Radiation dose-reduction techniques in North American dental schools

Cross-contamination and infection control in intraoral digital imaging: a comprehensive review

Dental health care workers are subjected to various infectious disease agents that are present in patients' saliva and blood which make infection control and universal prevention methods indispensable to the dental practice given that some of these diseases cause loss of work and time for dental staff and patients; some of them cause serious morbidity; and some of them currently have a poor prognosis and no effective treatments. Although dental radiographic procedures are not invasive, and there are no incidents such as injuries caused by dental instruments, they are a potential infection source because of contamination with saliva and blood, and comprehensive infection control procedures also apply to the radiology clinic. In addition, contact with a large number of patients in dental schools and clinics in a short period of time, and the fact that radiographic procedures are performed in the same environment as other dental procedures in dental offices increase the significance of infection control in dental radiology. Major advances in computer technology have enabled digital imaging systems to develop rapidly and to become common in dental practice as an alternative to conventional film-based imaging. The use of digital sensors in dental radiology introduced unique infection control challenges and required the revision and modification of existing infection control techniques. In this review, studies concerning the risk of cross-contamination and challenges of infection control with digital image sensors are comprehensively reviewed and infection control protocols that should be followed in intraoral digital imaging using both direct and indirect systems are thoroughly examined.

Knowledge, Attitude, and Practice (KAP) of Radiographic Protection by Dental Undergraduate and Endodontic Postgraduate Students, General Practitioners, and Endodontists

The aim of this study is to evaluate the knowledge, attitude, and perception of radiation hazard and preventive measures among dental undergraduate students, general practitioners, endodontic postgraduate students, and endodontists in Saudi Arabia. Multiple choice questions questionnaires were distributed among undergraduate and endodontic postgraduate dental students, general practitioners, and endodontists in the colleges of dentistry in Saudi Arabia, government hospitals, and private clinics. The questionnaire included sociodemographic data, assessment of the knowledge of radiation physics and biology, assessment of the practice of dental radiography, and assessment of knowledge of radiation protection. Chi-square test was used for individual and multiresponse analysis. Level of statistical significance was set at P ≤ 0.05. Three hundred and twenty-nine responded to the questionnaire. More than half of the respondents agreed that dental X-ray is hazardous to health (60.79%), and 68.1% were familiar with ALARA (as low as reasonably achievable) principle. However, only 34% are familiar with the recommendations of the National Council on Radiation Protection (NCRP) and International Commission on Radiological Protection (ICRP). The use of lead apron and thyroid collar for patients' protection from X-ray radiation was practiced among endodontic postgraduate students more frequently as well as those who are proactive in the academic field. Undergraduate students, endodontic postgraduate students, and endodontists in the academic field were the most aware towards radiation reduction measures. The use of the preventive measures needs to be emphasized more among general practitioners, endodontic postgraduate students, and endodontists especially in governmental hospitals and private sectors.

Kerma area product (KAP) and scatter measurements for intraoral X-ray machines using three different types of round collimation compared with rectangular beam limiter

OBJECTIVES:

The objective of the study was to determine the radiation dose reduction achieved when rectangular collimation was used on various round collimators. In addition, we evaluated the tissue doses imparted to various head and neck organs.

METHODS:

To evaluate the variation in radiation output based on the variable geometric configurations, the kerma area product (KAP) was measured using a commercially available KAP-meter with an internal ion chamber capable of detecting both radiation dose (µGy) and the primary X-ray beam area. The KAP was measured using standard 20.4, 25.7, and 31.7 cm² round collimators with and without rectangular X-ray field restrictors. To evaluate the potential change in patient scatter radiation dose, an adult head phantom was loaded with thin strips of gafchromic film. A full mouth X-ray series was acquired with various geometric configurations. The films were quantified using a calibration factor to yield absorbed organ doses for the eyes, thyroid, and salivary glands.

RESULTS:

With the use of rectangular collimator, the KAP for a 31.7 cm² round collimator was reduced by up to 60% while the 20.4 cm² round collimator elicited a reduction from up to 40%. In the organ study, results of up to 81% reduction in scatter radiation dose were observed.

CONCLUSIONS:

Although, US FDA regulations allow a maximum beam size of 38.5 cm² on the patient skin, this study suggests that the use of rectangular collimators provide clinically relevant dose reduction for patients, even when using smaller round collimation, hence the use of rectangular collimation for all intraoral radiographic procedures is highly recommended.

