ORIGINAL ARTICLE
Maxillary arch width and buccal corridor changes with orthodontic treatment. Part 2: Attractiveness of the frontal facial smile in extraction and nonextraction outcomes Anna H. Meyer,a Michael G. Woods,b and David J. Mantonc Melbourne, Victoria, Australia
Introduction: This study was designed to assess the influence that the buccal corridor might have on the frontal facial attractiveness of subjects who had received orthodontic treatment with or without 4 premolar extractions. Methods: Posttreatment full-face frontal smiling photographs of 30 premolar extraction and 27 nonextraction patients were evaluated by 20 orthodontists, 20 dentists, and 20 laypeople using a visual analog scale. The ratings were analyzed according to rater group, rater sex, and number of years in practice for orthodontists and dentists to search for any statistically significant differences in the ratings on the basis of treatment groups, subject sex, and buccal corridor widths and areas. Results: Orthodontists and dentists gave higher mean overall frontal facial attractiveness scores than did laypeople. There were no significant differences in how men and women rated the study subjects. The number of years in practice did not affect how the orthodontists rated, but it did affect the ratings of the dentists. Female subjects were consistently rated as significantly more attractive than male subjects. There was no difference in ratings for the extraction and nonextraction subject groups. The buccal corridor widths and areas did not affect the frontal facial attractiveness ratings. Conclusions: If treatment has been carried out with thorough diagnosis and careful planning, neither the choice of extraction or nonextraction treatment, nor the resulting buccal corridor widths or areas appeared to affect the subjects' frontal facial attractiveness. (Am J Orthod Dentofacial Orthop 2014;145:296-304)
H
istorically, smile analysis has been treated as a separate entity from cephalometrics and cast analysis in orthodontic diagnosis and treatment planning.1 Even with a greater awareness of orthodontic influences on facial changes, a large proportion of the literature has been devoted to the lateral analysis of the face, with a relatively small emphasis on the frontal aspect.2,3 However, it is important to have a sound understanding of the factors that contribute to an esthetic smile from the frontal perspective. It can be argued that this is more important than the lateral
a
Private practice, Melbourne, Victoria, Australia. Professor, Royal Melbourne Hospital, Melbourne, Victoria, Australia. c Professor and Elsdon Storey Chair of Child Dental Health, Melbourne Dental School, University of Melbourne, Melbourne, Victoria, Australia. All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest, and none were reported. Address correspondence to: Michael Geoffrey Woods, 549 Dandenong Rd, Malvern 3143, Melbourne, Victoria, Australia; e-mail, [email protected]. Submitted, May 2013; revised and accepted, October 2013. 0889-5406/$36.00 Copyright Ó 2014 by the American Association of Orthodontists. http://dx.doi.org/10.1016/j.ajodo.2013.10.019 b
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viewpoint because it is the position from which most people interact and are viewed in social situations. The buccal corridor has been gaining widespread attention as a potentially important feature that can influence the attractiveness of the smile.1,2,4-12 To date, there is still no consensus in the literature on how to measure or assess the buccal corridors.12 Various studies have adopted different definitions of the buccal corridor, evaluating it in relation to the canines,3,13 to the last visible teeth,4,6,11,14-16 or to both.1,2,17 These differing definitions of buccal corridor epitomize the dilemma facing clinicians when planning treatment for a 3-dimensional entity using a 2-dimensional photograph. Consensus regarding the acceptable amount of buccal corridor display has varied throughout the years. In the 1950s, a wide smile with a negligible buccal corridor was deemed by some authors as unnatural and characteristic of a denture.18 There were opinions in the 1960s that the only teeth that should be shown in an attractive smile were the 6 anterior teeth.19 Current perceptions of what is deemed to be esthetically pleasing differ from those of 50 years ago, since a broad smile with minimal buccal
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corridors is now seen as a projection of youth and health.4 Even so, there are polarized opinions in the literature concerning the esthetic value of buccal corridors. Some authors have determined that the size of the buccal corridors is not critical to the esthetic value of a smile.1,2,10,13,14,20 Conversely, it is claimed that a smile with large buccal corridors is less esthetically pleasing than a smile with small buccal corridors.4-9,12,15,16 In line with this, there is a resurgence of resistance to orthodontic extractions for fear of causing detrimental effects on the smile. It has been suggested that a narrow maxillary arch might result from orthodontic treatment, particularly when maxillary premolars have been extracted—and that this dark space can detract from facial attractiveness as does a flat profile.21 Most investigators have used digitally altered photographs for panel assessments of buccal corridors.4-9,12,15,16 Comparatively few authors have used real, unaltered photographs to relate actual buccal corridor measurements to the esthetic value. Among these latter studies, either untreated subjects1,14,20 or subjects who had only nonextraction treatment11 have been assessed. Although useful in establishing potential relationships between buccal corridors and smile esthetics, these sample groups give no information about the possible esthetic effects of extracting teeth as part of contemporary orthodontic treatment. As a result, there are little objective data on the direct effect of extraction or nonextraction treatment on the overall facial attractiveness pertaining to buccal corridors. For this reason, this investigation was designed to assess the esthetic value of buccal corridors, as evaluated by orthodontists, dentists, and laypeople on unaltered posttreatment full-face photographs. MATERIAL AND METHODS
Ethics approval was obtained from the Melbourne Dental School Human Ethics Advisory Group and Dental Health Services Victoria. The photographic records of a previous sample of 57 patients (24 men, 33 woman) with a mean pretreatment age of 14.87 years (62.99) who had undergone orthodontic treatment at the Royal Melbourne Dental Hospital were selected and prepared for this retrospective study.22 These subjects were divided into 2 groups on the basis of their extraction pattern: 30 had 4 premolar extractions, and 27 had nonextraction treatment (Table I). All subjects were treated with maxillary and mandibular fixed appliances, with the aim in each case to provide an ideal interdigitating occlusion as suggested by Roth23 and Andrews.24 All subjects had early permanent dentitions with no congenitally missing teeth (with the possible exception of third molars) and had
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not undergone any separate maxillary expansion treatment. Each subject's posttreatment posed frontal smile photograph was taken with a digital camera (EOS 40D; Canon, Tokyo, Japan), macro lens (EF 100 mm, f/2.8 Macro USM; Canon), and ring flash (Macro ring lite MR-14 EX; Canon). The patients had their heads in natural head position and were asked to give a “relaxed, natural smile.” The full-face photographs were then uploaded as JPEG files at a native resolution of 1880 3 2816 pixels and converted into black and white images. The photographs were imported into PowerPoint (Office 2007; Microsoft, Redmond, Wash) in a random order. One photograph was enlarged to fill each slide, and a randomly assigned subject number was clearly marked in the bottom right corner (Fig 1). The panel consisted of 20 orthodontists (16 men, 4 women), 20 dentists (10 men, 10 women), and 20 laypeople (10 men, 10 women) (Table II). The number of years in clinical practice of each orthodontist and dentist was recorded. The slide show was presented individually (in the same order) to each rater, viewed on a laptop computer (13-in, 16:9 monitor, Vaio VGNZ16GN; Sony, Tokyo, Japan). Each slide was automated to display for 12 seconds with no repeated viewings. A click was sounded on cue as each new slide was displayed. Each rater was given a booklet with 10 visual analog scales (VAS) per page for them to fill out. The VAS was created with a 100-mm uninterrupted line that was anchored on the left at 0 (“very unattractive”) and on the right at 10 (“very attractive”) (Fig 2). The VAS was numbered according to the corresponding slides presented to them. The raters were advised of the time each slide would be displayed to them and the click they would hear to signify a change in slide. They were instructed to write their assessment of each smile in the context of the face at the appropriate point along the scale with a vertical line. Any facial blemishes, beauty spots, and hairstyles were to be disregarded as much as possible. All scores were measured to the nearest millimeter from the left anchor end to where the rater's scribe was made to give the final esthetic rating. The details of the method used to measure the photographs to obtain the various buccal corridor widths and areas have been reported previously.22 The posttreatment measurements of the buccal corridor widths and areas from part 1 of this study that relate to the photographs shown to the panel members are documented in Table III and Figures 3 to 5.22 Abbreviations used for the buccal corridor measurements are listed in Table IV. Statistical analysis
The final esthetic scores were entered into Excel spreadsheets (Office 2007; Microsoft) and then imported
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Table I. Pretreatment sample characteristics Age Treatment group Extraction (n 5 30)
Sex Mean (y) F (n 5 19) 14.07 M (n 5 11) 14.78 Total 14.33 Nonextraction (n 5 57) F (n 5 14) 15.44 M (n 5 13) 15.48 Total 15.46 Total (n 5 57) F (n 5 33) 14.65 M (n 5 24) 15.16 Total 14.87
Total treatment time SD 1.81 1.46 1.70 4.77 2.96 3.93 3.40 2.37 2.99
Mean (y) 2.22 2.10 2.18 2.12 2.18 2.15 2.18 2.15 2.16
SD 0.32 0.47 0.38 0.19 0.50 0.37 0.28 0.48 0.37
Ricketts' mandibular plane angle Mean ( ) 28.27 31.23 29.35 24.86 24.31 24.59 26.82 27.48 27.10
SD 5.98 5.16 5.79 4.58 5.31 4.85 5.62 6.22 5.83
Maxillary crowding Mean (mm) 6.11 6.86 6.39 0.54 0.55 0.54 3.29 2.85 3.11
SD 3.78 5.50 4.41 4.88 3.85 4.33 5.37 5.93 5.56
Overbite Mean (mm) 3.3 1.1 2.5 4.3 3.7 4.0 3.8 2.5 3.2
SD 1.3 2.4 2.1 2.0 3.1 2.5 1.7 3.0 2.4
F, Female; M, male.
