Introduction

Impacted teeth are one of the most common situations in dentistry. Insufficient space in the dental arch, malposition, and absence of eruption force are some etiologic factors for the impaction (1). Impacted teeth can be extracted because of inflammation and infection, cyst and tumors, destruction of adjacent teeth, periodontitis, caries, and etcetera (2). The most common impacted teeth are mandibular third molars followed by maxillary third molars, maxillary canines, and mandibular premolars, respectively. Approximately, one in every five mandibular third molars and maxillary third molars are impacted. Also, radiolucency around the crowns in radiographic examination are present in 37% of impacted mandibular third molars and 15% of maxillary third molars (1,2).

The crowns of impacted teeth are surrounded by a soft tissue called dental follicle. Radiographically, the dental follicle is a radiolucent space with a thin radiopaque border (1). Immune-histochemical studies showed that the dental follicle cells have a great potential for growth and proliferation (3). Thus, pathologic changes can occur from the dental follicle and it can be detected as an enlargement of the pericoronal space. Dentigerous cyst (DC) is the most common pathology associated with the dental follicle. Odontogenic keratocyst (OKC) and ameloblastoma are the other pathologies associated with impacted molars. Bifurcation cyst, glandular odontogenic cyst, calcifying epithelial odontogenic tumor, adenomatoid odontogenic tumor, ameloblastic fibroma, and ameloblastic fibro-odontoma are rarely seen in radiolucent lesions associated with impacted teeth (4).

Radiographic examination is routinely used to detect the presence or absence of any pathology associated with impacted teeth (5). Different types of cystic and cystic-appearing lesions can be easily detected by periapical, occlusal, and panoramic radiography. Adjunct to these radiographic techniques, cone-beam computed tomography (CBCT), computed tomography (CT), magnetic resonance imaging and scintigraphy are used for detailed three-dimensional imaging of the lesions (6). Especially CBCT provides three-dimensional images with axial, sagittal and coronal sections with a lower radiation dose compared to CT. CBCT is originally designed for the visualization of solid structures in the head and neck region because it produces a lower radiation dose with high spatial resolution. The clinical use of CBCT provides accurate information about the contents and borders of the lesions, their special relations with surrounding structures, and cortical expansion for which the conventional radiographic techniques are usually inadequate (7).

In the literature, there are a lot of studies about impacted teeth and the lesions (8-10). To the best of our knowledge, this paper is one of the very few multicenter studies that evaluate the pathologic lesions related with impacted teeth (11,12). In other multicenter studies, specific lesions have been evaluated. In contrast, in this study, the lesions associated with impacted teeth have been handled more comprehensively. The purpose of this retrospective study was to evaluate the radiographic and histopathologic features of the pathologic lesions associated with impacted tooth in maxilla and mandible of patients who were admitted to three different university hospitals located in different cities.

Materials and Methods

Data Collection

This multicenter study was conducted in three different university hospitals. Before starting the study, ethical approval was received (approval no: 36290600/63, date: 30.11.2015). This study was carried out in accordance with the principles of the Helsinki Declaration. CBCT images belonging to 101 patients (36 females and 65 males) having radiolucent lesions in conjunction with any impacted tooth/teeth were assessed. The CBCT images of patients who had a history of maxillofacial trauma, surgery, and artifacts were excluded from the study.

CBCT images in different centers were obtained by ProMax 3D Mid (Planmeca Oy, Helsinki, Finland), Morita Veraviewepocs 3D R100-CP (J Morita MFG Corp, Kyoto, Japan) and Kodak 9500 3D (Kodak Corp, Carestream Health, Rochester, New York) using parameters of 90 kilovoltage peak, 12-mile ampere, scanning time of 10.8-13.8 seconds and 0.4 mile meter voxel size according to imaging area. Sagittal, coronal, and axial CBCT sections of the radiolucent lesions in conjunction with any impacted tooth/teeth were evaluated in a quiet room with subdued ambient lighting, approximately 50 centimeters away from the screen by dentomaxillofacial radiologists with at least five years of experience. The dentomaxillofacial radiologists held a meeting to detect the evaluation criteria of the lesions before starting the evaluation process (Table 1). Surgical procedures of the lesions were performed by maxillofacial surgeons with at least seven years of experience. Histopathologic validations were carried out by pathologists with at least ten years of experience. Demographic data, CBCT findings and histopathologic validations of the patients were recorded.

