Diagnosis of Occlusal Caries with Dynamic Slicing of 3D Optical Coherence Tomography Images

Detecting the extent of occlusal caries is a clinically important but challenging task required for treatment decision making. The aim of this study was to assess the diagnostic power of 3D swept-source optical coherence tomography (OCT) for evaluation of occlusal caries in comparison with X-ray radiography. Extracted human molars not exhibiting American Dental Association (ADA) criteria advanced caries were mounted in a silicone block and digital dental radiographs were captured from the buccal side. Subsequently, occlusal surfaces were scanned with a prototype Yoshida Dental OCT. Thirteen examiners evaluated the presence and extent of caries on radiographs and dynamically sliced 3D OCT video images, using a 4 level scale—0: intact; 1: enamel demineralization without cavitation; 2: enamel caries with cavitation; 3: dentin caries with or without cavitation. Sensitivity, specificity and area under operating characteristic curves (Az) were statistically analyzed (α = 0.05). Reliability analysis showed an excellent agreement among the 13 examiners for both methods. The OCT presented a significantly higher sensitivity and Az value for the detection of caries compared to radiographs (p < 0.05). Radiography showed especially low sensitivity for dentin caries (0–2 versus 3). Dynamic slicing of 3D OCT volumes is a powerful adjunct tool to visual inspection to diagnose the dentin occlusal caries in vitro.

ESTIMATION OF EFFECTIVE DOSE OF DENTAL X-RAY DEVICES

This study aims to estimate the effective doses of dental X-ray devices under common scanning protocols. After putting TLDs in the Alderson Radiation Therapy Phantom, we exposed the phantom under common scanning protocols of three dental X-ray devices, namely CBCT, dental panoramic machine and intraoral round cone device. Then effective doses were calculated using the measured absorbed doses of organs and tissues. Tissue weighting factors recommended by the ICRP were adopted in the calculation. Effective doses under common scanning protocols of three Dental X-ray devices were obtained. The effective dose of dental CT was 0.20 mSv, and that of dental panoramic machine and intraoral radiography were 0.013 and 0.0050 mSv, respectively. The tissue absorbed doses of dental CT scan were 0.63 mGy of brain, 7.7 mGy of salivary glands, 8.7 mGy of thyroid and 4.0 mGy of the lens of the eye. The tissue absorbed doses from dental panoramic machine are 0.62 mGy of salivary glands and 0.25 mGy of thyroid. And finally the tissue absorbed dose of intraoral radiography was 0.80 mGy of salivary gland. Among the three dental X-ray devices studied, dental CBCT scan can cause much higher effective dose than the other two. Brain, salivary glands, thyroid and the lens of the eye are tissues receiving relatively higher absorbed doses.

Measurement of scattered and transmitted x-rays from intra-oral and panoramic dental x-ray equipment

The aim of this study was to quantify the levels of transmitted radiation arising from the use of intra-oral dental x-ray equipment and scattered radiation arising from the use of both intra-oral and panoramic x-ray equipment. Levels of scattered radiation were measured at 1 m from a phantom, using an ion chamber with a volume of 1800 cm³. Transmitted radiation was measured using both (i) a phantom and dose-area product (DAP) meter and (ii) a patient and a 1800 cm³ ion chamber. For intra-oral radiography the patient study gave a maximum transmission of 1.80% (range 0.04-1.80%, mean 0.26%) and the phantom study gave a maximum transmission of 6% (range 2-6%, mean 5%). The maximum scattered radiation, per unit DAP, was 5.5 nGy (mGy cm²)^-1 at 70 kVp and a distance of 1 m. For panoramic radiography the maximum scattered radiation was 9.3 nGy (mGy cm²)^-1 at 80 kVp and a distance of 1 m. Dose values are presented to enable the calculation of adequate protective measures for dental radiography rooms. Previous studies have used a phantom and measured radiation doses at 1 m from the phantom to determine the radiation dose transmitted through a patient, whereas this study uses both patient and phantom measurements together with a large-area dosemeter, positioned to capture the entire x-ray beam, to ensure that more realistic dose measurements can be made.

Extra-oral dental radiography for disaster victims using a flat panel X-ray detector and a hand-held X-ray generator

BACKGROUND

Forensic odontologists commonly incise the skin for post-mortem dental examinations when it is difficult to open the victim's mouth. However, it is prohibited by law to incise dead bodies without permission in Japan. Therefore, we attempted using extra-oral dental radiography, using a digital X-ray equipment with rechargeable batteries, to overcome this restriction.

