| Abstract|| |
Objectives: To evaluate the efficacy of ultrasound in differential diagnosis of periapical radiolucencies.
Materials and Methods: Ten patients aged between 19 years and 40 years with periapical lesions associated with anterior maxillary or mandibular teeth were selected and consented for the study. Pre-operative periapical radiographs were obtained. Measurements and provisional diagnoses of the apical areas were made by two specialist observers on two separate occasions. Preoperative ultrasound examinations with Doppler flowmetry were then performed and the images assessed by two specialist observers for the size, contents, vascular supply and a provisional diagnosis made as to whether the lesion was a cyst or granuloma. Endodontic surgery was performed including curettage of the apical tissues to enable histopathological investigation, which provided the gold standard diagnosis. All measurements and findings were compared and statistically analyzed.
Results: Total 10 lesions were identified in 10 patients. On periapical radiographs, lesions were readily identified but observers were unable to differentiate granuloma from cyst using either modality. Where sufficient buccal cortical bone had been resorbed, ultrasound imaging was simple but underestimated the size of the lesions compared with periapical radiographs. In all cases, the ultrasound diagnosis agreed with the histopathological gold standard.
Conclusion: Ultrasonography (USG) can provide accurate information about the nature of intraosseous lesions of the jaws before any surgical procedure. It is proposed that USG with Doppler flowmetry can provide an additional diagnostic tool without invasive surgery, where treatment option is nonsurgical.
Keywords: Diagnosis, periapical, radiolucent, ultrasound
|How to cite this article:|
Khambete N, Kumar R. Ultrasound in differential diagnosis of periapical radiolucencies: A radiohistopathological study. J Conserv Dent 2015;18:39-43
|How to cite this URL:|
Khambete N, Kumar R. Ultrasound in differential diagnosis of periapical radiolucencies: A radiohistopathological study. J Conserv Dent [serial online] 2015 [cited 2019 Jul 18];18:39-43. Available from: http://www.jcd.org.in/text.asp?2015/18/1/39/148889
| Introduction|| |
Imaging plays a very important role in diagnosis of various lesions. Periapical lesions secondary to endodontic infection are usually diagnosed and treated based on the initial radiological findings.  The final confirmatory diagnosis is performed by histopathological examination of the tissues.  The majority of periapical radiolucencies of endodontic origin include periapical granuloma, periapical cyst, and periapical abscess. , Conventional radiographs can only determine the mesiodistal and superoinferior extent of the pathology but not the buccolingual extent.  Several radiographic features, such as the size and shape of the lesion and the presence of sclerotic border demarcating the lesion, support the diagnosis of periapical lesions. Traditionally, the size of a periapical radiolucent lesion has been thought to give an indication as to the nature of the underlying disease process. Studies by Lalonde et al., show that the lesion is more likely to be a periapical cyst if the periapical radiolucency is more than 1.6 cm in diameter. However this crieteria cannot be solely used for differentiation as some granulomas can become larger than 2.5 cm. 
In a recent histopathologic study of periapical lesions, it was conclusively shown that no relation existed between the presence of sclerotic border and the histopathologic diagnosis of the cysts. Although the statistical probability of occurrence of cyst may be higher among larger lesions, a conclusive relationship between the size of the lesion and cystic nature has not yet been substantiated. Thus periapical lesions can't be differentiated into cystic and non-cystic based solely on radiographic features. 
Cotti et al., in 2003 proposed that ultrasound may help to make a differential diagnosis between cysts and granulomas by revealing the nature of the content of a bony lesion.  Ultrasound is based on the evaluation of the reflected echoes from the interface between two different tissues having different acoustic properties. Ultrasound is recognized as one of the most risk-free methods of evaluating any disease in the human body. In the head and neck region, it is being used routinely to diagnose salivary gland disease, but in the dental literature so far, only very few researchers have reported the use of ultrasound in the examination of bone lesions of endodontic origin. ,,
The purpose of this study was to assess the diagnostic efficacy of and ultrasound with power Doppler flowmetry in the diagnosis of large periapical lesions and compare the findings with histopathologic finding as gold standard.
| Materials and Methods|| |
Ten patients between the ages of 19-40 years having periapical lesions in anterior maxillary and mandibular teeth diagnosed by their symptoms, clinical signs and radiographic findings were selected for the study. Informed consent was taken from all the patients before their inclusion in the study. A patient record sheet was tabulated to record the history, clinical examination, radiographic findings, ultrasound examination and histopathological findings.
All patients had a preoperative periapical radiograph taken by the paralleling technique using the Sensor-Pro film-holder with beam aiming device, (Rinn XCP, Densply, USA) and an Bio-Dent (Biomedicare, Thane, India) dental X-ray unit (70 kVp, 8 mA, 1.5 mm aluminium filtration, 60 mm beam diameter, focus to skin distance (FSD) of 200 mm and Kodak E-speed (Eastman KodakCo., France) film (no. 2, 31 mm × 41 mm).
