Replacing the missing teeth to restore all functions as well as the aesthetic expectations that would be in close resemblance to the persons’ previous natural dentition has always been a great importance [1] . Choosing the size of the anterior teeth is one of the most important decisions to make when selecting maxillary anterior teeth. Selection of teeth can be very challenging especially to those in the most natural and aesthetically pleasing form easily acceptable by the patient and the dentist when there are no pre-extraction records available [2] . The lower teeth are usually set up to complement the arrangement of the maxillary anterior teeth of paramouth importance.

Patient’s records and information before extraction are always the best guides that should be collected with all wisdom. These records could be facial photographs, radiographs, casts and even previous dentures available. If no records are available, selecting the proper anterior teeth for edentulous patients could be difficult and confusing work [3] .

History has recorded several methods of determining tooth size from the use of dimensional measurements of the maxilla to the use or incorporation of facial or anthropological measurements [4] .

Facial measurements are one of the most frequently used measures for estimating maxillary teeth size in edentulous patients especially when there are no pre-extraction records available. In absence of the records they are various guidelines, such as bizygomatic width (BZW), inter pupillary distance (IPD), inter alar width (IAW), inter canthal distance (ICD), inter commissural width (ICoW) and other anatomical structures [5] [6] .

Different studies have been done to determine the width of the maxillary anterior using various anatomic, hard tissues, soft tissues and radiographic landmarks [7] [8] [9] . The anthropologic measurements have been proven useful in Caucasian population in selection of denture maxillary anterior; therefore, there is a need to investigate the Bantu population.

There are no studies conducted until now, which link inter-canine width and inter alar width, inter canthal distance or inter commissural width of Bantu, especially in DR Congo. Therefore, this study was undertaken to find credible evidence of the relationship between inter-canine width and inter alar width, inter canthal distance or inter commissural width in this population.

The Ethics committee of the National Center of Research for Dental Sciences in DR Congo approved the study protocol (CNRSB 1504.218).

Study design: It was a pilot study of 314 Congolese participants conducted in Prosthodontics Department, Faculty of Dental Medicine, University of Kinshasa. The participants’ medical records were obtained from the interview and dental examination.

The study population was established in April 2022, composed of participants aged at least 18 years, who did not present with a history of orthodontic treatment. In all, 314 participants firstly enrolled for this study, 202 dentulous were selected until August 2022 for this study.

Population selection: Participants were selected from Prosthodontics Department of University of Kinshasa. They ranged in age from 18 to 68 years. All participants Congolese had maxillary anterior teeth present without any caries, restorations, crowding, diastema or severe attrition were included. Those participants with a congenital abnormally, orbital disease, trauma, facial surgery, or pregnancy were excluded.

Data collection: Nature of the study was explained with participant information sheet, and an informed consent of all participants was obtained.

The inter-canine width (ICW), inter alar width (IAW), inter canthal distance (ICaD) and inter-commissural width (ICoW) of each participant were measured with a digital Vernier caliper (Mitutoyo, UK Ltd.,) (0.01 mm) ( Figure 1 ). Those parameters were divided in two categories:

1) Facial measurements: Facial parameters measured included:

The inter canthal distance (ICaD) is the distance between the median (inner) angles (canti) of one eye to the other. This distance was measured with a digital Vernier caliper without applying pressure by bringing the recording parts of the caliper just in contact with the medial angle ( Figure 2 ). For each participant, the ICaD was measured three times, and the average value was recorded.

The inter alar width (IAW) is the distance between the alae of the nose at the widest point. Two points were marked with a fine marked pencil on the widest outer surface of the alae of the nose on either side or width. Those two points were measured using a digital Vernier caliper without applying pressure by bringing the recording parts of the caliper just in contact with the outer surface. The participant was told to stop breathing shortly to avoid any change in shape of the nose ( Figure 3 ). For each participant, the IAW was measured three times, and the average value was recorded.

The inter-commissural width (ICoW) was determined by measuring the maxillary lip vermilion from commissure to commissure using a digital Vernier caliper without the application of pressure on the tissue in the relaxed state ( Figure 4 ). For each participant, the ICoW was measured three times, and the average value was recorded.

2) Dental measurements: Dental parameter to be measured is the inter-canine width (ICW). The ICW is the distance between the distal contact points of one canine to the other. It was measured indirectly using a dental floss. A dental floss was marked on one end prior to placement in the mouth. Using that point as reference, the dental floss was circumference along the curvature of the anterior dentition such that it passed along the contact point of all the teeth. The distal end of the canine teeth on both sides was then marked on the floss while it was stretched in the patient’s mouth. Floss was marked on both sides with the marker pencil. The distance between the two proximal contact points was measured using a Vernier caliper and recorded ( Figure 5 ). For each participant, the ICW was measured three times, and the average value was recorded.

Statistical analysis: Data, analysis and validation were performed the SPSS software (version 22.0, IBM SPSS Statistics, Chicago, IL, USA). Unpaired t-test was used, Kolmogorov-Smirnov (KS) test. Analysis of variance (ANOVA) test was used to test for comparability between socio-demographic characteristics dental measurements. Pearson’s correlation coefficient test was employed to determine the level of correlation between facial and dental parameters. Significance was set at P ≤ 0.01.

Of 314 participants who were enrolled in this study, only 202 were included ( Figure 6 ) and constituted the final sample, from which the data were collected

and statistically analyzed. Ninety-three (46%) participants were men and one hundred and nine (54%) were women ( Table 1 ). The age average was between 18 - 68 years old. The overall mean age was 40.62 ± 12.99 years. The different variables were higher for women than for men.

