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Biomedical subjects

L Martens

Publications and source records attributed to L Martens.

At least 37 records · Page 2Linked to original sources
PubMed1996

[Evaluation of long-term release of fluoride by type II glass ionomer cements with a conventional hardening reaction].

As a part of a fundamental investigation on the fluoride release of glass ionomer cements (GIC), this study investigates the operator dependency of the fluoride release. In this respect the GIC fluoride release of a classical powder-liquid based system (Fuji II) and a capsule-based system (Fuji Cap II) in water during 14 days was determined on the hand of 5 specimens per formulation, made by 5 different operators. The data reveal that the variance on the fluoride release as well as the mean fluoride release at a given time are independent of the operator for both Fuji II and Fuji Cap II. In order to derive fundamental factors affecting the GIC fluoride release, the long-term fluoride release of 10 conventional setting type II GIC is investigated. In this respect the fluoride release profiles (FRP) of each of 5 cylindrical specimens (d = 6 mm, h = 3 mm) of Fuji II (FP), Fuji Cap II (FC), Miracle Mix (MM), Chemfil II (CP), Chemfil II in caps. (CC), Chelon-Fil (CF), Ketac-Fil (KF), Shofu II (SH), Chelon-Silver (CS) and Ketac-Silver (KS) were determined. The specimens were made according to the manufacturer's instruction and equilibrated at 37 degrees C in 25 mL distilled water up to 140 days. The water was regularly renewed and the fluoride concentration [F] of the equilibrated solution determined. A Multivariate Data Analysis of the ¿[F]],t¿-profiles on the basis of Principal Component Analysis (PCA) reveals that the FRP can be classified into 4 distinct groups: ¿CS,KS,FP¿ - ¿FC,CC¿ - ¿CF,KF¿ and ¿MM¿, leaving SH and CP apart as unclassifiable. When the cumulative amount of fluoride released ([F]c) for each individual sample is calculated and fitted as a function of time, a regression analysis shows that [F]c is most adequately fitted (r > 0.99) by [F]c = [F]I/t + t1/2 + beta. Square root of t, indicating that 2 kinetic processes are responsible for the FRP. A comparison of the parameters of this equation ([F]I, t1/2 and beta) shows that the physicochemical rationale for this classification of the GIC conforms to differences in the kinetics of these processes. From the classification, it becomes apparent that different formulations can result in the same FRP.

Dental Caries↗
PubMed1996

[Evaluation of the long-term release of fluorides from type II glass ionomer cements with conventional setting reactions].

As a part of a fundamental investigation on the fluoride release of glass ionomer cements (GIC), this study investigates the operator dependency of the fluoride release. In this respect the GIC fluoride release of a classical powder-liquid based system (Fuji II) and a capsule-based system (Fuji Cap II) in water during 14 days was determined on the hand of 5 specimens per formulation, made by 5 different operators. The data reveal that the variance on the fluoride release as well as the mean fluoride release at a given time are independent of the operator for both Fuji II and Fuji Cap II. In order to derive fundamental factors affecting the GIC fluoride release, the long-term fluoride release of 10 conventional setting type II GIC is investigated. In this respect the fluoride release profiles (FRP) of each of 5 cylindrical specimens (d = 6 mm, h = 3 mm) of Fuji II (FP), Fuji Cap II (FC), Miracle Mix (MM), Chemfil II (CP), Chemfil II in caps. (CC), Chelon-Fil (CF), Ketac-Fil (KF), Shofu II (SH), Chelon-Silver (CS) and Ketac-Silver (KS) were determined. The specimens were made according to the manufacturer's instruction and equilibrated at 37 degrees C in 25 mL distilled water up to 140 days. The water was regularly renewed and the fluoride concentration [F] of the equilibrated solution determined. A Multivariate Data Analysis of the [[F], t]-profiles on the basis of Principal Component Analysis (PCA) reveals that the FRP can be classified into 4 distinct groups: [CS,KS,FP]-[FC,CC]-[CF,KF] and [MM], leaving SH and CP apart as unclassifiable. When the cumulative amount of fluoride released ([F]c) for each individual sample is calculated and fitted as a function of time, a regression analysis shows that [F]c is most adequately fitted (r > 0.99) by [F]c = [F]I/t+t1/2 + beta, square root of t, indicating that 2 kinetic processes are responsible for the FRP. A comparison of the parameters of this equation ([F]I, t1/2 and beta) shows that the physicochemical rationale for this classification of the GIC conforms to differences in the kinetics of these processes. From the classification, it becomes apparent that different formulations can result in the same FRP.