MATERIALS AND METHODS

A phantom was placed in the prone position on a table, and three plain dental radiographs were used per case: "lateral oblique radiographs" for left and right posterior teeth and a "contact radiograph" for anterior teeth were taken using a flat panel X-ray detector and a hand-held X-ray generator. The resolving power of the images was measured by a resolution test chart, and the scattered X-ray dose was measured using an ionization chamber-type survey meter.

RESULTS

The resolving power of the flat panel X-ray detector was 3.0 lp/mm, which was less than that of intra-oral dental methods, but the three extra-oral plain dental radiographs provided the overall dental information from outside of the mouth, and this approach was less time-consuming. In addition, the higher dose of scattered X-rays was laterally distributed, but the dose per case was much less than that of intra-oral dental radiographs.

CONCLUSION

Extra-oral plain dental radiography can be used for disaster victim identification by dental methods even when it is difficult to open the mouth. Portable and rechargeable devices, such as a flat panel X-ray detector and a hand-held X-ray generator, are convenient to bring and use anywhere, even at a disaster scene lacking electricity and water.

Influence of a Commercial Lead Apron on Patient Skin Dose Delivered During Oral and Maxillofacial Examinations under Cone Beam Computed Tomography (CBCT)

The purpose of this paper is to investigate the impact of a commercial lead apron on patient skin dose delivered during maxillofacial CBCT in five critical regions by means of solid-state-dosimetry. Five anatomical regions (thyroid gland, left and right breast, gonads, back of the phantom torso) in an adult female anthropomorphic phantom were selected for dose measurement by means of the highly sensitive solid-state dosimeter QUART didoSVM. Ten repeated single exposures were assessed for each patient body region for a total of five commercial CBCT devices with and without a lead apron present. Shielded and non-shielded exposures were compared under the paired Wilcoxon test, with absolute and relative differences computed. Reproducibility was expressed as the coefficient of variation (CV) between the 10 repeated assessments. The highest doses observed at skin level were found at the thyroid (mean shielded ± SD: 450.5 ± 346.7 μGy; non-shielded: 339.2 ± 348.8 μGy, p = 0.4922). Shielding resulted in a highly significant (p < 0.001) 93% dose reduction in skin dose in the female breast region with a mean non-shielded dose of approximately 35 μGy. Dose reduction was also significantly lower for the back-region (mean: -65%, p < 0.0001) as well as for the gonad-region (mean: -98%, p < 0.0001) in the shielded situation. Reproducibility was inversely correlated to skin dose (Rspearman = -0.748, p < 0.0001) with a mean CV of 10.45% (SD: 24.53 %). Skin dose in the thyroid region of the simulated patient was relatively high and not influenced by the lead apron, which did not shield this region. Dose reduction by means of a commercial lead apron was significant in all other regions, particularly in the region of the female breast.

Inspections of X-ray Use in Dental Practices and Common Regulatory Violations

Dental X-ray machine inspections are conducted by the California Department of Public Health’s Radiologic Health Branch (RHB). RHB’s mission is to protect public health and safety throughout California by ensuring the safe use of radiologic equipment and materials within industry, medicine and research, preventing radiologic health hazards and educating and enforcing applicable state and federal radiation laws and regulations.

CUSTOMISATION OF A MONTE CARLO DOSIMETRY TOOL FOR DENTAL CONE-BEAM CT SYSTEMS

A versatile EGSnrc Monte Carlo (MC) framework, initially designed to explicitly simulate X-ray tubes and record the output data into phase space data files, was modified towards dental cone-beam computed tomography (CBCT) dosimetric applications by introducing equivalent sources. Half value layer (HVL) measurements were conducted to specify protocol-specific energy spectra. Air kerma measurements were carried out with an ionisation chamber positioned against the X-ray tube to obtain the total filtration attenuation characteristics. The framework is applicable to bowtie and non-bowtie inherent filtrations, and it accounts for the anode heel effect and the total filtration of the tube housing. The code was adjusted to the Promax 3D Max (Planmeca, Helsinki, Finland) dental CBCT scanner. For each clinical protocol, calibration factors were produced to allow absolute MC dose calculations. The framework was validated by comparing MC calculated doses and measured doses in a cylindrical water phantom. Validation results demonstrate the reliability of the framework for dental CBCT dosimetry purposes.

