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 Table of Contents  
ORIGINAL ARTICLE
Year : 2017  |  Volume : 29  |  Issue : 1  |  Page : 20-24

Predicting pathology in impacted mandibular third molars


Department of Oral Medicine and Radiology, Pacific Dental College and Hospital, Debari, Rajasthan, India

Date of Submission18-Jul-2016
Date of Acceptance27-May-2017
Date of Web Publication04-Aug-2017

Correspondence Address:
Aveek Mukherji
33-D, Prasanna Naskar Lane, Kolkata - 700 039, West Bengal
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jiaomr.JIAOMR_83_16

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   Abstract 

Introduction: The rising incidence of the impacted mandibular third molars and their association with pathologies is now considered a public health problem. Aims and Objectives: The objective of this study was to assess the position of impacted mandibular third molars that are prone to developing pathologies and to determine the frequency and type of pathological conditions associated with these impacted teeth to facilitate planning for their prophylactic removal. Materials and Methods: Consecutive panoramic radiographs and clinical examination of 300 patients with impacted mandibular third molars were collected. They were segregated according to Pell and Gregory’s classification, Winter’s classification, and according to their state of eruption. These were correlated with associated pathologies based on clinical and radiological criteria. Statistical Analysis Used: Descriptive statistics included computation of percentages, mean, and standard deviations. The statistical test applied for the analysis was Pearson’s Chi-square test (χ2). For this test, confidence interval and P value were set at 93% and ≤0.03, respectively. Results: The pathology most commonly associated with impacted third molars was pericoronitis, which had the highest frequency of occurrence in partially erupted, distoangular, and IA positioned (as per Pell and Gregory classification) impacted teeth. Impacted mandibular third molars, which were in IA position, placed mesially, and partially erupted, were prone to develop pathologies such as dental caries and periodontitis. Conclusion: The clinical and radiographical features of impacted third molar may be correlated to the development of their pathological complications. The partially impacted mandibular third molars with mesioangularly aligned in IA position have the highest potential to cause pathological complications.

Keywords: Impacted tooth, mandibular third molar, pathology, position of tooth


How to cite this article:
Mukherji A, Singh MP, Nahar P, Balaji BS, Mathur H, Goel S. Predicting pathology in impacted mandibular third molars. J Indian Acad Oral Med Radiol 2017;29:20-4

How to cite this URL:
Mukherji A, Singh MP, Nahar P, Balaji BS, Mathur H, Goel S. Predicting pathology in impacted mandibular third molars. J Indian Acad Oral Med Radiol [serial online] 2017 [cited 2018 Dec 13];29:20-4. Available from: http://www.jiaomr.in/text.asp?2017/29/1/20/212094


   Introduction Top


Peterson characterized impacted teeth as those teeth that fail to erupt into the dental arch within the expected time.[1] Mandibular third molars are the most commonly impacted teeth.[2] The number of people reaching adult life with impacted third molars seems to be increasing to an epidemic extent.[3] A number of authors have related the type of pathologies associated with third molars to a series of anatomical parameters.[4] This study explores the correlation between the clinical manifestations produced by lower impacted third molars and their position within the mandible in an attempt to identify those teeth most likely to cause complications.


   Materials and Methods Top


Consecutive panoramic radiographs and clinical examination of patients with impacted mandibular third molars who attended the Department of Oral Medicine and Radiology, Pacific Dental College and Hospital, Udaipur, Rajasthan, India were collected for the study. The minimum age for inclusion was 18 years because of the accepted view that third molars normally start to erupt by that age. The patients who met the defined inclusion criteria were informed regarding the purpose and design of the study. They were examined clinically under aseptic conditions, and were made to sign the consent form. Case history was taken and relevant findings were recorded in the clinical examination form. Patients complaining of or giving a history of complaints associated with mandibular third molars were noted. Mucosal coverage was assessed and was used to divide the impacted mandibular third molars into partially erupted and completely unerupted teeth.

