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Biomedical subjects

A Lussi

Publications and source records attributed to A Lussi.

At least 91 records · Page 5Linked to original sources
PubMed1992

[The effect of 2 finishing methods on the micromorphology of the proximal box margin. An in-vivo study].

Minipreparations of class II cavities often are not employed in daily practice mainly because adequate instruments for finishing the axial box margin and the proximo-cervical curvature were not available. The purpose of this in vivo study was to assess the morphology of the proximal box margin after finishing with two different methods. 81 class II minicavities for amalgam restorations were prepared by 4 dental practitioners. One method for finishing the axial box margin and the proximo-cervical curved border was the use of a modified EVA-System with the total amplitude reduced to 0.4 mm and a highly flexible file (Cavishape, grain 25 microns). The other method was the use of an axial margin trimmer. The micromorphology of the two methods was investigated by means of scanning electron microscopy and a score system as described earlier (Lussi et al. 1987). The margins of the axial box as well as of the proximo-cervical curvature were significantly better finished with the EVA-System and the highly flexible file compared to the axial margin trimmer (p < 0.001). The finishing time for the box margin was not significantly different using the EVA instrument or the axial margin trimmer. These findings confirm other in vitro investigations. This in vivo study shows that the modified EVA instrument with the highly flexible file (Cavishape, grain 25 microns) is clearly superior to the axial margin trimmer in finishing the box margin. This device allowed a significant better finishing of the axial box margin and the proximo-cervical curvature of minicavities in daily practice.

Chi-Square Distribution↗
PubMed1992

[The preparation of enamel margin beveling in proximal cavities].

Minicavities for posterior composite resin restorations were prepared in 24 caries-free teeth. The aim of this in vitro study was to evaluate the micromorphology of the proximal cavosurface bevel. The cavosurface bevel has been employed for many years as an accepted modification for composite restorations in permanent anterior teeth. The bevel provides more exposed enamel rod ends available for bonding. Using the acid-etch technique the resin-enamel bond is stronger with etched transverse sections of enamel prisms than with longitudinal sections. Enamel in the proximal and gingival wall of class II cavity preparations for restoration with composite should be beveled because prism direction is at right angles to the surface. The aim of this study was therefore to compare two methods for beveling the box margins of small proximal cavity preparations. One method for the preparation of the proximal bevel was the use of a modified EVA-System with the total amplitude reduced to 0.4 mm, the fixation of the file position and a new developed file (Bevelshape, grain 40 microns). The form of this file was modified in order to produce a short cavosurface bevel of the gingival and proximal wall without danger of damaging the adjacent tooth. The other method was the use of an axial margin trimmer. The micromorphology of the two methods was investigated by means of scanning electron microscopy and a score system as described earlier (Lussi et al. 1987). Statistical analysis revealed significant differences between the two groups. As compared to the axial margin trimmer the new device allowed a significant better finishing of the proximal bevel (p < or = 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Dental Caries↗
PubMed1992

[The modification of the polymerization of composite materials by eugenol-containing temporary fillings].

The objective of this study was to evaluate the influence of eugenol-containing temporary fillings on the polymerisation of composite materials. Cavities of 2 mm in diameter and 2 mm in depth were prepared in enamel as well as in dentine. Immediately after preparation the cavities of the control group were filled with a light curing composite, a chemical curing composite, or a light and chemical curing composite. The cavities of the experimental group were filled with Nobetec (temporary filling material containing zinc-oxide-eugenol). After six weeks, the Nobetec fillings were removed by means of an excavator, the cavities were cleaned with water and filled with one of the above six composites. The specimens were embedded in Epofix and afterwards cut through the center of the filling. The cut surfaces were polished to 3 microns and afterwards (> 4 days) the hardness was measured with a Knoop hardness testing machine at different distances from the cavity wall. The results of the control group and of the experimental group were compared statistically. The polymerisation of five of the six materials was not inhibited by a temporary filling material containing zinc-oxide-eugenol. The difference in hardness for Brilliant Lux (light curing) was fer-highly significant (p < 0.001) between 0 micron and 100 microns from the cavity margin, if the cavity was first filled with a temporary filling material, containing zinc-oxide-eugenol. The results show that there exist certain composite filling materials that are inhibited in their polymerisation by the tested eugenol containing temporary filling material.