Capsules↗
PubMed1995

Magnetic field induced currents in a human head from use of portable appliances.

The induced currents in a model of the human head resulting from use of small hand-held appliances were computed. The source of the induced currents, i.e. the alternating (60 Hz) magnetic field was modelled as a magnetic dipole. The limits of applicability of this model are given. The model of the human head was obtained by translating MRI data into tissue conductivity data. Computations of the distribution of the induced currents were performed using the impedance method. The induced current density rapidly decreases with the distance from the appliance. The maximum, however, predictably is not at the surface, because of the geometry of the head. For typical appliances, the values of the maximum current densities are high as compared to those induced by a uniform magnetic field. Generalized graphs were obtained for the maximum induced current density normalized to the appliance magnetic moment, as a function of the distance from the appliance. These graphs are given for two representative locations of the appliance with respect to the head.

Electromagnetic Fields↗
PubMed1995

[Oral hygiene of handicapped subjects in Flanders].

As part of an epidemiology survey within the population of handicapped 12-year old in Flanders this article describes several parameters related to oral health. On the average, it became obvious that oral hygiene had to be seriously increased. The presence of plaque and calculus is very typical for types 1, 2, 4 and 8. In addition, it is most striking to conclude that groups where a maximum of self-handiness is expected, do not score any better. The application of chemical controlling agents and the use of fluoride supplements is found extremely low. Finally, a lack was found, with respect to adequate oral hygiene instructions. There is a real need for in-service training programs for educators as well as for parents.

Belgium↗
PubMed1995

[Status of the teeth and degree of care in handicapped in Flanders].

In general, handicapped 12-year old do not show statistical relevant differences with non-handicapped age-matched children in Flanders regarding general caries prevalence, caries distribution and total caries experience. However, important differences were found for the restorative index showing a higher caries treatment need in handicapped children. When the results were analysed according to the type of handicapping condition, it was seen that children with borderline and mild mental handicap and children with speech-, language and/or learning difficulties show the most unfavorable picture. They have a high caries prevalence and caries experience and a low restorative index. Additional analysis of the results can throw some light on the presence of additional caries risk indicators and contributing caries risk factors.

Belgium↗
PubMed1992

Comparison in shear bond strength of orthodontic brackets between five bonding systems related to different etching times: an in vitro study.

New adhesives are continuously being marketed. The adhesive-bracket bond is still the weakest point in orthodontic bonding. A new device for the measurement of shear bond strength values (SBS) of orthodontic brackets is presented in this article. With this device, five commercial products were evaluated for their SBS: Lee Bond (LB), Concise (C), Super C (SC), Achieve-no-mix (ANM), and Panavia Ex (PE). After applying Begg brackets of laminated minimesh on lower human incisors, the specimens were thermocycled. The products investigated produced high bond strengths. The products tested showed shear bond strengths that were significantly lower than those stained with PE. The application of PE yielded the highest shear values. Nevertheless, some characteristics of this product might be clinically somewhat inconvenient. There was no significant difference in shear bond strength between 15 and 60 seconds enamel etching before bond application.

Acid Etching, Dental↗
PubMed1992

[Determination of tooth length in endodontics].

Determination of the exact tooth length and subsequent working length remains a corner stone of proper endodontic treatment. Up to now, no system has proven to provide the exact location of the apical constriction under all circumstances. Several possibilities of determining tooth length are discussed. Factors influencing the outcome of the different techniques are described. A simple and rather accurate way for calculating tooth length on X-rays is elaborated. Apparently, electronic devices are becoming increasingly accurate, and may become a challenge for the radiographic tooth length determination. Actually, dentists have most of all to rely on X-rays for tooth length determination.

Humans↗
PubMed1991

The preventive Class II restoration: clinical application.

