Pathologies Associated with Second Mandibular Molar Due to Various Types of Impacted Third Molar: A Comparative Clinical Study

Abstract

Introduction

Impacted third molars are associated with various degrees of damage to the second molars. The possible complications also include distal cervical caries, root resorption of second molar, periodontal problems, odontogenic cysts, etc. Whether a particular impacted third molar is going to affect second molar depends upon its position and orientation in the bone.

Materials and Method

This study was carried out in 418 cases. Three examiners evaluated the patient clinically and radiographically and only those cases were included in this study where at least two observers agreed. A total of 341 cases (163 males and 178 female), age range (15–40 years) with impacted mandibular third molars, were included. Clinically and radiographically, the impacted mandibular third and second molars were evaluated; simultaneously, the prevalence of various pathologies associated with mandibular second molar (dental caries, periodontal pockets, root resorption) due to impacted third molar was also evaluated and compared among various types and positions of impactions.

Results

Statistical analysis was carried out using Pearson Chi-square and Asymp. Sig. (two-sided) test. Prevalence of mesioangular impactions was maximum (50.1%). Mesioangular impaction and position B (Pell and Gregory classification) were significantly associated with dental caries (32.20% and 33.90%, respectively), and periodontal pockets were seen higher with position B impactions (26.8%) {horizontal (14.7%), disto-angular (12.10%), vertical (14.5%) mesioangular (16.4%%)} in adjacent mandibular second molar. Root resorption was seen maximally in horizontal impaction (17.30%) with position c type (12.30%). The order of pathologies associated with second molar due to impacted third molar was dental caries (19.9%) > periodontal pockets (15.2%) > root resorption (8.5%).

Discussion

Evidence regarding pathologies are associated with second molar due to impacted third molar aids in decision making for surgical removal of third molars. Different types of impaction and the prevalence of pathologies related to them would aid in treatment planning of the impacted tooth as certain types have high probability of pathologies associated.

Introduction

Impacted tooth is a completely or partially unerupted tooth positioned against another tooth, bone or soft tissue such that its further eruption is unlikely, as described according to its anatomic position. Researchers have suggested many reasons in the literature that lead to the impaction of third molars. It has been suggested that with evolution it plays an important role in this. The gradual reduction in size of human mandible/maxilla has occurred, and the accommodation of the third molars in the arch has become an issue. It has been also assumed that consumption of modern diet results in less stimulation of growth in jaws as it does not provide a decided effort in mastication, and thus, an impacted or unerupted teeth is seen in present population [1]. The impacted mandibular third molar can be present in various spatial positions that include—vertical (90°), mesioangular ≤ 60°, distoangular ≥ 120°, horizontal (0°) or inverted (270°), all of which can affect the second molar in many ways [2] (Figs. 1, 2, 3, 4).

Fig. 1.

Vertical impaction irt 47

Fig. 2.

Mesioangular impaction irt 38 root resorption noted distal to 37

Fig. 3.

Distoangular impaction irt 48

Fig. 4.

Horizontal impaction irt 38 bone loss noted distal to 37

Impacted third molar is often associated with complications and damage to the adjacent second molar as well. Periodontal pockets and gingival bleeding on second molars are frequently associated with adjacent third molars [3]. Pericoronitis is the most common sequelae of impacted third molar which is followed by dental caries of third molar or adjacent second molar distal caries. The possible complications also include root resorption of second molar, periodontal problems, odontogenic cysts, tumors, etc. Contacting cementoenamel junction of second molar, a few impacted third molar poses a risk of distal cervical caries of the neighboring tooth. Efforts of erupting impacted tooth and the various chemical mediators which are released by reduced enamel epithelium are known to seed the root resorption of adjacent second molar. Impacted third molars besides root resorption also decrease bone amount distal to second molar and cause periodontal defects there [4] (Fig. 5).

Fig. 5.

