Swedish dental journal. Supplement最新文献

Purpose: The aims of this thesis were: 1. To study the effect of water and pH on composite resin materials in vitro by assessing sorption, solubility, monomers eluted and flexural properties. 2. To study adverse effects on the skin in dentists possibly caused by acrylic resin-based materials.

Materials and methods: Proprietary composite resin materials were used for the in vitro experiments. The tests were performed according to the ISO 4049 (1988) with the exception of McIlvaine's solution used in Study II and the storage times. The analysis of eluted monomers was performed using HPLC. The flexural properties were tested in a three-point bending equipment. The secant modulus and deflection at break were calculated for description of the viscoelastic behaviour of the material tested. To study the adverse effects on skin in dentists, a questionnaire was sent to 3500 randomly selected Swedish dentists. A response rate of 88% was achieved and the data were statistically analysed and compared with the results of two studies on skin symptoms among the general Swedish population. Dentists living in the three main cities in Sweden who had experienced hand eczema during the last 12 months were invited to a clinical examination in which a patch test was included.

Results: A wide range in sorption and solubility over the test period was found, with low sorption values observed for materials containing hydrophobic matrix monomers. A maximum concentration of monomers eluted was found after 7 days of storage, and TEGDMA was the main monomer released. pH affected the sorption and solubility behaviour for two of the three materials tested. The flexural strength and modulus of the composite resin material were lowered after water storage and the secant modulus and deflection at break could describe the viscoelastic behaviour. The prevalence of dry skin and hand eczema was high in dentists compared to two age-matched general population samples investigated using identical questions. The most important predictor for adult hand eczema was found to be childhood eczema. At the clinical examination, irritant contact dermatitis was the predominant diagnosis. Seven per cent reported skin symptoms when working with acrylic resin-based material but the true prevalence of hand eczema caused by acrylates was below 1%. Contact allergy was diagnosed, however, in 50% of the dentists, mainly due to other allergens such as nickel, perfumes or rubber chemicals.

Conclusions: The matrix composition was shown to be important for the sorption and solubility behaviour of the composite resin materials tested and a maximum release of monomers occurred after 7 days of storage. pH affected the water sorption and solubility behaviour. Calculation of the secant modulus and the deflection at break allowed the plasticising effect of water on composite resin material to be observed. The prevalence of hand

There were three general aims of the thesis. To investigate 1) the fulfillment of the judiciary Swedish goal of good dental care on equal conditions in an adult population born 1942 in two Swedish counties in 1992. Both selfrated oral health and clinical observations indicated good oral health in the study population. Full social equality of dental care was not attained, but the social gradient was modest. 2) To find models for risk prediction on population level for oral health, expressed as number of remaining teeth, as caries and as periodontitis. Relatively efficient such models were constructed, with the lowest efficiency for periodontitis indicators. Oral health and disease were found to be qualitatively different. Still, use of tobacco was a consistent risk factor for both poor health and presence of disease. 3) To investigate if questionnaires can be used to monitor oral health, disease and illness. It was found that this is the case on population level, but also that questionnaire surveys cannot wholly replace clinical studies, especially regarding periodontal disease. For number of remaining teeth and frequency of removable dentures, the questionnaire methodology is appropriate for monitoring in this type of population, which has been utilized by setting the present study as a baseline for ongoing longitudinal studies relying on survey methodology.

The general aim of the study was to evaluate and compare different solid-state and photo-stimulable phosphor systems for digital intra-oral radiography and to compare different generations of some of the systems. The evaluations concerned physical and psychophysical performance, subjective image quality and the influence of image processing. Physical performance was tested by means of large area transfer characteristics, noise, contrast, and modulation transfer function. For the physical performance it was found that grey level values in images from solid-state systems decreased faster with increasing exposure than in images from photo-stimulable phosphor systems. Noise increased with increased exposure for both solid-state and photo-stimulable phosphor systems. Solid-state systems reached their highest contrast index at lower doses than the photo-stimulable phosphor systems. Solid-state systems had better resolving power due to higher contrast and smaller pixel sizes than the PSP systems. The resolving power of the photo-stimulable phosphor systems improved when the images were enhanced. Psychophysical tests were performed by determining the sensitivity of the systems for detecting small mass differences in test objects. It was found that when contrast enhancement were applied lower exposures could be used to detect low contrast objects in images from both solid-state and photo-stimulable phosphor systems. Blooming effects deteriorated images from solid-state systems at lower doses than burn-out effects deteriorated conventional radiographs or images from a photo-stimulable phosphor system. Some improvement in physical and psychophysical performance could be seen in the new generation of solid-state systems. Subjective image quality was tested by visual grading analysis in which observers graded the visibility of structures important for the diagnosis of common dental diseases. All systems produced diagnostically acceptable image quality but the photo-stimulable phosphor systems over a much wider exposure range than the solid-state systems. Histogram equalization did not improve image quality. A common diagnostic task; measurement of marginal bone level around implants, was used to study the influence of image processing. Radiographic measurements of bone height around implants in images from a photo-stimulable phosphor system was as accurate and precise as film images. Image processing was found to be task dependent. For a specific task, related to marginal bone height measurements around implants, a strong edge enhancement algorithm was found to be best.

