Biomedical subjects

M Rohlin

Publications and source records attributed to M Rohlin.

At least 19 recordsLinked to original sources

PubMed1999

Effects of collimator size of a dental X-ray unit on image contrast.

OBJECTIVES: To examine the effect of collimator size on image contrast in dental radiography. METHODS: Two conventional collimators, one circular (53 mm in diameter) and one rectangular (35x45 mm2), were compared with a small rectangular collimator (26x39 mm2). Low-contrast and high-contrast resolution was assessed with the aid of contrast-detail and line-pair phantoms. RESULTS: Shallower holes were observed with the small rectangular collimator. Two-thirds of 17 observers assessing high-contrast resolution considered the small collimator to result in a clearer image than the conventional collimators. The same effect was demonstrated with the line-pair phantom and by microdensitometry. With the small collimator the energy imparted is estimated to be reduced by 54 and 36% compared with the conventional circular and rectangular collimators respectively. CONCLUSIONS: Decrease of the collimator size to fit the film size used for children will result in improved low-contrast and, under some conditions, improved high-contrast resolution. This improvement might have implications for caries diagnosis and monitoring.

Absorptiometry, Photon↗

PubMed1998

Intra-observer reliability regarding removal of asymptomatic third molars.

OBJECTIVE: To investigate reliability of practitioners' removal decisions and judgements of risk of pathology associated with asymptomatic third molars. SUBJECTS: 10 oral surgeons and 18 family dentists from South Wales with experience ranging from 5 to 28 years. METHOD: Participants were presented with periapical radiographs of 36 asymptomatic, mandibular third molars and were informed of the age and sex of the patients and the degree of eruption of the third molars. Participants were asked to assess, using visual analogue scales, the likelihood of future pathology if the third molars were left in situ and to indicate if they should be removed or not. To assess intra-observer reliability, the 36 cases were duplicated and presented to the participants on a different occasion, a month later. The same questions were asked as on the first occasion. RESULTS: Significant correlations (Pearsons correlation coefficients) were found between initial and repeat assessments of all measures but there was little agreement about the need for removal (Kappa values: 0.54 for oral surgeons and 0.41 for the family dentists). For every item studied, changes in position on the visual analogue scale of two-thirds or more of the total length occurred from the first to the second assessment. CONCLUSION: Treatment decisions about whether or not to remove asymptomatic third molars were not made on a rational basis. Since similar conclusions were recorded in a previous Swedish study, it is inferred that until further high quality evidence of disease prediction is published, decisions to remove third molars prophylactically cannot be made reliably.

Adult↗

PubMed1998

The Malmö model: a problem-based learning curriculum in undergraduate dental education.

A new undergraduate dental curriculum was introduced in Malmö in 1990 which is based on problem-based learning (PBL). The principles of PBL are strongly influenced by evidence from cognitive psychology and they form the educational strategy throughout the whole curriculum. Two further essential principles underpin the curriculum: a holistic attitude to patient care, and the promotion of oral health. Basic sciences and clinical dentistry are integrated within a structure based on oral conditions prevalent in the community. Students are encouraged to build their new knowledge, understanding and skills into the context of what they have already learned. This approach is facilitated by the presentation of conceptual models, one of which, The Oral Ecosystem is described in detail. The educational programme also gives students opportunities to learn in the clinical context from an early stage, and we endeavour to promote a scientific attitude from the very beginning of the programme. This paper describes the curriculum at three organisational levels (whole curriculum, single course, individual week).

Curriculum↗

PubMed1997

Trabecular bone pattern of the mandible. Comparison of panoramic radiography with computed tomography.

OBJECTIVES: To analyse the possible correlation between the trabecular bone pattern of the edentulous mandible visualized by panoramic radiography and the bone mineral density (BMD) measured by computed tomography (CT). METHODS: Panoramic radiography and CT were performed on 28 patients with edentulous mandibles. The trabecular bone pattern of 47 regions on the panoramic radiographs was classified into one of five grades. BMD was measured within circular regions of interest on the axial CT images in the corresponding trabecular area. The gradings were correlated with the CT values using one-way analysis of variance. RESULTS: There was a significant correlation between the grade of the trabecular bone pattern and the BMD (P < 0.0001). CONCLUSION: The proposed classification for the trabecular bone pattern on panoramic radiographs might be a useful aid for the evaluation of the edentulous mandible prior to implant placement.

