Memories of the first 50 years of the journal Dentomaxillofacial Radiology.

As Dentomaxillofacial Radiology celebrates 50 years of publication, some former editors who have helped the journal reach this milestone reminisce on their time at the helm of the journal.

First bone-cracking dog coprolites provide new insight into bone consumption in Borophagus and their unique ecological niche.

Borophagine canids have long been hypothesized to be North American ecological 'avatars' of living hyenas in Africa and Asia, but direct fossil evidence of hyena-like bone consumption is hitherto unknown. We report rare coprolites (fossilized feces) of Borophagus parvus from the late Miocene of California and, for the first time, describe unambiguous evidence that these predatory canids ingested large amounts of bone. Surface morphology, micro-CT analyses, and contextual information reveal (1) droppings in concentrations signifying scent-marking behavior, similar to latrines used by living social carnivorans; (2) routine consumption of skeletons; (3) undissolved bones inside coprolites indicating gastrointestinal similarity to modern striped and brown hyenas; (4) B. parvus body weight of ~24 kg, reaching sizes of obligatory large-prey hunters; and (5) prey size ranging ~35-100 kg. This combination of traits suggests that bone-crushing Borophagus potentially hunted in collaborative social groups and occupied a niche no longer present in North American ecosystems.

A basal ursine bear (Protarctos abstrusus) from the Pliocene High Arctic reveals Eurasian affinities and a diet rich in fermentable sugars.

The skeletal remains of a small bear (Protarctos abstrusus) were collected at the Beaver Pond fossil site in the High Arctic (Ellesmere I., Nunavut). This mid-Pliocene deposit has also yielded 12 other mammals and the remains of a boreal-forest community. Phylogenetic analysis reveals this bear to be basal to modern bears. It appears to represent an immigration event from Asia, leaving no living North American descendants. The dentition shows only modest specialization for herbivory, consistent with its basal position within Ursinae. However, the appearance of dental caries suggest a diet high in fermentable-carbohydrates. Fossil plants remains, including diverse berries, suggests that, like modern northern black bears, P. abstrusus may have exploited a high-sugar diet in the fall to promote fat accumulation and facilitate hibernation. A tendency toward a sugar-rich diet appears to have arisen early in Ursinae, and may have played a role in allowing ursine lineages to occupy cold habitats.

Feeding capability in the extinct giant Siamogale melilutra and comparative mandibular biomechanics of living Lutrinae.

At 50 kg in estimated weight, the extinct Siamogale melilutra is larger than all living otters, and ranks among the largest fossil otters. The biomechanical capability of S. melilutra jaws as related to their large size is unknown but crucial to reconstructing the species' potentially unique ecological niche. Here we compare the mandibular biomechanics of S. melilutra using engineering-based performance measures against ten extant otter biomechanical models. Despite a wide range of feeding preferences from durophagy to piscivory, living otter species exhibit a linear relationship between mandible stiffness and volume, as expected in isometric model scaling. In contrast, S. melilutra models exhibit a six-fold increase in stiffness from expected stiffness-volume relationships calculated from extant species models. Unlike stiffness, mechanical efficiency of biting is conserved among living otters and in S. melilutra. These findings indicate that although similar to living bunodont otters in morphology and biting efficiency, jaw strength in S. melilutra far surpasses molluscivores such as sea otters and Cape clawless otters, even after accounting for size. Therefore, Siamogale represents a feeding ecomorphology with no living analog, and its giant size and high mandibular strength confer shell-crushing capability matched only by other extinct molluscivores such as the marine bear Kolponomos.

Impact of cone-beam computed tomography on orthodontic diagnosis and treatment planning.

