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Biomedical subjects

M E Jensen

Publications and source records attributed to M E Jensen.

At least 19 recordsLinked to original sources
PubMed1992

An intra-oral single-section demineralization/remineralization model.

This paper reviews the use of our intra-oral crown single-section model for the evaluation of in situ demineralization and remineralization. The model uses normal, healthy adults who are in need of a gold crown. A slot is placed in the working crown which can hold 3-4 single sections. A typical experiment would use an enamel lesion, root lesion, and sound root section which are characterized with polarized light microscopy and/or microradiography prior to insertion in the crown. After the experimental regimen, the sections are removed and re-characterized for any changes. The model has been used to evaluate mineral changes from the use of fluoride dentifrices and rinses, chewing gum, and food sequencing. The advantages of the model system are the before-and-after measurements on the same section, a natural plaque formation, interaction with saliva, episodic demineralization and remineralization, no bulky appliances, and the use of reasonable time frames. This model, therefore, reduces the artificiality of the in situ study to a great extent and appears to be a useful predictor of demineralization/remineralization interactions.

Adult↗
PubMed1991

Association of vascular compression in trigeminal neuralgia versus other "facial pain syndromes" by magnetic resonance imaging.

Magnetic resonance imaging was performed in 13 patients with trigeminal neuralgia and 18 control patients with facial pain of other types. Among trigeminal neuralgia patients, eight (62%) had vessels seen abutting, or immediately adjacent to, the trigeminal nerve on the side of their symptoms. Only three control patients (17%) had such vessels. The proportion of patients having a trigeminal region vessel associated with their symptoms was significantly higher in patients with trigeminal neuralgia than in controls (p = 0.0086). These findings provide evidence supporting the theory that trigeminal neuralgia is associated with vascular compression of the fifth cranial nerve.

Constriction, Pathologic↗
PubMed1991

Fluoride-releasing core build-up materials and artificial caries.

UNLABELLED: This study examined the effect of fluoride-releasing core build-up materials upon both enamel and root demineralization in an artificial caries system. Thirty extracted human molars were randomly assigned to three treatment groups consisting of (1) conventional composite core build-up paste, (2) fluoridated core build-up paste and (3) glass cermet. Teeth were thermocycled 350 times between 5 degrees C and 55 degrees C using 30-second dwell times. Acid-resistant varnish was placed on the specimens to within 1 mm of the restoration and the teeth were subjected to an artificial-caries challenge at pH 4.2 for 72 hours. Teeth were then sectioned and the thin sections photographed using a polarized light microscope. Areas of the artificial-caries lesions were measured using a sonic digitizing pad. Mean lesion area (in arbitrary units from the digitizing pad) on enamel for Group 1 was 3.76 +/- 0.54; Group 2 was 2.53 +/- 1.17 and Group 3 was 2.32 +/- 0.68. Mean lesion area on root for Group 1 was 3.04 +/- 0.54; Group 2 was 2.34 +/- 0.58 and Group 3 was 2.51 +/- 0.53. ANOVA with Duncan's multiple range test of contrast indicates a significant difference (P less than 0.001) on both enamel (35 +/- 3%) and root (20 +/- 3%) between the non-fluoridated product and the two fluoridated products. There were no significant differences between Group 2 and 3. CLINICAL SIGNIFICANCE: This artificial caries study indicates that a fluoride-releasing core material may be of value in preventing demineralization of tooth structure adjacent to the restorative core material.

Analysis of Variance↗
PubMed1990

MRI of intracranial sinovenous thrombosis: the role of phase imaging.

Conventional spin-echo magnetic resonance (MR) imaging of venous thrombosis is complicated by the variable appearance produced by the stage of blood clot degradation and velocity of blood flow. Phase MR imaging is a simple method based primarily on whether protons are stationary or moving. A case of superior sagittal sinus thrombosis demonstrates the utility of phase imaging.

Adult↗
PubMed1990

Posterior composite Class II restorations: in vitro comparison of preparation designs and restoration techniques.