Radiographs were taken according to the specifications of the Panoramic Machine (Kodak 8000C), which has a constant magnification of 1.14 ± 10%. Minimum exposure to radiation was achieved by following different procedures such as the use of lead apron and thyroid collar. The radiographs were assessed to determine the presence of impacted mandibular third molars on either one side or on both the right and left sides. The angulation of the teeth were also noted based on Winter’s classification with reference to the angle formed between the intersected longitudinal axes of second molar and third molars. When in doubt, the angulation of the impacted tooth was measured using the method of Quek et al. [Table 1].
Table 1: Quek et al.'s modification of Winter's classification

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The depth of lower third molar in relation to occlusal plane was documented along with the distance or width between the vertical ascending mandibular ramus and distal surface of the second molar, according to the classification of Pell and Gregory [Table 2]. Radiographic evidence of pathologies associated with the third molars were also noted. These included caries of the adjacent teeth, periodontal bone loss of the adjacent tooth more than 5 mm below the cementoenamel junction, and pericoronal cysts.
Table 2: Pell and Gregory classification

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Data collected were entered into a spreadsheet computer programme (Excel 2010; Microsoft, US) and then exported to data editor page of SPSS 15 (SPSS Inc., Chicago, IL, USA). Descriptive statistics included computation of percentages, mean, and standard deviations. The statistical test applied for the analysis was Pearson’s Chi-square test (χ2). For this test, confidence interval and P value were set at 95% and ≤0.05, respectively.


   Results Top


Three hundred patients were included in the study, out of which 156 were males and 144 were females. The patients were divided into seven groups according to age. The maximum number of patients with impacted tooth belonged to the age group of 18–20, and the prevalence decreased to some extent with the increase in age [Graph 1]. The mean male age was 27.8 ± 10.6, the mean female age was 24.4 ± 7.2, and the mean age of the sample irrespective of the gender was 26.2 ± 9.3. Two hundred and nineteen patients (73%), i.e., almost three-fourth of the sample had impacted third molars on both the sides of the mandible. Among the rest who had impaction on only one side, 54 (18%) patients had fully erupted tooth on the other side, whereas 27 (9%) had the tooth missing on the other side. A total of 517 impacted teeth were present in the 300 patients. Among them, 263 (50.8%) belonged to the left side, whereas 255 (49.2%) belonged to the right side. Two hundred and seventy-three (52.7%) impacted mandibular third molars belonged to males, whereas 245 (47.3%) belonged to the female patients. When the pathologies were compared with the age groups, the highest number of teeth and the highest number of pathologies in the study belonged to the age group of 18–20 years. The number of pathologies in the groups mostly reduced with an increase in age. When Pearson Chi-square test was applied to these findings, the results were found to be significant [Graph 2].



The most number of teeth were positioned in the IIB position according to the Pell and Gregory classification. The greatest number and frequency of occurrence of pathology was found in the IA position [Graph 3]. On applying the Pearson Chi-square test, the comparison was found to be highly significant. Most of the teeth in the study were mesially impacted according to the Winter’s classification. The same group had the highest number and frequency of occurrence of pathologies [Graph 4]. According to the Pearson Chi-square test, the findings were highly significant. Two hundred and twelve teeth (41%) were completely unerupted, whereas 305 (59%) were partially erupted. The number and frequency of occurrence of pathology was higher in the partially erupted group. All the teeth with dental caries and bone loss, and most of the teeth with pericoronitis belonged to the group of partially erupted teeth, whereas all the teeth with dentigerous cyst belonged to the group of completely unerupted teeth [Graph 5]. When Pearson Chi-square test was applied to these findings, the result was highly significant. Among the 517 impacted mandibular third molar teeth, 424 did not have any associated pathology. Forty-two had pericoronitis, 38 had adjacent dental caries, 10 had associated bone loss, and only 3 had dentigerous cyst [Graph 6].




