Benign odontogenic tumors of the mandible and maxilla

Odontogenic Keratocyst Presented as Multi-Locular Radiolucency in Mandibular Canine and Premolar Region: A Case Report

An odontogenic keratocyst (OKC) was first described by Philipsen in 1956. They are benign cysts of odontogenic origin that behave aggressively and have a high recurrence rate. The present case report describes an unusual presentation of OKC as a multi-locular lesion in the anterior mandible. A 14-year-old male patient was referred to the oral maxillofacial surgery clinic in Tabuk Specialist Dental Centre by his orthodontist to evaluate a radiolucent lesion that had been identified in his lower anterior teeth during an OPG examination. The patient was medically fit and had multiple previous dental restorations. An intraoral examination revealed a small bony expansion in the cystic lesion on the buccal side. The panoramic radiograph showed well-defined multi-locular radiolucencies in the lower left canine area, despite there being no tooth resorption; however, there was a slight divergence noted between the teeth. An excisional biopsy was performed, and the subsequent histopathological examination revealed a cystic lesion diagnosed as an odontogenic keratocyst. The six-month follow-up OPG showed that the site had completely healed without any lesions recurring. OKCs can present at any age, irrespective of gender. The differential diagnosis included a lateral periodontal cyst or a radicular cyst when the tooth was not vital. In this case, the six-month follow-up OPG following surgery revealed no recurrence, although a close follow-up is recommended because of the high recurrence rate.

Odontogenic keratocyst in the mandibular condyle base region: A case report

Odontogenic keratocysts (OKCs) often occur in the molars in the mandibular ramus; they often progress asymptomatically and are discovered only after widespread development. Some cases of OKC progress to the mandibular condyle; however, very few cases exist only in the condyle. To the best of our knowledge, in all of the previously reported cases, OKCs occurred in the mandibular ramus, which underwent resection. The present study reports the case of a 31-year-old man in whom an OKC (13x12x6 mm) occurred discretely in the base of the condyle, in which the condylar head was successfully preserved. The tumor was removed under general anesthesia using the approach of shaving the anterior surface of the mandible. The extraction cavity was managed using the packed open technique and with an obturator. Approximately 20 months post-operation, the patient remained recurrence-free. This report presents a rare case of an OKC in the mandibular condyle base region. Resection was performed under general anesthesia and the condylar process was successfully preserved.

Evaluation of CT and MRI Imaging Results of Radicular Cysts, Odontogenic Keratocysts, and Dentigerous Cysts and their Contribution to the Differential Diagnosis

AIM

This study aimed to evaluate the contribution of the MRI and CT results to the differential diagnosis of histopathologically different odontogenic cysts.

BACKGROUND

Odontogenic cysts are commonly seen in the jaw bone and their surgical operations have an important place in the practice of maxillofacial surgery; treatment options for these cysts differ according to their histopathology. Differential results that can be obtained from the radiological evaluations of different cyst groups will allow the surgeon to plan a more accurate approach at the beginning of the operation. In this study, computed tomography (CT) and magnetic resonance imaging (MRI) results of different cyst groups were interpreted together with their histopathological diagnosis.

METHODS

CT and MRI results of 17 patients aged between 19-61 were evaluated, whose histopathological diagnosis consisted of 3 radicular cysts (RC), a total of 9 odontogenic keratocysts (OKC) of which 4 were inflamed, and a total of 5 dentigerous cysts (DC) of which one of them was inflammatory.

RESULTS

In the CT scan, all cysts showed lytic, a sclerotic surrounding, and showed MRI peripheral enhancement, whereas solid nodular enhancement was only observed in OKCs. Edema and/or air in the surrounding bone medulla was observed in the infected lesions. OKC was heterogeneous, whereas RC and DC were more homogeneous. Diffusion restriction was observed to be frequent in OKCs. The OKCs were ellipsoidal in appearance and were located parallel to the long axis of the bone, and their dimensions were observed to be larger than the other cysts. OKCs may be accompanied by unerupted teeth. Radicular cysts were located perpendicular to the long axis of the bone and were globular in appearance, and their dimensions were smaller and more homogeneous compared to the OKCs. Dentigerous cysts are also accompanied by an unerupted tooth, and their peripheral enhancement is minimal and homogeneous. However, dentigerous cysts can be dense in content and smaller in size, and ellipsoidal localization is more common than OKCs.