Dental MRI using wireless intraoral coils

Currently, the gold standard for dental imaging is projection radiography or cone-beam computed tomography (CBCT). These methods are fast and cost-efficient, but exhibit poor soft tissue contrast and expose the patient to ionizing radiation (X-rays). The need for an alternative imaging modality e.g. for soft tissue management has stimulated a rising interest in dental magnetic resonance imaging (MRI) which provides superior soft tissue contrast. Compared to X-ray imaging, however, so far the spatial resolution of MRI is lower and the scan time is longer. In this contribution, we describe wireless, inductively-coupled intraoral coils whose local sensitivity enables high resolution MRI of dental soft tissue. In comparison to CBCT, a similar image quality with complementary contrast was obtained ex vivo. In-vivo, a voxel size of the order of 250 ∙ 250 ∙ 500 μm(3) was achieved in 4 min only. Compared to dental MRI acquired with clinical equipment, the quality of the images was superior in the sensitive volume of the coils and is expected to improve the planning of interventions and monitoring thereafter. This method may enable a more accurate dental diagnosis and avoid unnecessary interventions, improving patient welfare and bringing MRI a step closer to becoming a radiation-free alternative for dental imaging.

The value of thyroid shielding in intraoral radiography

OBJECTIVES

To evaluate the utility of the application of a thyroid shield in intraoral radiography when using rectangular collimation.

METHODS

Experimental data were obtained by measuring the absorbed dose at the position of the thyroid gland in a RANDO(®) (The Phantom Laboratory, Salem, NY) male phantom with a dosemeter. Four protocols were tested: round collimation and rectangular collimation, both with and without thyroid shield. Five exposure positions were deployed: upper incisor (Isup), upper canine (Csup), upper premolar (Psup), upper molar (Msup) and posterior bitewing (BW). Exposures were made with 70 kV and 7 mA and were repeated 10 times. The exposure times were as recommended for the exposure positions for the respective collimator type by the manufacturer for digital imaging. The data were statistically analyzed with a three-way ANOVA test. Significance was set at p < 0.01.

RESULTS

The ANOVA test revealed that the differences between mean doses of all protocols and geometries were statistically significant, p < 0.001. For the Isup, thyroid dose levels were comparable with both collimators at a level indicating primary beam exposure. Thyroid shield reduced this dose with circa 75%. For the Csup position, round collimation also revealed primary beam exposure, and thyroid shield yield was 70%. In Csup with rectangular collimation, the thyroid dose was reduced with a factor 4 compared with round collimation and thyroid shield yielded an additional 42% dose reduction. The thyroid dose levels for the Csup, Psup, Msup and BW exposures were lower with rectangular collimation without thyroid shield than with round collimation with thyroid shield. With rectangular collimation, the thyroid shield in Psup, Msup and BW reduced the dose 10% or less, where dose levels were already low, implying no clinical significance.

CONCLUSIONS

For the exposures in the upper anterior region, thyroid shield results in an important dose reduction for the thyroid. For the other exposures, thyroid shield augments little to the reduction achieved by rectangular collimation. The use of thyroid shield is to be advised, when performing upper anterior radiography.

Reducing an already low dental diagnostic X-ray dose: does it make sense? Comparison of three cost-utility analysis methods used to assess two dental dose-reduction measures

OBJECTIVES

To find a method that is suitable for providing an objective assessment of the cost effectiveness of a dose-reducing measure used for diagnostic dental X-ray exposures.

METHODS

Three cost-utility analysis (CUA) methods were evaluated by comparing their assessments of two dose-reduction measures, a rectangular collimator and the combination of two devices that reduce the radiation dose received during orthodontic lateral cephalography. The following CUA methods were used: (1) the alpha value (AV), a monetary valuation of dose reduction used in the nuclear industry; (2) the value of a statistical life for valuation of the reduction in stochastic adverse effects; and (3) the time-for-time method, based on the postulate that risk reduction is effective when the number of years of life gained is more than the years that an average worker must work to earn the costs of the risk-reducing measure. The CUA methods were used to determine the minimum number of uses that was required for the dose-reducing device to be cost effective. The methods were assessed for coherence (are comparable results achieved for comparable countries?) and adaptability (can the method be adjusted for age and gender of specific patient groups?).

RESULTS

The performance of the time-for-time method was superior to the other methods. Both types of dose-reduction devices tested were assessed as cost effective after a realistic number of uses with all three methods except low AVs.

CONCLUSIONS

CUA for the methods of X-ray dose reduction can be performed to determine if investment in low dose reduction is cost effective. The time-for-time method proved to be a coherent and versatile method for performing CUA.

Comparison of physical quality assurance between Scanora 3D and 3D Accuitomo 80 dental CT scanners

BACKGROUND

The use of cone beam computed tomography (CBCT) in dentistry has proven to be useful in the diagnosis and treatment planning of several oral and maxillofacial diseases. The quality of the resulting image is dictated by many factors related to the patient, unit, and operator.

