Table of Contents

Roundtable
View Point
Continuing Education
Esthetics
Implants
Restorative

Inside Dentistry

November/December 2009, Volume 5, Issue 10
Published by AEGIS Communications

Comparing the perception of dentists and lay people to altered dental esthetics.

The effect of axial midline angulation on dental esthetics.

By Thomas JL, Hayes C, Zawaiden S. Angle Orthod. 2003; 73:359-364.

Abstract

The purpose of this study was to analyze the effect of various degrees of axial midline angulation on the attractiveness of a smile. We explored the influence of age, race, sex, direction of midline deviation, education, occupation, and dominant hand on each evaluator’s perception of dental esthetics. Photographs of smiling subjects—one man and one woman—were altered to produce both left and right axial midline angulations in 5 degree increments. Fifty orthodontists and 50 laypeople evaluated these altered photographs by assigning both a numerical attractiveness rating and an acceptable or unacceptable rating to each. The results showed that attractiveness scores and acceptability ratings declined consistently as axial midline angulation increased. Statistical analysis showed that both sex of the subject and occupation of the judge were significant variables (P < .05) in the evaluation of the subjects. Age, race, sex of the judge, education level, direction of midline deviation, and dominant hand were not statistically significant. The mean acceptable midline angulation for the male subject was 6.6 +/- 4.5 degrees for orthodontists and 10.7 +/- 6.2 degrees for laypeople. For the female subject, the mean acceptable threshold was 6.4 +/- 4.0 degrees for orthodontists and 10.0 +/- 6.1 degrees for laypeople (P < .001). Discrepancies of 10 degrees were unacceptable by 68% of orthodontists and 41% of laypeople.

Comparing the perception of dentists and lay people to altered dental esthetics.

By Kokich VO Jr, Kiyak HA, Shapiro PA. J Esthet Dent. 1999;11:311-324.

Abstract
This study was designed to determine the perceptions of lay people and dental professionals with respect to minor variations in anterior tooth size and alignment and their relation to the surrounding soft tissues. Smiling photographs were intentionally altered with one of eight common anterior esthetic discrepancies in varying degrees of deviation, including variations in crown length, crown width, incisor crown angulation, midline, open gingival embrasure, gingival margin, incisal plane, and gingiva-to-lip distance. Forty images were randomized in a questionnaire and rated according to attractiveness by three groups: orthodontists, general dentists, and lay people; 300 questionnaires were distributed. The response rate was 88.2% for orthodontists, 51.8% for general dentists, and 60.6% for lay people. The results demonstrated threshold levels of noticeable difference between the varying levels of discrepancy. A maxillary midline deviation of 4 mm was necessary before orthodontists rated it significantly less esthetic than the others. However, general dentists and lay people were unable to detect even a 4-mm midline deviation. All three groups were able to distinguish a 2-mm discrepancy in incisor crown angulation. An incisal plane cant of 1 mm as well as a 3-mm narrowing in maxillary lateral incisor crown width were required by orthodontists and general dentists to be rated significantly less esthetic. Lay people were unable to detect an incisal plane asymmetry until it was 3 mm, or a lateral incisor narrowing until it reached 4 mm. Threshold levels for open gingival embrasure and gingiva-to-lip distance were both at 2 mm for the orthodontic group. Open gingival embrasure became detectable by the general dentists and lay people at 3 mm, whereas gingiva-to-lip distance was classified by these groups as noticeably unattractive at 4 mm. The results of this study show that orthodontists, general dentists, and lay people detect specific dental esthetic discrepancies at varying levels of deviation, which may aid the dental professional in making specific treatment recommendations.

Commentary

These two studies present investigations on how dentofacial midline discrepancies and asymmetries affect perceptions of attractiveness. Kokich and his group compared perceptions of altered esthetics among general dentists, orthodontists, and laypersons. Do we all see dentofacial midline esthetics the same? According to that study, the midline discrepancy needs to be significant (4 mm) for orthodontists and laypersons to detect it, while the asymmetry of incisal plane discrepancies were noted at lower thresholds for the two dental groups when compared to laypersons. Angulations of the anterior teeth seem to play a greater role in both studies. For the Kokich study, all three groups noted angulations greater than 2 mm. The Thomas study demonstrated that vertical tooth angulation in the midline region was a more important criteria than horizontal midline discrepancies. Other studies parallel these findings. When laypersons, orthodontists, and prosthodontists evaluated original and altered images of “pleasant” female smiles, none of the groups noted an esthetic impact of a worn canine cusp; when shown midline discrepancies, orthodontists perceived the asymmetry when the midline shift was equal to or greater than 1 mm and prosthodontists perceived it at 3 mm or greater. Laypersons saw no alteration.1 Another study reached a similar conclusion in that it took a greater discrepancy of the dental to facial midline for the midline to be judged unattractive. In fact, more orthodontists considered a 4-mm discrepancy to be unattractive than laypersons.2 In another study, midline deviations were not rated as highly in esthetic perception when compared to other asymmetric esthetic alterations. When general dentists, orthodontists, and laypersons were compared, crown width discrepancies of 2 mm were noted, small midline diastemas were not rated as unattractive, but all three groups noted that a 3-mm distance from gingiva to lip was unattractive. Asymmetric alterations make teeth more unattractive to all three groups.3

What does this mean? The significance of these studies is twofold. First, everyone views dentofacial esthetics differently and generalizations may not be true for every patient. Second, there is no cookbook for dental esthetics that will work every time. Each treatment plan needs to be individualized to a patient’s perceptions and desires. Any limitations based on tooth position, musculoskeletal landmarks, and soft tissue landmarks will play a role in the final result. These findings might help general dentists and dental specialists to consider the patient’s esthetic expectations when planning treatment.

References

Pinho S, Ciriaco C, Faber J, Lenza MA. Impact of dental asymmetries on the perception of smile esthetics. Am J Orthod Dentofacial Orthop. 2007;132:748-753.

Shyagali TR, Chandralekha B, Bhayya DP, Kumar S, et al. Are ratings of dentofacial attractiveness influenced by dentofacial midline discrepancies? Aust Orthod J. 2008;24:91-95.

Kokich VO, Kokich VG, Kiyak HA. Perceptions of dental professionals and laypersons to altered dental esthetics: asymmetric and symmetric situations. Am J Orthod Dentofacial Orthop. 2006;130:141-151.

Commentary by Howard E. Strassler, DMD

Professor and Director of Operative Dentistry
Department of Endodontics, Prosthodontics and Operative Dentistry
University of Maryland Dental School
Baltimore, Maryland