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Biomedical subjects

A Lussi

Publications and source records attributed to A Lussi.

At least 19 recordsLinked to original sources
PubMed1995

Threshold of tactile sensitivity perceived with dental endosseous implants and natural teeth.

The aim of this study was to determine the threshold of tactile perception of endosseous dental implants and to assess the relative difference of that threshold between implants and teeth. Twenty-two subjects with implants of the ITI Dental Implant System were included in the study. All implants served as abutments for single tooth crowns and had been in function for a minimum of 1 year. A strain gauge glued to the shaft of an amalgam plugger served as a force sensor. It transformed the elastic deformation exerted onto the shaft into an electronic signal for recording. By use of the amalgam plugger, a continuously increasing force was exercised on the implants or teeth until the first sensation of touch was indicated by the patient. Statistical analysis revealed threshold values for the implants ranging from 13.2 to 189.4 g (1 g = 0.01 N) (mean 100.6; SD 47.7), while a range of 1.2 to 26.2 g (mean 11.5; SD 11.5) was found for control teeth. Thus, the mean threshold values for implants were 8.75 times higher than for teeth. This difference was highly statistically significant. A general linear models procedure was applied to determine the influence of patient age, jaw, implant position and the threshold values of teeth on the measurements obtained for implants. Only gender and the threshold values for contralateral teeth had a significant influence. These 2 parameters together explained 27% of the variability in threshold measurements. It is concluded that a more than 8-fold higher threshold value for tactile perception exists for implants compared with teeth.

Adolescent↗
PubMed1995

A new non-instrumental technique for cleaning and filling root canals.

The aim of this in vitro study was to test the ability of a novel non-instrumental technique to prepare and obturate root canals. Cleaning of the root canal system was achieved with a device which was able to develop, under reduced pressure, controlled cavitation. The same device was used for proper drying and subsequent obturation of the root canal system. A total of 55 freshly extracted molars with 120 canals were treated either by the step-back technique and lateral condensation of gutta-percha and AH26 as a sealer or by the new device. The teeth were then sectioned horizontal to the long axis of the root canal and examined by light microscopy. The cross-sectional area, area with residual pulpal tissue and voids were assessed morphometrically. Overall, the treatment with the new device resulted in similar cleanliness and obturation quality when compared with the control group. Total treatment time using the new non-instrumental technique, however, was less than half of that using hand instrumentation.

Analysis of Variance↗
PubMed1995

In vivo diagnosis of fissure caries using a new electrical resistance monitor.

The aim of this investigation was to study the accuracy of a newly developed electrical resistance monitor in diagnosing occlusal fissure caries in vivo in teeth without cavitation. The electrical resistance was measured in vivo on human third molars without existing restorations and without any macroscopic carious cavitation. Data from 41 sites on 26 occlusal surfaces were obtained. After measurement, the teeth were extracted, histologically prepared, and serially sectioned perpendicular to the occlusal surface and examined for the presence of caries. Nineteen sites had no caries, 7 had enamel caries, and 15 sites showed dentinal caries, 4 of which deep dentinal caries. For the diagnosis of occlusal caries with the electrical resistance monitor, the specificity was 0.77, the sensitivity 0.93, and the accuracy 0.83. Likelihood ratios for four diagnostic levels (no caries, enamel caries, dentinal caries, and deep dentinal caries) were 0.09, 0, 3.47, and 4.16, respectively. Diagnosis of occlusal caries using conventional bite-wing radiographs showed a specificity of 0.77, a sensitivity of 0.62, and an accuracy of 0.71. The electrical resistance monitor was well suited to detect in vivo occlusal caries under clinically intact fissures. The rather high value (0.23) of false-positive ratings, however, might lead to a substantial number of sound teeth being restored unnecessarily. Substantial improvement of occlusal, caries diagnosis may be achieved by combining this method with others.

Adult↗
PubMed1995

Prediction of the erosive potential of some beverages.

