Evaluation of Mini- and Micro-esthetic Components of the Smile in Extraction and Non-extraction Treatment Mechanics: A Clinical Photographic Study

Abstract

Introduction

Smile esthetics play a vital role in orthodontic treatment outcomes. Different treatment mechanics can influence mini-esthetic and micro-esthetic smile parameters differently.

Aim

To evaluate the mini-esthetic and micro-esthetic components of the smile in extraction and non-extraction treatment cases.

Materials and Methods

The study was conducted on 50 orthodontically treated patients, which were divided into two groups: Group I (25 extraction) and Group II (25 non-extraction). Pre- and post-treatment frontal smile photographs were analyzed using Adobe Photoshop CC 2023. Mini-esthetic parameters assessed were maxillary incisor display (MID), gingival display (GD), smile index (SI), and buccal corridor ratio (BCR), while micro-esthetic parameters included crown width–height ratio (WHR), golden percentage (GP), connector height (CH), and gingival zenith level (GZL). Statistical analysis was performed using Statistical Package for the Social Sciences (SPSS) version 18. Student’s t-test was used for intragroup comparisons, while intergroup comparison of change scores was performed descriptively.

Results

Both extraction and non-extraction groups demonstrated significant intragroup improvements in several esthetic parameters. Extraction cases showed a reduction in MID and BCR, while non-extraction cases demonstrated an increase in incisor display and CH. GP improved in both groups. Intergroup comparison of change scores revealed comparable esthetic outcomes between the two treatment modalities.

Conclusion

Both treatment modalities demonstrated improvement in smile esthetic parameters, though the pattern of changes differed between the groups. Extraction cases showed an enhanced width and height ratio and reduced buccal corridors, whereas non-extraction cases showed improved incisor display and CH. GP improved in both groups, highlighting the importance of individualized treatment planning for optimal esthetic results.

Keywords

Smile esthetics mini-esthetics micro-esthetics extraction non-extraction

Introduction

Esthetics in orthodontics combines art and science to enhance the appearance of a patient’s smile through precise dental and facial alignment. Smile esthetics is a multidimensional concept that significantly influences perceptions of facial attractiveness.¹ Creating an attractive smile requires a thorough understanding of the intricate relationship between dental, skeletal, and soft tissue elements.² These elements are critical in evaluating the overall success of orthodontic treatments.

Different treatment approaches, such as extraction and non-extraction treatment plans, have been extensively evaluated for their impact on smile esthetics.³ Orthodontic treatment not only focuses on dental alignment but also aims to enhance facial symmetry and overall esthetic harmony.⁴ This growing emphasis on esthetics has spurred the development of advanced technologies like clear aligners, lingual braces, and digital smile design.

Smile evaluation is often divided into different categories, such as mini-esthetics and micro-esthetics, to address these esthetic factors comprehensively.⁵ Mini-esthetics addresses moderate aspects that enhance both dental alignment and the visual appeal of the smile, including buccal corridors, smile index (SI), gingival display (GD), and incisor display.² On the other hand, micro-esthetics focuses on the intricate details of individual teeth, such as contacts and connector height (CH), crown length ratio, golden percentage (GP), and gingival zenith level (GZL), which define the fine characteristics of a smile.⁶

Different researchers have explored the effect on facial and smile esthetics with different treatment mechanics.^{3, 4, 6} However, there were very few studies to ascertain the influence of different mechanics on the esthetic display. Previous studies, such as Prasad et al.⁷ and Janson et al.,⁸ have evaluated smile esthetics following orthodontic treatment. However, these studies primarily focused on selected esthetic parameters or did not comprehensively analyze both mini- and micro-esthetic components in extraction and non-extraction cases using standardized photographic assessment. The present study aimed to provide a combined evaluation of mini- and micro-esthetic parameters to understand better the influence of treatment mechanics on overall smile esthetics. Therefore, the aim and objectives of the present study were to evaluate the mini-esthetics and micro-esthetics of the smile in extraction and non-extraction cases.

