Indian Journal of Dental Research

: 2013  |  Volume : 24  |  Issue : 2  |  Page : 183--187

Incidence of cystic changes in impacted lower third molar

Shridevi R Adaki1, BK Yashodadevi2, S Sujatha2, N Santana2, N Rakesh2, Raghavendra Adaki3,  
1 Department of Oral Medicine and Radiology, Bharati Vidyapeeth University Dental College, Sangli, Maharastra, India
2 Department of Oral Medicine and Radiology, M. S. Ramaiah Dental College, Bangalore, Karnataka, India
3 Department of Prosthodontics, Bharati Vidyapeeth University Dental College, Sangli, Maharastra, India

Correspondence Address:
Shridevi R Adaki
Department of Oral Medicine and Radiology, Bharati Vidyapeeth University Dental College, Sangli, Maharastra


Objective: To assess the incidence of cystic changes in the impacted lower third molar (ILTM) in which the pericoronal (follicular) space is less than 2.5 mm as measured from the radiograph. The relationship between the cystic changes and patient«SQ»s age, sex, and angular position and contact of ILTM with adjacent tooth was also evaluated. Materials and Methods: Follicular space less than 2.5 mm as measured from the panoramic radiograph was included in the study. A total of 73 tissue samples collected during the extraction ILTM were examined histopathologically. Then the data were analyzed for associations with age, sex, angular position, and contact of the ILTM with an adjacent tooth. Results: There were 37 male and 36 female patients, age ranging from 17 to 35 years (mean 23.95 years). Out of 73 specimens, 17 (23.3%) showed cystic changes; among them 16 (22.1%) showed dentigerous cysts and 1 (1.2%) showed odontogenic keratocysts. Most of the cystic changes occurred in the 26-30 year age range. The cystic changes showed male predominance but could not gain statistical significance. The relationship between cystic changes and angular position was statistically significant (P < 0.05). Higher probability was found in distoangular positioned ILTM. The relationship between cystic changes and communication of ILTM with the second molar was not statistically significant. Conclusion: Incidence of cystic changes in ILTM justifies extraction of the impacted tooth associated with symptoms. The decision to extract or not to extract impacted third molar should be individualized, rather than generalized.

How to cite this article:
Adaki SR, Yashodadevi B K, Sujatha S, Santana N, Rakesh N, Adaki R. Incidence of cystic changes in impacted lower third molar.Indian J Dent Res 2013;24:183-187

How to cite this URL:
Adaki SR, Yashodadevi B K, Sujatha S, Santana N, Rakesh N, Adaki R. Incidence of cystic changes in impacted lower third molar. Indian J Dent Res [serial online] 2013 [cited 2020 Oct 22 ];24:183-187
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Full Text

Third molar is the most common tooth to become impacted, accounting for 98% of all impacted teeth. [1] Third molars in the longer jaws of human ancestors have added benefit to the dentition million years ago, [2] but in the process of evolution, the jaw has become smaller, allowing less room for the third molars and causing numerous dental problems. The number of people reaching adult life with impacted third molars seems to be increasing to an epidemic extent. [1] and is stated that approximately 1/3 rd of the completely unerupted and partially erupted mandibular third molars are associated with pathologic conditions. [3]

The potential transformation of unerupted teeth into cystic or neoplastic ones is related to the constituent structures of the follicle, in particular the reduced enamel epithelium and remnants of dental lamina located in its connective tissue wall. [4]

Pathological processes associated with the pericoronal follicle can be early identified by radiographs that show an enlargement of the pericoronal space. Radiographically, the pericoronal follicle present as slight semicircular radiolucency around unerupted teeth. [5] Earlier study has shown that pericoronal radiolucency which is smaller than 2.5 mm in width is non-pathologic, [6] and if more, it is considered as "radiographic pathology" and these are associated with a high incidence of dentigerous cyst. [7]

Recently, the study has shown the incidence of pathologies even in those impacted teeth that have pericoronal radiolucency of less than 2.5 mm radiographically. [8] Quantifying the diagnostic use of radiographs in identifying pericoronal pathologies and making the histopathology of follicular tissue are mandatory.

