photograph was manipulated to simulate six lingual and labial inclinations at 5 degree increments to a maximum of 15 degrees. The seven photographs were randomly distributed in a binder to three groups of raters (30 dentists, 30 orthodontists, and 30 laypeople) who scored the attractiveness of the photographic variations using a visual analogue scale. Comparison of the mean scores was carried out by repeated analysis of variance, univariate tests, and multiple Bonferroni comparisons. The results showed a statistically significant interaction between the rater’s profession and the aesthetic preference of incisor inclination (P = 0.013). The profile smile corresponding to an increase of 5 degrees in a labial direction had the highest score among all professions and among male and female raters. Orthodontists preferred labial crown torque; dentists and laypeople did not appreciate excessive incisor inclination in either the lingual or the labial directions. The most preferred smile matched with a maxillary incisor inclined 93 degrees to the horizontal line and +7 degrees to the lower facial third. SUMMARY 229 EVALUATION OF INCISOR INCLINATION Image alteration The smiling photograph was altered using a commercially available image editing software program (Adobe Photoshop CS, version 8.0; Adobe Systems Inc., San Jose, California, USA). One parameter was changed: the inclination of the upper incisors. The crowns of the central and lateral incisors were separately cut by this program. Each tooth was considered as an object with a centre of rotation (CRO) at the incisal edge. For the central incisor, the CRO was the incisal tip superimposed from the tracing of lateral Table 1 Values of initial maxillary incisor inclination of the subject compared with the values of Bumann et al., (1994). Incisor inclination Norm Subject I/SN (°) I/FH (°) I/PBS (°) I/A–Pog (°) I/NA (°) 102–105 111 ± 5 70 ± 5 26 22 ± 4 107 112 64 28 24 Table 2 Values of facial profile of the subject according to Arnett and Bergman (1993) and Fitzgerald et al. (1992). SD, standard deviation. Measurement Norm (SD) Subject Facial angle (°) Angle of convexity (°) ANB (°) SGn/FH (°º) SGn/Sn (°) FMA (°) Naso-labial angle (°) Profile angle (G′–Sn–Pg′) (°) Nasal projection (Sn–NT; mm) Upper lip/Sn–Pg′ (mm) Lower lip/Sn–Pg′ (mm) 87.85 (1.71) 0.65 (5.30) 2.18 (1.97) 57.52 (3.32) 66.32 (4.14) 20.54 (5.59) 114.08 (9.58) 165–175 16–20 +3.5 (1.4) +2.2 (±1.6) 87 4.5 2 58 61 24 113 167 17 +2 +1.5 cephalogram. For the lateral incisor, the CRO was chosen as the midpoint of the mesio-distal width of the incisal edge for the basis of symmetry. Horizontal tangents to the incisal edges of both maxillary incisors were traced to preserve vertical positions. The vertical tangent medial to the canine was the distal limit for sagittal repositioning of the lateral incisor, followed by the central inciso (...truncated)