Pattern of Mandibular Third Molar Impaction and Distal Pathologies of the Second Molar in the Presence and Absence of the Mandibular Third Molar among Jazan Population, Saudi Arabia: A Radiographic Evaluation

Abstract

Objective Third molars that emerge in nonfunctional or partially functional jaw positions are referred to as impacted third molars. Third molar impaction is associated with several characteristics, and it is due to local and systemic causes. The severe position of the impacted tooth may be connected to increased delays in treatment, female gender, microdontia of the lateral incisors, and over-retained deciduous canine. Impaction of the third molar can cause pathological changes such as dental caries and root resorption in the adjoining second molar. Thus, the present study aimed to determine the frequency of distal pathologies of the mandibular second molar and the risk factors associated with the presence and absence of the third molar.

Materials and Methods A total of 699 panoramic radiographs of good image quality were assessed for the topographic anatomy of the right and left mandibular third molars, and the presence of pathology in relation to the second molar of the same quadrant was evaluated. The pathological status of the second molar, including the presence of dental caries and bone loss distal to the second molar, was recorded. The data obtained were subjected to statistical analysis using SPSS version 20.0 (IBM, Chicago, United States) at the significance level of p-value <0.05.

Results A total of 38.6% cases revealed no impaction of the third molar; maximum 34.3% cases had vertical impaction, with dental caries being the most common dental caries of all the observed pathologies in relation to second molar.

Conclusion The results of this study demonstrated that the dental caries over the distal aspect of second molar was mostly associated with mesioangular impaction followed by horizontal impaction of third molar. Maximum cases of root resorption and alveolar bone loss were seen in horizontal impaction followed by mesioangular impaction. Due to the high prevalence of these pathologies, a prophylactic removal of lower third molars with mesioangular and horizontal impaction is advisable.

Keywords

mandibular third molars - second molar - distal pathology - panoramic radiographs - impaction

Introduction

Based on its anatomic position, an impacted tooth is either fully or partially unerupted and is positioned against another tooth, bone, or soft tissue, making future eruption uncertain.[1] The third molars, which are commonly known as wisdom teeth, are the last four teeth out of the total 32 permanent teeth that erupt in the oral cavity. In general, the third molars erupt at the age of 17 to 21 years.[2] The third molars emerge and grow into the proper dental location within the arch. Conversely, the third molars that emerge in nonfunctional or partially functional jaw positions are referred to as impacted third molars.[3]

Impaction can affect any third molar, although it is more common to afflict the mandibular third molars. Third molar impaction is associated with several characteristics, including heredity, age, sex, ethnicity, and the structure of the face. Permanent tooth impaction is due to local and systemic causes. Systemic reasons include Down syndrome, cleidocranial dysplasia, and endocrine abnormalities such hypothyroidism and hypopituitarism. In general, local variables include cleft lip and palate, excess or supernumerary teeth, odontogenic tumors, a lack of arch-length tooth material, and malposed tooth germs.[4] [5]

The prevalence of third molar impaction varies, ranging from 16.7 to 68.6% based on reports from numerous research studies conducted globally.[6] [7] Several methods have been developed to categorize impaction based on the degree of impaction, the angulation of the third molar, and the relationship to the mandibular anterior border.[8] Different authors stated various factors that influence the severity of permanent tooth impaction. In a previous study, the severe position of the impacted tooth may be connected to increased delays in treatment, female gender, microdontia of the lateral incisors, and over retained deciduous canine.[8]

In various studies, impaction of the third molar can cause pathological changes such as dental caries and root resorption in the adjoining second molar. Several studies have been conducted in Saudi Arabia to assess the incidence of impacted third molars,[8] [9] [10] but only few evaluated the effect of impacted third molar in relation to the presence of pathologies affecting the adjacent second molar.[8] Thus, the present study aimed to determine the frequency of distal pathologies of the mandibular second molar and the risk factors associated with the presence and absence of the third molar.

Materials and Methods

Study Design and Settings

A descriptive retrospective study of panoramic radiographs was conducted in the Dento-maxilla-facial Radiology Department of the College of Dentistry, Jazan University, from January to April 2024. The research proposal was submitted, and ethical clearance (REC-45/05/879) was obtained from the Institutional Ethical Committee of Jazan University, Kingdom of Saudi Arabia. A total of 691 panoramic radiographs of good image quality, showing 699 seconds and third mandibular molars, were selected. Among these radiographs, nine had bilateral third molars assessed.