A pilot study of the effects of a vacuum sealing barrier method for photostimulable phosphor plates regarding plate damage and prevention of microbiologic cross-contamination

OBJECTIVE

The aim of this study was to evaluate the effectiveness of a new sealing method for preventing cross-contamination of photostimulable phosphor (PSP) plates.

STUDY DESIGN

Twelve new PSP plates were divided into 3 groups (PSP-a, PSP-b, and PSP- c) and placed in 3 different barriers (2 different brands of envelopes and a vacuum sealing method). All plates were exposed to X-rays with an aluminum step wedge, and the images were evaluated for the presence of any artifacts. After radiography, the PSP plates were removed from the barriers. The barriers and the PSP plates were disinfected and culture performed to assess any microorganism burden. Subsequently, the PSP plates were coated again with all barriers. The barriers were then contaminated and microbiologic specimens were collected. Subsequently, the barriers were wiped with alcohol. The PSP plates were removed, and microbiologic specimens were obtained.

RESULTS

No artifacts were recorded on the radiographic images on the sensors in any group. Microorganisms were detected on the PSP plates placed in envelopes. No colonization of microorganisms was detected on the vacuum sealed PSP plates.

CONCLUSIONS

The new vacuum-sealing method may be useful in preventing cross-contamination of PSP plates during radiographic procedures.

Evidence on radiation dose reduction using rectangular collimation: a systematic review

BACKGROUND

The goal of an intraoral radiograph is to be a valuable diagnostic tool while keeping the radiation exposure dose as low as reasonably achievable. The International Commission on Radiological Protection (ICRP) has strong recommendations for patient dose-reduction strategies.

OBJECTIVE

To answer the following research question: 'In either patient or in phantoms, does rectangular collimation compared with other forms of collimation reduce the radiation absorbed dose during intraoral imaging?'

METHODS

The search strategy was developed specifically for each electronic database. Information was collected from MEDLINE, all EBM Reviews including the Cochrane Library, EMBASE, LILACS, PubMed and Web of Science, and from a search of the grey literature via Google Scholar. Studies were included if they reported the radiation dose in intraoral imaging using rectangular collimation compared with any other type of collimation or the absence of it. Studies that did not involve comparison/control groups were excluded. A qualitative appraisal of the included studies was performed. The Methodological Index for NOn-Randomised Studies (MINORS) tool assessed the potential risk of bias among the studies, while the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach determined the level of available evidence.

RESULTS

Thirteen studies using different types of receptors, including D-speed film, E-speed film, phosphor storage plates (PSP) and direct digital sensors, were included. Different methods to access absorbed and effective dose by exploring distinct technical parameters, such as distance object-receptor, long- and short-cone, kVp and mA, exposure time and beam filtering, were used. High heterogeneity between the studies was found. The level of evidence was classified as moderate. The radiation dose reduction ranged from 40% to 92% compared with circular collimation. The limitations of the cross-sectional design and in vivo studies were discussed. As this systematic review applied validated tools and guidelines designed for population-based studies, the application for studies based on computer simulations and dosimetry measurements was challenging.

CONCLUSION

There is moderate evidence suggesting that rectangular collimation significantly reduces radiation dose when compared with round collimation, justifying its implementation in clinical settings/private practices while taking intraoral radiographs.

Thyroid Radiation Dose to Patients from Diagnostic Radiology Procedures over Eight Decades: 1930-2010

