Assessing mandibular anatomy using cone-beam computed tomography
Before placing implants or performing surgery in the anterior segment of the mandible, clinicians need complete information about the anatomy in this region to minimize the possibility of neural trauma and its sequelae. In this retrospective cross-sectional study published in the March issue of Journal of Dentistry of Tehran University of Medical Sciences, researchers evaluated the location and characteristics of the mental foramen, anterior loop, and mandibular incisive canal using cone-beam computed tomography (CBCT).
The investigators examined 200 CBCT scans of patients (110 women and 90 men) referred to a private radiology clinic. All of the scans were obtained using the same CBCT unit (ProMax 3D, Planmeca) using exposure settings of 84 kilovolts (peak), 14 milliamperes, 12 seconds’ duration, 8X8-centimeter field of view, and 0.16 mm voxel size.
The most common locations of the mental foramen were along the second premolar and between the second and first premolars. In 71% of cases, the mental foramina were located symmetrically on the right and left sides. In 45% of cases, they were located along the second premolar on both sides. The inferior alveolar neurovascular bundle often ascends for a few millimeters before curving back to the mental foramen; this is known as the anterior loop. Researchers observed the anterior loop in 59.5% of scans (bilateral in 39% and unilateral in 20.5%). The anterior loop was found in 65% of men and 54.5% of women.
CBCT scans showed the mandibular incisive canal in 97.5% of cases (bilateral in 94% and unilateral in 3.5%). Researchers noted that the canal was lower than the mental foramen in 74.6% of cases on the right side and in 81% of cases on the left side (P < .01).
When comparing the results for men with those for women, the investigators found shorter distances from the end point of the mandibular incisive canal to the buccal plate in the scans from women, as well as from the end point of the canal to the inferior border of the mandible. They attributed these differences to the smaller mandibular dimensions in women. Only one variable—distance from the end point of the canal to the buccal plate—was directly correlated with age, but this correlation was relatively weak.
Researchers conclude that because of the variability in size and position of the mandibular incisive canal and the high prevalence of anterior loop, CBCT is recommended before surgical manipulation of the interforaminal region.
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Consulting Editor: Laurie C. Carter, DDS, PhD
Past president, American Academy of Oral and Maxillofacial Radiology
Examining osteonecrosis of the jaw in two patient populations
The pathophysiology of osteonecrosis of the jaw (ONJ) is unclear, but it appears to be multifactorial, with infection playing a key role. Researchers present a case-based review of ONJ and apply recommendations from the International Task Force on ONJ in an article published online December 9 in Journal of Clinical Densitometry: Assessment & Management of Musculoskeletal Health.
Among the questions posed is this: Why does ONJ develop? “It is not known whether necrosis precedes or follows infection,” the authors stated. “Infection and inflammation clearly play a significant role in the development of ONJ.” Bisphosphonates may increase the risk of local infection and contribute to impaired healing of the oral mucosa. In addition, suppression of bone remodeling by bisphosphonates and denosumab may contribute to ONJ.
The prevalence of ONJ in patients with osteoporosis is low (about 0.001%-0.01%), according to estimates from surveys conducted in several countries. In patients receiving treatment with bisphosphonates or denosumab, the risk of developing ONJ appears to be “only slightly higher than the risk in the general population,” the authors reported.
However, in oncology patient populations, the incidence of ONJ is much higher than that in osteoporosis patient populations. The researchers pointed to a recent meta-analysis that reported a 1.7% incidence of ONJ in patients with cancer receiving denosumab treatment and an incidence between 1% and 15% in those receiving treatment with high-dose bisphosphonates, possibly tied to dose and duration of exposure. There may be confounding variables in this population, including use of other drugs that affect bone health, as well as other risk factors for ONJ such as chemotherapy, diabetes mellitus, poor dental hygiene, tooth extraction, neutropenia, and pre-existing local infection.
Intravenous (IV) bisphosphonate and denosumab therapy in patients with cancer involves doses that are 12 to 15 times higher than oral doses of these drugs used to treat osteoporosis. However, bisphosphonate and denosumab therapy results in a clinically significant reduction in the risk of skeletal-related events such as progression of metastatic bone deposits in people with cancer in comparison with the relatively low risk of developing ONJ, the researchers stress. Thus, the benefits of high-dose antiresorptive therapy far outweigh the risk of ONJ.
