105 research outputs found
Evaluation of Panoramic Radiographs in Relation to the Mandibular Third Molar and to Incidental Findings in an Adult Population
Objectivesâ
The aim was to evaluate the characteristics of the mandibular third molars, especially in relation to the inferior alveolar nerve. Further aims were to investigate incidental findings in panoramic radiographs in an adult population, and to investigate image quality related to patient positioning.
Materials and Methodsâ
From a previous study with 451 randomly selected adult participants who lived in Sweden, 442 panoramic radiographs from four dental public health clinics were used. The third molarsâ characteristics and relation to inferior alveolar nerve were evaluated. Incidental findings and patient positioning were recorded.
Statistical Analysisâ
Frequency analysis was used to investigate the occurrence of all findings and their possible interconnections. Whether the patientsâ age or gender had an impact or not was also analyzed.
Resultsâ
The third molars were erupted in vertical position among 73% regardless of age. When retained or semi-retained, they were most commonly in mesioangular positions. The inferior alveolar nerve was located inferior to the roots in 52%, whereas an overlapped position was most common if the third molar was retained (90%), semi-retained (83%) or the age was less than 30 years (66%). Common incidental findings were apical radiolucencies, idiopathic osteosclerosis, and tooth fragments. Suboptimal patient positioning was found in one-third of the radiographs.
Conclusionsâ
Panoramic radiography is a useful method to evaluate third molar prior to surgical removal and may be the only image required. Most incidental findings on panoramic radiographs does not seem to require any further odontological management.publishedVersio
The effect of rapid maxillary expansion on the upper airwayâs aerodynamic characteristics
Background
The effect of rapid maxillary expansion (RME) on the upper airway (UA) has been studied earlier but without a consistent conclusion. This study aims to evaluate the outcome of RME on the UA function in terms of aerodynamic characteristics by applying a computational fluid dynamics (CFD) simulation.
Methods
This retrospective cohort study consists of seventeen cases with two consecutive CBCT scans obtained before (T0) and after (T1) RME. Patients were divided into two groups with respect to patency of the nasopharyngeal airway as expressed in the adenoidal nasopharyngeal ratio (AN): group 1 was comprised of patients with an AN ratioâ<â0.6 and group 2 encompassing those with an AN ratioââ„â0.6. CFD simulation at inspiration and expiration were performed based on the three-dimensional (3D) models of the UA segmented from the CBCT images. The aerodynamic characteristics in terms of pressure drop (ÎP), maximum midsagittal velocity (Vms), and maximum wall shear stress (Pws) were compared by paired t-test and Wilcoxon test according to the normality test at T0 and T1.
Results
The aerodynamic characteristics in UA revealed no statistically significant difference after RME. The maximum Vms (m/s) decreased from 2.79 to 2.28 at expiration after RME (Pâ=â0.057).
Conclusion
The aerodynamic characteristics were not significantly changed after RME. Further CFD studies with more cases are warranted.publishedVersio
The effect of aging on luminance of standard liquid crystal display (LCD) monitors
Abstract
OBJECTIVES: The aim of this study was to evaluate the luminance level of monitors as a function of the burning time of the lamp in the monitor and further to evaluate if different areas of the monitor varied in luminance levels at a specific time.
MATERIAL AND METHODS: Nine standard liquid crystal display (LCD) monitor models, in total 180 monitors, were evaluated. The monitors' maximal luminance levels were measured, and the burning times of the lamps were noted. The estimated function between burning time and luminance was calculated. On 11 monitors, 9 areas distributed over the full screen were measured to evaluate the extent to which different areas had different luminance levels.
RESULTS: Over time, the luminance decreased in all monitor models. No difference was found among the monitor models in how rapidly the luminance levels decreased. Different luminance values were found for different areas on the monitors, but no area deteriorated faster than another.