Dental caries irt 37 secondary to impacted 38

Whether a particular impacted third molar is going to affect second molar depends upon its position in the bone. There are many studies about impacted teeth in both national and international literature, but relatively a few articles are available which describes the various pathologies associated with it. The aim of the study was to assess and compare the various pathologies associated with second mandibular molar due to various types of impacted third mandibular molar. The objectives were-

• To evaluate clinically and radiologically the impacted mandibular third and second molar and to evaluate the various pathologies associated with mandibular second molar due to impacted third molar.

• To compare the pathologies associated with second mandibular molar due to various types and positions of impacted third molars.

Materials and Method

Patients between the age of 15–40 years who reported to the Department of OMFS, with complaint of impacted mandibular third molar within the time duration (December 2016 to May 2017) were included in the study considering the inclusion and exclusion criteria.

Inclusion Criteria

Patients between the age group of 15–40 years and requiring surgical extraction of mandibular third molar.

Exclusion Criteria

• Patients who were not willing to participate or having second mandibular molar missing, were excluded.

• Periodontal disease in mandibular second molars which influences the probing pocket depth.

• Patients with past history of any major systemic illness such as diabetes and hypertension, underlying immunocompromised conditions.

• Patients with history of acute illness, infection or pregnancy were excluded.

The sample size was calculated using the formula, and the required sample size was 341.

$$n=\frac{\left(Z_{1-\frac{\alpha }{2}}^2\right)(1-p)p}{{\xi }^{2}p}$$

where p: expected proportion; ξ: relative precision; 1 − α/2: desired confidence level.

Ethical committee approval was obtained from Institutional Ethics committee (Ref. No. -IECKVGDCH/26/2016-17). Null hypothesis was no difference in pathologies observed in different classification of impacted teeth and different positions. A standard proforma was used to collect necessary information regarding each case. Written informed consent was obtained from all the patients, and records were maintained. Mouth mirror, Williams periodontal probe, explorer, various radiographs including OPG, IOPA, bite wing radiograph were used for obtaining data.

Proper case history was taken along with preoperative radiographic investigations. Patients were analyzed clinically and radiographically by three observers independently, observers were blinded, and by the agreement of at least two observers, cases were incorporated into the study. Matching observations of at least two observers were included in the study. The position and angulation of impacted third molars were noted according to Winter’s classification and Pell and Gregory classification using IOPA and panoramic radiography (OPG).

Winter’s classification [5]

1. Vertical—The long axis of third molar is parallel to the long axis of the second molar (10 to − 10°) (refer Fig. 1).

2. Mesioangular—The impacted tooth is tilted towards the second molar in mesial direction (11 to 79°) (refer Fig. 2),

3. Distoangular—The long axis of third molar is angled distally posteriorly away from the second molar (− 11 to − 79°) (refer Fig. 3).

4. Horizontal—The long axis of the third molar is horizontal (80 to 100°) (refer Fig. 4).

Pell and Gregory classification [5]

1. Position A impaction—The occlusal plane of the impacted tooth is the same as the second molar.

2. Position B—The occlusal plane of impacted third molar is between the occlusal plane and the cervical line of the second molar.

3. Position C—The occlusal plane of the impacted third molar is below the cervical line of the second molar.

The pathologies assessed in the adjacent second molar included cervical caries, root resorption and changes in the periodontium due to impacted third molar. The pathologies associated with second molars were noted, and their percentage were calculated from the total number of second molars assessed. Dental caries were detected clinically by visual tactile examination [6] as well as via IOPA radiograph at 70 kvp and 0.20 s time using Planmeca ProX™ intraoral X-ray unit, and periodontal pockets were checked and measured on six surfaces of second molars using a Williams periodontal probe. Highest value of periodontal probing depth was considered around second molar. Clinically periodontal bone loss of more than 4 mm below the cementoenamel junction was considered to be pathologic [7]. Root resorption was checked radiographically using IOPA and OPG as present and absent. Regular root surface was considered as having no resorption, whereas resorption was identified from small irregularity on root surface to advanced resorption with loss of root shape including pulp to complete root resorption [8].

