Dose reduction in dental radiography

EFFECTIVE DOSES AND RADIATION RISKS FROM COMMON DENTAL RADIOGRAPHIC, PANORAMIC AND CBCT EXAMINATIONS

This study was aimed at the estimation of the effective doses and radiation risks from dental X-ray examinations based on the data collection in St. Petersburg and the Leningrad Region. The range of mean values of effective doses for intraoral examinations on the X-ray units with film detectors was from 3.5 to 8.2 μSv and for the units with digital detectors-from 1.2 to 2.5 μSv. The mean effective doses for panoramic examinations were 22.9 μSv and for cone-beam computed tomography (CBCT)-530.6 μSv, respectively. The highest detriment-adjusted lifetime risk values were estimated for the 20-24-year-old age group: 40.8 × 10-6 in females and 32.7 × 10-6 in males for CBCT. Effective doses in St. Petersburg and Leningrad region were comparable or higher compared with the published data.

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.

Detection of artificial occlusal caries in a phosphor imaging plate system with two types of LCD monitors versus three different films

The aim of this study was to determine diagnostic performance of a storage phosphor plate system Digora Optime (Soredex, Helsinki, Finland) with two types of LCD monitor in the detection of artificial caries when compared to Ultraspeed (D), Ektaspeed Plus (E), and Insight (F) radiographic films. Seventy extracted human molars-with artificial caries-were radiographed under identical standardized conditions using (1) a storage phosphor plate system Digora (Soredex, Helsinki, Finland), (2) Insight, (3) Ektaspeed Plus, and (4) Ultraspeed (Carestream Health Inc, Rochester, NY). All digital images and radiographs were examined by three observers for the presence or absence of artificial caries using a five-point confidence scale. Digital images were evaluated both on a LCD computer monitor (Philips 170S, Holland) and medical monitor-3 megapixel monochrome display (Me355i2, Totoku, Tokyo)-with brightness and contrast enhancement. Observer responses were evaluated using ROC analysis and other measurements for diagnostic accuracy. Storage phosphor images with medical monitor demonstrated higher mean A (z) values (0.70 +/- 0.08) than digital images with computer monitor and conventional films. Storage phosphor images with medical monitor presented the highest score, 0.97, 0.90, 0.94, for each observer, respectively. Also, true positive observations (0.82) and positive likelihood ratios (2.71) were higher in enhanced storage phosphor images with medical monitor. Caries detection of mechanically created lesions by experienced radiologists is roughly comparable when examining D-speed film images and Digora images on both the computer and medical LCD monitors, and appears to be poorer on E- and F-speed film images.

A Study of the Prescription of Radiographs for Children by a Group of General Dental Practitioners in the South West of England

Objective

This study aimed to assess the familiarity of general dental practitioners (GDPs) in the South West of England with the guidelines in the first edition of the then Faculty of General Dental Practitioners (UK) ‘good practice guidelines’ publication Selection Criteria for Dental Radiography (henceforth referred to as ‘the guidelines’) by studying the prescription of radiographs for children in two case scenarios.

Method

A single mailshot of questionnaires containing questions relating to the guidelines and the two case scenarios was sent to 136 GDPs in the South West of England. Their recommendations for the prescription of radiographs for the children in the two scenarios were then compared with the guidelines.

Results

There was a 60% response rate. Of the respondents, 48% reported that they had access to the guidelines. Of those who responded to the question, 66% said that they found the guidelines easy to use. Seventy per cent of respondents reported that they preferred the concept of guidelines to that of protocols. The results from the case scenarios revealed an under-prescription of radiographs for patients presenting with developmental problems or trauma when compared to the recommendations in the guidelines. There was good correlation for the prescription of radiographs for caries but little consensus on radiographic review times.

Conclusions

The study highlighted (a) areas within the guidelines that require further clarification and research and (b) that in the group studied half did not have access to the guidelines.

A quality assurance program in dental radiographic units in western Greece

OBJECTIVE

This survey reports on successful efforts to establish a quality assurance (QA) program for 50 intraoral x-ray units in the public and private sectors in the region of Achaia, Greece. It was conducted in 2 phases, in 1996 and in 2003, including on-site inspections, QA tests, and standard questionnaires. The aim of the study was to assess equipment conditions, knowledge, and adoption of radiographic QA guidelines by general dentists and, more importantly, the impact of the recommendations and training provided.

