ORIGINALARTICLE

COINCIDENCE OF MAXILLARY DENTAL MIDLINE WITH THE ALA–CANTHUS INTERSECTION

POINT AMONG DENTAL STUDENTS

Sara Farid¹, Syed Nasir Shah², Asif Ullah Khan³, Aneela Jamshaid¹, Sana Saleem Khan¹, Humna Ali¹

How to cite this article

ABSTRACT

OBJECTIVES

Farid S, Shah S N, Khan A U, Jamshid

This study aimed to determine the frequency of dental midline coincidence

A, Khan S S, Ali H. Coincidence of

with the ala–canthus intersection point.

Maxillary Dental Midline with the

METHODOLOGY

Ala–Canthus Intersection Point

A cross-sectional study was conducted at the department of Prosthodontics,

Khyber College of Dentistry, Peshawar, from January to June 2025. A total

of 86 dental students, both male and female, were included in the study.

Facial portrait photographs were taken with a DSLR camera while smiling.

Photoshop software CC 2019 version 20.0 was used to analyze the

coincidence of the dental midline with the intersection point of ala-canthus

lines. Data were analyzed using SPSS version 22.0. Associations between

categorical variables were assessed using the Chi-square test or Fisher’s

exact test, where appropriate. A p-value < 0.05 was considered statistically

signicant.

Among Dental Students. J Gandhara

Med Dent Sci. 2026;13(3):76-80.

https://doi.org/10.37762/jgmds.13-3.851

Date of Submission:12-01-2026

Date Revised:

22-05-2026

Date Acceptance: 02-06-2026

²Professor Dean, Department of

Prosthodontics, Khyber College of

Dentistry, Peshawar

³Associate Professor, Department of

Prosthodontics, Khyber College of

Dentistry, Peshawar

RESULTS

The coincidence of the maxillary dental midline with the ala–canthus

intersection point was observed in 33.72% (29/86) of participants.

CONCLUSION

Correspondence

Maxillary dental midline coincidence was observed in only one-third of

participants. The dental midlines were coincident with the intersection point

of ala-canthus lines in less than half of the sample.

¹Sara Farid, Postgraduate Resident,

Department of Prosthodontics,

Khyber College of Dentistry

Peshawar

KEYWORDS: Coincidence, Dental Midline, Ala-Canthus Lines, Intersection

Point

+92-340-0914953

drsaralatif26@gmail.com

INTRODUCTION

when the dental and facial midlines are both aligned

and parallel.¹¹Faiz et al. reported that the coincident

Aesthetics is a primary concern in dentistry, particularly

in Prosthodontics, as it motivates patients to seek

treatment. In relation to one's age, the term "aesthetics"

alignment of the facial and dental midlines occurred in

approximately half of their study population, whereas

the remaining cases demonstrated non-coincidence.¹²

Although the assessment of facial midline has been

widely investigated, alternative facial landmarks for

determining dental midline remain underexplored. In

another study conducted by Niraula et al., 44 (30%) of

150 Nepalese subjects showed coincidence of the facial

midline with only the maxillary dental midline. The

dental midline discrepancy relative to the facial midline

was more prevalent in the maxillary arch. Midline

discrepancy was more common in males than in

females. The majority of the deviation was 1 mm,

followed by 2 mm and 3mm.¹³Although a dierent

landmark was used, Eskelsen et al. studied the bisector

of the interpupillary line as a reference for dental

midline determination in 102 subjects, among whom 12

(11.76%) males and 27 (26.47%) females demonstrated

coincidence.¹⁴The ala–canthus line connects the ala of

the nose to the outer canthus of the eye, both of which

are stable, easily identifiable soft tissue landmarks on

the mid-facial region. The intersection point of bilateral

ala–cantus lines provides a reproducible chairside

reference that may correspond to the maxillary dental

connotes beauty,

naturalness,

and

youthful

appearance.¹Improving facial aesthetics is one of the

main objectives of dental treatment.²An aesthetically

pleasing and well-balanced smile plays a crucial role in

the overall success of dental treatment.³People with

aesthetically appealing smiles have a greater chance of

being socially accepted, ensuring better interpersonal

relations.⁴Dental aesthetics is increasingly focused on

creating harmony between facial features and

dentition.⁵

Symmetry

refers

the

balanced

arrangement of structures in terms of size, shape, and

position on both sides of a central line, median plane, or

around a central axis.^6,7Asymmetry of the dental

midline and the extent to which deviation is considered

acceptable have been thoroughly explored in the

literature.⁸Patients are more likely to notice midline

discrepancies compared to other dental and occlusal

asymmetries.⁹Creation of a symmetrical dental midline

is a prerequisite in the arrangement of the anterior teeth

during

fixed

removable

dental

prosthesis

fabrication.¹⁰The optimal aesthetic outcome is achieved

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J Gandhara Med Dent Sci

Coincidence of Maxillary Dental Midline with the Ala-canthus Intersection Point

midline, which is critical in prosthodontic rehabilitation CC 2019, version 20.0, was used to analyze the