Results

A total of 341 cases (163 male and 178 female) (Fig. 6) of mandibular third molar impactions were included in the study out of 418 cases which were examined in the given time framework. Pearson Chi-square and Asymp. Sig. (two-sided) test were used for statistical evaluation.

Fig. 6.

Sex ratio

Out of the total cases studied, mesioangular and position C impactions were maximum (50.1%, 47.5%). The results were statistically significant (Table 1 and Figs. 7, 8). The various angulations, positions and the number of pathologies associated with it are explained in Table 1 (Figs. 9, 10, 11).

Table 1.

Descriptive statistics

Parameter	Frequency	Percentage
Sex
Male	163	47.8
Female	178	52.2
Total	341	100
Winters_classification
Mesoi-angular	171	50.1
Vertical	62	18.2
Disto_angular	33	9.7
Horizontal	75	22
Total	341	100
Pell_and_Gregory_classification
Position A	52	15.2
Position B	127	37.2
Position C	162	47.5
Total	341	100
Dental_Caries
Absent	273	80.1
Present	68	19.9
Total	341	100
Clinical_Periodontal_deapth
0	289	84.8
5	15	4.4
6	29	8.5
7	8	2.3
Total	341	100
Radiographic_root_resorption
Absent	312	91.5
Present	29	8.5
Total	341	100

Fig. 7.

Prevalence of impactions according to Winter’s classifications

Fig. 8.

Prevalence of impactions according to Pell and Gregory classifications

Fig. 9.

Prevalence of dental caries in various type of impactions

Fig. 10.

Prevalence of periodontal pockets in various type of impactions

Fig. 11.

Prevalence of radiographic root resorption in various type of impactions

Dental caries in second molar associated with impacted third molar (refer Fig. 5) were mostly prevalent in mesioangular impaction. 32.20% mesioangular impactions cases had dental caries, the results of which were statistically significant. The order is mesioangular > horizontal > vertical > distoangular (Table 2, Fig. 12). Position B impactions showed 33.90% dental caries on second molars followed by position C 14.20% and position A 3.80% (Table 3, Fig. 13). Mesioangular position B accounts for higher incidence of dental caries combined (48.68%) (Table 4).

Table 2.

Association between types of mandibular third molar impaction (Winters classification) with dental caries

	Dental caries		Total	Pearson Chi-Square	Asymp. Sig. (2-sided)
	Absent	Present
Winter’s classification
Mesoi-angular
Count	116	55	171	33.02	0.001
% within Winters_classification	67.80%	32.20%	100.00%
Vertical
Count	58	4	62
% within Winters_classification	93.50%	6.50%	100.00%
Disto_angular
Count	32	1	33
% within Winters_classification	97.00%	3.00%	100.00%
Horizontal
Count	67	8	75
% within Winters_classification	89.30%	10.70%	100.00%
Total
Count	273	68	341
% within Winters_classification	80.10%	19.90%	100.00%

Bold value indicates statistical significance at < 0.05

Fig. 12.

Bar diagram representing association between Winter’s classification and dental caries

Table 3.

Association between types of mandibular third molar impaction (Pell and Gregory classification) with dental caries

	Dental_Caries		Total	Pearson Chi-Square	Asymp. Sig. (2-sided)
	Absent	Present
Pell and Gregory classification
Position A
Count	50	2	52	27.19	0.001
% within Pell_and_Gregory_classification	96.20%	3.80%	100.00%
Position B
Count	84	43	127
% within Pell_and_Gregory_classification	66.10%	33.90%	100.00%
Position C
Count	139	23	162
% within Pell_and_Gregory_classification	85.80%	14.20%	100.00%
Total
Count	273	68	341
% within Pell_and_Gregory_classification	80.10%	19.90%	100.00%

Bold value indicates statistical significance at < 0.05

Fig. 13.

Bar diagram representing association between Pell and Gregory classification and dental caries

Table 4.