STUDY DESIGN

The tested parameters focused on radiation protection, equipment maintenance, film speed used, film processing conditions, and radiologic characteristics such as voltage, radiation leakage, type of collimation, source-to-skin distance, timer accuracy, and entrance dose.

RESULTS

The data gathered in 1996 demonstrate minimal compliance with equipment function requirements and radiation safety measures. 1 The comparative evaluation of all the parameters gathered from the 2 surveys, indicated that in 2003 the vast majority of the dentists followed the recommendations given in 1996. Only 2 dentists persisted in neglecting the guidelines.

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.

Rectangular Collimation and Radiographic Efficacy in Eight General Dental Practices in the West Midlands

Introduction

Rectangular collimation is recommended in order to reduce radiation doses to patients. However, anecdotal reports suggest that it may result in more retakes, with a possible net increase in patient dosage.

Method

To test this hypothesis, eight general dental practitioners were recruited to participate in a project. Each took 25 pairs of bitewing radiographs of patients before and 25 after fitting rectangular collimators to their x-ray machines. Double-pack films were used so that duplicates could be examined. These were assessed by a consultant oral radiologist according to the National Radiographic Protection Board (NRPB) grading system for positioning and general film quality.

Results

Initially, positioning quality was above the target level for six of the eight dentists; however, for all but one, this dropped after using rectangular collimation. General film quality was of a lower overall standard initially. Using rectangular collimation had an effect on general film quality but the direction and size of this varied among the dentists.

Conclusion

It was concluded that amongst the participating dentists, although numbers of retakes increased by 7%, there would be a net reduction in dosage to patients following rectangular collimation.

An investigation into the use of bitewing radiography in children in Greater Glasgow

AIM

In recent years there have been a number of reviews and guidelines published with respect to the diagnosis and management of caries in children. Bitewing radiography remains the recommended method of choice for caries diagnosis in most circumstances. The aims of the study were to investigate the usage of bitewing radiography by general dental practitioners (GDPs) in Greater Glasgow, for the diagnosis of caries in children and to assess the usefulness of the technique as perceived by these dental practitioners.

DESIGN

A questionnaire for self completion was sent to all GDPs with an NHS list number in the Greater Glasgow area.

RESULTS

An 80% response rate was obtained with 303 GDPs responding. Less than half the dentists (44%) indicated that they always carried out caries risk assessments for all children, but 71% reported doing this for 6 and 7-year-old children. Approximately 60% of dentists stated they had read the recent radiation and caries management guidelines. Only 72% stated that they used radiography as a caries diagnostic tool in children, with 12 GDPs (4%) indicating they would never consider using bitewing radiography in children. Only 17% would consider taking bitewing radiographs in children under 6 years, and the majority of dentists (61%) reported that they would first consider taking radiographs in the 6-11-year-old age group. However, only a low proportion of children in this age band had dental x-rays taken. Bitewing radiography was considered to be more important for 12-year-olds than for 6-year-olds. Recommended methods for decreasing radiation exposure such as rectangular collimation and film holders were not being used universally, with 41% and 58% respectively using these devices.

CONCLUSIONS

A significant proportion of dentists in Greater Glasgow are not complying with recent guidelines and recommendations and it would appear that the value of bitewing radiography as a diagnostic tool in children is not being fully exploited.

Use of the basic periodontal examination and radiographs in the assessment of periodontal diseases in general dental practice

OBJECTIVES

The aims of this study were to investigate (1) the use of the basic periodontal examination (BPE) by general dental practitioners (GDPs) and their selection of radiographs for the assessment of periodontal disease and (2) whether this selection concurred with existing selection (referral) criteria.

METHODS

Three mailings of a self-completion questionnaire were sent to 800 GDPs working in the National Health General Dental Service in England and Wales. Dentists were presented with six clinical scenarios for which they were asked to describe their use of radiographs.

RESULTS

Ninety-one percent of dentists reported that they used the BPE in new patients, with 56% using it for all patients; 84% of dentists used BPE in recall patients. BPE use was related to the dentists' age and postgraduate qualifications. There was a wide variation in the radiographic views used for periodontal disease assessment. The choice of radiographs was not generally in line with the Faculty of General Dental Practitioners (UK) 1998 selection criteria, particularly for the clinical scenarios of pocketing >5 mm, irregular pocketing or pockets associated with teeth with heavy restorations. Sixty seven percent of dentists concurred with recommendations for radiographs for a suspected periodontal-endodontic lesion.