Taking into consideration that the radiograph is the only option available for deciding between the removal and follow up of an impacted teeth, the present study was undertaken to know the incidence of cystic pathosis in impacted lower third molar (ILTM) where follicular space is less than 2.5 mm width and also its relationship with age, sex, angular position, and contact with an adjacent tooth.

 Materials and Methods

The study was conducted in 73 patients of both males and females, taken randomly in the age group of 20-35 years who visited the outpatient department of Oral Medicine and Radiology, "M. S. Ramaiah Dental College and Hospital", Bangalore, with chief complaint concerning to the ILTM. Inclusion criterion was completely ILTM with a follicular space less than 2.5 mm in width as measured from the panoramic radiograph. Exclusion criteria were partially erupted third molar and impacted third molar with follicular space more than 2.5 mm in width. Informed consent was obtained from each patient before the procedure. The patient's oral cavity was thoroughly examined with special attention to the lower third molar region for confirming the complete impaction. The patient was then transferred to the radiology section where panoramic radiograph was taken.

Measurement of follicular spce

In panoramic radiograph, the widest region of the pericoronal space was measured by tracing the contours of the tooth and of the pericoronal space on a tracer paper. [8] Two perpendicular lines (A-A and B-B) were drawn on the image of the tooth, one passing through the long axis and the other through the center of the crown. Starting from the intersection of the 2 lines, a ruler (C-C) was moved to the widest point of the pericoronal space, where the measurement was carried out with a caliper [Figure 1].{Figure 1}

Measurement of angular position of third molar

An angular position was determined by the angle formed by drawing the two lines, one along the longitudinal axis of the third molar and the other at the occlusal plane of the first and second molars. [3] A tooth would be categorized as Mesioangular if the angle is between 10° and 80°, Vertical if the angle is between 80° and 100°, Distoangular if the angle is more than 100°, and Horizontal if the angle is between 350° and 10° [Figure 2].{Figure 2}

Once the measurements were taken, the patient was referred to the Department of Oral Surgery for the extraction of the ILTM. Surgical procedure was performed on an outpatient basis under local anesthesia. Strict aseptic measures were followed during the time of extraction. The tooth was removed, and the follicular tissue attached to the cemento-enamel junction of the tooth was detached carefully with the tissue forcep.

For the histopathologic examination, the specimen was sent to Department of Oral Pathology where the follicular tissues were fixed in 10% neutral buffered formalin and processed routinely and stained with hematoxylin and eosin. All specimens were examined under a light microscope with the magnification of ×4, ×10, and ×40. For the purpose of study, specimens without an epithelial lining or those lines by reduced enamel epithelium without well-formed squamous epithelium were considered as normal follicular tissue, those with continuous stratified squamous epithelium of two to four cells in thickness were considered as a dentigerous cyst, and a lesion lined with orthokeratinization and many layers of stratified squamous epithelium was considered as an odontogenic keratocyst [Figure 3].{Figure 3}

Observations were tabulated and clinical details were then correlated for each patient with the histologic diagnosis, and the data were analyzed for associations with age, sex, angular position, and contact of the ILTM with the second molar.

The relationship between cystic changes and age, sex, angular position, and the relation between the cystic changes and communication of ILTM with the second molar were analyzed by the Chi-square test.


A total of 73 samples, (37 males and 36 females), age ranged from 17 to 35 years (mean 23.95 years, standard deviation 3.72), were collected for measuring the follicular space of less than 2.5 mm from the panoramic radiograph.

Histopathologic examination revealed 41 (56.2%) normal follicular tissue, 17 (23.3%) specimens showed cystic changes, among them 16 (22.1%) were dentigerous cysts and 1 (1.2%) was OKC.

Association of cystic changes with age distribution revealed that 3 (17.6%) were below 20 years of age, 5 (29.4%) in the age range of 21-25 years, 8 (47.1%) in the age range of 26-30 years, and 1 (5.9%) above the age of 30 years. A maximum number of cystic changes occurred in the age range of 26-30 years [Figure 4].{Figure 4}

Cystic changes as compared to gender revealed that 10 (58.8%) were males and 7 (41.2%) were females. This showed a trend toward increased incidence of cystic changes in men compared with women in the ratio of 1.4:1.

