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OBJECTIVE: Rectangular collimation is a popular method used in intraoral radiography to reduce patient exposure to ionizing radiation. One of the perceived drawbacks of rectangular collimation is the possibility of an increase in cone cut errors ultimately impacting the diagnostic value of the radiographs. Thus, the aim of this study was to explore the frequency of cone cut errors in radiographs taken using a rectangular collimator. MATERIALS AND METHODS: Radiographs taken using PSP plates at Academic Center for Dentistry Amsterdam in the Netherlands by staff and students from January to December 2015 were assessed for cone cut errors. The radiographs were grouped as bitewings, front teeth, inferior premolars and molars, and superior premolars and molars and categorized as no cone cut, cone cut but diagnostically usable, and cone cut but diagnostically not usable. The results were entered into Microsoft Excel and analyzed thereafter. RESULTS: A total of 53,684 radiographs were assessed, 79% had no cone cut errors and consequently 21% had some degree of cone cut. However, the diagnostic value was unaffected in 18% of the radiographs with cone cut. Only 3% of the radiographs were deemed diagnostically unusable due to cone cut. The most common area of cone cut was in the premolar and molar areas while cone cut in the front teeth was least likely to be diagnostically unusable. CONCLUSION: Cone cut from the use of a rectangular collimator does not seem to result in an increase of diagnostically unusable radiographs. Thus, rectangular collimation should be preferred as it decreases the amount of radiation exposure to the patient while producing diagnostically usable radiographs and thus allowing the dental professional to adhere to the ALADA principle and practice radiation stewardship. CLINICAL RELEVANCE: Scientific rationale for the study: rectangular collimation is a method used to reduce patient exposure to ionizing radiation; however, this benefit is negligible if radiographs must be retaken due to cone cut errors that make the radiograph diagnostically unusable. Therefore, the aim of this study was to explore the frequency of cone cut in radiographs taken using a rectangular collimator. PRINCIPAL FINDINGS: cone cut was observed in 21% of the radiographs; however, only 3% of the radiographs were considered diagnostically unusable. PRACTICAL IMPLICATIONS: rectangular collimation does not result in a high number of diagnostically unusable radiographs and should be used to reduce patient exposure to ionizing radiation.

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Opacities in the orofacial soft tissue rather than the bone are frequently seen on panoramic radiographs. The differential diagnosis of these opacities is diverse and concerns frequently occurring disorders but also rare ones. Due to the diversity of diagnoses, the clinical interpretation of a soft tissue opacity is often difficult. A distinction is made among heterotopic calcifications, heterotopic ossifications, and foreign bodies. Heterotopic calcifications are subdivided into 3 groups, i.e. dystrophic, idiopathic and metastatic calcifications. In this article, stress is placed on the radiographic and clinical characteristics of heterotopic ossifications and foreign bodies, and how they can be recognised on a panoramic radiograph. Besides this, attention will be paid to the need for possible additional imaging techniques and indications regarding treatment option.

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Opacities not in the bone but in the orofacial soft tissue, are frequently seen on panoramic radiographs. The differential diagnosis of these opacities is diverse and concerns frequently occurring disorders but also rare ones. Due to the diversity of diagnoses, the clinical interpretation of a soft tissue opacity is often difficult. A distinction is made among heterotopic calcifications, heterotopic ossifications, and foreign bodies. Heterotopic calcifications are subdivided into 3 groups, i.e. dystrophic calcifications, idiopathic calcifications, and metastatic calcifications. In this article, stress is placed on the radiographic and clinical characteristics ofidiopathic calcifications and how they can be recognised on a panoramic radiograph. Besides this, attention will be paid to the need for possible additional imaging techniques and indications regarding treatment options. Idiopathic calcification results from deposition of calcium salts in healthy tissue without an apparent cause. Calcium and phosphate levels in the serum are normal in these cases.

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Opacities in the orofacial soft tissue rather than the bone are frequently seen on panoramic radiographs. The differential diagnosis of these opacities is diverse and comprises abnormalities both frequently seen and rare. On account of this diversity, the clinical interpretation of a soft tissue opacity is often difficult. Heterotopic calcifications, heterotopic ossifications, and foreign bodies are distinguished. Heterotopic calcifications are subdivided into 3 groups, i.e. dystrophic calcifications, idiopathic calcifications, and metastatic calcifications. In this article, the emphasis will be on radiological and clinical characteristics of dystrophic calcifications and how to recognize these on panoramic radiographs. In dystrophic calcification, calcium salts are deposited in chronically inflamedor necrotic tissue.