Adult↗

PubMed1997

Observer agreement in the assessment of mandibular trabecular bone pattern from panoramic radiographs.

OBJECTIVES: To study the observer agreement in the assessment of trabecular pattern of the mandible from panoramic radiographs. METHODS: Seven observers were asked to classify the trabecular pattern of 100 edentulous regions of the mandible in 80 randomly selected panoramic radiographs into one of five grades with the aid of a written description and reference images. Intra- and interobserver agreement was calculated as overall agreement and Kappa index. RESULTS: The intra-observer agreement varied between 65% and 79%. The Kappa index for intra-observer agreement was moderate for three observers and substantial for four. For all seven observers, it varied according to the grade of trabecular bone pattern, but the majority deviated from each other by only one grade. CONCLUSION: The relatively high rates of observer agreement indicate that panoramic radiography can be used for the clinical assessment of the trabecular pattern of the mandible.

Adult↗

PubMed1997

Clinical and magnetic resonance imaging findings in temporomandibular joint disc displacement.

OBJECTIVES: To describe the clinical and MRI findings in patients with disc displacement of the temporomandibular joint. METHODS: Eighty-eight joints in 51 patients referred for suspected TMJ disc displacement were examined by MRI. Two oral radiologists assessed the images. The clinical findings were obtained by retrospective review of the patients' records. RESULTS: Clicking was the most common clinical finding, present in 47 joints. Pain was reported for only 30 joints. Anterior disc displacement with reduction was found in 39 joints, anterior disc displacement without reduction in 31 joints, compound dislocations (anterolateral or anteromedial) in 13 joints and sideways displacement in 5 joints respectively. In about one-fourth of the joints, MRI revealed abnormal configuration of both disc and condyle. The osseous changes were subtle. Only 9% of the joints exhibited an osteophyte. Joint effusion in either the upper or the lower joint compartment was found in 19 joints. Out of 14 patients with joint effusion, six patients complained of pain from the TMJ region. CONCLUSION: The most extensive soft and hard tissue changes were found in patients with anterior disc displacement without reduction. Pain was not a characteristic symptom for any type of disc displacement.

Adolescent↗

PubMed1997

Clinical guidelines and self-assessment in dental education.

This paper describes an educational programme where clinical guidelines are used in dental education and assesses the value of these guidelines as perceived by undergraduate students. It presents a comparison of students' own assessments of their performance with those of their instructors, according to such guidelines. The educational programme at the Faculty of Odontology, Lund University, is described through 3 main principles: problem-based learning, adoption of a holistic attitude to patient care and the promotion of oral health. The dental curriculum occupies 5 years comprising 10 semesters. 41, 5th semester students (16 male and 25 female) participated in the study. Students were introduced to guidelines in group discussions at the beginning of the semester. At the completion of a patient's planned course of treatment, the outcome was formally assessed both by students and clinical instructors. Performance was scored in various categories as "excellent", "acceptable" or "unacceptable" according to the standards defined. A total of 1373 scores were made by both students and instructors. 88% cent of students used the guidelines often or almost always and found them useful. Overall, no students received an "unacceptable" score and 40% of students achieved a score of "excellent". Female students tended towards a higher score, but this was not significant. Instructors' and students' scores agreed in almost 90% of instances. Students under-scored their performance more frequently than they over-scored it. It appears that the use of clinical guidelines may encourage an increased awareness of the decision-making processes involved in clinical practice, but it must be acknowledged that these guidelines are complex both in derivation and application.

Curriculum↗

PubMed1997

Bone histomorphometry using interactive image analysis. A methodological study with application on the human temporomandibular joint.

The aim was to develop a reproducible method for bone histomorphometry with the aid of a computerized image analysis program, and to examine the variation when assessing the total and the trabecular bone volume. Histologic sections of 18 temporomandibular joint autopsy specimens were read interactively using a cursor. The two parameters total bone volume and trabecular bone volume, of the condyle and the temporal component respectively, were estimated 2 x by 1 observer using 3 different threshold settings: an automatic, a semi-automatic and a manual technique. The threshold was based on the gray-scale distribution of the image. 2 observers read the same sections with the aid of the semi-automatic technique. The intra-observer variation expressed as coefficient of variation ranged between 1.9% and 7.1% for the different parameters, when the automatic threshold setting technique was employed, and between 2.8% and 8.7% with the semi-automatic technique. The manual technique resulted in a high intra-observer variation with a coefficient of variation between 5.2% and 19.9%. There was a systematic difference between the estimates of the 2 observers. In general, intra- and inter-observer variation was higher in the temporal component than in the condyle. The inter-section variation was moderate, the coefficient of variation ranging from 3.8% to 11.1%. The automatic and semi-automatic techniques resulted in comparable intra-observer variation, with a lower bias in the estimates of the semi-automatic technique. By letting one observer apply the semi-automatic technique, it was possible to achieve fast and reproducible analysis of the total and trabecular bone volume.