CONCLUSIONS

A majority of dentists reported clinical screening for periodontal diseases using the BPE. There was considerable variation in the selection and use of radiographs and practice was not in line with existing guidelines for many clinical situations. Evidence-based referral criteria should be actively promoted to ensure high standards of radiographic practice in general dental practice.

Radiographic equipment and techniques used in general dental practice: a survey of general dental practitioners in England and Wales

OBJECTIVES

The aims of this study were to determine the self-reported use of panoramic radiography, D- and E-speed film, rectangular collimation, film holders, equipment fitted with a long spacer cone (>200 mm) and the bisecting angle and paralleling techniques by general dental practitioners and to see if use was related to the dentists' age and postgraduate qualifications.

METHODS

Three mailings of a self-completion questionnaire were circulated to 800 general dental practitioners working in the National Health General Dental Service in England and Wales.

RESULTS

A response rate of 74% was achieved. Sixty-one percent of general dental practitioners reported use of panoramic equipment. Fifty percent of dentists always used E-speed film and 18% always used rectangular collimation. Sixty-eight percent of dentists always used bitewing film holders though fewer (37%) used periapical film holders. Sixty-three percent of dentists always used a long cone. The bisecting angle technique was used by 70% of dentists with 22% always using this technique for periapical radiographs. Thirty-one percent always used the paralleling technique. Use of panoramic equipment, periapical film holders, bisecting angle and paralleling techniques were associated with the dentists' age. Use of periapical film holders, bisecting angle and paralleling techniques and rectangular collimation were associated with dentists' postgraduate qualifications.

CONCLUSIONS

There are several features of radiographic equipment and techniques that can aid high quality imaging and reduce patient dose. Although a number of these are being used in general dental practice in England and Wales they have yet to achieve universal adoption.

Aspects of panoramic radiography in general dental practice

OBJECTIVES

To gather information on the types of panoramic x-ray equipment used in NHS dental practice and whether dentists satisfy the legal requirements for safety, to determine which practice personnel take panoramic radiographs and to assess the prevalence of the practice of 'routine' panoramic radiography among NHS dentists.

DESIGN

Postal questionnaire survey of general dental practitioners carried out during 1997 in selected FHSAs in England and Wales.

RESULTS

542 dentists returned the questionnaire, a 73.3% response. Panoramic x-ray equipment ranged in age from 27 years old to new, with 42.2% exceeding 10 years in age. The overwhelming majority of GDPs satisfied the requirement for regular maintenance and surveying of equipment. Almost all dentists (95.9%) performed a history and clinical examination prior to panoramic radiography but 42% practised 'routine screening' of new adult patients. A substantial proportion (36.7%) of dentists used unqualified personnel to take panoramic radiographs.

CONCLUSIONS

While some aspects of this study give reassurance about the prevalence of good practice, widespread panoramic screening and using unqualified staff to take radiographs causes concern. These findings have implications for educators and for those involved in maintaining clinical standards.

QUALITY OF RADIOGRAPHIC IMAGES: LABORATORY EVALUATION OF INTRAORAL FILMS, FILTERS, COLLIMATORS, AND RADIATION EXPOSURE

In order to evaluate density, radiographic contrast and dose of radiation exposure, the author analyzed 80 radiographs containing 640 optical density data of the images of a penetrometer, exposed to the radiation beam with combinations between D and E periapical films, aluminum and copper/aluminum filters, and circular or rectangular collimators. The data obtained were analyzed by ANOVA and allowed the following conclusions: 1) aluminum filtration resulted in improved image contrast; 2) the use of group D film and an aluminum filter produced improved image contrast quality; 3) the rectangular collimator contributed to the production of improved contrast and to the reduction of radiation exposure, but did not affect density; 4) the combination of copper/aluminum filter, E group film and rectangular collimation significantly reduced radiation exposure.

Attitudes of Swedish dentists to the choice of dental X-ray film and collimator for oral radiology

OBJECTIVES

To investigate the use of E-speed film and rectangular collimation by Swedish dentists as a means of dose limitation in relation to their attitudes towards radiation hazards.

METHODS

A questionnaire was sent to 2000 randomly selected general dental practitioners to assess their use of different types of dental X-ray film and collimators and their attitudes and knowledge on methods of dose reduction. Logistic regression analysis was used to analyse the effects of postgraduate courses, gender, age, working alone, and working in the Public Dental Health Service (PDHS) or private practice (PP) on the type of film and collimator used.

