A comparison of perceived diagnostic image quality in direct digital panoramic images between standard and advanced external GOP image processing

Objective: The objective of the present study was to study the effect of adaptive image processing (GOP processing) on the visibility of anatomical structures in direct digital panoramic images. Material and methods: The study comprised panoramic images of 50 consecutive adult individuals aged 18-60 years. Nine dentists working with dental radiology compared the structural image quality of all standard-processed and GOP-processed panoramic images for six anatomical structures, using a six-point scale for visual grading characteristics analysis. Results: For all anatomic structures a statistically significant difference in favour of the GOP was found. Conclusions: The present study shows that it is possible to improve perceived diagnostic image quality of direct digital panoramic radiography using GOP technology compared to the manufacturers' standard processing. Manufacturers' image-processing programs can be further developed, as there is a possibility of improving the perceived diagnostic content of an image with external processing.

Can adaptive post-processing of storage phosphor plate panoramic radiographs provide better image quality? A comparison of anatomical image quality of panoramic radiographs before and after adaptive processing

OBJECTIVE

The objective of the present study was to study the effect of adaptive image processing on the visibility of anatomical structures in storage phosphor plate (SPP) panoramic images.

MATERIALS AND METHODS

Three hundred SPP panoramic X-ray radiographs of children and adolescents were used. The radiographs were post-processed using general operator processor (GOP) technology, resulting in both a standard-processed and a GOP-processed radiograph. Four specialists in dental radiology compared the structural image quality of all standard-processed and GOP-processed panorama images for six anatomical structures, using a six-point scale for visual grading characteristics (VGC) analysis.

RESULTS

For three of the anatomic structures - the root canal space of the mandibular left first premolar, mandibular canal left side and periodontal ligament space of the mandibular right first molar - there was a statistically significant difference to the GOP's advantage. For the three remaining structures - dentino-enamel junction of the maxillary right first molar, crista alveolaris of the mandibular left molar area and floor of maxillary sinus right side - no significant difference between standard processing and GOP processing was obtained.

CONCLUSIONS

The study demonstrates that it is possible to improve the quality of SPP radiographs and the visibility of anatomical structures by using the GOP technique. Manufacturers' image-processing programs can be further developed, as there is a possibility of improving the diagnostic content of an image with external processing.

Dentists' use of digital radiographic techniques: Part II - extraoral radiography: a questionnaire study of Swedish dentists

OBJECTIVE

The present study aims to gain knowledge about the dentist's use and choice of digital extraoral imaging methods, panoramic radiography and cone beam computed tomography (CBCT).

MATERIALS AND METHODS

A questionnaire sent to 2481 dentists within the Swedish Dental Society contained questions about the panoramic technique and CBCT technique used, education, clinic size and type of service. The response rate was 53%.

RESULTS

The study showed that 61% of the Swedish dentists had access to panoramic techniques and that 84% used a direct digital sensor, while 6% used storage phosphor plate techniques. Around 8% of the Swedish dentists had access to CBCT. It was also observed that group practices had two times higher odds of having panoramic equipment compared with solo practices. Approximately 40% of the dentists had undergone postgraduate education in oral radiology during the last 5 years. Dental nurses and dental hygienists exposed 92% of the panoramic radiographs and 75% of the CBCTs. Thirty per cent of those clinics with access to a panoramic unit exposed >30 panoramic radiographs per month and 56% of the clinics having access to CBCT did more than 75 examinations per year.

CONCLUSIONS

Today 61% of Swedish dentists have access to panoramic radiography and 8% have access to CBCT. There is a greater likelihood of having access if the dentist works in the public dental health service or in a group practice and if the dentist has undergone any postgraduate course in oral radiology.

Dentists' use of digital radiographic techniques: Part I - intraoral X-ray: a questionnaire study of Swedish dentists

OBJECTIVE

The present study aims to gain knowledge about the dentist's use and choice of digital intraoral imaging methods.

MATERIALS AND METHODS

A questionnaire sent to 2481 dentists within the Swedish Dental Society contained questions about the type of X-ray technique used, problems experienced with digital radiography, and reasons for choosing digital technology, and about indications, clinic size and type of service. Response rate was 53%.

RESULTS

Ninety-eight percent of the dentists had made the transition to digital radiography; only 2% used film technique, and solid-state detector (SSD) was the most used digital technique. More years in service decreases the likelihood of applying individual indications for performing a full mouth examination. More retakes were done with SSDs compared to storage phosphor plates. Reasons for choosing digital techniques were that work was easier and communication with the patients improved. However, dentists also experienced problems with digital techniques, such as exposure and projection errors and inadequate image quality. The Swedish Radiation Safety Authority states that all radiological examinations should be justified, something not always followed.

