Role of ultrasound and color doppler in diagnosis of periapical lesions of endodontic origin at varying bone thickness.

AIMS: To access the role of ultrasound and color doppler in diagnosing periapical lesions of maxilla and mandible. SETTINGS AND
DESIGN: This study was conducted in the Department of Conservative Dentistry and Endodontics (Faculty of Dental Sciences), Department of Radiotherapy, and Department of Pathology.
MATERIALS AND METHODS: The study group comprised 30 patients with periapical lesions of endodontic origin in maxilla and mandible requiring endodontic surgery. After thorough clinical and radiographic examination patients were subjected to ultrasound and color doppler examination, where the lesions were assessed for their contents as to cystic or solid. Following which periapical surgery was done and the pathological tissue obtained was subjected to histopathological examination. The results of the ultrasound examination were correlated with histopathological features. The diagnostic validity of ultrasound was assessed by calculating the sensitivity, specificity, positive predictive value, and negative predictive value. STATISTICAL ANALYSIS USED: The statistical analysis was done using statistical package for social sciences (SPSS) version 15.0 statistical analysis software. The values were represented in number (%).
RESULTS: Within the limitations of the current study it can be stated that although ultrasound may not establish the definitive diagnosis, it can facilitate the differential diagnosis between cystic and solid granulomatous lesions. However, this technique may have a limited role in detecting periapical lesions present in the region with thick overlying cortical bone.
CONCLUSION: Ultrasound can routinely be recommended as a complimentary method for the diagnosis of periapical lesions of endodontic origin. However, this technique may have a limited role in detecting periapical lesions present in the region with thick overlying cortical bone.

INTRODUCTION

Imaging techniques play a very important role in the specialty of endodontics. Periapical lesions accompanying endodontic infections are usually diagnosed and treated based on the initial radiological findings. Conventional radiography is the most common and routine radiographic procedure employed and so is often referred to as the physician's first diagnostic aid. However, it does not provide conclusive evidence on the extent or limits, dimensions, and content of the lesions,[12] i.e., it cannot differentiate between cystic and noncystic lesions.[3] To be better able to predict the outcome of nonsurgical endodontic treatment and in some cases to try to avoid surgical trauma it is important to evaluate new and perhaps more promising methods of imaging for the study of periapical lesions.

Ultrasound has revolutionized every sphere of science and technology. It has abundant potentials to monitor physiological conditions, investigate suspected pathology and aid in the treatment of the same.[45] These applications are further enhanced by its high-end aspects of color power doppler to assess blood flow, three-dimensional imaging, and detection of tissue harmonies for improved resolution. In addition, the application of color doppler ultrasound can offer further information regarding the presence, direction, and velocity of blood flow within the examined tissue.[4567891011]

Ultrasound is based on the phenomenon of reflection of ultrasound waves (echoes) at the interface between two tissues that have different acoustic properties.[12] An interface or an area of tissue that causes a considerable reflection of ultrasound is described as hyperechoic, whereas an area that shows lower echo intensity than the surrounding tissues is described as hypoechoic or transonic. Anechoic is an area where there is no reflection of echoes, typically within homogeneous liquids. Although, ultrasound is recognized as one of the most risk-free methods of evaluating any disease in the human body it is not free of limitations. Bone surfaces demonstrate total reflection of ultrasound waves (hyperechoic/echogenic); thus structures in and beyond intact bones are not normally detectable by ultrasound.[5] However, where the bone cortex has become thinned or perforated, ultrasound imaging can still be performed through such bone “windows.” This limitation may affect the results when it is used for diagnosis of periapical lesions of endodontic origin. As bone thickness varies in different regions of the jaw[1213] the accuracy of ultrasound may as well vary in diagnosing periapical lesions in regions where cortical bone is relatively thicker.

The purpose of this study is to evaluate the efficacy of ultrasound and color doppler examination in diagnosis of periapical lesions of endodontic origin in different regions of the jaw with varying cortical bone thickness and to correlate the ultrasound diagnosis of the lesions with the histopathological findings.

MATERIALS AND METHODS

The present study, was conducted in the Department of Conservative Dentistry and Endodontics (Faculty of Dental sciences), Department of Radiotherapy and Department of Pathology. The study group comprised of 30 patients of both sexes with age from 14 years to 45 years, who reported to the outpatient department of the Department of Conservative Dentistry and Endodontics, with periapical lesions of endodontic origin in different regions of both maxilla and mandible. Depending on the average cortical bone thickness[11] maxilla and mandible can each be arbitrarily divided into the following three segments:

Anterior region, including incisors and canines

Premolar region, including first and second premolars

Molar region, including first, second, and third molars.

