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Biomedical subjects

A Meniga

Publications and source records attributed to A Meniga.

18 recordsLinked to original sources
PubMed2005

Influence of light intensity from different curing units upon composite temperature rise.

The unavoidable consequence of composite resin photopolymerization is temperature rise in tooth tissue. The temperature rise depends not only on the illumination time, but also on light intensity, distance of light guide tip from composite resin surface, composition and shade of composite resin and composite thickness. The most commonly used units for polymerization today are halogen curing units, which emit a large spectrum of wavelengths. A proportion of the spectrum has no influence on degree of conversion and therefore causes unnecessary temperature rise. Units based on light source - blue light emitting diodes (LED), as an alternative for halogen curing units, have been introduced in clinical practice. The aim of this study was to show the influence of the light intensity of curing units Elipar Trilight, Astralis 7 and Lux-o-Max unit on temperature rise in composite resin sample of Tetric Ceram. The temperature was measurement with Metex M-3850 D multimeter with the tip of temperature probe put into unpolymerized composite resin sample 1 mm depth. The highest temperature rise was recorded with standard curing mode for Elipar Trilight halogen curing unit (13.3 +/- 1.21 degrees C after 40 s illumination), while the lowest temperature rise was recorded for the Lux-o-Max unit based on LED technology (5.2 +/- 1.92 degrees C after 40 s illumination).

Composite Resins↗
PubMed2002

Composite conversion and temperature rise using a conventional, plasma arc, and an experimental blue LED curing unit.

The objective of this study was to evaluate the degree of conversion and temperature rise in three different composite materials when illuminated by an experimental light source [blue superbright light emitting diodes (LEDs)] and compared with plasma light and traditional photopolymerization unit. The degree of conversion and temperature rise were measured using Fourier transform infrared (FTIR) spectroscopy and digital multimeter, respectively. The results revealed significantly higher degree of conversion values in case of conventional curing than with other two light sources whereas temperature rise was significantly lower when blue LEDs and plasma light were used. There were great differences in light intensities between blue LEDs of only 9 mW cm-2 compared with plasma light of 1370 mW cm-2 and Elipar II of 560 mW cm-2. Better match of LED spectral distribution peak to camphorquinone absorption distribution peak probably explains much lower intensities used for similar photopolymerization effect like in the case of rapid plasma lamp curing.

Absorption↗
PubMed2002

Photopolymerization of composite resins with plasma light.

Everyday improvements in components and characteristics of composite materials have induced faster development of curing units. Besides standard halogen curing units and soft-start photopolymerization light sources, some experiments with argon and pulsed laser light and low intensity blue superbright light emitting diodes have been made. On the other hand, rapid polymerization with strong plasma light is also clinically applicable. The aim of this study was to measure the degree of conversion and temperature rise for three restorative composite materials: Tetric Ceram (Vivadent, Schaan, Liechtenstein), Pertac II (ESPE, Seefeld, Germany) and Z100 (3M Dental Products, St Paul, MN, USA) during polymerization with plasma light Apollo 95E (DMDS, Dental/Medical Diagnostic Systems, Fleury d'Aude, France) and compare it with the results of polymerization with a halogen curing unit, Elipar Trilight (ESPE, Seefeld, Germany). The results revealed the degree of conversion values in the case of polymerization with plasma light to be almost equal to those obtained by curing with the halogen curing unit, whereas the temperature rise was almost negligible.

Analysis of Variance↗
PubMed2001

Degree of conversion and temperature rise during polymerization of composite resin samples with blue diodes.

To ensure an adequate clinical composite filling light source for photopolymerization is of great importance. In everyday clinical conditions commonly used unit for polymerization of composite material is halogen curing unit. The development of new blue superbright light emitting diodes (LED) of 470 nm wavelengths comes as an alternative to standard halogen curing unit of 450-470 nm wavelengths. The purpose of this study was to compare the degree of conversion (DC) and temperature rise of four hybrid composite materials: Tetric Ceram, Pertac II, Valux Plus and Degufill Mineral during 40 s illumination with standard halogen curing unit Heliolux GTE of 600 mW cm(-2) intensity, Elipar Highlight soft-start curing unit of 100 mW cm(-2) (10 s) and 700 mW cm(-2) (30 s) intensity and 16 blue superbright LED of minimal intensity of 12 mW cm(-2) on the surface and 1 mm depth. The results revealed only a little bit higher DC values in case of polymerization with even 66 times stronger halogen curing units which showed twice higher temperature than blue diodes. Temperature and DC obtained are higher on the surface than on 1 mm depth regardless on the light source used.

Analysis of Variance↗
PubMed1998

The effect of the photopolymerization method on the quality of composite resin samples.