and aesthetic dental practice, where even minor photographs. A line was drawn from the outer canthus

deviations can compromise facial harmony and patient

satisfaction. Despite this potential, there is limited

evidence regarding the use of the ala–cantus

intersection point as a reference for dental midline

assessment. To the best of our knowledge, this is the

first study to specically evaluate its coincidence with

the maxillary dental midline across demographic and

morphological variables, highlighting the need for

further investigation.

of the eye to the ala of the nose on both sides of the

face, and the point of intersection was marked.

Coincidence of this point with the maxillary dental

midline was assessed and dened as alignment within

±1mm.

single calibrated examiner performed

measurements. Measurement reliability was assessed

after a two-week interval on a randomly selected 20%

subset of the total sample, and agreement for both intra-

examiner and inter-examiner reliability was evaluated

using Cohen‘s Kappa statistic. Data were analyzed

using SPSS version 22. Frequencies and percentages

were calculated for categorical variables. Associations

were analyzed using the Chi-square test orFischer‘s

exact test where appropriate. A p-value ≤ 0.05 was

considered statistically signicant. Results were

presented in tables.

METHODOLOGY

This cross-sectional study was conducted at the

department of prosthodontics from January to June

2025, after obtaining Institutional Review Committee

approval, Ref No. 48/ADR/KCD, Dated: 03-08-2023,

bearing CPSP approval number Ref no: CPSP/

REU/DSG-2021-019-3770. Dental students aged 18-30

years who provided informed consent were included.

RESULTS

Participants were required to have all maxillary and Intra-examiner reliability was almost perfect (κ = 0.89),

mandibular anterior teeth present and no restorations and inter-examiner reliability demonstrated substantial

involving the anterior teeth. Individuals with agreement (κ

0.80), indicating consistent and

generalized spacing, crowding, retained deciduous reproducible measurements across both examiners.

teeth, supernumerary teeth, malposed teeth, previous Table 1 presents the distribution of study variables

orthodontic treatment involving the anterior region, among the 86 participants. Males outnumbered females,

visible facial asymmetry, cleft lip, or facial scars were and the majority of participants were in the 25-30 age

excluded. A sample size of 86 participants was group. Mesofacial was the predominant facial form,

calculated using the WHO sample size calculator, followed by brachyfacial and dolichofacial forms.

assuming a prevalence of 12.5%, a 95% condence Regarding arch form, ovoid was the most frequently

level, and a 7% margin of error. Eligible participants observed, followed by tapering and square forms. The

were enrolled using convenience sampling. Dental coincidence of the maxillary dental midline with the

students were selected because they met the eligibility

ala–canthus intersection point was observed in 29 of 86

criteria more consistently, including intact anterior teeth participants (33.72%; 95% CI: 23.7%-43.7%).

and a relatively uniform age range. Patients presenting

Table 1: Frequency Distribution of Demographic and

Morphological Characteristics of Study Participants

to the Prosthodontics department frequently had

missing, restored, or altered anterior dentition, which

could inuence the assessment of dental midline

coincidence. Participants were seated upright with a

horizontal gaze and natural head position. Frontal full-

face smile photographs were captured using a Canon

DSLR camera (ISO: 100, Aperture: f/10, Shutter speed:

1/60-1/200s) mounted on a tripod at eye level. Three

photographs were taken per subject, and the most

accurate image demonstrating equal visibility of both

eyes and alae with no visible asymmetry was selected

for analysis. Facial form was assessed extraorally, and

dental arch form was recorded intraorally prior to image

capture. All photographs were captured using the same

camera under standardized lighting conditions at a

distance of 1.5m from the subject. Adobe Photoshop

Characteristics

N = 86

Age

18-24

25-30

38 (44.19%)

48 (55.81%)

Gender

Female

Male

24 (27.91%)

62 (72.09%)

Facial form

Mesofacial

Brachyfacial

Dolichofacial

Arch form

Ovoid

73 (84.88%)

7 (8.14%)

6 (6.98%)

67 (77.91%)

5 (5.81%)

14 (16.28%)

Square

Tapering

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Coincidence of Maxillary Dental Midline with the Ala-canthus Intersection Point

Table 1: Association Between Biliary Dilatation and CT Severity

employed dierent reference landmarks, populations,

and methodologies, which limit direct comparison. In

contrast, Niraula et al. observed slightly greater midline

deviation in males compared to females, suggesting a

possible sex-related trend that may be population-

specific.¹³Facial form was not signicantly associated

with maxillary dental midline coincidence in the

present study (p = 0.2). Among participants who

demonstrated coincidence, mesofacial individuals

accounted for the largest proportion (76%), followed by

dolichofacial (14%) and brachyfacial (10%) forms.