Materials and Methods

The present study was conducted in the Department of Orthodontics and Dentofacial Orthopedics. Fifty subjects were selected from the patients visiting the department and seeking orthodontic treatment. Ethical approval for the study was obtained from the Institutional Research Ethical Committee. The approval number has been withheld to maintain blinding. Informed consent was obtained from the patient, their parents, or a legal guardian. The sample size for the present study was calculated based on data adapted from a previous study by Tauheed et al.,⁴ which evaluated the micro-esthetic parameters of the smile in extraction and non-extraction orthodontic cases. In their study, the mean difference in esthetic measurements between pre-treatment and post-treatment values was approximately 1.4 ± 1.0 units. Considering a two-tailed significance level of α = 0.05, a statistical power (1 − β) of 0.80, and an effect size of approximately 0.8 (large effect), the minimum required sample size was estimated to be 25 subjects per group. Thus, a total of 50 subjects (25 extraction and 25 non-extraction cases) were included in the present study. This sample size was considered adequate to detect clinically meaningful changes in mini- and micro-esthetic parameters following orthodontic treatment.

The subjects were included on the basis of different inclusion and exclusion criteria. The inclusion criteria were subjects who had completed fixed orthodontic treatment with available pre-treatment and post-treatment photographs, with no history of maxillofacial surgery or craniofacial syndromes. The exclusion criteria were subjects with incomplete orthodontic treatment or records, dental anomalies like missing teeth, peg lateral, supernumerary teeth, and subjects with distorted or blurred photographs.

The subjects were divided into two groups on the basis of different treatment mechanics:

Group I: Extraction therapy and Group II: Non-extraction therapy.

Photographs of all subjects were taken in a natural head position.⁹ The Nikon D40 digital camera (Figure 1) with a 108 mm macro lens was used to take all the photographs.

Figure 1.

Nikon D40 Digital Camera.

Different parameters for mini-esthetics were as follows (Figure 2):

Figure 2.

Measurement of Mini-esthetic Parameters on Pre-treatment and Post-treatment Photographs. (A) BCR, buccal corridor ratio. (B) GD, gingival display; MID, maxillary incisor display; SI, smile index.

Maxillary incisor display (MID): Line drawn from the stomion superius to the maxillary incisal edge (Figure 2B).^10-12

GD: Line drawn from the visible gingival surface to the cervical margin of the teeth in a posed smile (Figure 2B).¹³

SI: Calculated by dividing the inter-commissure width by the interlabial gap (Figure 2B).

Inner commissure width—distance from the innermost corner of the mouth from one side to another.¹⁴

Interlabial gap—measured from stomion superius to stomion inferius¹⁴ (Figure 2B).

Buccal corridor ratio (BCR): The BCR was calculated according to the method given as: Buccal corridor ratio (%) = (Inter commissure width – Visible maxillary dentition width)/Inner commissure width (Figure 2A).¹⁵

Different parameters for micro-esthetics were as follows (Figure 3):

Figure 3.

Note: CH, connector height; GP, golden percentage; GZL, gingival zenith level; WHR, width–height ratio.

Crown width–height ratio (WHR): Width is taken between the maximum convexity of the crown mesiodistally, and height was taken from the most apical point on the gingival margin.^{16, 17}

GP: Width of the central incisor, lateral incisor, and canine is measured using the ruler tool in Adobe Photoshop Software, and each was divided by the total width of all six anterior teeth. The values obtained were then converted to percentages for each tooth.¹⁸

CH: Defined as the area where the teeth appear to be in contact when viewed from the facial aspect at 90 degrees to each interproximal area.¹⁹

GZL: Gingival zenith of the lateral incisor was measured relative to the gingival esthetic line.²⁰

Gingival esthetic line: Constructed by joining the tangents of the zeniths of the maxillary central incisors and canines.