The aim of this study was to evaluate conservative preparation designs for the restoration of Class II lesions with posterior resin composite. Fourteen primary and 14 permanent molars were obtained. Conservative modified MO and DO preparations were placed in half the teeth; conventional MO and DO preparations were placed in the remaining teeth. Randomly, a glass-ionomer liner was placed over the exposed dentin in one preparation of each tooth, a calcium hydroxide liner was placed in the remaining preparations. Posterior resin composite was placed in all teeth, and the teeth were loaded with a 17-kg force. Teeth were thermocycled, stored in 37 degrees C water, then immersed in 50% silver nitrate solution and placed in developer. The teeth were sectioned and photographed. Microleakage was calculated according to the depth of dye penetration, on a 6-degree scale. Results demonstrated the conservative modified restorations and conventional restorations, when glass-ionomer liner was used, to have less marginal microleakage, in both primary and permanent teeth, than their calcium hydroxide counterparts.

Calcium Hydroxide↗
PubMed1990

MR imaging appearance of childhood adrenoleukodystrophy with auditory, visual, and motor pathway involvement.

Childhood adrenoleukodystrophy is an X chromosome-linked disorder characterized by progressive demyelination of cerebral white matter and adrenal insufficiency. Magnetic resonance (MR) imaging was performed in 15 patients with symptomatic disease and three with presymptomatic disease. MR imaging findings were abnormal only in symptomatic patients. Major sites of disease were the occipital, parietal, and temporal lobes, with all patients showing involvement of occipital lobes, optic radiations, and splenium of the corpus callosum. Follow-up images obtained in four patients demonstrated a posterior-to-anterior progression of disease. Correlation of results from MR imaging with those from evoked potential studies indicated that MR imaging was the method of choice for detecting demyelination of visual, auditory, and motor systems in adrenoleukodystrophy.

Adrenoleukodystrophy↗
PubMed1990

Perineural tumor extension through the foramen ovale: evaluation with MR imaging.

Perineural tumor extension is a form of metastatic disease in which primary tumors spread along neural pathways and gain access to non-contiguous regions. The treatment and prognosis are altered when perineural extension occurs. Awareness and proper evaluation are critical for the radiologist. The third (mandibular) division of the trigeminal nerve (V3), passing through the skull base via the foramen ovale, is a common route of perineural spread of head and neck lesions. Seven patients with perineural tumor involvement of the mandibular nerve were evaluated with magnetic resonance imaging with use of standard spin-echo pulse sequences emphasizing T1-weighted information. Three patients had adenoid cystic carcinoma, three had squamous cell carcinoma, and one had well-differentiated lymphocytic lymphoma of the orbit. MR imaging signs of perineural involvement included smooth thickening of V3, concentric expansion of the foramen ovale, replacement of the normal trigeminal cistern hypointensity by an isointense mass, lateral bulging of cavernous sinus dural membranes, and atrophy of masticator muscles.

Carcinoma, Adenoid Cystic↗
PubMed1990

Effects of a fluoride-releasing fissure sealant on artificial enamel caries.

This study examined the effect of a fluoride-releasing fissure sealant upon enamel demineralization in an artificial-caries system. Twenty extracted human molars were randomly assigned to two treatment groups consisting of (1) conventional fissure sealant and (2) fluoride-releasing sealant. Specimens were acid-etched, rinsed, dried, sealant applied, and photocured for 20 seconds. Teeth were thermocycled 500x between 5 degrees C and 55 degrees C using 1 minute dwell times. Acid-resistant varnish was placed on the specimens to within 1 mm of the sealant and the teeth were subjected to an artificial-caries challenge at pH 4.2 for 62 hours. Teeth were then sectioned and the thin-sections photographed using a polarizing-light microscope. Areas of the artificial-caries lesions and their depths were measured using a sonic-digitizing pad. Mean lesion depths (in arbitrary units from the digitizing pads) were 4.17 +/- 0.95 for Group 1 and 1.22 +/- 0.61 for Group 2. Mean areas were 17.26 +/- 7.32 for Group 1 and 3.12 +/- 2.59 for Group 2. Students' t-tests indicated statistically significant differences (P less than 0.001) between groups for both measures. This artificial-caries study indicates that a fluoride-releasing fissure sealant substantially reduces the amount of enamel demineralization adjacent to the material.

Dental Caries↗
PubMed1990

Effects of processed cheese on human plaque pH and demineralization and remineralization.