Inclusion and Exclusion Criteria

Radiographs showing anatomical and metallic superimposition and artifacts that are incompatible with the reading of anatomical structures were excluded from the study. Panoramic radiographs of low image quality and showing third molars with incomplete root formation were also excluded from the study.

Data Collection

The topographic anatomy of the right and left mandibular third molars and the presence of pathology in relation to the second molar of the same quadrant were evaluated. Reading and morphometric analyses were performed on a computer screen by two examiners, one specialized in dentomaxillofacial radiology and other being the researcher himself. The topographical anatomy of the third molar, as well as the normal anatomical position of the third molar and its status as an enclosed or nonenclosed molar and its angle of inclination, was studied and classified on the basis of Winter's classification. The angle of inclination was calculated by measuring the angulation between the major axis of the mandibular third molar and the major axis of the adjacent second molar.

The pathological status of the second molar, such as the presence of dental caries and bone loss distal to the second molar, was also recorded. Dental caries was observed in the presence of a radiolucent image on the distal face of the crown or on the cervical border of the second molar in the presence and absence of the third molar. The distal bone loss of the second molar was objectified by the presence of a radiolucent image to replace the lamina dura.

Statistical Analysis

The data obtained were subjected to statistical analysis using SPSS version 20.0 (IBM, Chicago, United States) at the significance level of p-value <0.05.

Results

In the present retrospective study, 699 panoramic radiographs were evaluated. The maximum radiographs of study subjects accounted for 44.2% (age 20–30 years), followed by 33.76% (31–40 years), with a mean age of 32.90 ± 9.57 years and female predominance of 60.1% ([Table 1]). In 38.6% of radiographs, no impaction of the third molar was observed, whereas 34.3% of the radiographs had vertical impaction, followed by 12.3% showing mesioangular impaction, 8.7% showing horizontal impaction, and 6% showing distoangular impaction ([Table 1]).

Table 1 Demographic data

Variables		Frequency (n = 699)	Percentage (%)
Age groups (years)	<20	14	2.003
	20–30	309	44.206
	31–40	236	33.762
	41–50	101	14.449
	51–60	27	3.863
	>60	12	1.717
Mean age		32.90 ± 9.57
Gender	Female	420	60.1
	Male	279	39.9
Third molar impaction	Distoangular	42	6.008
	Mesioangular	86	12.303
	Vertical	240	34.335
	Horizontal	61	8.727
	No impaction	270	38.627

Pathologies in relation to the second molar were also observed. Most of the cases (41.7%) had dental caries ([Fig. 1]), followed by 12.7% with root resorption and 8.37% with bone loss ([Fig. 2]) ([Table 2]). In all types of impaction, most of the second molars had dental caries, followed by incidence of root resorption and bone loss ([Fig. 3]). Even in cases with no impaction of the third molar, incidence of dental caries, root resorption, and bone loss was recorded. Maximum cases (73.2%) of dental caries were reported in mesioangular impaction of the third molar, followed by horizontal impactions (70.5%). Maximum cases of root resorption (45.9%) were reported in horizontal impactions, followed by mesioangular impactions (33.7%). Bone loss was found to be maximum (19.7%) in horizontal and mesioangular impactions (18.6%). Thus, pathologies related to second molars were found to be maximum in horizontal and mesioangular impactions. A significant relation (p-value < 0.05) was found between the types of third molar impactions and all distal pathologies of the second molar ([Table 3]).

Fig. 1 Mesioangular impaction with 38, horizontal impaction with 48, dental caries over the distal aspect of 37 associated with impacted 38.

Fig. 2 Horizontal impaction with 48, root resorption over the distal aspect of 47 associated with impacted 48.

Table 2 Pathologies related to second molar

Second molar pathologies	Frequency (n)	Percentage (%)
Dental caries	289	41.703
Root resorption	88	12.698
Bone loss	58	8.369
Missing second molar	6	0.866
Total	693	100

Fig. 3 Alveolar bone loss over the distal aspect of 37 associated with mesioangular impaction of 38.

