Root and Root Canal Morphology Differences Between Genders: A Comprehensive in-vivo CBCT Study in a Saudi Population.

OBJECTIVES: To comprehensively explore the differences of all maxillary and mandibular permanent teeth in relation to number of roots, number of root canals, and root canal configuration between both genders in a Saudi Arabian population.
METHODS: This retrospective radiographic study comprised 208 subjects (48% males and 52% females) with a mean age 28.74±9.56 years. The CBCT images of the recruited subjects were evaluated for all permanent teeth. A careful examination was obtained by optimal visualization using all the software features. The data were analyzed using SPSS software program. Cohen's Kappa test was used for reliability and the Chi-squared test of association was used for the differences between both genders in relation to the study variables. A P-value < 0.05 was considered significant.
RESULTS: A total of 5254 maxillary and mandibular permanent teeth were evaluated. In relation to number of roots, there were no significant differences between both genders for all maxillary and mandibular teeth together (P= 0.064) as well as for maxillary and mandibular teeth separately (P= 0.315 and P= 0.100, respectively). A significant difference was found between males and females in relation to the number of canals of maxillary teeth (P= 0.014). For mandibular teeth, the significant level of difference was at the cut-off point (P= 0.050). For all maxillary and mandibular teeth together, the distribution among both genders was not significant (P= 0.082). The difference between both genders with regard to canal configuration of maxillary roots was highly statistically significant (P< 0.001). For mandibular teeth, the difference between males and females in relation canal configuration of anterior and premolar teeth was significant (P= 0.016) while, the difference was not significant when related to mesial roots of 1st and 2nd molars (P= 0.205). However, the difference was highly significant when related to distal roots of 1st and 2nd molars (P< 0.001).
CONCLUSION: No significant differences between both genders in relation to number of roots were found. Regarding the number of canals, significant differences were found only in three groups out of 14 groups of teeth with females who had a smaller number of canals than males. For canal configuration, two groups of maxillary teeth and three groups of mandibular teeth showed statistically significant differences between both genders.

Introduction

Differences between genders regarding some anatomical variations (), and the incidence and behavior of diseases are well documented in medicine (–) as well as in dentistry the differences between males and females regarding root morphology (, ) and the association with some diseases were also reported (, ). In the dental literature, many anatomical studies addressed different variations in root canal morphology according to ethnic background (–), while, scarce and inconclusive information are available regarding gender impact on teeth morphology (, ). The first in-vitro study reported the gender differences in all groups of teeth in the same patients was published in 2004 by Sert and Bayirli in a Turkish population (). The authors used clearing and dye technique, and concluded that gender needs to be considered carefully when performing the preoperative evaluation of nonsurgical endodontic treatment.

Upon conducting a literature search, there were only two published in-vivo studies which addressed the association of gender with number of roots and root canal system (RCS) in all groups of teeth. The first comprehensive in-vivo cone-beam computed tomography (CBCT) study on a Portuguese population was published in 2018 with a large sample size () showed that few differences were present between genders. The other in-vivo CBCT study was published in 2019, dealing with a Malaysian subpopulation (). It was reported that in general there were no significant differences between genders apart from few groups of teeth. Few in-vivo CBCT anatomical studies on different populations addressed the differences between genders in specific groups of teeth (, –). However, those studies did not give a complete picture of the influence of gender on teeth morphology. In addition, only few in-vivo CBCT anatomical studies were performed on a Saudi Arabian population which addressed gender differences in some groups of teeth (–). The results of those studies varied widely among different groups of teeth in favor of males or females while some teeth showed no significant differences.

Since the majority of the studies were not comprehensive (, -), the information retrieved are too fragmented and not conclusive, although some studies (, ) had a relatively large sample size for a specific group of teeth. The aim of the present in-vivo CBCT study, therefore, was to comprehensively evaluate the influence of gender on all permanent teeth morphology in a Saudi Arabian population, with a null hypothesis: no differences between genders with regard to root numbers, root canal numbers and root canal configurations.

Methodology

The sample:

A total of 208 patients (100 (48%) males and 108 (52%) females) with mean age 28.74±9.56 years (median= 26 years) ranging from 17 to 59 years were included in this study. From them, 5223 maxillary and mandibular permanent teeth were evaluated. The CBCT scans were retrieved from the database of College of Dentistry, Jazan University, Jazan, Saudi Arabia from the period from 2016 to 2018. The study protocol was approved by the local institutional review board. The teeth with fully developed roots and closed apices were included in the study. Previously treated-root canal or root canal treatment-initiated teeth; teeth with periapical lesions, calcification or resorption, and distorted CBCT images were excluded.

CBCT scans:

The CBCT machine used in this retrospective cross-sectional in-vivo study was 3D Accuitomo 170 (MORITA, Japan) and the scanning parameters were constant for all patients as follows: FOV 170-120 mm, 90 Kv, 5-8 mA, 17.5 seconds exposure time and 0.25mm voxel size. All CBCT images were processed and reconstructed using Morita’s i-Dixel 3D imaging software. Serial axial, coronal and sagittal sections were acquired to evaluate the number of roots, the number of the canals and RCS configurations on the basis of Vertucci’s classification. A careful examination was obtained by optimal visualization using all the software features, such as zooming, change in contrast and brightness. For reliability testing, the main author evaluated 20% of the sample twice within 4 weeks interval period.