Aged↗

PubMed1997

Cartilage matrix macromolecules in lavage fluid of temporomandibular joints before and 6 months after diskectomy.

The purpose was to investigate if antigenic fragments of aggrecan and cartilage oligomeric matrix protein (COMP) are detectable by enzyme-linked immunosorbent assay in lavage fluids from the temporomandibular joint (TMJ) and to examine if the relative content of these cartilage markers changes during development of osteoarthrosis (OA) after diskectomy. Lavage fluid was obtained at surgery and 6 months postoperatively in 13 patients. Computed tomography or magnetic resonance imaging was without evidence of hard-tissue changes prior to surgery in all patients. In 9 of the patients, sufficient material for analysis was obtained at both examinations. Aggrecan and COMP were detectable in all but 2 fluids, in which the COMP levels were below detection limit. The aggrecan/COMP ratio increased in all 9 patients during the 6-month period, indicating increased release of aggrecan relative to COMP fragments. The changed aggrecan/COMP ratio possibly reflects increased cartilage turnover during development of OA. Changes compatible with OA were present on computed tomography in all cases at the 6-month follow-up. This study shows that the lavage procedure is feasible for obtaining synovial fluid from the TMJ for immunochemical analyses of tissue-derived macromolecules.

Adolescent↗

PubMed1997

Direct digital radiography for the detection of periapical bone lesions: a clinical study.

The aim was to compare the observer performance of direct digital radiography, with and without image processing, with that of conventional radiography, for the detection of periapical bone lesions. For 50 patients, a conventional periapical radiograph using E-speed film was taken. Then, a direct digital image of the same area was made. The images presenting the periapical bone tissue of 59 roots were assessed by seven observers using a 5-point confidence scale. The digital images were first presented as original images, with default contrast and brightness set by the computer system. Following this, the observers were allowed to use the processing facilities for greyscale treatment. The results for original and processed direct digital images and for conventional radiographs were compared by Receiver Operating Characteristic (ROC) analysis. The area under the ROC curve, calculated as P(A) value, was 0.88 for conventional film, 0.82 for original digital images and 0.78 for processed images. Corresponding Az values were slightly higher, 0.89, 0.84 and 0.81. Statistically significant differences between ROC areas calculated as P(A) values for the methods were found. Comparison between Az values showed no significant differences between conventional radiographs and original digital images, whereas the difference between Az values for original and processed digital images was still significant. It was concluded that conventional film radiography performed slightly better for the detection of periapical bone lesions than direct digital radiography and that image processing did not improve the observer performance.

Alveolar Bone Loss↗

PubMed1997

Mandibular third molars as mediated by three cues. Dentists' treatment decisions on asymptomatic molars compared with molars associated with pathologic conditions.

The aim was to study how three cues (patient's age and angular position and degree of impaction of the molar) were distributed among removed mandibular third molars associated with pathologic conditions and to compare these results with dentists' treatment decisions in another group of molars consisting of asymptomatic mandibular third molars, as mediated by the same cues. The overall agreement was fairly high between the dentists' treatment decisions and the removal rate among the molars subjected to removal. Thus, molars partially covered by soft tissue in patients aged 19 to 40 years had a high removal rate, and molars totally covered by bone tissue had the lowest removal rate in accordance with the dentists' treatment decisions. There were some exceptions. For example, molars partially covered by soft tissue in horizontal and mesioangular positions were rated higher by the dentists than the removal rates indicated. Distoangular molars in patients aged 26 to 40 years had the highest removal rate but a considerably lower order according to the dentists' decisions. Scientific evidence indicates that molars in mesioangular and horizontal positions present a low risk and molars in distoangular position present the highest risk of developing pathologic conditions, compared with other angular positions.