The role of imaging in detecting and managing ONJ also was examined. Plain radiographs aid in evaluating the presence of early changes, such as thickening of the lamina dura and increased trabecular density of the alveolar bone. However, only a small portion of the mandible or maxilla could be assessed by means of conventional radiography. Computed tomography (CT) has many advantages over plain radiographs, including the ability to assess the cortical and trabecular architecture of the jaws and periosteal reactions. Cone-beam computed tomography (CBCT) offers the advantages of CT at a significantly lower radiation exposure. The authors stressed the importance of early detection of dental disease in patients receiving high-dose IV bisphosphonate or denosumab treatment in whom the risk of developing ONJ is significant. They recommend use of CBCT in these patients because of its superiority to conventional radiography in diagnosing periapical and periodontal diseases.
For oncology patients, invasive dental procedures such as tooth extraction and implant placement should be performed before initiation of high-dose IV bisphosphonate or denosumab therapy. Nonurgent dental procedures should be delayed if possible. Patients with osteoporosis who receive bisphosphonate or denosumab treatment can undergo needed dental procedures, including extractions and implant placement. The task force’s opinion was that decisions to continue or withhold antiresorptive therapy should be made jointly by the dental care provider and the patient’s physician, in keeping with current understanding of ONJ.
Treatment depends on the disease stage, lesion size, contributing drug therapy, and medical and pharmacologic comorbidities, the authors reported. Conservative therapy focuses on improving oral hygiene, treating active dental disease, using topical antibiotic mouthrinses, and initiating systemic antibiotic treatment. Surgery, including osteotomy of the affected area, should be considered for patients who do not respond to conservative treatment. The researchers concluded that the diagnostic and prognostic factors for ONJ need to be further refined to better identify patients at high risk of developing ONJ.
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Surgical guides for dental implants
• How CBCT technology is used for treatment planning for dental implants.
• How to use the CBCT scanning process to develop surgical guides.
• Review the principles of surgical-guide implementation for dental implants.
• List the benefits and limitations of surgical guides for dental implants.
General dentists’ awareness of radiation hazards, safety practices
General dentists’ awareness of radiation hazards and adherence to safety practices were the focus of a cross-sectional study published online October 12 in Journal of Pharmacy & Bioallied Sciences. Researchers administered an 18-question survey to 300 general dentists in the Trivandrum District in Kerala, India, and collected demographic data. On receipt of the completed questionnaires, they gave respondents an educational brochure pertaining to radiation safety.
A total of 247 female and 53 male dentists participated in this study. Eighty-three percent had been in practice for more than 5 years. More than 60% of respondents stated that they used intraoral radiography machines with conventional radiograph film, while 18% used digital radiography and 2% used panoramic radiography. A combination of machines and techniques was used by 17% of dentists. The survey results show that 71% of dentists instructed patients to hold the periapical film in their fingers while taking the radiographs. Only 16.7% reported that they used film holders, and 12.3% used other film placement methods.
Regarding safety practices in the dental office, 28.3% of respondents said they followed the “position and distance rule” exclusively in which the operator stands at least 6 feet from and at an angle of 90 to 135 degrees to the x-radiation source. Twenty-two percent used lead barriers, 16% used lead aprons, and 33.3% used a combination of techniques to reduce patients’ exposure to radiation. Almost all respondents were familiar with thermoluminescent dosimeter badges, but only 2% used them in their dental practice, the researchers noted.
Most general dentists (84.3%) responding to the questionnaire said they were aware of the ALARA (“as low as reasonably achievable”) principle, but almost 67% were unaware of India’s Atomic Energy Regulatory Board recommendation that 20 millisieverts per year is the occupational dose limit. Moreover, only 22% of respondents were aware of increased radiation risks in children and pregnant women.
When asked about the best way to improve dentists’ awareness of radiation hazards, 52.3% of respondents favored continuing dental education programs, 7.3% specified journals and other articles, 13% preferred Internet updates, and 27% preferred a combination of the preceding.
The survey findings show that most dentists were unaware of radiation hazards and safety procedures in dental settings, and few used safety measures such as lead aprons or shields. The authors emphasized the need for general dentists to be better informed about rules pertaining to radiation protection measures. Continuing education programs are a good way to improve dentists’ awareness of radiation hazards and the need to protect patients and dental care providers by following safety measures in the dental office.
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Evaluating endodontic treatment outcomes
To measure the success of endodontic treatment, health care providers must apply robust criteria for outcomes assessment. According to research published in the January issue of Dental Clinics of North America, evaluating outcomes involves clinical examination for resolution of signs and symptoms, radiographic assessment of periapical osseous status, and histopathologic analysis of biopsy specimens.