Table 3 Distal pathologies of second molar in different types of third molar impaction

Third molar impaction	Dental caries		Root resorption		Bone loss
	n	%	n	%	n	%
Distoangular (n = 42)	11	26.19	6	14.29	3	7.14
Mesioangular (n = 86)	63	73.2	29	33.72	16	18.6
Vertical (n = 240)	103	42.92	16	6.67	15	6.25
Horizontal (n = 61)	43	70.49	28	45.9	12	19.67
No impaction (n = 270)	69	25.56	9	3.33	12	4.44
Total	289	41.70	88	12.69	58	8.37
Pearson correlation coefficient (r)	10.189		9.178		10.077
p -Value	0.033[a]		0.041[a]		0.017[a]

^a p-Value <0.05 is significant.

The type of third molar impaction was correlated with gender and age. In both genders, vertical impaction was most common, followed by mesioangular impaction. All types of impactions except for the horizontal one appeared more frequent in females than in males. Comparable results were observed in both genders in relation to third molar impactions (p-value > 0.05; [Table 4]). With regard to age, patients aged <50 years showed a higher incidence of impactions than those aged >50 years, showing a statistically insignificant difference (p-value > 0.05; [Table 5]).

Table 4 Correlation of type of third molar impaction with gender

Third molar impaction	Female		Male		Total
	Freq. (n)	Percentage (%)	Freq. (n)	Percentage (%)	Freq. (n)	Percentage (%)
Distoangular	27	6.5	15	5.4	42	6.008
Mesioangular	53	12.6	33	11.8	86	12.303
Vertical	149	35.5	91	32.61	240	34.335
Horizontal	31	7.4	30	10.8	61	8.727
No impaction	160	38	110	39.43	270	38.627
Chi square	2.881
p-Value	0.065[a]

^a p-Value >0.05 is insignificant.

Table 5 Correlation of type of third molar impaction with age

Third molar impaction	≤50 (years)		>50 (years)		Total
	Freq. (n)	Percentage (%)	Freq. (n)	Percentage (%)	Freq. (n)	Percentage (%)
Distoangular	42	6.36	0	0	42	6.008
Mesioangular	85	12.9	1	2.6	86	12.303
Vertical	226	34.2	14	35.89	240	34.335
Horizontal	58	8.8	3	7.7	61	8.727
No impaction	247	36.9	23	59.0	270	38.627
Chi square	2.889
p-Value	0.080[a]

^a p-Value >0.05 is insignificant.

Discussion

In this study, the prevalence of impacted mandibular third molar was 61.37%. Similar to our study, a prevalence rate of 60% was reported in Morocco in a study conducted by Skitioui et al.[11] The incidence rate of impacted third molar (23.06%) was reported to be quite less in a study conducted by Ndiaye et al.[2] In a study conducted in Saudi Arabia by AlHobail et al,[5] 29.6% of the cases had third molar impaction. Another study on Jazan population by Idris et al revealed that the high prevalence of impacted third molar is due to the lack of posterior space and inadequate space between the ramus and the second molar.[12]

In this study, the maximum radiographs of study subjects aged 20 to 30 years accounted for 44.2%, followed by those aged 31 to 40 years (33.76%), with a mean age of 32.90 ± 9.57 years and female predominance of 60.1%. Similarly, Toedtling et al[13] observed that the mean age was 37 years, and the female-to-male gender ratio was 1:1.3. In a study on Saudi population by AlHobail et al,[5] the mean age of the study subjects was 32 ± 11.2 years, and 51.1% of the cases were in the 20 to 29 age group.

In addition, 38.6% of the radiographs showed no impaction of the third molar, whereas 34.3% of the radiographs exhibited vertical impaction (the long axes of the second molar and the impacted third molar are parallel), followed by 12.3% being mesioangular (the long axes of the second molar and the impacted third molar are coincident docoronally), 8.7% being horizontal (the long axes of the second molar and impacted third molar are at right angles), and 6% with distoangular impaction (the long axes of the second molar and impacted third molar are convergent apically).[14] Similar to our study, AlHobail et al[5] found that maximum 13.7% of cases had vertical impaction, followed by horizontal (6.9%), mesioangular (5.7%), and distoangular (3.4%) impactions. Toedtling et al[3] observed that mesial impaction (59.2%) is the frequently observed impaction, followed by horizontal impaction (20.1%). In another study on Saudi population by Al-Dajani et al,[9] similar results were observed, with vertical impaction of the third molar being the most common, followed by horizontal impactions.