RESULTS

The response rate was 69.3%. D-speed film was used by 52% and E-speed film by 47%. Round open-ended 6 cm collimators were used by 42%, while 29% used rectangular collimators. Dentists in the PDHS, who viewed dental radiography as a 'high-risk' procedure and who had attended a one-week continuing education course were twice as likely to use dose-limitation techniques.

CONCLUSIONS

Extended continuing education courses and working in PDHS promote the use of low-dose techniques. Prospects for changing the present situation are good, provided that efforts are made to increase the awareness of radiation hazards and knowledge of new techniques in under- and postgraduate education. Mandatory continuing education is proposed.

The use of panoramic radiology in dental practice

OBJECTIVES

Approximately 1.5 million panoramic radiographs are taken annually in the general dental service in England and Wales. The aim of this review was to assess the clinical role of panoramic radiology in the diagnosis of diseases associated with the teeth and to consider its value in routine screening of patients.

METHOD

This was carried out by critical review of the literature.

RESULTS

In addition to common problems with radiographic technique and processing, there are limitations in image quality inherent to panoramic radiology. These factors contribute to a reduced diagnostic accuracy for caries diagnosis, demonstration of periodontal bone support and periapical pathology when compared with intraoral radiography. Routine screening is unproductive for large proportions of dentate and edentulous populations, while in those cases where pathology is detected the diagnostic accuracy can be questioned. Furthermore, the "detection' of asymptomatic anomalies may have no effect on patient management. Attempts to develop and test panoramic radiographic selection criteria are reviewed.

CONCLUSIONS

New, high-yield selection criteria for panoramic radiography are proposed as a means of reducing unnecessary examinations, limiting radiation doses and reducing financial costs to patients and health service providers. However, research is indicated to develop further and to test such selection criteria.

The use of bitewing radiographs in the management of dental caries: scientific and practical considerations

The objective of this paper is to synthesize published research on the use of radiographs in caries diagnosis in order to produce recommendations for guidelines that are clinically oriented but scientifically based. The options available include the use of various types of radiographic examination alone or in conjunction with other diagnostic aids. The outcomes should facilitate the optimal management of lesions as either preventive care advised (PCA) or operative care advised (OCA). Small initial lesions (PCA) require prompt detection, the application of appropriate preventive care and subsequent monitoring to maintain the most favourable tooth state achievable in the long term. Larger dentinal lesions (OCA) also require prompt detection so that appropriate high-quality operative care can be provided before further loss of tooth substance. Evidence was collected from the literature by updating several recent reviews by the author. The values employed were broadly analogous to those of the Canadian Task Force on the Periodic Health Examination. The use of ionizing radiation is always associated with a degree of risk: therefore all exposures must be kept as low as is reasonably achievable. Present evidence on the balance of risk and benefit indicates that the diagnostic yield for caries diagnosis is high enough to justify individualized examinations, particularly as changes in the morphology of caries have rendered clinical diagnosis of dentinal lesions less sensitive. This issue must be kept under review as alternative diagnostic technologies develop. There is good evidence that initial posterior bitewing radiographs are required for all new dentate patients over five years of age with posterior teeth. This procedure is required as an adjunct to clinical examination for the detection of caries on both the approximal and occlusal surfaces of the teeth. Although a 'blanket' regimen of routine radiographic examination at fixed intervals cannot be advocated, individualized bitewing examinations at varying frequencies determined on the basis of caries risk are supported. At the initial visit, an assessment of caries risk of the individual patient should be made. Varying intervals of first radiographic recall can then be suggested on the basis of differing degrees of risk. At present, risk assessment is imprecise, and risk status may change over time. Therefore, intervals between subsequent radiographic examinations must be re-assessed for each period. The purpose of detecting individual lesions should be to facilitate the planning of appropriate preventive treatment decisions based on lesion severity, caries risk and the patient. Different treatment should be employed for lesions in the PCA and OCA categories. Further rigorous studies are required to evaluate diagnostic methods appropriate for use in individual patient care, epidemiology and clinical research, and to increase the understanding of how findings from these applications inter-relate. Development and validation of reliable methods of caries risk assessment which are usable in general practice is a priority. Investigations of the processes involved in, and the outcomes of, dental decision-making are required to ensure that existing and new methods are used appropriately. Further work should develop and evaluate effective mechanisms of disseminating and implementing research findings by information transfer to dental educators and clinicians.