INTRODUCTION: In this study, we measured the impact of cone-beam computed tomography (CBCT) on orthodontic diagnosis and treatment planning. METHODS: Participant orthodontists shown traditional orthodontic records for 6 patients were asked to provide a diagnostic problem list, a hypothetical treatment plan, and a clinical certainty. They then evaluated a CBCT scan for each patient and noted any changes, confirmations, or enhancements to their diagnosis and treatment plan. RESULTS: The number of diagnosis and treatment plan changes varied widely by patient characteristics. The most frequently reported diagnosis and treatment plan changes occurred in patients with unerupted teeth, severe root resorption, or severe skeletal discrepancies. We found no benefit in terms of changes in treatment plan for patients when the reason for obtaining a CBCT scan was to examine for abnormalities of the temporomandibular joint or airway, or crowding. Orthodontic participants who own CBCT machines or use CBCT scans frequently in practice reported significantly more diagnosis and treatment plan changes and greater confidence after viewing the CBCT scans during the study. CONCLUSIONS: The results of this study support obtaining a CBCT scan before orthodontic diagnosis and treatment planning when a patient has an unerupted tooth with delayed eruption or a questionable location, severe root resorption as diagnosed with a periapical or panoramic radiograph, or a severe skeletal discrepancy. We propose that CBCT scans should be ordered only when there is clear, specific, individual clinical justification.

Dentition, dental health habits, and dementia: the Leisure World Cohort Study.

OBJECTIVES: To explore the association between dentition and dental health behaviors and incident dementia. DESIGN: Longitudinal cohort. SETTING: Leisure World, Laguna Hills, CA; a retirement community. PARTICIPANTS: Five thousand four hundred sixty-eight older (median age 81) adults followed from 1992 to 2010. MEASUREMENTS: Questions regarding dental health focused on number of natural teeth, dentures worn, number of visits to a dentist, and oral health habits. Dementia status was determined from in-person evaluations, follow-up questionnaires, hospital data, and death certificates. Estimates of dementia risk were calculated using Cox regression analysis in men and women separately. RESULTS: Men with inadequate natural masticatory function who did not wear dentures had a 91% greater risk of dementia than those with adequate natural masticatory function (≥ 10 upper teeth and ≥ 6 lower teeth). This risk was also greater in women but not significantly so. Dentate individuals who reported not brushing their teeth daily had a 22% to 65% greater risk of dementia than those who brushed three times daily. CONCLUSION: In addition to helping maintain natural, healthy, functional teeth, oral health behaviors are associated with lower risk of dementia in older adults.

Update on the biological effects of ionizing radiation, relative dose factors and radiation hygiene.

Diagnostic imaging is an indispensable part of contemporary medical and dental practice. Over the last few decades there has been a dramatic increase in the use of ionizing radiation for diagnostic imaging. The carcinogenic effects of high-dose exposure are well known. Does diagnostic radiation rarely cause cancer? We don't know but we should act as if it does. Accordingly, dentists should select patients wisely - only make radiographs when there is patient-specific reason to believe there is a reasonable expectation the radiograph will offer unique information influencing diagnosis or treatment. Low-dose examinations should be made: intraoral imaging - use fast film or digital sensors, thyroid collars, rectangular collimation; panoramic and lateral cephalometric imaging - use digital systems or rare-earth film screen combinations; and cone beam computed tomography - use low-dose machines, restrict field size to region of interest, reduce mA and length of exposure arc as appropriate.

Dental health behaviors, dentition, and mortality in the elderly: the leisure world cohort study.

In the last decade the effect of oral health on the general health and mortality of elderly people has attracted attention. We explored the association of dental health behaviors and dentition on all-cause mortality in 5611 older adults followed from 1992 to 2009 (median = 9 years) and calculated risk estimates using Cox regression analysis in men and women separately. Toothbrushing at night before bed, using dental floss everyday, and visiting the dentist were significant risk factors for longevity. Never brushing at night increased risk 20-35% compared with brushing everyday. Never flossing increased risk 30% compared with flossing everyday. Not seeing a dentist within the last 12 months increased risk 30-50% compared with seeing a dentist two or more times. Mortality also increased with increasing number of missing teeth. Edentulous individuals (even with dentures) had a 30% higher risk of death compared with those with 20+ teeth. Oral health behaviors help maintain natural, healthy and functional teeth but also appear to promote survival in older adults.

Legal considerations in the use of cone beam computer tomography imaging.

Cone beam computed tomography imaging represents a paradigm shift for enhancing diagnosis and treatment planning. Questions regarding cone beam computed tomography's associated legal responsibility are addressed, including cone beam computed tomography necessity, recognition of pathosis in the scan's entire volume, adequate training, informed consent and/or refusal and current court status of cone beam computed tomography. Judicious selection and prudent use of cone beam computed tomography technology to protect and promote patient safety and efficacious treatment complies with the standard of care.