Percentage and number of second molars showing dental caries

Type of impactions	Total	Second molars having dental caries	Percentage
Mesioangular impaction
Position A	0	0	0
Position B	76	37	48.68%
Position C	95	18	18.94%
Total	171	55	32.16%
Disto-angular impaction
Position A	23	1	4.3%
Position B	10	0	0
Position C	0	0	0
Total	33	1	3.03%
Vertical impaction
Position A	29	1	3.4%
Position B	26	3	11.5%
Position C	7	0	0
Total	62	4	6.45%
Horizontal impaction
Position A	0	0	0
Position B	17	3	17.64%
Position C	58	5	8.62%
Total	75	8	10.66%

Prevalence of periodontal pockets in mandibular second molar(refer Fig. 4) due to impacted third molar according to the Winter’s classification and Pell and Greogry classification is shown in Tables 5 and 6. The periodontal depth of above 4 mm was considered to be pathologic. The values were obtained separately as depth of 5 mm, 6 mm, 7 mm. No tooth showed value of more than 7 mm. The values were nonsignificantly more for mesioangular impaction (16.40%). The order is mesioangular (16.40%) > horizontal (14.70%) > vertical (14.50%) > distoangular (12.10%) (Table 5, Fig. 14). The position B (26.80%) shows statistically significant results in causing periodontal pathology (p value < 0.001) (Table 6, Fig. 15). Horizontal position B has the highest percentage of periodontal pathology in relation to second molar (Table 7).

Table 5.

Association between types of mandibular third molar impaction (Winters classification) with clinical periodontal depth

	Clinical_Periodontal_depth				Total	Pearson Chi-Square	Asymp. Sig. (2-sided)
	0	5	6	7
Winters classification
Mesoi-angular
Count	143	10	16	2	171	15.52	0.078
% within Winters_classification	83.60%	5.80%	9.40%	1.20%	100.00%
Vertical
Count	53	0	5	4	62
% within Winters_classification	85.50%	0.00%	8.10%	6.50%	100.00%
Disto_angular
Count	29	0	2	2	33
% within Winters_classification	87.90%	0.00%	6.10%	6.10%	100.00%
Horizontal
Count	64	5	6	0	75
% within Winters_classification	85.30%	6.70%	8.00%	0.00%	100.00%
Total
Count	289	15	29	8	341
% within Winters_classification	84.80%	4.40%	8.50%	2.30%	100.00%

Table 6.

Association between types of mandibular third molar impaction (Pell and Gregory classification) with clinical periodontal depth

	Clinical_Periodontal_depth				Total	Pearson Chi-Square	Asymp. Sig. (2-sided)
	0	5	6	7
Pell and Gregory classification
Position A
Count	46	0	3	3	52	27.44	0.001
% within Pell_and_Gregory_classification	88.50%	0.00%	5.80%	5.80%	100.00%
Position B
Count	93	10	19	5	127
% within Pell_and_Gregory_classification	73.20%	7.90%	15.00%	3.90%	100.00%
Position C
Count	150	5	7	0	162
% within Pell_and_Gregory_classification	92.60%	3.10%	4.30%	0.00%	100.00%
Total
Count	289	15	29	8	341
% within Pell_and_Gregory_classification	84.80%	4.40%	8.50%	2.30%	100.00%

Bold value indicates statistical significance at < 0.05

Fig. 14.

Bar diagram representing association between Winter’s classification and clinical periodontal depth

Fig. 15.

Bar diagram representing association between Pell and Gregory classification and clinical periodontal depth

Table 7.