were also used to test each fixed-factor group against subject treatment groups, sex, and buccal corridor widths and areas to detect any differences in the overall scores of each fixed factor group of these dependent variables. Differences in attractiveness ratings of each subgroup of each fixed factor group were analyzed using a 4-way factorial ANOVA test (Table VI). Through these analyses, relationships between the esthetic ratings and the treatment groups, buccal corridor widths and areas, and subject sex in turn were investigated. To enable objective statistical testing on the influence of the buccal corridors, each parameter (IC:SW, IL:SW, BCC:TSA, BCL:TSA) was grouped into either “small” or “large.” This was done by categorizing the values that were smaller than or equal to the median of that parameter as “small” and the values that were larger than this number as “large.” Post-hoc testing was conducted using the Tukey-Kramer method. Statistical significance was established at P \0.05. RESULTS Fig 1. Example of a slide presented to the panel members.
into SPSS (version 19; IBM, Somers, NY) for statistical analysis. Reliability analyses were conducted for each fixed-factor group (rater group, rater sex, orthodontists' years in practice, and dentists' years in practice) with an interclass correlation coefficient (ICC) and a 95% confidence interval. This was to establish how similarly the raters rated in each fixed-factor group. Since the ICC values were all high (lowest ICC, 0.832), it was justified to average the VAS scores across all raters in each group to produce an overall average rating for each subject for all subsequent statistical analyses. Overall mean VAS scores for each fixed-factor group was conducted with analysis of variance (ANOVA) tests (Table V), which
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There was a significant difference between the overall mean VAS scores between each rater group. Post-hoc testing showed that both orthodontists and dentists rated significantly higher than did laypeople (Table V). This difference was greater for orthodontists than for dentists when compared with laypeople, but there was no significant difference between the ratings of orthodontists and dentists. No significant difference was found between the overall ratings of male and female raters, nor did the number of years in practice affect the ratings of orthodontists (Table V). However, the number of years in practice did significantly affect the dentists' VAS scores. The dentists with 21 to 30 years in practice gave the highest ratings, followed by those with 1 to 10 years in practice and those with
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Table II. Panel members by sex and years in practice (where applicable) Orthodontists Years in practice 1-10 11-20 21-30 Total
Male 7 3 6 16
Female 2 1 1 4
Dentists Both 9 4 7 20
Male 6 4 0 10
Female 6 3 1 10
Laypeople Both 12 7 1 20
Male
Female
Both
10
10
20
Fig 2. VAS (and an example scribe) used to evaluate the esthetic value of smile photographs.
Table III. Posttreatment equivalent buccal corridor
percentages within and between each treatment group Extraction
IC:SW IL:SW BCC:TSA BCL:TSA
Mean (%) 32.7 15.1 17.2 4.7
SD (%) 7.0 6.6 6.4 2.6
Nonextraction Mean (%) 36.5 14.1 22.3 4.9
SD (%) 6.3 5.3 7.1 2.9
IC:SW, Ratio between the intercanine distance and the smile width; IL:SW, ratio between the interlast visible maxillary tooth distance and the smile width; BCC:TSA, ratio between the buccal corridor area in relation to the canines and the total smile area; BCL:TSA, ratio between the buccal corridor area in relation to the last visible maxillary teeth.
Fig 4. The linear (IL:SW) and area (BCL:TSA) measurements of a buccal corridor in relation to the last visible maxillary teeth.
Fig 5. The linear smile width (SW) and total smile area (TSA) measurements. Fig 3. The linear (IC:SW) and area (BCC:TSA) measurements of a buccal corridor in relation to the canines.
11 to 20 years in practice (Table V). There were no significant differences between the overall ratings of treatment group (extraction or nonextraction), buccal corridor widths and areas between different rater groups, rater sex, or years in practice for both orthodontists and dentists.
There were no significant differences between the ratings of subjects who had extraction or nonextraction treatment by orthodontists, dentists, laypeople, male raters, female raters, orthodontists grouped by years in practice, and dentists grouped by years in practice (Table VI). The amounts of buccal corridor width and area displayed by the subjects also did not have an effect on these ratings (Table VI). The only significant
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Table IV. List of buccal corridor index abbreviations Abbreviation IC (intercanine distance) IL (interlast visible maxillary tooth distance) SW (smile width) BCC (buccal corridor area in relation to the canines) BCL (buccal corridor area in relation to the last visible maxillary teeth) TSA (total smile area)
Definition The distance between the most distal surfaces of the canines. The distance between the most distal surfaces of the last visible maxillary teeth, to give the width of the visible dentition. The intercommissural width. The bilateral area bordered by the most distal surface of each canine and the inner vermilion border of the lips. The bilateral area bordered by the most distal surface of the last visible maxillary tooth on either side and the inner vermilion border of the lips. The total area bordered by the inner vermilion border of the lips.
Table V. Overall mean VAS ratings of each fixed factor group and significant differences within each group Rater group
Mean SD
Orthodontists 6.16a 0.84
Dentists 5.84b 0.84
Sex Laypersons 5.26a,b 1.21
Male 5.59 0.89
Orthodontists' years in practice
Female 6.00 0.95
1-10 6.00 0.93
11-20 6.21 1.10
21-30 6.32 0.72
Dentists' years in practice 1-10 6.06c 0.80
11-20 5.38c 1.02
21-30 6.42d 0.93
Superscript letters denote groups that were significantly different from each other (P \0.05).