Adult↗

PubMed1997

Bone volume in human temporomandibular autopsy joints with and without erosive changes.

The aim was to compare the trabecular bone volume (TBV) and the total bone volume (TOBV) of human temporomandibular joints (TMJ) with erosive changes with those of joints without erosive changes. We examined 35 TMJ autopsy specimens from 19 individuals aged 66 88 years. Sagittal sections of the joints were analyzed microscopically for erosive hard-tissue changes. The TBV and the TOBV of the sections were assessed with the aid of computerized image analysis. A significant increase in trabecular and total bone volume was found in condyles with erosive changes (TBV = 21%, TOBV = 54%) as compared with condyles without erosive changes (TBV = 15%, TOBV = 40%). The trabecular bone volume of the temporal component was also increased (TBV = 24%) in joints with erosive changes in the condyle as compared with joints with unaffected condyles (TBV = 16%). The findings indicate that the relative bone mass may play a role in the development of erosive changes in the TMJ.

Age Factors↗

PubMed1997

Agreement between practitioners concerning removal of asymptomatic third molars.

OBJECTIVE: To investigate and compare agreement within two groups of dental practitioners, family dentists and oral surgeons, in their decisions regarding removal of asymptomatic mandibular third molars. SUBJECTS: Ten oral surgeons and 18 family dentists from South Wales with experience ranging from 5 to 28 years. METHODOLOGY: Participants were presented with periapical radiographs of 36 asymptomatic, mandibular third molars and were informed of the age and gender of the patients and the degree of eruption of the third molars. Participants were asked to indicate whether they thought that the third molar should be removed or not. The degree of agreement between participants was measured by kappa indices for multiple raters. RESULTS: The kappa indices were 0.14 for the oral surgeons and 0.09 for the family dentists, indicating poor agreement beyond chance. Although in most cases the participants decided not to remove the third molar, they did so inconsistently, that is, they did not make this decision on the same cases. There were also differences in the inclination of the participants to suggest removal of the 36 third molars. CONCLUSION: Poor inter-observer agreement suggested that treatment decisions regarding asymptomatic third molars are based more on subjective beliefs and habitual practices than on rational decision making.

Adult↗

PubMed1996

Assessment of the trabecular pattern before endosseous implant treatment: diagnostic outcome of periapical radiography in the mandible.

OBJECTIVES: To study the diagnostic outcome of periapical radiography in the assessment of the bone trabecular pattern of the mandible. STUDY DESIGN: Mandibular autopsy specimens were radiographed. Seven observers assessed the radiographs with the aid of a proposed classification with and without reference images and the classification presented by Lekholm and Zarb. Accuracy was estimated on the basis of morphometric measurements of trabecular bone volume. Observer agreement was calculated as the estimated probability of agreement between and within observers and as kappa index. RESULTS: With the classification proposed by us, the overall accuracy was 58% with and 50% without reference images. The accuracy for assessing dense trabeculation was higher (78%) than that for sparse trabeculation (28%). The accuracy of the proposed classification by Lekholm and Zarb was not possible to evaluate. The interobserver agreement varied between 49% and 64% and the intraobserver agreement between 75% and 86%. CONCLUSION: A new classification with reference images is recommended to assess the trabecular pattern in periapical radiographs before implant treatment.

Aged↗

PubMed1996

Diagnostic accuracy of direct digital dental radiography for the detection of periapical bone lesions: overall comparison between conventional and direct digital radiography.

OBJECTIVES: The diagnostic accuracy of direct digital radiography for the detection of small, experimentally made, periapical lesions was compared with that of E speed film. The high- and low-contrast resolutions of the imaging systems were also compared. STUDY DESIGN: The high-contrast resolution was evaluated with a line pair plate. The low-contrast resolution was determined with a contrast-detail plexiglass phantom. To evaluate the diagnostic accuracy, the periapical region of dry human mandibles was examined. Receiver operating characteristic based on the readings of seven observers were generated. RESULTS: The high-contrast resolution of the digital system was inferior, but the low-contrast resolution was comparable to that of E-speed film. For diagnostic accuracy no significant difference was seen between the areas under the receiver operating characteristic curves. CONCLUSIONS: The quality of the direct digital images is comparable to that of E-speed film for the detection of periapical bone lesions.

