Evaluation and correlation of facial and anterior teeth proportions in periodontally healthy patients with different facial types: A gender-based cross-sectional study

Abstract

Objective:

Significant association is exhibited between periodontal phenotypes and tooth crown morphology. The present study was planned to evaluate and correlate the facial and anterior teeth proportions among different facial types (FTs) based on gender in periodontally healthy patients.

Materials and Methods:

Two hundred patients within an age range of 20–40 years were assigned equally into two groups based on gender. The extraoral and intraoral parameters of facial height (FH), facial width (FW), crown width (CW), crown height (CH), and intercommissural width (ICOW) were recorded on digitized photographs. From these values, tooth type (TT), FT, and facial index (FI) were calculated.

Results:

The mean values of FI, CH, CW, and ICOW were greater while FH and FW lesser in females than males. The predominant presence of average FI (55%), mesoprosopic FT (58%), and triangular TT (51%) was observed in males, whereas in females, it was average FI (51%), mesoprosopic FT (55%), and triangular TT (51%). A2 tailed significant positive correlation was exhibited at (0.745) and (0.799) between TT and FI and (0.772) and (0.808) between TT and FT for males and females, respectively. Both the correlations were statistically significant (P < 0.05).

Conclusion:

The results suggest gender variability of the extraoral and intraoral parameters along with significant positive correlations between TT and FI and TT and FT. These extraoral and intraoral exhibits along with the periodontal phenotypes can be considered as critical aspects in smile designing procedures.

INTRODUCTION

Human evolution has led to reduced genetic inequalities and reproductive isolation, which are recognized as ethnic differences in biological characteristics. An individual’s pleasing appearance influences the prospects of social acceptance and is often related to understanding of beauty with belief of intellect and happiness.[1,2] The presence of proportionate facial geometric characteristics and anatomical structures are considered to be of prime importance in facial esthetics. Overall facial characteristics are a combination of dental and skeletal hard tissues which are presumably followed by soft tissues.[3,4]

Anthropometric measurements of the face and the intraoral dimensions of the maxillary anterior teeth have been linked in preliminary experiments, and these findings have been recommended as criteria for physicians to follow.[5,6] Extraoral dimensions which have been suggested include facial height (FH), facial width (FW), facial index (FI), bizygomatic width, and intercommisural width (ICOW). It was previously thought that the soft-tissue profile was closely related to basic skeletal configuration and would change in relation to age of an individual, but reports have indicated otherwise.[7]

FI signifies the dimensional details and is a numerical expression of ratio between FH and bizygomatic width. Based on FI, types of face shapes are classified into europrosopic, mesoprosopic, and leptoprosopic. A positive correlation was demonstrated to exist between tooth group width/height ratios within genders by Sterrett et al. while Owens et al. demonstrated gender and racial differences in gingival tissue display and type of malocclusion.[8,9] Literature reveals that gingival biotypes differ by gender, with men often having thicker biotypes than women.[10,11] Numerous researchers have found a positive association between the two parameters,[12,13] but there have also been contradicting reports of no correlation or a poor link.[14,15] According to Banister’s classification, the different face shapes can be categorized into the following five groups based on the FI.

At present, there is a paucity of knowledge regarding the correlation of extraoral and intraoral parameters in males and females. Thus, the aim of this study was to evaluate and correlate facial and anterior teeth proportions among different facial types (FTs) based on gender in periodontally healthy patients.

MATERIALS AND METHODS

The clinical investigation included 200 patients equally divided into two groups based on gender within age range of 20–40 years and was conducted between November 2021 and June 2022. The investigation protocol was designed as per the guidelines of Helsinki Declaration and presented to the Institutional Ethics Committee which approved same following which it was registered with Clinical Trials Registry (CTRI/2022/02/040678). The complete study protocol was explained to patients and their willingness for voluntary participation in study was obtained in writing before commencement. The study participants were recruited from those attending Department of Periodontics and Implantology of our institute.

In an article by Wadud et al.,[16] the authors compared facial proportions, analyzed maxillary anterior teeth proportions and determined the relationships between teeth with facial measurement. To obtain correlation of 0.35 between parameters, using two-sided test with 5% significance level and 80% power, estimated number of samples was 100 individuals. Hence, accordingly, 100 males and 100 females were included in the current study.

The included patients satisfied inclusion criteria which were: (a) Patients exhibiting properly aligned maxillary anterior teeth, (b) periodontally healthy individuals as assessed by plaque index (PI)[17] and gingival index (GI)[18] scores of 0–1, and (c) patients without any evidence of dental caries or restorations associated with teeth. Patients were excluded from trial if (a) they had a history of orthodontic treatment or any surgical periodontal treatment, (b) systemic diseases, or (c) were on medications which would have affected gingival tissues and (d) patients with facial asymmetry.