The aim of this study was to investigate whether the erosive potential of a beverage on human enamel can be predicted by examining the composition of the beverage. The buccal surfaces of 84 caries-free premolars were embedded in resin and polished flat. Two hundred micrometers of the enamel surface were removed. Then the slabs were divided into 14 groups and immersed for 20 min in commercially available beverages. Surface microhardness was measured before and after immersion. Further, the phosphate concentration, the fluoride concentration, the baseline pH as well as the titrated amount of base to raise the pH to 7.0 of each beverage were determined. Surface microhardness values after immersion were calculated with an equation derived in a recent study and compared with the values measured in this investigation. Apple juice showed the greatest significant decrease (p < 0.05) in surface microhardness, followed by Schweppes, Orangina and Grapefruit soft drink. The smallest decrease in surface microhardness that was significant resulted from Fendant and Isostar orange. The mean absolute deviation of the calculated to the effective erosion was 7.1%, it ranged between 14.6% (apple juice) and 1.6% (Fendant). The data suggest the possibility of predicting erosion caused by a beverage with an accuracy of 7%. This information can be of value in the prevention of dental erosion.

Beverages↗
PubMed1995

Radiographic evaluation of occlusal caries: effect of training and experience.

The purpose of this study was to investigate what effect differing levels of didactic education and clinical experience have on the ability to diagnose occlusal caries from radiographs. Freshman and senior dental students and dental school faculty were asked to evaluate bitewing radiographs for the presence of occlusal caries and for a recommendation for restorative treatment. The agreement between histologic and radiographic diagnosis was assessed by calculating sensitivity, specificity, accuracy, and interexaminer agreement. It was concluded that dental students and faculty did differ in their abilities to evaluate radiographs for occlusal caries, and that education and clinical experience especially affected interexaminer agreement.

Clinical Competence↗
PubMed1995

[Damage to neighboring teeth during the preparation of proximal cavities. An in-vivo study].

It has been shown that iatrogenic preparation damage increases caries progression and the need for restorative therapy of the adjacent tooth. The aim of this study was to quantify the damage of the adjacent tooth using three different preparation techniques: (1) diamond bur alone; (2) diamond bur combined with the EVA system and the Cavishape file; (3) diamond bur combined with an axial margin trimmer. All 136 preparations were performed by dental practitioners in their own practice. Examination of the area directly opposite to the axial box margin revealed significantly less damage (p < 0.01) using additionally the EVA system with the Cavishape file or the axial margin trimmer compared to using only diamond burs. The area opposite between the two box margins, which was in all three methods prepared only by the diamond bur, showed no significant differences between the methods under study. There were only a few teeth (overall 5%) with no damage of the adjacent surface. In order to reduce iatrogenic damage for the adjacent teeth the preparation technique has to be modified.

Crowns↗
PubMed1995

[The cariostatic mechanisms of action of fluorides. A review].

In the past the inhibition of caries by fluorides was ascribed to the reduced solubility of enamel due to the incorporation of F- into the enamel mineral. During the last years the understanding of the cariostatic mechanism has changed fundamentally. Based on these new findings the loosely bound fluorides, which are present in the surroundings of the teeth after application of topicals, are regarded as decisive for the caries preventing effect by causing an inhibition of demineralization, enhancing the remineralization process and supporting the precipitation of CaF2. The formation of CaF2 is induced after application of topicals, and the material stays relatively stable in the mouth, due to adsorbed HPO4(2-) ions at the surface of CaF2. During the cariogenic challenge, CaF2 releases F- ions due to the reduced concentration of HPO4(2-) ions at acidic pH values. The CaF2 therefore functions as a pH-controlled F(-)-reservoir and is the most important supplier of free F- ions during the cariogenic challenge.

Dental Enamel↗
PubMed1995

[A mathematical model for the treatment of root surfaces with rigid and flexible instruments].