CONCLUSIONS

This study showed that 98% of the respondents, Swedish dentists within the Swedish Dental Society, used digital techniques, and the most used was the solid-state technique.

Effectiveness of enamel matrix derivative on the clinical and microbiological outcomes following surgical regenerative treatment of peri-implantitis. A randomized controlled trial

OBJECTIVE

This randomized clinical trial aimed at comparing radiological, clinical and microbial effects of surgical treatment of peri-implantitis alone or in combination with enamel matrix derivative (EMD).

METHODS

Twenty-six subjects were treated with open flap debridement and decontamination of the implant surfaces with gauze and saline preceding adjunctive EMD or no EMD. Bone level (BL) change was primary outcome and secondary outcomes were changes in pocket depth (PD), plaque, pus, bleeding and the microbiota of the peri-implant biofilm analyzed by the Human Oral Microbe Identification Microarray over a time period of 12 months.

RESULTS

In multivariate modelling, increased marginal BL at implant site was significantly associated with EMD, the number of osseous walls in the peri-implant bone defect and a Gram+/aerobic microbial flora, whereas reduced BL was associated with a Gram-/anaerobic microbial flora and presence of bleeding and pus, with a cross-validated predictive capacity (Q(2) ) of 36.4%. Similar, but statistically non-significant, trends were seen for BL, PD, plaque, pus and bleeding in univariate analysis.

CONCLUSION

Adjunctive EMD to surgical treatment of peri-implantitis was associated with prevalence of Gram+/aerobic bacteria during the follow-up period and increased marginal BL 12 months after treatment.

The effect of anatomical noise on perception of low contrast in intra-oral radiographs: an in vitro study

OBJECTIVES

Radiographic images suffer from varying amounts of noise. The most studied and discussed of these is random noise. However, recent research has shown that the projected anatomy contributes substantially to noise, especially when detecting low-contrast objects in the images. Our aim, therefore, was to evaluate the extent to which overprojected anatomical noise affects the detection of low-contrast objects in intra-oral images.

METHODS

Our study used four common sensor models. With each sensor, we took four series of images, three series with and one series without an anatomical phantom present. In each series, we exposed a low-contrast phantom at 18 different exposure times using a standardized method. 4 observers evaluated all 288 images.

RESULTS

The low-contrast characteristics differed substantially when imaging low contrast on a homogeneous background compared with imaging low contrast when an anatomical phantom was present. For three of the sensors, optimal exposure times for low-contrast imaging were found, while the fourth sensor displayed a completely different behaviour.

CONCLUSIONS

Calibrating the low-contrast properties of an imaging system using low-contrast objects on a homogeneous background is not recommended. On an anatomical background, low-contrast properties are completely different, and these will mimic the clinical situation much more closely, directing the operator how to best use the system. There is a clear demand for further research on this subject.

Optimization of exposure in panoramic radiography while maintaining image quality using adaptive filtering

Objective The purpose of the present study was to investigate the potential of using advanced external adaptive image processing for maintaining image quality while reducing exposure in dental panoramic storage phosphor plate (SPP) radiography. Materials and methods Thirty-seven SPP radiographs of a skull phantom were acquired using a Scanora panoramic X-ray machine with various tube load, tube voltage, SPP sensitivity and filtration settings. The radiographs were processed using General Operator Processor (GOP) technology. Fifteen dentists, all within the dental radiology field, compared the structural image quality of each radiograph with a reference image on a 5-point rating scale in a visual grading characteristics (VGC) study. The reference image was acquired with the acquisition parameters commonly used in daily operation (70 kVp, 150 mAs and sensitivity class 200) and processed using the standard process parameters supplied by the modality vendor. Results All GOP-processed images with similar (or higher) dose as the reference image resulted in higher image quality than the reference. All GOP-processed images with similar image quality as the reference image were acquired at a lower dose than the reference. This indicates that the external image processing improved the image quality compared with the standard processing. Regarding acquisition parameters, no strong dependency of the image quality on the radiation quality was seen and the image quality was mainly affected by the dose. Conclusions The present study indicates that advanced external adaptive image processing may be beneficial in panoramic radiography for increasing the image quality of SPP radiographs or for reducing the exposure while maintaining image quality.