This two-part study was undertaken to examine the effects of processed cheese on human plaque pH and de- and remineralization of enamel and root lesions in a human in situ caries model system. In the first part of the study the selected processed cheese (Kraft American Singles Processed Cheese Food) was eaten alone and followed by a 10% sucrose rinse after the acidogenicity of the plaque was demonstrated. A 10% sucrose rinse alone resulted in a mean minimum pH of 4.26. The cheese alone showed a mean minimum pF of 6.32 and cheese followed by sucrose resulted in a mean minimum pH of 6.48. The plaque pH of cheese eaten alone stayed at pH above 5.7 (the "safe for teeth" level). Cheese consumption also prevented the acid challenge when followed by sucrose. The second part of the study utilized the thin-sections of artificially created caries-like lesions on enamel and root, and sound root sections. One-month periods were used in a cross-over design to examine the effect of eating the cheese q.i.d. Polarized light microscopy was used to determine changes in the size of lesion areas. The addition of the processed cheese to the diet resulted in statistically significant reductions in enamel lesion size as well as a reduction in progression of root lesions. Lesions created on the sound root surfaces were approximately one-third the size of those created during the control period. This study indicates that processed cheese is hypoacidogenic, anti-acidogenic, and prevents demineralization as well as enhances remineralization.

Adult↗
PubMed1990

Artificial root caries in amalgam restorations: effect of light-cured fluoride releasing liners.

The purpose of this study was to examine artificial root caries when light-cured fluoride releasing liners were placed under amalgam restorations. Class V preparations in extracted third molars were used with gingival margins on root surfaces. Ten restorations were used for each of the following groups: 1) Amalgam alone; 2) Two layers of copal varnish and amalgam; 3) Vitrabond, amalgam; 4) Timeline, amalgam; 5) XR Ionomer, amalgam. The teeth were thermocycled and artificial caries were created using a liquid system acidified to pH 4.20 containing 2.2 mM calcium and phosphate but without fluoride. The teeth were sectioned, polished and photographed using polarized light. Areas of recurrent caries were measured using a sonic digitizing pad. The data were analyzed using ANOVA and Duncan's Multiple Range Test. Areas for root lesions for the different groups were: 1) 2.17 +/- 0.35; 2) 1.90 +/- 0.40; 3) 1.30 +/- 0.18; 4) 1.77 +/- 0.28; 5) 1.50 +/- 0.33. Groups 3 and 5 were statistically different from groups 1 and 2, while no differences were observed for enamel lesions. The use of the photo-activated/fluoride releasing liners significantly reduced lesion area.

Analysis of Variance↗
PubMed1990

Glomus tumours. An immunohistochemical study.

The histological and immunohistochemical features of 20 glomus tumours (glomangiomas) were studied retrospectively in routinely processed material. The tumours came from 18 patients (9 women and 9 men, aged 25 to 80 years); two were recurring lesions. Twelve were classified as solid glomus tumours, eight as glomangiomas. Small nerve fibres were present in all except one. A variable number of mast cells were found in the stroma. The glomus tumour cells were negative when stained for Neuron-Specific Enolase, Glial Fibrillic Acidic Protein, S-100 Protein, Chromogranin, or with the Ulex Europaeus Lectin type 1. Conversely, all were found to be positive for Actin, Myosin, and Vimentin. Four exhibited an equivocal reaction for Desmin, the rest were negative. This immunohistochemical profile is in accordance with the findings of other investigators and can be helpful in differential diagnosis. It also shows the glomus cell to be related to smooth muscle cells and pericytes. The majority of these lesions are probably hamartomas, but a few may be true neoplasms.

Adult↗
PubMed1989

Human plaque pH responses to meals and the effects of chewing gum.

Interproximal plaque pH responses to five different meals were investigated in this study. All meals were found to be acidogenic, with pH challenges lasting well over one hour. The effects of chewing one sorbitol and two different types of sucrose-containing gum for 20 minutes after the meal were examined. All three types of gum reversed the acid challenge of the meal and resulted in an interproximal pH level that is considered 'safe for teeth'. This study indicates that meals can be very acidogenic and that, in addition to normal preventive dental procedures, chewing gum for 20 minutes after meal consumption should be considered, to reduce the cariogenic challenge to the teeth.

Adult↗
PubMed1989

Load transfer of posts and cores to roots through cements.

This study evaluated differences in load transfer when cast posts are fixed to roots with different cements. Cast posts and cores were cemented with 40 endodontically prepared teeth by using four different cement mediums. The load exerted on the root surface through the post was evaluated using a strain gauge. The increased flexure after cementation was statistically analyzed. In conclusion, there was load transfer from post to root structure when posts were cemented, but no difference was found between cementation mediums.