Data analysis:

The collected data were introduced to the Statistical Package of Social Sciences software program for Windows (SPSS V25; IBM, Chicago, IL), and were subsequently coded and analyzed. The number of roots, the number of canals and canal system configurations of all permanent teeth apart from the third molars were evaluated. The differences by gender were assessed for the above-mentioned variables. The results were expressed as frequencies and percentages. The Chi-squared test was used for finding the differences between both genders. Kappa test was also used for intra-rater reliability. The level of significance for all statistical tests was set at P-value < 0.05.

Results

Cohen’s kappa test revealed an agreement of measurement with the value of 0.85 and P < 0.001.

Maxillary and mandibular teeth

In general, there were no significant differences between both genders in relation to the number of roots of maxillary and mandibular teeth separately (P= 0.315 and P= 0.100, respectively). Also, no significant differences were found for all maxillary and mandibular teeth together (P= 0.064). However, a significant difference was found between males and females in relation to the number of canals of maxillary teeth (P= 0.014) where the teeth with 1 or 3 canals were found more frequently in females than in males, while the teeth with 2 or 4 canals were found more frequently in males than in females. For mandibular teeth, the significant level of difference between males and females in relation to the number of canals was at the cut-off point (P= 0.050). For all maxillary and mandibular teeth together, the distribution among both genders in relation to the number of canals was not significant (P= 0.082) (Table 1) (Figure 1 and Figure 2).

Table 1

Distribution of maxillary teeth, mandibular teeth, and all maxillary and mandibular teeth together among both genders according to number of roots and number of canals

		Upper Teeth				Lower Teeth				ALL Teeth
		M	F	Total	P	M	F	Total	P	M	F	Total	P
Number of roots
	1 root	777 (64.4)	836 (65.3)	1613 (64.9)	0.315	962 (74.5)	1033 (76.9)	1995 (75.7)	0.100	1739 (69.6)	1869 (71.2)	3608 (70.5)	0.064
	2 roots	130 (10.8)	115 (9.0)	245 (9.9)		321 (24.5)	296 (22.0)	617 (23.4)		451 (18.1)	411 (15.7)	862 (16.8)
	3 roots	299 (24.8)	329 (25.7)	628 (25.3)		8(0.6)	15 (1.1)	23 (0.9)		307 (12.3)	344 (13.1)	651 (12.7)
Total		1206 (48.5)	1280 (51.5)	2486 (100.0)		1291 (49.0)	1344 (51.0)	2635 (100.0)		2497 (48.8)	2624 (51.2)	5121 (100.0)
Number of canals
	1 canal	621 (51.5)	679 (53.0)	1300 (52.3)	0.014*	751 (58.2)	851 (63.3)	1602 (60.8)	0.050	1372 (54.9)	1530 (58.3)	2902 (56.7)	0.082
	2 canals	283 (23.5)	268 (20.9)	551 (22.2)		220 (17.0)	203 (15.1)	423 (16.1)		503 (20.1)	471 (17.9)	974 (19.0)
	3 canals	59(4.9)	98 (7.7)	157 (6.3)		260 (20.1)	229 (17.0)	489 (18.6)		319 (12.8)	327 (12.5)	646 (12.6)
	4 canals	243 (20.1)	235 (18.4)	478 (19.2)		60 (4.6)	61 (4.5)	121 (4.6)		303 (12.1)	296 (11.3)	599 (11.7)
Total		1206 (48.5)	1280 (51.5)	2486 (100.0)		1291 (49.0)	1344 (51.0)	2635 (100.0)		2497 (48.8)	2624 (51.2)	5121 (100.0)
* Significant at P< 0.05

Figure 1

CBCT axial sections showing maxillary (a) and mandibular (b) anterior and premolar teeth with one canal and Vertucci Type I

Figure 2

CBCT axial sections showing maxillary molars with 4 canals and premolars with 2 canals (a); and mandibular molars with 3 canals and premolars with 2 canals (b)

The difference between both genders with regard to canal configuration of maxillary roots was highly statistically significant (P< 0.001). The roots with Vertucci type I, III, and V were more frequently found in females than in males while, the roots with Vertucci type II, IV, VI, and VII were more frequently found in males than in females. For mandibular teeth, the difference between males and females in relation to the canal configuration of anterior and premolar teeth was significant (P= 0.016), while the difference was not significant when related to the canal configuration of mesial roots of the first and the second (P= 0.205). However, the difference between males and females was highly significant when related to canal configuration of distal roots of the first and the second molars together (P< 0.001) (Table 2) (Figures 3 and 4).