Reduction of absorbed doses to the thyroid gland in orthodontic treatment planning by reducing the area of irradiation

The objectives were to study whether a smaller area of irradiation resulted in a significant reduction in the dose of absorbed radiation to the thyroid gland for three radiographic modalities commonly used in cephalometric treatment planning. The aim of this research, was to study the effect of the field size on the absorbed dose of radiation to the thyroid gland, as measured with thermoluminescent dosimeters (TLD) in a phantom. Three radiographic modalities were used: panoramic, cephalometric, and intra-oral. For each modality, a large and a small collimator were used. A Rando Alderson phantom comprising a natural human cranium and cervical vertebrae embedded in a thermoplastic material simulating human soft tissue was used to measure absorbed dose to the thyroid gland. These measurements were made using lithium fluoride (LiF) TLDs. A significant reduction in absorbed dose to the thyroid gland was obtained by reducing the collimator in all three modalities. A 15% reduction in absorbed dose to the thyroid gland was achieved for the combination of small field sizes compared to the combination of large field sizes. Combining the use of selection criteria together with a smaller field of irradiation than normally used made a reduction in absorbed dose to the thyroid gland of around 30% possible.

Early implant failures in patients treated with Brånemark System titanium dental implants: a retrospective study

Implant failure has been associated with factors such as poor bone quality, insufficient bone volume, implant instability, unfavorable implant loading, and smoking habits. Infections and host responses may also be important factors in dental implant failure. The objectives of the present study were to identify various explanatory factors associated with titanium implant failure. Forty subjects with stage 1 non-osseointegrated titanium dental implants (NOTI) ad modum Brånemark and 40 age- and gender-matched control subjects with successfully osseointegrated titanium implants (SOTI) were studied. Clinical data and gamma G immunoglobulin (IgG) antibody titers were studied. An independent t test revealed that significantly longer implants were placed in subjects with SOTI (P < .05). Statistically significant differences in bone shape and resorption (BSR) scores were found between SOTI and NOTI (P < .05). Logistic regression analysis identified 3 significant explanatory outcome variables: serum antibody avidity scores for Bacteroides forsythus (P < .0001), serum antibody titers to Staphylococcus aureus (P < .001), and the BSR scores (P < .05). Antibody avidity to B forsythus and antibody titer to S aureus were therefore the 2 most important factors associated with early implant failures and with a significant predictive ability. This indicates that immunologic factors are involved in osseointegration.

Progression rate of approximal carious lesions in Swedish teenagers and the correlation between caries experience and radiographic behavior. An analysis of the survival rate of approximal caries lesions

The objectives were to study the progression rate of approximal caries in 14 to 19-year-old adolescents and to assess the influence of experience of previous caries as a predictor of caries progression during the following years. The study population comprised 100 adolescents, all 19 years old, randomly selected. In all, there were 93 adolescents included in the study, for whom all sets of bitewing radiographs from 14 up to and including the age of 19 were assessed with respect to approximal caries. It could be noted that 32% of the adolescents had had at least one bitewing examination every year from 14 to 19 years of age. At the age of 14, 38% of the males and 24% of the females were radiographically without any sign of caries lesions (caries-free). The median survival time of initial caries in the present study was >5 years, while for manifest caries it was 3.2 years. It was found that 37% of the surfaces with manifest caries in males and 18% of the corresponding surfaces in females were restored within a year. The results show that experience of previous caries does not seem to be a significant indicator and does not influence when the next radiographic examination should be performed. It is thus concluded that individualized bitewing examination is the exception rather than the rule.

Five-year results with fixed complete-arch mandibular prostheses supported by 4 implants

This study examined whether it is possible to restore an edentulous mandible with a complete-arch fixed prosthesis retained by only 4 implants without decreasing the survival rate. One hundred nineteen patients received complete-arch mandibular prostheses retained by 4 implants. Most patients were followed for 3 years or more. All patients followed a routine protocol, including annual check-ups and regular radiographic examinations. Twenty-one patients dropped out. Radiographic measurements used the threads of the implants as a basis for comparison. No indication was found that the number of supporting implants could have influenced the observed frequency of technical and surgical complications. Three implants were lost, 2 after 1 year and 1 after 5 years. A statistically significant difference in bone loss between the mesial and distal implants was found. The number of fractured resin teeth in mandibular prostheses was higher when patients had an implant-supported prosthesis in the maxilla. The present study revealed an implant survival rate of 98.6% after 5 years. Therefore, it was concluded that there may not be a need for more than 4 implants to support a fixed mandibular prosthesis, when implants at least 10 mm long can be used.