This study summarizes and compares estimates of radiation absorbed dose to the thyroid gland for typical patients who underwent diagnostic radiology examinations in the years from 1930 to 2010. The authors estimated the thyroid dose for common examinations, including radiography, mammography, dental radiography, fluoroscopy, nuclear medicine, and computed tomography (CT). For the most part, a clear downward trend in thyroid dose over time for each procedure was observed. Historically, the highest thyroid doses came from the nuclear medicine thyroid scans in the 1960s (630 mGy), full-mouth series dental radiography (390 mGy) in the early years of the use of x rays in dentistry (1930s), and the barium swallow (esophagram) fluoroscopic exam also in the 1930s (140 mGy). Thyroid uptake nuclear medicine examinations and pancreatic scans also gave relatively high doses to the thyroid (64 mGy and 21 mGy, respectively, in the 1960s). In the 21st century, the highest thyroid doses still result from nuclear medicine thyroid scans (130 mGy), but high thyroid doses are also associated with chest/abdomen/pelvis CT scans (18 and 19 mGy for males and females, respectively). Thyroid doses from CT scans did not exhibit the same downward trend as observed for other examinations. The largest thyroid doses from conventional radiography came from cervical spine and skull examinations. Thyroid doses from mammography (which began in the 1960s) were generally a fraction of 1 mGy. The highest average doses to the thyroid from mammography were about 0.42 mGy, with modestly larger doses associated with imaging of breasts with large compressed thicknesses. Thyroid doses from dental radiographic procedures have decreased markedly throughout the decades, from an average of 390 mGy for a full-mouth series in the 1930s to an average of 0.31 mGy today. Upper GI series fluoroscopy examinations resulted in up to two orders of magnitude lower thyroid doses than the barium swallow. There are considerable uncertainties associated with the presented doses, particularly for characterizing exposures of individual identified patients. Nonetheless, the tabulations provide the only comprehensive report on the estimation of typical radiation doses to the thyroid gland from medical diagnostic procedures over eight decades (1930-2010). These data can serve as a resource for epidemiologic studies that evaluate the late health effects of radiation exposure associated with diagnostic radiologic examinations.

Microbial contamination in intraoral phosphor storage plates: the dilemma

OBJECTIVES

The aims of this study were to evaluate microbial contamination in phosphor storage plates in dental radiology services and discuss the possible origin of this contamination.

MATERIALS AND METHODS

The sample comprised 50 phosphor plates: 14 plates from service A, 30 from service B, and 6 in the control group, consisting of plates never used. Damp sterile swabs were rubbed on the phosphor plates, and then transferred to tests tubes containing sterile saline solution. Serial dilutions were made, and then inoculated in triplicate on Mueller Hinton agar plates and incubated at 37 °C/48 h, before counting the colony-forming units (CFU). The samples were also seeded in brain-heart infusion medium to confirm contamination by turbidity of the culture medium. All solutions, turbid and clean, were seeded in selective and non-selective media.

RESULTS

At service A and B, 50 and 73.3 % of the phosphor plates were contaminated, respectively. This contamination was mainly due to bacteria of the genus Staphylococcus. CFU counts ranged from 26.4 to 80.0 CFU/plate.

CONCLUSIONS

Most of the phosphor plates evaluated shown to be contaminated, mainly by Staphylococcus ssp. Quantitatively, this contamination occurred at low levels, possibly arising from handling of the plates. The use of a second plastic barrier may have diminished contamination by microorganisms from the oral cavity.

CLINICAL RELEVANCE

There is a risk of cross-contamination by phosphor storage plates used in dental radiology services.

Oral Radiology Safety Standards Adopted by the General Dentists Practicing in National Capital Region (NCR)

INTRODUCTION

With advancement in diagnostic techniques, the utilization of radiologic examination has risen to many folds in the last two decades. Ionizing radiations from the radiographic examination carry the potential for harm by inducing carcino-genesis in addition to the diagnostic information extracted. Radiation doses utilized in the course of dental treatment might be low for individual examinations but patients are exposed to repeated examinations very often and many people are exposed during the course of dental care. Therefore, principles of radiation protection and safety are necessary for the dentists to follow to ensure minimum and inevitable exposure.

AIM

The aim of this study was to investigate the knowledge and behaviour of general dentists practicing in the National Capital Region (NCR) regarding radiation safety during oral radiographic procedures.

MATERIALS AND METHODS

The study was a questionnaire based cross-sectional study. A total of 500 general dentists were contacted to participate in the study. The target population entailed of general dentists practicing in the National Capital Region. Data was computed and tabulated in Microsoft excel sheet and statistical analysis was performed with the help of SPSS version 21.0.

RESULTS

The total response rate recovered was 70.6% and the respondents comprised of 59% and 41% males & females respectively. Only 64.8% of the general dentists contemplated thyroid to be the most important organ for radiation protection. Only 28.8% of the general dentists followed the position & distance rule appropriately.

CONCLUSION

The results showed that the knowledge and behaviour of the general dentists and the practices adopted by them regarding radiation safety is not satisfactory. To ensure the following of basic and necessary guidelines for radiation safety and protection, strict rules with penalties should be implemented by the state councils and new and interesting methods of education for this spectrum of the field should be introduced.