Cementation↗
PubMed1989

Epithelial cyst in cerebellopontine angle with xanthogranulomatous changes simulating cholesterol granuloma.

We describe the clinical, radiological, and pathological features of an epithelial lined cyst in the cerebellopontine angle of a 54-year-old man who presented with headaches, ataxia, and multiple cranial nerve dysfunction. The surgically excised lesion showed a cyst lined by ciliated columnar epithelium with copious mucin secretion similar to that seen in colloid cysts of the third ventricle and enterogenous cysts of the spinal canal. In addition the cyst contained brownish material with an exuberant xanthogranulomatous reaction and numerous cholesterol clefts. This lesion closely resembled a cholesterol granuloma by radiographic and pathologic studies. Although two examples of neuroepithelial lined cysts have been described in the cerebellopontine angle, to our knowledge a lesion similar to that in our patient has not been reported previously.

Cerebellar Diseases↗
PubMed1989

Non-neoplastic lesions of vertebral bodies: findings in magnetic resonance imaging.

This paper presents examples of non-neoplastic lesions of the spine that produce focal or diffuse signal alterations on MR images, and that may, therefore, be confused with metastases or primary neoplasms. Examples include endplate changes associated with degenerative disk disease, hemispherical spondylosclerosis, osteoporotic compression fractures, Paget's disease, focal and diffuse fatty infiltration, osteomyelitis, and changes associated with various arthritides. Distinguishing signal intensity characteristics on T1 and T2 weighted images and distinctive morphology are emphasized.

Fractures, Bone↗
PubMed1989

Effect of etching glass-ionomer cements on bond strength to composite resin.

The use of glass-ionomer cement in restorative dentistry has seen a revival because of its capacity for being etched and bonded to composite resin. Past investigators compared an etched cement surface with an unetched surface that was set against a smooth surface. Clinically, however, a glassy smooth surface is not produced when the cement is used as a base. Using Scotchbond bonding resin, we developed this two-part study to evaluate the tensile bond strengths of P-30TM composite resin to several glass-ionomer cements that were (a) unetched but allowed to set in air and (b) etched for 30 s with orthophosphoric acid, and to compare them with the cohesive strength of the respective cement. Using a silver nitrate staining technique, we also evaluated the microleakage of class V cavities restored with SiluxTM composite resin under a base of etched or unetched Ketac Bond cement. Although there were significant differences among three cements between their cohesive strength and the resin bond strength after the two surface treatments (p less than 0.01), the bond to the unetched surface was generally similar to that of the etched surface of the cement. The remaining groups showed no statistical difference. The microleakage was similar in the two groups. SEM micrographs showed a rough topography of the unetched cement that resembled that of the etched surface. This in vitro study suggests that acid-etching a glass-ionomer base for resin-bonding may not be necessary for specific materials. Further clinical evaluation is recommended to validate this observation intra-orally.

Acid Etching, Dental↗
PubMed1989

An in vitro investigation of the effects of glass inserts on the effective composite resin polymerization shrinkage.

We placed an MOD preparation in each of 12 permanent molars, then restored each tooth with a posterior composite resin by means of six different application techniques (I-polymerization as one complete unit; II--polymerization as one complete unit with glass inserts; III--polymerization in gingivo-occlusal increments; IV-polymerization in gingivo-occlusal increments with glass inserts; V--polymerization in bucco-lingual increments; and VI--polymerization in a gingival increment with glass inserts, then bucco-lingual increments). A precision strain gauge was attached to the buccal surface of each tooth and balanced at zero. After each increment was polymerized, the strain appearing on the strain gauge indicator was recorded. Each tooth was restored by use of all techniques; two teeth started with each technique. Results demonstrated the average microstrain units to be 127-I, 102-II, 105-III, 86-IV, 72-V, and 66-VI. A randomized block design was the format used for data evaluation. Scheffé's Test indicated that composite resin placement and polymerization in bucco-lingual increments (V) created significantly less cuspal deflection than polymerization as one complete unit, with or without glass inserts (I and II), p less than 0.001, and gingivo-occlusal increments (III), p less than 0.05. Placement and polymerization in a gingival increment with glass inserts, then bucco-lingual increments (VI), also created significantly less internal deflection than polymerization as one complete unit, with or without glass inserts (I and II), p less than 0.001, and gingivo-occlusal increments (III), p less than 0.005.

Analysis of Variance↗