CONCLUSION

In addition to classic panoramic radiography in the evaluation and differential diagnosis of maxillary and mandibular lesions, CT and MRI evaluations can provide helpful information to the surgeon and pathologist in making the diagnosis and may further help plan the operation.

Contribution of three-dimensional images in the planning of cementoblastoma resection

Cementoblastomas are rare benign tumours that represent less than 1% of all odontogenic tumours. Complete resection is mandatory to avoid recurrence. This case report describes the contribution of three-dimensional imaging and three-dimensional printing in the pre-operative surgical planning of a large cementoblastoma that not only caused substantial compression on the inferior alveolar and mental nerves, but also caused thinning and partial erosion of the lingual and vestibular cortical bone, thus increasing the risk of pre-operative mandibular fracture.

Imaging of Mixed and Radiopaque Jaw Lesions

Radiopaque lesions and lesions of mixed density are less frequent than radiolucent lesions of the jawbones. They comprise a spectrum of odontogenic and non-odontogenic lesions. The latter group includes inherited and developmental disorders, osteomyelitis, and benign and malignant primary bone tumors and metastases. Most odontogenic radiopaque or mixed lesions are either related to the apex or more rarely to the crown of the tooth, although there are exceptions to this rule. Some lesions, such as a torus mandibularis and torus palatinus, have a characteristic location, whereas others show no relationship to the dentition. This article describes the most characteristic and prevalent radiopaque and mixed lesions of the jaws and their imaging characteristics. Paget's disease, fibrous dysplasia, and rare sclerotic bone diseases of the maxillofacial bones are discussed elsewhere in this issue. Careful correlation of clinical presentation, panoramic radiographs, cone beam computed tomography, and histopathology are the cornerstones for appropriate lesion characterization.

Is peripheral cortication of intraosseous lesions accurately displayed on panoramic radiography?

OBJECTIVE

The aim of this study was to calculate the sensitivity, specificity, and positive and negative predictive values (PPV and NPV) for the detection of the presence and continuity of peripheral cortication (PC) around benign intraosseous lesions on panoramic radiography (PR), with cone beam computed tomography (CBCT) as the reference standard.

STUDY DESIGN

The sample consisted of the mesial, distal, superior, and inferior borders of 40 bony lesions (n = 160) depicted on both PR and CBCT. Ten observers assessed the PRs. CBCT images were assessed by 2 radiologists. For each lesion, observers classified the 4 borders with regard to the presence of PC, and if present, its continuity. Sensitivity, specificity, PPV, and NPV were calculated for the presence and continuity of PC. Intra- and interobserver agreements were calculated.

RESULTS

PR had sensitivity, specificity, PPV, and NPV for PC detection of 0.844, 0.435, 0.435, and 0.844, respectively. With regard to PC continuity, those values were 0.750, 0.810, 0.577, and 0.904. Observer agreement was slight to fair.

CONCLUSIONS

The high sensitivity and low specificity for the presence of PC indicate a large false-positive rate. The high NPVs suggest greater validity for negative decisions. The findings corroborate the influence of the eggshell effect. Observer agreement rates indicate that interpretation of PC is substantially subjective.

Multiple b values of diffusion-weighted magnetic resonance imaging in evaluation of solid head and neck masses

Background

Differentiation between malignant and benign masses is essential for treatment planning and helps in improving the prognosis of malignant tumors; the aim of this work is to determine the role of diffusion-weighted magnetic resonance imaging (DW-MRI) and the apparent diffusion coefficient (ADC) in the differentiation between benign and malignant solid head and neck masses by comparing diagnostic performance of low b values (0.50 and 400 s/mm2) versus high b values (800 and 1000 s/mm2) and comparing the result with histopathological finding.