Table 2

Distribution of maxillary teeth, mandibular teeth, and all maxillary and mandibular teeth together among both genders according to canal configuration

		Maxillary teeth				Mandibular teeth
		All teeth†				Anterior teeth and Premolars				Molars (1st and 2nd molars)
										Mesial root				Distal root
		M	F	Total	P	M	F	Total	P	M	F	Total	P	M	F	Total	P
Vertucci types
	Type I	672 (55.7)	771 (60.2)	1443 (58.0)	<0.001*	751 (77.7)	851 (81.7)	1602 (79.8)	0.016*	10(3.1)	14(4.6)	24(3.8)	0.205	267 (82.4)	255 (84.2)	522 (83.3)	<0.001*
	Type II	132 (10.9)	122 (9.5)	254 (10.2)		0(0.0)	0(0.0)	0(0.0)		89(27.5)	102 (33.7)	191 (30.5)		1(0.3)	11(3.6)	12(1.9)
	Type III	39 (3.2)	61 (4.8)	100 (4.0)		163 (16.9)	124 (11.9)	287 (14.3)		29(9.0)	29(9.6)	58(9.3)		27(8.3)	26(8.6)	53(8.5)
	Type IV	302 (25.0)	245 (19.1)	547 (22.0)		0(0.0)	0(0.0)	0(0.0)		170 (52.5)	131 (43.2)	301 (48.0)		0(0.0)	2(0.7)	2(0.3)
	Type V	40 (3.3)	69 (5.4)	109 (4.4)		49 (5.1)	63 (6.1)	112 (5.6)		26(8.0)	27(8.9)	53(8.5)		29(9.0)	9(3.0)	38(6.1)
	Type VI	9(0.7)	3(0.2)	12 (0.5)		0(0.0)	0(0.0)	0(0.0)		0(0.0)	0(0.0)	0(0.0)		0(0.0)	0(0.0)	0(0.0)
	Type VII	5(0.4)	3(0.2)	8(0.3)		0(0.0)	1(0.1)	1(0.0)		0(0.0)	0(0.0)	0(0.0)		0(0.0)	0(0.0)	0(0.0)
	Others	7(0.6)	6(0.5)	13 (0.5)		4(0.4)	2(0.2)	6(0.3)		0(0.0)	0(0.0)	0(0.0)		0(0.0)	0(0.0)	0(0.0)
Total		1206 (48.5)	1280 (51.5)	2486 (100.0)		967 (48.2)	1041 (51.8)	2008 (100.0)		324 (51.7)	303 (48.3)	627 (100.0)		324 (51.7)	303 (48.3)	627 (100.0)
* Significant at P< 0.05; † Only mesiobuccal roots of maxillary teeth were included in the analysis

Figure 3

CBCT images showing sagittal sections (a) of mandibular central incisors with 2 canals and Vertucci type III; and coronal sections (b) of mandibular first premolar with 2 canals and Vertucci type V.

Figure 4

CBCT coronal sections showing different Vertucci types in maxillary premolars; Type II (a), Type IV (b), Type III (c), Type V (d).

Maxillary teeth (Tables 3 and 4)

Central incisors

In comparison between males and females, 200 (52.1%) teeth were found in females and 184 (47.9%) teeth in males. However, the significance of difference could not be computed because all teeth (100%) in males and all teeth (100%) in females had one root, one canal, and Vertucci type I.

Lateral incisors

Similar to central incisors, the number of teeth in females was larger than in males (200 (52.1%) teeth in females compared to 184 (47.9%) teeth in males). Also, the significance of difference was not applicable because all teeth (100%) in females and all teeth (100%) in males had one root, one canal, and belonged to Vertucci type I.

Canines

There were 200 (52%) teeth in females and 180 (48%) teeth in males. All teeth (100%) in both genders had one root. All teeth (100%) in females had one canal while, in males, 180 (97.8%) teeth had one canal, and 4 (2.2%) teeth had 2 canals, with no significant differences between both genders (P= 0.052). Similarly, all teeth (100%) in females belonged to Vertucci type I while, 180 (97.8%) teeth in males belonged to Vertucci type I, and 4 (2.2%) teeth belonged to Vertucci type III. No significant differences between both genders were found (P= 0.052).

First premolars

Out of 176 (50.1% of all maxillary first premolars) teeth in females, 53.4% had 2 roots, 45.5% had one root, and 1.1% (2 teeth) had 3 roots. However, 108 (61.7%) out of 175 teeth in males had 2 roots, 36% had one root, and 2.3% had 3 roots. The difference between both genders was not statistically significant (P= 0.161). The majority of teeth in both genders (96.0% of teeth in females and 90.3% of teeth in males) had 2 canals. No teeth in females had 4 canals, and only 2 teeth in males had 4 canals. The teeth with one canal and 3 canals were found in fewer percentages. Similarly, no significant differences were found regarding the number of canals (P= 0.125). A significant difference was found between both genders in relation to Vertucci types (P< 0.001). More than half of teeth (59.7%) in females had Vertucci type IV, followed by Vertucci type V (21.0%), and Vertucci type III (11.4%). In males, 68.0% of teeth had Vertucci type IV, followed by Vertucci type II (10.3%), and Vertucci type V (8.6%).