Alveolar Bone Loss↗

PubMed1996

Pathoses associated with mandibular third molars subjected to removal.

OBJECTIVES: To measure the prevalence of disease of mandibular third molars referred for removal and to estimate the risk for development of pathoses for two cues. STUDY DESIGN: A prospective cohort study on molars subjected to removal was performed. The prevalence of different diseases and the patient's age, angular position, and degree of impaction of the molars were registered. Odds ratio for molars with different positions and impaction states were estimated. RESULTS: Pericoronitis was found in 64% of cases, caries in the third molar in 31%, periodontitis in association with 8%, caries in the second molar in 5%, and root resorption of the second molar with 1% of the molars with pathoses. Odds ratio was highest for distoangular molars (5.8) and for molars partially covered by soft tissue (6.7). CONCLUSIONS: The odds ratio is about 22 and 34 times higher for molars partially covered by soft tissue than for molars completely covered by soft or bone tissue. For distoangular molars the odds ratio is 5 to 12 times higher than for molars in other positions.

Adolescent↗

PubMed1996

Concavity of the posterior surface of the temporomandibular condyle: clinical cases and autopsy correlation.

OBJECTIVES: To elucidate the significance of the radiographic finding of a concavity of the posterior surface of the temporomandibular condyle. METHODS: Three clinical cases with a concavity were followed up clinically and radiographically. A total of 39 temporomandibular joint (TMJ) autopsy specimens were examined by corrected sagittal tomography and seven condyles with a concavity of the posterior surface found. They were analysed microscopically together with three joints with a normal, rounded condyle. RESULTS: At follow-up tomography, two of the clinical cases revealed no change while the third patient had erosive changes after 7 months. The microscopic findings of the autopsy specimens varied. The articular cartilage in three of the seven joints with a concavity was similar to that in the normal condyles. The outer surface of the articular cartilage was sometimes uneven and the cartilage thickened, with an irregular junction between the articular cartilage and subchondral bone. In three joints the cartilage in the concavity had been replaced by granulation tissue. All seven joints had increased cellular activity in the concavity. CONCLUSIONS: The radiographic finding of a concavity in the posterior surface of the condyle is not specific. When small and well-defined it is indicative of remodelling and of osteoarthrosis when larger and with a diffuse outline.

Adult↗

PubMed1996

Evidence-based evaluation of three imaging methods for the temporomandibular disc.

OBJECTIVES: To review the literature and evaluate the evidence for the diagnostic outcome of arthrography, computed tomography (CT) and magnetic resonance imaging (MRI) in the assessment of temporomandibular joint (TMJ) disc position. METHODS: A literature search from 1978 to 1994 was conducted. Data on sensitivity, specificity, predictive values and likelihood ratios were collected and, if not available, calculated for each imaging method. Measures of observer performance were also recorded. RESULTS: In total, more than 400 publications were retrieved on imaging of TMJ disc position, 219 on arthrography, 99 on CT and 147 on MRI, with a marked decrease in recent years. The majority of the publications (54%) presented series of patients. The diagnostic outcome cold be obtained from only 7% of the studies and the observer performance from only two of these. Arthrography had the highest diagnostic outcome for the diagnosis of anterior disc position; sensitivity 0.90, specificity 0.80, positive predictive value 0.88 and negative predictive value 0.82. Corresponding figures for CT were 0.66, 0.68, 0.66 and 0.74 and for MRI 0.86, 0.63, 0.67 and 0.83. The diagnostic outcomes expressed as the likelihood ratios for positive test outcome were 4.5 for arthrography, 2.3 for MRI and 2.1 for CT. The outcomes in diagnosing sideways and rotational displacements were higher for MRI (sensitivity 0.81, specificity 0.87, positive predictive value 0.82, negative predictive value 0.88) than for arthrography (0.64, 0.83, 0.70, 0.79). The likelihood ratios were 6.2 for MRI and 3.8 for arthrography. The interobserver performance ranged between moderate to substantial for arthrography and was almost perfect for MRI. CONCLUSIONS: Based on current evidence on the diagnostic outcome, MRI seems to be the method of choice for diagnosing TMJ disc position. Arthrography has a higher diagnostic outcome for anterior disc position but the disadvantage of being an invasive method. We suggest that the quality of the evidence should be improved and that an analysis of the impact of the imaging methods on patient treatment should be performed.

Arthrography↗