Results

The study included 60 patients (34 male and 26 female) with solid head and neck masses > 1 cm who referred to radiodiagnosis department for MRI evaluation. Multiple b values were used 50, 400, 800, and 1000 s/mm2 (at least 2 b values). DWI and ADC value of all 60 patients were acquired. Mean ADC values of both malignant and benign masses were statistically measured and compared, and cut off value was determined. Solid head and neck masses in our study DWI with the use of high b value 800 and 1000 s/mm2 were of higher significance (P value 0.001*). There was a significant difference in the mean ADC value between benign and malignant masses (P < 0.01); solid masses were divided into 2 categories: (a) malignant lesions 46.7% (n = 28) with mean ADC value (0.82 ± 0.19) × 10−3 s/mm2 and (b) benign lesions 53.3% (n = 32) with mean ADC value (2.05 ± 0.46) × 10−3 s/mm2) with ADC cutoff value of 1.0 × 10−3 s/mm2 and 94% sensitivity, 93% specificity, negative predictive value (NPV) = 94%, positive predictive value (PPV) 93%, and an accuracy of 93.5%.

Conclusion

The DWI with ADC mapping were valuable as non-invasive tools in differentiating between benign and malignant solid head and neck masses. The use of high b value 800 and 1000 s/mm2 was of higher significance (P value 0.001*) in differentiation between benign and malignant lesion than that with low b values 0, 50, and 400 s/mm2 (0.01). The mean ADC values were significantly lower in malignant solid masses. Attention had to be paid to the choice of b values in MRI-DWI in the head and neck region.

Nonsyndromic Examples of Odontogenic Keratocysts: Presentation of Interesting Cases with a Literature Review

The odontogenic keratocyst (OKC) may occur at any age. However, it mostly occurs during the second and third decades of life. Compared to other odontogenic cysts, this type occurs with a frequency of 5-15%. It is more common in the mandible region and in the male sex. Histologically, odontogenic keratocysts are characterized by the presence of an external connective tissue capsule, with keratinizing lining of the epithelium consisting of 5-8 cell layers with marked palisadisation of polarized basal cells and a corrugated parakeratin layer. The objective of this study is to present cases of odontogenic keratocysts, with reference to the latest classification and dilemmas in therapeutic doctrine. This project was realized in the form of descriptive studies, specifically in a series of cases. A collection of four individual cases was found at the Department of Oral Surgery. Due to the proper approach towards diagnosis, adequate and detailed histopathological analysis, and suitable therapeutic procedures, all cases of odontogenic keratocysts were successfully treated without complications. Enucleation of OKC, with a regular follow-up, proved to be the effective therapeutic choice for the patients described in this paper. Only in the case of recurrence would we consider other therapeutic options, primarily enucleation in combination with Carnoy's solution.

Cone Beam Computed Tomography in Oral and Maxillofacial Surgery: An Evidence-Based Review

Cone Beam Computed Tomography (CBCT) is a valuable imaging technique in oral and maxillofacial surgery (OMS) that can help direct a surgeon’s approach to a variety of conditions. A 3-dimensional analysis of head and neck anatomy allows practitioners to plan appropriately, operate with confidence, and assess results post-operatively. CBCT imaging has clear indications and limitations. CBCT offers the clinician 3-dimensional and multi-planar views for a more accurate diagnosis and treatment without the financial burden and radiation exposure of conventional computed tomography (CT) scans. Furthermore, CBCT overcomes certain limitations of 2-dimensional imaging, such as distortion, magnification, and superimposition. However, CBCT lacks the detailed depiction of soft tissue conditions for evaluation of pathologic conditions, head and neck infections, and temporomandibular joint (TMJ) disc evaluation. This review evaluates the evidence-based research supporting the application of CBCT in the various fields of oral and maxillofacial surgery, including dentoalveolar surgery, dental implants, TMJ, orthognathic surgery, trauma, and pathology, and will assess the value of CBCT in pre-operative assessment, surgical planning, and post-operative analysis when applicable. Additionally, the significant limitations of CBCT and potential areas for future research will be discussed.