A renewed interest in conservative cavity preparations has emerged in recent years. In this paper, a substance-saving cavity preparation for the treatment of small, interproximal carious lesions, the preventive Class II preparation, is presented. The indications, the cavity preparation, and the obturation are discussed. The combined use of both amalgam and a light-curing pit and fissure sealant is suggested. Clinically, this type of restoration seems to be acceptable. Nevertheless, more clinical experience and in vitro research regarding this type of restoration is needed.

Dental Amalgam↗
PubMed1990

Effects of a multidisciplinary management program on neurologically impaired patients with dysphagia.

Dysphagia is a major problem in patients with neurologic disorders. Aspiration pneumonia and impaired nutritional status are consequences of dysphagia that result in high morbidity and mortality rates. Assessment and treatment of the dysphagic patient by a multidisciplinary team have been advocated but to date the effects of such an approach have not been demonstrated quantitatively. This prospective study was conducted to determine if a dysphagia program would improve patients' caloric intake and body weight, decrease the instances of aspiration pneumonia, or improve patients' feeding ability. Patients were referred from a 26 bed neurology/neurosurgery unit. A time series design was utilized. The control group consisted of 15 patients (mean age = 46.1 years), managed according to the existing ward routine. Subsequently, nursing staff attended a dysphagia training program. Following this, the treated group of 16 patients, (mean age = 49.3 years) was assessed by the dysphagia team, using bedside and videofluoroscopic examinations to determine the specific swallowing disorder. An individualized treatment program was designed for each patient. The groups were compared on the basis of deviation from their baseline weight, deviation from ideal energy intake, and the incidence of aspiration pneumonia. Statistical analysis revealed that the groups were comparable in age, number of days on the study, and Glasgow Coma Scale score; and that a significant weight gain and increase in caloric intake occurred in the treated group. No incidence of aspiration pneumonia was reported in either group. We speculate that this may have been influenced by the meticulousness of the care delivered in an acute unit as well as greater attention to prevention given in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

A decision tree for the treatment of caries in posterior teeth.

Because of a better understanding of the caries process, a decrease in the prevalence of caries, and the rapid development of dental materials, a renewed approach to the treatment of dental caries in the posterior region is possible. A decision tree for the treatment of caries in posterior teeth, taking into account some of the most recent tooth substance-saving treatment options, is presented. These possibilities gradually evolve from nondestructive to conventional cavity preparations. In addition, the "preventive Class II restoration" is introduced. The application of this conservative attitude toward invasive techniques offers great advantages for both the patient and the dentist. Unfortunately, this approach is time-consuming. Long-term clinical evaluation of the application of the proposed decision tree on a wide scale is needed to confirm its potential benefits or to modify and improve treatment options.

Bicuspid↗
PubMed1989

A scanning electron microscopic and tensile bond strength evaluation of Gluma dentin bond application, as a function of dentinal pretreatment.

Scanning Electron Micrographs (SEM) and Tensile Bond Strength (TBS) measurements were used to evaluate the influence of three different dentinal pretreatments. A new testing device was developed for the TBS measurements. Human tooth roots were ground with a diamond bur. Tap water, Gluma Cleanser, and Neo-Sabenyl-Tubulicid were used to clean the surfaces before SEM inspection. The adhesion between root dentin and Lumifor Composite restorations was mediated by Gluma Bond. SEM observations revealed that a 30-second application of Gluma Cleanser removes the smear layer totally. Neo-Sabenyl-Tubulicid produced a very smooth surface. Application of Gluma Bond did not alter this appearance. Mean TBS values for surfaces sprayed with tap water, Gluma Cleanser, and Neo-Sabenyl-Tubulicid were 10 MPa, 7.3 MPa, and 10 MPa, respectively. There was a significant difference between group 2 (Gluma Cleanser) and the other groups. From this in vitro study, it is concluded that total removal of the smear layer with opening of the dentinal tubules (e.g., by means of Gluma Cleanser) reduces the TBS of Gluma Dentin Bond-Lumifor restorations to ground root dentin.

Aldehydes↗
PubMed1989

Evaluation of dowel space preparation on the apical seal using an image processing system.