Absorbed doses to radiosensitive organs in the head and neck from pre-implant conventional hypocycloidal, conventional spiral and computed tomography (CT) were measured with thermoluminescent dosimeters in an anthropomorphic phantom head. From conventional tomography organ doses, except to the major salivary glands, were below 0.2 mGy. They were considerably higher with CT than conventional tomography. Tomographic images of posterior lower jaw regions were evaluated regarding measurement reliability in conventional spiral tomograms. Observers measured the distance marginal crest-mandibular canal, marked their measuring points and estimated the length of an intended Brånemark implant. The variability between observers, mainly due to the intra-observer variation, decreased with multiple readings and optimized image quality. The suggested implant length was the same as the one inserted in 70% of the cases. Tomographic images from mandibular body segments were used to test the influence of radiation exposure and scanning mode on image quality in CT and compare the quality of the CT images with that in conventional spiral tomograms. Mandibular canal and marginal bone crest visibility was unaffected by radiation dose in CT examinations. Differences among CT scanning modes and between CT and conventional spiral tomography were highly significant. Frontal CT scans or conventional spiral tomograms were preferred. In cross-sectional images of the posterior lower jaw image quality in conventional spiral and reformatted CT at 40 mAs and 80 mAs was compared. Observers graded the acceptability of images for implant planning and traced the contours of the mandibular body and canal. Conventional, spiral tomograms were subjectively preferred over reformatted CT images. Differences between CT images at different mAs settings were not statistically significant. The mandibular canal was more frequently untraceable in high-dose CT. The use of tomography for dental implant planning was studied by means of a survey among oral radiology clinics in Sweden and implantology clinics in other countries. It was used by 93.4% but varied markedly between and within anatomic regions. CT was used by 73%. Radiation doses varied considerably within and between different CT brands. The availability rather than the clinical need strongly influenced the choice of technique. From the point of view of radiation dose and information necessary for implant planning conventional spiral tomography is to be preferred over reformatted CT. However, when CT is the only technique at hand, it can be performed with a lower than standard mA-setting.

The relationship between orthodontic treatment and symptoms and signs of temporomandibular disorders (TMD) was studied prospectively and longitudinally in 65 adolescent girls with Class II malocclusion. The subjects received orthodontic fixed appliance treatment with the straight-wire technique combined with or without extractions and were examined for symptoms and signs of TMD before, during, after, and finally one year post-treatment. Both symptoms and signs of TMD showed considerable fluctuations over the three-year period within the individuals. The general tendency was a decreased prevalence of symptoms of TMD over the three years. The prevalence of pain on mandibular movement and tenderness to palpation of the masticatory muscles was significantly less common during and after orthodontic treatment than before. Clinically registered TMJ clicking increased slightly over the three year period. One orthodontic treatment effect when normalizing Class II malocclusions with fixed appliances was a decreased prevalence of functional occlusal interferences. We concluded that the orthodontic treatment either with or without tooth extractions did not increase the risk for TMD or worsen pre-existing signs of TMD. Subjects with Class II malocclusion and pre-treatment signs of TMD of muscular origin seemed rather to benefit functionally from orthodontic treatment in a three-year perspective.

The thesis included five methodological studies and one caries epidemiological investigation, the general aim being to study how to measure and report dental health, time for dental care, treatment panorama, and dental care outcomes, within a Public Dental Service organization. The specific aims were to monitor dental clinic activities using a time study method, to apply time study results of a dental health-related patient group system for the 3-19 year age groups, and to compare time study results with corresponding results from computerized systems used for reporting dental care. Other specific aims were to compare longitudinal caries index data results between cohort and cross-sectional samples, to analyse caries index for extreme caries groups among adolescents leaving organized dental care, and--using time series methods--to analyse dental health development of the 15-19 year age groups. Results from the time studies portrayed the dental clinic as a working unit, showed that reported values can represent dental care only for intervention procedures, and indicated that clinic patterns were not adapted to the health situation of the patient groups. Longitudinal cohort attempts gave different values from those of the cross-sectional year classes, which should be the primary focus when presenting caries index mean values in dental health reviews. Caries-free groups from 15 to 19 years of age seem to be stable in their caries development in about 60%-80% of cases; while the 20% groups with the highest index values accounted for about 80% of all approximal lesions. In times of major economic adjustment, dental health for adolescents in Göteborg was an example of sustainable dental health development. A model system for monitoring, analysing, and reporting dental health and dental care outcomes within a dental care-giving organization calls for several conditions, for example, a dental health-related patient group system, and a rationale for the choice of dental team models. These areas could be gathered into a system where contemporary socio-economic factors and dental research results interact with performed dental care, and also with different methods for reporting and evaluating dental health, dental care costs, and the demand for dental care competence.