Five patients diagnosed to have periapical lesions of endodontic origin, in each of the above segment by clinical and radiographic examinations were chosen for the study both for maxilla and mandible [Table 1]. Only those individuals who agreed to undergo these procedures were included in the study and written informed consent was taken from each. Based upon the inclusion criteria, 30 individuals became part of this study. Recording of history regarding the periapical lesion, general history, and clinical examination were performed in a systematic manner. All the appropriate conventional radiographs, needed to diagnose the jaw lesions, were taken. After thorough clinical and radiographic examination all patients were subjected to ultrasound and color doppler examination in the Department of Radiotherapy, using the imaging device Toshiba Nemio-SSA550A, (Nishimura Medical Instrument Co., Ltd, Kyoto-shi, Japan). The high-frequency and high-resolution probe having a frequency of 7-9 Mhz was used extraorally that was moved over the site of interest in such a manner to obtain an adequate number of transversal scans to define the bony defect. The interpretation of grey values on an image is based on a qualitative comparison of the echo intensity with that of normal tissue.[14] The following lesion parameters were checked by ultrasound and color doppler examination:

Table 1

Distribution of subjects according to the site

Dimensions of the periapical lesion

Type of echo from lesions—hypoechoic or hyperechoic

Quantitative and qualitative analysis of vascularity of the affected area was done in form of peak systolic and peak diastolic vascularity.

Nature of vascularity—arterial or venous

Periapical surgery was performed using aseptic techniques. After fixation in 10% buffered formalin, the surgical specimens were subjected to histopathological examination. So depending upon the histologic presentation of the lesion a definitive diagnosis was made. The lesions were classified as: Cystic or granulomatous. Histological observation was used as validating criteria and taken as the gold standard. The results of ultrasound were correlated with histopathological findings and were statistically analyzed.

RESULTS

Out of the 30 subjects, 3 subjects were diagnosed by ultrasound and color doppler examination to have cystic lesion, 20 subjects to have granulomatous lesion, and 7 subjects were found to have no lesion at all in spite of the well-defined radiolucent lesion present on the radiograph [Figure 1]. Histopathologic examination confirmed the diagnosis of all cystic and granulomatous lesions diagnosed by ultrasound [Figure 2]. However, in those subjects where no lesion was detected by ultrasound, definite granulomatous pathology was detected in all seven of them [Table 2]. All the subjects with cortical bone thickness below 1.6 mm (mean value) were correctly diagnosed to be having lesion, whereas out of those having ≥1.6 mm bone thickness only 65% turned out to be having lesion; thus, showing an association with bone thickness and detection of presence of lesion (P = 0.033), which is statistically significant [Table 3].

Figure 1

Radiograph showing well defined radiolucent lesion and hypoechoeic cystic lesion seen in ultrasound

Figure 2

Histopathologal features suggestive of periapical cyst

Table 2

Correlation between ultrasonography and histopathological features

Table 3

Accuracy of ultrasonographic diagnosis depending on cortical bone thickness

Diagnostic validity tests (sensitivity, specificity, positive predictive value, and negative predictive value) were performed to know the diagnostic value of ultrasound comparing with histologic features. Out of 27 cases of granuloma confirmed histopathologically, 20 (74.1%) were diagnosed correctly by ultrasound while all the 3 (100%), who were cystic, were diagnosed correctly by ultrasound. Thus, showing the sensitivity and specificity of the technique to be 74.1% and 100%, respectively. All the 20 cases diagnosed to be positive for granuloma by ultrasound were positive histopathologically too, thus, meaning that the positive predictive value of ultrasound was 100% accurate. On the other hand, negative predictive value of the test was only 30%. The findings indicated that the ultrasound was missing detecting lesion substantially (26.9%). The low negative predictive value shows that the technique was falsely ruling out the positive cases.

DISCUSSION

The detection of an intrabony inflammatory process such as a periapical granuloma or cyst is difficult by conventional radiography. This is due to the diffuse and infiltrative nature of the inflammatory process in bone and the insensitivity of radiographic film along with blind radiographic techniques to demonstrate these density changes. There is no such radiographic procedure by which we can measure and monitor small, incremental periradicular changes through the use of conventional intraoral x-ray film.[123] In 1960, Forsberg and Hagglund[15] reported the use of an x-ray contrast medium that they injected into periapical lesions through prepared root canals. In those lesions that later proved histologically to be cysts, the injected contrast medium assumed a round, smooth-bordered, evenly dense appearance. In lesions that proved to be granulomas, the contrast medium assumed an irregular shape with ragged borders and variable radiographic density. However, Cunningham and Penick[16] in 1968 were unable to show any correlation between the radiographic appearance of injected lesions and the histological diagnoses. Howell and De la Rosa[17] in 1968 reported on the cytologic examination of aspirates from the lesions. On the basis of their results, they concluded that the characteristic cell patterns found in cyst aspirates might permit an accurate provisional diagnosis of these lesions.