Included study participants were examined clinically and PI and GI were recorded at the initial visit. The study models were prepared at same visit with irreversible hydrocolloid alginate impression material (Mariflex, Septodent Ltd., India) which were then poured with stone plaster (Dental stone, Neelkanth Pvt. Ltd., India). Digital photographs in the frontal view from a standard distance of three feet were taken for participants at physiologic rest position. The uniformity in taking photographs ensured prevention of any discrepancies in photographic measurements and intruding in to patient’s personal space. These images were observed using Adobe Photoshop (Adobe Systems) under the resolution of 1680 × 1050 pixels. Additional standardization of photographs was done with 1:1.2 as an enlargement ratio. The vertical center of photograph was philtrum of maxillary lip. Photographic (Dental Treatment Simulation Software) and on cast parameters were measured by two examiners (RK and PT). Before the commencement of clinical trial, examiners were calibrated for precise recordings of measurements. The intra-class correlation coefficient as a measure of reliability of observations on different parameters was obtained considering two-way mixed effect model. Data show excellent inter-observer variability (>0.90) for different parameters in both male and female patients and correlations were statistically significant.

• A. FH: FH was measured on frontal image photograph by marking trichion point (frontline of hairs midline) to menton (lowest soft-tissue point of mandible) at rest [Figure 1]

• B. FW: FW was recorded on frontal image photograph as maximum horizontal distance between right and left facial boundary (bizygomatic width) at rest [Figure 1]

• C. FI: The proportional relationship of morphologic FH to maximum FW establishes FI[19] and overall facial form and can be calculated according to the following formula: FI = FH/FW × 100

Figure 1.

Representation of measurement of facial height (Trichion point to menton at rest), facial width (the maximum horizontal distance between right and left facial boundary i.e. bizygomatic width at rest) and intercommisural width (the distance between commissure on the right and the left side)

The values of FI were used to determine the incidence of certain FTs according to Martin-Saller’s Scale.[20] On the basis of FI, FT was classified as euryprosopic (Broad), mesoprosopic (average), and leptoprosopic (Narrow) with range of FI 79.0% to 83.9%, 84.0% to 87.9%, and 88.0% to 92.9%, respectively. The patients were placed in their respective categories based on their FI values

• D. Determination of crown width (CW): It was measured on the study model as maximum distance between mesial and distal contact points of tooth using digital caliper [Figure 2b]

• E. Determination of crown height (CH): It was measured on study model as maximum vertical distance from cervical margin to incisal edge of tooth using digital caliper [Figure 2c]

• F. Tooth type (TT): CW/length ratio – represents narrowness of one third of apical portion of clinical crown [Figure 2b and c]. Contact surface (CS)/length ratio – enabled differentiation of tooth forms into three morphology types [Figure 2a and c]. If CS/crown length ratio was: <43% – triangular crown shape; between 43% and 57% – tapered squarish crown shape; >57% – squarish crown shape[21,22]

• G. ICOW: This parameter was recorded on frontal image photograph as distance between commissure on right and left side [Figure 1].

Figure 2.

(a) Measurement of height of contact surface area. (b) Measurement of crown width (the maximum distance between the mesial and distal contact points of the tooth using digital caliper). (c) Measurement of crown height (maximum vertical distance from the cervical margin to the incisal edge of the tooth using digital caliper)

The primary outcome variables assessed in the current clinical trial were FH, FW, FI, CW, CH, TT, and ICOW while correlation of FI and FT with TT in males and females was recorded as secondary outcome variable.

Statistical analysis

All the data regarding age, FH, FW, FI, CW/CH ratio, and ICOW were presented as mean ± standard deviation and were compared using the unpaired t-test. Categorical variables (FT and TT) were expressed as actual numbers and percentages. FI between genders types was compared Mann–Whitney U-test. Similarly, FT and TT between genders was also compared using Mann–Whitney U-test. Correlation of TT with FI and FT among males and females was obtained using Spearman’s rho correlation test. Data analysis was done using IBM SPSS version 21 (IBM Corporation, New York, NY, USA). Statistical significance was tested at 5% level.

RESULTS

Two hundred periodontally healthy patients with an equal allocation were divided into two groups based on gender. The photographic, clinical, and on cast parameters of FH, FW, PI GI, CW, CH, and ICOW were recorded while FI, FT, and TT were calculated based on measurements.

Table 1 shows the comparison of parameters for all participants, which demonstrate FH and FW were greater in females as compared to males. The difference for FH did not achieve statistical significance while FW mean values of 175.63 ± 43.3 of females were significantly greater than those for males which were 164.42 ± 24.9 mm. All other parameters of FI, CW, CH, and ICOW were found to be greater for males than females. The differences in the mean values were significant for FI, CW, and CH while they were insignificantly different for ICOW with P = 0.753.