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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.

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OBJECTIVES: During a cone beam CT scan, the patient is in an upright or supine position. This position depends on the brand and type of the scanner. The aims of this study are: (1) to investigate if the head position has an effect on cephalometric evaluation of the soft-tissue facial profile, comparing the recordings in natural head position (NHP) and supine head position (SHP) and (2) to investigate if age, gender and body mass index (BMI) are contributing factors to the effect of the head position. METHODS: 90 subjects were photographed in profile both in NHP and in SHP. 12 soft-tissue angular and linear cephalometric values were calculated. Two-way random intraclass correlation coefficients were calculated to determine observer reliability. Paired t-tests and linear regression analyses were performed to investigate the differences between the head positions and the influence of age, gender and BMI. RESULTS: Intraobserver reliability was generally high. Paired t-tests showed significant changes as a result of head positioning (p < 0.0001) in 9 of the 12 measurements. These differences were small and clinically not relevant, except for the "lower face-throat angle". Regression analysis revealed no relevant influence of age, gender and BMI. CONCLUSIONS: Cephalometric soft-tissue evaluation from a recording in SHP is generally reliable, except for the throat-chin area where a clinically relevant difference was found. The contour of the submandibular tissues in SHP causes the chin to appear more prominently. This can cause incorrect orthodontic diagnosis and treatment planning.

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OBJECTIVE: The aim of this study was to evaluate the influence of thyroid collars on radiation dose during cone beam CT (CBCT) scanning. METHODS: Average tissue-absorbed dose for a NewTom 9000 CBCT scanner (Quantitative Radiology, Verona, Italy) was measured using thermoluminescent dosemeter chips in a phantom. The scans were carried out with and without thyroid collars. Effective organ dose and total effective dose were derived using International Commission on Radiological Protection 2007 recommendations. RESULTS: The effective organ doses for the thyroid gland and oesophagus were 31.0 µSv and 2.4 µSv, respectively, during CBCT scanning without a collar around the neck. When the thyroid collars were used loosely around the neck, no effective organ dose reduction was observed. When one thyroid collar was used tightly on the front of the neck, the effective organ dose for the thyroid gland and oesophagus were reduced to 15.9 µSv (48.7% reduction) and 1.4 µSv (41.7% reduction), respectively. Similar organ dose reduction (46.5% and 41.7%) was achieved when CBCT scanning was performed with two collars tightly on the front and back of the neck. However, the differences to the total effective dose were not significant among the scans with and without collars around the neck (p = 0.775). CONCLUSIONS: Thyroid collars can effectively reduce the radiation dose to the thyroid and oesophagus if used appropriately.

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OBJECTIVES: To compare proximal caries depth between conventional film images, unenhanced and enhanced storage phosphor plate images. METHOD: Bitewing radiographs were taken on 100 patients presenting for Conservative and Periodontal treatment. Only one bitewing was taken on a patient either the right or left hand side of the patient A DenOptics storage phosphor plate and size 3 Kodak Insight film were simultaneously placed into a Rinn bitewing holder. The Insight film was placed behind the phosphor plate. Both were simultaneously exposed to radiation. The unenhanced phosphor plate images were copied four times. Contrast and brightness were either increased or decreased on the copied images. A five point scale was chosen for proximal caries depth: 0--sound, 1--caries in enamel, 2--caries reaching dentino-enamel junction, 3--caries into dentine, 4--caries in a restored area. The bitewing images were evaluated by 4 clinicians. Images with technical errors were excluded from the study. RESULTS: Altogether 1848 tooth surfaces were evaluated of which 136 surfaces were excluded due to technical errors. The results show that for the detection of proximal caries there is no significant difference in accuracy between unenhanced storage phosphor plate and Kodak Insight film images (p > 0.001). When decreasing both contrast and brightness there was no significant difference in diagnostic accuracy (p > 0.001) between unenhanced and enhanced storage phosphor plate images. More surfaces were analyzed for caries into the dentine on the enhanced images when both contrast and brightness were increased. CONCLUSION: Although contrast-enhanced and brightness-enhanced images retween conventional film, unenhanced and enhanced images.