Cystic changes as compared to the angular position of the third molar showed 5 of 40 (12.5%) mesioangular, 8 of 22 (36.4%) vertical, 2 of 3 (66.7%) distoangular, and 2 of 8 (25%) horizontally impacted. The highest probability of cystic change was found in distoangularly ILTM (66.7%), followed by vertical (36.4%), horizontal (25%), and mesioangular (12.5%) teeth [Figure 5].{Figure 5}

Cystic changes as compared to contact of the third molar with adjacent tooth revealed 68 of the 73 teeth were in contact with second molar, 5 of the cases had no contact with the second molar [Figure 4].

The Chi square value obtained from the analysing the cystic change with the angular position was 7.884 with a "P" value 0.048 showing dependency.


The impacted tooth is one of the most common complaint of patients presenting to the dentist for treatment. The decision to remove the impacted tooth is less challenging when signs and symptoms of pathosis are present but it is made more demanding when the patient is asymptomatic. [9]

Many reports in the literature discuss the prevalence of cyst and tumor development associated with impacted teeth. The overall consensus seems to be that pericoronal cyst and tumor development is rare. [10],[11] Some reviews have used this information to support the rationale for no treatment of impacted teeth.

Majority of the studies use data collected from analysis of radiographs including some with long-term follow-up. [9],[10],[11] The fact that not all pericoronal cysts and tumors are symptomatic or that radiographic evidence of their presence may be subtle or nonexistent was not considered, and the actual presence of cysts or tumors in the majority of cases was not confirmed.

A true cyst is a sac-like structure that is lined by epithelium and surrounds a pathologic cavity. Widely accepted criteria for separation between dental follicle and dentigerous cyst do not exist: this remains area of controversy. Some authors believe that dentigerous cyst development coincides with the completion of enamel formation. At this time, the ameloblasts disengage from the surface of the enamel, creating a space between the lining and the crown of the tooth. [12],[13] In many cases, the reduced enamel epithelium is replaced by stratified squamous epithelium. Many investigators require a continuous lining of stratified squamous epithelium for the diagnosis of a dentigerous cyst. In the current study, the chosen definition is most widely accepted and requires the presence of a continuous lining of stratified squamous epithelium.

In the present study, 23.3% of samples exhibited histologic changes among them 22.1% showed a dentigerous cyst and 1.2% showed an odontogenic keratocyst. The results of present study are in consistent with study of Yildirim et al. [14] in which evaluation of ITML was done histopathologically and pathological conditions were found in 23% of cases.

Adelsperger et al. [15] in their study evaluated soft tissue pathosis in pericoronal tissues of impacted third molars that did not exhibit pathologic pericoronal radiolucency, in which 34% showed squamous metaplasia suggestive of cystic change equivalent to that found in a dentigerous cyst. Glosser and Campbell [7] in their study evaluated the incidence of histological abnormalities in soft tissues surrounding impacted third molar teeth when there were no pathological conditions apparent on the corresponding radiograph, and showed 37% of dentigerous cyst in mandibular specimen and 25% of dentigerous cyst in maxillary specimens. Rakprasitkul [16] found an incidence of pathologic tissues in 58.65% of pericoronal tissues of unerupted third molar in which incidence of dentigerous cyst accounted for 50.96% and an odontogenic keratocyst accounted for 4.81%. The result of this study showed lower incidence than that has been reported in previous studies related to ILTM.