Second premolars

The distribution of teeth was approximately similar in both genders (50.7% in males compared to 49.3% in females). The majority of teeth in both genders had one root with no significant differences (P= 1.000). About two thirds (65.9%) of teeth in males and about half of teeth (55.9%) in females had 2 canals with a statistically significant difference (P= 0.046). The Vertucci type I was found in 62 (34.1%) teeth in males followed by Vertucci type IV which was found in 41 (22.5%) teeth. However, Vertucci type III was found in 31 (17.5%) teeth in females followed by Vertucci type IV which was found in 28 (15.8%) teeth. Nevertheless, no significant differences were found between males and females (P= 0.064).

First molars

In total, 354 molars were evaluated (330 with 3 normal roots and 24 molars were fused-rooted)

Molars with 3 normal roots (n= 330 teeth):

In comparison between both genders, all teeth in males (n= 151, representing 45.76% of 330 molars) and all teeth in females (n= 179, representing 54.24% of 330 molars) had 3 roots with Vertucci type I in distobuccal (DB) and palatal (P) roots. The significance test was not applicable regarding the number of roots. However, a significant difference between males and females was found with regards to the number of canals (P= 0.007). Teeth with 4 canals were found in higher percentages in males than in females (91.4% in males compared to 81.0% in females) while, 19.0% of teeth in females and 8.6% of teeth in males had 3 canals. Regarding Vertucci types in mesiobuccal roots, the majority of teeth in males and females (52.3% and 44.7%, respectively) had Vertucci type IV followed Vertucci type II (35.8% of teeth in males and 34.6% of teeth in females). No significant differences between both genders were found (P= 0.068).

Fused-rooted molars (24 teeth):

The prevalence of fused-rooted first molars is 7% out of the total sample (354 molars) with 0.6% presence of merged canals (only in 2 teeth). The distribution of teeth with non-merged canals from the fused-rooted molars (n= 22) among both genders is presented in Table 5. No significant differences between both genders were found in relation to the number of roots, the number of canals, and Vertucci types.

Table 5

Distribution of 1st and 2nd maxillary molars with fused roots among both genders according to number of roots, number of canals, and canal configuration

		1st molar (N= 22)				2nd molar (N= 53)
		M	F	Total	P	M	F	Total	P
Number of roots
	1 root	5 (33.3)	1 (14.3)	6 (27.3)	0.616	1 (4.5)	6 (19.4)	7 (13.2)	0.218
	2 roots	10 (66.7)	6 (85.7)	16 (72.7)		21 (95.5)	25 (80.6)	46 (86.8)
Total		15 (68.2)	7 (31.8)	22 (100.0)		22 (41.5)	31 (58.5)	53 (100.0)
Number of canals
	3 canals	5 (33.3)	2 (28.6)	7 (31.8)	1.000	18 (81.8)	20 (64.5)	38 (71.7)	0.223
	4 canals	10 (66.7)	5 (71.4)	15 (68.2)		4 (18.2)	11 (35.5)	15 (28.3)
Total		15 (68.2)	7 (31.8)	22 (100.0)		22 (41.5)	31 (58.5)	53 (100.0)
MB. Vertucci types
	Type I	5 (33.3)	2 (28.6)	7 (31.8)	0.273	18 (81.8)	20 (64.5)	38 (71.7)	0.452
	Type II	5 (33.3)	5 (71.4)	10 (45.5)		2 (9.1)	3 (9.7)	5 (9.4)
	Type IV	4 (26.7)	0 (0.0)	4 (18.2)		2 (9.1)	7 (22.6)	9 (17.0)
	Type V	1 (6.7)	0 (0.0)	1 (4.5)		0 (0.0)	1 (3.2)	1 (1.9)
Total		15 (68.2)	7 (31.8)	22 (100.0)		22 (41.5)	31 (58.5)	53 (100.0)
Only mesiobuccal roots were included in the analysis, other roots had Vertucci type I

Second molars

In total, 370 molars were evaluated (292 with normal 3 roots and 78 were fused-rooted)

Molars with normal 3 roots: (292 molars)

All teeth in males (n= 144, representing 49.3% of 292 molars) and all teeth in females (n= 148, representing 50.7% of 292) had three roots, with Vertucci type I in DB and P roots. A significant difference was found between both genders in relation to number of canals (P= 0.047). More than two thirds (72.2%) of teeth in males had 4 canals and 27.8% had 3 canals while, 60.8% of teeth in females had 4 canals and 39.2% had 3 canals. The most frequent Vertucci type in mesiobuccal roots in males was Vertucci type IV (43.8% of teeth), followed by Vertucci type I (26.4% of teeth), and Vertucci type II (25.7% of teeth). However, this is was not the case in females where the most frequent Vertucci type in mesiobuccal roots was Vertucci type I (39.2% of teeth), followed by Vertucci type II (27.0% of teeth), and Vertucci type IV (21.6% of teeth). Highly significant difference between males and females was found (P< 0.001).