Odontogenic keratocyst: imaging features of a benign lesion with an aggressive behaviour

Abstract

The latest (4th) edition of the World Health Organization (WHO) Classification of Head and Neck Tumours, published in January 2017, has reclassified keratocystic odontogenic tumour as odontogenic keratocyst. Therefore, odontogenic keratocysts (OKCs) are now considered benign cysts of odontogenic origin that account for about 10% of all odontogenic cysts. OKCs arise from the dental lamina and are characterised by a cystic space containing desquamated keratin with a uniform lining of parakeratinised squamous epithelium. The reported age distribution of OKCs is considerably wide, with a peak of incidence in the third decade of life and a slight male predominance. OKCs originate in tooth-bearing regions and the mandible is more often affected than the maxilla. In the mandible, the most common location is the posterior sextant, the angle or the ramus. Conversely, the anterior sextant and the third molar region are the most common sites of origin in the maxilla. OKCs are characterised by an aggressive behaviour with a relatively high recurrence rate, particularly when OKCs are associated with syndromes. Multiple OKCs are typically associated with the nevoid basal cell carcinoma syndrome (NBCCS), an autosomal dominant multisystemic disease. Radiological imaging, mainly computed tomography (CT) and, in selected cases, magnetic resonance imaging (MRI), plays an important role in the diagnosis and management of OKCs. Therefore, the main purpose of this pictorial review is to present the imaging appearance of OKCs underlining the specific findings of different imaging modalities and to provide key radiologic features helping the differential diagnoses from other cystic and neoplastic lesions of odontogenic origin.

Key Points

• Panoramic radiography is helpful in the preliminary assessment of OKCs.

• CT is considered the tool of choice in the evaluation of OKCs.

• MRI with DWI or DKI can help differentiate OKCs from other odontogenic lesions.

• Ameloblastoma, dentigerous and radicular cysts should be considered in the differential diagnosis.

• The presence of multiple OKCs is one of the major criteria for the diagnosis of NBCCS.

Diffusion-Weighted MR Imaging of Unicystic Odontogenic Tumors for Differentiation of Unicystic Ameloblastomas from Keratocystic Odontogenic Tumors

Objective

Differentiating unicystic ameloblastomas from keratocystic odontogenic tumors (KCOT) is necessary for the planning of different treatment strategies; however, it is difficult based on conventional CT and MR sequences alone. The purpose of this study was to investigate the utility of diffusion-weighted imaging (DWI) and apparent diffusion coefficients (ADCs) in the differentiation of the two tumors.

Materials and Methods

We prospectively studied 40 patients with odontogenic cysts and tumors of the maxillomandibular region using conventional MR imaging and DWI. ADCs were measured using 2 b factors (500 and 1000).

Results

Unicystic ameloblastomas (n = 11) showed free diffusion on DWI and a mean ADC value of 2.309 ± 0.17 × 10^-3 mm²/s. KCOT (n = 15) showed restricted diffusion on DWI with a mean ADC value of 0.923 ± 0.20 × 10^-3 mm²/s. The ADC values of unicystic ameloblastomas were significantly higher than those of KCOT (p < 0.001, Mann-Whitney U-test). An ADC cut-off value of 2.0 × 10^-3 mm²/s to differentiate KCOT and unicystic ameloblastomas resulted in a 100% sensitivity and 100% specificity. Dentigerous cysts (n = 3) showed restricted diffusion on DWI and similar ADC values (1.257 ± 0.05 × 10^-3 mm²/s) to those of KCOT.

Conclusion

Diffusion-weighted imaging and ADC determination can be used as an adjuvant tool to differentiate between unicystic ameloblastomas and KCOT, although the ADC values of dentigerous cysts overlap with those of KCOT.

Evaluation of keratocystic odontogenic tumors using cone beam computed tomography

Purpose:

The aim of this retrospective study is to determine the radiological features of keratocystic odontogenic tumors (KCOT) using cone-beam computed tomography (CBCT).

Materials and Methods:

CBCT images of 28 patients who had histopathologically-confirmed KCOT were retrospectively reviewed from the archives of the Department of Dentomaxillofacial Radiology, Gazi University Faculty of Dentistry. The location and size of KCOT, cortical expansion, cortical perforation, relation with the impacted teeth, and the impact on the mandibular canal were evaluated.