Questionnaire surveys of dentists on radiology

OBJECTIVES

Survey by questionnaire is a widely used research method in dental radiology. A major concern in reviews of questionnaires is non-response. The objectives of this study were to review questionnaire studies in dental radiology with regard to potential survey errors and to develop recommendations to assist future researchers.

METHODS

A literature search with the software search package PubMed was used to obtain internet-based access to Medline through the website www.ncbi.nlm.nih.gov/pubmed. A search of the English language peer-reviewed literature was conducted of all published studies, with no restriction on date. The search strategy found articles with dates from 1983 to 2010. The medical subject heading terms used were "questionnaire", "dental radiology" and "dental radiography". The reference sections of articles retrieved by this method were hand-searched in order to identify further relevant papers. Reviews, commentaries and relevant studies from the wider literature were also included.

RESULTS

53 questionnaire studies were identified in the dental literature that concerned dental radiography and included a report of response rate. These were all published between 1983 and 2010. In total, 87 articles are referred to in this review, including the 53 dental radiology studies. Other cited articles include reviews, commentaries and examples of studies outside dental radiology where they are germane to the arguments presented.

CONCLUSIONS

Non-response is only one of four broad areas of error to which questionnaire surveys are subject. This review considers coverage, sampling and measurement, as well as non-response. Recommendations are made to assist future research that uses questionnaire surveys.

Compliance of Iranian dentists with safety standards of oral radiology

OBJECTIVES

Dentists use radiographs in their daily practice. Their knowledge and behaviour towards radiographic examination can affect patients' exposure to radiation. The aim of this study was to survey the knowledge and behaviour of Iranian dentists regarding oral radiology safety standards.

METHODS

1000 questionnaires were given to the participants of the 48th Annual Congress of the Iranian Dental Association, of which 700 were returned. The participants were asked about demographic data, primary knowledge of radiation protection, selection criteria, radiographic equipment and technique, methods of patient and personnel protection and management of radiographic waste. Descriptive analysis of data was performed.

RESULTS

44% of respondents said the initial radiograph they took was of the periapical view of a limited area. 12% preferred the periapical paralleling technique. F-speed film was used by 9% and E-speed film by 62%. Only 2% had digital receptors. Proper exposure time was selected by 26.5%. The use of long and rectangular collimators was 15% and 6%, respectively. 34% occasionally covered their patients with both thyroid shields and lead aprons. 36% used the position and distance rule correctly for their own protection. Proper disposal of the used processing solutions and the lead foils were done by only 1% and 3%, respectively.

CONCLUSIONS

It can be concluded that the majority of dentists in the study group did not select the proper method, material and equipment in order to minimize the exposure of their patient to unnecessary radiation in dental radiography.

Diagnostic Dental Radiation Risk during Pregnancy: Awareness among General Dentists in Tabriz

Background and aims

Pregnant women often do not receive proper dental care in emergency visits due to a lack of awareness of the effect of radiation doses and the involved risks for the fetus. The aim of the present study was to assess the awareness of general dentists practicing in Tabriz, Iran, of the risks involved during exposure to diagnostic dental radiation in pregnant women.

Materials and methods

In this descriptive/cross-sectional study, 250 general dentists, who had attended continuing education courses under the supervision of the Faculty of Dentistry, filled out questionnaires on their awareness of radiation risks. Data was analyzed by Spearman's correlation coefficient test.

Results

The mean of correct answers was 6.47±1.66, with the least and highest correct answers of 2 and 10, respectively. The highest and the lowest levels of awareness were related to the use of a lead apron (92%) and a long rectangular collimator (3.2%), respectively. There was a statistically significant correlation between the age of practitioners and awareness of radiation risks (P=0.02). However, no statistically significant correlation was observed between job experience (P=0.25) and the number of continuing education courses attended (P=0.16) and awareness of radiation risks.

Conclusion

The studied population of dentists does not seem to have the sufficient knowledge regarding the diagnostic dental radiation risk during pregnancy. Further educational courses and pamphlets are recommended for increasing their awareness of this subject.

A comparison between bitewing radiographs taken with rectangular and circular collimators in UK military dental practices: a retrospective study

OBJECTIVES

The aim of this study was to determine any increase in the incidence of cone cut errors that adversely affected diagnostic yield resulting in more retakes using rectangular collimation with film holders in bitewing radiography. Comparisons were also made with other positioning errors that occurred when bitewings were taken with circular collimation, with and without film holders.