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OBJECTIVES: To investigate the effect of the scanning resolution of storage phosphor plate (SPP) radiographs on the detection of proximal caries lesions. METHODS: 10 dentists evaluated 72 proximal surfaces of premolars with respect to caries from SPP radiographs scanned with theoretical spatial resolutions of: (1) the Digora FMX at 7.8 lp mm(-1); (2) the Digora Optime at both 7.8 lp mm(-1) and 12.5 lp mm(-1); and (3) the Dürr VistaScan at 10 lp mm(-1) and 20 lp mm(-1), respectively. The lesions were validated by histological examination. Receiver operating characteristic (ROC) analysis was employed. RESULTS: The A(z) value for the radiographs scanned with the Dürr VistaScan at 10 lp mm(-1) is significantly lower than those for the other series of radiographs (P = 0.000). CONCLUSIONS: For SPP radiographs, an increased theoretical spatial resolution per se is not related to an improved detection of proximal caries.

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AIMS: The aim of this study was to: (1) compare the diagnostic accuracy of the high-resolution and standard resolution settings of four digital imaging systems for caries diagnosis and (2) compare the effect on the diagnostic accuracy of reducing the high-resolution image sizes to the standard resolution dimensions, and vice versa. MATERIALS AND METHODS: 90 extracted human premolars were mounted in groups of 5 in plaster blocks, containing 4 test teeth and 1 non-test tooth. Two blocks at a time were placed in a jig to simulate a bitewing radiograph. Radiographs were taken using four digital systems (Planmeca Dixi 2; Gendex Visualix HDI; Dürr Vistascan; Digora Optime), each at two resolution settings. Next, the teeth were sectioned and a total of 65 surfaces were incorporated in the study. Additionally, the bicubic interpolation method was applied to reduce the high-resolution original images and to enlarge the standard resolution images. The original, reduced and enlarged images were randomly shown to five observers in two random sessions. The observers were asked to assess caries depth on a 4-point scale. The observers' scores were compared with the results from a histological examination. Data were analysed using the statistical theory for multivariate discrete data. Cohen's kappa was used to determine the agreement with the gold standard. RESULTS: None of the comparisons between the spatial resolution settings, or the comparisons between increased or reduced image size and the original image sizes, showed significant differences in the probability of caries detection (chi2=26.59, df=26, P approximately 0.50). The four digital systems used in this study differ significantly in the probability of caries detection (chi2=41.55, df=24, P<0.02). Compared with the gold standard, the Gendex Visualix HDI CCD sensor has the highest measure of agreement (kappa=0.31). CONCLUSION: Caries diagnosis does not improve when using high-resolution settings compared with the standard settings. The use of bicubic convolution interpolation for zooming has no detectable effect on caries diagnosis and therefore is recommended to use when enlarging or reducing radiographs. The probability of caries detection, however, was different for the sensor systems of the different manufacturers.

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Eight dentists evaluated 72 proximal surfaces of premolars with respect to all caries lesions and to lesions into dentine in digital images from a storage phosphor plate system. The images were processed in four different ways: (1) the default algorithm of the standard imaging system (DF); (2) an algorithm correcting for attenuation and visual response (AV), and two proprietary caries-specific enhancement algorithms (3) K1, and (4) K2, respectively. The lesions were validated by histological examination. There were no significant differences in the areas under the receiver operating characteristic curves between differently processed radiographs for the categories of all caries lesions and caries into dentine.

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OBJECTIVES: To investigate the range of diagnostically acceptable digital radiographs and film as a function of exposure time, as well as the relationship to dose reduction and consequences for dental practice. METHODS: Five systems for intraoral radiography were used to take a series of radiographs, with increasing exposure times, of five different dry bone specimens. Seven observers evaluated the 25 series of radiographs. The observers had to determine which radiographs of each series were acceptable for dental diagnostics and which radiograph of each series they preferred. RESULTS: For Ektaspeed Plus film, the exposure time for the preferred radiograph was 0.52 s, with a range of diagnostically acceptable radiographs from 0.23-1.02 s. The preferred radiograph of the solid-state systems required less radiation than film (Sirona, 0.13 s; MPDx 0.35 s). The exposure range of these systems is narrow. In contrast, the exposure range of the phosphor plate systems is very wide. The preferred radiograph of the phosphor plate systems required high exposure (Digora, 1.21 s; Gendex DenOptix, 1.16 s). CONCLUSIONS: All digital systems require less exposure than film for diagnostically acceptable radiographs, but this is less obvious for preferred radiographs. Solid-state systems alert the dentist when a too long exposure time is used by a lack of image quality; phosphor plate systems, however, produce good quality radiographs even at high exposure times, which may result in an unnecessarily high dose.