Results:

The mean age of patients at initial diagnosis was 34.5 years. Patients with an impacted tooth were significantly younger than those without an impacted tooth (p<0.05). Among KCOTs, 21% were localized in the maxilla whereas 79% were found in the mandible. The lesions localized in the mandible were mostly found in the retromolar-ramus region. Of these patients, 93% had cortical expansion and 75% had bone perforation. Of the 22 mandibular lesions, 20 were in close proximity of the mandibular canal and 18 (90%) of these lesions had caused destruction in the mandibular canal.

Conclusion:

KCOTs exhibit their aggressive nature in the jaw bone. CBCT is a useful radiological imaging method to examine the radiologic characteristics of KCOTs such as bone destruction and their spatial relations with the neighboring anatomic structures.

Benign Jaw Lesions

There are both odontogenic and nonodontogenic benign lesions in the maxilla and mandible. These lesions may have similar imaging features, and the key radiographic features are presented to help the clinician narrow the differential diagnosis and plan patient treatment. Both intraoral and panoramic radiographs and advanced imaging features are useful in assessing the benign lesions of the jaws. The location, margins, internal contents, and effects of the lesions on adjacent structures are important features in diagnosing the lesions.

Magnetic resonance imaging of the maxilla and mandible: signal characteristics and features in the differential diagnosis of common lesions

The maxilla and mandible are among the most difficult areas of the body to image with magnetic resonance techniques owing to the geometry of the jaws as well as the frequent susceptibility artifacts from dental restorations or appliances. This chapter briefly reviews the essentials of imaging techniques and basic anatomy and discusses the most common inflammatory conditions, benign and malignant lesions of the jaws, and temporomandibular joint. This review emphasizes and illustrates specific magnetic resonance features that facilitate characterization and diagnostic differentiation of these lesions. As the focus of this review is on the differentiation of infection and benign and malignant disease, a discussion of internal derangements and associated inflammatory disorders of the temporomandibular joint is beyond the scope of this review and is not discussed.

Lesions of the Jaw

Imaging of lesions within the maxilla and mandible is often fraught with difficulty owing to the similarity in the imaging appearance of a diverse array of pathological processes. Principally, lesions arise from either odontogenic sources or from primary bone lesions. The response of the cancellous and cortical bone to pathologic insult can be expressed either through an osteolytic or an osteoblastic response; thus the majority of lesions within the jaws can be classified as cystic or lytic appearing, sclerotic, or a mixture of the two. This article will review the imaging features of the most common cysts, fibro-osseous lesions, benign and malignant neoplasms, and highlight those features key to the differential diagnosis.

Radiopaque jaw lesions: an approach to the differential diagnosis

Radiopaque jaw lesions are frequently encountered at radiography and computed tomography, but they are usually underevaluated or underdescribed in radiology reports. A systematic approach to the evaluation of radiopaque jaw lesions is necessary to diagnose the lesion or at least provide a meaningful differential diagnosis. To evaluate a radiopaque jaw lesion, the first, most important step is to categorize the lesion according to its attenuation, its relationship to the teeth, and its location with respect to the tooth. These basic observations are essential to the evaluation of any type of jaw lesion. Once these observations have been made, it is easy to create a proper differential diagnosis. The presence of important characteristics, such as margination, a perilesional halo, bone expansion, and growth pattern, as well as whether the lesion is sclerotic, has ground-glass attenuation, or is mixed lytic and sclerotic, further narrows the differential diagnosis. It is important to note that some radiopaque jaw lesions may be entirely lucent early in their evolution. Awareness of the demographic distribution of these lesions and their associated clinical features, as well as the radiologic approach, is important to explore the "terra incognita" of radiopaque jaw lesions.

Contrast-enhanced multidetector computerized tomography for odontogenic cysts and cystic-appearing tumors of the jaws: is it useful?

OBJECTIVE

The purpose of this study was to investigate the usefulness of computerized tomography (CT), particularly contrast-enhanced CT, in differentiation of jaw cysts and cystic-appearing tumors.