The conventional radiographs were processed manually in fresh chemicals using accurate, time-temperature control and allowed to air dry. The radiographs were viewed and evaluated on a viewing box under optimum illumination and two specialist observers were asked to make a detailed description of the periapical lesions. Based on clinical and radiological findings, the presence of a periapical lesion was confirmed. The dimensions of all 10 lesions were measured in a superoinferior and a mesiodistal direction using callipers and a ruler on a millimeter scale by the three observers on two separate occasions, at day 1 and day 7 days to minimize the intraobserver and interobserver errors.
An ultrasound examination was then performed using the diagnostic ultrasound machine, LOGIQ-500 PRO (GE Medical System, USA), with color Doppler function, incorporating a high definition, multifrequency, 40 mm linear foot print, ultrasonic Probe (LA-39) operating at a frequency of 8-11 MHz. The ultrasound probe was first covered with disposable cling film for control of infection, and then covered with a layer of ultrasound gel (Ultragel, Medicon, India). The probe was positioned outside the mouth against the skin corresponding to the radicular area of tooth of interest. Once the bony defect was identified, the probe was moved slightly around the area, and its position was changed several times to obtain an adequate number of transverse (axial plane) and longitudinal scans (sagittal plane) to define the bony defect. The thin anterior buccal bone and possible fenestration allowed ultrasound images to be obtained in all cases and the echo characteristics (hypoechoic/anechoic) of the apical lesions to be determined. Color Doppler was applied to each examination to detect blood flow. A tentative differential diagnosis was agreed upon, based on the following principles:
Cystic lesion: A hypoechoic well-contoured cavity surrounded by reinforced bone walls, filled with fluid and with no evidence of internal vascularization on color Doppler examination.
Granuloma: A poorly defined hypoechoic area, showing rich vascular supply on color Doppler examination.
Mixed lesion: Predominantly hypoechoic area with focal anechoic area, showing vascularity in some areas on color Doppler examination.
Surgical endodontics and histopathological examination:
Following conventional principles of periradicular surgery, all 10 cases were operated on and biopsies were obtained from the periapical areas. After fixation in 10% buffered formalin, the 10 surgical specimens were processed for routine histopathological examination. All 10 patients healed uneventfully and have reported being symptom-free. The collected data was analyzed statistically using SPSS software (version 17) using inter-class corelation.
| Results|| |
Conventional radiographic examination showed definite presence of periapical radiolucent lesions in all 10 cases [Table 1]. Two observers recorded measurements taken on days 1 and 7 showed the mean superoinferior measurement to be 1.12 cm (±0.52) whilst the mean for mesiodistal width was 1.18 cm (±0.40 ). Statistical analysis using intraclass correlation showed that the two observers were in very good agreement with each other. However the observers were unable to differentiate whether the apical radiolucency indicated an underlying cyst or granuloma.
|Table 1: Recording of findings of radiographic and ultrasonographic findings|
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Echographic evaluation showed presence of periapical lesions in all 10 cases and were classified into three groups on the basis of echo characteristics and vascularity, that is Cystic, Mixed and granulomas. Four lesions showed anechoic areas with well-defined smooth contours and margins. There was no evidence of internal vascularization on application of power Doppler flowmetry. These cases were diagnosed as cystic fluid-filled cavities. Four cases showed ill-defined margins with predominantly hypoechoic areas and traces of vascularization. These lesions were classified as granulomas. Two cases showed predominantly anechoic lesions with focal hypoechoic areas with no evidence of internal vascularization. These findings of mixed lesions were indicative of pus-filled cavities.
In all 10 cases, histopathologic findings were in agreement with the ultrasonographic findings as shown in [Table 1]. In four cases the specimen revealed cystic lining consistency of non-keratinized stratified squamous epithelium of varying thickness with epithelial proliferation in an arcading pattern in certain areas suggestive of radicular cyst. Four cases were confirmed to be periapical granuloma, while one case was confirmed as infected radicular cyst and one was confirmed as periapical abcess [Figure 1] and [Figure 2].