Fused-rooted molars: (78 molars)

There were 78 fused-rooted maxillary second molars representing 21.1% of all maxillary second molars. Out of them, 32.1% (25 teeth) had merged canals and 53 (67.9%) teeth with fused roots but non-merged canals. The distribution of these teeth among both genders is presented in Table 5. No significant differences between males and females were found in relation to number of roots, number of canals, and Vertucci types.

Mandibular teeth (Tables 6-8)

Regarding the comparison between males and females, both genders had all their mandibular central incisors with one root. Significance tests could not be computed. Females had more teeth with one canal (170 teeth, representing 79.4% of teeth in females) compared to males who had 132 teeth (67.3% of teeth in males) with one canal. However, the prevalence of two canals was higher in males than in females (64 teeth, representing 32.7% of teeth in males) who had only 44 teeth (20.6% of teeth in females) with 2 canals. The difference was statistically significant (P= 0.007). Similarly, there was a significant difference (P= 0.007) in relation to Vertucci classification among both genders with the same percentages applied.

Amongst 214 teeth in females, there were 213 (99.5%) teeth with one root, and only one tooth (0.5%) was found with 2 roots. Similarly, amongst 198 teeth in males, there were 197 (99.5%) teeth with one root, and only one tooth (0.5%) was found with 2 roots. No significant differences were observed (P= 1.000). One hundred and fifty two (71.0%) teeth in females and 133 (67.2%) in males had one canal, while 62 (29.0%) teeth in females and 65 (32.8%) teeth in males had 2 canals, with no significant differences (P= 0.455). Regarding Vertucci classification, 133 (67.2%) teeth in males had Vertucci type I, 63 (31.8%) teeth had Vertucci type III, and only 2 (1.0%) teeth had Vertucci type V. In females, 152 (71.0%) teeth had Vertucci type I, 60 (28.0%) teeth had Vertucci type III, and only 2 (1.0%) teeth had Vertucci type V. No significant differences were found between both genders (P= 0.698).

Amongst 197 mandibular canines in males, there were 195 (99.0%) with one root and 2 (1.0%) teeth with 2 roots, while amongst 213 mandibular canines in females there were 204 (95.8%) teeth with one root, and 9 (4.2%) teeth with 2 roots. No significant differences were found between both genders (P= 0.064). One hundred and eighty four (93.4%) mandibular canines in males had one canal, while 188 (88.3%) mandibular canines in females had one canal. No significant differences were observed between both genders (P= 0.088). Vertucci type I was more frequent in males than in females (93.4% compared to 88.3%), while Vertucci types III and V were more frequent in females than in males. The significant level of difference between both genders was near the cut-off point (P= 0.049).

First premolars

Although the prevalence of teeth with one root was higher in females than in males (100% compared to 98.9%), no significant differences between both genders was found (P= 0.224). Similarly, no significant differences (P= 0.229) were found between both genders with regard to the number of canals. However, a significant difference (P= 0.012) was found between both genders in relation to canal configuration. The teeth with Vertucci types I and V had higher prevalence in females than in males, while the teeth with Vertucci type III had higher prevalence in males.

Regarding comparison between genders, all teeth (100.0%) in males and all teeth (100.0%) in females had one root. No significant differences (P= 0.055) were found between both genders with regard to the number of canals although the prevalence of teeth with one canal was higher in females compared to males (99.0% compared to 94.7%, respectively). Similarly, no significant differences (P= 0.098) were found in relation to canal configuration. Nevertheless, the prevalence of the teeth with Vertucci type I in females was 189 (99.0%) compared to their male counterparts, 178 (94.7%).

Most teeth in both genders had 2 roots and 3 canals with no significant differences (P= 0.305 and P= 0.987, respectively). Similarly, no significant differences (P= 0.471) were found between both genders with regard to Vertucci types in mesial canals. However, a significant difference (P= 0.005) was found between both genders in relation to Vertucci types in distal canals, with higher prevalence of Vertucci types II and III in females and Vertucci type V in males.

No significant differences were found between both genders in relation to the number of roots (P= 0.162, with higher prevalence of teeth with 2 roots in males), the number of canals (P= 0.253, with higher prevalence of teeth with 3 canals in males), Vertucci types in mesial canals (P= 0.336, with higher prevalence of teeth with Vertucci type IV in males and Vertucci type II in females), and Vertucci types in distal canals (P= 0.112, with higher prevalence of teeth with Vertucci type I in females). The prevalence of C-shaped canal configuration was found in 29 cases out of 367 teeth (7.9%) in mandibular second molars with no significant differences found between both genders

Discussion

Over the past few years, various techniques have been developed to study root canal morphology including CBCT which has increased in popularity nowadays although the micro-CT evaluates the root canal morphology with high resolution, thus producing accurate results. This technique, however, does not work well in daily practice settings to examine patients (), whereas CBCT, compared to other techniques, is a clinically non-invasive tool being used in daily practice which, apart from being reliable, accurately detects root canal anatomy (, ). In-vivo CBCT is a great tool for retrospective prevalence studies because a big number of patients could be examined safely. Therefore, this tool was chosen for this study to provide a large number of teeth with known genders for a more reliable outcome. Also, in this study, we overcame the problem of exposing the subjects to unnecessary radiation doses by retrieving old records from the database and by using a voxel size 0.25 μm of the CBCT machine, which is similar to another in-vivo CBCT study which has evaluated the root anatomy of all groups of teeth successfully ().