METHODS

A preliminary questionnaire was used to determine the year that rectangular collimation was adopted by military dental practice. 3 time-framed subsets, each of 1000 bitewing radiographs, were identified: subset 1, films taken with circular collimators without film holders; subset 2, films taken with circular collimators with film holders; and subset 3, films taken with rectangular collimators with film holders. Each subset was assessed for positioning errors of cone cut, horizontal overlap, vertical distortion and film centring. The χ(2) test was used to test significant differences amongst the three subsets.

RESULTS

The use of film holders with circular collimation significantly reduced the incidence of cone cut errors from 21.7% to 3.3%. There was an increase in the incidence of cone cut errors from 3.3% to 20.9% when rectangular collimation was used, but the actual number considered "rejects" was very small, only 0.1% (1 in 1000 films) in subset 2 and 0.3% (3 of 1000 films) in subset 3, when assessed for diagnostic yield.

CONCLUSIONS

This study provides evidence that rectangular collimation did not significantly affect the diagnostic yield of bitewing radiographs despite the presence of cone cut. Therefore, all practitioners should adopt rectangular collimation.

Exposing the thyroid to radiation: a review of its current extent, risks, and implications

Radiation exposure of the thyroid at a young age is a recognized risk factor for the development of differentiated thyroid cancer lasting for four decades and probably for a lifetime after exposure. Medical radiation exposure, however, occurs frequently, including among the pediatric population, which is especially sensitive to the effects of radiation. In the past, the treatment of benign medical conditions with external radiation represented the most significant thyroid radiation exposures. Today, diagnostic medical radiation represents the largest source of man-made radiation exposure. Radiation exposure related to the use of computerized tomography is rising exponentially, particularly in the pediatric population. There is direct epidemiological evidence of a small but significant increased risk of cancer at radiation doses equivalent to computerized tomography doses used today. Paralleling the increasing use of medical radiation is an increase in the incidence of papillary thyroid cancer. At present, it is unclear how much of this increase is related to increased detection of subclinical disease from the increased utilization of ultrasonography and fine-needle aspiration, how much is due to a true increase in thyroid cancer, and how much, if any, can be ascribed to medical radiation exposure. Fortunately, the amount of radiation exposure from medical sources can be reduced. In this article we review the sources of thyroid radiation exposure, radiation risks to the thyroid gland, strategies for reducing radiation exposure to the thyroid, and ways that endocrinologists can participate in this effort. Finally, we provide some suggestions for future research directions.

Flemish general dental practitioners' knowledge of dental radiology

The aim of this study was to assess general dental practitioners' knowledge of dental radiography and radiation protection in order to alert the Belgian authorities and dental professional societies. Prior to attending a postgraduate course on intraoral radiology, general dental practitioners in Flanders, Belgium, were asked to fill in a questionnaire regarding the radiological equipment and the techniques they used for intraoral radiography. The availability and type of dental panoramic equipment were also assessed. A total of 374 questionnaires were available for this study. 15% of the attendants used radiographic equipment that was more than 27 years old and 43% reported equipment that operated with a clockwork timer. 32% and 75% respectively had no idea what the kV or mA settings were on their intraoral equipment. 5% were unaware which cone geometry or geometric technique (paralleling or bisecting angle technique) they were using. 81% claimed to be using a short cone technique. 47% did not know what collimation meant, whereas 40% stated that they were using circular collimation. 38% used digital intraoral image detectors (63% were photostimulable storage phosphorplate (PSPP)), but 16% were not sure about the type of sensor they were using (PSPP or solid-state sensors). 61% also had dental panoramic equipment available, 25% of which was digital (10% charge coupled device (CCD) and 15% PSPP). These results clearly indicate the need for continued education on this subject. The latter is an important signal to Belgian authorities and dental professional societies.

An evaluation of microbiologic contamination on a phosphor plate system: is weekly gas sterilization enough?

OBJECTIVE

This study was performed to determine: 1) the rate and source of microbiologic contamination of photostimulable phosphor plates (PSP) in a predoctoral clinic; and 2) whether a combination of weekly gas sterilization and barrier protocols can prevent contamination of PSP plates.

METHODS

Fifty plates in clinical use and 25 gas-sterilized control plates were selected for examination. The PSP plates were pressed onto blood agar medium and incubated at 37 degrees C. The number, size, distribution, and variety of resulting colonies were noted. To test whether these bacteria could have come from oral sources, 17 colonies were selected for culture on Mitis-Salivarius (M-S) agar. Those colonies that grew on the M-S agar were Gram stained.