MATERIALS AND METHODS

In this work, two dental CBCT units, namely Scanora 3D and 3D Accuitomo 80, were assessed and compared in terms of quantitative effective dose delivered to specific locations in a dosimetry phantom. Resolution and contrast were evaluated in only 3D Accuitomo 80 using special quality assurance phantoms.

RESULTS

Scanora 3D, with less radiation time, showed less dosing values compared to 3D Accuitomo 80 (mean 0.33 mSv, SD±0.16 vs. 0.18 mSv, SD±0.1). Using paired t-test, no significant difference was found in Accuitomo two scan sessions (p>0.05), while it was highly significant in Scanora (p>0.05). The modulation transfer function value (at 2 lp/mm), in both measurements, was found to be 4.4%. The contrast assessment of 3D Accuitomo 80 in the two measurements showed few differences, for example, the grayscale values were the same (SD=0) while the noise level was slightly different (SD=0 and 0.67, respectively).

CONCLUSIONS

The radiation dose values in these two CBCT units are significantly less than those encountered in systemic CT scans. However, the dose seems to be affected more by changing the field of view rather than the voltage or amperage. The low doses were at the expense of the image quality produced, which was still acceptable. Although the spatial resolution and contrast were inferior to the medical images produced in systemic CT units, the present results recommend adopting CBCTs in maxillofacial imaging because of low radiation dose and adequate image quality.

Justification and good practice in using handheld portable dental X-ray equipment: a position paper prepared by the European Academy of DentoMaxilloFacial Radiology (EADMFR)

Handheld portable X-ray devices are increasingly used for intraoral radiography. This development introduces new challenges to staff and patient safety, for which new or revised risk assessments must be made and acted upon prior to use. Major issues might be: difficulties in using rectangular collimation with beam aiming devices, more complex matching of exposure settings to the X-ray receptor used (e.g. longer exposure times), movements owing to the units' weight, protection of the operator and third persons, and the use in uncontrolled environments. These problems may result in violation of the "as low as reasonably achievable'', that is, ALARA principle by an increase in (re)exposures compared with the other available intraoral X-ray devices. Hence, the use of handheld portable X-ray devices should be considered only after careful and documented evaluation (which might be performed based on medical physics support), when there is evidence that handheld operation has benefits over traditional modalities and when no new risks to the operators and/or third parties are caused. It is expected that the use of handheld portable X-ray devices will be very exceptional, and for justified situations only. Special attention should be drawn to beam-aiming devices, rectangular collimation, the section of the X-ray receptor, focus-skin distance, and backscatter shielding, and that the unit delivers reproducible dose over the full set of environmental conditions (e.g. battery status and temperature).

Spatial resolution in CBCT machines for dental/maxillofacial applications-what do we know today?

Spatial resolution is one of the most important parameters objectively defining image quality, particularly in dental imaging, where fine details often have to be depicted. Here, we review the current status on assessment parameters for spatial resolution and on published data regarding spatial resolution in CBCT images. The current concepts of visual [line-pair (lp) measurements] and automated [modulation transfer function (MTF)] assessment of spatial resolution in CBCT images are summarized and reviewed. Published measurement data on spatial resolution in CBCT are evaluated and analysed. Effective (i.e. actual) spatial resolution available in CBCT images is being influenced by the two-dimensional detector, the three-dimensional reconstruction process, patient movement during the scan and various other parameters. In the literature, the values range between 0.6 and 2.8 lp mm(-1) (visual assessment; median, 1.7 lp mm(-1)) vs MTF (range, 0.5-2.3 cycles per mm; median, 2.1 lp mm(-1)). Spatial resolution of CBCT images is approximately one order of magnitude lower than that of intraoral radiographs. Considering movement, scatter effects and other influences in real-world scans of living patients, a realistic spatial resolution of just above 1 lp mm(-1) could be expected.

Assessment of the radiological safety of a Genoray portable dental X-ray unit

OBJECTIVES

The portable dental radiographic systems are generally used in emergency situations (e.g. during natural disasters) for disabled/aged patients and in patient rooms. This study assesses the output exposure of a portable dental radiographic system measured using thermoluminescent dosemeters (TLDs).

METHODS

Occupational exposure of the operator was determined when the portable dental unit was used for mandibular and maxillary teeth exposure.

RESULTS

The doses of some critical organs of an operator were measured using TLDs implanted within the Rando phantom.

CONCLUSIONS

Considering the annual organ dose limits, the eye lens dose limit is the main factor determining the frequency of system application.