Since mesofacial was the predominant facial type in the

sample, its greater representation in the coincidence

group reects the sample composition rather than a true

association with facial form. Rakhshan et al.

demonstrated that facial form signicantly inuences

the perception of midline deviations among clinicians

and laypeople, supporting the clinical relevance of

facial form in midline evaluation.¹¹However, the non-

significant result in the present study (p = 0.2) is largely

Index (CTSI) Categories (n = 146)

Characteristics Coincidece

No Coincidence p-value

N = 57

N = 29

Age

18-24

12 (41%)

17 (59%)

26 (46%)

31 (54%)

0.7

0.6

0.2

25-30

Gender

Female

9 (31%)

15 (26%)

42 (74%)

Male

20 (69%)

Facial form

Mesofacial

Brachyfacial

Dolichofacial

Arch form

Ovoid

22 (76%)

3 (10%)

4 (14%)

51 (89%)

4 (7.0%)

2 (3.5%)

17 (59%)

2 (6.9%)

10 (34%)

50 (88%)

3 (5.3%)

4 (7.0%)

0.004

Square

Tapering

Total

Coincidence

attributable

the

disproportionately

small

33.72%

dolichofacial (n=6) and brachyfacial (n=7) subgroups,

which substantially reduced statistical power to detect

any true association. Future studies with a larger, more

balanced distribution across facial types are needed to

draw denitive conclusions about the inuence of

facial form on ala–cantus midline coincidence. Arch

form was the only variable signicantly associated with

maxillary dental midline coincidence in the present

study (p = 0.004). Among participants demonstrating

coincidence, the ovoid arch form accounted for the

highest proportion (59%), followed by tapering (34%)

and square (6.9%). However, since the ovoid was the

predominant arch form in the sample (77.91%), its

greater representation in the coincidence group reects

the sample‘s composition. The tapered arch form

showed a disproportionately higher representation in

the coincidence group than its prevalence in the sample

DISCUSSION

Although the facial midline has traditionally been

considered the primary reference for evaluating

maxillary dental midline position, recent studies

suggest that its reliability may vary across

populations.¹⁴In the present study, the coincidence of

the maxillary dental midline with the intersection point

of the ala-canthus lines was observed in only 33.72% of

participants, indicating that complete alignment is

uncommon. Age was not signicantly associated with

maxillary dental midline coincidence in the present

study (p = 0.7). This contrasts with Faiz et al., who

reported a signicant age-related association, possibly

due to their broader age range and larger sample size,

which may have increased the likelihood of detecting

age-related dierences.¹²Furthermore, the use of a

dierent reference landmark in the present study limits

direct comparison between the two ndings. Gender

was not signicantly associated with maxillary dental

midline coincidence in the present study (p = 0.6).

Among participants who demonstrated coincidence,

males showed a higher frequency than females, though

this dierence did not reach statistical signicance.

This nding is consistent with Maharjan et al., who

reported no signicant sex-based dierence in facial-

dental midline coincidence in a Nepalese population.¹⁵

Similarly, Melo et al. found no signicant inuence of

sex on maxillary midline alignment in a prospective

study of Caucasian patients.¹⁶Maiti et al. also reported

(16.28%), suggesting

midline coincidence. This nding is supported by

Kostic et al., who demonstrated signicant

relationship between dental arch shape and facial form,

genuine association with

indirectly suggesting that arch morphology is

clinically

relevant

determinant

midline

relationships.

The signicant association observed

here warrants further investigation in larger samples to

establish arch form as a reliable predictor of midline

coincidence with the ala–canthus intersection point.

Compared with other populations, the coincidence rate

of 33.72% is higher than that reported in a Peruvian

population (23.3%) but lower than those in Saudi

(57.5%) and North Bihar (80.6%) populations.^17,18,21

a non-significant sex dierence in their cross-sectional However, these comparisons must be interpreted

analysis of maxillary and mandibular midline alignment

cautiously, as the referenced studies used the facial

in an Indian population.¹⁹However, these studies midline rather than the ala–canthus intersection point,

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Coincidence of Maxillary Dental Midline with the Ala-canthus Intersection Point

5. Reviansyah FH, Ristin AD, Almughni WH, Yolanda Y, Takarini

applied dierent coincidence thresholds, and employed

V, Susilawati S, et al. Eco-friendly approaches to enhance dental

aesthetics and patient satisfaction using digital smile design: a

systematic review. Clin Cosmet Investig Dent. 2025;17:391–404.

https://doi.org/10.2147/CCIDE.S535436 PMID: 40306483.

distinct measurement methodologies, all of which limit

direct comparison. Among the variables examined, only

arch form demonstrated a statistically signicant

association with midline coincidence (p = 0.004), while

age, gender, and facial form did not reach signicance.