Composite Resins↗
PubMed1992

[The status of the dentition in 2 Swiss population groups before the introduction of refined sugar].

Caries and parodontitis have been one of the most spread diseases of mankind. In an archaeological study, 53 graves of Bernese patricians were exhumed. 22 skulls of adults with 392 teeth were examined. They lived between the 16th and the 18th century in the community of Worb BE. In some cases identification could be accomplished by comparison of oil paintings with skulls, using a computerized technique. The aim of this study was to evaluate the prevalence of caries, the loss of periodontal bone, the amount of calculus and of abrasion. To compare the dental situation with another population segment sex- and age-matched dates were used. This second population segment lived between the 12th and 18th century and belonged to a lower social class than the patricians from Worb. The comparison of these two groups showed significant differences only in the abrasion pattern. We conclude that the social class did not significantly influence most of the parameters studied here. The different abrasion pattern could be due to different dietary habits.

Alveolar Bone Loss↗
PubMed1992

[The release of mercury and copper from in vivo aged amalgam fillings].

Release of mercury and copper in water over time from in vivo annealed amalgams in an unpolished and polished state was measured. Mercury and copper loss from unpolished amalgams was on the average 1,00 micrograms/cm2.d and 0.06 micrograms/cm2.d, respectively. Polishing the amalgams reduced these values significantly to 0.19 micrograms/cm2.d for mercury (p = 0.004) and to 0.03 micrograms/cm2.d for copper (p = 0.009). It was concluded that polishing amalgam surfaces (under water cooling) reduces release of mercury and copper significantly.

Copper↗
PubMed1991

Comparison of the sealing ability of four cavity varnishes: an in vitro study.

The purpose of this study was to test and to compare, in vitro, the sealing ability of four different cavity varnishes used to minimize the marginal leakage of amalgam fillings. For this purpose, a model was developed in order to avoid quality-deteriorating effects (such as condensation forces used during placement of amalgam) and temperature changes. In this model, raw ceramic disks were used instead of dentin. The four varnishes showed significant reducing effect on the penetration of the dye (Methylene Blue) compared with the control. There was no cavity varnish with optimal sealing.

Analysis of Variance↗
PubMed1991

Dental erosion in a population of Swiss adults.

The purpose of this study was to determine the prevalence of dental erosion in an adult population in Switzerland. 391 randomly selected persons from two age groups (26-30 and 46-50 yr) were examined for frequency and severity of erosion on all tooth surfaces. Information was gathered by interview about lifestyle, dietary and oral health habits. For facial surfaces 7.7% of the younger age group and 13.2% of the older age group showed at least one tooth affected with erosion with involvement of dentin (grade 2). 3.5 teeth per person in the younger and 2.8 teeth per person in the older age group were affected. Occlusally, at least one severe erosion was observed in 29.9% of the younger and 42.6% of the older sample with 3.2 and 3.9 erosion-affected teeth per person, respectively. 3.6% of the younger age group and 6.1% of the older age group showed slight lingual erosion on the maxillary anterior teeth. Severe lingual erosions were scarce. Data from interviews and multiple regression analyses revealed that acids from beverages are significantly associated with presence of erosion.

Adult↗
PubMed1991

Validity of diagnostic and treatment decisions of fissure caries.

The purpose of this in vitro study was to test the accuracy and the reproducibility of diagnostic and treatment decisions of fissure caries with and without explorer. 34 dentists were asked to diagnose 61 teeth and decide upon possible treatment. The teeth were then histologically prepared and diagnosed. The agreement between histological and clinical diagnoses was assessed. The results showed no difference in diagnostic accuracy between explorer and visual technique only. Sensitivity (62%) and specificity (84%) showed that the dentists were more likely not to treat decayed teeth than to restore sound teeth. The percentage 'correctly diagnosed teeth' was approximately 42%. As there was an inherent possibility of a correct diagnosis by chance, this value had to be corrected to 23% (kappa statistics). The percentage of 'clinically' correct treatment decisions, however, was 73%. The reproducibility test gave kappa values of 0.47 for diagnostic and 0.44 for treatment decisions. It was concluded that the use of an explorer does not improve the validity of the diagnosis of fissure caries when compared to that of a visual inspection alone.