Percentage and number of second molars showing periodontal pockets

Type of impactions	Total	Second molar having periodontal pockets	Percentage
Mesioangular impaction
Position A	0	0	0
Position B	76	21	27.63%
Position C	95	7	7.36%
Total	171	28	16.37%
Disto-angular impaction
Position A	23	1	4.3%
Position B	10	3	30%
Position C	0	0	0
Total	33	4	12.12%
Vertical impaction
Position A	29	5	17.24%
Position B	26	4	15.38%
Position C	7	0	0
Total	62	9	14.51%
Horizontal impaction
Position A	0	0	0
Position B	17	6	35.29%
Position C	58	5	8.62%
Total	75	11	14.66%

Root resorption in mandibular second molar (refer Fig. 2) was more in horizontal impaction (17.30%) followed by mesioangular (9.40%) (Table 8, Fig. 16). Position C is 12.30% (Table 9, Fig. 17). The order is horizontal > mesioangular. Vertical and horizontal impaction showed no root resorption. Horizontal position B shows root resorption in 23.52% of second molars followed by horizontal position C (15.51%) (Table 10).

Table 8.

Association between types of mandibular third molar impaction (Winters classification) with radiographic root resorption

	Radiographic_root_resorption		Total	Pearson Chi-Square	Asymp. Sig. (2-sided)
	Absent	Present
Winters classification
Mesoi-angular
Count	155	16	171	16.5	0.001
% within Winters_classification	90.60%	9.40%	100.00%
Vertical
Count	62	0	62
% within Winters_classification	100.00%	0.00%	100.00%
Disto_angular
Count	33	0	33
% within Winters_classification	100.00%	0.00%	100.00%
Horizontal
Count	62	13	75
% within Winters_classification	82.70%	17.30%	100.00%
Total
Count	312	29	341
% within Winters_classification	91.50%	8.50%	100.00%

Bold value indicates statistical significance at < 0.05

Fig. 16.

Bar diagram representing association between Winters classification and radiographic root resorption

Table 9.

Association between types of mandibular third molar impaction (Pell and Gregory classification) with radiographic root resorption

	Radiographic_root_resorption		Total	Pearson Chi-Square	Asymp. Sig. (2-sided)
	Absent	Present
Pell and Gregory classification
Position A
Count	52	0	52	8.23	0.016
% within Pell_and_Gregory_classification	100.00%	0.00%	100.00%
Position B
Count	118	9	127
% within Pell_and_Gregory_classification	92.90%	7.10%	100.00%
Position C
Count	142	20	162
% within Pell_and_Gregory_classification	87.70%	12.30%	100.00%
Total
Count	312	29	341
% within Pell_and_Gregory_classification	91.50%	8.50%	100.00%

Bold value indicates statistical significance at < 0.05

Fig. 17.

Bar diagram representing association between Pell and Gregory classification and radiographic root resorption

Table 10.

Percentage and number of second molars showing root resorption

Type of impactions	Total	Second molar having root resorption	Percentage
Mesioangular impaction
Position A	0	0	0
Position B	76	5	6.57%
Position C	95	11	11.57%
Total	171	16	9.3%
Disto-angular impaction
Position A	23	0	0
Position B	10	0	0
Position C	0	0	0
Total	33	0	0
Vertical impaction
Position A	29	0	0
Position B	26	0	0
Position C	7	0	0
Total	62	0	0
Horizontal impaction
Position A	0	0	0
Position B	17	4	23.52%
Position C	58	9	15.51%
Total	75	13	17.33%

The comparative data of different angulation of impactions with different positions are shown in Tables 11, 12, 13 and 14.

Table 11.

Mann–Whitney test used in comparison of mesio angular impaction position B and C among dental caries, periodontal pockets and root resorption parameters

Mesio angular groups	N	Mean rank	Asymp. Sig. (2-tailed)
Dental caries
Position B	76	100.13	0.001
Position C	95	74.7
Total	171
Periodontal pockets
Position B	76	95.63	0.001
Position C	95	78.3
Total	171
Root resorption
Position B	76	80.63	0.029
Position C	95	90.3
Total	171

Bold values indicate statistical significance at < 0.05

Table 12.

Mann–Whitney test used in comparison of disto angular impaction position A and B among dental caries, periodontal pockets and root resorption parameters

Disto angular groups	N	Mean rank	Asymp. Sig. (2-tailed)
Dental caries
Position A	23	17.22	0.51
Position B	10	16.5
Total	33
Periodontal pockets
Position A	23	15.72	0.041
Position B	10	19.95
Total	33
Root resorption
Position A	23	17	1
Position B	10	17
Total	33

*Statistical significance set at 0.05

Table 13.