The objective of this study was to assess the accessibility of root surfaces using stiff instruments in order to evaluate the advantages of a new flexible instrument-set for the treatment of periodontally diseased roots. 100 extracted human teeth were sectioned and histologically prepared. They were divided into two groups each containing 50 sections. Group I showing the interproximal, group II the buccal/lingual morphology. Slides were taken of each section under a constant magnification (3.2x) and a selected number of distances and angles were measured on each section. Using trigonometric functions the following parameters were calculated and set in relation with hypothetical probing depths ranging from 0-15 mm: 1.) instrument length; 2.) change of the instrument angulation; 3.) theoretical deflection of the gums. Statistical analysis was performed using Student's t-test. For a given probing depth the instrument length was independent of the sites and the deflection of the gums. When a deflection of the gums was assumed, the instrument angulation was constant; an exponential decrease of the angulation with increasing probing depth was found with gum deflection. The deflection was increasing with increasing probing depth, showing statistically significant differences between interproximal and buccal/lingual sites (p < or = 0.05). In conclusion the instrument length seems not to be an impeding factor for the accessibility of root surfaces in contrast to the instrument angulation and the fact that teeth are encircled by the gum. Due to morphological reasons stiff instruments seem to be inferior to flexible instruments when a non-surgical root treatment is performed.(ABSTRACT TRUNCATED AT 250 WORDS)

Dental Scaling↗
PubMed1994

A comparison between a new vacuum obturation technique and lateral condensation: an in vitro study.

A new machine that allows cleaning root canals without conventional instruments has been introduced. Because this noninstrumented technique does not enlarge the root canal system, a new device had to be developed to fill the root canal system. The new machine was able to produce a vacuum that allowed proper drying and filling of a root canal system. This study evaluated the new vacuum filling method and compared it with lateral condensation. Canals of 40 extracted human molars, instrumented using the step-back technique, were either filled with the new vacuum obturation technique using AH26 sealer and a gutta-percha single cone or by lateral condensation. Teeth were coated with wax and placed into India ink for 7 days. The wax was then removed and the teeth were cleared. All teeth were evaluated for linear dye penetration using a x20 viewer. Obturation with the new vacuum technique resulted in significantly less leakage than lateral condensation.

Analysis of Variance↗
PubMed1994

The effect of experience and training on the diagnosis of approximal coronal caries from bitewing radiographs. A Swiss-American comparison.

The purpose of the present study was to compare the development of skills in the radiographic diagnosis of approximal coronal caries. Swiss (Bern) and American (Alabama) dental students with and without clinical experience, Swiss general practitioners, and Swiss and American dental school faculty viewed bitewing radiographic films of 13 teeth. The observers examined the 26 approximal surfaces on the radiographic films and responded, on a five point certainty scale, whether approximal caries was present. Mean sensitivity ranged from a low of 0.59 for American faculty to a high of 0.80 for Swiss students with clinical experience, mean specificity ranged from 0.84 for Swiss pre-clinical students to 0.95 for American faculty. For a summary measure of accuracy, i.e., area under the receiver operating characteristic (ROC) curve, the scores for student observers tended to increase with experience. The scores for Swiss and American students with clinical experience and faculty did not differ significantly. Inter-examiner agreement (Kappa) could only be characterized as moderate at best. Formal didactic instruction and clinical experience produced dental students with skills in the diagnosis of approximal caries from bitewing radiographs similar to that of faculty dentists.

Alabama↗
PubMed1993

A novel noninstrumented technique for cleansing the root canal system.

The aim of this study was to develop a machine to clean root canals without conventional instruments. This goal was achieved with a device which was able to develop controlled cavitation in the root canal. Under reduced pressure, alternating pressure fields generated microscopic and macroscopic cavitation bubbles. Subsequently, these vapor-filled cavitation bubbles collapsed, creating hydrodynamic turbulence. These two phenomena allowed the irrigant to penetrate the canal system and then be exchanged with new irrigant. To test the cleaning ability of the device 79 freshly extracted vital molars with 222 root canals were collected. The control group (27 molars, 73 canals) was prepared with the step-back technique using NaOCl (3%) as an irrigant. The three test groups (52 molars, 149 canals) were prepared with the new machine using NaOCl (1, 2, or 3%). The treatment time ranged from 16 to 32 min in the hand group and from 10 to 15 min in the machine groups. The teeth were then prepared histologically and examined by light microscopy. Overall, the treatment with NaOCl (2 and 3%) resulted in similar or better cleanliness in all three root sections when comparing machine and hand instrumentation. In curved canals, however, the apical one third was also significantly cleaner when using the machine and 3% NaOCl than with hand instrumentation. This in vitro study shows that it is possible to clean a root canal system by a noninstrumented technique as well as by conventional hand instrumentation.