The descriptive statistics including mean, standard deviation, and values of recorded measurements grouped by sex are listed in Table 2 . Facial and dental measurements were greater in women than men with significant difference for ICW (p = 0.04). However, no significant difference was seen between men and women for IAW, ICaD and ICoW (p = 0.44, p = 0.23, p = 0.31 respectively) ( Table 3 ).

The correlation including Pearson’s correlation coefficient and P-values for all participants is demonstrated in Table 4 . For whole participants, none of the facial measurements showed significant correlation with ICW (p > 0.01) ( Table 5 ).

The main goal of this study was to determine the relationship between facial

Legend: ICoW: Inter-Commissural Width, ICaD: Inter-Canthus Distance, IAW: Inter-Alar Width, ICW: Inter-Canine Width.

*ANOVA. Legends: ICoW: Inter-Commissural Width, ICaD: Inter-Canthus Distance, IAW: Inter-Alar Width, ICW: Inter-Canine Width.

*Legend: ICoW: Inter-Commissural Width, ICaD: Inter-Canthus Distance IAW: Inter-Alar Width, ICW: Inter-Canine Width.

*Correlation is weak; r = Pearson correlation coefficient. Legends: ICW: Inter-Commissural Width, ICaD: Inter-Canthus Distance, IAW: Inter-Alar Width, ICW: Inter-Canine Width.

measurements and maxillary anterior teeth width in Bantu population. The mean widths of six maxillary anterior teeth are wider for women than men, as supported by previous studies [5] [10] . However, many studies on the others population have shown contrasting results [11] [12] [13] .

The average distance between the distal surfaces of maxillary canines is (56.82 mm ± 5.82) ( Figure 5 ), which is higher than the values reported by Omotayo et al. (55.15 mm ± 3.63), Arigbede et al. (47.4 mm), Deograde et al. (43.86 mm), Esan et al. (36.1 mm) [4] [14] [15] [16] . The minor variations may be attributed to differences in measurements methods and difference of the populations.

The study showed a statistically significant difference between sex and ICW (p = 0.048). This is similar to results gotten from previous studies [15] [17] . The higher values seen in women may be due to the influence of young women dominance factor, which also accounts for larger size of long bones and height differences seen between women and men in this study. Although the mean ICW is slightly higher in women (57.57 mm ± 6.22) than men (55.94 mm ± 5.21), this difference is not significant. In contrary, the previous studies reported the higher values in men than women [4] [9] .

In the present study, the average of ICaD was found to be 39.96 mm ± 8.87 for the whole study group and found to be 39.16 mm ± 8.91 and 40.64 mm ± 8.83 for men and women respectively. The part in which this variation is most significant, studies reported that ICaD is attained mostly by the first year and there is no difference between young and older groups in the inter canthal distance. Our result is similar to that obtained by Omotayo, Esan and Arigbede in their studies among the Nigerian for the whole participants that may indicate a similar ethnic background [4] [14] [16] . However, it is higher than the result obtained by others authors [9] [18] [19] . In the previous study, Bouhadana et al. demonstrate that the intercanthal distance varies significantly across different ethnicities and genders [20] . Participants from African backgrounds had higher ICaD values than their counterparts, and women had higher ICaD than men across ethnicities.

Additionally, the IAW in this work showed a mean of 43.70 mm ± 5.52, with statistically non-significant differences between men and women, which is similar to the findings of Alshamri et al. [12] , but contrasts with some published investigations [6] [21] [22] . The IAW differ among different ethnicity. Studies proposed that climate plays a role in determining the IAW. The nasal aperture becomes much wider in hot climate than cold. The wider nasal aperture existing in all African and Asian ethnic groups in both genders ( Figure 3 ) [23] . This study showed that the IAW was larger in women than men. This is similar to result from other study [24] .

When considering the ICoW of participants, it was found to be (59.17 mm ± 6.43) for the whole study group and found to be 64.10 mm ± 9.44 and 54.97 mm ± 8.12 for men and women respectively. The mean ICoW was higher than values reported for other ethnic groups by Omotayo et al. (57.85 ± 4.59), Arigbede et al. (53.3 mm), and Hamid et al. (46.84 ± 5.8) [4] [14] [21] , but lower than values reported by Esan et al. (74.6 mm ± 4.59) [16] . This variation may be due to different method used or it may indicate a multiple ethnic origin among population.

The Pearson’s correlation coefficient (r) between ICW and IAW, ICW and ICoW were negative with respectively (r = −0.09, p = 0.2) and (r = −0.07, p = 0.28). The correlation between ICW and ICaD were no significant (r = 0.014, p = 0.84).

This present study did not find any significant correlation between ICW and other facial measurements. In similar previous studies in Nigerian population, any significant correlation was reported [14] [16] .

Facial and dental measurements exhibit variations across age, sex, race, geographic locations, climate conditions, and the historical backgrounds of different subjects; these measurements are closely associated with human DNA, such as facial shape and features [25] .

Although this research was carefully prepared, there were some unavoidable limitations.

First, the sample size is only limited to 202 participants who were attending at teaching hospital. The second limitation was the geographical region that this study was conducted. The sample was only taken from the teaching hospital of Kinshasa University, thus the sample cannot be the representative of the rest of the population.

Within the limitations of this study, the results suggest that IAW, ICaD and ICoW cannot be used as a preliminary method for determining the width of the maxillary for anterior teeth for edentulous Bantu population (DR Congo).

This study received support from the National Center of Research in Dental Sciences, Kinshasa, Democratic Republic of the Congo. The authors would like to thank Professor Joke Duyck and Doctor Philippe Vuylsteke from KU Leuven University for their support and collaboration.