Kruskal–Wallis test used in comparison of vertical impaction position A, position B and C among dental caries, periodontal pockets and root resorption parameters

Vertical groups	N	Mean rank	Asymp. Sig.
Dental caries
Position A	29	30.57	0.368
Position B	26	33.08
Position C	7	29.5
Total	62
Periodontal pockets
Position A	29	32.34	0.508
Position B	26	31.77
Position C	7	27
Total	62
Root resorption
Position A	29	31.5	1
Position B	26	31.5
Position C	7	31.5
Total	62

*Statistical significance set at 0.05

Table 14.

Mann–Whitney test used in comparison of horizontal impaction position B and C among dental caries, periodontal pockets and root resorption parameters

Horizontal groups	N	Mean rank	Asymp. Sig. (2-tailed)
Dental caries
Position B	17	40.62	0.292
Position C	58	37.23
Total	75
Periodontal pockets
Position B	17	45.74	0.007
Position C	58	35.73
Total	75
Root resorption
Position B	17	38.82	0.803
Position C	58	37.76
Total	75

Bold value indicates statistical significance at < 0.05

The order of pathologies associated with second molar due to impacted third molar were dental caries (19.9%) > periodontal pockets (15.2%) > root resorption (8.5%) (Fig. 18).

Fig. 18.

Percentage of pathologies

Discussion

The mandibular third molars are the most common impacted teeth present [9, 10], ranging from 16.7 to 68.8% in the oral cavity [11]. The decision regarding elective surgical extraction of asymptomatic mandibular third molar is not well defined in the literature. According to Tulloch et al., various schools of thoughts exist in relation to their controversial management protocol [12]. Some authors suggest that when third molars cause complications, then they should be extracted as the surgical procedures itself becomes uncomplicated with less morbidity [12]. A second group of researchers believe that it is better to wait as only those teeth which remain impacted lead to various complications and only those teeth need to be extracted which do not erupt in a good functional position [12]. A third group suggests that only those teeth that are associated with pathologic process should be extracted as evidence regarding that all impacted third molars undoubtedly cause complication is not present in the literature, so, it is better to wait [12]. On the other hand, American association of oral and maxillofacial surgery believes that the removal of such teeth is valid at early age if there is insufficient anatomical space to accommodate them [13]. Surgical extraction of mandibular third molar is thus governed by many factors one being the prevention of associated pathologies to second molar. The literature classifies the potential problems associated with the retention of impacted third molar teeth as periodontal problems, caries, root resorption and other pathologies.

In our study, dental caries account for 19.9% of second molars associated with third molars. Studies conducted by Allen et al. [14] and Chang et al. [15] were in accordance with our study where the percentage was 19.3% and 17.2% respectively. The most common type of impaction showing distal caries in second molars is mesioangular impaction in our study. Table 15 shows the percentage and common angulations responsible for distal caries in second molar given in the literature.

Table 15.

Various studies showing percentage of second molars having dental caries associated with impacted third molars

Study	Year	Percentage of second molar having caries (%)	Most common type of impaction
			Type	Percentage (%)
Chu et al. [10]	2003	7	–	–
Allen et al. [11]	2009	19.3	Mesio angular	42
Chang et al. [12]	2009	17.2	Mesio angular	79.6
Ozeç et al. [13]	2009	20	Mesio angular	47
Falci et al. [14]	2012	13.4	Mesio angular	37.2
Sheikh et al. [15]	2012	42.5	Mesio angular	51
Srivastava et al. [16]	2017	37.5	Mesio angular	55
Syed et al. [17]	2017	39	Mesio angular	60.47
Ali et al. [18]	2017	23.36	Mesio angular	68.3
Altiparmak et al. [19]	2017	38.7	Horizontal	54.21
Marques et al. [20]	2017	25.4	Horizontal	27.7
Khanji et al. [21]	2018	20	–	–
Our study	2019	19.9	Mesio angular	32.20