Adolescent↗
PubMed1991

[The mercury release of different amalgams in vitro].

Release of mercury from 8 different amalgams was tested in water initially and after annealing für 2 years. The measuring methodology was geared to warrant minimum mercury losses due to evaporation and adsorption. Mercury loss during the first 24 hours ranged between 17.4 micrograms/cm2.d and 34.5 micrograms/cm2.d. Annealing of the amalgams for 2 years reduced mercury leaching significantly, to about 1.5 micrograms/cm2.d with no significant differences between the different amalgam brands.

Analysis of Variance↗
PubMed1990

Mercury and copper release from amalgams in different soft drinks.

Release of mercury and copper over time from three different non-gamma-2 amalgams in a polished and unpolished state was tested in water and two soft drinks. The measuring methodology was geared to warrant minimum Hg losses due to evaporation and adsorption. Initial (24 h) values for Hg and Cu were relatively high in water, but were much lower in the soft drinks. The 24-104-hour values were much lower than the initial readings for all amalgams and all environments. Polishing reduced leaching--significantly, however, only in water and for only two of the three amalgams. The lower values in the soft drinks and over time could be due to passivation of the amalgam. Passivation appears to be time-dependent and chemically influenced by the environment.

Carbonated Beverages↗
PubMed1989

Mineral induction by immobilized polyanionic proteins.

The purpose of this study was to investigate the mineral induction capacity in vitro of polyanionic proteins covalently bound to a surface. Rat dentin gamma-carboxyglutamate-containing protein of the osteocalcin type (Gla-protein), proteoglycan (PG), and phosphoprotein (PP-H), as well as phosvitin (PhV) and bovine serum albumin (BSA), were covalently linked to agarose beads. There were incubated at 37 degrees C in solutions with a Ca/P molar ratio of 1.67, [Ca][P] molar products in the range 1.0-1.8 mM2, and an ionic strength of 0.165. The incubations were performed at constant pH and composition conditions; no spontaneous precipitation occurred under these conditions. Mineral formation, as monitored by scanning electron microscopy (SEM), was induced by all immobilized polyanions, including enzymatically dephosphorylated PP-H and PhV. No mineral was induced by BSA. The mineral inductive capacity of immobilized polyanionic proteins, as judged by the SEM after identical incubations, was found to differ between the different ligands. The mineral induced by PP-H and PG was shown by X-ray diffraction to be apatitic. It was concluded that, although polyanionic proteins in solution may inhibit mineral induction and growth, very minute quantities of such molecules, when immobilized on a surface, induce mineral at physiological concentrations of calcium and phosphate ions. The data presented may be taken to suggest that PP-H and PG, and perhaps other polyanions, may possibly be responsible for mineral nucleation in dentin and bone. The results, however, also point to the rather limited specificity in this type of reaction.

Animals↗
PubMed1989

Mineral induction by polyanionic dentin and bone proteins at physiological ionic conditions.

Polyanionic proteins of calcified tissues have been postulated to provide calcium ion-binding sites which initiate mineral formation, even though it is known that such proteins in solution may inhibit apatite induction and growth. In the studies reviewed here, it was shown that minute amounts of non-collagenous macromolecules from dentin and bone, such as phosphoprotein and proteoglycan, are capable to induce apatite at physiological ion concentrations in vitro, when immobilized on a stable support.

Animals↗
PubMed1989

[Curing ability of polymerization lights for composite materials].

An in-vivo study has been conducted with four different brands of activator light sources. 38 light units in service by different dental practitioners were compared with new light sources. Curing depth profiles were obtained using Knoop microhardness measurements. It was observed that with an exposure time of up to 60 s the polymerization was not sufficient below 2 mm of depth. The "old" light sources showed worse curing properties than the new ones, especially below this depth. Generally, the polymerization units with rigid glass fiber light guide showed better results than the units with a flexible fiber-optic cable. Other reasons for insufficient polymerization were polymerized composite material at the end of the light guide, a defect in the cooling system of the light source and, for two brands of light sources, a reduction of the voltage below 220 V.

Composite Resins↗