Radiographic examinations as an aid to orthodontic diagnosis and treatment planning

Seventy consecutive adolescents were examined to evaluate radiographic examinations as an aid to orthodontic diagnosis and treatment planning in combination with clinical examination. The clinical examination included dental impressions and extra- and intraoral photographs. The radiographic examination comprised a panoramic radiograph, a lateral cephalogram and six intraoral anterior periapical radiographs. Initially, only records from the clinical examination were used for diagnosis and treatment planning. If required, the dentist could choose any of the radiographs to accomplish the task. The number of radiographs ordered, the sequence of ordering and any change in diagnosis and treatment plan caused by the radiographs were registered. In 29% of the cases the initial diagnosis, based on the clinical examination, study models and photographs, coincided with the final diagnosis. In 93% of all cases the initial treatment plan coincided with the final one. Although the panoramic examination was the most common choice, it had only a minor effect on diagnostic and treatment decisions, while the cephalometric examination had a major impact on the diagnosis. In most cases the clinical examination, supplemented with study models and photographs, can provide adequate information for orthodontic treatment planning. The result stresses the importance of using individually based selection criteria for radiographic examination in order to prevent radiographs being obtained routinely.

Proximal caries prevalence in 19-year-olds living in Sweden. A radiographic study in four counties

A random sample of all 19-year-olds in four counties in the middle of Sweden in 1994 constituted the group studied. The material consisted of posterior bitewing radiographs from 511 19-year-old patients. The purpose was to study the prevalence and distribution of initial and manifest caries. It was found that on the manifest caries level 56% of the subjects were 'free from caries', in good correspondence with the official epidemiological data from the Swedish National Board of Health and Welfare, but only 27% when initial caries was added. Initial caries lesions constituted 90% of all lesions. The distribution of caries was highly skewed on the manifest caries level whereas initial caries had a broader distribution. Thus, on the surface level 75% of the individuals had 16% of all manifest caries and restorations, and 33% of all initial caries. A high correlation was found between initial and manifest caries, besides increasing with the number of initial lesions. Thus, only 2.5% of individuals without initial caries had manifest caries, compared to 54% of individuals with more than eight affected surfaces. A correlation was also found between the prevalence of manifest caries and restoration. The prevalence of initial caries and its obvious significance for further caries development should be a reason for finding new strategies in caries prevention on a population basis.

Number and frequency of bitewing radiographs and assessment of approximal caries in 14-to-19-year-old Swedish adolescents

The hypothesis of the present study was that previous experience of caries may serve as an indicator for individualised bitewing examinations in 15-19-old adolescents. One hundred adolescents, all 19 years old, were randomly selected from the files of public dental clinics in the County of Orebro. For 93 adolescents the total number of radiographs were summed for every patient from the age of 3 to 19 by assessing the files of public dental clinics and by assessing the files of the dental radiology department. All sets of bitewing radiographs from 14 up to and including the age of 19 were assessed with respect to approximal caries. The average number of intraoral radiographs exposed in a patient from the age of 3 through 19 was 24.4. It was shown that 70 to 80% of 14-19-year-old-adolescents had had a bitewing examination every year. The decision to perform a bite-wing examination in a 15-year-old was significantly correlated to the number of surfaces with initial caries at the age of 14. In the other age groups, none of the investigated variables was found to be significantly correlated to the performance of radiographic examinations.

A logistic regression model for analyzing the relation between dentists' attitudes, behavior, and knowledge in oral radiology

The aim was to study the relation between risk attitude and knowledge in technical, patient-oriented, and organizationally related behavior within oral radiology. A questionnaire was mailed to 2000 randomly selected dentists listed in the register of the Swedish Dental Society, with a response rate of 69.3%. Regression analysis was used for analyzing the effects of the independent variables knowledge, risk attitude, continuing education in oral radiology, counties with specialists in oral radiology, type of practice, work experience, and sex on three categories of dependent variables: 1) technical behaviors: type of film, type of collimator, dose level, frequency of change of chemicals; 2) patient-oriented behaviors: use of patient protection barriers, strict indications for performing full-mouth X-ray examinations and bitewing radiography on new patients and recall patients; and 3) organizationally related behaviors: delegation of X-ray examinations to dental auxiliaries, influence on choice of collimator, influence on choice of film. Knowledge and education had strong direct effects for most of the dependent variables. The technical behaviors were mainly influenced by knowledge, education, and risk attitude, while organizationally related behaviors were influenced by type of practice and sex. The patient-oriented behaviors were influenced by a number of independent variables, such as education, type of practice, work experience, and sex. The present results indicate that both knowledge and the organizational context of dentists influence work.

A sensitometric comparison of four dental X-ray films and their diagnostic accuracy

OBJECTIVES

To compare the sensitometric properties and accuracy in the diagnosis of approximal caries of two E-speed (Ektaspeed Plus and EV 57) and two D-speed (Ultra-speed and DV 57) films.