The researchers discuss a landmark 1956 study by Strindberg that established criteria for evaluating endodontic treatment outcomes. According to these clinical and radiographic criteria, outcomes are defined as “success,” “failure,” or “uncertain.” Radiographic success is demonstrated by normal contours and width of periodontal ligament. Endodontic failure is defined as “unchanged periradicular rarefaction,” a “decrease in periradicular rarefaction but no resolution,” or the “appearance of new rarefaction or an increase in the size of initial rarefaction,” the researchers report. Uncertain endodontic treatment outcomes are defined as “ambiguous or technically unsatisfactory radiograph,” “periradicular rarefaction less than 1 mm and disrupted lamina dura,” or a “tooth extract[ion] prior to recall due to reasons not related to endodontic outcome.” The article includes many radiographic images that illustrate Strindberg’s criteria for success, failure, and uncertain outcomes.
Since publication of Strindberg’s study, other, less rigid, systems have been introduced to assess endodontic treatment outcomes. The authors describe the periapical index (PAI), a structured scoring system for categorizing radiographic features of apical periodontitis. The 5-point ordinal scale (1 = normal periapical features, 5 = severe apical periodontitis, with exacerbating features) is based on a visual scale of periapical periodontitis severity.
The use of cone-beam computed tomography (CBCT) in endodontic diagnosis and treatment planning led to the development of the CBCT-PAI. This index provides a standardized approach to assessing apical periodontitis by means of CBCT. It consists of a 6-point scale (0 = intact periapical bone structures, 5 = diameter of periapical radiolucency, 8 mm) and 2 variables that assess cortical bone expansion and destruction. Because CBCT is more sensitive than conventional radiography, CBCT-PAI likely reduces the number of false-negative diagnoses on periapical radiographs, the authors note.
The American Association of Endodontists (AAE) and the Academy of Oral and Maxillofacial Radiology (AAOMR) jointly developed guidelines for the appropriate use of CBCT in endodontics. The authors explain that “these guidelines define clinical scenarios and 2-D radiographic appearances that are likely to benefit from CBCT imaging.” Despite its greater sensitivity, the AAE-AAOMR guidelines “recommend against using CBCT as a routine diagnostic and outcome assessment tool.”
Resolution of periradicular inflammatory changes and regeneration of osseous and periodontal structures around the tooth apex are evidence of successful endodontic treatment, the authors report. For these changes to be radiographically apparent, adequate remineralization of the bone must occur, sometimes over an extended period. Consequently, health care providers must consider radiographic changes in the context of the tooth’s functional status and clinical symptoms. After reviewing existing criteria and comparing them with outcome measures used in other specialties, AAE defined new terms using valid measures appropriate for endodontics. These definitions of endodontic outcomes include “healed,” “nonhealed,” “healing,” and “functional.”
This review also examines outcome assessments and success rates for orthograde endodontic treatment, endodontic treatment of immature teeth, vital pulp therapy, apexification procedures, and regenerative endodontic procedures. The authors conclude by stating that disease-free outcomes should be the goal of all endodontic treatments.
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ADA brochure explains X-ray exams to patients
To help reinforce the value of radiographs as a diagnostic tool, the ADA offers the patient education brochure, “Dental X-Ray Exams.” This brochure explains how finding and treating dental problems at an early stage can help save time and money and prevent pain.
Featuring vivid photos of the different types of dental radiographs, this reference explains how each of these types might be important in their dental exam. In addition, patients will have an understanding of the types of problems that dental practitioners can find when using X-rays. It assures patients of the safety of X-rays and that dental offices take steps to reduce the amount of radiation to which patients are exposed.
“Dental X-Ray Exams” is a 6-panel brochure available in packs of 50 from the ADA Catalog. A sample can be viewed here. To order, call 1-800-947-4746 or go to adacatalog.org. Readers who use the code 17402E before February 10 can save 15 percent on all ADA Catalog products.
Look at the type of dentistry you perform
Before you invest in a CBCT unit, Dr. Terry Work suggests you think about the profile of your practice to determine which scanner is best for your practice. Do you place implants? Do you take on endodontic cases? Do you perform oral surgery? But don’t limit yourself by just focusing on today. Think about what procedures you might want to offer in the future. Read more — download today.
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 first in the series on this topic for 2017. Other Specialty Scan issues are devoted to endodontics, oral pathology, orthodontics, pediatric dentistry, periodontics and prosthodontics. The ADA has engaged the specialty organizations in these areas as well as its own Science Institute and Division of Legal Affairs to assist with these newsletters. We welcome feedback on this and all Specialty Scan issues.
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