Dental Cavity Preparation↗
PubMed1993

Mineral induction in vivo by dentine proteins.

The mineral-inductive capacity of polyanionic noncollagenous proteins, isolated from calcified tissues, has earlier been demonstrated in vitro. These macromolecules possess this capacity, provided that they are immobilized on a solid support, whereas in solution they inhibit crystal mineral induction and growth. The present study demonstrates this capacity also in vivo. Phosphoprotein, proteoglycan and gamma-carboxyglutamate-containing protein (Gla-protein) of the osteocalcin type were covalently coupled to AH-Sepharose beads, and these were implanted subcutaneously in minipigs for periods between 3 and 24 weeks. Similarly, demineralized rat incisor dentine was implanted for 3 weeks, as was predentine dissected from dentinogenically active bovine incisors. The results were analyzed by scanning electron microscopy and energy dispersive X-ray analysis. Dentine proteoglycan and phosphoprotein coupled to beads were found to be inducers of calcium/phosphate-containing mineral, whereas the efficacy of Gla-protein was negligible. Dissected predentine did not induce any mineral, but demineralized dentine preparations, still containing some noncollagenous anionic components, were found to induce mineral. The results indicate that macromolecules such as proteoglycan and phosphoprotein may be responsible for mineral induction during mineralization of calcified tissues. The results further imply that such molecules may be of importance for the remineralization of dentine in conjunction with the caries process.

Animals↗
PubMed1993

The influence of different factors on in vitro enamel erosion.

The aim of this study was to use two demineralization test methods to analyze the erosive potential of beverages and foodstuffs. In addition, the surface microhardness test and the iodide permeability test were compared. Surface microhardness and iodide permeability were measured before and after exposure. To characterize the beverages and foodstuffs the content of phosphate, calcium and fluoride, pH, the titrable amount of base to pH 5.5 and 7.0 as well as the buffer capacity at pH 5.5 were determined. Sprite light showed the highest significant decrease in surface microhardness (p < or = 0.05) followed by grapefruit juice, apple juice and salad dressing. The highest significant increase in iodide permeability (p < or = 0.05) was caused by exposure to grapefruit juice followed by apple juice (Sprite light was not tested). Multiple linear regression analyses revealed that the erosive capacity of different drinks, juices and foodstuffs are statistically significantly associated with their acidity, pH values, phosphate and fluoride contents as well as the baseline surface microhardness or iodide permeability values of the exposed enamel.

Beverages↗
PubMed1993

Comparison of different methods for the diagnosis of fissure caries without cavitation.

The aim of this study was to compare the accuracy of several common methods for the diagnosis of fissure caries. 63 human teeth without fillings and without any macroscopic carious cavitation but with different degrees of fissure discoloration and decalcification were selected from a pool. Dentists were asked to examine embedded teeth for fissure caries. The examination was done under standard conditions in a professional dental unit. The methods employed were: visual inspection (VI, n = 26 dentists), visual inspection with a magnifying glass (2x; VIM; n = 26), conventional bite-wing radiography (BW; n = 24), visual inspection combined with conventional bite-wing radiography (VI + BW; n = 10), and visual inspection combined with light pressure probing (VI + P; n = 23 dentists). In order to measure the reproducibility, VI and VI + BW were repeated. After the last inspection, the teeth were histologically prepared, serially sectioned perpendicular to the occlusal surface, and diagnosed for the presence of caries. The agreement between histological and clinical diagnosis was assessed. Specificities and sensitivities were: VI = 93 and 12%, VIM = 89 and 20%, BW = 83 and 45%, VI + BW = 87 and 49%, and VI + P = 93 and 14%, respectively. The following likelihood ratios were found: VI = 1.84, VIM = 1.86, BW = 2.6, VI + BW = 3.85, and VI + P = 2.05. It was concluded that the rather low sensitivity especially for VI and VI + P may lead to a significant number of teeth with dentinal caries being undetected.(ABSTRACT TRUNCATED AT 250 WORDS)

Dental Enamel↗