Pre- and post-treatment photographs were taken in the same camera settings to assess the different parameters of mini-esthetics and micro-esthetics of the smile. These photographs were then imported into computer software (Adobe Photoshop CC 2023). For this study, measurements were taken with the help of a ruler tool in Adobe Photoshop Software (Figure 4). All measurements were calculated, tabulated, and statistically analyzed using Statistical Package for the Social Sciences (SPSS) version 18. The distribution of the data was evaluated using the Shapiro–Wilk test for normality. Since the data demonstrated a normal distribution (P > .05), parametric statistical tests were employed. To assess intraexaminer reliability,¹⁵ randomly selected photographs were re-measured after a 2-week interval by the same investigator. Intraexaminer reliability was evaluated using intraclass correlation coefficients (ICCs), which ranged from 0.86 to 0.93 for all mini-esthetic and micro-esthetic parameters, indicating excellent measurement reliability. Student’s t-test was used for intragroup comparison of mini-esthetic and micro-esthetic parameters. Intergroup comparison of mean change scores (post-treatment minus pre-treatment values) between extraction and non-extraction groups was performed descriptively to assess the direction and magnitude of changes. A P value < .05 was considered statistically significant.

Figure 4.

Image Showing Ruler Tool in Adobe Photoshop Software.

Results

The present study evaluated the mini-esthetic and micro-esthetic components of the smile in subjects treated with extraction and non-extraction orthodontic treatment mechanics. A total of 50 subjects were included and divided into two groups based on the treatment approach employed. Student’s t-test was used for intragroup comparisons of the evaluated mini-esthetic and micro-esthetic parameters, and intergroup comparison was performed descriptively using mean change scores. In Group I (extraction group), intragroup comparison of pre-treatment and post-treatment mean values revealed statistically significant differences in MID and BCR among the mini-esthetic parameters (P < .05), as shown in Table 1. With respect to micro-esthetic parameters, WHR and GP demonstrated statistically significant changes following treatment (P < .05), as presented in Table 2. In Group II (non-extraction group), intragroup comparison of mini-esthetic parameters showed a statistically significant difference in MID (P < .05), as highlighted in Table 3. Additionally, a comparison of micro-esthetic parameters revealed statistically significant differences in CH and GP following treatment (P < .05), as illustrated in Table 4. The intergroup comparison of mean change scores between the extraction and non-extraction groups is shown in Table 5 for mini-esthetic parameters and in Table 6 for micro-esthetic parameters. Although certain parameters showed differences in the direction of change, the overall intergroup comparison revealed comparable esthetic outcomes between Group I and Group II.

Table 1.

Intragroup Comparison of Different Components of Mini-esthetics in Group I.

Variable	Pre-treatment		Post-treatment
Variable	Mean (mm) ± SD		Mean (mm) ± SD		P Value
Maxillary incisal display (MID)	12.54	2.40	10.40	2.47	.01*
Gingival display (GD)	0.67	1.09	0.44	1.03	.52
Smile index (SI)	6.52	2.30	7.40	2.06	.84
Buccal corridor ratio (BCR)	12.45	1.12	10.57	1.77	.03*

Notes: *P < 0.05 = statistically significant *P < .05 = statistically significant; P > .05 = not significant. SD, standard deviation.

Table 2.

Intragroup Comparison of Different Components of Micro-esthetics in Group I.

Variable	Pre-treatment		Post-treatment
Variable	Mean (mm) ± SD		Mean (mm) ± SD		P Value
Width–height ratio (WHR)	0.78	0.07	0.83	0.10	.01*
Connector height (CH)	38.43	12.30	41.20	8.07	.07
Golden percentage central incisor (GPCI)	21.53	1.53	22.38	1.80	.004*
Golden percentage lateral incisor (GPL)	12.70	2.01	13.62	1.19	.03*
Golden percentage canine (GPC)	10.16	2.57	8.53	1.97	.001*
Gingival zenith level (GZL)	0.67	0.54	0.42	0.37	.34

Notes: *P < .05 = statistically significant; P > .05 = not significant. SD, standard deviation.

Table 3.

Intragroup Comparison of Different Components of Mini-esthetics in Group II.

Variable	Pre-treatment		Post-treatment
Variable	Mean (mm) ± SD		Mean (mm) ± SD		P Value
Maxillary incisal display (MID)	10.54	1.40	12.90	2.06	.01*
Gingival display (GD)	0.67	1.42	0.59	1.24	.56
Smile index (SI)	5.74	2.32	5.81	1.59	.20
Buccal corridor ratio (BCR)	13.77	5.31	12.89	6.30	.02*

Notes: *P < .05 = statistically significant; P > .05 = not significant. SD, standard deviation.

