SEARCH · PubMed Health
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
The methods and techniques involved in dental radiography are presented to familiarize the radiologic technologist with this practice. Additionally, the uses and pathologies commonly encountered in dental radiography are discussed. Although dental radiography is seldom performed by many radiographers, the techniques and methods used may be of interest and use to the radiographer.
The principles and applications of sensitometry in dental radiography are discussed. A method is described for determining the sensitometric properties of films and processing techniques used in dental radiography. This method has been used to demonstrate the relationship between density and exposure for a dental emulsion processed in an automatic processor. Examples of other applications of the method are included.
Dental radiography doses in Hiroshima and Nagasaki were estimated on the basis of survey data from dental hospitals and clinics in Hiroshima and Nagasaki, and doses were measured by thermoluminescent dosimeters and a phantom. Doses to organs, including the lens, pituitary fossa, thyroid gland, and skin were calculated from data obtained during a 2-week survey in both cities. The mean caput doses were calculated from the data indicating frequency per year and were tabulated by organs, age, teeth examined, type of examination, population, sex, and city. No significant difference was observed by age, population, sex, or city. Currently the doses incurred during dental radiography may not be sufficiently high to cause bias in the assessments for late radiation effects among atomic-bomb survivors. However, the mean caput thyroid doses of 62 mrad and 67 mrad in Hiroshima and Nagasaki, respectively, cannot be ignored from the standpoint of their potential in contributing to radiation-induced carcinogenesis.
Some measurements of doses to patients by conventional dental radiography and orthopantomography are presented. Doses to the red bone marrow are calculated. The bonemarrow doses by two different exposures, Maxilla incisor and Molar bite-wing, were calculated to 0.4 and 1.0 mrad respectively. The average dose to red bone marrow from a full-mouth examination (10 exposures) was 0.7 mrad/exposure, An orthopantomographic examination involved 2 mrad to the bone marrow. The greatest doses by an orthopantomographic examination were found around the lateral rotational axis, namely 700 mrad. The dose distributions by the two different cone lengths did not differ as much as expected, mainly due to scattered radiation.
The increasing popularity of pantographic dental radiography and particularly its recent use for routine screening of asymptomatic patients have prompted the NRPB to compare the risks to patients from this technique with those from more conventional dental diagnostic procedures. Pantographic equipment from seven manufacturers have been investigated along with five procedures for obtaining similar information using conventional dental X-ray sets. Lithium borate thermoluminescent dosimeters located at 141 sites in the head and neck of a Rando phantom have been used to measure the mean absorbed dose to organs of interest as well as the total energy imparted to the phantom. Relative values of the energy imparted by the various techniques provide an estimate of their relative somatic risk to the patient. Pantomographic techniques were generally found to impart less than half the energy to the phantom than that given by a conventional full-mouth periapical series conducted at 45 kV, and a similar amount of energy to four bitewing intra-oral films. The restriction of the frequency of pantomographic examinations to no more than once per year during adolescence and once per three to five years during adulthood has been shown to involve only a minimal increase in the risk of somatic injury to the patient.
This review on dose reduction in dental radiography focuses on criteria for selecting the frequency and type of radiographs to be performed on patients. By making radiographs only when there is a reasonable probability of a finding that will influence patient care, patient exposure and other radiographic costs may be substantially reduced. Patient dose may also be reduced by half by changing from D-speed film to E-speed film for intraoral radiography and by more than half by changing from calcium tungstate intensifying screens to rare-earth intensifying screens for panoramic and cephalometric radiography. Using rectangular collimation for intraoral radiography will also further reduce patient exposure by about fourfold. Finally, the use of time-temperature processing will prevent overexposure of the patient and underprocessing of the radiographs; optimal radiographs will be provided.
OBJECTIVES: To determine the optimum X-ray spectrum in digital dental radiography once the dose around an implant and the diagnostic usefulness of the image are taken into account. MATERIALS AND METHODS: A Monte Carlo code (MCNP4B) was employed for computing the dose distribution across the bone-titanium interface. The X-ray spectra used were those met in digital dental radiography; 50-70 kVp, 2 mm Al total filtration, 5 kVp increment. RESULTS: The variation of the ratio of dose with as opposed to without implant against depth reaches maximum values at the bone-implant interface that vary between 2.9 and 3.2. For the same number of photon histories followed, the higher the tube potential setting, the greater the dose both in contact and inside the implant. CONCLUSION: In digital dental radiography, a 60-65 kVp spectrum accompanied by the known 30% reduction in mAs leads to lower dose to the patient for a diagnostically useful image.