An optimal degree of conversion and minimal polymerization shrinkage are generally antagonistic goals, as increased monomer conversion invariably leads to elevated polymerization shrinkage values. However, both parameters are indispensable for an optimal resin composite restoration. A number of approaches have been used to reduce the stress on the restoration cavity wall interface, such as dentine bonding agents to counteract polymerization shrinkage, stress-absorbing lining materials and low-intensity curing lights to control the flow capacity of the material during polymerization. However, the configuration of the cavity and cohesive fractures of the material and surrounding tooth tissues are still a problem in day-to-day clinical practice. A new photopolymerization light source, pulsed laser, ensures a higher degree of conversion and lower polymerization shrinkage, and differentiates this technique from standard polymerization methods and continuous-wave argon laser polymerization. The coherence and monochromacity of pulsed laser light set at 468 nm and the far greater intensity of laser nanopulses produce a saturation effect in the depths of the composite, thus resulting in higher monomer conversion. The total amount of energy illuminating the sample surface, which is only one-fifth of that of conventional methods, and the cooling and relaxation of the material between nanopulses may be responsible for the reduced net polymerization shrinkage.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1997

Pulsed blue laser curing of hybrid composite resins.

Clinical performance of light-curing composite restorations is greatly influenced by the quality of the curing-light. Currently used photopolymerization units have some important drawbacks, such as decreasing light output with time and distance, which results in a relatively low degree of conversion and shallow depth of cure, particularly of darker shades. Experiments with continuous argon laser polymerization showed overheating of the composite sample, as well as increased shrinkage of the material. In this study a pulsed laser, set at 468 nm (the maximum of the camphorquinone absorption coefficient), with 20-ns pulse duration, repetition rate of 10 Hz and energy of 10 mJ per pulse, was used as a light source. The aim of the study was to evaluate the effect of polymerization of light and dark shades of three different hybrid composites cured by pulsed laser at the surface and at 3.0 mm depth. The degree of conversion was measured by Fourier transform infrared spectroscopy (FTIR). Applying pulsed blue laser, significantly better results were obtained for both shades compared to standard polymerization values. Very weak dependence of the degree of conversion, between the surface measurements and those at 3.0 mm, were observed in the case of pulsed laser polymerization due to the piercing nanopulses and the monochromatic light at 468 nm.

Dental Cements↗
PubMed1995

Polymerization of composites using pulsed laser.

The quality of visible-light-cured composites depends on the capability of the light source to properly polymerize the material within a specified exposure time. In this study, the degree of conversion of different composite materials (hybrid and microfilled) of light and dark shades was compared after illumination by a standard curing unit and pulsed laser (lambda=468) respectively. The degree of conversion was measured by Fourier transform infrared spectroscopy. Results obtained by the analysis of the pulsed laser-induced polymerization were significantly higher for all the materials and shades observed. All values of the degree of conversion were lower for dark shades of all types of composites, regardless of the photopolymerization technique used. Besides the surface, better polymerization was recorded also at depths of 1.0, 2.0 and 3.0 mm, respectively. These values varied from 59.7%+/-2.14 to 84.5%+/-0.33 for pulsed laser (including all depths) caused by the saturation effect induced by high power laser pulses and from 42.7%+/-1.48 to 74.7%+/-0.99 for standard polymerization.

Acrylic Resins↗
PubMed1991

Indium light source for curing composite resins.

There is an existing problem of cumulative hazardous effect of violet and near ultra-violet light which is produced by standard polymerisation units. Another restrict is shallow depth of cure, particularly of darker composite shades in premolar and molar region. Searching for better light source we used indium resonance lines from several indium high pressure lamps and tested curing effect on three different composite resins. The overall results are better with the lamp in which two strong resonance lines of indium are present, rather than with a lamp with just one strong resonance line. The improvements in lamp design are necessary to overcome conventional polymerisation lamps.

Composite Resins↗
PubMed1991

[Evaluation of the reconstruction of occlusal plane by use of Ponans angle].

In this study, teleroentgenocephalograms of 34 subjects with at least 20 natural teeth were used. Correlation between the angle formed by linking the PORION-NASION-SPINA NASALIS ANTERIOR (PONANS angle) points and the angle made by Frankfort horizontal and occlusion plane was studied. The coefficient of correlation was 0.1263. It is considered that there is no correlation if the coefficient of correlation is less than 0.5. Thus, there was no correlation in the study sample, which is consistent with the results reported by Karkazis and Polyzois, but in disagreement with those published by Monteith. In our sample, the occlusion plane could not be oriented in the articulatory space or in toothless mouth by means of the method proposed by Monteith.

Adolescent↗
PubMed1990

[Glass-ionomer cements].

Glass-ionomer cements represent a new type of dental materials widely clinically applied owing to their good adhesion to dental tissue, caries-protective effects, biocompatibility and simple handling. They are two-component materials commercially available in forms of powder or liquid. The two components are mixed manually or automatically in a vibrator to produce a compact mixture. In addition to chemical, light-polymerizing hybrid glass-ionomer cements are also available. A description is given of physical and chemical features of these materials, their classification and use in particular clinical cases.

Glass Ionomer Cements↗
PubMed1990

Zinc and sodium high pressure lamps for curing composite resins.

Polymerisation characteristics of conventional units for curing composite resins are insufficient considering handling feasibilities particularly in the premolar and molar region. There is also hazardous ocular effect of near ultra-violet part of visible spectra. Sodium high pressure lamp technology has been applied to develop a new high pressure zinc lamp, which is for the first time used for curing composite materials. The results of polymerisation measurements show that future improvements over the usual halogen light sources are possible. Zinc lamp was also compared with the high pressure sodium lamp filled with mercury or cadmium.

Cadmium↗