Statistical Analysis

Obtained data were statistically analyzed by using SPSS program version 21.0 (SPSS Inc., Chicago, USA). The findings were categorized and statistically analyzed with descriptive statistics, crosstabs, chi-square tests and Fisher’s Exact tests where appropriate. Statistical analyses were performed both in 95% and 99% confidence intervals. The patients were categorized into three age groups: 8-30 years old (<30 years old), 31-50 years old and 51 years old and over (51> years old) for the analysis.

Results

CBCT and histopathologic data belonging to 101 patients (36 females; 35.6% and 65 males; 64.4%) aged between 8 and 67 years (mean age ± standard deviation: 38.8±15.7) were evaluated in the study (Table 2). 65 lesions were diagnosed in males, while 36 lesions were diagnosed in females. The lesions consisted of DC (n=72; 71.29%) (Figure 1), OKC (n=15; 14.85%) (Figure 2,3), inflammation (n=7; 6.93%), ameloblastoma (n=5; 4.95%), and glandular odontogenic cyst (n=2; 1.98%) respectively (Table 3).

Majority of the lesions were in the posterior region of the mandible (n=63; 62.4%) and related with the mandibular third molars (n=60; 59.4%). The most common features of the lesions were unilocular radiolucency (n=92, 91.1%), well-circumscribed (n= 91, 90.1%), and expansive (n=86, 85.1%). More than half of the lesions did not cause any migration of the related impacted tooth (n=53, 52.5%), resorption of adjacent tooth/teeth (n=52, 51.2%) and migration of adjacent tooth/teeth (n=62, 61.4%). The cortical bone thinning (n=89, 88.1%) and perforation (n=90, 89.1%) were a common finding. The distribution and statistical analysis of the variables were shown in Table 4 in detail according to gender.

A statistically significant relationship was found between the migration of the impacted tooth/teeth related to the lesion (p<0.05) and the expansion of the lesion (p<0.01) according to gender. The migration both the buccal and lingual/palatal direction of impacted tooth/teeth was more common in males than in females. Expansion of the lesion was more common in males than in females. No statistically significant difference was found between gender and the other variables (Table 4).

A statistically significant relationship was found between the migration of the impacted tooth/teeth related to the lesion (p<0.05) and the histopathological diagnosis of the lesion (p<0.01) according to age groups. The migration towards buccal direction of impacted tooth/teeth was more common in the patients ≤30 years old, while the migration towards lingual/palatal was more common in the patients 51≥ years old. Most of the patients with DC were 31-50 years old and 51≥ years old, while other lesions were more common among patients ≤30 years old. No statistically significant difference was found between the age groups and the other variables (Table 5).

Discussion

The multicenter studies are very important and valuable to determine the real prevalence of lesions. Actually it is very difficult to collect the data in these types of studies but obtained results are so valuable. Essentially, in the literature some studies which were evaluated the prevalence and characteristics of jaw lesions (8,13,14) can be found and there are a lot of studies about impacted teeth and the lesions (8-10). But the number of the multicenter studies about the impacted teeth and the lesions related with them is limited (11,12). Our study is one of the few studies with these properties.

According to our results, majority of the lesions were in the posterior region of the mandible and related with mandibular third molars. This result is compatible with previous studies (10-12). Additionally, in this study, the most frequently impacted teeth were found as the third molar, canine and other teeth, respectively. Because the third molars account for 98% of all impacted teeth. Generally, impaction of mandibular molars is seen more frequently compared with maxillary molars (7,14).

According to CBCT findings, the most common features of the lesions were unilocular radiolucency, well-circumscribed and expansive. More than a half of the lesions did not cause any migration of the related impacted tooth, resorption of adjacent tooth/teeth and migration of adjacent tooth/teeth. The cortical bone thinning and perforation were a common finding in general. These radiographic findings are common in benign lesions. In general, cysts and tumors present in the study had benign characters (15).

There were statistically significant differences between gender with the migration of impacted tooth/teeth in conjunction with the lesion and expansion of the lesion. This could be related with the type of lesion. The benign and aggressive lesions show different growth patterns. The radiographic findings of these lesions depend on morphologic findings and the relationship of adjacent structures. The size, growth stage, and localization of the lesions have effect on the radiographic features of the lesions, even one having the same histopathological diagnosis. On the other hand, lesions with different histopathologic structures could share similar radiographic features (16,17).

