| Abstract|| |
In dental practice, impacted third molar teeth are a common finding. The dentists usually remove them if they are associated with some radiographic finding suggestive of a cyst or a tumor or if they cause pain or resorption of the adjacent teeth. It has been found that, in many cases, even the radiographically and clinically asymptomatic impacted mandibular third molars are associated with some pathology. This paper brings into the light two cases with clinically and radiographically normal impacted third molar teeth associated with dentigerous cyst, thus highlighting that the radiographic appearance is not a reliable indicator of the absence or presence of pathology associated with the impacted third molars.
Keywords: Cyst, follicle, impacted
|How to cite this article:|
Kaushal N. Is radiographic appearance a reliable indicator for the absence or presence of pathology in impacted third molars?. Indian J Dent Res 2012;23:298
|How to cite this URL:|
Kaushal N. Is radiographic appearance a reliable indicator for the absence or presence of pathology in impacted third molars?. Indian J Dent Res [serial online] 2012 [cited 2021 Jan 23];23:298. Available from: https://www.ijdr.in/text.asp?2012/23/2/298/100470
| Introduction|| |
Impacted teeth are a common finding among patients seen in dental practice. An impacted tooth is the one that is prevented from erupting into position because of malposition, lack of space, or other impediments.  Approximately, one in every five, third molars, both mandibular and maxillary, is impacted. 37% of the mandibular and 15% of the maxillary impacted third molars have some type of radiolucency around their crowns.  Infection, non-restorable carious lesions, cysts, tumors, and destruction of the adjacent teeth and bone have been defined as indications for the removal of impacted third molars according to the National Institutes of Health Consensus Development Conference.  Among the various diseases which can affect the impacted teeth, the most common are the dentigerous cyst, odontogenic keratocysts, ameloblastoma and nonspecific inflammatory tissue. 
Over the years, radiographic appearance has been used as an indicator of absence or presence of pathology associated with the impacted third molar teeth. Pericoronal radiolucency less than 2.5mm in width usually was considered to be an indicative of no pathology. However, this is not a reliable method. The other reliable method to know the pathologies, which might be associated with the impacted teeth is to do a histological examination of the pericoronal tissues of the impacted teeth. The absence of radiographic disease is not necessarily reflective of the absence of the disease. There can be high incidence of cystic changes associated with the impacted teeth that have no radiographic evidence of the disease. The incidence of the pathological changes associated with impacted teeth seems to be higher than reported from the radiographic studies. It is not possible to determine which radiographically normal follicles will progress into clinically detectable lesions. During the histologic examination, there can be high incidence of microscopic disease. The removal of the asymptomatic impacted teeth will minimize the risk of cyst and tumor development.  Cystic changes may be encountered in the histopathologic examination of asymptomatic impacted molars.
| Case Reports|| |
In the first case, a 20 year old female patient reported for a routine dental checkup, where the orthopantomogram showed four impacted third molars in both maxillary and mandibular arch. The third molars in the mandibular arch were seen to be in a mesioangular impaction as shown in [Figure 1]. These impacted mandibular third molar teeth as seen in the orthopantomogram were impinging upon the roots of the mandibular second molar teeth as seen in [Figure 1]. These two impacted mandibular third molar teeth were extracted. The pericoronal space around these two impacted mandibular third molar teeth was less than 2.5mm as is seen in the [Figure 1]. After the removal of the two mandibular impacted third molars, the pericoronal soft tissues were sent for the histopathological examination.
|Figure 1: Orthopantomogram showing the impacted teeth with a pericoronal space less than 2.5mm|
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In the second case, a 25 year old female patient reported with a chief complaint of retained deciduous teeth. When the orthopantomogram was taken, it was found that along with the retained deciduous teeth, the patient also had an impacted lower left mandibular third molar in a mesioangular impaction which was impinging upon the roots of the second molar tooth as seen in [Figure 2]. Hence, it was decided to remove the impacted lower left mandibular third molar. The pericoronal space around this impacted third molar was also less than 2.5mm as seen in [Figure 2]. After its removal, the pericoronal soft tissue which surrounded this impacted tooth was sent for the histopathological examination.