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OBJECTIVES: Two digital image processing algorithms, one aimed at correction for exponential attenuation and one at correction for visual response, have been developed. The aims of the present study were to test whether digital radiographs processed with these algorithms improve determination of the length of endodontic files and whether such processed radiographs are comparable with the radiographs processed with a default image processing method employed by one commercially available digital intraoral system. METHODS: A dried human skull embedded in an acrylic compound was used for exposing radiographs of the upper and lower premolars and molars with endodontic files (Kerr files size 10 and size 15) positioned to the full length of the roots or 1.5 mm short of it. Radiographs were then processed in three sets. In one set, the radiographs were processed to compensate for exponential attenuation and the response of the human visual system. In the second, the radiographs were processed with the same compensation but with an additional shift in grey levels so that the output luminance in dentin at root tips corresponds to the mean of the luminance range of a computer monitor. In the third, the radiographs were processed with the default processing method in the Sidexis program. Ten viewers evaluated all radiographs. Receiver operating characteristic (ROC) curves were obtained and areas under the curves were calculated. RESULTS: For file size 10, ROC curves for processed radiographs were higher than that for originals, while for file size 15, ROC curves for processed and original radiographs were close to each other. Significant differences were found between processed and original radiographs regarding areas under ROC curves for file size 10 but not between the differently processed radiographs. For file size 15, no significant differences were found. CONCLUSION: Radiographs processed to correct for attenuation and visual response may improve determination of the length of thin endodontic files. Such processed radiographs are comparable with the radiographs processed with the default processing method in the Sidexis program.

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We developed a computer-assisted learning (CAL) program to improve student caries diagnosis from bitewing radiographs. In order to decide on its appropriateness, dental teachers independently evaluated the program before it was introduced. Our objective was to describe an evaluation by the teachers of the CAL diagnostic module and to compare the diagnostic performance with the evaluation score of the program. Key dental teachers involved in teaching clinical caries diagnosis and epidemiology (n = 22) viewed the CAL program. They evaluated aspects of the program by scoring 10 criteria on a visual analogue scale. Measures of the teachers' initial diagnostic accuracy assessed during use of the program were: sensitivity and specificity for the presence of dentine caries. Using Pearson's correlation coefficients, these measures of the teachers' diagnostic accuracy were compared separately with their evaluation score of one aspect of the program: the overall functionality of the program for a 2nd-year dental student. The teachers' mean sensitivity for dentine caries diagnosis was 76.5% (median 77.8%; SD 15.4%) and the mean specificity was 93.7% (median 94.2%; SD 3.9%). The teachers gave the program a mean overall functionality score of 68% (median 75.1%; SD 21%). Dentists with a lower sensitivity (P = 0.065) for dentine caries tended to give the CAL program a higher overall functionality score than the other teachers. The CAL program was valued as generally useful. It tended to be more highly valued by the dentists with initially lower scores for diagnostic accuracy.

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OBJECTIVES: To compare the number of radiographs taken in general dental practices equipped with digital radiography vs conventional film-based radiography and to determine the reasons for any difference in numbers. METHODS: In a mail survey, 473 questionnaires were sent to Dutch General Dental Practitioners (GDPs) using digital radiography and 105 questionnaires were sent to GDPs using film. The questionnaire concerned the number of intraoral radiographs taken in the dental practice, as well as possible reasons to take more or fewer radiographs after conversion to digital radiography. RESULTS: The response rate was 73%. Users of a phosphor plate system on average take 42.8 radiographs per week and solid-state system users take 48.4 radiographs, whereas film users take on average only 32.5 radiographs per week. The need for more certainty about the planned or ongoing treatment as well as better diagnostics were the most important reasons for taking more radiographs. CONCLUSIONS: It seems that GDPs using a system for digital radiography are more inclined to take radiographs than dentists taking conventional radiographs. Although digital intraoral radiography requires 50-80% less radiation per exposure than film, it is likely that the effective dose reduction after converting from conventional to digital radiography is less than 25% owing to the greater numbers of radiographs taken.