In the present study, a comparison between males and females regarding the number of roots, the number of root canals, and root canal configurations according to Vertucci’s classification was performed. Regarding the number of roots, no significant differences were found between genders in all 14 groups of teeth. This is in agreement with an in-vivo CBCT study of all permanent dentition in a Malaysian subpopulation (). However, another comprehensive in-vivo CBCT study in a Portuguese population reported significant differences between genders in four of 14 tooth groups with females who had a smaller numbers of roots per tooth in maxillary first premolars, and second molars, while mandibular canines showed the opposite (). In a Saudi population, anatomical studies using in-vivo CBCT are consistent with our findings with no significant differences between genders in the number of roots of maxillary premolars (), maxillary first molars (), mandibular canines (), and mandibular first molars (). Another two in-vivo CBCT studies in different populations reported some significant differences between genders in number of roots of maxillary and mandibular first and second premolars, where they found that males had higher prevalence of 2-rooted premolars, while females had higher prevalence of single-rooted premolars (, ). Also, similar results were obtained in other CBCT studies on maxillary and mandibular molars, where females had lower prevalence of roots compared to males (, , ). In the literature, there is a tendency of females to have a smaller number of roots per tooth while, many studies, however, support that there were some CBCT studies reported otherwise but with no significant differences (, , ).

Generally, the internal canal morphology follows the external anatomy of the root (), and that might have an impact on a smaller number of roots in different genders. In regards to the number of canals in the present study, only 3 groups out of 14 teeth groups (two in maxillary teeth and one in mandibular teeth) showed significant differences between genders. Maxillary first and second molars had 4 canals with higher percentages in males than in females. However, in mandibular teeth groups, only central incisors showed statistically significant differences (P= 0.007), where males had a larger number of teeth with 2 canals compared to females. In a study of all permanent dentition in a Malaysian subpopulation (), only 2 groups of teeth (second premolars and second molars) showed that males had a significantly larger number of canals compared to females, while the rest of teeth groups had no significant differences. In a Saudi population, some studies reported similar results to our findings, where in maxillary first molars males had a significantly larger number of canals compared to females (). However, other studies reported that there were no significant differences between genders regarding maxillary premolars, mandibular canines, and mandibular first molars (, ).

In the present study, we also investigated the association between genders with RCS configurations. In total, maxillary teeth showed highly statistically significant differences (P< 0.001) between both genders with regard to canals configurations where, roots with Vertucci type II, IV, VI, and VII were more frequent in males than in females, while the roots with Vertucci type I, III, and V were more frequent in females. However, only 2 groups (first premolars and second molars) out of 7 teeth groups of maxillary teeth showed statistically significant differences between both genders in relation to canal configurations. These findings are generally consistent with a study performed in a Portuguese population where all teeth showed higher prevalences of Vertucci type I configurations in females, which is highly statistically significant in both maxillary premolars (). However, in a Malaysian subpopulation there were no statistically significant differences between genders regarding RCS configurations in all teeth groups (). In addition, a study of maxillary first premolars in a Saudi population () showed no differences between genders regarding the canal configuration, while the findings of German subpopulation study () are in agreement with our results where Vertucci type I for maxillary first premolars had higher prevalence in females. Another study in a Korean population () on maxillary second molars, mesial buccal roots, showed similar canal configurations compared to our study with higher prevalence of Vertucci type I in females. However, the differences were not statistically significant. In contrast, other studies in different populations reported (with no significant differences) higher prevalence of Vertucci type I in mesial buccal roots of both maxillary molars in males compared to females (, ). The differences in findings of the above mentioned studies might be related to ethnic background and/or sample size.

In mandibular teeth, generally, there were significant differences between males and females in relation to the canal configuration of anterior and premolar teeth (P= 0.016), and distal roots of first and second molars together (P< 0.001). Specifically, only three groups out of seven teeth groups showed statistically significant differences between genders in regards to canal configurations. The prevalence of Vertucci type I canal configuration was significantly higher in females in mandibular central incisors and first premolars, whereas in distal roots of mandibular first molars, the prevalence of Vertucci types II and III was highly significant in females and Vertucci type V in males. In a Portuguese study (), the results showed differences in five of the seven groups of mandibular teeth with a higher tendency for Vertucci type I in females, while in central incisors and first premolars the differences were significant with females who had higher prevalence of Vertucci type I. Regarding canines, males had a significantly higher prevalence of Vertucci type I. These results are generally in agreement with our findings. In another comprehensive CBCT study (), the authors found no statistical differences between genders regarding canal configuration, except that females had a significantly higher prevalence of second molar teeth with C-shaped morphology, while in our study, mandibular second molars with C-shaped canals had no gender association. In a Saudi population, the prevalence of Vertucci type I in mandibular canines in female patients was significantly higher than in males (), which is contrary to our findings where no statistical differences between genders were found. Another study () in the same population on mandibular first molars showed no association between genders and canal configurations, whereas our study showed a significant difference in distal roots canal systems, with higher prevalence of Vertucci types II and III in females and Vertucci type V in males. These inconsistencies between studies in the same Saudi population could be related to the region in the same country where the sample was obtained and the sample size. In addition, studies from different populations showed that females have higher percentage of Vertucci type I compared to males in mandibular central incisors () and first premolars (). All the above mentioned studies were in-vivo CBCT anatomical studies addressing gender differences related to roots and root morphology.