|Figure 2: Orthopantomogram showing pericoronal space less than 2.5 mm around the impacted mandibular left impacted third molar|
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During the histopathological examination, it was found that in both the cases, there was the presence of an epithelium and connective tissue as seen in [Figure 3] and [Figure 4]. The epithelium in both the cases was stratified squamous type, discontinuous in nature, few cells in thickness as shown in [Figure 3] and [Figure 4]. The rete peg formation was absent and epithelium was separated from the underlying connective tissue at few places. The underlying connective tissue was made up of loosely arranged collagen fiber bundles. Variable number of islands of odontogenic epithelium were also seen in the connective tissue.
|Figure 3: 10× magnification of Hematoxylin and Eosin stained section for case 1|
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|Figure 4: 10× magnification Hematoxylin and Eosin stained section for case 2|
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All these features were suggestive of a dentigerous cyst in both the cases.
| Discussion|| |
Tooth eruption has been defined as the movement of a tooth from its site of development within the alveolar process towards its functional position in the oral cavity.  Impacted teeth are a common finding among the patients seen in dental practice.  Impacted tooth is the one that is prevented from erupting into position because of malposition, lack of space, or other impediments.  One of every five third molars, both mandibular and maxillary, is impacted.  There is a considerable variation in the prevalence and the distribution of impacted teeth in different regions of the jaw.  The most common impacted teeth are the third molars (98% of all impacted teeth), ,, then the maxillary canines,  then the others.  Similarly, in this report, all the impacted teeth were third molars as they are the most commonly impacted teeth as stated by Chu et al,  followed by the canines. The crowns of unerupted teeth are normally surrounded by a soft tissue remnant known as the dental follicle.  When an unerupted third molar is removed, the pericoronal tissue should be a dental follicle. If an unerupted third molar is retained in the jaw bone, the pericoronal tissue may develop pathological conditions that will subject the patient to health risks. ,
Radiographically, the pericoronal follicles present as slight semicircular radiolucencies around unerupted teeth. ,, This radiolucent space around the tooth has a thin radiopaque border.  It is often assumed that, the absence of pericoronal radiolucency reflects the absence of pathosis. It has been suggested that, pericoronal radiolucency of <2.5mm in width is non-pathologic. , However, more than half of the specimens with radiographically normal follicular radiolucency developed pathological entities.  Baykul et al, in their study also said that the incidence of soft tissue pathologic condition is higher than generally assumed from the radiographic examination alone.  Therefore, it can be concluded that the radiographic appearance may not be a reliable indicator for the absence of disease within a dental follicle. ,,,, These findings are similar to the findings observed in this report, where the pericoronal spaces were radiographically normal with a pericoronal space of < 2.5mm. Impacted third molars are known to be associated with an increased risk of different disorders and complications.  Odontogenic tissue surrounding impacted tissue has the potential to differentiate into a wide variety tissue types, and the potential for cysts and tumors exists.  Among the pathologic changes, that may develop in the pericoronal follicles of the impacted third molars, are dentigerous cyst. ,,,
A dentigerous cyst is one that encloses the crown of an unerupted tooth by expansion of its follicle, and is attached to its neck. , This is one of the most common type of odontogenic cyst, estimated to be 20% of all jaw cysts.  Different radiographic criteria have been put forward in various studies to differentiate the dentigerous cyst from a dental follicle. Weuhrmann said that, if the pericoronal space exceeds 1mm in width, it raises the suspicion of possible development of a dentigerous cyst. A slightly widened pericoronal space, up to 1.5mm in width, may be considered a questionable dentigerous cyst. This space could be an evidence of the early stage of development of a dentigerous cyst. If the pericoronal space is 2mm in width, this may be considered suggestive of a dentigerous cyst. If the width of the pericoronal space has reached 2.5mm or more, this may be considered a probable dentigerous cyst in most instances.  Others say that, some unerupted teeth have a slightly dilated follicle in the pre-eruptive phase and this does not signify a cyst, nor even necessarily a potential cyst unless the pericoronal width is at least 3mm to 4mm.  However, smaller pericoronal radiolucency may present either as a large dental follicle or a small dentigerous cyst.  Glosser JW and Campbell JH,  in their study found a high incidence of dentigerous cyst associated with impacted third molars which were radiographically normal with follicular space <2.4mm. In this study, all the impacted third molars had a pericoronal space of <2.4mm. The percentage of dentigerous cysts in the follicles varies from 1.8% as reported by Maaita J,  14.1% as reported by Yildirim et al,  34% as reported by Adelsperger et al,  and 38% as reported by Mesgarzadeh et al.  [Figure 3] and [Figure 4] shows the dentigerous cyst-like changes seen in this report.