CONCLUSIONS: Standard liquid crystal display monitors undergo gradual deteriorations in luminance levels over time, and these deteriorations are correlated with the time that the monitors have been switched on. The degradation in luminance is similar over all areas of the monitors
Exotic, Eccentric Japan : Representation of Japan in the travel magazine Vagabond in 1990 and 2010
Syftet med denna studie Ă€r att undersöka hur Japan framstĂ€lls i svenska resereportage och huruvida framstĂ€llningssĂ€ttet har förĂ€ndrats över tid. För att besvara dessa frĂ„gor har jag valt ut tvĂ„ resereportage om Japan ur resemagasinet Vagabond, ett frĂ„n 1990 och ett frĂ„n 2010, och utfört en sprĂ„kvetenskaplig textanalys utifrĂ„n Hellspong och Ledins textanalysmodell. Jag fokuserar frĂ€mst pĂ„ den ideationella aspekten av textstrukturen, men Ă€ven andra aspekter, sĂ„som textens kontext och interpersonella struktur, kompletterar analysen. Min första slutsats Ă€r att reportagen som jag undersökt framstĂ€ller Japan som ett annorlunda, otillgĂ€ngligt och obegripligt land. Detta gĂ€ller framför allt reportaget frĂ„n 1990, men Ă€ven det frĂ„n 2010 om Ă€n i mindre utstrĂ€ckning. Detta görs pĂ„ flera sĂ€tt: framhĂ€vningen av ett motsatsförhĂ„llande mellan svenskar och japaner, framhĂ€vningen av otillgĂ€nglighet och obegriplighet genom beskrivningen av skribenten som maktlös nybörjare, kollektiva uttryck sĂ„som âjapanerâ som förstĂ€rker intrycket av en anonym folkmassa, ett utifrĂ„nperspektiv, osv. PĂ„ sĂ„ sĂ€tt framstĂ„r Japan som motsatsen till den ânormalaâ vĂ€rld som âvi svenskarâ lever i. Det hĂ€r motsatstĂ€nkandet Ă€r förknippat med postkolonialism och orientalism. Min andra slutsats Ă€r att framstĂ€llningen av Japan har blivit mer nyanserad i reportaget frĂ„n 2010, jĂ€mfört med det frĂ„n 1990. Oppositionen mellan âviâ och âdemâ Ă€r svagare; vĂ€rdeord och kollektiva uttryck Ă€r mer sĂ€llsynta; intrycket av otillgĂ€nglighet och obegriplighet har försvagats i och med att skribenternas nybörjarintryck har minskat
Quality Aspects of Digital Radiography in General Dental Practice
POPULĂRVETENSKAPLIG SAMMANFATTNING
Det övergripande syftet med denna avhandling var att klargöra hur digital röntgenteknik anvÀnds hos allmÀntandlÀkaren och framför allt har syftet varit att undersöka kvaliteten hos röntgenbilderna och hur den skulle kunna förbÀttras. I det första arbetet studerades digitala röntgenbilder som var inskickade i samband med förhandsprövningar till FörsÀkringskassan. Dessa var signifikant sÀmre nÀr det gÀllde bildkvalitet Àn röntgenbilder tagna med film. DÄ riktades uppmÀrksamheten pÄ vad som kunde vara problemet och en enkÀt skickades ut till samtliga tandlÀkare i SkÄne som enligt ett brev hade svarat att man arbetade med digital röntgenteknik (n=139). De viktigaste fynden i enkÀten var att ca 30 % av tandlÀkarna hade problem med den digitala detektorn och programmen. 20 % hade problem med datorerna. Enbart 40 % av tandlÀkarna gjorde nÄgon form av kvalitetskontroll.
Som en följd av enkÀtsvaren frÄn tandlÀkarna besöktes 19 slumpmÀssigt utvalda tandlÀkare som arbetade med digital röntgenteknik, inom bÄde folktandvÄrden och privattandvÄrden. DÀr fann vi att bakgrundsbelysningen hade stor betydelse för möjligheten att urskilja lÄgkontrastobjekt vilket Àr likvÀrdigt med kariesskador. Dessutom visade det sig att monitorn har stor betydelse för bildkvaliteten. Det finns möjlighet att stÀlla in monitorn med hÀnsyn till parametrarna kontrast och ljusstyrka. Dessa visade sig vara mycket viktiga nÀr det gÀller att optimera det digitala systemet. Dagens bildbehandlingsprogram har mÄnga möjligheter till justering av bilder. TandlÀkarna Àndrade, om nÄgot, ljus och kontrast. Det fanns mÄnga och stora variationer mellan de besökta klinikerna nÀr det gÀllde bildkvalitet och hur man arbetade med digital röntgenteknik.
I det sista arbetet undersöktes hur stor betydelse en riktigt instÀlld monitor och belysningen har nÀr man diagnostiserar karies. Studien gjordes med hjÀlp av extraherade tÀnder som röntgenundersöktes och granskades av sju tandlÀkare. Fynden visade att bakgrundbelysningen i rummet har stor betydelse för möjligheten att diagnostisera kariesskador. Diagnostiken blev bÀttre nÀr granskningen skedde i dÀmpad belysning och nÀr monitorns ljusstyrka och kontrast var rÀtt justerad.
Sammanfattningsvis sÄ gÀller det att sÀkerstÀlla bildkvaliteten pÄ digitala röntgenbilder. Det krÀvs en omfattande utbildning nÀr man ska börja arbeta med en helt ny teknik. Det mÄste finnas utrymme för en inkörningsperiod och en vilja till att lÀra sig den nya tekniken. Den digitala röntgentekniken pÄverkas av mÄnga fler faktorer Àn traditionell filmteknik nÀr gÀller den slutliga röntgenbildens kvalitet.ABSTRACT
The number of dentists who have converted from conventional film radiography to digital radiography continues to grow. A digital system has numerous advantages, but there are also many new aspects to consider. The overall aim of this thesis was to study how digital radiography was used in general dental practices. The specific aims were to study how different factors affected image quality.