STUDY DESIGN

We retrospectively analyzed contrast-enhanced CT images of 90 patients with odontogenic jaw cysts or cystic-appearing tumors. The lesion size and CT values were measured and the short axis to long axis (S/L) ratio, contrast enhancement (CE) ratio, and standard deviation ratio were calculated.

RESULTS

The lesion size and the S/L ratio of keratocystic odontogenic tumors were significantly different from those of radicular cysts and follicular cysts. There were no significant differences in the CE ratio among the lesions.

CONCLUSIONS

Multidetector CT provided diagnostic information about the size of odontogenic cysts and cystic-appearing tumors of the jaws that was related to the lesion type, but showed no relation between CE ratio and the type of these lesions.

Radiographic assessment of a keratocystic odontogenic tumour using cone-beam computed tomography

BACKGROUND

The keratocystic odontogenic tumour (KCOT), formerly known as the odontogenic keratocyst, is a benign intra-osseous odontogenic tumour. The KCOT is characterised by a potential for locally destructive behaviour and a relatively high recurrence rate. Most KCOT are incidentally discovered as well-defined unilocular or multilocular radiolucencies on routine panoramic radiographs.

CASE REPORT

A 15-year-old boy was referred to dental care with a non-syndromic KCOT in the right angle of the mandible. Using cone-beam computed tomography (CBCT) as a diagnostic instrument for precise assessment of the KCOT, the exact location of the lesion was determined.

TREATMENT

The cystic formation was enucleated without peripheral ostectomy.

FOLLOW-UP

At post-operative follow-up after 3 and 6 months, the boy reported no pain and there was no residual swelling or fracture. Imaging was planned after 1 year to decide whether further surgical treatment is indicated.

CONCLUSION

The CBCT is considered beneficial in cases of cystic formations to determine the localisation and borders of the lesion in all three dimensions.

Two- and three-dimensional models for the visualization of jaw tumors based on CT-MRI image fusion

PURPOSE

The objective of this study was to demonstrate the feasibility of two- and three-dimensional (2D and 3D) models based on computed tomography-magnetic resonance imaging (CT-MRI) image fusion for the visualization of jaw tumors.

METHODS

Seven patients with proved jaw tumors were involved in this study. Both preoperative CT and MRI image data were acquired in DICOM format and imported into Surgicase CMF software, respectively. Then, the structures of interest, including tumor, muscle, and vascular, and so on, were segmented based on different thresholds and reconstructed in 3D texture. Finally, CT-MRI image fusion was semiautomatically performed to obtain the fused 2D images and 3D models for the visualization of jaw tumors. The qualities of the fused 2D images and 3D models together with their potential applications in surgical management of jaw tumors were qualitatively assessed. Besides, the importance of this imaging technique in terms of training junior surgeons was also discussed in detail.

RESULTS

Computed tomography-MRI image fusion clearly showed the relationship between tumors and adjacent structures. The qualitative assessment of fused images was satisfied.

CONCLUSIONS

Although there are some limitations, the 2D images and 3D models based on CT-MRI image fusion can provide a powerful tool for the visualization of jaw tumors. It may offer surgeons an assisted tool for the subject-specific preoperative planning, surgical simulation, and intraoperative guidance for jaw tumors. Furthermore, it also may offer valuable 2D and 3D models for training junior surgeons or provide a useful tool for surgeons to communicate well with patients.

Application of cone beam computed tomography in oral and maxillofacial surgery

In the past decade, the utility of cone beam computed tomography (CBCT) images in oral and maxillofacial surgery has seen continuous increase. However, CBCT images are not always able to replace other imaging modalities. Based on the current published knowledge, this paper discusses advantages and limitations of CBCT images in the diagnosis and surgical planning of dentoalveolar procedures, odontogenic cysts, benign and malignant tumours, inflammatory changes, orthognathic surgery, maxillofacial trauma, sinus disorders, and systemic and osseous conditions that manifest in the maxillofacial area. This paper also suggests alternative imaging modalities when CBCT images are not adequate for surgical planning.