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OBJECTIVES: To investigate whether using a computer-assisted learning (CAL) calibration program improves the accuracy of dental students in caries detection from bitewing radiographs. METHODS: Dental students were assigned to an experimental (n=33) and control (n=34) group using a randomized block design. The experimental group used the CAL program with feedback to calibrate themselves against experts in radiographic caries detection and a histological gold standard of the actual clinical condition. Feedback was provided visually of the actual tooth surface condition and in the form of graphics showing diagnostic accuracy performance measures. Performance was tested before the program (for the control group) and after the program (for the experimental group) by assessing surfaces (n=56) from a new independent digital test set of evaluation radiographs for the presence, histologically, of dentine caries (n=23). The summary receiver operating characteristic (SROC) method for summarizing true positive ratio (TPR) (sensitivity) and false positive ratio (FPR) (1-specificity) was used to analyse the dichotomous data. Differences between the control and experimental groups were tested for (a) the area under the SROC curve (A(z)) and (b) the TPR, FPR and diagnostic odds ratio (DOR) using the Mann-Whitney test (P<0.05). RESULTS: The mean TPR for dentine caries detection was 76.3% (SD 13.0%) for the experimental group and 66.9% (SD 14.8%) for the control group (P=0.005). Mean FPRs were similar (experimental 28.1% and control 28.7%; P>0.5). The area under the SROC curve A(z) was 0.832 for the experimental group and 0.773 for the control group (P=0.002). The mean DOR for dentine caries in the experimental group (12.4) was better than that in the control group (8.8) (P=0.003). CONCLUSIONS: The CAL program does improve diagnostic performance. Improving the cognitive feedback provided by the program should be considered before implementation.

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OBJECTIVES: To assess the effect of two compression algorithms (JPEG and wavelet) on the detection of approximal caries. METHODS: Fifteen bitewing radiographs were generated using 100 posterior teeth mounted in blocks. The images were produced on conventional films (Ektaspeed Plus) and scanned at 300 d.p.i. Digital images were then compressed 9:1 with JPEG and wavelet methods. Nine observers detected the presence and depth of approximal caries recorded on a 5-point confidence scale and a 4-point depth scale from images viewed in random order. Histological examination provided the true depth of the lesions. Data were analysed by means of ANOVA. The null hypothesis was that there is no significant difference between the two compression algorithms and the original uncompressed images. RESULTS: JPEG performed significantly worse than the original and the wavelet algorithm (P<0.001) for the detection of dentinal lesions. However, no significant differences were found for the detection of sound surfaces, enamel lesions, and lesions up to the DEJ between JPEG-compressed images and each of the other two modalities. There was also no significant difference between the wavelet-compressed images and the original for all lesion depths. CONCLUSIONS: At a compression ratio of 9:1, there were no significant differences among the original images, JPEG and wavelet compressed images for the detection of enamel caries. JPEG-compressed images performed inferiorly to the original and wavelet-compressed images for the detection of dentinal lesions. Wavelet compression is a better choice than JPEG at the compression ratio investigated in this study.

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OBJECTIVES: The purpose of this study was to assess the experiences of general dental practitioners (GDPs) with solid-state and storage phosphor digital sensors compared to film. METHODS: In a mail survey 578 questionnaires were sent to Dutch GDPs who were users of digital X-ray detectors and film. The questionnaire requested demographic data, information about the digital system used and the user-friendliness of the X-ray detector system. In the analysis of the data these variables were related to the type of system used and also to the demographic data. The data were analysed using descriptive statistics, variance-analysis (One-Way ANOVA) and nonparametric tests (Kruskal-Wallis, Mann-Whitney and Wilcoxon) (SPSS 9.0). RESULTS: Four hundred and twenty-four questionnaires were returned (overall response rate 73%). The user-friendliness of the handling of the different systems before exposing the radiograph is better for conventional film, whereas the handling after exposing the radiograph favoured the digital X-ray detector systems. CONCLUSIONS: The user-friendliness was best for film pre-exposure and digital sensors post-exposure.

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Objective. The purpose of this study was to determine the dose profile of the Cranex Tome radiography unit and compare it with that of the Scanora machine. Study design. The radiation dose delivered by the Cranex Tome radiography unit during the cross-sectional mode was determined. Single tooth gaps in regions 3 (16) and 30 (46) were simulated. Dosimetry was carried out with 2 phantoms, a head and neck phantom and a full-body phantom loaded with 142 thermoluminescent dosimeters (TLD) and 280 TLD, respectively; all locations corresponded to radiosensitive organs or tissues. The recorded local mean organ doses were compared with those measured in another study evaluating the Scanora machine.Results. Generally, dose values from the Cranex Tome radiography unit reached only 50% to 60% of the values measured for the Scanora machine. The effective dose was calculated as 0.061 mSv and 0.04 mSv for tooth regions 3 (16) and 30 (46), respectively. Corresponding values for the Scanora machine were 0.117 mSv and 0.084 mSv.Conclusion. Cross-sectional imaging in the molar region of the upper and the lower jaw can be performed with the Cranex Tome unit, which delivers only approximately half of the dose that the Scanora machine delivers.

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