The Association Between Skeletal Facial Types and Third Molars Impaction in a Saudi Arabian Subpopulation: A CBCT Study

Figures & data

Figure 1 A CBCT-derived lateral cephalogram showing SN-GoGn angle (red), and effective length of maxilla (green), and effective length of mandible (yellow).

Figure 2 A CBCT-derived lateral cephalogram showing ANB angle.

Figure 3 Pell & Gregory’s classification of ramus relation and impaction depth of lower third molars, (A) Class 1, Level A, (B) Class 2 Level B, (C) Class 3 Level C.

Figure 4 Winter’s classification, showing a mesioangular impaction.

Figure 5 Lower third molar horizontal position, showing a lingually positioned third molar.

Figure 6 Archer l classification of upper third molars, (A) Type A, (B) Type B, (C) Type C, (D) Type D, (E) Type E.

Figure 7 Archer ll classification of upper third molars, (A) mesioangular, (B) distoangular, (C) vertical, (D) buccoangular, (E) horizontal.

Table 1 Descriptive Characteristics of Study Participants

		N	%
Gender	Male	90	45.5
	Female	108	54.5
Upper Third Molar (Archer l)	Type A	68	34.3
	Type B	19	9.6
	Type C	27	13.6
	Type D	4	2.0
	Type E	6	3.0
Upper Third Molar (Archer ll)	Mesioangular	14	7
	Distoangular	42	21.2
	Vertical	62	31.3
	Buccoangular	4	2.0
	Horizontal	1	0.5
Lower Third Molar (Pell & Gregory’s Classification of Ramus Relation)	Class 1	105	53.0
	Class 2	34	17.2
	Class 3	10	5.1
Lower Third Molar (Pell & Gregory’s Classification of Impaction Depth)	Type A	101	51.0
	Type B	37	18.7
	Type C	11	5.6
Pell & Gregory’s Classification of Ramus Relation and Impaction Depth	Type 1A	92	46.5
	Type 1B	12	6.1
	Type 1C	1	0.5
	Type 2A	9	4.5
	Type 2B	23	11.6
	Type 2C	2	1.0
	Type 3B	2	1.0
	Type 3C	8	4.0
Lower Third Molar Horizontal Position	Class 1	69	34.8
	Class 2	16	8.1
	Class 3	35	17.7
Facial Types Classification	Brachyfacial	80	40.4
	Mesiofacial	96	48.5
	Dolichofacial	22	11.1
Skeletal Profile (ANB)	Class 1	76	38.4
	Class 2	100	50.5
	Class 3	22	11.1

Table 2 Association Between Facial Types and Study Variables (Categorical)

		Facial Type Classification						P value
		Brachyfacial		Mesiofacial		Dolichofacial
		N	%	N	%	N	%
Gender	Male	40	50.0%	40	41.7%	10	45.5%	0.543
	Female	40	50.0%	56	58.3%	12	54.5%
Upper Third Molar (Archer l)	Type A	28	50.0%	31	56.4%	9	69.2%	0.301
	Type B	11	19.6%	6	10.9%	2	15.4%
	Type C	15	26.8%	11	20.0%	1	7.7%
	Type D	0	0.0%	4	7.3%	0	0.0%
	Type E	2	3.6%	3	5.5%	1	7.7%
Upper Third Molar (Archer ll)	Mesioangular	5	8.9%	7	13.0%	1	7.7%	0.106
	Distoangular	14	25.0%	23	42.6%	5	38.5%
	Vertical	33	58.9%	23	42.6%	6	46.2%
	Buccoangular	3	5.4%	1	1.9%	0	0.0%
	Horizontal	1	1.8%	0	0.0%	0	0.0%
Lower Third Molar (Pell & Gregory’s Classification of Ramus Relation)	Class 1	35	61.4%	58	75.3%	12	80.0%	0.247
	Class 2	18	31.6%	13	16.9%	3	20.0%
	Class 3	4	7.0%	6	7.8%	0	0.0%
Lower third molar (Pell & Gregory’s Classification of Impaction Depth)	Type A	37	64.9%	54	70.1%	10	66.7%	0.972
	Type B	15	26.3%	18	23.4%	4	26.7%
	Type C	5	8.8%	5	6.5%	1	6.7%
Pell & Gregory’s Classification of Ramus Relation and Impaction Depth	Type 1A	32	56.1%	51	66.2%	9	60.0%	0.239
	Type 1B	3	5.3%	7	9.1%	2	13.3%
	Type 1C	0	0.0%	0	0.0%	1	6.7%
	Type 2A	5	8.8%	3	3.9%	1	6.7%
	Type 2B	11	19.3%	10	13.0%	2	13.3%
	Type 2C	2	3.5%	0	0.0%	0	0.0%
	Type 3B	1	1.8%	1	1.3%	0	0.0%
	Type 3C	3	5.3%	5	6.5%	0	0.0%
Lower Third Molar Horizontal Position	Class 1	26	54.2%	33	57.9%	10	66.7%	0.082
	Class 2	3	6.3%	12	21.1%	1	6.7%
	Class 3	19	39.6%	12	21.1%	4	26.7%

Table 3 Association Between Facial Type and Study Variables (Continuous)

		N	Mean	SD	P value
Age	Brachyfacial	80	36.825	12.09	0.044*
	Mesiofacial	96	32.458	11.56
	Dolichofacial	22	35.818	10.75
Lower Third Molar (Winter’s angle)	Brachyfacial	49	32.280	30.03	0.11
	Mesiofacial	73	32.733	30.11
	Dolichofacial	11	52.864	37.82

Note: ANOVA test, *Statistical significance at p≤0.05.