METHODS

Speed and contrast for the four films were determined following 30 exposures for each film. Base plus fog density was measured on unexposed films and the increase was studied over a 18-month period. Seventy-five extracted premolars with known pathology were radiographed under standardized conditions and the radiographs assessed by nine observers for approximal caries. Receiver Operating Characteristic (ROC) curve technique was used to analyse the diagnostic accuracy.

RESULTS

The sensitometric analysis showed that the Ektaspeed Plus film had the highest speed of the four films. At a density of 1.0 it was 2.28 times faster than Ultra-speed. The contrast of Ektaspeed Plus was comparable with that of the other films and base plus fog density plateaued at 0.4 ten months before expiry date. There were no statistically significant differences in diagnostic accuracy for white spot lesions between the four films. For cavitations there was a significant difference between EV 57 and DV 57 and Ektaspeed Plus (P = 0.005) but not between Ultra-speed and Ektaspeed Plus nor between Ultra-speed and EV 57 and DV 57.

CONCLUSION

Ektaspeed Plus film is comparable with D-speed and a conventional E-speed film. Since it is at present the fastest available dental film it should be recommended for general dental practice.

Knowledge of oral radiology among Swedish dentists

OBJECTIVES

To develop a method of measuring Swedish dentists' knowledge of oral radiology and to relate the knowledge measure to a number of characteristics including risk attitude and use of low dose techniques.

METHODS

A questionnaire was mailed to 2000 randomly selected dentists listed in the register of the Swedish Dental Society, with a response rate of 69.2%. An index for measuring knowledge was constructed, based on the answers to the questions. The measure was cross-tabulated with a number of demographic variables.

RESULTS

Dentists with 5-25 years in practice had a higher level of knowledge than those with either fewer or more years in practice. Dentists working in the Public Dental Health Service had a higher level of knowledge compared with those in private practice. Specialists had a significantly higher level of knowledge compared with dentists who were not. Forty-two per cent of the dentists had not attended any course in oral radiology since graduation. Seventy-nine per cent of the dentists using a 'low' dose technique had a 'high' level of knowledge. The difference between dentists using a 'low-dose' and a 'high-dose' technique was statistically significant (P = 0.000). Dentists' attitude to risk is related to their knowledge. Seventy-one per cent of the dentists in counties with a specialist in oral radiology had a 'high level of knowledge' compared with 57% in those without.

CONCLUSIONS

It is possible to study the relationship between knowledge and demographic variables by a survey. Work experience and extended education affect dentists' knowledge. There is an association between knowledge, use of low-dose techniques and risk attitude.

Analysis of dentists' attitudes towards risks in oral radiology

OBJECTIVES

To develop a method of measuring dentists' attitudes towards radiation hazards and to describe their prevalence among Swedish general dental practitioners.

METHODS

A questionnaire was mailed to 2000 randomly selected dentists listed in the register of the Swedish Dental Society, with a response rate of 69.3%. An index for measurements of attitudes towards radiation hazards was constructed.

RESULTS

Those dentists who showed high concern at radiation hazards also restricted their use of X-ray examinations. Years in practice and attendance at extended (one-week) courses in oral radiology both had significant associations with risk attitude. Inexperienced dentists showed less concern for radiation hazards compared with those more experienced and were less scrupulous in their choice of radiographic procedures. Gender, working alone, in the public dental health services or in private practice had no significant association with attitude. Dentists who considered regulations laid down by the Swedish National Institute of Radiation Protection as wholly adequate had a high care attitude.

CONCLUSIONS

It is possible to study the relationship between attitudes and clinical behaviour by postal survey. Experience and continuing education affect dentists' attitudes towards risk and these attitudes in turn influence their clinical behaviour.

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.

Imaging of dental implants in severely resorbed maxillae using detailed narrow-beam radiography. A methodological study

OBJECTIVE

To evaluate the accuracy of the detailed narrow-beam (DNB) technique with the Scanora multimodal X-ray unit for the assessment of dental implants in severely resorbed maxillae as an alternative to conventional intra-oral radiography.

METHODS

The DNB technique was used in 15 consecutive patients with maxillary overdentures supported by implants in the canine regions. Both conventional intra-oral radiographs and DNB radiographs were also obtained for a further 15 consecutive patients with maxillary fixed prostheses on implants in the canine region. The marginal bone height was scored in relation to the threads on the implants.

RESULTS

Intra-observer agreement was 95%. There was an 84% agreement between the two radiographic methods: the difference was at most one thread and was not significant (p = 0.43).