difference found was how male and female subjects were rated. Female subjects were consistently rated as significantly more attractive than male subjects by dentists and orthodontists, but not by laypeople (Table VI, Figs 6-8). DISCUSSION
In response to the increasing interest in dentofacial esthetics, several quantitative techniques have been devised to evaluate the esthetic judgments of dental professionals and laypeople. Due to its clinical and statistical applicability, a continuous rating scale was used in this study. Although a VAS allows parametric testing to be carried out and is also a simple and rapid method for raters to judge attractiveness, it is not without limitations.25 The scale might mean different things to different raters, with comparable positioning of marks on the scale by 2 raters not necessarily implying the same feeling each has to what is being rated.26 Different portions of the scale can be used, with the extremes of the scale tending to be underused.27 However, overall, the VAS system has been determined to provide valid, reproducible, and representative ratings of dental and facial appearances28 and is the method used in many dental esthetic studies.1,3,6,7,14,16,29,30 A possible limitation of this study was that the images were shown in the same sequence to each rater. Although it has previously been shown that this does not affect esthetic ratings,31 it could be argued that this could have introduced an order effect.7 For instance, raters might have begun by rating subjects either more or less
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critically at the start of the slide show until they became used to the process. However, if the images were shown in a different order to each rater, there could still have been variability in the results, since several images would have then undergone the initial variable ratings, in turn skewing the overall mean rating for each image. The method used in our study ensured that the order of each image was consistent and would have been likely to exert a similar influence on each rater's score. It would be of interest to know whether potential patients and parents rate smiles in the same way that dental professionals do. The results of our study showed that both orthodontists and dentists gave higher overall ratings than did laypeople. This is not consistent with the results of previous studies that have shown no difference in the perceptions of dental professionals and laypeople.1,3,5,14,16,27,29 It is also not consistent with previous reports of a difference in the perceptions within such groups, where laypeople rated more highly than did dental professionals.6,7,12,30,32,33 It has been suggested that differences seen in the previous studies might have been due to the likelihood that the perceptions of dental professionals are biased because of their training.6 The fact that laypeople were more critical than dental professionals in this study might be at least partly explained by our methodology. Full-face photographs were evaluated instead of perioral photographs. The reason for using this method was that the esthetic assessment of a smile cannot be judged on the smile alone.34,35 The context of the smile of each subject's face is also critically important if the interaction between all smile-related tissues is to be demonstrated.36 For
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Table VI. Mean VAS ratings of all fixed-factor rater groups according to subject groups Fixed-factor rater groups Rater group Subject group Treatment group Extraction Mean SD Nonextraction Mean SD Sex group Male Mean SD Female Mean SD IC:SW Small Mean SD Large Mean SD IL:SW Small Mean SD Large Mean SD BCC:TSA Small Mean SD Large Mean SD BCL:TSA Small Mean SD Large Mean SD
Sex
Orthodontists' years in practice
Dentists' years in practice
Ortho
Dent
Lay
Male
Female
1-10
11-20
21-30
1-10
11-20
21-30
6.22 0.83
5.95 0.77
5.54 1.04
5.70 0.82
6.19 0.83
6.11 0.90
6.26 1.10
6.34 0.74
6.16 0.71
5.49 1.01
6.53 0.89
6.09 0.85
5.72 0.91
4.97 0.13
5.45 0.96
5.80 1.04
5.89 0.96
6.15 1.12
6.31 0.71
5.94 0.90
5.26 1.02
6.31 0.97
5.89a 0.87
5.54b 0.88
4.89 1.11
5.26c 0.90
5.70d 0.89
5.70e 0.94
6.00 1.11
6.07f 0.78
5.79g 0.80
5.03h 1.09
6.13i 1.07
6.35a 0.77
6.06b 0.75
5.54 1.22
5.82c 0.82
6.22d 0.95
6.23e 0.87
6.36 1.09
6.51f 0.62
6.26g 0.76
5.63h 0.89
6.64i 0.76
6.14 0.86
5.82 0.85
5.38 1.39
5.56 0.84
5.99 0.94
5.92 0.87
5.99 1.12
6.31 0.65
6.07 0.80
5.35 0.90
6.47 0.80
6.17 0.83
5.86 0.84
5.18 1.08
5.62 0.95
6.02 0.98
6.09 1.00
6.44 1.05
6.34 0.80
6.05 0.82
5.42 1.15
6.37 1.07
6.14 0.78
5.86 0.84
5.29 1.29
5.45 0.89
5.98 0.94
5.78 0.87
6.01 1.10
6.17 0.66
6.01 0.82
5.37 1.04
6.28 0.86
6.19 0.93
5.82 0.85
5.23 1.21
5.66 0.89
6.02 0.97
6.13 0.94
6.33 1.10
6.41 0.74
6.08 0.81
5.39 1.02
6.51 0.97
6.03 0.86
5.71 0.82
5.11 1.20
5.52 0.92
5.93 0.99
5.98 0.96
6.24 1.08
6.24 0.79
6.00 0.84
5.29 1.04
6.31 0.98
6.28 0.81
5.96 0.85
5.41 1.23
5.68 0.86
6.11 0.91
6.04 0.90
6.17 1.15
6.44 0.60
6.14 0.76
5.50 1.00
6.59 0.85
6.08 1.00
5.86 0.87
5.34 1.19
5.60 0.87
5.95 0.93
6.06 0.90
6.30 1.12
6.34 0.74
6.04 0.79
5.35 1.00
6.48 0.97
6.22 0.68
5.81 0.81
5.20 1.21
5.56 0.94
6.08 0.99
5.92 0.98
6.06 1.11
6.29 0.70
6.08 0.84
5.43 1.06
6.34 0.88
Superscript letters denote groups that were significantly different from each other (P \0.05). Ortho, Orthodontist; dent, dentist; lay, layperson; IC:SW, ratio between the intercanine distance and the smile width; IL:SW, ratio between the interlast visible maxillary teeth distance and the smile width; BCC:TSA, ratio between the buccal corridor area in relation to the canines and the total smile area; BCL:TSA, ratio between the buccal corridor area in relation to the last visible maxillary teeth and the total smile area.
instance, a broad smile in a short-faced person might have a different esthetic impact than the same smile would have in a long-faced subject. The patient's vertical facial pattern has been a vital part of orthodontic treatment planning for many years and should be taken into account when assessing the overall esthetics of a smile. It has been postulated that extremely short-faced and
extremely long-faced persons are most likely to be affected by positional changes in tooth width in the buccal corridors, with mesofacial subjects seemingly able to better tolerate increased transverse or vertical changes.37 Yang et al38 found a significant negative correlation for the vertical facial pattern and the buccal corridors, suggesting that long-faced persons might have
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Fig 6. Relationships between the mean VAS ratings of each rater group with subjects' sex. Orthodontists and dentists rated the subjects more highly than did laypeople.
Fig 7. Relationships between the mean VAS ratings of orthodontists according to their years in practice with the subjects' sex. Orthodontists' years since graduation did not seem to affect the ratings of the subjects.
naturally smaller buccal corridors compared with shortfaced persons. Several authors have used full-face frontal photographs for this reason.4,9,12 However, a shortcoming of using full-face frontal photographs is that the esthetic impact of dental features decreases when a full-face photograph is viewed, because other features of the face can confound the esthetic rating of the smile.39 This might have been
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Fig 8. Nonsignificant relationship between the mean VAS ratings of dentists according to their years in practice with the subjects' sex. Dentists' years since graduation did seem to affect the ratings of the subjects.
demonstrated in our study, in which these potential confounders could have been more pertinent to laypeople because they might not have been able to focus on the smile. This influence appears to have occurred despite our best efforts to specifically instruct all panel members to assess each smile within the context of the face. In contrast, because of their training and experience, dental professionals might have more easily focused on the smile and rated it alone.6 In turn, this could have led to the differences in the VAS ratings. It is, however, debatable as to whether confounding facial features in full-face photographs are a genuine shortcoming of the method. Daily interactions involve the whole face and not just the smile. The buccal corridors are just one of many dental characteristics that make up a smile, and a smile is just 1 component of the face. Literature regarding the effects of extraction treatment on smiles when viewed from the frontal aspect is scarce, but research interest in this area is increasing. The results of this study show that there do not appear to be discernable differences in perceived attractiveness in those treated with or without premolar extractions. These results support those of Kim and Gianelly,10 who also failed to find a significant difference in the mean esthetic score in frontal perioral photographs of 2 such treatment groups when assessed by a lay panel. Boley et al40 also found no differences in the esthetic scores of experienced dentists and orthodontists who evaluated extraction and nonextraction frontal facial photographs. Furthermore, our results support the conclusions of a recent systematic review of the factors influencing an attractive smile: that
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well-indicated extraction treatment does not necessarily have a deleterious effect on frontal facial esthetics.41 A common method by which previous authors have conducted buccal corridor panel assessments is by digitally altering the size of the buccal corridors on a small selection of photographs.4-9,12,15,16 Proponents of this method have heralded the digital age as a great opportunity for orthodontic esthetic research and stated that “extremely realistic images, indistinguishable from actual clinical images, can have a single or a combination of variables modified in precise and repeatable ways so that a range of variations can be proposed.”15 However, the clinical validity of the results of such studies has been called into question. Digitally altered buccal corridors appear to start abruptly as a sharply defined dark space distal to the last posterior teeth.6 In reality, buccal corridors have a gradually darker shade as the light passes through to the posterior teeth, creating an illusion of distance and therefore depth.42 This reasoning questions the clinical significance of the results of digital studies that have labeled wide buccal corridors as unattractive. With this in mind, all previous investigations that showed a correlation between larger buccal corridors and a lower esthetic rating have involved the use of digitally altered photographs. The findings of these studies have directly contradicted those in which raters assessed unaltered, real clinical photographs. All studies that did not show a relationship between the buccal corridor and smile esthetics were those that used unaltered clinical photographs.1,2,10,11,13,14,20 The findings of this investigation support the results of the studies that used unaltered photographs. These findings, together with the results of the previously mentioned studies, provide evidence that the buccal corridor appears to have little direct effect on the perception of overall facial attractiveness. Our study sample had on average a 14.1% buccal corridor width for nonextraction subjects and a 15.1% buccal corridor width for extraction subjects, related to the last visible maxillary teeth. These proportions are far greater than the “ideal” proportions denoted in previous studies by Parekh et al,15,16 who established from a pilot study that the ideal buccal corridor was 6% for males and 11% for females. Despite the greater buccal corridor proportions in this study, there was still no detraction from or apparent influence of the buccal corridors on overall facial attractiveness as assessed by the raters. This might be due to other factors that affect how the buccal corridor could be perceived. These include different lighting conditions,43-45 different levels of posterior vertical gingival display,46 and the angle at which the subject is facing in relation to the viewer. These factors all potentially affect what is perceived to be the “shadowy” area at the corners of
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a smile. It would seem that there is no single universal ideal buccal corridor width or area because this feature is so dependent on external factors and is therefore intrinsically variable in the same person. It seems that orthodontic treatment (with or without extractions) is not likely to have a deleterious effect on the frontal facial attractiveness of patients if it has been carried out after a thorough diagnosis and treatment-planning process. Individual treatment plans tend to be biased toward broader maxillary arches in short-faced patients and narrow maxillary arches in longer-faced patients. It is likely then that maxillary arch narrowness in a broad face or excessive maxillary arch width in a narrow face is most likely to be unesthetic. We have shown in parts 1 and 2 of this study that the extraction of premolars does not inevitably lead to reduced maxillary arch width or decreased frontal facial attractiveness. CONCLUSIONS
The following conclusions assume that an orthodontic patient will be treated after a thorough planning and diagnostic process. With the limitations already outlined, the following conclusions can be drawn from this study, 1.