Impact of rare earth element added filters on the X-ray beam spectra: a Monte Carlo approach

The effectiveness of added filters including conventional and rare earth materials for dental radiography tasks was investigated using a simulation approach. Current study focuses on the combination of a range of various filters to investigate the reduction of radiation absorbed dose and improving the quality of a radiography image. To simulate the X-ray beam spectrum, a MCNP5 code was applied. Relative intensity, beam quality, and mean energy were investigated for a typical dental radiography machine. The impact of different rare-earth materials with different thicknesses and tube voltages on the X-ray spectrum was investigated. For Aluminum as a conventional filter, the modeled X-ray spectra and HVL values were in a good agreement with those reported by IPEM. The results showed that for a 70 kVp voltage, with an increase of the thickness and atomic number of a given added filters, an increase of HVL values were observed. However, with the increase of the attenuator thickness, X-ray beam intensity decreases. For mean energy, different results were observed. It was also found that rare earth made filters reduce high energy X-ray radiation due to k-edge absorption. This leads to an ideal beam for intra-oral radiography tasks. However, as a disadvantage of rare earth added filters, the reduction of the tube output levels should also be considered.

Responsible use of cone beam computed tomography: minimising medico-legal risks

This communication highlights some of the ethical and possible legal responsibilities which pertain to the taking, reading, reporting, and communication of findings from cone-beam computed tomography (CBCT) scans. The importance of knowledge of head and neck anatomy and pathology to reduce the likelihood of incorrect interpretation is emphasised. Failure to detect critical findings in any diagnostic image can potentially result in medico-legal consequences. CBCT is no exception to this rule. Dental schools are advised to include CBCT imaging as a diagnostic tool in their under- and postgraduate curricula thereby equipping graduates to use 3D imaging in general and CBCT in particular. Existing dental practitioners are advised to seek continuing education on 3D imaging as part of their required lifelong learning.

Implementation of acceptability criteria for dental radiology in Belgium

The implementation of routine quality control (QC) tests in dental radiology in Belgium has been neglected for many years. In 2008, the (Belgian) Federal Agency for Nuclear Control determined acceptability criteria for X-ray equipment used for dentomaxillofacial imaging. An overview of the development of the criteria, together with implementation and the first results of dental QC in Belgium, is discussed.

Optimized marker for template-guided intraoral surgery

Template-guided intraoral surgery is attracting interest due to its accuracy and convenience. Usually, fiducial markers are used for registration of the different model coordinates for patients or plaster and fabrication coordinates in template-guided dental surgery. The accuracy of markers is important because it is directly related to the accuracy of the template-guide, which ultimately affects the success of surgical results. In this paper, we present the methods of determining optimal marker parameters such as size, shape, and material. We have defined parameters that could potentially influence the accuracy of markers and tested them with various values for each parameter. Experiments were performed to measure repeatability, and we tested accuracy and minimized potential error by comparing the actual and calculated dimensions. As a result, the following optimal marker parameters were identified: 3-mm diameter, positively tapered cylindrical shape, and titanium composition.

Radiation in dental practice: awareness, protection and recommendations

Radiation is the transmission of energy through space and matter. There are several forms of radiation, including ionizing and nonionizing. X-rays are the ionizing radiation used extensively in medical and dental practice. Even though they provide useful information and aid in diagnosis, they also have the potential to cause harmful effects. In dentistry, it is mainly used for diagnostic purposes and in a dental set-up usually the practicing dentist exposes, processes and interprets the radiograph. Even though such exposure is less, it is critical to reduce the exposure to the dental personnel and patients in order to prevent the harmful effects of radiation. Several radiation protection measures have been advocated to ameliorate these effects. A survey conducted in the Bengaluru among practicing dentists revealed that radiation protection awareness was very low and the necessary measures taken to reduce the exposure were not adequate. The aim of the article is to review important parameters that must be taken into consideration in the clinical set-up to reduce radiation exposure to patients and dental personnel.

Proposals for revised factors in intra-oral radiography shielding calculations

The current value for weighted average primary plus scatter kerma at 1 m for intra-oral radiography shielding assessment is based on scatter radiation measurements made with the trunk of a RANDO phantom and an assessment of primary transmission that is unverified. Measurements of primary transmission and scatter radiation during intra-oral radiography were made at 30° intervals through a full 360° rotation using two anthropomorphic head phantoms and similar equipment at three different sites. The results suggest that a scatter factor of 5 µGy (Gy cm(2))(-1) and a primary transmission of 0.03% of the entrance surface dose are more appropriate and, therefore, we recommend that the weighted average primary plus scatter kerma used for shielding calculations can be reduced from 1 to 0.5 µGy per exposure at 1 m. This factor will adequately account for exposures made at 60 and 70 kV using a range of intra-oral units.

