Radiology - A Quarterly Newsletter on Dental SpecialtiesJADA Specialty Scan

Surgical trauma and osteoradionecrosis of the jaws

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Seeking greater insight into understanding and managing osteoradionecrosis (ORN) of the jaws, scientists at the Ninth People’s Hospital in Shanghai, China, conducted a retrospective study of ORN patients who received surgical treatment there. Researchers focused on treatment and risk factors in their study, which was published in the March 2015 issue of The Journal of Craniofacial Surgery.

One of the most serious complications of radiotherapy for head and neck malignancies, there is little consensus about ORN incidence. Multiple factors could be associated with its development, including high radiation dose, dental extractions, unsuitable dentures, primary tumor sites, chemotherapy, infection, smoking and alcohol. A recent systematic review published in the dental literature points to a wide range of incidence among the head- and neck-irradiated population, from 4.74% to 37.5%.

Scientists analyzed the clinical data of 120 people who received surgical treatment for the involved tissue at the hospital between January 2003 and January 2013. All of the subjects had a shared history of external-beam radiation. Scientists evaluated their inpatient and outpatient records for variables, such as age, gender, primary tumor location, risk factors and outcomes.

Most published research agrees that the higher the radiation dose, the higher the risk of ORN. Scientists found that to be true in this study, as well, with 57.5% of patients’ experiencing total radiation over 60 Gy, a recommended limit (the amount of radiation used in therapy is measured in gray, or Gy). However, in 42.5% of the study subjects, ORN occurred even though the patients had received radiation doses of less than 60 Gy. Upon closer inspection, scientists found that 90.2% of these latter patients had experienced surgical trauma (extensive bone resection).

They asserted that there was no doubt that previous surgical trauma was the primary accomplice for these low-dose radiation populations to be inflicted with ORN. “If we excluded the side effects of radiation therapy, surgical trauma was the most important factor leading to this result as far as we are concerned. The more extensive the antecedent resection of the mandible, the sooner ORN would occur.”

Among other results consistent with past research, scientists found that the mandible was much more vulnerable to ORN compared with the maxilla, affecting a respective 82.5% and 11.7% of jaws. Some 68.3% of patients developed ORN within the first three years after radiation therapy, with the two peaks of incidence at 12 months in 46.4% of patients and 24-60 months in 16%. A positive relationship was found between primary tumor sites located in the mouth (especially in the tongue, retromolar region and floor of the mouth) and higher incidence of ORN.

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Consulting Editor: Laurie C. Carter, DDS, PhD
Past president, American Academy of Oral and Maxillofacial Radiology

Predicting canine impaction

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Cone beam computed tomography (CBCT) is an excellent imaging method for predicting canine impactions, according to research published in the March 2015 issue of the American Journal of Orthodontics and Dentofacial Orthopedics.

The finding is important because early predictive measures can enable interceptive orthodontic treatment to guide teeth into a normal position and prevent impaction. Early diagnosis is important because older patients with impacted canines require more time and are more difficult to treat than younger patients.

A common problem affecting up to 5% of patients seeking orthodontic treatment, such impactions can cause root resorption of adjacent teeth (particularily lateral incisors). More females have impacted upper canines than males.

Research shows that early prediction and early diagnosis with two-dimensional radiographs remains problematic. However, several studies have still endeavored to investigate the possible predictors of canine impaction and orthodontic treatment choices with two-dimensional radiographs.  Although three-dimensional (3D) views offered by CBCT allow more diagnostic questions related to impacted canines to be answered, study authors found no straightforward formula in the literature for the prediction of canine impactions based on CBCT and no guidance for the use of CBCT to identify impaction for treatment planning. Scientists compared 3D CBCT images of unilaterally impacted canines with the normal canines on the other side of the mouth to detect possible radiographic factors involved.

They examined the radiographic records of 65 patients (43 girls and 22 boys at an average age of 12.1 years). Of the impacted maxillary canines, 32 were located on the right side and 33 on the left. All patients underwent CBCT scanning and radiographs were analyzed by one investigator.

Rotation, crown position, cusp tip to midline and to occlusal plane, angle to midline and angle to lateral incisor were considered variables in a prediction model for canine impaction.