Table 4.

Intragroup Comparison of Different Components of Micro-esthetics in Group II.

Variable	Pre-treatment		Post-treatment
Variable	Mean (mm) ± SD		Mean (mm) ± SD		P Value
Width–height ratio (WHR)	0.76	0.10	0.76	0.20	.44
Connector height (CH)	31.54	16.40	37.42	11.20	.001*
Golden percentage central incisor (GPCI)	21.74	1.50	22.46	1.18	.06
Golden percentage lateral incisor (GPL)	11.97	2.80	13.45	1.30	.04*
Golden percentage canine (GPC)	10.24	1.07	9.45	1.64	.01*
Gingival zenith level (GZL)	0.74	0.44	0.82	0.52	.20

Notes: *P < .05 = statistically significant; P > .05 = not significant. SD, standard deviation.

Table 5.

Intergroup Comparison of Change in Mini-esthetic Parameters.

Parameter	Extraction Group (Mean Change) mm	Non-extraction Group (Mean Change) mm	Clinical Interpretation
Maxillary incisor display (MID)	−2.14	+2.36	Opposite directional change
Gingival display (GD)	−0.23	−0.08	Comparable change
Smile index (SI)	+0.88	+0.07	Minimal difference
Buccal corridor ratio (BCR)	−1.88	−0.88	Comparable reduction

Note: Positive values indicate an increase and negative values indicate a decrease from pre-treatment to post-treatment.

Table 6.

Intergroup Comparison of Change in Micro-esthetic Parameters.

Parameter	Extraction Group (Mean Change) mm	Non-extraction Group (Mean Change) mm	Clinical Interpretation
Width–height ratio (WHR)	+0.05	+0.001	Greater change in extraction
Connector height (CH)	+2.77	+5.88	Greater increase in non-extraction
Golden percentage central incisor (GPCI)	+0.85	+0.72	Comparable improvement
Golden percentage lateral incisor (GPL)	+0.92	+1.48	Comparable improvement
Golden percentage canine (GPC)	−1.63	−0.79	Comparable change
Gingival zenith level (GZL)	−0.25	+0.08	Minimal difference

Note: Positive values indicate an increase and negative values indicate a decrease from pre-treatment to post-treatment. Intergroup comparisons are presented descriptively using mean change scores due to the retrospective nature of the study and lack of baseline matching.

Discussion

Esthetics in dentistry has increasingly become a major concern for patients and often serves as a reason for seeking dental care. A harmonious smile not only boosts individual confidence but also positively impacts social interactions and self-esteem. Achieving an appealing smile involves understanding the complex interplay between dental, skeletal, and soft tissue elements. This emphasized the need for an interdisciplinary approach to evaluate, diagnose, and resolve dental problems. So, the aims and objectives of the present study were to evaluate the mini-esthetic and micro-esthetics of the smile in extraction and non-extraction treatment cases.

The results of the present study showed that the intragroup comparison of pre-treatment and post-treatment mean values of MID in Group I showed a statistically significant decrease (P = .01), as shown in Table 1. Possible explanation for the decreased incisor display could be the mild reverse curve of Spee incorporated in the 0.019 × 0.025-inch stainless steel (SS) archwire during retraction after premolar extraction. Additionally, the altered incisor position impacts lip positioning, resulting in reduced incisor display. On intragroup comparison, there was a statistically significant increase in MID in Group II, as shown in Table 3. A possible explanation could be because of more space created by shifting the maxillary incisors forward and slightly upward during alignment, which results in a greater visible portion of the upper teeth when smiling. These results were in accordance with the study done by Kumar et al.²

Furthermore, the results of the present study showed that the intragroup comparison of mean values of the BCR in pre-treatment and post-treatment of Group I (P = .03) and Group II (P = .02) showed a significant decrease, as shown in Tables 1 and 3. This decrease in Group I might be because of the changes in arch width in the maxillary arch due to the distal movement of the canine after extraction, as they shifted to a wider part of the dental arch, which was according to the results observed by Maganzini et al.¹⁵