2.
There are unlikely to be any significant differences in the frontal facial attractiveness of orthodontic patients treated either with or without premolar extractions. It is unlikely that the size of the buccal corridor widths or areas will affect the frontal facial attractiveness of orthodontic patients.
ACKNOWLEDGMENTS
We thank Steve Vander Hoorn of the Statistical Consulting Centre at the University of Melbourne for his guidance with the statistical analysis of the study data and all panel members who took part in this investigation. REFERENCES 1. McNamara L, McNamara JA Jr, Ackerman MB, Baccetti T. Hardand soft-tissue contributions to the esthetics of the posed smile in growing patients seeking orthodontic treatment. Am J Orthod Dentofacial Orthop 2008;133:491-9. 2. Johnson DK, Smith RJ. Smile estheties after orthodontic treatment with and without extraction of four first premolars. Am J Orthod Dentofacial Orthop 1995;108:162-7. 3. Roden-Johnson D, Gallerano R, English J. The effects of buccal corridor spaces and arch form on smile esthetics. Am J Orthod Dentofacial Orthop 2005;127:343-50. 4. Moore T, Southard KA, Casko JS, Qian F, Southard TE. Buccal corridors and smile esthetics. Am J Orthod Dentofacial Orthop 2005;127:208-13.
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5. Gracco A, Cozzani M, D'Elia L, Manfrini M, Peverada C, Siciliani G. The smile buccal corridors: aesthetic value for dentists and laypersons. Prog Orthod 2006;7:56-65. 6. Martin AJ, Buschang PH, Boley JC, Taylor RW, McKinney TW. The impact of buccal corridors on smile attractiveness. Eur J Esthet Dent 2007;29:530-7. 7. Ioi H, Nakata S, Counts A. Effects of buccal corridors on smile esthetics in Japanese. Angle Orthod 2009;79:628-33. 8. McLeod C, Fields H, Hechter F, Wiltshire W, Rody W Jr, Christensen J. Esthetics and smile characteristics evaluated by laypersons. Angle Orthod 2011;81:198-205. 9. Gul-e-Erum, Fida M. Changes in smile parameters as perceived by orthodontists, dentists, artists and laypeople. World J Orthod 2008;9:132-40. 10. Kim E, Gianelly AA. Extraction vs nonextraction: arch widths and smile esthetics. Angle Orthod 2003;73:354-8. 11. Schabel BJ, Franchi L, Baccetti T, McNamara JA Jr. Subjective vs objective evaluations of smile esthetics. Am J Orthod Dentofacial Orthop 2009;135(Suppl):S72-9. 12. Zange S, Ramos A, Cuoghi O, de Mendonc¸a M, Suguino R. Perceptions of laypersons and orthodontists regarding the buccal corridor in longand short-face individuals. Angle Orthod 2011;81:88-92. 13. Hulsey C. An esthetic evaluation of lip-teeth relationships present in the smile. Am J Orthod 1970;57:132-44. 14. Ritter DE, Gandini LG Jr, Pinto AS, Locks A. Esthetic influence of negative space in the buccal corridor during smiling. Angle Orthod 2006;76:198-203. 15. Parekh S, Fields HW, Beck FM, Rosenstiel SF. The acceptability of variations in smile arc and buccal corridor space. Orthod Craniofac Res 2007;10:15-21. 16. Parekh SM, Fields HW, Beck M, Rosenstiel S. Attractiveness of variations in the smile arc and buccal corridor space as judged by orthodontists and laymen. Angle Orthod 2006;76:557-63. 17. Is¸iksal E, Hazar S, Akyalc¸in S. Smile esthetics: perception and comparison of treated and untreated smiles. Am J Orthod Dentofacial Orthop 2006;129:8-16. 18. Frush JP, Fisher RD. The dynesthetic interpretation of the dentogenic concept. J Prosthet Dent 1958;8:558-81. 19. Stallard H. Survival of the periodontium during and after orthodontic treatment. Am J Orthod 1964;50:584-92. 20. Rigsbee OI, Sperry T, BeGole E. The influence of facial animation on smile characteristics. Int J Adult Orthod Orthognath Surg 1988;3:233-9. 21. Ghafari JG. Emerging paradigms in orthodontics—an essay. Am J Orthod Dentofacial Orthop 1997;111:573-80. 22. Meyer AH, Woods MG, Manton DJ. Maxillary arch width and buccal corridor changes with orthodontic treatment. Part I: differences between premolar extraction and nonextraction treatment outcomes. Am J Orthod Dentofacial Orthop 2014;145:207-16. 23. Roth R. Functional occlusion for the orthodontist: part III. J Clin Orthod 1981;15:174-9, 182-98. 24. Andrews L. The six keys to normal occlusion. Am J Orthod 1972; 62:296-309. 25. Phillips C, Tulloch C, Dann C. Rating of facial attractiveness. Community Dent Oral Epidemiol 1992;20:214-20. 26. Aitken RC. Measurement of feelings using visual analogue scales. Proc R Soc Med 1969;62:989-93.
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27. Schabel B, McNamara JA Jr, Franchi L, Baccetti T. Q-sort assessment vs visual analog scale in the evaluation of smile esthetics. Am J Orthod Dentofacial Orthop 2009;135(Suppl):S61-71. 28. Howells DJ, Shaw WC. The validity and reliability of ratings of dental and facial attractiveness for epidemiologic use. Am J Orthod 1985;88:402-8. 29. Krishnan V, Daniel S, Lazar D, Asok A. Characterization of posed smile by using visual analog scale, smile arc, buccal corridor measures, and modified smile index. Am J Orthod Dentofacial Orthop 2008;133:515-23. 30. Kokich V Jr, Kiyak H, Shapiro P. Comparing the perception of dentists and lay people to altered dental esthetics. J Esthet Restor Dent 1999;11:311-24. 31. Rodrigues CD, Magnani R, Machado M, Oliveira O. The perception of smile attractiveness. Angle Orthod 2009;79:634-9. 32. Kerr W, O'Donnell J. Panel perception of facial attractiveness. J Orthod 1990;17:299-304. 33. Bowman S, Johnston L Jr. The esthetic impact of extraction and nonextraction treatments on Caucasian patients. Angle Orthod 2000;70:3-10. 34. Valiathan A, Gandhi S. Buccal corridor spaces, arch form, and smile esthetics. Am J Orthod Dentofacial Orthop 2005;128:557. 35. Valiathan A, Gandhi S. Esthetic influence of negative space in the buccal corridor during smiling. Angle Orthod 2006;76(4):vii. 36. Ker A, Chan R, Fields H, Beck M, Rosenstiel S. Esthetics and smile characteristics from the layperson's perspective: a computer-based survey study. J Am Dent Assoc 2008;139: 1318-27. 37. Ackerman M. Buccal smile corridors. Am J Orthod Dentofacial Orthop 2005;127:528-9. 38. Yang I, Nahm D, Baek S. Which hard and soft tissue factors relate with the amount of buccal corridor space during smiling? Angle Orthod 2008;78:5-11. 39. Flores-Mir C, Silva E, Barriga M, Lagravere M, Major P. Lay person's perception of smile aesthetics in dental and facial views. J Orthod 2004;31:204-9. 40. Boley JC, Pontier JP, Smith S, Fulbright M. Facial changes in extraction and nonextraction patients. Angle Orthod 1998;68: 539-46. 41. Janson G, Branco N, Fernandes T, Sathler R, Garib D, Lauris J. Influence of orthodontic treatment, midline position, buccal corridor and smile arc on smile attractiveness. Angle Orthod 2011;81: 155-63. 42. Lombardi RE. The principles of visual perception and their clinical application to denture esthetics. J Prosthet Dent 1973;29: 358-82. 43. Ackerman M, Ackerman J. Smile analysis and design in the digital era. J Clin Orthod 2002;36:221-36. 44. Ackerman MB, Brensinger C, Landis JR. An evaluation of dynamic lip-tooth characteristics during speech and smile in adolescents. Angle Orthod 2004;74:43-50. 45. Schabel B, Baccetti T, Franchi L, McNamara J Jr. Clinical photography vs digital video clips for the assessment of smile esthetics. Angle Orthod 2010;80:678-84. 46. Nangia A, Darendeliler M. Finishing occlusion in Class II or Class III molar relation: therapeutic Class II and III. Aust Orthod J 2001; 17:89-94.