Table 1.

Comparison of parameters between male and female population

	Male, mean±SD	Female, mean±SD	Unpaired t-test	Significance (P)
FH (mm)	147.57±24.4	154.06±39.6	−1.394	0.165 (NS)
FW (mm)	164.42±24.9	175.63±43.3	−2.239	0.026*
FI (mm)	89.84±5.88	86.66±6.86	3.514	0.001*
CH (mm)	54.52±9.96	51.42±8.76	2.314	0.02*
CW (mm)	22.02±5.32	20.49±3.23	2.459	0.015*
ICOW (mm)	44.2±8.09	43.83±8.77	0.316	0.753 (NS)

*P<0.05 – significant difference. P>0.05 (NS) No significant difference. NS: Not significant; FH – Facial height; FW – Facial width; FI – Facial index; CH – Crown height; CW – Crown width; ICOW – Intercommisural width; SD – Standard deviation; P – Significance; t – Unpaired t test

Table 2 provides the difference between frequency and respective percentage of participants in various categories of FI, FT, and TT. The FI in the maximum number of patients belonged to average category with 55% in males, while it was 52% in females, followed by narrow category with 35% and 30% and least being exhibited in broad FI category with 10% and 18% in males and females, respectively. Gender differences for all the categories of FI did not achieve statistical significance. FT for all categories in both sexes followed same trend with maximum of them belonging to mesoprosopic with 58% and 55%, leptoprosopic being 34% and 30% while europrosopic being 8% and 15%, respectively, in males and females. The gender difference was statistically nonsignificant for each of categories of FT. The TT parameter exhibited crown morphologies being triangular shaped in maximum of patients at 51% followed by square shaped in 27% and least being 22% identified as tapered shaped in males. In females, maximum crown shapes were triangular at 51%, tapered at 29%, and square shaped at 20%, respectively, with differences being nonsignificant (P = 0.647).

Table 2.

Difference in facial index, facial type, and tooth type with respect to gender

Parameter	Category	Males, frequency (%)	Females, frequency (%)	Mann–Whitney U-test	Significance (P)
FI	Broad	10 (10)	18 (18)	4515	0.188 (NS)
	Average	55 (55)	52 (52)
	Narrow	35 (35)	30 (30)
Facial type	Average/mesoproscpic	58 (58)	55 (55)	4985	0.967 (NS)
	Broad/europrosopic	8 (8)	15 (15)
	Narrow/leptoprosopic	34 (34)	30 (30)
Tooth type	Square shape	27 (27)	20 (20)	4828	0.647 (NS)
	Tapered shape	22 (22)	29 (29)
	Triangular shape	51 (51)	51 (51)

P>0.05 (NS)–No significant difference; FI – Facial index; P – Significance; U – Mann Whitney U test

Correlation between the recorded variables of TT and FI was determined using Spearman’s rho correlation test which indicated a significant positive correlation between TT and FI amongst both males and females [Table 3]. A two-tailed significance was seen for FI and TT at <0.0001 with a correlation coefficient of 0.745 in males and for females correlation coefficient was 0.799. The said significance was calculated at P < 0.05. Similarly, when correlation between TT and FT amongst both gender was determined by Spearman’s rho correlation test a significant positive correlation was revealed between TT and FT [Table 4]. A two-tailed significance was seen for TT and FT at < 0.0001 with a correlation coefficient of 0.772 in males, while it was 0.808 in females. The significance was calculated at P < 0.05.

Table 3.

Correlation between tooth type and facial index among males and females

Gender	Applied test and variable	Tooth type	FI
Male	Spearman’s rho
	Tooth type
	Correlation coefficient	1	0.745**
	Significant (two-tailed)		<0.0001*
	n	100	100
	FI
	Correlation coefficient	0.745**	1
	Significant (two-tailed)	<0.0001*	.
	n	100	100
Female	Spearman’s rho
	Tooth type
	Correlation coefficient	1	0.799**
	Significant (two-tailed)	.	<0.0001*
	n	100	100
	FI
	Correlation coefficient	0.799**	1
	Significant (two-tailed)	<0.0001*	.
	n	100	100

*P<0.05– significant difference. P>0.05 (NS)– No significant difference. FI – Facial index

Table 4.