The decrease in the BCR in Group II may be attributed to the transverse widening of the dental arches. This widening is necessary to achieve a harmonious dental arch shape and proper alignment of teeth without resorting to the creation of additional space through extractions, which were according to the results observed by Herzog et al.²¹ On intragroup comparison of mean values of WHR, there was a statistically significant increase in Group I, as shown in Table 2. This increase may occur following extraction and subsequent alignment. The teeth are repositioned, resulting in an increased visible width and width-to-height ratio. Extractions provide space for alignment and retraction of the anterior teeth. However, these movements can cause tipping, rotation, and vertical intrusion, which alter tooth dimensions and contribute to the increase in the width-to-height ratio,²² which was according to the results observed by Tauheed et al.⁴

Furthermore, the results of the present study showed that the comparison of mean values of CH in pre-treatment and post-treatment of Group II (P = .001) showed significant differences, as shown in Table 4. A significant overall improvement in the CH of anterior teeth was observed in Group II. This finding may be attributed to treatment mechanics involving arch expansion and alignment, wherein teeth are repositioned without extraction, consistent with the observations reported by Raj et al.¹⁹

Further in the present study, it was found that on comparison of the mean values of GP in pre-treatment and post-treatment of Group I (P = .004 golden percentage central incisor (GPCI), P = .03 golden percentage lateral (GPL), P = .001 golden percentage canine (GPC)) and Group II (P = .04 GPL, P = .01 GPC) showed significant differences, as shown in Tables 2 and 4. GP increased in both groups due to the better alignment of the arch form, increased canine visibility, symmetry, and proportionality. These results were in accordance with the study done by Murthy and Ramani.²³

Smile esthetics encompasses a variety of attributes that must be carefully evaluated during orthodontic treatment planning. A comprehensive analysis of facial and smile esthetics is a prerequisite for initiating treatment, as this forms the foundation for achieving the desired outcome. The esthetic management of a patient begins with understanding their perceptions, preferences, and individual concepts of a beautiful smile. These insights must then be seamlessly integrated with the orthodontist’s diagnosis, treatment plan, and biomechanics. While efforts are made to minimize errors, it is acknowledged that operator and instrumental errors cannot be entirely eliminated. Further studies with larger sample sizes and the consideration of additional parameters are essential to validate and authenticate the findings. Furthermore, the present study was retrospective in nature, and the allocation of subjects to extraction and non-extraction groups was based on individual diagnostic and treatment requirements. Consequently, the study groups were not matched for initial malocclusion severity, which may have influenced baseline esthetic characteristics. This factor should be considered when interpreting the intergroup comparisons.

Conclusion

The conclusions drawn from the study were as follows:

In mini-esthetics, MID was decreased in extraction cases, while it increased in non-extraction cases. The BCR showed a statistically significant decrease in extraction as well as non-extraction cases.

In micro-esthetics, the GP was improved in both extraction as well as non-extraction cases after fixed orthodontic treatment. While the width-height ratio increased post-treatment in extraction cases, whereas non-extraction showed no significant difference. Furthermore, CH was increased in post-treatment non-extraction cases, while no significant changes were found in extraction cases.

Overall, the intergroup comparison revealed comparable esthetic outcomes between extraction and non-extraction treatment modalities, indicating that the choice of treatment should be guided by individual diagnostic requirements rather than esthetic considerations alone.

Footnotes

Declaration of Conflicting Interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Ethical Approval

The study was approved by the Institutional Ethics Committee (vide No: EC/NEW/INST/2024/4435-31).

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Informed Consent

Written informed consent was obtained from all participants prior to inclusion in the study.

ORCID iDs

Vibhuti Sharma

Shikha Thakur

References

Joy

, Kumar

Smile esthetics in orthodontics: A literature review. Int J Sci Res . 2018;7:367–371.

Kumar

, Antony

, Shaloob

, Parayaruthottam

, Raheesh

, Shahanamol

. Assessment of miniaesthetics in Class I malocclusion subjects who underwent orthodontic treatment with or without extraction of four premolars– A prospective study. J Contemp Orthod 2024; 8(3): 348–353.