CONCLUSIONS

The DNB technique is an accurate alternative when conventional intra-oral techniques cannot be used properly.

Marginal bone levels around maxillary implants supporting overdentures or fixed prostheses: a comparative study using detailed narrow-beam radiographs

The issue of changes in marginal bone levels around maxillary implants supporting overdentures has been studied very little because of radiographic difficulties when using conventional intraoral techniques. The present study used detailed narrow-beam radiography, which offers excellent opportunities to depict implants and the surrounding bone in severely resorbed maxillae. Marginal bone levels around implants in patients with overdentures were compared to corresponding bone levels in a group of matched control patients with fixed prostheses supported by osseointegrated implants. No statistically significant difference in marginal bone height was noted between the groups. This finding is not in accordance with an earlier report on continuous loss of marginal bone around many maxillary implants supporting overdentures.

Long-term changes in marginal and periapical periodontal conditions in patients with fixed prostheses: a radiographic study

Patients treated at a prosthodontic department during the years 1968-73 with fixed restorations (at least five units) were followed up in 1991-92. The aim of the present study was to compare marginal and periapical periodontal conditions on radiographs from 1968-73 and 1991-92 and relate the changes to the results of the prosthodontic treatment. In the group in which the restorations remained unchanged, 90% of the abutments that were not root filled and showed no periapical radiolucency when the restorations were placed, were still not root filled and showed no periapical radiolucency at the follow-up examination. The corresponding figure for the group in which the restorations had been replaced was only 69%. The changes in marginal bone levels also differed between the groups. In the group with remaining restorations, 66% of the surfaces were given the same score on a five-point scale both in 1968-73 and in 1991-92. In the other group, only 54% were scored the same on both occasions. Thus, unfavourable changes in both periapical and marginal periodontal conditions were associated with poorer results for the fixed restorations.

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)

Quality of intraoral radiographs used for prosthodontic treatment planning by general dentists in the public dental health service

The image quality of intraoral radiographs used by general public health dentists in prosthodontic treatment planning was evaluated on 763 radiographs from 72 consecutive cases. It was found that 349 (45.7%) radiographs were without any type error and that 414 radiographs had a total of 577 errors. The most common errors were projection and film density errors. The number of submitted radiographs ranged from 2 to 22. Three prosthodontists evaluated if the radiographs gave "satisfactory" or "not satisfactory" information for approval or not of the proposed treatment. Of the 72 cases did 34 (47%) not meet the criteria for acceptance. For the cases where the prosthodontists found the radiographic documentation "satisfactory", the mean number of periapical radiographs was 10.8, while for cases found "not satisfactory" the mean number was 7.1. This difference was found to be statistically significant (p < 0.01). It was shown that nearly every seventh tooth planned to be used as an abutment was radiographically not properly documented. The poor radiographic quality found in this study and in other similar studies should be taken into serious consideration, especially as prosthodontic treatment accounts for a substantial part of the total costs for dental insurance in Sweden.

Exposure parameters and their effects on diagnostic accuracy

A new method for analyzing diagnostic accuracy is introduced. A diagnostic accuracy curve may be obtained by plotting receiver operating characteristic analysis data, P(A), as a function of exposure. By means of diagnostic accuracy curves the effects on diagnostic accuracy of tube potential, exposure, and size of carious lesions was studied. It was found that the effect of the tube potential on the accuracy of caries diagnosis is negligible. About 25% of the variation in diagnostic accuracy depends on the exposure and about 80% on lesion depth. With the lesion depth constant, about 75% of the variance in diagnostic accuracy depended on observer performance. The peak of a diagnostic accuracy curve indicates optimum performance. This is found at an exposure that gives a radiographic density of about 1 in enamel and dentin although the tolerable exposure increases with increased lesion depth.

Effects of early placement of a single tooth implant. A case report

A single tooth implant was placed in a boy aged 12 years and 3 months. The case has been followed for more than 4.5 years. The fixture did not move together with the adjacent teeth as the maxillary growth went on. There was no "loss" of marginal bone on the side of one adjacent tooth where the distance between implant and tooth was appropriate. But a "loss" of marginal bone (measured from the cemento-enamel junction) was noted on the other adjacent tooth where the fixture had been placed too close to the tooth.