Cone-beam imaging in dentistry.

Cone-beam imaging has gained broad acceptance in dentistry in the last 5 years. The purpose of this review is to describe the use in dentistry and consider issues requiring further development. Cone-beam machines emit an x-ray beam shaped liked a cone rather than a fan as in conventional computed tomography (CT) machines. After this beam passes through the patient the remnant beam is captured on an amorphous silicon flat panel or image intensifier/charge-coupled device (CCD) detector. The beam diameter ranges from 4 to 30 cm and exposes the head in one pass around the patient capturing from 160 to 599 basis images. These images are used to compute a volume from which planar or curved reconstructions can be extracted in any orientation. Voxels are isotropic and can be as small as 0.125 mm. 3-D images of bone or soft tissue surfaces can also be generated. In dentistry the most common indications for cone-beam imaging are assessment of the jaws for placement of dental implants, evaluation of the temporomandibular joints for osseous degenerative changes, examination of teeth and facial structures for orthodontic treatment planning, evaluation of the proximity of lower wisdom teeth to the mandibular nerve prior to extraction, and evaluation of teeth and bone for signs of infections, cysts, or tumors. Cone-beam images have largely replaced conventional tomography for these tasks. The effective dose from cone-beam imaging ranges from 6 to 477 microSv. The cost of the equipment is relatively low, about $150,000 to $300,000. Issues to be considered are the training of individuals making and interpreting cone-beam images, as well as means to further reduce patient exposure.

Patient risk related to common dental radiographic examinations: the impact of 2007 International Commission on Radiological Protection recommendations regarding dose calculation.

BACKGROUND: In 2007, the International Commission on Radiological Protection (ICRP) revised estimates of the radiosensitivity of tissues including those in the maxillofacial region. The authors conducted a study to reassess patients' risk related to common dental radiographic exposures using the 2007 ICRP recommendations. METHODS: The authors used a tissue-equivalent head phantom to measure dose. They calculated effective doses by using both 1990 and revised 2007 ICRP recommendations. Effective dose is a calculation that takes into consideration the different sensitivities of organs to long-term effects from ionizing radiation. It is the preferred method for comparing doses between different types of exposures. RESULTS: Effective doses (per the 2007 ICRP) in microsieverts were as follows: full-mouth radiographs (FMX) with photo-stimulable phosphor (PSP) storage or F-speed film with rectangular collimation, 34.9 microSv; four-image posterior bitewings with PSP or F-speed film with rectangular collimation, 5.0 microSv; FMX using PSP or F-speed film with round collimation, 170.7 microSv; FMX with D-speed film and round collimation, 388 microSv; panoramic Orthophos XG (Sirona Group, Bensheim, Germany) with charge-coupled device (CCD), 14.2 microSv; panoramic ProMax (Planmeca, Helsinki, Finland) with CCD, 24.3 microSv; posteroanterior cephalogram with PSP, 5.1 microSv; and lateral cephalogram with PSP, 5.6 microSv. These values are 32 to 422 percent higher than those determined according to the 1990 ICRP guidelines. CONCLUSIONS: Although radiographs are an indispensable diagnostic tool, the increased effective doses of common intraoral and extraoral imaging techniques are high enough to warrant reconsideration of means to reduce patients' exposure. CLINICAL IMPLICATIONS: Clinicians can reduce patients' dose substantively by using digital receptors or F-speed film instead of D-speed film, rectangular collimation instead of round collimation and radiographic selection criteria.

The evolution and application of dental maxillofacial imaging modalities.

During the last decades, an exciting new array of imaging modalities, such as digital imaging, CT, MRI, positron emission tomography, and cone-beam CT (CBCT), has provided astounding new images that continually contribute to the accuracy of diagnostic tasks of the maxillofacial region. The most recent, cone-beam imaging, is gaining rapid acceptance in dentistry because it provides cross-sectional imaging that is often a valuable supplement to intraoral and panoramic radiographs. The information content in such examinations is high and the dose and costs are low. The increasing trend toward the use of CBCT in dental offices may be expected to result in improved diagnosis, but with increased patient dose and health care costs. Using CBCT as a secondary imaging tool helps optimize health-to-risk ratio.

A diagnostic challenge: anterior variant of mandibular lingual bone depression.