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Maxillary arch width and buccal corridor changes with orthodontic treatment. Part 2: Attractiveness of the frontal facial smile in extraction and nonextraction outcomes Anna H. Meyer,a Michael G. Woods,b and David J. Mantonc Melbourne, Victoria, Australia
Introduction: This study was designed to assess the influence that the buccal corridor might have on the frontal facial attractiveness of subjects who had received orthodontic treatment with or without 4 premolar extractions. Methods: Posttreatment full-face frontal smiling photographs of 30 premolar extraction and 27 nonextraction patients were evaluated by 20 orthodontists, 20 dentists, and 20 laypeople using a visual analog scale. The ratings were analyzed according to rater group, rater sex, and number of years in practice for orthodontists and dentists to search for any statistically significant differences in the ratings on the basis of treatment groups, subject sex, and buccal corridor widths and areas. Results: Orthodontists and dentists gave higher mean overall frontal facial attractiveness scores than did laypeople. There were no significant differences in how men and women rated the study subjects. The number of years in practice did not affect how the orthodontists rated, but it did affect the ratings of the dentists. Female subjects were consistently rated as significantly more attractive than male subjects. There was no difference in ratings for the extraction and nonextraction subject groups. The buccal corridor widths and areas did not affect the frontal facial attractiveness ratings. Conclusions: If treatment has been carried out with thorough diagnosis and careful planning, neither the choice of extraction or nonextraction treatment, nor the resulting buccal corridor widths or areas appeared to affect the subjects' frontal facial attractiveness. (Am J Orthod Dentofacial Orthop 2014;145:296-304)
H
istorically, smile analysis has been treated as a separate entity from cephalometrics and cast analysis in orthodontic diagnosis and treatment planning.1 Even with a greater awareness of orthodontic influences on facial changes, a large proportion of the literature has been devoted to the lateral analysis of the face, with a relatively small emphasis on the frontal aspect.2,3 However, it is important to have a sound understanding of the factors that contribute to an esthetic smile from the frontal perspective. It can be argued that this is more important than the lateral
a
Private practice, Melbourne, Victoria, Australia. Professor, Royal Melbourne Hospital, Melbourne, Victoria, Australia. c Professor and Elsdon Storey Chair of Child Dental Health, Melbourne Dental School, University of Melbourne, Melbourne, Victoria, Australia. All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest, and none were reported. Address correspondence to: Michael Geoffrey Woods, 549 Dandenong Rd, Malvern 3143, Melbourne, Victoria, Australia; e-mail, [email protected]. Submitted, May 2013; revised and accepted, October 2013. 0889-5406/$36.00 Copyright Ó 2014 by the American Association of Orthodontists. http://dx.doi.org/10.1016/j.ajodo.2013.10.019 b
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viewpoint because it is the position from which most people interact and are viewed in social situations. The buccal corridor has been gaining widespread attention as a potentially important feature that can influence the attractiveness of the smile.1,2,4-12 To date, there is still no consensus in the literature on how to measure or assess the buccal corridors.12 Various studies have adopted different definitions of the buccal corridor, evaluating it in relation to the canines,3,13 to the last visible teeth,4,6,11,14-16 or to both.1,2,17 These differing definitions of buccal corridor epitomize the dilemma facing clinicians when planning treatment for a 3-dimensional entity using a 2-dimensional photograph. Consensus regarding the acceptable amount of buccal corridor display has varied throughout the years. In the 1950s, a wide smile with a negligible buccal corridor was deemed by some authors as unnatural and characteristic of a denture.18 There were opinions in the 1960s that the only teeth that should be shown in an attractive smile were the 6 anterior teeth.19 Current perceptions of what is deemed to be esthetically pleasing differ from those of 50 years ago, since a broad smile with minimal buccal
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corridors is now seen as a projection of youth and health.4 Even so, there are polarized opinions in the literature concerning the esthetic value of buccal corridors. Some authors have determined that the size of the buccal corridors is not critical to the esthetic value of a smile.1,2,10,13,14,20 Conversely, it is claimed that a smile with large buccal corridors is less esthetically pleasing than a smile with small buccal corridors.4-9,12,15,16 In line with this, there is a resurgence of resistance to orthodontic extractions for fear of causing detrimental effects on the smile. It has been suggested that a narrow maxillary arch might result from orthodontic treatment, particularly when maxillary premolars have been extracted—and that this dark space can detract from facial attractiveness as does a flat profile.21 Most investigators have used digitally altered photographs for panel assessments of buccal corridors.4-9,12,15,16 Comparatively few authors have used real, unaltered photographs to relate actual buccal corridor measurements to the esthetic value. Among these latter studies, either untreated subjects1,14,20 or subjects who had only nonextraction treatment11 have been assessed. Although useful in establishing potential relationships between buccal corridors and smile esthetics, these sample groups give no information about the possible esthetic effects of extracting teeth as part of contemporary orthodontic treatment. As a result, there are little objective data on the direct effect of extraction or nonextraction treatment on the overall facial attractiveness pertaining to buccal corridors. For this reason, this investigation was designed to assess the esthetic value of buccal corridors, as evaluated by orthodontists, dentists, and laypeople on unaltered posttreatment full-face photographs. MATERIAL AND METHODS
Ethics approval was obtained from the Melbourne Dental School Human Ethics Advisory Group and Dental Health Services Victoria. The photographic records of a previous sample of 57 patients (24 men, 33 woman) with a mean pretreatment age of 14.87 years (62.99) who had undergone orthodontic treatment at the Royal Melbourne Dental Hospital were selected and prepared for this retrospective study.22 These subjects were divided into 2 groups on the basis of their extraction pattern: 30 had 4 premolar extractions, and 27 had nonextraction treatment (Table I). All subjects were treated with maxillary and mandibular fixed appliances, with the aim in each case to provide an ideal interdigitating occlusion as suggested by Roth23 and Andrews.24 All subjects had early permanent dentitions with no congenitally missing teeth (with the possible exception of third molars) and had
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not undergone any separate maxillary expansion treatment. Each subject's posttreatment posed frontal smile photograph was taken with a digital camera (EOS 40D; Canon, Tokyo, Japan), macro lens (EF 100 mm, f/2.8 Macro USM; Canon), and ring flash (Macro ring lite MR-14 EX; Canon). The patients had their heads in natural head position and were asked to give a “relaxed, natural smile.” The full-face photographs were then uploaded as JPEG files at a native resolution of 1880 3 2816 pixels and converted into black and white images. The photographs were imported into PowerPoint (Office 2007; Microsoft, Redmond, Wash) in a random order. One photograph was enlarged to fill each slide, and a randomly assigned subject number was clearly marked in the bottom right corner (Fig 1). The panel consisted of 20 orthodontists (16 men, 4 women), 20 dentists (10 men, 10 women), and 20 laypeople (10 men, 10 women) (Table II). The number of years in clinical practice of each orthodontist and dentist was recorded. The slide show was presented individually (in the same order) to each rater, viewed on a laptop computer (13-in, 16:9 monitor, Vaio VGNZ16GN; Sony, Tokyo, Japan). Each slide was automated to display for 12 seconds with no repeated viewings. A click was sounded on cue as each new slide was displayed. Each rater was given a booklet with 10 visual analog scales (VAS) per page for them to fill out. The VAS was created with a 100-mm uninterrupted line that was anchored on the left at 0 (“very unattractive”) and on the right at 10 (“very attractive”) (Fig 2). The VAS was numbered according to the corresponding slides presented to them. The raters were advised of the time each slide would be displayed to them and the click they would hear to signify a change in slide. They were instructed to write their assessment of each smile in the context of the face at the appropriate point along the scale with a vertical line. Any facial blemishes, beauty spots, and hairstyles were to be disregarded as much as possible. All scores were measured to the nearest millimeter from the left anchor end to where the rater's scribe was made to give the final esthetic rating. The details of the method used to measure the photographs to obtain the various buccal corridor widths and areas have been reported previously.22 The posttreatment measurements of the buccal corridor widths and areas from part 1 of this study that relate to the photographs shown to the panel members are documented in Table III and Figures 3 to 5.22 Abbreviations used for the buccal corridor measurements are listed in Table IV. Statistical analysis
The final esthetic scores were entered into Excel spreadsheets (Office 2007; Microsoft) and then imported
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Table I. Pretreatment sample characteristics Age Treatment group Extraction (n 5 30)
Sex Mean (y) F (n 5 19) 14.07 M (n 5 11) 14.78 Total 14.33 Nonextraction (n 5 57) F (n 5 14) 15.44 M (n 5 13) 15.48 Total 15.46 Total (n 5 57) F (n 5 33) 14.65 M (n 5 24) 15.16 Total 14.87
Total treatment time SD 1.81 1.46 1.70 4.77 2.96 3.93 3.40 2.37 2.99
Mean (y) 2.22 2.10 2.18 2.12 2.18 2.15 2.18 2.15 2.16
SD 0.32 0.47 0.38 0.19 0.50 0.37 0.28 0.48 0.37
Ricketts' mandibular plane angle Mean ( ) 28.27 31.23 29.35 24.86 24.31 24.59 26.82 27.48 27.10
SD 5.98 5.16 5.79 4.58 5.31 4.85 5.62 6.22 5.83
Maxillary crowding Mean (mm) 6.11 6.86 6.39 0.54 0.55 0.54 3.29 2.85 3.11
SD 3.78 5.50 4.41 4.88 3.85 4.33 5.37 5.93 5.56
Overbite Mean (mm) 3.3 1.1 2.5 4.3 3.7 4.0 3.8 2.5 3.2
SD 1.3 2.4 2.1 2.0 3.1 2.5 1.7 3.0 2.4
F, Female; M, male.