In most of the studies, the prevalence of dentigerous cyst was more in men than in women as reported by Daley et al,  Glosser and Campbell,  Saravana GHL and Subhashraj K,  Benn et al.  However, in this report, both of the dentigerous cysts were found in female patients which is contrary to the findings of the above mentioned studies.
Dentigerous cysts occur most often in the second and the third decade of life as reported by Rajendran R,  Daley et al.  All of the dentigerous cysts in this report were seen in the age group of 21-30 years of age.
Histologic features of a dentigerous cyst are a thin connective tissue wall with a thin layer of stratified squamous epithelium lining the lumen. Rete peg formation is generally absent except in the cases that are secondarily infected. , The connective tissue wall is frequently quite thickened and is composed of a very loose fibrous connective tissue. There is the presence of varying number of islands of odontogenic epithelium.  Similar findings were seen in this report also as depicted in [Figure 3] and [Figure 4].
Precautions and recent advances
Even though surgical removal of impacted third molar is one of the most frequent procedures performed in oral and maxillofacial surgery, neurosensory dysfunction of iatrogenic origin is a common and distressing sequel to the surgical procedure. ,, Damage to the inferior alveolar occurs in about 1% to 22% of the surgical procedures.  To avoid this, it is important that an accurate preoperative assessment of the topographic relationship between the impacted third molar and the inferior alveolar nerve is performed.  A close nerve - tooth relation indicates a higher risk of post operative nerve impairment.  An orthopantomogram (OPG) is the most commonly utilized imaging technique prior to the surgical removal of the impacted third molar.  However, it represents a 2- dimensional view of an intricate, 3- dimensional anatomic relationship, and it lacks in furnishing diagnostic information regarding an anatomic relationship of the impacted third molars and the inferior alveolar nerve for planning and treatment of the difficult impactions.  These drawbacks can be overcome by utilizing 3-dimensional imaging techniques. Since the development of computerized tomography (CT) in 1972, 3-dimensional (3D) imaging has become more and more routine, and has been, of course, used including before impacted third molar removal.  Currently, cone beam computer tomographic images are significantly superior to the panoramic images in sensitivity and specificity of diagnosis, resulting in a higher level of intrasurgical safety.  Hence, when the risk factors are detected or when they cannot be excluded in a conventional 2-dimensional radiography, 3-dimensional imaging is justified to improve the risk assessment and surgical decision making.  However, in view of the socioeconomic conditions of some developing countries, high cost of computed tomography scans, , the use of panoramic radiography is justified in planning the surgery of the impacted teeth, despite the fact that its predictability is low.  Similar challenges were faced in this report of cases.
| Conclusion|| |
Radiographically dental follicle is seen as semicircular radiolucency around the crown of the unerupted teeth with a thin radiopaque border. It is assumed that an absence of pericoronal radiolucency reflects an absence of disease in the dental follicle. However, pathologic changes can be seen in dental follicles that are radiographically normal. Hence, the radiographic appearance may not be a reliable indicator of an absence of disease within a dental follicle, and that clinical judgment based solely on the radiographic appearance may be quite deceptive. New techniques like immunochemical methods might provide further assistance in histological diagnosis of abnormalities associated with dental impactions.
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Department of Oral Pathology, B.R.S. Dental College and Hospital, Village Sultanpur, Panchkula, Haryana
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4]