Correlation between tooth type and facial types among males and females

Gender	Applied test and variable	Facial type	Tooth type
Male	Spearman’s rho
	Tooth type
	Correlation coefficient	1	0.772**
	Significant (two-tailed)		<0.0001*
	n	100	100
	Facial type
	Correlation coefficient	0.772**	1
	Significant (two-tailed)	<0.0001*	.
	n	100	100
Female	Spearman’s rho
	Tooth type
	Correlation coefficient	0.808**	1
	Significant (two-tailed)	<0.0001*	.
	n	100	100
	Facial type
	Correlation coefficient	1	0.808**
	Significant (two-tailed)	.	<0.0001*
	n	100	100

*P<0.05– significant difference. P>0.05 (NS)– No significant difference

DISCUSSION

One of the most important factors in giving our patients a lovely smile is the integration of extra and intraoral anatomical features in clinical practice. Despite being widely acknowledged to be extremely important, the expected association between some of these traits has not yet been well studied, leaving a significant gap in our knowledge of these features. Maxillary anterior teeth especially tooth forms have been considered as one of governing factors often being correlated with facial forms.[23,24] The present study was conducted to evaluate and correlate FI, FT, CW, and CH of maxillary anterior teeth in males and females.

The intraoral and extraoral attributes are likely to differ in males and females which have been aptly reflected in the findings of the present study. Mean values of FW, FI, CW, CH, and ICOW parameters significantly differed between gender of participants. The values of FI, CW, CH, and ICOW were greater in males as compared to females while FW was found to be greater in females. These parameters especially extraoral have an influence over FT which have been categorized as mesoprosopic, leptoprosopic, and europrosopic. Mesoprosopic FT was found in the majority of the research population, both males and females. Leptoprosopic FT and europrosopic FT were the next most common types. These findings are somewhat similar and in partial agreement to those reported by previous trials with agreement being on most prevalent FT while observations regarding second most prevalent FT differed, although difference was minimal.[24,25,26] According to the authors of these research, europrosopic FT was the second most common FT in the sample population, particularly among females. A prior study[16] found that the majority of FT was leptoprosopic, which is contrary to the data above. Due to significant differences in genetic composition, these FT variations are mostly ascribed to various populations and ethnic divergences. Furthermore, uniformity in the study population being equally segregated as per age and gender in the present study findings appear to be more reasonable as compared to other trials.

The majority of FI in the current trial was average for both males and females, which is also consistent with FT, which is mesoprosopic. In addition, the FI was shown to be more noticeable in men than in women, which could be a sign that the male population is progressively moving from mesoprosopic to leptoprosopic. This may be inferred from the fact that girls have higher FH and FW than males, which implies that even though males are more composed due to these two factors, they are primarily classified as having average FI and FT.

The CW and CH investigated in the trial reveal that most of participants displayed triangular crown morphology in both the sexes, however, the second most predominant crown shapes in males were squarish while it was tapered in females. These observations are contradictory to Melo et al.[27] but are in accordance with those reported by Gobbato et al. and Kolte et al.[21,22] and have been assumed to be representation of sexual dimorphism amongst gender indicating masculine and feminine features for males and females respectively. The parameter of ICOW did not reveal any significant differences according to gender, but it differed from CW dimensions which are a consistent finding with previous investigations. The ICOW is affected with musculature of lips and its flexibility and so it is not considered to be a stable facial attribute.

Considering results of this study indicate greater FI, CW, and CH in male patients, a correlation between TT and FI parameters was examined. It was interesting to note that there was a significant positive correlation (0.745) and (0.799) between TT and FI in males and females, respectively, and this correlation was found to be statistically significant in both gender. On similar lines, correlation was appraised of TT and FT. The observations from the Spearman’s rank correlation coefficient also revealed a significant positive correlation (0.772) and (0.808) between TT and FT for males and females, respectively, and this correlation was found to be statistically significant in both gender. On interpretation, these observations would mean that tooth dimensions have a direct impact on facial dimensions as well as FI. This is arguably one of the few studies that have examined the relationship between extraoral and intraoral characteristics, and the results can be used to help formulating guidelines for physicians performing implant, periodontal, and restorative procedures.

The results of the present study revealed some of interesting aspects such as gender variations in extraoral and intraoral features and positive correlations between TT and FI and TT and FT mainly through dimensional influences of both parameters which can be of value for clinicians in crafting esthetic smiles. Additional studies with larger sample size with different ethnic study populations and age groups are desired to substantiate these findings and further improve on our understandings.

CONCLUSION

Within the limitations, the findings of the present study can be utilized in concurrence with treatment objectives to facilitate clinicians in imparting esthetically pleasing and functionally appropriate smiles to their patients. Significant positive correlations between TT and FT and TT and FI, as well as the gender variability of extraoral and intraoral parameters including FH, FW, FI, CW, CH, and ICOW, offer valuable guidelines that can be used in maxillary anterior sextant. These findings can be accepted as preliminary findings which may require further exploration for substantiation and advancing our understandings in these areas of specialty science.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.