were also used to test each fixed-factor group against subject treatment groups, sex, and buccal corridor widths and areas to detect any differences in the overall scores of each fixed factor group of these dependent variables. Differences in attractiveness ratings of each subgroup of each fixed factor group were analyzed using a 4-way factorial ANOVA test (Table VI). Through these analyses, relationships between the esthetic ratings and the treatment groups, buccal corridor widths and areas, and subject sex in turn were investigated. To enable objective statistical testing on the influence of the buccal corridors, each parameter (IC:SW, IL:SW, BCC:TSA, BCL:TSA) was grouped into either “small” or “large.” This was done by categorizing the values that were smaller than or equal to the median of that parameter as “small” and the values that were larger than this number as “large.” Post-hoc testing was conducted using the Tukey-Kramer method. Statistical significance was established at P \0.05. RESULTS Fig 1. Example of a slide presented to the panel members.
into SPSS (version 19; IBM, Somers, NY) for statistical analysis. Reliability analyses were conducted for each fixed-factor group (rater group, rater sex, orthodontists' years in practice, and dentists' years in practice) with an interclass correlation coefficient (ICC) and a 95% confidence interval. This was to establish how similarly the raters rated in each fixed-factor group. Since the ICC values were all high (lowest ICC, 0.832), it was justified to average the VAS scores across all raters in each group to produce an overall average rating for each subject for all subsequent statistical analyses. Overall mean VAS scores for each fixed-factor group was conducted with analysis of variance (ANOVA) tests (Table V), which
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There was a significant difference between the overall mean VAS scores between each rater group. Post-hoc testing showed that both orthodontists and dentists rated significantly higher than did laypeople (Table V). This difference was greater for orthodontists than for dentists when compared with laypeople, but there was no significant difference between the ratings of orthodontists and dentists. No significant difference was found between the overall ratings of male and female raters, nor did the number of years in practice affect the ratings of orthodontists (Table V). However, the number of years in practice did significantly affect the dentists' VAS scores. The dentists with 21 to 30 years in practice gave the highest ratings, followed by those with 1 to 10 years in practice and those with
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Table II. Panel members by sex and years in practice (where applicable) Orthodontists Years in practice 1-10 11-20 21-30 Total
Male 7 3 6 16
Female 2 1 1 4
Dentists Both 9 4 7 20
Male 6 4 0 10
Female 6 3 1 10
Laypeople Both 12 7 1 20
Male
Female
Both
10
10
20
Fig 2. VAS (and an example scribe) used to evaluate the esthetic value of smile photographs.
Table III. Posttreatment equivalent buccal corridor
percentages within and between each treatment group Extraction
IC:SW IL:SW BCC:TSA BCL:TSA
Mean (%) 32.7 15.1 17.2 4.7
SD (%) 7.0 6.6 6.4 2.6
Nonextraction Mean (%) 36.5 14.1 22.3 4.9
SD (%) 6.3 5.3 7.1 2.9
IC:SW, Ratio between the intercanine distance and the smile width; IL:SW, ratio between the interlast visible maxillary tooth distance and the smile width; BCC:TSA, ratio between the buccal corridor area in relation to the canines and the total smile area; BCL:TSA, ratio between the buccal corridor area in relation to the last visible maxillary teeth.
Fig 4. The linear (IL:SW) and area (BCL:TSA) measurements of a buccal corridor in relation to the last visible maxillary teeth.
Fig 5. The linear smile width (SW) and total smile area (TSA) measurements. Fig 3. The linear (IC:SW) and area (BCC:TSA) measurements of a buccal corridor in relation to the canines.
11 to 20 years in practice (Table V). There were no significant differences between the overall ratings of treatment group (extraction or nonextraction), buccal corridor widths and areas between different rater groups, rater sex, or years in practice for both orthodontists and dentists.
There were no significant differences between the ratings of subjects who had extraction or nonextraction treatment by orthodontists, dentists, laypeople, male raters, female raters, orthodontists grouped by years in practice, and dentists grouped by years in practice (Table VI). The amounts of buccal corridor width and area displayed by the subjects also did not have an effect on these ratings (Table VI). The only significant
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Table IV. List of buccal corridor index abbreviations Abbreviation IC (intercanine distance) IL (interlast visible maxillary tooth distance) SW (smile width) BCC (buccal corridor area in relation to the canines) BCL (buccal corridor area in relation to the last visible maxillary teeth) TSA (total smile area)
Definition The distance between the most distal surfaces of the canines. The distance between the most distal surfaces of the last visible maxillary teeth, to give the width of the visible dentition. The intercommissural width. The bilateral area bordered by the most distal surface of each canine and the inner vermilion border of the lips. The bilateral area bordered by the most distal surface of the last visible maxillary tooth on either side and the inner vermilion border of the lips. The total area bordered by the inner vermilion border of the lips.
Table V. Overall mean VAS ratings of each fixed factor group and significant differences within each group Rater group
Mean SD
Orthodontists 6.16a 0.84
Dentists 5.84b 0.84
Sex Laypersons 5.26a,b 1.21
Male 5.59 0.89
Orthodontists' years in practice
Female 6.00 0.95
1-10 6.00 0.93
11-20 6.21 1.10
21-30 6.32 0.72
Dentists' years in practice 1-10 6.06c 0.80
11-20 5.38c 1.02
21-30 6.42d 0.93
Superscript letters denote groups that were significantly different from each other (P \0.05).