Blakey et al. [22] found that asymptomatic third molar teeth (25%) are frequently associated with periodontal probing depths of ≥ 5 mm on distal surface of a second molar or around a third molar (mandible more affected than maxilla). Around these teeth, gingivae harbors bacteria which are known to be associated with periodontitis. These bacteria are initially present in the region of third molar teeth, which later form a reservoir for progression of disease into a more generalized form [23, 24]. The pathogenic bacteria after colonizing at one site involve the adjacent teeth in the same quadrant as well as in the other quadrants also which will harbor the same bacteria [25, 26].

Impacted third molars which are visible clinically have greater periodontal probing depths overall, especially on second molars as it offers a greater surface area of the biofilm-gingival interface [27]. Some studies have shown that around second molar there is reduction in periodontopathic bacteria after third molar removal [28]. Study conducted by Gröndahl et al. [29] showed that following the removal of third molars the periodontal conditions of adjacent second molars improved. In contrast, studies conducted by Peng et al. [30] and Chinquee et al. [31] showed worsening of periodontal condition after third molar extraction. Study conducted by Blakey et al. [7] assessed the changes in periodontal status in the third molar region and concluded that increased periodontal PDs ≥ 2 mm was found in the third molar region for asymptomatic subjects and at least 1 PD ≥ 4 mm at enrollment. These values indicate an increased periodontal pathology with deteriorating periodontal condition.

In our study, 15.2% of second molars were affected periodontally due to impacted third molar; out of them, the most common type of impaction responsible for it is mesioangular closely followed by horizontal. The study conducted by Chu et al. [14] showed 9% of periodontal problems in second molar.

Several factors affect the root resorption of the mandibular second molar. The pressure is exerted by mandibular third molar, pericoronitis, periodontal disease of the second molar. Association of completely impacted third molar with second molar root resorption is more than the partially impacted third molar [32]. During eruption of the impacted third molar, the mechanical forces generated cause the adjacent second molar distal root to resorb as it lies in a close proximity to it [8]. The resorption occurring is inflammatory in nature due to the obstruction of blood vessels of the adjacent tooth [33].

In our study, the root resorption was seen in 8.50% of second molars with horizontal impactions being 17.30% and position C being 12.30%. The mesioangular impaction accounts for 9.40% root resorption with position B causing 7.10% resorption. Oenning et al. [34] found out that teeth positioned in class C were less associated with external root resorption (ERR) in second molars compared with other classes, whereas in our study position C accounted for highest root resorption rates of second molars, and this study also concluded that the probability of ERR in second molars is more with mesioangular and horizontal impactions which was in accordance with the present study. They also concluded that in patients older than 24 years, class A and B third molars were more related to the presence of ERR. Study conducted by Lacerda-Santos et al. [35] found ERR to be more in mandible (42.1%) with cervical (57.1%) and medium (58.8%) thirds being high in proportion and mesioangular position of the impacted teeth being the most common type responsible (p = 0.26). Nemcovsky et al. [8] found evidence of root resorption in 24.2% of second molars in which 6.5% had moderate to complete resorption of root. The study also found out that non-erupted tooth, 60° mesioinclination or impacted third molar placed close to the distal root of the second molar were associated with more root resorption of second molar. Study by D’Costa et al. [36] found position B on Pell and Gregory classification to be the most common cause.

Summary

Our study has emphasized on the pathologies associated with second molar due to impacted third molar that would help in decision making for the operative removal of unerupted or impacted third molars. Prophylactic removal of mandibular third molar having a particular orientation should be strongly buttressed with evidence regarding the pathologies that could happen in future with them as well as with the second molars which are in intimate contact with them. Our study provides information concerning the different types of impaction and the prevalence of pathologies related to each type which would aid in treatment planning of the unerupted tooth as certain types are highly associated with the pathologies.

Compliance with Ethical Standards

Conflict of interest

The authors declare that there is no conflict of interests.