To determine whether there were any differences in image quality between conventional film radiographs and digital radiographs, 4863 images (540 cases) were evaluated. The cases had been sent to the Swedish Dental Insurance Office for prior treatment approval. The image quality of digital radiographs was found to be significantly lower than that of film radiographs. This result led to a questionnaire study of dentists experienced in digital radiography. In 2003, a questionnaire was sent to the 139 general practice dentists who worked with digital radiography in SkÄne, Sweden; the response rate was 94%. Many general practice dentists had experienced several problems (65%), and less than half of the digital systems (40%) underwent some kind of quality control.
One of the weaker links in the technical chain of digital radiography appeared to be the monitor. A field study to 19 dentists at their clinics found that the brightness and contrast settings of the monitors had to be adjusted to obtain the subjectively best image quality. The ambient light in the evaluation room was also found to affect the diagnostic outcome of low-contrast patterns in radiographs.
To evaluate the effects of ambient light and technical adjustments of the monitor, a study using standardised set-ups was designed. Seven observers evaluated radiographs of 100 extracted human teeth for approximal caries under five different combinations of brightness and contrast settings on two different occasions with high and low ambient light levels in the evaluation room. The ability to diagnose carious lesions was found to be significantly better in a room with lower ambient light and on a monitor with well-adjusted brightness and contrast values than in a room with bright light and on an unadjusted monitor.
In conclusion, many problems with dental digital radiography were identified. Knowledge of digital techniques and how to optimise each link in the system to maintain high radiographic quality at all times must be improved
Exotic, Eccentric Japan : Representation of Japan in the travel magazine Vagabond in 1990 and 2010
Syftet med denna studie Ă€r att undersöka hur Japan framstĂ€lls i svenska resereportage och huruvida framstĂ€llningssĂ€ttet har förĂ€ndrats över tid. För att besvara dessa frĂ„gor har jag valt ut tvĂ„ resereportage om Japan ur resemagasinet Vagabond, ett frĂ„n 1990 och ett frĂ„n 2010, och utfört en sprĂ„kvetenskaplig textanalys utifrĂ„n Hellspong och Ledins textanalysmodell. Jag fokuserar frĂ€mst pĂ„ den ideationella aspekten av textstrukturen, men Ă€ven andra aspekter, sĂ„som textens kontext och interpersonella struktur, kompletterar analysen. Min första slutsats Ă€r att reportagen som jag undersökt framstĂ€ller Japan som ett annorlunda, otillgĂ€ngligt och obegripligt land. Detta gĂ€ller framför allt reportaget frĂ„n 1990, men Ă€ven det frĂ„n 2010 om Ă€n i mindre utstrĂ€ckning. Detta görs pĂ„ flera sĂ€tt: framhĂ€vningen av ett motsatsförhĂ„llande mellan svenskar och japaner, framhĂ€vningen av otillgĂ€nglighet och obegriplighet genom beskrivningen av skribenten som maktlös nybörjare, kollektiva uttryck sĂ„som âjapanerâ som förstĂ€rker intrycket av en anonym folkmassa, ett utifrĂ„nperspektiv, osv. PĂ„ sĂ„ sĂ€tt framstĂ„r Japan som motsatsen till den ânormalaâ vĂ€rld som âvi svenskarâ lever i. Det hĂ€r motsatstĂ€nkandet Ă€r förknippat med postkolonialism och orientalism. Min andra slutsats Ă€r att framstĂ€llningen av Japan har blivit mer nyanserad i reportaget frĂ„n 2010, jĂ€mfört med det frĂ„n 1990. Oppositionen mellan âviâ och âdemâ Ă€r svagare; vĂ€rdeord och kollektiva uttryck Ă€r mer sĂ€llsynta; intrycket av otillgĂ€nglighet och obegriplighet har försvagats i och med att skribenternas nybörjarintryck har minskat
Effect of two X-ray tube voltages on detection of approximal caries in digital radiographs. An in vitro study
This study evaluated the effect of two different tube voltages on clinicians' ability to diagnose approximal carious lesions in digital radiographs. One hundred extracted teeth were radiographed twice at two voltage settings, 60 and 70 kV, using a standardized procedure. Seven observers evaluated the radiographs on a standard color monitor pre-calibrated according to DICOM part 14. Evaluations were made at ambient light levels below 50 lx. All observations were analyzed with receiver operating characteristic curves. A histological examination of the teeth served as the criterion standard. A paired t test compared the effects of the two voltages. The significance level was set to p < 0.05. Weighted kappa statistics estimated intra-observer agreement. No significant difference in accuracy of approximal carious lesion diagnosis was found between the two voltage settings. But five observers rated dentin lesions on radiographs exposed at 70 kV better than on radiographs exposed at 60 kV. Intra-observer agreement differed from fair to moderate. There was no significant difference in accuracy of approximal carious lesion diagnosis between digital radiographs exposed with 60 or 70 kV
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