The present in-vivo CBCT study is the first comprehensive study conducted in a Saudi Arabian population evaluating all teeth groups in the same individuals with a large sample. The results from the available literature led to a hypothesis that males tend to have a larger number of roots and root canals than females regardless of the statistical significance of the results. However, previous studies that were performed on specific teeth groups might not have observed this tendency (). So far, only 3 studies (, ) including our study which used in-vivo CBCT on all teeth groups have partially accepted this hypothesis. Other in-vivo CBCT studies are recommended on all teeth groups in different populations with a large sample, adding to the present ones, which could either support the global tendency that is mentioned in the hypothesis or prove that the differences exist only in the specific group(s) of teeth.

Conclusion

Within the limitations of the present study, the following conclusions could be drawn: No significant differences in relation to the number of roots between both genders were found. Significant differences with regard to number of canals were detected only in three groups out of 14 groups of teeth with females having a smaller number of canals; In relation to canal configuration, two groups of maxillary teeth and three groups of mandibular teeth showed statistically significant differences between both genders.

Table 3

Distribution of maxillary teeth among both genders according to number of roots, and number of canals

		Central		Lateral		Canine		1st Premolar		2nd Premolar		1st Molar			2nd Molar
		M	F	M	F	M	F	M	F	M	F	M	F	M		F
Number of roots
	1 root	184 (47.9)	200 (52.1)	184 (48.2)	200 (51.8)	184 (100.0)	200 (100.0)	63 (36.0)	80 (45.5)	160 (87.9)	156 (88.1)	0(0.0)	0(0.0)	0(0.0)		0(0.0)
	2 roots	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	108 (61.7)	94 (53.4)	22 (12.1)	21 (11.9)	0(0.0)	0(0.0)	0(0.0)		0(0.0)
	3 roots	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	4 (2.3)	2(1.1)	0(0.0)	0(0.0)	151 (100.0)	179 (100.0)	144 (100.0)		148 (100.0)
Number of canals
	1 canal	184 (47.9)	200 (52.1)	184 (48.2)	200 (51.8)	180 (97.8)	200 (100.0)	9 (5.1)	4(2.3)	62 (34.1)	75 (42.4)	0(0.0)	0(0.0)	0(0.0)		0(0.0)
	2 canals	0(0.0)	0(0.0)	0(0.0)	0(0.0)	4(2.2)	0(0.0)	158 (90.3)	169 (96.0)	120 (65.9)	99 (55.9)	0(0.0)	0(0.0)	0(0.0)		0(0.0)
	3 canals	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	6 (3.4)	3(1.7)	0(0.0)	3(1.7)	13 (8.6)	34 (19.0)	40 (27.8)		58 (39.2)
	4 canals	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	2 (1.1)	0(0.0)	0(0.0)	0(0.0)	138 (91.4)	145 (81.0)	104 (72.2)		90 (60.8)
Bold numbers refer to significant difference (P< 0.05); Only mesiobuccal roots of 1st and 2nd molars were included in analysis

Table 4

Distribution of maxillary teeth among both genders according to canal configuration

		Central		Lateral		Canine		1st Premolar		2nd Premolar		1st Molar		2nd Molar
		M	F	M	F	M	F	M	F	M	F	M	F	M	F
Vertucci types
	Type I	184 (47.9)	200 (52.1)	184 (48.2)	200 (51.8)	180 (97.8)	200 (100.0)	9 (5.1)	4(2.3)	62 (34.1)	75 (42.4)	13 (8.6)	32 (17.9)	38 (26.4)	58 (39.2)
	Type II	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	18 (10.3)	6(3.4)	23 (12.6)	16 (9.0)	54 (35.8)	62 (34.6)	37 (25.7)	40 (27.0)
	Type III	0(0.0)	0(0.0)	0(0.0)	0(0.0)	4(2.2)	0(0.0)	7 (4.0)	20 (11.4)	24 (13.2)	31 (17.5)	3(2.0)	3(1.7)	1(0.7)	7(4.7)
	Type IV	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	119 (68.0)	105 (59.7)	41 (22.5)	28 (15.8)	79 (52.3)	80 (44.7)	63 (43.8)	32 (21.6)
	Type V	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	15 (8.6)	37 (21.0)	23 (12.6)	21 (11.9)	0(0.0)	2(1.1)	2(1.4)	9(6.1)
	Type VI	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0 (0.0)	1(0.6)	4(2.2)	0(0.0)	2(1.3)	0(0.0)	3(2.1)	2(1.4)
	Type VII	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	5(2.7)	3(1.7)	0(0.0)	0(0.0)	0(0.0)	0(0.0)
	Others	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	7 (4.0)	3(1.7)	0(0.0)	3(1.7)	0(0.0)	0(0.0)	0(0.0)	0(0.0)
Bold numbers refer to significant difference (P< 0.05); Only mesiobuccal roots of 1st and 2nd molars were included in analysis