difference found was how male and female subjects were rated. Female subjects were consistently rated as significantly more attractive than male subjects by dentists and orthodontists, but not by laypeople (Table VI, Figs 6-8). DISCUSSION
In response to the increasing interest in dentofacial esthetics, several quantitative techniques have been devised to evaluate the esthetic judgments of dental professionals and laypeople. Due to its clinical and statistical applicability, a continuous rating scale was used in this study. Although a VAS allows parametric testing to be carried out and is also a simple and rapid method for raters to judge attractiveness, it is not without limitations.25 The scale might mean different things to different raters, with comparable positioning of marks on the scale by 2 raters not necessarily implying the same feeling each has to what is being rated.26 Different portions of the scale can be used, with the extremes of the scale tending to be underused.27 However, overall, the VAS system has been determined to provide valid, reproducible, and representative ratings of dental and facial appearances28 and is the method used in many dental esthetic studies.1,3,6,7,14,16,29,30 A possible limitation of this study was that the images were shown in the same sequence to each rater. Although it has previously been shown that this does not affect esthetic ratings,31 it could be argued that this could have introduced an order effect.7 For instance, raters might have begun by rating subjects either more or less
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critically at the start of the slide show until they became used to the process. However, if the images were shown in a different order to each rater, there could still have been variability in the results, since several images would have then undergone the initial variable ratings, in turn skewing the overall mean rating for each image. The method used in our study ensured that the order of each image was consistent and would have been likely to exert a similar influence on each rater's score. It would be of interest to know whether potential patients and parents rate smiles in the same way that dental professionals do. The results of our study showed that both orthodontists and dentists gave higher overall ratings than did laypeople. This is not consistent with the results of previous studies that have shown no difference in the perceptions of dental professionals and laypeople.1,3,5,14,16,27,29 It is also not consistent with previous reports of a difference in the perceptions within such groups, where laypeople rated more highly than did dental professionals.6,7,12,30,32,33 It has been suggested that differences seen in the previous studies might have been due to the likelihood that the perceptions of dental professionals are biased because of their training.6 The fact that laypeople were more critical than dental professionals in this study might be at least partly explained by our methodology. Full-face photographs were evaluated instead of perioral photographs. The reason for using this method was that the esthetic assessment of a smile cannot be judged on the smile alone.34,35 The context of the smile of each subject's face is also critically important if the interaction between all smile-related tissues is to be demonstrated.36 For
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Table VI. Mean VAS ratings of all fixed-factor rater groups according to subject groups Fixed-factor rater groups Rater group Subject group Treatment group Extraction Mean SD Nonextraction Mean SD Sex group Male Mean SD Female Mean SD IC:SW Small Mean SD Large Mean SD IL:SW Small Mean SD Large Mean SD BCC:TSA Small Mean SD Large Mean SD BCL:TSA Small Mean SD Large Mean SD
Sex
Orthodontists' years in practice
Dentists' years in practice
Ortho
Dent
Lay
Male
Female
1-10
11-20
21-30
1-10
11-20
21-30
6.22 0.83
5.95 0.77
5.54 1.04
5.70 0.82
6.19 0.83
6.11 0.90
6.26 1.10
6.34 0.74
6.16 0.71
5.49 1.01
6.53 0.89
6.09 0.85
5.72 0.91
4.97 0.13
5.45 0.96
5.80 1.04
5.89 0.96
6.15 1.12
6.31 0.71
5.94 0.90
5.26 1.02
6.31 0.97
5.89a 0.87
5.54b 0.88
4.89 1.11
5.26c 0.90
5.70d 0.89
5.70e 0.94
6.00 1.11
6.07f 0.78
5.79g 0.80
5.03h 1.09
6.13i 1.07
6.35a 0.77
6.06b 0.75
5.54 1.22
5.82c 0.82
6.22d 0.95
6.23e 0.87
6.36 1.09
6.51f 0.62
6.26g 0.76
5.63h 0.89
6.64i 0.76
6.14 0.86
5.82 0.85
5.38 1.39
5.56 0.84
5.99 0.94
5.92 0.87
5.99 1.12
6.31 0.65
6.07 0.80
5.35 0.90
6.47 0.80
6.17 0.83
5.86 0.84
5.18 1.08
5.62 0.95
6.02 0.98
6.09 1.00
6.44 1.05
6.34 0.80
6.05 0.82
5.42 1.15
6.37 1.07
6.14 0.78
5.86 0.84
5.29 1.29
5.45 0.89
5.98 0.94
5.78 0.87
6.01 1.10
6.17 0.66
6.01 0.82
5.37 1.04
6.28 0.86
6.19 0.93
5.82 0.85
5.23 1.21
5.66 0.89
6.02 0.97
6.13 0.94
6.33 1.10
6.41 0.74
6.08 0.81
5.39 1.02
6.51 0.97
6.03 0.86
5.71 0.82
5.11 1.20
5.52 0.92
5.93 0.99
5.98 0.96
6.24 1.08
6.24 0.79
6.00 0.84
5.29 1.04
6.31 0.98
6.28 0.81
5.96 0.85
5.41 1.23
5.68 0.86
6.11 0.91
6.04 0.90
6.17 1.15
6.44 0.60
6.14 0.76
5.50 1.00
6.59 0.85
6.08 1.00
5.86 0.87
5.34 1.19
5.60 0.87
5.95 0.93
6.06 0.90
6.30 1.12
6.34 0.74
6.04 0.79
5.35 1.00
6.48 0.97
6.22 0.68
5.81 0.81
5.20 1.21
5.56 0.94
6.08 0.99
5.92 0.98
6.06 1.11
6.29 0.70
6.08 0.84
5.43 1.06
6.34 0.88
Superscript letters denote groups that were significantly different from each other (P \0.05). Ortho, Orthodontist; dent, dentist; lay, layperson; IC:SW, ratio between the intercanine distance and the smile width; IL:SW, ratio between the interlast visible maxillary teeth distance and the smile width; BCC:TSA, ratio between the buccal corridor area in relation to the canines and the total smile area; BCL:TSA, ratio between the buccal corridor area in relation to the last visible maxillary teeth and the total smile area.
instance, a broad smile in a short-faced person might have a different esthetic impact than the same smile would have in a long-faced subject. The patient's vertical facial pattern has been a vital part of orthodontic treatment planning for many years and should be taken into account when assessing the overall esthetics of a smile. It has been postulated that extremely short-faced and
extremely long-faced persons are most likely to be affected by positional changes in tooth width in the buccal corridors, with mesofacial subjects seemingly able to better tolerate increased transverse or vertical changes.37 Yang et al38 found a significant negative correlation for the vertical facial pattern and the buccal corridors, suggesting that long-faced persons might have
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Fig 6. Relationships between the mean VAS ratings of each rater group with subjects' sex. Orthodontists and dentists rated the subjects more highly than did laypeople.
Fig 7. Relationships between the mean VAS ratings of orthodontists according to their years in practice with the subjects' sex. Orthodontists' years since graduation did not seem to affect the ratings of the subjects.
naturally smaller buccal corridors compared with shortfaced persons. Several authors have used full-face frontal photographs for this reason.4,9,12 However, a shortcoming of using full-face frontal photographs is that the esthetic impact of dental features decreases when a full-face photograph is viewed, because other features of the face can confound the esthetic rating of the smile.39 This might have been
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Fig 8. Nonsignificant relationship between the mean VAS ratings of dentists according to their years in practice with the subjects' sex. Dentists' years since graduation did seem to affect the ratings of the subjects.
demonstrated in our study, in which these potential confounders could have been more pertinent to laypeople because they might not have been able to focus on the smile. This influence appears to have occurred despite our best efforts to specifically instruct all panel members to assess each smile within the context of the face. In contrast, because of their training and experience, dental professionals might have more easily focused on the smile and rated it alone.6 In turn, this could have led to the differences in the VAS ratings. It is, however, debatable as to whether confounding facial features in full-face photographs are a genuine shortcoming of the method. Daily interactions involve the whole face and not just the smile. The buccal corridors are just one of many dental characteristics that make up a smile, and a smile is just 1 component of the face. Literature regarding the effects of extraction treatment on smiles when viewed from the frontal aspect is scarce, but research interest in this area is increasing. The results of this study show that there do not appear to be discernable differences in perceived attractiveness in those treated with or without premolar extractions. These results support those of Kim and Gianelly,10 who also failed to find a significant difference in the mean esthetic score in frontal perioral photographs of 2 such treatment groups when assessed by a lay panel. Boley et al40 also found no differences in the esthetic scores of experienced dentists and orthodontists who evaluated extraction and nonextraction frontal facial photographs. Furthermore, our results support the conclusions of a recent systematic review of the factors influencing an attractive smile: that
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well-indicated extraction treatment does not necessarily have a deleterious effect on frontal facial esthetics.41 A common method by which previous authors have conducted buccal corridor panel assessments is by digitally altering the size of the buccal corridors on a small selection of photographs.4-9,12,15,16 Proponents of this method have heralded the digital age as a great opportunity for orthodontic esthetic research and stated that “extremely realistic images, indistinguishable from actual clinical images, can have a single or a combination of variables modified in precise and repeatable ways so that a range of variations can be proposed.”15 However, the clinical validity of the results of such studies has been called into question. Digitally altered buccal corridors appear to start abruptly as a sharply defined dark space distal to the last posterior teeth.6 In reality, buccal corridors have a gradually darker shade as the light passes through to the posterior teeth, creating an illusion of distance and therefore depth.42 This reasoning questions the clinical significance of the results of digital studies that have labeled wide buccal corridors as unattractive. With this in mind, all previous investigations that showed a correlation between larger buccal corridors and a lower esthetic rating have involved the use of digitally altered photographs. The findings of these studies have directly contradicted those in which raters assessed unaltered, real clinical photographs. All studies that did not show a relationship between the buccal corridor and smile esthetics were those that used unaltered clinical photographs.1,2,10,11,13,14,20 The findings of this investigation support the results of the studies that used unaltered photographs. These findings, together with the results of the previously mentioned studies, provide evidence that the buccal corridor appears to have little direct effect on the perception of overall facial attractiveness. Our study sample had on average a 14.1% buccal corridor width for nonextraction subjects and a 15.1% buccal corridor width for extraction subjects, related to the last visible maxillary teeth. These proportions are far greater than the “ideal” proportions denoted in previous studies by Parekh et al,15,16 who established from a pilot study that the ideal buccal corridor was 6% for males and 11% for females. Despite the greater buccal corridor proportions in this study, there was still no detraction from or apparent influence of the buccal corridors on overall facial attractiveness as assessed by the raters. This might be due to other factors that affect how the buccal corridor could be perceived. These include different lighting conditions,43-45 different levels of posterior vertical gingival display,46 and the angle at which the subject is facing in relation to the viewer. These factors all potentially affect what is perceived to be the “shadowy” area at the corners of
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a smile. It would seem that there is no single universal ideal buccal corridor width or area because this feature is so dependent on external factors and is therefore intrinsically variable in the same person. It seems that orthodontic treatment (with or without extractions) is not likely to have a deleterious effect on the frontal facial attractiveness of patients if it has been carried out after a thorough diagnosis and treatment-planning process. Individual treatment plans tend to be biased toward broader maxillary arches in short-faced patients and narrow maxillary arches in longer-faced patients. It is likely then that maxillary arch narrowness in a broad face or excessive maxillary arch width in a narrow face is most likely to be unesthetic. We have shown in parts 1 and 2 of this study that the extraction of premolars does not inevitably lead to reduced maxillary arch width or decreased frontal facial attractiveness. CONCLUSIONS
The following conclusions assume that an orthodontic patient will be treated after a thorough planning and diagnostic process. With the limitations already outlined, the following conclusions can be drawn from this study, 1.