Table 4 Association Between Skeletal Profile and Study Variables (Categorical)

		Skeletal Profile ANB						P value
		Class I		Class II		Class III
		N	%	N	%	N	%
Gender	Male	34	44.7%	48	48.0%	8	36.4%	0.603
	Female	42	55.3%	52	52.0%	14	63.6%
Upper Third Molar (Archer l)	Type A	30	58.8%	32	53.3%	6	46.2%	0.745
	Type B	6	11.8%	9	15.0%	4	30.8%
	Type C	12	23.5%	13	21.7%	2	15.4%
	Type D	2	3.9%	2	3.3%	0	0.0%
	Type E	1	2.0%	4	6.7%	1	7.7%
Upper Third Molar (Archer ll)	Mesioangular	9	17.6%	4	6.8%	0	0.0%	0.013*
	Distoangular	8	15.7%	28	47.5%	6	46.2%
	Vertical	29	56.9%	26	44.1%	7	53.8%
	Buccoangular	4	7.8%	0	0.0%	0	0.0%
	Horizontal	1	2.0%	0	0.0%	0	0.0%
Lower Third Molar (Pell & Gregory’s Classification of Ramus Relation)	Class 1	39	70.9%	56	70.0%	10	71.4%	0.993
	Class 2	13	23.6%	18	22.5%	3	21.4%
	Class 3	3	5.5%	6	7.5%	1	7.1%
Lower Third Molar (Pell & Gregory’s Classification of Impaction Depth)	Type A	39	70.9%	52	65.0%	10	71.4%	0.952
	Type B	12	21.8%	22	27.5%	3	21.4%
	Type C	4	7.3%	6	7.5%	1	7.1%
Pell & Gregory’s Classification of Ramus Relation and Impaction Depth	Type 1A	35	63.6%	47	58.8%	10	71.4%	0.960
	Type 1B	4	7.3%	8	10.0%	0	0.0%
	Type 1C	0	0.0%	1	1.3%	0	0.0%
	Type 2A	4	7.3%	5	6.3%	0	0.0%
	Type 2B	8	14.5%	12	15.0%	3	21.4%
	Type 2C	1	1.8%	1	1.3%	0	0.0%
	Type 3B	0	0.0%	2	2.5%	0	0.0%
	Type 3C	3	5.5%	4	5.0%	1	7.1%
Lower Third Molar Horizontal Position	Class 1	21	48.8%	41	61.2%	7	70.0%	0.378
	Class 2	9	20.9%	6	9.0%	1	10.0%
	Class 3	13	30.2%	20	29.9%	2	20.0%

Note: Chi-Square test, *Statistical significance at p≤0.05.

Table 5 Association Between Skeletal Profile and Study Variables (Continuous)

	Skeletal Profile	N	Mean	SD	P value
Age	Class I	76	35.76	11.81	0.53
	Class II	100	33.74	12.38
	Class III	22	34.45	9.12
Lower Third Molar (Winter’s angle)	Class I	52	32.96	32.30	0.24
	Class II	71	37.19	31.26
	Class III	10	19.80	17.13

Table 6 Association Between Effective Length of Maxilla with Upper Third Molar Variables

Effective Length of Maxilla
		N	Mean	SD	P value
Upper Third Molar (Archer l)	Type A	68	78.67	13.19	0.269
	Type B	19	74.85	15.70
	Type C	27	83.02	13.40
	Type D	4	85.92	12.58
	Type E	6	79.91	8.30
Upper Third Molar (Archer ll)	Mesioangular	13	77.58	16.04	0.275
	Distoangular	42	77.36	16.46
	Vertical	62	81.81	10.64
	Buccoangular	4	69.93	8.98
	Horizontal	1	85.81

Table 7 Association Between Effective Length of Mandible with Lower Third Molar Variables

Effective Length of Mandible
		N	Mean	SD	P value
Lower Third Molar (Pell & Gregory’s Classification of Ramus Relation)	Class 1	105	106.97	16.75	0.902
	Class 2	34	108.28	19.22
	Class 3	10	108.91	27.86
Lower Third Molar (Pell & Gregory’s Classification of Impaction Depth)	Type A	101	108.3	17.40	0.655
	Type B	37	105.15	16.99
	Type C	11	106.52	27.38

Table 8 Correlation Between the Continuous Variables

		Age	Lower Third Molar (Winter’s Angle)	Effective Length of Mandible
Age	r value	1	0.049	0.168
	p value		0.575	0.018*
Lower Third Molar (Winter’s angle)	r value	0.049	1	−0.064
	p value	0.575		0.462
Effective Length of Mandible	r value	0.168	−0.064	1
	p value	0.018	0.462

Note: Pearson correlation test, *statistical significance at p≤0.05.