Several explanations are possible for the difference in cystic incidence reported. Spontaneous cyst involution could occur over time, eliminating the need for surgical enucleation. Similarly, the tissue could undergo conversion to a quiescent state, persisting only as a histologic aberration of little clinical significance. Alternatively, removal of third molar teeth would, in most cases, result in removal of cystic tissue before it could progress to a radiographically detectable lesion. [15]

Presently accepted definitions of a dentigerous cyst do not necessarily mandate radiographic or histologic correlation as World Health Organization (1985) definition describes the entity as "a cyst originating in the enamel organ of an unerupted tooth", and Daley and Wysocki as "a fluid-filled space of variable size located between the crown of an impacted or unerupted tooth and the epithelium lining the pericoronal dental follicle." It is also believed that the diagnosis of a dentigerous cyst cannot be made in the absence of histologic epithelial change and it logically follows that such a microscopic change will precede the bony alterations characteristic of a true dentigerous cyst. [16] The study by Daley and Wysocki [17] reported squamous metaplasia to be a "normal" age-related change in pericoronal tissues of impacted teeth, but Adelsperger et al. [15] stated metaplasia represents early pathosis. This is supported by the findings of increased cellular activity as evidenced by the presence of detectable PCNA (proliferating cell nuclear antigen) in the majority of cystic tissues evaluated and its absence in healthy follicular tissues.

In most of the previous studies, a correlation between the incidence of cystic changes in follicular tissues and age was found. The groups older than the second decade showed higher incidences of pathologic changes. In this study, 82.6% of the patients showed cystic changes in patients older than 20 years of age and most of them were between 25 and 30 years age. This result is consistent with the previous reports.

Shear [12] showed a peak incidence in the 2 nd decade of life, whereas the present study showed a peak incidence in the third decade. A study had shown a remarkable, progressive decrease in the incidence of dentigerous cysts in patients older than 29 years, with only about 30% occurring in patients older than 39 years. [17] Stanley et al. [10] in their study found that all follicles of patients older than 26 years were lined by squamous epithelium rather than the cuboidal to columnar cells of reduced enamel epithelium. Browne [6] hypothesized that squamous metaplasia would lead to the production of increased numbers of dentigerous cysts because the attachment of this epithelium to the enamel was considered less as compared to that of reduced enamel epithelium.

Therefore, age may be used as an indication for surgical removal of ILTM, as the risk of surgical morbidity also increases with the increasing age.

Histopathologic diagnosis of cystic changes showed a male to female ratio of 1.4:1 in this study. Similar male predominance was reported in several studies, [8],[6],[17] but the reason for this gender difference is still unknown.

The angular position and the relationship with the second molar were also evaluated in this study. The higher probability of cystic changes was found in the distoangularly positioned ILTM, followed by the vertical, horizontal and mesioangular positions.

With regard to the relationship between the risk of acute disease and third molar position, Venta et al. [18] reported that the risk was greatest for distoangular lower third molars followed by vertical and mesioangular third molars. They explained this in terms of the likelihood of food particles accumulating in such third molars. Similarly, Knutsson et al. [19] showed that the higher percentage risk of developing a pathologic condition was associated with the vertical and mesioangular positions, because these positions occur much more frequently than the distoangular position. Eliasson and Heimdahl [6] also reported higher incidence of pathological changes in horizontal impacted third molars in their radiographic study.

A significant correlation could not be found between the incidence of cystic changes and the relation of the ILTM with the adjacent tooth in our study. Yamaoka et al., [20] in their radiographic study, reported that fully impacted third molars should be removed if there is a contact with the adjacent tooth because of the higher incidence of inflammation, but, according to our results, the possibility of cystic changes do not differ whether ILTM is with or without a contact with the adjacent tooth.

From the above results it is observed that incidence of cystic changes associated with ILTM is higher than radiographic examination alone. Age, angular position, and contact with adjacent tooth should be considered while decision making regarding extraction of impacted third molar.


The data from the present study justifies the extraction of the impacted third molars that are associated with signs and symptoms. Overall, the risk for the pathologies in follicular tissues associated with impacted third molars is high as compared to radiographic examination alone. However, at present, it does not appear possible to determine, which radiographically non-pathologic impaction with histopathologic evidence of cyst formation will progress to clinically detectable lesions. So all impacted third molars should be subjected to radiographic follow up and any follicular tissue obtained from extraction of such teeth should be sent for a histopathologic investigation and attention should be directed to age and type of impaction for the treatment planning of an impacted third molar.


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