Image quality of intraoral radiographs used by general practitioners in prosthodontic treatment planning

A number of studies have shown a low standard of radiographic image quality in general dental practices. Image quality was evaluated on 1094 radiographs from 100 consecutive cases submitted to a dental insurance office for approval of planned prosthodontic treatment. It was found that only 404 radiographs were without any type of error and that 690 radiographs had a total of 959 errors. The most common errors were projection and film density errors. The number of submitted radiographs ranged from one to 40. Nearly every fourth tooth proposed for treatment was not properly documented. The results also showed that 43 of 100 cases did not meet the criteria for acceptance for assessment of the proposed prosthodontic treatment. This means that they were incompletely documented radiographically so that the treatment plan could not be evaluated. This study suggests that new or additional radiographic documentation ought to be requested frequently before approval of proposed treatment plans.

A comparison of Flow and Kodak dental X-ray films by means of perceptibility curves

Flow D- and E-speed group dental X-ray films (DX-58 and EX-58) have recently been introduced to the market. By means of perceptibility curves these films were compared with commonly used dental X-ray films (Kodak Ultraspeed and Ektaspeed). No major differences between the films were found with regard to contrast and the subjectively assessed number of small contrast differences. The exposure for EX-58 had to be lowered by 66% and Ektaspeed by 39% compared with Ultraspeed film to obtain the same density. DX-58 and Ultraspeed were of the same sensitivity.

A comparison of a new dental X-ray film, Agfa Gevaert Dentus M4, with Kodak Ektaspeed and Ultraspeed dental X-ray films

A new dental X-ray film, Agfa Gevaert Dentus M4, has recently been introduced. Its diagnostic ability for approximal caries and its sensitometric properties were compared with those of Kodak Ultraspeed and Ektaspeed dental X-ray films. Seven general practitioners and six consultants in oral radiology recorded both incipient and manifest approximal caries on radiographs of 100 extracted premolars. ROC-curve technique was used to analyse the results. A significant difference in diagnostic accuracy for both incipient and manifest caries was found between Ektaspeed and Dentus M4, but not between Ektaspeed and Ultraspeed or between Ultraspeed and Dentus M4. Ektaspeed had the highest diagnostic accuracy, 0.79, while Dentus M4 had the lowest, 0.72. No significant differences were found between the different films in their ability to separate sound from cavitated surfaces. The speed and contrast of the three dental X-ray films were measured according to ISO 3665. Dentus M4 film was found to be 1.8 times faster than Ektaspeed and 2.8 times faster than Ultraspeed. Dentus M4 had a lower film contrast than both Ultraspeed and Ektaspeed. Films of the three different types and with about the same expiry date were stored in seven different clinics. One film of each type was developed each month over a 16-month period under standardized conditions. Base plus fog density was measured. The Dentus M4 had a more rapid build up of fog compared to Ultraspeed and Ektaspeed films. We conclude that the new Dentus M4 film has a limited value in the diagnosis of incipient caries.

Assessment of a new processor containing a self-cleaning synthetic-web transport mechanism

The effect of two different types of automatic X-ray processing machines (a roller-based Pantomat P10 and the Velopex which has a novel web transport system) on the accuracy of radiographic diagnosis of caries in extracted premolars was evaluated. Seven observers graded the occurrence of caries and their findings were compared with actual prevalence of the disease. The accuracy was measured with the ROC technique. Kodak Ektaspeed dental X-ray film was used. The results showed no significant differences in diagnostic accuracy between the two developing machines. The Velopex gave a check pattern to the films, but it was not so marked as to have a major influence on diagnostic accuracy.

Influence of different developing solutions and developing times on radiographic caries diagnosis

One hundred extracted premolars were radiographed under standardized conditions with D- and E-speed films. The films were developed with conventional and rapid processors using varying developing times. The influence of different developers and developing times on the diagnostic accuracy of radiographic caries diagnosis was evaluated with the aid of ROC technique. Rapid processing using the developing time recommended by the manufacturer led to a lower density and contrast compared with the conventional developer. Underdeveloped films using the rapid processors resulted in an unacceptable low level of diagnostic accuracy, but otherwise it was the same for all developers, developing times and both types of film.

Influence of film fog on radiographic caries diagnosis

Increasing film speed may potentially jeopardize diagnostic quality because of a more rapid build up of fog and an ensuing decrease in image contrast. A standardized amount of fog was simulated by pre-exposing E-speed dental films before use to obtain images of extracted teeth with and without approximal caries. Three experiments were performed. In the first, no effort was made to compensate for the increased density caused by fog. In the other two, density was kept constant by reducing exposure and developing time respectively. Nine dentists recorded the presence and absence of caries using a rating scale to indicate diagnostic confidence. As a measure of diagnostic accuracy, the area under the binormal ROC curve was used and the values averaged across observers. The results showed that fog, up to a level of base plus fog of 0.6 optical density units, had no influence on the diagnostic accuracy in the absence of any compensation. When exposure was lowered to compensate for the increased density, significantly lower diagnostic accuracy was found. On the other hand, when developing time was decreased, no significant difference was found. Observers ranked radiographs with higher levels of fog as being of lower quality. However, no significant correlation was found between subjective ranking of image quality and diagnostic accuracy obtained from the same radiographs. It is concluded that relatively high levels of fog do not exert a negative influence on approximal caries diagnosis and no attempt should therefore be made to compensate for the increased density.