The effect of post preparation on the apical seal of endodontically treated specimens was studied. The canals prepared in bovine bone were instrumented and obturated using five obturation techniques: the silver point technique, the lateral condensation of gutta-percha technique, the warm vertical condensation of gutta-percha technique, the Hygenic Ultrafil injection system and the Obtura technique. In addition to these five control groups, the five experimental groups were also subjected to post preparation. In the latter group, the gutta-percha was removed with an engine-driven root canal reamer 48 hours after obturation. Both the control and experimental groups were suspended in a 0.5 per cent crystal violet solution for 48 hours. After dye penetration, the specimens were immersed in liquid nitrogen and then split longitudinally. Linear measurements of the resultant apical dye leakage were determined by image processing. For each obturation technique, all specimens in both the control and experimental groups were recorded if they showed leakage. Using Fisher's exact probability test, it was shown that there was no significant difference between the obturation techniques used.

Animals↗
PubMed1989

[Criteria for a judicious indication for the application of pit and fissure sealants].

The caries reducing effect of the application of pit and fissure sealants has been demonstrated by several studies. It remains however a matter of debate, if every newly erupted fissure has to be sealed. From this article it becomes clear that the decision for sealing depends on several factors as there are: the general health status of the patient, the socio-economic situation, the responsibility of the child for his/her own hygiene, the motivation of the patient, the caries history of the patient: his/her dietary habits, fluoride-use and regular six-month recalls. The motivation of the practitioner and his/her knowledge of fissure caries (including morphology and caries susceptibility) are also very important. So, an individual application after giving the matter a careful thought is recommended and proposing general rules is not possible. Finally an attempt is made to suggest some guidelines.

Child↗
PubMed1989

[Choosing a dentifrice].

Actually, there are so many products available on the market and the claims made by the manufacturers are so variable that questioning the choice of a toothpaste became self-evident. In the present article one cannot find "which toothpaste" has to be used. The aim of this review is to describe some groups of toothpastes, notably the fluoride toothpastes, the pastes for hypersensitive teeth and the anti-calculus toothpastes. So, this article gives a lot of information on the development of new products with new active components. Although scientific knowledge has expanded, we have to realize that the consumer makes the choice...

Dentifrices↗
PubMed1988

The localization of (Ca2+ or Mg2+)-ATPase in plasma membranes of renal proximal tubular cells.

Basolateral and brush-border vesicles from pig kidney cortex were prepared by differential centrifugation followed by free-flow electrophoresis. A low-affinity (Ca2+ or Mg2+)-ATPase which co-migrated with alkaline phosphatase was demonstrated. A considerable enrichment (by a factor of 10) of this ATPase activity was only observed in the brush-border and not in the basolateral membrane fractions. Maximal stimulation of this brush-border enzyme by Ca2+ was achieved when the ratio of Ca2+ to ATP reached a value between 1 and 2. The enzyme was not inhibited by excess Ca2+ or Mg2+. A kinetic analysis of the azide-insensitive (Ca2+ or Mg2+)-ATPase gave a Km of 0.43 mM for Ca-ATP and of 0.14 mM for Mg-ATP.

Adenosine Triphosphate↗
PubMed1987

Comparative QSAR studies on vasodilatory and negative inotropic properties of ring-varied verapamil congeners.

In the present study quantitative structure-activity relationships (QSAR) for the vasodilator properties of verapamil have been derived: Potency of ring-varied verapamil congeners on the phasic and tonic component of K+-contractures has been measured in aortic rings of the cat. Potency of verapamil derivatives on the phasic component significantly correlates with lipophilic properties of the compounds. Inhibition of the tonic component best correlates with a parameter combination of steric and electronic properties (MV, sigma). These results contrast with investigations with dihydropyridine derivatives where identical SAR have been found for both response components. Furthermore, SAR analyses yield disparate results in comparison to investigations in heart muscle where primarily electronic and secondarily steric parameters best explain the potency of verapamil derivatives. The postulate of chemically differing binding sites for verapamil congeners in heart and smooth muscle is substantiated by calculating binding energies to the hypothetical binding site arginine. While negative inotropic potency of verapamil derivatives significantly correlates with binding energy to the model binding site arginine, this correlation fails in case of aortic ring. These results obtained for verapamil congeners contrast with observations with dihydropyridine derivatives where the chemistry of binding sites in heart and smooth muscle seems to be identical.

Animals↗