Maintaining radiation exposures as low as reasonably achievable (ALARA) for dental personnel operating portable hand-held x-ray equipment

Clinical experience indicates that newly available portable hand-held x-ray units provide advantages compared to traditional fixed properly installed and operated x-ray units in dental radiography. However, concern that hand-held x-ray units produce higher operator doses than fixed x-ray units has caused regulatory agencies to mandate requirements for use of hand-held units that go beyond those recommended by the manufacturer and can discourage the use of this technology. To assess the need for additional requirements, a hand-held x-ray unit and a pair of manikins were used to measure the dose to a simulated operator under two conditions: exposures made according to the manufacturer's recommendations and exposures made according to manufacturer's recommendation except for the removal of the x-ray unit's protective backscatter shield. Dose to the simulated operator was determined using an array of personal dosimeters and a pair of pressurized ion chambers. The results indicate that the dose to an operator of this equipment will be less than 0.6 mSv y⁻¹ if the device is used according to the manufacturer's recommendations. This suggests that doses to properly trained operators of well-designed, hand-held dental x-ray units will be below 1.0 mSv y⁻¹ (2% of the annual occupational dose limit) even if additional no additional operational requirements are established by regulatory agencies. This level of annual dose is similar to those reported as typical dental personnel using fixed x-ray units and appears to satisfy the ALARA principal for this class of occupational exposures.

New multipurpose endodontic device developed in Germany for use in predoctoral and continuing dental education and science

The purpose of this article is to describe a simple and versatile aid for the endodontic treatment of extracted teeth and its possible applications. The Med*-box is a new endodontic multipurpose device made of transparent acrylic that permits all elements of root canal treatment to be performed and evaluated either visually or radiologically. The Med*-box represents a valuable addition to the spectrum of educational and practical means in endodontic training. It is well suited for students, dentists, and endodontists for learning the handling of new materials, methods, and instruments in endodontics before they work clinically upon a patient. Also in the context of scientific endodontic issues, the Med*-box represents a simple, economical, and easily manageable aid.

Assessment of microbial contamination of radiographic equipment and materials during intraoral imaging procedures

AIM

Aim of the present study was to assess microbial contamination of radiology procedures.

METHODS

Patients who needed radiographic exams were selected and the bisecting technique was used: G1 - (control): absence of plastic barrier and overgloving or disinfectant solutions; G2 - alcohol spraying; G3 - protection of the film with a plastic barrier and alcohol spray; G4 - protection of film with plastic barrier, use of overgloving and alcohol spray. The following regions were assessed: trigger switch, X-ray tube, sleeve of the portable dark chamber, water, developer and fixer. The areas for microbiological sample collection were standardized with a label cut internally so that the hollow area was 5 cm long and 2 cm wide. One mL of the developer, water and fixer were also collected before and after developing the films. The samples were incubated under anaerobiosis and aerobiosis. The results were submitted to the Cochran's Q and Mann-Whitney tests.

RESULTS

The sleeve of the developing chamber showed greater anaerobic contamination followed by the X-ray tube and only the use of alcohol associated with mechanical barriers was efficient to control this microbiota. The trigger showed higher aerobic microbial contamination and the use of alcohol or alcohol associated with mechanical barriers was efficient to control this microbiota. The developing solutions presented no significant growth of anaerobic and aerobic bacteria.

CONCLUSION

The characteristic of an aerobic or anaerobic microbial strain influences microbial contamination while radiographic projections are being taken and the use of alcohol associated with a plastic barrier and overgloving is indicated to reduce this microbiota.

Bacterial survival in the radiographic processes

AIM

The purpose of this study was to investigate the microbial contamination in hand-operated and automatic radiographic solutions and on contact surfaces during radiographic procedures such as X-ray cone and button and surface of hand-operated and automatic radiographic solution tanks in dental clinics.

METHODS

A 10 mL liquid solution was taken with syringe at 5, 10, 24, and 48 hour time intervals from freshly prepared hand-operated and automatic processing solution. The swab samples were taken from the surfaces of radiographic solution tanks, X-ray cone and its button. The specimens were inoculated into blood agar and Eosin Methylene-Blue (EMB) agar. The plates were incubated in an incubator for 48 hours at 37 °C. Becton Dickinson Phoenix Automated Microbiology System was used for determining the microorganisms.

RESULTS

Although the microbiologic analyses of the samples revealed no microbial growth in the hand-operated and automatic radiographic solutions in all observation periods, the microbial growth on the contact surfaces was observed. Staphylococcus epidermidis, metisillin resistant from the surface of radiographic solution tanks, X-ray cone and switch. Streptococcus mitis was found on the X-ray switch.