RESULTS

Twenty-eight test plates (56%) exhibited growth of bacterial colonies on blood agar. Seventeen of those bacterial colonies were selected for growth on M-S agar, and 13 (76.47%) showed growth, 69% of them gram positive.

CONCLUSION

Our results indicate reinforcing standard precautions of infection control for intraoral radiography, and that gas sterilization of plates after each day's clinical use is a potential solution.

An evaluation of microbiologic contamination on phosphor plates in a dental school

OBJECTIVE

The objective of this study was to determine if phosphor plates used in predoctoral clinics are microbiologically contaminated and to identify the source of contamination.

STUDY DESIGN

Forty-five of 300 phosphor plates (15%) were randomly selected for examination. The plates were pressed into individual blood agar plates, were incubated using standard techniques at 37 degrees C, and were monitored for 72 hours. The number, size, distribution, and variety of resulting colonies were noted. A representative of each type of colony was selected to be Gram stained using the standard technique.

RESULTS

Of the plates, 42.2% were uncontaminated, 57.8% yielded bacterial colonies, and 15.6% of those colonies demonstrated hemolytic growth. The hemolytic growth included combined alpha and beta hemolysis and beta only hemolysis. Six colonies were gram-positive rods and 7 were gram-positive cocci.

CONCLUSION

Meticulous infection-control techniques are inevitable and continuous reinforcement and training for staff and students are mandatory. Periodic gas sterilization of phosphor plates may be necessary.

Diagnostic accuracy ofin vitropanoramic radiographs depending on the exposure

OBJECTIVES

The aim was to evaluate the effect of dose reduction on diagnostic accuracy in panoramic radiographs with increased tube potential and reduced milliampere settings.

METHODS

Panoramic radiographs of 12 dried human skulls prepared with lesions in the bone, teeth and peri-implant bone in ascending size were taken. Medium and regular film--screen combinations and a storage phosphor system were used for imaging. All systems were exposed at a low and a high tube potential level. To compare the dose at different tube potential settings, dose length product was measured at the secondary collimator. Five observers assessed the presence (response: 1) or absence (response: 0) of lesions. Sensitivity, specificity and diagnostic accuracy were evaluated and 36 000 ratings were made in all. All settings were repeated once. Intrarater agreement was expressed by Cohen's kappa coefficient.

RESULTS

There was no significant difference in diagnostic accuracy between a medium and a regular film--screen combination at a low tube potential level (70 kV; 0.935 and 0.930) and the medium film--screen system at a high tube potential level (85 kV; 0.926). Compared with this group, the regular film-screen combinations at high tube potential level (85 kV, 0.906) and all digital radiographs were significantly different (0.886 and 0.866), irrespective of the tube potential level. The digital panoramic radiograph was only comparable with the best film--screen combinations with an exposure for a medium film-screen system and at a low tube potential level. Sensitivity was 89.9% and specificity 93.7%. The kappa coefficient for intrarater agreement was high (0.81).

CONCLUSIONS

The medium intensifying screen can be used at high tube potential settings instead of low tube potential settings, or the regular intensifying screen can be used at low tube potential settings with the same diagnostic value. A dose reduction of about 40% is possible. The storage phosphor plates should be exposed at least like a regular film-screen system and at a low tube potential level.

Influence of tube potential setting and dose on the visibility of lesions in intraoral radiography

OBJECTIVES

The objectives were to determine the diagnostic accuracy of different image receptors when first, the tube potential setting was increased from 60 kV to 90 kV and second, when the milliampere setting was reduced at unchanged tube potential for storage phosphor plates.

METHODS

Intraoral radiographs (films of speed class F, storage phosphor plates) were taken of 12 dried human skulls prepared with lesions in both teeth and peri-implant bone, in ascending size. Five observers assessed the presence (response=1) or absence (response=0) of lesions. The digital intraoral radiograph was exposed at 60 kV and 90 kV with half and a quarter of the film exposure. Some of the radiographs were assessed a second time. In total, 6000 assessments were made. Intrarater agreement was expressed by Cohen's kappa coefficient.

RESULTS

The digital combinations showed the lowest diagnostic accuracy in all combinations, but the results demonstrated an equivalence of all combinations of films and storage phosphor plates. The differences in diagnostic accuracy were low (94-96.5%). The kappa coefficient for intrarater agreement was high (0.85).