Patient exposure to medical and dental x rays has long been of interest to the radiological health community. With the cooperation of state and local agencies and professional groups, the Center for Devices and Radiological Health has conducted three major surveys of patient exposure to x rays. The latest of these surveys, the Nationwide Evaluation of X-ray Trends (NEXT), collected x-ray exposure data for each year starting in 1972. Two earlier studies, the 1964 and 1970 X-ray Exposure Studies collected x-ray data during the years these surveys were conducted. Exposure trends presented are based on results of all three studies. Major improvements in beam limitation are seen for medical and dental radiography. Since 1964, when the first nationwide survey was conducted, dental exposures have decreased about 75%. Decreases of up to one-third occurred in exposures for medical examinations. The current exposure data presented continue to show a wide variation in medical exposures. Also presented are organ doses for four organs (ovaries, testes, thyroid and active bone marrow).
Panoramic radiography using a slit beam and film/screen receptor is standard for the emergency room evaluation of mandibular fractures and also in dentistry. This study compared the spatial resolution, area distortion factors, and the dosage considerations for a panoramic system where standard film/screen and a charge-coupled device were alternatively employed as the image receptor. Resolution and image contours were determined using a lead resolution grid positioned at selected beam projection angulations. Exposure measurements were carried out using a RANDO average man phantom and a 3 cc beryllium-windowed ionization chamber. The maximum spatial resolution with film approached 5 lp mm-1 whereas with the CCD the maximum resolution was just above 4 lp mm-1. Consequently, the image layer was reduced slightly in width when using the CCD receptor. The use of the CCD resulted in skin exposure reduction exceeding 70%.
A responsible approach to dose reduction in dental radiography requires that relative exposure be related to the specific diagnostic task performed. All but the most demanding tasks can be performed when suitable film is used in conjunction with high-speed screens. Placing the source of radiation inside the mouth permits radiographic information to be recorded on an improved Polaroid cassette that has a relatively high quantum efficiency. As a result, the radiation dose can be significantly reduced in a versatile system which provides for instantaneous processing and interpretation from prints rather than negatives.
Computed dental radiography is a filmless system of dental x-ray imaging. It features multiple sensors with receptive areas and image quality that approach the size and resolution of film. The system is able to match the utility of film on levels such as multiple-sized images and printing output. It approaches film in quality of image and diagnostic capacity. In features such as speed of image acquisition, reduction in radiation dose, retrieval of data, and organization and storage of images, the computed dental radiography system surpasses traditional x-ray film.
Five epidemiological studies of brain, cranial meninge, and salivary gland tumor sites reviewed implicate prior dental radiography with increased risk of subtentorial intracranial meningiomas and tumors of the parotid gland. Diagnostic radiography (medical and dental) was the most important risk factor identified for parotid gland cancers; among Los Angeles County residents, about 85% of the cumulative parotid dose from diagnostic radiography came from dental examinations. Irradiation of patients during dental radiography declined substantially from 1920 to 1988; it is uncertain whether current low doses increase risk. Recommendations for exposure reduction are made.
This study was designed to determine if digital images stored on the hard drive of a Schick computer dental radiography system could be exported, altered, and then restored to the drive without any visible signs of alteration. Digital images were downloaded from the computer dental radiography system using an I-Omega Zip Drive, 100-MB capacity, and then opened in Corel Photo Paint where images were altered and manufacturer export symbols were edited. The resulting images were printed to a default printer (Fargo Foto Fun). The ease of manipulation of the exported digital images reflects the need for the manufacturer to implement safeguards so that the integrity of digital imaging cannot be compromised. Computer dental radiography has many advantages: conservation of time (instant radiographs), less radiation (50 to 60%), no chemical waste, and many viewing options. However, questions that might be raised regarding the ability of persons with minimal computer expertise, using a commercially available program to alter images should be addressed.
A quick, inexpensive quality assurance test for clinical dental radiography is described. Data on operator error in matching test radiographs and the use of the test in some radiographic facilities for 3 years indicate that the test can be useful in monitoring film processing and X-ray machine output in clinical practice.