   Discussion Top


The prevalence of mandibular third molar impactions is variable in different populations, ranging from almost nil in Nigerians to approximately 72% in the Swedish.[5] In this study, the maximum number of patients with impacted tooth belonged to the age group of 18–20 years. This was in contradiction with the study conducted by Syed et al.[6] and Doğan et al.[7] who found the highest incidence of impaction to be in the age group of 20–25 years and 20–29 years, respectively. The discrepancy in the age group is probably because a large number of students from the surrounding colleges in the age group of 18–20 years regularly visit the hospital for routine check-up. In a study conducted in south India by Ramamurthy et al.,[8] bilateral impaction of mandibular third molar was more common (71%) than unilateral impaction. Similarly, 73% of the participants for this study had bilateral impaction.

The clinical status of an unerupted tooth can be accurately determined not only through use of radiographs but also by means of oral examination; although panoramic radiography is a standard technique that yields high-quality information about the anatomic condition of the retromolar region.[9] Therefore, in this study, clinical evaluation of the patients was followed by evaluation with the panoramic radiographs. The impacted third molars were classified clinically according to the state of mucosal coverage and divided into teeth that were partially erupted, or completely unerupted, as done by Kaushik et al.[10] Pell and Gregory and Winter’s classifications were used on the panoramic radiograph in this study as they were simple, practical, and easy to apply.

In our study, mesioangularly (44.9%) impacted mandibular molars were most common, whereas vertical (30.9%) angulation was the next most common finding. The result was in accordance with that found by Hyczy et al.,[7] Kanneppady et al.,[11] and Ramamurthy et al.,[8] all of whom found the mesiangular position to be the most common one. Almendros Marqués et al.[4] in their study found the position IIB (49.9%), to be the most predominant position according to the Pell and Gregory classifi cation, followed by IIA (37.5%). In our study also, the most common position was IIB (38.9%). The next most prevalent position was IA (22.4%), followed by IIA (19.9%).

In the present study, the most common pathology was pericoronitis, followed closely by dental caries. This is in accordance with the findings of Ma’aita et al.[12] Pericoronitis was also found to be the most prevalent pathology by Almendros Marqués et al.[4] and Doğan et al.[7] Indira et al. found that the vertical and distoangular impactions have slightly more prevalence of pericoronitis when compared to other types. The risk of an acute problem was the greatest for distoangular lower third molars.[9] In our study, the number of pericoronitis cases were equal in the mesioangular, vertical, and distal position, however, the frequency of occurrence was highest in the distoangular position (21.2%), followed by vertical (8.8%), and mesioangular (6%). This may be explained by the following: The accumulated food on the occlusal surface of a distoangularly impacted tooth slope downwards and distally by occlusal movements. The amount of soft tissue surrounding a distoangular third molar may be greater than that with mesioangular and horizontal impaction.[9]

In this study, 35 out of 42 (83%) of the teeth with pericoronitis were partially erupted and 7 out of 42 (17%) were completely unerupted. This finding is in accordance with the study conducted by Indira et al.[9] who found that 86% cases of mandibular third molars with pericoronitis were partially erupted and 14% cases were completely impacted. Studies have demonstrated that vertical and Class A impaction have high potential for developing pericoronitis.[11] In our study also, the maximum number of cases of pericoronitis belonged to the Class A group. Indira et al. found that there was an increased prevalence of pericoronitis in the position IA followed by IIB and IIA.[9] In our study, the position with the highest frequency of pericoronitis according to Pell and Gregory was IA, followed by IIA. Hence, our study predicts that impacted mandibular third molar in partially erupted, distoangular, and IA position had the highest chances of developing pericoronitis.