CONCLUSIONS

Regarding peri-implant and decayed lesions, intraoral films and storage phosphor plates demonstrated equal quality in this in vitro study regardless of exposure at 60 kV or 90 kV.

Possibilities of dose reduction in lateral cephalometric radiographs and its effects on clinical diagnostics

OBJECTIVES

The aim of the present study was to determine (1) the absorbed and the exit radiation doses for cephalometric exposures on a phantom head with various exposure settings and image receivers, and (2) the diagnostic image quality for various modalities assessed on cephalometric radiographs of patients.

METHODS

The dose measurements for lateral cephalometric radiographs were performed with a semiconductor detector, and also with thermoluminescent detectors and an Alderson phantom. Both the integral and the effective doses were determined. Two radiographs of each patient (n=119) were taken at two different times, one at a low tube potential setting, 75+/-5 kV, and one with a decreased dose. Film-screen systems with speed class 400 and one storage phosphor plate were used. Five observers assessed the radiographs for the visualization of six cephalometric reference points on a three-point scale with -1, 0 and 1. Twenty-seven image pairs were rescored to determine inter- and intrarater reliability. The statistical analysis was done using analysis of variance and Tukey's HSD (honestly significant difference) post hoc test.

RESULTS

Increasing the tube potential setting led to an average dose reduction to 83% (integral dose) or to 87% (effective dose). Instead of taking the radiograph at a low tube potential setting (75 kV), a dose reduction of about 15% was feasible at a high tube potential setting (90 kV). A significant difference in reference point visibility existed between film radiographs at low tube potential settings (mean score 0.984) and at high tube potential settings (90 kV, mean score 0.958). For the storage phosphor plates, there was no significant difference to the film-screen combinations at low tube potential and halved milliampere seconds settings. In the second assessment, there was a high degree of agreement (96.6%) compared with the first assessment (unadjusted for random agreement).

CONCLUSIONS

As there is only minimal dose reduction at increased tube potential settings, for a dose reduction, it seems to be more useful to use storage phosphor plates at unchanged tube potential and halved milliampere seconds settings compared with the film-screen combination.

A review of dentists' use of digital radiography and caries diagnosis with digital systems

OBJECTIVES

To investigate the evidence for (1) dentists' use of digital radiography and (2) the outcome of caries diagnosis with digital systems.

METHODS

A literature search with the software search package PubMed was used to get internet-based access to Medline through the website www.ncbi.nlm.nih.gov/pubmed. The search was limited to the years 1999-2005 since most papers dealing with the diagnostic value of digital radiography systems published before 1999 will hold little interest for today's users due to changes in the systems. The search strategies resulted in 123 articles (Table 1, #4 and #5). Original research articles (not reviews) were selected by the following inclusion criteria: (1) questionnaire studies on the use of direct digital intraoral radiography systems (not digitized film), (2) studies which used human teeth and natural caries lesions, and further in laboratory studies, the sectioned tooth was the gold standard for validating the presence or depth of a lesion.

RESULTS

The search resulted in 42 articles fulfilling the above criteria, which could be grouped into three types of studies: (a) questionnaire studies, (b) clinical (in vivo) studies, and (c) laboratory (in vitro) studies. Nine questionnaire studies, five clinical studies and 28 laboratory studies were found. These studies and their results are summarized in Tables 2-5.

CONCLUSIONS

The number of studies was limited, and some of the digital systems were evaluated in only one or two studies. A conclusive judgment may therefore not be possible for the majority of the digital systems selected for this review. There is a continuous need for the evaluation of new digital intraoral radiography systems that appear on the market, first and foremost for their image quality and diagnostic accuracy, but certainly also for their performance in the clinic, a clear deficiency observed after the literature search for the present review.

The effect of dose reduction on the detection of anatomical structures on panoramic radiographs

OBJECTIVES

The aim was to evaluate the effect of dose reduction on diagnostic accuracy using different screen-film combinations and digital techniques for panoramic radiography.