OBJECTIVE: A few studies were reported in China on radiological risk of dental radiography. The aim of this study is to evaluate the absorbed doses of patients from the full mouth radiographs, and to find out the contribution from each projection to the total absorbed dose of the organs. METHODS: Absorbed doses to critical organs were measured from 14-film complete dental radiography. The organs included pituitary, optical lens, parotid glands, submandibular glands, sublingual glands, thyroid, breasts, ovary, testes and the skin in center field of each projection were studied. A-radiation analog dosimetry system (RANDO) phantom with thermoluminescent dosimeters (ILD200) was used for the study. All of the exposure parameters were fixed. The total filtration was 2 mm Al equivalent. The column collaboration was 6 cm in diameter and 20 cm in length. The absorbed doses of organs were measured three times in each projection of the full-mouth series (FMS) exposures. RESULTS: The absorbed dose of lenses in FMS (249 microGy) in present study was much less (10%) than the doses (2,630 microGy) reported in 1976. The doses absorbed of other organs in the present study were thyroid gland (125 microGy), pituitary gland (112 microGy), parotid gland (153 microGy), submandibular gland (629 microGy), sublingual gland (1,900 microGy), and breast gland (12 microGy). The doses of the ovary and testis were to small to further analysis. CONCLUSION: All of the results show that the radiation risk to patients in intraoral radiograph has been reduced significantly. In the pituitary, half of the dose is from both sides of the maxillary molar projection. For the lenses, the largest contribultions of radiation (60%) come from the ipsilateral molar and premolar projection of maxilla. In parotid gland, up to 57% of the dose is from the contralateral molar, pre-molar and canine of maxilla. It could be derived that about 90% of the absorbed doses could be avoided in FMS if the column collimator is 20 cm long and the filter is 2.0 mm thick. If we use the 10-film complete mouth radiograph instead of the 14-film series, more 20% of the doses would be reduced.
An apparatus was designed for experimental dental radiography, which permitted separate adjustment of the subject, target and film. The precision of the apparatus was tested by radiographing a test subject, consisting of small steel globes embedded in a plastic plate. The subject was placed in the apparatus and exposed 30 times on dental X-ray film with different adjustments of angles and distances. All exposures were repeated after readjustment of the same form. Three linear distances between pairs of the projected steel globes were selected and measured on each radiograph. Depending on the different orientations of film, target and subject, the distances measured ranged from 9.0-11.1 mm, from 7.0-10.7 mm and from 12.7-17.3 mm, respectively. From the measurements on the radiographs the error of method was calculated to be 0.07-0.08 mm and the error of measurement to be 0.05-0.06 mm. The precision of the apparatus was thus found to be adequate for measurement of differences in small, but clinically relevant, distances.
OBJECTIVE: To establish reference doses for use within dental radiography. DESIGN: Retrospective analysis, single centre. SETTING: UK General Dental Practice, 1995-1998. METHOD: A statistical analysis was performed on the results from NRPB evaluations of dental x-ray equipment within general practice. The third quartile patient entrance dose was determined from 6,344 assessments of intra-oral x-ray equipment. The third quartile dose-width product was determined from 387 assessments of panoramic x-ray equipment. RESULTS: The third quartile patient entrance dose for an adult mandibular molar intra-oral radiograph is 3.9 mGy. The third quartile dose-width product for a standard adult panoramic radiograph is 66.7 mGy mm. CONCLUSION: NRPB recommends the adoption of reference doses of 4 mGy for an adult mandibular molar intra-oral radiograph and 65 mGy mm for a standard adult panoramic radiograph. These reference values can be used as a guide to accepted clinical practice. Where radiography is carried out using doses above these reference values, a thorough review of radiographic practice should be made to either improve techniques, or justify keeping the current techniques. However, attainment of doses at or below the reference values cannot be construed as achievement of optimum performance; further dose reductions below the reference value are still practicable.
Direct digital imaging systems are becoming increasingly common in dental radiography. The majority of these systems are based on charge coupled device (CCD) technology. A relatively new system, based on photo-stimulable phosphor luminescence (PSPL), is now commercially available. This system appears to overcome some of the restrictions of CCD systems including those associated with the bulky detector, connecting wire, limited image size and limited exposure latitude. A physical evaluation of the PSPL system was conducted including measurements of sensitometric response, modulation transfer function (MTF), noise power spectrum (NPS), noise equivalent quanta (NEQ) and detective quantum efficiency (DQE). These measurements were compared with results obtained previously for Kodak Ektaspeed (E-speed) film. The results of the evaluation indicate that the PSPL system may be capable of operating at exposures up to 80% lower than for film with comparable image quality.