Diffusion-weighted imaging in the evaluation of odontogenic cysts and tumours

OBJECTIVE

The differentiation between keratocystic odontogenic tumour (KCOT) and other cystic/predominantly cystic odontogenic tumours is difficult on conventional CT and MR sequences as there is overlap in the imaging characteristics of these lesions. The purpose of this study was to evaluate the role of diffusion-weighted imaging (DWI) and to assess the performance of apparent diffusion coefficients (ADCs) in the differential diagnosis of odontogenic cysts and tumours.

METHODS

20 patients with odontogenic cysts and tumours of the maxillomandibular region were examined with DWI. Diffusion-weighted images were obtained with a single-shot echoplanar technique with b-values of 0, 500 and 1000 s mm(-2). An ADC map was obtained at each slice position.

RESULTS

The cystic areas of ameloblastoma (n=10) showed free diffusion with a mean ADC value of 2.192±0.33×10(-3) mm(2) s(-1), whereas the solid areas showed restricted diffusion with a mean ADC value of 1.041±0.41×10(-3) mm(2) s(-1). KCOT (n=5) showed restricted diffusion with a mean ADC value of 1.019±0.07×10(-3) mm(2) s(-1). There was a significant difference between the ADC values of KCOT and cystic ameloblastoma (p<0.01, Mann-Whitney U-test). The cut-off with which KCOT and predominantly cystic ameloblastomas were optimally differentiated was 2.013×10(-3) mm(2) s(-1), which yielded 100% sensitivity and 100% specificity.

CONCLUSION

DWI can be used to differentiate KCOT from cystic (or predominantly cystic) odontogenic tumours.

[Imaging of odontogenic tumors of the maxilla]

Odontogenic tumors of the maxilla are frequent, mainly represented by cysts of the jaw. However, this group of tumors include a large number of potentially intricate pathologies whose evolution is dominated by frequent recurrences justifying long-term follow-up. When such a lesion is discovered, evaluation of imaging features combined with an extensive knowledge of the different patterns of other lesions (particularly their potentially evolutive patterns related to growth) can often suggest the diagnosis. While definitive diagnosis frequently relies on histology, it is not rare that the patterns are so intricate that final diagnosis is based on a correlation between clinical, imaging and histological findings.

The use of multidirectional cross-sectional tomography for localizing an odontome

BACKGROUND

A 7-year old boy was referred with retained maxillary right primary central and lateral incisors. Radiographic exam revealed a large calcified radio-opaque mass overlying the roots of these primary teeth preventing the permanent teeth from erupting.

CASE REPORT

The purpose of this paper is to describe the pre-operative use of multi-directional cross-sectional tomography in establishing the relationship between a large complex odontome that was preventing the eruption of a maxillary permanent central incisor.

CONCLUSION

Low dose, multi-directional cross-sectional tomography was beneficial in visualisation of the precise relationship between the large complex odontome and the unerupted permanent incisor. This allowed correct judgement of the position on the odontome prior to its surgical removal.

Radiologic and pathologic characteristics of benign and malignant lesions of the mandible

Mandibular lesions develop from both odontogenic and nonodontogenic origins and have varying degrees of destructive potential. Common benign cystic lesions include periapical (radicular) cysts, follicular (dentigerous) cysts, and odontogenic keratocysts. Benign solid tumors represent a broad spectrum of lesions such as ameloblastomas, odontomas, ossifying fibromas, and periapical cemental dysplasia. Malignant tumors that often involve the mandible include squamous cell carcinomas, osteosarcomas, and metastatic tumors. In addition, vascular lesions such as hemangiomas and arteriovenous malformations may develop, further expanding the differential diagnosis. Because mandibular lesions have a wide range of pathologic features but similar imaging appearances, familiarity with embryologic characteristics and secondary findings is crucial. Patient age at manifestation, prevalence, location within the mandible, cystic or solid appearance, border contour, and effect of the lesion on adjacent structures are all considerations in making the diagnosis. Despite this information, however, many lesions are impossible to differentiate without biopsy. In such cases, defining the degree of malignant potential is very helpful. Although imaging will not always provide a specific diagnosis, it should help narrow the differential diagnosis, thereby helping to guide patient treatment.