Mandibular lingual bone depressions are considered to be developmental anomalies and most clinicians are familiar with the posterior variant (known as Stafne's bone cavity) that occurs in lingual mandibular molar regions, adjacent to the submandibular gland and below the mandibular canal. The anterior variant of the mandibular lingual bone depression is an asymptomatic bone cavity that occurs adjacent to the sublingual gland in the anterior mandible. Radiographically, it appears as a well-corticated radiolucency that retains a normal trabecular pattern internally. CT imaging is diagnostic and avoids surgical and sialographic procedures. This article reviews radiographic and CT features of a case involving the anterior variant of mandibular lingual bone depression.

Risk factors for fractures in older men and women: The Leisure World Cohort Study.

BACKGROUND: Osteoporosis results in >1.5 million fractures in the United States each year, leading to substantial health care costs and loss of quality of life. One major gap in our knowledge is how to effectively identify individuals at risk of developing a fracture. OBJECTIVE: We examined a population-based cohort for risk factors for fractures of the hip, wrist, and spine in men and women. METHODS: The Leisure World Cohort Study was established between 1981 and 1985 when residents of a southern California retirement community completed a postal health survey. Multiple lifestyle, medical, attitudinal, and anthropomorphic factors were self-reported. Fractures were identified from 4 follow-up surveys, hospital discharge records, and death certificates. Fracture rates were determined separately for men and women. Cox proportional hazards regression was used to identify predictors of fracture. RESULTS: Incident fractures of the hip (n = 1,227), wrist (n = 445), and spine (n = 729) incurred over the course of 2 decades were identified in the 13,978 residents surveyed. Mean (SD) age at entry was 74.9 (7.2) years for men and 73.7 (7.4) years for women. The most important risk factors for fracture were the same in men and women: age increased risk of hip and spine fractures (hazard ratio [HR] = 2.3-3.2 per 10 years) and history of fracture increased fracture risk at all 3 sites (HR = 1.4-3.2). In both men and women, glaucoma was a significant risk factor for hip fracture (HR = 1.9 and 1.3, respectively), and smoking was a risk factor for hip and spine fractures. Men and women with a positive mental attitude had fewer hip and spine fractures (HR = 0.7-0.9). High body mass index was protective at all 3 fracture sites in women (HR = 0.7-0.8), but those who used vitamin A supplements had increased rates of hip and wrist fracture (HR = 1.1 per 10,000 IU per day). CONCLUSIONS: Attitude, lifestyle choices, and the presence of medical conditions may influence the rate of osteoporotic fracture in older women and men and may help identify individuals at high risk.

Menstrual and reproductive factors and fracture risk: the Leisure World Cohort Study.

BACKGROUND: Because menopausal estrogen is related to the development of osteoporosis, we investigated the potential associations of the estrogen-related events of menarche, pregnancy, and menopause with fracture risk in a population-based, prospective study of older women. METHODS: The Leisure World Cohort was established in the early 1980s when residents of a California retirement community, including 8877 women, completed a health survey. Incident fractures of the hip (n = 1220), wrist (n = 463), and spine (n = 613) incurred over two decades were identified from four follow-up questionnaires, hospital discharge records, and (for hip fracture) death certificates. Hazard ratios (HR) adjusted for age and other potential confounders were calculated using proportional hazards regression. RESULTS: Late age at menarche was associated with decreased hip fracture risk (HR = 0.84, 95% CI 0.72-0.98, for age > or = 14 vs. < or = 12 years) but was unrelated to fractures at other sites. Hip fracture risk was also reduced in women who had been pregnant (HR = 0.83, 95% CI 0.72- 0.95). Women who reported menopause at age 45+ had a lower risk of wrist fracture compared with those with menopause at age < or = 44 (HR = 0.74, 95% CI 0.58-0.95 for ages 45-54; HR = 0.71, 95% CI 0.49-1.04 for ages 55+). Although fracture risks did not differ between ever and never users of menopausal estrogen, recency since last use was related to wrist fractures (HR = 1.09, 95% CI 1.03-1.16 for each 5 years since last years). CONCLUSIONS: The estrogen-related events of menarche, pregnancy, and menopause were not associated with osteoporotic fracture risk in a consistent manner. Other factors related to these events may be influencing development of osteoporosis and the likelihood of sustaining a fracture in older women.