A laboratory evaluation of Ektaspeed Plus dental X-ray film

OBJECTIVES

The aim of this study was to make a laboratory evaluation of the image quality of a new dental X-ray film, Ektaspeed Plus, compared with Ektaspeed and Ultraspeed films.

METHODS

Films of each emulsion type underwent a range of exposures at both 50 kVp and 70 kVp, and characteristic curves were constructed to give a comparison of fog, speed and contrast. Line pair and contrast detail test objects were used to assess the resolution of radiographs and the ability of the two film types to reproduce minor differences in subject contrast. The sensitivity of the emulsions to safelighting for a range of times was also tested.

RESULTS

Ektaspeed Plus had the same speed, a slightly higher base plus fog density but a higher contrast (50 and 70 kVp) than Ektaspeed. The speed of Ektaspeed Plus was higher and the contrast similar to that of Ultraspeed film. Limiting resolutions of the three films were the same. There was a slightly better imaging of one contrast detail phantom with Ektaspeed Plus compared to Ektaspeed at 70 kVp only. All three emulsions were insensitive to recommended safelighting conditions.

CONCLUSION

The improved image contrast of Ektaspeed Plus may be more acceptable to dentists than Ektaspeed and lead to a greater acceptance of E-speed film, contributing to dose reduction.

Questionnaire survey on the use of dental X-ray film and equipment among general practitioners in the Swedish Public Dental Health Service

A questionnaire was sent to all clinics in the Public Dental Health Service in Orebro County in 1989 and 1993. The survey comprised questions about X-ray film and developing technique. The questionnaire of 1993 was accompanied by questions on the type of dental X-ray film and collimator each dentist used, altogether 175 dentists. The results showed that Kodak Ektaspeed dental X-ray film was used by 53% of the dentists in 1993. The mean number of months to the expiry date for all film packages irrespective of film type increased from a mean of 7.5 months to a mean of 13 months from 1989 to 1993. Only 11% of the Ektaspeed film packages in 1989 had a base plus fog < or = 0.25, whereas the figure in 1993 was 30%. Rectangular collimation adjusted to the size-2 film (31 mm x 41 mm) was used by 36% of the dentists in 1993. In 1993, 88% of the clinics used automatic processing, and in 85% of the clinics both automatic and manual processing was used. The processing time and temperature varied greatly for both automatic and manual processing. The results indicate that film and developing procedures in Swedish general dental practice are not always in accordance with the recommendations and guidelines of the Swedish National Radiation Protection Institute (SSI) and that attempts should be made to improve dentists' behavior with regard to radiation safety. A major dose reduction would be achievable without jeopardizing diagnosis if the regulations of the SSI were followed by using the fastest available film and optimum developing procedures.(ABSTRACT TRUNCATED AT 250 WORDS)

The use of E-speed film for root canal length determination

This study compared the use of D-speed and E-speed dental X-ray film for assessing the working length of root canals. Root canal files of varying size (ISO 06, 08, 10 and 15) were placed in the root canals of a maxillary molar and a mandibular molar in a dried skull and mandible. Files were set at various lengths relative to the radiographic apex. The X-ray projections were kept constant. Exposure settings for the two film types that gave comparable radiographic density were selected. Films were developed manually under standardized conditions. A total of 48 films of each type were examined at various magnifications by four trained examiners for the estimation of distance between the file tip and radiographic apex. There were no differences between examiners in estimating working length. The effect of file size, root and magnification were also not significant. The differences between the film types were not significant (P > 0.05). It is concluded that clinicians should use E-speed film instead of D-speed film for root canal length measurement, because the exposure time was reduced by over 40% but the quality of the radiographic image was not significantly different.

Some of the factors to be considered in the prescription and timing of bitewing radiography in the diagnosis and management of dental caries

This article describes some of the factors to be considered by the practitioner when prescribing bitewing radiographs in the diagnosis and management of dental caries and draws on the literature of a number of disciplines including restorative dentistry, cariology, epidemiology and oral radiology. It seems appropriate to re-assess current practice in the light of information on changes in the disease of dental caries, its behaviour and the way this behaviour may vary in high and low caries risk groups. The diagnostic potential of the bitewing examination appears, at present, to be unrivalled, but other diagnostic methods, such as fibreoptic transillumination and tooth separation, must also be considered. Some methods to minimize radiation doses and increase diagnostic yield are discussed. Current knowledge of prescribing patterns is reviewed and areas of ignorance are mentioned as findings from future research in these areas may influence decisions about when to use and re-use bitewing radiographs.