CONCLUSION

Radiographic procedures can cause cross contamination; clinicians should therefore apply disinfection protocols in all radiographic procedures.

Ionizing radiation regulations and the dental practitioner: 1. The nature of ionizing radiation and its use in dentistry

Legislation governing the use of ionizing radiation in the workplace and in medical treatment first became law in 1985 and 1988, being superseded by the Ionizing Radiations Regulations 1999 (IRR99) and the Ionizing Radiation (Medical Exposure) Regulations 2000, (IR(ME)R 2000), respectively. This legislation ensures a safe environment in which to work and receive treatment and requires that those involved in the radiographic process must be appropriately trained for the type of radiographic practice they perform. A list of the topics required is detailed in Schedule 2 of IR(ME)R 2000 and is paraphrased in Table 1, with the extent and amount of knowledge required depending on the type of radiographic practice undertaken.

CLINICAL RELEVANCE

Virtually all dental practitioners undertake radiography as part of their clinical practice. Legislation requires that users of radiation, including dentists and members of the dental team, understand the basic principles of radiation physics, hazards and protection, and are able to undertake dental radiography safely with the production of high quality, diagnostic images.

Dental staff doses with handheld dental intraoral x-ray units

A handheld portable dental intraoral x-ray system is available in the United States and elsewhere. The system is designed to minimize the user's radiation dose. It includes specially designed shielding of the x-ray tube housing and an integral radiation shield to minimize backscatter. Personnel radiation dose records were obtained from 18 dental facilities using both the handheld system and a wall mounted dental x-ray system, providing 661 individual dose measurements. Dental staff doses were also compared for the handheld and conventional systems using both film and digital imaging for the same facilities and staff members. The results indicate that the doses for the handheld systems are significantly less than for wall-mounted systems. The average monthly dose for the handheld systems was 0.28 μSv vs. 7.86 μSv (deep dose equivalent) for the wall-mounted systems, a difference that is statistically significant at the p = 0.01 level. Consequently, there should be no concern about the use of this handheld dental intraoral x-ray system. Additional shielding efforts, (e.g., wearing a lead apron) will not provide significant benefit nor reduce staff radiation dose.

The clinical application of the dental mini C-arm for the removal of broken instruments in soft and hard tissue in the oral and maxillofacial area

Many kinds of broken instruments, such as needles, probes, scalpels and catheters, are reported to be left in patients after surgery. These parts should be removed as soon as possible to prevent further complications. However, it is not easy to identify the exact location of the instrument intraoperatively, and a risk of damage exists for neighbouring nerves or vessels during the removal. The C-arm used in orthopaedic surgery, is seen as a useful and safe way to detect metal materials intraoperatively. However, its application for removal of broken instruments in the oral and maxillofacial area is not practical because of its large size. In our experiences with the removal of eight broken instruments in the oral and maxillofacial area, the newly developed dental mini C-arm was useful in finding broken instruments in soft tissue (five cases) and in paranasal sinus (one case), because it gives real time in situ information. This is important, because the position of the broken instrument can be changed due to traction of the soft tissue or swelling. The dental mini C-arm was less helpful in finding broken instruments in soft tissues compared to hard tissues (two cases) as the position of instruments did not change.

[Experience of using a filmless system in dental practice at Hiroshima University Hospital, a former university dental hospital]

Our university hospital has had a policy of electronic patient recordkeeping, replacing paper-based recordkeeping, since September 1, 2008. Because the Department of Oral and Maxillofacial Radiology had already been using computed radiography for X-ray systems except for intraoral radiography and storing data in Digital Imaging and Communications in Medicine (DICOM) format, the following three conditions form the basis of the changes we made in relation to the introduction of this policy. We started 1. using imaging plates for intraoral radiography as well and storing the data in DICOM format; 2. diagnosed without the need for film; and 3. referred to past images displayed on the screen of our Radiology Information System (RIS). The introduction of digital intraoral radiography has many advantages: not only does it not require film and can all past images be referred to on the screen of the RIS, but radiation exposure times are also shorter, images can be saved electronically, and thus, film processing is redundant. The system improves efficiency and is also advantageous to patients and staff in other departments.

[Methods of roentgenologic study comprehension for appreciation of root canal obturation quality]

Comparison of methods comprehension was done with intraoral roentgenography, orthopantomography (OPG), cone-beam computer tomography (CBCT) on the devices with optical amplifier of roentgenologic image (OARI) and sensor resolution (SR) 2 pair of lines per mm and without OARI with SR 2.5 pair of lines per mm. There were used extracted earlier teeth with adequate root canal obturation. According to the results of the study the image received with the help of CBCT with high SR let have the biggest information volume about filling quality of root canal and root canal structure peculiarities that testified to pro of the method over CBCT with OARI. The most widespread in the practice methods of intraoral roentgenography and orthopantomography not in all cases reflected reliably the root canal obturation degree.