2.
There are unlikely to be any significant differences in the frontal facial attractiveness of orthodontic patients treated either with or without premolar extractions. It is unlikely that the size of the buccal corridor widths or areas will affect the frontal facial attractiveness of orthodontic patients.
ACKNOWLEDGMENTS
We thank Steve Vander Hoorn of the Statistical Consulting Centre at the University of Melbourne for his guidance with the statistical analysis of the study data and all panel members who took part in this investigation. REFERENCES 1. McNamara L, McNamara JA Jr, Ackerman MB, Baccetti T. Hardand soft-tissue contributions to the esthetics of the posed smile in growing patients seeking orthodontic treatment. Am J Orthod Dentofacial Orthop 2008;133:491-9. 2. Johnson DK, Smith RJ. Smile estheties after orthodontic treatment with and without extraction of four first premolars. Am J Orthod Dentofacial Orthop 1995;108:162-7. 3. Roden-Johnson D, Gallerano R, English J. The effects of buccal corridor spaces and arch form on smile esthetics. Am J Orthod Dentofacial Orthop 2005;127:343-50. 4. Moore T, Southard KA, Casko JS, Qian F, Southard TE. Buccal corridors and smile esthetics. Am J Orthod Dentofacial Orthop 2005;127:208-13.
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5. Gracco A, Cozzani M, D'Elia L, Manfrini M, Peverada C, Siciliani G. The smile buccal corridors: aesthetic value for dentists and laypersons. Prog Orthod 2006;7:56-65. 6. Martin AJ, Buschang PH, Boley JC, Taylor RW, McKinney TW. The impact of buccal corridors on smile attractiveness. Eur J Esthet Dent 2007;29:530-7. 7. Ioi H, Nakata S, Counts A. Effects of buccal corridors on smile esthetics in Japanese. Angle Orthod 2009;79:628-33. 8. McLeod C, Fields H, Hechter F, Wiltshire W, Rody W Jr, Christensen J. Esthetics and smile characteristics evaluated by laypersons. Angle Orthod 2011;81:198-205. 9. Gul-e-Erum, Fida M. Changes in smile parameters as perceived by orthodontists, dentists, artists and laypeople. World J Orthod 2008;9:132-40. 10. Kim E, Gianelly AA. Extraction vs nonextraction: arch widths and smile esthetics. Angle Orthod 2003;73:354-8. 11. Schabel BJ, Franchi L, Baccetti T, McNamara JA Jr. Subjective vs objective evaluations of smile esthetics. Am J Orthod Dentofacial Orthop 2009;135(Suppl):S72-9. 12. Zange S, Ramos A, Cuoghi O, de Mendonc¸a M, Suguino R. Perceptions of laypersons and orthodontists regarding the buccal corridor in longand short-face individuals. Angle Orthod 2011;81:88-92. 13. Hulsey C. An esthetic evaluation of lip-teeth relationships present in the smile. Am J Orthod 1970;57:132-44. 14. Ritter DE, Gandini LG Jr, Pinto AS, Locks A. Esthetic influence of negative space in the buccal corridor during smiling. Angle Orthod 2006;76:198-203. 15. Parekh S, Fields HW, Beck FM, Rosenstiel SF. The acceptability of variations in smile arc and buccal corridor space. Orthod Craniofac Res 2007;10:15-21. 16. Parekh SM, Fields HW, Beck M, Rosenstiel S. Attractiveness of variations in the smile arc and buccal corridor space as judged by orthodontists and laymen. Angle Orthod 2006;76:557-63. 17. Is¸iksal E, Hazar S, Akyalc¸in S. Smile esthetics: perception and comparison of treated and untreated smiles. Am J Orthod Dentofacial Orthop 2006;129:8-16. 18. Frush JP, Fisher RD. The dynesthetic interpretation of the dentogenic concept. J Prosthet Dent 1958;8:558-81. 19. Stallard H. Survival of the periodontium during and after orthodontic treatment. Am J Orthod 1964;50:584-92. 20. Rigsbee OI, Sperry T, BeGole E. The influence of facial animation on smile characteristics. Int J Adult Orthod Orthognath Surg 1988;3:233-9. 21. Ghafari JG. Emerging paradigms in orthodontics—an essay. Am J Orthod Dentofacial Orthop 1997;111:573-80. 22. Meyer AH, Woods MG, Manton DJ. Maxillary arch width and buccal corridor changes with orthodontic treatment. Part I: differences between premolar extraction and nonextraction treatment outcomes. Am J Orthod Dentofacial Orthop 2014;145:207-16. 23. Roth R. Functional occlusion for the orthodontist: part III. J Clin Orthod 1981;15:174-9, 182-98. 24. Andrews L. The six keys to normal occlusion. Am J Orthod 1972; 62:296-309. 25. Phillips C, Tulloch C, Dann C. Rating of facial attractiveness. Community Dent Oral Epidemiol 1992;20:214-20. 26. Aitken RC. Measurement of feelings using visual analogue scales. Proc R Soc Med 1969;62:989-93.
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27. Schabel B, McNamara JA Jr, Franchi L, Baccetti T. Q-sort assessment vs visual analog scale in the evaluation of smile esthetics. Am J Orthod Dentofacial Orthop 2009;135(Suppl):S61-71. 28. Howells DJ, Shaw WC. The validity and reliability of ratings of dental and facial attractiveness for epidemiologic use. Am J Orthod 1985;88:402-8. 29. Krishnan V, Daniel S, Lazar D, Asok A. Characterization of posed smile by using visual analog scale, smile arc, buccal corridor measures, and modified smile index. Am J Orthod Dentofacial Orthop 2008;133:515-23. 30. Kokich V Jr, Kiyak H, Shapiro P. Comparing the perception of dentists and lay people to altered dental esthetics. J Esthet Restor Dent 1999;11:311-24. 31. Rodrigues CD, Magnani R, Machado M, Oliveira O. The perception of smile attractiveness. Angle Orthod 2009;79:634-9. 32. Kerr W, O'Donnell J. Panel perception of facial attractiveness. J Orthod 1990;17:299-304. 33. Bowman S, Johnston L Jr. The esthetic impact of extraction and nonextraction treatments on Caucasian patients. Angle Orthod 2000;70:3-10. 34. Valiathan A, Gandhi S. Buccal corridor spaces, arch form, and smile esthetics. Am J Orthod Dentofacial Orthop 2005;128:557. 35. Valiathan A, Gandhi S. Esthetic influence of negative space in the buccal corridor during smiling. Angle Orthod 2006;76(4):vii. 36. Ker A, Chan R, Fields H, Beck M, Rosenstiel S. Esthetics and smile characteristics from the layperson's perspective: a computer-based survey study. J Am Dent Assoc 2008;139: 1318-27. 37. Ackerman M. Buccal smile corridors. Am J Orthod Dentofacial Orthop 2005;127:528-9. 38. Yang I, Nahm D, Baek S. Which hard and soft tissue factors relate with the amount of buccal corridor space during smiling? Angle Orthod 2008;78:5-11. 39. Flores-Mir C, Silva E, Barriga M, Lagravere M, Major P. Lay person's perception of smile aesthetics in dental and facial views. J Orthod 2004;31:204-9. 40. Boley JC, Pontier JP, Smith S, Fulbright M. Facial changes in extraction and nonextraction patients. Angle Orthod 1998;68: 539-46. 41. Janson G, Branco N, Fernandes T, Sathler R, Garib D, Lauris J. Influence of orthodontic treatment, midline position, buccal corridor and smile arc on smile attractiveness. Angle Orthod 2011;81: 155-63. 42. Lombardi RE. The principles of visual perception and their clinical application to denture esthetics. J Prosthet Dent 1973;29: 358-82. 43. Ackerman M, Ackerman J. Smile analysis and design in the digital era. J Clin Orthod 2002;36:221-36. 44. Ackerman MB, Brensinger C, Landis JR. An evaluation of dynamic lip-tooth characteristics during speech and smile in adolescents. Angle Orthod 2004;74:43-50. 45. Schabel B, Baccetti T, Franchi L, McNamara J Jr. Clinical photography vs digital video clips for the assessment of smile esthetics. Angle Orthod 2010;80:678-84. 46. Nangia A, Darendeliler M. Finishing occlusion in Class II or Class III molar relation: therapeutic Class II and III. Aust Orthod J 2001; 17:89-94.
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