METHODS

Five observers assessed 201 pairs of panoramic radiographs (a total of 402 panoramic radiographs) taken with the Orthophos Plus (Sirona, Bensheim, Germany), for visualization of 11 anatomical structures on each side, using a 3-point scale -1, 0 and 1. Two radiographs of each patient were taken at two different times (conventional setting and setting with decreased dose, done by increasing tube potential settings or halving tube current). To compare the dose at different tube potential settings dose-length product was measured at the secondary collimator. Films with medium and regular intensifying screens (high and low tube potential settings) and storage phosphor plates (low tube potential setting, tube current setting equivalent to regular intensifying screen and halved) were compared. The five observers made 27 610 assessments. Intrarater agreement was expressed by Cohen's kappa coefficient.

RESULTS

The results demonstrated an equivalence of regular screens (low tube potential setting) and medium screens (high and low tube potential settings). A significant difference existed between medium screens (low tube potential setting, mean score 0.92) and the group of regular film-screen combinations at high tube potential settings (mean score 0.89) and between all film-screen combinations and the digital system irrespective of exposure (mean score below 0.82). There were no significant differences between medium and regular screens (mean score 0.88 to 0.92) for assessment of the periodontal ligament space, but there was a significant difference compared with the digital system (mean score below 0.76). The kappa coefficient for intrarater agreement was moderate (0.55).

CONCLUSIONS

New regular intensifying screens can replace medium screens at low tube potential settings. Digital panoramic radiographs should be taken at low tube potential levels with an exposure equivalent at least to a regular intensifying screen.

Thyroid shields and neck exposures in cephalometric radiography

BACKGROUND

The thyroid is among the more radiosensitive organs in the body. The goal of this study was twofold: (1) to evaluate age-related changes in what is exposed to ionizing radiation in the neck area, and (2) to assess thyroid shield presence in cephalometric radiographs

METHODS

Cephalometric radiographs at one academic setting were sampled and neck exposure was related to calendar year and patient's gender and age.

RESULTS

In the absence of shields, children have more vertebrae exposed than adults (p < 0.0001) and females have more neck tissue exposed inferior to the hyoid bone than males (p < 0.0001). The hyoid bone-porion distance increased with age (p <0.01). Thyroid shields were visible in 19% of the radiographs and depended strongly on the calendar year during which patient was seen (p-value <0.0001). Compared to adults, children were less likely to wear thyroid shields, particularly between 1973 and 1990 (1.8% versus 7.3% -p-value < 0.05) and between 2001 and 2003 (7.1% versus 42.9% -p-value < 0.05).

CONCLUSION

In the absence of a thyroid shield, children have more neck structure exposed to radiation than adults. In agreement with other reports, thyroid shield utilization in this study was low, particularly in children.

Survey of dental radiological practice in Turkey

OBJECTIVES

The aim of this study was to determine the dentist's knowledge about dose reduction techniques, radiographic equipment and quality of dental radiographic service in general dental practice in Turkey.

METHODS

The survey was performed on 636 dentists who attended the 11th International Congress organized by the Turkish Dental Association. Information on the demographic characteristics of the dentists, radiographic equipment, techniques and processing they used and radiation protection was obtained with a 32 point questionnaire.

RESULTS

The respondents' knowledge concerning the technical details of their equipment was limited, with 512 (86.9%) not knowing the kilovoltage peak (kVp) of their machine. Only 34 (5.5%) respondents reported having rectangular collimators. The dentists had little knowledge about the speed of film they used. D-speed film was the most preferred one with 21.6%. Fifty-eight (10.2%) dentists used E-speed film and the F-speed film was used only by 13 (2.3%) dentists. The most preferred technique (62%) for periapical radiography was the bisecting angle technique. Four hundred and eighty five (82.5%) of the dentists reported that they took the radiographs by themselves.

CONCLUSIONS

In the present study, the results indicate that for minimizing any unnecessary radiation, attempts should be made to improve dentists' knowledge about radiation dose reduction techniques.

Digital radiographic equipment in the Belgian dental office

A survey was performed among Belgian dentists to evaluate the use and management of digital radiographic equipment. The majority of respondents work as general dental practitioners. One out of eight sets of equipment for extraoral exposures is digital. For intraoral radiography, 30% of the equipment is digital. While exposure time is reduced by about 50% for digital intraoral radiography compared with conventional radiography, no differences can be found between different conventional film speed classes. Appropriate collimation of the radiation beam is only sparingly used. Beam aiming devices to hold the film and position the radiation beam are not used by the majority of dentists. While 25% of the respondents stand behind a protective wall during exposure, 8% of dentists remain next to the patient during exposure while assisting in holding the film inside the mouth. A minority of the latter practitioners wear lead aprons.