The characteristics of dental X-ray fluoroscopic equipment 'DreamRay 60F'

This study examined the characteristics of the dental X-ray fluoroscopic equipment, 'DreamRay 60F', which was recently developed in Korea. The output linearity, output reproducibility, half-value layer (HVL), leakage radiation and scattered radiation were measured using an ionisation chamber. The surface dose equivalent rate and estimated dose equivalent of the operator were also calculated. The output linearity was 0.0015-0.0175 and the coefficient of variation for the output reproducibility was 0.0013-0.0074. The experimental HVL was 2.1 mm Al, and the leakage dose rate at 100 cm from the X-ray focus ranged from 2.70 to 19.66 microGy h (-1) depending on the direction. The scattered radiation doses differed significantly (1.7-16.8 times) depending on the distance and direction. If an operator is exposed for 10 min per procedure, 5 procedures a day at 5 days a week, he/she sitting at a 90 degrees direction will receive an annual dose equivalent of 13.0 mSv (at 30 cm) and 63.7 mSv (at 50 cm) in the trunk and face surface, respectively.

A comparative study for spatial resolution and subjective image characteristics of a multi-slice CT and a cone-beam CT for dental use

PURPOSE

Multi-slice CT (MSCT) and cone-beam CT (CBCT) are widely used in dental practice. This study compared the spatial resolution of these CT systems to elucidate which CT modalities should be selected for various clinical cases.

MATERIALS AND METHODS

As MSCT and CBCT apparatuses, Somatom Sensation 64 and 3D Accuitomo instruments, respectively, were used. As an objective evaluation of spatial resolution of these CT systems, modulation transfer function (MTF) analysis was performed employing an over-sampling method. The results of MTF analysis were confirmed with a line-pair test using CATPHAN. As a subjective evaluation, a microstructure visualization ability study was performed using a Jcl:SD rat and a head CT phantom.

RESULTS

MTF analysis showed that for the in-plane direction, the z-axis ultrahigh resolution mode (zUHR) of the Sensation 64 and 3D Accuitomo instruments had higher spatial resolutions than the conventional mode (64×) of the Sensation 64, but for the longitudinal direction, the 3D Accuitomo had clearly higher spatial resolution than either mode of the Sensation 64. A line-pair test study and microstructure visualization ability studies confirmed the results for MTF analysis. However, images of the rat and the CT phantom revealed that the 3D Accuitomo demonstrated the failure to visualize the soft tissues along with aliasing and beam-hardening artifacts, which were not observed in the Sensation 64.

CONCLUSIONS

This study successfully applied spatial resolution analysis using MSCT and CBCT systems in a comparative manner. These findings could help in deciding which CT modality should be selected for various clinical cases.

An assessment of the relative safety of dental x-ray equipment

Concern among patients, often prompted by medical practitioners, regarding the harmful effects of radiation caused by dental x-ray procedures, has caused several patients of the dental school of the University of Pretoria to refuse dental radiographic procedures. Buch and Fensham in a previous article demonstrated that radiation doses to the eyes and thyroid resulting from a single pantomogram constituted less than 10% of that which would be imparted by a transatlantic flight in terms of added natural background radiation. The authors in this study investigated doses to the same organs resulting from a full-mouth periapical series first using films and then digital imaging. Doses to the uterus resulting from these same examinations as well as from a pantomogram were also determined both with and without the use of a lead apron. Doses to the eye from a full-mouth examination using film compared favourably with those for a panoramic examination, but were much reduced when digital imaging techniques were employed. Doses to the uterus were small (equivalent to half a day of background radiation) for both a full-mouth examination using digital imaging, as well as for a pantomogram. However, from the results it would appear that there is little difference in the dose of scatter radiation to the uterus from a full-mouth examination whether or not a lead apron is used. The use of a lead apron for a pantomogram significantly reduces the dose to the uterus.

Portable dental equipment: dental units and x-ray equipment

Portable dental equipment makes it possible for clinicians to provide dental care to patients who are unable to travel to a traditional dental clinic. Nonambulatory, homebound, and institutionalized patients benefit greatly when portable equipment is used to address their dental treatment needs on-site. In recent years, more brands of portable equipment have been introduced to the market, some of which are quite sophisticated in terms of their design and uses. This article seeks to describe two kinds of commercially available portable equipment--dental units and x-ray devices--and to discuss their capabilities and features.