Accuracy of radiographic caries diagnosis using different X-ray generators

Dental X-ray machines utilizing five different combinations of X-ray generators and tube voltages (Philips Oralix 65 kV, Siemens Heliodent EC 60 kV, Siemens Heliodent 70 kV, Soredex Minray DC 60 kV and Soredex Minray DC 70 kV) were compared with respect to the accuracy of radiographic diagnosis of proximal caries. Nine observers diagnosed proximal caries in radiographs of extracted premolars. The findings of the observers were compared to the actual presence or absence of caries. The ROC-curve technique was used to evaluate differences in diagnostic accuracy between the X-ray machines. The results showed small differences in diagnostic accuracy between the different X-ray generators but they proved to be statistically non-significant.

Comparison of solutions for TM-polarized nonlinear guided waves

We show that physically realistic solutions for nonlinear TM waves guided by thin dielectric films are obtained in the uniaxial approximation for a dielectric constant proportional to the square of the normal-field component and not of the parallel-field component as assumed previously.

Perceptual, motor and attentional deficits in seven-year-old children: neurological and neurodevelopmental aspects

This study presents the results of neurological assessments of a representative sample of seven-year-old Swedish children with perceptual, motor and attentional deficits and their controls (N = 141). Among those children diagnosed as suffering from minimal brain dysfunction (MBD), the majority showed neurodevelopmental deviations indicative of the "clumsy child syndrome'. However, 20 per cent had slight signs of choreoathetosis, diparesis, hemiparesis or ataxia. Other associated neurodevelopmental deviations are considered. The correlation between neurological findings and background factors is discussed: the MBD group had higher scores for various "organic' background factors than the comparison children, and the children with neurological syndromes had somewhat higher scores than the remaining children with MBD. The difficulties in distinguishing MBD from mental retardation, cerebral palsy and childhood psychoses is clearly illustrated. Long-term follow-up will indicate the prognostic significance of these findings.

Mental retardation in Swedish urban children: some epidemiological considerations

The total population of children born in 1971 and living in Gothenburg, Sweden, by the end of 1977 was screened in order to estimate prevalence figures for various neurodevelopmental disorders. Ninety-four percent of all children assessed attended public preschools. Questionnaires aimed at detecting perceptual, conceptual, motor, and attentional deficits were completed by preschool teachers for 72% of children in these schools. Samples of children with and without problems on the questionnaire were given neuropsychiatric examinations. National registers were searched to identify mentally retarded children not in public preschools. The total population frequency figure for unequivocal mental retardation was almost 1% with an additional 1% of the total population deemed to be of borderline intelligence.

Perceptual, motor and attentional deficits in six-year-old children. Epidemiological aspects

A total population study of 4797 six-year-old children attending the public preschools in the city of Göteborg (Gothenburg) has been carried out. A questionnaire with 34 questions about MBD-related problems was distributed to all pre-school teachers. Three thousand four hundred and forty-eight questionnaires were completed. Factor analysis of the questionnaire and empirical results from a pilot study provided the basis for selecting for further study children with pre-school signs and symptoms suggestive of MBD. Neurological, psychiatric and psychological assessment of 82 children with, and 59 children without, pre-school symptoms of MBD revealed that in the index groups 41% of the children, and in the control group 3% of the children, had MBD. Extrapolation procedures gave a total population frequency of 1.2% with severe MBD and a further 5.9% with mild-moderate MBD. A very large questionnaire refusal rate (28%) is discussed. The relevance of the calculated frequency figures, especially as regards the mild-moderate MBD category, cannot be properly evaluated until long-term follow-up has been completed.

The effects of a combined alpha- and beta-blocking drug, labetalol, on some aspects of platelet function

The effects of the combined alpha- and beta-adrenoreceptor blocking agent labetalol on human blood platelets as estimated by platelet aggregation, platelet count, bleeding time and platelet factor 3 activity were studied in 5 patients. The drug reduced adrenaline-induced platelet aggregation in vitro. However, it did not influence the above platelet function test in therapeutic plasma concentrations in vivo.