|Figure 1: (a) IOPA showing large well-defi ned, corticated periapical radiolucency associated with maxillary left canine, first and second premolar suggestive of periapical cyst. (b) Ultrasound image shows surface of thinned buccal cortical plate of bone as hyperechoic border and the deep surface of the periapical lesion, and the anechoic area in between the two due to fluid contents suggestive of periapical cyst. (c) No evidence of vascularization in the wall on color Doppler examination also suggestive of periapical cyst. (d) Histopathological section of lesion confirming the diagnosis of periapical cyst|
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|Figure 2: (a) IOPA of case 2 showing well-defined, partially corticated periapical radiolucency associated with maxillary left lateral incisor suggestive of periapical cyst. (b) Ultrasound image shows showing well-defined anechoic areas with floating internal echoes indicative of an infected cyst. (c) Histopathologic section of the lesion confirming the diagnosis of infected periapical cyst|
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| Discussion|| |
Endodontics has traditionally relied heavily on radiography pre-operatively, during treatment and post-operatively, and the endodontic patient can often be exposed to repeated radiation of a single site. However, in spite of multiple radiographs, the nature of the underlying disease is notoriously difficult to determine from radiography alone. It is important to differentiate between periapical granuloma and cyst, because that helps not only in treatment planning and but also in predicting the treatment outcome. The conventional root canal therapy is the main treatment modality for periapical granuloma but has no benefit for periapical cysts, because true cysts are less likely to be resolved by conventional root canal therapy and require surgical intervention. Periapical pocket cysts, particularly smaller ones, heal completely after root canal therapy whereas true cysts, particularly large ones, are leof periapical lesions as cysts, and to improve the treatment outcome, it is necessary to evaluate using new and promising diagnostic methods likely to resolve by nonsurgical endodontics and therefore may affect the treatment outcome. Similarly, periapical surgery performed based on the radiographic diagnosis of cysts might have resolved by root canal therapy alone.  Therefore, to prevent the disproportionate application of periapical surgery based on unfounded radiographic diagnosis research into alternative non-invasive imaging techniques is necessary to see if they can provide the endodontist with more information, while at the same time reducing radiation exposure. 
Ultrasound real time imaging (also known as sonography) has wide application in numerous diagnostic fields of medicine. It is based on the phenomenon of reflection of ultrasound waves (echoes) at the interface between two tissues that have different acoustic properties. An interface or an area of tissue that causes a considerable reflection of ultrasound is described as hyperechoic, whereas an area which shows lower echo intensity than surrounding tissues is described as hypoechoic or transonic. Anechoic is an area where there is no reflection of echoes, typically within homogeneous liquids. ,
Various studies have concluded that ultrasound imaging provides sufficient information regarding the nature of the periapical lesions and is a reliable diagnostic technique for differentiating periapical lesions, that is, periapical cysts and granulomas, based on the echotexture of their contents and the presence of vascularity using color power Doppler. According to study conducted by Raghav et al., Ultrasound had 95.2% accuracy in diagnosing periapical lesion. It also had a very high sensitivity and specificity in diagnosing periapical lesions as compared to conventional and digital radiography. 
In present study, total 10 periapical lesions were evaluated using conventional periapical radiographs and ultrasound imaging. The two observers were uncertain about the exact diagnosis of lesions on conventional radiographs. Ultrasound unequivocally identified the contents and nature of the lesion in all 10 cases. The Ultrasound diagnosis was in agreement with that of histopathological diagnosis in all 10 cases. These results show that there is a definite co-relation between the echostructure of lesions and histopathological findings. This study confirms that ultrasound imaging is a very useful imaging technique which can give significant diagnostic information in relation to periapical lesions in the anterior region where the buccal bone is thin. The results suggest that, if only clinical findings were available, an endodontist trained to use ultrasound should be able to diagnose a periapical lesion without taking a periapical radiograph and be sure of the underlying disease process. This will ultimately help in determining the exact treatment plan.
Ultrasound real-time imaging is easy, reproducible and convenient to use. The equipment is relatively cheap compared with other advanced imaging modalities. The images obtained are easy to read once the observer is trained. They are also simple to store and retrieve. By obtaining a real-time image, a working diagnosis could be made without delay and may prevent unnecessary exposure of the patient to ionizing radiation. No harmful effects of ultrasound waves have been observed in the tissues as a result of ultrasound examination.  Ultrasound can provide more accurate information about the nature of the lesion which helps in predicting treatment outcome. The limitations of US imaging are operator dependency, difficulty in attributing the lesions to a specific area of bone because the dental landmarks (that is, roots) were not specifically visualized, and that thinning or discontinuity in the labial or buccal cortical plate is required for US waves to penetrate and diagnose periapical lesions.
| Conclusion|| |
Ultrasound imaging can be used as an adjunct to routine use of conventional radiography in the diagnosis of periapical lesions and would be an important contribution to the trend toward radiation-free oral diagnostics. It can prove to be a very valuable tool in the noninvasive method of diagnosis of periapical lesions. Further studies with larger sample size would need to be conducted in future to confirm this finding.
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Dr. Rahul Kumar
Shop No. G2, Queensgate CHS, Hiranandani Estate, Patlipada, Thane - 400 607, Maharashtra
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2]