Mackley

RJ.

An evaluation of smiles before and after orthodontic treatment. Angle Orthod . 1993;63(3):183–190.

Tauheed

, Shaikh

, Fida

Microaesthetics of the smile: Extraction vs. non-extraction. J Coll Physicians Surg Pak . 2012;22(4):230–234.

Boley

, Pontier

, Smith

, Fulbright

Facial changes in extraction and non-extraction patients. Angle Orthod . 1998;68:539–546.

Alomari

, Alhaija

ESJA

, Alwathnani

AM.

Smile micro-esthetics as perceived by dental professionals and laypersons. Clin Cosmet Investig Dent . 2021;13:595–605.

Prasad

, Tandon

, Singh

, Nagar

, Maurya

RP.

Comparison of smile esthetics after extraction and non-extraction orthodontic treatment. Indian J Orthod Dentofacial Res . 2018;4(4):182–189.

Janson

, Branco

, Fernandes

TMF

, Sathler

, Garib

Influence of orthodontic treatment, midline position, buccal corridor and smile arc on smile attractiveness. Am J Orthod Dentofacial Orthop . 2011;139(4):285–292.

Meiyappan

, Tamizharasi

, Senthilkumar

, Janardhanan

Natural head position: An overview. J Pharm Bioallied Sci . 2015;7(Suppl 2):S424–S427.

10.

Parayaruthottam

, Antony

Midline mini-implant-assisted true intrusion of maxillary anterior teeth for improved smile esthetics in gummy smile. Contemp Clin Dent . 2021;12(3):332–335.

11.

Sarver

, Ackerman

MB.

Dynamic smile visualization and quantification: Part 2. Smile analysis and treatment strategies. Am J Orthod Dentofacial Orthop . 2003;124(2):116–123.

12.

Heo

, Park

, Lee

, Kim

, Jung

, Chae

JM.

Maxillary incisor position-based orthodontic treatment with miniscrews. Semin Orthod . 2022;28(3):123–135.

13.

Ali

, Sukhia

, Fida

Effect of class II extractions and functional appliance treatment on smile esthetics. Dent Med Probl . 2020;57(2):157–163.

14.

Ahrari

, Heravi

, Rashed

, Zarrabi

, Setayesh

Which factors affect dental esthetics and smile attractiveness in orthodontically treated patients. J Dent (Tehran) . 2015;12(7):491–503.

15.

Maganzini

, Schroetter

, Freeman

Improvement in smile esthetics following orthodontic treatment: A retrospective study utilizing standardized smile analysis. Angle Orthod . 2014;84(3):492–501.

16.

Hulsey

CM.

An esthetic evaluation of lip-teeth relationships present in the smile. Am J Orthod . 1970;57:137–144.

17.

Konikoff

, Johnson

, Schenkein

, Kwarta

, Waldrop

TC.

Clinical crown length of the maxillary anterior teeth pre-orthodontics and post-orthodontics. J Periodontol . 2007;78:645–653.

18.

Snow

SR.

Esthetic smile analysis of maxillary anterior tooth width: The golden percentage. J Esthet Dent . 1999;11(4):177–184.

19.

Raj

, Heymann

, Hershey

, Ritter

, Casko

JS.

The apparent contact dimension and covariates among orthodontically treated and non-treated subjects. J Esthet Restor Dent . 2009;21:96–102.

20.

Waldrop

TC.

Gummy smile: The challenge of gingival excess: Prevalence and guidelines for clinical management. Semin Orthod . 2008;14:260–271.

21.

Herzog

, Konstantonis

, Konstantoni

, Eliades

Arch-width changes in extraction vs. non-extraction treatments in matched Class I borderline malocclusions. Am J Orthod Dentofacial Orthop . 2017;151(4):735–743.

22.

Baek

, Hwang

CJ.

Total intrusion and distalization of the maxillary arch to improve smile esthetics. Korean J Orthod . 2017;47(1):53–60.

23.

Murthy

, Ramani

Evaluation of natural smile: Golden proportion, red or golden percentage. J Conserv Dent . 2008;11:16–21.