Given that a coincidence was observed in only one-

third of participants, clinicians should consider

integrating multiple anatomical landmarks rather than

relying solely on the ala–canthus intersection point for

dental midline determination.

6. Ko EWC, Huang CS, Lin CH, Chen YR. Orthodontic perspective

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face

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LIMITATIONS

Participants were selected by convenience sampling

from a single dental student group, which may

introduce selection bias and limit generalizability. The

relatively small sample size may have reduced the

strength of subgroup analyses. The use of two-

dimensional imaging to assess an inherently three-

Orthop.

2014;145(2):249–55.

https://doi.org/10.1016/j.ajodo.2013.02.034 PMID: 24485734.

10. Khan MF, Khezran Q, Sajid N. Coincidence of facial midline

with dental midline. Pak Oral Dent J. 2014;34(2):355–7.

11. Rakhshan V, Atashkar N, Rekabi A, Paydar Z, Hashemi Ashtiani

A, Ashoori N, et al. Eects of facial forms and midline deviations

on female facial beauty according to laypeople, orthodontists, and

restorative

dentists.

Sci

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dimensional

anatomical

relationship

may

have

https://doi.org/10.1038/s41598-024-71262-0 PMID: 39228787.

12. Faiz N, Jessy P, Nasim I, Maiti S. Evaluation of coincidence

between facial and dental midlines in relation to esthetics: a

retrospective study. Int J Dent Oral Sci. 2020;7(12):1216–21.

https://doi.org/10.19070/2377-8075-20000241

introduced measurement limitations and aected the

accuracy of midline coincidence determination.

CONCLUSIONS

13. Niraula N, Acharya R, Humagain M, Khurshid Z, Adanir N,

Rokaya D. Dental-facial midline: an esthetic-based classication.

The coincidence of maxillary dental arch midlines with

the intersection point of the ala-canthus lines was

observed in only one-third of the participants. This

indicates that complete alignment of dental and facial

reference points is uncommon. Clinicians should

consider multiple anatomical landmarks rather than rely

solely on a single reference point when planning

aesthetic or prosthodontic treatments to achieve optimal

functional and cosmetic outcomes.

Open

Dent

2021;15(1):95–100.

PMID:

https://doi.org/10.2174/1874210602115010095

34188470.

14. Eskelsen E, Fernandes CB, Pelogia F, Cunha LG, Pallos D,

Neisser MP, et al. Concurrence between the maxillary midline

and bisector to the interpupillary line. J Esthet Restor Dent.

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8240.2008.00229.x PMID: 19250546.

15. Maharjan S, Rajbhandari A, Pradhan R, Bajracharya M,

Manandhar P, Pant BD. Evaluation of facial and dental midline

discrepancies in Nepalese population. Europasian J Med Sci.

2020;2(2):51–5. https://doi.org/10.46405/ejms.v2i1.37

16. Melo M, Ata-Ali J, Ata-Ali F, Bulsei M, Grella P, Cobo T, et al.

Evaluation of the maxillary midline, curve of the upper lip, smile

line and tooth shape: a prospective study of 140 Caucasian

CONFLICT OF INTEREST: None

FUNDING SOURCES: None

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AUTHORS CONTRIBUTION

Sara Farid - Concept & Design; Data Acquisition; Data

Analysis/Interpretation;

Revision; Final Approval

Drafting

Manuscript;

Critical

Syed Nasir Shah - Concept & Design; Data Acquisition;

Drafting Manuscript; Supervision; Final Approval

Asif Ullah Khan - Concept & Design; Data Acquisition;

Drafting Manuscript; Critical Revision; Final Approval

Aneela Jamshaid - Concept & Design; Data Acquisition;

Drafting Manuscript; Final Approval

Sana Saleem - Concept & Design; Data Acquisition; Drafting

Manuscript; Final Approval

Humna Ali - Concept & Design; Data Acquisition; Drafting

Manuscript; Final Approval

The authors accept responsibility for all aspects of the work

and will ensure that any concerns regarding the accuracy or

integrity of any part are properly investigated and resolved.

LICENSE: JGMDS publishes its articles under a Creative Commons Attribution Non-Commercial Share-Alike license (CC-BY-NC-SA 4.0).

COPYRIGHTS: Authors retain the rights without any restrictions to freely download, print, share and disseminate the article for any lawful purpose.

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