In the study conducted by Chu et al.,[13] approximately 7% of mandibular second molars associated with impacted third molars had dental caries. In our study, 7.3% of the impacted teeth had dental caries in the associated second molars. Sheikh et al.[14] in their study proved that susceptibility to distal caries in the second molar teeth is linked to mesioangular positioning of the impacted third molar in particular at level B and Class I position. In our study, the highest incidence of dental caries was in the mesioangular position. The position with highest frequency of occurrence was IA (16.3%) followed by IB (11%).

In case of mesioangular lower third molars partially exposed in the oral cavity, occlusal surfaces form plaque accumulative crevices against the distal surfaces of the second molars. Such teeth are more critical to adjacent second molar because impacted teeth in these positions cause caries and resorb distal surface and root on distal aspect of mandibular second molars.[14] In our study, the maximum frequency of occurrence of dental caries according to the mucosal coverage was in the partially erupted teeth (12.5%). Our study predicts that partially erupted mandibular third molars in mesioangular and IA position are most capable of causing dental caries in the distal surface of the adjacent second molars.

Stanley et al.[15] had suggested that, after recognizing the magnification factor in panoramic films, a cyst should have a pericoronal space of at least 5.0 mm and exhibit a well-defined circumscribed border. We found only three teeth in our study that matched these criteria. Stanley et al.[15] in their study found the incidence of cyst in 0.81% of the teeth. In our study, the incidence was in 0.6% teeth. Though the finding is close to the finding by Stanley et al., it was closer to the finding by Troller et al., who found the incidence of cyst to be 0.68%.[16]

Ideally, 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.[3] This was not possible in our study as many patients, especially those with symptom free impacted mandibular third molars were reluctant to get their teeth extracted.

Periodontal defects frequently occur at the distal aspect of mandibular second molars, which are next to mesioangular impacted third molars that have oral communication.[17],[18] In our study, 7 out of the 10 impacted mandibular third molars associated with bone loss in the distal part of the adjacent second molars were mesioangularly impacted. The other three were horizontally impacted. Nine of them were partially erupted, whereas one was completely unerupted. Thus, we can predict that partially impacted mandibular third molars in mesiangular position are at a higher risk of developing bone loss distal to the adjacent second molars.

When Pearson Chi-square test was applied to the findings, the pathologies associated with the impacted mandibular third molars was found to be significant with the age group. The comparison with the side of involvement (left or right) or gender (male or female) was not significant.


   Conclusion Top


Being the last teeth to erupt, impacted mandibular third molars possess high chances of getting impacted. According to our study, the pathology most commonly associated with impacted mandibular third molars was pericoronitis, which had the highest chances of occurrence in partially erupted, distoangular, and IA position. Dental caries in the adjacent second molar was the second most common pathology, mostly associated with partially erupted mandibular third molars in mesioangular and IA position. Impacted mandibular third molars which were in IA position, placed mesially, and partially erupted were most prone to develop pathologies.

Asymptomatic patients who decide to retain their third molars should have periodic clinical and radiographic examinations to detect any disease before it becomes symptomatic. A more elaborate study, keeping genetics, race, and food habit (altered intensity of the use of the masticatory apparatus) in mind, might give a better insight about the subject. A longitudinal study with a bigger sample size consisting of patients who retain their impacted mandibular third molars can help in more precise planning of prophylactic extraction.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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Doğan N, Orhan K, Günaydin Y, Köymen R, Okçu K, Uçok O. Unerupted mandibular third molars: Symptoms, associated pathologies, and indications for removal in a Turkish population. Quintessence Int 2007;38:e497-505.  Back to cited text no. 7
    
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Chu FC, Li TK, Lui VK, Newsome PR, Chow RL, Cheung LK. Prevalence of impacted teeth and associated pathologies— A radiographic study of the Hong Kong Chinese population. Hong Kong Med J 2003;9:138-63.  Back to cited text no. 13
    
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Stanley HR, Alattar M, Collett WK, Stringfellow HR Jr, Spiegel EH. Pathological sequelae of “neglected” impacted third molars. J Oral Pathol 1988;17:113-7.  Back to cited text no. 15
    
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