The use of ultrasound as a complimentary diagnostic procedure to differentiate periapical lesions of endodontic origin is well recognized.[45678910] But ultrasound waves are unable to penetrate cortical bone, because of the high reflectivity of the soft tissue-bone interface. The cortical bone thickness varies significantly in different regions of maxilla and mandible. Studies have been done on human cadavers to calculate an average thickness of cortical bone of both buccal and lingual cortical bone in different regions of maxilla and mandible.[1213] It has been seen that buccal cortical bone thickness is greater in the mandible than in the maxilla and thickness increases with increasing distance from the alveolar crest in the mandible.[18] Considering the limitation of total reflection of ultrasound waves by thicker, intact bone, the present study was undertaken with an aim to assess the diagnostic capability of ultrasound and color doppler examination in detecting and diagnosing periapical lesions in different regions of maxilla and mandible that have different buccal cortical bone thickness.

In the present study of 30 subjects, ultrasound identified 3 periapical lesions to be cystic (10%) and 20 were diagnosed to be solid granulomatous lesions (66.66%). In the remaining seven cases ultrasound was not able to detect the presence of any lesion (23.33%) [Table 2]. The cystic lesions on the ultrasound imaging appeared as anechoic or hypoechoic lesion with well defined contours. Some amount of posterior enhancement was seen in all the three cases. In cases identified as cystic in this study, only perilesional blood flow could be appreciated on color doppler examination and there was no evidence of internal vascularization. The results from the histopathologic examination confirmed the echographic observation. All the three lesions showed the presence of a cavity lined with stratified squamous epithelium. Within the lumen of the cavity, necrotic debris was also seen. Granulomatous lesions appeared as uniformly hypoechoic areas with evidence of fragmented echogenic foci in ultrasound examination. Slight hyperechogenicity was also observed in some cases. On color doppler imaging, all the lesions showed internal vascularization that varied from scattered to rich. The results from the histopathologic examination confirmed the ultrasound observation in all the 20 cases and showed widespread granulation tissue with widespread areas containing polymorphonuclear neutrophills, lymphocytes, monocytes along with newly formed blood vessels showing neovascularization. Plasma cells were also seen in a few cases. Out of the 30 lesions in the present study, ultrasound accurately detected and diagnosed 3 lesions to be cystic and 20 lesions to be granuloma, which was confirmed by histopathologocal diagnosis. All the cases with cortical bone thickness below 1.6 mm were diagnosed to be having lesion, whereas out of those having ≥1.6 mm bone thickness only 65% turned out to be having lesion; thus, showing a significant association with bone thickness and lesion (P = 0.033), which is statistically significant [Table 3]. Out of 27 cases of granuloma confirmed histopathologically, 20 (74.1%) were diagnosed correctly by ultrasound and all the 3 cases that were confirmed to be cystic were correctly diagnosed by ultrasound (100%). Thus, showing the sensitivity and specificity of the technique to be 74.1% and 100%, respectively. All the 20 cases diagnosed positive by ultrasound were positive histopathologically too, thus meaning that the positive predictive value of ultrasound was 100% accurate. On the other hand, negative predictive value of the test was only 30%. The findings indicated that the ultrasound was missing detecting lesion substantially (26.9%). The low negative predictive value shows that the technique was falsely ruling out the positive cases. The statistical analysis showed that the ultrasound and histopathologic diagnosis were in moderate agreement (k = 0.402) [Table 2].

Within the limitations of the current study it can be stated that although ultrasound may not establish the definitive diagnosis, it can facilitate the differential diagnosis between cystic and solid granulomatous lesions. The findings of a hypoechoic image are indicative of a solid lesion and it is an indication for biopsy before treatment. Presence of an anechoic image is indicative of a cystic lesion and a complete enucleation could be performed. All the lesions with inconclusive ultrasound examination should be biopsied before treatment.

CONCLUSION

Based on the experimental conditions used in the present study, and its subsequent observation and discussion following conclusions can be drawn:

There is a definite association between cortical bone thickness and the ability of ultrasound to detect the presence of periapical lesion (P = 0.033), which is statistically significant.

In cases where there is thick overlying bone, ultrasound may have a limited role. It was observed that the ultrasound was falsely ruling out the positive cases in the regions of greater bone thickness.

Ultrasound was highly accurate in differentiating cystic and granulomatous lesions. All the lesions detected by ultrasound were also correctly diagnosed by this technique, which was confirmed histopathologically.

Therefore, ultrasound can routinely be recommended as a complimentary method for the diagnosis of periapical lesions of endodontic origin. However, this technique may have a limited role in detecting periapical lesions present in the region with thick overlying cortical bone.

Though the results of our study are quite promising, study on larger samples and on different types of lesions would perhaps established more definitely the diagnostic capability of ultrasound.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.