Regarding histopathological diagnosis almost two third of the lesions were DC, followed by OKC, inflammation, ameloblastoma and glandular odontogenic cysts. In some studies, the relationship between the impacted tooth and the frequency of odontogenic cyst and tumors has been discussed. Curran et al. (18) showed that the frequency of the lesions associated with impacted teeth was DC, OKC, odontoma, ameloblastoma, calcifying epithelial odontogenic tumor, carcinoma, and myxoma, respectively. Shoaee et al. (19) reported that the three most common lesions associated with impacted teeth were DC, OKC, and ameloblastoma. In a previous study, the most common type of lesion associated with impacted third molar teeth was defined as DC followed by OKC, ameloblastoma, paradental cyst, and glandular odontogenic cyst (20). Our results show similarity with recent research indicating DC is the most common lesion associated with impacted teeth (10,15,21).

According to our results, majority of the patients with DC were between 31-50 years old, while other lesions were more common among patients <30 years old. The migration and root resorption in the adjacent tooth and expansion were seen in the evaluated cases in our study. DC was more common among males compared to females. The studies have reported that the DC is usually seen more common in adolescents and young adults between 20-40 years. In addition, it has been shown that DC is typically enveloping the crown of the impacted, leads to migration and is resorbed of adjacent tooth/teeth, and makes expansion buccally or medially, especially in large lesions radiographically (22,23). Also, DC is reported to be seen more common among males in the literature (24). Our findings show similarity with previous studies.

We found that other lesions associated with impacted teeth were OKC, inflammation, ameloblastoma and glandular odontogenic cyst. Many studies have shown that these lesions are associated with impacted teeth (18-20). It has reported that OKC usually appears between second and fourth decades. This lesion is frequently located at posterior body of the mandible and ramus and represented as unilocular or multilocular radiolucency having well-defined borders, with minimal mediolateral expansion. Also, it has been informed that OKC may include the crown of the impacted teeth resembling the DC in some cases (22). In contrast, ameloblastoma is a benign lesion, a locally invasive tumor. It has reported that ameloblastoma is usually seen in patients 20-50 years old and develops in the molar-ramus regions of the mandible. It has been presented that this lesion usually shows unilocular or multilocular radiolucency and performs root resorption and tooth migration on the radiograph (24). In a recent study, it was reported that OKC and ameloblastoma lead to mesial-distal displacement of the impacted teeth more frequently compared with DC. OKC and ameloblastoma showed more aggressive growth pattern with higher rate of bony discontinuity and cortical bone expansion compared with DC (22).

Conclusion

We can say that this study is one of the few multicenter studies when viewed from this angle. In this study, statistically significant differences were found between age groups and migration of impacted tooth/teeth in conjunction with the lesion and histopathological diagnosis of the lesion. The migration of impacted tooth/teeth towards buccal direction was more common in the patients ≤30 years old, while lingual/palatal migration was more common in the patients 51≥ years old.

The clinical and radiographic features of lesions located in jaws show some similarity according to their growth patterns. Majority of these lesions are benign but certain lesions are aggressive and show a destructive growth pattern. These affect the treatment choice, surgical techniques, and post-operative recurrence rates. CBCT findings could help the surgeons’ initial diagnosis, pre-operative surgery planning and treatment choice. Knowing all clinical, radiological, and histopathological features of the lesions provide the surgeon to reach the correct diagnosis, thus the doctors achieve high success in treatment with the right treatment plan.

Ethics

Ethics Committee Approval: The present cohort study was designed as a survey and was approved by the Clinical Research Ethics Committee of Ankara University Faculty of Dentistry (approval no: 36290600/63, date: 30.11.2015).

Informed Consent: Retrospective study.

Peer-review: Internally peer-reviewed.

Authorship Contributions

Surgical and Medical Practices: Z.F.Z., Z.A., E.B., S.K., D.G., İ.P., Concept: Z.F.Z., Z.A., E.B., S.K., D.G., İ.P., Design: Z.F.Z., Z.A., Y.T.K., C.D., E.B., S.K., D.G., İ.P., Data Collection or Processing: Z.F.Z., Z.A., N.H., Y.T.K., C.D., E.B., İ.S., M.İ., D.G., Analysis or Interpretation: N.H., Y.T.K., C.D., İ.S., N.B., Literature Search: Z.F.Z., Z.A., N.H., Y.T.K., C.D., N.B., Writing: Z.F.Z.

Conflict of Interest: No conflict of interest was declared by the authors.

Financial Disclosure: The authors declared that this study received no financial support.