Table 6

Distribution of mandibular teeth (anterior and premolars) among both genders according to number of roots, and number of canals

		Central		Lateral		Canine		1st premolar		2nd premolar
		M	F	M	F	M	F	M	F	M	F
Number of roots
	1 root	196 (100)	214 (100)	197 (99.5)	213 (99.5)	195 (99.0)	204 (95.8)	186 (98.9)	209 (100.0)	188 (100.0)	191 (100.0)
	2 roots	0(0.0)	0(0.0)	1(0.5)	1(0.5)	2(1.0)	9(4.2)	2(1.1)	0(0.0)	0(0.0)	0(0.0)
	3 roots	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)
Number of canals
	1 canal	132 (67.3)	170 (79.4)	133 (67.2)	152 (71.0)	184 (93.4)	188 (88.3)	124 (66.0)	152 (72.7)	178 (94.7)	189 (99.0)
	2 canals	64 (32.7)	44 (20.6)	65 (32.8)	62 (29.0)	13(6.6)	25 (11.7)	61 (32.4)	56 (26.8)	7(3.7)	1(0.5)
	3 canals	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	3(1.6)	1(0.5)	3(1.6)	1(0.5)
	4 canals	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)
Bold numbers refer to significant difference (P< 0.05)

Table 7

Distribution of mandibular teeth (anterior and premolars) among both genders according to canal configuration

		Central		Lateral		Canine		1st premolar		2nd premolar
		M	F	M	F	M	F	M	F	M	F
Vertucci types
	Type I	132 (67.3)	170 (79.4)	133 (67.2)	152 (71.0)	184 (93.4)	188 (88.3)	124 (66.0)	152 (72,7)	178 (94.7)	189 (99.0)
	Type II	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)
	Type III	64 (32.7)	44 (20.6)	63 (31.8)	60 (28.0)	11(5.6)	14(6.6)	20 (10.6)	5(2.4)	5(2.7)	1(0.5)
	Type IV	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)
	Type V	0(0.0)	0(0.0)	2(1.0)	2(1.0)	2(1.0)	11(5.2)	42 (22.3)	50 (23.9)	3(1.6)	0(0.0)
	Type VI	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)
	Type VII	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	1(0.5)	0(0.0)	0(0.0)
	Others	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	2(1.1)	1(0.5)	2(1.1)	1(0.5)
Bold numbers refer to significant difference (P< 0.05)

Table 8

Distribution of mandibular teeth (1st and 2nd molars) among both genders according to number of roots, number of canals canal configuration

		1st molar				2nd molar
			M	F			M	F
Number of roots
	1 root		0(0.0)	0(0.0)			0(0.0)	2(1.2)
	2 roots		145 (96.0)	129 (92.8)			171 (98.8)	157(95.7)
	3 roots		6(4.0)	10(7.2)			2(1.2)	5(3.0)
Number of canals
	1 canal		0(0.0)	0(0.0)			0(0.0)	0(0.0)
	2 canals		1(0.7)	1(0.7)			9(5.2)	14(8.5)
	3 canals		98 (64.9)	89 (64.0)			156 (90.2)	138(84.1)
	4 canals		52 (34.4)	49 (35.3)			8(4.6)	12(7.3)
Vertucci types		Mesial root		Distal root		Mesial root		Distal root
		M	F	M	F	M	F	M	F
	Type I	2(1.3)	1(0.7)	103 (68.2)	97 (69.8)	8(4.6)	13(7.9)	164(94.8)	158(96.3)
	Type II	48 (31.8)	57 (41.0)	1(0.7)	8(5.8)	41 (23.7)	45 (27.4)	0(0.0)	3(1.8)
	Type III	3(2.0)	1(0.7)	25 (16.6)	25 (18.0)	26 (15.0)	28 (17.1)	2(1.2)	1(0.6)
	Type IV	93 (61.6)	75 (54.0)	0(0.0)	2(1.4)	77 (44.5)	56 (34.1)	0(0.0)	0(0.0)
	Type V	5(3.3)	5(3.6)	22 (14.6)	7(5.0)	21 (12.1)	22 (13.4)	7(4.0)	2(1.2)
	Type VI	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)
	Type VII	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)
	Others	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)	0(0.0)
Bold numbers refer to significant difference (P< 0.05)