Results showed significant difference between the impacted and nonimpacted teeth. Crown position, canine cusp tip to the occlusal plane and canine angulation to the lateral incisor were all relevant predictors.

“The probability of canine impaction obtained from the precision model can help orthodontists to define the optimal intervention method and its timing,” authors said.

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Diagnosing and managing vascular masses

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What radiology methods are best for which types of vascular lesions? How can each member of a multidisciplinary team charged with diagnosing and managing treatment best refer to head and neck anomalies in the same way?

A report including a common lexicon to classify specific vascular lesions and an overview of principles for potential imaging methods also incorporates key diagnostic and treatment approaches. It was published in the March 2015 issue of the Atlas of the Oral and Maxillofacial Surgery Clinics.

“A patient’s history cannot be overemphasized, as it aids the radiologist in deciding on imaging modalities, tailoring studies to the needs of the patient, and making the diagnosis,” authors said. They reported that magnetic resonance imaging (MRI), is the study of choice for vascular lesions, providing superior soft-tissue differentiation and the finest characterization of the lesion. Post-procedure evaluations (including examination of the residual nidus after embolization and residual tumor after resection) are also best accomplished by MRI, they said.

They described the role of ultrasonography (US) as “significant” in evaluating such anomalies.

“US allows for measurement of lesion size and depth, classification of the lesion as vascular and differentiation of cystic and solid components,” they asserted. “Benefits of US include general availability (office or bedside), lack of ionizing radiation and assessment of physiology.” Difficulties in differentiating tissue types and the necessity of an experienced sonographer are among the issues to consider when using US, they said.

Researchers also covered conventional radiography computed tomography and computed tomographic angiography, conventional angiography, positron emission tomography combined with computed tomography and image-guided procedures.

A comprehensive glossary of descriptions defining and naming various vascular lesions and vascular-like tumors, including their characteristics and prognoses, introduces the article. It also provided a section on embolic materials. Treatment recommendations include:

“A coordinated, multidisciplinary approach to vascular anomalies of the neck will optimize patient outcomes,” authors said. “High-quality imaging, usually MRI, answers many of the clinical questions that arise before intervention.

Vascular anomaly interventions range from oral medication, to image-guided definitive treatments, to combined preoperative embolization and surgery.”

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Chronic kidney disease and jaw changes

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An article about the radiologic changes associated with an increasing public health concern — chronic kidney disease — was published in the March 2015 issue of Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology.

Chronic kidney disease mineral and bone disorder syndrome (CKD-MBD) is used to express the bone and extra skeletal complications of CKD that occur due to metabolic alterations that induce bone and soft tissue changes.  Scientists in South Africa reported on notable radiologic manifestations of skeletal and jaw changes.

The dental literature shows that facial skeletal changes display three distinct radiographic patterns. The authors’ research included case studies of two women with the rarest craniofacial pattern resulting from CKD-MBD, expansive jaw lesions. Authors recommended the description — expansive renal osteitis fibrosa — to distinguish it from other common causes of facial bone enlargement, such as brown tumor of hyperparathyroidism, fibrous dysplasia and Paget’s disease, they said.

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Why x-rays are worth it

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When a patient wonders why radiographs are needed, the ADA has a brochure to reinforce your points. “Dental X-Ray Exams: Answers to Common Questions” explains that finding and treating dental problems at an early stage can save time and money and prevent pain.

The handout assures patients of the safety of x-rays and shows how dental offices take steps to reduce radiation exposure. This 6-panel brochure features new x-ray images and comes in packs of 50, with volume discounts available. 

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What is Specialty Scan?

This is one in a series of quarterly newsletters updating dentists on selected specialties in dentistry. Information presented is aggregated and summarized from previously published materials, each item attributed to its publication of origin. This issue of JADA Specialty Scan focuses on oral and maxillofacial radiology, the second in the series on this topic for 2015. Other Specialty Scan issues are devoted to periodontics, orthodontics, endodontics and prosthodontics. The ADA has engaged the specialty organizations in these areas as well as its own divisions of Science and Legal to assist with these newsletters. We welcome feedback on this and all Specialty Scan issues.

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