Moreover, with regard to pathologies in relation to the second molar, most of the cases (41.7%) had dental caries, followed by 12.7% with root resorption and 8.37% with bone loss. In all types of impactions, most of the second molars had dental caries, followed by incidence of root resorption and bone loss. Even in cases with no impaction of the third molar, incidence of dental caries, root resorption, and bone loss was recorded. A significant relation (p-value < 0.05) was found between the types of third molar impactions and all distal pathologies of the second molar. Similar to our study, AlHobail et al[5] found that 48.6% of the cases had dental caries of the second molar. Ndiaye et al[2] found that impacted third molar caused dental caries (33% cases) and bone loss (64.5%) of the mandibular second molar. Similar to our study, they also reported that most of the cases had dental caries in permanent second molar because of impacted third molar, followed by incidence of bone loss.

Srivastava et al[15] and McArdle et al[16] found a 1 to 47% prevalence of distal second molar caries in relation to partially or totally impacted third molars. Caries in the distal surface of the second molar is a late effect of impaction or eruption of the third molar. This result may indicate that a long-term patient has neglected to practice good dental hygiene in this area.

In this study, most of the cases (73.2%) of dental caries were reported in mesioangular third molar impactions, followed by horizontal impactions (70.5%). In addition, most of the cases of root resorption (45.9%) were observed in horizontal impaction, followed by mesioangular impaction (33.7%). Bone loss was found to be maximum (19.7%) in horizontal and mesioangular impactions (18.6%). Thus, pathologies related to the second molars were found to be maximum in horizontal and mesioangular impactions. Similarly, Ali et al[17] found that third molars positioned horizontally and mesioangularly are likely to be associated with the development of caries in the neighboring second molars. These results are consistent with our investigation, in which a strong correlation was found between mesioangular, horizontal, and vertical impactions and caries in the distal surface of the second molar.

Skitioui et al[11] found that root resorption of the second molar was most common in cases of horizontal impactions (36.5%), followed by mesioangular (24.3%) impactions. Vandeplas et al,[18] Passarelli et al,[19] and Sun et al[20] stated that distal pathology of the second molar coexists in the presence of the third molar. The likelihood of mandibular second molar pathology would be greatly increased by the third molar's enclosed state.

In our study, in both genders, vertical impaction was most common, followed by mesioangular impaction. All types of impactions except for the horizontal one occurred more frequently in females than in males. Thus, dental caries involving the second molars occurred more frequently in males than in females. Comparable results were observed between female and male with regard to third molar impactions (p-value > 0.05). Similar results were found in a study conducted by Syed et al,[6] who found that dental caries occurred more frequently in males than in females. With regard to age, patients aged <50 years showed higher incidence of impactions than those aged >50 years, showing a statistically insignificant difference (p-value > 0.05). Silva et al[21] stated that the prevalence of impactions and distal caries was higher in patients around 35 years of age.

The limitations of this study were that all the subjects included in the study were taken from the dental clinics in one location. This may not accurately reflect the larger Jazan City population. In validating the findings of this study, more extensive population, larger sample size, and a higher number of factors would be needed for future research.

Conclusion

The results of this study demonstrated that the dental caries over the distal aspect of second molar was mostly associated with mesioangular impaction followed by horizontal impaction of third molar. Maximum cases of root resorption and alveolar bone loss were seen in horizontal impaction followed by mesioangular impaction. Due to the high prevalence of these pathologies, a prophylactic removal of lower third molars with mesioangular and horizontal impaction is advisable.

The eruption status and the type of angulation are useful predictors to indicate the likelihood of pathologies occurring on the distal aspect of the second mandibular molar. If patient's third molar teeth are not removed, prevention and regular monitoring such as reinforcing caries prevention measures and regular radiographic screening of second molars with bitewing radiographs need to be considered.

Conflict of Interest

None declared.

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Publication History

Article published online:
03 March 2025